bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of Membrane Potentials to Energy Conversion in Photosynthetic Membranes
Authors: Huber H.‐L. , Rumberg B. , Siggel U. 
Published: August 2012

AbstractThe conversion of the energy of light into the chemical energy of ATP occurs at the photosynthetic membrane with the transmembrane electrochemical gradient of protons as intermediate. The electric portion, i.e. the light‐induced change of the electric potential difference (photopotential), quickly attains a maximum of 200 mV after the onset of illumination and decreases toward the steady state for the benefit of the H+‐concentration gradient. The resulting stationary photopotential is determined by two different methods, on the one hand directly through the electrochromic absorption change of membrane pigments, on the other hand by calculating the change of the surface potential at the inner side of the membrane from the surface charge densities. The charge density in the dark state is derived from the kinetics of an electron transfer reaction in the membrane (reduction of oxidized chlorophyll‐aI) sensitive to the pH of the inner surface. Its dependence on pH is characterized by an isoelectric point of 4.8. The light‐induced change of the charges is determined from the amount of protons additionally bound to the inner membrane surface. For the calculation of surface potentials from the charge densities the conventional Gouy‐Chapman theory is modified by assuming a transverse spreading of surface charges over a layer of 20 A thickness. — The results of both the methods are similar. The stationary transmembrane photopotential is dependent on the concentration of electrolyte and exhibits a maximal value of 60–70 mV at 6 mM KCl. Under physiological conditions the contribution of the photopotential is below 20 mV and can be neglected compared to the light‐induced difference in proton concentration with respect to energetic and kinetic considerations.
Magnetische Eigenschaften von FeTi und dessen Hydriden
Authors: Stucki F. , Schlapbach L. , Seiler A. 
Published: August 2012

AbstractMagnetisierungsmessungen am Wasserstoffspeicher FeTi weisen auf eine reversible Änderung der magnetischen Eigenschaften des Volumens und eine irreversible Änderung der magnetischen Eigenschaften der Oberfläche als Folge des Hydrierens hin. Verantwortlich für die irreversible Änderung sind superparamagnetische Fe‐Teilchen, die hauptsächlich in einer Oberflächenschicht ausgeschieden werden. Die Suszeptibilität des Volumens der FeTi‐Hydride ist kleiner als die des Ausgangsmaterials.
Kinetics of the Steam Reforming of Methane on Iron as a Catalyst
Authors: Münster P. , Grabke H. J. 
Published: August 2012

AbstractThe kinetics of the reaction CH4 + H2O → CO + 3H2 have been investigated in the temperature range of 700°C to 900°C on iron as a catalyst. In the reaction sequence

the first step, the decomposition of methane, is rate controlling. The reaction is retarded with increasing H2O/H2‐ratio, which indicates site blocking by adsorbed oxygen. The rate equation can be written

As can be derived from the reaction kinetics, in the flowing gas mixture the steady state carbon activity will be very low on and in the iron catalyst, this was confirmed by electrical conductivity measurements.
The Spherical Crystal Potential and Physical Properties of Ions in Crystals. A HF‐Calculation for the 10, 18, and 36 Electron Closed Shell Ions of X‐Ray Scattering Factors, Diamagnetic Susceptibilities, and Dipole Polarizabilities
Authors: Schmidt P. C. , Sen K. D. , Weiss Alarich 
Published: August 2012

AbstractThe diamagnetic susceptibilities χd, the dipole polarizabilities αD, and the atomic form factors f are calculated for 10, 18, and 36 electron closed shell ions (Na⊕, Mg2⊕, Al3⊕, N3⊖, O2⊖, F⊖, K⊕, Ca2⊕, P3⊖, S2⊖, Cl⊖, Rb⊕, Sr2⊕, Br⊖). Three effects on the physical properties are studied
the quantum mechanical method to calculate the wave functions;
the influence of the spherical crystal potential on the wave functions and
the inclusion of self consistency in deriving αD from the wave functions.
The investigation of the polarizability shows that the best choice for the crystal potential is to adjust the charged compensating sphere to the Madelung potential; thereby agreement between experimental and theoretical data is good. — Deviations of atomic form factors for crystal ions from free ion values are high; for soft ions such as N3⊖, O2⊖, and S2⊖ f is changed up to 18% (N3⊖) near sin ϑ/λ = 0.1 Å−1 compared to the quasi free ion value. From the crystal ion atomic scattering factors ffree ion is deduced by extrapolation for the unstable free ions N3⊖, O2⊖, and S2⊖.
Invariant expansion coefficients of the molecular pair correlation function of ZX4‐systems
Authors: Steinhauser O. , Bertagnolli H. 
Published: July 2012

AbstractThe general relationship between atom pair correlation functions gαβ(R) and the expansion coefficients gn1n211l2l12(R12) of the generalized pair correlation function g(R12, Ω1, Ω2, Ω12) is presented and tested numerically with the aid of the results of a computer simulation of liquid CCl4. For the structure factor of ZX4‐systems a symmetry adapted expansion in terms of g n1n2l1l2l12(R12) is given together with the corresponding molecular form factors. In evaluating the g‐coefficients a cartesian representation was used instead of Eulerian angles. It is shown how one can extract principal molecular configurations by a detailed g‐coefficient analysis.
An ESR study of TiO2 treated with atomic hydrogen
Authors: Serwicka E. , Schindler R. N. , Schumacher R. 
Published: July 2012

AbstractPowdered TiO2 samples were reduced by hydrogen plasma treatment at room temperature. The ESR spectra reveal the formation of Ti3+ ions with similar concentrations as obtained in samples which were reduced conventionally, i.e. at elevated temperature either in vacuo or with hydrogen gas. The effect of O2 adsorption on plasma and conventionally treated TiO2 samples is compared and discussed.
Ultrahigh vacuum cryostat for spectroscopy and laser‐induced processes
Authors: Heidberg Joachim , Stein Helmut , Hoefs Eugene 
Published: July 2012

AbstractAn ultrahigh vacuum cryostat consisting of a stainless steel body flanged to an analyzer cell for spectroscopy and laser‐induced processes in the entire spectral region between ca. 50 and 0.2 μm at base pressures in the low 10−10 mbar range and sample temperatures between 10 and 600 K is described for the first time. ‐ Under helium bath operation, (4 ± 1) K was measured on the sample holder and (10 ± 2) K in the sample without using thermal contact materials. The metal to metal joint between helium reservoir (stainless steel) and sample holder (OFHC copper) according to the conflat flange method proved to be tight for many baking cycles. The integral leak rate of the whole ultrahigh vacuum apparatus as well as the optical transmission are reported. The windows developed do not show irradiation effects at peak intensities of 10 MW · cm−2 per CO2 laser pulse. The cryostat is equipped with a quadrupole mass spectrometer and evaporation sources for salts and metals. The analyzer cells are compatible with the sample chamber dimensions of most commercial spectrometers. ‐ Examples of applications are presented in the fields of low temperature gassolid interaction, cryospectroscopy of stable and new metastable adsorbates, selective and efficient evaporation and desorption induced by laser infrared.
Vibrational nonadiabatic model calculations on the unimolecular cis‐trans isomerization of dideuteroethylene
Authors: Russegger P. 
Published: July 2012

AbstractWith the aid of a model hamiltonian for the isomerization‐ and vibrational motions, we have investigated the quantum dynamics of the cis‐trans isomerization of dideuteroethylene. The importance of nonseparability of the motion along the reaction coordinate and the other degrees of freedom is demonstrated by means of the differential rate constants — Comparison with the statistical theories of unimolecular reactions is also presented.
Absolute measurements of the thermal conductivity of liquids at pressures up to 500 MPa
Authors: Menashe J. , Wakeham W. A. 
Published: July 2012

AbstractAn apparatus for the accurate measurement of the thermal conductivity of liquids is described. The instrument, which is of the transient hot‐wire type, operates over the pressure range 0.1 to 700 MPa and the temperature range 20–200°C. The precision of the thermal conductivity measurements is estimated to be one of ±0.2% over the entire range. — Experimental data are reported for the thermal conductivity of n‐heptane in the temperature range 35–75°C and the pressure range 50–500 MPa. The accuracy of the present results is estimated to be one of ±0.5%, which is slightly worse than their precision because the lack of suitable data for the optical properties of the liquid at high pressures only allows an approximate correction to be applied for the systematic effects of radiative heat transfer. Along an isochore the thermal conductivity of n‐heptane is found to increase with temperature although along an isobar the temperature derivative is negative. The density dependence of the thermal conductivity is almost independent of temperature.
Doppelkaskaden‐Knudsenzelle zur Dampfdruckuntersuchung an Arsenolith und Claudetit
Authors: Bradaczek H. , Denzer P. , Woköck H.‐D. 
Published: July 2012

AbstractThe twin cascaded Knudsen cell makes possible improved comparative measurements of effusion processes on sample pairs exhibiting widely differing evaporation temperature ranges. Investigating the polymorph system Arsenolite‐Claudetite no significant differences in the evaporation behaviour of both polymorphs can be found.
Arrhenius Parameters for the System (CH3)3Si + D2 ⇄ (CH3)3SiD + D. The (CH3)3Si — D Bond Dissociation Energy
Authors: Ellul R. , Potzinger P. , Reimann B. , Camilleri P. 
Published: July 2012

AbstractThe Arrhenius parameters of the reaction (3)
equation image
have been determined relative to the recombination of the trimethylsilyl radicals
equation image
yielding EA (3) — 1/2EA(6) = 67 ± 6 kJ mol−1 and A(3)/A (6)1/2 = 10−7±0.5 cm3/2 s−1/2. The rate constant for the back reaction (‐3)
equation image
has been determined to be
equation image
.Assuming a negligible activation energy for the recombination reaction (6) gives HD0((CH3)3Si — D) = 388 ± 7 kJ mol−1 in accordance with the accepted literature value. In the experimental part a pulsed Hg sensitized photolysis‐resonance absorption technique is described to obtain rate constants for hydrogen atom‐molecule reactions. For testing the apparatus the rate constants
equation image
at room temperature have been determined.
The Effect of Some Surface Treatments on the Characteristics of the Cd‐Chalcogenide/Polysulfide Schottky Barrier
Authors: Tenne R. 
Published: July 2012

AbstractA potentiostatic study of Cd‐chalcogenide/polysulfide Schottky junction, was undertaken. The effect of various surface preparation techniques, in particular photoelectrochemical etching [1, 2] upon the properties of the junction was studied and analyzed in terms of thermionic emission over the Schottky barrier, surface roughness and tunneling through an insulating layer. It has been found that close to the flat band situation the time course of the current is not the same as at small forward bias and it is suggested that the potential distribution within the Helmholtz layer is changed leading to unpining of the bands. Implications to the optimalization of the performance of photoelectrochemical cells are discussed in brief.
Vibrational Relaxation in Liquids with Rather Strong Intermolecular Interactions
Authors: Scheibe D. , Döge G. 
Published: July 2012

AbstractTo understand more about vibrational relaxation in liquids with rather strong intermolecular interactions, the Ramanband of the C = O‐stretching vibration of methyl ethyl ketone was measured in a temperature range from 233 to 343 K, and at 293 K in various solvents changing the concentration. — An interpretation for the behaviour of such polar bands in terms of dipole‐dipole interactions was evaluated in the frequency picture. This allows to explain, at least qualitatively, the variation of band shape parameters under different conditions.
Viscosity of Acidic Lithium Chloroaluminate Melts
Authors: Tørklep K. , Øye H. A. 
Published: July 2012

AbstractThe viscosity of LiCl — AlCl3 melt mixtures has been determined in the range 0.50 ≦ XAlCl3 ≦ 0.80, 110°C to 300°C. The method, which utilizes closed cylindrical cups subjected to vapour pressures exceeding 11 atm, is absolute and requires no calibration against reference liquids. Results are corrected for surface effects. Applying Arrhenius temperature dependencies and the Arrhenius mixing rule, the viscosity is expressed as a function of temperature and composition with an overall standard deviation of 0.22% when the presence of AlCl4−, Al2Cl7−, Al3Cl10−, and Al2Cl6 is assumed. The results are also discussed with respect to an earlier study of the NaCl—AlCl3 system.
Interaction of CFCl3 with an Fe(100) Surface Part II: Adsorption and Decomposition at Ambient Temperatures
Authors: Dowben P. A. , Grunze M. , Jones R. G. , Illenberger E. 
Published: July 2012

AbstractIn the second part of our communication on CFCl3 adsorption on an Fe(100) surface we present the results obtained for room temperature adsorption and annealing the adsorbate covered surface up to 800 K. Dissociative adsorption at 300 K proceeds with a high and constant sticking coefficient which is explained by the long lifetime (>3 ± 10−5 s) of the molecule in the extrinsic precursor state. Chlorine adsorbs on the surface forming a noncoincidence overlayer raft while carbon and fluorine are absorbed in the selvedge. These absorbed atoms have a distinct influence on the surface structure and the stability of the chlorine overlayer. Absorbed fluorine stabilizes the chlorine overlayer up to 700 K, which is a significantly higher temperature than observed for the stability of chlorine overlayers formed by Cl2 or CCl4 adsorption.
Two Photon Spectroscopy of Dipole Forbidden Transitions III. Experimental Determination of Two Photon Absorption Spectra Including Polarization Control
Authors: Dick B. , Gonska H. , Hohlneicher G. 
Published: July 2012

AbstractA new experimental technique is described which allows the measurement of two‐photon absorption spectra of luminescent molecules and simultaneously the evaluation of the two‐photon polarization parameter Ω over a wide spectral range. The resolution obtained is comparable to conventional UV absorption and polarization spectra. Examples are shown for different types of unsaturated hydrocarbons. The influence of S1 → Sm excitations and of variations of the profile of the exciting laser pulse are discussed. It is shown that careful control of both the quadratic nature of the two‐photon process and the beam profile is essential to avoid artificial features in wide range two‐photon spectra.
Electron Correlation in Weakly Coupled Transition Metal Compounds: Poly‐Decker Systems
Authors: Böhm Michael C. 
Published: July 2012

AbstractThe Thouless instability conditions in the poly‐decker sandwich compounds 1–8 have been investigated by means of semiempirical INDO calculations. Hartree‐Fock (HF) fluctuations of the singlet, non‐singlet (triplet) and non‐real type have been detected. The reasons for the various instability conditions are analysed. The charge density waves (CDW) of the singlet route are of helical type, the spin density wave (SDW) of the non‐singlet route corresponds to a longitudinal modulation. Singlet fluctuations in complexes with identical 3d centers are the result of intraatomic angular and interatomic left‐right correlation. The non‐singlet variation corresponds to a spin decoupling between the two 3d centers. The HF instabilities in the closed shell species 1 – 8 are compared with doublet fluctuations in open shell complexes and are extrapolated to infinite polymer chains.
Phase Transition of the Bilayer Membrane of Synthetic Dialkyl Amphiphiles as Studied by Differential Scanning Calorimetry
Authors: Okahata Yoshio , Ando Reiko , Kunitake Toyoki 
Published: July 2012

AbstractThe phase transition behavior of dilute aqueous solutions of the bilayer membrane of dialkyl (C12 to C18 in most cases) amphiphiles was investigated by differential scanning calorimetry (DSC). The extent of the sample dispersion affected the DSC behavior for dialkyl amphiphiles with ammonium, phosphate and sulfonate head groups. The well‐sonicated aqueous sample of the ammonium amphiphiles showed broader transition peaks at lower temperatures than the corresponding frozen sample did. The discrepancy became less pronounced when the interacting group was introduced at or near the head group. The wel DSC behavior was not observed for amphiphiles with nonionic (polyoxyethylene) and zwitterionic (phosphocholine) head groups. The phase transition temperature (0 – 80°C) was enhanced progressively with increasing alkyl chain lengths (C12 to C18), but the transition enthalpy (2–12 kcal/mol) did not obey simple relations.
The Pressure Dependence of the Excess Enthalpy of Mixtures of Isopropanol with Heptane and Isooctane up to 553 bar
Authors: Heintz A. 
Published: July 2012

AbstractExcess enthalpies HE of isopropanol + n‐heptane and isopropanol + isooctane mixtures are reported measured at 298 K and various pressures up to 553 bar. The HE values are endothermic and show a remarkable decrease with pressure. The real associated solution model has been applied taking into account the volume change due to hydrogen bonding of the alcohol and was found to be insufficient for describing quantitatively the pressure dependence observed.
Characterization of the Order/Disorder Transition of Poly‐1‐Methyl Adenylic Acid in Neutral Solution by Raman Difference Spectroscopy
Authors: Klump Horst , Sturm Jean , Peticolas Warner L. 
Published: July 2012

AbstractA detailed analysis of the hypo‐ and hyper‐chromic intensity changes as well as the changes in frequency and band shape in the Raman spectra of poly(m1A) upon melting has been made using a newly developed Raman difference technique. An interpretation of these changes allows us to suggest a structure for the double‐helix of this polymer in neutral solution which resembles that of poly(A) in acid pH. In the helix the backbone geometry is shown to be similar to the C 3 endo or A genus and the existence of a hydrogen bond is inferred from the asymmetric band shape of 1100 cm−1 PO−2 stretching vibration wich is not found either in self‐stacked poly(A) at neutral pH. It is expected that the application of the Raman difference technique will result in a detailed description of conformational features of these important macromolecules which cannot be drawn from the resuits of other optical methods.
Katalysatoraktivitäten α, Gleichgewichte und Kinetik in den homogenen Bulk‐H2‐Transfer‐Reaktionen als Funktion der H2‐Donatoren und Acceptoren
Authors: Graser Barbara , Strohmeier Walter , Marčec Radovan , Steigerwald Hannelore 
Published: July 2012

AbstractKetons are reduced under mild conditions to the corresponding alcohols by secondary alcohols in homogeneous bulk hydrogen transfer reactions, catalysed by Ru(CF3CO2)2CO(Pø3)2. The reactions are reversible, the equilibrium constants vary from 0.1 to 21, and under optimized conditions time to establish equilibrium varies from 5 to 90 minutes at 140°C. The rate determining step seems to be the dehydrogenation of the alcohols. The conversion can be described by the rate law of a reversible second‐order reaction.
Photoelectrochemical Cells for the Oxidation of Water and Bromide Ions by Visible Light
Authors: Neumann‐Spallart Michael , Kalyanasundaram K. 
Published: July 2012

AbstractAnodic oxidation of water to molecular oxygen and of bromide ions to Br2 photosensitized by tris‐bipyridylruthenium(II), Ru(bpy)32+, has been investigated in photoelectrochemical cells. An irreversible photoredox reaction between Ru(bpy)32+ and electron acceptors (S2O2–, Tl3+, Co(NH3)5Cl2+) generates Ru(bpy)33+ which is reduced at the cathode (Pt or Carbon) with concomittant oxidation of H2O or Br− with RuO2, Pt (or Carbon) anodes respectively. Cell performances have been examined in terms of photocurrents, potentials under illumination, stability, turn‐overs, and the data explained in terms of i‐e curves of the redox couples involved in Evans‐type diagrams. Under optimal conditions, photocurrents upto 10 mA (with a 250 W lamp) have been drawn and 2 · 10−4 mdes Br2 generated in one hour photolysis. Possible extensions, scope and limitations are discussed.
Wechselwirkungskräfte in flüssigen Dünnschichten
Authors: Lyklema J. 
Published: July 2012

AbstractThe forces operating in thin liquid films of colloidal dimensions are reviewed. These forces are: Van der Waals (dispersion‐), electrical and steric interactions. A discussion is given on their evaluation in situations of practical interest, including dynamic conditions. The review covers both symmetrical and asymmetrical films. A few examples are given to indicate possible applications.
Interfacial Convection
Authors: Sawistowski H. 
Published: July 2012

AbstractInterfacial convection is a general term used for the description of surface flow produced by the appearance in the interface of gradients of surface parameters. It embraces three types of phenomena: Marangoni instabilities, Marangoni disturbances and thin‐film behaviour. Each of them is discussed in turn and criteria presented for their appearance. Finally, practical implications are described in terms of effects on mass transfer coefficients, interfacial area and hydrodynamic behaviour of mass transfer equipment.
Conformal‐Solution‐Theorie für Mischungen konvexer Moleküle
Authors: Naumann K.‐H. , Chen Y. P. , Leland T. W. 
Published: July 2012

AbstractThe Hard Spheres Expansion Conformal Solution Theory [1], originally developed to predict the thermodynamic properties of mixtures of spherical molecules, is generalized for the treatment of fluids that are composed of particles interacting via Kihara type potentials [2].—A perturbation expansion is generated by dividing the intermolecular pair potential into a repulsive and an attractive part. The hard‐core reference system is represented by a mixture of hard convex bodies. It's thermodynamic functions are obtained from a new accurate equation of state. The attractive contributions are evaluated from the known attractive interactions of a pure reference fluid using the principles of conformal solution theory and a new type of pseudoparameters.—A method for the determination of temperature and density dependent effective hard‐core parameters is presented.
Influence of Water on the Capacitance/Potential Distribution at the TiO2/CH3CN Junction
Authors: Heinzel A. B. , Teschner D. M. , Schumacher R. 
Published: July 2012

AbstractIt is reported on changes of the flat band potential Vfb at the n‐TiO2/CH3CN junction upon water addition. It is shown that these shifts are related to the increasing density of H+ ions in the CH3CN electrolyte by adding water to it. The results are discussed in terms of specific adsorption of H+ ions at the TiO2 electrode that affects the potential/capacitance distribution of the junction.
Bestimmung der Elektronendichte in Hochfrequenz‐Entladungen mehratomiger Gase
Authors: Kruppa G. , Suhr H. , Janzen G. , Staib W. 
Published: July 2012

AbstractElectron densities ne have been measured in rf plasmas of He, Ar, H2, N2, O2, CO, CO2, H2O, SO2, NH3, CH4, CH3NH2, CH3NO2, CH3OH, CH3OCH3, C2H5OC2H5, CH3COCH3, CH3COOH, CH3COOCH3, and trans‐CH3CHCHCH3. Electron densities ranged from 3 · 108 cm−3 to 23.4 · 1010 cm−3. At constant rf power log ne decays linearly with distance from the end of the exciter coil. A rise in pressure increases ne of He and Ar and decreases ne for the other gases. Some gases show a linear dependence and others a quadratic or mixed dependence of ne, on the rf power. This can be correlated to differences in ionisation processes. Electron densities in plasmas of organic compounds resemble eachother very closely but differ significantly from the ne values of He, Ar, H2, and O2.