bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of Burning Velocity and Flame Structure in Methanol – Air Mixtures
Authors: Dove J. E. , Warnatz J. 
Published: July 2012

AbstractAn a priori calculation has been made of laminar burning velocities of methanol‐air mixtures over the composition range 8% to 20% CH3OH at 298 K and 1 bar, and for stoichiometric mixtures over the pressure range 0.0625 to 16 bar and over the temperature range 298 to 1200 K. The time dependent conservation equations were solved repeatedly until a time undependent solution was obtained, giving the required flame profiles. The kinetic data set was based on a full survey of high temperature literature data, and comprised 40 elementary reactions with 15 chemical species. The results show generally very good agreement with experimentally measured burning velocities. A kinetic sensitivity analysis shows which elementary reactions are important in determining the flame properties, and enables us to state for which of these reactions it is particularly important to obtain improved rate data.
Temperature Measurements in Flames by Laser Raman Techniques
Authors: Kreutner W. , Stricker W. , Just Th. 
Published: July 2012

AbstractLaser Raman techniques are assuming an ever increasing role in evaluating temperature data from combustion systems. Non‐intrusive and spatially resolved temperature measurements can be very helpful to improve the understanding of combustion processes. An important possibility of these techniques may be a more detailed check of computer codes for the modelling of flames. In order to test the influence of molecular parameters on the CARS model and the evaluation procedure a comparison of temperature measurements in a premixed propane‐air flame at atmospheric pressure by spontaneous Raman spectroscopy and by CARS (Coherent Anti‐Stokes Raman Scattering) was made.
Laser‐Induced Saturated Fluorescence as a Method for the Determination of Radical Concentrations in Flames
Authors: Kohse‐Höinghaus K. , Perc W. , Just Th. 
Published: July 2012

AbstractThe laser‐induced saturated fluorescence method was further developed with the aim of increasing the accuracy of radical concentration measurements in flames. Absolute number densities for CH and OH in a low‐pressure acetylene/oxygen flame were obtained from saturation curves based on a two‐level rate equation model, whose validity was checked for the experimental conditions. From these saturation curves, approximate oscillator strengths could be deduced, which could serve as a cross‐check for the evaluated number densities. Temperatures were determined from rotational spectra of the excited molecules. – For CH as well as for OH, the concentrations obtained with different excitation methods agree well with each other. They were compared with kinetic model calculations. For the extension of the saturated fluorescence method to higher pressures, a multi‐level model is being developed.
Analyse des Verbrennungsablaufes im Ottomotor
Authors: Müller H. 
Published: July 2012

AbstractThe analysis of the combustion process in spark ignition engines is important because their operation accounts for about 20% of the total oil consumption. A gain in efficiency will be beneficial for both energy consumption and exhaust emissions. Combustion in an engine differs in several points from ideal combustion process. Detailed information is given in the paper by considering three consecutive parts of combustion: the inflammation period, the main burning period, the afterburning period. In spark ignition engines practically only the inflammation period depends on the equivalence ratio. Quantitative details of the combustion process and of flame spread is obtained by pressure measurements, ionisation gaps and local radiation measurements.
Investigation of the Formation of High Molecular Hydrocarbons and Soot in Premixed Hydrocarbon‐Oxygen Flames
Authors: Bockhorn H. , Fetting F. , Wenz H. W. 
Published: July 2012

AbstractMeasurements of concentrations of high molecular hydrocarbons in laminar flat low pressure flames with various hydrocarbons under sooting conditions are reported. The results show that for all fuels investigated in that region of the flames where the bulk of soot is formed besides the main combustion products some characteristic groups of species are to be found. Within these groups of species only few fuel specific characteristics are stated. The main fuel specific influence lies in the relative concentration for the species. A reaction scheme for the qualitative explanation of the results found is discussed.
Charged Particles in Sooting Flames II. Determination of the Fraction of Charged Soot
Authors: Homann K. H. , Wolf H. 
Published: July 2012

AbstractA new technique has been developed allowing the determination of the relative amounts of charged and neutral soot in fuel‐rich premixed low‐pressure flames. Results on C2H2 and C6H6 flames are reported and used, together with charged particle number densities, to calculate soot mass fractions and particle sizes. The occurrence of charged soot particles is discussed within the adopted mechanism of soot formation.
Rußbildung in verschiedenen Brennstoff‐Luft‐Flammen
Authors: Baumgärtner L. , Jander H. , Wagner H. Gg. 
Published: July 2012

AbstractThe mass growth of soot and coagulation of soot particles were measured for different fuels in mixture with air on a flat flame burner. Neither the coagulation rate constant kcoag nor the rate constant for the mass growth of soot kf show a pronounced dependence of the type of fuel used. The total amount of soot formed increases strongly with increasing fuel content of the mixture for all fuels investigated; it decreases with increasing temperature within the used temperature range.
Die gezielte Oxidation der Kohle: Synthesegas durch Kohlevergasung
Authors: Cornils B. 
Published: July 2012

AbstractIn the medium and long term a reconnection between coal – as a source of carbon – and chemistry – as a consumer of carbon – will prove to be necessary. Syngas will be the most effective means of establishing this link, and coal gasification processes will be required which produce the syngas by partial oxidation. – This contribution reviews the existing coal gasification plants of the “first generation” and reports on the status of the “second generation” processes under development.
An ESCA Study on the Electrochemical Double Layer of Emersed Electrodes
Authors: Kolb P. M. , Rath D. L. , Wille R. , Hansen W. N. 
Published: July 2012

AbstractGold electrodes were emersed from the electrolyte during potential control and subsequently transferred into a UHV chamber for their surfaces to be analysed by ESCA as a function of emersion potential and electrolyte composition. The ESCA measurements confirm the view that electrodes can be removed from the electrochemical cell with the electrochemical double layer unchanged and the bulk electrolyte otherwise absent. The potential power of ex‐situ studies, such as ESCA, on emersed electrodes is demonstrated by determining surface excesses and adsorption isotherms for a number of weakly and strongly adsorbing ions, as well as for metal deposits. Observations of chemical shifts for double‐layer constituents are reported and briefly discussed.
Small Angle Neutron Scattering Studies on Viscoelastic Detergents
Authors: Hoffmann H. , Kalus J. , Thurn H. , Ibel K. 
Published: July 2012

AbstractSmall angle neutron scattering experiments (SANS) on solutions of cetylpyridiniumsalicylate (CPS) in D2O over a large concentration range show a characteristic scattering maximum due to mutual interactions between the rodlike micelles. From the scattering rates structure factors S(Q), pair correlation functions g(r) and corresponding mean potentials W(r) are derived. Furthermore it is shown, that the length L of the scatterers decreases in a concentration range from 20 mM to 160 mM CPS. To study the influence of interaction on the rods, increasing amount of salt (NaCl and NaSal) was added to a 5 mM solution of CPS. As one would expect, the scattering maximum decreases, while the length of the micelles increases. It is shown, that the rods remain rather stiff when small amounts of salt are added. In the case of 32 mM NaCl it was also possible to fit the data with a persistence length model showing that the rods may become flexible when large amounts of salt are added. A persistence length of 8000 – 12000 Å was evaluated for these conditions.
Low Temperature Photoreactivity of Diacetylene – Phenazine Complex Crystals
Authors: Bubeck C. , Xuan T. H. Nguyen , Sixl H. , Tieke B. , Bloor D. 
Published: July 2012

AbstractThe low temperature photoreactivity of diacetylene‐phenazine complex crystals has been studied by ESR‐ and optical spectroscopy. The optical excitation of phenazine at 4.2 K creates a stable, triplet diradical. It is caused by an electron‐transfer reaction from the diacetylene to the phenazine and a protonation of the phenazine. The diradical can be bleached optically at 4.2 K and thermally at temperatures above 90 K. The diacetylene units polymerize in the dark, as soon as the preirradiated crystals are warmed up to temperatures above 200 K. The solid‐state photochemistry of phenazine at low temperatures and its relation to the sensitized photopolymerization are discussed.
Thermodynamics of Polydimethylsiloxane Solutions. I. Calorimetric Results of the Enthalpy of Dilution with Seven Organic Solvents
Authors: Neff B. , Heintz A. , Lichtenthaler R. N. 
Published: July 2012

AbstractA titration calorimetric method is described which has been used for the determination of heats of dilution of seven Polydimethylsiloxane (PDMS)/solvent systems with different molecular weight of the PDMS samples at 25°C and 40°C. From the data obtained the χH‐parameter due to Flory's theory has been calculated. A systematic increase of χH with concentration of PDMS and a decrease with increasing molecular weight of PDMS has been observed.
p‐V‐T and Bubble‐point Measurements in the System HBr – H2O and its Critical Behaviour
Authors: Rau Hans , Friedrichs Hans Adolf , Mathia Wolfgang 
Published: July 2012

Abstractp‐V‐T measurements on HBr/H2O mixtures up to 820 K and 1500 bar in the complete range between pure H2O and pure HBr are reported. The bubble‐point line has been determined by visual observation up to about 690 K and 500 bar. – For the vapour phase an equation of state (Dieterici‐type) with mixing rules is applied. The experimental data including literature values are analyzed by integration of the Gibbs‐Duhem equation. – The system HBr/H2O is azeotropic even at elevated pressures. The azeotropic line intersects the high temperature branch of the critical curve at about xHBr = 0.045, 684 K and 335 bar. The low temperature branch of the critical curve is nearly identical to the critical point of HBr.
Diffusion Coefficients and Thermal Diffusion Factors for the Systems H2–N2, D2–N2, H2–O2 and D2–O2
Authors: Trengove R. D. , Robjohns H. L. , Dunlop P. J. 
Published: July 2012

AbstractDiffusion coefficients and thermal diffusion factors are reported for the systems H2–N2, D2–N2, H2–O2 and D2–O2. Using approximate spherical potential functions for the like and unlike interactions, the experimental results are compared with corresponding values predicted by the Chapman‐Enskog theory.
The Nitroprusside Ion as a Nitrosating Reagent. Kinetic Studies on the Nitrosation of Morpholine
Authors: Casado J. , Quintela M. A. López , Mosquera M. , Rodr Prieto M. F. Íguez , Tato J. Vázquez 
Published: July 2012

AbstractThis article reports a kinetic study of the nitrosation of morpholine (MOR) by the nitroprusside ion, [Fe(CN)5NO]2−, to form N‐nitrosomorpholine, a substance of proven carcinogenicity. The reaction is of order one with respect to the nitroprusside ion and order two with respect to morpholine. The influence of the pH and the ionic strength of the medium on the rate of reaction has been studied in detail. A reaction mechanism is proposed whose first step is a fast reaction between the amine and the coordinated nitrosyl group to form a complex which reaches equilibrium with the reagents and then reacts with another molecule of amine to produce the corresponding nitrosamine and the complex [Fe(CN)5MOR]3−. The acidity constant of morpholine has been determined kinetically.
The Reaction Mechanism of the Nitrosation of Ureas
Authors: Casado J. , Castro A. , Mosquera M. , Rodr Prieto M. F. Íguez , Tato J. Vázquez 
Published: July 2012

AbstractThe nitrosation of methylurea has been studied under catalysis by acetate and mono‐, di‐ and trichloroacetate buffers. The following general equation for the rate of reaction as a function of the total concentrations of the reagents has been deduced:

where K1 is the acidity constant of nitrous acid and K2 that of carboxylic acid. The catalysis observed has been found to be due to the organic anions, and Brønsted relation is obeyed with β = 0.24. – The experimental results have been interpreted in terms of a reaction mechanism which features the rapid formation of a intermediate, MeNH(NO)CONH2, when the methylurea is nitrosated. The rate controlling step is the transfer of a proton from this intermediate to the solvent or to a basic catalyst (the nitrite ion or the organic anion). That it is this step that controls the overall rate of reaction is supported by the isotopic effect (kH/kD = 3.5) observed on carrying out kinetic measurements in D2O.
Differential Electrochemical Mass Spectroscopy (DEMS) — a New Method for the Study of Electrode Processes
Authors: Wolter O. , Heitbaum J. 
Published: July 2012

AbstractA new technique is presented which allows the gaseous and volatile products of electrochemical reactions to be measured quantitatively and with high sensitivity. The equipment consists of the electrochemical cell, the membrane inlet system and the mass spectrometer. Products being formed at the porous working electrode are sucked through the porous membrane into the ion source of the mass spectrometer. The mass intensity detected is proportional to the corresponding faradaic current. A rate of formation of 5 · 10−11 mol s−1 can well be measured. The rise time of the mass intensity is short enough to allow it to be quantitatively correlated to the faradaic current even at variing electrode potential. This is utilized in mass spectroscopic cyclic voltammetry. The feasibility of the method is described.
Scanning Calorimetry as an Analytical Tool to Characterize DNAs
Authors: Klump Horst , Herzog Klaus 
Published: July 2012

AbstractThe investigation of the native DNA structure of various sources with the help of X‐ray diffraction techniques of fibres reveals a striking similarity of the structural dimensions of all DNAs. Contrary to these results sequence analysis of the nucleotide bases demonstrates the uniqueness of the vast majority of domains even within the DNA of a single species. In this paper we will demonstrate that there is a possibility to characterize the different DNAs by the help of differential adiabatic scanning calorimetry. The heat capacity as a function of temperature is unique for each DNA and can serve to identify the particular DNA and can help to group the eucariotic, procariotic and the viral DNAs. This will be shown for eleven different DNAs.
Die Temperaturabhängigkeit der optischen Konstanten des Chlorbenzols im infraroten Spektralbereich
Authors: Köser Heinz J. K. 
Published: July 2012

AbstractThe optical constants of chlorobenzene between 1500 and 600 cm−1 have been determined with the help of ATR spectroscopy in the temperature range between — 30 and + 80°C. — The observed decrease of the integral intensity with temperature can be explained by the change of density and lokal field. The increase of the band half‐width is a result of faster molecular motion. Form and intensity of the band near 900 cm−1 are temperature insensitive. — The temperature dependence of the refractive index in regions with negligible absorption has to be explained by the combined influence of density and change of lokal field with density. Even after taking due account of this effect the real and imaginary parts of the molecular polarizability remain temperature dependent within the band region.
Rate Constants for the Reactions of OH Radicals with Aromatics: Benzene, Phenol, Aniline, and 1,2,4‐Trichlorobenzene
Authors: Rinke Monika , Zetzsch Cornelius 
Published: July 2012

AbstractReactions of OH radicals with aromatics were investigated in the presence of He at pressures ranging from 5 to 800 mbar using pulsed vacuum uv photolysis of H2O for the production of OH and time resolved resonance fluorescence for the detection of OH. At room temperature (296 K) in the presence of 133 mbar He the rate constants, k, were observed to be in the high pressure limit. The rate constants, (k ± Δk)/10−12 cm3 s−1, were determined to be: (1.0 ± 0.2) for benzene; (120 ± 24) for aniline; (28 ± 6) for phenol, (0.50 ± 0.10) for 1,2,4‐trichlorobenzene. — For the temperature dependence of the rate constant for 1,2,4‐trichlorobenzene the Arrhenius expression (k ± 3σ) = (2.3 ± 1) · 10−12 exp [ — (430 ± 125) K/T] cm3 s−1 is obtained from measurements at 273 to 368 K. — The rate constants at room temperature can be correlated with the ionization potential, I, of the aromatics, yielding the equation: logk/cm3s−1 = 0.74–1.36 · I/eV. This equation is seen to represent the rate data on 18 aromatics to within a precision of a factor of two; with some precautions it might be used to predict rate constants for further substituted benzene aromatics. Outliers in such a diagram are benzaldehyde and the cresols (being more reactive than predicted), and diphenyl and chlorinated aromatics (being less reactive).
Spectral Properties and Kinetics of Cationic Transients Generated in Electron Pulse Irradiated C7‐ to C16‐Alkanes
Authors: Mehnert R. , Brede O. , Naumann W. 
Published: July 2012

AbstractAfter electron pulse irradiation of n‐heptane, 3‐methylheptane, n‐decane, n‐dodecane, n‐tetradecane, and n‐hexadecane containing CCl4 as electron scavenger, transient optical absorption bands were observed with peak wavelengths between 550 and 880 nm. The bands are assigned to the corresponding alkane radical cations. For n‐heptane radical cations a maximum extinction coefficient of 8.8 · 103 dm3 mol−1 cm−1 is estimated. Alkene radical cations were also identified in neat alkane solutions. They seem to be generated by fragmentation of vibronically excited alkane radical cations and exhibit strong optical absorption bands (π‐π*‐transitions) around 280 nm. — The kinetics of the electron transfer from n‐hexadecane as solute to cationic transients present in n‐heptane after irradiation was experimentally studied and compared with calculations using the phenomenological model of ion pair recombination presented by Infelta and Rzad [1]. From two alternative reaction mechanisms applied, differing mainly in that one assumes short‐lived mobile holes, it is concluded that positive mobile holes should also exist in n‐heptane at times <10−9 s. Then they should be transformed into massive n‐heptane radical cations. — Electron transfer efficiencies were determined in n‐heptane for 11 solutes such as alkanes, alkenes and aromatics. These efficiencies are related to rate constants of the electron transfer from the solutes to mobile positive holes. The observed dependence of the rate constants on the free energy ΔG of the electron transfer reaction is explained in terms of changes in the Franck‐Condon vibrational overlap factors.
On the Mechanism of Reversible Unimolecular Reactions and the Canonical (“High Pressure”) Limit of the Rate Coefficient at Low Pressures*)
Authors: Quack Martin 
Published: July 2012

AbstractJost's [1] treatment of generalized first order kinetics is used for a new discussion of the mechanism of reversible unimolecular reactions. A detailed analysis of time dependent average microscopic rate coefficients and level populations is presented using exact solutions for a realistic model of an isomerization reaction. It is shown that unimolecular fall‐off for the macroscopic relaxation is not mainly due to a reduced population of reactive levels as suggested by the irreversible Lindemann mechanism, but rather due to a fast reverse reaction even at early times. It is furthermore shown that the average microscopic rate coefficients can be measured directly, in principle. At equilibrium they are equal to the canonical (“high pressure”) limit of the rate coefficient even for arbitrarily low pressures. Practical experimental schemes are suggested for thus obtaining high pressure limiting rate coefficients without extrapolation procedures.
A Generalized van der Waals Equation of State III. Calculation of Excess Thermodynamic Quantities from Density Measurements
Authors: Kohler F. , Svejda P. 
Published: July 2012

AbstractAn equation of state reported previously is further developed for the calculation of thermodynamic excess functions in mixtures. The only mixture quantity used is the excess volume. With this quantity, one of the two mixing rules is determined. For the second rule, a plausible, but essentially empirical prescription is applied. Numerical calculations are carried out for the system benzene + cyclohexane.
Temperature Dependence of Number and Size of Triton‐X‐100 Micelles in Aqueous Solution
Authors: Rau Hermann , Greiner Gerhard , Hämmerle Hugo 
Published: July 2012

AbstractStationary and dynamic fluorescence experiments with pyrene as a probe molecule indicate higher aggregation numbers in Triton‐X‐100 micelles at higher temperatures well below the cloud point. The structure of the micelles is changed considerably as (in spite of higher aggregation) the hydrophobic compartment available to the probe molecules becomes smaller. The increase of aggregation is combined with a decrease of the number of micelles, i. e. micelles are dissolved or merge with others.
Mass Spectrometric Study of the Vaporization of Cesium Iodide and Thermochemistry of (CsI)2(g) and (CsI)3(g)
Authors: Viswanathan R. , Hilpert K. 
Published: July 2012

AbstractKnudsen cell mass spectrometric investigations of the vapour over CsI(s) between 604 and 833 K show the existence of CsI(g), (CsI)2(g), and (CsI)3(g). The enthalpies of sublimation to monomer and to dimer as well as the enthalpy of dimerization are determined with both, the second and third law method, at 298 K as 191.2 ± 2.0, 233.3 ± 4.6 and –149.2 ± 4.4 kJ mol−1, respectively. The values obtained with the second law method at 768 K for the enthalpy of sublimation to trimer and for the enthalpy of trimerization are 256.9 ± 8.3 and –289.9 ± 8.6 kJ mol−1, respectively. Equations for the partial pressures of (CsI)i(g) (i = 1, 2, 3) are given for the temperature range of measurements. The appearance potentials 14.5 ± 0.2(I+), 7.5 ± 0.2(CsI+), 7.2 ± 0.2(CsI+), 12.0 ± 0.2(Cs2I+), 7.2 ± 0.2(Cs2I+), 6.3 ± 0.2(Cs2I2I+), and 7.0 ± 0.2 V (Cs3I2I+) are obtained for the ions given in parentheses which are detected upon vaporizing CsI(s). The obtained findings are compared with data reported in the literature.