Ionic Graphitization of Ultrathin Films of Ionic Compounds.

PubMed

Kvashnin, A G; Pashkin, E Y; Yakobson, B I; Sorokin, P B

2016-07-21

On the basis of ab initio density functional calculations, we performed a comprehensive investigation of the general graphitization tendency in rocksalt-type structures. In this paper, we determine the critical slab thickness for a range of ionic cubic crystal systems, below which a spontaneous conversion from a cubic to a layered graphitic-like structure occurs. This conversion is driven by surface energy reduction. Using only fundamental parameters of the compounds such as the Allen electronegativity and ionic radius of the metal atom, we also develop an analytical relation to estimate the critical number of layers.

[Distribution of chemical elements in whole blood and plasma].

PubMed

Barashkov, G K; Zaĭtseva, L I; Kondakhchan, M A; Konstantinova, E A

2003-01-01

The distribution factor (Fd) of 35 elements of plasma and whole blood in 26 healthy men and women was detected by ICP-OES. Usilig this parameter the elements were subdivided in 3 pools. 9 of them have Fd higher than 1.5 ("elements of plasma"-Ag, Ca, Cu, In, Li, Na, Se, Si, Sr); 6 have lower than 0.5 ("elements of blood cells"-Fe, K, Mn, Ni, V, Zn), other 20-about 1 ("blood elements"). Fd of all elements depends on ionic radius. Elements of 2nd sub-groups of all groups of Mendeleev's periodic table ("heavy metals") depend on the similar law: "with growing of ionic radius the concentration of elements in plasma enhances". In alkaline metals Fd depends on the opposite law:" with growing of ionic radius of alkaline metal the quantity of elements in blood cells enhance". Dependence of Fd on the value of atomic mass in periods or in exterior electronic cloud (s-, p-, d-, f-) was not established. The table of distribution of all detected elements in whole blood in relation to 8 macroelements (Ca, Mg, K, Na, S, P, Fe, Zn,) is presented, as a basic diagnostic criteria in metal-ligand homeostasis disturbance.

Effect of water on structure and dynamics of [BMIM][PF6] ionic liquid: An all-atom molecular dynamics simulation investigation.

PubMed

Sharma, Anirban; Ghorai, Pradip Kr

2016-03-21

Composition dependent structural and dynamical properties of aqueous hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (IL) have been investigated by using all-atom molecular dynamics simulation. We observe that addition of water does not increase significant number of dissociated ions in the solution over the pure state. As a consequence, self-diffusion coefficient of the cation and anion is comparable to each other at all water concentration similar to that is observed for the pure state. Voronoi polyhedra analysis exhibits strong dependence on the local environment of IL concentration. Void and neck distributions in Voronoi tessellation are approximately Gaussian for pure IL but upon subsequent addition of water, we observe deviation from the Gaussian behaviour with an asymmetric broadening with long tail of exponential decay at large void radius, particularly at higher water concentrations. The increase in void space and neck size at higher water concentration facilitates ionic motion, thus, decreasing dynamical heterogeneity and IL reorientation time and increases self-diffusion coefficient significantly.

Effect of water on structure and dynamics of [BMIM][PF{sub 6}] ionic liquid: An all-atom molecular dynamics simulation investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Anirban; Ghorai, Pradip Kr., E-mail: pradip@iiserkol.ac.in

2016-03-21

Composition dependent structural and dynamical properties of aqueous hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF{sub 6}]) ionic liquid (IL) have been investigated by using all-atom molecular dynamics simulation. We observe that addition of water does not increase significant number of dissociated ions in the solution over the pure state. As a consequence, self-diffusion coefficient of the cation and anion is comparable to each other at all water concentration similar to that is observed for the pure state. Voronoi polyhedra analysis exhibits strong dependence on the local environment of IL concentration. Void and neck distributions in Voronoi tessellation are approximately Gaussian for pure ILmore » but upon subsequent addition of water, we observe deviation from the Gaussian behaviour with an asymmetric broadening with long tail of exponential decay at large void radius, particularly at higher water concentrations. The increase in void space and neck size at higher water concentration facilitates ionic motion, thus, decreasing dynamical heterogeneity and IL reorientation time and increases self-diffusion coefficient significantly.« less

Predictions of Crystal Structure Based on Radius Ratio: How Reliable Are They?

ERIC Educational Resources Information Center

Nathan, Lawrence C.

1985-01-01

Discussion of crystalline solids in undergraduate curricula often includes the use of radius ratio rules as a method for predicting which type of crystal structure is likely to be adopted by a given ionic compound. Examines this topic, establishing more definitive guidelines for the use and reliability of the rules. (JN)

Estimation of electronegativity values of elements in different valence states.

PubMed

Li, Keyan; Xue, Dongfeng

2006-10-05

The electronegativities of 82 elements in different valence states and with the most common coordination numbers have been quantitatively calculated on the basis of an effective ionic potential defined by the ionization energy and ionic radius. It is found that for a given cation, the electronegativity increases with increasing oxidation state and decreases with increasing coordination number. For the transition-metal cations, the electronegativity of the low-spin state is higher than that of the high-spin state. The ligand field stabilization, the first filling of p orbitals, the transition-metal contraction, and especially the lanthanide contraction are well-reflected by the relative values of our proposed electronegativity. This new scale is useful for us to estimate some quantities (e.g., the Lewis acid strength for the main group elements and the hydration free energy for the first transition series) and predict the structure and property of materials.

Trace element partitioning between ionic crystal and liquid

NASA Technical Reports Server (NTRS)

Tsang, T.; Philpotts, J. A.; Yin, L.

1978-01-01

The partitioning of trace elements between ionic crystals and the melt has been correlated with lattice energy of the host. The solid-liquid partition coefficient has been expressed in terms of the difference in relative ionic radius of the trace element and the homogeneous and heterogeneous strain of the host lattice. Predictions based on this model appear to be in general agreement with data for alkali nitrates and for rare-earth elements in natural garnet phenocrysts.

Heat capacity of rare-earth cuprates, orthovanadates, and aluminum garnets, gallium garnets, and iron garnets

NASA Astrophysics Data System (ADS)

Denisova, L. T.; Kargin, Yu. F.; Denisov, V. M.

2015-08-01

The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R 3+ has been analyzed. It has been shown that the values of C {/p 0} change consistently depending on the radius R 3+ within the corresponding tetrads (La-Nd, Pm-Gd, Gd-Ho, Eu-Lu).

CdO as the archetypical transparent conducting oxide. Systematics of dopant ionic radius and electronic structure effects on charge transport and band structure.

PubMed

Yang, Yu; Jin, Shu; Medvedeva, Julia E; Ireland, John R; Metz, Andrew W; Ni, Jun; Hersam, Mark C; Freeman, Arthur J; Marks, Tobin J

2005-06-22

A series of yttrium-doped CdO (CYO) thin films have been grown on both amorphous glass and single-crystal MgO(100) substrates at 410 degrees C by metal-organic chemical vapor deposition (MOCVD), and their phase structure, microstructure, electrical, and optical properties have been investigated. XRD data reveal that all as-deposited CYO thin films are phase-pure and polycrystalline, with features assignable to a cubic CdO-type crystal structure. Epitaxial films grown on single-crystal MgO(100) exhibit biaxial, highly textured microstructures. These as-deposited CYO thin films exhibit excellent optical transparency, with an average transmittance of >80% in the visible range. Y doping widens the optical band gap from 2.86 to 3.27 eV via a Burstein-Moss shift. Room temperature thin film conductivities of 8,540 and 17,800 S/cm on glass and MgO(100), respectively, are obtained at an optimum Y doping level of 1.2-1.3%. Finally, electronic band structure calculations are carried out to systematically compare the structural, electronic, and optical properties of the In-, Sc-, and Y-doped CdO systems. Both experimental and theoretical results reveal that dopant ionic radius and electronic structure have a significant influence on the CdO-based TCO crystal and band structure: (1) lattice parameters contract as a function of dopant ionic radii in the order Y (1.09 A) < In (0.94 A) < Sc (0.89 A); (2) the carrier mobilities and doping efficiencies decrease in the order In > Y > Sc; (3) the dopant d state has substantial influence on the position and width of the s-based conduction band, which ultimately determines the intrinsic charge transport characteristics.

Disaggregation of adenylate cyclase during polyacrylamide-gel electrophoresis in mixtures of ionic and non-ionic detergents

PubMed Central

Newby, Andrew C.; Chrambach, Andreas

1979-01-01

1. Adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] solubilized from the rat liver plasma membrane with 1% Lubrol PX and partially purified by gel filtration in buffer containing 0.01% Lubrol PX was physically characterized by polyacrylamide-gel electrophoresis. 2. The molecular radius determined for the partially purified enzyme was 4.9nm, compared with the value of 3.9nm obtained for the enzyme before gel filtration. 3. This difference, representing an approximate doubling of the molecular volume of the enzyme, implied that aggregation with itself or other proteins had occurred during partial purification. 4. Aggregation was not reversed by electrophoresis in the presence of high Lubrol concentrations. 5. Substitution of deoxycholate or N-dodecylsarcosinate for Lubrol PX either for solubilization or during electrophoresis led to poorer resolution of membrane proteins at concentrations giving greater than 70% loss of enzyme activity. 6. Partially purified adenylate cyclase was electrophoresed in the presence of mixed micelles of Lubrol PX and deoxycholate or Lubrol PX and N-dodecylsarcosinate. Different mixtures were examined simultaneously in a suitable apparatus. 7. Electrophoresis in the presence of 0.1% Lubrol plus 0.03% deoxycholate decreased the molecular radius of the cyclase to 4.0nm, with greater than 90% recovery of enzymic activity. The net charge of the enzyme was also increased, indicating ionic detergent binding. 8. With 0.1% Lubrol plus 0.03% N-dodecylsarcosinate the molecular radius was 4.3nm, recovery approx. 50% and net charge similar to that seen in Lubrol plus deoxycholate. 9. The resolution of cyclase from bulk protein, on an analytical scale, was improved in the presence of detergent mixtures, as compared with resolution in Lubrol alone. 10. The results demonstrate the usefulness of polyacrylamide-gel electrophoresis to detect and overcome aggregation problems with membrane proteins and suggest that detergent mixtures in specific ratios may be useful in the purification of adenylate cyclase and other intrinsic membrane proteins. ImagesFig. 3. PMID:435255

Calorimetric and Neutron Scattering Studies on Glass Transitions and Ionic Diffusions in Imidazolium-based Ionic Liquids

NASA Astrophysics Data System (ADS)

Yamamuro, O.; Kofu, M.

2017-05-01

Glass transition is one of the central research issues of ionic liquids (ILs). In particular, the most typical ILs, imidazolium-basedones (ImILs) are readily supercooled and exhibit glass transitions below room temperature. We have measured the heat capacities of several ImILs, encoded as CnmimX (n: alkyl carbon number, n = 2-8, X: anion, X = Cl, I, FeCl4, TFSI) using an adiabatic calorimeter. We found that most of ImILs exhibit glass transitions with large Cp jumps in a temperature range between 170 K and 230 K. The large Cp jumps reflect that these ILs are fragile liquids that exhibit large structural change depending on temperature near the glass transition temperature T g. It is also revealed that T g does not depend much on n but on the anion radius. We have investigated the dynamics of CnmimX (n = 2-8, X = Cl, NO3, PF6, TF, FSI, TFSI) by means of a quasielastic neutron scattering (QENS) technique. It was clarified that the ionic diffusion is directly associated with the viscosity and glass transition. The activation energy ΔE a of the ionic diffusion increases with decreasing anion size but remains almost unchanged with n as found for T g. These systematic change of T g and ΔE a can be explained well by taking account the nano-domain structure which is the most characteristic feature of ImILs.

Teaching light scattering spectroscopy: the dimension and shape of tobacco mosaic virus.

PubMed Central

Santos, N C; Castanho, M A

1996-01-01

The tobacco mosaic virus is used as a model molecular assembly to illustrate the basic potentialities of light scattering techniques (both static and dynamic) to undergraduates. The work has two objectives: a pedagogic one (introducing light scattering to undergraduate students) and a scientific one (stabilization of the virus molecular assembly structure by the nucleic acid). Students are first challenged to confirm the stabilization of the cylindrical shape of the virus by the nucleic acid, at pH and ionic strength conditions where the coat proteins alone do not self-assemble. The experimental intramolecular scattering factor is compared with the theoretical ones for several model geometries. The data clearly suggest that the geometry is, in fact, a rod. Comparing the experimental values of gyration radius and hydrodynamic radius with the theoretical expectations further confirms this conclusion. Moreover, the rod structure is maintained over a wider range of pH and ionic strength than that valid for the coat proteins alone. The experimental values of the diffusion coefficient and radius of gyration are compared with the theoretical expectations assuming the dimensions detected by electron microscopy techniques. In fact, both values are in agreement (length approximately 300 nm, radius approximately 20 nm). PMID:8874039

Cr.sup.4+-doped mixed alloy laser materials and lasers and methods using the materials

NASA Technical Reports Server (NTRS)

Alfano, Robert R. (Inventor); Petricevic, Vladimir (Inventor); Bykov, Alexey (Inventor)

2008-01-01

A laser medium includes a single crystal of Cr.sup.4+:Mg.sub.2-xM.sub.xSi.sub.1-yA.sub.yO.sub.4, where, where M is a bivalent ion having an ionic radius larger than Mg.sup.2+, and A is a tetravalent ion having an ionic radius larger than Si.sup.4+. In addition, either a) 0.ltoreq.x<2 and 0

Molecular dynamics study of the vaporization of an ionic drop.

PubMed

Galamba, N

2010-09-28

The melting of a microcrystal in vacuum and subsequent vaporization of a drop of NaCl were studied through molecular dynamics simulations with the Born-Mayer-Huggins-Tosi-Fumi rigid-ion effective potential. The vaporization was studied for a single isochor at increasing temperatures until the drop completely vaporized, and gaseous NaCl formed. Examination of the vapor composition shows that the vapor of the ionic drop and gaseous NaCl are composed of neutral species, the most abundant of which, ranging from simple NaCl monomers (ion pairs) to nonlinear polymers, (Na(n)Cl(n))(n=2-4). The enthalpies of sublimation, vaporization, and dissociation of the different vapor species are found to be in reasonable agreement with available experimental data. The decrease of the enthalpy of vaporization of the vapor species, with the radius of the drop decrease, accounts for a larger fraction of trimers and tetramers than that inferred from experiments. Further, the rhombic dimer is significantly more abundant than its linear isomer although the latter increases with the temperature. The present results suggest that both trimers and linear dimers may be important to explain the vapor pressure of molten NaCl at temperatures above 1500 K.

Evolution of Anisotropic Displacement Parameters and Superconductivity with Chemical Pressure in BiS2-Based REO0.5F0.5BiS2 (RE = La, Ce, Pr, and Nd)

NASA Astrophysics Data System (ADS)

Mizuguchi, Yoshikazu; Hoshi, Kazuhisa; Goto, Yosuke; Miura, Akira; Tadanaga, Kiyoharu; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

2018-02-01

In order to understand the mechanisms behind the emergence of superconductivity by the chemical pressure effect in REO0.5F0.5BiS2 (RE = La, Ce, Pr, and Nd), where bulk superconductivity is induced by the substitutions with a smaller-radius RE, we performed synchrotron powder X-ray diffraction, and analyzed the crystal structure and anisotropic displacement parameters. With the decrease of the RE3+ ionic radius, the in-plane disorder of the S1 sites significantly decreased, very similar to the trend observed in the Se-substituted systems: LaO0.5F0.5BiS2-xSex and Eu0.5La0.5FBiS2-xSex. Therefore, the emergence of bulk superconductivity upon the suppression of the in-plane disorder at the chalcogen sites is a universal scenario for the BiCh2-based superconductors. In addition, we indicated that the amplitude of vibration along the c-axis of the in-plane chalcogen sites may be related to the Tc in the BiCh2-based superconductors.

Molecular Insights into Carbon Nanotube Supercapacitors: Capacitance Independent of Voltage and Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Guang; Li, Song; Atchison, Jennifer S.

2013-04-12

Molecular dynamics (MD) simulations of supercapacitors with single-walled carbon nanotube (SWCNT) electrodes in room-temperature ionic liquids were performed to investigate the influences of the applied electrical potential, the radius/curvature of SWCNTs, and temperature on their capacitive behavior. It is found that (1) SWCNTs-based supercapacitors exhibit a near-flat capacitance–potential curve, (2) the capacitance increases as the tube radius decreases, and (3) the capacitance depends little on the temperature. We report the first MD study showing the influence of the electrode curvature on the capacitance–potential curve and negligible dependence of temperature on capacitance of tubular electrode. The latter is in good agreementmore » with recent experimental findings and is attributed to the similarity of the electrical double layer (EDL) microstructure with temperature varying from 260 to 400 K. The electrode curvature effect is explained by the dominance of charge overscreening and increased ion density per unit area of electrode surface.« less

Anomalously large capacitance of an ionic liquid described by the restricted primitive model

NASA Astrophysics Data System (ADS)

Loth, M. S.; Skinner, Brian; Shklovskii, B. I.

2010-11-01

We use Monte Carlo simulations to examine the simplest model of a room-temperature ionic liquid (RTIL), called the “restricted primitive model,” at a metal surface. We find that at moderately low temperatures the capacitance of the metal-RTIL interface is so large that the effective thickness of the electrostatic double layer is up to three times smaller than the ion radius. To interpret these results we suggest an approach which is based on the interaction between discrete ions and their image charges in the metal surface and which therefore goes beyond the mean-field approximation. When a voltage is applied across the interface, the strong image attraction causes counterions to condense onto the metal surface to form compact ion-image dipoles. These dipoles repel each other to form a correlated liquid. When the surface density of these dipoles is low, the insertion of an additional dipole does not require much energy. This leads to a large capacitance C that decreases monotonically with voltage V , producing a “bell-shaped” curve C(V) . We also consider what happens when the electrode is made from a semimetal rather than a perfect metal. In this case, the finite screening radius of the electrode shifts the reflection plane for image charges to the interior of the electrode, and we arrive at a “camel-shaped” C(V) . These predictions seem to be in qualitative agreement with experiment.

Inelastic neutron scattering study on boson peaks of imidazolium-based ionic liquids

DOE PAGES

Kofu, Maiko; Inamura, Yasuhiro; Podlesnyak, Andrey A.; ...

2015-07-26

Low energy excitations of 1-alkyl-3-methylimidazolium ionic liquids (ILs) have been investigated by means of neutron spectroscopy. In the spectra of inelastic scattering, a broad excitation peak referred to as a “boson peak” appeared at 1–3 meV in all of the ILs measured. The intensity of the boson peak was enhanced at the Q positions corresponding to the diffraction peaks, reflecting the in-phase vibrational nature of the boson peak. Furthermore the boson peak energy (E BP) was insensitive to the length of the alkyl-chain but changed depending on the radius of the anion. From the correlation among E BP, the anionmore » radius, and the glass transition temperature T g, we conclude that both E BP and T g in ILs are predominantly governed by the inter-ionic Coulomb interaction which is less influenced by the alkyl-chain length. Furthermore, we also found that the E BP is proportional to the inverse square root of the molecular weight as observed in molecular glasses.« less

Comparative biokinetics of trivalent radionuclides with similar ionic dimensions: promethium-147, curium-242 and americium-241.

PubMed

Priest, N D

2007-09-01

Data on the distribution and redistribution patterns in the laboratory rat of three trivalent elements with a similar ionic radius have been compared. This showed that these distributions for the two ions with the same ionic radius (111 pm), i.e., those of promethium (a lanthanoid) and curium (an actinoid), were indistinguishable and that americium, with a slightly larger ion size (111.5 pm), behaved similarly. The results are consistent with the suggestion that ion size is the only important factor controlling the deposition and redistribution patterns of trivalent lanthanoids and actinoids in rats. The result is important because it suggests that the same radiological protection dosimetry models should be used for trivalent actinoids and lanthanoids, that human volunteer data generated for lanthanoid isotopes can be used to predict the behavior of actinoids with the same ion size, and that appropriate pairs of beta-particle-emitting lanthanoid and alpha-particle-emitting actinoids could be used to study the relative toxicity of alpha and beta particles in experimental animals.

Thermoelectric Properties of the Ca1- x R x MnO3 Perovskite System (R: Pr, Nd, Sm) for High-Temperature Applications

NASA Astrophysics Data System (ADS)

Choi, Soon-Mok; Lim, Chang-Hyun; Seo, Won-Seon

2011-05-01

Perovskite oxides have attracted considerable attention in the area of thermoelectrics owing to the advantages of their isotropic crystal structure and straightforward control of their electrical properties. Among the many perovskites, different types of polycrystalline Ca1- x R x MnO3 (R: Pr, Nd, Sm) were prepared by solid-state reaction in this study. Three different rare-earth dopants were substituted at the Ca-ion site at various amounts. Considering phase stability, rare-earth ions with nearly the same ionic radius as Ca2+ were selected. To assess thermoelectric performance, the electrical conductivity, Seebeck coefficient, and power factor were measured, and phase analysis was conducted. The effects of ionic radius variation on single phase formation and the effect of doping amount on carrier concentration are discussed.

Viscoelasticity of nano-alumina dispersions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rand, B.; Fries, R.

1996-06-01

The flow and viscoelastic properties of electrostatically stabilized nano-alumina dispersions have been studied as a function of ionic strength and volume fraction of solids. At low ionic strength the suspensions were deflocculated and showed a transition from viscous to elastic behavior as the solid content increased associated with the onset of double layer interpenetration. The phase transition was progressively shifted to higher solids fractions with increasing ionic strength. At higher ionic strength, above the critical coagulation concentration, the suspensions formed attractive networks characterized by high elasticity. Two independent methods of estimating the effective radius of electrostatically stabilized {open_quotes}soft{close_quotes} particles, a{submore » eff}, are presented based on phase angle data and a modified Dougherty-Krieger equation. The results suggest that a{sub eff} is not constant for a given system but changes with both solids fraction and ionic strength.« less

Mass transport in polyelectrolyte solutions

NASA Astrophysics Data System (ADS)

Schipper, F. J. M.; Leyte, J. C.

1999-02-01

The self-diffusion coefficients of the three components of a salt-free heavy-water solution of polymethacrylic acid, completely neutralized with tetra-methylammonium hydroxide, were measured over a broad concentration range. Three concentration regions were observed for the self-diffusion of both the polyions and the counterions. At polyion concentrations below 0.01 mol monomer kg-1, the dilute concentration regime for the polymer, the polyion self-diffusion coefficient approaches the self-diffusion coefficient of a freely diffusing rod upon dilution. At polyelectrolyte concentrations above 0.1 mol monomer kg-1, the self-diffusion coefficients of the solvent, the counterions and the polymer decreased with concentration, suggesting that this decrease is due to a topological constraint on the motions of the components. In the intermediate-concentration region, the self-diffusion coefficients of the polyions and the counterions are independent of the concentration. The polyion dynamic behaviour is, in the intermediate- and high-concentration regions, reasonably well described by that of a hard sphere, with a radius of 3.7 nm. A correct prediction for the solvent dynamics is given by the obstruction effect of this hard sphere on the solvent. The relative counterion self-diffusion coefficient is predicted almost quantitatively over the entire concentration range with the Poisson-Boltzmann-Smoluchowski model for the spherical cell, provided that the sphere radius and the number of charges are chosen appropriately (approximately the number of charges in a persistence length). Using this model, the dependence of the counterion self-diffusion coefficient on the ionic strength, polyion concentration and counterion radius is calculated quantitatively over a large concentration range.

Local structures around the substituted elements in mixed layered oxides

PubMed Central

Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

2017-01-01

The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M1−xM′x)O2 (M and M′ are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (dM-O) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M. PMID:28252008

Recent developments in the formation and structure of tin-iron oxides by laser pyrolysis

NASA Astrophysics Data System (ADS)

Alexandrescu, R.; Morjan, I.; Dumitrache, F.; Birjega, R.; Fleaca, C.; Soare, I.; Gavrila, L.; Luculescu, C.; Prodan, G.; Kuncser, V.; Filoti, G.

2011-04-01

Complex oxides demonstrate specific electric and magnetic properties which make them suitable for a wide variety of applications, including dilute magnetic semiconductors for spin electronics. A tin-iron oxide Sn 1- xFe xO 2 nanoparticulate material has been successfully synthesized by using the laser pyrolysis of tetramethyl tin-iron pentacarbonyl-air mixtures. Fe doping of SnO 2 nanoparticles has been varied systematically in the 3-10 at% range. As determined by EDAX, the Fe/Sn ratio (in at%) in powders varied between 0.14 and 0.64. XRD studies of Sn 1- xFe xO 2 nanoscale powders, revealed only structurally modified SnO 2 due to the incorporation of Fe into the lattice mainly by substitutional changes. The substitution of Fe 3+ in the Sn 4+ positions (Fe 3+ has smaller ionic radius as compared to the ionic radius of 0.69 Å for Sn 4+) with the formation of a mixed oxide Sn 1- xFe xO 2 is suggested. A lattice contraction consistent with the determined Fe/Sn atomic ratios was observed. The nanoparticle size decreases with the Fe doping (about 7 nm for the highest Fe content). Temperature dependent 57Fe Mössbauer spectroscopy data point to the additional presence of defected Fe 3+-based oxide nanoclusters with blocking temperatures below 60 K. A new Fe phase presenting magnetic order at substantially higher temperatures was evidenced and assigned to a new type of magnetism relating to the dispersed Fe ions into the SnO 2 matrix.

Reduced grain boundary energies in rare-earth doped MgAl 2O 4 spinel and consequent grain growth inhibition

DOE PAGES

Hasan, Md M.; Dholabhai, Pratik P.; Dey, Sanchita; ...

2017-05-15

In this paper, grain growth inhibition in MgAl 2O 4 spinel nanostructure was achieved by grain boundary (GB) segregation of rare-earth dopants. Microcalorimetric measurements showed that dense spinel compacts doped with 3 mol% of R 2O 3 (R = Y, Gd, and La) had decreased GB energies as compared to the undoped spinel, representing reduction in the driving force for grain growth. Segregation energies of the three dopants to the Σ3 (111) GB were calculated by atomistic simulation. The dopants with higher ionic radius tend to segregate more strongly to GBs. The GB energies were calculated from atomistic simulation and,more » consistent with experiments, a systematic reduction in GB energy with dopant ionic size was found. Finally, high temperature grain growth experiments revealed a significant reduction of grain growth in the doped nanostructures as compared to the undoped one, which was attributed to increased metastability or possibly also a GB dragging originated from the dopant segregation.« less

Acoustic phonon spectrum engineering in bulk crystals via incorporation of dopant atoms

NASA Astrophysics Data System (ADS)

Kargar, Fariborz; Penilla, Elias H.; Aytan, Ece; Lewis, Jacob S.; Garay, Javier E.; Balandin, Alexander A.

2018-05-01

We report results of Brillouin—Mandelstam spectroscopy of transparent Al2O3 crystals with Nd dopants. The ionic radius and atomic mass of Nd atoms are distinctively different from those of the host Al atoms. Our results show that even a small concentration of Nd atoms incorporated into the Al2O3 samples produces a profound change in the acoustic phonon spectrum. The velocity of the transverse acoustic phonons decreases by ˜600 m/s at the Nd density of only ˜0.1%. Interestingly, the decrease in the phonon frequency and velocity with the doping concentration is non-monotonic. The obtained results, demonstrating that modification of the acoustic phonon spectrum can be achieved not only by traditional nanostructuring but also by low-concentration doping, have important implications for thermal management as well as thermoelectric and optoelectronic devices.

Coalescence of repelling colloidal droplets: a route to monodisperse populations.

PubMed

Roger, Kevin; Botet, Robert; Cabane, Bernard

2013-05-14

Populations of droplets or particles dispersed in a liquid may evolve through Brownian collisions, aggregation, and coalescence. We have found a set of conditions under which these populations evolve spontaneously toward a narrow size distribution. The experimental system consists of poly(methyl methacrylate) (PMMA) nanodroplets dispersed in a solvent (acetone) + nonsolvent (water) mixture. These droplets carry electrical charges, located on the ionic end groups of the macromolecules. We used time-resolved small angle X-ray scattering to determine their size distribution. We find that the droplets grow through coalescence events: the average radius (R) increases logarithmically with elapsed time while the relative width σR/(R) of the distribution decreases as the inverse square root of (R). We interpret this evolution as resulting from coalescence events that are hindered by ionic repulsions between droplets. We generalize this evolution through a simulation of the Smoluchowski kinetic equation, with a kernel that takes into account the interactions between droplets. In the case of vanishing or attractive interactions, all droplet encounters lead to coalescence. The corresponding kernel leads to the well-known "self-preserving" particle distribution of the coalescence process, where σR/(R) increases to a plateau value. However, for droplets that interact through long-range ionic repulsions, "large + small" droplet encounters are more successful at coalescence than "large + large" encounters. We show that the corresponding kernel leads to a particular scaling of the droplet-size distribution-known as the "second-scaling law" in the theory of critical phenomena, where σR/(R) decreases as 1/√(R) and becomes independent of the initial distribution. We argue that this scaling explains the narrow size distributions of colloidal dispersions that have been synthesized through aggregation processes.

Removal of Radionuclides from Waste Water at Fukushima Daiichi Nuclear Power Plant: Desalination and Adsorption Methods - 13126

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kani, Yuko; Kamosida, Mamoru; Watanabe, Daisuke

Waste water containing high levels of radionuclides due to the Fukushima Daiichi Nuclear Power Plant accident, has been treated by the adsorption removal and reverse-osmosis (RO) desalination to allow water re-use for cooling the reactors. Radionuclides in the waste water are collected in the adsorbent medium and the RO concentrate (RO brine) in the water treatment system currently operated at the Fukushima Daiichi site. In this paper, we have studied the behavior of radionuclides in the presently applied RO desalination system and the removal of radionuclides in possible additional adsorption systems for the Fukushima Daiichi waste water treatment. Regarding themore » RO desalination system, decontamination factors (DFs) of the elements present in the waste water were obtained by lab-scale testing using an RO unit and simulated waste water with non-radioactive elements. The results of the lab-scale testing using representative elements showed that the DF for each element depended on its hydrated ionic radius: the larger the hydrated ionic radius of the element, the higher its DF is. Thus, the DF of each element in the waste water could be estimated based on its hydrated ionic radius. For the adsorption system to remove radionuclides more effectively, we studied adsorption behavior of typical elements, such as radioactive cesium and strontium, by various kinds of adsorbents using batch and column testing. We used batch testing to measure distribution coefficients (K{sub d}s) for cesium and strontium onto adsorbents under different brine concentrations that simulated waste water conditions at the Fukushima Daiichi site. For cesium adsorbents, K{sub d}s with different dependency on the brine concentration were observed based on the mechanism of cesium adsorption. As for strontium, K{sub d}s decreased as the brine concentration increased for any adsorbents which adsorbed strontium by intercalation and by ion exchange. The adsorbent titanium oxide had higher K{sub d}s and it was used for the column testing to obtain breakthrough curves under various conditions of pH and brine concentration. The breakthrough point had a dependency on pH and the brine concentration. We found that when the pH was higher or the brine concentration was lower, the longer it took to reach the breakthrough point. The inhibition of strontium adsorption by alkali earth metals would be diminished for conditions of higher pH and lower brine concentration. (authors)« less

Minor elements incorporation control by ionic radius and growth rate on a stalagmite from the Chauvet Cave (SE-France)

NASA Astrophysics Data System (ADS)

Bourdin, C.; Douville, E.; Genty, D.

2009-12-01

A multi-elemental study focusing on earth-alkalis (Mg, Ca, Sr and Ba), uranium and rare-earth elements (REE) in the calcite of a stalagmite from the Chauvet Cave (SE of France) has been achieved by ICP-MS. The Chau-stm6 stalagmite which grew from 33 to 11.5 ky had already been dated and the published d13C and d18O profile is used as a paleoclimatic benchmark. Ba and Sr profiles show an abrupt concentration increase at the beginning of the last deglaciation whereas U and Mg feature a decreasing trend. REY (REE+yttrium) concentrations decrease markedly during early deglaciation (between 15 and 14.5 ky). The transition corresponds to a change from a slow to a fast growth rate. These variations can be explained by the crystallographic control of ionic radii of the minor elements: incorporation of small ions compared to Ca such as U, Mg, heavy REE are favoured during slow growth period (i.e. glacial) whereas large ions such as Ba, Sr and light REE are preferentially precipitated during fast growth period (i.e. Bolling-Allerod). This crystallographic effect seems to be dominant here because the soil above the cave is sparse. And may not have played a major role on the opposite to the water-limestone interaction.

Effect of alcaline cations in zeolites on their dielectric properties.

PubMed

Legras, Benoît; Polaert, Isabelle; Estel, Lionel; Thomas, Michel

2012-01-01

The effect on dielectric properties of alkaline cations Li+, Na+ and K+ incorporated in a zeolite Faujasite structure X or Y, has been investigated. Two major phenomena have been proved to occur: ionic conductivity and rotational polarization of the water molecules adsorbed. The polarizability of the cation which is directly linked to its radius, affects ionic conductivity as well as rotational polarization. Li cations are more strongly Linked to the framework than K+ and Na+ and induce a lower ionic conductivity. K+ is weakly fixed and induces a ionic conductivity even at low solvation level. At low water content, the cation nature and number mainly control the free rotation of the water molecules and affect the relaxation frequency. Close to saturation, the water molecules are mainly linked together by H bonds: the cation nature and number do not really affect the global dielectric properties anymore.

Structure and reactivity of a mononuclear gold(II) complex

NASA Astrophysics Data System (ADS)

Preiß, Sebastian; Förster, Christoph; Otto, Sven; Bauer, Matthias; Müller, Patrick; Hinderberger, Dariush; Hashemi Haeri, Haleh; Carella, Luca; Heinze, Katja

2017-12-01

Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold. The reactivity of this gold(II) complex towards dioxygen, nitrosobenzene and acids is discussed. This study provides insight on the ionic radius of gold(II), and allows it to be placed within the homologous series of nd9 Cu/Ag/Au divalent ions and the 5d8/9/10 Pt/Au/Hg 'relativistic' triad in the periodic table.

Pyrochlore structure and spectroscopic studies of titanate ceramics. A comparative investigation on SmDyTi2O7 and YDyTi2O7 solid solutions

NASA Astrophysics Data System (ADS)

Garbout, A.; Férid, M.

2018-06-01

Considering the features in changing the structure and properties of rare earth titanates pyrochlores, the substituted Dy2Ti2O7 may be very attractive for various applications. Effect of Sm and Y substitution on the structural properties of Dy2Ti2O7 ceramic was established. These ceramics were prepared by solid-state reaction and characterized by X-ray diffraction and Raman spectroscopy. Both analysis show that YDyTi2O7 with the pyrochlore structure is obtained after heating at 1400 °C, but SmDyTi2O7 has already formed after sintering at 1200 °C. SEM images revealed that the average grain size was increased with the increase of heating temperature, and an un-homogeneous grain growth was detected. The average size was about 37 nm and 135 nm for the SmDyTi2O7 and YDyTi2O7 particles, respectively. Structural Rietveld refinements indicate that all prepared ceramics crystallize in cubic structure with space group of Fd3m. The refined cell parameters demonstrate an almost linear correlation with the ionic radius of Ln3+. The vibrational spectra revealed that the positions of bands are sensitive to the Ln3+-ionic radius, and the Tisbnd O bond strength decreased linearly with the increase of cubic lattice parameter. Raman spectra indicate that the wavenumber of Osbnd Tisbnd O bending mode is considerably shifted to lower region with increasing in mass of the Ln atom. This paper provides solid foundations for additional research of these solid solutions, which are very attractive for different fields as promising catalytic compounds for combustion applications or as frustrated magnetic pyrochlore ceramics.

[Determination of Chloride Salt Solution by NIR Spectroscopy].

PubMed

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

2015-07-01

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

Electronegativity, charge transfer, crystal field strength, and the point charge model revisited.

PubMed

Tanner, Peter A; Ning, Lixin

2013-02-21

Although the optical spectra of LnCl(6)(3-) systems are complex, only two crystal field parameters, B(40) and B(60), are required to model the J-multiplet crystal field splittings in octahedral symmetry. It is found that these parameters exhibit R(-5) and R(-7) dependence, respectively, upon the ionic radius Ln(3+)(VI), but not upon the Ln-Cl distance. More generally, the crystal field strengths of LnX(6) systems (X = Br, Cl, F, O) exhibit linear relationships with ligand electronegativity, charge transfer energy, and fractional ionic character of the Ln-X bond.

Electron core ionization in compressed alkali metal cesium

NASA Astrophysics Data System (ADS)

Degtyareva, V. F.

2018-01-01

Elements of groups I and II in the periodic table have valence electrons of s-type and are usually considered as simple metals. Crystal structures of these elements at ambient pressure are close-packed and high-symmetry of bcc and fcc-types, defined by electrostatic (Madelung) energy. Diverse structures were found under high pressure with decrease of the coordination number, packing fraction and symmetry. Formation of complex structures can be understood within the model of Fermi sphere-Brillouin zone interactions and supported by Hume-Rothery arguments. With the volume decrease there is a gain of band structure energy accompanied by a formation of many-faced Brillouin zone polyhedra. Under compression to less than a half of the initial volume the interatomic distances become close to or smaller than the ionic radius which should lead to the electron core ionization. At strong compression it is necessary to assume that for alkali metals the valence electron band overlaps with the upper core electrons, which increases the valence electron count under compression.

Theoretical study of room temperature ferromagnetism and band gap energy of pure and ion doped In2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

2018-06-01

Using the s-d microscopic model including the electron-phonon interaction and the Green's function theory we have considered the origin of room temperature ferromagnetism (RTFM) in pure and ion doped In2O3 nanoparticles (NPs). The magnetization M increases with decreasing particle size. M of Fe, Tb and Mn doped In2O3 NPs is investigated, which increases, decreases and has a maximum, respectively, with increasing doping concentration. The RTFM is due to surface oxygen vacancies and different ionic radius of the dopants compared to that of the host ions. This differences lead to different strains which changes the exchange interaction constants. We have calculated the dependence of the band gap energy on the particle size in In2O3 NPs and the Fe concentration of Fe doped In2O3 NPs. The results are in good qualitative agreement with the experimental data.

Effect of cation size at Gd and Al site on ce energy levels in Gd3(GaAl)5O12 sintered pellets

NASA Astrophysics Data System (ADS)

Tyagi, Mohit; Meng, Fang; Darby, Kaitlyn; Koschan, Merry; Melcher, C. L.

2013-02-01

Radioluminescence and reflectivity measurements performed on sintered powder pellets of garnet compositions R3GaxAl5-xO12 (where R: Lu, Gd, Sc, Y) have shown that replacing "R" in these compositions with ions of larger radius shifts the excited 5d states of Ce to lower energy, while increased ionic radius at Ga/Al sites shifts these levels to higher energy. Stokes shifts were also calculated and results were verified by comparing the performance of the pellets with that of single crystals.

Theory of polyelectrolytes in solvents.

PubMed

Chitanvis, Shirish M

2003-12-01

Using a continuum description, we account for fluctuations in the ionic solvent surrounding a Gaussian, charged chain and derive an effective short-ranged potential between the charges on the chain. This potential is repulsive at short separations and attractive at longer distances. The chemical potential can be derived from this potential. When the chemical potential is positive, it leads to a meltlike state. For a vanishingly low concentration of segments, this state exhibits scaling behavior for long chains. The Flory exponent characterizing the radius of gyration for long chains is calculated to be approximately 0.63, close to the classical value obtained for second order phase transitions. For short chains, the radius of gyration varies linearly with N, the chain length, and is sensitive to the parameters in the interaction potential. The linear dependence on the chain length N indicates a stiff behavior. The chemical potential associated with this interaction changes sign, when the screening length in the ionic solvent exceeds a critical value. This leads to condensation when the chemical potential is negative. In this state, it is shown using the mean-field approximation that spherical and toroidal condensed shapes can be obtained. The thickness of the toroidal polyelectrolyte is studied as a function of the parameters of the model, such as the ionic screening length. The predictions of this theory should be amenable to experimental verification.

Electroviscous Effects in Ceramic Nanofiltration Membranes.

PubMed

Farsi, Ali; Boffa, Vittorio; Christensen, Morten Lykkegaard

2015-11-16

Membrane permeability and salt rejection of a γ-alumina nanofiltration membrane were studied and modeled for different salt solutions. Salt rejection was predicted by using the Donnan-steric pore model, in which the extended Nernst-Planck equation was applied to predict ion transport through the pores. The solvent flux was modeled by using the Hagen-Poiseuille equation by introducing electroviscosity instead of bulk viscosity. γ-Alumina particles were used for ζ-potential measurements. The ζ-potential measurements show that monovalent ions did not adsorb on the γ-alumina surface, whereas divalent ions were highly adsorbed. Thus, for divalent ions, the model was modified, owing to pore shrinkage caused by ion adsorption. The ζ-potential lowered the membrane permeability, especially for membranes with a pore radius lower than 3 nm, a ζ-potential higher than 20 mV, and an ionic strength lower than 0.01 m. The rejection model showed that, for a pore radius lower than 3 nm and for solutions with ionic strengths lower than 0.01 m, there is an optimum ζ-potential for rejection, because of the concurrent effects of electromigration and convection. Hence, the model can be used as a prediction tool to optimize membrane perm-selectivity by designing a specific pore size and surface charge for application at specific ionic strengths and pH levels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Canopy Dynamics in Nanoscale Ionic Materials Probed by NMR

NASA Astrophysics Data System (ADS)

Mirau, Peter

2013-03-01

Nanoscale ionic materials (NIMs) are hybrids prepared from ionically functionalized nanoparticles (NP) neutralized by oligomeric polymer counter-ions. NIMs are designed to behave as liquids under ambient conditions in the absence of solvent and have no volatile organic content, making them useful for a number of applications. We have used NMR relaxation and pulse-field gradient NMR to probe local and collective canopy dynamics in NIMs based on silica nanoparticles (NP), fullerols and proteins in order to understand the relationship between the core and canopy structure and the bulk properties. The NMR studies show that the canopy dynamics depend on the degree of neutralization, the canopy radius of gyration and molecular crowding at the ionically modified NP surface. The viscosity in NIMs can be directly controlled with the addition of ions that enhance the exchange rate for polymers at the NP surface. These results show that NIMs for many applications can be prepared by controlling the dynamics of the NP interface.

Hybrid MD-Nernst Planck Model of Alpha-hemolysin Conductance Properties

NASA Technical Reports Server (NTRS)

Cozmuta, Ioana; O'Keefer, James T.; Bose, Deepak; Stolc, Viktor

2006-01-01

Motivated by experiments in which an applied electric field translocates polynucleotides through an alpha-hemolysin protein channel causing ionic current transient blockade, a hybrid simulation model is proposed to predict the conductance properties of the open channel. Time scales corresponding to ion permeation processes are reached using the Poisson-Nemst-Planck (PNP) electro-diffusion model in which both solvent and local ion concentrations are represented as a continuum. The diffusion coefficients of the ions (K(+) and Cl(-)) input in the PNP model are, however, calculated from all-atom molecular dynamics (MD). In the MD simulations, a reduced representation of the channel is used. The channel is solvated in a 1 M KCI solution, and an external electric field is applied. The pore specific diffusion coefficients for both ionic species are reduced 5-7 times in comparison to bulk values. Significant statistical variations (17-45%) of the pore-ions diffusivities are observed. Within the statistics, the ionic diffusivities remain invariable for a range of external applied voltages between 30 and 240mV. In the 2D-PNP calculations, the pore stem is approximated by a smooth cylinder of radius approx. 9A with two constriction blocks where the radius is reduced to approx. 6A. The electrostatic potential includes the contribution from the atomistic charges. The MD-PNP model shows that the atomic charges are responsible for the rectifying behaviour and for the slight anion selectivity of the a-hemolysin pore. Independent of the hierarchy between the anion and cation diffusivities, the anionic contribution to the total ionic current will dominate. The predictions of the MD-PNP model are in good agreement with experimental data and give confidence in the present approach of bridging time scales by combining a microscopic and macroscopic model.

Influence of the ionic liquid [C4mpy][Tf2N] on the structure of the miniprotein Trp-cage.

PubMed

Baker, Joseph L; Furbish, Jeffrey; Lindberg, Gerrick E

2015-11-01

We examine the effect of the ionic liquid [C4mpy][Tf2N] on the structure of the miniprotein Trp-cage and contrast these results with the behavior of Trp-cage in water. We find the ionic liquid has a dramatic effect on Trp-cage, though many similarities with aqueous Trp-cage are observed. We assess Trp-cage folding by monitoring root mean square deviation from the crystallographic structure, radius of gyration, proline cis/trans isomerization state, protein secondary structure, amino acid contact formation and distance, and native and non-native contact formation. Starting from an unfolded configuration, Trp-cage folds in water at 298 K in less than 500 ns of simulation, but has very little mobility in the ionic liquid at the same temperature, which can be ascribed to the higher ionic liquid viscosity. At 365 K, the mobility of the ionic liquid is increased and initial stages of Trp-cage folding are observed, however Trp-cage does not reach the native folded state in 2 μs of simulation in the ionic liquid. Therefore, in addition to conventional molecular dynamics, we also employ scaled molecular dynamics to expedite sampling, and we demonstrate that Trp-cage in the ionic liquid does closely approach the aqueous folded state. Interestingly, while the reduced mobility of the ionic liquid is found to restrict Trp-cage motion, the ionic liquid does facilitate proline cis/trans isomerization events that are not seen in our aqueous simulations. Copyright © 2015 Elsevier Inc. All rights reserved.

Structural Characterization of Am(III)- and Pu(III)-DOTA Complexes.

PubMed

Audras, Matthieu; Berthon, Laurence; Berthon, Claude; Guillaumont, Dominique; Dumas, Thomas; Illy, Marie-Claire; Martin, Nicolas; Zilbermann, Israel; Moiseev, Yulia; Ben-Eliyahu, Yeshayahu; Bettelheim, Armand; Cammelli, Sebastiano; Hennig, Christoph; Moisy, Philippe

2017-10-16

The complexation of 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) ligand with two trivalent actinides (Am 3+ and Pu 3+ ) was investigated by UV-visible spectrophotometry, NMR spectroscopy, and extended X-ray absorption fine structure in conjunction with computational methods. The complexation process of these two cations is similar to what has been previously observed with lanthanides(III) of similar ionic radius. The complexation takes place in different steps and ends with the formation of a (1:1) complex [(An(III)DOTA)(H 2 O)] - , where the cation is bonded to the nitrogen atoms of the ring, the four carboxylate arms, and a water molecule to complete the coordination sphere. The formation of An(III)-DOTA complexes is faster than the Ln(III)-DOTA systems of equivalent ionic radius. Furthermore, it is found that An-N distances are slightly shorter than Ln-N distances. Theoretical calculations showed that the slightly higher affinity of DOTA toward Am over Nd is correlated with slightly enhanced ligand-to-metal charge donation arising from oxygen and nitrogen atoms.

Influence of Ca2+ doped on structural and optical properties of RPO4 (R = Ce3+, Nd3+ and Pr3+) compounds

NASA Astrophysics Data System (ADS)

Lemdek, El Mokhtar; Benkhouja, Khalil; Touhtouh, Samira; Sbiaai, Khalid; Arbaoui, Abdezzahid; Bakasse, Mina; Hajjaji, Abdelowahed; Boughaleb, Yahia; Saez-Puche, Regino

2013-11-01

This paper investigates the effect of doping by Ca2+ ions on the structural and optical properties of RPO4 (R = Ce3+, Nd3+ and Pr3+) compounds. A simple ceramic method in air at 900 °C was used to prepare all compounds. The structural characterization of compounds was carried out by using X-ray powder diffraction (XRD) and IR spectroscopy. Optical properties were characterized by reflectance spectral data and by colorimeter. The results reveal a single monazite phase for x values up to 0.4. The lattice parameters of the synthesized samples decrease linearly with the reduction of ionic radius of the Ce3+. These rare earth phosphates based materials have a potential to be adopted for the eco-friendly colorants for paints and plastics.

Sticky ions in biological systems.

PubMed Central

Collins, K D

1995-01-01

Aqueous gel sieving chromatography on Sephadex G-10 of the Group IA cations (Li+, Na+, K+, Rb+, Cs+) plus NH4+ as the Cl- salts, in combination with previous results for the halide anions (F-, Cl-, Br-, I-) as the Na+ salts [Washabaugh, M.W. & Collins, K.D. (1986) J. Biol. Chem. 261, 12477-12485], leads to the following conclusions. (i) The small monovalent ions (Li+, Na+, F-) flow through the gel with water molecules attached, whereas the large monovalent ions (K+, Rb+, Cs+, Cl-, Br-, I-) adsorb to the nonpolar surface of the gel, a process requiring partial dehydration of the ion and implying that these ions bind the immediately adjacent water molecules weakly. (ii) The transition from strong to weak hydration occurs at a radius of about 1.78 A for the monovalent anions, compared with a radius of about 1.06 A for the monovalent cations (using ionic radii), indicating that the anions are more strongly hydrated than the cations for a given charge density. (iii) The anions show larger deviations from ideal behavior (an elution position corresponding to the anhydrous molecular weight) than do the cations and dominate the chromatographic behavior of the neutral salts. These results are interpreted to mean that weakly hydrated ions (chaotropes) are "pushed" onto weakly hydrated surfaces by strong water-water interactions and that the transition from strong ionic hydration to weak ionic hydration occurs where the strength of ion-water interactions approximately equals the strength of water-water interactions in bulk solution. PMID:7539920

Crystal chemistry and the role of ionic radius in rare earth tetrasilicates: Ba2RE2Si4O12F2 (RE = Er3+-Lu3+) and Ba2RE2Si4O13 (RE = La3+-Ho3+).

PubMed

Fulle, Kyle; Sanjeewa, Liurukara D; McMillen, Colin D; Kolis, Joseph W

2017-10-01

Structural variations across a series of barium rare earth (RE) tetrasilicates are studied. Two different formulas are observed, namely those of a new cyclo-silicate fluoride, BaRE 2 Si 4 O 12 F 2 (RE = Er 3+ -Lu 3+ ) and new compounds in the Ba 2 RE 2 Si 4 O 13 (RE = La 3+ -Ho 3+ ) family, covering the whole range of ionic radii for the rare earth ions. The Ba 2 RE 2 Si 4 O 13 series is further subdivided into two polymorphs, also showing a dependence on rare earth ionic radius (space group P{\\overline 1} for La 3+ -Nd 3+ , and space group C2/c for Sm 3+ -Ho 3+ ). Two of the structure types identified are based on dinuclear rare earth units that differ in their crystal chemistries, particularly with respect to the role of fluorine as a structural director. The broad study of rare earth ions provides greater insight into understanding structural variations within silicate frameworks and the nature of f-block incorporation in oxyanion frameworks. The single crystals are grown from high-temperature (ca 953 K) hydrothermal fluids, demonstrating the versatility of the technique to access new phases containing recalcitrant rare earth oxides, enabling the study of structural trends.

Effects of feed solution chemistry on low pressure reverse osmosis filtration of cesium and strontium.

PubMed

Ding, Shiyuan; Yang, Yu; Huang, Haiou; Liu, Hengchen; Hou, Li-an

2015-08-30

The objective of this study was to identify the removal mechanisms of radionuclides by reverse osmosis (RO) membranes under conditions relevant to full-scale water treatment. For this purpose, the effects of feed solution chemistry on the removal of Cs and Sr by a low pressure RO system was investigated by systematically varying membrane surface charge, ionic composition, and organic matter concentrations. The results showed that the effects of solution chemistry on the filtration of Cs and Sr were related to their hydrated ionic radius, resulting in the predominance of the Donnan's effect and electrostatic interactions, respectively. Consequently, the rejection of Cs increased more pronouncedly than Sr with the increases of feed concentration. Due to the Donnan's effect, different anions decreased the rejection of Cs to different extents in accordance to the order of anions' radii as SO4(2-)>Cl(-)>NO3(-)>F(-). The variations in Sr rejection were influenced by the electrostatic interactions between Sr(2+) and the membrane. In addition, humic acid (HA) lowered the rejection of Cs and caused significant membrane flux decline, but did not change the rejection of Sr. Sr also aggravated HA fouling of the membrane. Copyright © 2015 Elsevier B.V. All rights reserved.

Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids

DOE PAGES

Griffin, Philip J.; Wang, Yangyang; Holt, Adam P.; ...

2016-04-21

In this paper, we report measurements of the ionic conductivity, shear viscosity, and structural dynamics in a homologous series of quaternary ammonium ionic liquids (ILs) and a prototypical imidazolium-based IL over a wide range of temperatures down to the glass transition. We find that the ionic conductivity of these materials generally decreases, while the shear viscosity correspondingly increases, with increasing volume fraction of aliphatic side groups. Upon crossing an aliphatic volume fraction of ~0.40, we observe a sharp, order-of-magnitude decrease in ionic conductivity and enhancement of viscosity, which coincides with the presence of long-lived, nanometer-sized alkyl aggregates. These strong changesmore » in dynamics are not mirrored in the ionicity of these ILs, which decreases nearly linearly with aliphatic volume fraction. Finally, our results demonstrate that nanophase segregation in neat ILs strongly reduces ionic conductivity primarily due to an aggregation-induced suppression of dynamics.« less

Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales

PubMed Central

Zhang, Yonghe

2010-01-01

Ionocovalency (IC), a quantitative dual nature of the atom, is defined and correlated with quantum-mechanical potential to describe quantitatively the dual properties of the bond. Orbiotal hybrid IC model scale, IC, and IC electronegativity scale, XIC, are proposed, wherein the ionicity and the covalent radius are determined by spectroscopy. Being composed of the ionic function I and the covalent function C, the model describes quantitatively the dual properties of bond strengths, charge density and ionic potential. Based on the atomic electron configuration and the various quantum-mechanical built-up dual parameters, the model formed a Dual Method of the multiple-functional prediction, which has much more versatile and exceptional applications than traditional electronegativity scales and molecular properties. Hydrogen has unconventional values of IC and XIC, lower than that of boron. The IC model can agree fairly well with the data of bond properties and satisfactorily explain chemical observations of elements throughout the Periodic Table. PMID:21151444

The influence of melt composition on the partitioning of REEs, Y, Sc, Zr and Al between forsterite and melt in the system CMAS

NASA Astrophysics Data System (ADS)

Evans, Thomas M.; O'Neill, Hugh St. C.; Tuff, James

2008-12-01

Partition coefficients for a range of Rare Earth Elements (REEs), Y, Sc, Al and Zr were determined between forsteritic olivine (nearly end-member Mg 2SiO 4) and ten melt compositions in the system CaO-MgO-Al 2O 3-SiO 2 (CMAS) at 1 bar and 1400 °C, with concentrations of the trace elements in the olivine and the melt measured by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The REEs and Sc were added at levels sufficient to ensure that concentrations in the olivine were well above the detection limits. The REE partition coefficients (DREEol/melt) decrease with increasing silica in the melt, indicating strong bonding between REEO 1.5 and SiO 2 in the melt. The variation of DREEol/melt as a function of ionic radius is well described by the Brice equation for each composition, although a small proportion of this variation is due to the increase in the strength of the REEO 1.5-SiO 2 interactions in the melt with ionic radius. Scandium behaves very similarly to the REEs, but a global fit of the data from all ten melt compositions suggests that DScol/melt deviates somewhat from the parabolas established by the REE and Y, implying that Sc may substitute into olivine differently to that of the REEs. In contrast to the behaviour of the large trivalent cations, the concentration of Al in olivine is proportional to the square root of its concentration in the melt, indicating a coupled substitution in olivine with a high degree of short-range order. The lack of any correlation of REE partition coefficients with Al in olivine or melt suggests that the REE substitution in olivine is charge-balanced by cation vacancies. The partition coefficient of the tetravalent trace element Zr, which is highly incompatible in olivine, depends on the CaO content of the melt.

Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

PubMed

Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

2015-06-03

On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

Partitioning of Nb, Mo, Ba, Ce, Pb, Th and U between immiscible carbonate and silicate liquids: Evaluating the effects of P2O5,F, and carbonate composition

NASA Technical Reports Server (NTRS)

Jones, J. H.; Walker, D.

1993-01-01

Previously we have reported carbonate liq./silicate liq. partition coefficients (D) for a standard suite of trace elements (Nb, Mo, Ba, Ce, Pb, Th, and U) and Ra and Pa as well. In brief, we have found that immiscible liquid partitioning is a strong function of temperature. As the critical temperature of the carbonate-silicate solvus is approached, all partition coefficients approach unity. Additionally, for the overwhelming majority of the partitioning elements, InD is a linear function of 'ionic field strength,' z/r, where z is the charge of the partitioned cation and r is its ionic radius.

Studies on phase transition temperature of rare earth niobates Ln3NbO7 (Ln = Pr, Sm, Eu) with orthorhombic fluorite-related structure

NASA Astrophysics Data System (ADS)

Hinatsu, Yukio; Doi, Yoshihiro

2017-06-01

The phase transition of ternary rare earth niobates Ln3NbO7 (Ln = Pr, Sm, Eu) was investigated by the measurements of high-temperature and low-temperature X-ray diffraction, differential scanning calorimetry (DSC) and differential thermal analysis (DTA). These compounds crystallize in an orthorhombic superstructure derived from the structure of cubic fluorite (space group Pnma for Ln = Pr; C2221 for Ln = Sm, Eu). Sm3NbO7 undergoes the phase transition when the temperature is increased through ca. 1080 K and above the transition temperature, its structure is well described with space group Pnma. For Eu3NbO7, the phase transition was not observed up to 1273 K Pr3NbO7 indicates the phase transition when the temperature is increased through ca. 370 K. The change of the phase transition temperature against the Ln ionic radius for Ln3NbO7 is quite different from those for Ln3MO7 (M = Mo, Ru, Re, Os, or Ir), i.e., no systematic relationship between the phase transition temperature and the Ln ionic radius has been observed for Ln3NbO7 compounds.

Thermal Conductivity and Expansion Coefficient of (Sm1- x Yb x )2Ce2O7 Ceramics for Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Xiaoge, Chen; Hongsong, Zhang; Kun, Sun; Xudan, Dang; Haoming, Zhang; Bo, Ren; An, Tang

2017-12-01

In the current paper, the (Sm1- x Yb x )2Ce2O7 ceramics were prepared via sol-gel and high-temperature solid reaction methods. The phase composition, microstructure, thermal conductivity, and expansion coefficient were investigated. Results indicate that pure (Sm1- x Yb x )2Ce2O7 ceramics with single defect-fluorite structure are synthesized successfully. Owing to the phonon scattering caused by Yb addition, the thermal conductivity of (Sm1- x Yb x )2Ce2O7 ceramics decreases with increasing Yb2O3 content at identical temperatures, which is lower than that of YSZ. Due to the relatively low ionic radius of Yb3+ ions, the addition of Yb2O3 decreases the thermal expansion coefficient of (Sm1- x Yb x )2Ce2O7 ceramics, which is higher than that of 8YSZ. The synthesized (Sm1- x Yb x )2Ce2O7 ceramics can be explored as candidate materials for thermal barrier coatings.

Interaction of Cellulose Chains with Ionic Liquids and Water via MD simulations

NASA Astrophysics Data System (ADS)

Ismail, Ahmed; Rabideau, Brooks

2012-02-01

One promising route for combustible fuel sources which are both renewable and have a low environmental impact is the conversion of waste biomass into tailor-made fuels. An important aspect of this process is the low-energy separation of cellulose from the biomass. Ionic liquids (ILs) have proven to be very good in dissolving cellulose with the added benefit of being essentially non-volatile making them ideal for ``green'' processing. IL research, however, remains relatively new, with many parts of this dissolution process remaining uncertain. We examine the behavior of cellulose with the ionic liquids [BMIM]Cl, [EMIM]Ac and [DMIM]DMP as well as water via MD simulation. All three ionic liquids have been observed to dissolve cellulose quite well yet have differently sized anions. We explore these differences and the impacts they have on their interactions with cellulose. First we examine the dynamics of a single cellulose strand in these ionic liquids. We determine the radius of gyration and the hydrogen bonds that are formed between the anions and cellulose. Next, we probe the dissolution mechanism of multiple, bound cellulose strands examining of multiple, bound cellulose strands examining interactions at the IL/cellulose interface and the breakup of inter-cellulose hydrogen bonds.

Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitoma, Nobuhiko, E-mail: MITOMA.Nobuhiko@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Kizu, Takio; Lin, Meng-Fang

The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InO{sub x}) thin film transistors (TFTs) is reported. In a-InO{sub x} TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InO{sub x} matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InO{sub x} TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.

An Investigation of Ionic Wind Propulsion

NASA Technical Reports Server (NTRS)

Wilson, Jack; Perkins, Hugh D.; Thompson, William K.

2009-01-01

A corona discharge device generates an ionic wind and thrust, when a high voltage corona discharge is struck between sharply pointed electrodes and larger radius ground electrodes. The objective of this study was to examine whether this thrust could be scaled to values of interest for aircraft propulsion. An initial experiment showed that the thrust observed did equal the thrust of the ionic wind. Different types of high voltage electrodes were tried, including wires, knife-edges, and arrays of pins. A pin array was found to be optimum. Parametric experiments, and theory, showed that the thrust per unit power could be raised from early values of 5 N/kW to values approaching 50 N/kW, but only by lowering the thrust produced, and raising the voltage applied. In addition to using DC voltage, pulsed excitation, with and without a DC bias, was examined. The results were inconclusive as to whether this was advantageous. It was concluded that the use of a corona discharge for aircraft propulsion did not seem very practical.

Influence of electrostatic forces on particle propulsion in the evanescent field of silver ion-exchanged waveguides.

PubMed

Gebennikov, Dmytro; Mittler, Silvia

2013-02-26

The effect of electrostatic interaction between carboxylate- and amino-functionalized polystyrene particles and a charged waveguide surface on the propulsion speed in optical tweezers is considered to be a function of the pH and ionic strength. It was shown that with the variation of the pH of the aqueous solution in which the particles were immersed, a systematic change in propulsion speed with a maximum speed could be achieved. The appearance of a maximum speed was ascribed to changes in the particle-waveguide separation as a result of the combination of two forces: Coulomb repulsion/attraction and induced dipole forces. The highest maximum speed at low ionic strength was around 12 μm/s. Changes in the ionic strength of the solution influenced the gradient of the dielectric constant near the involved surfaces and also led to a slightly reduced hydrodynamic radius of the particles. The combination of these effects subsequently increased the maximum speed to about 23 μm/s.

Characterisation of cationic potato starch by asymmetrical flow field-flow fractionation. Influence of ionic strength and degree of substitution.

PubMed

Santacruz, Stalin

2014-06-15

The properties of a paper sheet depend on the absorption together with the physico-chemical properties of additives used in the paper processing. The effect of ionic strength and degree of substitution of cationic potato starch on the elution pattern of asymmetrical flow field-flow fractionation was analysed. The effect of starch derivatisation, in either dry or wet phase, was also investigated. Average molar mass showed no difference between the starches obtained from the two derivatisation processes. Apparent densities showed that dry cationic starch had higher density than wet cationic starch for a hydrodynamic radius between 50 and 100 nm. Elution times of native and three cationic starches increased when the ionic strength increased from 50 to 100mM. No differences in the molar mass among cationic starches with different degree of substitution suggested no degradation due to a derivatisation process. Large sample loads can be used at 100mM without overloading. Copyright © 2014 Elsevier Ltd. All rights reserved.

Contribution of capillary electrophoresis to an integrated vision of humic substances size and charge characterizations

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Orlye, Fanny; Reiller, Pascal E.

2014-02-15

The physicochemical properties of three different humic substances (HS) are probed using capillary zone electrophoresis in alkaline carbonate buffers, pH 10. Special attention is drawn to the impact of the electrolyte ionic strength and counter-ion nature, chosen within the alkali-metal series, on HS electrophoretic mobility. Taylor-Aris dispersion analysis provides insights into the hydrodynamic radius (R-H) distributions of HS. The smallest characterized entities are of nano-metric dimensions, showing neither ionic strength- nor alkali-metal-induced aggregation. These results are compared with the entities evidenced in dynamic light scattering measurements, the size of which is two order of magnitude higher, ca. 100 nm. Themore » extended Onsager model provides a reasonable description of measured electrophoretic mobilities in the ionic strength range 1-50 mM, thus allowing the estimation of limiting mobilities and ionic charge numbers for the different HS samples. An unexpected HS electrophoretic mobility increase (in absolute value) is observed in the order Li{sup +} ≤ Na{sup +} ≤ K{sup +} ≤ Cs{sup +} and discussed either in terms of retarding forces or in terms of ion-ion interactions. (authors)« less

How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

PubMed Central

Huang, Xiaokun; Zhang, Weiyi

2016-01-01

The misfit layered Bi2A2Co2O8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A’s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi2Ca2Co2O8 and Bi2Sr2Co2O8 and intermediate-spin low-spin mixed-state of Bi2Ba2Co2O8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal. PMID:27901119

How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

PubMed

Huang, Xiaokun; Zhang, Weiyi

2016-11-30

The misfit layered Bi 2 A 2 Co 2 O 8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A's ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co 3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO 2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi 2 Ca 2 Co 2 O 8 and Bi 2 Sr 2 Co 2 O 8 and intermediate-spin low-spin mixed-state of Bi 2 Ba 2 Co 2 O 8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal.

The effect of temperature and chitosan concentration during storage on the growth of chitosan nanoparticle produced by ionic gelation method

NASA Astrophysics Data System (ADS)

Handani, Wenny Rinda; Sediawan, Wahyudi Budi; Tawfiequrrahman, Ahmad; Wiratni, Kusumastuti, Yuni

2017-05-01

The objective of this research was to get the mechanism of nano size chitosan particle growth during storage by observing the effect of temperature and initial concentration of chitosan. The products were analyzed using PSA to have the average of particle radius. Nanochitosan solution was prepared by ionic gelation method. This method is described as an electrostatic interaction between positively charged amine with negatively charged polyanion, such as tripolyphosphate (TPP). Chitosan was dissolved in 1% acetic acid and was stirred for 30 minutes. Tween 80 was added to avoid agglomeration. TPP was prepared by dissolving 0.336 g into distilled water. The nano size chitosan was obtained by mixing TPP and chitosan solution dropwise while stirring for 30 minutes. This step was done at 15°C and ambient temperature (about 30°C) and chitosan concentration 0.2%, 0.4% and 0.6%. The results show that temperature during ionic gelation process (15°C and 30°C) does not affect the initial size of the nanoparticles produced as well as the growth of the nanoparticles during storage. On the other hand, initial chitosan concentration strongly affects initial size of the nanoparticles produced and the growth of the nanoparticles during storage. The concentration of chitosan at 0.2%, 0.4%, 0.6% gave initial size of nanoparticle chitosan of 175.3 nm, 337.9 nm, 643.3 nm respectively. On the other hand, the growth mechanism of chitosan nanoparticle depended on its radius(R). At R<500 nm, the growth rate of nanoparticles is controlled by adsorption at the surface of the particles, while at R>500 nm, it is controlled by diffusion in the liquid film around the particles.

Chemical Trend of Superconducting Critical Temperatures in Hole-Doped CuBO2, CuAlO2, CuGaO2, and CuInO2

NASA Astrophysics Data System (ADS)

Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi; Ishikawa, Takahiro; Shimizu, Katsuya

2016-09-01

We calculated the superconducting critical temperature (Tc) for hole-doped CuXO2 (X = B, Al, Ga, and In) compounds using first-principles calculations based on rigid band model. The compounds with X = Al, Ga, and In have delafosite-type structures and take maximum Tc values at 0.2-0.3 with respect to the number of holes (Nh) in the unit-cell: 50 K for CuAlO2, 10 K for CuGaO2, and 1 K for CuInO2. The decrease of Tc for this change in X is involved by covalency reduction and lattice softening associated with the increase of ionic mass and radius. For CuBO2 which is a lighter compound than CuAlO2, the delafosite structure is unstable and a body-centered tetragonal structure emerges as the most stable structure. As the results, the electron-phonon interaction is decreased and Tc is lower by approximately 43 K than that of CuAlO2 at the hole-doping conditions of Nh = 0.2-0.3.

Doping effects on the relaxation of frustration and magnetic properties of YMn0.9Cu0.1O3

NASA Astrophysics Data System (ADS)

Xiao, L. X.; Xia, Z. C.; Wang, X.; Ni, Y.; Yu, W.; Shi, L. R.; Jin, Z.; Xiao, G. L.

2017-12-01

The crystal structure and magnetic properties of hexagonal YMn0.9Cu0.1O3 single crystal are systematically investigated. The refinement results of XRD show the lattice constant decreases, which is unusually due to the doped Cu2+ ion has a larger ionic radius than the Mn3+ ions. The XPS results show that the coexistence of Mn2+, Mn3+ and Mn4+ ions in YMn0.9Cu0.1O3 single crystal. Magnetization measurements show that Cu doped YMn0.9Cu0.1O3 and parent YMnO3 have almost the same antiferromagnetic transition temperature TN, which indicates the AFM interaction is robust in the geometry frustrated system. Because doping directly destroy some of the Mn3+ ions nets, the relaxation of frustration of Mn in-plane 2D triangular geometry network leads to the significantly decrease of Mn3+ ions AFM interaction. In addition, the coexistence and competition between the ferromagnetic and antiferromagnetic interactions among the Mn2+, Mn3+ and Mn4+ ions lead to a complicated and irreversible magnetization behavior in YMn0.9Cu0.1O3 single crystal.

Effect of screening on the transport of polyelectrolytes through nanopores

NASA Astrophysics Data System (ADS)

Oukhaled, G.; Bacri, L.; Mathé, J.; Pelta, J.; Auvray, L.

2008-05-01

We study the transport of dextran sulfate molecules (Mw=8000 Da) through a bacterial α-hemolysin channel inserted into a bilayer lipid membrane submitted to an external electric field. We detect the current blockades induced by the molecules threading through one pore and vary the ionic strength in an unexplored range starting at 10-3 M. In the conditions of the experiment, the polyelectrolyte molecules enter the pore only if the Debye screening length is smaller than the pore radius in agreement with theory. We also observe that large potentials favour the passage of the molecules. The distribution of blockade durations suggests that a complex process governs the kinetics of the molecules. The dwelling time increases sharply as the Debye length increases and approaches the pore radius.

Electrophoretic and Electrolytic Deposition of Ceramic Particles on Porous Substrates

DTIC Science & Technology

1990-08-30

hydrodynamic drag force exerted on the particle due to the electroosmotic flow of the solvent inside the pore, the electrophoretic force exerted on the...8217 - electrophoretic velocity UN - electroosmotic velocity b - pore mean radius D - diffusion coefficient k - local deposition rate Large Peclet numbers and small...experimentally as the charge is acquired spontaneously on mixing the particles with the solvent and it may be reversed upon addition ot ionic compounds. The

Infrared Chemiluminescence Studies of Ion-Molecule Reactions in a Flowing Afterglow.

DTIC Science & Technology

1982-01-01

reaction rate constants and branching ratios have been addressed in drift tubes and flow drift systems, and the translational energy distribution of atomic...composed of about 40 thin cylindrical sections of flow tube , separated by mylar spacers and connected by precision resistors. In the region of LIF... tube radius (Albritton, 1967). For proper operation of a drift tube , ionic species of only one polarity can be present. Efficient separation of

Spectroscopic Evidence of Formation of Small Polarons in Doped Manganites

NASA Astrophysics Data System (ADS)

Moritomo, Yutaka; Machida, Akihiko; Nakamura, Arao

1998-03-01

Temperature dependence of absorption spectra for thin films of doped manganites R_0.6Sr_0.4MnO_3, where R is rare-earth atom, has been investigated systematically changing averaged ionic radius < rA > of perovskite A-site. We have observed a specific absorption band at ~1.5eV due to optical excitations from small polarons (SP)(Machida et al.), submitted.. Spectral weight of the SP band increases with decreasing temperature and eventually disappears at the insulator-metal (IM) transition, indicating that SP in the paramagnetic state (T >= T_C) changes into bare electrons (or large polarons) in the ferromagnetic state due to the enhanced one-electron bandwidth W. We further derived important physical quantities, i.e., W, on-site exchange interaction J and binding energy Ep of SP, and discuss material dependence of stability of SP. This work was supported by a Grant-In-Aid for Scientific Research from the Ministry of Education, Science, Sport and Culture and from PRESTO, Japan Scienece and Technology Corporation (JST), Japan.

Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

NASA Astrophysics Data System (ADS)

Morgan, Sh. M.; El-Ghamaz, N. A.; Diab, M. A.

2018-05-01

Co(II) complexes (1-4) and Ni(II) complexes (5-8) were prepared and characterized by elemental analysis, IR spectra and thermal analysis data. Thermal decomposition of all complexes was discussed using thermogravimetric analysis. The dielectric properties and alternating current conductivity were investigated in the frequency range 0.1-100 kHz and temperature range 300-660 K. The thermal activation energies of electrical conductivity (ΔE1 and ΔE2) values for complexes were calculated and discussed. The values of ΔE1 and ΔE2 for complexes (1-8) were found to decrease with increasing the frequency. Ac electrical conductivity (σac) values increases with increasing temperatures and the values of σac for Co(II) complexes are greater than Ni(II) complexes. Co(II) complexes showed a higher conductivity than other Ni(II) complexes due to the higher crystallinity as confirmed by X-ray diffraction analysis.

Semi-Interpenetrating Polymer Networks for Enhanced Supercapacitor Electrodes.

PubMed

Fong, Kara D; Wang, Tiesheng; Kim, Hyun-Kyung; Kumar, R Vasant; Smoukov, Stoyan K

2017-09-08

Conducting polymers show great promise as supercapacitor materials due to their high theoretical specific capacitance, low cost, toughness, and flexibility. Poor ion mobility, however, can render active material more than a few tens of nanometers from the surface inaccessible for charge storage, limiting performance. Here, we use semi-interpenetrating networks (sIPNs) of a pseudocapacitive polymer in an ionically conductive polymer matrix to decrease ion diffusion length scales and make virtually all of the active material accessible for charge storage. Our freestanding poly(3,4-ethylenedioxythiophene)/poly(ethylene oxide) (PEDOT/PEO) sIPN films yield simultaneous improvements in three crucial elements of supercapacitor performance: specific capacitance (182 F/g, a 70% increase over that of neat PEDOT), cycling stability (97.5% capacitance retention after 3000 cycles), and flexibility (the electrodes bend to a <200 μm radius of curvature without breaking). Our simple and controllable sIPN fabrication process presents a framework to develop a range of polymer-based interpenetrated materials for high-performance energy storage technologies.

Effect of A-site La and Ba doping on threshold field and characteristic temperatures of PbSc0.5Ta0.5O3 relaxor studied by acoustic emission

NASA Astrophysics Data System (ADS)

Dul'kin, E.; Mihailova, B.; Gospodinov, M.; Roth, M.

2012-09-01

The structural transitions in Pb1-xLaxSc(1+x)/2Ta(1-x)/2O3, x = 0.08 (PLST) relaxor crystals were studied by means of acoustic emission (AE) under an external electric field (E) and compared with those observed in pure PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PBST) [E. Dul'kin et al., EPL 94, 57002 (2011)]. Similar to both the PST and PBST compounds, in zero field PLST exhibits AE corresponding to a para-to-antiferroelectric incommensurate phase transition at Tn = 276 K, lying in the vicinity of dielectric temperature maximum (Tm). This AE signal exhibits a nontrivial behavior when applying E resembling the electric-field-dependence of Tn previously observed for both the PST and PBST, namely, Tn initially decreases with the increase of E, attains a minimum at a threshold field Eth = 0.5 kV/cm, accompanied by a pronounced maximum of the AE count rate Ṅ = 12 s-1, and then starts increasing as E enhances. The similarities and difference between PST, PLST, and PBST with respect to Tn, Eth, and Ṅ are discussed from the viewpoint of three mechanisms: (i) chemically induced random local electric field due to the extra charge on the A-site ion, (ii) disturbance of the system of stereochemically active lone-pair electrons of Pb2+ by the isotropic outermost electron shell of substituting ion, and (iii) change in the tolerance factor and elastic field to the larger ionic radius of the substituting A-site ion due to the different radius of the substituting ion. The first two mechanisms influence the actual values of Tn and Eth, whereas the latter is shown to affect the normalized Ṅ, indicating the fractions undergoing a field-induced crossover from a modulated antiferroelectric to a ferroelectric state. Creation of secondary random electric field, caused by doping-induced A-site-O ionic chemical bonding, is discussed.

F region above Kauai - Measurement, model, modification

NASA Technical Reports Server (NTRS)

Johnson, C. Y.; Sjolander, G. W.; Oran, E. S.; Young, T. R.; Bernhardt, P. A.; Da Rosa, A. V.

1980-01-01

Results of the Lagopedo II experiment conducted from Kauai, Hawaii to investigate the ionospheric modification that occurs when rocket combustion products are introduced into the O(+)-rich F region are presented. The experiment involved the detonation of a chemical explosion in the F2 peak accompanied by rocket-borne measurements of ion composition and electron content in the vicinity of the explosion. The experimental data is found to be in good agreement with the predictions of a model of the nighttime ion densities in the midlatitude laminar ionosphere, with the exception of N2(+) densities before the explosion. H2O(+) and H3O(+) currents produced by considerable H2O outgassing from the rocket are used to determine a H3O(+)/H2O(+) dissociative recombination rate averaging 1.6 to 1.08, depending on model assumptions. At the time of the explosion, an ionic void 1 km in radius is observed, the boundary of which is characterized by a steep gradient in ionic densities. Evidence of variations in the concentrations of ambient ion species, new reactant species and ionic depletion by sweeping is also obtained.

Ionic liquids screening for desulfurization of natural gasoline by liquid-liquid extraction.

PubMed

Likhanova, Natalya V; Guzmán-Lucero, Diego; Flores, Eugenio A; García, Paloma; Domínguez-Aguilar, Marco A; Palomeque, Jorge; Martínez-Palou, Rafael

2010-11-01

Seventy five ionic liquids (ILs) were tested as a sequestering agent of sulfured compounds in natural gasoline (NG). Desulphurization of NG was performed by means of liquid-liquid extraction method at room temperature and atmospheric pressure. Experimental ILs containing imidazolium, pyridinium, and ammonium cations along with organic and inorganic anions were synthesized conventionally and under microwave and sonochemical conditions. The effect of the molecular structure of ILs on the desulfurization efficiency of NG with high sulfur content was evaluated. Analysis indicated that the anion type played a more important role than the cation on the desulphurization process. ILs based on halogen-ferrates and halogen-aluminates exhibited the highest efficiency in sulfur removal, and their efficiency is further improved when there is an excess of metallic salt in a ratio of at least 1:1.3 during the synthesis of the corresponding IL. An explanation for the ability of metallic ILs to remove sulfur-containing compounds from natural gasoline based on the ratio of the ionic charge to the atomic radius is proposed. Furthermore, a method to recover and reuse water-sensitive to halogenated precursors is described.

Optimal network modification for spectral radius dependent phase transitions

NASA Astrophysics Data System (ADS)

Rosen, Yonatan; Kirsch, Lior; Louzoun, Yoram

2016-09-01

The dynamics of contact processes on networks is often determined by the spectral radius of the networks adjacency matrices. A decrease of the spectral radius can prevent the outbreak of an epidemic, or impact the synchronization among systems of coupled oscillators. The spectral radius is thus tightly linked to network dynamics and function. As such, finding the minimal change in network structure necessary to reach the intended spectral radius is important theoretically and practically. Given contemporary big data resources such as large scale communication or social networks, this problem should be solved with a low runtime complexity. We introduce a novel method for the minimal decrease in weights of edges required to reach a given spectral radius. The problem is formulated as a convex optimization problem, where a global optimum is guaranteed. The method can be easily adjusted to an efficient discrete removal of edges. We introduce a variant of the method which finds optimal decrease with a focus on weights of vertices. The proposed algorithm is exceptionally scalable, solving the problem for real networks of tens of millions of edges in a short time.

Molecular Dynamics Modeling of Ionic Liquids in Electrospray Propulsion

DTIC Science & Technology

2010-06-01

surface equipotential and a correspondes to the model sphere radius. It can also see that the applied voltage is necessary to obtain the surface ...between the tip and extractor, the equipotential line whose angle relative to the x axis is approximately 49 degrees is selected as the Taylor cone surface ...model. Then the electric field on such equipotential line is found by equation 7.5 and used for the distribution along the cone surface . This

Tuning Frustration in Rare Earth Pyrochlores by Platinum Substitution

NASA Astrophysics Data System (ADS)

Hallas, Alannah; Gaudet, Jonathan; Sharma, Arzoo; Wilson, Murray; Cai, Yipeng; Tachibana, Makoto; Wiebe, Chris; Gaulin, Bruce; Luke, Graeme

A successful mechanism for exploring the rich physics of rare earth pyrochlores, R2B2O7, is to substitute the non-magnetic B-site. Varying the ionic radius of the B-site induces an internal chemical pressure. Some rare earths are robust to substitutions; for example, the holmium-based pyrochlores all exhibit a dipolar spin ice state. In the case of other rare earths such as ytterbium, the ground states are remarkably fragile to chemical pressure. In this talk, I will introduce two materials with a new non-magnetic B-site: platinum. The ionic radius of platinum is comparable to that of titanium, which occupies the B-site in the most well-studied family of pyrochlores. Thus, platinum does not induce a strong chemical pressure on the lattice. Nevertheless, using Gd2Pt2O7 and Er2Pt2O7 as examples, I will show that platinum does affect a dramatic change on the magnetic properties. We trace this effect to platinum's empty eg orbitals, which mediate superexchange pathways not available in other rare earth pyrochlores. In Gd2Pt2O7, this results in a striking 160% enhancement of TN as compared to other Gd-based pyrochlores. In Er2Pt2O7, the ordering temperature is strongly suppressed and the ground state is altered.

Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

NASA Astrophysics Data System (ADS)

Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

2016-08-01

The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

Method for producing iron-based catalysts

DOEpatents

Farcasiu, Malvina; Kaufman, Phillip B.; Diehl, J. Rodney; Kathrein, Hendrik

1999-01-01

A method for preparing an acid catalyst having a long shelf-life is provided comprising doping crystalline iron oxides with lattice-compatible metals and heating the now-doped oxide with halogen compounds at elevated temperatures. The invention also provides for a catalyst comprising an iron oxide particle having a predetermined lattice structure, one or more metal dopants for said iron oxide, said dopants having an ionic radius compatible with said lattice structure; and a halogen bound with the iron and the metal dopants on the surface of the particle.

Theory of space-charge polarization for determining ionic constants of electrolytic solutions

NASA Astrophysics Data System (ADS)

Sawada, Atsushi

2007-06-01

A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA +(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.

Experimental measurements of the SP response to concentration and temperature gradients in sandstones with application to subsurface geophysical monitoring

NASA Astrophysics Data System (ADS)

Leinov, E.; Jackson, M. D.

2014-09-01

Exclusion-diffusion potentials arising from temperature gradients are widely neglected in self-potential (SP) surveys, despite the ubiquitous presence of temperature gradients in subsurface settings such as volcanoes and hot springs, geothermal fields, and oil reservoirs during production via water or steam injection. Likewise, with the exception of borehole SP logging, exclusion-diffusion potentials arising from concentration gradients are also neglected or, at best, it is assumed that the diffusion potential dominates. To better interpret these SP sources requires well-constrained measurements of the various coupling terms. We report measurements of thermoelectric and electrochemical exclusion-diffusion potentials across sandstones saturated with NaCl brine and find that electrode effects can dominate the measured voltage. After correcting for these, we find that Hittorf transport numbers are the same within experimental error regardless of whether ion transport occurs in response to temperature or concentration gradients over the range of NaCl concentration investigated that is typical of natural systems. Diffusion potentials dominate only if the pore throat radius is more than approximately 4000 times larger than the diffuse layer thickness. In fine-grained sandstones with small pore throat diameter, this condition is likely to be met only if the saturating brine is of relatively high salinity; thus, in many cases of interest to earth scientists, exclusion-diffusion potentials will comprise significant contributions from both ionic diffusion through, and ionic exclusion from, the pore space of the rock. However, in coarse-grained sandstones, or sandstones saturated with high-salinity brine, exclusion-diffusion potentials can be described using end-member models in which ionic exclusion is neglected. Exclusion-diffusion potentials in sandstones depend upon pore size and salinity in a complex way: they may be positive, negative, or zero depending upon sandstone rock texture (expressed here by the pore radius r) and salinity.

Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids

NASA Astrophysics Data System (ADS)

Garaev, V.; Pavlovica, S.; Reinholds, I.; Vaivars, G.

2013-12-01

In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite preparation.

Dynamics of Charged Species in Ionic-Neutral Block Copolymer and Surfactant Complexes [Structural Relaxation and Dynamics of Ionic-Neutral Block Copolymer Surfactant Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borreguero, Jose M.; Pincus, Philip A.; Sumpter, Bobby G.

Structure–property relationships of ionic block copolymer (BCP) surfactant complexes are critical toward the progress of favorable engineering design of efficient charge-transport materials. In this paper, molecular dynamics simulations are used to understand the dynamics of charged-neutral BCP and surfactant complexes. The dynamics are examined for two different systems: charged-neutral double-hydrophilic and hydrophobic–hydrophilic block copolymers with oppositely charged surfactant moieties. The dynamics of the surfactant head, tails, and charges are studied for five different BCP volume fractions. We observe that the dynamics of the different species solely depend on the balance between electrostatic and entropic interactions between the charged species andmore » the neutral monomers. The favorable hydrophobic–hydrophobic interactions and the unfavorable hydrophobic–hydrophilic interactions determine the mobilities of the monomers. The dynamical properties of the charge species influence complex formation. Structural relaxations exhibit length-scale dependent behavior, with slower relaxation at the radius of gyration length-scale and faster relaxation at the segmental length-scale, consistent with previous results. The dynamical analysis correlates ion-exchange kinetics to the self-assembly behavior of the complexes.« less

Binding in alkali and alkaline-earth tetrahydroborates: Special position of magnesium tetrahydroborate

NASA Astrophysics Data System (ADS)

Łodziana, Zbigniew; van Setten, Michiel J.

2010-01-01

Compounds of light elements and hydrogen are currently extensively studied due to their potential application in the field of hydrogen or energy storage. A number of new interesting tetrahydroborates that are especially promising due to their very high gravimetric hydrogen content were recently reported. However, the determination and understanding of their complex crystalline structures has created considerable debate. Metal tetrahydroborates, in general, form a large variety of structures ranging from simple for NaBH4 to very complex for Mg(BH4)2 . Despite the extensive discussion in the literature no clear explanation has been offered for this variety so far. In this paper we analyze the structural and electronic properties of a broad range of metal tetrahydroborates and reveal the factors that determine their structure: ionic bonding, the orientation of the BH4 groups, and the coordination number of the metal cation. We show, in a simple way, that the charge transfer in the metal tetrahydroborates rationally explains the structural diversity of these compounds. Being ionic systems, the metal tetrahydroborates fall into the classification of Linus Pauling. By using the ionic radius for the BH4 group as determined in this paper, this allows for structural predictions for new and mixed compounds.

Experimental demonstration of scaling behavior for ionic transport and its fluctuations in individual carbon nanotube

NASA Astrophysics Data System (ADS)

Bocquet, Lyderic; Secchi, Eleonora; Nigues, Antoine; Siria, Alessandro

2015-11-01

We perform an experimental study of ionic transport and current fluctuations inside individual Carbon Nanotubes (CNT) with a size ranging from 40 down to 7 nanometers in radius. The conductance exhibits a power law behavior dependence on the salinity, with an exponent close to 1/3. This is in contrast to Boron-Nitride nanotubes which exhibits a constant surface conductance. This scaling behavior is rationalized in terms of a model accounting for hydroxide adsorption at the (hydrophobic) carbon surface. This predicts a density dependent surface charge with a exponent 1/3 in full agreement with the experimental observations. Then we measure the low frequency noise of the ionic current in single CNTs. The noise exhibits a robust 1/f characteristic, with an amplitude which scales proportionaly to the surface charge measured independently. Data for the various CNT at a given pH do collapse on a master curve. This behavior is rationalized in terms of the fluctuations of the surface charge based on the adsorption behavior. This suggests that the low frequency noise takes its origin in the process occuring at the surface of the carbon nanotube.

Dynamics of Charged Species in Ionic-Neutral Block Copolymer and Surfactant Complexes [Structural Relaxation and Dynamics of Ionic-Neutral Block Copolymer Surfactant Complexes

DOE PAGES

Borreguero, Jose M.; Pincus, Philip A.; Sumpter, Bobby G.; ...

2017-06-21

Structure–property relationships of ionic block copolymer (BCP) surfactant complexes are critical toward the progress of favorable engineering design of efficient charge-transport materials. In this paper, molecular dynamics simulations are used to understand the dynamics of charged-neutral BCP and surfactant complexes. The dynamics are examined for two different systems: charged-neutral double-hydrophilic and hydrophobic–hydrophilic block copolymers with oppositely charged surfactant moieties. The dynamics of the surfactant head, tails, and charges are studied for five different BCP volume fractions. We observe that the dynamics of the different species solely depend on the balance between electrostatic and entropic interactions between the charged species andmore » the neutral monomers. The favorable hydrophobic–hydrophobic interactions and the unfavorable hydrophobic–hydrophilic interactions determine the mobilities of the monomers. The dynamical properties of the charge species influence complex formation. Structural relaxations exhibit length-scale dependent behavior, with slower relaxation at the radius of gyration length-scale and faster relaxation at the segmental length-scale, consistent with previous results. The dynamical analysis correlates ion-exchange kinetics to the self-assembly behavior of the complexes.« less

An FCS study of unfolding and refolding of CPM-labeled human serum albumin: role of ionic liquid.

PubMed

Sasmal, Dibyendu Kumar; Mondal, Tridib; Sen Mojumdar, Supratik; Choudhury, Aparajita; Banerjee, Rajat; Bhattacharyya, Kankan

2011-11-10

The effect of a room temperature ionic liquid (RTIL) on the conformational dynamics of a protein, human serum albumin (HSA), is studied by fluorescence correlation spectroscopy (FCS). For this, the protein was covalently labeled by a fluorophore, 7-dimethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM). On addition of a RTIL ([pmim][Br]) to the native protein, the diffusion coefficient (D(t)) decreases and the hydrodynamic radius (R(h)) increases. This suggests that the RTIL ([pmim][Br]) acts as a denaturant when the protein is in the native state. However, addition of [pmim][Br] to a protein denatured by GdnHCl causes an increases in D(t) and decrease in R(h). This suggests that in the presence of GdnHCl addition of RTIL helps the protein to refold. In the native state, the conformational dynamics of protein is described by three distinct time constants: ~3.6 ± 0.7, ~29 ± 4.5, and 133 ± 23 μs. The faster components (~3.6 ± 0.7 and ~29 ± 4.5 μs) are ascribed to chain dynamics of the protein, while the slowest component (133 μs) is responsible for interchain interaction or concerted motion. On addition of [pmim][Br], the conformational dynamics of HSA becomes slower (~5.1 ± 1, ~43.5 ± 2.8, and ~311 ± 2.3 μs in the presence of 1.5 M [pmim][Br]). The time constants for the protein denatured by 6 M GdnHCl are 3.2 ± 0.4, 34 ± 6, and 207 ± 38 μs. When 1.5 M [pmim][Br] is added to the denatured protein (in 6 M GdnHCl), the time constants become ~5 ± 1, ~41 ± 10, and ~230 ± 45 μs. The lifetime histogram shows that, on addition of GdnHCl to HSA, the contribution of the shorter lifetime component decreases and vanishes at 6 M GdnHCl. The shorter lifetime component immediately reappears after addition of RTIL to unfolded HSA. This suggests recoiling of the unfolded protein by RTIL.

The infrared signature of water associated with trivalent cations in olivine

NASA Astrophysics Data System (ADS)

Berry, Andrew J.; O'Neill, Hugh St. C.; Hermann, Jörg; Scott, Dean R.

2007-09-01

Forsterite crystals were synthesised under water saturated conditions at 1400 °C and 1.5 GPa doped with trace amounts of either B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ga, Y, Zr, In, Sm, Gd, Dy, Tm, or Lu. The common and intense hydroxyl stretching bands in the infrared spectra of spinel peridotite olivine, at 3572 and 3525 cm -1, were only reproduced in the presence of Ti. Those samples where the trace element substitutes as the trivalent cation on the Mg 2+ site were identified from a systematic variation in concentration with the trivalent ionic radius. The hydroxyl region of all samples is essentially identical except for between 3300 and 3400 cm -1. This region is characterised by one or more bands, with the energy of the most intense feature being correlated with the ionic radius of the trivalent cation. The integrated intensity of these hydroxyl bands also correlates with the concentration of the trivalent cation. These correlations provide unambiguous evidence that bands, or peaks, in this region correspond to water at defect sites associated with trivalent cations. "Trivalent peaks" are sometimes observed in samples of mantle olivine and most likely indicate water associated with Fe 3+. The water at this site is not incorporated under normal mantle conditions and should not be included in estimates of the water capacity of mantle olivine. These results emphasise the importance of identifying the infrared signature of different water substitution mechanisms.

Probing the cellular damage in bacteria induced by GaN nanoparticles using confocal laser Raman spectroscopy

NASA Astrophysics Data System (ADS)

Sahoo, Prasana; Murthy, P. Sriyutha; Dhara, S.; Venugopalan, V. P.; Das, A.; Tyagi, A. K.

2013-08-01

Understanding the mechanism of nanoparticle (NP) induced toxicity in microbes is of potential importance to a variety of disciplines including disease diagnostics, biomedical implants, and environmental analysis. In this context, toxicity to bacterial cells and inhibition of biofilm formation by GaN NPs and their functional derivatives have been investigated against gram positive and gram negative bacterial species down to single cellular level. High levels of inhibition of biofilm formation (>80 %) was observed on treatments with GaN NPs at sub-micro molar concentrations. These results were substantiated with morphological features investigated with field emission scanning electron microscope, and the observed changes in vibrational modes of microbial cells using Raman spectroscopy. Raman spectra provided molecular interpretation of cell damage by registering signatures of molecular vibrations of individual living microbial cells and mapping the interplay of proteins at the cell membrane. As compared to the untreated cells, Raman spectra of NP-treated cells showed an increase in the intensities of characteristic protein bands, which confirmed membrane damage and subsequent release of cellular contents outside the cells. Raman spectral mapping at single cellular level can facilitate understanding of the mechanistic aspect of toxicity of GaN NPs. The effect may be correlated to passive diffusion causing mechanical damage to the membrane or ingress of Ga3+ (ionic radius 0.076 nm) which can potentially interfere with bacterial metabolism, as it resembles Fe2+ (ionic radius 0.077 nm), which is essential for energy metabolism.

On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study.

PubMed

Lovelock, Kevin R J; Ejigu, Andinet; Loh, Sook Fun; Men, Shuang; Licence, Peter; Walsh, Darren A

2011-06-07

The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 μm Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied.

Stability Mechanisms of a Thermophilic Laccase Probed by Molecular Dynamics

PubMed Central

Christensen, Niels J.; Kepp, Kasper P.

2013-01-01

Laccases are highly stable, industrially important enzymes capable of oxidizing a large range of substrates. Causes for their stability are, as for other proteins, poorly understood. In this work, multiple-seed molecular dynamics (MD) was applied to a Trametes versicolor laccase in response to variable ionic strengths, temperatures, and glycosylation status. Near-physiological conditions provided excellent agreement with the crystal structure (average RMSD ∼0.92 Å) and residual agreement with experimental B-factors. The persistence of backbone hydrogen bonds was identified as a key descriptor of structural response to environment, whereas solvent-accessibility, radius of gyration, and fluctuations were only locally relevant. Backbone hydrogen bonds decreased systematically with temperature in all simulations (∼9 per 50 K), probing structural changes associated with enthalpy-entropy compensation. Approaching T opt (∼350 K) from 300 K, this change correlated with a beginning “unzipping” of critical β-sheets. 0 M ionic strength triggered partial denucleation of the C-terminal (known experimentally to be sensitive) at 400 K, suggesting a general salt stabilization effect. In contrast, F− (but not Cl−) specifically impaired secondary structure by formation of strong hydrogen bonds with backbone NH, providing a mechanism for experimentally observed small anion destabilization, potentially remedied by site-directed mutagenesis at critical intrusion sites. N-glycosylation was found to support structural integrity by increasing persistent backbone hydrogen bonds by ∼4 across simulations, mainly via prevention of F− intrusion. Hydrogen-bond loss in distinct loop regions and ends of critical β-sheets suggest potential strategies for laboratory optimization of these industrially important enzymes. PMID:23658618

Synthesis and morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with tungsten bronze structure in RE{sub 2}O{sub 3}-BaO-Nb{sub 2}O{sub 5}-B{sub 2}O{sub 3} glasses (RE: Sm, Eu, Gd, Dy, Er)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ida, H.; Shinozaki, K.; Honma, T.

2012-12-15

Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with a tetragonal tungsten bronze (TTB) structure are synthesized using a conventional glass crystallization technique in 2.3RE{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3} (mol%) (RE=Sm, Eu, Gd, Dy, and Er) glasses. One sharp crystallization peak is observed at {approx}670 Degree-Sign C in both powdered and bulk glasses, and the formation of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with unit cell parameters of a{approx}1.24 nm and c{approx}0.39 nm was confirmed. It is found from high resolution transmission electron microscope observations that the morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals is ellipsoidal. Their average particlemore » size is in the range of 15-60 nm and decreases with decreasing ionic radius of RE{sup 3+} being present in the precursor glasses. The optical transparent crystallized glass (bulk) shows the total photoluminescence (PL) quantum yield of 53% in the visible region of Eu{sup 3+} ions, suggesting a high potential of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals as PL materials. - Graphical abstract: This figure shows a TEM photograph for the heat-treated (667 Degree-Sign C, 3 h) sample of 2.3Dy{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3}. An ellipsoidal-shaped Ba{sub 1-x}Dy{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystal with diameters of 17 and 28 nm is observed. The ellipsoidal morphology is a common feature in Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals synthesized by the crystallization of 2.3RE{sub 2}O{sub 3}-27.4BaO-34.3Nb{sub 2}O{sub 5}-36B{sub 2}O{sub 3} glasses. Highlights: Black-Right-Pointing-Pointer Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals with a tetragonal tungsten bronze structure are synthesized. Black-Right-Pointing-Pointer A glass crystallization technique was applied. Black-Right-Pointing-Pointer The morphology of Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals is ellipsoidal. Black-Right-Pointing-Pointer The average particle size with 15-60 nm decreases with decreasing ionic radius of RE{sup 3+}. Black-Right-Pointing-Pointer Ba{sub 1-x}RE{sub 2x/3}Nb{sub 2}O{sub 6} nanocrystals have a high potential as photoluminescence materials.« less

Physical and optical properties of lithium borosilicate glasses doped with Dy3+ ions

NASA Astrophysics Data System (ADS)

Ramteke, D. D.; Gedam, R. S.; Swart, H. C.

2018-04-01

The borosilicate glasses with Dy3+ ions were prepared by the melt quench technique with varying concentration of Dy2O3. The glasses were characterized by the density calculation, absorbance and photoluminescence (PL) spectroscopy measurements. Density and molar volume of the glasses increases with increase in Dy3+ ions in the glass matrix. This behavior is correlated with the higher molecular weight and larger ionic radius of Dy3+ ion compared to the other constituents of glass matrix. Emission of Dy3+ doped glasses showed three bands at 482, 573 and at 665 nm which correspond to 6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red) transitions. The emission spectra of glasses with different concentration of Dy3+ ions shows that, glasses with 0.5 mol% of Dy2O3 shows highest emission and decreases with further doping. CIE 1931 chromaticity diagram showed that the emission of these glasses was in the white region. Photographs of these glasses under 349 nm Light emitting diode excitation also confirmed the white light emission from these glasses.

One-dimensional coordination polymers of whole row rare earth tris-pivalates

NASA Astrophysics Data System (ADS)

Tsymbarenko, Dmitry; Martynova, Irina; Grebenyuk, Dimitry; Shegolev, Vsevolod; Kuzmina, Natalia

2018-02-01

Fourteen 1D coordination polymers of rare earth pivalates [Ln(Piv)3]∞ (Ln = Y, La, Pr, Nd, Sm-Lu) were synthesized and characterized by powder X-ray diffraction, IR spectroscopy, TGA, and conventional elemental analysis. Crystal structures of [La(Piv)3]∞, [Yb(Piv)3]∞, [Lu(Piv)3]∞ were determined by means of single crystal X-ray analysis at 120 K, those of [Y(Piv)3]∞ and [Ho(Piv)3]∞ - from powder XRD data at 293 K. Transformation of [Ln(Piv)3]∞ structure and Piv- anions coordination mode along the whole row has been derived from powder XRD and IR spectroscopy results, and shown to crucially affect the relative location of 1D chains in the crystal structure, as well as the Ln···Ln distance within the single chain. Negative thermal expansion along 1D [Ln(Piv)3]∞ chain was revealed for Ln = Tm, Yb, Lu. Enforcement of 1D polymeric structure with the decrease of Ln ionic radius has been established from solid-state DFT calculations.

Adsorption preference for divalent metal ions by Lactobacillus casei JCM1134.

PubMed

Endo, Rin; Aoyagi, Hideki

2018-05-09

The removal of harmful metals from the intestinal environment can be inhibited by various ions which can interfere with the adsorption of target metal ions. Therefore, it is important to understand the ion selectivity and adsorption mechanism of the adsorbent. In this study, we estimated the adsorption properties of Lactobacillus casei JCM1134 by analyzing the correlation between its maximum adsorption level (q max ) for seven metals and their ion characteristics. Some metal ions showed altered adsorption levels by L. casei JCM1134 as culture growth time increased. Although it was impossible to identify specific adsorption components, adsorption of Sr and Ba may depend on capsular polysaccharide levels. The maximum adsorption of L. casei JCM1134 (9 h of growth in culture) for divalent metal ions was in the following order: Cu 2+  > Ba 2+  > Sr 2+  > Cd 2+  > Co 2+  > Mg 2+  > Ni 2+ . The q max showed a high positive correlation with the ionic radius. Because this tendency is similar to adsorption occurring through an ion exchange mechanism, it was inferred that an ion exchange mechanism contributed greatly to adsorption by L. casei JCM1134. Because the decrease in the amount of adsorption due to prolonged culture time was remarkable for metals with a large ion radius, it is likely that the adsorption components involved in the ion exchange mechanism decomposed over time. These results and analytical concept may be helpful for designing means to remove harmful metals from the intestinal tract.

Ionic calcium determination in skim milk with molecular probes and front-face fluorescence spectroscopy: simple linear regression.

PubMed

Gangidi, R R; Metzger, L E

2006-11-01

The purpose of this study was to determine if the ionic calcium content of skim milk could be determined using molecular probes and front-face fluorescence spectroscopy. Current methods for determining ionic calcium are not sensitive, overestimate ionic calcium, or require complex procedures. Molecular probes designed specifically for measuring ionic calcium could potentially be used to determine the ionic calcium content of skim milk. The goal of the current study was to develop foundation methods for future studies to determine ionic calcium directly in skim milk and other dairy products with molecular probes and fluorescence spectroscopy. In this study, the effect of pH on calcium-sensitive fluorescent probe (Rhod-5N and Fluo-5N) performance using various concentrations of skim milk was determined. The pH of diluted skim milk (1.9 to 8.9% skim milk), was adjusted to either 6.2 or 7.0, after which the samples were analyzed with fluorescent probes (1 microM) and front-face fluorescence spectroscopy. The ionic calcium content of each sample was also determined using a calcium ion-selective electrode. The results demonstrated that the ionic calcium content of each sample was highly correlated (R2 > 0.989) with the fluorescence intensities of the probe-calcium adduct using simple linear regression. Higher than suggested ionic calcium contents of 1,207 and 1,973 microM were determined with the probes (Fluo-5N and Rhod-5N) in diluted skim milk with pH 7.0 and 6.2, respectively. The fluorescence intensity of the probe-calcium adduct decreased with a decrease in pH for the same ionic calcium concentration. This study demonstrates that Fluo-5N and Rhod-5N can be used to determine the ionic-calcium content of diluted milk with front-face fluorescence spectroscopy. Furthermore, these probes may also have the potential to determine the ionic calcium content of undiluted skim milk.

A Reynolds Number Study of Wing Leading-Edge Effects on a Supersonic Transport Model at Mach 0.3

NASA Technical Reports Server (NTRS)

Williams, M. Susan; Owens, Lewis R., Jr.; Chu, Julio

1999-01-01

A representative supersonic transport design was tested in the National Transonic Facility (NTF) in its original configuration with small-radius leading-edge flaps and also with modified large-radius inboard leading-edge flaps. Aerodynamic data were obtained over a range of Reynolds numbers at a Mach number of 0.3 and angles of attack up to 16 deg. Increasing the radius of the inboard leading-edge flap delayed nose-up pitching moment to a higher lift coefficient. Deflecting the large-radius leading-edge flap produced an overall decrease in lift coefficient and delayed nose-up pitching moment to even higher angles of attack as compared with the undeflected large- radius leading-edge flap. At angles of attack corresponding to the maximum untrimmed lift-to-drag ratio, lift and drag coefficients decreased while lift-to-drag ratio increased with increasing Reynolds number. At an angle of attack of 13.5 deg., the pitching-moment coefficient was nearly constant with increasing Reynolds number for both the small-radius leading-edge flap and the deflected large-radius leading-edge flap. However, the pitching moment coefficient increased with increasing Reynolds number for the undeflected large-radius leading-edge flap above a chord Reynolds number of about 35 x 10 (exp 6).

ATPase activity and light scattering of acto-heavy meromyosin: dependence on ATP concentration and on ionic strength.

PubMed

Dancker, P

1975-01-01

1. The dependence on ATP concentration of ATPase activity and light scattering decrease of acto-HMM could be described at very low ionic strength by one hyperbolic adsorption isotherm with a dissociation constant of 3 X 10(-6)M. Hence the increase of ATP ase activity was paralleled by a decrease in light scattering. At higher values of ionic strength ATPase activity stopped rising before HMM was completely saturated with ATP. Higher ionic strength prevented ATPase activity from further increasing when the rigor links (links between actin and nucleotide-free myosin), which have formerly protected the ATPase against the suppressing action of higher ionic strength have fallen below a certain amount. This protecting influence of rigor links did not require tropomyosin-troponin. 2. For complete activation of ATPase activity by actin less actin was needed when HMM was incompletely saturated with ATP than when it was completely saturated with ATP. 3. The apparent affinity of ATP to regulated acto-HMM (which contained tropomyosin-troponin) was lower than to unregulated acto-HMM (which was devoid of tropomyosin-troponin). In the presence of rigor complexes (indicated by an incomplete decrease of light scattering) the ATPase activity of regulated acto-HMM was higher than that of unregulated acto-HMM. At increasing ATP concentrations the ATPase activity of regulated acto-HMM stopped rising at a similar degree of saturation with ATP as the ATPase activity of unregulated acto-HMM at the same ionic strength.

Characterization of gold nanoparticles with different hydrophilic coatings via capillary electrophoresis and Taylor dispersion analysis. Part I: determination of the zeta potential employing a modified analytic approximation.

PubMed

Pyell, Ute; Jalil, Alaa H; Pfeiffer, Christian; Pelaz, Beatriz; Parak, Wolfgang J

2015-07-15

Taking gold nanoparticles with different hydrophilic coatings as an example, it is investigated whether capillary electrophoresis in combination with Taylor dispersion analysis allows for the precise determination of mean electrophoretic mobilities, electrophoretic mobility distributions, and zeta potentials in a matrix of exactly known composition and the calibration-free determination of number-weighted mean hydrodynamic radii. Our experimental data confirm that the calculation of the zeta potential for colloidal nanoparticles with ζ>25 mV requires to take the relaxation effect into account. Because of the requirement to avoid particle-wall interactions, a solution of disodiumtetraborate decahydrate (borax) in deionized water had been selected as suitable electrolyte. Measurements of the electrophoretic mobility at different ionic strength and application of the analytic approximation developed by Ohshima show that in the present case of a buffered solution with a weak electrolyte co-ion and a strong electrolyte counterion, the effective ionic drag coefficient should be approximated with the ionic drag coefficient of the counterion. The obtained results are in good agreement with theoretical expectations regarding the dependence of the zeta potential and the electrokinetic surface charge density on the ionic strength. We also show that Taylor dispersion analysis (besides estimation of the number-weighted mean hydrodynamic radius) provides additional information on the type and width of the number-weighted particle distribution. Copyright © 2015 Elsevier Inc. All rights reserved.

Ionically cross-linked poly(allylamine) as a stimulus-responsive underwater adhesive: ionic strength and pH effects.

PubMed

Lawrence, Patrick G; Lapitsky, Yakov

2015-02-03

Gel-like coacervates that adhere to both hydrophilic and hydrophobic substrates under water have recently been prepared by ionically cross-linking poly(allylamine) (PAH) with pyrophosphate (PPi) and tripolyphosphate (TPP). Among the many advantages of these underwater adhesives (which include their simple preparation and low cost) is their ability to dissolve on demand when exposed to high or low pH. To further analyze their stimulus-responsive properties, we have investigated the pH and ionic strength effects on the formation, rheology and adhesion of PAH/PPi and PAH/TPP complexes. The ionic cross-linker concentrations needed to form these adhesives decreased with increasing pH and ionic strength (although the complexes ceased to form when the parent solution pH exceeded ca. 8.5; i.e., the effective pKa of PAH). Once formed, their ionic cross-links were most stable (as inferred from their relaxation times) at near-neutral or slightly alkaline pH values (of roughly 6.5-9) and at low ionic strengths. The decrease in ionic cross-link stability within complexes prepared at other pH values and at elevated (150-300 mM) NaCl concentrations diminished both the strength and longevity of adhesion (although, under most conditions tested, the short-term tensile adhesion strengths remained above 10(5) Pa). Additionally, the sensitivity of PAH/PPi and PAH/TPP complexes to ionic strength was demonstrated as a potential route to injectable adhesive design (where spontaneous adhesive formation was triggered via injection of low-viscosity, colloidal PAH/TPP dispersions into phosphate buffered saline). Thus, while the sensitivity of ionically cross-linked PAH networks to pH and ionic strength can weaken their adhesion, it can also impart them with additional functionality, such as minimally invasive, injectable delivery, and ability to form and dissolve their bonds on demand.

Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering.

PubMed

Kontro, Inkeri; Svedström, Kirsi; Duša, Filip; Ahvenainen, Patrik; Ruokonen, Suvi-Katriina; Witos, Joanna; Wiedmer, Susanne K

2016-12-01

The effects of ionic liquids on model phospholipid membranes were studied by small-angle X-ray scattering, dynamic light scattering (DLS) and zeta potential measurements. Multilamellar 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes and large unilamellar vesicles composed of l-α-phosphatidylcholine (eggPC) and l-α-phosphatidylglycerol (eggPG) (80:20mol%) or eggPC, eggPG, and cholesterol (60:20:20mol%) were used as biomimicking membrane models. The effects of the phosphonium-based ionic liquids: tributylmethylphosphonium acetate, trioctylmethylphosphonium acetate, tributyl(tetradecyl)-phosphonium acetate, and tributyl(tetradecyl)-phosphonium chloride, were compared to those of 1-ethyl-3-methyl-imidazolium acetate. With multilamellar vesicles, the ionic liquids that did not disrupt liposomes decreased the lamellar spacing as a function of concentration. The magnitude of the effect depended on concentration for all studied ionic liquids. Using large unilamellar vesicles, first a slight decrease in the vesicle size, then aggregation of vesicles was observed by DLS for increasing ionic liquid concentrations. At concentrations just below those that caused aggregation of liposomes, large unilamellar vesicles were coated by ionic liquid cations, evidenced by a change in their zeta potential. The ability of phosphonium-based ionic liquids to affect liposomes is related to the length of the hydrocarbon chains in the cation. Generally, the ability of ionic liquids to disrupt liposomes goes hand in hand with inducing disorder in the phospholipid membrane. However, trioctylmethylphosphonium acetate selectively extracted and induced a well-ordered lamellar structure in phospholipids from disrupted cholesterol-containing large unilamellar vesicles. This kind of effect was not seen with any other combination of ionic liquids and liposomes. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Effect of salts on the kinetic parameters and thermal stability of bovine brain acid phosphatase.

PubMed

Bittencourt, H M; Chaimovich, H

1976-08-01

Bovine brain acid phosphatase is inhibited, at any pH, by an increase in ionic strength. The rate decrease is associated at pH 5, with a marked decrease in Km and, at pH 8, with a noticeable decrease in Vm. The rate of thermal inactivation of the enzyme is unaffected by increasing ionic strength up to 300 mM. These results are discussed in terms of interactions at the active site of the enzyme.

Synthesis and characterization of ionic polymer networks in a room-temperature ionic liquid.

PubMed

Stanzione, Joseph F; Jensen, Robert E; Costanzo, Philip J; Palmese, Giuseppe R

2012-11-01

Ionic liquid gels (ILGs) for potential use in ion transport and separation applications were generated via a free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N,N'-methylene(bis)acrylamide (MBA) using 1-ethyl-3-methylimidazolium ethylsulfate (IL) as a room temperature ionic liquid solvent medium. The AMPS and MBA monomer solubility window in the IL in the temperature range of 25 to 65 °C was determined. In situ ATR-FTIR showed near complete conversion of monomers to a cross-linked polymer network. ILGs with glass transition temperatures (T(g)s) near -50 °C were generated with T(g) decreasing with increasing IL content. The elastic moduli in compression (200 to 6600 kPa) decreased with increasing IL content and increasing AMPS content while the conductivities (0.35 to 2.14 mS cm⁻¹) increased with increasing IL content and decreasing MBA content. The polymer-IL interaction parameter (χ) (0.48 to 0.55) was determined via a modified version of the Bray and Merrill equation.

Large enhancement of capacitance driven by electrostatic image forces

NASA Astrophysics Data System (ADS)

Loth, Matthew Scott

The purpose of this thesis is to examine the role of electrostatic images in determining the capacitance and the structure of the electrostatic double layer (EDL) formed at the interface of a metal electrode and an electrolyte. Current mean field theories, and the majority of simulations, do not account for ions to form image charges in the metal electrodes and claim that the capacitance of the double layer cannot be larger than that of the Helmholtz capacitor, whose width is equal to the radius of an ion. However, in some experiments, and simulations where the images are included, the apparent width of the capacitor is substantially smaller. Monte Carlo simulations are used to examine the interface between a metal electrode and a room temperature ionic liquid (RTIL) modeled by hard spheres (the "restricted primitive model"). Image charges for each ion are included in the simulated electrode. At moderately low temperatures the capacitance of the metal/RTIL interface is so large that the effective thickness of the electrostatic double-layer is up to 3 times smaller than the ion radius. To interpret these results, an approach is used that is based on the interaction between discrete ions and their image charges, which therefore goes beyond the mean-field approximation. When a voltage is applied across the interface, the strong image attraction causes counterions to condense onto the metal surface to form compact ion-image dipoles. These dipoles repel each other to form a correlated liquid. When the surface density of these dipoles is low, the insertion of an additional dipole does not require much energy. This leads to a large capacitance C that decreases monotonically with voltage V, producing a "bell-shaped" C( V) curve. In the case of a semi-metal electrode, the finite screening radius of the electrode shifts the reflection plane for image charges to the interior of the electrode resulting in a "camel-shaped" C(V) curve, which is parabolic near V = 0, reaches a maximum and then decreases. These predictions are in qualitative agreement with experiment. A similarly simple model is employed to simulate the EDL of superionic crystals. In this case only small cations are mobile and other ions form an oppositely charged background. Simulations show an effective thickness of the EDL that may be 3 times smaller than the ion radius. The weak repulsion of ion-image dipoles again plays a central role in determining the capacitance in this theory, which is in reasonable agreement with experiment. Finally, the problem of a strongly charged, insulating macroion in a dilute solution of multivalent counterions is considered. While an ideal conductor does not exist in the problem, and no images are explicitly included, simulations demonstrate that adsorbed counterions form a strongly correlated liquid of at the surface of the macroion and acts as an effective metal surface. In fact, the surface screens the electric field of distant ions with a negative screening radius. The simulation results serve to confirm existing non-mean-field theories.

Ionic strength-induced formation of smectite quasicrystals enhances nitroaromatic compound sorption.

PubMed

Li, Hui; Pereira, Tanya R; Teppen, Brian J; Laird, David A; Johnston, Cliff T; Boyd, Stephen A

2007-02-15

Sorption of organic contaminants by soils is a determinant controlling their transport and fate in the environment. The influence of ionic strength on nitroaromatic compound sorption by K+- and Ca2+ -saturated smectite was examined. Sorption of 1,3-dinitrobenzene by K-smectite increased as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorption by Ca-smectite at CaCl2 ionic strengths of 0.015 and 0.15 M remained essentially the same. The "salting-out" effect on the decrease of 1,3-dinitrobenzene aqueous solubility within this ionic strength range was <1.5% relative to the solubility in pure water. This decrease of solubility is insufficient to account for the observed increase of sorption by K-smectite with increasing KCl ionic strength. X-ray diffraction patterns and light absorbance of K-clay suspensions indicated the aggregation of clay particles and the formation of quasicrystal structures as KCI ionic strength increased. Sorption enhancement is attributed to the formation of better-ordered K-clay quasicrystals with reduced interlayer distances rather than to the salting-out effect. Dehydration of 1,3-dinitrobenzene is apparently a significant driving force for sorption, and we show for the first time that sorption of small, planar, neutral organic molecules, namely, 1,3-dinitrobenzene, causes previously expanded clay interlayers to dehydrate and collapse in aqueous suspension.

Improvement of thermostability and activity of firefly luciferase through [TMG][Ac] ionic liquid mediator.

PubMed

Ebrahimi, Mehdi; Hosseinkhani, Saman; Heydari, Akbar; Khavari-Nejad, Ramazan Ali; Akbari, Jafar

2012-10-01

Firefly luciferase catalyzes production of light from luciferin in the presence of Mg(2+)-ATP and oxygen. This enzyme has wide range of applications in biotechnology and development of biosensors. The low thermal stability of wild-type firefly luciferase is a limiting factor in most applications. Improvements in activity and stability of few enzymes in the presence of ionic liquids were shown in many reports. In this study, kinetic and thermal stability of firefly luciferase from Photinus pyralis in the presence of three tetramethylguanidine-based ionic liquids was investigated. The enzyme has shown improved activity in the presence of [1, 1, 3, 3-tetramethylguanidine][acetate], but in the presence of [TMG][trichloroacetate] and [TMG][triflouroacetate] activity, it decreased or unchanged significantly. Among these ionic liquids, only [TMG][Ac] has increased the thermal stability of luciferase. Incubation of [TMG][Ac] with firefly luciferase brought about with decrease of K(m) for ATP.

Scaling effects in sodium zirconium silicate phosphate (Na 1+ xZr 2Si xP 3- xO 12) ion-conducting thin films

DOE PAGES

Ihlefeld, Jon F.; Gurniak, Emily; Jones, Brad H.; ...

2016-05-04

Preparation of sodium zirconium silicate phosphate (NaSICon), Na 1+xZr 2Si xP 3–xO 12 (0.25 ≤ x ≤ 1.0), thin films has been investigated via a chemical solution approach on platinized silicon substrates. Increasing the silicon content resulted in a reduction in the crystallite size and a reduction in the measured ionic conductivity. Processing temperature was also found to affect microstructure and ionic conductivity with higher processing temperatures resulting in larger crystallite sizes and higher ionic conductivities. The highest room temperature sodium ion conductivity was measured for an x = 0.25 composition at 2.3 × 10 –5 S/cm. In conclusion, themore » decreasing ionic conductivity trends with increasing silicon content and decreasing processing temperature are consistent with grain boundary and defect scattering of conducting ions.« less

Role of Heavy Meromyosin in Heat-Induced Gelation in Low Ionic Strength Solution Containing L-Histidine.

PubMed

Hayakawa, Toru; Yoshida, Yuri; Yasui, Masanori; Ito, Toshiaki; Wakamatsu, Jun-ichi; Hattori, Akihito; Nishimura, Takanori

2015-08-01

The gelation of myosin has a very important role in meat products. We have already shown that myosin in low ionic strength solution containing L-histidine forms a transparent gel after heating. To clarify the mechanism of this unique gelation, we investigated the changes in the nature of myosin subfragments during heating in solutions with low and high ionic strengths with and without L-histidine. The hydrophobicity of myosin and heavy meromyosin (HMM) in low ionic strength solution containing L-histidine was lower than in high ionic strength solution. The SH contents of myosin and HMM in low ionic strength solution containing l-histidine did not change during the heating process, whereas in high ionic strength solution they decreased slightly. The heat-induced globular masses of HMM in low ionic strength solution containing L-histidine were smaller than those in high ionic strength solution. These findings suggested that the polymerization of HMM molecules by heating was suppressed in low ionic strength solution containing L-histidine, resulting in formation of the unique gel. © 2015 Institute of Food Technologists®

Low Thermal Conductivity of RE-Doped SrO(SrTiO3)1 Ruddlesden Popper Phase Bulk Materials Prepared by Molten Salt Method

NASA Astrophysics Data System (ADS)

Putri, Yulia Eka; Said, Suhana Mohd; Refinel, Refinel; Ohtaki, Michitaka; Syukri, Syukri

2018-04-01

The SrO(SrTiO3)1 (Sr2TiO4) Ruddlesden Popper (RP) phase is a natural superlattice comprising of alternately stacking perovskite-type SrTiO3 layers and rock salt SrO layers along the crystallographic c direction. This paper discusses the properties of the Sr2TiO4 and (La, Sm)-doped Sr2TiO4 RP phase synthesized via molten salt method, within the context of thermoelectric applications. A good thermoelectric material requires high electrical conductivity, high Seebeck coefficient and low thermal conductivity. All three conditions have the potential to be fulfilled by the Sr2TiO4 RP phase, in particular, the superlattice structure allows a higher degree of phonon scattering hence resulting in lowered thermal conductivity. In this work, the Sr2TiO4 RP phase is doped with Sm and La respectively, which allows injection of charge carriers, modification of its electronic structure for improvement of the Seebeck coefficient, and most significantly, reduction of thermal conductivity. The particles with submicron size allows excessive phonon scattering along the boundaries, thus reduces the thermal conductivity by fourfold. In particular, the Sm-doped sample exhibited even lower lattice thermal conductivity, which is believed to be due to the mismatch in the ionic radius of Sr and Sm. This finding is useful as a strategy to reduce thermal conductivity of Sr2TiO4 RP phase materials as thermoelectric candidates, by employing dopants of differing ionic radius.

Crystal structures of (Mg1-x,Fe(x))SiO3 postperovskite at high pressures.

PubMed

Yamanaka, Takamitsu; Hirose, Kei; Mao, Wendy L; Meng, Yue; Ganesh, P; Shulenburger, Luke; Shen, Guoyin; Hemley, Russell J

2012-01-24

X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg(0.9)Fe(0.1))SiO(3) and (Mg(0.6)Fe(0.4))SiO(3) at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO(3)-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density (ρ = 6.119(1) g/cm(3)) than the former (ρ = 5.694(8) g/cm(3)) due to both the larger amount of iron and the smaller ionic radius of Fe(2+) as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe(2+) also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe(2+) in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered.

The Influence of Magnetic Field on Electrokinetic Potential of Colloidal Particles

NASA Astrophysics Data System (ADS)

Koshoridze, S. I.; Levin, Yu. K.

2018-06-01

The influence of a magnetic field on the electrokinetic potential of colloidal particles in a water flow oversaturated with deposited salts is reported. For the first time, the ionic hydration and dielectric permittivity of water in the double electrical layer are taken into consideration. It is demonstrated that the magnetic field influence is increased with the decreasing dielectric permittivity of water but is decreased due to ionic hydration.

Continuously tunable microdroplet-laser in a microfluidic channel.

PubMed

Tang, Sindy K Y; Derda, Ratmir; Quan, Qimin; Lončar, Marko; Whitesides, George M

2011-01-31

This paper describes the generation and optical characterization of a series of dye-doped droplet-based optical microcavities with continuously decreasing radius in a microfluidic channel. A flow-focusing nozzle generated the droplets (~21 μm in radius) using benzyl alcohol as the disperse phase and water as the continuous phase. As these drops moved down the channel, they dissolved, and their size decreased. The emission characteristics from the drops could be matched to the whispering gallery modes from spherical micro-cavities. The wavelength of emission from the drops changed from 700 to 620 nm as the radius of the drops decreased from 21 μm to 7 μm. This range of tunability in wavelengths was larger than that reported in previous work on droplet-based cavities.

Atomic and electronic structures of an extremely fragile liquid.

PubMed

Kohara, Shinji; Akola, Jaakko; Patrikeev, Leonid; Ropo, Matti; Ohara, Koji; Itou, Masayoshi; Fujiwara, Akihiko; Yahiro, Jumpei; Okada, Junpei T; Ishikawa, Takehiko; Mizuno, Akitoshi; Masuno, Atsunobu; Watanabe, Yasuhiro; Usuki, Takeshi

2014-12-18

The structure of high-temperature liquids is an important topic for understanding the fragility of liquids. Here we report the structure of a high-temperature non-glass-forming oxide liquid, ZrO2, at an atomistic and electronic level. The Bhatia-Thornton number-number structure factor of ZrO2 does not show a first sharp diffraction peak. The atomic structure comprises ZrO5, ZrO6 and ZrO7 polyhedra with a significant contribution of edge sharing of oxygen in addition to corner sharing. The variety of large oxygen coordination and polyhedral connections with short Zr-O bond lifetimes, induced by the relatively large ionic radius of zirconium, disturbs the evolution of intermediate-range ordering, which leads to a reduced electronic band gap and increased delocalization in the ionic Zr-O bonding. The details of the chemical bonding explain the extremely low viscosity of the liquid and the absence of a first sharp diffraction peak, and indicate that liquid ZrO2 is an extremely fragile liquid.

Probing spatial locality in ionic liquids with the grand canonical adaptive resolution molecular dynamics technique

NASA Astrophysics Data System (ADS)

Shadrack Jabes, B.; Krekeler, C.; Klein, R.; Delle Site, L.

2018-05-01

We employ the Grand Canonical Adaptive Resolution Simulation (GC-AdResS) molecular dynamics technique to test the spatial locality of the 1-ethyl 3-methyl imidazolium chloride liquid. In GC-AdResS, atomistic details are kept only in an open sub-region of the system while the environment is treated at coarse-grained level; thus, if spatial quantities calculated in such a sub-region agree with the equivalent quantities calculated in a full atomistic simulation, then the atomistic degrees of freedom outside the sub-region play a negligible role. The size of the sub-region fixes the degree of spatial locality of a certain quantity. We show that even for sub-regions whose radius corresponds to the size of a few molecules, spatial properties are reasonably reproduced thus suggesting a higher degree of spatial locality, a hypothesis put forward also by other researchers and that seems to play an important role for the characterization of fundamental properties of a large class of ionic liquids.

Atomic and electronic structures of an extremely fragile liquid

PubMed Central

Kohara, Shinji; Akola, Jaakko; Patrikeev, Leonid; Ropo, Matti; Ohara, Koji; Itou, Masayoshi; Fujiwara, Akihiko; Yahiro, Jumpei; Okada, Junpei T.; Ishikawa, Takehiko; Mizuno, Akitoshi; Masuno, Atsunobu; Watanabe, Yasuhiro; Usuki, Takeshi

2014-01-01

The structure of high-temperature liquids is an important topic for understanding the fragility of liquids. Here we report the structure of a high-temperature non-glass-forming oxide liquid, ZrO2, at an atomistic and electronic level. The Bhatia–Thornton number–number structure factor of ZrO2 does not show a first sharp diffraction peak. The atomic structure comprises ZrO5, ZrO6 and ZrO7 polyhedra with a significant contribution of edge sharing of oxygen in addition to corner sharing. The variety of large oxygen coordination and polyhedral connections with short Zr–O bond lifetimes, induced by the relatively large ionic radius of zirconium, disturbs the evolution of intermediate-range ordering, which leads to a reduced electronic band gap and increased delocalization in the ionic Zr–O bonding. The details of the chemical bonding explain the extremely low viscosity of the liquid and the absence of a first sharp diffraction peak, and indicate that liquid ZrO2 is an extremely fragile liquid. PMID:25520236

Evolution of the composition, structure, and piezoelectric performance of (K1-xNax)NbO3 nanorod arrays with hydrothermal reaction time

NASA Astrophysics Data System (ADS)

Jin, Wenchao; Wang, Zhao; Li, Meng; He, Yahua; Hu, Xiaokang; Li, Luying; Gao, Yihua; Hu, Yongming; Gu, Haoshuang; Wang, Xiaolin

2018-04-01

Lead-free (K,Na)NbO3 (KNN) nanorod arrays were synthesized with the assistance of a Nb: SrTiO3 single-crystal substrate through the hydrothermal process. The evolutions of the morphology, composition, and structure of the as-synthesized KNN nanorods with the increase in reaction time were investigated. The results confirmed that the increase in reaction time up to 3 h led to the increase in the length and aspect ratio of the well-aligned KNN nanorods. All samples have K-rich orthorhombic crystal structures, while the diffraction peaks shifted towards a higher degree. The peak shifts should be attributed to the increase in the Na content in the KNN lattice, which could decrease the lattice parameters owing to the small ionic radius of Na+ than that of K+. Moreover, the increase in reaction time also resulted in the suppression of oxygen vacancies on the surface of the KNN nanorods. These evolutions of the composition and crystal structure, as well as the decrease in the defect content, lead to great enhancement of the nanorod's piezoelectric response, as their d33 value was increased from 19 to 64 pm/V. These results demonstrated the significant impact of reaction time on the hydrothermal growth of high-performance lead-free KNN one-dimensional nanomaterials.

Synthesis and morphology of Ba1-xRE2x/3Nb2O6 nanocrystals with tungsten bronze structure in RE2O3-BaO-Nb2O5-B2O3 glasses (RE: Sm, Eu, Gd, Dy, Er)

NASA Astrophysics Data System (ADS)

Ida, H.; Shinozaki, K.; Honma, T.; Oh-ishi, K.; Komatsu, T.

2012-12-01

Ba1-xRE2x/3Nb2O6 nanocrystals with a tetragonal tungsten bronze (TTB) structure are synthesized using a conventional glass crystallization technique in 2.3RE2O3-27.4BaO-34.3Nb2O5-36B2O3 (mol%) (RE=Sm, Eu, Gd, Dy, and Er) glasses. One sharp crystallization peak is observed at ∼670 °C in both powdered and bulk glasses, and the formation of Ba1-xRE2x/3Nb2O6 nanocrystals with unit cell parameters of a∼1.24 nm and c∼0.39 nm was confirmed. It is found from high resolution transmission electron microscope observations that the morphology of Ba1-xRE2x/3Nb2O6 nanocrystals is ellipsoidal. Their average particle size is in the range of 15-60 nm and decreases with decreasing ionic radius of RE3+ being present in the precursor glasses. The optical transparent crystallized glass (bulk) shows the total photoluminescence (PL) quantum yield of 53% in the visible region of Eu3+ ions, suggesting a high potential of Ba1-xRE2x/3Nb2O6 nanocrystals as PL materials.

Structural and Magnetic Properties of Transition-Metal-Doped Zn 1-x Fe x O.

PubMed

Abdel-Baset, T A; Fang, Yue-Wen; Anis, B; Duan, Chun-Gang; Abdel-Hafiez, Mahmoud

2016-12-01

The ability to produce high-quality single-phase diluted magnetic semiconductors (DMS) is the driving factor to study DMS for spintronics applications. Fe-doped ZnO was synthesized by using a low-temperature co-precipitation technique producing Zn 1-x Fe x O nanoparticles (x= 0, 0.02, 0.04, 0.06, 0.08, and 0.1). Structural, Raman, density functional calculations, and magnetic studies have been carried out in studying the electronic structure and magnetic properties of Fe-doped ZnO. The results show that Fe atoms are substituted by Zn ions successfully. Due to the small ionic radius of Fe ions compared to that of a Zn ions, the crystal size decreases with an increasing dopant concentration. First-principle calculations indicate that the charge state of iron is Fe (2+) and Fe (3+) with a zinc vacancy or an interstitial oxygen anion, respectively. The calculations predict that the exchange interaction between transition metal ions can switch from the antiferromagnetic coupling into its quasi-degenerate ferromagnetic coupling by external perturbations. This is further supported and explains the observed ferromagnetic bahaviour at magnetic measurements. Magnetic measurements reveal that decreasing particle size increases the ferromagnetism volume fraction. Furthermore, introducing Fe into ZnO induces a strong magnetic moment without any distortion in the geometrical symmetry; it also reveals the ferromagnetic coupling.

Biodegradation of diesel fuel by a microbial consortium in the presence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues.

PubMed

Chrzanowski, Lukasz; Stasiewicz, Monika; Owsianiak, Mikołaj; Szulc, Alicja; Piotrowska-Cyplik, Agnieszka; Olejnik-Schmidt, Agnieszka K; Wyrwas, Bogdan

2009-09-01

Fast development of ionic liquids as gaining more and more attention valuable chemicals will undoubtedly lead to environmental pollution. New formulations and application of ionic liquids may result in contamination in the presence of hydrophobic compounds, such as petroleum mixtures. We hypothesize that in the presence of diesel fuel low-water-soluble ionic liquids may become more toxic to hydrocarbon-degrading microorganisms. In this study the influence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues (side-chain length from C(3) to C(18)) on biodegradation of diesel fuel by a bacterial consortium was investigated. Whereas test performed for the consortium cultivated on disodium succinate showed that toxicity of the investigated ionic liquids decreased with increase in side-chain length, only higher homologues (C(8)-C(18)) caused a decrease in diesel fuel biodegradation. As a result of exposure to toxic compounds also modification in cell surface hydrophobicity was observed (MATH). Disulphine blue active substances method was employed to determine partitioning index of ionic liquids between water and diesel fuel phase, which varied from 1.1 to 51% for C(3) and C(18) homologues, respectively. We conclude that in the presence of hydrocarbons acting as a solvent, the increased bioavailability of hydrophobic homologues is responsible for the decrease in biodegradation efficiency of diesel fuel.

Effect of SiO2 addition and gamma irradiation on the lithium borate glasses

NASA Astrophysics Data System (ADS)

Raut, A. P.; Deshpande, V. K.

2018-01-01

The physical properties like density, glass transition temperature (Tg), and ionic conductivity of lithium borate (LB) glasses with SiO2 addition were measured before and after gamma irradiation. Remarkable changes in properties have been obtained in the physical properties of LB glasses with SiO2 addition and after gamma irradiation. The increase in density and glass transition temperature of LB glasses with SiO2 addition has been explained with the help of increase in density of cross linking due to SiO4 tetrahedra formation. The increase in ionic conductivity with SiO2 addition was explained with the help of ‘mixed glass former effect’. The increase in density and Tg of LB glasses with SiO2 addition after gamma irradiation has been attributed to fragmentation of bigger ring structure into smaller rings, which increases the density of cross linking and hence compaction. The exposure of gamma irradiation has lead to decrease in ionic conductivity of LB glasses with SiO2 addition. The atomic displacement caused by gamma irradiation resulted in filling of interstices and decrease in trapping sites. This explains the obtained decrease in ionic conductivity after gamma irradiation of glasses. The obtained results of effect of SiO2 addition and gamma irradiation on the density, Tg and ionic conductivity has been supported by FTIR results.

Boson peak of alkali and alkaline earth silicate glasses: influence of the nature and size of the network-modifying cation.

PubMed

Richet, Nicolas F

2012-01-21

The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b). © 2012 American Institute of Physics

Formation and stability of nanoemulsions with mixed ionic-nonionic surfactants.

PubMed

Wang, Lijuan; Tabor, Rico; Eastoe, Julian; Li, Xuefeng; Heenan, Richard K; Dong, Jinfeng

2009-11-14

A simple, low-energy two-step dilution process has been applied with binary mixtures of ionic-nonionic surfactants to prepare nanoemulsions. The systems consist of water/DDAB-C(12)E(5)/decane. Nanoemulsions were obtained by dilution of concentrates located in bicontinuous microemulsion or lamellar liquid crystal phase regions. The nanoemulsions generated were investigated both by contrast-variation small-angle neutron scattering (SANS) and dynamic light scattering (DLS). The SANS profiles show that C(12)E(5) nanodroplets suffer essentially no structural change on incorporation of the cationic DDAB surfactant, except for increased electrostatic repulsive interactions. Interestingly, SANS indicated that the preferred droplet sizes were hardly affected by the surfactant mixture composition (up to a DDAB molar ratio (m(DDAB)/(m(DDAB) + m(C(12)E(5))) of 0.40) and droplet volume fraction, phi, between 0.006 and 0.120. No notable changes in the structure or radius of nanoemulsion droplets were observed by SANS over the test period of 1 d, although the droplet number intensity decreased significantly in systems stabilized by C(12)E(5) only. However, the DLS sizing shows a marked increase with time, with higher droplet volume fractions giving rise to the largest changes. The discrepancy between apparent nanoemulsion droplet size determined by DLS and SANS data can be attributed to long-range droplet interactions occurring outside of the SANS sensitivity range. The combined SANS and DLS results suggest flocculation is the main mechanism of instability for these nanoemulsions. The flocculation rate is shown to be significantly retarded by addition of the charged DDAB, which may be due to enhanced electrostatic repulsive forces between droplets, leading to improved stability of the nanoemulsions.

Generalized stacking fault energies, cleavage energies, ionicity and brittleness of Cu(Al/Ga/In)Se2 and CuGa(S/Se/Te)2

NASA Astrophysics Data System (ADS)

Xue, H. T.; Tang, F. L.; Gruhn, T.; Lu, W. J.; Wan, F. C.; Rui, Z. Y.; Feng, Y. D.

2014-04-01

We calculate the generalized stacking fault (GSF) energies and cleavage energies γcl of the chalcopyrite compounds CuAlSe2, CuGaSe2, CuInSe2, CuGaS2 and CuGaTe2 using first principles. From the GSF energies, we obtain the unstable stacking fault energies γus and intrinsic stacking fault energies γisf. By analyzing γus and γisf, we find that the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) direction is the easiest slip direction for these five compounds. Also, for CuInSe2, it is most possible to undergo a dislocation-nucleation-induced plastic deformation along the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) slip direction. We show that the (1 1 2) plane is the preferable plane for fracture in the five compounds by comparing γcl of the (0 0 1) and (1 1 2) planes. It is also found that both γus and γcl decrease as the cationic or anionic radius increases in these chalcopyrites, i.e. along the sequences CuAlSe2 → CuGaSe2 → CuInSe2 and CuGaS2 → CuGaSe2 → CuGaTe2. Based on the values of the ratio γcl/γus, we discuss the brittle-ductile properties of these compounds. All of the compounds can be considered as brittle materials. In addition, a strong relationship between γcl/γus and the total proportion of ionic bonding in these compounds is found.

Structure and bulk modulus of Ln-doped UO2 (Ln = La, Nd) at high pressure

NASA Astrophysics Data System (ADS)

Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; Zhang, Lei; Palomares, Raul I.; Lang, Maik; Navrotsky, Alexandra; Mao, Wendy L.; Ewing, Rodney C.

2017-07-01

The structure of lanthanide-doped uranium dioxide, LnxU1-xO2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ∼50-55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ∼ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ∼ 0.25-0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. This trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO2, such as Young's modulus.

Biophysical characterization of V3-lipopeptide liposomes influencing HIV-1 infectivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rizos, Apostolos K.; Baritaki, Stavroula; Department of Virology, Medical School, University of Crete, Heraklion, Crete

2007-04-20

The V3-loop of the HIV-1 gp120 alters host cell immune function and modulates infectivity. We investigated biophysical parameters of liposome constructs with embedded lipopeptides from the principle neutralizing domain of the V3-loop and their influence on viral infectivity. Dynamic light scattering measurements showed liposome supramolecular structures with hydrodynamic radius of the order of 900 and 1300 nm for plain and V3-lipopeptide liposomes. Electron paramagnetic resonance measurements showed almost identical local microenvironment. The difference in liposome hydrodynamic radius was attributed to the fluctuating ionic environment of the V3-lipopeptide liposomes. In vitro HIV-1 infectivity assays showed that plain liposomes reduced virus productionmore » in all cell cultures, probably due to the hydrophobic nature of the aggregates. Liposomes carrying V3-lipopeptides with different cationic potentials restored and even enhanced infectivity (p < 0.05). These results highlight the need for elucidation of the involvement of lipid bilayers as dynamic components in supramolecular structures and in HIV-1 fusion mechanisms.« less

Membrane rejection of nitrogen compounds

NASA Technical Reports Server (NTRS)

Lee, S.; Lueptow, R. M.

2001-01-01

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

Structure and bulk modulus of Ln-doped UO 2 (Ln = La, Nd) at high pressure

DOE PAGES

Rittman, Dylan R.; Park, Sulgiye; Tracy, Cameron L.; ...

2017-04-10

The structure of lanthanide-doped uranium dioxide, Ln xU 1-xO 2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both themore » ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO 2, such as Young's modulus.« less

Influence of Zwitterions on Thermomechanical Properties and Morphology of Acrylic Copolymers: Implications for Electroactive Applications

DTIC Science & Technology

2011-09-30

transducers from branched sulfonated polysulfones.7 The mechanical strength of the membranes drastically decreased upon introduction of ionic liquids to... liquids ,8 and zwitterionomers maintained mechanical strengths upon swelling with 10 wt % ionic liquid . Zwitterions are chargedmolecules that contain...water purification5 to biotechnology.6 A unique combination of physical properties of ionomeric membranes is the ionic con- ductivity of lowmolar mass

Ionic liquids as novel solvents for ionic polymer transducers

NASA Astrophysics Data System (ADS)

Bennett, Matthew D.; Leo, Donald J.

2004-07-01

The use of ionic liquids as solvents for ionic polymer (specifically, Nafion) transducers is demonstrated. Ionic liquids are attractive for this application because of their high inherent stability. Ionic liquids are salts that exist as liquids at room temperature and have no measureable vapor pressure. Therefore, the use of ionic liquids as solvents for ionic polymer transducers can eliminate the traditional problem of water evaporation in these devices. Another benefit of the use of ionic liquids in this way is the reduction or elimination of the characteristic back-relaxation common in water-solvated ionic polymer actuators. The results demonstrate that the viscosity of the ionic liquid and the degree to which the ionic liquid swells the membrane are the important physical parameters to consider. Five ionic liquids were studied, based on substituted pyrrolidinium, phosphonium, or imidazolium cations and fluoroanions. Of these five ionic liquids, transduction is demonstrated in three of them and the best results are obtained with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid. This substance has an electrochemical stability window of 4.1 V, a melting point of -10 °C, and a viscosity of 35-45 cP [19]. Results demonstrate that platinum-plated Nafion transducers solvated with this ionic liquid exhibit sensing and actuation responses and that these transducers are stable in air. Endurance testing of this sample reveals a decrease in the free strain of only 25 % after 250,000 actuation cycles in air.

Improving Cellulose Dissolution in Ionic Liquids by Tuning the Size of the Ions: Impact of the Length of the Alkyl Chains in Tetraalkylammonium Carboxylate.

PubMed

Meng, Xiangqian; Devemy, Julien; Verney, Vincent; Gautier, Arnaud; Husson, Pascale; Andanson, Jean-Michel

2017-04-22

Twenty ionic liquids based on tetraalkylammonium cations and carboxylate anions have been synthesized, characterized, and tested for cellulose dissolution. The amount of cellulose dissolved in these ionic liquids depends strongly on the size of the ions: from 0 to 22 wt % cellulose can be dissolved at 90 °C. The best ionic liquids are less viscous and ammonium carboxylate based ionic liquids can dissolve as much as imidazolium-based ones. The viscosity of an ionic liquid can be decreased by the addition of DMSO as a cosolvent. After the addition of cosolvent, similar amounts of cellulose per ions are reached for most ionic liquids. As observed by rheology, ionic liquids with the longest alkyl chains form a gel when a high amount of cellulose is dissolved; this drastically limits their potential. Molecular simulations and IR spectroscopy have also been used with the aim of understanding how molecular interactions differ between efficient and inefficient ionic liquids. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Influence of non-ionic surfactants on sludge dewaterability].

PubMed

Hou, Hai-Pan; Pu, Wen-Hong; Shi, Ya-Fei; Yu, Wen-Hua; Fan, Ming-Ming; Liu, Huan; Yang, Chang-Zhu; Li, Ye; Yang, Jia-Kuan

2012-06-01

The water content of dewatered sludge cake decreases to about 80% by current sludge dewatering technologies, which hardly satisfies the stricter standards of sludge disposal. In order to evaluate the effects of non-ionic surfactants on sludge dewaterability, two kinds of non-ionic surfactants (OPEO and APG) were studied by using two evaluation indexes, i. e. , specific resistance to filtration (SRF) and dewatering efficiency. Moreover, morphologies of conditioned sewage sludge and raw sludge were comparatively investigated. Results showed that non-ionic surfactants can decrease the particle size of sewage sludge floc and generate more homogenous and regular shape, and then improve the dewatering efficiency. APG has better effect on sewage sludge dewatering than OPEO. SRF of conditioned sludge with APG dosage of 0.05% DS decreased to 42% of SRF of raw sludge, and its dewatering efficiency was as high as 93%. Plate-frame pressure filter experiment demonstrated that, the water content of dewatered cake conditioned with APG dosage of 0.05% DS was lower by about 10% than that of dewatered cake without APG, and its dewatering efficiency reached 97%. Therefore, this research provides some reference for the application of APG in sludge dewatering.

A molecular dynamics study of lithium-containing aprotic heterocyclic ionic liquid electrolytes

NASA Astrophysics Data System (ADS)

Lourenço, Tuanan C.; Zhang, Yong; Costa, Luciano T.; Maginn, Edward J.

2018-05-01

Classical molecular dynamics simulations were performed on twelve different ionic liquids containing aprotic heterocyclic anions doped with Li+. These ionic liquids have been shown to be promising electrolytes for lithium ion batteries. Self-diffusivities, lithium transference numbers, densities, and free volumes were computed as a function of lithium concentration. The dynamics and free volume decreased with increasing lithium concentration, and the trends were rationalized by examining the changes to the liquid structure. Of those examined in the present work, it was found that (methyloxymethyl)triethylphosphonium triazolide ionic liquids have the overall best performance.

Systematic variation of rare earths in monazite

USGS Publications Warehouse

Murata, K.J.; Rose, H.J.; Carron, M.K.

1953-01-01

Ten monazites from widely scattered localities have been analyzed for La, Ce, Pr, Nd, Sm, Gd, Y and Th by means of a combined chemical and emission spectrographic method. The analytical results, calculated to atomic percent of total rare earths (thorium excluded), show a considerable variation in the proportions of every element except praseodymium, which is relatively constant. The general variation trends of the elements may be calculated by assuming that the monazites represent different stages in a fractional precipitation process, and by assuming that there is a gradational increase in the precipitability of rare earth elements with decreasing ionic radius. Fractional precipitation brings about an increase in lanthanum and cerium, little change in praseodymium, and a decrease in neodymium, samarium, gadolinium, and yttrium. Deviations from the calculated lines of variation consist of a simultaneous, abnormal increase or decrease in the proportions of cerium, praseodymium, and neodymium with antipathetic decrease or increase in the proportions of the other elements. These deviations are ascribed to abnormally high or low temperatures that affect the precipitability of the central trio of elements (Ce, Pr, Nd) relatively more than that of the other elements. The following semiquantitative rules have been found useful in describing the composition of rare earths from monazite: 1. 1. The sum of lanthanum and neodymium is very nearly a constant at 42 ?? 2 atomic percent. 2. 2. Praseodymium is very nearly constant at 5 ?? 1 atomic percent. 3. 3. The sum of Ce, Sm, Gd, and Y is very nearly a constant at 53 ?? 3 atomic percent. No correlation could be established between the content of Th and that of any of the rare earth elements. ?? 1953.

Handling performance control for hybrid 8-wheel-drive vehicle and simulation verification

NASA Astrophysics Data System (ADS)

Ni, Jun; Hu, Jibin

2016-08-01

In order to improve handling performance of a hybrid 8-Wheel-Drive vehicle, the handling performance control strategy was proposed. For armoured vehicle, besides handling stability in high speed, the minimum steer radius in low speed is also a key tactical and technical index. Based on that, the proposed handling performance control strategy includes 'Handling Stability' and 'Radius Minimization' control modes. In 'Handling Stability' control mode, 'Neutralsteer Radio' is defined to adjust the steering characteristics to satisfy different demand in different speed range. In 'Radius Minimization' control mode, the independent motors are controlled to provide an additional yaw moment to decrease the minimum steer radius. In order to verify the strategy, a simulation platform was built including engine and continuously variable transmission systems, generator and battery systems, independent motors and controllers systems, vehicle dynamic and tyre mechanical systems. The simulation results show that the handling performance of the vehicle can be enhanced significantly, and the minimum steer radius can be decreased by 20% which is significant improvement compared to the common level of main battle armoured vehicle around the world.

Interconnected ionic domains enhance conductivity in microphase separated block copolymer electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arges, Christopher G.; Kambe, Yu; Dolejsi, Moshe

Block copolymer electrolytes (BCEs) represent an attractive choice as solid-state ionic conductors for electrochemical technologies used in energy storage and conversion, water treatment, sensors, and data storage and processing. Unlocking the maximum ionic conductivity of BCEs requires an intimate understanding as to how the microphase separated structure influences transport properties. However, elucidating such knowledge remains elusive due to the challenging task of precisely engineering BCEs with a defined structure in bulk materials. In this work, we examined BCEs in a thin film format because it was amenable to attaining BCEs with a desired nanostructure. Specifically, we systematically investigated anion-conducting BCEsmore » with different degrees of connectivity of the ionic domains. For the first time, we demonstrate that increasing terminal defects in the ionic domain from 1 terminal defect per mu m(2) to 20 terminal defects per mu m(2) ( a relatively small amount of defects) decreased ionic conductivity by 67% compared to the maximum value attained. Conversely, maximizing ionic domain connectivity increased the ionic conductivity by two-fold over a non-ordered BCE film. These experiments highlight that microphase separation alone was insufficient for ameliorating ionic conductivity in BCEs. Rather, microphase separation coupled with complete ionic domain connectivity realized BCEs with significantly enhanced ionic conductivity.« less

Diversity of band gap and photoluminescence properties of lead halide perovskite: A halogen-dependent spectroscopic study

NASA Astrophysics Data System (ADS)

Yu, Wenlei; Jiang, Yunfeng; Zhu, Xiuwei; Luo, Chunhua; Jiang, Kai; Chen, Liangliang; Zhang, Juan

2018-05-01

The effects of halogen substitution on microstructure, optical absorption, and phonon modes for perovskite CH3NH3PbX3 (MAPbX3, X = I/Br/Cl) films grown on FTO substrates have been investigated. The X-ray diffraction analysis exhibited good crystallization, and the strong diffraction peak assigned to (1 0 0) c for X = Br/Cl shifted toward a higher angle compared to (1 1 0) t of MAPbI3. Band-gap tuning from 1.63 to 2.37 to 3.11 eV in the I-Br-Cl series can be found due to the halogen effects. These energy values closely match the positions of peak determined from photoluminescence experiments. The remarkable absorption dip and emission peak appear for the MAPbBr3, suggesting higher crystallinity under the same preparation conditions. The wavenumbers of main IR-vibrations slightly decrease with ionic radius of the halogen increasing (in the order of Cl-Br-I), which related to the increasing polarizability. These results provide important progress towards the understanding of the halide role in the realization of high performance MAPbX3-based solar cells.

Effect of iron doping at Mn-site on complex impedance spectroscopy properties of Nd0.67Ba0.33MnO3 perovskite

NASA Astrophysics Data System (ADS)

Hsini, Mohamed; Hamdaoui, Nejeh; Hcini, Sobhi; Bouazizi, Mohamed Lamjed; Zemni, Sadok; Beji, Lotfi

2018-03-01

The effect of Fe-doping at Mn-site on the structural and electrical properties of Nd0.67Ba0.33Mn1-xFexO3 (0 ≤ x ≤ 0.05) perovskites has been investigated. X-ray diffraction patterns show that the structural parameters change slightly due to the fact that the Fe3+ ions replacing the Mn3+ have similar ionic radius. The electrical properties of these samples have been investigated using complex impedance spectroscopy technique. a function of the frequency at different temperatures. When increasing the Fe-content, a decrease of dc conductivity was observed throughout the whole explored temperature range and the deduced activation energy values are found to increase from 128 meV for x = 0 to 166 meV for x = 0.05. The curves of the imaginary part of impedance (Z″) show the presence of relaxation phenomenon in our samples. The complex impedance spectra show semicircle arcs at different temperatures and an equivalent circuit of the type of Rg + (Rgb//Cgb) has been proposed to explain the impedance results.

Synthesis, morphology and electrical properties of Co2+ substituted NiCuZn ferrites for MLCI applications

NASA Astrophysics Data System (ADS)

Kabbur, S. M.; Waghmare, S. D.; Ghodake, U. R.; Suryavanshi, S. S.

2018-04-01

Co2+ is a fast relaxing ion which can enhance microwave properties. This work focuses on the synthesis and analysis of Ni0.25-xCoxCu0.30Zn0.45Fe2O4 (x = 0.00, 0.05, 0.01, 0.15, 0.20 and 0.25) ferrites by auto combustion method using glycine as the chelating agent. From X-ray Diffraction (XRD) spectra, the structural parameters are analysed. The lattice parameter (a) decreases due to smaller ionic radius of Co2+ (0.072 nm) which replaces Ni2+ (0.078 nm). Bulk density and porosity measurements show that there are pores and lattice imperfections. The cation distribution of the ferrites based on Neel's two sublattice model is proposed. Transmission Electron Micrographs (TEM) indicate narrow size distribution of spherical shaped nanoparticles. DC electrical resistivity (ρD.C.) is very important factor of low temperature sintered ferrites for MLCI applications. Electroplating of the devices is much affected by electrical resistivity. Maximum DC resistivity (2.89 × 106 Ω-cm) is observed for the sample with x=0.20. The dielectric parameters (ɛ', ɛ″ and tan δ) decrease as the alternating field increases which is due to space charge distribution and hopping mechanism. AC resistivity (ρAC) decreases with frequency, increased concentration of Fe2+ ions induces electron hopping: Fe3+ ↔ Fe2+ at B sites thereby reducing the resistivity. The low dielectric loss factor of 0.07 for x=0.20 ferrite indicates that the sample can be potential candidate for MLCI applications.

Optimization of post-column reactor radius in capillary high performance liquid chromatography Effect of chromatographic column diameter and particle diameter

PubMed Central

Xu, Hongjuan; Weber, Stephen G.

2006-01-01

A post-column reactor consisting of a simple open tube (Capillary Taylor Reactor) affects the performance of a capillary LC in two ways: stealing pressure from the column and adding band spreading. The former is a problem for very small radius reactors, while the latter shows itself for large reactor diameters. We derived an equation that defines the observed number of theoretical plates (Nobs) taking into account the two effects stated above. Making some assumptions and asserting certain conditions led to a final equation with a limited number of variables, namely chromatographic column radius, reactor radius and chromatographic particle diameter. The assumptions and conditions are that the van Deemter equation applies, the mass transfer limitation is for intraparticle diffusion in spherical particles, the velocity is at the optimum, the analyte’s retention factor, k′, is zero, the post-column reactor is only long enough to allow complete mixing of reagents and analytes and the maximum operating pressure of the pumping system is used. Optimal ranges of the reactor radius (ar) are obtained by comparing the number of observed theoretical plates (and theoretical plates per time) with and without a reactor. Results show that the acceptable reactor radii depend on column diameter, particle diameter, and maximum available pressure. Optimal ranges of ar become narrower as column diameter increases, particle diameter decreases or the maximum pressure is decreased. When the available pressure is 4000 psi, a Capillary Taylor Reactor with 12 μm radius is suitable for all columns smaller than 150 μm (radius) packed with 2–5 μm particles. For 1 μm packing particles, only columns smaller than 42.5 μm (radius) can be used and the reactor radius needs to be 5 μm. PMID:16494886

Sulfide bonded atomic radii

NASA Astrophysics Data System (ADS)

Gibbs, G. V.; Ross, N. L.; Cox, D. F.

2017-09-01

The bonded radius, r b(S), of the S atom, calculated for first- and second-row non-transition metal sulfide crystals and third-row transition metal sulfide molecules and crystals indicates that the radius of the sulfur atom is not fixed as traditionally assumed, but that it decreases systematically along the bond paths of the bonded atoms with decreasing bond length as observed in an earlier study of the bonded radius of the oxygen atom. When bonded to non-transition metal atoms, r b(S) decreases systematically with decreasing bond length from 1.68 Å when the S atom is bonded to the electropositive VINa atom to 1.25 Å when bonded to the more electronegative IVP atom. In the case of transition metal atoms, rb(S) likewise decreases with decreasing bond length from 1.82 Å when bonded to Cu and to 1.12 Å when bonded to Fe. As r b(S) is not fixed at a given value but varies substantially depending on the bond length and the field strength of the bonded atoms, it is apparent that sets of crystal and atomic sulfide atomic radii based on an assumed fixed radius for the sulfur atom are satisfactory in that they reproduce bond lengths, on the one hand, whereas on the other, they are unsatisfactory in that they fail to define the actual sizes of the bonded atoms determined in terms of the minima in the electron density between the atoms. As such, we urge that the crystal chemistry and the properties of sulfides be studied in terms of the bond lengths determined by adding the radii of either the atomic and crystal radii of the atoms but not in terms of existing sets of crystal and atomic radii. After all, the bond lengths were used to determine the radii that were experimentally determined, whereas the individual radii were determined on the basis of an assumed radius for the sulfur atom.

Radial position-momentum uncertainties for the infinite circular well and Fisher entropy

NASA Astrophysics Data System (ADS)

Torres-Arenas, Ariadna J.; Dong, Qian; Sun, Guo-Hua; Dong, Shi-Hai

2018-07-01

We show how the product of the radial position and momentum uncertainties can be obtained analytically for the infinite circular well potential. Some interesting features are found. First, the uncertainty Δr increases with the radius R and the quantum number n, the n-th root of the Bessel function. The variation of the Δr is almost independent of the quantum number n for n > 4 and it will arrive to a constant for a large n, say n > 4. Second, we find that the relative dispersion Δr / 〈 r 〉 is independent of the radius R. Moreover, the relative dispersion increases with the quantum number n but decreases with the azimuthal quantum number m. Third, the momentum uncertainty Δp decreases with the radius R and increases with the quantum numbers m > 1 and n. Fourth, the product ΔrΔpr of the position-momentum uncertainty relations is independent of the radius R and increases with the quantum numbers m and n. Finally, we present the analytical expression for the Fisher entropy. Notice that the Fisher entropy decreases with the radius R and it increases with the quantum numbers m > 0 and n. Also, we find that the Cramer-Rao uncertainty relation is satisfied and it increases with the quantum numbers m > 0 and n, too.

Excitation wavelength dependence of excited state intramolecular proton transfer reaction of 4'-N,N-diethylamino-3-hydroxyflavone in room temperature ionic liquids studied by optical Kerr gate fluorescence measurement.

PubMed

Suda, Kayo; Terazima, Masahide; Sato, Hirofumi; Kimura, Yoshifumi

2013-10-17

Excited state intramolecular proton transfer reactions (ESIPT) of 4'-N,N-diethylamino-3-hydroxyflavone (DEAHF) in ionic liquids have been studied by steady-state and time-resolved fluorescence measurements at different excitation wavelengths. Steady-state measurements show the relative yield of the tautomeric form to the normal form of DEAHF decreases as excitation wavelength is increased from 380 to 450 nm. The decrease in yield is significant in ionic liquids that have cations with long alkyl chains. The extent of the decrease is correlated with the number of carbon atoms in the alkyl chains. Time-resolved fluorescence measurements using optical Kerr gate spectroscopy show that ESIPT rate has a strong excitation wavelength dependence. There is a large difference between the spectra at a 200 ps delay from different excitation wavelengths in each ionic liquid. The difference is pronounced in ionic liquids having a long alkyl chain. The equilibrium constant in the electronic excited state obtained at a 200 ps delay and the average reaction rate are also correlated with the alkyl chain length. Considering the results of the steady-state fluorescence and time-resolved measurements, the excitation wavelength dependence of ESIPT is explained by state selective excitation due to the difference of the solvation, and the number of alkyl chain carbon atoms is found to be a good indicator of the effect of inhomogeneity for this reaction.

Understanding the impact of nanoscale aggregation on charge transport and structural dynamics in room temperature ionic liquids

NASA Astrophysics Data System (ADS)

Griffin, Philip; Holt, Adam; Wang, Yangyang; Sokolov, Alexei

2015-03-01

Amphiphilic room temperature ionic liquids (ILs) segregate on the nanoscale, forming intricate networks of charge-rich ionic domains intercalated with charge-poor aliphatic domains. While this structural phenomenon has been well established through x-ray diffraction studies and atomistic MD simulations, the precise effects of nanophase segregation on ion transport and structural dynamics in ILs remains poorly understood. Using a combination of broadband dielectric spectroscopy, light scattering spectroscopy, and rheology, we have characterized the ionic conductivity, structural dynamics, and shear viscosity of a homologous series of quaternary ammonium ionic liquids over a wide temperature range. Upon increasing the length and volume fraction of the alkyl side chains of these quaternary ammonium ILs, ionic conductivity decreases precipitously, although no corresponding slowing of the structural dynamics is observed. Instead, we identify the dynamical signature of supramolecular aggregates. Our results directly demonstrate the role that chemical structure and ionic aggregation plays in determining the charge transport properties of amphiphilic ILs.

Predictive model for ionic liquid extraction solvents for rare earth elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grabda, Mariusz; Oleszek, Sylwia; Institute of Environmental Engineering of the Polish Academy of Sciences, ul. M. Sklodowskiej-Curie 34, 41-819, Zabrze

2015-12-31

The purpose of our study was to select the most effective ionic liquid extraction solvents for dysprosium (III) fluoride using a theoretical approach. Conductor-like Screening Model for Real Solvents (COSMO-RS), based on quantum chemistry and the statistical thermodynamics of predefined DyF{sub 3}-ionic liquid systems, was applied to reach the target. Chemical potentials of the salt were predicted in 4,400 different ionic liquids. On the base of these predictions set of ionic liquids’ ions, manifesting significant decrease of the chemical potentials, were selected. Considering the calculated physicochemical properties (hydrophobicity, viscosity) of the ionic liquids containing these specific ions, the most effectivemore » extraction solvents for liquid-liquid extraction of DyF{sub 3} were proposed. The obtained results indicate that the COSMO-RS approach can be applied to quickly screen the affinity of any rare earth element for a large number of ionic liquid systems, before extensive experimental tests.« less

Hg⁰ removal from flue gas by ionic liquid/H₂O₂.

PubMed

Cheng, Guangwen; Bai, Bofeng; Zhang, Qiang; Cai, Ming

2014-09-15

1-Alkyl-3-methylimidazolium chloride ionic liquids ([Cnmim] Cl, n=4, 6, 8) were prepared. The ionic liquid was then mixed with hydrogen peroxide (H2O2) to form an absorbent. The Hg(0) removal performance of the absorbent was investigated in a gas/liquid scrubber using simulated flue gas. It was found that the ionic liquid/H2O2 mixture was an excellent absorbent and could be used to remove Hg(0) from flue gas. When the mass ratio of H2O2 to ionic liquid was 0.5, the absorbent showed high Hg(0) removal efficiency (up to 98%). The Hg(0) removal efficiency usually increased with the absorption temperature, while decreased with the increase of alkyl chain length in ionic liquid molecule. The Hg(0) removal mechanism involved with Hg(0) oxidation by H2O2 and Hg(2+) transfer from aqueous phase to ionic liquid phase. Copyright © 2014 Elsevier B.V. All rights reserved.

Excess plasma membrane and effects of ionic amphipaths on mechanics of outer hair cell lateral wall.

PubMed

Morimoto, Noriko; Raphael, Robert M; Nygren, Anders; Brownell, William E

2002-05-01

The interaction between the outer hair cell (OHC) lateral wall plasma membrane and the underlying cortical lattice was examined by a morphometric analysis of cell images during cell deformation. Vesiculation of the plasma membrane was produced by micropipette aspiration in control cells and cells exposed to ionic amphipaths that alter membrane mechanics. An increase of total cell and vesicle surface area suggests that the plasma membrane possesses a membrane reservoir. Chlorpromazine (CPZ) decreased the pressure required for vesiculation, whereas salicylate (Sal) had no effect. The time required for vesiculation was decreased by CPZ, indicating that CPZ decreases the energy barrier required for vesiculation. An increase in total volume is observed during micropipette aspiration. A deformation-induced increase in hydraulic conductivity is also seen in response to micropipette-applied fluid jet deformation of the lateral wall. Application of CPZ and/or Sal decreased this strain-induced hydraulic conductivity. The impact of ionic amphipaths on OHC plasma membrane and lateral wall mechanics may contribute to their effects on OHC electromotility and hearing.

Ionic liquid as an electrolyte additive for high performance lead-acid batteries

NASA Astrophysics Data System (ADS)

Deyab, M. A.

2018-06-01

The performance of lead-acid battery is improved in this work by inhibiting the corrosion of negative battery electrode (lead) and hydrogen gas evolution using ionic liquid (1-ethyl-3-methylimidazolium diethyl phosphate). The results display that the addition of ionic liquid to battery electrolyte (5.0 M H2SO4 solution) suppresses the hydrogen gas evolution to very low rate 0.049 ml min-1 cm-2 at 80 ppm. Electrochemical studies show that the adsorption of ionic liquid molecules on the lead electrode surface leads to the increase in the charge transfer resistance and the decrease in the double layer capacitance. I also notice a noteworthy improvement of battery capacity from 45 mAh g-1 to 83 mAh g-1 in the presence of ionic liquid compound. Scanning electron microscopy and energy dispersive X-ray analysis confirm the adsorption of ionic liquid molecules on the battery electrode surface.

Chemical association in simple models of molecular and ionic fluids. III. The cavity function

NASA Astrophysics Data System (ADS)

Zhou, Yaoqi; Stell, George

1992-01-01

Exact equations which relate the cavity function to excess solvation free energies and equilibrium association constants are rederived by using a thermodynamic cycle. A zeroth-order approximation, derived previously by us as a simple interpolation scheme, is found to be very accurate if the associative bonding occurs on or near the surface of the repulsive core of the interaction potential. If the bonding radius is substantially less than the core radius, the approximation overestimates the association degree and the association constant. For binary association, the zeroth-order approximation is equivalent to the first-order thermodynamic perturbation theory (TPT) of Wertheim. For n-particle association, the combination of the zeroth-order approximation with a ``linear'' approximation (for n-particle distribution functions in terms of the two-particle function) yields the first-order TPT result. Using our exact equations to go beyond TPT, near-exact analytic results for binary hard-sphere association are obtained. Solvent effects on binary hard-sphere association and ionic association are also investigated. A new rule which generalizes Le Chatelier's principle is used to describe the three distinct forms of behaviors involving solvent effects that we find. The replacement of the dielectric-continuum solvent model by a dipolar hard-sphere model leads to improved agreement with an experimental observation. Finally, equation of state for an n-particle flexible linear-chain fluid is derived on the basis of a one-parameter approximation that interpolates between the generalized Kirkwood superposition approximation and the linear approximation. A value of the parameter that appears to be near optimal in the context of this application is obtained from comparison with computer-simulation data.

Crystal structures of (Mg1-x,Fex)SiO3postperovskite at high pressures

PubMed Central

Yamanaka, Takamitsu; Hirose, Kei; Mao, Wendy L.; Meng, Yue; Ganesh, P.; Shulenburger, Luke; Shen, Guoyin; Hemley, Russell J.

2012-01-01

X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg0.9Fe0.1)SiO3 and (Mg0.6Fe0.4)SiO3 at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO3-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density (ρ = 6.119(1) g/cm3) than the former (ρ = 5.694(8) g/cm3) due to both the larger amount of iron and the smaller ionic radius of Fe2+ as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe2+ also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe2+ in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered. PMID:22223656

Short-time vibrational dynamics of metaphosphate glasses

NASA Astrophysics Data System (ADS)

Kalampounias, Angelos G.

2012-02-01

In this paper we present the picosecond vibrational dynamics of a series of binary metaphosphate glasses, namely Na2O-P2O5, MO-P2O5 (M=Ba, Sr, Ca, Mg) and Al2O3-3P2O5 by means of Raman spectroscopy. We studied the vibrational dephasing and vibrational frequency modulation by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The fitting method used enables one to model the real line profiles intermediate between Lorentzian and Gaussian by an analytical function, which has an analytical counterpart in the time domain. The symmetric stretching modes νs(PO2-) and νs(P-O-P) of the PO2- entity of PØ2O2- units and of P-O-P bridges in metaphosphate arrangements have been investigated by Raman spectroscopy and we used them as probes of the dynamics of these glasses. The vibrational time correlation functions of both modes studied are rather adequately interpreted within the assumption of exponential modulation function in the context of Kubo-Rothschield theory and indicate that the system experiences an intermediate dynamical regime that gets only slower with an increase in the ionic radius of the cation-modifier. We found that the vibrational correlation functions of all glasses studied comply with the Rothschild approach assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α with increasing ionic radius of the cation indicates the deviation from the model simple liquid indicating the reduction of the coherence decay in the perturbation potential as a result of local short lived aggregates. The results are discussed in the framework of the current phenomenological status of the field.

Enzyme activity in dialkyl phosphate ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, M.F.; Dunn, J.; Li, L.-L.

2011-12-01

The activity of four metagenomic enzymes and an enzyme cloned from the straw mushroom, Volvariellavolvacea were studied in the following ionic liquids, 1,3-dimethylimidazolium dimethyl phosphate, [mmim][dmp], 1-ethyl-3-methylimidazolium dimethyl phosphate, [emim][dmp], 1-ethyl-3-methylimidazolium diethyl phosphate, [emim][dep] and 1-ethyl-3-methylimidazolium acetate, [emim][OAc]. Activity was determined by analyzing the hydrolysis of para-nitrobenzene carbohydrate derivatives. In general, the enzymes were most active in the dimethyl phosphate ionic liquids, followed by acetate. Generally speaking, activity decreased sharply for concentrations of [emim][dep] above 10% v/v, while the other ionic liquids showed less impact on activity up to 20% v/v.

Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution.

PubMed

Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

2016-05-19

Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances.

Enhancement of force generated by individual myosin heads in skinned rabbit psoas muscle fibers at low ionic strength.

PubMed

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca(2+)-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca(2+)-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca(2+)-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca(2+) activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca(2+)-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca(2+)-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction.

Tension in Skinned Frog Muscle Fibers in Solutions of Varying Ionic Strength and Neutral Salt Composition

PubMed Central

Gordon, A. M.; Godt, R. E.; Donaldson, S. K. B.; Harris, C. E.

1973-01-01

The maximal calcium-activated isometric tension produced by a skinned frog single muscle fiber falls off as the ionic strength of the solution bathing this fiber is elevated declining to zero near 0.5 M as the ionic strength is varied using KCl. When other neutral salts are used, the tension always declines at high ionic strength, but there is some difference between the various neutral salts used. The anions and cations can be ordered in terms of their ability to inhibit the maximal calcium-activated tension. The order of increasing inhibition of tension (decreasing tension) at high ionic strength for anions is propionate- ≃ SO4 -- < Cl- < Br-. The order of increasing inhibition of calcium-activated tension for cations is K+ ≃ Na+ ≃ TMA+ < TEA+ < TPrA+ < TBuA+. The decline of maximal calcium-activated isometric tension with elevated salt concentration (ionic strength) can quantitatively explain the decline of isometric tetanic tension of a frog muscle fiber bathed in a hypertonic solution if one assumes that the internal ionic strength of a muscle fiber in normal Ringer's solution is 0.14–0.17 M. There is an increase in the base-line tension of a skinned muscle fiber bathed in a relaxing solution (no added calcium and 3 mM EGTA) of low ionic strength. This tension, which has no correlate in the intact fiber in hypotonic solutions, appears to be a noncalcium-activated tension and correlates more with a declining ionic strength than with small changes in [MgATP], [Mg], pH buffer, or [EGTA]. It is dependent upon the specific neutral salts used with cations being ordered in increasing inhibition of this noncalcium-activated tension (decreasing tension) as TPrA+ < TMA+ < K+ ≃ Na+. Measurements of potentials inside these skinned muscle fibers bathed in relaxing solutions produced occasional small positive values (<6 mV) which were not significantly different from zero. PMID:4543066

Efficient removal of H2S at high temperature using the ionic liquid solutions of [C4mim]3PMo12O40-An organic polyoxometalate.

PubMed

Ma, Yunqian; Liu, Xinpeng; Wang, Rui

2017-06-05

An innovative approach to H 2 S capture and sulfur recovery via liquid redox at high temperature has been developed using [C 4 mim] 3 PMo 12 O 40 at temperatures ranging from 80 to 180°C, which is superior to the conventional water-based system with an upper limit of working temperature normally below 60°C. The ionic liquids used as solvents include [C 4 mim]Cl, [C 4 mim]BF 4 , [C 4 mim]PF 6 and [C 4 mim]NTf 2 . Microscopic observation and turbidity measurement were used to investigate the dissolution of [C 4 mim] 3 PMo 12 O 40 in the ionic liquids. Stabilization energy between H 2 S and the anion of ionic liquid as well as H 2 O was calculated to illustrate the interaction between H 2 S and the solvents. The cavity theory can be adopted to illustrate the mechanism for H 2 S absorption: the Cl - ion with small radius can be incorporated into the cavities of [C 4 mim] 3 PMo 12 O 40 , and interact with H 2 S strongly. The underlying mechanism for sulfur formation is the redox reaction between H 2 S and PMo 12 O 40 3- . H 2 S can be oxidized to elemental sulfur and Mo 6+ is partly reduced during absorption, according to UV-vis and FTIR spectra. The [C 4 mim] 3 PMo 12 O 40 -[C 4 mim]Cl after reaction can be readily regenerated by air and thus enabling its efficient and repeatitive use. The absorbent of [C 4 mim] 3 PMo 12 O 40 -ionic liquid system provides a new approach for wet oxidation desulfurization at high temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of ionic strength and OH(-) ion concentration on the Cu(II) complex formation with EDTA in alkaline solutions.

PubMed

Norkus, E; Vaskelis, A; Zakaite, I

1996-03-01

D.c. polarographic data show that the complex formation of copper ions with EDTA depends markedly on the ionic strength of the solution at pH 8-10. This is primarily associated with the dependence of the fourth deprotonization constant of EDTA on the solution ionic strength: when it increases from 0.4 to 3.4, the pK(a4) value decreases from 9.5 to 8.2. According to polarographic and spectrophotometric data the degree of Cu(II) complexation increases at pH>10 due to transformation of the complex CuY(2-) to the more stable CuY(OH)(3-) (Y(4-), a fully deprotonized anion of EDTA), but it decreases with increase in alkalinity in a highly alkaline solution (pH>13.5). The latter result could be explained by the decrease in the EDTA anion activity. The calculated values of the activity coefficient are lower than 0.05 at pH>14.

Removal of organic contaminants by RO and NF membranes

NASA Technical Reports Server (NTRS)

Yoon, Yeomin; Lueptow, Richard M.

2005-01-01

Rejection characteristics of organic and inorganic compounds were examined for six reverse osmosis (RO) membranes and two nanofiltration (NF) membranes that are commercially available. A batch stirred-cell was employed to determine the membrane flux and the solute rejection for solutions at various concentrations and different pH conditions. The results show that for ionic solutes the degree of separation is influenced mainly by electrostatic exclusion, while for organic solutes the removal depends mainly upon the solute radius and molecular structure. In order to provide a better understanding of rejection mechanisms for the RO and NF membranes, the ratio of solute radius (r(i,s)) to effective membrane pore radius (r(p)) was employed to compare rejections. An empirical relation for the dependence of the rejection of organic compounds on the ratio r(i,s)/r(p) is presented. The rejection for organic compounds is over 75% when r(i,s)/r(p) is greater than 0.8. In addition, the rejection of organic compounds is examined using the extended Nernst-Planck equation coupled with a steric hindrance model. The transport of organic solutes is controlled mainly by diffusion for the compounds that have a high r(i,s)/r(p) ratio, while convection is dominant for compounds that have a small r(i,s)/r(p) ratio. c2005 Elsevier B.V. All rights reserved.

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

PubMed Central

Muthukumar, M.

2012-01-01

Polyelectrolyte chains are well known to be strongly correlated even in extremely dilute solutions in the absence of additional strong electrolytes. Such correlations result in severe difficulties in interpreting light scattering measurements in the determination of the molecular weight, radius of gyration, and the second virial coefficient of charged macromolecules at lower ionic strengths from added strong electrolytes. By accounting for charge-regularization of the polyelectrolyte by the counterions, we present a theory of the apparent molecular weight, second virial coefficient, and the intermolecular structure factor in dilute polyelectrolyte solutions in terms of concentrations of the polymer and the added strong electrolyte. The counterion adsorption of the polyelectrolyte chains to differing levels at different concentrations of the strong electrolyte can lead to even an order of magnitude discrepancy in the molecular weight inferred from light scattering measurements. Based on counterion-mediated charge regularization, the second virial coefficient of the polyelectrolyte and the interchain structure factor are derived self-consistently. The effect of the interchain correlations, dominating at lower salt concentrations, on the inference of the radius of gyration and on molecular weight is derived. Conditions for the onset of nonmonotonic scattering wave vector dependence of scattered intensity upon lowering the electrolyte concentration and interpretation of the apparent radius of gyration are derived in terms of the counterion adsorption mechanism. PMID:22830728

Internal electric fields of electrolytic solutions induced by space-charge polarization

NASA Astrophysics Data System (ADS)

Sawada, Atsushi

2006-10-01

The dielectric dispersion of electrolytic solutions prepared using chlorobenzene as a solvent and tetrabutylammonium tetraphenylborate as a solute is analyzed in terms of space-charge polarization in order to derive the ionic constants, and the Stokes radius obtained is discussed in comparison with the values that have been measured by conductometry. A homogeneous internal electric field is assumed for simplicity in the analysis of the space-charge polarization. The justification of the approximation by the homogeneous field is discussed from two points of view: one is the accuracy of the Stokes radius value observed and the other is the effect of bound charges on electrodes in which they level the highly inhomogeneous field, which has been believed in the past. In order to investigate the actual electric field, numerical calculations based on the Poisson equation are carried out by considering the influence of the bound charges. The variation of the number of bound charges with time is clarified by determining the relaxation function of the dielectric constant attributed to the space-charge polarization. Finally, a technique based on a two-field approximation, where homogeneous and hyperbolic fields are independently applied in relevant frequency ranges, is introduced to analyze the space-charge polarization of the electrolytic solutions, and further improvement of the accuracy in the determination of the Stokes radius is achieved.

Non-equilibrium diffusion combustion of a fuel droplet

NASA Astrophysics Data System (ADS)

Tyurenkova, Veronika V.

2012-06-01

A mathematical model for the non-equilibrium combustion of droplets in rocket engines is developed. This model allows to determine the divergence of combustion rate for the equilibrium and non-equilibrium model. Criterion for droplet combustion deviation from equilibrium is introduced. It grows decreasing droplet radius, accommodation coefficient, temperature and decreases on decreasing diffusion coefficient. Also divergence from equilibrium increases on reduction of droplet radius. Droplet burning time essentially increases under non-equilibrium conditions. Comparison of theoretical and experimental data shows that to have adequate solution for small droplets it is necessary to use the non-equilibrium model.

Electrokinetic motion of a rectangular nanoparticle in a nanochannel

NASA Astrophysics Data System (ADS)

Movahed, Saeid; Li, Dongqing

2012-08-01

This article presents a theoretical study of electrokinetic motion of a negatively charged cubic nanoparticle in a three-dimensional nanochannel with a circular cross-section. Effects of the electrophoretic and the hydrodynamic forces on the nanoparticle motion are examined. Because of the large applied electric field over the nanochannel, the impact of the Brownian force is negligible in comparison with the electrophoretic and the hydrodynamic forces. The conventional theories of electrokinetics such as the Poisson-Boltzmann equation and the Helmholtz-Smoluchowski slip velocity approach are no longer applicable in the small nanochannels. In this study, and at each time step, first, a set of highly coupled partial differential equations including the Poisson-Nernst-Plank equation, the Navier-Stokes equations, and the continuity equation was solved to find the electric potential, ionic concentration field, and the flow field around the nanoparticle. Then, the electrophoretic and hydrodynamic forces acting on the negatively charged nanoparticle were determined. Following that, the Newton second law was utilized to find the velocity of the nanoparticle. Using this model, effects of surface electric charge of the nanochannel, bulk ionic concentration, the size of the nanoparticle, and the radius of the nanochannel on the nanoparticle motion were investigated. Increasing the bulk ionic concentration or the surface charge of the nanochannel will increase the electroosmotic flow, and hence affect the particle's motion. It was also shown that, unlike microchannels with thin EDL, the change in nanochannel size will change the EDL field and the ionic concentration field in the nanochannel, affecting the particle's motion. If the nanochannel size is fixed, a larger particle will move faster than a smaller particle under the same conditions.

Structural silicon nitride materials containing rare earth oxides

DOEpatents

Andersson, Clarence A.

1980-01-01

A ceramic composition suitable for use as a high-temperature structural material, particularly for use in apparatus exposed to oxidizing atmospheres at temperatures of 400 to 1600.degree. C., is found within the triangular area ABCA of the Si.sub.3 N.sub.4 --SiO.sub.2 --M.sub.2 O.sub.3 ternary diagram depicted in FIG. 1. M is selected from the group of Yb, Dy, Er, Sc, and alloys having Yb, Y, Er, or Dy as one component and Sc, Al, Cr, Ti, (Mg +Zr) or (Ni+Zr) as a second component, said alloy having an effective ionic radius less than 0.89 A.

Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

PubMed

Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

2016-04-01

In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs).

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte.

PubMed

Arya, Anil; Sharma, A L

2018-04-25

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO 8 -NaPF 6 +  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ([Formula: see text]) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ([Formula: see text]) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot ([Formula: see text]) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Ionic Conduction in Lithium Ion Battery Composite Electrode Governs Cross-sectional Reaction Distribution

PubMed Central

Orikasa, Yuki; Gogyo, Yuma; Yamashige, Hisao; Katayama, Misaki; Chen, Kezheng; Mori, Takuya; Yamamoto, Kentaro; Masese, Titus; Inada, Yasuhiro; Ohta, Toshiaki; Siroma, Zyun; Kato, Shiro; Kinoshita, Hajime; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

2016-01-01

Composite electrodes containing active materials, carbon and binder are widely used in lithium-ion batteries. Since the electrode reaction occurs preferentially in regions with lower resistance, reaction distribution can be happened within composite electrodes. We investigate the relationship between the reaction distribution with depth direction and electronic/ionic conductivity in composite electrodes with changing electrode porosities. Two dimensional X-ray absorption spectroscopy shows that the reaction distribution is happened in lower porosity electrodes. Our developed 6-probe method can measure electronic/ionic conductivity in composite electrodes. The ionic conductivity is decreased for lower porosity electrodes, which governs the reaction distribution of composite electrodes and their performances. PMID:27193448

Appearance of small polaron hopping conduction in iron modified cobalt lithium bismuth borate glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahiya, M. S.; Khasa, S., E-mail: skhasa@yahoo.com; Yadav, Arti

2016-05-23

Lithium bismuth borate glasses containing different amounts of cobalt and iron oxides having chemical composition xFe{sub 2}O{sub 3}•(20-x)CoO•30Li{sub 2}O•10Bi{sub 2}O{sub 3}•40B{sub 2}O{sub 3} (x = 0, 5, 10, 15 and 20 mol% abbreviated as CFLBB1-5 respectively) prepared via melt quench technique have been investigated for their dc electrical conductivity. The amorphous nature of prepared glasses has been confirmed through X-ray diffraction measurements. The dc electrical conductivity has been analyzed by applying Mott’s small polaron hopping model. Activation energies corresponding to lower and higher temperature region have been evaluated. The iron ion concentration (N), mean spacing between iron ions (R) and polaronmore » radius (R{sub p}) has been evaluated using the values of phonon radius (R{sub ph}) and Debye temperature (θ{sub D}). The glass sample without iron (CFLBB1) shows ionic conductivity but the incorporation of iron in the glass matrix results in the appearance of electronic conductivity.« less

High ionic strength depresses muscle contractility by decreasing both force per cross-bridge and the number of strongly attached cross-bridges.

PubMed

Wang, Li; Bahadir, Anzel; Kawai, Masataka

2015-06-01

An increase in ionic strength (IS) lowers Ca(2+) activated tension in muscle fibres, however, its molecular mechanism is not well understood. In this study, we used single rabbit psoas fibres to perform sinusoidal analyses. During Ca(2+) activation, the effects of ligands (ATP, Pi, and ADP) at IS ranging 150-300 mM were studied on three rate constants to characterize elementary steps of the cross-bridge cycle. The IS effects were studied because a change in IS modifies the inter- and intra-molecular interactions, hence they may shed light on the molecular mechanisms of force generation. Both the ATP binding affinity (K1) and the ADP binding affinity (K 0) increased to 2-3x, and the Pi binding affinity (K5) decreased to 1/2, when IS was raised from 150 to 300 mM. The effect on ATP/ADP can be explained by stereospecific and hydrophobic interaction, and the effect on Pi can be explained by the electrostatic interaction with myosin. The increase in IS increased cross-bridge detachment steps (k2 and k-4), indicating that electrostatic repulsion promotes these steps. However, IS did not affect attachment steps (k-2 and k4). Consequently, the equilibrium constant of the detachment step (K2) increased by ~100%, and the force generation step (K4) decreased by ~30%. These effects together diminished the number of force-generating cross-bridges by 11%. Force/cross-bridge (T56) decreased by 26%, which correlates well with a decrease in the Debye length that limits the ionic atmosphere where ionic interactions take place. We conclude that the major effect of IS is a decrease in force/cross-bridge, but a decrease in the number of force generating cross-bridge also takes place. The stiffness during rigor induction did not change with IS, demonstrating that in-series compliance is not much affected by IS.

High Ionic Strength Depresses Muscle Contractility by Decreasing both Force per Cross-bridge and the Number of Strongly Attached Cross-bridges

PubMed Central

Wang, Li; Bahadir, Anzel; Kawai, Masataka

2015-01-01

An increase in ionic strength (IS) lowers Ca2+ activated tension in muscle fibres, however, its molecular mechanism is not well understood. In this study, we used single rabbit psoas fibres to perform sinusoidal analyses. During Ca2+ activation, the effects of ligands (ATP, Pi, and ADP) at IS ranging 150 mM – 300 mM were studied on three rate constants to characterize elementary steps of the cross-bridge cycle. The IS effects were studied because a change in IS modifies the inter- and intra-molecular interactions, hence they may shed light on the molecular mechanisms of force generation. Both the ATP binding affinity (K1) and the ADP binding affinity (K0) increased to 2-3x, and the Pi binding affinity (K5) decreased to 1/2, when IS was raised from 150 mM to 300 mM. The effect on ATP/ADP can be explained by stereospecific and hydrophobic interaction, and the effect on Pi can be explained by the electrostatic interaction with myosin. The increase in IS increased cross-bridge detachment steps (k2 and k−4), indicating that electrostatic repulsion promotes these steps. However, IS did not affect attachment steps (k−2 and k4). Consequently, the equilibrium constant of the detachment step (K2) increased by ~100%, and the force generation step (K4) decreased by ~30%. These effects together diminished the number of force-generating cross-bridges by 11%. Force/cross-bridge (T56) decreased by 26%, which correlates well with a decrease in the Debye length that limits the ionic atmosphere where ionic interactions take place. We conclude that the major effect of IS is a decrease in force/cross-bridge, but a decrease in the number of force generating cross-bridge also takes place. The stiffness during rigor induction did not change with IS, demonstrating that in-series compliance is not much affected by IS. PMID:25836331

Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay

NASA Astrophysics Data System (ADS)

Cui, D.; Xiang, W.

2011-12-01

The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film

Ion Dynamics in a Mixed-Cation Alkoxy-Ammonium Ionic Liquid Electrolyte for Sodium Device Applications.

PubMed

Pope, Cameron R; Kar, Mega; MacFarlane, Douglas R; Armand, Michel; Forsyth, Maria; O'Dell, Luke A

2016-10-18

The ion dynamics in a novel sodium-containing room-temperature ionic liquid (IL) consisting of an ether-functionalised quaternary ammonium cation and bis(trifluoromethylsulfonyl)amide [NTf 2 ] anion with various concentrations of Na[NTf 2 ] have been characterised using differential scanning calorimetry, impedance spectroscopy, diffusometry and NMR relaxation measurements. The IL studied has been specifically designed to dissolve a relatively large concentration of Na[NTf 2 ] salt (over 2 mol kg -1 ) as this has been shown to improve ion transport and conductivity. Consistent with other studies, the measured ionic conductivity and diffusion coefficients show that the overall ionic mobility decreases with decreasing temperature and increasing salt content. NMR relaxation measurements provide evidence for correlated dynamics between the ether-functionalised ammonium and Na cations, possibly with the latter species acting as cross-links between multiple ammonium cations. Finally, preliminary cyclic voltammetry experiments show that this IL can undergo stable electrochemical cycling and could therefore be potentially useful as an electrolyte in a Na-based device. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Specific binding of (/sup 3/H-Tyr8)physalaemin to rat submaxillary gland substance P receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahouth, S.W.; Lazaro, D.M.; Brundish, D.E.

1985-01-01

(/sup 3/H)Physalaemin ((/sup 3/H)PHY) binds to a single class of noninteracting sites on rat submaxillary gland membranes suspended in high ionic strength media with a KD of 2.7 nM, a Bmax of 240 fmol/mg of protein, and low nonspecific binding. The relative potencies of substance P (SP) and its fragments in competing with (/sup 3/H)PHY correlate with their relative salivation potencies. This indicates that (/sup 3/H)PHY interacts with a physiologically relevant SP receptor. In low ionic strength media, the KD of (/sup 3/H)PHY does not change, but SP and some of its fragments are more potent than PHY in competingmore » with (/sup 3/H) PHY. Computer-assisted analysis of (/sup 3/H)PHY and (/sup 3/H)SP binding in high and low ionic strength media demonstrated that both peptides are equipotent in high ionic strength but that the affinity of SP increases by 70-fold in low ionic strength. The SP fragments that contain a basic residue in positions 1 and/or 3 also display an increased affinity in low ionic strength. These findings document that (/sup 3/H)PHY binding in high ionic strength (mu . 0.6) accurately reflects the pharmacological potencies of agonists on the SP-P receptor. The binding of (/sup 3/H)PHY, like that of (/sup 3/H)SP, increases by the addition of divalent cations (Mg2+ greater than Ca2+ greater than Mn2+). Guanine nucleotides decrease (/sup 3/H)PHY binding by decreasing the Bmax to the same level (160 fmol/mg of protein), in the presence or absence of Mg2+.« less

Computer Simulation Study of Graphene Oxide Supercapacitors: Charge Screening Mechanism.

PubMed

Park, Sang-Won; DeYoung, Andrew D; Dhumal, Nilesh R; Shim, Youngseon; Kim, Hyung J; Jung, YounJoon

2016-04-07

Graphene oxide supercapacitors in the parallel plate configuration are studied via molecular dynamics (MD) simulations. The full range of electrode oxidation from 0 to 100% is examined by oxidizing the graphene surface with hydroxyl groups. Two different electrolytes, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI(+)BF4(-)) as an ionic liquid and its 1.3 M solution in acetonitrile as an organic electrolyte, are considered. While the area-specific capacitance tends to decrease with increasing electrode oxidation for both electrolytes, its details show interesting differences between the organic electrolyte and ionic liquid, including the extent of decrease. For detailed insight into these differences, the screening mechanisms of electrode charges by electrolytes and their variations with electrode oxidation are analyzed with special attention paid to the aspects shared by and the contrasts between the organic electrolyte and ionic liquid.

Lattice model of ionic liquid confined by metal electrodes

NASA Astrophysics Data System (ADS)

Girotto, Matheus; Malossi, Rodrigo M.; dos Santos, Alexandre P.; Levin, Yan

2018-05-01

We study, using Monte Carlo simulations, the density profiles and differential capacitance of ionic liquids confined by metal electrodes. To compute the electrostatic energy, we use the recently developed approach based on periodic Green's functions. The method also allows us to easily calculate the induced charge on the electrodes permitting an efficient implementation of simulations in a constant electrostatic potential ensemble. To speed up the simulations further, we model the ionic liquid as a lattice Coulomb gas and precalculate the interaction potential between the ions. We show that the lattice model captures the transition between camel-shaped and bell-shaped capacitance curves—the latter characteristic of ionic liquids (strong coupling limit) and the former of electrolytes (weak coupling). We observe the appearance of a second peak in the differential capacitance at ≈0.5 V for 2:1 ionic liquids, as the packing fraction is increased. Finally, we show that ionic size asymmetry decreases substantially the capacitance maximum, when all other parameters are kept fixed.

Correlating morphology to dc conductivity in polymerized ionic liquids

NASA Astrophysics Data System (ADS)

Iacob, Ciprian; Matusmoto, Atsushi; Inoue, Tadashi; Runt, James

Polymerized ionic liquids (PILs) combine the attractive mechanical characteristics of polymers and unique physico-chemical properties of low molecular weight ionic liquids in the same material. PILs have shown remarkable advantages when employed in electrochemical devices such as dye-sensitized solar cells and lithium batteries, among others. Understanding their ionic transport mechanism is the key for designing highly conductive PILs. In the current study, the correlation between morphology and charge transport in two homologous series of PILs with systematic variation of the alkyl chain length and anions is investigated using broadband dielectric spectroscopy, rheology, differential scanning calorimetry and X-ray scattering. As the alkyl chain length increases, the backbone-to-backbone separation increases, and dc-conductivity consequently decreases. The cations dominate structural dynamics since they are attached to the polymer chains, while the anions are smaller and more mobile ionic species thereby controlling the ionic conductivity. Further interpretation of decoupling of dc conductivity from the segmental relaxation enabled the correlation between polymer morphology and dc conductivity. Supported by the National Science Foundation, Polymers Program.

The electronic and optical properties of quantum nano-structures

NASA Astrophysics Data System (ADS)

Ham, Heon

In semiconducting quantum nano-structures, the excitonic effects play an important role when we fabricate opto-electronic devices, such as lasers, diodes, detectors, etc. To gain a better understanding of the excitonic effects in quantum nano-structures, we investigated the exciton binding energy, oscillator strength, and linewidth in quantum nano-structures using both the infinite and finite well models. We investigated also the hydrogenic impurity binding energy and the photoionization cross section of the hydrogenic impurity in a spherical quantum dot. In our work, the variational approach is used in all calculations, because the Hamiltonian of the system is not separable, due to the different symmetries of the Coulomb and confining potentials. In the infinite well model of the semiconducting quantum nanostructures, the binding energy of the exciton increases with decreasing width of the potential barriers due to the increase in the effective strength of the Coulomb interaction between the electron and hole. In the finite well model, the exciton binding energy reaches a peak value, and the binding energy decreases with further decrease in the width of the potential barriers. The exciton linewidth in the infinite well model increases with decreasing wire radius, because the scattering rate of the exciton increases with decreasing wire radius. In the finite well model, the exciton linewidth in a cylindrical quantum wire reaches a peak value and the exciton linewidth decreases with further decrease in the wire radius, because the exciton is not well confined at very smaller wire radii. The binding energy of the hydrogenic impurity in a spherical quantum dot has also calculated using both the infinite and the finite well models. The binding energy of the hydrogenic impurity was calculated for on center and off center impurities in the spherical quantum dots. With decreasing radii of the dots, the binding energy of the hydrogenic impurity increases in the infinite well model. The binding energy of the hydrogenic impurity in the finite well model reaches a peak value and decreases with further decrease in the dot radii for both on center and off center impurities. We have calculated the photoionization cross section as a function of the radius and the frequency using both the infinite and finite well models. The photoionizaton cross section has a peak value at a frequency where the photon energy equals the difference between the final and initial state energies of the impurity. The behavior of the cross section with dot radius depends upon the location of the impurity and the polarization of the electromagnetic field.

Effects of the spaces available for cations in strongly acidic cation-exchange resins on the exchange equilibria by quaternary ammonium ions and on the hydration states of metal ions.

PubMed

Watanabe, Yuuya; Ohnaka, Kenji; Fujita, Saki; Kishi, Midori; Yuchi, Akio

2011-10-01

The spaces (voids) available for cations in the five exchange resins with varying exchange capacities and cross-linking degrees were estimated, on the basis of the additivity of molar volumes of the constituents. Tetraalkylammonium ions (NR(4)(+); R: Me, Et, Pr) may completely exchange potassium ion on the resin having a larger void radius. In contrast, the ratio of saturated adsorption capacity to exchange capacity of the resin having a smaller void radius decreased with an increase in size of NR(4)(+) ions, due to the interionic contacts. Alkali metal ions could be exchanged quantitatively. While the hydration numbers of K(+), Rb(+), and Cs(+) were independent of the void radius, those of Li(+) and Na(+), especially Na(+), decreased with a decrease in void radius. Interionic contacts between the hydrated ions enhance the dehydration. Multivalent metal ions have the hydration numbers, comparable to or rather greater than those in water. A greater void volume available due to exchange stoichiometry released the interionic contacts and occasionally promoted the involvement of water molecules other than directly bound molecules. The close proximity between ions in the conventional ion-exchange resins having higher exchange capacities may induce varying interactions.

Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

Microwave vector radiative transfer equation of a sea foam layer by the second-order Rayleigh approximation

NASA Astrophysics Data System (ADS)

Wei, En-Bo

2011-10-01

The microwave vector radiative transfer (VRT) equation of a coated spherical bubble layer is derived by means of the second-order Rayleigh approximation field when the microwave wavelength is larger than the coated spherical particle diameter. Meanwhile, the perturbation method is developed to solve the second-order Rayleigh VRT equation for the small ratio of the volume scattering coefficient to the extinction coefficient. As an example, the emissive properties of a sea surface foam layer, which consists of seawater coated bubbles, are investigated. The extinction, absorption, and scattering coefficients of sea foam are obtained by the second-order Rayleigh approximation fields and discussed for the different microwave frequencies and the ratio of inner radius to outer radius of a coated bubble. Our results show that in the dilute limit, the volume scattering coefficient decreases with increasing the ratio of inner radius to outer radius and decreasing the frequencies. It is also found that the microwave emissivity and the extinction coefficient have a peak at very thin seawater coating and its peak value decreases with frequency decrease. Furthermore, with the VRT equation and effective medium approximation of densely coated bubbles, the mechanism of sea foam enhancing the emissivity of a sea surface is disclosed. In addition, excellent agreement is obtained by comparing our VRT results with the experimental data of microwave emissivities of sea surface covered by a sea foam layer at L-band (1.4 GHz) and the Camps' model.

Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

NASA Astrophysics Data System (ADS)

Iwano, Keisuke; Yamanoi, Kohei; Iwasa, Yuki; Mori, Kazuyuki; Minami, Yuki; Arita, Ren; Yamanaka, Takuma; Fukuda, Kazuhito; Empizo, Melvin John F.; Takano, Keisuke; Shimizu, Toshihiko; Nakajima, Makoto; Yoshimura, Masashi; Sarukura, Nobuhiko; Norimatsu, Takayoshi; Hangyo, Masanori; Azechi, Hiroshi; Singidas, Bess G.; Sarmago, Roland V.; Oya, Makoto; Ueda, Yoshio

2016-10-01

We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ˜ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

Enhancement of Force Generated by Individual Myosin Heads in Skinned Rabbit Psoas Muscle Fibers at Low Ionic Strength

PubMed Central

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca2+-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca2+-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca2+-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca2+ activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca2+-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca2+-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction. PMID:23691080

Beneficial effect of added water on sodium metal cycling in super concentrated ionic liquid sodium electrolytes

NASA Astrophysics Data System (ADS)

Basile, Andrew; Ferdousi, Shammi A.; Makhlooghiazad, Faezeh; Yunis, Ruhamah; Hilder, Matthias; Forsyth, Maria; Howlett, Patrick C.

2018-03-01

The plating and stripping performance of sodium metal in an ionic liquid electrolyte is improved when including water as an additive. Herein we report for the first time the trend of improved cycling behavior of Na0/+ in N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide with 500 ppm H2O. The addition of water to this ionic liquid electrolyte promotes the breakdown of the [FSI]- anion towards beneficial SEI formation. The benefits during plating and stripping of sodium is observed as lower total polarization during symmetrical cell cycling and decreased electrode/electrolyte interface impedance. Sodium metal surfaces after cycling with 500 ppm H2O are shown to be smooth in morphology in comparison to lower additive concentrations. The outcome of adventitious moisture benefiting Na0/+ cycling in an ionic liquid, contrary to conventional electrolytes, allows flexibility in ionic liquid electrolyte design to the benefit of battery manufacturers.

Interaction between 2',4-dihydroxychalcone and the N, f, e conformers of bovine serum albumin: influence of temperature and ionic strength.

PubMed

Curvale, Rolando A; Debattista, Nora B; Pappano, Nora B

2012-04-01

UV-Vis spectroscopy was used to study the interaction between the 2',4- dihydroxychalcone, flavonoid which is known to have anti-tumor activity in vitro, and others biological properties, and the N, F and E conformers of bovine serum albumin at different ionic strengths and temperatures. The Klotz model was found to be adequate to determine the constants and number of binding sites. The reaction was found to be exothermic and spontaneous. The number of binding sites decreases and the reaction is more exergonic along with the increase in ionic strength and the conformational change of N to E. The reactions were necessarily hydrophobic and followed by a process of ionic character.

Overcharging and charge reversal in the electrical double layer around the point of zero charge.

PubMed

Guerrero-García, G Iván; González-Tovar, Enrique; Chávez-Páez, Martín; Lozada-Cassou, Marcelo

2010-02-07

The ionic adsorption around a weakly charged spherical colloid, immersed in size-asymmetric 1:1 and 2:2 salts, is studied. We use the primitive model (PM) of an electrolyte to perform Monte Carlo simulations as well as theoretical calculations by means of the hypernetted chain/mean spherical approximation (HNC/MSA) and the unequal-radius modified Gouy-Chapman (URMGC) integral equations. Structural quantities such as the radial distribution functions, the integrated charge, and the mean electrostatic potential are reported. Our Monte Carlo "experiments" evidence that near the point of zero charge, the smallest ionic species is preferentially adsorbed onto the macroparticle, independently of the sign of the charge carried by this tiniest electrolytic component, giving rise to the appearance of the phenomena of charge reversal (CR) and overcharging (OC). Accordingly, colloidal CR, due to an excessive attachment of counterions, is observed when the macroion is slightly charged and the coions are larger than the counterions. In the opposite situation, i.e., if the counterions are larger than the coions, the central macroion acquires additional like-charge (coions) and hence becomes "overcharged," a feature theoretically predicted in the past [F. Jiménez-Angeles and M. Lozada-Cassou, J. Phys. Chem. B 108, 7286 (2004)]. In other words, here we present the first simulation data on OC in the PM electrical double layer, showing that close to the point of zero charge, this novel effect surges as a consequence of the ionic size asymmetry. We also find that the HNC/MSA theory captures well the CR and OC phenomena exhibited by the computer experiments, especially as the macroion's charge increases. On the contrary, even if URMGC also displays CR and OC, its predictions do not compare favorably with the Monte Carlo data, evidencing that the inclusion of hard-core correlations in Monte Carlo and HNC/MSA enhances and extends those effects. We explain our findings in terms of the energy-entropy balance. In the field of electrophoresis, it has been generally agreed that the charge of a colloid in motion is partially decreased by counterion adsorption. Depending on the location of the macroion's slipping surface, the OC results of this paper could imply an increase in the expected electrophoretic mobility. These observations aware about the interpretation of electrokinetic measurements using the standard Poisson-Boltzmann approximation beyond its validity region.

Short communication: Serum composition of milk subjected to re-equilibration by dialysis at different temperatures, after pH adjustments.

PubMed

Zhao, Zhengtao; Corredig, Milena

2016-04-01

The objective of this work was to investigate the properties of casein micelles after pH adjustment and their re-equilibration to the original pH and serum composition. Re-equilibration was carried out by dialyzing against skim milk at 2 different temperatures (4 or 22 °C). Turbidity, the average radius of the casein micelles, and the composition of the soluble phase were measured at different pH values, ranging between 5.5 and 8. Acidification led to the solubilization of colloidal calcium phosphate and decrease of the average radius of the micelles. With re-equilibration, casein dissociation occurred. In milk with pH values greater than 6.0, the average radius was recovered after re-equilibration. At pH values greater than neutral, an increase of the radius of casein micelles and increased dissociation of the casein were found. After re-equilibration, the radius of micelles and soluble protein in the serum decreased. The results were not affected by the temperature of re-equilibration. The changes to the calcium phosphate equilibrium and the dissociation of the micelles will have important consequences to the functionality of casein micelles. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Stabilization of MgAl 2O 4 spinel surfaces via doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Md. M.; Dholabhai, Pratik P.; Castro, Ricardo H. R.

Here, the surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. We report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl 2O 4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y 3+, Gd 3+,more » La 3+) and one tetravalent dopant (Zr 4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.« less

Permeation of halide anions through phospholipid bilayers occurs by the solubility-diffusion mechanism

NASA Technical Reports Server (NTRS)

Paula, S.; Volkov, A. G.; Deamer, D. W.

1998-01-01

Two alternative mechanisms are frequently used to describe ionic permeation of lipid bilayers. In the first, ions partition into the hydrophobic phase and then diffuse across (the solubility-diffusion mechanism). The second mechanism assumes that ions traverse the bilayer through transient hydrophilic defects caused by thermal fluctuations (the pore mechanism). The theoretical predictions made by both models were tested for halide anions by measuring the permeability coefficients for chloride, bromide, and iodide as a function of bilayer thickness, ionic radius, and sign of charge. To vary the bilayer thickness systematically, liposomes were prepared from monounsaturated phosphatidylcholines (PC) with chain lengths between 16 and 24 carbon atoms. The fluorescent dye MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) served as an indicator for halide concentration inside the liposomes and was used to follow the kinetics of halide flux across the bilayer membranes. The observed permeability coefficients ranged from 10(-9) to 10(-7) cm/s and increased as the bilayer thickness was reduced. Bromide was found to permeate approximately six times faster than chloride through bilayers of identical thickness, and iodide permeated three to four times faster than bromide. The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores. Halide permeation therefore differs from that of a monovalent cation such as potassium, which has been accounted for by a combination of the two mechanisms depending on bilayer thickness.

Stabilization of MgAl2O4 spinel surfaces via doping

NASA Astrophysics Data System (ADS)

Hasan, Md. M.; Dholabhai, Pratik P.; Castro, Ricardo H. R.; Uberuaga, Blas P.

2016-07-01

Surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. Here, we report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl2O4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y3+, Gd3+, La3+) and one tetravalent dopant (Zr4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.

Modeling and simulation of Li-ion conduction in poly(ethylene oxide)

NASA Astrophysics Data System (ADS)

Gitelman, L.; Israeli, M.; Averbuch, A.; Nathan, M.; Schuss, Z.; Golodnitsky, D.

2007-12-01

Polyethylene oxide (PEO) containing a lithium salt (e.g., LiI) serves as a solid polymer electrolyte (SPE) in thin-film batteries and its ionic conductivity is a key parameter of their performance. We model and simulate Li + ion conduction in a single PEO molecule. Our simplified stochastic model of ionic motion is based on an analogy between protein channels of biological membranes that conduct Na +, K +, and other ions, and the PEO helical chain that conducts Li + ions. In contrast with protein channels and salt solutions, the PEO is both the channel and the solvent for the lithium salt (e.g., LiI). The mobile ions are treated as charged spherical Brownian particles. We simulate Smoluchowski dynamics in channels with a radius of ca. 0.1 nm and study the effect of stretching and temperature on ion conductivity. We assume that each helix (molecule) forms a random angle with the axis between these electrodes and the polymeric film is composed of many uniformly distributed oriented boxes that include molecules with the same direction. We further assume that mechanical stretching aligns the molecular structures in each box along the axis of stretching (intra-box alignment). Our model thus predicts the PEO conductivity as a function of the stretching, the salt concentration and the temperature. The computed enhancement of the ionic conductivity in the stretch direction is in good agreement with experimental results. The simulation results are also in qualitative agreement with recent theoretical and experimental results.

Stabilization of MgAl 2O 4 spinel surfaces via doping

DOE PAGES

Hasan, Md. M.; Dholabhai, Pratik P.; Castro, Ricardo H. R.; ...

2016-02-06

Here, the surface structure of complex oxides plays a vital role in processes such as sintering, thin film growth, and catalysis, as well as being a critical factor determining the stability of nanoparticles. We report atomistic calculations of the low-index stoichiometric magnesium aluminate spinel (MgAl 2O 4) surfaces, each with two different chemical terminations. High temperature annealing was used to explore the potential energy landscape and provide more stable surface structures. We find that the lowest energy surface is {100} while the highest energy surface is {111}. The surfaces were subsequently doped with three trivalent dopants (Y 3+, Gd 3+,more » La 3+) and one tetravalent dopant (Zr 4+) and both the surface segregation energies of the dopants and surface energies of the doped surface were determined. All of the dopants reduce the surface energy of spinel, though this reduction in energy depends on both the size and valence of the dopant. Dopants with larger ionic radius tend to segregate to the surface more strongly and reduce the surface energy to a greater extent. Furthermore, the ionic valence of the dopants seems to have a stronger influence on the segregation than does ionic size. For both undoped and doped spinel, the predicted crystal shape is dominated by {100} surfaces, but the relative fraction of the various surfaces changes with doping due to the unequal changes in energy, which has implications on equilibrium nanoparticle shapes and therefore on applications sensitive to surface properties.« less

Conductivity-Relaxation Relations in Nanocomposite Polymer Electrolytes Containing Ionic Liquid.

PubMed

Shojaatalhosseini, Mansoureh; Elamin, Khalid; Swenson, Jan

2017-10-19

In this study, we have used nanocomposite polymer electrolytes, consisting of poly(ethylene oxide) (PEO), δ-Al 2 O 3 nanoparticles, and lithium bis(trifluoromethanesolfonyl)imide (LiTFSI) salt (with 4 wt % δ-Al 2 O 3 and PEO:Li ratios of 16:1 and 8:1), and added different amounts of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesolfonyl)imide (BMITFSI). The aim was to elucidate whether the ionic liquid is able to dissociate the Li-ions from the ether oxygens and thereby decouple the ionic conductivity from the segmental polymer dynamics. The results from DSC and dielectric spectroscopy show that the ionic liquid speeds up both the segmental polymer dynamics and the motion of the Li + ions. However, a close comparison between the structural (α) relaxation process, given by the segmental polymer dynamics, and the ionic conductivity shows that the motion of the Li + ions decouples from the segmental polymer dynamics at higher concentrations of the ionic liquid (≥20 wt %) and instead becomes more related to the viscosity of the ionic liquid. This decoupling increases with decreasing temperature. In addition to the structural α-relaxation, two more local relaxation processes, denoted β and γ, are observed. The β-relaxation becomes slightly faster at the highest concentration of the ionic liquid (at least for the lower salt concentration), whereas the γ-relaxation is unaffected by the ionic liquid, over the whole concentration range 0-40 wt %.

Comparative in vitro study of cholinium-based ionic liquids and deep eutectic solvents toward fish cell line.

PubMed

Radošević, Kristina; Železnjak, Jelena; Cvjetko Bubalo, Marina; Radojčić Redovniković, Ivana; Slivac, Igor; Gaurina Srček, Višnja

2016-09-01

With the advent of ionic liquids, much was expected concerning their applicability as an alternative to organic solvents in the chemical technology and biotechnology fields. However, the most studied and commonly used ionic liquids based on imidazolium and pyridinium were found not to be as environmentally friendly as it was first expected. Therefore, a new generation of alternative solvents named natural ionic liquids and deep eutectic solvents, composed of natural and/or renewable compounds, have come into focus in recent years. Since the number of newly synthesized chemicals increases yearly, simple and reliable methods for their ecotoxicological assessment are necessary. Permanent fish cell lines can serve as a test system for the evaluation of a chemical's cytotoxicity. This paper presents research results on the cytotoxic effects on Channel Catfish Ovary (CCO) cell line induced by fifteen cholinium-based ionic liquids and deep eutectic solvents. Based on the decrease in cell viability, the most obvious toxic effect on CCO cells was caused by ionic liquid choline oxalate, while other solvents tested exhibited low cytotoxicity. Therefore, we can conclude that cholinium-based ionic liquids and deep eutectic solvents are comparatively less toxic to CCO cells than conventional ionic liquids. Copyright © 2016 Elsevier Inc. All rights reserved.

Observations of a probable change in the solar radius between 1715 and 1979

NASA Technical Reports Server (NTRS)

Dunham, D. W.; Sofia, S.; Fiala, A. D.; Muller, P. M.; Herald, D.

1980-01-01

A decrease in the solar radius is determined using the technique of Dunham and Dunham (1973), in which timed observations are made just inside the path edges. When the method is applied to the solar eclipses of 1715, 1976, and 1979, the solar radius for 1715 is 0.34 + or - 0.2 arc second larger than the recent values, with no significant change between 1976 and 1979. The duration of totality is examined as a function of distance from the edges of the path. Corrections to the radius of the sun derived from observations of the 1976 and 1979 eclipses by the International Occultation Timing Association are also presented.

Temporal length-scale cascade and expansion rate on planar liquid jet instability

NASA Astrophysics Data System (ADS)

Sirignano, William; Zandian, Arash; Hussain, Fazle

2016-11-01

Using the local radius of curvature of the surface and the local transverse dimension of the two-phase (i.e., spray) domain as length scales, we obtained two PDFs over a wide range of length-scales at different times and for different Reynolds and Weber (We) numbers. The PDFs were developed via post-processing of DNS Navier-Stokes results for a 3D planar liquid sheet segment with level-set and Volume-of-Fluid surface tracking, giving better statistical data for the length scales compared to the former methods. The radius PDF shows that, with increasing We , the average radius of curvature decreases, number of small droplets increases, and cascade occurs at a faster rate. In time, the mean of the radius PDF decreases while the rms increases. The other PDF represents the spray expansion in a more realistic and meaningful form, showing that the spray angle is larger at higher We and density-ratios. Both the mean and the rms of the spray-size PDF increase with time. The PDFs also track the transitions between symmetric and anti-symmetric modes.

The Sun's Seismic Radius as Measured from the Fundamental Modes of Oscillations and Its Implications for the TSI Variations

NASA Astrophysics Data System (ADS)

Jain, Kiran; Tripathy, S. C.; Hill, F.

2018-05-01

In this Letter we explore the relationship between the solar seismic radius and total solar irradiance (TSI) during the last two solar cycles using the uninterrupted data from space-borne instruments on board the Solar and Heliospheric Observatory (SoHO) and the Solar Dynamics Observatory (SDO). The seismic radius is calculated from the fundamental (f) modes of solar oscillations utilizing the observations from SoHO/Michelson Doppler Imager (MDI) and SDO/Helioseismic and Magnetic Imager (HMI), and the TSI measurements are obtained from SoHO/VIRGO. Our study suggests that the major contribution to the TSI variation arises from the changes in magnetic field, while the radius variation plays a secondary role. We find that the solar irradiance increases with decreasing seismic radius; however, the anti-correlation between them is moderately weak. The estimated maximum change in seismic radius during a solar cycle is about 5 km, and is consistent in both solar cycles 23 and 24. Previous studies ;suggest a radius change at the surface of the order of 0.06 arcsec to explain the 0.1% variation in the TSI values during the solar cycle; however, our inferred seismic radius change is significantly smaller, hence the TSI variations cannot be fully explained by the temporal changes in seismic radius.

Probing the interaction of ionic liquids with graphene using surface-enhanced Raman spectroscopy

DOE PAGES

Mahurin, Shannon Mark; Dai, Sheng; Surwade, Sumedh P.; ...

2015-12-17

We report an in situ measurement of the interaction of an imidazolium-based room temperature ionic liquid with both pure silver and a graphene-over-silver electrode under an applied electrochemical potential. At a negative applied potential, overall signal intensity increased indicating enhanced ionic liquid concentration at both silver and graphene electrodes. Vibrational modes associated with the imidazolium ring exhibited greater intensity enhancements and larger peak shifts compared with the anion indicating that the cation adsorbs with the ring and alkyl chain parallel to the electrode surface for both silver and graphene. In contrast to the silver, the surface enhanced Raman spectra ofmore » the ionic liquid near graphene showed shifts in the cation peaks even at no applied potential because of the strong π–π interaction between the ionic liquid and the graphene. Furthermore, the intensity of the graphene peak decreased in the presence of ionic liquid possibly due to the interaction between the ionic liquid and graphene. In conclusion, these results illustrate the effectiveness of surface-enhanced Raman spectroscopy to investigate electrolyte interactions with graphene at the liquid/electrode interface.« less

Influence of the ionic liquid 1-butyl-3-methylimidazolium bromide on amyloid fibrillogenesis in lysozyme: Evidence from photophysical and imaging studies.

PubMed

Basu, Anirban; Bhattacharya, Subhash Chandra; Kumar, Gopinatha Suresh

2018-02-01

Many proteins can abnormally fold to form pathological amyloid deposits/aggregates that are responsible for various degenerative disorders called amyloidosis. Here we have examined the anti-amyloidogenic potency of an ionic liquid, 1-butyl-3-methylimidazolium bromide, using lysozyme as a model system. Thioflavin T fluorescence assay demonstrated that the ionic liquid suppressed the formation of lysozyme fibrils significantly. This observation was further confirmed by the Congo red assay. Fluorescence microscopy, intrinsic fluorescence studies, nile red fluorescence assay, ANS binding assay and circular dichroism studies also testified diminishing of the fibrillogenesis in the presence of ionic liquid. Formation of amyloid fibrils was also characterized by α to β conformational transition. From far-UV circular dichroism studies it was observed that the β-sheet content of the lysozyme samples decreased in the presence of the ionic liquid which in turn implied that fibrillogenesis was supressed by the ionic liquid. Atomic force microscopy imaging unequivocally established that the ionic liquid attenuated fibrillogenesis in lysozyme. These results may be useful for the development of more effective therapeutics for amyloidosis. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermodynamic Stability of Transition Metal Substituted LiMn 2-xMxO 4 (M=Cr, Fe, Co, and Ni) Spinels

NASA Astrophysics Data System (ADS)

Lai, Chenying

The formation enthalpies from binary oxides of LiMn2O 4, LiMn2-xCrxO4 (x = 0.25, 0.5, 0.75 and 1), LiMn2-xFexO4 (x = 0.25 and 0.5), LiMn2-xCoxO4 (x = 0.25, 0.5, and 0.75) and LiMn1.75Ni 0.25O4 at 25 °C have been measured by high-temperature oxide-melt-solution calorimetry and were found to be strongly exothermic. Increasing Cr, Co and Ni content leads to more thermodynamically stable spinels, but increasing Fe content does not significantly affect the stability. The formation enthalpies from oxides of the fully substituted spinels, LiMnMO 4 (M = Cr, Fe and Co) become more exothermic (implying increasing stability) with decreasing ionic radius of the metal and lattice parameters of the spinel. The trend in enthalpy versus metal content is roughly linear, suggesting a close-to-zero heat of mixing in LiMn2O4 - LiMnMO 4 solid solutions. These data confirm that transition metal doping is beneficial for stabilizing these potential cathode materials for lithium-ion batteries.

Role of lattice distortion on diffuse phase transition temperatures in Bi0.5Na0.5TiO3-BaTiO3 [BNBTO] solid solutions

NASA Astrophysics Data System (ADS)

Pradhan, Lagen Kumar; Pandey, Rabichandra; Kumar, Sunil; Supriya, Sweety; Kar, Manoranjan

2018-04-01

Effect of lattice distortion on diffuse phase transition in BNBTO solid solutions near Morphotropic phase boundary (MPB) has been investigated. Solid solutions of (Bi0.5Na0.5)1-xBaxTiO3 (with mole % of x= 0.04, 0.05, 0.06, 0.07 and 0.08) were prepared by the planetary ball mill method in ethanol medium. Rietveld refinement technique with rhombohedral (R3c) and tetragonal (P4bm) crystal symmetry has been employed for structural as well as phase analysis of the solid solutions. Both rhombohedral and tetragonal lattice distortion (c/a) tends toward the pseudo-cubic crystal symmetry with the increase of mole fraction of Ba2+ near MPB (x= 6 mole %). Also, the average crystallite size and grain size decrease with increase of mole fraction of Ba2+ in BNT ceramic are due to larger ionic radius of Ba2+ and grain boundary pinning process in the solid solutions respectively. Additionally, depolarization temperature (Td) and maximum temperature (Tm) reduces due to the lattice distortion of both the phases in BNBTO solid solutions, which is explained extensively. Significant increase of dielectric constant has been observed near MPB composition (x=6%) in BNBTO solid solutions.

Improving CO2 permeation and separation performance of CO2-philic polymer membrane by blending CO2 absorbents

NASA Astrophysics Data System (ADS)

Cheng, Jun; Hu, Leiqing; Li, Yannan; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

2017-07-01

To research effects of CO2 absorption capacity and type of CO2 absorbent on the CO2 separation and free-volume properties of facilitated transport membranes, two types of CO2 absorbents, namely monoethanolamine (MEA) and ionic liquids (ILs:[P66614][Triz] and [P66614][2-Op]), were adopted. The CO2 absorption capacities of MEA, [P66614][Triz] and [P66614][2-Op] were about 0.561 mol CO2 per mol, 0.95 mol CO2 per mol and 1.60 mol CO2 per mol, respectively. All mean free-volume hole radiuses of membranes decreased after blending CO2 absorbents. After polymer membrane blended with two ILs, number of free-volume hole increased, resulting in modest increase of the fractional free volume. Both CO2 permeability and selectivity increased after blending MEA and ILs. The increasing range of CO2 permeability corresponded with CO2 absorption capacity of CO2 absorbents, and membrane blending with [P66614][2-Op] showed the highest CO2 permeability of 672.1 Barrers at 25 °C. Pebax/PEGDME membrane blending with MEA obtained the highest CO2/H2 and CO2/CH4 selectivity at 17.8 and 20.5, respectively.

Metal-Insulator Transition in Epitaxial Pyrochlore Iridates Bi2Ir2O7 thin Films

NASA Astrophysics Data System (ADS)

Chu, Jiun-Haw; Liu, Jian; Yi, Di; Rayan-Serrao, C.; Suresha, S.; Marti, Xavi; Riggs, Scott; Shapiro, Max; Ian, Fisher; Ramesh, R.

2013-03-01

Recently there is a surge of interest in searching for topological order in correlated electronic systems such as transition metal oxides. The strong spin-orbit interaction of 5d electrons and the geometric frustration in the crystal lattice make the pyrochlore iridate(A2Ir2O7) an ideal candidate to achieve this goal. Pioneering experiments on bulk polycrystalline and single crystal samples revealed a temperature dependent metal-insulator transition coupled to a long range magnetic order, and the transition temperature can be tuned by either A-site ionic radius or an external pressure. In this talk we present our efforts to understand and control the metal-insulator transition and the underlying electronic structure of pyrochlore iridates via epitaxial Bi2Ir2O7 thin films. Bulk Bi2Ir2O7 is located at the metallic side of the phase diagram. However as the film's thickness decreases the transport evolves from a metallic to a strongly localized character. Resonant X-ray spectroscopy suggests that the density of states near Fermi level is dominated by the Ir Je ff =1/2 states. Intriguingly, the magnetoresistance shows a linear field dependence over a wide range of fields at low temperatures, which is possibly consistent with the existence of Dirac nodes.

Measuring effects of refractive surgery on corneas using Taylor series polynomials

NASA Astrophysics Data System (ADS)

Corbin, Jacob A.; Klein, Stanley A.; van de Pol, Corina

1999-06-01

Corneal topographers have made it possible to accurately map corneal shape. We applied this technology to model the post- refractive surgery cornea using Taylor series polynomials. Topography data was taken from 58 patient eyes with photorefractive keratectomy (PRK) or astigmatic photorefractive keratectomy (PARK). We looked at the changes the cornea underwent surgically, as well as the healing process. We compared the post-ablation cornea to the pre-ablation cornea and to the intended correction using novel topography maps. From the refractive map, we quantified the spherical aberration as areas of defocus on the cornea. From the pre-op exam to the first post-op exam, we measured 0.19+/-0.10 mm radius decrease in PRK and a 0.13+/-0.08 mm radius decrease in PARK in the areas where rays come to within two diopeters of defocus. As this change occurs within the optical zone, this corresponds to an increase in spherical aberration for both the PRK and the PARK patient. As the patient healed, we found additional decrease in radius of the zones of best vision in PRK patients, whereas we found no significant decrease in PARK patients. This corresponds to increased spherical aberration in the PRK patient.

[Mechanism of action of antiepileptic drugs].

PubMed

Saidón, Patricia

2003-01-01

Antiepileptic drugs (DAEs) act through different mechanisms of action: increase in central inhibition, inhibition of excitatorios mechanisms and modification of the excitability through their action on the ionic channels. Epilepsy is characterized by an abnormal and hypersynchronic unloading of a neuronal population. The activity of numerous drugs is associated to increase in gabaergic activity. Another group of drugs decreases excitatory mechanisms, through the inhibition of ionic channels, or through a decrease in the activity of the excitatory neurotransmitters. There are some of antiepileptic drugs, especially within the group of drugs of recent appearance, for wich the mechanism of action remains unknown.

Effective on-site Coulomb interaction and electron configurations in transition-metal complexes from constraint density functional theory

NASA Astrophysics Data System (ADS)

Nawa, Kenji; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori; Weinert, Michael

Effective on-site Coulomb interactions (Ueff) and electron configurations in the localized d and f orbitals of metal complexes in transition-metal oxides and organometallic molecules, play a key role in the first-principles search for the true ground-state. However, wide ranges of values in the Ueff parameter of a material, even in the same ionic state, are often reported. Here, we revisit this issue from constraint density functional theory (DFT) by using the full-potential linearized augmented plane wave method. The Ueff parameters for prototypical transition-metal oxides, TMO (TM =Mn, Fe, Co, Ni), were calculated by the second derivative of the total energy functional with respect to the d occupation numbers inside the muffin-tin (MT) spheres as a function of the sphere radius. We find that the calculated Ueff values depend significantly on the MT radius, with a variation of more than 3 eV when the MT radius changes from 2.0 to 2.7 a.u., but importantly an identical valence band structure can be produced in all the cases, with an approximate scaling of Ueff. This indicates that a simple transferability of the Ueff value among different calculation methods is not allowed. We further extend the constraint DFT to treat various electron configurations of the localized d-orbitals in organometallic molecules, TMCp2 (TM =Cr, Mn, Fe, Co, Ni), and find that the calculated Ueff values can reproduce the experimentally determined ground-state electron configurations.

Removal of haloacetic acids from swimming pool water by reverse osmosis and nanofiltration.

PubMed

Yang, Linyan; She, Qianhong; Wan, Man Pun; Wang, Rong; Chang, Victor W-C; Tang, Chuyang Y

2017-06-01

Recent studies report high concentrations of haloacetic acids (HAAs), a prevalent class of toxic disinfection by-products, in swimming pool water (SPW). We investigated the removal of 9 HAAs by four commercial reverse osmosis (RO) and nanofiltration (NF) membranes. Under typical SPW conditions (pH 7.5 and 50 mM ionic strength), HAA rejections were >60% for NF270 with molecular weight cut-off (MWCO) equal to 266 Da and equal or higher than 90% for XLE, NF90 and SB50 with MWCOs of 96, 118 and 152 Da, respectively, as a result of the combined effects of size exclusion and charge repulsion. We further included 7 neutral hydrophilic surrogates as molecular probes to resolve the rejection mechanisms. In the absence of strong electrostatic interaction (e.g., pH 3.5), the rejection data of HAAs and surrogates by various membranes fall onto an identical size-exclusion (SE) curve when plotted against the relative-size parameter, i.e., the ratio of molecular radius over membrane pore radius. The independence of this SE curve on molecular structures and membrane properties reveals that the relative-size parameter is a more fundamental SE descriptor compared to molecular weight. An effective molecular size with the Stokes radius accounting for size exclusion and the Debye length accounting for electrostatic interaction was further used to evaluate the rejection. The current study provides valuable insights on the rejection of trace contaminants by RO/NF membranes. Copyright © 2017. Published by Elsevier Ltd.

Determination of effective droplet radius and optical depth of liquid water clouds over a tropical site in northern Thailand using passive microwave soundings, aircraft measurements and spectral irradiance data

NASA Astrophysics Data System (ADS)

Nimnuan, P.; Janjai, S.; Nunez, M.; Pratummasoot, N.; Buntoung, S.; Charuchittipan, D.; Chanyatham, T.; Chantraket, P.; Tantiplubthong, N.

2017-08-01

This paper presents an algorithm for deriving the effective droplet radius and optical depth of liquid water clouds using ground-based measurements, aircraft observations and an adiabatic model of cloud liquid water. The algorithm derives cloud effective radius and cloud optical depth over a tropical site at Omkoi (17.80°N, 98.43°E), Thailand. Monthly averages of cloud optical depth are highest in April (54.5), which is the month with the lowest average cloud effective radius (4.2 μm), both occurring before the start of the rainy season and at the end of the high contamination period. By contrast, the monsoon period extending from May to October brings higher cloud effective radius and lower cloud optical depth to the region on average. At the diurnal scale there is a gradual increase in average cloud optical depth and decrease in cloud effective radius as the day progresses.

Interaction of indole-papaverine with DNA in solutions of various ionic strength

NASA Astrophysics Data System (ADS)

Travkina, V. I.; Moroshkina, E. B.; Osinnikova, D. N.

2017-11-01

Interaction of synthetic alkaloid of isoquinoline series, which is an analogue of the biologically active compound papaverine, was studied by spectral, microcalorimetric, optical and hydrodynamic methods at different ionic strengths of medium. It was found that the investigated compound may interact with DNA in various ways depending on the ratio of ligand - DNA concentrations and ionic strength of solution (μ). When μ = 0.001, indole-papaverine intercalates into the double helix of DNA. The increase of μ resulted in a decrease of the affinity of the compound to DNA and a change its binding method.

[Verification of a decrease in the rigidity of the phage lambda DNA polymeric chain in low ionic strength aqueous solutions by testing the polymer-polymer interlink interactions].

PubMed

Arutiunian, A V; Ivanova, M A; Kurliand, D I; Kapshin, Iu S; Landa, S B; Poshekhonov, S T; Drobchenko, E A; Shevelev, I V

2011-01-01

Changes in the rigidity of the polymetric chain of phage lambda double-strand DNA have been studied by laser correlation spectroscopy. It was shown that, as the ionic strength increases, the effect of the screening of the hydrodynamic interaction of the links of the polymeric chain specific for polymeric coils arises in a DNA solution. It is assumed that the screening occurs when the threshold of the overlapping of DNA coils is achieved. The overlapping of coils is the result of a previously observed significant rise of DNA coil size from abnormally small DNA coils in low ionic strength buffers (about 10(-2) M Na+ or less) to maximum possible large coils in the 5SSC and 5SSC-like buffers. Further analysis of the far interlink interactions in linear lambda phage DNA coils in similar buffers at pH 7 and 4 confirms the earlier proposal about the role of H+ ions in the appearance of abnormally small DNA coils. The abnormal decrease in the DNA coil size in low ionic strength buffers is not a specific feature of lambda phage DNA only.

Selective interactions of trivalent cations Fe³⁺, Al³⁺ and Cr³⁺ turn on fluorescence in a naphthalimide based single molecular probe.

PubMed

Janakipriya, Subramaniyan; Chereddy, Narendra Reddy; Korrapati, Purnasai; Thennarasu, Sathiah; Mandal, Asit Baran

2016-01-15

Synthesis and fluorescence turn-on behavior of a naphthalimide based probe is described. Selective interactions of trivalent cations Fe(3+), Al(3+) or Cr(3+) with probe 1 inhibit the PET operating in the probe, and thereby, permit the detection of these trivalent cations present in aqueous samples and live cells. Failure of other trivalent cations (Eu(3+), Gd(3+) and Nb(3+)) to inhibit the PET process in 1 demonstrates the role of chelating ring size vis-à-vis ionic radius in the selective recognition of specific metal ions. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparing the 2,2'-Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium

DOE PAGES

Cross, Justin N.; Macor, Joseph A.; Bertke, Jeffery A.; ...

2016-09-15

Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear-fuel cycles. Here in this paper, we describe the preparation of (NBu 4)Am[S 2P( tBu 2C 12H 6)] 4 and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd III) and an isoelectronic one (Eu III). The results include the first measurement of an Am-S bond length, with a mean value of 2.921(9) Å, by single-crystal X-ray diffraction. Comparison with the Eu III and Nd III complexes revealed subtle electronic differences between the complexes of Am III and the lanthanides.

Biokinetic data and models for occupational intake of lanthanoids

DOE PAGES

Leggett, Richard Wayne; Ansoborlo, Eric; Bailey, Michael; ...

2014-05-12

The lanthanoid (or lanthanide) chemical elements comprise fifteen elements with atomic numbers 57 (lanthanum) through 71 (lutetium). This paper reviews data related to the biological behavior of these elements in the human body and proposes biokinetic models for application to occupational intake of radio-lanthanoids. Generic (element-independent) absorption rates from the respiratory and alimentary tracts to blood are proposed. The proposed systemic models are largely generic but include some element-specific parameter values to reflect regular changes with ionic radius in certain aspects of the behavior of the lanthanoids. This work was performed within the internal dosimetry task group (INDOS) of Committeemore » 2 of the International Commission on Radiological Protection (ICRP).« less

Superconducting transition temperature in the Y(1-x)M(x)Ba2Cu3O(y) system

NASA Astrophysics Data System (ADS)

Suzuki, Takeyuki; Yamazaki, Tsutomu; Sekine, Ryuuta; Koukitsu, Akinori; Seki, Hisashi

1989-04-01

Experimental results are presented for the inclusion of compositional additives, M, to the sintered high-temperature superconductor Y(1-x)M(x)Ba2Cu3O(y); M can be the oxides of Mg, Ce, Gd, Yb, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Te, as well as Li, Na, K, Ca, Sr, and La carbonates. Temperature dependence of the electrical resistance was measured down to about 80 K. Attention is given to the influence of ionic radius and the valence of the M species.

Effect of tip radius on the incipient plasticity of chromium studied by nanoindentation

DOE PAGES

Wu, Dong; Morris, James R.; Nieh, T. G.

2014-10-01

The onset of plasticity in Cr was investigated by nanoindentation using indenters with tip radii ranging from 60 to 759 nm. The stress for incipient plasticity was found to increase with decreasing tip radius. We find that the cumulative pop-in probability on load could be described successfully by a combined model over the full range of tip radius, indicating that the incipient plasticity might be triggered either by the homogeneous nucleation of dislocation or by the activation of existing dislocations underneath the indenter.

Benzyl-Functionalized Room Temperature Ionic Liquids for CO2/N2 Separation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahurin, Shannon Mark; Dai, Thomas N; Yeary, Joshua S

2011-01-01

In this work, three classes of room temperature ionic liquids (RTILs), including imidazolium, pyridinium, and pyrrolidinium ionic liquids with a benzyl group appended to the cation, were synthesized and tested for their performance in separating CO{sub 2} and N{sub 2}. All RTILs contained the bis(trifluoromethylsulfonyl)imide anion, permitting us to distinguish the impact of the benzyl moiety attached to the cation on gas separation performance. In general, the attachment of the benzyl group increased the viscosity of the ionic liquid compared with the unfunctionalized analogs and decreased the CO{sub 2} permeability. However, all of the benzyl-modified ionic liquids exhibited enhanced CO{submore » 2}/N{sub 2} selectivities compared with alkyl-based ionic liquids, with values ranging from 22.0 to 33.1. In addition, CO{sub 2} solubilities in the form of Henry's constants were also measured and compared with unfunctionalized analogs. Results of the membrane performance tests and CO{sub 2} solubility measurements demonstrate that the benzyl-functionalized RTILs have significant potential for use in the separation of carbon dioxide from combustion products.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, S.; Ghosh, A., E-mail: sspag@iacs.res.in

We have studied ionic conductivity and dielectric permittivity of PEO-LiClO{sub 4} solid polymer electrolyte plasticized with propylene carbonate. Differential scanning calorimetry and X-ray diffraction studies confirm minimum volume fraction of crystalline phase for the polymer electrolyte with 40 wt. % propylene carbonate. The ionic conductivity exhibits a maximum for the same composition. The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. Ion-ion interactions in the polymer electrolytes have been studied using Raman spectra and the concentrations of free ions, ion-pairs and ion-aggregates have been determined. The ionic conductivity increases due to the increase of freemore » ions with the increase of propylene carbonate content. But for higher content of propylene carbonate, the ionic conductivity decreases due to the increase of concentrations of ion-pairs and ion-aggregates. To get further insights into the ion dynamics, the experimental data for the complex dielectric permittivity have been studied using Havriliak–Negami function. The variation of relaxation time with temperature obtained from this formalism follows Vogel-Tamman-Fulcher equation similar to the ionic conductivity.« less

Structural and Dielectric Properties of Ionic Liquid Doped Metal Organic Framework based Polymer Electrolyte Nanocomposites

NASA Astrophysics Data System (ADS)

Dutta, Rituraj; Kumar, Ashok

2016-10-01

Metal Organic Frameworks (MOFs) are mesoporous materials that can be treated as potential hosts for trapping guest molecules in their pores. Ion conduction and phase behavior dynamics of Ionic Liquids (ILs) can be controlled by tunable interactions of MOFs with the ILs. MOFs incorporated with ionic liquid can be dispersed in the polymers to synthesize polymer electrolyte nanocomposites with high ionic conductivity, electrochemical and thermal stability for applications in energy storage and conversion devices such as rechargeable Li-ion batteries. In the present work we have synthesized Cu-based MOF [Cu3(l,3,5-benzene tricarboxylate)2(H2O)] incorporated with the ionic liquid 1-Butyl-3-methylimidazolium bromide at different weight ratios of MOF and IL. The synthesized MOF-IL composites are dispersed in Poly (ethylene oxide) (PEO). Frequency dependent behavior of permittivity and dielectric loss of the nanocomposites depict the non-Debye dielectric relaxation mechanism. The room temperature Nyquist plots reveal decreasing bulk resistance upto 189 Ω with optimum ionic conductivity of 1.3×10-3S cm-1at maximum doping concentration of IL in the nanocomposite system.

A Flemion-based actuator with ionic liquid as solvent

NASA Astrophysics Data System (ADS)

Wang, Jin; Xu, Chunye; Taya, Minoru; Kuga, Yasuo

2007-04-01

A perfluorinated carboxylic acid membrane, i.e. Flemion, shows improved performance as actuator material compared with Nafion (perfluorinated sulfonic acid). Flemion has a higher ion exchange capacity and good mechanical strength. In particular, Flemion will deform with no back relaxation under applied electrical stimulus. However, with water as solvent, the operation of Flemion in air has serious problems, since water would evaporate quickly in air. Moreover, the electrochemical stability for use in water is around 1 V at room temperature. In previous work, investigations on Nafion with ionic liquid as solvents have been carried out by some researchers and good results have been obtained. In this work, we explore the use of highly stable ionic liquid instead of water as solvent in Flemion. Experimental results indicate that Flemion-based actuators with ionic liquid as solvent have improved stability as compared to the water samples. Although the forces exhibited by Flemion-based actuators with the use of ionic liquid decreased dramatically compared to water, these preliminary results suggest good potential for the use of Flemion with ionic liquid in future applications.

Flemion-based actuator with ionic liquid as solvent

NASA Astrophysics Data System (ADS)

Wang, Jin; Xu, Chunye; Taya, Minoru; Kuga, Yasuo

2006-03-01

A perfluorinated carboxylic acid membrane, i.e. Flemion, shows improved performance as actuator material compared with Nafion (perfluorinated sulfonic acide). Flemion has a higher ion exchange capacity and good mechanical strength. Especially, Flemion will deform with no back relaxation when applied electrical stimulus. However, with water as solvent, the operation of Flemion in air has serious problems. Since water would evaporate quickly in air. Moreover, the electrochemical stability for use in water is around 1V at room temperature. In previous work, investigations on Nafion with ionic liquid as solvents have been carried out and good results have been obtained. In this work, we explore the use of highly stable ionic liquid instead of water as solvent in Flemion. Experimental results indicate that Flemion based actuators with ionic liquid as solvent have improved stability as compared to the water samples. Although the forces exhibited by Flemion based actuators with the use of ionic liquid decreased dramatically as compared to water, these preliminary results suggest a good potential for use of Flemion with ionic liquid in some applications.

Local structure and polarization resistance of Ce doped SrMnO{sub 3} using extended x-ray fine structure analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, Jiseung; Lee, Heesoo, E-mail: heesoo@pusan.ac.kr

2014-09-15

Changes to the local structure of Sr and Mn atoms in Sr{sub 1−x}Ce{sub x}MnO{sub 3} (SCM) according to increasing Ce content and the effect of the structural change on the polarization resistance of SCM were investigated. The reduction of manganese was confirmed by the absorption edge shift of the Mn K-edge toward lower energies. The noise of oscillation in extended X-ray absorption fine structure k{sup 3}χ data at Mn K-edge reveals the distortion of the local structure of Mn atoms, and the peak that indicates the bonding length of Mn-O, Sr/Ce, and -Mn decreased with the addition of Ce contentmore » in Fourier transformations of the Mn K-edge. The distortion of the local structure at Mn atoms was affected by the reduced manganese ions having larger ionic radii than Mn{sup 4+}. Meanwhile, few distortions of local atomic structures of Sr atoms occurred, and the average nearest neighboring distances of Sr-O and Sr-Mn are ∼2.13 Å and ∼2.95 Å, respectively. The average bonding lengths of the Ce-O and Ce-Mn increased because the ionic radius of substituted Ce ion with 12 coordination number is smaller than that of Sr ion, which leads the reduction of Mn ions and the distortion of local structure at the substituted A-site. Therefore, we reasoned that the distortion of the local atomic structure at Mn atoms in MnO{sub 6} and Ce atoms in A-site is one of the causes for interrupting oxygen ion transfers as a geometric factor, which results in an increase in the polarization resistance of SCM within the Ce composition range from 10 mol. % to 30 mol. %.« less

Conductance of solutions of lithium tris(trifluoromethanesulfonyl) methide in water, acetonitrile, propylene carbonate, N,N-dimethylformamide, and nitromethane at 25 C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Croce, F.; D`Aprano, A.; Nanjundiah, C.

1996-01-01

In order to determine the solution properties of lithium tris(trifluoromethanesulfonyl) methide (LiMe) in water and the aprotic solvents acetonitrile (AN), propylene carbonate (PC), N,N-dimethylformamide (DMF), and nitromethane (MeNO{sub 2}), conductance measurements have been carried out at 25 C. Molar conductivities at infinite dilution ({Lambda}{degree}) and ion pair association constants (K{sub a}) were obtained analyzing the experimental data with the Fuoss-Hsia conductance equation using the expansion of Fernandez-Prini and Justice with and without inclusion of the Chen effect. The results show that according to the ability of the solvents to solvate lithium ion, ion-pair formation is small or nonexistent in solventsmore » with high donor number (water, PC, DMF, and AN) but fairly moderate in nitromethane. Single-ion molar conductivities at infinite dilution for ClO{sub 4}{sup {minus}}, AsF{sub 6}{sup {minus}}, PF{sub 6}{sup {minus}} CF{sub 3}SO{sub 3}{sup {minus}}, N(CF{sub 3}SO{sub 2}){sub 2}{sup {minus}}, and C(CF{sub 3}SO{sub 2}){sub 3}{sup {minus}} anions, obtained by combining these results with literature data, decrease as expected as the ionic radius increases, and with one exception are always greater than that of the lithium ion. This general trend does not, however, apply in water where the limiting ionic conductance of the lithium cation is greater than that of the methide anion. This anomalous behavior is attributed to significant solvation of the methide ion in water. Voltammetric measurements indicate high electrochemical stability of methide anion. Such anodic stability and the increase in the transference number of lithium ion in LiMe solutions strongly support the use of this electrolyte in high energy, high voltage lithium batteries.« less

Solar radius determination from SODISM/PICARD and HMI/SDO observations of the decrease of the spectral solar radiance during the 2012 June Venus transit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hauchecorne, A.; Meftah, M.; Irbah, A.

On 2012 June 5-6, the transit of Venus provided a rare opportunity to determine the radius of the Sun using solar imagers observing a well-defined object, namely, the planet and its atmosphere, partially occulting the Sun. A new method has been developed to estimate the solar radius during a planetary transit. It is based on the estimation of the spectral solar radiance decrease in a region around the contact between the planet and the Sun at the beginning of the ingress and at the end of the egress. The extrapolation to zero of the radiance decrease versus the Sun-to-Venus apparentmore » angular distance allows estimation of the solar radius at the time of first and fourth contacts. This method presents the advantage of being almost independent on the plate scale, the distortion, the refraction by the planetary atmosphere, and on the point-spread function of the imager. It has been applied to two space solar visible imagers, SODISM/PICARD and HMI/SDO. The found results are mutually consistent, despite their different error budgets: 959.''85 ± 0.''19 (1σ) for SODISM at 607.1 nm and 959.''90 ± 0.''06 (1σ) for HMI at 617.3 nm.« less

Dynamic and cyclic fatigue of engine-driven rotary nickel-titanium endodontic instruments.

PubMed

Haïkel, Y; Serfaty, R; Bateman, G; Senger, B; Allemann, C

1999-06-01

The absence of adequate testing standards for engine-driven nickel-titanium (NiTi) instruments necessitates further study of these instruments in all areas. This study examined three groups of engine-driven rotary NiTi endodontic instruments (Profile, Hero, and Quantec) and assessed the times for dynamic fracture in relation to the radius of curvature to which the instruments were subjected during preparation, with the instrument diameter determined by size and taper and the mode by which the fracture occurred. Ten instruments were randomly selected representing each size and taper for each group and for each radius of curvature: 600 in total. The instruments were rotated at 350 rpm and introduced into a tempered steel curve that simulated a canal. Two radii of curvature of canals were used: 5 and 10 mm. Time at fracture was noted for all files, and the fracture faces of each file were analyzed with scanning electron microscopy. Radius of curvature was found to be the most significant factor in determining the fatigue resistance of the files. As radius of curvature decreased, fracture time decreased. Taper of files was found to be significant in determining fracture time. As diameter increased, fracture time decreased. In all cases, fracture was found to be of a ductile nature, thus implicating cyclic fatigue as a major cause of failure and necessitating further analyses and setting of standards in this area.

Analytical solution and numerical simulation of the liquid nitrogen freezing-temperature field of a single pipe

NASA Astrophysics Data System (ADS)

Cai, Haibing; Xu, Liuxun; Yang, Yugui; Li, Longqi

2018-05-01

Artificial liquid nitrogen freezing technology is widely used in urban underground engineering due to its technical advantages, such as simple freezing system, high freezing speed, low freezing temperature, high strength of frozen soil, and absence of pollution. However, technical difficulties such as undefined range of liquid nitrogen freezing and thickness of frozen wall gradually emerge during the application process. Thus, the analytical solution of the freezing-temperature field of a single pipe is established considering the freezing temperature of soil and the constant temperature of freezing pipe wall. This solution is then applied in a liquid nitrogen freezing project. Calculation results show that the radius of freezing front of liquid nitrogen is proportional to the square root of freezing time. The radius of the freezing front also decreases with decreased the freezing temperature, and the temperature gradient of soil decreases with increased distance from the freezing pipe. The radius of cooling zone in the unfrozen area is approximately four times the radius of the freezing front. Meanwhile, the numerical simulation of the liquid nitrogen freezing-temperature field of a single pipe is conducted using the Abaqus finite-element program. Results show that the numerical simulation of soil temperature distribution law well agrees with the analytical solution, further verifies the reliability of the established analytical solution of the liquid nitrogen freezing-temperature field of a single pipe.

A review of the distribution coefficients of trace elements in soils: influence of sorption system, element characteristics, and soil colloidal properties.

PubMed

Shaheen, Sabry M; Tsadilas, Christos D; Rinklebe, Jörg

2013-12-01

Knowledge about the behavior and reactions of separate soil components with trace elements (TEs) and their distribution coefficients (Kds) in soils is a key issue in assessing the mobility and retention of TEs. Thus, the fate of TEs and the toxic risk they pose depend crucially on their Kd in soil. This article reviews the Kd of TEs in soils as affected by the sorption system, element characteristics, and soil colloidal properties. The sorption mechanism, determining factors, favorable conditions, and competitive ions on the sorption and Kd of TEs are also discussed here. This review demonstrates that the Kd value of TEs does not only depend on inorganic and organic soil constituents, but also on the nature and characteristics of the elements involved as well as on their competition for sorption sites. The Kd value of TEs is mainly affected by individual or competitive sorption systems. Generally, the sorption in competitive systems is lower than in mono-metal sorption systems. More strongly sorbed elements, such as Pb and Cu, are less affected by competition than mobile elements, such as Cd, Ni, and Zn. The sorption preference exhibited by soils for elements over others may be due to: (i) the hydrolysis constant, (ii) the atomic weight, (iii) the ionic radius, and subsequently the hydrated radius, and (iv) its Misono softness value. Moreover, element concentrations in the test solution mainly affect the Kd values. Mostly, values of Kd decrease as the concentration of the included cation increases in the test solution. Additionally, the Kd of TEs is controlled by the sorption characteristics of soils, such as pH, clay minerals, soil organic matter, Fe and Mn oxides, and calcium carbonate. However, more research is required to verify the practical utilization of studying Kd of TEs in soils as a reliable indicator for assessing the remediation process of toxic metals in soils and waters. © 2013 Elsevier B.V. All rights reserved.

Novel ascorbic acid based ionic liquids for the in situ synthesis of quasi-spherical and anisotropic gold nanostructures in aqueous medium.

PubMed

Dinda, Enakshi; Si, Satyabrata; Kotal, Atanu; Mandal, Tarun K

2008-01-01

A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi-spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1-alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3-methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature (Tg) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape-directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry-like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.

Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples.

PubMed

da Silva, Meire Ribeiro; Mauro Lanças, Fernando

2018-03-10

Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MacBurn's cylinder test problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shestakov, Aleksei I.

2016-02-29

This note describes test problem for MacBurn which illustrates its performance. The source is centered inside a cylinder with axial-extent-to-radius ratio s.t. each end receives 1/4 of the thermal energy. The source (fireball) is modeled as either a point or as disk of finite radius, as described by Marrs et al. For the latter, the disk is divided into 13 equal area segments, each approximated as a point source and models a partially occluded fireball. If the source is modeled as a single point, one obtains very nearly the expected deposition, e.g., 1/4 of the flux on each end andmore » energy is conserved. If the source is modeled as a disk, both conservation and energy fraction degrade. However, errors decrease if the source radius to domain size ratio decreases. Modeling the source as a disk increases run-times.« less

Effect of Catalytic Cylinders on Autothermal Reforming of Methane for Hydrogen Production in a Microchamber Reactor

PubMed Central

Yan, Yunfei; Guo, Hongliang; Zhang, Li; Zhu, Junchen; Yang, Zhongqing; Tang, Qiang; Ji, Xin

2014-01-01

A new multicylinder microchamber reactor is designed on autothermal reforming of methane for hydrogen production, and its performance and thermal behavior, that is, based on the reaction mechanism, is numerically investigated by varying the cylinder radius, cylinder spacing, and cylinder layout. The results show that larger cylinder radius can promote reforming reaction; the mass fraction of methane decreased from 26% to 21% with cylinder radius from 0.25 mm to 0.75 mm; compact cylinder spacing corresponds to more catalytic surface and the time to steady state is decreased from 40 s to 20 s; alteration of staggered and aligned cylinder layout at constant inlet flow rates does not result in significant difference in reactor performance and it can be neglected. The results provide an indication and optimize performance of reactor; it achieves higher conversion compared with other reforming reactors. PMID:25097877

An Ultrastable Ionic Chemiresistor Skin with an Intrinsically Stretchable Polymer Electrolyte.

PubMed

Jin, Ming Liang; Park, Sangsik; Kim, Jong-Seon; Kwon, Sung Hyun; Zhang, Shuye; Yoo, Min Seok; Jang, Sungwoo; Koh, Hyeong-Jun; Cho, Soo-Yeon; Kim, So Young; Ahn, Chi Won; Cho, Kilwon; Lee, Seung Geol; Kim, Do Hwan; Jung, Hee-Tae

2018-05-01

Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound (VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices. The ICS displays highly sensitive and stable sensing of representative VOCs (including toluene, hexane, propanal, ethanol, and acetone) that are found in the exhaled breath of lung cancer patients. In particular, the sensor is found to be fully operational even after being subjected to long-term storage or harsh environmental conditions (relative humidity of 85% or temperature of 100 °C) or severe mechanical deformation (bending to a radius of curvature of 1 mm, or stretching strain of 100%), which can be an effective method to realize a human-adaptive and skin-attachable biosensor platform for daily use and early diagnosis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hidden Criticality of Counterion Condensation Near a Charged Cylinder.

PubMed

Cha, Minryeong; Yi, Juyeon; Kim, Yong Woon

2017-09-05

Counterion condensation onto a charged cylinder, known as the Manning transition, has received a great deal of attention since it is essential to understand the properties of polyelectrolytes in ionic solutions. However, the current understanding is still far from complete and poses a puzzling question: While the strong-coupling theory valid at large ionic correlations suggests a discontinuous nature of the counterion condensation, the mean-field theory always predicts a continuous transition at the same critical point. This naturally leads to a question how one can reconcile the mean-field theory with the strong-coupling prediction. Here, we study the counterion condensation transition on a charged cylinder via Monte Carlo simulations. Varying the cylinder radius systematically in relation to the system size, we find that in addition to the Manning transition, there exists a novel transition where all counterions are bound to the cylinder and the heat capacity shows a drop at a finite Manning parameter. A finite-size scaling analysis is carried out to confirm the criticality of the complete condensation transition, yielding the same critical exponents with the Manning transition. We show that the existence of the complete condensation is essential to explain how the condensation nature alters from continuous to discontinuous transition.

The effect of human microtubule-associated-protein tau on the assembly structure of microtubules and its ionic strength dependence

NASA Astrophysics Data System (ADS)

Choi, M. C.; Raviv, U.; Miller, H. P.; Gaylord, M. R.; Kiris, E.; Ventimiglia, D.; Needleman, D. J.; Chung, P. J.; Deek, J.; Lapointe, N.; Kim, M. W.; Wilson, L.; Feinstein, S. C.; Safinya, C. R.

2010-03-01

Microtubules (MTs), 25 nm protein nanotubes, are among the major filamentous elements of the eukaryotic cytoskeleton involved in intracellular trafficking, cell division and the establishment and maintenance of cell shape. Microtubule-associated-protein tau regulates tubulin assembly, MT dynamics and stability. Aberrant tau action has long been correlated with numerous neurodegenerative diseases, including Alzheimer's, and fronto-temporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17) Using synchrotron small angle x-ray scattering (SAXS) and binding assay, we examine the effects of tau on the assembly structure of taxol-stabilized MTs. We find that tau regulates the distribution of protofilament numbers in MTs as reflected in the observed increase in the average radius of MTs with increasing the tau/tubulin molar ratio. Additionally, tau-MT interactions are mediated to a large extent via electrostatic interactions: the binding affinity of tau to MTs is ionic strength dependent. Supported by DOE-BES DE-FG02-06ER46314, NSF DMR-0803103, NIH NS35010, NIH NS13560. (Ref) M.C. Choi, S.C. Feinstein, and C.R. Safinya et al. Biophys. J. 97; 519 (2009).

Ginzburg-Landau theory for the solid-liquid interface of bcc elements. II - Application to the classical one-component plasma, the Wigner crystal, and He-4

NASA Technical Reports Server (NTRS)

Zeng, X. C.; Stroud, D.

1989-01-01

The previously developed Ginzburg-Landau theory for calculating the crystal-melt interfacial tension of bcc elements to treat the classical one-component plasma (OCP), the charged fermion system, and the Bose crystal. For the OCP, a direct application of the theory of Shih et al. (1987) yields for the surface tension 0.0012(Z-squared e-squared/a-cubed), where Ze is the ionic charge and a is the radius of the ionic sphere. Bose crystal-melt interface is treated by a quantum extension of the classical density-functional theory, using the Feynman formalism to estimate the relevant correlation functions. The theory is applied to the metastable He-4 solid-superfluid interface at T = 0, with a resulting surface tension of 0.085 erg/sq cm, in reasonable agreement with the value extrapolated from the measured surface tension of the bcc solid in the range 1.46-1.76 K. These results suggest that the density-functional approach is a satisfactory mean-field theory for estimating the equilibrium properties of liquid-solid interfaces, given knowledge of the uniform phases.

Influence of the counteranion on the ability of 1-dodecyl-3-methyltriazolium ionic liquids to form mesophases

DOE PAGES

Stappert, Kathrin; Unal, Derya; Spielberg, Eike T.; ...

2014-11-25

The influence of the counteranion on the ability of the mesogenic cation 1-methyl-3-dodecyl-triazolium to form mesophases is explored. To that avail, salts of the cation with anions of different size, shape, and hydrogen bonding capability such as Cl –, Br –, I –, I 3 –, PF 6 –, and Tf 2N – [bis(trifluorosulfonyl)amide] were synthesized and characterized. The crystal structures of the bromide, the iodide, and the triiodide reveal that the cations form bilayers with cations oriented in opposite directions featuring interdigitated alkyl tails. Within the layers, the cations are separated by anions. The rod-shaped triiodide anion forces themore » triazolium cation to align with it in this crystal structure but due to its space requirement reduces the alkyl chain interdigitation which prevents the formation of a mesophase. Rather the compound transforms directly from a crystalline solid to an (ionic) liquid like the analogous bis(trifluorosulfonyl)amide. In contrast, the simple halides and the hexafluorophosphate form liquid crystalline phases. As a result, their clearing points shift with increasing anion radius to lower temperatures.« less

Boundary layer charge dynamics in ionic liquid-ionic polymer transducers

NASA Astrophysics Data System (ADS)

Davidson, Jacob D.; Goulbourne, N. C.

2011-01-01

Ionic polymer transducers (IPTs), also known as ionic polymer-metal composites, are soft sensors and actuators which operate through a coupling of microscale chemical, electrical, and mechanical interactions. The use of an ionic liquid as solvent for an IPT has been shown to dramatically increase transducer lifetime in free-air use, while also allowing for higher applied voltages without electrolysis. In this work, we apply Nernst-Planck/Poisson theory to model charge transport in an ionic liquid IPT by considering a certain fraction of the ionic liquid ions as mobile charge carriers, a phenomenon which is unique to ionic liquid IPTs compared to their water-based counterparts. Numerical simulations are performed using the finite element method to examine how the introduction of another pair of mobile ions affects boundary layer charge dynamics, concentration, and charge density distributions in the electric double layer, and the overall charge transferred and current response of the IPT. Due to interactions with the Nafion ionomer, not all of the ionic liquid ions will function as mobile charge carriers; only a certain fraction will exist as "free" ions. The presence of mobile ionic liquid ions in the transducer will increase the overall charge transferred when a voltage is applied, and cause the current in the transducer to decay more slowly. The additional mobile ions also cause the ionic concentration profiles to exhibit a nonlinear dynamic response, characterized by nonmonotonic ionic concentration profiles in space and time. Although the presence of mobile ionic liquid ions increases the overall amount of charge transferred, this additional charge transfer occurs in a somewhat symmetric manner. Therefore, the additional charge transferred due to the ionic liquid ions does not greatly increase the net bending moment of the transducer; in fact, it is possible that ionic liquid ion movement actually decreases the observed bending response. This suggests that an optimal electromechanical conversion efficiency for bending actuation is achieved by using an ionic liquid where only a relatively small fraction of the ionic liquid ions exist as free ions. Conversely, if it is desired to increase the overall amount of charge transferred, an ionic liquid with a large fraction of free ions should be used. These theoretical considerations are found to be in good qualitative agreement with recent experimental results.

Nutrient-substituted hydroxyapatites: synthesis and characterization

NASA Technical Reports Server (NTRS)

Golden, D. C.; Ming, D. W.

1999-01-01

Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into HA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg-1, Zn ranged from 57 to 1279 mg kg-1, Fe from 211 to 2573 mg kg-1, and Mn from 190 to 1719 mg kg-1, depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P.

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte

NASA Astrophysics Data System (ADS)

Arya, Anil; Sharma, A. L.

2018-04-01

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO8-NaPF6+  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ({{τ }{{\\varepsilon \\prime}}}>~{{τ }tanδ }>{{τ }z}>{{τ }m} ) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ({{σ }\\prime\\prime}~versus~{{σ }\\prime} ) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole–Cole plot ({{\\varepsilon }\\prime\\prime}~versus~{{\\varepsilon }\\prime} ) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Modeling the adsorption of metal ions (Cu 2+, Ni 2+, Pb 2+) onto ACCs using surface complexation models

NASA Astrophysics Data System (ADS)

Faur-Brasquet, Catherine; Reddad, Zacaria; Kadirvelu, Krishna; Le Cloirec, Pierre

2002-08-01

Activated carbon cloths (ACCs), whose efficiency has been demonstrated for microorganics adsorption from water, were here studied in the removal of metal ions from aqueous solution. Two ACCs are investigated, they are characterized in terms of porosity parameters (BET specific surface area, percentage of microporosity) and chemical characteristics (acidic surface groups, acidity constants, point of zero charge). A first part consists in the experimental study of three metal ions removal (Cu 2+, Ni 2+ and Pb 2+) in a batch reactor. Isotherms modeling by Freundlich and Brunauer-Emmett-Teller (BET) equations enables the following adsorption order: Cu 2+>Ni 2+>Pb 2+ to be determined for adsorption capacities on a molar basis. It may be related to adsorbates characteristics in terms of electronegativity and ionic radius. The influence of adsorbent's microporosity is also shown. Adsorption experiments carried out for pH values ranging from 2 to 10 demonstrate: (i) an adsorption occurring below the precipitation pH; (ii) the strong influence of pH, with a decrease of electrostatic repulsion due to the formation of less charged hydrolyzed species coupled with a decrease of activated carbon surface charge as pH increases. The second part focuses on the modeling of adsorption versus the pH experimental data by the diffuse layer model (DLM) using Fiteql software. The model is efficient to describe the system behavior in the pH range considered. Regarding complexation constants, they show the following affinity for ACC: Pb 2+>Cu 2+>Ni 2+. They are related to initial concentrations used for the three metal ions.

High Temperature Superconductivity in Praseodymium Doped (0%, 2%, 4%) in Melt-Textured Y(1-x)Pr(x)Ba2Cu3O(7-delta) Systems

NASA Technical Reports Server (NTRS)

James, Claudell

1995-01-01

A study of the magnetic and structural properties of the alloy Y(1-x)Pr(x)Ba2Cu3O(7-delta) of 0%, 2%, and 4% doping of praseodymium is presented. The resulting oxides of the alloy series are a high-temperature superconductor Y-Ba-Cu-O, which has an orthorhombic superconducting crystal-lattice. Magnetic relaxation studies have been performed on the Y-Pr-Ba-CuO bulk samples for field orientation parallel to the c-axis, using a vibrating sample magnetometer. Relaxation was measured at several temperatures to obtain the irreversible magnetization curves used for the Bean model. Magnetization current densities were derived from the relaxation data. Field and temperature dependence of the logarithmic flux-creep relaxation was measured in critical state. The data indicates that the effective activation energy U(eff) increases with increasing T between 77 K and 86 K. Also, the data shows that U(eff)(T) and superconducting transition temperature, Tc, decreased as the lattice parameters increased with increasing Pr ion concentration, x, for the corresponding Y(1-x)Pr(x)Ba(x)Cu3O(7-delta) oxides. One contribution to Tc decrease in this sampling is suspected to be due to the larger ionic radius of the Pr(3+) ion. The upper critical field (H(sub c2)) was measured in the presence of magnetic field parallel to the c axis. A linear temperature dependence with H(sub c2) was obtained.

First-principles study of crystal and electronic structure of rare-earth cobaltites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Topsakal, M.; Leighton, C.; Wentzcovitch, R. M.

Using density functional theory plus self-consistent Hubbard U (DFT + U{sub sc}) calculations, we have investigated the structural and electronic properties of the rare-earth cobaltites RCoO{sub 3} (R = Pr – Lu). Our calculations show the evolution of crystal and electronic structure of the insulating low-spin RCoO{sub 3} with increasing rare-earth atomic number (decreasing ionic radius), including the invariance of the Co-O bond distance (d{sub Co–O}), the decrease of the Co-O-Co bond angle (Θ), and the increase of the crystal field splitting (Δ{sub CF}) and band gap energy (E{sub g}). Agreement with experiment for the latter improves considerably with the use of DFT + U{sub sc}more » and all trends are in good agreement with the experimental data. These trends enable a direct test of prior rationalizations of the trend in spin-gap associated with the spin crossover in this series, which is found to expose significant issues with simple band based arguments. We also examine the effect of placing the rare-earth f-electrons in the core region of the pseudopotential. The effect on lattice parameters and band structure is found to be small, but distinct for the special case of PrCoO{sub 3} where some f-states populate the middle of the gap, consistent with the recent reports of unique behavior in Pr-containing cobaltites. Overall, this study establishes a foundation for future predictive studies of thermally induced spin excitations in rare-earth cobaltites and similar systems.« less

Coupled factors influencing detachment of nano- and micro-sized particles from primary minima.

PubMed

Shen, Chongyang; Lazouskaya, Volha; Jin, Yan; Li, Baoguo; Ma, Zhiqiang; Zheng, Wenjuan; Huang, Yuanfang

2012-06-01

This study examined the detachments of nano- and micro-sized colloids from primary minima in the presence of cation exchange by laboratory column experiments. Colloids were initially deposited in columns packed with glass beads at 0.2 M CaCl(2) in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Then, the columns were flushed with NaCl solutions with different ionic strengths (i.e., 0.001, 0.01, 0.1 and 0.2 M). Detachments were observed at all ionic strengths and were particularly significant for the nanoparticle. The detachments increased with increasing electrolyte concentration for the nanoparticle whereas increased from 0.001 M to 0.01 M and decreased with further increasing electrolyte concentration for the micro-sized colloid. The observations were attributed to coupled influence of cation exchange, short-range repulsion, surface roughness, surface charge heterogeneity, and deposition in the secondary minima. The detachments of colloids from primary minima challenge the common belief that colloid interaction in primary minimum is irreversible and resistant to disturbance in solution ionic strength and composition. Although the significance of surface roughness, surface charge heterogeneity, and secondary minima on colloid deposition has been widely recognized, our study implies that they also play important roles in colloid detachment. Whereas colloid detachment is frequently associated with decrease of ionic strength, our results show that increase of ionic strength can also cause detachment due to influence of cation exchange. Copyright © 2012 Elsevier B.V. All rights reserved.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

2016-05-01

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengwa, R. J., E-mail: rjsengwa@rediffmail.com; Dhatarwal, Priyanka, E-mail: dhatarwalpriyanka@gmail.com; Choudhary, Shobhna, E-mail: shobhnachoudhary@rediffmail.com

2016-05-06

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF{sub 4}) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governedmore » by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10{sup −6} S cm{sup −1} which suggests the suitability of the SPE film for rechargeable lithium batteries.« less

Effect of Aprotic Solvents on the Dynamics of a Room Temperature Ionic Liquid

NASA Astrophysics Data System (ADS)

Osti, Naresh; van Aken, Katherine; Thompson, Matthew; Tiet, Felix; Jiang, De-En; Cummings, Peter; Gogotsi, Yury; Mamontov, Eugene

Room temperature ionic liquids (RTILs) have attracted much attention as electrolytes in energy storage devices because of their peculiar physical and chemical characteristics. However, their remarkably high viscosity, which results in low conductivity and diffusivity, may adversely affect the charging and discharging rates. Despite changing molecular configurations, use of aprotic solvent allows to enhance the transport properties of ionic liquids by disrupting the cation-anion interactions. We explore the impact of dipole moment of aprotic solvents on the cation-anion interaction and transport in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMIM +][Tf2N-], RTIL using molecular dynamics (MD) simulations and quasi-elastic neutrons scattering (QENS) measurements. We observed an increase in cation diffusivity with the increasing dipole moment of the solvent. This effect is due to a decrease in the solvation free energy induced by the increasing solvent polarity. A clear nano-phase separation into ionic liquid-rich and ionic liquid-poor phases as observed by QENS will be also discussed.

Predictive modeling studies for the ecotoxicity of ionic liquids towards the green algae Scenedesmus vacuolatus.

PubMed

Das, Rudra Narayan; Roy, Kunal

2014-06-01

Hazardous potential of ionic liquids is becoming an issue of high concern with increasing application of these compounds in various industrial processes. Predictive toxicological modeling on ionic liquids provides a rational assessment strategy and aids in developing suitable guidance for designing novel analogues. The present study attempts to explore the chemical features of ionic liquids responsible for their ecotoxicity towards the green algae Scenedesmus vacuolatus by developing mathematical models using extended topochemical atom (ETA) indices along with other categories of chemical descriptors. The entire study has been conducted with reference to the OECD guidelines for QSAR model development using predictive classification and regression modeling strategies. The best models from both the analyses showed that ecotoxicity of ionic liquids can be decreased by reducing chain length of cationic substituents and increasing hydrogen bond donor feature in cations, and replacing bulky unsaturated anions with simple saturated moiety having less lipophilic heteroatoms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impact of water dilution and cation tail length on ionic liquid characteristics: Interplay between polar and non-polar interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hegde, Govind A.; Bharadwaj, Vivek S.; Kinsinger, Corey L.

2016-08-14

The recalcitrance of lignocellulosic biomass poses a major challenge that hinders the economical utilization of biomass for the production of biofuel, plastics, and chemicals. Ionic liquids have become a promising solvent that addresses many issues in both the pretreatment process and the hydrolysis of the glycosidic bond for the deconstruction of cellulosic materials. However, to make the use of ionic liquids economically viable, either the cost of ionic liquids must be reduced, or a less expensive solvent (e.g., water) may be added to reduce the overall amount of ionic liquid used in addition to reducing the viscosity of the binarymore » liquid mixture. In this work, we employ atomistic molecular dynamics simulations to investigate the impact of water dilution on the overall liquid structure and properties of three imidazolium based ionic liquids. It is found that ionic liquid-water mixtures exhibit characteristics that can be grouped into two distinct regions, which are a function of the ionic liquid concentration. The trends observed in each region are found to correlate with the ordering in the local structure of the ionic liquid that arises from the dynamic interactions between the ion pairs. Simulation results suggest that there is a high level of local ordering in the molecular structure at high concentrations of ionic liquids that is driven by the aggregation of the cationic tails and the anion-water interactions. It is found that as the concentration of ionic liquids in the binary mixture is decreased, there is a point at which the competing self and cross interaction energies between the ionic liquid and water shifts away from a cation-anion dominated regime, which results in a significant change in the mixture properties. This break point, which occurs around 75% w/w ionic liquids, corresponds to the point at which water molecules percolate into the ionic liquid network disrupting the ionic liquids’ nanostructure. It is observed that as the cationic alkyl tail length increases, the changes in the binary mixtures’ properties become more pronounced.« less

Modification of the erythrocyte membrane dielectric constant by alcohols.

PubMed

Orme, F W; Moronne, M M; Macey, R I

1988-08-01

Aliphatic alcohols are found to stimulate the transmembrane fluxes of a hydrophobic cation (tetraphenylarsonium, TPA) and anion (AN-12) 5-20 times in red blood cells. The results are analyzed using the Born-Parsegian equation (Parsegian, A., 1969, Nature (London) 221:844-846), together with the Clausius-Mossotti equation to calculate membrane dielectric energy barriers. Using established literature values of membrane thickness, native membrane dielectric constant, TPA ionic radius, and alcohol properties (partition coefficient, molar volume, dielectric constant), the TPA permeability data is predicted remarkably well by theory. If the radius of AN-12 is taken as 1.9 A, its permeability in the presence of butanol is also described by our analysis. Further, the theory quantitatively accounts for the data of Gutknecht and Tosteson (Gutknecht, J., Tosteson, D.C., 1970, J. Gen. Physiol. 55:359-374) covering alcohol-induced conductivity changes of 3 orders of magnitude in artificial bilayers. Other explanations including perturbations of membrane fluidity, surface charge, membrane thickness, and dipole potential are discussed. However, the large magnitude of the stimulation, the more pronounced effect on smaller ions, and the acceleration of both anions and cations suggest membrane dielectric constant change as the primary basis of alcohol effects.

Ferrate(VI)-prompted removal of metals in aqueous media: mechanistic delineation of enhanced efficiency via metal entrenchment in magnetic oxides.

PubMed

Prucek, Robert; Tuček, Jiří; Kolařík, Jan; Hušková, Ivana; Filip, Jan; Varma, Rajender S; Sharma, Virender K; Zbořil, Radek

2015-02-17

The removal efficiency of heavy metal ions (cadmium(II), Cd(II); cobalt(II), Co(II); nickel(II), Ni(II); copper(II), Cu(II)) by potassium ferrate(VI) (K2FeO4, Fe(VI)) was studied as a function of added amount of Fe(VI) (or Fe) and varying pH. At pH = 6.6, the effective removal of Co(II), Ni(II), and Cu(II) from water was observed at a low Fe-to-heavy metal ion ratio (Fe/M(II) = 2:1) while a removal efficiency of 70% was seen for Cd(II) ions at a high Fe/Cd(II) weight ratio of 15:1. The role of ionic radius and metal valence state was explored by conducting similar removal experiments using Al(III) ions. The unique combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), in-field Mössbauer spectroscopy, and magnetization measurements enabled the delineation of several distinct mechanisms for the Fe(VI)-prompted removal of metal ions. Under a Fe/M weight ratio of 5:1, Co(II), Ni(II), and Cu(II) were removed by the formation of MFe2O4 spinel phase and partially through their structural incorporation into octahedral positions of γ-Fe2O3 (maghemite) nanoparticles. In comparison, smaller sized Al(III) ions got incorporated easily into the tetrahedral positions of γ-Fe2O3 nanoparticles. In contrast, Cd(II) ions either did not form the spinel ferrite structure or were not incorporated into the lattic of iron(III) oxide phase due to the distinct electronic structure and ionic radius. Environmentally friendly removal of heavy metal ions at a much smaller dosage of Fe than those of commonly applied iron-containing coagulants and the formation of ferrimagnetic species preventing metal ions leaching back into the environment and allowing their magnetic separation are highlighted.

The relationship between bond ionicity, lattice energy, coefficient of thermal expansion and microwave dielectric properties of Nd(Nb(1-x)Sb(x))O4 ceramics.

PubMed

Zhang, Ping; Zhao, Yonggui; Wang, Xiuyu

2015-06-28

The crystalline structure refinement, chemical bond ionicity, lattice energy and coefficient of thermal expansion were carried out for Nd(Nb(1-x)Sb(x))O4 ceramics with a monoclinic fergusonite structure to investigate the correlations between the crystalline structure, phase stability, bond ionicity, lattice energy, coefficient of thermal expansion, and microwave dielectric properties. The bond ionicity, lattice energy, and coefficient of thermal expansion of Nd(Nb(1-x)Sb(x))O4 ceramics were calculated using a semiempirical method based on the complex bond theory. The phase structure stability varied with the lattice energy which was resulted by the substitution constant of Sb(5+). With the increasing of the Sb(5+) contents, the decrease of Nb/Sb-O bond ionicity was observed, which could be contributed to the electric polarization. The ε(r) had a close relationship with the Nb/Sb-O bond ionicity. The increase of the Q×f and |τ(f)| values could be attributed to the lattice energy and the coefficient of thermal expansion. The microwave dielectric properties of Nd(Nb(1-x)Sb(x))O4 ceramics with the monoclinic fergusonite structure were strongly dependent on the chemical bond ionicity, lattice energy and coefficient of thermal expansion.

Quasielastic neutron scattering studies on glass-forming ionic liquids with imidazolium cations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kofu, Maiko; Inamura, Yasuhiro; Miyazaki, Kyoko

2015-12-21

Relaxation processes for imidazolium-based ionic liquids (ILs) were investigated by means of an incoherent quasielastic neutron scattering technique. In order to clarify the cation and anion effects on the relaxation processes, ten samples were measured. For all of the samples, we found three relaxations at around 1 ps, 10 ps, and 100 ps-10 ns, each corresponding to the alkyl reorientation, the relaxation related to the imidazolium ring, and the ionic diffusion. The activation energy (E{sub a}) for the alkyl relaxation is insensitive to both anion and alkyl chain lengths. On the other hand, for the imidazolium relaxation and the ionicmore » diffusion processes, E{sub a} increases as the anion size decreases but is almost independent of the alkyl chain length. This indicates that the ionic diffusion and imidazolium relaxation are governed by the Coulombic interaction between the core parts of the cations (imidazolium ring) and the anions. This is consistent with the fact that the imidazolium-based ILs have nanometer scale structures consisting of ionic and neutral (alkyl chain) domains. It is also found that there is a clear correlation between the ionic diffusion and viscosity, indicating that the ionic diffusion is mainly associated with the glass transition which is one of the characteristics of imidazolium-based ILs.« less

Ionic Liquids as Surfactants for Layered Double Hydroxide Fillers: Effect on the Final Properties of Poly(Butylene Adipate-Co-Terephthalate)

PubMed Central

Livi, Sébastien; Lins, Luanda Chaves; Peter, Jakub; Kredatusova, Jana; Pruvost, Sébastien

2017-01-01

In this work, phosphonium ionic liquids (ILs) based on tetra-alkylphosphonium cations combined with carboxylate, phosphate and phosphinate anions, were used for organic modification of layered double hydroxide (LDH). Two different amounts (2 and 5 wt %) of the organically modified LDHs were mixed with poly(butylene adipate-co-terephthalate) (PBAT) matrix by melt extrusion. All prepared PBAT/IL-modified-LDH composites exhibited increased mechanical properties (20–50% Young’s modulus increase), decreased water vapor permeability (30–50% permeability coefficient reduction), and slight decreased crystallinity (10–30%) compared to the neat PBAT. PMID:28956811

Observational study of the relationship between entrainment rate and relative dispersion in deep convective clouds

NASA Astrophysics Data System (ADS)

Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; Liu, Yangang; Zhang, Guang Jun; Luo, Shi

2018-01-01

This study investigates the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius < 3.75 μm (N1), radius in the range of 3.75-12.75 μm (N2) and 12.75-23.25 μm (N3), respectively. The results indicate that although the droplet concentration at different sizes generally decrease simultaneously as λ increases, the variation of standard deviation (σ) depends mainly on N3, while the mean radius (rm) decreases with decreasing N3, but increases with decreasing N1. So the influence of entrainment on CDSD causes a more dramatical decrease in σ than that in rm, and further leads to the decrease of ε as entrainment enhances. In addition, a conceptual model of CDSD evolution during entrainment-mixing processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found to be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.

Observational study of the relationship between entrainment rate and relative dispersion in deep convective clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang

We investigate the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius < 3.75 μm (N 1), radius in the range of 3.75–12.75 μm (N 2) and 12.75–23.25 μm (N 3), respectively. Our results indicate that although the droplet concentration atmore » different sizes generally decrease simultaneously as λ increases, the variation of standard deviation (σ) depends mainly on N 3, while the mean radius (r m) decreases with decreasing N 3, but increases with decreasing N 1. So the influence of entrainment on CDSD causes a more dramatical decrease in σ than that in r m, and further leads to the decrease of ε as entrainment enhances. In addition, a conceptual model of CDSD evolution during entrainment-mixing processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found to be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.« less

Observational study of the relationship between entrainment rate and relative dispersion in deep convective clouds

DOE PAGES

Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; ...

2017-09-23

We investigate the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius < 3.75 μm (N 1), radius in the range of 3.75–12.75 μm (N 2) and 12.75–23.25 μm (N 3), respectively. Our results indicate that although the droplet concentration atmore » different sizes generally decrease simultaneously as λ increases, the variation of standard deviation (σ) depends mainly on N 3, while the mean radius (r m) decreases with decreasing N 3, but increases with decreasing N 1. So the influence of entrainment on CDSD causes a more dramatical decrease in σ than that in r m, and further leads to the decrease of ε as entrainment enhances. In addition, a conceptual model of CDSD evolution during entrainment-mixing processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found to be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.« less

The effect of varying linker length on ion-transport properties in polymeric ionic liquids

NASA Astrophysics Data System (ADS)

Keith, Jordan; Mogurampelly, Santosh; Wheatle, Bill; Ganesan, Venkat

We report results of atomistic molecular dynamics simulations on polymerized 1-butyl-3-(n-alkyl)imidazolium ionic liquids with PF6- counterions. Consistent with experimental observations, we observe that the mobility of the PF6- ions increases with increasing n-alkyl linker length. Analysis of our results suggests that the motion of PF6- ions is driven by intermolecular ion hopping between chains, which in turn is influenced by ion-pair coordination numbers and intermolecular ionic separation distances. With increasing linker length, we observe 1) the anions coordinating less closely with cations and 2) intermolecular hopping distances decreasing.

Molecular dynamics simulation of the ionic liquid N-octylpyridinium tetrafluoroborate and acetonitrile: Thermodynamic and structural properties

NASA Astrophysics Data System (ADS)

Zhou, Siwen; Zhu, Guanglai; Kang, Xianqu; Li, Qiang; Sha, Maolin; Cui, Zhifeng; Xu, Xinsheng

2018-06-01

Using molecular dynamics simulation, the research obtained the thermodynamic properties and microstructures of the mixture of N-octylpyridinium tetrafluoroborate and acetonitrile, including density, self-diffusion coefficients, excess properties, radial distribution functions (RDFs) and spatial distribution functions (SDFs). Both RDFs and SDFs indicate that the local microstructure of the polar region is different from the nonpolar region with different mole fraction of ionic liquids. Acetonitrile could increase the order of the polar regions. While with acetonitrile increasing, the orderliness of the nonpolar region increases firstly and then decreases. In relatively dilute solution, ionic liquids were dispersed to form small aggregates wrapped by acetonitrile.

Expression of a Deschampsia antarctica Desv. Polypeptide with Lipase Activity in a Pichia pastoris Vector

PubMed Central

Rabert, Claudia; Gutiérrez-Moraga, Ana; Navarrete-Gallegos, Alejandro; Navarrete-Campos, Darío; Bravo, León A.; Gidekel, Manuel

2014-01-01

The current study isolated and characterized the Lip3F9 polypeptide sequence of Deschampsia antarctica Desv. (GeneBank Accession Number JX846628), which was found to be comprised of 291 base pairs and was, moreover, expressed in Pichia pastoris X-33 cells. The enzyme was secreted after 24 h of P. pastoris culture incubation and through induction with methanol. The expressed protein showed maximum lipase activity (35 U/L) with an optimal temperature of 37 °C. The lipase-expressed enzyme lost 50% of its specific activity at 25 °C, a behavior characteristic of a psychrotolerant enzyme. Recombinant enzyme activity was measured in the presence of ionic and non-ionic detergents, and a decrease in enzyme activity was detected for all concentrations of ionic and non-ionic detergents assessed. PMID:24514564

Carbon nanotube-graphene composite for ionic polymer actuators

NASA Astrophysics Data System (ADS)

Yang, Woosung; Choi, Hyonkwang; Choi, Suho; Jeon, Minhyon; Lee, Seung-Yop

2012-05-01

In this paper, we develop a new ionic polymer-metal composite (IPMC) by replacing a typical platinum or gold electrode with a multi-walled carbon nanotube (MWNT)-graphene based electrode. A solvent of MWNT and graphene is formed on both sides of the ionic polymer membranes as electrodes by means of spray coating and baking. Then, the ionic liquid process is performed for actuating in air. The four kinds of IPMC samples with different MWNT-graphene ratios are fabricated with the same solid Nafion film. Experimental results show that the IPMC with a pure MWNT based electrode exhibits higher displacement compared to the conventional IPMC with a platinum electrode. Also, the increment of the ratio of graphene to the MWNT-graphene electrode decreases the resultant displacement but increases the fundamental natural frequency of the polymer actuator.

Concentration Fluctuations and Capacitive Response in Dense Ionic Solutions.

PubMed

Uralcan, Betul; Aksay, Ilhan A; Debenedetti, Pablo G; Limmer, David T

2016-07-07

We use molecular dynamics simulations in a constant potential ensemble to study the effects of solution composition on the electrochemical response of a double layer capacitor. We find that the capacitance first increases with ion concentration following its expected ideal solution behavior but decreases upon approaching a pure ionic liquid in agreement with recent experimental observations. The nonmonotonic behavior of the capacitance as a function of ion concentration results from the competition between the independent motion of solvated ions in the dilute regime and solvation fluctuations in the concentrated regime. Mirroring the capacitance, we find that the characteristic decay length of charge density correlations away from the electrode is also nonmonotonic. The correlation length first decreases with ion concentration as a result of better electrostatic screening but increases with ion concentration as a result of enhanced steric interactions. When charge fluctuations induced by correlated ion-solvent fluctuations are large relative to those induced by the pure ionic liquid, such capacitive behavior is expected to be generic.

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents.

PubMed

Brown, Aidan T; Poon, Wilson C K; Holm, Christian; de Graaf, Joost

2017-02-08

Polar solvents like water support the bulk dissociation of themselves and their solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., H 2 O 2 ⇌ H + + HO 2 - . Using continuum theory, we study the influence of these association-dissociation reactions on the self-propulsion of colloids driven by surface chemical reactions (chemical swimmers). We find that association-dissociation reactions should have a strong influence on swimmers' behaviour, and therefore should be included in future modelling. In particular, such bulk reactions should permit charged swimmers to propel electrophoretically even if all species involved in the surface reactions are neutral. The bulk reactions also significantly modify the predicted speed of chemical swimmers propelled by ionic currents, by up to an order of magnitude. For swimmers whose surface reactions produce both anions and cations (ionic self-diffusiophoresis), the bulk reactions produce an additional reactive screening length, analogous to the Debye length in electrostatics. This in turn leads to an inverse relationship between swimmer radius and swimming speed, which could provide an alternative explanation for recent experimental observations on Pt-polystyrene Janus swimmers [S. Ebbens et al., Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2012, 85, 020401]. We also use our continuum theory to investigate the effect of the Debye screening length itself, going beyond the infinitely-thin-screening-length approximation used by previous analytical theories. We identify significant departures from this limiting behaviour for micron-sized swimmers under typical experimental conditions and find that the approximation fails entirely for nanoscale swimmers.

Cation radius effects on the helix-coil transition of DNA. Cryptates and other large cations.

PubMed Central

Trend, B L; Knoll, D A; Ueno, M; Evans, D F; Bloomfield, V A

1990-01-01

Most polyelectrolyte theories of the effect of ions on the thermal melting of DNA assume that the predominant influence of the cations comes through their charge. Ion size and structure are treated, for analytic convenience, as negligible variables. We have examined the validity of this assumption by measuring the melting temperature of calf thymus DNA as a function of salt concentration with four univalent cations of different hydrated radii. These are K+ (3.3 A), (n-Pr)4N+ (4.5 A), (EtOH)4N+ (4.5 A), and C222-K+ (5 A). C222-K+ is a complex of cryptand C222 with K+. With K+ as the sole cation, Tm varies linearly with the log of ionic strength over the range 0.001-0.1 M. With all the K+ sequestered by an equimolar amount of C222, Tm is depressed by 10-20 degrees C and the slope of Tm vs. ionic strength is lower. At low ionic strength, an even greater reduction in Tm is achieved with (n-Pr)4N+; but the similar-sized (EtOH)4N+ gives a curve more similar to K+. Theoretical modeling, taking into account cation size through the Poisson-Boltzmann equation for cylindrical polyelectrolytes, predicts that larger cations should be less effective in stabilizing the double helix; but the calculated effect is less than observed experimentally. These results show that valence, cation size, and specific solvation effects are all important in determining the stability of the double-helical form of DNA. PMID:2344467

Effect of conducting core on the dynamics of a compound drop in an AC electric field

NASA Astrophysics Data System (ADS)

Soni, Purushottam; Dixit, Divya; Juvekar, Vinay A.

2017-11-01

Dynamics of 0.1M NaCl/castor oil/silicone oil compound drop in an alternating electric field of frequency 1 Hz was investigated experimentally in a parallel plate electrode cell. A novel yet simple method was used for producing the compound drop with different ratios of the core radius to shell radius. Deformation dynamics under both transient and cyclical steady states were recorded using high-speed imaging. We observed that with an increase in the radius ratio, deformation of the shell increases and that of the core decreases. The temporal deformation of the core always leads that of the shell. The phase lead between the core and the shell is independent of electric field strength and salt concentration in the core but strongly depends on the viscosity of the medium and radius ratio. At a small radius ratio, the breakup of the core is similar to the disintegration of the isolated drop in an infinite fluid; whereas the core attends a diamond-like shape at a high radius ratio before ejecting the small droplets from the tips.

Oxygen, water, and sodium chloride transport in soft contact lenses materials.

PubMed

Gavara, Rafael; Compañ, Vicente

2017-11-01

Oxygen permeability, diffusion coefficient of the sodium ions and water flux and permeability in different conventional hydrogel (Hy) and silicone-hydrogel (Si-Hy) contact lenses have been measured experimentally. The results showed that oxygen permeability and transmissibility requirements of the lens have been addressed through the use of siloxane containing hydrogels. In general, oxygen and sodium chloride permeability values increased with the water content of the lens but there was a percolation phenomenon from a given value of water uptake mainly in the Si-Hy lenses which appeared to be related with the differences between free water and bound water contents. The increase of ion permeability with water content did not follow a unique trend indicating a possible dependence of the chemical structure of the polymer and character ionic and non-ionic of the lens. Indeed, the salt permeability values for silicone hydrogel contact lenses were one order of magnitude below those of conventional hydrogel contact lenses, which can be explained by a diffusion of sodium ions occurring only through the hydrophilic channels. The increase of the ionic permeability in Si-Hy materials may be due to the confinement of ions in nanoscale water channels involving possible decreased degrees of freedom for diffusion of both water and ions. In general, ionic lenses presented values of ionic permeability and diffusivity higher than most non-ionic lenses. The tortuosity of the ionic lenses is lower than the non-ionic Si-Hy lenses. Frequency 55 and PureVision exhibited the highest water permeability and flux values and, these parameters were greater for ionic Si-Hy lenses than for ionic conventional hydrogel lenses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2218-2231, 2017. © 2016 Wiley Periodicals, Inc.

Effect of Micellization on the Adsorption Kinetics of Polymeric Surfactants to the Solid/Water Interface

NASA Astrophysics Data System (ADS)

Toomey, Ryan; Tirrell, Matthew

2002-03-01

We have studied the adsorption kinetics of two classes of hydrophobic/ionic diblock copolymer surfactants in aqueous environments to understand the role that micellization plays in the adsorption process. The two systems studied were poly(t-butyl styrene)-block-poly(styrene sulfonate) (PtBS-b-PSS) and polystyrene-block-poly(acrylic acid) (PS-b-PAA). It is found that by changing the hydrophobicity of the adsorbing surface, micelle adsorption can be turned on or off. When micelle adsorption occurs, the initial adsorption rate is always slower than the supply rate of micelles to the surface, indicating “reaction-limited” adsorption. Since these micelles have essentially frozen cores, the adsorption cannot be explained by the release of unimers from the micelles. Rather, micelles directly adsorb, and they have to overcome the potential barrier imposed by their corona. Due to micellization, the adsorption rate can also be a complex function of ionic strength. A regime was found where the initial adsorption rate decreased with increasing ionic strength. This anomaly can be explained by the onset of micellization. As the salt concentration is increased, more micelles are formed. However micelles adsorb roughly an order of magnitude slower than free chains. Therefore, if increasing the ionic strength produces more micelles, the adsorption rate will simultaneously decrease.

Quantifying particulate and colloidal release of radionuclides in waste-weathered hanford sediments.

PubMed

Perdrial, Nicolas; Thompson, Aaron; LaSharr, Kelsie; Amistadi, Mary Kay; Chorover, Jon

2015-05-01

At the Hanford Site in the state of Washington, leakage of hyperalkaline, high ionic strength wastewater from underground storage tanks into the vadose zone has induced mineral transformations and changes in radionuclide speciation. Remediation of this wastewater will decrease the ionic strength of water infiltrating to the vadose zone and could affect the fate of the radionuclides. Although it was shown that radionuclide host phases are thermodynamically stable in the presence of waste fluids, a decrease in solution ionic strength and pH could alter aggregate stability and remobilize radionuclide-bearing colloids and particulate matter. We quantified the release of particulate, colloidal, and truly dissolved Sr, Cs, and I from hyperalkaline-weathered Hanford sediments during a low ionic strength pore water leach and characterized the released particles and colloids using electron microscopy and X-ray diffraction. Although most of the Sr, Cs, and I was released in dissolved form, between 3 and 30% of the Sr and 4 to 18% of the Cs was associated with a dominantly zeolitic mobile particulate fraction. Thus, the removal of hyperalkaline wastewater will likely induce Sr and Cs mobilization that will be augmented by particulate- and colloid-facilitated transport. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Through-plane conductivities of membranes for nonaqueous redox flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Travis Mark; Small, Leo J.; Pratt, III, Harry D.

In this study, nonaqueous redox flow batteries (RFB) leverage nonaqueous solvents to enable higher operating voltages compared to their aqueous counterparts. Most commercial components for flow batteries, however, are designed for aqueous use. One critical component, the ion-selective membrane, provides ionic conductance between electrodes while preventing crossover of electroactive species. Here we evaluate the area-specific conductances and through-plane conductivities of commercially available microporous separators (Celgard 2400, 2500) and anion exchange membranes (Neosepta AFX, Neosepta AHA, Fumasep FAP-450, Fumasep FAP-PK) soaked in acetonitrile, propylene carbonate, or two imidazolium-based ionic liquids. Fumasep membranes combined with acetonitrile-based electrolyte solutions provided the highest conductancemore » values and conductivities by far. When tested in ionic liquids, all anion exchange membranes displayed conductivities greater than those of the Celgard microporous separators, though the separators’ decreased thickness-enabled conductances on par with the most conductive anion exchange membranes. Ionic conductivity is not the only consideration when choosing an anion exchange membrane; testing of FAP-450 and FAP-PK membranes in a nonaqueous RFB demonstrated that the increased mechanical stability of PEEK-supported FAP-PK minimized swelling, in turn decreasing solvent mediated crossover and enabling greater electrochemical yields (40% vs. 4%) and Coulombic efficiencies (94% vs. 90%) compared to the unsupported, higher conductance FAP-450.« less

Through-plane conductivities of membranes for nonaqueous redox flow batteries

DOE PAGES

Anderson, Travis Mark; Small, Leo J.; Pratt, III, Harry D.; ...

2015-08-13

In this study, nonaqueous redox flow batteries (RFB) leverage nonaqueous solvents to enable higher operating voltages compared to their aqueous counterparts. Most commercial components for flow batteries, however, are designed for aqueous use. One critical component, the ion-selective membrane, provides ionic conductance between electrodes while preventing crossover of electroactive species. Here we evaluate the area-specific conductances and through-plane conductivities of commercially available microporous separators (Celgard 2400, 2500) and anion exchange membranes (Neosepta AFX, Neosepta AHA, Fumasep FAP-450, Fumasep FAP-PK) soaked in acetonitrile, propylene carbonate, or two imidazolium-based ionic liquids. Fumasep membranes combined with acetonitrile-based electrolyte solutions provided the highest conductancemore » values and conductivities by far. When tested in ionic liquids, all anion exchange membranes displayed conductivities greater than those of the Celgard microporous separators, though the separators’ decreased thickness-enabled conductances on par with the most conductive anion exchange membranes. Ionic conductivity is not the only consideration when choosing an anion exchange membrane; testing of FAP-450 and FAP-PK membranes in a nonaqueous RFB demonstrated that the increased mechanical stability of PEEK-supported FAP-PK minimized swelling, in turn decreasing solvent mediated crossover and enabling greater electrochemical yields (40% vs. 4%) and Coulombic efficiencies (94% vs. 90%) compared to the unsupported, higher conductance FAP-450.« less

Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations.

PubMed

Zheng, Zhiqiang; Xu, Qiming; Guo, Jiangna; Qin, Jing; Mao, Hailei; Wang, Bin; Yan, Feng

2016-05-25

The structure-antibacterial activity relationship between the small molecular compounds and polymers are still elusive. Here, imidazolium-type ionic liquid (IL) monomers and their corresponding poly(ionic liquids) (PILs) and poly(ionic liquid) membranes were synthesized. The effect of chemical structure, including carbon chain length of substitution at the N3 position and charge density of cations (mono- or bis-imidazolium) on the antimicrobial activities against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by determination of minimum inhibitory concentration (MIC). The antibacterial activities of both ILs and PILs were improved with the increase of the alkyl chain length and higher charge density (bis-cations) of imidazolium cations. Moreover, PILs exhibited lower MIC values relative to the IL monomers. However, the antibacterial activities of PIL membranes showed no correlation to those of their analogous small molecule IL monomers and PILs, which increased with the charge density (bis-cations) while decreasing with the increase of alkyl chain length. The results indicated that antibacterial property studies on small molecules and homopolymers may not provide a solid basis for evaluating that in corresponding polymer membranes.

Studies on structural, thermal and AC conductivity scaling of PEO-LiPF6 polymer electrolyte with added ionic liquid [BMIMPF6

NASA Astrophysics Data System (ADS)

Chaurasia, S. K.; Saroj, A. L.; Shalu, Singh, V. K.; Tripathi, A. K.; Gupta, A. K.; Verma, Y. L.; Singh, R. K.

2015-07-01

Preparation and characterization of polymer electrolyte films of PEO+10wt.% LiPF6 + xwt.% BMIMPF6 (1-butyl-3-methylimidazolium hexafluorophosphate) containing dopant salt lithium hexafluorophosphate (LiPF6) and ionic liquid (BMIMPF6) having common anion PF6 - are reported. The ionic conductivity of the polymer electrolyte films has been found to increase with increasing concentration of BMIMPF6 in PEO+10 wt.% LiPF6 due to the plasticization effect of ionic liquid. DSC and XRD results show that the crystallinity of polymer electrolyte decreases with BMIMPF6 concentration which, in turn, is responsible for the increase in ionic conductivity. FTIR spectroscopic study shows the complexation of salt and/or ionic liquid cations with the polymer backbone. Ion dynamics behavior of PEO+LiPF6 as well as PEO+LiPF6 + BMIMPF6 polymer electrolytes was studied by frequency dependent conductivity, σ(f) measurements. The values σ(f) at various temperatures have been analyzed in terms of Jonscher power law (JPL) and scaled with respect to frequency which shows universal power law characteristics at all temperatures.

Individual and Co Transport Study of Titanium Dioxide NPs and Zinc Oxide NPs in Porous Media

PubMed Central

Kumari, Jyoti; Mathur, Ankita; Rajeshwari, A.; Venkatesan, Arthi; S, Satyavati; Pulimi, Mrudula; Chandrasekaran, Natarajan; Nagarajan, R.; Mukherjee, Amitava

2015-01-01

The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1−10 mM) and CaCl2 (0.01–0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand. PMID:26252479

Atomic radii for atoms with the 6s shell outermost: The effective atomic radius and the van der Waals radius from {sub 55}Cs to {sub 80}Hg

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatewaki, Hiroshi, E-mail: htatewak@nsc.nagoya-cu.ac.jp; Institute of Advanced Studies in Artificial Intelligence, Chukyo University, Toyota, Aichi 470-0393; Hatano, Yasuyo

We consider, for atoms from {sub 55}Cs to {sub 80}Hg, the effective atomic radius (r{sub ear}), which is defined as the distance from the nucleus at which the magnitude of the electric field is equal to that in He at one half of the equilibrium bond length of He{sub 2}. The values of r{sub ear} are about 50% larger than the mean radius of the outermost occupied orbital of 6s, . The value of r{sub ear} decreases from {sub 55}Cs to {sub 56}Ba and undergoes increases and decreases with rising nuclear charge from {sub 57}La to {sub 70}Y b. Inmore » fact r{sub ear} is understood as comprising two interlaced sequences; one consists of {sub 57}La, {sub 58}Ce, and {sub 64}Gd, which have electronic configuration (4f{sup n−1})(5d{sup 1})(6s{sup 2}), and the remaining atoms have configuration (4f{sup n})(6s{sup 2}). The sphere defined by r{sub ear} contains 85%–90% of the 6s electrons. From {sub 71}Lu to {sub 80}Hg the radius r{sub ear} also involves two sequences, corresponding to the two configurations 5d{sup n+1}6s{sup 1} and 5d{sup n}6s{sup 2}. The radius r{sub ear} according to the present methodology is considerably larger than r{sub vdW} obtained by other investigators, some of who have found values of r{sub vdW} close to .« less

Upscaling of nanoparticle transport in porous media under unfavorable conditions: Pore scale to Darcy scale

NASA Astrophysics Data System (ADS)

Seetha, N.; Raoof, Amir; Mohan Kumar, M. S.; Majid Hassanizadeh, S.

2017-05-01

Transport and deposition of nanoparticles in porous media is a multi-scale problem governed by several pore-scale processes, and hence, it is critical to link the processes at pore scale to the Darcy-scale behavior. In this study, using pore network modeling, we develop correlation equations for deposition rate coefficients for nanoparticle transport under unfavorable conditions at the Darcy scale based on pore-scale mechanisms. The upscaling tool is a multi-directional pore-network model consisting of an interconnected network of pores with variable connectivities. Correlation equations describing the pore-averaged deposition rate coefficients under unfavorable conditions in a cylindrical pore, developed in our earlier studies, are employed for each pore element. Pore-network simulations are performed for a wide range of parameter values to obtain the breakthrough curves of nanoparticle concentration. The latter is fitted with macroscopic 1-D advection-dispersion equation with a two-site linear reversible deposition accounting for both equilibrium and kinetic sorption. This leads to the estimation of three Darcy-scale deposition coefficients: distribution coefficient, kinetic rate constant, and the fraction of equilibrium sites. The correlation equations for the Darcy-scale deposition coefficients, under unfavorable conditions, are provided as a function of measurable Darcy-scale parameters, including: porosity, mean pore throat radius, mean pore water velocity, nanoparticle radius, ionic strength, dielectric constant, viscosity, temperature, and surface potentials of the particle and grain surfaces. The correlation equations are found to be consistent with the available experimental results, and in qualitative agreement with Colloid Filtration Theory for all parameters, except for the mean pore water velocity and nanoparticle radius.

Metal-metal bond lengths in complexes of transition metals.

PubMed

Pauling, L

1976-12-01

In complexes of the transition metals containing clusters of metal atoms the cobalt-cobalt bond lengths are almost always within 1 pm of the single-bond value 246 pm given by the enneacovalent radius of cobalt, whereas most of the observed iron-iron bond lengths are significantly larger than the single-bond value 248 pm, the mean being 264 pm, which corresponds to a half-bond. A simple discussion of the structures of these complexes based on spd hybrid orbitals, the electroneutrality principle, and the partial ionic character of bonds between unlike atoms leads to the conclusion that resonance between single bonds and no-bonds would occur for iron and its congeners but not for cobalt and its congeners, explaining the difference in the bond lengths.

A Phosphine-mediated Synthesis of 2,3,4,5-tetra-substituted N-hydroxypyrroles from α-oximino Ketones and Dialkyl Acetylenedicarboxylates Under Ionic Liquid Green-media.

PubMed

Shahvelayati, Ashraf S; Ghazvini, Maryam; Yadollahzadeh, Khadijeh; Delbari, Akram S

2018-01-01

The development of multicomponent reactions (MCRs) in the presence of task-specific ionic liquids (ILs), used not only as environmentally benign reaction media, but also as catalysts, is a new approach that meet with the requirements of sustainable chemistry. In recent years, the use of ionic liquids as a green media for organic synthesis has become a chief study area. This is due to their unique properties such as non-volatility, non-flammability, chemical and thermal stability, immiscibility with both organic compounds and water and recyclability. Ionic liquids are used as environmentally friendly solvents instead of hazardous organic solvents. We report the condensation reaction between α-oximinoketone and dialkyl acetylene dicarboxylate in the presence of triphenylphosphine to afford substituted pyrroles under ionic liquid conditions in good yields. Densely functionalized pyrroles was easily prepared from reaction of α-oximinoketones, dialkyl acetylene dicarboxylate in the presence of triphenylphosphine in a quantitative yield under ionic liquid conditions at room temperature. In conclusion, ionic liquids are indicated as a useful and novel reaction medium for the selective synthesis of functionalized pyrroles. This reaction medium can replace the use of hazardous organic solvents. Easy work-up, synthesis of polyfunctional compounds, decreased reaction time, having easily available-recyclable ionic liquids, and good to high yields are advantages of present method. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Stick-Jump (SJ) Evaporation of Strongly Pinned Nanoliter Volume Sessile Water Droplets on Quick Drying, Micropatterned Surfaces.

PubMed

Debuisson, Damien; Merlen, Alain; Senez, Vincent; Arscott, Steve

2016-03-22

We present an experimental study of stick-jump (SJ) evaporation of strongly pinned nanoliter volume sessile water droplets drying on micropatterned surfaces. The evaporation is studied on surfaces composed of photolithographically micropatterned negative photoresist (SU-8). The micropatterning of the SU-8 enables circular, smooth, trough-like features to be formed which causes a very strong pinning of the three phase (liquid-vapor-solid) contact line of an evaporating droplet. This is ideal for studying SJ evaporation as it contains sequential constant contact radius (CCR) evaporation phases during droplet evaporation. The evaporation was studied in nonconfined conditions, and forced convection was not used. Micropatterned concentric circles were defined having an initial radius of 1000 μm decreasing by a spacing ranging from 500 to 50 μm. The droplet evaporates, successively pinning and depinning from circle to circle. For each pinning radius, the droplet contact angle and volume are observed to decrease quasi-linearly with time. The experimental average evaporation rates were found to decrease with decreasing pining radii. In contrast, the experimental average evaporation flux is found to increase with decreasing droplet radii. The data also demonstrate the influence of the initial contact angle on evaporation rate and flux. The data indicate that the total evaporation time of a droplet depends on the specific micropattern spacing and that the total evaporation time on micropatterned surfaces is always less than on flat, homogeneous surfaces. Although the surface patterning is observed to have little effect on the average droplet flux-indicating that the underlying evaporation physics is not significantly changed by the patterning-the total evaporation time is considerably modified by patterning, up to a factor or almost 2 compared to evaporation on a flat, homogeneous surface. The closely spaced concentric circle pinning maintains a large droplet radius and small contact angle from jump to jump; the result is a large evaporation rate leading to faster evaporation.

Phase behavior of 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C12MIm(FH)(n)F, n = 1.0-2.3) and their anisotropic ionic conductivity as ionic liquid crystal electrolytes.

PubMed

Xu, Fei; Matsumoto, Kazuhiko; Hagiwara, Rika

2012-08-23

The effects of the HF composition, n, in 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C(12)MIm(FH)(n)F, n = 1.0-2.3) on their physicochemical and structural properties have been investigated using infrared spectroscopy, thermal analysis, polarized optical microscopy, X-ray diffraction, and anisotropic ionic conductivity measurements. The phase diagram of C(12)MIm(FH)(n)F (n vs transition temperature) suggests that C(12)MIm(FH)(n)F is a mixed crystal system that has a boundary around n = 1.9. For all compositions, a liquid crystalline mesophase with a smectic A interdigitated bilayer structure is observed. The temperature range of the mesophase decreases with increasing n value (from 61.8 °C for C(12)MIm(FH)(1.0)F to 37.0 °C for C(12)MIm(FH)(2.3)F). The layer spacing of the smectic structure decreases with increasing n value or increasing temperature. Two structural types with different layer spacings are observed in the crystalline phase (type I, 1.0 ≤ n ≤ 1.9, and type II, 1.9 ≤ n ≤ 2.3). Ionic conductivities parallel and perpendicular to the smectic layers (σ(||) and σ([perpendicular])) increase with increasing n value, whereas the anisotropy of the ionic conductivities (σ(||)/σ([perpendicular])) is independent of the n value, since the thickness of the insulating sheet formed by the dodecyl group remains nearly unchanged.

The Effect of Lengthening Cation Ether Tails on Ionic Liquid Properties

DOE PAGES

Lall-Ramnarine, S.; Rodriguez, C.; Fernandez, R.; ...

2016-08-30

In order to explore the effect of multiple ether functionalities on ionic liquid properties, a series of ten pyrrolidinium ionic liquids and ten imidazolium ionic liquids bearing ether and alkyl side chains of varying lengths (4 to 10 atoms in length) were prepared for this study. Their physical properties, such as viscosity, conductivity and thermal profile were measured and compared. Consistent with earlier literature, a single ether substituent substantially decreases the viscosity of pyrrolidinium and imidazolium ILs compared to their alkyl congeners. Remarkably, as the number of ether units in the pyrrolidinium ILs increases there is hardly any increase inmore » the viscosity, in contrast to alkylpyrrolidinium ILs where the viscosity increases steadily with chain length. Viscosities of imidazolium ether ILs increase with chain length but always remain well below their alkyl congeners. These results provide significant insight on the choice of starting materials for researchers designing ILs for specific applications.« less

Insight into the grain boundary effect on the ionic transport of yttria-stabilized zirconia at elevated temperatures from a molecular modeling perspective

NASA Astrophysics Data System (ADS)

Chang, Kai-Shiun; Lin, Yi-Feng; Tung, Kuo-Lun

A molecular dynamics (MD) simulation is used to reveal the grain boundary effect on the ionic transport of yttria-stabilized zirconia (YSZ). The oxygen ion displacements and diffusivities of the ideal and grain boundary-inserted YSZ models are analyzed at elevated temperatures. An optimized Y 2O 3 concentration within YSZ for the best ionic conductivity is achieved by balancing the trade-off between the increased vacancies and the decreased accessible free space. The mass transfer resistance of the grain boundary in YSZ can be more easily found at higher temperatures by observing the oxygen ion diffusivities or traveling trajectories. At lower temperatures, the grain interior and the grain boundary control the ionic transport. In contrast, the grain boundary effect on the diffusion barrier is gradually eliminated at elevated temperatures. The modeled results in this work agree well with previous experimental data.

Robust half-metallic ferromagnetism and curvature dependent magnetic coupling in fluorinated boron nitride nanotubes.

PubMed

Guo, Chunsheng; Zhou, Yu; Shi, Xin-Qiang; Gan, Li-Yong; Jiang, Hong; Zhao, Yong

2016-04-28

The fluorinated boron nitride (F-BN) nanostructures are found to be fully spin polarized and half-metallic by means of first-principles calculations based on the Heyd-Scuseria-Ernzerhof hybrid functional. It is found that the full spin polarization and 1 μB local moment in F-BN nanotubes are independent of tube radius and it is also robust in planar ribbons and sheets. The long-ranged ferromagnetic coupling between local moments decreases with decreasing tube radius. This suggests that F-BN systems with small local curvatures could be more easily experimentally observed and have greater potential applications in spin devices.

Long-range electrostatic screening in ionic liquids

PubMed Central

Gebbie, Matthew A.; Dobbs, Howard A.; Valtiner, Markus; Israelachvili, Jacob N.

2015-01-01

Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems. PMID:26040001

Supercapacitors based on modified graphene electrodes with poly(ionic liquid)

NASA Astrophysics Data System (ADS)

Trigueiro, João Paulo C.; Lavall, Rodrigo L.; Silva, Glaura G.

2014-06-01

The improved accessibility of the electrolyte to the surface of carbon nanomaterials is a challenge to be overcome in supercapacitors based on ionic liquid electrolytes. In this study, we report the preparation of supercapacitors based on reduced graphene oxide (RGO) electrodes and ionic liquid as the electrolyte (specifically, 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide or [MPPy][TFSI]). Two types of electrodes were compared: the RGO-based electrode and a poly(ionic liquid)-modified RGO electrode (PIL:RGO). The supercapacitor produced with the PIL:RGO electrode and [MPPy][TFSI] showed an electrochemical stability of 3 V and provided a capacitance of 71.5 F g-1 at room temperature; this capacitance is 130% higher with respect to the RGO-based supercapacitor. The decrease of the specific capacitance after 2000 cycles is only 10% for the PIL:RGO-based device. The results revealed the potential of the PIL:RGO material as an electrode for supercapacitors. This composite electrode increases the compatibility with the ionic liquid electrolyte compared to an RGO electrode, promoting an increase in the effective surface area of the electrode accessible to the electrolyte ions.

Covalent Incorporation of Ionic Liquid into Ion-Conductive Networks via Thiol-Ene Photopolymerization.

PubMed

Tibbits, Andrew C; Yan, Yushan S; Kloxin, Christopher J

2017-07-01

Ene-functionalized ionic liquids with a range of different cationic groups and counteranions react stoichiometrically within a tetrathiol-divinyl ether formulation within 20 minutes to form thiol-ene polymers with measurable ionic conductivities via a photoinitiated polymerization and crosslinking reaction. Dynamic mechanical analysis indicates that these networks are more spatially heterogeneous and possess higher glass transition temperatures (T g ) compared with thiol-ene formulations without charge. While tuning the molar content of ionic liquid monomer is one method for adjusting the crosslink and charge densities of the thiol-ene polymeric ionic liquid networks, the presence of cation-anion interactions also plays a critical role in dictating the thermomechanical and conductive properties. Particularly, while cationic structure effects are not significant on the polymer properties, the use of a weakly coordinating hydrophobic anion (bistriflimide) instead of bromide-based networks results in an apparent decrease in hydrated ion conductivity (7.4 to 1.5 mS cm -1 ) and T g (-9.6 to -17.8 °C). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vector Analysis of Ionic Collision on CaCO3 Precipitation Based on Vibration Time History

NASA Astrophysics Data System (ADS)

Mangestiyono, W.; Muryanto, S.; Jamari, J.; Bayuseno, A. P.

2017-05-01

Vibration effects on the piping system can result from the internal factor of fluid or the external factor of the mechanical equipment operation. As the pipe vibrated, the precipitation process of CaCO3 on the inner pipe could be affected. In the previous research, the effect of vibration on CaCO3 precipitation in piping system was clearly verified. This increased the deposition rate and decreased the induction time. However, the mechanism of vibration control in CaCO3 precipitation process as the presence of vibration has not been recognized yet. In the present research, the mechanism of vibration affecting the CaCO3 precipitation was investigated through vector analysis of ionic collision. The ionic vector force was calculated based on the amount of the activation energy and the vibration force was calculated based on the vibration sensor data. The vector resultant of ionic collision based on the vibration time history was analyzed to prove that vibration brings ionic collision randomly to the planar horizontal direction and its collision model was suspected as the cause of the increasing deposition rate.

Solubilization of octane in cationic surfactant-anionic polymer complexes: Effect of ionic strength.

PubMed

Zhang, Hui; Deng, Lingli; Sun, Ping; Que, Fei; Weiss, Jochen

2016-01-01

Polymers may alter the ability of oppositely charged surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. This study was conducted to investigate the effect of ionic strength on the solubilization thermodynamics of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using isothermal titration calorimetry (ITC). Results indicated that the CTAB binding capacity of carboxymethyl cellulose increased with increasing NaCl concentrations up to 100 mM, and the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to have a strong dependence on ionic strength. The increasing ionic strength caused the solubilization in CTAB micelles to be less endothermic or even exothermic, but increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be driven by enthalpy. It is indicated that increasing ionic strength gave rise to a larger Gibbs energy decrease but a smaller unfavorable entropy increase for octane solubilization in cationic surfactant micelles. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantitative, Comparative Assessment of Gait Between Single-Radius and Multi-Radius Total Knee Arthroplasty Designs.

PubMed

Larsen, Bethany; Jacofsky, Marc C; Jacofsky, David J

2015-06-01

Gait of single-radius (SR, n=16) and multi-radius (MR, n=16) posterior stabilized total knee arthroplasties was compared, along with controls (n=16), pre-op and 1 year post-op. Computer navigation and standard order sets controlled confounding variables. Post-operatively, SR knees did not differ from controls while MR knees continued to differ in important knee kinetic and kinematic properties. MR knees remained more extended (P=0.019) and had decreased power absorption (P=0.0001) during weight acceptance compared to the SR knees. Both surgical groups had similar KSS for Knee Scores (P=0.22) and Function Scores (P=0.58). The significant biomechanical differences are likely influenced by patella-femoral moment arm geometry and changing ligament laxity throughout the active range of motion. Copyright © 2015 Elsevier Inc. All rights reserved.

Pulsed Flow Pinch

NASA Astrophysics Data System (ADS)

Hartman, Charles

2005-10-01

Formation of a Pulsed Flow Pinch is discussed, based on 2-D, MHD numerical calculations. The PFP utilizes the observed stable, Btheta magnetic ``bubble'' which propagates from breach to muzzle during the run-down phase of the coaxial Marshall gun. We consider two ways of launching a PFP onto a fiber or cylindrical gas cloud: 1) by propagating the bubble to small radius along an exponentially-decreasing-radius center conductor and, 2) by a radial launch to form reflex PFP's propagating in opposite directions along a fiber. We show that the bubble velocity increases to high values as the radius is decreased making the rise time of Btheta at an axial point very short. A bubble, launched into uniform gas is found to undergo unstable pinching of the front. Results will be presented of calculations of a PFP driven, neutron-producing, snow-plow pinch. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Numerical simulation on dimension decrease for annular casing of one centrifugal boiler circulation pump

NASA Astrophysics Data System (ADS)

Fan, Y. Z.; Zuo, Z. G.; Liu, S. H.; Wu, Y. L.; Sha, Y. J.

2012-11-01

Primary formulation derivation indicates that the dimension of one existing centrifugal boiler circulation pump casing is too large. As great manufacture cost can be saved by dimension decrease, a numerical simulation research is developed in this paper on dimension decrease for annular casing of this pump with a specific speed equaling to 189, which aims at finding an appropriately smaller dimension of the casing while hydraulic performance and strength performance will hardly be changed according to the requirements of the cooperative company. The research object is one existing centrifugal pump with a diffuser and a semi-spherical annular casing, working as the boiler circulation pump for (ultra) supercritical units in power plants. Dimension decrease, the modification method, is achieved by decreasing the existing casing's internal radius (marked as "Ri0") while keeping the wall thickness. The research analysis is based on primary formulation derivation, CFD (Computational Fluid Dynamics) simulation and FEM (Finite Element Method) simulation. Primary formulation derivation estimates that a design casing's internal radius should be less than 0.75 Ri0. CFD analysis indicates that smaller casing with 0.75 Ri0 has a worse hydraulic performance when working at large flow rates and a better hydraulic performance when working at small flow rates. In consideration of hydraulic performance and dimension decrease, an appropriate casing's internal radius is determined, which equals to 0.875 Ri0. FEM analysis then confirms that modified pump casing has nearly the same strength performance as the existing pump casing. It is concluded that dimension decrease can be an economical method as well as a practical method for large pumps in engineering fields.

Ion imprinted polymeric nanoparticles for selective separation and sensitive determination of zinc ions in different matrices

NASA Astrophysics Data System (ADS)

Shamsipur, Mojtaba; Rajabi, Hamid Reza; Pourmortazavi, Seied Mahdi; Roushani, Mahmoud

2014-01-01

Preparation of Zn2+ ion-imprinted polymer (Zn-IIP) nanoparticles is presented in this report. The Zn-IIP nanoparticles are prepared by dissolving stoichiometric amounts of zinc nitrate and selected chelating ligand, 3,5,7,20,40-pentahydroxyflavone, in 15 mL ethanol-acetonitrile (2:1; v/v) mixture as a porogen solvent in the presence of ethylene glycol-dimethacrylate (EGDMA) as cross-linking, methacrylic acid (MAA) as functional monomer, and 2,2-azobisisobutyronitrile (AIBN) as initiator. After polymerization, Cavities in the polymer particles corresponding to the Zn2+ ions were created by leaching the polymer in HCl aqueous solution. The synthesized IIPs were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal analysis techniques. Also, the pH range for rebinding of Zn2+ ion on the IIP and equilibrium binding time were optimized, using flame atomic absorption spectrometry. In selectivity study, it was found that imprinting results increased affinity of the material toward Zn2+ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for six times without any significant decrease in polymer binding affinities. Finally, the prepared sorbent was successfully applied to the selective recognition and determination of zinc ion in different real samples.

Probing influence of rare earth ions (Er3+, Dy3+ and Gd3+) on structural, magnetic and optical properties of magnetite nanoparticles

NASA Astrophysics Data System (ADS)

Jain, Richa; Luthra, Vandna; Gokhale, Shubha

2018-06-01

Fe3-xRExO4 (RE = Er, Dy and Gd) nanoparticles with x varying from 0 to 0.1 were synthesized using co-precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and UV-Vis spectroscopy techniques. TEM images reveal round shaped particles of ∼8-14 nm diameter in case of undoped magnetite (Fe3O4) nanoparticles whereas there is evolution of rod like structures by the doping of RE ions with aspect ratio in the range of 6-16. The room temperature saturation magnetization (Ms) values show gradual increase with doping till a critical doping level which is found to depend on the ionic radius of dopant ion (x = 0.01 for Er, 0.03 for Dy and 0.04 for Gd). There is a variation in the maximum value of saturation magnetization which is directly proportional to the number of unpaired 4f electrons in the dopant element. Low temperature magnetization study, carried out at 5 K and 120 K reveal an increase in the value of Ms as well as coercivity. The direct bandgaps calculated from UV-Visible data are found to decrease with increasing number of unpaired electrons in the dopant ions.

Preparation of polycrystalline FeTe1- x S x ( x = 0.00-0.30) via solid-state reaction method at ambient pressure

NASA Astrophysics Data System (ADS)

Lim, Edmund H. H.; Liew, Josephine Y. C.; Awang Kechik, M. M.; Halim, S. A.; Chen, S. K.; Tan, K. B.; Qi, X.

2017-06-01

Polycrystalline samples with nominal composition FeTe1- x S x ( x = 0.00-0.30) were synthesized via solid state reaction method with intermittent grinding in argon gas flow. X-ray diffraction (XRD) patterns revealed the tetragonal structure (space group P4/nmm) of the samples with the presence of impurities Fe3O4 and FeTe2. By substitution with S, the a and c lattice parameters shrink probably due to the smaller ionic radius of S2- compared to Te2-. Scanning electron microscopy images showed that the samples developed plate-like grains with increasing S substitution. Substitution of Te with S suppresses the structural transition of the parent compound FeTe as shown by both the temperature dependence of resistance and magnetic moment measurements. All of the S-substituted samples showed a rapid drop of resistance at around 9-10 K but zero resistance down to 4 K was not observed. In addition, negative magnetic moment corresponds to diamagnetism was detected in the samples for x = 0.25 and 0.30 suggesting the coexistence of magnetic and superconducting phase in these samples. The magnetization hysteresis loops measured at room temperature showed ferromagnetic behavior for the pure and S substituted samples. However, the magnetization, rentivity and coercivity decreased with S content.

Chemical element accumulation in tree bark grown in volcanic soils of Cape Verde-a first biomonitoring of Fogo Island.

PubMed

Marques, Rosa; Prudêncio, Maria Isabel; Freitas, Maria do Carmo; Dias, Maria Isabel; Rocha, Fernando

2017-05-01

Barks from Prosopis juliflora (acacia) were collected in 12 sites of different geological contexts over the volcanic Fogo Island (Cape Verde). Elemental contents of Ba, Br, Co, Cr, Fe, K, Na, Zn and some rare earth elements (REE)-La, Ce, Sm, Eu, Tb, Yb, and Lu, were obtained for biological samples and topsoils by using k 0 -standardized and comparative method of instrumental neutron activation analysis (INAA), aiming the evaluation of chemical elements uptake by acacia bark. This first biomonitoring study of Fogo Island showed that, in general, significant accumulations of trace elements present in high amounts in these soils occur. This can be partially explained by the semi-arid climate with a consequent bioavailability of chemical elements when rain drops fall in this non-polluted environment. REE enrichment factors (EFs) increase with the decrease of ionic radius. Heavy REE (HREE) are significantly enriched in bark, which agrees with their release after the primary minerals breakdown and the formation of more soluble compounds than the other REE, and uptake by plants. Among the potential harmful chemical elements, Cr appears to be partially retained in nanoparticles of iron oxides. The high EFs found in tree barks of Fogo Island are certainly of geogenic origin rather than anthropogenic input since industry and the use of fertilizers is scarce.

Effects of rare-earth size on the electronic structure of La1−xLuxVO3.

PubMed

Chen, B; Laverock, J; Newby, D; McNulty, J F; Smith, K E; Glans, P-A; Guo, J-H; Qiao, R-M; Yang, W-L; Lees, M R; Tung, L D; Singh, R P; Balakrishnan, G

2015-03-18

The electronic structure of La(1-x)Lu(x)VO(3)(x = 0, 0.2, 0.6 and 1) single crystals has been investigated using soft x-ray absorption spectroscopy, soft x-ray emission spectroscopy, and resonant soft x-ray inelastic scattering to study the effects of rare-earth size. The x-ray absorption and emission spectra at the O K-edge present a progressive evolution with R-site cation, in agreement with local spin density approximation calculations. This evolution with R, together with the temperature dependence of the O K-edge spectra, is attributed to changes in the crystal structure of La(1-x)Lu(x)VO(3). The crystal-field dd. excitations probed by resonant inelastic x-ray scattering at the V L(3)-edge exhibit an increase in energy and enhanced intensity with the decrease of R-site ionic radius, which is mainly attributed to the increased tilting magnitude of the VO(6) octahedra. Upon cooling to ~95 K, the dd* excitations are prominently enhanced in relative Intensity, in agreement with the formation of the Jahn.Teller distortion int he orbital ordering phase. Additionally, the dd* transitions of the mixed compounds are noticeably suppressed with respect to those of the pure compounds, possibly owing to the formation of C-type orbital ordering induced by large R-site size variances.

Epidemic threshold in directed networks.

PubMed

Li, Cong; Wang, Huijuan; Van Mieghem, Piet

2013-12-01

Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ξ as the percentage of unidirectional links. The epidemic threshold τ(c) for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/λ(1) in directed networks, where λ(1), also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ξ. The effect of ξ on the spectral radius λ(1), principal eigenvector x(1), spectral gap (λ(1)-|λ(2)|), and algebraic connectivity μ(N-1) is studied. Important findings are that the spectral radius λ(1) decreases with the directionality ξ, whereas the spectral gap and the algebraic connectivity increase with the directionality ξ. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ρ(D). Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution.

Epidemic threshold in directed networks

NASA Astrophysics Data System (ADS)

Li, Cong; Wang, Huijuan; Van Mieghem, Piet

2013-12-01

Epidemics have so far been mostly studied in undirected networks. However, many real-world networks, such as the online social network Twitter and the world wide web, on which information, emotion, or malware spreads, are directed networks, composed of both unidirectional links and bidirectional links. We define the directionality ξ as the percentage of unidirectional links. The epidemic threshold τc for the susceptible-infected-susceptible (SIS) epidemic is lower bounded by 1/λ1 in directed networks, where λ1, also called the spectral radius, is the largest eigenvalue of the adjacency matrix. In this work, we propose two algorithms to generate directed networks with a given directionality ξ. The effect of ξ on the spectral radius λ1, principal eigenvector x1, spectral gap (λ1-λ2), and algebraic connectivity μN-1 is studied. Important findings are that the spectral radius λ1 decreases with the directionality ξ, whereas the spectral gap and the algebraic connectivity increase with the directionality ξ. The extent of the decrease of the spectral radius depends on both the degree distribution and the degree-degree correlation ρD. Hence, in directed networks, the epidemic threshold is larger and a random walk converges to its steady state faster than that in undirected networks with the same degree distribution.

Primary Hyperparathyroidism is Associated with Abnormal Cortical and Trabecular Microstructure and Reduced Bone Stiffness in Postmenopausal Women

PubMed Central

Stein, Emily M; Silva, Barbara C; Boutroy, Stephanie; Zhou, Bin; Wang, Ji; Udesky, Julia; Zhang, Chiyuan; McMahon, Donald J; Romano, Megan; Dworakowski, Elzbieta; Costa, Aline G.; Cusano, Natalie; Irani, Dinaz; Cremers, Serge; Shane, Elizabeth; Guo, X Edward; Bilezikian, John P

2013-01-01

Typically, in the milder form of primary hyperparathyroidism (PHPT), seen in most countries now, bone density by DXA and detailed analyses of iliac crest bone biopsies by histomorphometry and µCT show detrimental effects in cortical bone, whereas the trabecular site (lumbar spine by DXA) and the trabecular compartment (by bone biopsy) appear to be relatively well preserved. Despite these findings, fracture risk at both vertebral and non-vertebral sites is increased in PHPT. Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HRpQCT), may provide additional insight into microstructural features at sites such as the forearm and tibia that have heretofore not been easily accessible. Using HRpQCT, we determined cortical and trabecular microstructure at the radius and tibia in 51 postmenopausal women with PHPT and 120 controls. Individual trabecula segmentation (ITS) and micro finite element (µFE) analyses of the HRpQCT images were also performed to further understand how the abnormalities seen by HRpQCT might translate into effects on bone strength. Women with PHPT showed, at both sites, decreased volumetric densities at trabecular and cortical compartments, thinner cortices, and more widely spaced and heterogeneously distributed trabeculae. At the radius, trabeculae were thinner and fewer in PHPT. The radius was affected to a greater extent in the trabecular compartment than the tibia. ITS analyses revealed, at both sites, that plate-like trabeculae were depleted, with a resultant reduction in the plate/rod ratio. Microarchitectural abnormalities were evident by decreased plate-rod and plate-plate junctions at the radius and tibia, and rod-rod junctions at the radius. These trabecular and cortical abnormalities resulted in decreased whole bone stiffness and trabecular stiffness. These results provide evidence that in PHPT, microstructural abnormalities are pervasive and not limited to the cortical compartment. They may help to account for increased global fracture risk in PHPT. PMID:23225022

Molecular simulations and experimental studies of solubility and diffusivity for pure and mixed gases of H2, CO2, and Ar absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]).

PubMed

Shi, Wei; Sorescu, Dan C; Luebke, David R; Keller, Murphy J; Wickramanayake, Shan

2010-05-20

Classical molecular dynamics and Monte Carlo simulations are used to calculate the self-diffusivity and solubility of pure and mixed CO(2), H(2), and Ar gases absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf(2)N]). Overall, the computed absorption isotherms, Henry's law constants, and partial molar enthalpies for pure H(2) agree well with the experimental data obtained by Maurer et al. [J. Chem. Eng. Data 2006, 51, 1364] and the experimental values determined in this work. However, the agreement is poor between the simulations and the experimental data by Noble et al. [Ind. Eng. Chem. Res. 2008, 47, 3453] and Costa Gomes [J. Chem. Eng. Data 2007, 52, 472] at high temperatures. The computed H(2) permeability values are in good agreement with the experimental data at 313 K obtained by Luebke et al. [J. Membr. Sci. 2007, 298, 41; ibid, 2008, 322, 28], but about three times larger than the experimental value at 573 K from the same group. Our computed H(2) solubilities using different H(2) potential models have similar values and solute polarizations were found to have a negligible effect on the predicted gas solubilities for both the H(2) and Ar. The interaction between H(2) and the ionic liquid is weak, about three times smaller than between the ionic liquid and Ar and six times smaller than that of CO(2) with the ionic liquid, results that are consistent with a decreasing solubility from CO(2) to Ar and to H(2). The molar volume of the ionic liquid was found to be the determining factor for the H(2) solubility. For mixed H(2) and Ar gases, the solubilities for both solutes decrease compared to the respective pure gas solubilities. For mixed gases of CO(2) and H(2), the solubility selectivity of CO(2) over H(2) decreases from about 30 at 313 K to about 3 at 573 K. For the permeability, the simulated values for CO(2) in [hmim][Tf(2)N] are about 20-60% different than the experimental data by Luebke et al. [J. Membr. Sci. 2008, 322, 28].

Ion Conduction in Polymerized Ionic Liquids with Different Pendant Groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Fei; Wang, Yangyang; Hong, Tao

2015-07-17

Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviationmore » from the ideal line increases upon approaching the glass transition temperature (T g). Moreover, the conductivity for these PolyILs at their Tgs are much higher than the usually reported value 10 15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These results indicate a decoupling of ionic conductivity from the segmental relaxation in these materials. The degree of decoupling increases with the increase of the fragility of polymer segmental relaxation. Finally, we relate this observation to a decrease in polymer packing efficiency with an increase in fragility.« less

Electrokinetic mixing at high zeta potentials: ionic size effects on cross stream diffusion.

PubMed

Ahmadian Yazdi, Alireza; Sadeghi, Arman; Saidi, Mohammad Hassan

2015-03-15

The electrokinetic phenomena at high zeta potentials may show several unique features which are not normally observed. One of these features is the ionic size (steric) effect associated with the solutions of high ionic concentration. In the present work, attention is given to the influences of finite ionic size on the cross stream diffusion process in an electrokinetically actuated Y-shaped micromixer. The method consists of a finite difference based numerical approach for non-uniform grid which is applied to the dimensionless form of the governing equations, including the modified Poisson-Boltzmann equation. The results reveal that, neglecting the ionic size at high zeta potentials gives rise to the overestimation of the mixing length, because the steric effects retard liquid flow, thereby enhancing the mixing efficiency. The importance of steric effects is found to be more intense for channels of smaller width to height ratio. It is also observed that, in sharp contrast to the conditions that the ions are treated as point charges, increasing the zeta potential improves the cross stream diffusion when incorporating the ionic size. Moreover, increasing the EDL thickness decreases the mixing length, whereas the opposite is true for the channel aspect ratio. Copyright © 2014 Elsevier Inc. All rights reserved.

Protic ammonium carboxylate ionic liquids: insight into structure, dynamics and thermophysical properties by alkyl group functionalization.

PubMed

Reddy, Th Dhileep N; Mallik, Bhabani S

2017-04-19

This study is aimed at characterising the structure, dynamics and thermophysical properties of five alkylammonium carboxylate ionic liquids (ILs) from classical molecular dynamics simulations. The structural features of these ILs were characterised by calculating the site-site radial distribution functions, g(r), spatial distribution functions and structure factors. The structural properties demonstrate that ILs show greater interaction between cations and anions when alkyl chain length increases on the cation or anion. In all ILs, spatial distribution functions show that the anion is close to the acidic hydrogen atoms of the ammonium cation. We determined the role of alkyl group functionalization of the charged entities, cations and anions, in the dynamical behavior and the transport coefficients of this family of ionic liquids. The dynamics of ILs are described by studying the mean square displacement (MSD) of the centres of mass of the ions, diffusion coefficients, ionic conductivities and hydrogen bonds as well as residence dynamics. The diffusion coefficients and ionic conductivity decrease with an increase in the size of the cation or anion. The effect of alkyl chain length on ionic conductivity calculated in this article is consistent with the findings of other experimental studies. Hydrogen bond lifetimes and residence times along with structure factors were also calculated, and are related to alkyl chain length.

Ionic strength effects on silicic acid (H4SiO4) sorption and oligomerization on an iron oxide surface: an interesting interplay between electrostatic and chemical forces.

PubMed

Hamid, Rossuriati Dol; Swedlund, Peter J; Song, Yantao; Miskelly, Gordon M

2011-11-01

The effect of ionic strength on reactions at aqueous interfaces can provide insights into the nature of the chemistry involved. The adsorption of H(4)SiO(4) on iron oxides at low surface silicate concentration (Γ(Si)) forms monomeric silicate complexes with Fe-O-Si linkages, but as Γ(Si) increases silicate oligomers with Si-O-Si linkages become increasingly prevalent. In this paper, the effect of ionic strength (I) on both Γ(Si) and the extent of silicate oligomerization on the ferrihydrite surface is determined at pH 4, 7, and 10, where the surface is, respectively, positive, nearly neutral, and negatively charged. At pH 4, an increase in ionic strength causes Γ(Si) to decrease at a given H(4)SiO(4) solution concentration, while the proportion of oligomers on the surface at a given Γ(Si) increases. At pH 10, the opposite is observed; Γ(Si) increases as I increases, while the proportion of surface oligomers at a given Γ(Si) decreases. Ionic strength has only a small effect on the surface chemistry of H(4)SiO(4) at pH 7, but at low Γ(Si) this effect is in the direction observed at pH 4 while at high Γ(Si) the effect is in the direction observed at pH 10. The pH where the surface has zero charge decreases from ≈8 to 6 as Γ(Si) increases so that the surface potential (Ψ) is positive at pH 4 for all Γ(Si) and at pH 7 with low Γ(Si). Likewise, Ψ < 0 at pH 10 for all Γ(Si) and at pH 7 with high Γ(Si). The diffuse layer model is used to unravel the complex and subtle interactions between surface potential (Ψ) and chemical parameters that influence interfacial silicate chemistry. This analysis reveals that the decrease in the absolute value of Ψ as I increases causes Γ(Si) to decrease or increase where Ψ is, respectively, positive or negative. Therefore, at a given Γ(Si), the solution H(4)SiO(4) concentration changes with I, and because oligomerization has a higher H(4)SiO(4) stoichiometry coefficient than monomer adsorption, this results in the observed dependence of the extent of silicate oligomerization on I.

Effect of Detergent on Electrical Properties of Squid Axon Membrane

PubMed Central

Kishimoto, Uichiro; Adelman, William J.

1964-01-01

The effects of detergents on squid giant axon action and resting potentials as well as membrane conductances in the voltage clamp have been studied. Anionic detergents (sodium lauryl sulfate, 0.1 to 1.0 mM; dimethyl benzene sulfonate, 1 to 20 mM, pH 7.6) cause a temporary increase and a later decrease of action potential height and the value of the resting potential. Cationic detergent (cetyl trimethyl ammonium chloride, 6 x 10-5 M or more, pH 7.6) generally brings about immediate and irreversible decreases in the action and resting potentials. Non-ionic detergent (tween 80, 0.1 M, pH 7.6) causes a slight reversible reduction of action potential height without affecting the value of the resting potential. Both anionic and cationic detergents generally decrease the sodium and potassium conductances irreversibly. The effect of non-ionic detergent is to decrease the sodium conductance reversibly, leaving the potassium conductance almost unchanged. PMID:14158665

[Membrane lipids and electron transfer. Effects of four detergents on NADH-ferricyanide reductase and NADH-cytochrome c reductase activities of potato tuber microsomes].

PubMed

Jolliot, A; Mazliak, P

1977-10-17

The NADH-ferricyanure reductase activity of Potato microsomes is stimulated by non ionic detergents (Triton X100 and Tween80) and is partially inhibited by ionic detergents (sodium-cholate and deoxycholate). All these four detergents progressively decreased the NADH-cytochrome c reductase in the following order: sodium deoxycholate greater than Triton X100 greater than sodium cholate greater than Tween80.

Transformation of CuO Nanoparticles in the Aquatic Environment: Influence of pH, Electrolytes and Natural Organic Matter

PubMed Central

Peng, Cheng; Shen, Chensi; Zheng, Siyuan; Yang, Weiling; Hu, Hang; Liu, Jianshe; Shi, Jiyan

2017-01-01

Many studies have shown the effect of solution chemistry on the environmental behavior of metal-based nanoparticles (NPs), except CuO NPs. Here, we investigated the agglomeration, sedimentation, dissolution, and speciation of CuO NPs by varying pH, ionic strength, ionic valence, and natural organic matter (NOM). The results showed that as the pH moved away from 6, the size of CuO agglomerates decreased, along with the enhanced NP suspension stabilization, due to the increase of electrostatic repulsive force. Increasing ionic strength and valence intensified the agglomeration and sedimentation of CuO NPs because of the compression of electrical double layers. The presence of humic acid and citric acid enhanced the dispersion and stabilization of CuO NP suspension, but l-cysteine showed a different impact. Decreasing pH, increasing ionic strength and all NOM improved the dissolution of CuO NPs, but the divalent electrolyte (CaCl2) inhibited the Cu2+ release from CuO NPs compared to the monovalent electrolyte (NaCl). In addition, X-ray absorption near edge structure (XANES) analysis demonstrated that the presence of l-cysteine transformed more than 30% of CuO NPs to Cu(I)-cysteine by coordinating with thiol group. This study can give us an in-depth understanding on the environmental behavior and fate of CuO NPs in the aquatic environment. PMID:29036921

Pretreatment of Oil Palm Frond (OPF) with Ionic Liquid

NASA Astrophysics Data System (ADS)

Azmi, I. S.; Azizan, A.; Salleh, R. Mohd

2018-05-01

Pretreatment is the key to unlock the recalcitrance of lignocellulose for cellulosic biofuel production. Increasing attention has been drawn to ionic liquids (ILs) for pretreatment of lignocellulosic biomass because this approach was considered as a green engineering method over other conventional methods. In this work, Oil palm frond (OPF) was pretreated by using the ionic liquid 1-ethyl-3-methylimidazolium acetate [EMIM] Ac at the temperature of 99˚C for 3 hours. The characterization of the untreated and pretreated OPF was conducted by using different techniques which are Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The pretreatment of OPF with [EMIM] Ac was demonstrated to be effective evidenced by the significant reduction of Lateral Order Index (LOI) from FTIR, reduction of Crystallinity Index (CI) based on XRD and the significant morphology changes indicated by SEM. The CI value for the pretreated OPF decreased from 0.47 (untreated sample) to 0.28 while the LOI value decreased from 1.10 to 0.24 after pretreatment with [EMIM]Ac and the SEM morphology showed that the pretreated OPF becomes distorted and disordered.

Understanding cation ordering and oxygen vacancy site preference in Ba3CaNb2O9 from first-principles

NASA Astrophysics Data System (ADS)

Ding, Hepeng; Virkar, Anil; Liu, Feng

2014-03-01

We investigate the physical mechanism underlying the formation of the B-site cation ordering and the oxygen vacancy site selection in Ba3CaNb2O9 using density functional theory calculations. We found that either cation site exchange or oxygen vacancy formation induces negligible lattice strain. This implies that the ionic radius plays an insignificant role in governing these two processes. Furthermore, the electrostatic interactions are found dominant in the ordering of mixed valence species on one or more sites, the ionic bond strength is identified as the dominant force in governing both the 1:2 B-site cation ordering along the <111>direction and the oxygen vacancy site preference in Ba3CaNb2O9. Specifically, the cation ordering can be rationalized by the increased mixing bonding energy of the Ca-O-Nb bonds over the Ca-O-Ca and Nb-O-Nb bonds, i.e., 1/2(Ca-O-Ca + Nb-O-Nb)

4-(2-Pyridylazo)-resorcinol Functionalized Thermosensitive Ionic Microgels for Optical Detection of Heavy Metal Ions at Nanomolar Level.

PubMed

Zhou, Xianjing; Nie, Jingjing; Du, Binyang

2015-10-07

4-(2-Pyridylazo)-resorcinol (PAR) functionalized thermosensitive ionic microgels (PAR-MG) were synthesized by a one-pot quaternization method. The PAR-MG microgels were spherical in shape with radius of ca. 166.0 nm and narrow size distribution and exhibited thermo-sensitivity in aqueous solution. The PAR-MG microgels could optically detect trace heavy metal ions, such as Cu(2+), Mn(2+), Pb(2+), Zn(2+), and Ni(2+), in aqueous solutions with high selectivity and sensitivity. The PAR-MG microgel suspensions exhibited characteristic color with the presence of various trace heavy metal ions, which could be visually distinguished by naked eyes. The limit of colorimetric detection (DL) was determined to be 38 nM for Cu(2+) at pH 3, 12 nM for Cu(2+) at pH 7, and 14, 79, 20, and 21 nM for Mn(2+), Pb(2+), Zn(2+), and Ni(2+), respectively, at pH 11, which was lower than (or close to) the United States Environmental Protection Agency standard for the safety limit of these heavy metal ions in drinking water. The mechanism of detection was attributed to the chelation between the nitrogen atoms and o-hydroxyl groups of PAR within the microgels and heavy metal ions.

Magnetocaloric effect and critical field analysis in Eu substituted La0.7-xEuxSr0.3MnO3 (x = 0.0, 0.1, 0.2, 0.3) manganites

NASA Astrophysics Data System (ADS)

Vadnala, Sudharshan; Asthana, Saket

2018-01-01

In this study, we have investigated magnetic behavior, magnetocaloric effect and critical exponent analysis of La0.7-xEuxSr0.3MnO3 (x = 0.0, 0.1, 0.2, 0.3) manganites synthesized through solid state reaction route. The crystallographic data obtained from refinement of X-ray diffraction patterns reveal that crystal structure changes from rhombohedral (for x = 0.0) to orthorhombic (for x ≥ 0.1). The average ionic radius of A-site is decreased from 1.384 Å (for x = 0.0) to 1.360 Å (for x = 0.3) with Eu3+ substitution which in turn decreases the Mn-O-Mn bond angles. Magnetization measurements are performed in the vicinity of TC to determine magnetocaloric effect (MCE) and critical field behavior. The maximum magnetic entropy change (Δ SMmax) (for μ0ΔH = 6T) increases with the Eu3+ substitution from 3.88 J/kg K (for x = 0.0) to 5.03 J/kg K (for x = 0.3) at the transition temperature. The critical field behaviour of compounds was analysed using various methods such as modified Arrott plots, Kouvel-Fisher method and critical isotherm to determine critical temperature and critical exponents (β, γ and δ). The obtained critical exponents are in good accordance with scaling relation. The temperature dependence of the order parameter n, for different magnetic fields, is studied using the relation ΔSMαHn. The values of n are found to obey the Curie-Weiss law for temperatures above the transition temperature. The rescaled change in entropy data for all compounds collapses into the same universal curve, revealing a second order phase transition.

Robust Pinhole-free Li3N Solid Electrolyte Grown from Molten Lithium

PubMed Central

2017-01-01

Lithium metal is the ultimate anode choice for high energy density rechargeable lithium batteries. However, it suffers from inferior electrochemical performance and safety issues due to its high reactivity and the growth of lithium dendrites. It has long been desired to develop a materials coating on Li metal, which is pinhole-free, mechanically robust without fracture during Li metal deposition and stripping, and chemically stable against Li metal and liquid electrolytes, all while maintaining adequate ionic conductivity. However, such an ideal material coating has yet to be found. Here we report a novel synthesis method by reacting clean molten lithium foil directly with pure nitrogen gas to generate instantaneously a pinhole-free and ionically conductive α-Li3N film directly bonded onto Li metal foil. The film consists of highly textured large Li3N grains (tens of μm) with (001) crystalline planes parallel to the Li metal surface. The bonding between textured grains is strong, resulting in a mechanically robust film which does not crack even when bent to a 0.8 cm curvature radius and is found to maintain pinhole-free coverage during Li metal deposition and stripping. The measured ionic conductivity is up to 5.2 × 10–4 S cm–1, sufficient for maintaining regular current densities for controllable film thicknesses ranging from 2 to 30 μm. This Li3N coating is chemically stable, isolating the reactive metallic lithium from liquid electrolyte, prevents continuous electrolyte consumption during battery cycling, and promotes dendrite-free uniform lithium plating/stripping underneath. We demonstrated Li|Li4Ti5O12 cells with stable and flat potential profiles for 500 cycles without capacity decay or an increase in potential hysteresis. PMID:29392181

Compressible liquid flow in nano- or micro-sized circular tubes considering wall-liquid Lifshitz-van der Waals interaction

NASA Astrophysics Data System (ADS)

Zhang, Xueling; Zhu, Weiyao; Cai, Qiang; Shi, Yutao; Wu, Xuehong; Jin, Tingxiang; Yang, Lianzhi; Song, Hongqing

2018-06-01

Although nano- and micro-scale phenomena for fluid flows are ubiquitous in tight oil reservoirs or in nano- or micro-sized channels, the mechanisms behind them remain unclear. In this study, we consider the wall-liquid interaction to investigate the flow mechanisms behind a compressible liquid flow in nano- or micro-sized circular tubes. We assume that the liquid is attracted by the wall surface primarily by the Lifshitz-van der Waals (LW) force, whereas electrostatic forces are negligible. The long-range LW force is thus introduced into the Navier-Stokes equations. The nonlinear equations of motion are decoupled by using the hydrodynamic vorticity-stream functions, from which an approximate analytical perturbation solution is obtained. The proposed model considers the LW force and liquid compressibility to obtain the velocity and pressure fields, which are consistent with experimentally observed micro-size effects. A smaller tube radius implies smaller dimensionless velocity, and when the tube radius decreases to a certain radius Rm, a fluid no longer flows, where Rm is the lower limit of the movable-fluid radius. The radius Rm is calculated, and the results are consistent with previous experimental results. These results reveal that micro-size effects are caused by liquid compressibility and wall-liquid interactions, such as the LW force, for a liquid flowing in nano- or micro-sized channels or pores. The attractive LW force enhances the flow's radial resistance, and the liquid compressibility transmits the radial resistance to the streaming direction via volume deformation, thereby decreasing the streaming velocity.

Rotational dynamics of coumarin-153 and 4-aminophthalimide in 1-ethyl-3-methylimidazolium alkylsulfate ionic liquids: effect of alkyl chain length on the rotational dynamics.

PubMed

Das, Sudhir Kumar; Sarkar, Moloy

2012-01-12

Rotational dynamics of two neutral organic solutes, coumarin-153 (C-153) and 4-aminophthalimide (AP), with only the latter having hydrogen-bond-donating ability, has been investigated in a series of 1-ethyl-3-methylimidazolium alkyl sulfate ionic liquids as a function of temperature. The ionic liquids differ only in the length of the linear alkyl side chain (alkyl = ethyl, butyl, hexyl, and octyl) on the anionic moiety. The present study has been undertaken to examine the role of alkyl side chains on the rotational dynamics of the two solutes in these ionic liquids. Analysis of the results using Stokes-Einstein-Debye hydrodynamic theory indicates that the rotational dynamics of C-153 lies between the stick and slip boundary condition in the ethyl analogue and finally reaches subslip condition as in case of the octyl substituent. The observed rotational behavior of C-153 has been explained on the basis of an increase in the size of the solvent, which offers lower friction for solute rotation. On the other hand, AP shows superstick behavior in the ethyl system and exceeds the stick limit in the octyl derivative. Superstick behavior of AP has been attributed to the specific hydrogen-bonding interaction between AP and the sulfate moiety. Proton NMR investigation confirms the hydrogen-bonding interaction between the N-H hydrogen of AP and the ionic liquid. The decrease in rotational coupling constant values for AP with increasing length of alkyl side chains has been attributed to the decrease in the solute-solvent-specific interaction with an increase in the alkyl side chain length on the sulfate moiety.

Differential impact of ionic and coordinate covalent chromium (Cr)-DNA binding on DNA replication.

PubMed

Fornsaglio, Jamie L; O'Brien, Travis J; Patierno, Steven R

2005-11-01

The reactive species produced by the reduction of Cr(VI), particularly Cr(III), can form both ionic and coordinate covalent complexes with DNA. These Cr(III)-DNA interactions consist of Cr-DNA monoadducts, Cr-DNA ternary adducts, and Cr-DNA interstrand cross-links (Cr-ICLs), the latter of which are DNA polymerase arresting lesions (PALs). We sought to determine the impact of Cr-DNA interactions on the formation of replication blocking lesions in S. cerevisiae using a PCR-based method. We found that target sequence (TS) amplification using DNA isolated from Cr(VI)-treated yeast actually increased as a function of Cr(VI) concentration. Moreover, the enhanced TS amplification was reproduced in vitro using Cr(III)-treated DNA. In contrast, PCR amplification of TS from DNA isolated from yeast exposed to equitoxic doses of the inorganic DNA cross-linking agent cisplatin (CDDP), was decreased in a concentration-dependent manner. This paradox suggested that a specific Cr-DNA interaction, such as an ionic Cr-DNA complex, was responsible for the enhanced TS amplification, thereby masking the replication-blocking effect of certain ternary Cr-DNA adducts (i.e. interstrand cross-links). To test this possibility, we removed ionically associated Cr from the DNA using salt extraction prior to PCR analysis. This procedure obviated the increased amplification and revealed a dose-dependent decrease in TS amplification and an increase in Cr-PALs. These data from DNA analyzed ex vivo after treatment of intact cells indicate that ionic interactions of Cr with DNA result in increased DNA amplification whereas coordinate-covalent Cr-DNA complexes lead to formation of Cr-PALs. Thus, these results suggest that treatment of living cells with Cr(VI) leads to two modes of Cr-binding, which may have conflicting effects on DNA replication.

Iodinated contrast media and contrast-induced nephropathy: is there a preferred cost-effective agent?

PubMed

Sharma, Samin K

2008-05-01

Over 20 years have passed since the introduction of the tri-iodinated low-osmolar nonionic contrast agents such as iopamidol, iohexol, ioversol and iopromide. During this time, most cardiology practices have switched to these nonionic agents to avoid the nuisance side effects and cardiac adverse events associated with the older ionic contrast agents. Although the improved tolerability of the nonionic agents is generally attributed to their decreased osmolality (approximately half that of the older ionic contrast agents), in fact, these contrast agents also differ from the older agents in their ionicity, viscosity and direct chemotoxicity. The impact of these properties on safety, together with cost differences, should be considered when selecting a contrast agent.

Salting out of proteins using ammonium sulfate precipitation.

PubMed

Duong-Ly, Krisna C; Gabelli, Sandra B

2014-01-01

Protein solubility is affected by ions. At low ion concentrations (<0.5 M), protein solubility increases along with ionic strength. Ions in the solution shield protein molecules from the charge of other protein molecules in what is known as 'salting-in'. At a very high ionic strength, protein solubility decreases as ionic strength increases in the process known as 'salting-out'. Thus, salting out can be used to separate proteins based on their solubility in the presence of a high concentration of salt. In this protocol, ammonium sulfate will be added incrementally to an E. coli cell lysate to isolate a recombinantly over-expressed protein of 20 kDa containing no cysteine residues or tags. © 2014 Elsevier Inc. All rights reserved.

Clustering effects in ionic polymers: Molecular dynamics simulations.

PubMed

Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S

2015-08-01

Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. These ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing the electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Decrease in electrostatic interaction significantly enhances the mobility of the polymer.

Embedding of polyaniline molecules on adhesive tape using successive ionic layer adsorption and reaction (SILAR) technique

NASA Astrophysics Data System (ADS)

Pamatmat, J. K.; Gillado, A. V.; Herrera, M. U.

2017-05-01

Polyaniline molecules are embedded on adhesive tape using successive ionic layer adsorption and reaction (SILAR) technique. The infrared spectrum shows the existence of molecular vibrational modes associated with the presence of polyaniline molecules on the sample. With the addition of polyaniline molecules, the conductivity of adhesive tape increases. Surface conductivity increases with number of dipping cycle until it reaches a certain value. Beyond this value, surface conductivity begins to decrease. The surface conductivity of the sample is associated with the connectivity of the embedded polyaniline molecules. The connectivity increases as the number of dipping cycle progresses. Meanwhile, the decrease in surface conductivity is attributed to the eroding of existing embedded structure at higher number of dipping cycle.

MD simulations of the formation of stable clusters in mixtures of alkaline salts and imidazolium-based ionic liquids.

PubMed

Méndez-Morales, Trinidad; Carrete, Jesús; Bouzón-Capelo, Silvia; Pérez-Rodríguez, Martín; Cabeza, Óscar; Gallego, Luis J; Varela, Luis M

2013-03-21

Structural and dynamical properties of room-temperature ionic liquids containing the cation 1-butyl-3-methylimidazolium ([BMIM](+)) and three different anions (hexafluorophosphate, [PF6](-), tetrafluoroborate, [BF4](-), and bis(trifluoromethylsulfonyl)imide, [NTf2](-)) doped with several molar fractions of lithium salts with a common anion at 298.15 K and 1 atm were investigated by means of molecular dynamics simulations. The effect of the size of the salt cation was also analyzed by comparing these results with those for mixtures of [BMIM][PF6] with NaPF6. Lithium/sodium solvation and ionic mobilities were analyzed via the study of radial distribution functions, coordination numbers, cage autocorrelation functions, mean-square displacements (including the analysis of both ballistic and diffusive regimes), self-diffusion coefficients of all the ionic species, velocity and current autocorrelation functions, and ionic conductivity in all the ionic liquid/salt systems. We found that lithium and sodium cations are strongly coordinated in two different positions with the anion present in the mixture. Moreover, [Li](+) and [Na](+) cations were found to form bonded-like, long-lived aggregates with the anions in their first solvation shell, which act as very stable kinetic entities within which a marked rattling motion of salt ions takes place. With very long MD simulation runs, this phenomenon is proved to be on the basis of the decrease of self-diffusion coefficients and ionic conductivities previously reported in experimental and computational results.

Impenetrable barriers for positrons in neighbourhood of superheavy nuclei with Z>118

NASA Astrophysics Data System (ADS)

Neznamov, V. P.

2017-12-01

Analysis of quantum mechanical motion of charged half-spin particles in the repulsive Coulomb field results in that an impenetrable potential barrier not explored earlier was found. For a particle at rest with a reduced mass m, the barrier radius is equal to half classical radius: the barrier radius decreases with increase in the particle energy. For the stable and quasi-stable nuclei with Z > 118, presence of an impenetrable barrier as β +-decay leads to the existence of “traps” for positrons in the neighbourhood of nuclei and as Zcr ≃ 170 (with emission of electron-positron pairs by vacuum) leads to the existence of a quasi-constant source of annihilation quanta.

Emittance Theory for Cylindrical Fiber Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1998-01-01

A fibrous rare earth selective emitter is approximated as an infinitely long cylinder. The spectral emittance, epsilon(lambda), is obtained by solving the radiative transfer equations with appropriate boundary conditions and uniform temperature. For optical depths, Kappa(R) = alpha(lambda)R, where alpha(lambda) is the extinction coefficient and R is the cylinder radius, greater than 1 the spectral emittance is nearly at its maximum value. There is an optimum cylinder radius, R(opt), for maximum emitter efficiency, eta(E). Values for R(opt) are strongly dependent on the number of emission bands of the material. The optimum radius decreases slowly with increasing emitter temperature, while the maximum efficiency and useful radiated power increase rapidly with increasing temperature.

Improvement of the Coercivity of Cobalt Ferrites Induced by Substitution of Sr2+ Ions for Co2+ Ions

NASA Astrophysics Data System (ADS)

Zhou, Kaiwen; Chen, Wen; Wu, Xuehang; Wu, Wenwei; Lin, Cuiwu; Wu, Juan

2017-07-01

Spinel Co1- x Sr x Fe2O4 ( x = 0.0, 0.1, 0.2, and 0.3) ferrites have been successfully synthesized by calcining a mixture of oxalates in air. X-ray diffraction study shows that the sample with the concentration of x = 0 has a single spinel phase CoFe2O4 structure and the samples with concentrations of x = 0.1-0.3 have a small amount of foreign phase SrFe12O19 and/or Sr7Fe10O22 along the spinel phase. The lattice parameter of the ferrites at first increases with increasing Sr2+ content, then decreases to x = 0.3 due to the large ionic radius of Sr2+ (0.144 nm) as compared to Co2+ (0.072 nm); for higher doping levels, part of the Sr2+ ions could not enter the tetrahedral (A) and/or octahedral (B) sites but forms a second phase Sr7Fe10O22. The addition of Sr2+ ions decreases the average crystallite size of Co1- x Sr x Fe2O4, which is attributed to the foreign phase Sr7Fe10O22 and/or SrFe12O19 restraining the growth of the Co1- x Sr x Fe2O4 crystallite. The trend of specific saturation magnetization ( Ms), remanence ( Mr), and anisotropy constant ( K eff) decreases with the increase in Sr2+ content, whereas that of coercivity is increased. In this study, Co0.8Sr0.2Fe2O4 obtained at 800°C exhibits the highest coercivity (1699.25 ± 40.78 Oe), and Co0.7Sr0.3Fe2O4 obtained at 900°C exhibits the highest squareness (0.470 ± 0.008).

Electronic structure and O vacancy formation/migration in La0.825(Mg/Ca/Ba)0.125CoO3

NASA Astrophysics Data System (ADS)

Omotayo Akande, Salawu; Gan, Li-Yong; Schwingenschlögl, Udo

2016-04-01

The effect of A-site hole doping (Mg2+, Ca2+ or Ba2+) on the electronic and magnetic properties as well as the O vacancy formation and migration in perovskite LaCoO3 is studied using first-principles calculations. All three dopants are found to facilitate O vacancy formation. Substitution of La3+ with Ba2+/Mg2+ yields the lowest O vacancy formation energy for low/intermediate spin Co, implying that not only the structure but also the spin state of Co is a key parameter. Only for low spin Co the ionic radius is correlated with the O migration barrier. Enhanced migration for intermediate spin Co is ascribed to the availability of additional space at the transition state.

Metal-metal bond lengths in complexes of transition metals*

PubMed Central

Pauling, Linus

1976-01-01

In complexes of the transition metals containing clusters of metal atoms the cobalt-cobalt bond lengths are almost always within 1 pm of the single-bond value 246 pm given by the enneacovalent radius of cobalt, whereas most of the observed iron-iron bond lengths are significantly larger than the single-bond value 248 pm, the mean being 264 pm, which corresponds to a half-bond. A simple discussion of the structures of these complexes based on spd hybrid orbitals, the electroneutrality principle, and the partial ionic character of bonds between unlike atoms leads to the conclusion that resonance between single bonds and no-bonds would occur for iron and its congeners but not for cobalt and its congeners, explaining the difference in the bond lengths. PMID:16592368

The geometry of the ionic chànnel lumen formed by alpha-latroinsectotoxin from black widow spider venom in the bilayer lipid membranes.

PubMed

Shatursky, Oleg Ya; Volkova, Tatyana M; Himmelreich, Nina H; Grishin, Eugene V

2007-11-01

The dependence of single channel conductance formed by alpha-latroinsectotoxin (alpha-LIT) from black widow spider venom in the planar phospholipid membrane on the hydrodynamic radii of different nonelectrolytes allowed to determine the geometry of alpha-LIT water lumen. It was found that the cis- and trans-entrances of alpha-LIT channel had the same effective radii of 0.55-0.58 nm. Relatively small conductance of alpha-LIT channel (23.5+3.7 pS) in a symmetrical membrane bathing solution of 100 mM KCl (pH 7.4) may result from the constriction inside the channel with apparent radius of 0.37 nm located 32.5% of channel length away from the cis-entrance.

Superconductivity in REO0.5F0.5BiS2 with high-entropy-alloy-type blocking layers

NASA Astrophysics Data System (ADS)

Sogabe, Ryota; Goto, Yosuke; Mizuguchi, Yoshikazu

2018-05-01

We synthesized new REO0.5F0.5BiS2 (RE: rare earth) superconductors with high-entropy-alloy-type (HEA-type) REO blocking layers. The lattice constant a systematically changed in the HEA-type samples with the RE concentration and the RE ionic radius. A sharp superconducting transition was observed in the resistivity measurements for all the HEA-type samples, and the transition temperature of the HEA-type samples was higher than that of typical REO0.5F0.5BiS2. The sharp superconducting transition and the enhanced superconducting properties of the HEA-type samples may indicate the effectiveness of the HEA states of the REO blocking layers in the REO0.5F0.5BiS2 system.

Theoretical Study on Structural Stability of Fully Filled p-Type Skutterudites RETM4Sb12 ( RE = Rare Earth; TM = Fe, Ru)

NASA Astrophysics Data System (ADS)

Chen, Zhuo; Yang, Jiong; Liu, Ruiheng; Xi, Lili; Zhang, Wenqing; Yang, Jihui

2013-08-01

The structural stability of filled p-type skutterudites RETM4Sb12 ( RE = rare earth; TM = Fe, Ru) was studied via ab initio calculations. Most of the RE metals (La-Ho and Yb) could be filled into the cages (voids) of Fe4Sb12 to form stable filled skutterudites. However, only a few RE metals (La-Nd and Eu) could be stably filled into the cage of Ru4Sb12-based skutterudites. Systematic analysis of bonding energy showed that the structural stability could be attributed to ionic radius and effective charge state differences of the RE fillers. Resonant rattling frequencies of the fillers in both Fe4Sb12- and Ru4Sb12-based skutterudites were also studied.

Iterated Stretching of Viscoelastic Jets

NASA Technical Reports Server (NTRS)

Chang, Hsueh-Chia; Demekhin, Evgeny A.; Kalaidin, Evgeny

1999-01-01

We examine, with asymptotic analysis and numerical simulation, the iterated stretching dynamics of FENE and Oldroyd-B jets of initial radius r(sub 0), shear viscosity nu, Weissenberg number We, retardation number S, and capillary number Ca. The usual Rayleigh instability stretches the local uniaxial extensional flow region near a minimum in jet radius into a primary filament of radius [Ca(1 - S)/ We](sup 1/2)r(sub 0) between two beads. The strain-rate within the filament remains constant while its radius (elastic stress) decreases (increases) exponentially in time with a long elastic relaxation time 3We(r(sup 2, sub 0)/nu). Instabilities convected from the bead relieve the tension at the necks during this slow elastic drainage and trigger a filament recoil. Secondary filaments then form at the necks from the resulting stretching. This iterated stretching is predicted to occur successively to generate high-generation filaments of radius r(sub n), (r(sub n)/r(sub 0)) = square root of 2[r(sub n-1)/r(sub 0)](sup 3/2) until finite-extensibility effects set in.

Fractional cable equation for general geometry: A model of axons with swellings and anomalous diffusion.

PubMed

López-Sánchez, Erick J; Romero, Juan M; Yépez-Martínez, Huitzilin

2017-09-01

Different experimental studies have reported anomalous diffusion in brain tissues and notably this anomalous diffusion is expressed through fractional derivatives. Axons are important to understand neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. Indeed, abnormal accumulation of proteins and organelles in axons is a hallmark of these diseases. The diffusion in the axons can become anomalous as a result of this abnormality. In this case the voltage propagation in axons is affected. Another hallmark of different neurodegenerative diseases is given by discrete swellings along the axon. In order to model the voltage propagation in axons with anomalous diffusion and swellings, in this paper we propose a fractional cable equation for a general geometry. This generalized equation depends on fractional parameters and geometric quantities such as the curvature and torsion of the cable. For a cable with a constant radius we show that the voltage decreases when the fractional effect increases. In cables with swellings we find that when the fractional effect or the swelling radius increases, the voltage decreases. Similar behavior is obtained when the number of swellings and the fractional effect increase. Moreover, we find that when the radius swelling (or the number of swellings) and the fractional effect increase at the same time, the voltage dramatically decreases.

Fractional cable equation for general geometry: A model of axons with swellings and anomalous diffusion

NASA Astrophysics Data System (ADS)

López-Sánchez, Erick J.; Romero, Juan M.; Yépez-Martínez, Huitzilin

2017-09-01

Different experimental studies have reported anomalous diffusion in brain tissues and notably this anomalous diffusion is expressed through fractional derivatives. Axons are important to understand neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. Indeed, abnormal accumulation of proteins and organelles in axons is a hallmark of these diseases. The diffusion in the axons can become anomalous as a result of this abnormality. In this case the voltage propagation in axons is affected. Another hallmark of different neurodegenerative diseases is given by discrete swellings along the axon. In order to model the voltage propagation in axons with anomalous diffusion and swellings, in this paper we propose a fractional cable equation for a general geometry. This generalized equation depends on fractional parameters and geometric quantities such as the curvature and torsion of the cable. For a cable with a constant radius we show that the voltage decreases when the fractional effect increases. In cables with swellings we find that when the fractional effect or the swelling radius increases, the voltage decreases. Similar behavior is obtained when the number of swellings and the fractional effect increase. Moreover, we find that when the radius swelling (or the number of swellings) and the fractional effect increase at the same time, the voltage dramatically decreases.

Surface interactions between nanoscale iron and organic material: Potential uses in water treatment process units

NASA Astrophysics Data System (ADS)

Storms, Max

Membrane systems are among the primary emergent technologies in water treatment process units due to their ease of use, small physical footprint, and high physical rejection. Membrane fouling, the phenomena by which membranes become clogged or generally soiled, is an inhibitor to optimal efficiency in membrane systems. Novel, composite, and modified surface materials must be investigated to determine their efficacy in improving fouling behavior. Ceramic membranes derived from iron oxide nanoparticles called ferroxanes were coated with a superhydrophillic, zwitterionic polymer called poly (sulfobetaine methacrylate) (polySBMA) to form a composite ceramic-polymeric membrane. Membrane samples with and without polySBMA coating were subjected to fouling with a bovine serum albumin solution and fouling was observed by measuring permeate flux at 10 mL intervals. Loss of polySBMA was measured using total organic carbon analysis, and membrane samples were characterized using x-ray diffraction, scanning electron microscopy, and optical profilometry. The coated membrane samples decreased initial fouling rate by 27% and secondary fouling rate by 24%. Similarly, they displayed a 30% decrease in irreversible fouling during the initial fouling stage, and a 27% decrease in irreversible fouling in the secondary fouling stage; however, retention of polySBMA sufficient for improved performance was not conclusive. The addition of chemical disinfectants into drinking water treatment processes results in the formation of compounds called disinfection by-products (DBPs). The formation of DBPs occurs when common chemical disinfectants (i.e. chlorine) react with organic material. The harmful effects of DBP exposure require that they be monitored and controlled for public safety. This work investigated the ability of nanostructured hematite derived from ferroxane nanoparticles to remove organic precursors to DBPs in the form of humic acid via adsorption processes. The results show that pH and ionic strength have an effect on adsorption capacity and mechanism. At lower ionic strengths, the adsorption isotherms are closely correlated with the Freundlich adsorption isotherm model, while at higher ionic strength, the isotherms are closely related to the Langmuir adsorption isotherm model. Lower pH systems facilitate better adsorption capacities than higher pH systems, and lower ionic strength systems facilitate better adsorption than higher ionic strength systems.

Heavy Element Abundances in NGC 5846

NASA Technical Reports Server (NTRS)

Jones, Christine

2000-01-01

In this paper we analyze the diffuse X-ray coronae surrounding the elliptical galaxy NGC 5846, combining measurements from two observatories, ROSAT and the Advanced Satellite for Cosmology and Astrophysics. We map the gas temperature distribution and find a central cool region within an approximately isothermal gas halo extending to a radius of about 50 kpc and evidence for a temperature decrease at larger radii. With a radially falling temperature profile, the total mass converges to (9.6 +/- 1.0) x 10(exp 12) solar mass at 230 kpc radius. This corresponds to a total mass to blue light ratio of 53 +/- 5 solar mass/solar luminosity. As in other early type galaxies, the gas mass is only a few percent of the total mass. Using the spectroscopic measurements, we also derive radial distributions for the heavy elements silicon and iron and find that the abundances of both decrease with galaxy radius. The mass ratio of Si to Fe lies between the theoretical predictions for element production in SN Ia and SN II, suggesting an important role for SN Ia, as well as SN II, for gas enrichment in ellipticals. Using the 2 SN la yield of Si, we set an upper limit of 0.012 h(sup 2, sub 50) solar neutrino units (SNU) for the SN Ia rate at radii >50 kpc, which is independent of possible uncertainties in the iron L-shell modeling. We compare our observations with the theoretical predictions for the chemical evolution of ellipticals. We conclude that the metal content in stars, if explained by the star formation duration, requires a significant decline in the duration of star formation with galaxy radius, ranging from 1 Gyr at the center to 0.01 Gyr at 100 kpc radius. Alternatively, the decline in metallicity with galaxy radius may be caused by a similar drop with radius in the efficiency of star formation. Based on the Si and Fe measurements presented in this paper, we conclude that the latter scenario is preferred unless a dependence of the SN Ia rate on stellar metallicity is invoked.

Two-Term Asymptotic Approximation of a Cardiac Restitution Curve*

PubMed Central

Cain, John W.; Schaeffer, David G.

2007-01-01

If spatial extent is neglected, ionic models of cardiac cells consist of systems of ordinary differential equations (ODEs) which have the property of excitability, i.e., a brief stimulus produces a prolonged evolution (called an action potential in the cardiac context) before the eventual return to equilibrium. Under repeated stimulation, or pacing, cardiac tissue exhibits electrical restitution: the steady-state action potential duration (APD) at a given pacing period B shortens as B is decreased. Independent of ionic models, restitution is often modeled phenomenologically by a one-dimensional mapping of the form APDnext = f(B – APDprevious). Under some circumstances, a restitution function f can be derived as an asymptotic approximation to the behavior of an ionic model. In this paper, extending previous work, we derive the next term in such an asymptotic approximation for a particular ionic model consisting of two ODEs. The two-term approximation exhibits excellent quantitative agreement with the actual restitution curve, whereas the leading-order approximation significantly underestimates actual APD values. PMID:18080006

Electrophoretic mobilities of erythrocytes in various buffers

NASA Technical Reports Server (NTRS)

Plank, L. D.; Kunze, M. E.; Todd, P. W.

1985-01-01

The calibration of space flight equipment depends on a source of standard test particles, this test particle of choice is the fixed erythrocyte. Erythrocytes from different species have different electrophoretic mobilities. Electrophoretic mobility depends upon zeta potential, which, in turn depends upon ionic strength. Zeta potential decreases with increasing ionic strength, so cells have high electrophoretic mobility in space electrophoresis buffers than in typical physiological buffers. The electrophoretic mobilities of fixed human, rat, and rabbit erythrocytes in 0.145 M salt and buffers of varying ionic strength, temperature, and composition, to assess the effects of some of the unique combinations used in space buffers were characterized. Several effects were assessed: glycerol or DMSO (dimethylsulfoxide) were considered for use as cryoprotectants. The effect of these substances on erythrocyte electrophoretic mobility was examined. The choice of buffer depended upon cell mobility. Primary experiments with kidney cells established the choice of buffer and cryoprotectant. A nonstandard temperature of EPM in the suitable buffer was determined. A loss of ionic strength control occurs in the course of preparing columns for flight, the effects of small increases in ionic strength over the expected low values need to be evaluated.

Using FT-IR Spectroscopy to Measure Charge Organization in Ionic Liquids

PubMed Central

Burba, Christopher M.; Janzen, Jonathan; Butson, Eric D.; Coltrain, Gage L.

2013-01-01

A major goal in the field of ionic liquids is correlating transport property trends with the underlying liquid structure of the compounds, such as the degree of charge organization among the constituent ions. Traditional techniques for experimentally assessing charge organization are specialized and not readily available for routine measurements. This represents a significant roadblock in elucidating these correlations. We use a combination of transmission and polarized-ATR infrared spectroscopy to measure the degree of charge organization for ionic liquids. The technique is illustrated with a family of 1-alkyl-3-methylimidazolium trifluoromethansulfonate ionic liquids at 30°C. As expected, the amount of charge organization decreases as the alkyl side chain is lengthened, highlighting the important role of short-range repulsive interactions in defining quasilattice structure. Inherent limitations of the method are identified and discussed. The quantitative measurements of charge organization are then correlated with trends in the transport properties of the compounds to highlight the relationship between charge and momentum transport and the underlying liquid structure. Most research laboratories possess infrared spectrometers capable of conducting these measurements, thus, the proposed method may represent a cost-effective solution for routinely measuring charge organization in ionic liquids. PMID:23781877

New Insights into the Compositional Dependence of Li-Ion Transport in Polymer-Ceramic Composite Electrolytes.

PubMed

Zheng, Jin; Hu, Yan-Yan

2018-01-31

Composite electrolytes are widely studied for their potential in realizing improved ionic conductivity and electrochemical stability. Understanding the complex mechanisms of ion transport within composites is critical for effectively designing high-performance solid electrolytes. This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration. The results show that with increase in the fraction of ceramic Li 7 La 3 Zr 2 O 12 (LLZO) phase in the LLZO-poly(ethylene oxide) composites, ion mobility decreases, ion transport pathways transit from polymer to ceramic routes, and the active ion concentration increases. These changes in ion mobility, transport pathways, and concentration collectively explain the observed trend of ionic conductivity in composite electrolytes. Liquid additives alter ion transport pathways and increase ion mobility, thus enhancing ionic conductivity significantly. It is also found that a higher content of LLZO leads to improved electrochemical stability of composite electrolytes. This study provides insight into the recurring observations of compositional dependence of ionic conductivity in current composite electrolytes and pinpoints the intrinsic limitations of composite electrolytes in achieving fast ion conduction.

Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling.

PubMed

Reid, Michael S; Kedzior, Stephanie A; Villalobos, Marco; Cranston, Emily D

2017-08-01

This work explores cellulose nanocrystal (CNC) thin films (<50 nm) and particle-particle interactions by investigating film swelling in aqueous solutions with varying ionic strength (1-100 mM). CNC film hydration was monitored in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

Effects of Ionic Dependence of DNA Persistence Length on the DNA Condensation at Room Temperature

NASA Astrophysics Data System (ADS)

Mao, Wei; Liu, Yan-Hui; Hu, Lin; Xu, Hou-Qiang

2016-05-01

DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. A series of experiments pointed out that, in the DNA condensation process by multivalent cations, the condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in ionic concentration. At the same time, single molecule experiments carried out in solution with multivalent cations (such as spermidine, spermine) indicated that DNA persistence length strongly depends on the ionic concentration. In order to revolve the effects of ionic concentration dependence of persistence length on DNA condensation, a model including the ionic concentration dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the ionic concentration dependence of toroidal conformations. With an increase in ion concentration, the first periodic oscillation contained in the autocorrelation function shifts, the number of segment contained in the first periodic oscillation decreases gradually. According to the experiments, the average long-axis length is defined to estimate the ionic concentration dependence of condensation process further. The relation between long-axis length and ionic concentration matches the experimental results qualitatively. Supported by National Natural Science Foundation of China under Grant Nos. 11047022, 11204045, 11464004 and 31360215; The Research Foundation from Ministry of Education of China (212152), Guizhou Provincial Tracking Key Program of Social Development (SY20123089, SZ20113069); The General Financial Grant from the China Postdoctoral Science Foundation (2014M562341); The Research Foundation for Young University Teachers from Guizhou University (201311); The West Light Foundation (2015) and College Innovation Talent Team of Guizhou Province, (2014) 32

Can the scaling behavior of electric conductivity be used to probe the self-organizational changes in solution with respect to the ionic liquid structure? The case of [C8MIM][NTf2].

PubMed

Paluch, Marian; Wojnarowska, Zaneta; Goodrich, Peter; Jacquemin, Johan; Pionteck, Jürgen; Hensel-Bielowka, Stella

2015-08-28

Electrical conductivity of the supercooled ionic liquid [C8MIM][NTf2], determined as a function of temperature and pressure, highlights strong differences in its ionic transport behavior between low and high temperature regions. To date, the crossover effect which is very well known for low molecular van der Waals liquids has been rarely described for classical ionic liquids. This finding highlights that the thermal fluctuations could be dominant mechanisms driving the dramatic slowing down of ion motions near Tg. An alternative way to analyze separately low and high temperature dc-conductivity data using a density scaling approach was then proposed. Based on which a common value of the scaling exponent γ = 2.4 was obtained, indicating that the applied density scaling is insensitive to the crossover effect. By comparing the scaling exponent γ reported herein along with literature data for other ionic liquids, it appears that γ decreases by increasing the alkyl chain length on the 1-alkyl-3-methylimidazolium-based ionic liquids. This observation may be related to changes in the interaction between ions in solution driven by an increase in the van der Waals type interaction by increasing the alkyl chain length on the cation. This effect may be related to changes in the ionic liquid nanostructural organization with the alkyl chain length on the cation as previously reported in the literature based on molecular dynamic simulations. In other words, the calculated scaling exponent γ may be then used as a key parameter to probe the interaction and/or self-organizational changes in solution with respect to the ionic liquid structure.

Preliminary investigation of phosphorus adsorption onto two types of iron oxide-organic matter complexes.

PubMed

Yan, Jinlong; Jiang, Tao; Yao, Ying; Lu, Song; Wang, Qilei; Wei, Shiqiang

2016-04-01

Iron oxide (FeO) coated by natural organic matter (NOM) is ubiquitous. The associations of minerals with organic matter (OM) significantly changes their surface properties and reactivity, and thus affect the environmental fate of pollutants, including nutrients (e.g., phosphorus (P)). In this study, ferrihydrite/goethite-humic acid (FH/GE-HA) complexes were prepared and their adsorption characteristics on P at various pH and ionic strength were investigated. The results indicated that the FeO-OM complexes showed a decreased P adsorption capacity in comparison with bare FeO. The maximum adsorption capacity (Qmax) decreased in the order of FH (22.17 mg/g)>FH-HA (5.43 mg/g)>GE (4.67 mg/g)>GE-HA (3.27 mg/g). After coating with HA, the amorphous FH-HA complex still showed higher P adsorption than the crystalline GE-HA complex. The decreased P adsorption observed might be attributed to changes of the FeO surface charges caused by OM association. The dependence of P adsorption on the specific surface area of adsorbents suggests that the FeO component in the complexes is still the main contributor for the adsorption surfaces. The P adsorptions on FeO-HA complexes decreased with increasing initial pH or decreasing initial ionic strength. A strong dependence of P adsorption on ionic strength and pH may demonstrate that outer-sphere complexes between the OM component on the surface and P possibly coexist with inner-sphere surface complexes between the FeO component and P. Therefore, previous over-emphasis on the contributions of original minerals to P immobilization possibly over-estimates the P loading capacity of soils, especially in humic-rich areas. Copyright © 2015. Published by Elsevier B.V.

Entrainment and scattering in microswimmer-colloid interactions

NASA Astrophysics Data System (ADS)

Shum, Henry; Yeomans, Julia M.

2017-11-01

We use boundary element simulations to study the interaction of model microswimmers with a neutrally buoyant spherical particle. The ratio of the size of the particle to that of the swimmer is varied from RP/RS≪1 , corresponding to swimmer-tracer scattering, to RP/RS≫1 , approximately equivalent to the swimmer interacting with a fixed, flat surface. We find that details of the swimmer and particle trajectories vary for different swimmers. However, the overall characteristics of the scattering event fall into two regimes, depending on the relative magnitudes of the impact parameter, ρ , and the collision radius, Rcoll=RP+RS . The range of particle motion, defined as the maximum distance between two points on the trajectory, has only a weak dependence on the impact parameter when ρ Rcoll the range decreases as a power law in ρ and is insensitive to the size of the particle. We also demonstrate that large particles can cause swimmers to be deflected through large angles. In some instances, this swimmer deflection can lead to larger net displacements of the particle. Based on these results, we estimate the effective diffusivity of a particle in a dilute bath of swimmers and show that there is a nonmonotonic dependence on particle radius. Similarly, we show that the effective diffusivity of a swimmer scattering in a suspension of particles varies nonmonotonically with particle radius.

The dynamics of nucleation and growth of a particle in the ternary alloy melt with anisotropic surface tension.

PubMed

Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min

2017-08-28

The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.

Simultaneous spreading and evaporation: recent developments.

PubMed

Semenov, Sergey; Trybala, Anna; Rubio, Ramon G; Kovalchuk, Nina; Starov, Victor; Velarde, Manuel G

2014-04-01

The recent progress in theoretical and experimental studies of simultaneous spreading and evaporation of liquid droplets on solid substrates is discussed for pure liquids including nanodroplets, nanosuspensions of inorganic particles (nanofluids) and surfactant solutions. Evaporation of both complete wetting and partial wetting liquids into a nonsaturated vapour atmosphere are considered. However, the main attention is paid to the case of partial wetting when the hysteresis of static contact angle takes place. In the case of complete wetting the spreading/evaporation process proceeds in two stages. A theory was suggested for this case and a good agreement with available experimental data was achieved. In the case of partial wetting the spreading/evaporation of a sessile droplet of pure liquid goes through four subsequent stages: (i) the initial stage, spreading, is relatively short (1-2 min) and therefore evaporation can be neglected during this stage; during the initial stage the contact angle reaches the value of advancing contact angle and the radius of the droplet base reaches its maximum value, (ii) the first stage of evaporation is characterised by the constant value of the radius of the droplet base; the value of the contact angle during the first stage decreases from static advancing to static receding contact angle; (iii) during the second stage of evaporation the contact angle remains constant and equal to its receding value, while the radius of the droplet base decreases; and (iv) at the third stage of evaporation both the contact angle and the radius of the droplet base decrease until the drop completely disappears. It has been shown theoretically and confirmed experimentally that during the first and second stages of evaporation the volume of droplet to power 2/3 decreases linearly with time. The universal dependence of the contact angle during the first stage and of the radius of the droplet base during the second stage on the reduced time has been derived theoretically and confirmed experimentally. The theory developed for pure liquids is applicable also to nanofluids, where a good agreement with the available experimental data has been found. However, in the case of evaporation of surfactant solutions the process deviates from the theoretical predictions for pure liquids at concentration below critical wetting concentration and is in agreement with the theoretical predictions at concentrations above it. Crown Copyright © 2013. All rights reserved.

Study of surface-bonded dicationic ionic liquids as stationary phases for hydrophilic interaction chromatography.

PubMed

Qiao, Lizhen; Li, Hua; Shan, Yuanhong; Wang, Shuangyuan; Shi, Xianzhe; Lu, Xin; Xu, Guowang

2014-02-21

In the present study, several geminal dicationic ionic liquids based on 1,4-bis(3-allylimidazolium)butane and 1,8-bis(3-allylimidazolium)octane in combination with different anions bromide and bis(trifluoromethanesulphonyl)imide were prepared and then bonded to the surface of 3-mercaptopropyl modified silica materials through the "thiol-ene" click chemistry as stationary phases for hydrophilic interaction chromatography (HILIC). Compared with their monocationic analogues, the dicationic ionic liquids stationary phases presented effective retention and good selectivity for typical hydrophilic compounds under HILIC mode with the column efficiency as high as 130,000 plates/m. Moreover, the influence of different alkyl chain spacer between dications and combined anions on the retention behavior and selectivity of the dicationic ionic liquids stationary phases under HILIC mode was displayed. The results indicated that the longer linkage chain would decrease the hydrophilicity and retention on the dicationic ionic liquid stationary phase, and while differently combined anions had no difference due to the exchangeability under the common HILIC mobile phase with buffer salt. Finally, the retention mechanism was investigated by evaluating the effect of chromatographic factors on retention, including the water content in the mobile phase, the mobile phase pH and buffer salt concentration. The results showed that the dicationic ionic liquids stationary phases presented a mixed-mode retention behavior with HILIC mechanism and anion exchange. Copyright © 2014 Elsevier B.V. All rights reserved.

Response surface method (RSM) for optimization of ionic conductivity of membranes polymer electrolyte poly (vinylidene fluoride) (PVDF) with polyvinyl pyrrolidone (PVP) as pore forming agent

NASA Astrophysics Data System (ADS)

Dyartanti, E. R.; Susanto, H.; Widiasa, I. N.; Purwanto, A.

2017-06-01

The Membranes Polymer Gel Electrolyte (MPGEs) based poly (vinylidene fluoride) (PVDF) was prepared by a phase inversion method using polyvinyl pyrrolidone (PVP) as a pore-forming agent and N, N-dimethyl acetamide (DMAc) as a solvent and water as non solvet. The membranes were then soaked in 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate (EC) / dimethyl carbonate (DMC) / Diethyl carbonate (DEC) (4:2:4 %vol) solution in order to prepare polymer electrolyte membranes. The MPEGs PVDF/PVP/Nanoclay was applied using central composite design (CCD) experimental design to obtain a quantitative relationship between selected membranes prepared parameters namely (PVDF, PVP as pore forming agent and nanoclay filler concentration) and Ionic conductivity MPEGs. The model was used to find the optimum ionic conductivity from polymer electrolyte membranes. The polymer electrolyte membranes show good ionic conductivity on the order of 6.3 - 8.7 x 10-3 S cm-1 at the ambient temperatures. The ionic conductivity tended to increase with PVP and nanoclay concentration and decrease with PVDF composition. The model predicted the maximum ionic conductivity of 8.47 x 10-3 S cm-1 when the PVDF, PVP and nanoclay concentration were set at 8.01 %, 8.04 % and 10.12%, respectively. The first section in your paper.

Effect of Structure on Transport Properties (Viscosity, Ionic Conductivity, and Self-Diffusion Coefficient) of Aprotic Heterocyclic Anion (AHA) Room Temperature Ionic Liquids. 2. Variation of Alkyl Chain Length in the Phosphonium Cation.

PubMed

Sun, Liyuan; Morales-Collazo, Oscar; Xia, Han; Brennecke, Joan F

2016-06-30

A series of room-temperature ionic liquids (ILs) composed of triethyl(alkyl)phosphonium cations paired with three different aprotic heterocyclic anions (AHAs) (alkyl = butyl ([P2224](+)) and octyl ([P2228](+))) were prepared to investigate the effect of cationic alkyl chain length on transport properties. The transport properties and density of these ILs were measured from 283.15 to 343.15 K at ambient pressure. The dependence of the transport properties (viscosity, ionic conductivity, diffusivity, and molar conductivity) on temperature can be described by the Vogel-Fulcher-Tamman (VFT) equation. The ratio of the molar conductivity obtained from the molar concentration and ionic conductivity measurements to that calculated from self-diffusion coefficients (measured by pulsed gradient spin-echo nuclear magnetic resonance spectroscopy) using the Nernst-Einstein equation was used to quantify the ionicity of these ILs. The molar conductivity ratio decreases with increasing number of carbon atoms in the alkyl chain, indicating that the reduced Coulombic interactions resulting from lower density are more than balanced by the increased van der Waals interactions between the alkyl chains. The results of this study may provide insight into the design of ILs with enhanced dynamics that may be suitable as electrolytes in lithium ion batteries and other electrochemical applications.

Solvent effects on polysulfide redox kinetics and ionic conductivity in lithium-sulfur batteries

DOE PAGES

Fan, Frank Y.; Pan, Menghsuan Sam; Lau, Kah Chun; ...

2016-11-25

Lithium-sulfur (Li-S) batteries have high theoretical energy density and low raw materials cost compared to present lithium-ion batteries and are thus promising for use in electric transportation and other applications. A major obstacle for Li-S batteries is low rate capability, especially at the low electrolyte/sulfur (E/S) ratios required for high energy density. Herein, we investigate several potentially rate-limiting factors for Li-S batteries. We study the ionic conductivity of lithium polysulfide solutions of varying concentration and in different ether-based solvents and their exchange current density on glassy carbon working electrodes. We believe this is the first such investigation of exchange currentmore » density for lithium polysulfide in solution. Exchange current densities are measured using both electrochemical impedance spectroscopy and steady-state galvanostatic polarization. In the range of interest (1-8 M [S]), the ionic conductivity monotonically decreases with increasing sulfur concentration while exchange current density shows a more complicated relationship to sulfur concentration. The electrolyte solvent dramatically affects ionic conductivity and exchange current density. Finally, the measured ionic conductivities and exchange current densities are also used to interpret the overpotential and rate capability of polysulfide-nanocarbon suspensions; this analysis demonstrates that ionic conductivity is the rate-limiting property in the solution regime (i.e. between Li 2S 8 and Li 2S 4).« less

The presence of functional groups key for biodegradation in ionic liquids: effect on gas solubility.

PubMed

Deng, Yun; Morrissey, Saibh; Gathergood, Nicholas; Delort, Anne-Marie; Husson, Pascale; Costa Gomes, Margarida F

2010-03-22

The effect of the incorporation of either ester or ester and ether functions into the side chain of an 1-alkyl-3-methylimidazolium cation on the physico-chemical properties of ionic liquids containing bis(trifluoromethylsulfonyl)imide or octylsulfate anions is studied. It is believed that the introduction of an ester function into the cation of the ionic liquids greatly increases their biodegradability. The density of three such ionic liquids is measured as a function of temperature, and the solubility of four gases-carbon dioxide, ethane, methane, and hydrogen-is determined between 303 K and 343 K and at pressures close to atmospheric level. Carbon dioxide is the most soluble gas, followed by ethane and methane; the mole fraction solubilities vary from 1.8 x 10(-3) to 3.7 x 10(-2). These solubilities are of the same order of magnitude as those determined for alkylimidazolium-based ionic liquids. The chemical modification of the alkyl side chain does not result in a significant change of the solvation properties of the ionic liquid. All of the solubilities decrease with increasing temperature, corresponding to an exothermal solvation process. From the variation of this property with temperature, the thermodynamic functions of solvation (Gibbs energy, enthalpy, and entropy) are calculated and provide information about the solute-solvent interactions and the molecular structure of the solutions.

Pair distribution function analysis of sulfide glassy electrolytes for all-solid-state batteries: Understanding the improvement of ionic conductivity under annealing condition.

PubMed

Shiotani, Shinya; Ohara, Koji; Tsukasaki, Hirofumi; Mori, Shigeo; Kanno, Ryoji

2017-08-01

In general, the ionic conductivity of sulfide glasses decreases with their crystallization, although it increases for a few sulphide glasses owing to the crystallization of a highly conductive new phase (e.g., Li 7 P 3 S 11 : 70Li 2 S-30P 2 S 5 ). We found that the ionic conductivity of 75Li 2 S-25P 2 S 5 sulfide glass, which consists of glassy and crystalline phases, is improved by optimizing the conditions of the heat treatment, i.e., annealing. A different mechanism of high ionic conductivity from the conventional mechanism is expected in the glassy phase. Here, we report the glassy structure of 75Li 2 S-25P 2 S 5 immediately before the crystallization by using the differential pair distribution function (d-PDF) analysis of high-energy X-ray diffraction. Even though the ionic conductivity increases during the optimum annealing, the d-PDF analysis indicated that the glassy structure undergoes no structural change in the sulfide glass-ceramic electrolyte at a crystallinity of 33.1%. We observed the formation of a nanocrystalline phase in the X-ray and electron diffraction patterns before the crystallization, which means that Bragg peaks were deformed. Thus, the ionic conductivity in the mixture of glassy and crystalline phases is improved by the coexistence of the nanocrystalline phase.

Demarcating Circulation Regimes of Synchronously Rotating Terrestrial Planets within the Habitable Zone

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Wolf, Eric. T.; Joshi, Manoj; Zhang, Xi; Kopparapu, Ravi Kumar

2018-01-01

We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model. The surface temperature contrast between the day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen in gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from the day to the night sides, which occurs for planets around stars with effective temperatures of 3300–4500 K (rotation period > 20 days), with both the Rossby deformation radius and the Rhines length exceeding the planetary radius. Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period < 5 days), with the Rossby deformation radius less than the planetary radius. In between is the Rhines rotation regime, which retains a thermally direct circulation from the day side to the night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000–3300 K (rotation period ∼5–20 days), where the Rhines length is greater than the planetary radius but the Rossby deformation radius is less than the planetary radius. The dynamical state can be observationally inferred from a comparison of the morphologies of the thermal emission phase curves of synchronously rotating planets.

Prominent roles of impurities in ionic liquid for catalytic conversion of carbohydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Haibo; Brown, Heather M.; Holladay, Johnathan E.

2012-02-07

In the last two decades, ionic liquids have emerged as new and versatile solvents, and many of them are also catalysts for a broad range of catalytic reactions. Certain ionic liquids have been found to possess the unique capability of dissolving cellulosic biomass. The potential of such ionic liquids as solvent to enable catalytic conversion of cellulosic polymers was first explored and demonstrated by Zhao et al. This field of research has since experienced a rapid growth. Most ionic liquids have negligible vapor pressure and excellent thermal stability over a wide temperature range. For example, ionic liquids composed of 1-ethyl-3-methylimidazoliummore » (EMIM+) cation and Cl- anion was reported to be stable up to 285 C, while salts of the same cation with other anions such as BF4- and PF6- are thermally stable above 380 C under inert atmosphere. It is well known that presence of impurities in ionic liquids typically causes changes in physical properties, e.g. decreasing in melting point and viscosity. Addition of Lewis acidic metal chlorides, e.g. AlCl3 to 1-alkyl-3-methylimidazolium chloride, [AMIM]Cl, is an exothermic reaction and considerably reduces the melting point by forming [AMIM]AlCl4 or [AMIM]Al2Cl7 that are also ionic liquids but have much lower melting point than the parent [AMIM]Cl. While most early research on catalysis of ionic liquids involving metallohalide anions were typically conducted from stoichiometric ratio of such anions to organic cations, e.g. [AMIM]+, the use of pure ionic liquids only as a solvent to carry out catalysis by a catalytic amount of a metal halide as catalyst truly displayed the solvent property of such ionic liquids.4 In such reaction systems, catalytic amounts of metal halides were used to catalyze the conversion of glucose and cellulose.4,11,12 The metal chloride catalyst concentration was in the order of 10-3 M. The presence of another metal chloride in the ionic liquids, even in the order of 10-5 M concentration was found to bring a dramatic synergistic effect. Therefore, the catalytic performance of the metal halide catalyst for the conversion of carbohydrates in the ionic liquid systems is highly sensitive to the presence of impurities. This work presents findings on the role of impurities that were present in some commercially available ionic liquids used for the conversion of the cellulose.« less

Trace Metal-Humic Complexes in Natural Waters: Insights From Speciation Experiments

NASA Astrophysics Data System (ADS)

Stern, J. C.; Salters, V.; Sonke, J.

2006-12-01

The DOM cycle is intimately linked to the cycling and bioavailability of trace metals in aqueous environments. The presence or absence of DOM in the water column can determined whether trace elements will be present in limited quantities as a nutrient, or in surplus quantities as a toxicant. Humic substances (HS), which represent the refractory products of DOM degradation, strongly affect the speciation of trace metals in natural waters. To simulate metal-HS interactions in nature, experiments must be carried out using trace metal concentrations. Sensitive detection systems such as ICP-MS make working with small (nanomolar) concentrations possible. Capillary electrophoresis coupled with ICP-MS (CE-ICP-MS) has recently been identified as a rapid and accurate method to separate metal species and calculate conditional binding constants (log K_c) of metal-humic complexes. CE-ICP-MS was used to measure partitioning of metals between humic substances and a competing ligand (EDTA) and calculate binding constants of rare earth element (REE) and Th, Hf, and Zr-humic complexes at pH 3.5-8 and ionic strength of 0.1. Equilibrium dialysis ligand exchange (EDLE) experiments to validate the CE-ICP-MS method were performed to separate the metal-HS and metal-EDTA species by partitioning due to size exclusion via diffusion through a 1000 Da membrane. CE-ICP-MS experiments were also conducted to compare binding constants of REE with humic substances of various origin, including soil, peat, and aquatic DOM. Results of our experiments show an increase in log K_c with decrease in ionic radius for REE-humic complexes (the lanthanide contraction effect). Conditional binding constants of tetravalent metal-humic complexes were found to be several orders of magnitude higher than REE-humic complexes, indicating that tetravalent metals have a very strong affinity for humic substances. Because thorium is often used as a proxy for the tetravalent actinides, Th-HS binding constants can allow us to assess the importance of tetravalent actinide-humic complexes in groundwater transport from nuclear repositories. Our results suggest that tetravalent actinide-humic complexes couild be more important to account for in predictive speciation models than previously thought.

Vapor-liquid phase behavior of a size-asymmetric model of ionic fluids confined in a disordered matrix: The collective-variables-based approach

NASA Astrophysics Data System (ADS)

Patsahan, O. V.; Patsahan, T. M.; Holovko, M. F.

2018-02-01

We develop a theory based on the method of collective variables to study the vapor-liquid equilibrium of asymmetric ionic fluids confined in a disordered porous matrix. The approach allows us to formulate the perturbation theory using an extension of the scaled particle theory for a description of a reference system presented as a two-component hard-sphere fluid confined in a hard-sphere matrix. Treating an ionic fluid as a size- and charge-asymmetric primitive model (PM) we derive an explicit expression for the relevant chemical potential of a confined ionic system which takes into account the third-order correlations between ions. Using this expression, the phase diagrams for a size-asymmetric PM are calculated for different matrix porosities as well as for different sizes of matrix and fluid particles. It is observed that general trends of the coexistence curves with the matrix porosity are similar to those of simple fluids under disordered confinement, i.e., the coexistence region gets narrower with a decrease of porosity and, simultaneously, the reduced critical temperature Tc* and the critical density ρi,c * become lower. At the same time, our results suggest that an increase in size asymmetry of oppositely charged ions considerably affects the vapor-liquid diagrams leading to a faster decrease of Tc* and ρi,c * and even to a disappearance of the phase transition, especially for the case of small matrix particles.

Clustering effects in ionic polymers: Molecular dynamics simulations

DOE PAGES

Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.

2015-08-18

Ionic clusters control the structure, dynamics, and transport in soft matter. Incorporating a small fraction of ionizable groups in polymers substantially reduces the mobility of the macromolecules in melts. Furthermore, these ionic groups often associate into random clusters in melts, where the distribution and morphology of the clusters impact the transport in these materials. Here, using molecular dynamic simulations we demonstrate a clear correlation between cluster size and morphology with the polymer mobility in melts of sulfonated polystyrene. We show that in low dielectric media ladderlike clusters that are lower in energy compared with spherical assemblies are formed. Reducing themore » electrostatic interactions by enhancing the dielectric constant leads to morphological transformation from ladderlike clusters to globular assemblies. Finally, decrease in electrostatic interaction significantly enhances the mobility of the polymer.« less

[Ionic mechanisms of depolarization responses induced by glutamate application to nerve cells of Helix pomatia].

PubMed

Gerasimov, V D

1982-01-01

The reversal potentials for transmembrane ionic currents induced by glutamate were measured in different D-neurons of the snail Helix pomatia. The first group of neurons had a mean reversal potential--10.6 +/- 1.2 mV and the second one--40.0 +/- 0.6 mV. Under normal conditions glutamate evoked spike discharges in the first group of neurons but not in the second one. At higher concentrations of glutamate the amplitude of D-responses in the latter group increased only to a certain level, not reaching the critical level for cell firing. Decrease in external Cl concentration led to a shift of their reversal potential in depolarizing direction. Ionic mechanisms of depolarizing responses induced by glutamate in these groups of neurons are discussed.

Influence of Ambient Humidity on the Voltage Response of Ionic Polymer-Metal Composite Sensor.

PubMed

Zhu, Zicai; Horiuchi, Tetsuya; Kruusamäe, Karl; Chang, Longfei; Asaka, Kinji

2016-03-31

Electrical potential based on ion migration exists not only in natural systems but also in ionic polymer materials. In order to investigate the influence of ambient humidity on voltage response, classical Au-Nafion IPMC was chosen as the reference sample. Voltage response under a bending deformation was measured in two ways: first, continuous measurement of voltage response in the process of absorption and desorption of water to study the tendency of voltage variation at all water states; second, measurements at multiple fixed ambient humidity levels to characterize the process of voltage response quantitatively. Ambient humidity influences the voltage response mainly by varying water content in ionic polymer. Under a step bending, the amplitude of initial voltage peak first increases and then decreases as the ambient humidity and the inherent water content decrease. This tendency is explained semiquantitatively by mass storage capacity related to the stretchable state of the Nafion polymer network. Following the initial peak, the voltage shows a slow decay to a steady state, which is first characterized in this paper. The relative voltage decay during the steady state always decreases as the ambient humidity is lowered. It is ascribed to progressive increase of the ratio between the water molecules in the cation hydration shell to the free water. Under sinusoidal mechanical bending excitation in the range of 0.1-10 Hz, the voltage magnitude increases with frequency at high ambient humidity but decreases with frequency at low ambient humidity. The relationship is mainly controlled by the voltage decay effect and the response speed.

High-Performing, Low-Temperature-Operating, Long-Lifetime Aerospace Lubricants

NASA Technical Reports Server (NTRS)

Joshi, Prakash

2015-01-01

Long-duration space exploration will require spacecraft systems that can operate effectively over several years with minimal or no maintenance. Aerospace lubricants are key components of spacecraft systems. Physical Sciences Inc., has synthesized and characterized novel ionic liquids for use in aerospace lubricants that contribute to decreased viscosity, friction, and wear in aerospace systems. The resulting formulations offer low vapor pressure and outgassing properties and thermal stability up to 250 C. They are effective for use at temperatures as low as -70 C and provide long-term operational stability in aerospace systems. In Phase II, the company scaled several new ionic liquids and evaluated a novel formulation in a NASA testbed. The resulting lubricant compounds will offer lower volatility, decreased corrosion, and better tribological characteristics than standard liquid lubricants, particularly at lower temperatures.

Low-Temperature Carrier Transport in Ionic-Liquid-Gated Hydrogen-Terminated Silicon

NASA Astrophysics Data System (ADS)

Sasama, Yosuke; Yamaguchi, Takahide; Tanaka, Masashi; Takeya, Hiroyuki; Takano, Yoshihiko

2017-11-01

We fabricated ionic-liquid-gated field-effect transistors on the hydrogen-terminated (111)-oriented surface of undoped silicon. Ion implantation underneath electrodes leads to good ohmic contacts, which persist at low temperatures down to 1.4 K. The sheet resistance of the channel decreases by more than five orders of magnitude as the gate voltage is changed from 0 to -1.6 V at 220 K. This is caused by the accumulation of hole carriers. The sheet resistance shows thermally activated behavior at temperatures below 10 K, which is attributed to hopping transport of the carriers. The activation energy decreases towards zero with increasing carrier density, suggesting the approach to an insulator-metal transition. We also report the variation of device characteristics induced by repeated sweeps of the gate voltage.

Electric analog studies of flow to wells in the Punjab aquifer of West Pakistan

USGS Publications Warehouse

Mundorff, Maurice John; Bennett, G.D.; Ahmad, Masood

1972-01-01

A series of experiments was performed with a steady-state electric analog simulating a cylindrical segment of the aquifer underlying the plains of the Punjab region of West Pakistan. In most of the experiments recharge was assumed to be from the surface, within a specified radius of influence, and distributed uniformly over the area within this radius. Experiments were made with different anisotropies (ratios of lateral to vertical resistance) so that various possible combinations of aquifer thickness and effective radius or radius of influence and combinations .of lateral and vertical permeability could be included in the models. Flow nets were constructed to show distribution of potential in the vertical section and intersections of stream surfaces with the vertical plane. The series of experiments in which the screened interval is in the upper part of the aquifer shows that flow decreases and stream tubes shift progressively toward the upper part of the aquifer as anisotropy increases. Another series illustrates that total yield increases and yield per foot of screen decreases as screen length increases. The experiments indicate that, under conditions prevalent in the Punjab, the Distance-drawdown method for determining permeability gives results with an error of 10 percent or less provided that at least one piezometer or observation well is within a few feet of the pumped well and that no observation well or piezometer used is more than 100 feet from the pumped well. Relative traveltime for each of 10 stream tubes is given for three models. Relative traveltimes for one-fourth and one-half the effective radius are given for selected stream tubes. By substituting values for the aquifer parameters, actual traveltimes are computed from the relative-traveltime data.

Failure of ProTaper rotary Ni-Ti instruments used by undergraduate students

PubMed Central

Duran-Sindreu, Fernando; Morello-Castro, Sergio; Mercade-Bellido, Montserrat; Bueno-Martínez, Rufino; Roig-Cayón, Miguel

2012-01-01

Objective: To evaluate the effect of number of uses, angle and radius of curvature and type of instrument on the fracture of ProTaper rotary instruments when used by undergraduate students. Study Design: Three hundred and seventy-six molars, with a total of 1114 root canals, extracted were instrumented by undergraduate students using ProTaper instruments according to the manufacturer´s recommendations. When fracture occurred, data were collected concerning the number of uses, type of instrument, level of fracture, angle and radius of curvature. ANOVA test were used to determine the influence of type of instrument in the incidence of instrument fracture. Logistic regression model was used to determine the influence of number of uses, angle and radius of curvature in the incidence of instrument fracture. Significance was set at p< 0.05. Results: A total of 37 Ni-Ti rotary instruments fractured during the treatment. Fracture occurred in 9.84% (37/376) of the teeth treated and 3.32% of the canals prepared with Ni-Ti rotary instruments (37/1114). A decrease in the radius of curvature of the canal significantly increased the likelihood of fracture (p=0.0001). Instrument fracture significantly increased as the number of uses increased (p=0.0037). No significant differences were found between the 6 types of ProTaper instruments (p=0.8). A reduction in the angle of curvature did not produce a significant decrease in the incidence of instrument separation (p=0.08). Conclusions: The results of this study imply that instrument fracture is linked to radius of curvature and number of uses. Key words:Fracture, ProTaper ®, root canal preparation, undergraduate students. PMID:24558555

Effect of Plate Curvature on Blast Response of Structural Steel Plates

NASA Astrophysics Data System (ADS)

Veeredhi, Lakshmi Shireen Banu; Ramana Rao, N. V.; Veeredhi, Vasudeva Rao

2018-04-01

In the present work an attempt is made, through simulation studies, to determine the effect of plate curvature on the blast response of a door structure made of ASTM A515 grade 50 steel plates. A door structure with dimensions of 5.142 m × 2.56 m × 10 mm having six different radii of curvatures is analyzed which is subjected to blast load. The radii of curvature investigated are infinity (flat plate), 16.63, 10.81, 8.26, 6.61 and 5.56 m. In the present study, a stand-off distance of 11 m is considered for all the cases. Results showed that the door structure with smallest radius of curvature experienced least plastic deformation and yielding when compared to a door with larger radius of curvature with same projected area. From the present Investigation, it is observed that, as the radius of curvature of the plate increases, the deformation mode gradually shifts from indentation mode to flexural mode. The plates with infinity and 16.63 m radius of curvature have undergone flexural mode of deformation and plates with 6.61 and 5.56 m radius of curvature undergo indentation mode of deformation. Whereas, mixed mode of deformation that consists of both flexural and indentation mode of deformations are seen in the plates with radius of curvature 10.81 and 8.26 m. As the radius of curvature of the plate decreases the ability of the plate to mitigate the effect the blast loads increased. It is observed that the plate with smaller radius of curvature deflects most of the blast energy and results in least indentation mode of deformation. The most significant observation made in the present investigation is that the strain energy absorbed by the steel plate gets reduced to 1/3 rd when the radius of curvature is approximately equal to the stand-off distance which could be the critical radius of curvature.

Ion Transport in Nanostructured Block Copolymer/Ionic Liquid Membranes

NASA Astrophysics Data System (ADS)

Hoarfrost, Megan Lane

Incorporating an ionic liquid into one block copolymer microphase provides a platform for combining the outstanding electrochemical properties of ionic liquids with a number of favorable attributes provided by block copolymers. In particular, block copolymers thermodynamically self-assemble into well-ordered nanostructures, which can be engineered to provide a durable mechanical scaffold and template the ionic liquid into continuous ion-conducting nanochannels. Understanding how the addition of an ionic liquid affects the thermodynamic self-assembly of block copolymers, and how the confinement of ionic liquids to block copolymer nanodomains affects their ion-conducting properties is essential for predictable structure-property control. The lyotropic phase behavior of block copolymer/ionic liquid mixtures is shown to be reminiscent of mixtures of block copolymers with selective molecular solvents. A variety of ordered microstructures corresponding to lamellae, hexagonally close-packed cylinders, body-centered cubic, and face-centered cubic oriented micelles are observed in a model system composed of mixtures of imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) and poly(styrene- b-2-vinyl pyridine) (PS-b-P2VP). In contrast to block copolymer/molecular solvent mixtures, the interfacial area occupied by each PS-b-P2VP chain decreases upon the addition of [Im][TFSI], indicating a considerable increase in the effective segregation strength of the PS-b-P2VP copolymer with ionic liquid addition. The relationship between membrane structure and ionic conductivity is illuminated through the development of scaling relationships that describe the ionic conductivity of block copolymer/ionic liquid mixtures as a function of membrane composition and temperature. It is shown that the dominant variable influencing conductivity is the overall volume fraction of ionic liquid in the mixture, which means there is incredible freedom in designing the block copolymer architecture in order to optimize the mechanical and other properties of the membrane without sacrificing conductivity. The derived scaling relationships are shown to be general for many block copolymer and ionic liquid chemistries. In certain cases, the mechanism of ion conduction in the ionic liquid is affected by block copolymer nanoconfinement. The introduction of excess neutral imidazole to [Im][TFSI] leads to enhanced proton conductivity as well as a high H+ transference number due to facilitated proton hopping between imidazole molecules. We show that there is increased proton hopping when the nonstoichiometric ionic liquid is confined to lamellar block copolymer nanodomains, which we hypothesize is due to changes in the hydrogen bond structure of the ionic liquid under confinement. This, in combination with unique ion aggregation behavior, leads to a lower activation energy for macroscopic ion transport compared to that in a corresponding homopolymer/ionic liquid mixture. Through this work, we further the understanding of the relationship between membrane composition, structure, and ion transport. The findings presented herein portend the rational design of nanostructured membranes having improved mechanical properties and conductivity.

Computation of methodology-independent single-ion solvation properties from molecular simulations. IV. Optimized Lennard-Jones interaction parameter sets for the alkali and halide ions in water

NASA Astrophysics Data System (ADS)

Reif, Maria M.; Hünenberger, Philippe H.

2011-04-01

The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [M. A. Kastenholz and P. H. Hünenberger, J. Chem. Phys. 124, 224501 (2006), 10.1529/biophysj.106.083667; M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144103 (2010)], the application of appropriate correction terms permits to obtain methodology-independent results. The corrected values are then exclusively characteristic of the underlying molecular model including in particular the ion-solvent van der Waals interaction parameters, determining the effective ion size and the magnitude of its dispersion interactions. In the present study, the comparison of calculated (corrected) hydration free energies with experimental data (along with the consideration of ionic polarizabilities) is used to calibrate new sets of ion-solvent van der Waals (Lennard-Jones) interaction parameters for the alkali (Li+, Na+, K+, Rb+, Cs+) and halide (F-, Cl-, Br-, I-) ions along with either the SPC or the SPC/E water models. The experimental dataset is defined by conventional single-ion hydration free energies [Tissandier et al., J. Phys. Chem. A 102, 7787 (1998), 10.1021/jp982638r; Fawcett, J. Phys. Chem. B 103, 11181] along with three plausible choices for the (experimentally elusive) value of the absolute (intrinsic) hydration free energy of the proton, namely, Δ G_hyd^{ominus }[H+] = -1100, -1075 or -1050 kJ mol-1, resulting in three sets L, M, and H for the SPC water model and three sets LE, ME, and HE for the SPC/E water model (alternative sets can easily be interpolated to intermediate Δ G_hyd^{ominus }[H+] values). The residual sensitivity of the calculated (corrected) hydration free energies on the volume-pressure boundary conditions and on the effective ionic radius entering into the calculation of the correction terms is also evaluated and found to be very limited. Ultimately, it is expected that comparison with other experimental ionic properties (e.g., derivative single-ion solvation properties, as well as data concerning ionic crystals, melts, solutions at finite concentrations, or nonaqueous solutions) will permit to validate one specific set and thus, the associated Δ G_hyd^{ominus }[H+] value (atomistic consistency assumption). Preliminary results (first-peak positions in the ion-water radial distribution functions, partial molar volumes of ionic salts in water, and structural properties of ionic crystals) support a value of Δ G_hyd^{ominus }[H+] close to -1100 kJ.mol-1.

Effect of electrostatic interactions on the ultrafiltration behavior of charged bacterial capsular polysaccharides.

PubMed

Hadidi, Mahsa; Buckley, John J; Zydney, Andrew L

2016-11-01

Charged polysaccharides are used in the food industry, as cosmetics, and as vaccines. The viscosity, thermodynamics, and hydrodynamic properties of these charged polysaccharides are known to be strongly dependent on the solution ionic strength because of both inter- and intramolecular electrostatic interactions. The goal of this work was to quantitatively describe the effect of these electrostatic interactions on the ultrafiltration behavior of several charged capsular polysaccharides obtained from Streptococcus pneumoniae and used in the production of Pneumococcus vaccines. Ultrafiltration data were obtained using various Biomax™ polyethersulfone membranes with different nominal molecular weight cutoffs. Polysaccharide transmission decreased with decreasing ionic strength primarily because of the expansion of the charged polysaccharide associated with intramolecular electrostatic repulsion. Data were in good agreement with a simple theoretical model based on solute partitioning in porous membranes, with the effective size of the different polysaccharide serotypes evaluated using size exclusion chromatography at the same ionic conditions. These results provide fundamental insights and practical guidelines for exploiting the effects of electrostatic interactions during the ultrafiltration of charged polysaccharides. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1531-1538, 2016. © 2016 American Institute of Chemical Engineers.

Effect of degree of crosslinking and polymerization of 3D printable polymer/ionic liquid composites on performance of stretchable piezoresistive sensors

NASA Astrophysics Data System (ADS)

Lee, Jeongwoo; Faruk Emon, Md Omar; Vatani, Morteza; Choi, Jae-Won

2017-03-01

Ionic liquid (IL)/polymer composites (1-ethyl-3-methyl-imidazolium tetrafluoroborate (EMIMBF4)/2-[[(butylamino)carbonyl]oxy]ethyl acrylate (BACOEA)) were fabricated to use as sensing materials for stretchable piezoresistive tactile sensors. The detectability of the IL/polymer composites was enhanced because the ionic transport properties of EMIMBF4 in the composites were improved by the synergic actions between the coordinate sites generated by the local motion of BACOEA chain segments under enough activation energy. The performance of the piezoresistive sensors was investigated with the degree of crosslinking and polymerization of the IL/polymer composites. As the compressive strain was increased, the distance between two electrodes decreased, and the motion of polymer chains and IL occurred, resulting in a decrease in the electrical resistance of the sensors. We have confirmed that the sensitivity of the sensors are affected by the degree of crosslink and polymerization of the IL/polymer composites. In addition, all of the materials (skins, sensing material, and electrode) used in this study are photo-curable, and thus the stretchable piezoresistive tactile sensors can be successfully fabricated by 3D printing.

Role of the Strength of Drug-Polymer Interactions on the Molecular Mobility and Crystallization Inhibition in Ketoconazole Solid Dispersions.

PubMed

Mistry, Pinal; Mohapatra, Sarat; Gopinath, Tata; Vogt, Frederick G; Suryanarayanan, Raj

2015-09-08

The effects of specific drug-polymer interactions (ionic or hydrogen-bonding) on the molecular mobility of model amorphous solid dispersions (ASDs) were investigated. ASDs of ketoconazole (KTZ), a weakly basic drug, with each of poly(acrylic acid) (PAA), poly(2-hydroxyethyl methacrylate) (PHEMA), and polyvinylpyrrolidone (PVP) were prepared. Drug-polymer interactions in the ASDs were evaluated by infrared and solid-state NMR, the molecular mobility quantified by dielectric spectroscopy, and crystallization onset monitored by differential scanning calorimetry (DSC) and variable temperature X-ray diffractometry (VTXRD). KTZ likely exhibited ionic interactions with PAA, hydrogen-bonding with PHEMA, and weaker dipole-dipole interactions with PVP. On the basis of dielectric spectroscopy, the α-relaxation times of the ASDs followed the order: PAA > PHEMA > PVP. In addition, the presence of ionic interactions also translated to a dramatic and disproportionate decrease in mobility as a function of polymer concentration. On the basis of both DSC and VTXRD, an increase in strength of interaction translated to higher crystallization onset temperature and a decrease in extent of crystallization. Stronger drug-polymer interactions, by reducing the molecular mobility, can potentially delay the crystallization onset temperature as well as crystallization extent.

Computation of energy states of hydrogenic quantum dot with two-electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakar, Y., E-mail: yuyakar@yahoo.com; Özmen, A., E-mail: aozmen@selcuk.edu.tr; Çakır, B., E-mail: bcakir@selcuk.edu.tr

2016-03-25

In this study we have investigated the electronic structure of the hydrogenic quantum dot with two electrons inside an impenetrable potential surface. The energy eigenvalues and wavefunctions of the ground and excited states of spherical quantum dot have been calculated by using the Quantum Genetic Algorithm (QGA) and Hartree-Fock Roothaan (HFR) method, and the energies are investigated as a function of dot radius. The results show that as dot radius increases, the energy of quantum dot decreases.

Analysis of a deflating soap bubble

NASA Astrophysics Data System (ADS)

Jackson, David P.; Sleyman, Sarah

2010-10-01

A soap bubble on the end of a cylindrical tube is seen to deflate as the higher pressure air inside the bubble escapes through a tube. We perform an experiment to measure the radius of the slowly deflating bubble and observe that the radius decreases to a minimum before quickly increasing. This behavior reflects the fact that the bubble ends up as a flat surface over the end of the tube. A theoretical analysis reproduces this behavior and compares favorably with the experimental data.

Thermodynamics of aggregate formation between a non-ionic polymer and ionic surfactants: An isothermal titration calorimetric study.

PubMed

Patel, Salin Gupta; Bummer, Paul M

2017-01-10

This report examines the energetics of aggregate formation between hydroxypropyl methylcellulose (HPMC) and model ionic surfactants including sodium dodecyl sulfate (SDS) at pharmaceutically relevant concentrations using the isothermal titration calorimetry (ITC) technique and a novel treatment of calorimetric data that accounts for the various species formed. The influence of molecular weight of HPMC, temperature and ionic strength of solution on the aggregate formation process was explored. The interaction between SDS and HPMC was determined to be an endothermic process and initiated at a critical aggregation concentration (CAC). The SDS-HPMC interactions were observed to be cooperative in nature and dependent on temperature and ionic strength of the solution. Molecular weight of HPMC significantly shifted the interaction parameters between HPMC and SDS such that at the highest molecular weight (HPMC K-100M;>240kDa), although the general shape of the titration curve (enthalpogram) was observed to remain similar, the critical concentration parameters (CAC, polymer saturation concentration (C sat ) and critical micelle concentration (CMC)) were significantly altered and shifted to lower concentrations of SDS. Ionic strength was also observed to influence the critical concentration parameters for the SDS-HPMC aggregation and decreased to lower SDS concentrations with increasing ionic strength for both anionic and cationic surfactant-HPMC systems. From these data, other thermodynamic parameters of aggregation such as ΔH agg ° , ΔG agg ° , H agg ° , ΔS agg ° , and ΔC p were calculated and utilized to postulate the hydrophobic nature of SDS-HPMC aggregate formation. The type of ionic surfactant head group (anionic vs. cationic i.e., dodecyltrimethylammonium bromide (DTAB)) was found to influence the strength of HPMC-surfactant interactions wherein a distinct CAC signifying the strength of HPMC-DTAB interactions was not observed. The interpretation of the microcalorimetric data at different temperatures and ionic strengths while varying properties of polymer and surfactant was a very effective tool in investigating the nature and energetics of HPMC and ionic surfactant interactions. Copyright © 2016 Elsevier B.V. All rights reserved.

Soluble minerals in chemical evolution. II - Characterization of the adsorption of 5-prime-AMP and 5-prime-CMP on a variety of soluble mineral salts

NASA Technical Reports Server (NTRS)

Chan, Stephen; Orenberg, James; Lahav, Noam

1987-01-01

The adsorption of 5-prime-AMP and 5-prime-CMP is studied in the saturated solutions of several mineral salts as a function of pH, ionic strength, and surface area of the solid salt. It is suggested that the adsorption which results from the binding between the nucleotide molecule and the salt surface is due to electrostatic forces. The adsorption is reversible in nature and decreases with increasing ionic strength.

Extending Stability Through Hierarchical Clusters in Echo State Networks

PubMed Central

Jarvis, Sarah; Rotter, Stefan; Egert, Ulrich

2009-01-01

Echo State Networks (ESN) are reservoir networks that satisfy well-established criteria for stability when constructed as feedforward networks. Recent evidence suggests that stability criteria are altered in the presence of reservoir substructures, such as clusters. Understanding how the reservoir architecture affects stability is thus important for the appropriate design of any ESN. To quantitatively determine the influence of the most relevant network parameters, we analyzed the impact of reservoir substructures on stability in hierarchically clustered ESNs, as they allow a smooth transition from highly structured to increasingly homogeneous reservoirs. Previous studies used the largest eigenvalue of the reservoir connectivity matrix (spectral radius) as a predictor for stable network dynamics. Here, we evaluate the impact of clusters, hierarchy and intercluster connectivity on the predictive power of the spectral radius for stability. Both hierarchy and low relative cluster sizes extend the range of spectral radius values, leading to stable networks, while increasing intercluster connectivity decreased maximal spectral radius. PMID:20725523

Gas loss in simulated galaxies as they fall into clusters

PubMed Central

Cen, Renyue; Pop, Ana Roxana; Bahcall, Neta A.

2014-01-01

We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights into how galaxies lose their cold gas at low redshift as they migrate from the field to the high-density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching <10% near the cluster center. Our results suggest galaxies start to feel the effect of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas-to-baryon ratio greater than 1%). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip. PMID:24843167

Gas loss in simulated galaxies as they fall into clusters.

PubMed

Cen, Renyue; Pop, Ana Roxana; Bahcall, Neta A

2014-06-03

We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights into how galaxies lose their cold gas at low redshift as they migrate from the field to the high-density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching <10% near the cluster center. Our results suggest galaxies start to feel the effect of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas-to-baryon ratio greater than 1%). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip.

Lipid-glass adhesion in giga-sealed patch-clamped membranes.

PubMed

Opsahl, L R; Webb, W W

1994-01-01

Adhesion between patch-clamped lipid membranes and glass micropipettes is measured by high contrast video imaging of the mechanical response to the application of suction pressure across the patch. The free patch of membrane reversibly alters both its contact angle and radius of curvature on pressure changes. The assumption that an adhesive force between the membrane and the pipette can sustain normal tension up to a maximum Ta at the edge of the free patch accounts for the observed mechanical responses. When the normal component of the pressure-induced membrane tension exceeds Ta membrane at the contact point between the free patch and the lipid-glass interface is pulled away from the pipette wall, resulting in a decreased radius of curvature for the patch and an increased contact angle. Measurements of the membrane radius of curvature as a function of the suction pressure and pipette radius determine line adhesion tensions Ta which range from 0.5 to 4.0 dyn/cm. Similar behavior of patch-clamped cell membranes implies similar adhesion mechanics.

Swelling and erosion properties of hydroxypropylmethylcellulose (Hypromellose) matrices--influence of agitation rate and dissolution medium composition.

PubMed

Kavanagh, Nicole; Corrigan, Owen I

2004-07-26

The effect of dissolution medium variables, such as medium composition, ionic strength and agitation rate, on the swelling and erosion of Hypromellose (hydroxypropylmethylcellulose, HPMC) matrices of different molecular weights was examined. Swelling and erosion of HPMC polymers was determined by measuring the wet and subsequent dry weights of matrices. It was possible to describe the rate of dissolution medium uptake in terms of a square root relationship and the erosion of the polymer in terms of the cube root law. The extent of swelling increased with increasing molecular weight, and decreased with increasing agitation rate. The erosion rate was seen to increase with decrease in polymer molecular weight, with a decrease in ionic strength and with increasing agitation rate. The sensitivity of polymer erosion to the degree of agitation may influence the ability of these polymers to give reproducible, agitation-independent release, compared to more rigid non-eroding matrix materials, in the complex hydrodynamic environment of the gastrointestinal tract.

Determination of the Effects of Medium Composition on the Monochloramine Disinfection Kinetics of Nitrosomonas europaea by the Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods ▿

PubMed Central

Wahman, David G.; Schrantz, Karen A.; Pressman, Jonathan G.

2010-01-01

Various medium compositions (phosphate, 1 to 50 mM; ionic strength, 2.8 to 150 meq/liter) significantly affected Nitrosomonas europaea monochloramine disinfection kinetics, as determined by the Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR) methods (lag coefficient, 37 to 490 [LD] and 91 to 490 [PMA-qPCR] mg·min/liter; Chick-Watson rate constant, 4.0 × 10−3 to 9.3 × 10−3 [LD] and 1.6 × 10−3 to 9.6 × 10−3 [PMA-qPCR] liter/mg·min). Two competing effects may account for the variation in disinfection kinetic parameters: (i) increasing kinetics (disinfection rate constant [k] increased, lag coefficient [b] decreased) with increasing phosphate concentration and (ii) decreasing kinetics (k decreased, b increased) with increasing ionic strength. The results support development of a standard medium for evaluating disinfection kinetics in drinking water. PMID:20952645

Pole-strength of the earth from Magsat and magnetic determination of the core radius

NASA Technical Reports Server (NTRS)

Voorhies, G. V.; Benton, E. R.

1982-01-01

A model based on two days of Magsat data is used to numerically evaluate the unsigned magnetic flux linking the earth's surface, and a comparison of the 16.054 GWb value calculated with values from earlier geomagnetic field models reveals a smooth, monotonic, and recently-accelerating decrease in the earth's pole strength at a 50-year average rate of 8.3 MWb, or 0.052%/year. Hide's (1978) magnetic technique for determining the radius of the earth's electrically-conducting core is tested by (1) extrapolating main field models for 1960 and 1965 downward through the nearly-insulating mantle, and then separately comparing them to equivalent, extrapolated models of Magsat data. The two unsigned fluxes are found to equal the Magsat values at a radius which is within 2% of the core radius; and (2) the 1960 main field and secular variation and acceleration coefficients are used to derive models of 1930, 1940 and 1950. The same core magnetic radius value, within 2% of the seismic value, is obtained. It is concluded that the mantle is a nearly-perfect insulator, while the core is a perfect conductor, on the decade time scale.

Spread of the dust temperature distribution in circumstellar disks

NASA Astrophysics Data System (ADS)

Heese, S.; Wolf, S.; Dutrey, A.; Guilloteau, S.

2017-07-01

Context. Accurate temperature calculations for circumstellar disks are particularly important for their chemical evolution. Their temperature distribution is determined by the optical properties of the dust grains, which, among other parameters, depend on their radius. However, in most disk studies, only average optical properties and thus an average temperature is assumed to account for an ensemble of grains with different radii. Aims: We investigate the impact of subdividing the grain radius distribution into multiple sub-intervals on the resulting dust temperature distribution and spectral energy distribution (SED). Methods: The temperature distribution, the relative grain surface below a certain temperature, the freeze-out radius, and the SED were computed for two different scenarios: (1) Radius distribution represented by 16 logarithmically distributed radius intervals, and (2) radius distribution represented by a single grain species with averaged optical properties (reference). Results: Within the considered parameter range, I.e., of grain radii between 5 nm and 1 mm and an optically thin and thick disk with a parameterized density distribution, we obtain the following results: in optically thin disk regions, the temperature spread can be as large as 63% and the relative grain surface below a certain temperature is lower than in the reference disk. With increasing optical depth, the difference in the midplane temperature and the relative grain surface below a certain temperature decreases. Furthermore, below 20 K, this fraction is higher for the reference disk than for the case of multiple grain radii, while it shows the opposite behavior for temperatures above this threshold. The thermal emission in the case of multiple grain radii at short wavelengths is stronger than for the reference disk. The freeze-out radius (snowline) is a function of grain radius, spanning a radial range between the coldest and warmest grain species of 30 AU.

Supplemental vitamin D3 and zilpaterol hydrochloride. II. Effect on calcium concentration, muscle fiber type, and calpain gene expression of feedlot steers.

PubMed

Korn, K T; Lemenager, R P; Claeys, M C; Waddell, J N; Engstrom, M; Schoonmaker, J P

2013-07-01

Two hundred and ten Angus × Simmental steers (initial BW 314 ± 11 kg) were separated into heavy and light BW blocks and allotted evenly by BW to 6 treatments (3 heavy and 2 light pens per treatment) to determine the effect of supplemental vitamin D3: 0 IU (no D), 250,000 IU for 165 d (long-term D), or 5 × 10(6) IU for 10 d (short-term D) on plasma and muscle calcium concentrations and gene expression in steers fed either 0 (NZ) or 8.38 mg/kg (ZH) zilpaterol hydrochloride (ZH) daily for 21 d. Placebo or ZH was added to the diet 24 d, and short-term D was added 13 d before slaughter. Treatments were removed from all diets 3 d before slaughter. Plasma total calcium (Ca(2+)) was determined at study initiation, start of ZH and short-term D feedings, and at vitamin D3 and ZH withdrawal. Both plasma total and ionic Ca(2+) were determined when animals were sent to harvest. Longissimus muscle total and ionic Ca(2+) were determined in meat aged 7 and 4 d postmortem, respectively. When ZH was fed, long-term D decreased plasma total Ca(2+) at slaughter (P < 0.04). Short-term D increased (P < 0.01) plasma total and ionic Ca(2+) at slaughter regardless of ZH inclusion in the diet. Long- and short-term D, with or without ZH, did not affect (P > 0.28) LM total Ca(2+); however, both long- and short-term D increased LM ionic Ca(2+) when ZH was not fed (P < 0.01). Long-term D reduced LM ionic Ca(2+) when ZH was fed (P < 0.02). Neither long- nor short-term D affected PPARα or δ gene expression (P = 0.19) whether or not ZH was fed. Expression of MYH1 and 2A (P < 0.05) but not 2X (P = 0.21) was decreased in steers fed ZH. Long-term D had no effect on MYH2A expression (P = 0.21). Short-term D increased MYH2A expression when ZH was not fed (P < 0.03). Calpain mRNA tended to be lower in steers fed ZH (P = 0.09), but was not affected by long- or short-term D regardless of whether or not ZH was fed (P = 0.39). Expression of calpastatin did not differ with vitamin D supplementation (P = 0.35). In conclusion, ZH decreased oxidative myosin expression, and when combined with long-term D, ZH decreased LM ionic Ca(2+). Moreover, vitamin D3 supplementation did not increase calpain mRNA. These results help explain why vitamin D3 does not improve tenderness in steers fed ZH.

All-solid-state flexible supercapacitors fabricated with bacterial nanocellulose papers, carbon nanotubes, and triblock-copolymer ion gels.

PubMed

Kang, Yu Jin; Chun, Sang-Jin; Lee, Sung-Suk; Kim, Bo-Yeong; Kim, Jung Hyeun; Chung, Haegeun; Lee, Sun-Young; Kim, Woong

2012-07-24

We demonstrate all-solid-state flexible supercapacitors with high physical flexibility, desirable electrochemical properties, and excellent mechanical integrity, which were realized by rationally exploiting unique properties of bacterial nanocellulose, carbon nanotubes, and ionic liquid based polymer gel electrolytes. This deliberate choice and design of main components led to excellent supercapacitor performance such as high tolerance against bending cycles and high capacitance retention over charge/discharge cycles. More specifically, the performance of our supercapacitors was highly retained through 200 bending cycles to a radius of 3 mm. In addition, the supercapacitors showed excellent cyclability with C(sp) (~20 mF/cm(2)) reduction of only <0.5% over 5000 charge/discharge cycles at the current density of 10 A/g. Our demonstration could be an important basis for material design and development of flexible supercapacitors.

Electrochemical-mechanical coupled modeling and parameterization of swelling and ionic transport in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Sauerteig, Daniel; Hanselmann, Nina; Arzberger, Arno; Reinshagen, Holger; Ivanov, Svetlozar; Bund, Andreas

2018-02-01

The intercalation and aging induced volume changes of lithium-ion battery electrodes lead to significant mechanical pressure or volume changes on cell and module level. As the correlation between electrochemical and mechanical performance of lithium ion batteries at nano and macro scale requires a comprehensive and multidisciplinary approach, physical modeling accounting for chemical and mechanical phenomena during operation is very useful for the battery design. Since the introduced fully-coupled physical model requires proper parameterization, this work also focuses on identifying appropriate mathematical representation of compressibility as well as the ionic transport in the porous electrodes and the separator. The ionic transport is characterized by electrochemical impedance spectroscopy (EIS) using symmetric pouch cells comprising LiNi1/3Mn1/3Co1/3O2 (NMC) cathode, graphite anode and polyethylene separator. The EIS measurements are carried out at various mechanical loads. The observed decrease of the ionic conductivity reveals a significant transport limitation at high pressures. The experimentally obtained data are applied as input to the electrochemical-mechanical model of a prismatic 10 Ah cell. Our computational approach accounts intercalation induced electrode expansion, stress generation caused by mechanical boundaries, compression of the electrodes and the separator, outer expansion of the cell and finally the influence of the ionic transport within the electrolyte.

Correlation between cation conduction and ionic morphology in a PEO-based single ion conductor

NASA Astrophysics Data System (ADS)

Lin, Kan-Ju; Maranas, Janna

2011-03-01

We use molecular dynamics simulation to study ion transport and backbone mobility of a PEO-based single ion conductor. Ion mobility depends on the chemical structure and the local environment of the ions, which consequently impact ionic conductivity. We characterize the aggregation state of the ions, and assess the role of ion complexes in ionomer dynamics. In addition to solvated cations and pairs, higher order ion clusters are found. Most of the ion clusters are in string-like structure and cross-link two or more different ionomer chains through ionic binding. Ionic crosslinks decrease mobility at the ionic co-monomer; hence the mobility of the adjacent PEO segment is influenced. Na ions show slow mobility when they are inside large clusters. The hopping timescale for Na varies from 20 ns to 200. A correlation is found between Na mobility and the number of hops from one coordination site to another. Besides ether oxygens, Na ions in the ionomer also use the anion and the edge of the cluster as hopping sites. The string-like structure of clusters provide less stable sites at the two ends thus ions are more mobile in those regions. We observed Grotthus like mechanism in our ionomer, in which the positive charge migrates within the string-like cluster without the cations actually moving.

Influence of Ionic Liquids on Thermodynamics of Small Molecule-DNA Interaction: The Binding of Ethidium Bromide to Calf Thymus DNA.

PubMed

Mishra, Arpit; Ekka, Mary Krishna; Maiti, Souvik

2016-03-17

Ionic liquids (ILs) are salts with poor ionic coordination, resultantly remaining in liquid state below 100 °C and some may retain liquid state even at room temperature. ILs are known to provide a conducive environment for many biological enzymatic reactions, but their interaction with biomacromolecules are poorly understood. In the present study, we investigate the effect of various ionic liquids on DNA-small molecule interaction using calf thymus DNA (ctDNA)-ethidium bromide (EB) as a model system. The effect of various ionic liquids on these interactions is studied by an array of techniques such as circular dichroism (CD), UV melting, fluorescence exclusion and isothermal titration calorimetry. Interestingly, we observed that presence of IL increased the stability of ctDNA without altering its structure. The binding affinities Kbs for EB binding to ctDNA in the presence of 300 mM ILs are about half order of magnitude smaller than the Kbs in absence of ILs and correspond to a less favorable free energy. We noted that, when adjusted to corresponding buffer condition, the unfavorable shift in ΔG of ctDNA-EB interaction is attributed to decreased entropy in the case of ILs, whereas the same effect by NaCl was due to increased enthalpy.

Adaptive Adjustment in Taraxacum Officinale Wigg. in the Conditions of Overburden Dump

NASA Astrophysics Data System (ADS)

Legoshchina, Olga; Egorova, Irina; Neverova, Olga

2017-11-01

Morphological and anatomical features of the leaves and roots of Taraxacum officinale Wigg., growing under the conditions of the rocky dump of the Kedrovsky coal mine of the Kemerovo region, were studied. It was revealed that the specific environmental conditions of the dump cause morphological and anatomical changes in the leaves and roots of the dandelion. At the level of morphology, a decrease in the average leaf area, a thickening of leaf blades, a tendency to decrease the number of leaves in the rosette, a significant decrease in the mass and length of the roots. At the level of the anatomical structure of the leaves, there is a significant increase in the thickness of the mesophyll, a tendency to decrease the thickness of the tissues of the upper and lower epidermis, a decrease in the number of cells in 1 mm2 and an increase in the size of stomata in the tissues of the lower and upper epidermis, a decrease in the number of stomata by 1 mm2 and a stomatal index on the upper epidermis. At the level of the anatomical structure of the roots, the radius of the root decreases, the radius of the cortex and phloem, the diameter of the xylem.

Effects of Bi doping on structural and magnetic properties of double perovskite oxides Sr2FeMoO6

NASA Astrophysics Data System (ADS)

Lan, Yaohai; Feng, Xiaomei; Zhang, Xin; Shen, Yifu; Wang, Ding

2016-08-01

A new series of double perovskite compounds Sr2 - δBixFeMoO6 have been synthesized by solid-state reaction. δ refers to the nominal doping content of Bi (δ = 0, 0.1, 0.2, 0.3, 0.4, 0.5), while the Bi content obtained by the Rietveld refinement is x = 0, 0.01, 0.05, 0.08, 0.10 and 0.12. Their crystal structure and magnetic properties are investigated. Rietveld analysis of the room temperature XRD data shows all the samples crystallize in the cubic crystal structure with the space group Fm 3 ‾ m and have no phase transition. SEM images show that substituted samples present a denser microstructure and bigger grains than Sr2FeMoO6, which is caused by a liquid sintering process due to the effumability of Bi. The unit cell volume increases with augment of Bi3+ concentration despite the smaller ionic radius Bi3+ compared with the Sr2+, which is attributed to the electronic effect. The degree of Fe/Mo order (η) increases first and then decreases to almost disappearance with augment of Bi doping, which is the result of contribution from electronic effect. Calculated saturation magnetization Ms(3) according to our phase separation likeness model matches well with the experimental ones. The observed variations of magnetoresistance (MR) are consistent with the Fe/Mo order (η) due to the internal connection with anti-site defect (ASD).

Optical and Physical Investigations of Lanthanum Bismuth Borate glasses doped with Ho2O3

NASA Astrophysics Data System (ADS)

Ramesh, P.; Jagannath, G.; Eraiah, B.; Kokila, M. K.

2018-02-01

Holmium doped 10La2O3-15Bi2O3-(75-x) B2O3 (Ho3+: LBB) glasses have been prepared by melt quench technique and the impact of holmium ions concentration on optical and physical properties of present glasses have been examined. Ho3+ dependent density, molar volume, refractive index, rare earth ion concentration, polaron radius, inter ionic distance, field strength and energy band gap are calculated and tabulated. Amorphous nature of the all glasses has been confirmed by XRD patterns. The room temperature (RT) Uv-Vis absorption spectrum doped with 1 mol% of Ho2O3 exhibit eight prominent bands centred at 895, 641, 537, 486, 472, 467, 451 and 416 due to transition between ground state to various excited states. The results show that, the density is increases and molar volume of the glasses is decreases with an increase in Ho2O3 concentration and consequently generate more non-bridging oxygen (NBOs) in the glass matrix. The Urbach energy is increases with holmium concentration which exemplifies the degree of disorder present in the LBB glasses. The considerable increase in field strength observed in present glasses is attributed to occurrence of strong bridge between Ho3+ and B- ions and this strong bridge is possibly due to the displacement between Ho3+ and oxygen atoms which are generated from the conversion BO3-BO4 units.

The estimation of H-bond and metal ion-ligand interaction energies in the G-Quadruplex ⋯ Mn+ complexes

NASA Astrophysics Data System (ADS)

Mostafavi, Najmeh; Ebrahimi, Ali

2018-06-01

In order to characterize various interactions in the G-quadruplex ⋯ Mn+ (G-Q ⋯ Mn+) complexes, the individual H-bond (EHB) and metal ion-ligand interaction (EMO) energies have been estimated using the electron charge densities (ρs) calculated at the X ⋯ H (X = N and O) and Mn+ ⋯ O (Mn+ is an alkaline, alkaline earth and transition metal ion) bond critical points (BCPs) obtained from the atoms in molecules (AIM) analysis. The estimated values of EMO and EHB were evaluated using the structural parameters, results of natural bond orbital analysis (NBO), aromaticity indexes and atomic charges. The EMO value increase with the ratio of ionic charge to radius, e/r, where a linear correlation is observed between EMO and e/r (R = 0.97). Meaningful relationships are also observed between EMO and indexes used for aromaticity estimation. The ENH value is higher than EOH in the complexes; this is in complete agreement with the trend of N⋯Hsbnd N and O⋯Hsbnd N angles, the E (2) value of nN → σ*NH and nO → σ*NH interactions and the difference between the natural charges on the H-bonded atom and the hydrogen atom of guanine (Δq). In general, the O1MO2 angle becomes closer to 109.5° with the increase in EMO and decrease in EHB in the presence of metal ion.

Ruthenium nanoparticles in ionic liquids: structural and stability effects of polar solutes.

PubMed

Salas, Gorka; Podgoršek, Ajda; Campbell, Paul S; Santini, Catherine C; Pádua, Agílio A H; Costa Gomes, Margarida F; Philippot, Karine; Chaudret, Bruno; Turmine, Mireille

2011-08-14

Ionic liquids are a stabilizing medium for the in situ synthesis of ruthenium nanoparticles. Herein we show that the addition of molecular polar solutes to the ionic liquid, even in low concentrations, eliminates the role of the ionic liquid 3D structure in controlling the size of ruthenium nanoparticles, and can induce their aggregation. We have performed the synthesis of ruthenium nanoparticles by decomposition of [Ru(COD)(COT)] in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(1)C(4)Im][NTf(2)], under H(2) in the presence of varying amounts of water or 1-octylamine. For water added during the synthesis of metallic nanoparticles, a decrease of the solubility in the ionic liquid was observed, showed by nanoparticles located at the interface between aqueous and ionic phases. When 1-octylamine is present during the synthesis, stable nanoparticles of a constant size are obtained. When 1-octylamine is added after the synthesis, aggregation of the ruthenium nanoparticles is observed. In order to explain these phenomena, we have explored the molecular interactions between the different species using (13)C-NMR and DOSY (Diffusional Order Spectroscopy) experiments, mixing calorimetry, surface tension measurements and molecular simulations. We conclude that the behaviour of the ruthenium nanoparticles in [C(1)C(4)Im][NTf(2)] in the presence of 1-octylamine depends on the interaction between the ligand and the nanoparticles in terms of the energetics but also of the structural arrangement of the amine at the nanoparticle's surface.

Nanoparticle transport in water-unsaturated porous media: effects of solution ionic strength and flow rate

NASA Astrophysics Data System (ADS)

Prédélus, Dieuseul; Lassabatere, Laurent; Louis, Cédric; Gehan, Hélène; Brichart, Thomas; Winiarski, Thierry; Angulo-Jaramillo, Rafael

2017-03-01

This paper presents the influence of ionic strength and flow on nanoparticle (NP) retention rate in an unsaturated calcareous medium, originating from a heterogeneous glaciofluvial deposit of the region of Lyon (France). Laboratory columns 10 cm in diameter and 30 cm in length were used. Silica nanoparticles (Au-SiO2-FluoNPs), with hydrodynamic diameter ranging from 50 to 60 nm and labeled with fluorescein derivatives, were used to simulate particle transport, and bromide was used to characterize flow. Three flow rates and five different ionic strengths were tested. The transfer model based on fractionation of water into mobile and immobile fractions was coupled with the attachment/detachment model to fit NPs breakthrough curves. The results show that increasing flow velocity induces a decrease in nanoparticle retention, probably as the result of several physical but also geochemical factors. The results show that NPs retention increases with ionic strength. However, an inversion of retention occurs for ionic strength >5.10-2 M, which has been scarcely observed in previous studies. The measure of zeta potential and DLVO calculations show that NPs may sorb on both solid-water and air-water interfaces. NPs size distribution shows the potential for nanoparticle agglomeration mostly at low pH, leading to entrapment in the soil pores. These mechanisms are highly sensitive to both hydrodynamic and geochemical conditions, which explains their high sensitivity to flow rates and ionic strength.

Interaction of inorganic anions with iron-mineral adsorbents in aqueous media--a review.

PubMed

Kumar, Eva; Bhatnagar, Amit; Hogland, William; Marques, Marcia; Sillanpää, Mika

2014-01-01

A number of inorganic anions (e.g., nitrate, fluoride, bromate, phosphate, and perchlorate) have been reported in alarming concentrations in numerous drinking water sources around the world. Their presence even in very low concentrations may cause serious environmental and health related problems. Due to the presence and significance of iron minerals in the natural aquatic environment and increasing application of iron in water treatment, the knowledge of the structure of iron and iron minerals and their interactions with aquatic pollutants, especially inorganic anions in water are of great importance. Iron minerals have been known since long as potential adsorbents for the removal of inorganic anions from aqueous phase. The chemistry of iron and iron minerals reactions in water is complex. The adsorption ability of iron and iron minerals towards inorganic anions is influenced by several factors such as, surface characteristics of the adsorbent (surface area, density, pore volume, porosity, pore size distribution, pHpzc, purity), pH of the solution, and ionic strength. Furthermore, the physico-chemical properties of inorganic anions (pore size, ionic radius, bulk diffusion coefficient) also significantly influence the adsorption process. The aim of this paper is to provide an overview of the properties of iron and iron minerals and their reactivity with some important inorganic anionic contaminants present in water. It also summarizes the usage of iron and iron minerals in water treatment technology. © 2013.

CMC prediction for ionic surfactants in pure water and aqueous salt solutions based solely on tabulated molecular parameters.

PubMed

Karakashev, Stoyan I; Smoukov, Stoyan K

2017-09-01

The critical micelle concentration (CMC) of various surfactants is difficult to predict accurately, yet often necessary to do in both industry and science. Hence, quantum-chemical software packages for precise calculation of CMC were developed, but they are expensive and time consuming. We show here an easy method for calculating CMC with a reasonable accuracy. Firstly, CMC 0 (intrinsic CMC, absent added salt) was coupled with quantitative structure - property relationship (QSPR) with defined by us parameter "CMC predictor" f 1 . It can be easily calculated from a number of tabulated molecular parameters - the adsorption energy of surfactant's head, the adsorption energy of its methylene groups, its number of carbon atoms, the specific adsorption energy of its counter-ions, their valency and bare radius. We applied this method to determine CMC 0 to a test set of 11 ionic surfactants, yielding 7.5% accuracy. Furthermore, we calculated CMC in the presence of added salts using the advanced version of Corrin-Harkins equation, which accounts for both the intrinsic and the added counter-ions. Our salt-saturation multiplier, accounts for both the type and concentration of the added counter-ions. We applied our theory to a test set containing 11 anionic/cationic surfactant+salt systems, achieving 8% accuracy. Copyright © 2017 Elsevier Inc. All rights reserved.

Formation of hybrid ABX3 perovskite compounds for solar cell application: first-principles calculations of effective ionic radii and determination of tolerance factors.

PubMed

Becker, Markus; Klüner, Thorsten; Wark, Michael

2017-03-14

The development of hybrid organic-inorganic perovskite solar cells is one of the most rapidly growing fields in the photovoltaic community and is on its way to challenge polycrystalline silicon and thin film technologies. High power conversion efficiencies can be achieved by simple processing with low cost. However, due to the limited long-term stability and environmental toxicity of lead in the prototypic CH 3 NH 3 PbI 3 , there is a need to find alternative ABX 3 constitutional combinations in order to promote commercialization. The Goldschmidt tolerance factor and the octahedral factor were found to be necessary geometrical concepts to evaluate which perovskite compounds can be formed. It was figured out that the main challenge lies in estimating an effective ionic radius for the molecular cation. We calculated tolerance factors and octahedral factors for 486 ABX 3 monoammonium-metal-halide combinations, where the steric size of the molecular cation in the A-position was estimated concerning the total charge density. A thorough inquiry about existing mixed organic-inorganic perovskites was undertaken. Our results are in excellent agreement with the reported hybrid compounds and indicate the potential existence of 106 ABX 3 combinations hitherto not discussed in the literature, giving hints for more intense research on prospective individual candidates.

Caesalpinia bonduc serine proteinase inhibitor CbTI-2: Exploring the conformational features and antimalarial activity.

PubMed

Bhattacharyya, Arindam; Babu, C R

2017-10-01

Seeds of tropical legumes posses a repertoire of proteinase inhibitors (PI) and the current study highlights some structural/functional features of a strong serine PI from the seeds of Caesalpinia bonduc (CbTI-2). Following purification, N-terminal sequence of CbTI-2 revealed over 40% similarity with a few serine PIs of Caesalpinioideae subfamily. Upon exposure to metal ions and ionic/non ionic surfactants, CbTI-2 showed immense variation in the levels of antitryptic activity. Exposure of CbTI-2 to 1,4-Dithiothreitol, Guanidinium HCl, H 2 O 2 and Dimethyl sulfoxide led to a steady loss of inhibitory activity. Chemical modification of amino acids suggested an arginine as the active site residue. Circular Dichroism spectrum of native CbTI-2 revealed an unordered state. Secondary structure composition of CbTI-2 following exposure to extreme conditions (heat, acidic/alkaline environment, Guanidine hydrochloride and DTT) showed considerable perturbations that caused severe loss of antiproteolytic activity. DLS studies yielded a hydrodynamic radius of ∼2.2nm for CbTI-2 and also reconfirmed 1:1 stoichiometry for the trypsin-CbTI-2 complex. Initial studies indicated CbTI-2 to be a potent antiplasmodial agent by being highly toxic towards growth, schizont rupture process and erythrocytic invasion of Plasmodium falciparum. Copyright © 2017 Elsevier B.V. All rights reserved.

Single-coil properties and concentration effects for polyelectrolyte-like wormlike micelles: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Cannavacciuolo, Luigi; Skov Pedersen, Jan; Schurtenberger, Peter

2002-03-01

Results of an extensive Monte Carlo (MC) study on both single and many semiflexible charged chains with excluded volume (EV) are summarized. The model employed has been tailored to mimic wormlike micelles in solution. Simulations have been performed at different ionic strengths of added salt, charge densities, chain lengths and volume fractions Φ, covering the dilute to concentrated regime. At infinite dilution the scattering functions can be fitted by the same fitting functions as for uncharged semiflexible chains with EV, provided that an electrostatic contribution bel is added to the bare Kuhn length. The scaling of bel is found to be more complex than the Odijk-Skolnick-Fixman predictions, and qualitatively compatible with more recent variational calculations. Universality in the scaling of the radius of gyration is found if all lengths are rescaled by the total Kuhn length. At finite concentrations, the simple model used is able to reproduce the structural peak in the scattering function S(q) observed in many experiments, as well as other properties of polyelectrolytes (PELs) in solution. Universal behaviour of the forward scattering S(0) is established after a rescaling of Φ. MC data are found to be in very good agreement with experimental scattering measurements with equilibrium PELs, which are giant wormlike micelles formed in mixtures of nonionic and ionic surfactants in dilute aqueous solution, with added salt.

Evanescent-wave particle velocimetry measurements of zeta-potentials in fused-silica microchannels.

PubMed

Cevheri, Necmettin; Yoda, Minami

2013-07-01

The wall ζ-potential ζ(w), the potential at the shear plane of the electric double layer, depends on the properties of the BGE solution such as the valence and type of electrolyte, the pH and the ionic strength. Most of the methods estimate ζ(w) from measurements of the EOF velocity magnitude ueo , usually spatially averaged over the entire capillary. In these initial studies, evanescent-wave particle velocimetry was used to measure ueo in steady EOF for a variety of monovalent aqueous solutions to evaluate the effect of small amounts of divalent cations, as well as the pH and ionic strength of BGE solutions. In brief, the magnitude of the EOF velocity of NaCl-NaOH and borate buffer-NaOH solutions was estimated from the measured velocities of radius α = 104 nm fluorescent polystyrene particles in 33 μm fused-silica microchannels. The particle ζ-potentials were measured separately using laser-Doppler micro-electrophoresis; ζ(w) was then determined from ueo. The results suggest that evanescent-wave particle velocimetry can be used to estimate ζ(w) for a variety of BGE solutions, and that it can be used in the future to estimate local wall ζ-potential, and hence spatial variations in ζ(w). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scattering properties of alumina particle clusters with different radius of monomers in aerocraft plume

NASA Astrophysics Data System (ADS)

Li, Jingying; Bai, Lu; Wu, Zhensen; Guo, Lixin; Gong, Yanjun

2017-11-01

In this paper, diffusion limited aggregation (DLA) algorithm is improved to generate the alumina particle cluster with different radius of monomers in the plume. Scattering properties of these alumina clusters are solved by the multiple sphere T matrix method (MSTM). The effect of the number and radius of monomers on the scattering properties of clusters of alumina particles is discussed. The scattering properties of two types of alumina particle clusters are compared, one has different radius of monomers that follows lognormal probability distribution, another has the same radius of monomers that equals the mean of lognormal probability distribution. The result show that the scattering phase functions and linear polarization degrees of these two types of alumina particle clusters are of great differences. For the alumina clusters with different radius of monomers, the forward scatterings are bigger and the linear polarization degree has multiple peaks. Moreover, the vary of their scattering properties do not have strong correlative with the change of number of monomers. For larger booster motors, 25-38% of the plume being condensed alumina. The alumina can scatter radiation from other sources present in the plume and effect on radiation transfer characteristics of plume. In addition, the shape, size distribution and refractive index of the particles in the plume are estimated by linear polarization degree. Therefore, accurate scattering properties calculation is very important to decrease the deviation in the related research.

Truncated disks - advective tori solutions around BHs. I. The effects of conduction and enhanced Coulomb coupling

NASA Astrophysics Data System (ADS)

Hujeirat, A.; Camenzind, M.

2000-10-01

We present the first 2D quasi-stationary radiative hydrodynamical calculations of accretion flows onto BHs taking into account cooling via Bremsstrahlung, Compton, Synchrotron and conduction. The effect of enhanced Coulomb coupling is investigated also. Based on the numerical results obtained, we find that two-temperature (2T) accretion flows are best suited to describe hard states, and one-temperature (1T) in the soft states, with transition possibly depending on the accretion rate. In the 2T case, the ion-conduction enlarges the disk-truncation-radius from 5 to 9 Schwarzschild radii (RS). The ion-pressure powers outflows, hence substantially decreasing the accretion rate with decreasing radius. The spectrum is partially modified BB with hard photons emitted from the inner region and showing a cutoff at 100 keV. In the 1T case, conduction decreases the truncation radius from 7 to 5 RS and lowers the maximum gas temperature. The outflows are weaker, the spectrum is pre-dominantly modified BB and the emitted photons from the inner region are much harder (up to 175 keV). In both cases, the unsaturated Comptonization region coincides with the transition region between the disk and the advective torus. When gradually enhancing the Coulomb coupling, we find that the ion-temperature Ti decreases and the electron temperature Te increases, asymptotically converging to 1T flows. However, once the dissipated energy goes into heating the ions, ion-electron thermal decoupling is inevitable within the last stable orbit (RMS) even when the Coulomb interaction is enhanced by an additional two orders of magnitude.

Decreasing DOC trends in soil solution along the hillslopes at two IM sites in southern Sweden--geochemical modeling of organic matter solubility during acidification recovery.

PubMed

Löfgren, Stefan; Gustafsson, Jon Petter; Bringmark, Lage

2010-12-01

Numerous studies report increased concentrations of dissolved organic carbon (DOC) during the last two decades in boreal lakes and streams in Europe and North America. Recently, a hypothesis was presented on how various spatial and temporal factors affect the DOC dynamics. It was concluded that declining sulphur deposition and thereby increased DOC solubility, is the most important driver for the long-term DOC concentration trends in surface waters. If this recovery hypothesis is correct, the DOC levels should increase both in the soil solution as well as in the surrounding surface waters as soil pH rises and the ionic strength declines due to the reduced input of SO(4)(2-) ions. In this project a geochemical model was set up to calculate the net humic charge and DOC solubility trends in soils during the period 1996-2007 at two integrated monitoring sites in southern Sweden, showing clear signs of acidification recovery. The Stockholm Humic Model was used to investigate whether the observed DOC solubility is related to the humic charge and to examine how pH and ionic strength influence it. Soil water data from recharge and discharge areas, covering both podzols and riparian soils, were used. The model exercise showed that the increased net charge following the pH increase was in many cases counteracted by a decreased ionic strength, which acted to decrease the net charge and hence the DOC solubility. Thus, the recovery from acidification does not necessarily have to generate increasing DOC trends in soil solution. Depending on changes in pH, ionic strength and soil Al pools, the trends might be positive, negative or indifferent. Due to the high hydraulic connectivity with the streams, the explanations to the DOC trends in surface waters should be searched for in discharge areas and peat lands. Copyright © 2010 Elsevier B.V. All rights reserved.

Cardiovascular Responses of Snakes to Gravitational Gradients

NASA Technical Reports Server (NTRS)

Hsieh, Shi-Tong T.; Lillywhite, H. B.; Ballard, R. E.; Hargens, A. R.; Holton, Emily M. (Technical Monitor)

1998-01-01

Snakes are useful vertebrates for studies of gravitational adaptation, owing to their elongate body and behavioral diversification. Scansorial species have evolved specializations for regulating hemodynamics during exposure to gravitational stress, whereas, such adaptations are less well developed in aquatic and non-climbing species. We examined responses of the amphibious snake,\\italicize (Nerodia rhombifera), to increments of Gz (head-to-tail) acceleration force on both a short- and long-arm centrifuge (1.5 vs. 3.7 m radius, from the hub to tail end of snake). We recorded heart rate, dorsal aortic pressure, and carotid arterial blood flow during stepwise 0.25 G increments of Gz force (referenced at the tail) in conscious animals. The Benz tolerance of a snake was determined as the Gz level at which carotid blood flow ceased and was found to be significantly greater at the short- than long-arm centrifuge radius (1.57 Gz vs. 2.0 Gz, respectively; P=0.016). A similar pattern of response was demonstrated in semi-arboreal rat snakes,\\italicize{Elaphe obsoleta}, which are generally more tolerant of Gz force (2.6 Gz at 1.5m radius) than are water snakes. The tolerance differences of the two species reflected cardiovascular responses, which differed quantitatively but not qualitatively: heart rates increased while arterial pressure and blood flow decreased in response to increasing levels of Gz. Thus, in both species of snakes, a reduced gradient of Gz force (associated with greater centrifuge radius) significantly decreases the Gz level that can be tolerated.

Interactions of carbon nanotubes with the nitromethane-water mixture governing selective adsorption of energetic molecules from aqueous solution.

PubMed

Liu, Yingzhe; Lai, Weipeng; Yu, Tao; Kang, Ying; Ge, Zhongxue

2015-03-14

The structure and dynamics of the nitromethane-water (NM-WT) binary mixture surrounding single walled carbon nanotubes (SWNTs) have been investigated by molecular dynamics simulations. The simulation trajectories show that the NM molecules can be selectively adsorbed both outside the surface and inside the cavity of SWNTs mainly dominated by van der Waals attractions because SWNTs have a higher binding affinity for NM than WT. The binding energies of SWNTs with NM and WT obtained from electronic structure calculations at the M06-2X/6-31+G* level are 15.31 and 5.51 kcal mol(-1), respectively. Compared with the SWNT exterior, the selective adsorption of NM is preferentially occurred in the SWNT interior due to the hydrophobic interactions and the dipole-dipole interactions, which induces the decrease of the hydrogen-bond number of NM with WT and ordered structures of NM with preferred intermolecular orientation in the SWNT cavity. Furthermore, the selective adsorption dynamics of NM from the aqueous solution is regardless of the chirality and radius of SWNTs. The SWNT radius plays a negligible role in the mass density distributions of NM outside the SWNTs, while the mass density of NM in the SWNT interior decreases gradually as the SWNT radius increases. The structural arrangements and intermolecular orientations of NM in the SWNT cavity are greatly dependent on the SWNT radius due to the size effect.

Optical receiving system based on a compound parabolic concentrator and a hemispherical lens for visible light communication.

PubMed

Wang, Yun; Lan, Tian; Ni, Guoqiang

2016-12-20

We propose a scheme for designing a new optical receiving system that can reduce the received-energy spot size via integration of a compound parabolic concentrator with a hemispherical lens. SolidWorks is used to model the receiving system, while TracePro is employed for simulations. The field of view is set to 30° and the radius of the compound parabolic concentrator outlet is 5 mm, which is also the radius of the hemispherical lens. Ray-tracing results show that under the given simulation conditions, the radius of the spot area is reduced from 5 to 3 mm at the receiving system and the gain is 5.2. In regard to the relations between received power and the radius of the hemispherical lens R, and the received power and the distance d between the compound parabolic concentrator and hemispherical lens, our detailed analysis yields the following characteristics: (1) the received power increases as R increases, but decreases as d increases; (2) as R increases, the spot area increases and the received flux is dispersed over the receiving plane, which dispersion is disadvantageous for high-speed communication; (3) the gain of the receiving system also varies with R and d; (4) an increase in d leads to decrease in the received flux and gain when d>-2  mm. Based on these characteristics, we set R=5  mm and calculate the energy efficiency. We obtain maximum energy efficiencies for different detection areas.

Covalently bonded ionic liquid onto cellulose for fast adsorption and efficient separation of Cr(VI): Batch, column and mechanism investigation.

PubMed

Dong, Zhen; Zhao, Long

2018-06-01

Combining the advantages of both cellulose and ionic liquid, ionic liquid functionalized cellulose (ILFC) as adsorbent was prepared through radiation grafting glycidyl methacrylate onto cellulose microsphere following by reaction with ionic liquid 1-aminopropyl-3-methyl imidazolium nitrate. Its adsorption properties towards Cr(VI) were investigated in batch and column experiments. In batch experiments, the adsorption kinetics was well fitted with pseudo-second-order mode with equilibrium time of 2 h and the adsorption capacity reached 181.8 mg/g at pH 2 calculated from Langmuir model. In fixed column, both Yoon-Nelson and Thomas models gave satisfactory fit to experimental data and breakthrough curves, and equilibrium adsorption capacity calculated by Thomas model was 161.0 mg/g. Moreover, ILFC exhibited high selectivity towards Cr(VI) even in synthetic chrome-plating wastewater. Besides, adsorption/desorption test revealed ILFC can be regenerated and reused several times without obvious decrease in adsorbed amount. The adsorption process was demonstrated to anion exchange-reduction mechanism via XPS analysis. Copyright © 2018 Elsevier Ltd. All rights reserved.

Temperature-dependent gel-type ionic liquid compounds based on vanadium-substituted polyoxometalates with Keggin structure.

PubMed

Huang, Tianpei; Xie, Zhirong; Wu, Qingyin; Yan, Wenfu

2016-03-07

A series of temperature-dependent gel-type ionic liquid compounds have been synthesized from 1-(3-sulfonic group) propyl-3-methyl imidazolium (abbreviated as MIMPS) and three vanadium-substituted heteropoly acids H5SiW11VO40, H5SiMo11VO40 and H7SiW9V3O40. The designed and synthesized gel-type polyoxometalate ionic liquids (POM-ILs) have demonstrated a tendency to exhibit a layered structure. Moreover, they can undergo a phase transformation from a viscous gel-state to a liquid-state below 100 °C, and ionic conductivity up to 10(-3) S cm(-1) was observed at 120 °C. Cyclic voltammetry was carried out to study their electrochemical properties in organic solutions, and it was found that the oxidizability of the three POM-ILs decreases in the order: [MIMPS]7SiW9V3O40 > [MIMPS]5SiMo11VO40 > [MIMPS]5SiW11VO40. This result indicates that the redox behavior can be tuned by changing the chemical composition of the heteropolyanions.

Superradiance of charged black holes in Einstein–Gauss–Bonnet gravity

NASA Astrophysics Data System (ADS)

Fierro, Octavio; Grandi, Nicolás; Oliva, Julio

2018-05-01

In this paper we show that electrically charged black holes in Einstein–Gauss–Bonnet gravity suffer from a superradiant instability. It is triggered by a charged scalar field that fulfils Dirichlet boundary conditions at a mirror located outside the horizon. As in general relativity, the unstable modes exist provided that the mirror is located beyond a critical radius, making the instability a long wavelength one. We explore the effects of the Gauss–Bonnet corrections on the critical radius and find evidence that the critical radius decreases as the Gauss–Bonnet coupling α increases. Due to the, up to date, lack of an analytic rotating solution for Einstein–Gauss–Bonnet theory, this is the first example of a superradiant instability in the presence of higher curvature terms in the action.

Emittance Theory for Cylindrical Fiber Selective Emitter

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1998-01-01

A fibrous rare earth selective emitter is approximated as an infinitely long, cylinder. The spectral emittance, e(sub x), is obtained L- by solving the radiative transfer equations with appropriate boundary conditions and uniform temperature. For optical depth, K(sub R), where alpha(sub lambda), is the extinction coefficient and R is the cylinder radius, greater than 1 the spectral emittance depths, K(sub R) alpha(sub lambda)R, is nearly at its maximum value. There is an optimum cylinder radius, R(sub opt) for maximum emitter efficiency, n(sub E). Values for R(sub opt) are strongly dependent on the number of emission bands of the material. The optimum radius decreases slowly with increasing emitter temperature, while the maximum efficiency and useful radiated power increase rapidly with increasing, temperature.

Enhanced pearl-chain formation by electrokinetic interaction with the bottom surface of vessel.

PubMed

Nishimura, Satoshi; Matsumura, Hideo; Kosuge, Katsunori; Yamaguchi, Tomohiko

2007-08-14

Counterions in an electric double layer (EDL) around a colloidal particle accumulate on one side of the EDL and are deficient on the other side under an electric field, resulting in an imbalance of ionic concentration in the EDL, that is to say, the ionic polarization of EDL. It is well known that the ionic polarization of EDL induces electric dipole moments whereby the alignments of colloidal particles (e.g., pearl chains) are formed under alternating electric fields. In this study, we focus on the effect of the frequency of applied electric fields (100 Hz-1 kHz) on the alignment of silica particles settling at the bottom of a silica glass vessel. In digital imaging analyses for pearl chains of silica particles, it is confirmed that surface distances between two neighboring particles decrease but the number of particles in a pearl chain increases as the frequency of the applied electric field is lowered from 1 kHz to 100 Hz. More interestingly, electrical conductance measurements suggest that the induced ionic polarization of EDL around silica particles at the bottom of the silica vessel is enhanced as the frequency is lowered from 1 kHz to 100 Hz, whereas the ionic polarization around isolated silica particles in uniform dispersions is alleviated by the relaxation of ionic concentration in the EDL as a result of the diffusion of counterions. This curious phenomenon can be explained by considering that the ionic polarization of EDL of silica particles at the bottom of a vessel is affected by the electro-osmosis of the silica surface at the bottom of the vessel.

Temperature- and pressure-dependent infrared spectroscopy of 1-butyl-3-methylimidazolium trifluoromethanesulfonate: A dipolar coupling theory analysis

NASA Astrophysics Data System (ADS)

Burba, Christopher M.; Chang, Hai-Chou

2018-03-01

Continued growth and development of ionic liquids requires a thorough understanding of how cation and anion molecular structure defines the liquid structure of the materials as well as the various properties that make them technologically useful. Infrared spectroscopy is frequently used to assess molecular-level interactions among the cations and anions of ionic liquids because the intramolecular vibrational modes of the ions are sensitive to the local potential energy environments in which they reside. Thus, different interaction modes among the ions may lead to different spectroscopic signatures in the vibrational spectra. Charge organization present in ionic liquids, such as 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4mim]CF3SO3), is frequently modeled in terms of a quasicrystalline structure. Highly structured quasilattices enable the dynamic coupling of vibrationally-induced dipole moments to produce optical dispersion and transverse optical-longitudinal optical (TO-LO) splitting of vibrational modes of the ionic liquid. According to dipolar coupling theory, the degree of TO-LO splitting is predicted to have a linear dependence on the number density of the ionic liquid. Both temperature and pressure will affect the number density of the ionic liquid and, therefore, the amount of TO-LO splitting for this mode. Therefore, we test these relationships through temperature- and pressure-dependent FT-IR spectroscopic studies of [C4mim]CF3SO3, focusing on the totally symmetric Ssbnd O stretching mode for the anion, νs(SO3). Increased temperature decreases the amount of TO-LO splitting for νs(SO3), whereas elevated pressure is found to increase the amount of band splitting. In both cases, the experimental observations follow the general predictions of dipolar coupling theory, thereby supporting the quasilattice model for this ionic liquid.

Stability and activity of lysozyme in stoichiometric and non-stoichiometric protic ionic liquid (PIL)-water systems

NASA Astrophysics Data System (ADS)

Wijaya, Emmy C.; Separovic, Frances; Drummond, Calum J.; Greaves, Tamar L.

2018-05-01

There has been a substantial increase in enzyme applications within the biochemical and pharmaceutical industries, for example, as industrial biocatalysts. However, enzymes have narrow marginal stability which makes them prone to become inactive and/or denature with a slight change in the solvent environment. Typically industrial applications require harsher solvent environments than enzyme native environments, and hence there is a need to understand solvent-protein interactions in order to develop strategies to maintain, or enhance, the enzymatic activity under industrially relevant solvent conditions. Previously we have shown that protic ionic liquids (PILs) with water can have a stabilising effect on lysozyme, with a large variation dependent on which PIL ions are present, and the water concentration [E. C. Wijaya et al., Phys. Chem. Chem. Phys. 18(37), 25926-25936 (2016)]. Here we extend on this work using non-stoichiometric aqueous PIL solvents to investigate, and isolate, the role of pH and ionicity on enzymes. We have used the PILs ethylammonium nitrate (EAN) and ethanolammonium formate (EOAF) since our previous work has identified these as good solvents for lysozyme. Solvent libraries were made from these two PILs with an additional precursor acid or base to modify the acidity/basicity of the neutral stoichiometric PIL, and with water added, to have solutions with 4-17 mol. % of the PIL ions in water. Molar ratios of base:acid were varied between 1:1.05 and 2:1 for EAN and 1:1.25 and 2:1 for EOAF, which enabled from highly basic to highly acidic solutions to be obtained. This was to modify the acidity/basicity of the neutral stoichiometric PILs, without the addition of buffers. The structure and stability of hen egg white lysozyme (HEWL) were explored under these solvent conditions using synchrotron small angle X-ray scattering (SAXS), Fourier transform infrared (FTIR), and activity assays. The radius of gyration and Kratky plots obtained from the SAXS data showed little change with varying ionicity or acid:base ratio. FTIR showed that α-helix was maintained in all, except for the most acidic solvent conditions. The activity data show that HEWL was active between pH 0 and 11 for the EA:N-water system and pH 4.4 and 11 for the EOA:F-water system. This work indicates that ionic liquids have the potential to enable enzymes to maintain activity across a broader range of solvent conditions.

Influence of Gd2O3 on thermal and spectroscopic properties of aluminosilicate glasses

NASA Astrophysics Data System (ADS)

Kasprzyk, Marta; Środa, Marcin

2018-06-01

A series of aluminosilicate glasses 25SiO2·(20-x)Al2O3·40Na2O·15BaO-xGd2O3 with 0 ≤ x ≤ 10 were prepared in order to analyze the influence of gadolinium on thermal and spectroscopic properties of these materials. Increasing of thermal parameters (Tg, Tx, Δcp, ΔT) values with higher Gd2O3 content was determined using DSC method. Crystalline phases, formed during heat treatment, were identified with XRD - NaAlSiO4 and BaSiO3 in glass with 0% mol. Gd2O3 and Gd9.33(SiO4)6O2, NaAlSiO4 and BaAl2Si2O6 in glass with 10% mol. Gd2O3. Spectroscopic analysis - FTIR and Raman - revealed Gd2O3 influence on glass structure in the same way like Al2O3, but some differences appear due to the differ bond strength and ionic radius between Gd and Al. Raman spectra confirmed higher network polymerization (enriched with Q2 units). Optical band gap energy (Eopt) and Urbach energy (ΔE) were calculated from the Tauc plot. Mechanical tests demonstrated lower microhardness with increasing content of Gd2O3 content, as a result of higher concentration of atoms with larger radius.

MHD Instabilities in Simple Plasma Configuration

DTIC Science & Technology

1984-01-01

current near the plasma boundary) which can be detected outside the plasma ring . A concept which has proved to b- of great significance for the stability...decrease in the major radius of the plasma ring , a significant loss of plasma energy and particles (from the core of the plasma) and a decrease in the

Charge carrier dynamics and relaxation in (polyethylene oxide-lithium-salt)-based polymer electrolyte containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as ionic liquid

NASA Astrophysics Data System (ADS)

Karmakar, A.; Ghosh, A.

2011-11-01

In this paper we report the dynamics of charge carriers and relaxation in polymer electrolytes based on polyethylene oxide (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) ionic liquid prepared by solution cast technique. It has been observed that the incorporation of BMPTFSI into PEO-LiTFSI electrolyte is an effective way for increasing the amorphous phase to a large extent. It has also been observed that both the glass transition and melting temperatures decrease with the increase of BMPTFSI concentration. The ionic conductivity of these polymer electrolytes increases with the increase of BMPTFSI concentration. The highest ionic conductivity obtained at 25 °C is ˜3×10-4 S cm-1 for the electrolyte containing 60 wt % BMPTFSI and ethylene oxide (EO)/Li ratio of 20. The temperature dependence of the dc conductivity and the hopping frequency show Vogel-Tamman-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The frequency dependence of the ac conductivity exhibits a power law with an exponent n which decreases with the increase of temperature. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and BMPTFSI concentrations. We have also presented the electric modulus data which have been analyzed in the framework of a Havriliak-Negami equation and the shape parameters obtained by the analysis show slight temperature dependence, but change sharply with BMPTFSI concentration. The stretched exponent β obtained from Kohlrausch-Williams-Watts fit to the modulus data is much lower than unity signifying that the relaxation is highly nonexponential. The decay function obtained from analysis of experimental modulus data is highly asymmetric with time.

Stability of Secondary and Tertiary Structures of Virus-Like Particles Representing Noroviruses: Effects of pH, Ionic Strength, and Temperature and Implications for Adhesion to Surfaces.

PubMed

Samandoulgou, Idrissa; Hammami, Riadh; Morales Rayas, Rocio; Fliss, Ismail; Jean, Julie

2015-11-01

Loss of ordered molecular structure in proteins is known to increase their adhesion to surfaces. The aim of this work was to study the stability of norovirus secondary and tertiary structures and its implications for viral adhesion to fresh foods and agrifood surfaces. The pH, ionic strength, and temperature conditions studied correspond to those prevalent in the principal vehicles of viral transmission (vomit and feces) and in the food processing and handling environment (pasteurization and refrigeration). The structures of virus-like particles representing GI.1, GII.4, and feline calicivirus (FCV) were studied using circular dichroism and intrinsic UV fluorescence. The particles were remarkably stable under most of the conditions. However, heating to 65°C caused losses of β-strand structure, notably in GI.1 and FCV, while at 75°C the α-helix content of GII.4 and FCV decreased and tertiary structures unfolded in all three cases. Combining temperature with pH or ionic strength caused variable losses of structure depending on the particle type. Regardless of pH, heating to pasteurization temperatures or higher would be required to increase GII.4 and FCV adhesion, while either low or high temperatures would favor GI.1 adhesion. Regardless of temperature, increased ionic strength would increase GII.4 adhesion but would decrease GI.1 adhesion. FCV adsorption would be greater at refrigeration, pasteurization, or high temperature combined with a low salt concentration or at a higher NaCl concentration regardless of temperature. Norovirus adhesion mediated by hydrophobic interaction may depend on hydrophobic residues normally exposed on the capsid surface at pH 3, pH 8, physiological ionic strength, and low temperature, while at pasteurization temperatures it may rely more on buried hydrophobic residues exposed upon structural rearrangement. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Characteristics of ionic polymer-metal composite with chemically doped TiO2 particles

NASA Astrophysics Data System (ADS)

Jung, Youngsoo; Kim, Seong Jun; Kim, Kwang J.; Lee, Deuk Yong

2011-12-01

Many studies have investigated techniques to improve the bending performance of ionic polymer-metal composite (IPMC) actuators, including 'doping' of metal particles in the polymer membrane usually by means of physical processes. This study is mainly focused on the characterization of the physical, electrochemical and electromechanical properties of TiO2-doped ionic polymer membranes and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. X-ray and UV-visible spectra indicate the presence of anatase-TiO2 in the modified membranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. The glass transition temperature of these membranes, measured using differential scanning calorimetry (DSC), increases with the increase of the amount of TiO2 in the membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of dried TiO2-doped ionic polymer membranes increases as the amount of TiO2 in the membrane increases, whereas the storage modulus of hydrated samples is closely related to the level of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of TiO2-doped membranes decreases with increasing TiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection of TiO2-doped IPMC decreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higher TiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependent on the level of water uptake.

Memory in a fractional-order cardiomyocyte model alters properties of alternans and spontaneous activity

NASA Astrophysics Data System (ADS)

Comlekoglu, T.; Weinberg, S. H.

2017-09-01

Cardiac memory is the dependence of electrical activity on the prior history of one or more system state variables, including transmembrane potential (Vm), ionic current gating, and ion concentrations. While prior work has represented memory either phenomenologically or with biophysical detail, in this study, we consider an intermediate approach of a minimal three-variable cardiomyocyte model, modified with fractional-order dynamics, i.e., a differential equation of order between 0 and 1, to account for history-dependence. Memory is represented via both capacitive memory, due to fractional-order Vm dynamics, that arises due to non-ideal behavior of membrane capacitance; and ionic current gating memory, due to fractional-order gating variable dynamics, that arises due to gating history-dependence. We perform simulations for varying Vm and gating variable fractional-orders and pacing cycle length and measure action potential duration (APD) and incidence of alternans, loss of capture, and spontaneous activity. In the absence of ionic current gating memory, we find that capacitive memory, i.e., decreased Vm fractional-order, typically shortens APD, suppresses alternans, and decreases the minimum cycle length (MCL) for loss of capture. However, in the presence of ionic current gating memory, capacitive memory can prolong APD, promote alternans, and increase MCL. Further, we find that reduced Vm fractional order (typically less than 0.75) can drive phase 4 depolarizations that promote spontaneous activity. Collectively, our results demonstrate that memory reproduced by a fractional-order model can play a role in alternans formation and pacemaking, and in general, can greatly increase the range of electrophysiological characteristics exhibited by a minimal model.

The mixed alkali effect in ionically conducting glasses revisited: a study by molecular dynamics simulation.

PubMed

Habasaki, Junko; Ngai, Kia L

2007-09-07

When more than two kinds of mobile ions are mixed in ionic conducting glasses and crystals, there is a non-linear decrease of the transport coefficients of either type of ion. This phenomenon is known as the mixed mobile ion effect or Mixed Alkali Effect (MAE), and remains an unsolved problem. We use molecular dynamics simulation to study the complex ion dynamics in ionically conducting glasses including the MAE. In the mixed alkali lithium-potassium silicate glasses and related systems, a distinct part of the van Hove functions reveals that jumps from one kind of site to another are suppressed. Although, consensus for the existence of preferential jump paths for each kind of mobile ions seems to have been reached amongst researchers, the role of network formers and the number of unoccupied ion sites remain controversial in explaining the MAE. In principle, these factors when incorporated into a theory can generate the MAE, but in reality they are not essential for a viable explanation of the ion dynamics and the MAE. Instead, dynamical heterogeneity and "cooperativity blockage" originating from ion-ion interaction and correlation are fundamental for the observed ion dynamics and the MAE. Suppression of long range motion with increased back-correlated motions is shown to be a cause of the large decrease of the diffusivity especially in dilute foreign alkali regions. Support for our conclusion also comes from the fact that these features of ion dynamics are common to other ionic conductors, which have no glassy networks, and yet they all exhibit the MAE.

The relationship between galaxy and dark matter halo size from z ˜ 3 to the present

NASA Astrophysics Data System (ADS)

Somerville, Rachel S.; Behroozi, Peter; Pandya, Viraj; Dekel, Avishai; Faber, S. M.; Fontana, Adriano; Koekemoer, Anton M.; Koo, David C.; Pérez-González, P. G.; Primack, Joel R.; Santini, Paola; Taylor, Edward N.; van der Wel, Arjen

2018-01-01

We explore empirical constraints on the statistical relationship between the radial size of galaxies and the radius of their host dark matter haloes from z ∼ 0.1-3 using the Galaxy And Mass Assembly (GAMA) and Cosmic Assembly Near Infrared Deep Extragalactic Legacy Survey (CANDELS) surveys. We map dark matter halo mass to galaxy stellar mass using relationships from abundance matching, applied to the Bolshoi-Planck dissipationless N-body simulation. We define SRHR ≡ re/Rh as the ratio of galaxy radius to halo virial radius, and SRHRλ ≡ re/(λRh) as the ratio of galaxy radius to halo spin parameter times halo radius. At z ∼ 0.1, we find an average value of SRHR ≃ 0.018 and SRHRλ ≃ 0.5 with very little dependence on stellar mass. Stellar radius-halo radius (SRHR) and SRHRλ have a weak dependence on cosmic time since z ∼ 3. SRHR shows a mild decrease over cosmic time for low-mass galaxies, but increases slightly or does not evolve for more massive galaxies. We find hints that at high redshift (z ∼ 2-3), SRHRλ is lower for more massive galaxies, while it shows no significant dependence on stellar mass at z ≲ 0.5. We find that for both the GAMA and CANDELS samples, at all redshifts from z ∼ 0.1-3, the observed conditional size distribution in stellar mass bins is remarkably similar to the conditional distribution of λRh. We discuss the physical interpretation and implications of these results.

Numerical simulation study on the optimization design of the crown shape of PDC drill bit.

PubMed

Ju, Pei; Wang, Zhenquan; Zhai, Yinghu; Su, Dongyu; Zhang, Yunchi; Cao, Zhaohui

The design of bit crown is an important part of polycrystalline diamond compact (PDC) bit design, although predecessors have done a lot of researches on the design principles of PDC bit crown, the study of the law about rock-breaking energy consumption according to different bit crown shape is not very systematic, and the mathematical model of design is over-simplified. In order to analyze the relation between rock-breaking energy consumption and bit crown shape quantificationally, the paper puts forward an idea to take "per revolution-specific rock-breaking work" as objective function, and analyzes the relationship between rock properties, inner cone angle, outer cone arc radius, and per revolution-specific rock-breaking work by means of explicit dynamic finite element method. Results show that the change law between per revolution-specific rock-breaking work and the radius of gyration is similar for rocks with different properties, it is beneficial to decrease rock-breaking energy consumption by decreasing inner cone angle or outer cone arc radius. Of course, we should also consider hydraulic structure and processing technology in the optimization design of PDC bit crown.

Sorption of Metal Ions on Clay Minerals.

PubMed

Schlegel; Charlet; Manceau

1999-12-15

The mechanism of Co uptake from aqueous solution onto hectorite (a magnesian smectite) and its impact on the stability of this clay mineral were investigated as a function of Co concentration (TotCo = 20 to 200 µM, 0.3 M NaNO(3)) and ionic strength (0.3 and 0.01 M NaNO(3), TotCo = 100 µM) by combining kinetics measurements and Co K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The morphology of the sorbent phase was characterized by atomic force microscopy (AFM) and consists of lath-type particles bounded by large basal planes and layer edges. At low ionic strength (0.01 M NaNO(3)), important Co uptake occurred within the first 5 min of reaction, consistent with Co adsorption on exchange sites of hectorite basal planes. Thereafter, the sorption rate dramatically decreased. In contrast, at high ionic strength (0.3 M NaNO(3)), Co uptake rate was much slower within the first 5 min and afterward higher than at 0.01 M NaNO(3), consistent with Co adsorption on specific surface sites located on the edges of hectorite. Time-dependent isotherms for Co uptake at high ionic strength indicated the existence of several sorption mechanisms having distinct equilibration times. The dissolution of hectorite was monitored before and after Co addition. A congruent dissolution regime was observed prior to Co addition. Just after Co addition, an excess release of Mg relatively to congruent dissolution rates occurred at both high and low ionic strengths. At high ionic strength, this excess release nearly equaled the amount of sorbed Co. The dissolution rate of hectorite then decreased at longer Co sorption times. EXAFS spectra of hectorite reacted with Co at high and low ionic strengths and for reaction times longer than 6 h, exhibited similar features, suggesting that the local structural environments of Co atoms are similar. Spectral simulations revealed the occurrence of approximately 2 Mg and approximately 2 Si neighboring cations at interatomic distances characteristic of edge-sharing linkages between Co and Mg octahedra and corner-sharing linkages between Co octahedra and Si tetrahedra, respectively. This local structure is characteristic of inner sphere mononuclear surface complexes at layer edges of hectorite platelets. The occurrence of these complexes even at low ionic strength apparently conflicts with kinetics results, as exchangeable divalent cations are known to form outer sphere surface complexes. To clarify this issue, the amount of Co adsorbed on exchange sites was calculated from the solute Co concentration, assuming that cation exchange was always at equilibrium. These calculations showed that sorbed Co was transferred within 48 h from exchange sites to edge sorption sites. Copyright 1999 Academic Press.

Micromagnetic simulation study of magnetization reversal in torus-shaped permalloy nanorings

NASA Astrophysics Data System (ADS)

Mishra, Amaresh Chandra; Giri, R.

2017-09-01

Using micromagnetic simulation, the magnetization reversal of soft permalloy rings of torus shape with major radius R varying within 20-100 nm has been investigated. The minor radius r of the torus rings was increased from 5 nm up to a maximum value rmax such that R- rmax = 10 nm. Micromagnetic simulation of in-plane hysteresis curve of these nanorings revealed that in the case of very thin rings (r ≤ 10 nm), the remanent state is found to be an onion state, whereas for all other rings, the remanent state is a vortex state. The area of the hysteresis loop was found to be decreasing gradually with the increment of r. The normalized area under the hysteresis loops (AN) increases initially with increment of r. It attains a maximum for a certain value of r = r0 and again decreases thereafter. This value r0 increases as we decrease R and as a result, this peak feature is hardly visible in the case of smaller rings (rings having small R).

Natural convection in annular cone: Influence of radius ratio

NASA Astrophysics Data System (ADS)

Ahmed, N. J. Salman; Kamangar, Sarfaraz; Al-Rashed, Abdullah A. A. A.; Govindaraju, Kalimuthu; Khan, T. M. Yunus

2018-05-01

The viscous dissipation in the fluid flow refers to the transformation of the kinetic energy to the internal energy due to the viscosity of the fluid. The current work investigates the effect of viscous dissipation and radius ratio on the heat transfer characteristics and fluid flow behavior in an annular cone embedded with the porous medium. It is observed that the viscous dissipation effect leads to the decrease in the heat transfer rate from the external wall of the cone to the inner region of the geometry.

Underwater gas tornado

NASA Astrophysics Data System (ADS)

Byalko, Alexey V.

2013-07-01

We present the first experimental observation of a new hydrodynamic phenomenon, the underwater tornado. Simple measurements show that the tornado forms a vortex of the Rankine type, i.e. the rising gas rotates as a solid body and the liquid rotates with a velocity decreasing hyperbolically with the radius. We obtain the dependence of the tornado radius a on the gas stream value j theoretically: a ∼ j2/5. Processing of a set of experiments yielded the value 0.36 for the exponent in this expression. We also report the initial stages of the theoretical study of this phenomenon.

Dependence of Strain Distribution on In Content in InGaN/GaN Quantum Wires and Spherical Quantum Dots

NASA Astrophysics Data System (ADS)

Sharma, Akant Sagar; Dhar, S.

2018-02-01

The distribution of strain, developed in zero-dimensional quantum spherical dots and one-dimensional cylindrical quantum wires of an InGaN/GaN system is calculated as functions of radius of the structure and indium mole fraction. The strain shows strong dependence on indium mole fraction at small distances from the center. The strain associated with both the structures is found to decrease exponentially with the increase in dot or cylinder radius and increases linearly with indium content.

Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, Er) at high pressure

NASA Astrophysics Data System (ADS)

Turner, Katlyn M.; Tracy, Cameron L.; Mao, Wendy L.; Ewing, Rodney C.

2017-12-01

Lanthanide stannate pyrochlores (Ln2Sn2O7; Ln  =  Nd, Gd, and Er) were investigated in situ to 50 GPa in order to determine their structural response to compression and compare their response to that of lanthanide titanate, zirconate, and hafnate pyrochlores. The cation radius ratio of A3+/B4+ in pyrochlore oxides (A2B2O7) is thought to be the dominant feature that influences their response on compression. The ionic radius of Sn4+ is intermediate to that of Ti4+, Zr4+, and Hf4+, but the 〈Sn-O〉 bond in stannate pyrochlore is more covalent than the 〈B-O〉 bonds in titanates, zirconate, and hafnates. In stannates, based on in situ Raman spectroscopy, pyrochlore cation and anion sublattices begin to disorder with the onset of compression, first measured at 0.3 GPa. The extent of sublattice disorder versus pressure is greater in stannates with a smaller Ln3+ cation. Stannate pyrochlores (Fd-3m) begin a sluggish transformation to an orthorhombic, cotunnite-like structure at ~28 GPa similar transitions have been observed in titanate, zirconate, and hafnate pyrochlores at varying pressures (18-40 GPa) with cation radius ratio. The extent of the phase transition versus pressure varies directly with the size of the Ln3+ cation. Post-decompression from ~50 GPa, Er2Sn2O7 and Gd2Sn2O7 adopt a pyrochlore structure, rather than the multi-scale defect-fluorite  +  weberite-type structure adopted by Nd2Sn2O7 that is characteristic of titanate, zirconate, and hafnate pyrochlores under similar conditions. Like pyrochlore titanates, zirconates, and hafnates, the bulk modulus, B 0, of stannates varies linearly and inversely with cation radius ratio from 1 1 1 GPa (Nd2Sn2O7) to 251 GPa (Er2Sn2O7). The trends of bulk moduli in stannates in this study are in excellent agreement with previous experimental studies on stannates and suggest that the size of the Ln3+ cation is the primary determining factor of B 0. Additionally, when normalized to r A/r B, the bulk moduli of stannates are comparable to those of zirconates and hafnates, which vary from titanates. Our results suggest that the cation radius ratio strongly influences the bulk moduli of stannates, as well as their overall compression response.

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

PubMed

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 bound water as ionic strengths increased. Texture analysis was employed to determine the gel strength and also to explain the drug release for the diltiazem hydrochloride. This methodology can be used as a valuable tool for predicting potential ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices. Copyright © 2013 Elsevier B.V. All rights reserved.

Rapid Polymer Transport in a Single Nanometer-Scale Pore

NASA Astrophysics Data System (ADS)

Kasianowicz, J. J.

1998-03-01

Protein ion channels are nanometer-scale pores that control the transport of ions and polymers across cell membranes. We compared the ability of charged and nonelectrolyte linear polymers to partition into a single channel reconstituted into a planar lipid bilayer membrane. The entry of each polymer (e.g. monodisperse length single-stranded homopolymeric RNA1 or poly(ethylene glycol)2,3) into the pore caused characteristic transient decreases in the channel's ionic conductance. The ionic current blockades yield detailed information about the physical properties of the polymers and the pore. The biological and technological significance of the results will be discussed.

The effects of non-ionic polymeric surfactants on the cleaning of biofouled hydrogel materials.

PubMed

Guan, Allan; Li, Zhenyu; Phillips, K Scott

2015-01-01

Block co-polymer surfactants have been used for cleaning hydrogel medical devices that contact the body (e.g., contact lenses) because of their biocompatibility. This work examined the relationship between concentration and detergency of two non-ionic polymeric surfactants (Pluronic F127 and Triton X-100) for cleaning protein soil, with anionic surfactants (sodium dodecyl sulfate and sodium laureth sulfate) as positive controls. Surface plasmon resonance was used to quantify removal of simulated tear soil from self-assembled monolayer surfaces, and a microplate format was used to study the removal of fluorescently labeled soil proteins from contact lenses. While detergency increased as a function of concentration for anionic surfactants, it decreased with concentration for the two polymeric surfactants. The fact that the protein detergency of some non-ionic polymeric surfactants did not increase with concentration above the critical micelle concentration could have implications for optimizing the tradeoff between detergency and biocompatibility.

Dynamic mechanism of equivalent conductivity minimum of electrolyte solution

NASA Astrophysics Data System (ADS)

Yamaguchi, T.; Matsuoka, T.; Koda, S.

2011-10-01

The theory on electric conductivity of electrolyte solutions we have developed [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys. 127, 064508 (2007)] is applied to a model electrolyte solution that shows a minimum of equivalent conductivity as the function of concentration [T. Yamaguchi, T. Akatsuka, and S. Koda, J. Chem. Phys. 134, 244506 (2011)]. The theory succeeds in reproducing the equivalent conductivity minimum, whereas the mode-coupling theory (MCT) underestimates the conductivity in the low-concentration regime. The theory can also reproduce the decrease in the relaxation time of conductivity with increasing the concentration we have demonstrated with a Brownian dynamics simulation. A detailed analysis shows that the relaxation of the conductivity occurs through two processes. The faster one corresponds to the collision between a cation and an anion, and the slower one does to the polarization of the ionic atmosphere. The increase in the equivalent conductivity with concentration is attributed to the decrease in the effect of the ionic atmosphere, which is in turn explained by the fact that the counter ion cannot penetrate into the repulsive core when the Debye screening length is compatible or smaller than the ionic diameter. The same mechanism is also observed in MCT calculation with static structure factor determined by mean-spherical approximation.

Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors

PubMed Central

Rennie, Anthony J. R.; Martins, Vitor L.; Smith, Rachel M.; Hall, Peter J.

2016-01-01

Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (<25 mVs−1) and the efficiency decreases as the volume fraction of the smaller particles increases. Efficiency loss was attributed to side reactions, particularly electrolyte decomposition, arising from interactions with the smaller particles. The effect of reduced efficiency is confirmed by cycling for over 15,000 cycles, which has the important implication that diminished performance and reduced cycle life is caused by the presence of submicron-sized particles. PMID:26911531

Screening out the non-Arrhenius behaviour of nematic-isotropic transition by room temperature ionic liquid.

PubMed

Dan, K; Datta, A; Yoshida, Y; Saito, G; Yoshikawa, K; Roy, M

2016-02-28

Differential Scanning Calorimetry (DSC) and optical polarization microscopy of a mixture of the liquid crystalline material (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) and a Fe-based room temperature ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate ([Emim](+) [FeCl4](-), EMIF) indicate a decrease in the nematic-isotropic (N-I) phase transition temperature (T(NI)) with an increase in EMIF concentration, explained by a proposed model of Coulomb "screening" of MBBA quadrupoles by the EMIF ions along with ionic "self screening." DSC studies of EMIF-MBBA and pure EMIF and comparison with pure MBBA results show that the major transitions in pure EMIF have Arrhenius behaviour, but more importantly the previously found convex Arrhenius behaviour of the pristine MBBA [K. Dan et al., Europhys. Lett. 108, 36007 (2014)] becomes Arrhenius in the mixture, indicating a conversion of the entropic N-I activation barrier to an enthalpic one. In presence of EMIF, a drastic decrease in the intensity of out-of-plane distortions of benzene rings in MBBA is found from Fourier transform infrared spectroscopy, consistent with significant reduction in the conformational states of MBBA. This suppression of large amplitude motion is again consistent with a Coulomb screening and gives a molecular basis for the entropic-to-enthalpic conversion of the N-I activation barrier.

Temperature and chain length dependence of ultrafast vibrational dynamics of thiocyanate in alkylimidazolium ionic liquids: A random walk on a rugged energy landscape.

PubMed

Brinzer, Thomas; Garrett-Roe, Sean

2017-11-21

Ultrafast two-dimensional infrared spectroscopy of a thiocyanate vibrational probe (SCN - ) was used to investigate local dynamics in alkylimidazolium bis-[trifluoromethylsulfonyl]imide ionic liquids ([Im n,1 ][Tf 2 N], n = 2, 4, 6) at temperatures from 5 to 80 °C. The rate of frequency fluctuations reported by SCN - increases with increasing temperature and decreasing alkyl chain length. Temperature-dependent correlation times scale proportionally to temperature-dependent bulk viscosities of each ionic liquid studied. A multimode Brownian oscillator model demonstrates that very low frequency (<10 cm -1 ) modes primarily drive the observed spectral diffusion and that these modes broaden and blue shift on average with increasing temperature. An Arrhenius analysis shows activation barriers for local motions around the probe between 5.5 and 6.5 kcal/mol that are very similar to those for translational diffusion of ions. [Im 6,1 ][Tf 2 N] shows an unexpected decrease in activation energy compared to [Im 4,1 ][Tf 2 N] that may be related to mesoscopically ordered polar and nonpolar domains. A model of dynamics on a rugged potential energy landscape provides a unifying description of the observed Arrhenius behavior and the Brownian oscillator model of the low frequency modes.

Influence of concentration polarization on DNA translocation through a nanopore.

PubMed

Zhai, Shengjie; Zhao, Hui

2016-05-01

Concentration polarization can be induced by the unique ion-perm selectivity of small nanopores, leading to a salt concentration gradient across nanopores. This concentration gradient can create diffusio-osmosis and induce an electric field, affecting ionic currents on DNA that translocates through a nanopore. Here this influence is theoretically investigated by solving the continuum Poisson-Nernst-Planck model for different salt concentrations, DNA surface charge densities, and pore properties. By implementing the perturbation method, we can explicitly compute the contribution of concentration polarization to the ionic current. The induced electric field by concentration polarization is opposite to the imposed electric field and decreases the migration current, and the induced diffusio-osmosis can decrease the convection current as well. Our studies suggest that the importance of the concentration polarization can be determined by the parameter λ/G where λ is the double-layer thickness and G is the gap size. When λ/G is larger than a critical value, the influence of concentration polarization becomes more prominent. This conclusion is supported by the studies on the dependence of the ionic current on salt concentration and pore properties, showing that the difference between two models with and without accounting for concentration polarization is larger for low salts and small pores, which correspond to larger λ/G.

Effect of Brönsted acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride on growth and co-fermentation of glucose, xylose and arabinose by Zymomonas mobilis AX101.

PubMed

Gyamerah, M; Ampaw-Asiedu, M; Mackey, J; Menezes, B; Woldesenbet, S

2018-06-01

The potential of large-scale lignocellulosic biomass hydrolysis to fermentable sugars using ionic liquids has increased interest in this green chemistry route to fermentation for fuel-ethanol production. The ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride compared to other reported ionic liquids has the advantage of hydrolysing lignocellulosic biomass to reducing sugars at catalytic concentrations (≤0·032 mol l -1 ) in a single step. However, effects of this ionic liquid on co-fermentation of glucose, xylose and arabinose to ethanol by recombinant Zymomonas mobilisAX101 has not been studied. Authentic glucose, xylose and arabinose were used to formulate fermentation media at varying catalytic 1-(1-propylsulfonic)-3-methylimidazolium chloride concentrations for batch co-fermentation of the sugars using Z. mobilisAX101. The results showed that at 0·008, 0·016 and 0·032 mol l -1 ionic liquid in the culture medium, cell growth decreased by 10, 27 and 67% respectively compared to the control. Ethanol yields were 62·6, 61·8, 50·5 and 23·1% for the control, 0·008, 0·016 and 0·032 mol l -1 ionic liquid respectively. The results indicate that lignocellulosic biomass hydrolysed using 0·008 mol l -1 of 1-(1-propylsulfonic)-3-methylimidazolium chloride would eliminate an additional separation step and provide a ready to use fermentation substrate. This is the first reported study of the effect of the Brönsted acidic ionic liquid 1-(1-propylsulfonic)-3-methylimidazolium chloride on growth and co-fermentation of glucose, xylose and arabinose by Zymomonas mobilisAX101 in batch culture. Growth on and co-fermentation of the sugars by Z. mobilisAX 101 with no significant inhibition by the ionic liquid at the same catalytic amounts of 0·008 mol l -1 used to hydrolyse lignocellulosic biomass to reducing sugars overcome two major hurdles that adversely affect the process economics of large-scale industrial cellulosic fuel ethanol production; the energy-intensive hydrolysis and ionic liquid separation steps. © 2018 The Society for Applied Microbiology.

Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aliahmad, Nojan; Shrestha, Sudhir; Varahramyan, Kody

2016-06-15

Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10{sup −3} S cm{sup −1}. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providingmore » flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g{sup −1} for standard metallic current collectors and (ii) 99.5 mAh g{sup −1} for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed.« less

Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

NASA Astrophysics Data System (ADS)

Aliahmad, Nojan; Shrestha, Sudhir; Varahramyan, Kody; Agarwal, Mangilal

2016-06-01

Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10-3 S cm-1. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providing flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g-1 for standard metallic current collectors and (ii) 99.5 mAh g-1 for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed.

Relativistic stars in vector-tensor theories

NASA Astrophysics Data System (ADS)

Kase, Ryotaro; Minamitsuji, Masato; Tsujikawa, Shinji

2018-04-01

We study relativistic star solutions in second-order generalized Proca theories characterized by a U (1 )-breaking vector field with derivative couplings. In the models with cubic and quartic derivative coupling, the mass and radius of stars become larger than those in general relativity for negative derivative coupling constants. This phenomenon is mostly attributed to the increase of star radius induced by a slower decrease of the matter pressure compared to general relativity. There is a tendency that the relativistic star with a smaller mass is not gravitationally bound for a low central density and hence is dynamically unstable, but that with a larger mass is gravitationally bound. On the other hand, we show that the intrinsic vector-mode couplings give rise to general relativistic solutions with a trivial field profile, so the mass and radius are not modified from those in general relativity.

Distal radius osteotomy with volar locking plates based on computer simulation.

PubMed

Miyake, Junichi; Murase, Tsuyoshi; Moritomo, Hisao; Sugamoto, Kazuomi; Yoshikawa, Hideki

2011-06-01

Corrective osteotomy using dorsal plates and structural bone graft usually has been used for treating symptomatic distal radius malunions. However, the procedure is technically demanding and requires an extensive dorsal approach. Residual deformity is a relatively frequent complication of this technique. We evaluated the clinical applicability of a three-dimensional osteotomy using computer-aided design and manufacturing techniques with volar locking plates for distal radius malunions. Ten patients with metaphyseal radius malunions were treated. Corrective osteotomy was simulated with the help of three-dimensional bone surface models created using CT data. We simulated the most appropriate screw holes in the deformed radius using computer-aided design data of a locking plate. During surgery, using a custom-made surgical template, we predrilled the screw holes as simulated. After osteotomy, plate fixation using predrilled screw holes enabled automatic reduction of the distal radial fragment. Autogenous iliac cancellous bone was grafted after plate fixation. The median volar tilt, radial inclination, and ulnar variance improved from -20°, 13°, and 6 mm, respectively, before surgery to 12°, 24°, and 1 mm, respectively, after surgery. The median wrist flexion improved from 33° before surgery to 60° after surgery. The median wrist extension was 70° before surgery and 65° after surgery. All patients experienced wrist pain before surgery, which disappeared or decreased after surgery. Surgeons can operate precisely and easily using this advanced technique. It is a new treatment option for malunion of distal radius fractures.

Ion transport with charge-protected and non-charge-protected cations in alcohol-based electrolytes using the compensated Arrhenius formalism. Part I: ionic conductivity and the static dielectric constant.

PubMed

Petrowsky, Matt; Fleshman, Allison; Frech, Roger

2012-05-17

The temperature dependence of ionic conductivity and the static dielectric constant is examined for 0.30 m TbaTf- or LiTf-1-alcohol solutions. Above ambient temperature, the conductivity increases with temperature to a greater extent in electrolytes whose salt has a charge-protected cation. Below ambient temperature, the dielectric constant changes only slightly with temperature in electrolytes whose salt has a cation that is not charge-protected. The compensated Arrhenius formalism is used to describe the temperature-dependent conductivity in terms of the contributions from both the exponential prefactor σo and Boltzmann factor exp(-Ea/RT). This analysis explains why the conductivity decreases with increasing temperature above 65 °C for the LiTf-dodecanol electrolyte. At higher temperatures, the decrease in the exponential prefactor is greater than the increase in the Boltzmann factor.

The new approaches to preservation of graft cell integrity in preservation for transplantation.

PubMed

Gewartowska, Magdalena; Olszewski, Waldemar L

2005-01-01

Restoration of cell plasma membrane integrity after injury is essential for the survival of animal cells. In case of graft preservation or during chemotherapy in cancer, cell membrane integrity and the process of its repair are disrupted. Cytoprotective substances are important in such cases, as well as in other diseases, for example in myocardial infarction, acute insults and in chronic neurodegenerative diseases. Hyperosmolarity is a condition in which cell membrane stability may be damaged in vivo but preserved in the in vitro conditions. Hypertonicity causes water leaving from cells by osmosis, decreasing cell volume and increasing of intracellular ionic strength. High intracellular ionic strength perturbs cellular function by decreasing the rates of biochemical reaction. We review the new experimentally studied cytoprotective substances and their application in cell membrane protection. Moreover, we present our data on the effects of hyperosmolarity and its protective effect on cell internal structure.

Ionic-to-Electronic Conductivity Crossover in CdTe-AgI-As2Te3 Glasses: An 110mAg Tracer Diffusion Study.

PubMed

Kassem, M; Alekseev, I; Bokova, M; Le Coq, D; Bychkov, E

2018-04-12

Conductivity isotherms of (CdTe) x (AgI) 0.5- x/2 (As 2 Te 3 ) 0.5- x/2 glasses (0.0 ≤ x ≤ 0.15) reveal a nonmonotonic behavior with increasing CdTe content reminiscent of mixed cation effect in oxide and chalcogenide glasses. Nevertheless, the apparent similarity appears to be partly incorrect. Using 110m Ag tracer diffusion measurements, we show that semiconducting CdTe additions produce a dual effect: (i) decreasing the Ag + ion transport by a factor of ≈200 with a simultaneous increase of the diffusion activation energy and (ii) increasing the electronic conductivity by 1.5 orders of magnitude. Consequently, the conductivity minimum at x = 0.05 reflects an ionic-to-electronic transport crossover; the silver-ion transport number decreases by 3 orders of magnitude with increasing x.

Influence of ionic strength, anions, cations, and natural organic matter on the adsorption of pharmaceuticals to silica.

PubMed

Bui, Tung Xuan; Choi, Heechul

2010-08-01

The adsorption of four wide-use pharmaceuticals (carbamazepine, diclofenac, ibuprofen, and ketoprofen) onto a porous silica was investigated under varied ionic strengths, different anions, divalent cations (Ca(2+) and Mg(2+)), trivalent cations (Al(3+) and Fe(3+)), and natural organic matter (NOM). The experiments demonstrated that at a given pH the adsorption was most affected by ionic strength, trivalent cations, and properties of pharmaceuticals. The increase of ionic strength resulted in an increase in the adsorption of ketoprofen, but a decrease in the adsorption of carbamazepine. Trivalent metal cations made intense increases in the adsorption of three acidic pharmaceuticals, which could be due to the formation of inner-sphere complex of the cations on the surface and/or complexation of the pharmaceuticals with both surface and aqueous metal species. It was found that the adsorption of carbamazepine was not affected by divalent and trivalent cations, whereas the adsorption of diclofenac was solely impacted by the presence of Al(3+). Moreover, divalent cations at low concentration could slightly enhance the adsorption of ibuprofen and ketoprofen, whereas NOM caused a reduction in the adsorption of the tested pharmaceuticals except for diclofenac. These results suggest that ionic strength, divalent cations, trivalent cations, and NOM are notable factors affecting the adsorption of pharmaceuticals and thus the ultimate fate of pharmaceuticals in the aqueous environment. Copyright 2010 Elsevier Ltd. All rights reserved.

Effect of unsaturation on the absorption of ethane and ethylene in imidazolium-based ionic liquids.

PubMed

Moura, Leila; Mishra, Manas; Bernales, Varinia; Fuentealba, Patricio; Padua, Agilio A H; Santini, Catherine C; Costa Gomes, Margarida F

2013-06-20

The influence of the presence of imidazolium side chain unsaturation on the solubility of ethane and ethylene was studied in three ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide-saturated alkyl side-chain in the cation; 1-methyl-3-(buten-3-yl)imidazolium bis(trifluorosulfonyl)imide-double bond in the side-chain of the cation; and 1-methyl-3-benzylimidazolium bis(trifluorosulfonyl)imide-benzyl group in the side-chain of the cation. The solubility of both gases decreases when the side-chain of the cations is functionalized with an unsaturated group. This can be explained by a less favorable enthalpy of solvation. The difference of solubility between ethane and ethylene can be explained from a balance of enthalpic and entropic factors: for the ionic liquid with the saturated alkyl side-chain and the benzyl-substituted side-chain, it is the favorable entropy of solvation that explains the larger ethylene solubility, whereas in the case of the saturated side-chain, it is the more favorable enthalpy of solvation. Molecular simulation allowed the identification of the mechanisms of solvation and the preferential solvation sites for each gas in the different ionic liquids. Simulations have shown that the entropy of solvation is more favorable when the presence of the gas weakens the cation-anion interactions or when the gas can be solvated near different sites of the ionic liquid.

Structure and lifetimes in ionic liquids and their mixtures.

PubMed

Gehrke, Sascha; von Domaros, Michael; Clark, Ryan; Hollóczki, Oldamur; Brehm, Martin; Welton, Tom; Luzar, Alenka; Kirchner, Barbara

2018-01-01

With the aid of molecular dynamics simulations, we study the structure and dynamics of different ionic liquid systems, with focus on hydrogen bond, ion pair and ion cage formation. To do so, we report radial distribution functions, their number integrals, and various time-correlation functions, from which we extract well-defined lifetimes by means of the reactive flux formalism. We explore the influence of polarizable force fields vs. non-polarizable ones with downscaled charges (±0.8) for the example of 1-butyl-3-methylimidazolium bromide. Furthermore, we use 1-butyl-3-methylimidazolium trifluoromethanesulfonate to investigate the impact of temperature and mixing with water as well as with the chloride ionic liquid. Smaller coordination numbers, larger distances, and tremendously accelerated dynamics are observed when the polarizable force field is applied. The same trends are found with increasing temperature. Adding water decreases the ion-ion coordination numbers whereas the water-ion and water-water coordination is enhanced. A domain analysis reveals that the nonpolar parts of the ions are dispersed and when more water is added the water clusters increase in size. The dynamics accelerate in general upon addition of water. In the ionic liquid mixture, the coordination number around the cation changes between the two anions, but the number integrals of the cation around the anions remain constant and the dynamics slow down with increasing content of the chloride ionic liquid.

Integrated study of first principles calculations and experimental measurements for Li-ionic conductivity in Al-doped solid-state LiGe2(PO4)3 electrolyte

NASA Astrophysics Data System (ADS)

Kang, Joonhee; Chung, Habin; Doh, Chilhoon; Kang, Byoungwoo; Han, Byungchan

2015-10-01

Understanding of the fundamental mechanisms causing significant enhancement of Li-ionic conductivity by Al3+ doping to a solid LiGe2(PO4)3 (LGP) electrolyte is pursued using first principles density functional theory (DFT) calculations combined with experimental measurements. Our results indicate that partial substitution Al3+ for Ge4+ in LiGe2(PO4)3 (LGP) with aliovalent (Li1+xAlxGe2-x(PO4)3, LAGP) improves the Li-ionic conductivity about four-orders of the magnitude. To unveil the atomic origin we calculate plausible diffusion paths of Li in LGP and LAGP materials using DFT calculations and a nudged elastic band method, and discover that LAGP had additional transport paths for Li with activation barriers as low as only 34% of the LGP. Notably, these new atomic channels manifest subtle electrostatic environments facilitating cooperative motions of at least two Li atoms. Ab-initio molecular dynamics predict Li-ionic conductivity for the LAGP system, which is amazingly agreed experimental measurement on in-house made samples. Consequently, we suggest that the excess amounts of Li caused by the aliovalent Al3+ doping to LGP lead to not only enhancing Li concentration but also opening new conducting paths with substantially decreases activation energies and thus high ionic conductivity of LAGP solid-state electrolyte.

Optimizing interconnections to maximize the spectral radius of interdependent networks

NASA Astrophysics Data System (ADS)

Chen, Huashan; Zhao, Xiuyan; Liu, Feng; Xu, Shouhuai; Lu, Wenlian

2017-03-01

The spectral radius (i.e., the largest eigenvalue) of the adjacency matrices of complex networks is an important quantity that governs the behavior of many dynamic processes on the networks, such as synchronization and epidemics. Studies in the literature focused on bounding this quantity. In this paper, we investigate how to maximize the spectral radius of interdependent networks by optimally linking k internetwork connections (or interconnections for short). We derive formulas for the estimation of the spectral radius of interdependent networks and employ these results to develop a suite of algorithms that are applicable to different parameter regimes. In particular, a simple algorithm is to link the k nodes with the largest k eigenvector centralities in one network to the node in the other network with a certain property related to both networks. We demonstrate the applicability of our algorithms via extensive simulations. We discuss the physical implications of the results, including how the optimal interconnections can more effectively decrease the threshold of epidemic spreading in the susceptible-infected-susceptible model and the threshold of synchronization of coupled Kuramoto oscillators.

Contact Modelling of Large Radius Air Bending with Geometrically Exact Contact Algorithm

NASA Astrophysics Data System (ADS)

Vorkov, V.; Konyukhov, A.; Vandepitte, D.; Duflou, J. R.

2016-08-01

Usage of high-strength steels in conventional air bending is restricted due to limited bendability of these metals. Large-radius punches provide a typical approach for decreasing deformations during the bending process. However, as deflection progresses the loading scheme changes gradually. Therefore, modelling of the contact interaction is essential for an accurate description of the loading scheme. In the current contribution, the authors implemented a plane frictional contact element based on the penalty method. The geometrically exact contact algorithm is used for the penetration determination. The implementation is done using the OOFEM - open source finite element solver. In order to verify the simulation results, experiments have been conducted on a bending press brake for 4 mm Weldox 1300 with a punch radius of 30 mm and a die opening of 80 mm. The maximum error for the springback calculation is 0.87° for the bending angle of 144°. The contact interaction is a crucial part of large radius bending simulation and the implementation leads to a reliable solution for the springback angle.

Age-related Changes in the Fracture Resistance of Male Fischer F344 Rat Bone

PubMed Central

Uppuganti, Sasidhar; Granke, Mathilde; Makowski, Alexander J.; Does, Mark D.; Nyman, Jeffry S.

2015-01-01

In addition to the loss in bone volume that occurs with age, there is a decline in material properties. To test new therapies or diagnostic tools that target such properties as material strength and toughness, a pre-clinical model of aging would be useful in which changes in bone are similar to those that occur with aging in humans. Toward that end, we hypothesized that similar to human bone, the estimated toughness and material strength of cortical bone at the apparent-level decreases with age in the male Fischer F344 rat. In addition, we tested whether the known decline in trabecular architecture in rats translated to an age-related decrease in vertebra (VB) strength and whether non-X-ray techniques could quantify tissue changes at micron and sub-micron length scales. Bones were harvested from 6-, 12-, and 24-month (mo.) old rats (n=12 per age). Despite a loss in trabecular bone with age, VB compressive strength was similar among the age groups. Similarly, whole-bone strength (peak force) in bending was maintained (femur) or increased (radius) with aging. There was though an age-related decrease in post-yield toughness (radius) and bending strength (femur). The ability to resist crack initiation was actually higher for the 12-mo. and 24-mo. than for 6-mo. rats (notch femur), but the estimated work to propagate the crack was less for the aged bone. For the femur diaphysis region, porosity increased while bound water decreased with age. For the radius diaphysis, there was an age-related increase in non-enzymatic and mature enzymatic collagen crosslinks. Both Raman spectroscopy and reference point indentation detected differences in tissue properties with age, though the trends did not necessarily match observations from human tissue. PMID:26610688

Age-related changes in the fracture resistance of male Fischer F344 rat bone.

PubMed

Uppuganti, Sasidhar; Granke, Mathilde; Makowski, Alexander J; Does, Mark D; Nyman, Jeffry S

2016-02-01

In addition to the loss in bone volume that occurs with age, there is a decline in material properties. To test new therapies or diagnostic tools that target such properties as material strength and toughness, a pre-clinical model of aging would be useful in which changes in bone are similar to those that occur with aging in humans. Toward that end, we hypothesized that similar to human bone, the estimated toughness and material strength of cortical bone at the apparent-level decreases with age in the male Fischer F344 rat. In addition, we tested whether the known decline in trabecular architecture in rats translated to an age-related decrease in vertebra (VB) strength and whether non-X-ray techniques could quantify tissue changes at micron and sub-micron length scales. Bones were harvested from 6-, 12-, and 24-month (mo.) old rats (n=12 per age). Despite a loss in trabecular bone with age, VB compressive strength was similar among the age groups. Similarly, whole-bone strength (peak force) in bending was maintained (femur) or increased (radius) with aging. There was though an age-related decrease in post-yield toughness (radius) and bending strength (femur). The ability to resist crack initiation was actually higher for the 12-mo. and 24-mo. than for 6-mo. rats (notch femur), but the estimated work to propagate the crack was less for the aged bone. For the femur diaphysis region, porosity increased while bound water decreased with age. For the radius diaphysis, there was an age-related increase in non-enzymatic and mature enzymatic collagen crosslinks. Raman spectroscopy analysis of embedded cross-sections of the tibia mid-shaft detected an increase in carbonate subsitution with advanced aging for both inner and outer tissue. Published by Elsevier Inc.

Scroll-Wave Dynamics in Human Cardiac Tissue: Lessons from a Mathematical Model with Inhomogeneities and Fiber Architecture

PubMed Central

Majumder, Rupamanjari; Nayak, Alok Ranjan; Pandit, Rahul

2011-01-01

Cardiac arrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF), are among the leading causes of death in the industrialized world. These are associated with the formation of spiral and scroll waves of electrical activation in cardiac tissue; single spiral and scroll waves are believed to be associated with VT whereas their turbulent analogs are associated with VF. Thus, the study of these waves is an important biophysical problem. We present a systematic study of the combined effects of muscle-fiber rotation and inhomogeneities on scroll-wave dynamics in the TNNP (ten Tusscher Noble Noble Panfilov) model for human cardiac tissue. In particular, we use the three-dimensional TNNP model with fiber rotation and consider both conduction and ionic inhomogeneities. We find that, in addition to displaying a sensitive dependence on the positions, sizes, and types of inhomogeneities, scroll-wave dynamics also depends delicately upon the degree of fiber rotation. We find that the tendency of scroll waves to anchor to cylindrical conduction inhomogeneities increases with the radius of the inhomogeneity. Furthermore, the filament of the scroll wave can exhibit drift or meandering, transmural bending, twisting, and break-up. If the scroll-wave filament exhibits weak meandering, then there is a fine balance between the anchoring of this wave at the inhomogeneity and a disruption of wave-pinning by fiber rotation. If this filament displays strong meandering, then again the anchoring is suppressed by fiber rotation; also, the scroll wave can be eliminated from most of the layers only to be regenerated by a seed wave. Ionic inhomogeneities can also lead to an anchoring of the scroll wave; scroll waves can now enter the region inside an ionic inhomogeneity and can display a coexistence of spatiotemporal chaos and quasi-periodic behavior in different parts of the simulation domain. We discuss the experimental implications of our study. PMID:21483682

Nanoscale Interparticle Distance within Dimers in Solution Measured by Light Scattering

PubMed Central

2017-01-01

We demonstrate a novel approach to quantify the interparticle distance in colloidal dimers using Mie scattering. The interparticle distance is varied in a controlled way by changing the ionic strength of the solution and the magnetic attraction between the particles. The measured scaling behavior is interpreted using an energy–distance model that includes the repulsive electrostatic and attractive magnetic interactions. The center-to-center distances of particles with a 525 nm radius can be determined with a root-mean-square accuracy of 12 nm. The data show that the center-to-center distance is larger by 83 nm compared to perfect spheres. The underlying distance offset can be attributed to repulsion by charged protrusions caused by particle surface roughness. The measurement method accurately quantifies interparticle distances that can be used to study cluster formation and colloid aggregation in complex systems, e.g., in biosensing applications. PMID:29183122

On the significance of including the thermal motion of ions in determining the ion distribution behind a satellite

NASA Technical Reports Server (NTRS)

Samir, U.; Widjaja, D.

1981-01-01

A comparative investigation concerning the spatial distribution of ions in the wake of small bodies was conducted using the theoretical wake models of Call (1969) and Parker (1976). Results for bodies with radius/ambient Debye length ratios of 2 and 5, with an electron temperature equal to the ambient electron temperature, and for the ionic Mach numbers S = 2, 4, 6, 8 are presented. Since the main physical difference between the models is in the consideration of the thermal motion of ions (Parker) versus ignoring this component (Call), a comparison between the models yields the quantitative significance of this component in determining the distribution of ions in the wake of artificial satellites. The application of this result to future experiments to be conducted on board the Spacelab and for any other large space platform in the area of space plasma physics is mentioned.

Viscosity and transient electric birefringence study of clay colloidal aggregation.

PubMed

Bakk, Audun; Fossum, Jon O; da Silva, Geraldo J; Adland, Hans M; Mikkelsen, Arne; Elgsaeter, Arnljot

2002-02-01

We study a synthetic clay suspension of laponite at different particle and NaCl concentrations by measuring stationary shear viscosity and transient electrically induced birefringence (TEB). On one hand the viscosity data are consistent with the particles being spheres and the particles being associated with large amount bound water. On the other hand the viscosity data are also consistent with the particles being asymmetric, consistent with single laponite platelets associated with a very few monolayers of water. We analyze the TEB data by employing two different models of aggregate size (effective hydrodynamic radius) distribution: (1) bidisperse model and (2) log-normal distributed model. Both models fit, in the same manner, fairly well to the experimental TEB data and they indicate that the suspension consists of polydisperse particles. The models also appear to confirm that the aggregates increase in size vs increasing ionic strength. The smallest particles at low salt concentrations seem to be monomers and oligomers.

Phosphate glass useful in high power lasers

DOEpatents

Hayden, Joseph S.; Sapak, David L.; Ward, Julia M.

1990-01-01

A low- or no-silica phosphate glass useful as a laser medium and having a high thermal conductivity, K.sub.90.degree. C. >0.8 W/mK, and a low coefficient of thermal expansion, .alpha..sub.20.degree.-40.degree. C. <80.times.10.sup.-7 /.degree.C., consists essentially of (on a batch composition basis): the amounts of Li.sub.2 O and Na.sub.2 O providing an average alkali metal ionic radius sufficiently low whereby said glass has K.sub.90.degree. C. >0.8 W/mK and .alpha..sub.20.degree.-40.degree. C. <80.times.10.sup.-7 /.degree.C., and wherein, when the batch composition is melted in contact with a silica-containing surface, the final glass composition contains at most about 3.5 mole % of additional silica derived from such contact during melting. The Nd.sub.2 O.sub.3 can be replaced by other lasing species.

Na⁺ and K⁺ ion selectivity by size-controlled biomimetic graphene nanopores.

PubMed

Kang, Yu; Zhang, Zhisen; Shi, Hui; Zhang, Junqiao; Liang, Lijun; Wang, Qi; Ågren, Hans; Tu, Yaoquan

2014-09-21

Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K(+) channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K(+) and Na(+) channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K(+), the smaller radius of Na(+) leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 Å between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na(+) and K(+) ions.

Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy.

PubMed

Johnston-Peck, Aaron C; Winterstein, Jonathan P; Roberts, Alan D; DuChene, Joseph S; Qian, Kun; Sweeny, Brendan C; Wei, Wei David; Sharma, Renu; Stach, Eric A; Herzing, Andrew A

2016-03-01

Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce(3+) influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce(3+) ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions. Published by Elsevier B.V.

Optical Experiments With Manganese Doped Yttrium Orthoaluminate, a Potential Material for Holographic Recording and Data Storage

NASA Technical Reports Server (NTRS)

Warren, Matthew E.; Loutts, George

1998-01-01

The YAlO3 host crystal has a distorted perovskite structure that belongs to the orthorhombic centrosymmetric Pbnm space group. The cationic sites in the structure available for Mn substitution are the relatively large strongly distorted YO12 polyhedral (Y3+ ionic radius R(sub Y) = 1.02 A) and the smaller nearly ideal AlO6 octahedra R(sub Al) = 0.53 A). Manganese may enter YAlO3 in the form of Mn2+ ions (R(sub Mn)= 0.96 A), substituting most likely Y3+ ions, and Mn3+ ions (R(sub Mn) = 0.65 A) or Mn4+ ions (R(sub Mn) = 0.53 A) substituting Al3+ ions. The latter substitution is most probable because of dimensional parameters. Point defects, which are common in YAl03, may provide the charge compensation required for substitution.

Radius morphology and its effects on rotation with contoured and noncontoured plating of the proximal radius.

PubMed

Rupasinghe, Shavantha L; Poon, Peter C

2012-05-01

The radius has a sagittal bow and a coronal bow. Fractures are often treated with volar anterior plating. However, the sagittal bow is often overlooked when plating. This study looks at radial morphology and the effect of plating the proximal radius with straight plates and then contoured plates bowed in the sagittal plane. We report our findings and their effect on forearm rotation. Morphology was investigated in 14 radii. Attention was paid to the proximal shaft of the radius and its sagittal bow; from this, 6-, 7-, and 8-hole plates were contoured to fit this bow. A simple transverse fracture was then made at the apex of this bow in 23 cadaver arms. Supination and pronation were compared when plating with a straight plate and a contoured plate. Ten cadavers underwent ulna plating at the same level. The effect on rotation of fractures plated in the distal-third shaft was also measured. A significant reduction in rotation was found when a proximal radius fracture was plated with a straight plate compared with a contoured plate: 10.8°, 12.8°, and 21.7° for 6-, 7-, and 8-hole plates, respectively (P < .05). Forearm rotation was decreased further when a longer plate was used. Ulna or distal shaft plating did not reduce rotation. This study has shown a significant sagittal bow of the proximal shaft of the radius. Plating this with contoured plates in the sagittal plane improves rotation when compared with straight plates. Additional ulna plating is not a source of reduced forearm rotation. Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

Sidecut radius and kinetic energy: equipment designed to reduce risk of severe traumatic knee injuries in alpine giant slalom ski racing

PubMed Central

Kröll, Josef; Spörri, Jörg; Gilgien, Matthias; Schwameder, Hermann; Müller, Erich

2016-01-01

Background Kinetic energy (Ekin) increases with speed by the power of 2 and is considered a major risk factor for injuries in alpine ski racing. There is no empirical knowledge about the effect of ski geometry on Ekin. Consequently, the aim of this study was to investigate the influence of sidecut radius on the progress of Ekin while skiing through a multigate section in giant slalom (GS). Methods 5 European-Cup level athletes skied on three different pairs of GS skis varying in sidecut radii (30, 35 and 40 m). Each athlete's position over time within a six gate section (including flat and steep terrain) was captured by the use of a differential Global Navigational Satellite System. Ekin, speed, time and path length were analysed for each pair of skis used. Results When using skis with greater sidecut radius, average Ekin was significantly lower over the entire six gate section, but not locally at every turn cycle. Particular decreases of Ekin were observed for both turns on the flat terrain, as well as for the turn at the terrain transition and the first turn on the steep terrain. The observed decreases in Ekin were found to be primarily explainable by increases in turn time. Conclusions With respect to typical sport mechanisms that cause severe knee injuries, using skis with greater sidecut radius potentially provides additional injury preventative gain, particularly in specific areas within a run. However, this injury preventative gain during falls in GS should not be overestimated. PMID:26702015

Probing the interaction of 1-ethyl-3-methylimidazolium ethyl sulfate ([Emim][EtSO4]) with alcohols and water by solvent and rotational relaxation.

PubMed

Sarkar, Souravi; Pramanik, Rajib; Ghatak, Chiranjib; Setua, Palash; Sarkar, Nilmoni

2010-03-04

The effect of the addition of cosolvents in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethyl sulfate ([Emim][EtSO(4)]) was probed by the solvent and rotational relaxation studies of coumarin 153 in neat ionic liquid [Emim][EtSO(4)] and [Emim][EtSO(4)]-cosolvent mixtures by using steady-state and time-resolved fluorescence spectroscopy. With gradual addition of cosolvents in the RTIL, both the average solvation time and rotational relaxation times gradually decrease. Addition of cosolvents in the IL decreases the viscosity of the medium. We have optimized the geometry of [Emim][EtSO(4)] and [Emim][EtSO(4)]-cosolvent mixtures by using quantum chemical calculations using density functional theory methods, which show the formation of hydrogen bond between cosolvents with [Emim][EtSO(4)]. With addition of the same amount of alcohols in neat [Emim][EtSO(4)], the rotational relaxation time decreases more compared to the addition of the same amount of water.

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

PubMed

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 CaCl 2 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 CaCl 2 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 CaCl 2 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 CaCl 2 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.

Effect of environmental factors on the kinetics of insulin fibril formation: elucidation of the molecular mechanism.

PubMed

Nielsen, L; Khurana, R; Coats, A; Frokjaer, S; Brange, J; Vyas, S; Uversky, V N; Fink, A L

2001-05-22

In the search for the molecular mechanism of insulin fibrillation, the kinetics of insulin fibril formation were studied under different conditions using the fluorescent dye thioflavin T (ThT). The effect of insulin concentration, agitation, pH, ionic strength, anions, seeding, and addition of 1-anilinonaphthalene-8-sulfonic acid (ANS), urea, TMAO, sucrose, and ThT on the kinetics of fibrillation was investigated. The kinetics of the fibrillation process could be described by the lag time for formation of stable nuclei (nucleation) and the apparent rate constant for the growth of fibrils (elongation). The addition of seeds eliminated the lag phase. An increase in insulin concentration resulted in shorter lag times and faster growth of fibrils. Shorter lag times and faster growth of fibrils were seen at acidic pH versus neutral pH, whereas an increase in ionic strength resulted in shorter lag times and slower growth of fibrils. There was no clear correlation between the rate of fibril elongation and ionic strength. Agitation during fibril formation attenuated the effects of insulin concentration and ionic strength on both lag times and fibril growth. The addition of ANS increased the lag time and decreased the apparent growth rate for insulin fibril formation. The ANS-induced inhibition appears to reflect the formation of amorphous aggregates. The denaturant, urea, decreased the lag time, whereas the stabilizers, trimethylamine N-oxide dihydrate (TMAO) and sucrose, increased the lag times. The results indicated that both nucleation and fibril growth were controlled by hydrophobic and electrostatic interactions. A kinetic model, involving the association of monomeric partially folded intermediates, whose concentration is stimulated by the air-water interface, leading to formation of the critical nucleus and thence fibrils, is proposed.

Photoresponse of a Bilayer Graphene p-n Junction Using a Combination of Electrostatic and Electrolytic Gating

NASA Astrophysics Data System (ADS)

Grover, Sameer; Joshi, Anupama; Tulapurkar, Ashwin; Deshmukh, Mandar

Electrolyic gating can induce large carrier densities in graphene and other 2D-materials. We demonstrate a technique for the formation of p-n junctions in graphene using a combination of electrostatic and electrolytic gating. This was done by patterning the negative resist hydrogen silsesquioxane (HSQ) to cover part of a bilayer graphene flake. We performed electrical and photoresponse measurements with the ionic liquid EMI-Im as the top gate and with a silicon back gate. The device characteristics were measured both at room temperature, where the ions are mobile, and at low temperatures, where the ionic liquid is frozen. We created p-n junctions that work at both room temperature and at low temperatures below the freezing point of the ionic liquid. This technique is suited for studying the photoresponse of graphene p-n junctions because of the larger transparency of ionic liquids compared to metallic gates as used in previous studies. We found that the photoresponse is dominated by the photo-thermoelectric effect, characterized by a six fold pattern in the photovoltage. The photovoltage increases as the temperature decreases which is indicative of hot electron thermalization by disorder assisted supercollisions. DST, DAE, Government of India.

Changes in the quaternary structure of phosphoenolpyruvate carboxylase induced by ionic strength affect its catalytic activity.

PubMed

Wagner, R; Gonzalez, D H; Podesta, F E; Andreo, C S

1987-05-04

Phosphoenolpyruvate carboxylase from maize leaves dissociated into dimers and/or monomers when exposed to increasing ionic strength (e.g. 200-400 mM NaCl) as indicated by gel filtration experiments. Changes in the oligomerization state were dependent on pH, time of preincubation with salt and protein concentration. A dissociation into dimers and monomers was observed at pH 8, while at pH 7 dissociation into the dimeric form only was observed. Exposure of the enzyme to higher ionic strength decreased the activity in a time-dependent manner. Turnover conditions and glucose 6-phosphate protected the carboxylase from the decay in activity, which was faster at pH 7 than at pH 8. The results suggest that changes in activity of the enzyme, following exposure to high ionic strength, are the consequence of dissociation. Tetrameric and dimeric forms of the phosphoenolpyruvate carboxylase seemingly reveal different catalytic properties. We suggest that the distinct catalytic properties of the different oligomeric species of phosphoenolpyruvate carboxylase and changes in the equilibrium between them could be the molecular basis for an effective regulation of metabolite levels by this key enzyme of C4 plants.

An Electrochemical NO2 Sensor Based on Ionic Liquid: Influence of the Morphology of the Polymer Electrolyte on Sensor Sensitivity

PubMed Central

Kuberský, Petr; Altšmíd, Jakub; Hamáček, Aleš; Nešpůrek, Stanislav; Zmeškal, Oldřich

2015-01-01

A systematic study was carried out to investigate the effect of ionic liquid in solid polymer electrolyte (SPE) and its layer morphology on the characteristics of an electrochemical amperometric nitrogen dioxide sensor. Five different ionic liquids were immobilized into a solid polymer electrolyte and key sensor parameters (sensitivity, response/recovery times, hysteresis and limit of detection) were characterized. The study revealed that the sensor based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][N(Tf)2]) showed the best sensitivity, fast response/recovery times, and low sensor response hysteresis. The working electrode, deposited from water-based carbon nanotube ink, was prepared by aerosol-jet printing technology. It was observed that the thermal treatment and crystallinity of poly(vinylidene fluoride) (PVDF) in the solid polymer electrolyte influenced the sensitivity. Picture analysis of the morphology of the SPE layer based on [EMIM][N(Tf)2] ionic liquid treated under different conditions suggests that the sensor sensitivity strongly depends on the fractal dimension of PVDF spherical objects in SPE. Their deformation, e.g., due to crowding, leads to a decrease in sensor sensitivity. PMID:26569248

Mobilization of natural colloids from an iron oxide-coated sand aquifer--Effect of pH and ionic strength

USGS Publications Warehouse

Bunn, Rebecca A.; Magelky, Robin D.; Ryan, Joseph N.; Elimelech, Menachem

2002-01-01

Field and laboratory column experiments were performed to assess the effect of elevated pH and reduced ionic strength on the mobilization of natural colloids in a ferric oxyhydroxide-coated aquifer sediment. The field experiments were conducted as natural gradient injections of groundwater amended by sodium hydroxide additions. The laboratory experiments were conducted in columns of undisturbed, oriented sediments and disturbed, disoriented sediments. In the field, the breakthrough of released colloids coincided with the pH pulse breakthrough and lagged the bromide tracer breakthrough. The breakthrough behavior suggested that the progress of the elevated pH front controlled the transport of the mobilized colloids. In the laboratory, about twice as much colloid release occurred in the disturbed sediments as in the undisturbed sediments. The field and laboratory experiments both showed that the total mass of colloid release increased with increasing pH until the concurrent increase in ionic strength limited release. A decrease in ionic strength did not mobilize significant amounts of colloids in the field. The amount of colloids released normalized to the mass of the sediments was similar for the field and the undisturbed laboratory experiments.

Criticality in charge-asymmetric hard-sphere ionic fluids.

PubMed

Aqua, Jean-Noël; Banerjee, Shubho; Fisher, Michael E

2005-10-01

Phase separation and criticality are analyzed in z:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-Hückel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, Tc* (normalized by z), decrease with charge asymmetry, while the critical densities increase rapidly with . The results compare favorably with simulations and represent a distinct improvement over all current theories such as the mean spherical approximation, symmetric Poisson-Boltzmann theory, etc. For z not equal to 1, the interphase Galvani (or absolute electrostatic) potential difference, Deltaphi(T), between coexisting liquid and vapor phases is calculated and found to vanish as absolute value (T-Tc) beta when T-->Tc-with, since our approximations are classical, beta = (1/2). Above Tc, the compressibility maxima and so-called k-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong z dependence.

Understanding the impact of ionic liquid pretreatment on eucalyptus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Centikol, Ozgul; Dibble, Dean; Cheng, Gang

2010-01-01

The development of cost-competitive biofuels necessitates the realization of advanced biomass pretreatment technologies. Ionic liquids provide a basis for one of the most promising pretreatment technologies and are known to allow effective processing of cellulose and some biomass species. Here, we demonstrate that the ionic liquid 1-ethyl-3-methyl imidazolium acetate, [C2mim][OAc], induces structural changes at the molecular level in the cell wall of Eucalyptus globulus. Deacetylation of xylan, acetylation of the lignin units, selective removal of guaiacyl units (increasing the syringyl:guaiacyl ratio) and decreased {beta}-ether content were the most prominent changes observed. Scanning electron microscopy images of the plant cell wallmore » sections reveal extensive swelling during [C2mim][OAc] pretreatment. X-ray diffraction measurements indicate a change in cellulose crystal structure from cellulose I to cellulose II after [C2mim][OAc] pretreatment. Enzymatic saccharification of the pretreated material produced increased sugar yields and improved hydrolysis kinetics after [C2mim][OAc] pretreatment. These results provide new insight into the mechanism of ionic liquid pretreatment and reaffirm that this approach may be promising for the production of cellulosic biofuels from woody biomass.« less

Reactive solid surface morphology variation via ionic diffusion.

PubMed

Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

2012-08-14

In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

The effect of humidity on ionic wind velocity in ambient air

NASA Astrophysics Data System (ADS)

Chen, She; Nobelen, J. C. P. Y.; Nijdam, S.

2016-09-01

Due to the evolution of portable electronics and LED lightning system, advances in air cooling technologies must also keep pace. Active cooling by ionic wind, which is usually generated by corona discharge, can greatly reduce the noise and lifetime issues compared to the mechanical fans. The wind is induced when a gas discharge is formed, and neutral molecules gain their energy by the momentum transfer of ion-neutral collisions. However, there is few discussion about the effect of gas composition such as humidity on the wind generation and the physical mechanism is not clear. In the experiment, a positive 5-20 kV DC voltage is applied to the needle-cylinder electrodes with separation of 20 mm. The ionic wind velocity is measured by hot wire anemometry. As the relative humidity (RH) in the ambient air increases, the velocity is found to be severely inhibited. The current is also measured between the cylinder electrode and earth. The results show that the DC component of corona current decreases when RH increases. Since both the discharge current and the ion mobility are reduced when RH increases, their combined effects determine the ionic wind velocity. This work is supported by STW project 13651.

Revised Masses and Densities of the Planets around Kepler-10

NASA Astrophysics Data System (ADS)

Weiss, Lauren M.; Rogers, Leslie A.; Isaacson, Howard T.; Agol, Eric; Marcy, Geoffrey W.; Rowe, Jason F.; Kipping, David; Fulton, Benjamin; Lissauer, Jack; Howard, Andrew; Clark Fabrycky, Daniel

2015-12-01

Determining which small exoplanets have stony-iron compositions is necessary for quantifying the occurrence of such planets and for understanding the physics of planet formation. Kepler-10 hosts the stony-iron world Kepler-10b, and also contains what has been reported to be the largest solid silicate-ice planet, Kepler-10c. Using 220 radial velocities (RVs), including 72 new precise RVs from Keck-HIRES, and 17 quarters of Kepler photometry, we obtain the most complete picture of the Kepler-10 system to date. We find that Kepler-10b (Rp = 1.47 R⊕) has mass 3.70 ± 0.43 M⊕ and density 6.44 ± 0.73 g cm-3. Modeling the interior of Kepler-10b as an iron core overlaid with a silicate mantle, we find that the core constitutes 0.17 ± 0.11 of the planet mass. For Kepler-10c (Rp = 2.35 R⊕) we measure mass 13.32 ± 1.65 M⊕and density 5.67 ± 0.70 g cm-3, significantly lower than the mass in Dumusque et al. (2014, 17.2±1.9 M⊕). Kepler-10c is not sufficiently dense to have a pure stony-iron composition. Internal compositional modeling reveals that at least 10% of the radius of Kepler-10c is a volatile envelope composed of either hydrogen-helium (0.0027 ± 0.0015 of the mass, 0.172±0.037 of the radius) or super-ionic water (0.309±0.11 of the mass, 0.305±0.075 of the radius). Transit timing variations (TTVs) of Kepler-10c indicate the likely presence of a third planet in the system, KOI-72.X. The TTVs and RVs are consistent with KOI-72.X having an orbital period of 24, 71, 82, or 101 days, and a mass from 1-7 M⊕.

Biodiversity of soil bacteria exposed to sub-lethal concentrations of phosphonium-based ionic liquids: Effects of toxicity and biodegradation.

PubMed

Sydow, Mateusz; Owsianiak, Mikołaj; Framski, Grzegorz; Woźniak-Karczewska, Marta; Piotrowska-Cyplik, Agnieszka; Ławniczak, Łukasz; Szulc, Alicja; Zgoła-Grześkowiak, Agnieszka; Heipieper, Hermann J; Chrzanowski, Łukasz

2018-01-01

Little is known about the effect of ionic liquids (ILs) on the structure of soil microbial communities and resulting biodiversity. Therefore, we studied the influence of six trihexyl(tetradecyl)phosphonium ILs (with either bromide or various organic anions) at sublethal concentrations on the structure of microbial community present in an urban park soil in 100-day microcosm experiments. The biodiversity decreased in all samples (Shannon's index decreased from 1.75 down to 0.74 and OTU's number decreased from 1399 down to 965) with the largest decrease observed in the microcosms spiked with ILs where biodegradation extent was higher than 80%. (i.e. [P 66614 ][Br] and [P 66614 ][2,4,4]). Despite this general decrease in biodiversity, which can be explained by ecotoxic effect of the ILs, the microbial community in the microcosms was enriched with Gram-negative hydrocarbon-degrading genera e.g. Sphingomonas. It is hypothesized that, in addition to toxicity, the observed decrease in biodiversity and change in the microbial community structure may be explained by the primary biodegradation of the ILs or their metabolites by the mentioned genera, which outcompeted other microorganisms unable to degrade ILs or their metabolites. Thus, the introduction of phosphonium-based ILs into soils at sub-lethal concentrations may result not only in a decrease in biodiversity due to toxic effects, but also in enrichment with ILs-degrading bacteria. Copyright © 2017 Elsevier Inc. All rights reserved.

Gossiping in Jail

NASA Astrophysics Data System (ADS)

Miller, Avery

Consider a set of prisoners that want to gossip with one another, and suppose that these prisoners are located at fixed locations (e.g., in jail cells) along a corridor. Each prisoner has a way to broadcast messages (e.g. by voice or contraband radio) with transmission radius R and interference radius R' ≥ R. We study synchronous algorithms for this problem (that is, prisoners are allowed to speak at regulated intervals) including two restricted subclasses. We prove exact upper and lower bounds on the gossiping completion time for all three classes. We demonstrate that each restriction placed on the algorithm results in decreasing performance.

Negativly streched premixed flames

NASA Astrophysics Data System (ADS)

Krikunova, A. I.; Saveliev, A. S.; Son, E. E.

2018-01-01

An experimental study of gravity effect on the blow-off and flash-back borders of the conical methane-air flame (normal and ring-stabilized) was performed. The influence of the preferential diffusion on the flame behavior in vicinity of flash-back boundaries was observed. Under conditions at Lewis number Le > 1, the radius of curvature of the flame tip increased gradually approaching flash-back boundaries while for the lean methane-air flames (Le < 1) the radius decreased abruptly. It was shown that the burning velocity for lean flames is less than that for reach ones, so the flash-back occurs at higher strains.

Study of CdTe quantum dots grown using a two-step annealing method

NASA Astrophysics Data System (ADS)

Sharma, Kriti; Pandey, Praveen K.; Nagpal, Swati; Bhatnagar, P. K.; Mathur, P. C.

2006-02-01

High size dispersion, large average radius of quantum dot and low-volume ratio has been a major hurdle in the development of quantum dot based devices. In the present paper, we have grown CdTe quantum dots in a borosilicate glass matrix using a two-step annealing method. Results of optical characterization and the theoretical model of absorption spectra have shown that quantum dots grown using two-step annealing have lower average radius, lesser size dispersion, higher volume ratio and higher decrease in bulk free energy as compared to quantum dots grown conventionally.

Determining Concentration of Nanoparticles from Ellipsometry

NASA Technical Reports Server (NTRS)

Venkatasubbarao, Srivatsa; Kempen, Lothar U.; Chipman, Russell

2008-01-01

A method of using ellipsometry or polarization analysis of light in total internal reflection of a surface to determine the number density of gold nanoparticles on a smooth substrate has been developed. The method can be modified to enable determination of densities of sparse distributions of nanoparticles in general, and is expected to be especially useful for measuring gold-nanoparticle-labeled biomolecules on microarrays. The method is based on theoretical calculations of the ellipsometric responses of gold nanoparticles. Elements of the calculations include the following: For simplicity, the gold nanoparticles are assumed to be spherical and to have the same radius. The distribution of gold nanoparticles is assumed to be a sub-monolayer (that is, sparser than a monolayer). The optical response of the sub-monolayer is modeled by use of a thin-island-film theory, according to which the polarizabilities parallel and perpendicular to the substrate are functions of the wavelength of light, the dielectric functions (permittivities expressed as complex functions of frequency or wavelength) of the gold and the suspending medium (in this case, the suspending medium is air), the fraction of the substrate area covered by the nanoparticles, and the radius of the nanoparticles. For the purpose of the thin-island-film theory, the dielectric function of the gold nanoparticles is modeled as the known dielectric function of bulk gold plus a correction term that is necessitated by the fact that the mean free path length for electrons in gold decreases with decreasing radius, in such a manner as to cause the imaginary part of the dielectric function to increase with decreasing radius (see figure). The correction term is a function of the nanoparticle radius, the wavelength of light, the mean free path and the Fermi speed of electrons in bulk gold, the plasma frequency of gold, and the speed of light in a vacuum. These models are used to calculate ellipsometric responses for various concentrations of gold nanoparticles having an assumed radius. The modeled data indicates distinct spectral features for both the real and the imaginary part of the dielectric function. An ellipsometric measurement would determine this distinct feature and thus can be used to measure nanoparticle concentration. By "ellipsometric responses" is meant the intensities of light measured in various polarization states as functions of the angle of incidence and the polarization states of the incident light. These calculated ellipsometric responses are used as calibration curves: Data from subsequent ellipsometric measurements on real specimens are compared with the calibration curves. The concentration of the nanoparticles on a specimen is assumed to be that of the calibration curve that most closely matches the data pertaining to that specimen.

High-energy X-ray powder diffraction and atomic-pair distribution-function studies of charged/discharged structures in carbon-hybridized Li2MnSiO4 nanoparticles as a cathode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Moriya, Maki; Miyahara, Masahiko; Hokazono, Mana; Sasaki, Hirokazu; Nemoto, Atsushi; Katayama, Shingo; Akimoto, Yuji; Hirano, Shin-ichi; Ren, Yang

2014-10-01

The stable cycling performance with a high discharge capacity of ∼190 mAh g-1 in a carbon-hybridized Li2MnSiO4 nanostructured powder has prompted an experimental investigation of the charged/discharged structures using synchrotron-based and laboratory-based X-rays and atomic-pair distribution-function (PDF) analyses. A novel method of in-situ spray pyrolysis of a precursor solution with glucose as a carbon source enabled the successful synthesis of the carbon-hybridized Li2MnSiO4 nanoparticles. The XRD patters of the discharged (lithiated) samples exhibit a long-range ordered structure characteristic of the (β) Li2MnSiO4 crystalline phase (space group Pmn21) which dissipates in the charged (delithiated) samples. However, upon discharging the long-range ordered structure recovers in each cycle. The disordered structure, according to the PDF analysis, is mainly due to local distortions of the MnO4 tetrahedra which show a mean Mn-O nearest neighbor distance shorter than that of the long-range ordered phase. These results corroborate the notion of the smaller Mn3+/Mn4+ ionic radii in the Li extracted phase versus the larger Mn2+ ionic radius in Li inserted phase. Thus Li extraction/insertion drives the fluctuation between the disordered and the long-range ordered structures.

Electron detachment energies in high-symmetry alkali halide solvated-electron anions

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Berdys, Joanna; Simons, Jack; Skurski, Piotr

2003-07-01

We decompose the vertical electron detachment energies (VDEs) in solvated-electron clusters of alkali halides in terms of (i) an electrostatic contribution that correlates with the dipole moment (μ) of the individual alkali halide molecule and (ii) a relaxation component that is related to the polarizability (α) of the alkali halide molecule. Detailed numerical ab initio results for twelve species (MX)n- (M=Li,Na; X=F,Cl,Br; n=2,3) are used to construct an interpolation model that relates the clusters' VDEs to their μ and α values as well as a cluster size parameter r that we show is closely related to the alkali cation's ionic radius. The interpolation formula is then tested by applying it to predict the VDEs of four systems [i.e., (KF)2-, (KF)3-, (KCl)2-, and (KCl)3-] that were not used in determining the parameters of the model. The average difference between the model's predicted VDEs and the ab initio calculated electron binding energies is less than 4% (for the twelve species studied). It is concluded that one can easily estimate the VDE of a given high-symmetry solvated electron system by employing the model put forth here if the α, μ and cation ionic radii are known. Alternatively, if VDEs are measured for an alkali halide cluster and the α and μ values are known, one can estimate the r parameter, which, in turn, determines the "size" of the cluster anion.

Gating current studies reveal both intra- and extracellular cation modulation of K+ channel deactivation

PubMed Central

Wang, Zhuren; Zhang, Xue; Fedida, David

1999-01-01

The presence of permeant ions can modulate the rate of gating charge return in wild-type human heart K+ (hKv1.5) channels. Here we employ gating current measurements in a non-conducting mutant, W472F, of the hKv1.5 channel to investigate how different cations can modulate charge return and whether the actions can be specifically localized at the internal as well as the external mouth of the channel pore. Intracellular cations were effective at accelerating charge return in the sequence Cs+ > Rb+ > K+ > Na+ > NMG+. Extracellular cations accelerated charge return with the selectivity sequence Cs+ > Rb+ > Na+ = NMG+. Intracellular and extracellular cation actions were of relatively low affinity. The Kd for preventing slowing of the time constant of the off-gating current decay (τoff) was 20.2 mM for intracellular Cs+ (Csi+) and 358 mM for extracellular Cs+ (Cso+). Both intracellular and extracellular cations can regulate the rate of charge return during deactivation of hKv1.5, but intracellular cations are more effective. We suggest that ion crystal radius is an important determinant of this action, with larger ions preventing slowing more effectively. Important parallels exist with cation-dependent modulation of slow inactivation of ionic currents in this channel. However, further experiments are required to understand the exact relationship between acceleration of charge return and the slowing of inactivation of ionic currents by cations. PMID:10050001

Mechanisms of combustion synthesis and magnetic response of high-surface-area hexaboride compounds.

PubMed

Kanakala, Raghunath; Escudero, Roberto; Rojas-George, Gabriel; Ramisetty, Mohan; Graeve, Olivia A

2011-04-01

We present an analysis of the combustion synthesis mechanisms for the preparation of hexaboride materials using three compounds as model systems: EuB(6), YbB(6), and YB(6). These three hexaborides were chosen because of the differences in ionic radii between Eu(3+), Yb(3+), and Y(3+), which is a factor in their stability. The powders were prepared using metal nitrates, carbohydrazide, and two different boron precursor powders. The resulting materials were analyzed by X-ray diffraction, which showed that combustion synthesis is effective for the synthesis of EuB(6), since the Eu(3+) ion has an ionic radius greater than ∼1 Å. The synthesis of YbB(6) and YB(6) is not as effective because of the small size of the Yb(3+) and Y(3+) ions, making the hexaborides of these metals less stable and resulting in the synthesis of borates due to the presence of oxygen during the combustion process. Scanning electron microscopy and dynamic light scattering of the EuB(6) powders shows that the particle size of the hexaboride product is dependent on the particle size of the boron precursor. The magnetic susceptibility of our EuB(6) powders manifests irreversible behavior at low applied fields, which disappears at higher fields. This behavior can be attributed to the increase in size and number of magnetic polarons with increasing magnetic field. © 2011 American Chemical Society

[The value of the Kapandji-Sauvé procedure with considering clinical results and measurement of bone density. A clinical study].

PubMed

Wüstner-Hofmann, M C; Schober, F; Hofmann, A K

2003-05-01

Between 1989 and 1995, 33 patients were treated with a Kapandji-Sauvé procedure for malunited fracture of the distal radius and instabilities of the distal radioulnar joint. Thirty patients were followed up with a mean follow-up time of 91 months. Fourteen patients underwent a measurement of bone density of the distal forearm. Twenty-eight patients showed good ossification of the distal radioulnar arthrodesis. Forearm rotation improved by 17.3 %. Mean grip strength was 72 % of that of the contralateral hand. Evaluation by the Cooney score resulted in 10 % very good, in 65 % good, 22 % fair and in 3 % poor results. The measurement of bone density of the distal radius showed an increase of rotation and flexure firmness. The cortical density remained constant. In the subcortical bone of the distal radius, we found a decrease of the trabecular density in the radial part.

Finite Element Analysis and Experimental Study on Elbow Vibration Transmission Characteristics

NASA Astrophysics Data System (ADS)

Qing-shan, Dai; Zhen-hai, Zhang; Shi-jian, Zhu

2017-11-01

Pipeline system vibration is one of the significant factors leading to the vibration and noise of vessel. Elbow is widely used in the pipeline system. However, the researches about vibration of elbow are little, and there is no systematic study. In this research, we firstly analysed the relationship between elbow vibration transmission characteristics and bending radius by ABAQUS finite element simulation. Then, we conducted the further vibration test to observe the vibration transmission characteristics of different elbows which have the same diameter and different bending radius under different flow velocity. The results of simulation calculation and experiment both showed that the vibration acceleration levels of the pipeline system decreased with the increase of bending radius of the elbow, which was beneficial to reduce the transmission of vibration in the pipeline system. The results could be used as reference for further studies and designs for the low noise installation of pipeline system.

Effect of viscosity on steady-state voltammetry and scanning electrochemical microscopy in room temperature ionic liquids.

PubMed

Lovelock, Kevin R J; Cowling, Frances N; Taylor, Alasdair W; Licence, Peter; Walsh, Darren A

2010-04-08

The electrochemical properties of a series of room temperature ionic liquids (RTILs) were studied using voltammetric methods and scanning electrochemical microscopy (SECM). The RTILs consisted of 1-alkyl-3-methylimidazolium cations, [C(n)C(1)Im](+), and either bis[(trifluoromethyl)sulfonyl]imide anions, [Tf(2)N](-), or hexafluorophosphate anions, [PF(6)](-). The effect of RTIL viscosity on mass transfer dynamics within each RTIL was studied electrochemically using ferrocene as a redox probe. In the case of the [C(n)C(1)Im][Tf(2)N] RTILs, the viscosity was altered by changing the alkyl chain length. [C(4)C(1)Im][PF(6)] was used for comparison as its viscosity is significantly higher than that of the [C(n)C(1)Im][Tf(2)N] RTILs. The RTIL viscosity affected the ability to record steady-state voltammograms at ultramicroelectrodes (UMEs). For example, it was possible to record steady-state voltammograms at scan rates up to 10 mV s(-1) in [C(2)C(1)Im][Tf(2)N] using 1.5 mum radius disk UMEs, but non-steady-state behavior was observed at 50 mV s(-1). However, at 12.5 microm radius UMEs, steady-state voltammetry was only observed at 1 mV s(-1) in [C(2)C(1)Im][Tf(2)N]. The RTIL viscosity also affected the ability to record SECM feedback approach curves that agreed with conventional SECM theory. In the most viscous [C(n)C(1)Im][Tf(2)N] RTILs, feedback approach curves agreed with conventional theory only when very slow tip approach speeds were used (0.1 microm s(-1)). These observations were interpreted using the Peclet number, which describes the relative contributions of convective and diffusive mass transfer to the tip surface. By recording feedback approach curves in each RTIL at a range of tip approach speeds, we describe the experimental conditions that must be met to perform SECM in imidazolium-based RTILs. The rate of heterogeneous electron transfer across the RTIL/electrode interface was also studied using SECM and the standard heterogeneous electron transfer rate constant, k(0), for ferrocene oxidation recorded in each RTIL was higher than that determined previously using voltammetric methods.

How ion properties determine the stability of a lipase enzyme in ionic liquids: a molecular dynamics study.

PubMed

Klähn, Marco; Lim, Geraldine S; Wu, Ping

2011-11-07

The influence of eight different ionic liquid (IL) solvents on the stability of the lipase Candida antarctica lipase B (CAL-B) is investigated with molecular dynamics (MD) simulations. Considered ILs contain cations that are based either on imidazolium or guanidinium as well as nitrate, tetrafluoroborate or hexafluorophosphate anions. Partial unfolding of CAL-B is observed during high-temperature MD simulations and related changes of CAL-B regarding its radius of gyration, surface area, secondary structure, amount of solvent close to the backbone and interaction strength with the ILs are evaluated. CAL-B stability is influenced primarily by anions in the order NO(3)(-)≪ BF(4)(-) < PF(6)(-) of increasing stability, which agrees with experiments. Cations influence protein stability less than anions but still substantially. Long decyl side chains, polar methoxy groups and guanidinium-based cations destabilize CAL-B more than short methyl groups, other non-polar groups and imidazolium-based cations, respectively. Two distinct causes for CAL-B destabilization are identified: a destabilization of the protein surface is facilitated mostly by strong Coulomb interactions of CAL-B with anions that exhibit a localized charge and strong polarization as well as with polar cation groups. Surface instability is characterized by an unraveling of α-helices and an increase of surface area, radius of gyration and protein-IL total interaction strength of CAL-B, all of which describe a destabilization of the folded protein state. On the other hand, a destabilization of the protein core is facilitated when direct core-IL interactions are feasible. This is the case when long alkyl chains are involved or when particularly hydrophobic ILs induce major conformational changes that enable ILs direct access to the protein core. This core instability is characterized by a disintegration of β-sheets, diffusion of ions into CAL-B and increasing protein-IL van der Waals interactions. This process describes a stabilization of the unfolded protein state. Both of these processes reduce the folding free energy and thus destabilize CAL-B. The results of this work clarify the impact of ions on CAL-B stabilization. An extrapolation of the observed trends enables proposing novel ILs in which protein stability could be enhanced further. This journal is © the Owner Societies 2011

Water-Free Rare Earth-Prussian Blue Type Analogues: Synthesis, Structure, Computational Analysis, and Magnetic Data of {Ln[superscript III](DMF)[subscript 6]Fe[superscript III](CN)[subcsript 6]}[subscript infinity] (Ln = Rare Earths Excluding Pm)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Duane C.; Liu, Shengming; Chen, Xuenian

2009-11-04

Water-free rare earth(III) hexacyanoferrate(III) complexes, {l_brace}Ln(DMF){sub 6}({mu}-CN){sub 2}Fe(CN){sub 4}{r_brace}{sub {infinity}} (DMF = N,N-dimethylformamide; Ln = Sm, 1; Eu, 2; Gd, 3; Tb, 4; Dy, 5; Ho, 6; Er, 7; Tm, 8; Yb, 9; Lu, 10; Y, 11; La, 12; Ce, 13; Pr, 14; Nd, 15), were synthesized in dry DMF through the metathesis reactions of [(18-crown-6)K]{sub 3}Fe(CN){sub 6} with LnX{sub 3}(DMF){sub n} (X = Cl or NO{sub 3}). Anhydrous DMF solutions of LnX{sub 3}(DMF){sub n} were prepared at room temperature from LnCl{sub 3} or LnX{sub 3} {center_dot} nH{sub 2}O under a dynamic vacuum. All compounds were characterized by IR, X-raymore » powder diffraction (except for 10), and single crystal X-ray diffraction (except for 2, 7, 10). Infrared spectra reveal that a monotonic, linear relationship exists between the ionic radius of the lanthanide and the {nu}{sub {mu}-CN} stretching frequency of 1-10, 12-15 while 11 deviates slightly from the ionic radius relationship. X-ray powder diffraction data are in agreement with powder patterns calculated from single crystal X-ray diffraction results, a useful alternative for bulk sample confirmation when elemental analysis data are difficult to obtain. Eight-coordinate Ln(III) metal centers are observed for all structures. trans-cyanide units of [Fe(CN){sub 6}]{sup 3-} formed isocyanide linkages to Ln(III) resulting in one-dimensional polymeric chains. Structures of compounds 1-9 and 11 are isomorphous, crystallizing in the space group C2/c. Structures of compounds 12-15 are also isomorphous, crystallizing in the space group P2/n. One unique polymeric chain exists in the structures of 1-9 and 11 while two unique polymeric chains exist in structures of 12-15. One of the polymeric chains of 12-15 is similar to that observed for 1-9, 11 while the other is more distorted and has a shorter Ln-Fe distance. Magnetic susceptibility measurements for compounds 3-6, 8, 11 were performed on polycrystalline samples of the compounds.« less

Non-ionic surfactant vesicles in pulmonary glucocorticoid delivery: characterization and interaction with human lung fibroblasts.

PubMed

Marianecci, Carlotta; Paolino, Donatella; Celia, Christian; Fresta, Massimo; Carafa, Maria; Alhaique, Franco

2010-10-01

Non-ionic surfactant vesicles (NSVs) were proposed for the pulmonary delivery of glucocorticoids such as beclomethasone dipropionate (BDP) for the treatment of inflammatory lung diseases, e.g. asthma, chronic obstructive pulmonary disease and various type of pulmonary fibrosis. The thin layer evaporation method followed by sonication was used to prepare small non-ionic surfactant vesicles containing beclomethasone dipropionate. Light scattering experiments showed that beclomethasone dipropionate-loaded non-ionic surfactant vesicles were larger than unloaded ones and showed a significant (P<0.001) decrease of the zeta potential. The morphological analysis, by freeze-fracture transmission electron microscopy, showed the maintenance of a vesicular structure in the presence of the drug. The colloidal and storage stability were evaluated by Turbiscan Lab Expert, which evidenced the good stability of BDP-loaded non-ionic surfactant vesicles, thus showing no significant variations of mean size and no colloidal phase segregation. Primary human lung fibroblast (HLF) cells were used for in vitro investigation of vesicle tolerability, carrier-cell interaction, intracellular drug uptake and drug-loaded vesicle anti-inflammatory activity. The investigated NSVs did not show a significant cytotoxic activity at all incubation times for concentrations ranging from 0.01 to 1 μM. Confocal laser scanning microscopy showed vesicular carrier localization at the level of the cytoplasm compartment, where the glucocorticoid receptor (target site) is localized. BDP-loaded non-ionic surfactant vesicles elicited a significant improvement of the HLF intracellular uptake of the drug with respect to the free drug solution, drug/surfactant mixtures and empty vesicles used as references. The treatment of HLF cells with BDP-loaded non-ionic surfactant vesicles determined a noticeable increase of the drug anti-inflammatory activity by reducing the secretion of both constitutive and interleukin-1β-stimulated nerve growth factor (as inflammatory index) of 68% and 85%, respectively. Obtained data indicate that the investigated NSVs represent a promising tool as a pulmonary drug delivery system. Copyright © 2010 Elsevier B.V. All rights reserved.

Variation in emulsion stabilization behavior of hybrid silicone polymers with change in molecular structure: Phase diagram study.

PubMed

Mehta, Somil C; Somasundaran, P; Kulkarni, Ravi

2009-05-15

Silicone oils are widely used in cosmetics and personal care applications to improve softness and condition skin and hair. Being insoluble in water and most hydrocarbons, a common mode of delivering them is in the form of emulsions. Currently most applications use polyoxyethylene (non-ionic) modified siloxanes as emulsifiers to stabilize silicone oil emulsions. However, ionically grafted silicone polymers have not received much attention. Ionic silicones have significantly different properties than the non-ionic counterpart. Thus considerable potential exists to formulate emulsions of silicones with different water/silicone oil ratios for novel applications. In order to understand the mechanisms underlying the effects of hydrophilic modifications on the ability of hybrid silicone polymers to stabilize various emulsions, this article focuses on the phase diagram studies for silicone emulsions. The emulsifying ability of functional silicones was seen to depend on a number of factors including hydrophilicity of the polymer, nature of the functional groups, the extent of modification, and the method of emulsification. It was observed that the region of stable emulsion in a phase diagram expanded with increase in shear rate. At a given shear rate, the region of stable emulsion and the nature of emulsion (water-in-oil or oil-in-water) was observed to depend on hydrophilic-hydrophobic balance of the hybrid silicone emulsifier. At a fixed amount of modification, the non-ionically modified silicone stabilized an oil-in-water emulsion, whereas the ionic silicones stabilized inverse water-in-oil emulsions. This was attributed to the greater hydrophilicity of the polyoxyethylene modified silicones than the ionic counterparts. In general, it is postulated that with progressive increase in hydrophilicity of hybrid silicone emulsifiers, their tendency to stabilize water-in-oil emulsion decreases with corresponding increase in oil-in-water emulsion. Further, this behavior is hypothesized to depend on the nature of modifying functional groups. Thus a hybrid silicone polymer can be tailored by selecting the nature and degree of hydrophilicity to obtain a desired silicone emulsion.