bluuebunny/crossref_metadata_2025_split huggingface dataset:
PLIF Imaging of Fuel Fraction in Practical Devices and LII Imaging of Soot
Authors: Tait Nigel P. , Greenhalgh Douglas A. 
Published: July 2012

AbstractIn this paper we discuss the development and application of 2D imaging methods for the study of fuel‐air mixing and the in‐situ measurement of soot in flames. Fuel imaging is based on planar laser‐induced fluorescence (PLIF) with pulsed UV lasers. Fuel concentrations may be estimated from the fluorescence of common fuel components or through the addition of a fluorescent species or seed. PLIF of fuel is shown to be applicable to both premixed and non‐premixed combustion. The choice of fluorescent seed and the role of interfering species, such as combustion derived polyaromatic hydrocarbons (PAH) and laser‐induced incandescence from soot, are discussed. The application of the method is illustrated with an example of an isothermal mixing study in a gas turbine combustor sector rig and measurements in a simple flame. The results demonstrate that PLIF can achieve high spatial resolution, circa 0.4 mm, in a combustor with dimensions of order of 400 mm. The dynamic range of the measured intensities exceeds 1500 with typical signal‐to‐noise ratios of better than 100:1. A major source of interference in PLIF studies of non‐premixed flames is laser‐induced incandescence (LII) from soot particles. We discuss the role of LII both as an interference in PLIF imaging and as an imaging method for soot volume fraction. A detailed analysis of the physics of LII is presented on a theoretical model developed. Results from the model and supporting experimental data are presented. LII images from a highly turbulent sooting flame indicate that soot structures, probably in the form of thin sheets as small as 100 μm across, are formed through vortex mixing.
Analysis at Surfaces and Interfaces. Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) Diagnostics of Diamond Surface Chemistry
Authors: Chuang T. J. 
Published: July 2012

AbstractNonlinear second harmonic generation (SHG) and sum frequency generation (SFG) laser spectroscopies have been applied along with conventional surface analytical techniques to study the gaseous interactions on diamond surfaces. Recent results relevant to diamond CVD processes are discussed.
Laser Excitation of Surface Phonons and Wave Pulses
Authors: Hess Peter 
Published: July 2012

AbstractExcitation of surface phonons or surface acoustic wave (SAW) pulses with a broad frequency spectrum up to 200–300 MHz using focused laser pulses is discussed. Several optical and piezoelectric methods for broadband detection of the resulting surface displacements are considered. It is shown that for an anisotropic single crystal the SAW velocity can be measured with an accuracy of 0.1% as a function of the crystal plane and direction due to the short wave pulses achieved. In a layered system strong dispersion occurs, since the waves with different wavelengths probe different depths corresponding to their wavelength and thus travel with different velocities in the heterogeneous solid. From a non‐linear dispersion effect several film properties can be obtained, such as thickness, density and elastic constants (e.g. Young's modulus and Poisson's ratio). Results are presented for fullerite and diamondlike carbon films. The characteristics of the pulsed laser method are compared with Brillouin scattering, interdigital transducers and the acoustic microscope.
Photodynamics on Surfaces Revealed by Laser Studies
Authors: Hasselbrink E. 
Published: July 2012

AbstractFundamental mechanisms for photochemistry at metal and semiconductor surfaces are discussed. Experiments probing these mechanism are presented discussed for molecular oxygen adsorbed on palladium(111). Isotope effects in photodesorption and photodissociation are shown to provide insights into the excitation transfer mechanisms and the probability of nonquenching events.
Joint PDFs of Scalar Quantities in Turbulent Diffusion Flames by Raman and Rayleigh Scattering
Authors: Hassel F. , Hundhausen A. , Klos Th. , Sprenzel U. , Bockhorn H. 
Published: July 2012

AbstractSimultaneous time and space resolved measurements of CO2, O2, CO, N2, H2O mole fractions and temperature are performed by using Raman and Rayleigh scattering. The investigated system is a turbulent jet of CO injected into the coflowing hot exhaust of a lean CH4/N2/O2‐flame. Mean values, joint one‐point 6D‐pdfs and characteristic statistic quantities are determined. The results for mean values agree well with measurements from independent methods. Determined joint one‐point pdfs resemble more‐dimensional normal distributions. The pdfs are non‐symmetric in the reaction zone with positive or negative correlation coefficients for the reactants. This indicates that the low Damköhler number system under investigation is not diffusion controlled. A quantification for this is given by the calculation of correlation coefficients and turbulence intensities. The measurements are suitable to verify models for transport equations of pdfs in turbulent reacting flows at low Damköhler numbers.
Measurements of OH by LIF and Temperatures by Holographic Interferometry in Catalytically Stabilized Combustion of Hydrogen: Comparison of Measurements and Numerical Simulation
Authors: Buser S. , Benz P. , Schlegel A. , Bockhorn H. 
Published: July 2012

AbstractTo investigate the catalytically stabilized combustion of hydrogen in a duct, hydroxyl radical and temperature distributions have been measured by LIF and holographic interferometry, resp. A detailed two‐dimensional numerical model has been developed. For the heterogeneous reaction mechanism simplifications are introduced which are justified by an analysis of the elementary heterogeneous reaction mechanism proposed by Hellsing et al. 1991. Experimental results and numerical simulation are in good agreement. The numerical model allows the identification of the relevant coupling mechanism between heterogeneous and homogeneous combustion of hydrogen. These are: radical recombination reactions at the wall, diffusive fluxes of H2, O2, H2O due to the heterogeneous reactions and heat transfer from the wall to the gas. The desorption of radicals from the surface into the gas does not play a significant role in this system.
Time‐Resolved Fluorescence Studies of Labelled Nucleosides
Authors: Han K.‐T. , Sauer M. , Schulz A. , Seeger S. , Wolfrum J. 
Published: July 2012

AbstractSynthesis, steady‐state and time‐resolved fluorescence measurements of carboxycoumari labelled aminonucleosides (thymidine, cytidine, guanosine) are described. The data indicate a strong influence of the coupling position, the linker length and the structure of the coumarin dye on the quenching rates.
Preferential solvation of some copper (II) salts in dioxane‐dimethylsulphoxide (DMSO) mixtures
Authors: Sreekumar T. K. , Kalidas C. 
Published: July 2012

AbstractThe solvation behaviour of some copper(II) salts viz. copper(II) iodate, copper (II) benzoate and tetraDMSOcopper(II) perchlorate has been investigated by Gibbs transfer energy and solvent transport number measurements. The Gibbs transfer energies of the salts have been split into their ionic components by employing the nLJP method. The transfer energies of the copper (II) ions decrease continuously with the addition of DMSO while those of the anions increase under the same conditions. The solvent transport number, Δ, of DMSO is positive and passes through a maximum for all salts around XDMSO = 0.35 to 0.45. The results indicate a heteroselective solvation of the salts, the copper (II) ion being selectively solvated by DMSO and the anions by dioxane.
Static relative permittivity of sulfur hexafluoride up to 30 MPa
Authors: Kita T. , Uosaki Y. , Moriyoshi T. 
Published: July 2012

AbstractThe static relative permittivity ϵr of sulfur hexafluoride, SF6, has been measured along ten isotherms from 273.15 to 353.15 K at pressures up to 30 MPa. The experimental ϵr‐values obtained were accurate to within ±0.02 per cent, except for some values in the vicinity of the critical point. The critical relative permittivity ϵr,c was estimated to be 1.281 ±0.001 by application of the rectilinear diameter law. The ϵr‐values were combined with densities obtained from the equation of state in the literature to calculate the molar polarization Pm given by the Clausius‐Mossotti equation. The results of ϵr and Pm as a function of fluid density are discussed; the volume polarizability α' of SF6 was evaluated to be 6.67×10−30m3 and 6.59×10−30m3 using the values of the first dielectric virial coefficient Aϵ determined by two methods. Further, the values of α' for carbon dioxide and nitrous oxide were recalculated to be 2.94×10−30 m3 and 3.20×10−30m3, respectively, from Aϵ‐values obtained by the newly employed method.
A neural network hamiltonian governing the formation of RNA base‐pairing patterns
Authors: Fernández Ariel , Belinky Alejandro 
Published: July 2012

AbstractWe implement a neural network associating a two‐state unit to each pair of bases in a fixed RNA sequence. The connectivity matrix is constructed following the cooperativity rules of nucleation for RNA hairpin formation and base‐pair stacking. Attractive neural patterns correspond to stable RNA secondary structures. Moreover, the Gibbs probability of a pattern coincides with the Boltzmann weight of the corresponding structure.
Staining of biomembranes with amphiphilic hemicyanine dyes
Authors: Fromherz P. , Röcker C. 
Published: July 2012

AbstractThe binding of amphiphilic dyes to biomembranes is described as a distribution equilibrium between a three‐dimensional and a two‐dimensional phase. Ostwald‐type coefficients and formal binding constants are measured for lipid vesicles and hemicyanine dyes with different hydrophilic‐hydrophobic balance. The staining of neuron membranes is discussed as a basis for optical recording of membrane voltage by hemicyanine dyes.
The induced infrared spectrum of H2 Adsorbed on NaCl film at 8 K. Rotation of ortho‐H2 in the state J = 1 on the surface
Authors: Heidberg J. , Dierkes W. , Schönekäs O. , Schwarte R. 
Published: July 2012

AbstractThe induced fundamental infrared spectrum of H2 adsorbed on NaCl film at 8 K has been observed under ultrahigh vacuum conditions. There are two adsorption sites. For each site a splitting of the vibrational fundamental into a doublet is resolved. The doublet is assigned to para‐H2 and ortho‐H2 by its close resemblance to the doublet Q1 (0) and Q1(1) calculated and observed in gaseous and matrix‐isolated H2. According to Ben Ephraim and Folman the lowest adsorption potential corresponds to a H2 orientation parallel to the surface and slightly perturbed free rotation about an axis normal to the surface. However, because of space quantization, the ortho‐H2 molecules are tilted up in the rotational state J = 1 and perform a hindered rotation about an axis tilted to the surface.
Vibrational relaxation of HCl(v = 1) in HCl/CO/Ar gaseous mixtures between 296 and 173 K
Authors: Losert O. F. J. , Schramm B. 
Published: July 2012

AbstractVibrational relaxation of HCl(v = 1) in HCl/CO/Ar gaseous mixtures has been measured between room temperature and 173 K by the laser‐induced fluorescence (LIF) technique. Rate constants for the total relaxation and the V‐V relaxation have been determined showing that the relaxation is governed by the V‐V process. For the rates of the V‐R,T processes which relax HCl(v = 1) and CO(v = 1) upper limits are given. As in similar systems relaxation efficiency is higher at lower temperatures.
Elementary reactions of NH (a1Δ) and NH(X3Σ) with N, O and NO
Authors: Hack W. , Wagner H. Gg. , Zasypkin A. 
Published: July 2012

AbstractThe elementary reactions of NH(a1Δ) with N, O, and NO and the reactions of NH(X3Σ−) with N, O and NO were studied in a quasi static laser flash photolysis cell at room temperature (T=298T) and low pressures (15≤p/mbar≤20). NH(a) was produced by HN3 laser photolysis at λ = 248 nm. NH(X) was obtained from the fast quenching of NH(a) with Xe. The O atom source was the NO + N reaction ([N]0>>[NO]0), with N atoms formed in a microwave discharge of N2/He. NH(a), NO(X) and the primary products NH(X), OH(X) and NO (X) were detected by pulsed laser induced fluorescence (LIF). The absolute N atom concentrations were determined via the reaction of N with NO. Time resolution was achieved by time delay between photolysis and probe laser pulses.For overall depletion:magnified imagethe following rate constants were obtained: k1, = (6.0±1.5)·1011 cm3/(mol·s); k2 = (5.6±2)·1012cm3/(mol·s); and k3 = (1.8±0.2)·1013 cm3(mol·s).By fitting the NH(X) concentration profiles, determined experimentally, with computer simulations, the following rate constants for quenching channels were obtained: k1q = (6.0±1.2)·1011 cm3/(mol·s) and k2q = (1.2±0.3)·1012cm3/(mol·s). For the reaction pathways of reaction (2):magnified image
Viscosity of two non‐ionic amphiphile/water mixtures of critical composition: Study of the systems triethyleneglycolmonohexylether (C6E3)/water and tetraethyleneglycolmonooctylether (C8E4)/water
Authors: Zielesny A. , Limberg S. , Woermann D. 
Published: July 2012

AbstractThe shear viscosity of a C6E3/water and a C8E4/water mixture of critical composition (lower critical point) is measured in a wide temperature range (C6E3/water: 2 mK≤(Tc‐T)≤43.913 K; C8E4/water: 5 mK≤(Tc‐T)≤ 39.517 K) using capillary viscometry. The viscosity η is dominated by singular contributions in a narrow temperature range only (C6E3/water: (Tc‐T)≤0.8K; C8E4/water: (Tc‐T)≤0.2K). This temperature range is much smaller than that found in “simple” binary mixtures of low molar mass components. The temperature dependence of η of the system C6E3/water at temperatures away from Tc, in the crossover regime and in the critical regime close to Tc is analyzed successfully by the same methods developed for the analysis of viscosity data of binary mixtures of low molar mass components. The method fails in the analysis of the viscosity data of the system C8E4/water. This is probably caused by the temperature‐dependent influence of micelles on the viscosity.
Diffusion Coefficients in aqueous solutions of magnesium nitrate at 298 K
Authors: Lobo Victor M. M. , Ribeiro Ana Cristina F. , Verissimo Luis M. P. 
Published: July 2012

AbstractDifferential diffusion coefficients of magnesium nitrate in water, at 298 K and at different concentrations, have been measured using a conductimetric cell. The results are discussed on the basis of the Onsager‐Fuoss and Pikal theories. The cell uses an open‐ended capillary method and a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries at recorded times.
The electrochemical quartz‐microbalance in media of changing viscoelastic properties, and the design and characterization of a suitable driver electronics
Authors: Soares D. M. , Kautek W. , Fruböse C. , Doblhofer K. 
Published: July 2012

AbstractIn this work we develop a new description of the behaviour of the electrochemical quartz‐microbalance (EQMB). It takes into account the phase shift introduced by the driver and also the influence of changing visco‐elastic properties of the medium in contact with the quartz (i.e. film and/or liquid).Based on these concepts a new driver circuit has been designed. Its electronics is advanced relative to the classical drivers in two points: a) It allows a partial impedance analysis of the quartz, b) it introduces a controllable phase shift into the system driver+crystal. Thus, an evaluation and even correction of the obtained frequency‐results becomes possible.Experimental frequency data obtained in liquids with different visco‐elastic properties were corrected with the new approach and compared with theory.The capability of determining the resistive component of the quartz' impedance was also used to determine the limits of the rigid‐layer approximation for polypyrrole‐films.
Electrochemical reduction of anthracenes on poly(vinylferrocenium) coated Pt electrodes in acetonitrile
Authors: Gülce Handan , Özyörük Haluk , Yildiz* Attila 
Published: July 2012

AbstractThe electroreduction behaviour of anthracene and some of its derivatives on poly(vinylferrocenium) coated Pt electrodes was investigated and compared with that on uncoated Pt surface using' cyclic voltammetry in acetonitrile/0.1 M TBAP solutions. The changes occurring in the structure of the film after the electrode reactions were followed by IR spectroscopy and DSC measurements. Catalytic reduction of the anthracene derivatives occur when electrode reactions were carried out on the coated surface.
Phase transitions at Al and Au surfaces: Deconstruction, roughening and premelting
Authors: von Blanckenhagen P. 
Published: July 2012

AbstractA short outline of structural phase transitions at surfaces and their experimental verification will be given as an introduction, which will be followed by a review of experimental and theoretical results for Al and Au surfaces.We have studied Au(111)‐, Au(110)‐ and Au(100)‐surfaces by medium energy ion scattering (MEIS) experiments and Au(110)‐ as well as Al(110)‐surfaces by low energy electron diffraction (LEED) experiments.At the Au(110) (2×1)‐surface deconstruction is accompanied by the disappearance of monoatomic steps. At about 40 K above the deconstruction temperature roughening sets in. The rough surface begins to smoothen if due to the increasing diffusion the outermost layers start to transform into a quasi‐liquid state. The growth of the quasi‐liquid layer with increasing temperature follows a logarithmic law. Preroughening, roughening and premelting transitions have been detected at the Al(110)‐surface. Open questions regarding these phase transitions will be discussed.
X‐ray studies of the thickness and roughness of thin adsorbed fluid layers
Authors: Pershan P. S. 
Published: July 2012

AbstractThis paper is a brief summary of a talk delivered at the “Discussion Meeting on Phase Transitions at Interfaces”, Bad Herrenalb, Germany in September 1993 on the application of synchrotron X‐ray scattering to the study of liquid surfaces. More complete discussion of much of this material can be found in the publications cited in the manuscript. The oral presentation was concerned with the application of X‐ray specular reflectivity to study structure of the liquid/vapor interface for various liquids, including superfluid4He, liquid gallium and thin liquid wetting layers of classical liquids adsorbed on solid surfaces. The effects that correlations between the height fluctuations on the top and bottom surfaces of thin adsorbed liquids have on the reflectivity and diffuse scattering from thin films will be discussed.
Interfacial segregation and wetting transition in fluid binary metallic mixtures
Authors: Müller S. C. , Tostmann H. , Nattland D. , Freyland W. 
Published: July 2012

AbstractFirst indications of wetting transitions in alkalimetal‐alkalihalide solutions have been obtained in previous optical studies. In order to study this transition continuously as a function of temperature and composition along the coexisting curve and in the homogeneous phase we have started SHG‐measurements on these systems at the fluid‐sapphire interface. First results of this experiment in comparison with the ellipsometric results will be presented. On the other hand, in order to exclude influences of the substrate on the interfacial behaviour we have investigated the liquid‐vapour interface in the liquid alloy Ga‐Bi (metallic system with miscibility gap) by spectroscopic ellipsometry. The main interest concentrates on possible discontinuous changes of the optical constants at the interface with varying composition and temperature. First results are presented.
Experimental observation of prewetting in a binary liquid mixture
Authors: Bonn Daniel , Kellay Hamid , Meunier Jacques 
Published: July 2012

AbstractWe present experimental evidence for the existence of a prewetting transition for the binary liquid mixture of cyclohexane and methanol. For certain compositions in the mixed region of the phase diagram, a first‐order thin to thick film transition can be observed. The observed transition exhibits a large hysteresis. It is shown that the prewetting line approaches the coexistence curve tangentially. Also, the prewetting critical point displays 2‐D Ising‐like criticality. These findings are compared to recent experiments on other systems, in which prewetting was also observed.
Interfacial wetting in binary liquid mixtures
Authors: Getta X. , Dietrich S. 
Published: July 2012

AbstractWe classify the wetting behavior of binary liquid mixtures at their liquid‐vapor interface. The criteria with respect to the atomic interactions between the two species are whether the Hamaker constant of that interface fulfills either the sufficient conditions for the absence of a wetting transition, or the necessary conditions for critical wetting, or the necessary conditions either for being wet already at low temperatures of for undergoing a first‐order wetting transition upon approaching the critical end point along the triple line. Based on the Percus‐Yevick theory we scan the whole parameter space which determines the structure of the bulk phase diagrams. In addition we compare the predictions of the Percus‐Yevick theory for the bulk phase diagrams and the number densities of the fluid bulk phases with experimental and simulation data as well as with different theoretical approaches.
Wetting of laterally structured surfaces
Authors: Müller‐Buschbaum P. , Tolan M. , Press W. , Brinkop F. , Kotthaus J. P. 
Published: July 2012

AbstractAn x‐ray scattering study of a laterally structured solid surface wetted by a liquid is reported. GaAs (001) samples with etched trapezoidal surface gratings are used as substrates. Due to the lattice spacing of d = 5900 Å and the height h of about 450 Å such gratings can be regarded as a row of free edges and wedges. The special wetting behaviour of these wedges with a liquid film of CCl4 was studied using x‐ray reflectivity in the region of total external reflection. The reflectivity of the film on top of the laterally structured GaAs substrate is explained by model calculations which contain the electron density depth profile perpendicular to the surface. The thickness of the liquid wetting film on top of the stepped surface was obtained from the fit of the data.