bluuebunny/crossref_metadata_2025 huggingface dataset:
Average consensus with weighting matrix design for quantized communication on directed switching graphs
Authors: Li Shuai , Guo Yi , Fang Jun , Li Hongbin
Published: July 2012

We study average consensus for directed graphs with quantized communication under fixed and switching topologies. In the presence of quantization errors, conventional consensus algorithms fail to converge and may suffer from an unbounded asymptotic mean square error. We develop robust consensus algorithms to reduce the effect of quantization. Specifically, we introduce a robust weighting matrix design and use the H ∞  performance index to measure the sensitivity from the quantization error to the consensus deviation. Linear matrix inequalities are used as design tools. The mean square deviation is proven to converge and its upper bound is explicitly given in the case of fixed topology with probabilistic quantization. Numerical results demonstrate the effectiveness of this method. Copyright © 2012 John Wiley & Sons, Ltd.
Surface Composition of Wustite
Authors: Grabke H. J. , Viefhaus H.
Published: July 2012

Using a solid electrolyte cell inside an UHV‐system the surface composition of oxides and metals can be studied at high temperatures 700 to 1000°C and well defined oxygen activities in the range po2 = 10−10 to 10−25 bar. AES‐measurements on wustite have shown that at temperatures > 800°C the composition of the surface shows the same change with the varied oxygen activity as would be expected for the bulk. At temperatures below 800°C the change of surface oxygen content is larger than the change of bulk oxygen which indicates the presence of adsorbed oxygen. An adsorption isotherm obtained at 720°C shows that the degree of coverage θ ⋍ 0.07 is approached near the FeO/Fe3O4, phase boundary. — The information from the AES‐studies is used for a discussion of the kinetics of the oxygen transfer to wustite by the reactions CO2 = CO + O(ads) and H2O = H2 + O(ads). The dependence on the oxygen activity of the solid catalyst as observed for these reactions at temperatures > 800°C must be interpreted as being caused by participation of electrons in the dissociation of the molecules on the wustite surface.
Quantum Rate Theory for the Relaxation in Symmetrical Microscopic Systems I: The Dephasing Mechanism
Authors: Brickmann Jürgen
Published: July 2012

A quantum rate theory is evaluated for the isoenergetic relaxation in symmetrical microscopical systems. Three different approximations for the rate expression are presented which base on a transport theoretical concept of Fong [32], the isolated system approximation (ISR), the measurement time approximation (MT) and the first passage time approximation (FPT). The theoretical rate expressions are applied for the determination of the diffusion mechanism of hydrogen and deuterium in niobium. Only the rates obtained with the aid of the measurement time approximation are in sufficient agreement with experiments in this special case.
Ionic Transport in PbO  SiO2‐Melts (II) Transference Number Measurements
Authors: Petuskey W. , Schmalzried H.
Published: July 2012

The transference numbers of Pb and Si relative to the oxygen Hittorf reference frame in PbOSiO2 melts were determined at 850°C between 0.3 ≤ x ≤ 0.6 using galvanic cells with liquid junctions and reversible oxygen electrodes. Silicon transference becomes appreciable at high PbO concentrations. The transference numbers, interdiffusion coefficient and electrical conductivity are related through a theoretical treatment of independent transport equations. It is shown that only three coefficients are necessary to characterize electrochemical transport in this quasibinary system. These are calculated as a function of a composition.
Electron Transfer between Benzenediols and Tris(1,10‐phenanthroline)iron(III) in Micellar Systems [1]
Authors: Pelizzetti Ezio , Pramaaro Edmondo , Croce Daniele
Published: July 2012

The effect of both cationic and anionic micelles on the reaction rates and mechanisms of electron transfer between benzenediols and 1,10‐phenanthroline‐like ligands complexes of iron(III) has been investigated. In the cationic micellar system, the reactions have been found to occur in water phase, the reaction rates being lower in respect to the homogeneous solution. On the other hand, in the presence of anionic micelles, the reactions occur in the micellar phase or at the interface between micellar and water phase. In this case the reaction rates are enhanced with the exception of the experiments performed with a benzenediol derivative bearing two sulphonic groups. The binding constants of the benzenediols with the two different surfactants have been estimated.
Adsorption of Nitrogen on Polycrystalline Nickel Films between 77 K and 333 K
Authors: Wedler Gerd , Alshorachi George
Published: July 2012

The adsorption of nitrogen on polycrystalline nickel films has been studied by means of volumetric measurements, measurements of pressure, electric resistance, surface potential and thermal desorption. There are different states of molecular adsorbed nitrogen. — A dissociative adsorption could only be observed at temperatures above 273 K. At these temperatures the rate of adsorption was measured. The sticking probability is in the order of 10−8 and decreases with increasing temperature which leads to an apparent negative activation energy. An adsorption mechanism is proposed in which an adsorption equilibrium is the precursor state for the dissociative adsorption.
Calorimetry within Hysteresis Loops of Metal/H Systems: Application to Pd/H
Authors: Bowerman B. S. , Biehl G. E. , Wulff C. A. , Flanagan Ted B.
Published: July 2012

It was suggested many years ago by Carl Wagner that if H2 is added to Pd/H whilst the system is on a desorption pressure plateau within the two solid phase coexistence region, H2 dissolves in both solid phases without formation of additional β‐phase. Similar considerations apply for the removal of H2 whilst on the absorption pressure plateau. This model, which has not been previously verified, has been confirmed in this research by calorimetric measurements of the enthalpies of scans between branches of the hysteresis loop for well‐annealed Pd samples. The experimental enthalpies lie between the values which correspond to the solution of H2 in each of the two pure coexisting solid phases. Besides confirming Wagner's suggestion, the calorimetric measurements described here provide a means to obtain partial thermodynamic quantities for the coexisting pure phases which may be difficult to obtain directly. — Values of the change of chemical potential of dissolved hydrogen with total hydrogen content, nt = H to metal, atom ratio, have been measured for scans from one branch of the hysteresis loop to the other. These values are consistent with the model and the experimentally determined enthalpies of solution. They demonstrate that relatively more H2 enters (or leaves) the β‐phase than the α‐phase during hysteresis scans.
Das Nahordnungsverhalten in paramagnetischem LaCrO3
Authors: Dräger K.
Published: July 2012

An stöchiometrischen, polykristallinen Proben von LaCrO3 sind im Temperaturbereich zwischen 290 K und 490 K ESR‐Messungen durchgeführt worden. Danach kann die Néel‐Temperatur nach oben durch TN ≤ 285 K abgeschätzt werden. Die Linienbreite ΔB zeigt gegenüber den theoretischen Vorhersagen systematische Abweichungen; statt einer hyperbolischen Abnahme mit wachsender Temperatur wird ein Anstieg beobachtet. — Der Intensitätsverlauf der ESR ist auch für T > TN nicht streng paramagnetisch, sondern durch eine erhebliche antiferromagnetische Kopplung gekennzeichnet. Der Vergleich mit einem Nahordnungsmodell ergibt für die Energielücke zwischen dem gebundenen und dem paramagnetischen Zustand den Wert ΔE = 400 ± 15 cm−1. Die Konstante der Paarbindung wird zu J12 = 8,89 cm−1 ermittelt. Daraus kann der Schluß abgeleitet werden, daß sich die Nahordnung auch im Bereich der Néel‐Temperatur noch stetig verhält.
Über das Wachstum von Iodidschichten auf Silber‐ und Kupferunterlagen durch simultane Kondensation und Reaktion
Authors: Pittermann Udo , Weil Konrad G.
Published: July 2012

Die durch freie Verdampfung von Silber‐ und Kupferiodid erzeugten Dämpfe weisen erheblich höhere Iodanteile auf als die entsprechenden Gleichgewichtsdämpfe. Auf Silber‐ und Kupferunterlagen von Raumtemperatur wachsen in diesen Dämpfen Iodidschichten durch simultane Iodidkondensation und Reaktion der Unterlage mit Iod. Es werden Meßverfahren angegeben, mit denen die zeitlichen Verläufe und die Anteile beider Prozesse erfaßt werden können. Das Zeitgesetz des Schichtwachstums und die Abhängigkeit der kinetischen Parameter der Kondensation und Reaktion von den Aufdampfbedingungen zeigen, daß der Mechanismus eine unabhängige Überlagerung der beiden Einzelprozesse ist. Durch Vergleich der Stoffströme, die aus Gleichgewichtsdrücken berechnet werden, mit den aus den Kondensationsraten berechneten, können Verdampfungskoeffizienten abgeschätzt werden. Sie sind kleiner als 10−1.
On the Use of Electroreflectance in the Interpretation of Anodic Electrochemical Behavior of the ZnSe Semiconductor Electrode
Authors: Lemasson Philippe , Gautron Jacques , Dalbéra Jean‐Pierre
Published: July 2012

The flat band potential and the possible use of a Schottky barrier model for the description of the electrolyte/ZnSe interface indicate that in a large potential domain (vs. e.s.m.), ranging between −1.0 and +10.0 V, the semiconductor space charge region is a depletion layer. This fact enables the use of the electrolyte electroreflectance technique in the case of a fully depleted layer as an in situ method of study of the electrochemical behavior of zinc selenide. Over the electrode potential ranges between −1.0 and +6.0 V, the ZnSe decomposition gives soluble products and for potentials higher than +6.0 V the final result of the decomposition is the formation of a zinc oxide layer. The shape and energetic position of the electroreflectance spectra show that in the first case the ZnSe electrode surface remains unchanged whereas in the second case a surface transformation appears which is irreversible. These results correlate with data obtained in a purely electrochemical way.
On the Mechanism of Solute Singlet State Formation in Electron Irradiated Liquid Alkanes
Authors: Hermann R. , Brede O. , Bös J. , Mehnert R.
Published: July 2012

The naphthalene fluorescence induced by a 2 ns electron pulse was used to monitor the solute singlet state formation in liquid cyclohexane, decalin, n‐heptane, and n‐decane. At solute concentrations smaller than 10−3 M a fast formation of the solute singlet was observed. Additionally, at higher naphthalene concentrations a slowly rising emission component was obtained. The fast emission seems to be mainly caused by radiative excitation transfer and the slower one is formed by different ion‐recombination reactions. To explain the observed slow solute singlet formation by ion recombination two models were used: a phenomenological one [12] and a model based on the solution of the rate equations using time‐dependent rate constants. The latter model gives a reasonable description of the experimental results. Particularly the influence of the hole life‐time which varies for the alkanes used was studied. — Energy transfer from the alkane singlet to the solute was found to be of minor importance under our conditions.
Mixture Rules in Thermal Unimolecular Reactions
Authors: Troe J.
Published: July 2012

Low pressure rate constants and incubation times for thermal unimolecular reactions, which take place in mixtures of inert bath gases, are investigated theoretically. By solving the master equation analytically for an exponential collision model, non‐linear mixture rules are observed, if at least one component of the mixture is a weak collider. The non‐linearities, however, are generally small and at the limit of the sensitivity of today's experiments.
Stoßwellenmessungen zur Kinetik der Reaktion HCN + O
Authors: Roth P. , Löhr R. , Hermanns H. D.
Published: July 2012

Durch direkte Messung des zeitlichen Verlaufes der H‐ und O‐Atomkonzentration in der Reaktionszone hinter Stoßwellen konnte in Gemischen aus Argon mit geringen Konzentrationen an HCN (25 bis 200 ppm) und N2O (5 bis 40 ppm) die Geschwindigkeitskonstante der Reaktion chemical structure image in einem Temperaturbereich 1800 K ≤ T ≤ 2500 K bei Drücken um p = 1,7 bar bestimmt werden.
Über die Oxidation von o‐Xylol an V2O5‐Trägerkatalysatoren
Authors: Hauffe K. , Raveling H.
Published: July 2012

V2O5 ist bei Erreichen einer bestimmten Fehlordnung, erkenntlich an der Abweichung von der stöchiometrischen Zusammensetzung, ein wirkungsvoller Katalysator für die Oxidation von o‐Xylol zu Phthalsäureanhydrid. Da V2O5 allein aber schon nach kurzer Reaktionsdauer so stark anreduziert wird, daß es seine katalytische Wirksamkeit verliert, wurden zur Stabilisierung der katalytischen Fähigkeit die folgenden Oxide als Träger getestet: Al2O3, Nb2O5, MnO2, ZrO2, SiO2, SnO2 und TiO2. Von diesen Oxiden war TiO2 neben SnO2 und ZrO2 der wirkungsvollste Träger für die Oxidation zu Phthalsäureanhydrid. Gleichzeitig durchgeführte Messungen der Änderung der Masse von V2O5 und seines Widerstandes ergaben, daß der Ausbau von Sauerstoff langsamer als der Einbau ins Gitter von V2O5 erfolgt und somit der geschwindigkeitsbestimmende Teilschritt der Katalyse ist. Es wurde gefunden, daß die Geschwindigkeit des Ausbaus von Sauerstoff aus dem Gitter des Katalysators gleich der Geschwindigkeit des Sauerstoffverbrauchs von Xylol war. Ferner wurde festgestellt, daß unter unseren Versuchsbedingungen die stationäre Fehlordnung des besonders aktiven Katalysators auf TiO2 während der Katalyse V2O4,58 betrug. während der auf ZrO2 bzw. SnO2 befindliche Katalysator eine Zusammensetzung von V2O4,91 bzw. von V2O4,16 aufwies. Ein möglicher Reaktionsmechanismus wird vorgeschlagen.
Calculated and measured orientations of the axes of paramagnetic centers with distorted cubic environment
Authors: Siebert D.
Published: July 2012

A simple procedure is proposed for estimating the orientations of the axes of paramagnetic centers with distorted cubic environment using exact crystallographic data. For some centers the calculated results are compared with experimental data from ESR investigations.
The electronic spectra of aminophenazines
Authors: Lange A. , Tavan P. , Schröder D. , Baumgärtel H.
Published: July 2012

The influence of amino substituents on the excited π‐π* singlet states of phenazine is investigated by absorption, fluorescence, and polarization spectroscopy at 77 K and by PPP‐SCF‐CI calculations including all single and double excitations from the SCF ground state. The Coulomb interaction of the free electron pair of the amino groups with the π‐electrons of phenazine is shown to be responsible, essentially, for the drastic changes in the observed electronic spectra.
Concentration polarization in electrodialysis with cation exchange membranes
Authors: Khedr G. , Varoqui R.
Published: July 2012

Interfacial concentration values derived from overpotential measurements on the cation exchange membrane AMF C 100 are considered in relation to the corresponding current‐voltage curves. The concentration in the depleted layer was found to reach a limiting value as a function of current density which is still large compared to the H+ and OH− ion concentration. The pH shift and the cation transport number were also determined as a function of current density. It appeared that water splitting did not contribute significantly to the conductivity in the high polarization regime and could not be correlated with the constant value of the interfacial concentration nor with the additional conductivity which appears beyond the polarographic plateau.
Thermodynamic properties of RbAu and CsAu
Authors: Busse Bernd , Weil Konrad G.
Published: July 2012

Experiments are reported on the composition of the vapor phase over Cs/Au and Rb/Au mixtures. The vapors were analysed by Knudsen‐cell mass spectrometry. — From the experimental data, bond energies for the species CsAu and RbAu could be evaluated to be

Consistency of the results was checked by investigation of the equilibrium Cs + RbAu ⇄ Rb + CsAu. — It can be shown, that the bond character in the CsAu and RbAu molecules is predominantly ionic.
An excimer investigation of the effects of additives on SDS micelles
Authors: Miller Dennis J.
Published: July 2012

Time‐resolved and photostationary pyrene excimer fluorescence can be used to obtain the microviscosity and aggregation number of micelles. The microviscosity of sodium dodecyl sulphate micelles (33 cP) is hardly affected by Na2SO4 in spite of a considerable increase in micelle size. Mixed micelles of sodium octyl sulphate/dodecyl sulphate have the same microviscosity as pure SDS micelles. The addition of n‐hexanol, which is incorporated into the SDS micelles, can lower the microviscosity by a factor of nearly three.
Dynamics of a N × K‐Level Molecule Coupled to a Thermal Reservoir
Authors: Raab H.‐U. , Brickmann J.
Published: July 2012

The influence of intermolecular elastic (T2 processes) and inelastic (T1 processes) interactions on the population relaxation and phase relaxation of a specific molecular mode is studied in terms of a two mode model. Therein one mode (K‐level system) is assumed to undergo T1 and T2 relaxation processes as a consequence of its coupling to a thermal reservoir while the second mode (N‐level system) is not explicitly damped but is coupled to the first one. The quantum statistical equations of motion for the coupled two‐mode system are solved numerically with a special integration scheme in which the damping is considered in first order and the coupling of the modes in infinite order. Energy relaxation and dephasing of the N‐level system are studied as functions of the external relaxation behaviour and of the coupling between the modes. A dynamical decoupling of the two modes is found with decreasing intermolecular dephasing times T2.
Electrochemical Studies of Magnetron Sputtered ZnO Film Electrodes
Authors: Yonezawa Y. , Inaba H. , Hada H.
Published: July 2012

The electrochemical behavior of magnetron sputtered ZnO film electrode was studied. The photocurrent‐potential characteristics under irradiation of UV‐light were interpreted by the Gärtner‐Butler model. As ZnO films show a good transparency in the visible region of the spectrum and respond only to the shorter‐wavelength light less than ca. 500 nm, they offer excellent electrodes for the study of spectral sensitization of ZnO. The action spectra of the sensitized photocurrent by rhodamine B and sodium fluorescein reflect the absorption spectra of adsorbed dye layer at the ZnO film, respectively. The quantum efficiency of the photocurrent was determined and compared with that obtained for the ZnO single crystal electrode.
A Proton NMR Study of the Dynamics of Ligand Exchange on Tetrakis(1,1,3,3‐Tetramethylurea)Beryllium(II) and its Dimethyl Sulphoxide Analogue
Authors: Lincoln Stephen F. , Tkaczuk Michael N.
Published: July 2012

A1H (90 MHz) NMR study of 1,1,3,3‐tetramethylurea exchange on [Be(O=C(NMe2)2)4]2+in the non‐co‐ordinating diluents CD3NO2and CD3CN shows that the exchange rate is independent of the free 1,1,3,3‐tetramethylurea concentration. Typicallyk1(298.2 K) = 1.39 ± 0.09 s−1, ΔH#= 77.1 ± 1.5 kJ mol−1, and ΔS#= 16.4 ± 4.3 JK−1mol−1for a solution in which [Be(O=C(NMe2)2)42+], [O=C(NMe2)2]free, and [CD3NO2] = 0.00743, 0.0334, and 18.3 mol dm−3respectively. The exchange parameters determined in CD3CN differ slightly from those determined in CD3NO2but in both cases the data are considered to typify a dissociative (D) solvent exchange mechanism. Dimethyl sulphoxide exchange on [Be(O=SMe2)4]2+in CD3NO2diluent is characterised by an exchange rate =k2[Be(O=SMe2)42+][O=SMe2]freefor whichk2(298.2 K) = 143 ± 10 dm3mol−1s−1, ΔH#= 51.1 ± 0.6 kJ mol−1, and ΔS#= −32.3 ± 2.2 JK−1mol−1, and which is considered to typify an associative (A) solvent exchange mechanism. Mechanistic comparisons are made with the data from other studies of solvent exchange on beryllium(II).
Surface Enhanced Raman Scattering of Cyanide Chemisorption Layers on Silver/Electrolyte Interfaces; Potential‐ and Time Dependence
Authors: Plieth W. , Roy B. , Bruckner H.
Published: July 2012

The dependence of the surface enhanced Raman signal of CN− ions on silver/electrolyte interfaces at 2114 cm−1 on the electrode potential was investigated by a periodic pulse program allowing the registration of the time dependence. The results can be interpreted by concentration changes in the diffusion region in front of the electrode as well as by reorganization processes of silver deposits on the electrode surface.
A Comparative Study of the Viscosity Coefficients of Some Nematic Liquid Crystalss
Authors: Kneppe H. , Schneider F. , Sharma N. K.
Published: July 2012

The viscosity coefficients η1, η2, η3 and η12 of 4‐n‐pentyl‐4'‐cyanobiphenyl, 4‐n‐octyl‐4'‐cyanobiphenyl, 4‐methoxy‐4'‐n‐butylazoxybenzene and an aromatic ester mixture were determined in the nematic phase region. Except for 4‐n‐octyl‐4'‐cyanobiphenyl, the viscosity coefficients of the liquid crystals show the following properties: 1) Three of the viscosity coefficients are related by an equation of the form Σ Aiηi = 0, in which the corresponding constants Ai are very similar for the different liquid crystals. 2) The equation ηi =aijηj + bij is valid with the exception of the neighbourhood of the clearing point. 3) The reduced viscosity coefficients 3ηi/(η1 + η2 + η3) of the different liquid crystals exhibit a very similar dependence on the reduced temperature and a nearly linear dependence on the degree of order. The viscosity coefficients η2 and η12 of 4‐n‐octyl‐4' ‐cyanobiphenyl show a divergence at the transition to the smectic phase, whereas η1 and η3 show the normal temperature dependence.
Molecular Aggregation of Sodium Deoxycholate in Water and Water‐Urea Mixtures; a Multistep Process
Authors: Sesta B. , La Mesa C. , Bonincontro A. , Cametti C. , Di Biasio A.
Published: July 2012

Densimetric, viscometric, conductometric, and microwave dielectric measurements have been performed on sodium deoxycholate in water and water‐urea solutions, at several temperatures, in order to obtain further informations on the first critical micellar concentration and on super‐aggregation phenomena. – Some interesting results are obtained, especially those casting light on the interactions occurring at the interface between water molecules and micelles. These aggregation processes may be of interest in biological fluids, for example in the solubilization of cholesterol and several other lipids.
Hydrodynaimcal Properties of Nucleosomes
Authors: Bernengo J. C. , Bezot P. , Roux B. , Marion C.
Published: July 2012

Dynamic light scattering and electric birefringence have been used together to measure both translational and rotational diffusion constants of nucleosomes oligomers. Assuming an ellipsoïdic model, the overall size and shape of these oligomers have been calculated; incertitude determinations, carefully carried out, give an idea of the actual validity of this type of results. Monomer and dimer can be considered as weakly elongated ellipsoïds, while trimer to hexamer are better represented by spheres. De la Torre and Bloomfield modelisation has also been applied to interpret our experimental results, leading for the monomer and dimer to dimensions which are reasonnably well in accordance with electron microscopic determinations.
On the Mechanism of Water Cluster‐Ion Formation in Carbon Dioxide
Authors: Warneck Peter , Rakshit Asit B.
Published: July 2012

A drift chamber mass spectrometer has been used to study the formation of water cluster‐ions in carbon dioxide containing traces of water vapour. The dominant reaction sequences were identified up to the fourth generation of daughter ions starting with CO+2. The subsequent reaction mechanism remains uncertain and several possibilities are discussed. The final ions are H3O+ H2O and H3O+ (H2O)2. The significance of the reaction schemes to the radiation chemistry of carbon dioxide is pointed out.
The Influence of Counter‐Ion Concentration on the Aggregation Behaviour of Viscoelastic Detergents
Authors: Hoffmann H. , Platz G. , Rehage H. , Schorr W.
Published: July 2012

The influence of excess Sodiumsalicylate (NaSal) on the properties of viscoelastic detergent solutions of Cetylpyridiniumsalicylate (CPySal) has been studied by static and dynamic light scattering, electric birefringence and rheological measurements. It is observed that the rodlike micelles which are present in these solutions and which are responsible for the elastic behavior grow rapidly in length with the increase of the NaSal concentration until the NaSal reaches 5 · 10−4 M. At this excess NaSal a 1 · 10−3 M CPySal solution contains rods which are at least 2000 Å long. To higher concentrations of NaSal the lengh L and the molecular weight Mw of the micelles is independent on the NaSal concentration. The elasticity and the electric birefringence disappear for NaSal concentration above 5 · 10−3 M. The loss of these properties is believed to be due to the coiling of the long rods. In the viscoelastic region the viscosity of the solutions is shear rate dependent. It decreases with increasing shear rate.
The Surfactant‐Block Structure of Micelles, Synthesis of the Droplet and of the Bilayer Concept
Authors: Fromherz Peter
Published: July 2012

The experimental data concerned with the molecular structure of surfactant micelles are considered. A consistent rationalization of the observations is not attained by the conventional ideas of packing: The droplet‐model describes the thermodynamical data, the bilayer‐fragment model the structural data. A new packing mode is suggested which combines the features of those two models: The parallel correlation of the molecules is limited to a range corresponding to the length of the molecules. An isometric compact assembly is attained which provides a consistent description of the pertinent experimental data. The principle of block‐assembly is applied to the construction of narrow curvatures made from amphiphilic molecules as in liquid crystals, microemulsions and lipidmembranes.
Conductive and Convective Heat Transfer below Evaporating Liquid Surfaces
Authors: Schreiber D. , Cammenga H. K.
Published: July 2012

An apparatus for the measurement of the total heat flux and the subsurface temperature distribution and oscillation in evaporating liquids is described and measurements on water are reported. It is shown that the critical Rayleigh number for the transition from laminar to turbulent flow and the coefficient in the equation for laminar heat flow increase considerably with increasing aspect ratio. A stagnant conductive subsurface layer does not exist, but the amplitude of convective motions is damped in approaching the surface whereas their frequency remains unaltered.
Neue experimentelle Möglichkeiten für das Studium der molekularen Struktur und Dynamik von Flüssigkeiten
Authors: Versmold H.
Published: July 2012

The general space‐time‐pair distribution function G (RA (0), ΩA (0), RB (t), ΩB(t) plays an important role for the theoretical description of liquids. In this report first the relationship between the space‐time‐pair distribution function and static pair distribution functions, which characterize the liquid structure, and time correlation functions, which can be used to comprehend the dynamics of liquids, will be introduced. As an experimental method, which is particularly suited to determine the static pair distribution function, coherent neutron scattering is discussed. The power of this method for the determination of the liquid structure is demonstrated by considering the examples of a fused salt and a molecular liquid. For investigations of the dynamics of liquids incoherent neutron scattering and several spectroscopic experiments have been in use during the last few years. The relationship between these experiments and time correlation functions is presented. A discussion concerning the possibility to study translational and rotational dynamics by incoherent neutron scattering follows. Finally, by referring to a depolarized Rayleigh experiment, the relationship between spectroscopic experiments and orientational correlation functions, which describe the reorientational dynamics in liquids, is illustrated.
The Thermal Conductivity of Water to 250°C and 350 MPa
Authors: Dietz F. J. , De Groot J. J. , Franck E. U.
Published: July 2012

An apparatus is described to measure the thermal conductivity of aqueous and polar fluids at high pressures. The pulse heated wire method is used with a modification to permit AC heating and measurement. Experiments were performed with water from 30°C to 250°C and from 0.1 MPa to 350 MPa. With a pressure increase from saturation pressure to 350 MPa, the thermal conductivity increases at 30°C from 0.610 to 0.757 and at 250°C from 0.617 to 0.849 Wm−1 K−1. Isobars have maxima at 130°C for saturation pressure and at 200°C for 350 MPa. The accuracy of the present results is estimated to be ±0.8%. Isochors have no maxima. The thermal conductivity increases with temperature and density. A comparison with all previous high pressure data for water and with high pressure data for methanol, toluene and n‐heptane is made. The thermal conductivity of supercooled water at high pressures is discussed.
Bestimmung der partiellen Strukturfaktoren aus der Röntgenstrahlenbeugung an flüssigem Silicium‐ und Germaniumtetrachlorid und ihren Mischungen
Authors: Baier Hans‐Rudolf , Weidner Jörg‐Ulrich
Published: July 2012

Liquid SiCl4, liquid GeCl4 and mixtures SiCl4/GeCl4 are investigated to yield partial structure factors and pair correlation functions for a liquid tetrachloride system, applying the method of chemical substitution to obtain independent x‐ray diffraction experiments. The properties of the liquid system and the experimental results correspond to the criteria of applicability of the method.—X‐ray diffraction investigations were performed with the pure components and three differently concentrated mixtures at 20 °C. The molecular structure was determined by best fit procedures. The model parameters compare quite favourably with those of the literature. The three partial structure factors of pairs ZZ, ZL, LL were calculated from the five linear equations after separating the intramolecular contributions. Z refers to the molecular centre, L to the chloride atom. From the structure factors the partial pair correlation functions are accessible. The range of orientational correlation was estimated making use of the experimental results.
Depolarisierte Rayleighstreuung an flüssigen binären Mischungen
Authors: Vilhjalmsson R.
Published: July 2012

The molecular reorientation in mixtures of benzene with triethylamine and nitrobenzene with chloroform has been studied at several temperatures and solution concentration. The correlation time τLS for benzene in triethylamine is a linear function of η/T for every concentration but the slope depends on concentration indicating a slight change from “slip” towards “stick” boundary conditions with increasing triethylamine concentration. The extrapolated value for η/T is 0.7 ps for all concentrations. In the nitrobenzene‐chloroform system only the correlation times of nitrobenzene are linear dependent of η/T. The correlation times of chloroform are shorter and have also a smaller activation energy. A comparison with NMR‐data is discussed.
Messungen des zweiten Virialkoeffizienten von Gasen und Gasmischungen bei Zimmertemperatur mit einer Expansionsapparatur
Authors: Schramm B. , Müller W.
Published: July 2012

We describe an expansion apparatus for measurements of second virial coefficients of pure gases and mixtures at room temperature. We present experimental data of CO, CO2, Xe, CH4, CF4and of the binary mixtures Ne/Xe, Ar/N2, Ar/CO, Ar/CO2, and CH4/CF4.
Untersuchung der micellaren Eigenschaften von Tensidlösungen mit Hilfe eines solvatochromen Pyridinium‐N‐phenoxids
Authors: Plieninger P. , Baumgärtel H.
Published: July 2012

4‐(2,4,6‐Triphenylpyridinium)‐phenoxide exhibits a strong bathochromic shift of the lowest absorption band in aqueous micellar solutions. The spectroscopic behaviour reveals that the adsorption equilibrium of the dye depends on the concentration and chain length of the surfactant and on the ion strength of the solution. From our results we conclude that the betain is bound in the interface micelle/solution; it may be used as an indicator of polarity of the interface.
A Method to Determine Excess Energies in Dissociative Electron Attachment Processes
Authors: Illenberger E.
Published: July 2012

The initial translational energies of negative ion fragments arising from dissociative electron attachment have been measured over the resonance curve using a time‐of‐flight technique in combination with mass analysis in a quadrupole mass filter. This yields information on the distribution of the excess energy when the negative molecular ion formed on electron attachment decomposes. Experimental results are presented showing that this technique is a useful method to determine more accurately thermochemical parameters of the decomposition products involved in dissociative electron attachment processes.
The Continuum Analogue of Multipolar Lattice Sums
Authors: Steinhauser O.
Published: July 2012

After a short review on multipolar lattice sums their continuum analogue is derived extensively using the method of multipole expansion. Decomposing the total continuum energy into pair contributions the influence of long‐range interactions on the structure of polar liquids is discussed. The numerical efforts to compute the continuum energy are drastically reduced as compared to the lattice sum. Apart from this a close correspondence between the lattice sums and their continuum analogue can be established.
My Fifty Years of Theoretical Chemistry, I: Chemical Kinetics
Authors: Hirschfelder Joseph O.
Published: July 2012

The 1930's were the Golden Age of discovery; the 1980's are the Laser Age. Theoreticians used to solve practical problems; once again they are turning in that direction. Theoretical research led the way in the Golden Age. Although there has been great progress in the theory, we still have many of the same problems which were troublesome 50 years ago: We dont understand the semi‐empirical schemes (INDO, CNDO, MINDO, ) which are used to calculate the energy of organic molecules; and, the apriori calculation of reaction rates is still difficult. Many new theoretical techniques are being devised to respond to the fantastic precision of present experimental state‐to‐state chemistry!
Chemical Dynamics in Surface Reactions
Authors: Ertl G.
Published: July 2012

Chemical interactions of gaseous molecules with solid surfaces may proceed with or without bond‐breaking (dissociative and non‐dissociative chemisorption, respectively). The formation of new molecules via surface reactions of these species forms the basis of heterogeneous catalysis. Experimentally accessible information on the processes involved will be briefly outlined by means of a few selected examples.
Liquid Mixtures of Sodium and Sodium Hydride at High Pressures and Temperatures
Authors: Klostermeier W. , Franck E. U.
Published: July 2012

The hydrogen pressure in equilibrium with liquid phases of the system sodium‐sodium hydride has been measured from 650 to 900 °C and up to 900 bar. A detailed description of the apparatus is given. The autoclave was of a nickel base superalloy and contained an outer and an inner compartment with equilibrated hydrogen pressures. At 900°C and 650 bar the maximum solubility of NaH in liquid Na is 19 mole percent. Sieverts' law is closely obeyed to 5% NaH. Sodium solubility in the liquid NaH is below 2%. The melting point of NaH was found at 632 °C and 106 bar, the enthalpy and entropy of fusion as 26.2 ± 0.7 kJ mol−1 and 29.0 ± 0.8 JK−1 mol−1. The enthalpy of solution of liquid NaH in liquid Na is 27.4 kJ mol−1. Equations and data for solubility, activity coefficients etc. of NaH are given. The critical solution point for Na and NaH is estimated to be at 1500 ± 70 K, 2500 ± 600 bar and x(NaH) = 0.65 ± 0.05.
Diffusion and Thermal Diffusion in Binary Mixtures of Deuterium with Neon, Argon, Krypton and Xenon at 300 K
Authors: Trengove R. D. , Dunlop Peter J.
Published: July 2012

Diffusion coefficients and thermal diffusion factors are reported for binary mixtures of deuterium with neon, argon, krypton and xenon at 300 K. The data are used to test the Chapman‐Enskog theory and some of the potential functions which have been reported for these systems.
Application of the Protonic Model Potential Approach to the Infrared Spectra of HX and Hydrogen Bonded HX−2 Species
Authors: Goodfriend P. L.
Published: July 2012

The application of the protonic model potential approach to calculations of the infrared spectra of HF, HCl, HF−2, and HCl−2 is examined and compared with experimental results.
The Luminescence Properties of Some Ruthenium(II) Complexes and Solid Dye Films in Relation to Their Application in Photoelectrochemical Cells
Authors: Breddels P. A. , Blasse G.
Published: July 2012

Energy transfer phenomena in Ru(bpy)3(ClO4)2 are investigated in order to estimate the optimum layer thickness when this complex is used as a sensitizer on a semiconductor electrode in a photoelectrochemical cell. The optimum thickness appeared to be about five molecular layers. We also examined the luminescence properties of solid dye films of some Ru(bpy)2+3 complexes. It is shown that the luminescence intensity can be used as a probe for studying the behaviour of the light‐sensitive electrode in a photoelectrochemical cell.
Molecular Motion of [(CH3)3NH]⊕ Ions in Solid Trimethylammonium Hexahalometallates(IV) as Studied by 1H NMR and 35Cl NQR
Authors: Ikeda Ryuichi , Kadel Rainer , Weiss Alarich , Ishida Nobuko , Nakamura Daiyu
Published: July 2012

The temperature dependence of the 1H spin‐lattice relaxation time, T1, and of the second moment of 1H NMR spectra were studied in a series of trimethylammonium hexahalometallates(IV), (triMA)2MX6, (M = Pt, Sn, Te; X = Cl, Br, I). From X‐ray powder diagrams taken at room temperature, it was found that these complexes are isomorphous throughout the series. The unit cell dimensions were determined. A single 35Cl NQR line was observed for (triMA)2SnCl6 and for (triMA)2TeCl6 in agreement with the crystal symmetry of these complexes. By 1H NMR, two kinds of motions of the ion (triMA), a) the intraionic reorientations of the CH3 groups and b) the reorientation of the whole cation about its C3 axis, have been observed separately in most of the complexes studied. The activation energies of these motions imply that the ions (triMA) are more freely rotating in the hexahalometallate(IV) complexes as compared to the (triMA) halides.
Sustained Oscillations of an Autocatalytic Reaction in a Stirred Flow Reactor
Authors: Geiseler W.
Published: July 2012

In the present paper we report on the discovery and some initial investigations of sustained limit cycle oscillations in the stirred flow oxidation of cerous ions by acidic bromate. In order to find and measure the region of oscillations in the parametric plane of the inflow concentrations of bromate and bromide, a linear concentration gradient method was applied. At present the described flow oxidation is the simplest chemical oscillator fully understood in terms of elementary reaction steps.
Cotton‐Mouton Effect and Rotational Zeeman Effect in Dilute Gases — Two Complementary Methods for the Determination of Molecular Magnetic Properties
Authors: Geschka H. , Pferrer S. , Häußler H. , Hüttner W.
Published: July 2012

The first‐ and second‐order rotational Zeeman effect was investigated in isobutane. The magnetic‐field induced birefringence was measured at room temperature in several gases formed by axially symmetric molecules using pressures up to 1 bar. For benzene vapour these measurements were extended to higher temperatures. The susceptibility anisotropies obtained from the Cotton‐Mouton constants of the gases agree well with those measured directly by the rotational Zeeman effect which indicates that hyperpolarizabilities are negligible. The corresponding temperature independent contribution to the Cotton‐Mouton effect of benzene vapour proves to be less than 3% of the Cotton‐Mouton constant at room temperature.
Diode Laser Spectrum of the Fundamental v2 Band of HNCO
Authors: Lemoine B. , Yamada Koichi , Winnewisser G.
Published: July 2012

Infrared spectrum of HNCO near 5 μm was measured by a diode laser spectrometer with source frequency modulation and Stark modulation methods. The subbands of the v2 fundamental band were identified for Ka = 0 to 4. The subband origins and the effective rotational constants for these subbands were determined. The rotational fine structure of the v2 band suggests that the levels are perturbed by accidental resonances.
Charged Thermodynamically Stable Heterophase Fluctuations in Compressed Mercury Vapour
Authors: Hefner W. , Sonneborn‐Schmick B. , Hensel F.
Published: July 2012

Measurements of the real part of the infrared dielectric constant of sub‐ and supercritical mercury vapour indicate that the interaction of the thermally generated charged particles with neutral atoms stabilize regions of higher than average density in the compressed high temperature vapour. A model calculation supports the hypothesis that under certain conditions of the vapour charges tend to stabilize dense liquid droplets which approach metallic conditions while the macroscopic system is still in the nonmetallic region.
Messung des Bildungspotentials von flüssigem AgCl in der Schmelze mit KCl bzw. KCl, LiCl und Berechnung seiner thermodynamischen Exzeßeigenschaften
Authors: Giazitzoglou Z.
Published: July 2012

In order to carry out electromotive force measurements in molten chlorides at temperatures up to 850°C a reversible formation cell using a chlorine/chloride reference electrode of graphite was constructed. The formation potential of molten AgCl in liquid mixture with KCl and with KCl, LiCl depending on temperature was determined for several concentrations. The excess properties of the binary system AgCl, KCl were calculated. An analytical thermodynamical description of the ternary system AgCl, KCl, LiCl was made by means of literature data for the appropriate binary systems employing the Redlich‐Kister equation for the integral excess free energy. The results achieved thereby were verified by the measurements made in this work.
A Reinvestigation of the Effect of Pressure on the Reaction of Fe(III) with Thiocyanate Ions in Aqueous Solution
Authors: Doss R. , van Eldik R. , Kelm H.
Published: July 2012

The effect of pressure on the reaction between Fe(III) and NCS− ions was reinvestigated using a recently constructed high‐pressure Joule‐heating temperature‐jump instrument. The results differ significantly from those reported by Jost [1], and the volumes of activation for the reactions of Fe(OH2)63+ and Fe(OH2)5OH2+ with NCS− are 6.7 ± 0.4 and ∼0 cm3 mol−1, respectively, at 20°C. The pressure dependences of the Fe(OH2)33+/Fe(OH2)5OH2+ and Fe(OH2)63+, NCS−/Fe(OH2)5NCS2+ equilibria are in good agreement with earlier findings. The significance of the results are discussed in reference to recent data on the solvent exchange and substitution reactions of Fe(III).
Thermodynamic Investigations on Menshutkin Complexes IV. Complex Formation in Liquid SbCl3/Benzene Mixtures
Authors: Sondern Chr. , Perkampus H.‐H.
Published: July 2012

On the basis of a simple chemical model complex formation equilibria have been evaluated using recently measured thermodynamic excess functions of SbCl3/benzene mixtures. Assuming the presence of solved SbCl3 ‐ benzene and 2SbCl3 ‐ benzene complexes, the following thermodynamic data for the formation of liquid complexes from pure liquid components were calculated: (T = 350 K)

ΔH ≈ ΔH ≈ − 23.5 kJ mol−1; ΔS ≈ ΔS ≈ − 70 JK−1; mol−1
Development and validation of a rapid RP‐HPLC method for analysis of (−)‐copalic acid in copaíba oleoresin
Authors: Souza Ariana Borges , Moreira Monique Rodrigues , Borges Carly Henrique Gambeta , Simão Marília Rodrigues , Bastos Jairo Kenupp , de Sousa João Paulo Barreto , Ambrosio Sérgio Ricardo , Veneziani Rodrigo Cassio Sola
Published: July 2012

The Copaifera species (Leguminoseae) are popularly known as ‘copaíba’ or ‘copaíva’ and are grown in the states of Amazonas, Pará and Ceará in northern Brazil. The oleoresins obtained from these species have been extensively used owing to their pharmacological potential and their application in cosmetic and pharmaceutical preparations. In the present study, the development and validation of a novel, rapid and efficient RP‐HPLC methodology for the analysis of the diterpene (−)‐copalic acid (CA), pointed out as the only chemical marker of the Copaifera genus, are described. The regression equation (Y = 26,707x − 29,498) was obtained with good linearity (r2 = 0.9993) and the limits of quantification and detection were 9.182 and 3.032 µg/mL, respectively. The precision and the accuracy of the method were adequate (lower than 4%). Finally, the validation parameters evaluated were satisfactorily met, so the developed method represents a suitable tool for application in the quality control of such natural products. Further studies aiming to develop analytical methodologies for each Copaifera species using a more representative number of chemical markers should be performed. Copyright © 2012 John Wiley & Sons, Ltd.
Neural stimulation on human bone marrow‐derived mesenchymal stem cells by extremely low frequency electromagnetic fields
Authors: Cho Hyunjin , Seo Young‐Kwon , Yoon Hee‐Hoon , Kim Soo‐Chan , Kim Sung‐Min , Song Kye‐Yong , Park Jung‐Keug
Published: July 2012

Adult stem cells are considered multipotent. Especially, human bone marrow‐derived mesenchymal stem cells (hBM‐MSCs) have the potential to differentiate into nerve type cells. Electromagnetic fields (EMFs) are widely distributed in the environment, and recently there have been many reports on the biological effects of EMFs. hBM‐MSCs are weak and sensitive pluripotent stem cells, therefore extremely low frequency‐electromagnetic fields (ELF‐EMFs) could be affect the changes of biological functions within the cells. In our experiments, ELF‐EMFs inhibited the growth of hBM‐MSCs in 12 days exposure. Their gene level was changed and expression of the neural stem cell marker like nestin was decreased but the neural cell markers like MAP2, NEUROD1, NF‐L, and Tau were induced. In immunofluorescence study, we confirmed the expression of each protein of neural cells. And also both oligodendrocyte and astrocyte related proteins like O4 and GFAP were expressed by ELF‐EMFs. We suggest that EMFs can induce neural differentiation in BM‐MSCs without any chemicals or differentiation factors. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012