bluuebunny/crossref_metadata_2025_split huggingface dataset:
The determination of Lennard‐Jones potential parameters of fluid hydrogenchloride by RISM calculations over a broad range of densities
Authors: Gutwerk D. , Bausenwein T. , Bertagnolli H. 
Published: July 2012

AbstractSeveral interaction potentials of (12‐6) Lennard‐Jones type with added partial point charges were tested for fluid hydrogenchloride. The individual atom pair correlation functions were calculated with the extended RISM theory, and were compared with the weighted superposition of intermolecular atom pair correlation functions that can be determined by a neutron diffraction experiment on fluid deuteriumchloride. Since experimental results are available at the supercritical temperature of 100°C for densities ranging from 0.5 to 1.1 g·cm−3, the RISM‐calculations were performed over that range. By comparing the results of RISM‐calculations at different thermodynamic states with experimental results, we show that one can derive an interaction potential that represents the measured structure of the liquid better than potentials derived from measurements at only one thermodynamic state. Finally a new set of Lennard‐Jones parameters that leads to a fairly good agreement with the experimental results for all densities is deduced. The individual atom pair correlation functions are given and the dependence on density is discussed.
Viscosity of sodium cryolite‐aluminium fluoride‐lithium fluoride melt mixtures
Authors: Fellner P. , Silný A. 
Published: July 2012

AbstractThe viscosity of the molten system Na3AlF6–AlF3 – LiF was investigated using an oscillating cylinder viscometer. The melts contained up to 27.6 mass% AlF3 and 7.0 mass% LiF. The temperature ranges from 840 to 1060°C. The method is absolute and the accuracy of the viscosity data of cryolite‐based melts is better then 3%. A model is presented that reproduces reasonably well the measured data. The model assumes the presence of Na3AlF6, Li3AlF6, and NaAlF4 species in the melt, and the Arrhenius behaviour of the product of viscosity and of molar volume of the melt.
Hydrodynamic studies on benzethonium chloride micelles in dilute aqueous solution
Authors: Paradies Henrich H. , Hinze Ulrike , Thies Michael 
Published: July 2012

AbstractApparent micelle molecular weights, intrinsic viscosity, actual frictional coefficients and molal volumes have been determined for benzethonium chloride (BZCl) at 20°C in 0.01 M Tris‐HCl, containing 0.01 M NaCl. The weight average molecular weight of BZC1 was determined to 28 000 ± 1500 by static light scattering, revealing an apparent aggregation number (Napp) of 60–65. Average hydrodynamic dimensions of the BZCl micelle were obtained from measurements of sedimentation velocity, intrinsic viscosity and of the mutual diffusion coefficient above the CMC (8.4 × 10−4mol/l).By studying the autocorrelation function of light scattering of BZCl solutions above the CMC, the hydrodynamic and thermodynamic perturbations were determined. The dynamics of the micellar BZCl solutions are unperturbated by additions of polyhydric alcohols within the range of 10–40% (w/w). Above the CMC a classical hard‐sphere behavior is derived from the volume fraction dependence of the scattered intensity for BZCl. The diffusivity data are consistent with a micellar hydrodynamic radius, RH of 25.5 Å, with little or no growth of BZCl micelles upon increasing surfactant concentration evident between 0.01 M NaCl and 0.1 M NaCl at pH 7.5 (20°C).Applying the linear interaction theory we obtained theoretical fits to Dapp vs. BZCl concentrations over a region of low salt concentrations at pH 7.5 (20°C).
An EXAFS investigation of the Lewis acids zirconium tetrachloride and cyclopentadienylzirconium trichloride in tetrahydrofuran solutions
Authors: Bökman F. , Bertagnolli H. 
Published: July 2012

AbstractThe 1:2 Lewis adducts of zirconium tetrachloride (ZrCl4) and cyclopentadienylzirconium trichloride (CpZrCl3) with tetrahydrofuran (THF) have been studied in solutions by means of X‐ray absorption spectroscopy. The organometallic complex CpZrCl3(THF)2 has in THF solution a structure similar to the known crystallographic solid state structure. In solution the average zirconium‐carbon distance is 0.06 Å longer, and the average Zr‐oxygen distance as well as the average Zr‐chlorine distance are 0.05 Å shorter than in the solid state. In the inorganic complex ZrCl4(THF)2 the zirconium‐oxygen distance is short (2.22 Å), and the trans influence difference between chloride and tetrahydrofuran ligands gives two experimentally separable zirconium‐chlorine distances (2.39 Å and 2.49 Å).
Vibrational spectroscopy of purified C76
Authors: Michel R. H. , Schreiber H. , Gierden R. , Hennrich F. , Rockenberger J. , Beck R. D. , Kappes M. M. , Lehner C. , Adelmann P. , Armbruster J. F. 
Published: July 2012

AbstractC76 was generated by graphite contact arc discharge in helium and purified by high performance liquid chromatography (>98%). We report an infrared and first Raman spectroscopic study of the microcrystalline solid and compare the observed vibrational structure to existing calculations.
Spectral emission during high temperature pyrolysis of fullerene C60 in shock waves
Authors: Von Gersum Sabine , Kruse Thomas , Roth Paul 
Published: July 2012

AbstractSubmicron fullerence C60 particles were dispersed in Ar and heated by shock waves to temperatures between 2370 K and 3500 K. The aerosol particles evaporate under such conditions in a few microseconds to form C60 vapour. From the time‐dependent spectra at specified wavelengths the decomposition rate of C60 was determined. At temperatures above 2600 K spectral lines of C2 appear in the emission spectrum. A comparison between measured and calculated C2 spectra indicates an increasing amount of C2 with increasing temperature.
Changes of the oscillation frequency of a quartz resonator in contact with a binary liquid mixture of critical composition as function of temperature, revisited
Authors: Köhler Th. , Woermann D. 
Published: July 2012

AbstractNew results of measurements of the temperature dependence of changes of the oscillatory frequency Δf(T) of a quartz oscillator in contact with two binary liquid mixtures of critical composition are reported (systems: 2‐butoxyethanol/water; 2,6‐dimethyl pyridine/water, lower critical point). Both systems exhibit an unexpected Δf(T) behaviour approaching the critical temperature. The results lead to the conclusion that even near the critical temperature Δf(T) is determined only by the background viscosity of the systems. The influence of critical contributions to the viscosity can be neglected. It is assumed that this effect is caused by the large shear gradient produced by the quartz oscillator.
Evidence for competing electron and energy transfer for the fluorescence quenching of singlet oxygen sensitizers by molecular oxygen
Authors: Grewer Christof , Wirp Christoph , Neumann Marcus , Brauer Hans‐Dieter 
Published: July 2012

AbstractThe rate constant of fluorescence quenching by molecular oxygen k was measured for a series of singlet oxygen (1O2)‐sensitizers in toluene and adopts values between 3.5·1010 and 0.4·1010M−1 s−1. log(k) shows a correlation with the free energy of electron transfer ΔGel as calculated according to Rehm and Weller. k decreases with increasing ΔGel in the endergonic region. The efficiency ϕ for 1O2‐formation accompanying the S1‐state quenching by energy transfer of the S1‐state of the sensitizer is substantially >0 only in the cases, where the S1‐T1‐energy gap exceeds the excitation energy of 1O2(1Δg), 94 kJ/mol, where electron transfer is energetically unfavourable and the T2‐state of the sensitizer is lying above the S1‐state. Furthermore the temperature dependence of k was measured in toluene for two sensitizers. The quenching process for dicyanoanthracene (DCA) is activationless in the high temperature region which could be explained either by activationless energy transfer, or by exciplex formation.
Co‐adsorption of mono‐ and multivalent ions on silica and alumina
Authors: Kosmulski Marek 
Published: July 2012

AbstractAdsorption of calcium and europium from 0.001‐1 M solutions of different 1:1 electrolytes on silica and alumina was studied as a function of pH, surface charge density σ0, ionic strength and temperature. Adsorption of multivalent cations on a negatively charged surface is competitive with respect to monovalent cations, i.e., the increase of the ionic strength leads to a decrease of multivalent ions adsorption. In contrast, adsorption of multivalent cations on a positively charged surface is insensitive to the concentration of monovalent cations or even increases with the ionic strength.
Isochoric heat capacity and liquid‐gas coexistence curve of carbon dioxide in the region of the immediate vicinity of the critical point
Authors: Abdulagatov I. M. , Polikhronidi N. G. , Batyrova R. G. 
Published: July 2012

AbstractThe paper contains the results of new experimental measurements of the isochoric heat capacity and the liquid‐gas coexistence curve of carbon dioxide in the one‐phase region near the critical point. The measurements were performed in a high temperature adiabatic calorimeter used earlier for the determination of the isochoric heat capacity of several liquids and liquid mixtures near the critical points [1, 2].The experiments have been performed at seven isochores, namely: 461.2, 464.5, 467.5, 470.1, 477.7, 499.0, and 509.8 kg·m−3 in the neighbourhood of the critical point and the coexistence curve. The measurements were made with samples of constant mass contained in a calorimeter vessel of nearly constant volume. Uncertainties of the heat‐capacity measurements are estimated to be less than 2 percent far from Tc and 3 percent in the immediate vicinity of the critical point. The uncertainty in temperature was less than ±10 mK.
Solubility of carbon dioxide in aqueous solutions of ammonium chloride at temperatures from 313 K to 433 K and pressures up to 10 MPa
Authors: Rumpf B. , Nicolaisen H. , Maurer G. 
Published: July 2012

AbstractThe solubility of carbon dioxide in aqueous solutions of ammonium chloride was measured in the temperature range from 313 K to 433 K, up to 6 m salt solutions and total pressures up to 10 MPa. Pitzer's [1] model was used to correlate and predict the new data. Results are reported and compared to literature data and correlations.
The RNA world. Empirical explorations of sequence space: Host‐guest chemistry in the RNA world
Authors: Ellington Andrew D. 
Published: July 2012

AbstractUsing data from a number of recent in vitro selection experiments, general conclusions have been drawn about the shapes of landscapes that map nucleic acid sequences to functions (in particular, the ability to bind a ligand). It appears that local optima on these landscapes are dispersed; that is, that there are a variety of sequences that can bind to a given ligand. In addition, though, there are usually one or two apparently global optima. A comparison of aptamer shapes suggests that nucleic acids can easily form simple pockets by using short helical segments. These results have implications for the origin and evolution of metabolism: short nucleic acids may be much better suited to ligand‐binding than short peptides or other biopolymers.
Principles and origins of coding systems. Does information acquire meaning naturally?
Authors: Wills Peter R. 
Published: July 2012

AbstractNatural selection among replicative entities allows for the accumulation of information during biological evolution, but it does not account for the orderly development of selected biochemical processes which now constitute a restricted mapping from genotype to phenotype. The self‐organisation of biochemical processes is described in terms of a set of simple rate equations, which are solved for the special case of systems for which functions are mapped onto structures in a random fashion. When catalytic action is dependent on symbol recognition, so that biochemical synthesis is instructed by information, coding self‐organisation can take place, but loss of information beyond a certain threshold results in catastrophic loss of function. It is argued that a partnership between Darwinian selection and functional self‐organisation is fundamental to biological evolution.
Pattern formation by transcriptional cascades in the Drosophila embryo
Authors: Rivera‐Pomar Rolando , Hoch Michael , Sauer Frank , Brönner Günter , Wimmer Ernst A. , La Rosée Anna , Jäckle Herbert 
Published: July 2012

AbstractGenetic and molecular analyses have combined to yield insights into functional cascades of transcription factors necessary to establish the molecular blueprint of the Drosophila body pattern in response to positional information already present in the egg. This maternal information is based on a small set of asymmetrically distributed maternal transcription factors that act as graded morphogens along the anterior‐posterior and the dorsal‐ventral axes of the embryo. Recent progress in the field provides first insight into the molecular mechanisms by which long‐range positional information in the egg causes a series of localized zygotic transcription factor gradients to position development fate along the axes of the blastoderm embryo.
Lattice polymer automata
Authors: Rasmussen Steen , Smith Joshua R. 
Published: July 2012

AbstractWe present a new style of molecular dynamics and self‐assembly simulation, the Lattice Polymer Automaton [LPA]. In the LPA all interactions, including electromagnetic forces, are decomposed and communicated via propagating particles, “photons”. The monomer‐monomer bond forces, the molecular excluded volume forces, the longer range intermolecular forces, and the polymer‐solvent interactions may all be modeled with propagating particles.The LPA approach differs significantly from both of the standard approaches, Monte Carlo lattice methods and Molecular Dynamics simulations. On the one hand, the LPA provides more realism than Monte Carlo methods, because it produces a time series of configurations of a single molecule, rather than a set of causally unrelated samples from a distribution of configurations. The LPA can therefore be used directly to study dynamical properties; one can in fact watch polymers move in real time. On the other hand, the LPA is fully discrete, and therefore much simpler than traditional Molecular Dynamics models, which are continuous and operate on much shorter time scales. Due to this simplicity it is possible to simulate longer real time periods, which should enable the study of molecular self‐organization on workstations; supercomputers are not needed.
Emergence of regular superstructures in macromolecules
Authors: Botti S. A. , De Santis P. , Fuá M. 
Published: July 2012

AbstractA general method is described in which the harmonic analysis of perturbations is applied to the study of superstructures of macromolecular chains. The theoretical approach employed has been to apply harmonic perturbations on the conformational parameters in macromolecular helices of various periodicities and to study the overall variation in structure and its dependency on the periodicity of the perturbation. The results clearly show that when these perturbations do not contain harmonics close to the fundamental periodicities of the polymer chain, the consequent structural effects remain localized and are not productive at a superstructural level. Furthermore, the features of these superstructures are dependent only on the amplitude of the fundamental periodicity component of the perturbation and are generated by topologically equivalent transformations. These findings enable us to devise a model to study and identify transconformational pathways leading to global variations in the structure of the macromolecular chain.
Diffusion of C in TiC
Authors: Albertsen Knuth , Schaller Hans‐Jürgen 
Published: July 2012

AbstractDiffusion of carbon in titanium carbide was investigated over the entire phase field between 1179 and 2413 K using suitably designed diffusion couples.Concentration‐depth profiles of carbon were taken by SNMS and EMPA. The diffusion coefficients of carbon obtained by the two analytical techniques in different temperature ranges agree remarkably well. Above 1468 K, they exhibit a strong concentration dependence and can be expressed by

The thermodynamic factor obtained from a thermodynamic analysis of the TiC system was used to describe the concentration dependence. Tracer diffusion coefficients calculated from the chemical diffusion coefficients with the help of the thermodynamic factor are in accordance with literature data. Below 1468 K concentration‐independent diffusion coefficients were obtained which yielded a lower energy of activation:

This behavior is attributed to the preponderance of grain boundary diffusion over volume diffusion at low temperatures in the samples at hand.
An electrochemical study of the passive film formed on Ni–Cr (80/20) coating
Authors: Metikoš‐Huković M. , Omanović S. , Babić R. , Milošev I. 
Published: July 2012

AbstractThe passive state of Ni–Cr (80/20) coatings prepared by a plasma beam sputter deposition process was studied using cyclic voltammetry and impedance spectroscopy techniques. The highly protective quality of the film formed in acetate buffer, pH = 5.7, is probably based on chromic species. The nickel content in the film was very low and influenced only the electronic properties of the film.The appearance of a distinct transition in the capacitance potential characteristic may be correlated with the presence of higher valent chromium species. Cyclic voltammetry demonstrated that Cr(VI) was incorporated into the outer part of the oxide film, or was tenaciously adsorbed on the electrode surface. Its formation and reduction were reversible.
Photochromic reaction of peroxopolytungstic acid thin films
Authors: Itoh Kiminori , Yamagishi Kazunori , Nagasono Mitsuru , Murabayashi Masayuki 
Published: July 2012

AbstractSpin‐coated Thin films of peroxopolytungstic acid (PTA) showed pronounced photocoloration under UV irradiation only when the films contained a reducing reagent having OH groups. Decoloration occurred when the colored films were exposed to oxidizing reagents. The origin of the photocoloration is likely a reaction between excited triplet state of PTA and OH groups of the reducing reagents. Accumulation of reducing power in the films, and competition between the photocoloration and known photohardening process were discussed; an application of these characteristics was also shown.
Pulse radiolysis of benzyl chloride and ‐bromide; The UV‐visible absorption spectrum of the benzyl cation
Authors: Fujisaki Noboru , Comte Pascal , Gäumann Tino 
Published: July 2012

AbstractPulse radiolysis study of liquid benzyl chloride has been carried out at room temperature. In order to identify transient species that absorb in the UV‐vis region, various scavengers were used including oxygen, ethanol, pyrrole, biphenyl, and mesitylene (1,3,5‐trimethylbenzene). The spectrum of the benzyl cation was obtained by subtracting the transient spectrum for the 0.6 M solutions of ethanol in O2‐saturated benzyl chloride from that for O2‐saturated benzyl chloride. The difference spectrum obtained has a strong absorption band at 303±2 nm and a weak broad band near 500 nm. The analyses of end products formed in the γ radiolysis of benzyl chloride were done in the presence and absence of scavengers. The formation of benzyl ethyl ether with a G value of 0.9 from a 0.6 M solution of ethanol in O2‐saturated benzyl chloride was taken as evidence that added ethanol reacts with benzyl cations to give benzyl ethyl ether. Some pulse radiolysis experiments were performed with benzyl bromide. Transient spectra observed in benzyl bromide are similar to those observed in benzyl chloride. It is, however, inferred from the product analysis that the radiolytic mechanisms of benzyl bromide appreciably differ from those of benzyl chloride.
Quantitative interpretation of the red edge excitation (REE) effect of 9,9′‐bianthryl in polyisobutene by band shape analysis of the temperature‐dependent optical fluorescence spectra
Authors: Elich Karsten , Wortmann Rüdiger , Petzke Frank , Liptay Wolfgang 
Published: July 2012

AbstractOptical fluorescence spectra of 9,9′‐bianthryl (BA) in polyisobutene (PIB) were measured as a function of the excitation wavelength at various temperatures between 210 and 293 K. Irradiation at the red edge of the absorption spectra selectively excites distinct conformers with respect to the torsional angle. This leads to a strong dependence of the vibronic band shape of the fluorescence spectra on the excitation wavelength. The marked temperature dependence of the band shape may be attributed to the viscosity‐dependent deceleration of the torsional relaxation of BA in the highly viscous polymer which prevents the excited state ensemble from reaching thermal equilibrium. The predominant broadening mechanism affecting the band shape is given by a combination of the S1 torsional distribution and the torsional angle‐dependent transition frequency. These effects are interpreted quantitatively within a torsional relaxation model based on the description of the torsional dynamics according to a Smoluchowski equation which is adapted to the steady state case. The band shape analysis of the fluorescence spectra enables the determination of the effective S1 torsional potential as well as the friction coefficient related to the internal torsional motion of BA in the polymer matrix. A value of ΔV = 325 cm−1 is deduced for the local barrier of the S1 double minimum potential at ϕ = 90° while the minimum torsional angle is found to be ϕmin = 61°. Additionally, model calculations on time‐resolved fluorescence spectra of BA in apolar solvents are carried out as a function of excitation wavelength and temperature showing the importance of conformational relaxation for the interpretation of transient spectra of flexible molecules.
On the significance of molecular surfaces and thermodynamic interactions for the excess viscosities of liquid mixtures
Authors: Mertsch Rüdiger , Wolf B. A. 
Published: July 2012

AbstractThe viscosities η of homogeneous binary mixtures of liquids are usually approximated as In η = ϕ1 In η1 + ϕ2 In η2 where ϕi and ηi are the volume fractions and the viscosities, resp., of the i‐th pure substance; the behavior of real systems is then discussed in terms of Δ In η, the deviations from the above reference behavior. Here a semi‐empirical approach is presented according to which volume fractions are replaced by the surface fractions Ωi to create a more realistic reference state, and the thermodynamic interaction parameter g is taken into account. The new equation reads (expressing it for practical purposes still in the terms of ϕi)

γ is a geometric factor, measuring the difference between Ωi and ϕi, and δ  In (η2/η1). The comparison of calculations according to the above equation with experimental data demonstrates that the first term is decisive in the majority of cases and only with systems of large interaction does the second become important. For all nine systems under investigation quantitative agreement between experiment and theory can be achieved using a theoretical value for either γ or g, and adjusting the other within physically reasonable limits. Possible explanations for the necessity to fit one of the parameters are given.
Effective self‐diffusion coefficients of 14C‐urea in a polyphenolsulfonic acid cation exchange membrane in the presence of different counterions
Authors: Daniel T. , Seidel W. 
Published: July 2012

AbstractEffective self‐diffusion coefficients of the polar non‐electrolyte urea were obtained from tracer experiments with 14C‐urea. For a membrane loaded with Na+ the tracer‐diffusion coefficient was investigated as a function of the total urea concentration. Also tracer‐diffusion was observed for membranes loaded with different counterions at constant urea concentration in solution.