bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Electric Polarization of Molecules
Authors: Borovikov Yu. Ya. , Makovetskii V. P. , Pivovarova N. S. 
Published: July 2012

AbstractThe problem of molecular thermal (Pq) polarization estimation in the substances with different forms of aggregation and using different experimental techniques is discussed. It is shown on the base of numerous experimental data analysis that Pq includes both rotational (Prot) and orientational (Por) components, which may be commensurable in magnitude in gases and gasiform condensed media. The principle of equal distribution of molecules' thermal polarization over their kinetic degrees of freedom is being satisfied, so Prot term should not be neglected. The neglect of this fact on estimation of the molecular dipole moments using the first method of Debye results in √(5/3) or √(4/3) times overestimated dipole moment values.
Photochemical Formation of Colloidal Gold Particles in Chitosan Films
Authors: Yonezawa Y. , Kawabata I. , Sato T. 
Published: July 2012

AbstractThin films of chloroauric acid salt of chitosan (CTOAu films) were photolyzed with 253.7 nm light. On irradiating with UV light in air at room temperature, the CTOAu film first became yellow‐blue colored due to the formation of colloidal gold. When irradiation was continued, the irradiated surface of the film finally changed into clear gold mirror. Primary photochemical products are assumed to be gold atom, quaternary ammonium chloride of chitosan and chlorine. With aids of UV‐visible absorption spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy, aggregation of small gold particles to form colloidal gold and gold metal film has been investigated. It has been found that the aggregation state of small gold particles is controlled by reaction conditions; temperature, evacuation, the amount of chloroauric acid. When the CTOAu film was photolyzed in vacuum at room temperature, the gold particulate film was formed. Irradiation at liquid nitrogen temperature resulted in absorption spectrum characterized by the structureless absorption extending from λ = 400 nm to shorter wavelength. However, an introduction of air after photolysis brought about the development of the broad colloidal absorption band.
Tracking Unstable Periodic Orbits in a Model for Electrochemical Corrosion
Authors: Parmananda P. 
Published: July 2012

AbstractWe continuously track the unstable period one orbit through various bifurcations in a numerical model for electrochemical corrosion. The tracking strategy used is a combination of a continuation method and the map‐based control strategy (SPF) [1, 2] to stabilise periodic orbits in deterministic chaotic systems. After achieving control on the unstable periodic orbit using the control strategy (SPF), we use a continuation method to maintain control on the orbit as one of the system parameters is allowed to drift. This allows us to track the stabilised orbit over long ranges of parameters and through various bifurcations. Tracking could prove to be advantageous in controlling the dynamical behavior of experimental situations where the system response drifts with time
Topologically disordered hubbard models and the electronic structure of expanded Cs: A numerical study
Authors: Koslowski Thorsten , Rowan David G. , Logan David E. 
Published: July 2012

AbstractWe present a numerical study of the electronic properties of simple models of expanded alkali metals. An Anderson‐Hubbard model incorporating on‐site electron‐electron repulsion and liquid‐like disorder is solved within the unrestricted Hartree‐Fock approximation. We focus on the proper determination of the localization properties deciding the metallic or nonmetallic character of the model and on the computation of the electrical conductivity within the random phase model.With a realistic set of parameters we obtain good quantitative agreement with experiments on expanded Cs for i) the density at which the metal‐nonmetal transition occurs and ii) the electrical conductivity throughout the entire density interval accessible by experiments. The transport properties thus computed give additional support to recent claims that the description of liquid expanded metals requires the incorporation of both disorder and interaction effects.
Phenomenological Description for a Formation of Cylindrolites in Co‐Operative and Dynamic 2D‐(Bio)Polymeric Systems
Authors: Gadomski Adam 
Published: July 2012

AbstractA phenomenological description for the formation of cylindrolites in cooperative 2d‐(bio)polymeric systems in terms of the modified normal grain growth concept and stretched exponential kinetics in a linear regime is offered. As the principal result, a linear dependence of the cylindrolite radius as a function of time has been obtained which is in excellent accord with experimental data reported.
The Film Formation in Electrode Processes at the Electrode/Electrolyte Interface
Authors: Ivanov S. V. , Ivanova N. D. 
Published: July 2012

AbstractThe formation of a film at the electrode in aqueous electrolytes with organic ligands is shown. This film is presumed to be an intermediate product in the overall mechanism of the reduction or oxidation of metal ions. It consists of oxide‐hydroxide compounds with mixed conductivity as it takes place in electrolyte with inorganic ligand.
Phasendiagramm mit S‐förmigen Labilgrenzen
Authors: Bärner K. , Zavadskii E. A. 
Published: July 2012

AbstractMetastable regions which are bounded by S‐shaped lability lines can become infinitely large at temperatures which are significantly lower than a chosen critical point temperature. Such a behaviour is found in at first sight totally different systems: CoSiF6 (6H2O), MnAs0.96P0.04, β‐(ET)2I3, and is explained in the framework of the Landau‐theory.
The Effect of Temperature on the Adsorption of Dodecane onto Nonionic and Ionic Surfactant Monolayers at the Air‐Water Surface
Authors: Aveyard R. , Binks B. P. , Fletcher P. D. I. , Macnab J. R. 
Published: July 2012

AbstractWe have measured the adsorption isotherms for dodecane adsorption at the solution‐vapour surface for surfactant monolayer covered aqueous surfactant solutions at concentrations in excess of their critical micelle concentration (cmc) values. The temperature dependence of the adsorption have been determined for both a nonionic surfactant (H(CH2)12(OCH2CH2)5OH, abbreviated to C12E5) and an ionic surfactant (n‐dodecyltrimethyl‐ammonium bromide, abbreviated to DoTAB). For the nonionic surfactant, dodecane adsorption decreases with increasing temperature at low surface concentration of the oil whereas it increases at high surface concentrations. With the ionic surfactant DoTAB, the temperature effect shows a similar crossover in behaviour but the changes in adsorption are opposite in direction to those seen for the nonionic surfactant. The adsorption data are correlated to the effects of temperature on the microemulsion phase behaviour of ionic and nonionic surfactants and discussed in relation to the microstructures of the mixed oil/surfactant films as determined by neutron reflection methods.
Shape Similarities of Ultra‐Low Interfacial Tension Curves in Ternary Microemulsion Systems of the Water‐Alkane‐CiEj Type
Authors: Sottmann T. , Strey R. 
Published: July 2012

AbstractThe interfacial tensions between water‐ and oil‐rich phases in microemulsion systems have been measured for a series of ternary water‐alkane‐CiEj systems. It is found that interfacial tensions vary over orders of magnitude with temperature displaying a pronounced minimum for each surfactant. The center of the three‐phase temperature interval, Tu‐T1, i.e. the phase inversion temperature (PIT), corresponds to the temperature Tm of the minimum in interfacial tension. Increasing the surfactant chain length the minimum value decreases by 3 orders of magnitude for a change of i from 6 to 12. Interestingly, all interfacial tension curves have a similar shape. Centering the curves around Tm and reducing the temperature scale by Tu‐T1 permits determining the factors, by which the individual interfacial tension curves differ. The factors are found to be proportional, respectively, to square of the maximum length scale ζ or the inverse surfactant volume fraction Φc,i in the interface. Accordingly, plotting σab/Φc, j2 vs. 2(T‐Tm)/(Tu‐T1) an almost perfect superposition of all interfacial tension curves is observed.
Calculation of the Rigidity Constant in a Landau Model for Microemulsions
Authors: Blokhuis Edgar M. 
Published: July 2012

AbstractA theoretical investigation into the validity of different mean‐field formulas for the rigidity constant of a microemulsion system is presented. As a theoretical model for the microemulsion system we use a Landau‐theory‐like expression for the free‐energy in which, besides the usual gradient of the density squared term, a term proportional to the square of the second derivative is present, while the coefficient of the squared gradient term is taken to be negative in the microemulsion phase. Gompper and Zschocke (Phys. Rev. A 46, 4386 (1992)) used this model and derived mean‐field expressions for the surface tension, spontaneous curvature and rigidity constants. The formula for the rigidity constant of bending features the curvature dependent density profile. It was observed that approximating the curvature dependent density profile with the density profile of the planar interface, yields approximate values for the rigidity constant which are in good agreement with a numerical calculation of the free energy of the curved surface. This is somewhat surprising since the same approximation for the rigidity constant of a simple liquid‐vapour interface was shown to be incorrect. In this paper we investigate the differences and similarities between the two systems by calculating the approximate and exact values of the rigidity constant. We investigate when the approximate value of the rigidity constant is a good approximation to the exact one.
Transmission Electron Microscopy of Complex Fluids: The State of the Art
Authors: Talmon Y. 
Published: July 2012

AbstractTransmission electron microscopy (TEM) is potentially one of the most useful techniques in the study of micro‐structured fluid systems. It is the one technique that provides high resolution direct images, thus the interpretation of the data is not model‐dependent. But at the same time electron microscopy is probably the most abused experimental technique, and as such, a rather problematic one. People have taken liberties with the technique as with no other. In a critical review of the field, the inherent limitations on TEM of liquid systems are described, together with the technical solutions that have been developed to overcome them. Sample results of recent data that illustrate the potential of the techniques, as well as novel technical extensions of the basic technique are described. Also, artifacts, the result of improper specimen preparation, are demonstrated.
Microemulsions: A Medium for Polymerization Reactions
Authors: Lusvardi K. M. , Schubert K.‐V. , Kaler E. W. 
Published: July 2012

AbstractAqueous and nonaqueous microemulsions containing either of the monomers styrene or hexyl methacrylate polymerize when initiated with potassium persulfate. Reactions in both types of microemulsions lead to stable, bluish dispersions of latex particles with diameters ranging from 40 to 90 nm. By substituting formamide for water, one can investigate the effect of the monomer solubility in the continuous domain on the microemulsion polymerization mechanism in a way independent of the monomer type. When the monomer solubility in the polar domain is high, the latex particles are larger and have a larger number of polymer chains than when the monomer solubility is low. If the monomer solubility in the continuous domain is greater than the overall monomer concentration in the microemulsion, the reaction mechanism shifts from that of a microemulsion polymerization to one of a solution polymerization in the presence of empty micelles.
Nonfaradaic Two‐Dimensional Phase Transition on Smooth Surfaces ‐ An Example for Time‐Dependent Homogeneous Nucleation
Authors: Donner C. , Baumgärtel H. , Pohlmann L. , Retter U. , Philipp R. 
Published: July 2012

AbstractTwo dimensional film formation on smooth surfaces has been investigated theoretically. The commonly used exponential law for nucleation and its limiting cases in connection with the Avrami theorem are examined critically.A new model for describing nucleation on surfaces on the basis of the classical nucleation theory is proposed. This model takes into account the time‐dependent supersaturation caused by the simultaneous processes of adsorption of molecules from the bulk to the surface and the real phase transition. The model was proofed experimentally by the investigation of condensation of 5‐bromocytosine on mercury electrodes in aqueous Na2SO4‐electrolyte solution. On the basis of the new model the experimental results can be for the first time explained consistently.
Electron‐Deficient Palladium Clusters in Zeolites and Their Complexes with Probe CO Molecules. A Density Functional Model Cluster Study
Authors: Yakovlev Alexey L. , Zhidomirov Georgy M. , Neyman Konstantin M. , Nasluzov Vladimir A. , Rösch Notker 
Published: July 2012

AbstractTetrahedral and octahedral palladium clusters with an entrapped proton, [Pd4H]+ and [Pd6H]+, were considered as models of electron‐deficient palladium species encaged in a zeolite matrix. Density functional studies employing a gradient‐corrected exchange‐correlation potential have been carried out on the bare and protonated Pd4 and Pd6 clusters as well as on their complexes with a CO molecule adsorbed at the three‐fold hollow position. In line with the experimental data it is found that the protonation of palladium clusters leads to a reduced CO adsorption energy and an increased vibrational frequency of the adsorbed CO. The protonation energies of the clusters Pd4 and Pd6 were calculated to 9.4 eV and 9.9 eV, respectively. These large values are comparable to the proton affinity of such a strong base as NH3 (calc. 9.2 eV) and support the hypothesis that, as a result of the interaction of the guest metal particles with zeolitic protons, electron‐deficient [PdnHx]x+ species are formed.
Thermodynamic Activities in the Alloys of the Ti‐Al System
Authors: Eckert M. , Bencze L. , Kath D. , Nickel H. , Hilpert K. 
Published: July 2012

AbstractThe vaporization of the solid alloys of the Ti‐Al system has been extensively studied for the complete composition range of the system by using Knudsen effusion mass spectrometry at temperatures between 1113 and 1664 K. 19 alloy samples of different compositions covering the complete composition range were investigated and their Ti and Al partial pressures determined. Thermodynamic activities and chemical potentials of Ti and Al as well as Gibbs energies were evaluated for a temperature of 1473 K. Two independent methods were used for the determination of the Ti activities yielding consistent results. The large temperature range of the partial pressure measurement for three alloys in the homogeneity range of the TiAl phase rendered possible the determination of partial and integral thermodynamic functions (ΔH, ΔG) for the formation of this phase. The data obtained are discussed.
Phase Transitions and Ionic Motions in Solid Trimethylethylammonium Iodide Studied by 1H and 127I NMR, Electrical Conductivity, X‐ray Diffraction, and Thermal Analysis
Authors: Ishida Hiroyuki , Furukawa Yoshihiro , Kashino Setsuo , Sato Setsuko , Ikeda Ryuichi 
Published: July 2012

Abstract1H and 127I NMR, differential thermal analysis (DTA), differential scanning calorimetry (DSC), electrical conductivity, and powder and single crystal X‐ray diffractions were studied for trimethylethylammonium iodide. Three solid phases, named I, II, and III, were obtained above 410 K, between 336 and 410 K, and below 336 K, respectively. Powder X‐ray patterns showed that Phase I and II have a NaCl‐type cubic structure (a = 10.00(1) Å, Z = 4) and a tetragonal structure (a = 8.430(5), c = 6.216(4) Å, Z = 2), respectively. The structure of Phase III was determined to be orthorhombic (Pnam (#62), a = 11.294(4), b = 10.729(2), c = 7.158(6) Å, Z = 4) by single crystal X‐ray diffraction. In Phase III, the C3 reorientation of CH3 groups and the C3 reorientation of the whole (CH3)3N group in the cation were observed by 1H NMR. In Phase II, the cation is expected to perform the quasi‐isotropic reorientation. In Phase I, the cation was found to carry out the isotropic reorientation, while the spherical anion the translational self‐diffusion, as evidenced by 1H and 127I NMR, and electrical conductivity. Phase II and I are, therefore, dynamically disordered phases; especially, Phase I is highly disordered. From the dynamical behaviour of the cation and anion, and thermal properties, Phase I can be classified into an ionic plastic phase with a NaCl‐type structure.
Gaseous Diffusion Coefficients of ZnSe in Argon and Helium at 1140–1280 K and 70–100 mbar
Authors: Schönherr E. , Freiberg M. , Hartmann H. 
Published: July 2012

AbstractThe diffusion of subliming ZnSe in argon and helium gas has been investigated by a modified entrainment method with a flowing gas at a reduced pressure between 70 and 100 mbar. From the weight loss measurements an effective diffusion coefficient results for the (Zn+0.5 Se2, Ar) system as 0.0828 (T/273)1.47 cm2/s and for the (Zn+0.5 Se2, He) system as 0.177 (T/273)1.88 cm2/s between 1140 and 1280 K. With a simplified gas collision theory, rigid sphere diameters are estimated as 4.11×10−8 cm for Zn and 5.97 × 10−8 cm for Se2.
A Gaskinetic Investigation of HOBr Reactions with CI(2P), O(3P) and OH(2II). The Reaction of BrCl with OH(2II)
Authors: Kukui A. , Kirchner U. , Benter Th. , Schindler R. N. 
Published: July 2012

AbstractThe reactions of HOBr with atomic chlorine (1), with oxygen (2) and with hydroxyl radicals (3) have been investigated at 300 K using the discharge flow technique with mass‐spectrometric detection. The rate constants based on HOBr consumption have been determined to be k1 = (8.0±0.4)·10−11 and k2 = (3.1±0.2)·10−11. For the reaction with OH radicals k3<5×10−13 was obtained. All rate constants are given in units cm3 molecule−1 s−1.The reactions of HOBr with Cl and with O are shown to proceed via bromine abstraction with formation of BrCl and BrO, respectively. The predominant channel in the reaction of OH with BrCl was identified to be step (4a) OH+BrCl → HOBr+Cl	(4a) Based on the present kinetic investigation the heat of formation for HOBr at T = 300 K was evaluated to be ΔH0f (HOBr) = −(60.22±2) kJ · mol−1.
Reaction of NO3 Radicals with 1,3‐Cyclohexadiene, α‐Terpinene, and α‐Phellandrene: Kinetics and Products
Authors: Berndt T. , Böge O. , Kind I. , Rolle W. 
Published: July 2012

AbstractThe gas‐phase reaction of NO3 radicals with 1,3‐cyclohexadiene, α‐terpinene, and α‐phellandrene has been studied in a flow system at 298 K in the pressure range 8<P(mbar)<250 using GC‐MS/FID, MS, and long‐path FT‐IR as detection techniques. At a total pressure of 15 mbar N2 rate constants for the primary attack of NO3 were determined with the relative rate method to be (1.08±0.02) 10−11, (1.03±0.06) 10−10, and (5.98±0.20) 10−11, respectively (unit: cm3 molecule−1 s−1).As buffer gas in the product studies served N2 or He as well as O2/N2 mixtures. In the case of 1,3‐cyclohexadiene the formation of the corresponding oxirane (7‐oxa‐bicyclo[4.1.0]hept‐2‐ene) up to a yield of 90% at P<35 mbar and the formation of benzene (about 6%) was observed. The oxirane yield was independent on the amount of added O2 and decreased with increasing total pressure. In the case of α‐terpinene and α‐phellandrene no indication of oxirane formation was found. However, the corresponding aromatic compound (p‐cymene) was detected for both terpenes, maximum yield 6% for α‐terpinene and 22% for α‐phellandrene. For all reaction systems investigated the formation of organic nitrate‐compounds was proved by means of long‐path FT‐IR measurements. In the case of the 1,3‐cyclohexadiene degradation with [O2]>5·1015 molecule cm−3 an absorption band was detected in addition assigned to a carbonylic group. There were no indications for a reaction of O2 with the adduct radical (NO3/diene).
Liquid‐Liquid Extraction of Rare Earth Metals Using 25,27‐Dicarboxy‐26,28‐Dimethoxy‐5,11,17,23‐Tetra‐tert‐Butylcalix[4]Arene
Authors: Soedarsono J. , Hagège A. , Burgard M. , Asfari Z. , Vicens J. 
Published: July 2012

AbstractThe extraction of lanthane, erbium and yttrium by dicarboxy‐dimethoxy‐calix[4]arene in 1,2‐dichloroethane has been studied. Rare earth metal extraction has been shown to be accompanied by an important co‐extraction of alkali ions. The extraction takes place via the formation of a mixed complex L2(RE)M, where L is the ligand, RE a rare earth metal and M an alkali ion. The stoichiometry of the extracted species has been confirmed by mass spectrometry. A poor selectivity is observed.
Mixed‐Mode Oscillations in the Peroxodisulfate Reduction on Platinum and Gold Rotating Disk Electrodes
Authors: Koper Marc T. M. 
Published: July 2012

AbstractIt is shown experimentally that mixed‐mode oscillations may be observed in the peroxodisulfate reduction on platinum and gold rotating disk electrodes, in addition to previously reported monoperiodic (relaxation) oscillations. If account is made for the internal drift of the system, the typical features of the mixed‐mode oscillations are in good agreement with the predictions of a model which combines the negative faradaic impedance characteristics with a treatment of the mass transport that goes beyond the stationary diffusion layer approximation. Although the actual observation of mixed‐mode oscillations requires a pretreatment procedure the precise effect of which is poorly understood, these results may be interpreted as evidence for the importance of slow mass transport in the explanation of multiperiodic and chaotic electrochemical oscillations.
Rate and Mechanism of the Atmospheric Degradation of 1,1,1,2‐Tetrafluoroethane (HFC‐134a)
Authors: Bednarek G. , Breil M. , Hoffmann A. , Kohlmann J. P. , Mörs V. , Zellner R. 
Published: July 2012

AbstractThe atmospheric chemical behaviour of 1,1,1,2‐tetrafluoroethane (CF3CFH2, HFC‐134a) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of (1 a) CF3CFH2 + OH→CF3CFH + H2O has been determined in direct time‐resolved experiments using laser‐pulse initiation and laser long‐path absorption. A value of k1a = (4.6±0.5)×10−15 cm3/s at T = 295K has been found. The ratio of the rate coefficients for the reactions of the CF3CFHO‐radical with O2, (4) CF3CFHO + O2→CF3CFO + HO2, and C‐C bond fission, (5) CF3CFHO + M→CFHO + CF3 + M, for T = 295 K and ptotal = 50 mbar (O2) has been obtained to be k4/(k5 [M]) = 1.5×10−19 cm3, with the individual values being k4 = 2.7×10−15 cm3/s and k5 [M] = 1.8×104 s−1. The mechanism of the atmospheric degradation of HFC‐134a has been investigated in the temperature range 244‐295 K and ptotal = 1000 mbar using UV photolysis/FTIR product studies. From these experiments the Arrhenius expression k4/(k5 [M]) = 8.7±10−25 exp ((3240+990−610) K/T) cm3 was determined. Moreover, it is concluded that the major carbonyl products are CF3CFO, CFHO and CF2O which result from the two possible reactions of the oxy radical CF3CFHO. As a consequence the yield of these carbonyl products is dependent on temperature, O2 partial pressure and total pressure. For the reaction of CFHO with Cl atoms the Arrhenius expression k18 = 5.7×10−14exp (−(1130 ± 160) K/T) cm3/s was determined in the temperature range 244‐298 K.