bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osmotic Pressure of Aqueous Rod‐Like Polyelectrolyte Solutions with Mono‐ and Di‐valent Counterions
Authors: Bordi F. , Cametti C. , Di Biasio A. 
Published: March 2014

AbstractMembrane osmometry has been used to measure the Donnan osmotic pressure of different salts of carboxymethylcellulose (Na+‐ Li+‐ NH4‐ Ca++‐ Mg++‐CMC) in aqueous solutions of simple chloride electrolytes. The results are analyzed in terms of cylindrical cell model for linear polyelectrolyte solutions, using the Poisson‐Boltzmann equation in order to calculate the counterion densities at the cell boundaries. Significant deviations with increasing polyion concentration have been found for all the counterions investigated.
Thermodynamics and Solubility of Oxygen in Liquid Bismuth‐lead and Bismuth‐antimony Alloys
Authors: Anik Sabri , Frohberg Martin G. 
Published: March 2014

AbstractBy means of emf technique the oxygen activities in the systems bismuth‐oxygen‐lead and bismuth‐oxygen‐antimony were measured at 1173 K. From the results and with the help of quenching experiments the unknown phase boundaries in the isothermal sections could be fixed. The miscibility gaps of the limiting binary systems extend far into the ternary systems. Isoactivity lines of oxygen in the homogeneous melts and conodes in the miscibility gaps were determined. The evaluation of the experimental data leads to important thermodynamic values as activity coefficients, interaction parameters and free enthalpies of oxygen in the liquid alloys bismuth‐lead and bismuth‐antimony.
A Proton NMR Study of the Deuterium‐Protium Fractionation in Aqueous Solutions of Some Organic Ions
Authors: El Seoud Omar A. , Kiyan Nilo Z. , Vieira Paulo C. 
Published: March 2014

AbstractThe dependence of the proton chemical shift of water on the concentration of sodium methane sulphonate, tetramethylammonium bromide, and tetrabutylammonium bromide was measured in water and in water‐D2O mixtures. Chemical shift data were used to calculate the fractionation factors (ø) for the methane sulphonate anion, the tetramethylammonium‐, and the tetrabutylammonium cation. In agreement with the results of other studies the obtained fractionation factors (0.97 ± 0.03, 1.0 ± 0.05, 1.06 ± 0.05 for the above mentioned ions, respectively) indicate that the methane sulphonate anion decreases the structure of water (relative to that of bulk water) whereas the tetrabutylammonium cation is clearly a structure maker. The effect of the tetramethylammonium ion appears to be negligible.
Light‐Induced Hole Transfer Across a Langmuir‐Blodgett Double‐Layer Membrane with a Short Tunneling Barrier
Authors: Willig F. , Eichberger R. , Bitterling K. , Durfee W. S. , Storck W. , van Der Auweraer M. 
Published: March 2014

AbstractLight‐induced hole transfer across a membrane has been investigated with time resolved methods. The membrane has been assembled with the Langmuir‐Blodgett technique from two monolayers, one containing a modified dye, N,N'‐distearyl‐2,2'‐phenylindolocarbocyanine, and the other a modified anthracene molecule, 7‐(2‐anthryl)‐1 heptanoic acid. An anthracene single crystal has been employed as electrode to measure injection of holes from the above membrane as time‐resolved photocurrent transient with 100ps time resolution. The fluorescence decay of the excited dye layer was measured with 10ps time resolution. Comparison of both signals shows that the reaction sequence involves energy migration to dye aggregates and from there hole transfer through a short alkane chain tunneling barrier to the anthracene monolayer.
The Low‐Temperature Phase of the Organic Conductor (Fluoranthene)2PF6
Authors: Dormann Elmar , Sachs Günter 
Published: March 2014

AbstractPossessing single crystals of sufficient size and quality, we reconciled the informations available from the electrical conductivity and the magnetic susceptibility with the results of different magnetic resonance techniques for the low‐temperature phase of the organic conductor (FA)2PF6. The influence of localized paramagnetic defects and a bottleneck situation for the defect‐spin relaxation via the conduction electrons are crucial ingredients for an understanding of the ESR properties of this and related radical‐cation salts of arenes. We conclude from our analysis, that it is a decisive advantage for a “model system” of organic conductors, if it has a low‐temperature semiconductor phase that enables one to “switch off” the influence of the conduction electrons.
Electrochemically Prepared Radical Salts of BEDT‐TTF: Molecular Metals and Superconductors
Authors: Schweitzer D. , Gogu E. , Hennig I. , Klutz T. , Keller H. J. 
Published: March 2014

AbstractThe structural, electronic and superconducting properties of several electrochemically prepared BEDT—TTF radical salts are discussed.
Electronic Excitations in (BEDT‐TTF)‐Salts
Authors: Helberg H. W. 
Published: March 2014

AbstractThe indicatrix orientation, the birefringence, and the transmission spectra were measured in small crystals of the organic conductors α‐(BEDT‐TTF)2I3 and α‐(BEDT‐TTF)3(NO3)2 in the near infrared (NIR) and the visible (VIS) spectral range. The results are discussed with regard to the orientation of the BEDT‐TTF molecule axes and the arrangement of the intermolecular contact directions. — The principal polarizabilities are calculated by composing the polarizabilities along the BEDT‐TTF molecule axes and along the several contact directions. At high energies (Δ2 eV) in the VIS the orientation of the polarizability tensor is governed by the orientation of the stack forming molecules due to the intramolecular excitations. In the NIR the intermolecular excitations become dominant. — The transmission spectra are compared with calculations of the dipole interactions.
Ferroelectric Liquid Crystals – Properties of the Smectic C Phase and the Smectic A Phase of Compounds with High Spontaneous Polarization
Authors: Bahr Ch. , Heppke G. 
Published: March 2014

AbstractA short introduction to the properties of ferroelectric liquid crystals is given. Some new results concerning the coupling between the tilt angle and the polarization are presented for the SmC‐ and the SmA‐phase of a compound exhibiting very high values of the spontaneous polarization. A submicrosecond electrooptical effect in the SmA‐phase of this material is demonstrated.
Classification of Higher Excited States in (4N + 2)‐Annulenes and Related π‐Electron Systems
Authors: Hohlneicher Georg , Börsch‐Pulm Birgitt 
Published: March 2014

AbstractThe nomenclature introduced by Platt [1] for the assignment of electronically excited states of cata‐condensed benzenoid hydrocarbons is reinvestigated and extended to higher excited states. The extension to higher excited states was prompted by the increasing amount of knowledge on such states that result from new experimental techniques. The reinvestigation includes a careful consideration of pairing symmetries which were not a part of Platt's original concept. Further, it is shown that the subindices a and b cannot be used for higher excited states. These subindices have been introduced by Platt to distinguish between states that are degenerate in an ideal annulene. To combine the simplicity and generality of Platt's nomenclature with the higher quantitaty predicting ability of more sophisticated methods a formalism is provided that allows the analysis of the results of more advanced calculations in terms of certain “zero order perimeter states”. The analysis allows us to determine if a perimeter based assignment is possible, and if it is it tells us how to assign specific bands.
Experimental and Theoretical Studies on the Redox Properties of Conducting Polymers
Authors: Heinze Jürgen , Störzbach Michael , Mortensen John 
Published: March 2014

AbstractVoltammetric measurements on selected polypyrrole (PPy) films and defined soluble oligomers belonging to the oligo‐p‐phenylene and the oligo‐p‐phenylenevinylene series provide new insights into the charging/discharging properties of conducting polymers. It turns out that the current response in the whole accessible potential range of conventional conducting polymers is mainly caused by faradaic charge transfer reactions rather than capacitive effects. This is supported by digital simulations which are based on a model of n‐fold electron transfers within a finite layer. In addition, from the data of defined oligomers it becomes clear that the number and energies of accessible redox states in such materials depend on the extension of conjugation in the monomeric unit and on the chain length of the polymer. In general, in systems such as PPy up to a charging level of approximately 20 – 25 mol% all redox states are degenerated. Then, the successive redox states are gradually shifted to higher energies in accordance with increasing Coulomb repulsion between the charges. The results show that the bipolaron model must be amended. Nevertheless, experimental data reveal that the charging steps in conducting polymers are coupled with structural relaxation processes; but they occur, in contrast to the theoretical predictions, already on the polaron state.
Kinetics and Mechanism of the Oxidation of N,N‐Diethyl‐p‐phenylenediamine by 12‐Tungstocobaltate(III)
Authors: Nickel Ulrich , Klein Boris , Hsin‐min Jen 
Published: March 2014

AbstractThe almost irreversible oxidation of N,N‐diethyl‐p‐phenylenediamine by 12‐tungstocobaltate(III) was studied by means of a multi‐mixing, stopped‐flow apparatus with optical detection. Both unprotonated and simple protonated p‐phenylenediamine are oxidized rapidly to form p‐semiquinonediimine. The reaction rate is dependent on the concentration of all ions present in the solution, as well as on the choice and concentration of the buffer. The rate constant varies from 3·104 M–1 s–1 to 1.4·106 M–1 s–1 at 25°C. The activation energy in all cases is very small.
An Ultrasonic Method for the Accurate Determination of the Melting Line: Data for Cyclohexane and Benzene
Authors: Sun T. F. , Kortbeek P. J. , Biswas S. N. , Trappeniers N. J. , Schouten J. A. 
Published: March 2014

AbstractThe p‐T melting curves of cyclohexane and benzene were measured accurately at pressures up to 85 MPa and 175 MPa respectively using an ultrasonic method. Important features of this new method are that the phase transition is studied by monitoring changes in the attenuation of ultrasonic echoes and that the measurements start in a non‐equilibrium two‐phase region, the partially solidified liquid, created by superpressing the liquid sample. The accuracy of the experimental melting temperatures for both liquids is about 0.03 K. The Simon‐Glatzel equation, fitted to the experimental data, can be extrapolated to 500 MPa without introducing large errors.
High Pressure NMR Study of the Molecular Dynamics of Liquid Methylfluoride and Deutero‐Methylfluoride
Authors: Lang E. W. , Prielmeier F. X. , Radkowitsch H. , Lüdemann H.‐D. 
Published: March 2014

AbstractThe 2D‐, 1H‐ and 19F‐spin‐lattice relaxation rates R1, have been investigated in fluid methylfluoride in the temperature range 150 K ≤ T ≤ 450 K and at pressures up to p = 200 MPa. In addition, the self‐diffusion coefficient D has been obtained with NMR techniques in the same p. T‐interval. — The latter are interpreted within the rough hard sphere model yielding a temperature independent RHS diameter d and a strongly temperature dependent rotation‐translation coupling parameter A. The total 2D‐, 1H‐ and 19F‐relaxation rates in CD3F and CH3F are decomposed into their respective quadrupolar, dipolar and spin‐rotation contributions. Furthermore orientational and spin‐rotational correlation times are estimated. It is shown that they are in good agreement with the predictions of the extended M‐diffusion model (EDM). Inertial effects influence the molecular dynamics in the whole p, T‐range investigated. The self‐diffusion coefficients and orientational correlation times are in excellent agreement with MD‐simulation data.
IR‐Chemiluminescence in the Reaction Systems F + CH3I and F + CH2I2
Authors: Schwanke U. , Heydtmann H. 
Published: March 2014

AbstractInfrared chemiluminescence from HF is observed from the reactions of F atoms with CH3I and CH2I2in a fast flow apparatus under low pressure. The vibrational and rotational distributions for HF are determined for different nozzle configurations and changing reagent flows. The vibrational distributions forv= 1 – 3 are interpreted by proposing two microscopic channels for HF product formation in both reaction systems.
Laser Induced Thermal Diffusion
Authors: Scholz Malte 
Published: March 2014

AbstractThe concept of laser‐induced thermal diffusion was investigated by using a separation column in which a laser beam was aligned axially. This serves the same end as the heating wire normally employed in the Clusius‐Dickel method. The experimental runs used Ar‐SF6 mixtures to observe separation effects. The measurements showed a dependence on upward or downward direction of the beam and best results were obtained by changing the direction during the ran. Separation factors were measured as a function of pressure, beam diameter, radius of the column and laser power. Theoretical predictions could be confirmed within a factor of ≥ 5 as compared to a wire‐heated Clusius‐Dickel column.
2H‐NMR‐spectroscopic investigations of phospholipid bilayers
Authors: Hübner W. , Blume A. 
Published: March 2014

Abstract2H‐NMR‐spectroscopy has been used to determine structure and dynamics in phospholipid bilayers composed of phosphatidylcholines (PC)Abbreviations: PC, phosphatidylcholine; PE, phosphatidylethanolamine; DMPC, dimyristoyl‐phosphatidylcholine; DPPC, dipalmitoyl‐phosphatidylcholine; DSPC, distearoyl‐phosphatidylcholine; DMPE, dimyristoyl‐phosphatidylethanolamine; DPPE, dipalmitoyl‐phosphatidylethanolamine; DSPE, distearoyl‐phosphatidylethanolamine; DSC, differential scanning calorimetry.
and phosphatidylethanolamines (PE) of different chain length. The phospholipids were all labeled at the 4‐position of the sn‐2 chain. In pure lipid bilayers PEs always display wider quadrupole splittings than the corresponding PCs indicating a more condensed liquid‐crystalline phase for the PEs. In binary mixtures of PE and PC gel state immiscibility is observed when the two components differ in chain length by 4 CH2‐groups. In the liquid‐crystalline state deviations of the quadrupole splittings from linear behavior as a function of composition indicate the occurrence of clusters of different composition being in rapid exchange.
Optically detected NQR on matrix‐isolated organic molecules
Authors: von Borczyskowski C. 
Published: March 2014

AbstractDuring an optical pumping cycle involving electronically excited triplet states of organic molecules electron spin alignment can be transferred by the solid state effect to nuclear spin alignment. By this the sensitivity of NQR is enhanced by at least six orders of magnitude, which makes it possible to study low concentrated nuclear spin reservoirs. Applications to (1) photochemical reactions at defect site structures in molecular crystals, (2) doped organic glasses and (3) NQR on 33S in natural abundance will be discussed.
35Cl NQR spectra and crystal structures of 1,2,4,5‐tetrachloro‐3,6‐dinitrobenzene and of 1,3,5‐trichloro‐2,4‐dinitrobenzene
Authors: Wigand Silvia , Walz Leonhard , Weiden Norbert , Weiss Alarich 
Published: March 2014

AbstractThe crystal structures of 1,2,4,5‐Tetrachloro‐3,6‐dinitrobenzene and of 1,3,5‐Trichloro‐2,4‐dinitrobenzene were determined and the temperature dependence of the 35Cl NQR frequencies was investigated. 1,2,4,5‐Cl4‐3,6‐(NO2)2C6 crystallizes monoclinic, space group C32h‐C2/m with 2 molecules in the unit cell. The lattice constants are a = 990.4 pm, b = 923.4 pm, c = 573.5 pm, β = 92.721°. The plane of the nitro groups is perpendicular to the benzene ring. ‐ 1,3,5‐Cl3‐2,4‐(NO2)2C6H crystallizes monoclinic, space group C52h‐P21/c with 4 molecules in the unit cell. The lattice constants are a = 821.3 pm, b = 924.8 pm, c = 1300.0 pm, β = 92.39°. The nitro groups are tilted out of the ring plane (79.7° and 87.6°). — The 35Cl NQR spectra are in agreement with the crystal structures and in both cases no phase transition occurs in the temperature range 77 ≦ T/K ≦ melting point.
Application of photon count statistical measurements to the stationary fluorescence of fluoranthene
Authors: Degen Joachim 
Published: March 2014

AbstractThe broad S1 → S0 emission spectra of fluoranthene at room temperature in solution and in solid state down to T = 25 K have been recorded in a standard photon counting experiment. The wavelength dependence of the photon count statistics have been measured. In time scales of several microseconds deviations from poission statistics are found which exhibit a fine structure not or less resolved in the broad luminescence spectrum.
The calculated and observed vibrational spectra of the ordered phase of tris(hydroxymethyl)aminomethane
Authors: Schroetter S. , Bougeard D. 
Published: March 2014

AbstractThe ordered phase of Tris(hydroxymethyl)aminomethane can be described in terms of molecular layers with intermediate intralayer and weak interlayer hydrogen bonds. The results of a normal coordinate treatment prove the strong coupling of the OH and NH deformation modes with other internal vibrations. Except for the vibrations including the hydrogen bonded groups the calculations agree with the experimental data. In order to assign the OH and NH stretching vibrations polarized infrared spectra of an oriented polycrystalline sample have been used.
Nuclear quadrupole coupling and electronic structure of boron trihalide adducts with chalcogen ligands
Authors: Conrady R. , Müller‐Warmuth W. , Krebs B. , Schwetlik G. , Wienkenhöver M. 
Published: March 2014

Abstract11B NMR spectra of several boron trihalide (X = Cl, Br, I) adducts BX3 Y(CH3)2 with Y = S, Se, Te and BX3 S(CH2)4 have been measured at 96 MHz. Analyses of the well‐resolved first order quadrupole splittings have yielded coupling constants and asymmetry parameters at various temperatures. Applying the semiempirical Townes‐Dailey theory relative atomicorbital occupation numbers have been obtained and linked with the bonding configurations around boron. The results give information about the electron density distribution, the donor‐acceptor strength of the boron chalcogen bond, and the effect of various ligands.
Catalytic Effect of Metal Ions on the In: SnO2/Aqueous Polysulfide Interface: Application for Polysulfide Based Photoelectrochemical Cells
Authors: Tenne R. , Braun M. , Braun R. , Kerfin W. , Koschel W. 
Published: March 2014

AbstractLarge surface area photoelectrochemical cells exhibit low fill factors mainly due to mass transport polarizations in the electrolyte. To avoid that problem transparent (and conductive) materials must be used either as substrate to the photoelectrode or as a counter electrode. — It is shown here that cobalt(II), can reduce the overpotential at the interface between the transparent electrode and polysulfide electrolyte, without loss in transmittivity, rendering those materials good counter electrode. Surface analyses reveal that the metal ions form some kind of a sulfide superstructure with typical grain size of few tens of angstroms. The binding to the oxide layer is briefly discussed.
Activation Volume for Dimerization Reaction of 2,4,6‐Trimethylnitrosobenzene in Solution
Authors: Yoshimura Y. , Nakahara M. 
Published: March 2014

AbstractThe effect of pressure on the rate and equilibrium constants for the dimerization reaction of 2,4,6‐trimethylnitrosobenzene in acetonitrile was studied up to 196 MPa at 25°C in order to examine whether the dynamical effect on the reaction process in solution can be neglected as assumed in the transition state theory. All the rate constants relevant to the dimerization were determined by the pressure relaxation method. The configurational reaction volume for the dimerization and the activation volume for the dissociation were —17.4 ± 0.7 and + 5.1 ± 0.3 cm3 mol 1 at 98 MPa, respectively. The experimental results were in reasonable agreement with the theoretical ones that were calculated for the model system composed of hard spheres according to the liquid theory and the transition state theory. The dynamical effect on the activation volume was not detected in the present reaction system.
Assoziationsverhalten und Dipolmomente von Tetra(n‐Butyl)‐Ammoniumpertechnetat und Tetra(n‐Butyl)Ammoniumperchlorat in Benzol
Authors: Neck Volker , Maier Ralph , Kanellakopulos Basil 
Published: March 2014

AbstractAt very low concentrations tetra‐n‐butylammonium pertechnetate and tetra‐n‐butylammonium perchlorate form ion pairs in benzene Solutions. At room temperature, formation of dimers and larger aggregates begins to occur at concentrations of 10−5 mol/1. This behaviour has been investigated quantitatively by the determination of the molecular weight in the case of the perchlorate salt, and by the concentration‐dependence of the pertechnetate phase equilibrium between water and benzene. It could be demonstrated that Bu4NClO4‐dimers and larger aggregates have no apparent dipole moment. Knowing the relative concentration of the monomers from the extraction experiments, the dipole moment of 16.6 Debye has been calculated for the ion pair. Applying an extrapolation method, the dipole moment of Bu4NCIO4 was found to be 16.2 Debye. The similarity of the dipole moments is in good agreement with the similar ionic radii of the TcO4− and the ClO4− ions. The charge separation in the ion pairs however, calculated from the dipole moments, is smaller than the sum of cationic and anionic radii.
Untersuchung der Kohlenmonoxidoxidation an polykristallinem Platin bei gleichzeitiger Messung der Sauerstoffaktivität an der Katalysatoroberfläche
Authors: Häfele E. , Lintz H. G. 
Published: March 2014

AbstractSolid electrolyte potentiometry has been used to measure the oxygen activity at the catalyst surface during the oxidation of carbon monoxide by oxygen and/or nitrogen monoxide on platinum at ambient pressure. The results of the combined kinetic and electrochemical measurements can be interpreted consistently within the accepted concept of elementary steps. The findings of the simultaneous oxidation clearly confirm and explain the high selectivity of the carbon monoxide‐oxygen reaction.
Vector Correlations in the Photodissociation of CH3I, OCS, and Glyoxal
Authors: Hall G. E. , Loo R. Ogorzalek , Harri H.‐P. , Sivakumar N. , Chawla G. K. , Houston P. L. , Chandler D. W. , Hepburn J. W. , Burak I. 
Published: March 2014

AbstractThe use of vector correlations to elucidate the photodissociation dynamics of CH3I, OCS, and glyoxal is discussed. The correlations occur between the vectors Ě, the electric vector of the photolysis light, μ, the transition dipole moment of the parent, v, the relative recoil velocity of the fragments, and J, the angular momentum of one of the fragments. The Ě – μ – v correlation is illustrated by a direct imaging technique in the photodissociation of CH3I; it shows that dissociation takes place by a parallel transition and is rapid compared to parent rotation. The “triple vector correlation”, Ě – μ – (v – J), is used to show that the dissociation of OCS proceeds on two surfaces, one of A″ and one of A′ symmetry in the Cs point group. The v – J correlation in the dissociation of glyoxal illustrates two points, that dissociation of this molecule takes place in a plane and that vector correlations can exist even for dissociations which are slow compared to parent rotation.