bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic and Biological Polymers in Deionized Solution. 3. Expansion of Water‐soluble Neutral Polymers and Polymers Having a Small Amount of Ionizable Groups
Authors: Okubo Tsuneo 
Published: March 2014

AbstractViscosities of water‐soluble neutral polymers and the polymers having a small amount of carboxylic acid groups are measured in deionized solution and in the presence of a small amount of sodium chloride. These experiments are made in order to examine whether the electrical double layers are formed or not around the linear‐type neutral polymers in the deionized solution. The neutral polymers examined are poly(vinylpyrrolidone)s (PVP) of molecular weights of 3.6 · 105, 4 · 104 and 1 · 104, poly(vinylalcohol) (PVA) of molecular weight of 8.8 · 104, poly(ethyleneglycol), hydroxypropyl cellulose, and poly(acrylamide) having no carboxylic acid groups. The reduced viscosities of PVP having the highest molecular weight (3.6 · 105) in the deionized solution are slightly higher than those in the presence of sodium chloride. This supports that the polymer chain is expanded slightly by the electrical double layers formed around the polymer. It is highly plausible that the ionization effect occurs by the adsorption of ionic species on the polymer. For PVP of molecular weight of 4 · 104 and PVA, viscosities in the deionized solutions are higher, but very slightly, than those in the presence of sodium chloride. The viscosities of other neutral polymers are quite independent of the ionic concentration. The deionized polymers of poly(acrylamide‐co‐acrylic acid), which have a small amount of ionizable groups, are unexpectedly highly stretched by the electrostatic intersegment repulsive interaction because of the very long Debye‐screening length.
NMR and NIR Studies of the Tautomerism of 5,10,15,20‐Tetraphenylporphyrin including Kinetic HH/HD/DD Isotope and Solid State Effects
Authors: Schlabach Martin , Wehrle Bernd , Rumpel Helmut , Braun Jürgen , Scherer Gerd , Limbach Hans‐Heinrich 
Published: March 2014

AbstractThe liquid and solid state tautomerism of 5,10,15,20‐tetraphenylporphyrin‐15N4 (meso‐tetraphenylporphyrin, TPP) has been studied by dynamic NMR spectroscopy and by NIR spectroscopy. The kinetic HH/HD/DD isotope effects on the liquid state tautomerism were reinvestigated in the temperature region between 200 K and 300 K. It was confirmed that the kinetic HH/HD isotope effects are large and the HD/DD isotope effects small. At 298 K the values 9.7 and 1.8 were obtained. The Arrhenius curve of the HH reaction is non‐linear indicating that the proton transfer takes place by thermally activated tunneling at low temperatures. The kinetic isotope effects are consistent with a stepwise proton transfer pathway involving intermediate tautomeric states in which protons are bound to adjacent nitrogen atoms. Solid state NMR experiments were performed on triclinic TPP, where the reaction barrier is higher compared to TPP in the liquid state. In addition, the degeneracy of the tautomerism in the solid state is lost due to intermolecular interactions. The latter conclusion is supported by the finding that for tetragonal mixed crystals of [(TPP—14N4—Ni)0.1(TPP—15N4—H2)0.9] the degeneracy of the tautomerism and its barrier is equal to the values found for the liquid solution. The NIR measurements show the presence of NH‐stretching overtones in the region of about 6450 cm−1. The anharmonicity of this vibration is of the usual order, which indicates that the reaction coordinate of proton transfer is not identical with the normal modes of the NH‐stretching vibrations, but rather a combination of various vibrational modes including the stretching, bending and skeletal modes. As a consequence, there will be a large number of vibrational states from which tunneling might occur.
Fullerene ions and their relation to PAH and soot in low‐pressure hydrocarbon flames
Authors: Baum Th. , Löffler S. , Löffler Ph. , Weilmünster P. , Homann K.‐H. 
Published: March 2014

AbstractPositive and negative fullerene ions from C32 to over C600 have been analysed in low‐pressure premixed flames of acetylene and benzene with oxygen. Mass spectra were taken through a molecular beam sampling system by a linear time‐of‐flight mass spectrometer (TOF‐MS) and a reflectron TOF‐MS. Fullerenes are mainly formed during the beginning of soot formation, and less in the oxidation zone or under nonsooting conditions in benzene flames. When soot is present, the whole spectrum of fullerene ions is formed, whereas in the oxidation zone mainly smaller fullerenes, preferentially C60, C70 and C50 occur. — Polycyclic aromatic hydrocarbons (PAH) are the precursors of fullerenes, both in the presence of soot and under homogeneous conditions. However, hydrogenated fractions of carbon cages as intermediates could not be detected. This is attributed to fast unimolecular reactions and to formation reactions of fullerenes in young soot particles. On account of correlations with concentration profiles of large PAH ions, on the one hand, and with the soot particle mass distributions, on the other, possible mechanisms of fullerene formation are discussed. Fullerenes do not grow further, as do the soot particles, but they are oxidized at high temperature. Thermal decomposition was not observed. From comparison of fullerene formation with the two fuels and under different burning conditions it is concluded that negative fullerene ions are formed by electron attachment to neutral fullerenes and that for positive fullerene ions there is hardly any ionisation equilibrium.
Kinetics and mechanism of formation of iron(ii) complex with 8‐hydroxy‐7‐(2‐thiazolyl)azo‐5‐quinolinesulfonic acid
Authors: Noritake Masaki , Jitsukawa Koichiro , Einaga Hisahiko 
Published: March 2014

AbstractThermodynamic stability and kinetics and mechanism of formation of iron(II) complex with 8‐hydroxy‐7‐(2‐thiazolyl)azo‐5‐quinoline‐sulfonic acid (THQS) have been studied spectrophotometrically in an aqueous 0.10 mol dm−3 sodium chloride solution at 25°C. The iron(II) complex with coordinated 8‐quinolinolato moiety of THQS forms with the stability constant (β11) of logβ11/mol−1 dm3 = 8.52 ± 0.20. This complex exhibits a metal‐to‐ligand charge‐transfer band in the visible region. Stopped‐flow kinetics revealed biphasic processes with a faster formation of the complex with coordinated 2‐thiazolylazophenolato moiety followed by a slower linkage isomerization of this intermediate to the final, more stable complex with coordinated 8‐quinolinolato moiety. The reaction pathways and concomitant rate constants are elucidated and determined; the reaction mechanism is discussed in detail.
Contact‐complex formation reaction between solvent molecules in square‐well fluids 2. Two‐ and three‐dimensional fluids
Authors: Yoshimura Y. 
Published: March 2014

AbstractThe contact‐complex formation reaction between solvent molecules in square‐well fluids is studied for the two‐ and three‐dimensional system. The effect of the third body at the second‐virial limit is expressed by the following three factors: (1) the excluded volume effect, (2) the desolvation effect, and (3) the „glue effect”︁, where this effect means that the third body behaves like a glue binding a pair of molecules. The density derivative of the equilibrium constant of the contact‐complex formation, at the second‐virial limit, goes through a minimum with increasing temperature in both the two‐ and three‐dimensional fluids, whereas it increases monotonically in the one‐dimensional fluid. However, a Monte Carlo simulation shows that the difference due to the dimensionality of the system is rapidly smeared out with increasing density. The equilibrium constants of the contact‐complex formation in the two‐ and three‐dimensional square‐well fluids have qualitatively the same temperature and density dependence as in the one‐dimensional fluid at densities about 0.5 times higher than their critical densities
The reduction of hypohalites at GaAs electrodes: Charge‐transfer and recombination processes
Authors: Minks B. P. , Kelly J. J. 
Published: March 2014

AbstractResults obtained from electrical impedance spectroscopy at n‐GaAs in the dark with Fe(CN)63‐, ClO− and BrO− in alkaline solution indicate that the cathodic reduction current is due mainly to electron‐hole recombination at the surface. The same conclusion also holds for the recombination of photo‐generated holes at illuminated n‐GaAs in indifferent electrolyte. Electroluminescence measurements showed that surface recombination with the hypohalites is more effective than with Fe(CN)63‐. Quantum efficiency measurements at p‐GaAs revealed that the second charge transfer step of the hypohalite reduction can involve either the capture of an electron by or the injection of a hole from a surface intermediate. This result leads to a slight revision of a mechanism previously proposed for the reduction of ClO− and BrO− at GaAs.
Interactions of different nonylphenolepolyethyleneglycoles (NPG) with iron electrodes
Authors: Fahr T. , Reinhard G. 
Published: March 2014

AbstractNonylphenolepolyethyleneglycoles (NPG) are characterized by means of electrochemical methods. We made electrochemical impedance spectroscopy and current density‐potential measurements at superpure iron electrodes in KNO3 solution with and without addition of NPG. In order to acquire some knowledge about the electrical potential‐distance profile at the electrode surface of iron, we made Zeta potential measurements at dispersed α‐Fe2O3 particles. Adsorption phenomena of NPG at electrode surfaces free of any oxide layer were studied by a.c. polarography (tensammetry) at the dropping mercury electrode. It is shown that NPG can inhibit the corrosion reaction of superpure iron in neutral solutions as combined anodic/cathodic inhibitors, but increase the cathodic process in weak acid solutions.
Static light scattering experiments with aqueous solutions of the nonionic tenside C12E5 with critical and non‐critical composition
Authors: Sinn C. , Woermann D. 
Published: March 2014

AbstractConcentration fluctuations with long range correlations as well as non‐critical background contributions determine the light scattering properties of C12E5/H2O mixtures of critical composition near the lower critical point (critical mass fraction yc = 0.0123; critical temperature Tc = 31.8°C). If the influence of the non‐critical contributions is neglected, an evaluation of the light scattering data in terms of the power laws ξ = ξo · ϵ‐ν and χT = χT,o · ϵ−γ (ξ being the correlation length of local concentration fluctuations and χT the generalized susceptibility; ϵ = (Tc−T)/Tc is the reduced temperature) leads to values of the critical exponents ν and γ which are closer to the mean field values (ν = 0.5; γ = 1) than to the values theoretically expected for binary liquid mixtures from the Landau‐Ginzburg‐Wilson model (ν = 0.63, γ = 1.24). If the background contributions are taken into account empirically by adding temperature independent background terms ξb and χT,b respectively to the simple power laws, the analysis of the light scattering data leads to values of ν ≈︁ 0.65 and γ ≈︁ 1.2, which are close to the values given by the Landau‐Ginzburg‐Wilson model. The background term ξb has a value of about ξb ≈︁ 6 nm and the critical amplitude ξo a value of about ξo ≈︁ 1.2 nm. This value for ξo is one order of magnitude larger than that found for simple binary liquid mixtures (O(ξo) ≈︁ 0.1 nm). — In mixtures of non‐critical composition (−0.79 < (y−yc)/yc < 0.63) the scattered intensity shows an angular dependence which is also a function of temperature corresponding to correlation lengths 20 nm < ξ < 206 nm for 0.5 K < (TP−T) < 7.0 K. They are assumed to reflect contributions of micelles which also contribute to the scattering of the mixture of critical composition away from the critical temperature.
Impedance measurements of amorphous AgIx · (Ag3PO4)1−x over a wide composition range
Authors: Gross S. , Freyland W. 
Published: March 2014

AbstractUsing a rapid quenching technique amorphous samples of AgIx(Ag3PO4)1−x have been obtained over a wide composition range up to x = 0.85. Above this composition the cooling rate of > 106 K s−1 was not sufficient to prevent partial crystallinity. All samples have been characterized both by X‐ray diffraction and impedance spectroscopy for temperatures near room temperature. From impedance measurements the dc‐conductivity σ has been determined which for amorphous materials varies from 7.6 · 10−5 ω−1 cm−1 (x = 0.5) to 4.4 · 10−2 ω−1 cm−1 (x = 0.85) at 298 K. A plot of log σ versus x yields a straight line which at x = 1 hits the value of the pure fast ionic conductor α‐AgI extrapolated to 298 K.
Bifurcations — a possibility to generalize the thermodynamic description of phase diagrams of two‐component fluids
Authors: Boshkov L. Z. 
Published: March 2014

AbstractA new thermodynamic formalism has been developed for the analysis of the phase behaviour of two‐component fluids. Azeotropy and critical pressure maxima or minima in binary fluids have been interpreted as bifurcations of two‐phase equilibria and critical points, respectively. The analogous approach has been applied to some boundary states: hypercritical and isolated critical points, critical pressure step‐points. The thermodynamic conditions of these states have been derived for the first time by a uniform way.
Temperature dependence of interfacial tension of 2‐butoxyethanol/water mixtures near the lower critical point
Authors: Kreuser H. , Knecht B. , Woermann D. 
Published: March 2014

AbstractThe pendant drop method and the capillary rise method are used to measure the interfacial tension σ of 2‐butoxyethanol (2‐C4E1)/water mixtures near the lower critical point (critical composition, mass fraction of 2‐C4E1, yc = 0.2945; critical temperature Tc(visual) = 49.41°C) as function of temperature (0.6 K ≤ (T  Tc) ≤ 18.0 K). It is found that at temperatures 0.6 K ≤ (T  Tc) ≤ 7.0 K the temperature dependence of σ is represented by a power law of the form σ = σ0ϵμ (≤ = (T  Tc(visual))/Tc) with μ = (1.26 ± 0.02) and σ0 = (8.8 ± 0.2) mN m−1. The value of μ is consistent with the theoretically expected universal value of μ = 1.26. The amplitude ratio Rσ,ζ+ = σ0(ξ0ζ+)2/kBTc calculated from the system specific values of the critical amplitude σ0 and the critical amplitude ξ0 of the correlation length of local concentration fluctuations (ξ0ζ+ = (0.44 ± 0.04) nm) leads to a value of Rσ,ξ+ = (0.383 ± 0.070). It is close to the median value of Rσ,ξ+ calculated for several one‐ and two‐component fluids from experimental data taken from the literature (Moldover, Phys. Rev. A 31, 1022 (1985); median value Rσ,ξ+ = 0.386). – The ratio of [νT/R̄(∂T/∂z)] (νT, thermophoretic velocity (Marangoni convection); (∂T/∂z, temperature gradient) for droplets of radius R̄ of a 2‐C4E1) rich phase suspended in its coexisting H2O rich phase is calculated from the data.Values of [νT/R̄(∂T/∂z)] refering conditions along the liquid/liquid coexistence curve are given.
A new approach to the determination of fluid phase Equilibria: Concentration measurements by Raman spectroscopy
Authors: Kaiser T. , Voßmerbäumer C. , Schweiger G. 
Published: March 2014

AbstractWe present a new in‐situ method for the measurement of fluid phase equilibria, which offers many advantages in contrast to conventional sample techniques. To the author's knowledge, this is the first time that the vapor‐liquid‐equilibrium of a binary system is determined by measuring the concentrations in the gaseous as well as in the liquid phase by Raman spectroscopy. The isothermal data for the system cyclohexane‐toluene are compared to literature data at a temperature of T = 50°C and correlated by van Laar's equation. In addition some new data for the system mentioned above are given at temperatures of T = 60°C and T = 70°C.
Dielectric relaxation of aqueous electrolyte solutions. I. Solvent relaxation of 1:2, 2:1, and 2:2 electrolyte solutions
Authors: Barthel J. , Hetzenauer H. , Buchner R. 
Published: March 2014

AbstractComplex permittivity measurements on aqueous solutions of CdCl2, CuCl2, MgSO4, CdSO4, Na2SO4, Cd(ClO4)2, and MgCl2in the frequency range from 0.9 to 90 GHz are reported. The data analysis reveals the superposition of 2 Debye dispersion steps for the solvent thus supporting multi‐step relaxation mechanisms discussed for water in the literature. An additional low frequency process is found for CdCl2, CuCl2, MgSO4, CdSO4, and Na2SO4solutions due to solute relaxation, but not for Cd(ClO4)2and MgCl2solutions. – The decrease of the static solvent permittivity at increasing electrolyte concentrations is interpreted in terms of irrotational bonding and kinetic depolarization and is used to determine effective solvation numbers. The dependence of the main (low frequency) relaxation time of water on electrolyte concentration is explained with the help of the reorientation and residence times of water in the hydration spheres of ions and in the bulk. The high frequency relaxation time is approximately concentration independent, whereas the dispersion amplitude of the process increases with electrolyte concentration.
Enhanced catalytic activity of metal salts of metal phthalocyanine tetracarboxylic acids in the autoxidation of thiophenol in hexane
Authors: Kusuda Kousuke , Kanda Taiji , Tanisaka Keizo 
Published: March 2014

AbstractCatalytic activities of metal (Fe3+, Co2+, Ni2+ and Cu2+ salts of metal (FeCl2+, Co2+, Ni2+ and Cu2+)) phthalocyanine tetracarboxylic acids dispersed on a carrier in the autoxidation of thiophenol have been investigated. Absorptions of O2 in the presence of the catalysts were measured. P values (percentages of the absorbed O2 after 30 min. per theoretical volume) and T values (absorbed O2 mol s−1 (cat. mol)−1/substrate mol l−1) at the original point were adopted to evaluate the catalytic activities. Fe3+ salt of cobalt phthalocyanine tetracarboxylic acid showed the highest activity. The mechanism of the activity was investigated electrochemically by using carbon paste electrodes containing the catalyst.
The crystal and molecular structure of 3‐aminophthalhydrazide (Luminol)
Authors: Paradies Henrich H. 
Published: March 2014

AbstractThe crystal structure of 2‐aminophthalhydrazide (luminol) has been determined by X‐ray diffraction analysis. The space group determined was P&1macr; (No. 2) with cell constants of a = 12.714 Å, b = 14.132 Å. c = 7.1027 (Å), α = 101.24°, β = 94.84° and γ = 116.60° with six molecules per unit cell of formula molecular weight 177.16. The three luminol molecules form a hydrogen bonded trimeric unit. There is one intramolecular hydrogen bond per luminol molecule involving the NH2 group and the adjacent carbonyl group. All other hydrogen bonds are intermolecular. – Luminol crystallizes as amide‐hydroxyimunol tautomer. The protonated carbonyl group acts as hydrogen bond donor to a neightbouring unprotonated carbonyl group.
Generation of SnO by photoproduction and ‐mobilization of oxygen atoms in krypton matrices doped with N2O and Sn
Authors: Schriever U. , Hebert T. , Kolb D. M. 
Published: March 2014

AbstractSnO molecules are photochemically formed by irradiation of a Sn: N2O mixture in solid krypton. A KrxO complex which is produced by VUV photolysis of N2O at 8.8 eV has been identified from a new absorption band at 6.9 eV. The mobilization of oxygen in Sn:N2O:Kr matrices, photoinduced by excitation of the KrxO species, was studied by trapping the oxygen at Sn atoms and by using the SnO generation as a monitor. Photolysis studies in Sn:N2O:Kr matrices as well as in Sn:Kr/N2O:Kr sandwich structures revealed an extraordinary high mobility of oxygen. A qualitative model of the mobilization scheme is discussed.
Investigations of the reaction between CH2(X̃3B1) and O2 in the temperature range 233 K ≤ T ≤ 433 K
Authors: Bley U. , Temps F. , Wagner H. Gg. , Wolf M. 
Published: March 2014

AbstractThe reaction between CH2(X̃T3B1) radicals (3CH2) and O23CH2+O2→products,has been studied in a discharge flow reactor with Laser Magnetic Resonance (LMR) detection of 3CH2 and OH radicals and Electron Spin Resonance detection of O and H atoms. From the measured concentration‐versus‐time profiles of [3CH2] in the absence and presence of a large excess of O2 the overall rate coefficient of the reaction was found to bemagnified imageIn the temperature range 233 K ≤ T ≤ 433 K. A limit for the contribution of H atom forming reaction channels of <20% was determined. The results are discussed in relation to available literature data on the formation of stable products. Main reaction channels leading directly to production of CO + H2O and H2 + CO2 are concluded to be of importance.
Investigation of the 3CH2 + O2 reaction in shock waves
Authors: Dombrowsky Ch. , Wagner H. Gg. 
Published: March 2014

AbstractThe reaction of 3CH2 with O2 was investigated in incident shock waves for pressures near 1 bar and temperatures from 1000 to about 1800 K. 3CH2 source was diazomethane. The concentration time curves of CO and CO2 were obtained from infrared emission, the OH profiles by laser absorption measurements. Data for O and H atom formation in this reaction were reported recently. – The measurements show that about a quarter of the reaction proceeds by forming radicals directly. Three quarters of the reaction form stable products only. Main reaction product is CO with a CO to CO2 ratio near 4:1. Direct formation of OH does not exceed a few percent. A reaction channel distribution is given. – Rate constants for the total reaction 3CH2 + O2 obtained by computer simulation of the product profiles in the temperature range mentioned are below the data extrapolated from measurements performed by Vinckier et al. and Bley et al. in the temperature range around room temperature. A rate expression fitting the measured date over the whole temperature range is reported.
Electronics of Colloidal Nanometer Particles
Authors: Henglein Arnim 
Published: March 2014

AbstractSmall colloidal particles *) and clusters *) of semiconductors and metals exhibit unusual properties and may be considered as a new physico‐chemical dimension between the molecules and the bulk materials. The surface to volume ratio is extremely large; small‐particle research therefore constitutes a combination of solid state and surface science. The electronic properties of the particles (light absorption, colour, fluorescence, catalytic and photocatalytic activity, electrochemistry etc.) depend on particle size. Chemical surface modification affects these properties and allows one to prepare new nano‐structures in solution, in layers, and in the crystalline state. No attempt is made in the present article to review the whole field, but to describe this new branch of colloid chemistry by focussing on a few selected topics.
Internal Solid State Reaction: Formation of Perovskite in NiO‐Matrix
Authors: Schmalzried H. , Frick T. 
Published: March 2014

AbstractIsothermal internal reactions of the type A + B = AB taking place in a crystal matrix C are studied experimentally. The matrix crystal C is NiO, A = CaO, B = TiO2 (NiTiO3) and the reaction product AB is the perovskite CaTiO3. Both the morphology of the reaction product and the kinetics of its formation have been investigated and are discussed in the light of a previous theoretical study. In addition, chemical diffusivities of Ca‐ and Ti‐ions in the NiO‐matrix are determined.