bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Resolved Observation of Nascent OH Rovibronic Distribution and Benzyl Radicals Formed in the Infrared Multiphoton Dissociation of Benzyl Alcohol
Authors: Chowdhury P. K.
Published: July 2012

The infrared multiphoton dissociation (IRMPD) of benzyl alcohol (BENZAL) generates OH and benzyl radicals as the primary products. The IRMPD yield of benzyl alcohol shows a strong fluence dependence, with a threshold of 6 J cm−2 for the 10 R(30) CO2 laser line at 982 cm−1. The nascent OH fragments are probed via laser induced fluorescence (LIF) under collisionless conditions, to determine the initial product state distributions. There is no significant population ( <2%) in the excited vibrational level of OH (X2II). However, the initial rotational state distribution is Boltzmann‐like, characterized by a rotational temperature of about Trot = 1100 K. The time dependent measurement of OH by LIF is used to derive an average internal energy of BENZAL above its threshold dissociation, at CO2 laser fluences of 7‐11 J cm−2. The benzyl radical is also monitored by LIF in its 12A2←12B2 band system and is found to be produced vibrationally “hot”. About 500 collisions with argon are required for its thermalization.
Multilayer Adsorption of Nitrogen
Authors: Guil J. M. , Herrero J. E. , Noguerales P. , Masiá A. Pérez , Ruiz Paniego A.
Published: July 2012

A multilayer adsorption model previously developed in this laboratory has been applied to the adsorption of nitrogen at 77 K on eighteen samples: eight oxides, nine scheelites and a sample of cadmium chloride. The applicability range of the model begins at coverages close to the monolayer capacity, with an upper limit imposed by capillary condensation, if it exists. Surface heterogeneity is accounted for through an exponential distribution function of the adsorption sites, whose two parameters are calculated from the model equations; one of them gives the lowest energy of the adsorption sites and is related to the adsorption enthalpy; the other one governs the shape of the distribution curve and is related to surface heterogeneity. The equations yield also the exponent governing the variation of the interaction energy of the molecule with the distance to the surface, whose values for most of the samples are near 3, pointing to an interaction arising from London dispersion forces. The application of the model is not successful in a few cases, probably due to the inadequacy of the assumed exponential function to describe the surface energy distribution.
Solvation of Ions in Acetonitrile‐Methanol Solutions of Sodium Iodide
Authors: Hawlicka E. , Grabowski R.
Published: July 2012

The self‐diffusion coefficients of acetonitrile, methanol and ions in salt free acetonitrile‐methanol mixtures and in solutions of NaI have been measured at 25°C for the whole composition range of the binary solvent, for the salt molarity ranging from 1 · 10−4 to 1 · 10−2. The limiting self‐diffusion coefficients of sodium and iodide ions increase monotonously with increasing concentration of acetonitrile. The composition dependences of the ionic radii allow to postulate a preferential solvation of iodide ions by acetonitrile. That phenomenon has been found for those compositions of the mixed solvent, for which a microheterogeneity of the system has been observed. In methanol rich solvents (xAN < 0.5) the observed microheterogeneity results from the self‐association of methanol. The preferential solvation of iodide ions causes an enlargement of acetonitrile aggregates resulting in enhancement of microheterogeneity of the system. These results confirm a hypothesis that if interactions between ions and components of the mixed solvent are similar the preferential solvation of ions is promoted by the structure of solvent.
Chevrel Phase Type Compounds: Electronic, Chemical and Structural Factors in Oxygen Reduction Electrocatalysis
Authors: Jaegermann W. , Pettenkofer C. , Alonso Vante N. , Schwarzlose Th. , Tributsch H.
Published: July 2012

Chevrel type chalcogenides of stoichiometry Mo6Se8 and (Mo6‐Mx)MxSe8 (with Mx = Ru2; Re4) are investigated as electrocatalysts for the reduction of molecular oxygen in acidic medium. The catalytic activity is related to the surface corrosion tendency as investigated with XPS. The Ru‐cluster proved to be more stable to air oxidation than the Re and Mo cluster compounds. Only small amounts of oxidation products are found for all samples exposed to the electrolyte in the range of the oxygen reduction potential. At more positive bias with respect to the open circuit potential anodic corrosion currents are observed for all compounds which are due to formation of metal oxides. — The reactivity of the clusters seems to be associated to the electronic structure which was obtained from XPS and UPS measurements. In all cases the band edges are derived from metal d‐states which are hybridized with chalcogenide p‐states. The catalytic activity is discussed in terms of possible surface interactions which are determined by the electronic nature of the band edge states.
Determination of the Thermodynamic Properties of Liquid Methanol from 203 to 263 K and up to 280 MPa from Speed of Sound Measurements
Authors: Sun T. F. , Schouten J. A. , Biswas S. N.
Published: July 2012

The sound speed in liquid methanol has been measured up to 280 MPa and in the temperature range between 203 K and 263 K, using a phase comparison pulse‐echo technique operating at 2 MHz. The density, isothermal compressibility, isobaric thermal expansion and the specific heat have been evaluated from the measured sound speed, together with the density and specific heat at 0.1 MPa. A modified computational method originally developed by Davis and Gordon was used. The derived density data have been used to examine the validity of several empirical equations of state.
Investigations on the Kinetics of the Anodic Intercalation Process of Graphite in 65% HNO3 by Using AC Impedance Measurements
Authors: Scharff P. , Stumpp E. , Barteczko K. , Xu Z.‐Y.
Published: July 2012

The electrochemical properties of the interface between graphite sample and electrolyte solution will change during the anodic intercalation process. The physical quantities which indicate these electrochemical properties can be calculated from the results of the AC impedance measurements. An equivalent circuit is suggested for the calculation. The results of this method are in very good agreement with those from other methods, therefore it is very helpful for studying the kinetics of the anodic intercalation process into graphite in the electrolyte solution.
The Refractive Index of Perfluorinated Surfactant Solutions
Authors: Pößnecker Gerhard , Hoffman Heinz
Published: July 2012

The refractive index of several perfluorinated surfactant solutions was measured as a function of the concentration. The plot of the refractive index against the concentration for each surfactant shows a sharp break at the cmc. For several systems the slope of the refractive index changed even its sign. The extent of this change is much bigger for perfluorinated surfactants than the change that is shown by hydrocarbon surfactants. It is shown by density measurements that the difference of the refractive index increment above and below the cmc is due to the difference of the partial molar volumes of the surfactant molecules in the monomer and in the micellar state. It is thus possible to determine volume changes in surfactant systems by means of the measurement of the refractive index.
Parametrization of 4f – 4f Transition Probabilities of Eu3+ Ions in Na5Eu(MoO4)4 and Na5Eu(WO4)4
Authors: Hølsä Jorma , Porcher Pierre , Huang Jinggen
Published: July 2012

The simulation of the 4f—4f electric and magnetic dipole transition probabilities of Eu3+ ions in Na5Eu(MO4)4 (M = Mo and W) was carried out according to the Judd‐Ofelt theory. The experimental data consist of 29 5D0,1 → 7FJM transitions between crystal field sublevels. — The optimization of the six non‐zero Bλkg parameters allowed for the D2d symmetry yielded the following sets for Na5Eu(MoO4)4 and Na5Eu(WO4)4 (in 10−10 cm units). B232 = ‐2.01 (‐1.94), B432 = 0.66 (0.57), B452 = 3.31 (3.07), B652 = 8.47 (6.72), B672 = 2.27 (2.63) and B676 = 31.11 (30.93), respectively. These sets give reasonable simulation to the experimental transition probabilities. The conventional Judd‐Ofelt theory was, however, unable to simulate the intensity of the “hypersensitive” 5D0 → 7F2 transition. Most of the discrepancies are due to the uncertainty in experimental data although the influence of basis set truncation (only 671 |LJM> levels out of the total of 3003 were included in the basis set of wave functions) and the approximate symmetry (D2d symmetry was used instead of the real S4 one) cannot be neglected, either.
Investigation of Nickel Plating by Photoacoustic Spectroscopy (PAS) and Scanning Tunneling Microscopy (STM)
Authors: Yoshihara Sachio , Sato Ei‐ichi , Fujishima Akira
Published: July 2012

Photoacoustic technique was employed to study the plating of Nickel. And on the other hand, Scanning Tunneling Microscopy (STM) cleared the difference of the surface in the presence and in the absence of the brightener. Also Scanning Electron Microscopy (SEM) was used for supporting the data of STM.
The Importance of Metastable RNA Folding in Biological Regulation and Control
Authors: Fernández Ariel
Published: July 2012

We explain the radical difference in pause site patterns during the synthesis of MDV‐1 RNA, depending on the nature of the process involved. The two situations of interest are: a) Replication by Qβ‐replicase, a template‐instructed synthesis b) Transcription performed by E. Coli RNA polymerase. The starting point is an extended mode analysis of the backbone soliton‐like dynamics. These solitary waves induce a tautomerization of uracil which occurs exclusively in transcription with a definite probability. This tautomeric form of uracil forms base‐pairing with guanine and leads to a unique metastable folding of RNA. The assessment of this fact enables us to prove that in both replication and transcription, the pauses in the process are due to refolding events occurring in the replica chain as it is being synthesized and in the upstream portion of the template strand.
Kinetics and HO2 Product Yield of the Reaction C2H5O + O2 between 295 and 411 K
Authors: Hartmann D. , Karthäuser J. , Sawerysyn J. P. , Zellner R.
Published: July 2012

The kinetics of the reaction between ethoxy (C2H5O) radicals and O2 have been studied using a combined laser photolysis/LIF technique for the generation and detection of C2H5O. In the temperature range 295–411 K the rate coefficient has been found to be
equation image
.

Product investigations using a chemical titration of HO2 by NO and subsequent quantitative detection of OH by LIF indicate the dominance of the HO2 formation channel, viz.
equation image
with ϕ = 0.89 (−0.12+0.22). Energy correlations show that these products are formed by a direct metathesis reaction only. It is suggested, that the low pre‐exponential factor in the Arrhenius expression may be the result of a more complex than linear configuration of the moiety in the transition state and/or of tunneling.
2‐Butanol‐Water System in the Presence of Sodium Chloride and Potassium Chloride
Authors: Apelblat Alexander , Manzurola Emanuel
Published: July 2012

Partition of 2‐butanol, water, NaCl and KCl between the aqueous and alcoholic phases at 298.15 K is considered. Extraction of chlorides is represented as a formation of partially dissociated complexes in the alcoholic phase. The equilibrium constant for formation of the Na+(2‐BuOH)2Cl− complex is 0.11 and for formation of the K+(2‐BuOH)2Cl− complex is 0.16. Detailed thermodynamic analysis of the investigated systems is presented by evaluating activities of components from the mass‐action and Gibbs‐Duhem equations.
Kinetics of the Oxidative Silver Chloride Formation on Silver with CoIII(NH3)5Cl3 Studied by Galvanostatic Reduction of the Chemically Formed Silver Halide
Authors: Nickel U. , Haase E. , Liu C.‐Y.
Published: July 2012

Silver chloride was formed on a rotating silver disc electrode by oxidation with [CoIII(NH3)5Cl]2+ in acid solution and subsequently reduced galvanostatically in order to determine quantitatively the amount of silver(I) formed during the chemical oxidation. By varying both the oxidation time and the concentration of the cobalt complex as well as that of chloride the kinetics of the formation of silver chloride was studied indirectly. As long as the concentration of chloride exceeds that of the cobalt(III) complex the reaction is first order in [CoIII(NH3)5Cl]2+ and almost zero order in Cl−. The diffusion controlled process can be explained with the theory of mixture potential and mixture current and may therefore be regarded as a corrosion process.
Diffusion Coefficients in Systems with Inclusion Compounds. Part 2. α‐Cyclodextrin‐(DL)Norleucine‐Water at 25°C
Authors: Paduano Luigi , Sartorio Roberto , Vitagtiano Vincenzo , Costantino Lucia
Published: July 2012

Diffusion coefficients in the ternary system α‐cyclodextrin (at one concentration)‐(DL)norleucine (at three concentrations)‐water have been measured using the Gouy interferometric technique. — The effect of the inclusion equilibrium on the cross‐term diffusion coefficients was observed. — The measured diffusion coefficients in the ternary systems were used to calculate values of the binding constant. These values are in good agreement with that obtained from calorimetric studies.
Density and Dielectric Polarizability of n‐Alkane Liquids
Authors: Scaife W. G. , Lyons C. G.
Published: July 2012

Parameters for a form of the Tait equation which includes temperature, are given for n‐alkanes from n‐pentane to n‐decane. Taken with published data for dielectric polarizability, values of volume occupied per molecule Vm, and polarizability α per molecule have been computed at different pressures and temperatures. By plotting Vm and α as functions of carbon number a comparison can be made among these liquids and with other literature data. Density trends at the approach to boiling can be discerned.
The Static Dielectric Constant and Density of t‐Butyl Chloride to 200°C and 2000 bar
Authors: Vani V. C. , Michelberger Th. , Franck E. U.
Published: July 2012

The relative static dielectric constant or permittivity ϱ and density ρ of t‐butyl chloride was measured between 25°C and 200°C and from 100 to 2000 bar. The high pressure cell, simultaneously applicable to determine ε and ϱ, is described. Sample densities range from 0.694 to 0.949 g · cm−3. At 25°C and from 100 to 600 bar ε increases from 9.86 to 10.59. At 100°C between 100 and 2000 bar ε ranges from 6.75 to 8.57. At 200°C from 200 to 2000 bar ε grows from 4.12 to 5.69. Functions for ε and ρ in dependence of pressure with fitted parameters are given. Calculated Kirkwood correlation factors g are presented, which exceed unity only moderately (from 1.03 to 1.22). A comparison is made with ε‐values of high pressure HCl and CH3Cl.
Theoretical Prediction of the Primary Sequence for an RNA Species Fitted for Replication by Qß‐Replicase
Authors: Fernández Ariel
Published: July 2012

We predict the melting profile for a globular (folded) stable state of MDV‐1RNA. We search for sequences realizing those features in the melting profile which are sequence‐dependent. The search is subject to three constraints: a) Intra‐chain folding should be favored over double‐strand formation; b) At least one stable hairpin should occur every 35 nucleotides so that the RNA species can fulfill the regulatory function throughout replication; c) The subsequence for internal recognition by Qß‐replicase and the primers should be fixed at particular positions in the sequence. These constraints have enabled us to predict the full sequence of MDV‐1RNA, a naturally‐occurring template of Qß‐replicase.
Influence of the Phase Structure on the Gas Transport Behaviour Through Liquid Crystalline Side Chain Elastomer Membranes
Authors: Modler H. , Finkelmann H.
Published: July 2012

The dependence of hydrocarbon gas transport behaviour on the liquid crystalline (LC) and isotropic state of different liquid crystalline side chain elastometer membranes (LCSCE‐membranes) is investigated with respect to the LC‐phase structure of the membranes and the molecular shape of the gas molecules.—A distinct change of the transport behaviour at the phase transformation from the smectic to the nematic and from the nematic to the isotropic state is observed. Additionally, an odd‐even effect is detected determined by the spacer length of the mesogenic moieties at a temperature range a little above the phase transformation temperature from the LC‐ to the isotropic state. It is assumed that this odd‐even effect correlates with the stress temperature dependence of the LCSCE‐samples. An enhanced selectivity for linear shaped gases compared to spherical shaped gases occurs in a macroscopic ordered sample.—For these experiments the accuracy of the transport coefficient determination by a transport process through membranes is analysed with respect to the geometrical arrangement of the developed experimental apparatus. The experimental method of determing transport coefficients, already described by R. A. Pasternack, is discussed and further developed.—The LCSCE‐membranes are synthesized by adding a mesogenic side chain to a polymethylhydrogensiloxane network.
KrF Laser Induced Telomerization of Bromides with Olefins. Part 2: BrC2F4Br and BrC2F4C2H4Br with C2H4 and C2F4
Authors: Linyang Zhang , Buß W. , Kompa K. L.
Published: July 2012

We investigated the photochemical insertion of one to three olefin units into a CBr bond of two dibromides in gas phase. Unexpected high quantum yields (up to 30) were found in the system BrC2F4Br + C2H4 for the product BrC2F4C4H8C2F4Br and some others. Therefore they cannot be radical combination products, but must arise from chain propagation. To explain their formation, accumulation of C2F4 must be assumed. The addition of ethylene to a radical can be reversed by Br atoms. This reaction strongly influences the product spectrum. Synthesis of BrC2F4C4H8C2F8Br would be economic by the laser method. The preparation of BrC2H4C2F4C2H4Br was also much improved over previous methods.
Acid‐Base Equilibria of Hydrophilic Indicators in Water‐in‐Oil Microemulsions
Authors: Chinelatto Ana M. , Fonseca Maria T. M. , Kiyan Nilo Z. , Seoud Omar A. El
Published: July 2012

The apparent pKa values of the positively charged, hydrophilic indicators 2‐hydroxy‐5‐bromo‐trimethylanilinium chloride (HBTC) and 2‐hydroxy‐5‐nitro‐trimethylanilinium chloride (HNTC) in the presence of water‐in‐oil microemulsion of the surfactants benzylcetyldimethyl ammonium chloride (BCDC) in benzene and polyoxyethylene (4) dodecyl ether (Brij‐30) in heptane were determined spectrophotometrically. The experimental variables were the type of buffer (benzimidazole, phosphate, and tris) and the ratios [water]/[surfactant] and [buffer]/[surfactant]. It is shown that: a) the indicators are confined within the second hydration shell of the nanodroplet, i.e. are not adsorbed at the water/oil interface; b) the use of the starting pH values of the buffer solutions, i.e., those measured outside the micellar domain, to calculate the micellar pKa values of the indicators is inadequate; c) buffer‐independent micellar pKa values can be obtained if the starting pHs of the buffer solutions were corrected for ion exchange with the counter‐ion of the positively charged surfactant, and for the lower polarity of the micelle‐solubilized water (relative to bulk water); d) the micellar ΔpKa (=pKa in the aggregate −pKa in water) ranged from ‐0.45 to ‐0.20 unit for HBTC/BCDC, from ‐0.44 to ‐0.13 unit for HNTC/BCDC, from 0.22 to 0.64 unit for HBTC/Brij‐30, and from 0.27 to 0.59 unit for HNTC/Brij‐30; e) these micelle‐induced pKa shifts can be analyzed in terms of the lower polarity of the micelle‐solubilized water (relative to bulk water) and perturbation of the acid‐base equilibria by the electrostatic effect of the positively charged W/O interface (BCDC); f) the magnitude of latter effect, at the average solubilization site of the indicator was calculated to range from 28 to 67 mV.
Diffusion‐Viscous Flow Coupling and Global Transport Coefficients Symmetry in Matter Transport Through Porous Membranes
Authors: Bartoszkiewicz M. , Miekisz S.
Published: July 2012

If statistical mechanical theory of Bearman and Kirkwood is applied to describe isothermal permeation of an incompressible solution through a porous membrane at mechanical equilibrium and not far from thermodynamic equilibrium and if the pores are homogeneous and cylindrical, the global transport coefficients of the system are symmetric if and only if switching off the short‐ranged membrane‐solution interactions leads to an uncoupling of diffusion and viscous flow.
Eloflux Fuel Cells and Electrolysis Cells
Authors: Winsel August , Führer Oliver , Rühling Klaus , Fischer Christian
Published: July 2012

In recent years in a corporation of the VARTA research and development centre in Kelkheim and the University of Kassel, a new kind of Eloflux fuel cell and electrolysis cell system was developed. This alkaline hydrogen‐oxygen system is a continuation of the VARTA fuel cell system with sinter‐nickel electrodes of the 1960's. The decisive progress, was the development of the new Raney‐Nickel hydrogen electrode with its simple and inexpensive manufacturing technique in 1983. Together with a new oxygen‐electrode of the same kind, we built within the scope of the Hermes fuel cell project different types of Eloflux fuel cells in 1988. First Eloflux electrolysis cells, which have the same design and similar electrodes as the fuel cells, were made last year.—This report deals with the manufacturing and the characteristics of the electrodes, with the principle of Eloflux cells and with the characteristics of the latest fuel cells, electrolysis cells and electrolyte reconcentrators.
On the Electrocatalysis of the Oxygen Reduction in Acid Electrolyte
Authors: Fabjan Ch. , Frithum G. , Hartl H.
Published: July 2012

Considerable electrocatalytic activity for the oxygen reduction in acid electrolytes (HClO4, H2SO4) was obtained with heat treated polypyrrole prepared by anodic polymerization on a carbon substrate‐containing Co and Fe as transition metal ions, comparable to that for Pt loaded electrodes. Apart from structural effects (increase of active area) the activity is attributed to N4‐coordinated transition metal species formed in the pyrolysis process. The electrode performance significantly depends on the nature of the metal ions and temp. of the heat treatment.—A cathodic reaction order of +1 with respect to O2(po2) indicates a mechanism avoiding the formation of peroxide in a potential range in which charge transfer is the rate controlling step. Promising results were obtained in extended time tests up to 400 hrs at 60°C.
Electrochemical Investigation of Amperometric Ammonia Gas Sensors
Authors: Pfenning D.‐M. , Deprez J. , Kitzelmann D.
Published: July 2012

Results of potentiodynamic and potentiostatic measurements of the electrooxidation of ammonia traces with platinum as a catalyst in a strong alkaline electrolyte are reported. To improve the performance of a fuel cell, such as an electrochemical gas sensor for ammonia traces, the hydrophobicity of the Teflon‐bonded platinum black gas diffusion working electrode is varied. The expectation that with increasing Teflon content of the catalytic anode the long term characteristics are enhanced could not be confirmed. The weakening of the cell current is influenced much more by effects belonging to the incorporation of carbon dioxide in the electrolyte.—The optimal operating potential for a three‐electrode cell arrangement, which depends also on the cross sensitivities to other gases, is in the range of 1.1 to 1.3 Volts.
The Direct Oxidation of Methanol at Platinum Based Catalytic Electrodes: What is New Since Ten Years?
Authors: Leger J.‐M. , Lamy C.
Published: July 2012

Methanol is one of the best candidates as fuel in fuel cell systems for terrestrial applications. However, the development of Direct Methanol Fuel Cell (DMFC) have been limited during a long period by problems mainly related to poisoning phenomena which led to a decrease of the cell performances. Since 10–15 years, significant progresses were made in the understanding of the electrooxidation of methanol. For example, with the availability of new “in situ” spectroscopic methods, it is now well accepted that adsorbed CO is the poisoning species. Electrodes of well‐defined structure (such as single crystals) allow correlations between the activity of the electrode and its surface structure to be made. All these new results bring new insights in the mechanism of methanol electrooxidation and let to think that new improvements in the DMFC could be expected for the next few years.
On the Reaction of CH2(ã1A1) with HF
Authors: Wagener R. , Gg. Wagner H.
Published: July 2012

The insertion reaction of singlet methylene CH2(ã1A1) into the strongest element‐hydrogen bond, H‐F, is investigated. CH2(ã1A1) is generated by pulsed UV‐laser photolysis of CH2CO. Its removal is directly monitored via LIF‐detection. The experiments are carried out under first order reaction conditions at temperatures T = 295, 380, and 485 K. Second order rate constants are determined from plots of first order rate constants versus the partial pressure of HF. The expression k1 = (5.5 ± 1.5)·1013·(T/295 K)(‐0.5±0.5) cm3/mol s is derived for the rate constant of the total depletion of CH2(ã1A1 0,0,0) with HF. Thus at room temperature the reaction is slower than the analogous reactions with NH3, H2O and HCl. For the isotopically substituted CD2(ã1A1 0,0,0) with HF the following rate expression is determined: k2 = (1.0 ± 0.3)·1014 (T/295 K)(‐1.0±1.0) cm3/mol s. The reaction of vibrationally excited CH2(ã1A1 0,0,0) with HF has a room temperature rate constant of k3 = (2.0 ± 0.4)·1014 cm3/mol s. Fluorocarbene CHF is detected as primary reaction product by LIF. Thermochemical considerations show the formation of CHF is the only exothermic reaction pathway besides physical quenching of CH2(ã1A1).
Hydrogenated Amorphous Silicon by Infrared Multiphoton Absorption with a Pulsed CO2‐Laser
Authors: Roth A. , Chiussi S. , Dietrich T. R. , Comes F. J.
Published: July 2012

The following work gives a discussion on hydrogenated amorphous silicon (a‐Si:H) film preparation by laser induced chemical vapor deposition (LICVD) using a pulsed CO2‐laser in a parallel configuration. Deposition rate and initiation of polymerization were studied as a function of total pressure, gas flow, gas mixture (buffer gas, silane and/or disilane), substrate temperature, and radiation flux. The results lead to a reaction model where higher silane homologues play an important role for the film production. The film properties strongly depend on the substrate temperature Ts. The activation energy Ea of the dark conductivity decreases from 1.1 eV to 0.7 eV for films prepared at Ts = 230°C to 450°C. In the same temperature range, the dark conductivity σd increases from ∼10−14 to ∼10−10 (Ω cm)−1, whereas the photo conductivity σph shows a maximum of ∼10−6 (Ω cm)−1 at Ts = 320‐330°C. These values, especially their temperature behaviour, are compared with the results of other CO2‐LICVD works and further production methods. It is shown that the film formation depends on the gas phase chemistry as well as on the substrate temperature.
Evaluation of the Excess Gibbs Energy of Mixing in Binary Alcohol‐Water Mixtures from the Liquid‐Liquid Partition Data in Electrolyte‐Water‐Alcohol Systems
Authors: Apelblat Alexander
Published: July 2012

The excess Gibbs energies of mixing at 298.15 K in fully or partially miscible water‐alcohol mixtures (1‐propanol, 2‐propanol, 1‐butanol, 2‐butanol, 2‐methyl‐1‐propanol (isobutanol), 2‐methyl‐2‐propanol (tert. butanol), 1‐pentanol, 2‐pentanol, 1‐hexanol, 1‐heptanol, 1‐octanol, 2‐octanol and cyclohexanol) are reported. They were calculated from the solubility and partition data by applying the Gibbs‐Duhem relationship and changing the standard state of water from water saturated with alcohols to pure water. In the 1‐propanol‐water, 2‐propanol‐water, 1‐butanol‐water, 2‐butanol‐water, 1‐pentanol‐water and 2‐pentanol‐water systems the excess entropies of mixing were also determined.
Investigations of the Nature of Critical Line Very Close to a Double Critical Point
Authors: Narayanan T. , Prafulla B. V. , Kumar A. , Gopal E. S. R.
Published: July 2012

The curvature of the line of critical points in a reentrant ternary mixture is determined by approaching the double critical point (DCP) extremely closely. The results establish the continuous and quadratic nature of this line. Out study encompasses as small a loop size (ΔT) as 663 mK. The DCP is realized when ΔT becomes zero.
The Relevance of Nonlinear Energy Localization in RNA Self‐Splicing
Authors: Fernández Ariel
Published: July 2012

We implement a ϕ4‐model to analyze the localization of energy in collective modes along the sugar‐phosphate backbone of RNA strands. We focus on the relevance of soliton‐like excitations in the site‐specificity of intramolecular nucleophilic attacks leading to transesterifications in the sugar‐phosphate backbone. We provide evidence supporting the view that hot spots for transesterification of catalytic RNA are caused by a combination of two factors: nonlinear energy transfer and intra‐chain folding. In particular, our results might help understanding the physics of covalent cyclization and cycle‐reopening in the catalytic intervening sequence (IVS) of ribosomal RNA from Tetrahymena and also they might help identifying the nucleophilic agents and cosubstrate in IVS RNA excision from rRNA.
Interferometric Determination of Mean Polarizabilities and Second Density Virial Coefficients of Methane Between 128 K and 890 K
Authors: Hohm Uwe , Kerl Klaus
Published: July 2012

Mean dynamic dipole polarizabilities α0(λ, T) and second thermodynamic virial coefficients B(T) of meth‐ane have been determined for the first time in the extended temperature range 128 K ≦ T ≦ 890 K by means of only one apparatus using interferometric low‐pressure measurements (p ≦ 03 MPa) of the refractive index n(λ, T, p) in the visible wavelength range (λ = vacuum wavelength). α0(λ, T) is in good accordance with previously measured values, but an obvious small minimum at the critical temperature Tc seems to occur. The B(T)‐data determined in the low‐temperature range ΔT1 (128 K ≦ T ≦ 298 K) are in fair agreement with other published data. The high‐temperature B(T)‐values of the range ΔTII (760 K ≦ T ≦ 890 K) have been measured for the first time. They are in good accordance with extrapolated low‐temperature virial coefficients. The mean standard deviation | ΔB | ≈ 8 cm3 mol−1 of the measured B(T)‐values may be further reduced by means of more precise measurements of pressure p.
Crystal Structure and Hydrogen Bond in Mono‐, Di‐, and Trichloroacetates of 4‐Methylaniline and 3,4‐Dimethylaniline, An X‐Ray and 35Cl NQR Investigation
Authors: Basaran Reha , Dou Shi‐Qi , Weiss Alarich
Published: July 2012

The 35Cl NQR spectra of the mono‐, di‐, and trichloroacetates of 4‐methylaniline and 3,4‐dimethylaniline, [4‐(CH3)C6H4NH3⊕] [Cl3‐nHnCCOO⊖] and [3,4‐(CH3)2C6H3NH3⊕] [Cl3‐nHnCCOO⊖], n = 0, 1, 2, were studied in the range 77 ≦ T/K ≦ Tdecomposition or Tbleaching out. Whereas for the monochloroacetates of both aniline derivatives the 35Cl NQR is observable up to T > 353 K, broadening of the 35Cl NQR lines of both groups, ‐CHCl2 and ‐ CCl3, lead to a bleaching of the NQR signals in the range 114 ≦ T/K ≦ 280, far below the decomposition temperature of the respective compound. The crystal structures of [4‐(CH3)C6H4NH3⊕] [Cl2HCCOO⊖] and of [3,4‐(CH3)2C6H3NH3+] [Cl3‐nHnCCOO⊖], n = 0, 1 were determined at room temperature. The results of both, diffraction experiments and 35Cl NQR are compared and discussed.
The Debye‐Hückel Theory for Hydrated Ions. IV. Activity and Osmotic Coefficients in Aqueous Solutions with a 1:1 Electrolyte and a Hydrophilic Nonelectrolyte
Authors: Schönert Hansjürgen
Published: July 2012

Two thermodynamic models of stepwise hydration of solutes in aqueous solutions are merged: one for 1:1 electrolytes and a another one for hydrophilic nonelectrolytes. The theory is compared with measurements for six systems taken from the literature. Except for: H2O + HCl + glycerol, the agreement is satisfactory.
On the Nature of the Surface Aggregation in Surfactant Adsorption Onto Polar Surfaces
Authors: Narkiewicz‐Michalek J.
Published: July 2012

At a certain surfactant concentration called “critical” or “hemimicelle” concentration a spontaneous aggregation takes place of surfactant molecules adsorbed onto polar surfaces. In spite of many works which have been published, the nature of that surface aggregation is still not understood well. The aim of this paper is to explore to which extent the concept of 2D condensation can explain the observed features of that surface aggregation. To that purpose the recent theoretical approach by Koopal is generalized to take the surface heterogeneity into account. This is because the surface heterogeneity is believed to be an important factor affecting the surface aggregation. Some striking similarities between the observed features of surface aggregation and the theoretical predictions based on the concept of 2D condensation are found. That concept, however, cannot at the present stage of the theory explain yet the finite tangent of the linear sections in the experimental isotherms corresponding to the surface aggregation.
Diffusion Coefficients of Four‐Component Systems from Taylor Dispersion Profiles. Sucrose + LiCl + KCl + Water and NBu4Br + LiBr + KBr + Water
Authors: Leaist Derek G.
Published: July 2012

The Taylor dispersion (peak‐broadening) technique is used to measure the quaternary interdiffusion coefficients of the four‐component systems sucrose + LiCl + KCl + water and tetra‐n‐butylammonium bromide + LiBr + KBr + water at 25°C. The dispersion of the eluted solutes is followed by differential refractometry. Direct least‐squares analysis of the measured peak shapes is used to calculate the interdiffusion coefficients. Equations are developed to describe dispersion in multicomponent systems containing arbitrary numbers of components.
Excess Enthalpy HE of Binary and Ternary Mixtures Containing Methanol, Methyl‐Tert. Butyl Ether (MTBE) and n‐Heptane
Authors: Tusel‐Langer E. , Lichtenthaler R. N.
Published: July 2012

Molar excess enthalpies HE have been measured for ternary mixtures of methanol + MTBE + n‐heptane and for the three corresponding binary mixtures of these compounds using a quasi‐isothermal flow calorimeter. The measurements have been performed at atmospheric pressure and at 298.1 and 313.1 K. The experimental results are compared with those calculated using the ERAS‐(Extended Real Associated Solution) model and the NRTL‐equation.
Photo‐sinking Phenomenon: Photodecomposition Rate of Silane Bonded on TiO2 Powders
Authors: Patel K. , Yamagata S. , Fujishima A. , Loo B. H. , Kato T.
Published: July 2012

Photodecomposition of silane from silanized TiO2 powders in contact with water was determined from the change in wettability of surfaces, i.e. hydrophobic to hydrophilic conversion. The decomposition rate of silane, estimated from the amount of powder converted to hydrophilic, was found to correlate with their photocatalytic activity in the oxidation of ethanol. Anodic and cathodic processes in the Photo‐sinking phenomenon were explained from the qualitative effects, for example, addition of anions and cations on photo‐sinking phenomenon respectively indicated that the photo‐excited holes decomposed the bonded silane and the adsorbed oxygen trapped the electrons. The Photo‐sinking phenomenon was applied for the estimation of photocatalytic activities of TiO2 powders and the separation of the photoactive powder from a mixture.
Composition Dependent Electronic Conductivities and Hall Coefficients of Mixed Ionic‐Electronic Conductors. Part IV: The High‐Temperature Phase of Silver Telluride
Authors: Kellers J. , Hock S. , Funke K.
Published: July 2012

The electronic conductivity, σe, and the Hall coefficient, RH, of Ag2+δ Te are experimentally determined at temperatures from 200°C to 480°C and at values of the composition parameter, δ, covering the entire stability range. The composition is varied and monitored by in situ coulometric titration. The evaluation of the experimental data yields a harmonic conduction band, while the anharmonicity of the valence band becomes obvious at higher temperatures. The experimental data are consistent with predominant scattering of electrons and holes at longitudinal acoustic phonons. Accordingly, the electronic relaxation time depends on energy and temperature as τ ∼ ϵ−1/2 · T−1.
Communications On the Temperature of Sputtered Metal Cluster Ions Investigated in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer
Authors: Schnabel Patrick , Irion Manfred P. , Weil Konrad G.
Published: July 2012

We use the initial rates of the reaction of ammonia with iron cluster ions after different storage times in order to characterize their temperature. For well defined times before reaction they are in contact with xenon gas at p ≈ 10−7 mbar. We can show, that they approach the temperature of the heat bath within about 5 s. Immediately after being trapped in the cell, their temperature is higher by not more than 20°C.
Modelling Tropospheric OH; A New Approach
Authors: Herbert A. , Armerding W. , Comes F. J.
Published: July 2012

A new fully dynamic model for tropospheric OH has been developed. The model structure is especially designed to comply with the needs of small scale problems and comparison with field data. Using the local character of most measurements providing the boundary conditions to the calculations and the local character of the OH concentration itself, the model is able to simplify the description of transport and deposition processes. Additionally the required initial data set can be reduced thus leading generally to a minimization of the measurement based error of the model results. As a special feature this model can calculate fluxes of atmospheric constituents resulting from emissions and transport which are an input to most models. Combining the photochemical model with budget and sensitivity calculations this system is equipped with testing and self‐correction facilities which help to achieve a strong error reduction in tropospheric modelling. First tests simulating dynamic flux‐reaction systems have shown that this approach is a very promising new way to model fast tropospheric photochemistry.
On the Application of Kramers' Theory to Elementary Chemical Reactions
Authors: Troe J.
Published: July 2012

Kramers' diffusion model in the energy controlled low viscosity and the momentum controlled high viscosity range is confronted with reality for elementary unimolecular reactions and radical associations in dense media. Collisional energy transfer appears to be much more complicated than described by the idealized model. On the other hand, there are examples where the Kramers‐Smoluchowski equation well describes the transition to high viscosity behavior. In other cases, solvent shifts of the reaction barriers are pronounced and superimposed on the transport effects described by Kramers' model.
High Pressure NMR Studies of the Kramers Turnover for Reactions in Liquid Solutions
Authors: Jonas J. , Peng X.
Published: July 2012

Advantages of NMR techniques to obtain the rate data for simple isomerizations in liquid solutions and advantages of using high pressure to change the viscosity of the solution are discussed. After a brief overview of our experiments on cyclohexane, 1,1‐difluorocyclohexane, and N,N‐dimethyltrichloroacetamide, the discussion focuses on the ethylene rotation in μ‐cyclopentadienylethylenetetrafluoroethylene‐rhodium in several solvents. – The experimental data, as interpreted in terms of stochastic models of isomerization reactions, indicate a Kramers turnover for the pressure dependence of the rotation of coordinated ethylene in the Rh complex in solution. In fact, the observation of the energy‐controlled regime in this system may be the consequence of the so‐called heavy metal atom bottleneck effect which reduces the intramolecular energy transfer within the molecule. The experimental dependences of the rates upon solvent viscosity and/or Enskog collision frequency show that solvent shear viscosity represents only an approximative measure of the coupling of the reaction coordinate to the medium.
Rate Processes in Low Dimensional Chaotic Systems with Many Attractors
Authors: Arecchi F. T.
Published: July 2012

Kramers' paper and its successive elaborations up to the last decade have considered the transition rate between two stable situations. In the language of system dynamics, we say that the process consists in the transition between the basins of attraction of two fixed point attractors. – Here I present four situations of transitions in non equilibrium systems explored experimentally, and which await a formal treatment in terms of a generalized Kramers transition rate theory.

I) Since 1967, with reference to Q‐switched lasers, we have studied the decay out of an unstable state, exploring the passage time statistics in its first and higher order moments.

II) In the '80s we have been exploring situations of low dimensional chaos where two or more strange attractors coexist. The jumps from one to another are either noise induced jumps, or they are induced by a change in a control parameter which lowers the energy barrier separating the two attractors (crises).

III) Investigating a dynamics with competing unstable points we have shown evidence of Shil'nikov chaos. The identification is done in terms of the iteration map of the successive return times to a given surface of section. This may be considered as an extension of the passage time method to the case of multiple passages.

IV) We have given experimental evidence of “chaotic itinerancy”, that is, of jump processes self triggered by the same dynamics. So far, the corresponding understanding is based only on numerical simulations. Since chaotic itinerancy has been observed in optical systems displaying space‐time chaos, a short survey of these phenomena is presented for sake of completeness.
The Kramers Problem in the Turnover Regime: The Role of the Stochastic Separatrix
Authors: Klosek M. M. , Matkowsky B. J. , Schuss Z.
Published: July 2012

We consider the problem of activated escape of a Brownian particle from a potential well. We find the stochastic separatrix S (the locus of starting points of the phase space trajectories which have equal probabilities of ending up inside or outside the well) for (i) the extremely anisotropic overdamped motion of a two‐dimensional Brownian particle in a bistable potential, and (ii) the damped and underdamped motion of a one‐dimensional Brownian particle in a single metastable state. The significance of S is that (1) it defines the reactant and product wells in a natural though not necessarily intuitive way, and (2) it reduces the calculation of the escape rate to the solution of the stationary Fokker‐Planck equation inside S, with absorbing boundary conditions on S. Finally, employing this approach we derive an expression for the Kramers escape rate which bridges uniformly between Kramers weak damping regime and transition state theory.
Harmonic Noise Driven Bistable Dynamics
Authors: Schimansky‐Geier L. , Hesse J. J. , Zülicke Ch.
Published: July 2012

We consider bistable dynamics driven externally by a noisy harmonic oscillator. For small damping we derive a Markovian approximation for the energy dynamics. In conclusion we discuss the possibility of the inversion of bistable oscillators induced by colored noise.
Soliton – Assisted Activation Processes
Authors: Ebeling Werner , Jenssen Martin
Published: July 2012

This paper deals with the problem of energetic activation of one or few degrees of freedom of a spatially extended system. The fusion of soliton‐like excitations is an efficient nonlinear mechanism to generate high‐energy events at soft springs which are embedded in a one‐dimensional chain of hard springs. In equilibrium there exists an optimum temperature where thermal energy is mainly partitioned to the soft springs due to the superposition of thermally generated solitons. Some of the features obtained for the one‐dimensional system also apply to a solution of soft spheres in a hard‐sphere solvent.
Proton Quantum Tunneling in Hydrated Protein Surface
Authors: Careri G. , Consolini G.
Published: July 2012

We measure the protonic conductivity in water clusters adsorbed on lysozyme powders, below room temperature In the low temperature region the conductivity increases with temperature as exp T6, in agreement with prediction by the theory of dissipative quantum tunneling. We detect the onset of this effect near 180 K, where a glass transition in the protein matrix is known to take place. Quantum tunneling matches smoothly with thermal hopping near 271 K.
Quantum Brownian Motion and its Classical Limit
Authors: Ambegaokar Vinay
Published: July 2012

The Feynman‐Vernon, Caldeira‐Leggett model for a quantum dissipative system is used, via a general kinetic equation due to Chow, Browne, and the present author, to cast light on the classical limit of quantum Brownian motion, with special attention paid to the requirement of coarse graining in time.
Dynamics of an Impurity Spin Coupled to a Spin‐Boson Dissipative System
Authors: Dattagupta Sushanta , Qureshi Tabish
Published: July 2012

The dynamics of an impurity spin coupled to a spin‐boson dissipative system is studied using the resolvent expansion technique. In one particular physical realization the model simulates a highly anisotropic Kondo system. The transverse correlation function of the impurity spin is calculated and the result obtained is analyzed in various limiting cases. NMR lineshapes are also calculated for various temperatures which are relevant in another physical realization of the model. Motional narrowing is observed at high temperature.
Energy Transfer in Solid Solutions and on Fractal Polymer Surfaces
Authors: Kost S. H. , Breuer H. D.
Published: July 2012

The electronic energy transfer from rhodamine B to several acceptor dyes in cellulose nitrate solid solution and on the surface of membrane filters of the same polymer has been investigated at room temperature. In polymer matrix the Förster theory has been confirmed and critical distances Ro have been calculated from the theoretical equation and have also been determined by energy transfer experiments measuring the fluorescence decay time of the donor. Applying new fractal concepts to energy transfer in porous membranes, the fractal dimension of the polymer surface has been determined under several conditions. The values agree with others obtained by adsorption experiments.
Temperature Dependence of the Electric Conductivity of a Triethylamine/Water Mixture of Critical Composition
Authors: Höhn F. , Woermann D.
Published: July 2012

Results of measurements of the temperature dependence of the specific conductivity of a triethylamine (TEA)/water mixture of critical composition (xc(TEA) = 0.0777; mole fraction of TEA) as well as of mixtures of non‐critical composition are reported. They are analysed by fitting the function K = a + b · ϵ + c · ϵ2 + d · ϵthetas + e · ϵθ+Δ (ϵ = (Tc,vis – T)/Tc,vis; Tc,vis: visually determined critical temperature; θ: critical exponents; theoretical value Δ = 0.5) to the experimental data. For the analysis the critical exponent θ is fixed at values predicted by different models (θ = 0.65, θ = 0.89). Tc is fixed at the value determined visually for each mixture studied. The analysis of the data shows that in a triethylamine/water mixture of critical composition an anomalous decrease of the electrical conductivity as a function of temperature can be detected as the critical temperature is approached. The reproducibility of the conductivity data is limited by the chemical instability of the system. Therefore it is not possible to decide unequivocally which of the proposed values of the critical exponent Θ is consistent with the data.