bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Intermolecular Interaction in Liquid Crystalline Mixed Phases. Progress Report
Authors: Diele S. 
Published: July 2012

AbstractExamples of specific intermolecular interaction (dipole, EDA, steric interactions as well as hydrogen bonds) are discussed in binary mixtures of calamitic, columnar and polymeric systems. It is shown, that on the base of the complete miscibility in the liquid crystalline state a continuous change of the intermolecular interaction is achieved in dependence on the concentration. In this way the properties of the mixtures can be definitively influenced by admixing of a proper second component.
Bowl‐shaped Liquid Crystals — New Derivatives of Cyclotriveratrylene and Calix[4]arene
Authors: Budig H. , Paschke R. , Diele S. , Letko I. , Pelzl G. 
Published: July 2012

AbstractSome new Calix[4]arenes and Cyclotriveratrylenes incorporating cyclohexane rings, phenyl rings or ether oxygen atoms in their lateral chains have been synthesised and investigated by calorimetry and X‐ray studies. Only some long chain calix[4]arenes exhibit mesomorphic behaviour. The mesomorphic ranges and clearing temperatures of the mesophases of hexasubstituted cyclotriveratrylenes are largely increased by the introduction of cyclohexane rings or oxygen atoms into the alkyl chains. X‐ray studies proved the columnar structure of the mesophases.
First Observation of Selective Reflection and Blue Phases in Chiral Discotic Liquid Crystals
Authors: Krüerke D. , Kitzerow H.‐S. , Heppke G. , Vill V. 
Published: July 2012

AbstractWe investigated the helical structure of discotic cholesteric liquid crystals using cellobiose derivatives as chiral dopants in a discotic nematic host. A characteristic property of the new mixtures is the occurrence of a glass‐like state. Due to extremely small pitches we observed for the first time selective reflection in a chiral discotic system. In addition, we report on the first observation of discotic blue phases. Microscopic studies, reflection spectra, and Kossel diagrams indicate the appearance of three discotic blue phases, BPDI, BPDII, and BPDIII, which behave similar to the known calamitic modifications.
The Smectic‐C‐Smectic‐A Transition in Free‐Standing Liquid‐Crystal Films: An Example for Critical Behaviour Induced by a Confined Geometry
Authors: Bahr Ch. , Fliegner D. 
Published: July 2012

AbstractWe report on an ellipsometric study of a phase transition in thin free‐standing films of a smectic liquid crystal. The smectic‐C‐smectic‐A transition, which is first‐order in bulk, becomes continuous in films thinner than about 15 molecular layers indicating the influence of a strong ordering field resulting from surface interactions. The experimental results are discussed within the framework of a simple Landau model consisting of the bulk parameters and extended by a linear coupling to a surface field which decays exponentially from the surface to the interior of the film.
Time Reversal and the Law of Reciprocity in Raman Scattering
Authors: Hecht Lutz , Barron Laurence D. 
Published: July 2012

AbstractEmploying exact energy operators for the construction of effective polarizability operators, the previously derived approximate relationship (ααβ)mn = (αβα)θnθm) between a complex transition polarizability and the corresponding transition polarizability with time‐reversed initial and final molecular states has been found to represent an exact identity for a single microscopic Raman scattering event. Based on this result and the associated time ordered diagrams, macroscopic pictorial arguments are used to generalize the law of reciprocity to cover Raman scattering, thereby eliminating the prejudice that it applies only to Rayleigh scattering. Our predictions accord with the results of recent Stokes and anti‐Stokes resonance Raman experiments.
Thermophysical Properties of Alkali Metal Vapours Part I.A — Prediction and Correlation of Transport Properties for Monatomic Systems
Authors: Fialho P. S. , Fareleira J. M. N. A. , Ramires M. L. V. , Nieto De Castro C. A. 
Published: July 2012

AbstractNew calculations of the collision integrals for the singlet potential functions involved in the determination of viscosity, thermal conductivity and self‐diffusion coefficients of the monatomic alkali metal vapours are presented. An interpolation procedure for the calculation of the monatomic systems transport coefficients in a large temperature range is provided. This is based on temperature correlations of the collision integrals for the singlet and triplet potential functions.The calculations have been carried out using a new potential function for the ground singlet state of the alkali diatomics. This is a recent version of the Extended Hartree‐Fock Approximate Correlation Energy (EHFACE2U), proposed by Varandas et al., which is believed to give a correct description of the potential energy to vanishing internuclear distances.The results which are compared with previous calculations, are intended to be utilized in Part II of this paper in order to assess available experimental data on the viscosity and thermal conductivity coefficients of the alkali metal vapours.
Biodiagnostics and Polymer Identification with Multiplex Dyes
Authors: Seeger S. , Bachteler G. , Drexhage K. H. , Arden‐Jacob J. , Deltau G. , Galla K. , Han K. T. , Müller R. , Köllner M. , Rumphorst A. , Sauer M. , Schulz A. , Wolfrum J. 
Published: July 2012

AbstractA new analytical concept based on time‐resolved fluorescence spectroscopy is presented, which uses the characteristic fluorescence lifetimes as information to identify new fluorescent dyes, called multiplex dyes. Several dyes can be distinguished at nearly fixed excitation and emission wavelength by recognition of the lifetimes. A pattern recognition technique is used for data analysis. As light sources a pulsed laser diode is used. First experiments are shown in several application fields, like DNA sequencing, immunoassays and tagging of polymer material.
A Technique for Mixture Fraction Imaging in Turbulent Nonpremixed Flames
Authors: Long Marshall B. , Frank Jonathan H. , Lyons Kevin M. , Marran David F. , Stårner Sten H. 
Published: July 2012

AbstractA technique is presented for making instantaneous, two‐dimensional measurements of the mixture fraction in turbulent nonpremixed flames. The technique uses acetaldehyde fluorescence imaging and Rayleigh imaging to determine the mixture fraction in an iterative manner. Preliminary experimental results for the mixture fraction and its gradient in a turbulent acetaldehyde flame are presented. To verify the degree to which the acetaldehyde fluorescence tracks the fuel concentration, simultaneous fluorescence and fuel Raman scattering measurements are performed. The strength of the signals from the Rayleigh scattering and the fuel fluorescence allows computations of the mixture fraction high in spatial resolution and low in noise, thus making determination of the scalar dissipation feasible.
High Precision Optical Surface Topometry
Authors: Tiziani H. J. 
Published: July 2012

AbstractFor contactless measurement of the surface topography optical techniques are promissing. A lot of progress was made by the development of laser supported methods. It is due to the development of new different lasers, the introduction of solid state detectors and powerful computers for the information processing. Time of flight, phase measurements, active and passive triangulation and projected fringes are very robust techniques for industrial applications.A lot of progress was made in the application of interferometry to surface and vibration measurements. One or more wavelength together with diode lasers are used. Although interferometry requires polished surfaces, however, by using synthetic wavelengths, it can also be applied for optically rougher surfaces. In addition the unambiguity range will be extended when longer synthetic wavelengths are used.Furthermore scanning and whole field confocal microscopy can be used for macro‐ and microstructure analysis. New techniques will be described to extend the field of view.Some limits especially with respect to resolution and industrial application will be discussed for the methods presented together with some experimental results and future developments.
Determination of Alkali Traces in Coal Combustion by Excimer Laser Induced Fragmentation Fluorescence
Authors: Hartinger K. T. , Monkhouse P. B. , Wolfrum J. 
Published: July 2012

AbstractGas phase sodium concentrations were measured in situ in the flue gas of a fluidised bed reactor using the excimer laser induced fragmentation fluorescence (ELIF) technique. Several different coals were investigated for a fixed set of reactor conditions at ∼ 1 bar total pressure. Measured signals were converted to absolute concentrations using a calibration system that monitors alkali compounds under well‐defined conditions. Concentrations ranging from the sub‐ppb region to 25 ppb were obtained. Contrasting concentration histories were observed for the brown and hard coals studied.
Quantitative Determination of Fuel Air Mixture Distributions in an Internal Combustion Engine using PLIF of Acetone
Authors: Wolff D. , Schlüter H. , Beushausen V. , Andresen P. 
Published: July 2012

AbstractQuantitative determination of planar fuel/air mixture distribution in an internal SI engine are obtained using planar laser induced fluorescence of acetone. In order to get quantitative information different fuel tracer substances have been investigated. Special requirements have to be fulfilled by the tracer molecule with regard to the application under the unstationary and hostile conditions of internal combustion. The most important is that the fluorescence intensity has to be directly proportional to the fuel density. It must be unaffected by surrounding gas composition, temperature‐ and pressure‐fluctuations. As it turned out during the experiments acetone meets this unusual requirements almost perfectly.The experiments were carried out in one cylinder of a modified production line four cylinder SI engine from Volkswagen AG. Time resolved planar fuel distributions were obtained for the whole mixture formation process during the intake, the compression and at the beginning of the combustion stroke. Single shot and cyclic averaged measurements revealed a) cycle‐to‐cycle variations as well as recurring structures of the fuel distribution, b) mixture uniformity and c) flow field structures. The direct relationship between the acetone fluorescence intensity and the fuel density allows the quantitative determination of 2‐D fuel/air ratio maps for a multitude of different crankangles.
Microheterogeneity of monohydric alcohol/water mixtures. Extended view of ultrasonic relaxation
Authors: Kaatze U. , Brai M. , Menzel K. 
Published: July 2012

AbstractRecently measured broadband ultrasonic spectra of binary mixtures of water with various monohydric alcohols are discussed with respect to precritical behaviour of the liquids. It is shown that the frequency‐dependent excess absorption can indeed be empirically represented by a very few parameters if a special relaxation function is used. Moreover, the coupling of the acoustic field to the heterogeneous structure can be alternatively considered. The interest is particularly focussed on visco‐inertial and thermal conductivity effects which have so far been taken into account in acoustically more heterogeneous systems like emulsions, suspensions, and biological tissues only. Though the shape of the spectra of the alcohol/water mixtures excellently agrees with that predicted by the theories of frequency‐dependent visco‐inertial and thermal conductivity losses some discrepancies in the parameter values result if these theoretical models are fitted to the measured data. It is, however, suggested that such effects, in addition to the previously considered fluctuations in concentration, contribute to the precritical ultrasonic spectra. This view involves not only fluctuations of mass but also special modes of impuls and energy transport to be important at internal interfaces of the micro‐heterogeneous liquids.
Generalized van der Waals Model Applied to Tetramethylsilane
Authors: Baonza V. Garcia , Alonso M. Cáceres , Delgado J. Núñez 
Published: July 2012

AbstractThe Generalized van der Waals model has been examined and discussed using high‐pressure experimental data previously reported for tetramethylsilane over a wide range of temperature. The study has been focused on the temperature dependence of the two following characteristic quantities: the effective volume of the hard convex body ν*, which represents the molecules of the fluid, and the attractive van der Waals parameter (a/ν*). It has been confirmed that the nearly universal relation found between the medium densities correction to the compressibility factor (in the formulation of Móritz and Kohler) and the limiting value of the attractive parameter at high densities (a0/ν*) holds for tetramethylsilane. In addition, it has been studied the general form of the low density correction, which can be directly related to third virial coefficient.
Thermophysical properties of alkali metal vapours part II ‐ assessment of experimental data on thermal conductivity and viscosity
Authors: Fialho P. S. , Ramires M. L. V. , De Castro C. A. Nieto , Fareleira J. M. N. A. , Mardolcar U. V. 
Published: July 2012

AbstractAn analysis of the available data on the viscosity and thermal conductivity coefficients of the alkali metal vapours is presented. The analysis is based upon theoretical calculations of the properties of the monatomic systems, described in the preceeding parts I and I.A of the present paper, and making use of the kinetic theory of a binary gas reacting mixture. A summary of the measurement techniques used, including, whenever possible, the magnitude of the corrections performed on the raw data and the nominal precision of the results, complements the analysis.It is concluded that it is possible to select precise and mutually consistent sets of experimental results for both viscosity and thermal conductivity coefficients of lithium, sodium and potassium vapours among the available literature data and to classify all the data in uncertainty classes. Regarding rubidium and cesium no systematic discussion is possible due to a lack of experimental data with sufficient precision.
DISQUAC predictions on VLE andHEfor ternary mixtures containing 1‐alkanols and hydrocarbons
Authors: González Juan Antonio , La De Fuente Isaias Garcia , Cobos José Carlos , Casanova Carlos 
Published: July 2012

AbstractThermodynamic properties, vapor‐liquid equilibrium or excess enthalpy, for a set of 13 ternary mixtures including one or two 1‐alkanols and hydrocarbons are studied in the framework of the DISQUAC group contribution model. The study is extended for the binaries involved. The DISQUAC analysis is developed using interchange coefficients available in the literature. No ternary interactions are taken into account.The average relative standard deviations are 0.02 for pressure in the vapor‐liquid equilibria (4 systems); and 0.07 for the excess enthalpy (9 systems).
Rate and mechanism of the atmospheric degradation of 2H‐heptafluoropropane (HFC‐227)
Authors: Zellner R. , Bednarek G. , Hoffmann A. , Kohlmann J. P. , Mörs V. , Saathoff H. 
Published: July 2012

AbstractThe atmospheric chemical behaviour of 2H‐Heptafluoropropane (CF3CHFCF3, HFC‐227) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of HFC‐227 with OH radicals has been determined in direct time resolved experiments using a combination of laser‐pulse initiation and LIF. In the temperature range T=298‐463 K the Arrhenius expression k(T) = (3.8±0.8) 10−13 exp(‐1596±77K/T) cm3/s, which corresponds to k (298 K) = (1.8±0.3) 10−15cm3/s, was found. The mechanism of the atmospheric degradation of HFC‐227 has been investigated using both, laser‐pulse initiated/time resolved and UV photolysis/FTIR product studies. It is concluded that the major carbonyl products are CF3COF and CF2O which result from the decomposition of the oxy radical CF3CF(O)CF3 by C‐C bond fission. The rate coefficient for this decomposition process has been determined to be k = (2±1) 103s−1 at 298K. Based on the reactivity of HFC‐227 with respect to the reaction with OH radicals, the atmospheric lifetime and the GWP value for HFC‐227 are estimated to be ∼40 years and 0.6±0.2, respectively.
On the alignment of thermotropic nematic and smectic liquid crystals on lecithin coated surfaces
Authors: Hiltrop K. , Hasse J. , Stegemeyer H. 
Published: July 2012

AbstractThe orientation of thermotropic nematic and smectic liquid crystals at monomolecular films of lecithin on glass as well as germanium substrates has been studied by polarizing microscopy and FTIR spectroscopy. Nematic liquid crystals with only a weak tendency to form smectic phases exhibit a dependence of their orientation on the temperature and the packing density of the monolayer which can be explained by a sterical model. Liquid crystals in the smectic A phase as well as nematics with a strong tendency to build up smectic layers, however, align homeotropically, independent on the packing density of the lecithin film and the temperature. This can be understood as a screening of the lecithin film properties by the smectic‐like boundary layers of the nematic liquid crystal.
Interdiffusion in the quasibinary systems Cd3Te3/Ga2Te3 and Hg3Te3/Ga2Te3
Authors: Leute Volkmar , Zeppenfeld Astrid 
Published: July 2012

AbstractThe quasibinary systems Cd3Te3/Ga2Te3 (I) and Hg3Te3/Ga2Te3 (II) form regions of extended solid solution. The interdiffusion of the cationic components in these regions is coupled with a flux of so‐called structural vacancies. Peculiarities in the composition and temperature dependence of the interdiffusion coefficient, measured by an electron microprobe, are due to the effect of the thermodynamic factor. The calculation of the thermodynamic factor is based on a model of tetrahedral clusters. Special features of the phase diagrams of systems I and II are used to estimate the cluster energies. By use of these cluster energies the free excess enthalpy of the solid solution is calculated, and therefrom the thermodynamic factor can be derived. The course of the interdiffusion coefficient is caused by totally different influencies: in system I by a trend towards spinodal demixing, in system II by a trend towards ordering.
Ultrafiltration of an aqueous polymer solution in a hollow fiber dialyzer with a semipermeable membrane: Internal filtration
Authors: Wüpper A. , Röttger H. , Kreuser H. , Woermann D. , Baldamus C. A. 
Published: July 2012

AbstractAn experimental method is described to study internal filtration (back filtration) in a hollow fiber dialyzer during ultrafiltration of an aqueous polymer solution. This process takes place within a hollow fiber module if there exists a location along the axis of the fibers forming the module at which the radial volume flow density across the wall of the fibers changes its direction: Near the influx of the solution into the hollow fiber the radial volume flow density is directed into the external phase and near the efflux of the solution out of the hollow fiber it is directed into the lumen.
Microscopic derivation of the low‐T myoglobin‐CO recombination rate law by estimating statistical parameters of folding relaxation
Authors: Fernández Ariel 
Published: July 2012

AbstractThe low‐T recombination of carbon monoxide (CO) to myoglobin (Mb) obeys a rate law interpreted as a superposition of appropriately‐weighted Arrhenius‐type relaxations. We derive this rate law from microscopic principles by determining the random activation energy landscape for short timescale interconversion of myoglobin conformational substates that preserve CO‐storage capacity. Thus, the random energy model (REM) first introduced in the context of protein folding by Bryngelson and Wolynes is applied here to derive the nonexponential rate law of a reaction ‐ Mb‐CO recombination — built upon an REM‐type distribution of substate reactants.
Wetting in fluid systems. Wetting and capillary condensation of lattice gases in thin film geometry
Authors: Binder K. , Ferrenberg A. M. , Landau D. P. 
Published: July 2012

AbstractMonte Carlo studies of lattice gas models with attractive interactions between nearest neighbors on a simple cubic lattice are carried out for a L×L×D geometry with two hard walls of size L×L and periodic boundary conditions parallel to the wall. Two types of short‐range forces at the walls are considered:(i) Both walls are of the same type and exert an attractive force of the same strength (in Ising model terminology, surface fields HD = H1 occur). (ii) The walls differ, one attracts and the other repels particles, again with the same strength (HD = −H1). In the first case, capillary condensation occurs at a chemical potential differing from its value for phase coexistence in the bulk, and the (second‐order) wetting transition that occurs for D→∞ is rounded off. In the second case, an interface parallel to the walls is stabilized and we observe the interface delocalization transition predicted by Parry and Evans. A first attempt to study the nature of this “quasi wetting transition” by finite size scaling methods is reported, and discussed in the context of recent theories.
Critical point wetting from binary polymer mixtures
Authors: Steiner Ullrich , Eiser Erika , Budkowski Andrzej , Fetters Lewis , Klein Jacob 
Published: July 2012

AbstractCritical point wetting generally occurs whenever a binary fluid system in the demixed region of phase space, in contact with a surface, approaches its critical temperature. For the case of polymeric mixtures the segmental interaction parameter, which determines the interfacial tension between the coexisting phases, can be very low even far from the critical point. This suggests that polymer blends should be likely candidates to exhibit complete wetting even far below the critical point. Using nuclear reaction analysis, we have now observed such complete wetting behaviour from two different classes of binary polymer mixtures. These are mixtures of statistical olefinic copolymers, with slightly different chemical microstructures; and an isotopic pair of deuterated and protonated polymers. In the former case we have been able to follow the growth with time t of the wetting layer thickness l; our results indicate l ∼ log t.
Ellipsometric studies of wetting on low‐energy surfaces
Authors: Lawnik Wolfgang H. , Findenegg Gerhard H. 
Published: July 2012

AbstractThe physisorption of the vapor of pure nonpolar liquids (alkanes and cycloalkanes) and water onto a thermally oxidized silicon wafer was studied by means of a phase modulation ellipsometer. The resulting film thickness isotherms show complete wetting for all studied nonpolar liquids (n‐pentane, n‐hexane, cyclopentane, and cyclohexane) and incomplete wetting for water on the SiO2(27 nm)/Si‐wafer.The film thickness isotherms of the wetting systems were analysed in terms of the Frenkel‐Halsey‐Hill (FHH) equation, In (p/p0) = –(α/kT)·d−n, where n is expected to have a value of 3 for non‐retarded dispersion force interactions. The present systems, however, exhibit a much smaller value, n = 1.5±0.2. It appears that for small film thickness (a few monolayers) the exponent n depends on the nature of the adsorbent surface and increases with the strength of the adsorbate‐adsorbent interaction; in this regime the FHH equation can be taken merely as an empirical relation.