bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric properties of ultrathin poly(vinylchloride) films as generated by molecular association of ionic porphyrins at the polymer‐water interface
Authors: Yamada Sunao , Iida Hiroshi , Matsuo Taku 
Published: July 2012

AbstractAn amphiphilic porphyrin derivative, 4,4′,4″,4‴‐(21 H,23 H‐porphine‐5,10,15,20‐tetrayl)tetrakis[1‐hexadecyl‐pyridinium] cation or its zinc complex (abbreviated as MC16TPyP), was preferentially impregnated on a single surface of an ultrathin poly(vinylchloride) film prepared by casting the polymer solution on water. Enrichment of the cationic porphyrin moiety to the polymer‐water interface during the film preparation was strongly indicated by contact‐angle measurement of water‐droplets on the dry surface. A subsequent treatment of the film with an aqueous solution, which contained an anionic porphyrin (4,4′,4″,4‴‐(21 H, 23 H‐porphine‐5,10,15,20‐tetrayl)tetrakis[p‐benzenesulfonate] anion or its copper or zinc complex: MTPPS), led to molecular association of the two‐types of porphyrins (MC16TPyP‐M'TPPS) on the film surface. Spectroscopic evidences for the formation of molecular association on the thin film were obtained by measuring electronic absorption, fluorescence, and optical second‐harmonic generation.
69Ga NMR and 115In NMR in AB2X4 crystals
Authors: Breuer A. , Siebert D. 
Published: July 2012

AbstractFor several Ga defect chalcopyrites and one In spinel we determined nuclear quadrupole coupling constants and electric field gradients (EFG) from NMR measurements of the second order shift of the 69Ga and 115In resonances. A model is proposed for the lattice contribution and the orbital contribution of the EFG.
Molar excess enthalpies of n‐monohaloalkanes + n‐monohaloalkanes mixtures. Estimation of DISQUAC interchange energy parameters
Authors: Artal Manuela , Embid José Muñoz , Otín Santos , Velasco Inmaculada 
Published: July 2012

AbstractMolar excess enthalpies, H, at 298.15 K and atmospheric pressure were determined for six binary liquid mixtures [x{iodethane or 1‐iodobutane or bromoethane or 1‐bromobutane or 1‐chloropropane or 1‐chloropentane} + (1 ‐ x) 1‐fluoropentane]. These experimental results along with the data available in the literature on molar excess Gibbs energies, G, activity coefficients at infinite dilution, In γ, and molar excess enthalpies, H, for n‐monohaloalkane + n‐monohaloalkane mixtures, are examined on the basis of the DISQUAC group‐contribution model. The interchange energies of the contacts between two different halogen atoms are entirely dispersive and were determined in this work. The model reproduces reasonably well most of the experimental data. For a given n‐monohaloalkane, mixed with the other n‐monohaloalkanes, it can be seen that the values of the dispersive interchange energies coefficients of the Gibbs energy, C, and enthalpy, C, the contact between the two different halogen atoms, X and Y, and the experimental equimolar values of the excess thermodynamic properties G(x1 = 0.5), and H(x1 = 0.5), have the same trend as the gas‐phase electric dipole moment, p, of the molecule X‐Y. The same trend is also observed for the difference in the electric polarizability, Δα, between the halogen atoms X and Y.
An electrochemical study of some spirobenzopyran derivatives in dimethylformamide
Authors: Zhi Jin Fang , Baba Ryo , Fujishima Akira 
Published: July 2012

AbstractThe electrochemical behavior of spirobenzopyran derivatives with substituted groups of OCH3, Br and NO2 in the benzopyran ring and the indoline ring has been studied by cyclic voltammetry and spectro‐electrochemistry in a dimethylformamide (DMF) solvent at a platinum electrode. The six spirobenzopyran derivatives studied can be divided into two groups according to the presence or the absence of a nitro group substituted in the benzopyran ring. In the potential range of −1.8 V ∼ +1.0 V (vs. Ag QRE), neither redox reactivity nor reversible color changes were observed for those derivatives without a substituted nitro group, while the nitro‐substituted spirobenzopyrans exhibited appreciable redox behavior and the electrochromism corresponding to the redox reaction of the nitro group.In addition, an irreversible oxidation wave observed at about + 1.3 V (vs. Ag QRE) for all the derivatives studied (except SP‐18) was assigned to the oxidation of the nitrogen atom in indoline moiety. These oxidation wave potentials of the nitrogen atom are linear with the Hammett values Σσ* of the substituted group, and thus suggest that a significant electron‐induced interaction existed between the benzopyran and the indoline ring in the spirobenzopyran molecule.
Determination of interdiffusion coefficients in nematic liquid crystals by an optical method
Authors: Heuer H. W. , Kneppe H. , Schneider F. 
Published: July 2012

AbstractAn optical method for the determination of interdiffusion coefficients in mixtures of nematic liquid crystals is described. In this method a liquid crystal mixture with a concentration gradient is placed between the plates of a Fabry‐Perot etalon. Illumination with parallel monochromatic light gives an interference pattern from which the index of refraction and the concentration can be determined as a function of the position. This method of measurement does not require the addition of dyes, chiral substances or radioactive substances.The set‐up was tested with the isotropic system n‐hexane/n‐dodecane for which the diffusion coefficients are known. The diffusion coefficients in the system 4‐n‐butylbenzoic acid‐4'‐n‐hexylphenyl ester/4,4'‐di‐n‐hexylazoxybenzene were determined as a function of temperature. The system 4'‐n‐butyloxybenzylidene‐4‐n‐butylaniline/ethylhydroquinone‐di‐4‐n‐hexylbenzoate was studied at a temperature for which the first component is in the nematic phase slightly above an SA phase.
The internal conversion rate of the primary donor in reaction centers of Rhodobacter sphaeroides
Authors: Müller Peter , Bieser Gero , Hartwich Gerhard , Langenbacher Thomas , Lossau Harald , Ogrodnik Alexander , Michel‐Beyerle Maria‐Elisabeth 
Published: July 2012

AbstractThe most prominent cornerstone of reaction center function is the high quantum yield of transmembrane charge separation approaching unity in the systems studied so far. This feature necessarily implies that the deactivation rate of the excited primary donor 1P* not involving electron transfer is not accessible in native systems. Therefore, reaction centers of Rhodobacter sphaeroides have been modified via thermal exchange of the relevant primary electron acceptor BA. Substitution of BA with 3‐vinyl‐132‐OH‐bacteriochlorophyll increases the lifetime of 1P* from about 2 to 240 ps at 90 K. Transient absorption studies reveal that this increase is due to a decrease of the rate of charge separation. At 90 K this decrease causes a concomitant drop in the quantum yield of charge separation Y to 78% leading to a fast ground state P recovery of 22%. This directly translates into an internal conversion rate from 1P* to the ground state of kIC = (1.1 ns)−1 at 90 K. The corresponding data at 270 K (τF(1P*) = 66 ps; Y = 91%) result in kIC = (750 ps)−1 suggesting a weak thermal activation as usually observed for internal conversion processes. These internal conversion data constitute an important parameter for theoretical modelling of the primary charge separation along both, the active and inactive pigment branches.
Electrochemical and mass spectrometric investigations on the light‐induced oxygen and hydrogen gas exchange in cyanobacteria
Authors: Bader Klaus P. 
Published: July 2012

AbstractThe filamentous cyanobacterium Oscillatoria chalybea evolves molecular hydrogen upon illumination with one or more short (5 μs) saturating light flashes. This hydrogen evolution appears not to be linked to the nitrogen fixation capacity of this organism as the amplitudes are identical with nitrate‐grown and nitrogen free‐grown cultures. The hydrogen evolution amplitudes remain virtually constant over the whole series of flashes, i.e. no oscillatory pattern is observed. The dependence of the oxygen evolution signal under the third flash of a sequence on the light intensity shows significant differences, if the relative intensities of the first, second or third flash are modulated. In view of current discussions this might be interpreted in terms of a charge transfer between reaction centers and thus of a limited independence of the centers—as it has been suggested for e.g. Synechococcus. Addition of quaternary ammonium salts like alkylbenzyldimethyl ammoniumchloride (ABDAC; zephirol) strongly increases the oscillation of the oxygen evolution patterns but does not induce a (period‐2) oscillation in the case of hydrogen evolution. Our results suggest that also in the case of cyanobacteria (Oscillatoria chalybea) the reaction centers act independently so that the strong damping of the oscillation of the oxygen evolving amplitudes must be explained in terms of the ‘missed’ transitions between the sequential oxidation steps.
Nucleotide binding to chloroplast F1‐ATPase (CF1) cannot be explained by a two‐site model
Authors: Gunther Stephan , Urbanke Claus , Kindler Björn , Huchzermeyer Bernhard 
Published: July 2012

AbstractThe kinetics of nucleotide binding to the chloroplast coupling factor, CF1, have been analysed by stopped‐flow measurements using the fluorescent trinitrophenyl analog TNP‐ADP. Experimental determined time courses were compared with several different theoretical time courses. The following observations were obtained: (a) in stopped‐flow experiments the half time of the reaction was at highest with a ligand‐to‐enzyme ratio of 2:1. The half time of the binding reaction decreased, if the ratio was lower than 2:1. (b) This characteristic cannot be explained by a bimolecular reaction mechanism of several independent (classes of) binding sites, (c) Theoretical time courses according to a “two‐site” model with the inclusion of a conformational change of each site after binding of ligand showed the observed characteristic (see (a)), (d) However, this “two‐site” model including a conformational change of each site after binding of ligand failed to simulate the measured time courses of nucleotide binding.
ATP synthase: Driven and activated by protonmotive force
Authors: Häsle Katrin M. , Fritsch Olaf , Groth Georg , Junge Wolfgang 
Published: July 2012

AbstractATP synthase (F‐ATPase) of chloroplasts, CF0CF1, is both activated and driven by transmembtane protonmotive force. We dichotomized between activating and driving proton transfer by specific inhibitors, tentoxin and venturicidin. Thylakoid membranes were submitted to voltage steps (by flashing light) that were superimposed to a steady pH‐difference. Transient proton uptake, transfer and release by CF0CF1 were studied by spectroscopic probes. Both, activation and catalysis required all three partial reactions of the proton. A fast electrogenic reaction preceded the catalytic turnover of CF0CF1. This activating electrogenic event in response to the rapid onset of the electric potential is an integral portion of the reaction sequence producing ATP.
Transient magnetic resonance. Transient spin states in the primary processes of photosynthesis
Authors: Stehli D. , van der Est A. , Kamlowski A. 
Published: July 2012

AbstractThe role of the first stabilized charge separated state, P+•Q−•, generated in the course of the primary processes in photosynthesis is discussed. In particular, the adaptation of the properties of Q−• to the functional requirements in different types of photosynthetic reaction centers is considered. Time resolved EPR is shown to be very well‐suited for the characterization of P+•Q−• and that important structural and functional properties of the radical pair can be obtained from such data. The most recent spectroscopic information is presented and evaluated with the aim of correlating differences in the observed characteristics of the quinone acceptor with differences in the various types of photosynthetic reaction centers. It is suggested that the nature of the acceptors following the primary quinone (either an exchangeable quinone or a series of iron‐sulfur centers) has a marked influence on the nature of the quinone binding.
Photoinduced electron transfer in cyclophane‐bridged porphyrin‐quinone molecules. A subpicosecond transient absorption study
Authors: Pöllinger F. , Musewald C. , Heitele H. , Michel‐Beyerie M. E. , Anders C. , Futscher M. , Voit G. , Staab H. A. 
Published: July 2012

AbstractPhotoinduced charge separation and recombination in a series of cyclophane‐bridged porphyrin‐quinone systems (PQ) in toluene solution have been investigated by means of sub‐ps time‐resolved absorption spectroscopy. Temporal profiles and transient spectra of the porphyrin cation (P+) show the photoinduced formation and decay of the charge‐separated state P+Q−. The rate of charge recombination in these systems (P+Q−→PQ) is investigated as a function of the reaction free energy ΔG in the range (‐ ΔG) = 1.54–1.98 eV, which is in the so‐called inverted region of electron transfer. Combining values for charge separation and recombination the dependence of the electron transfer rate on ΔG fully covers the normal and inverted regions ((‐ ΔG) = (‐)0.02‐1.9 8 eV) with the rate varying over more than three orders of magnitude (≈︁2·109‐5·1012s−1).
Kinetics and molecular modelling of ligand binding to ribulose 1, 5‐bisphosphate carboxylase/oxygenase (RUBISCO)
Authors: Frank J. , Holzwarth J. F. , Koch P. , Vater J. 
Published: July 2012

AbstractThe dye 2‐toluidinonaphthalino‐6‐sulphonate TNS is sensitive to ligand binding events at the active site of RUBISCO purified from spinach or Rhodospirillum rubrum. Equilibrium binding curves of the substrate D‐ribulose 1, 5‐bisphosphate RUBP and the inhibitor 6‐D‐phosphogluconate 6‐PG to RUBISCO from spinach were apparently biphasic. Iodine laser temperature jump (ILTJ) experiments showed a fast and a slow bimolecular binding reaction of both ligands corresponding to a strong and a weak equilibrium binding process. In Stopped Flow (SF) experiments different reaction mechanisms were observed for the binding of the transition state analogue 2‐carboxy‐D‐arabinitol 1, 5‐bisphosphate CABP to RUBISCO in the presence and absence of magnesium ions. In the absence of magnesium ions CABP binds in a reversible bimolecular binding reaction to RUBISCO. In the presence of magnesium ions an irreversible two step reaction mechanism for the CABP binding was detected. Molecular dynamic (MD) simulations of ligand binding to RUBISCO were used for modelling of the strong influence of magnesium ions on the kinetics of ligand binding to RUBISCO.
Adsorption of Rigid‐Rod Trimers from Liquid Mixture with Monomers on Heterogeneous Surfaces
Authors: Borówko M. , Rżysko W. 
Published: July 2012

AbstractThe results of Monte Carlo simulation for adsorption of linear trimers from their mixtures with monomers on homogeneous and heterogeneous surfaces are analysed. The lattice model of the liquid mixture is used. The different surface topographies (strip‐like and chess‐board) are considered. An influence of surface topography, size of homogeneous patches and molecular interactions on adsorption and orientational ordering in the mixed fluid near the boundary plane is discussed.
Shear Viscosity of Hexane+Tetradecafluorohexane near the Upper Critical Endpoint
Authors: Mclure Ian A. , Clements Patricia J. 
Published: July 2012

AbstractThe shear viscosity of hexane+tetradecafluorohexane has been determined from five Kelvins below the upper critical solution temperature Tc – in the region of limited miscibility – to 19 Kelvins above Tc – in the region of total miscibility. The results show a critical anomaly described by a critical expression η = A exp (B/T)ϵ−y with a multiplicative amplitude or background term η0 = A exp (B/T) and a weakly anomalous term ϵ−y, where ϵ is the reduced temperature response function |T − T|/Tc calculated with Tc = 22.385°C, and the critical exponent y takes the universal value 0.040 predicted by the mode‐mode and renormalisation group theories. The measured viscosities show a definite but small dependence on shear gradient. The shear gradient dependence is entirely described by the Oxtoby treatment which yields an estimate of the critical amplitude of the correlation length ξ0 = (5.5 ± 1.5) Å in fair agreement with the light‐scattering value of Skripov et al. of (3 ± 1) Å. The ratio of the limiting amplitudes along the isochoric path and the coexistence path is 0.946 ±0.005, close to that predicted by Calmettes, 0.950.
An FTIR Study of the Products of the Reaction between CH2\documentclass{article}\pagestyle{empty}\begin{document}$$ ({{\rm \bar X}}^3 {{\rm B}}_1) $$\end{document} and NO
Authors: Grußdorf J. , Temps F. , Gg. Wagner H. 
Published: July 2012

AbstractThe product channels were investigated of the reaction between CH2

and NO in the gas phase at room temperature and near ambient pressure. Mixtures of CH2CO/NO/Ar were photolyzed at λ = 312 nm in a static reactor. The reaction products were analyzed by Fourier transform infrared (FTIR) spectroscopy. The main product (≈︁ 84%) was found to be fulminic acid, HCNO. A second channel (≈︁ 15%) was found to lead to HCN. Other products which were detected include CO, N2O, H2O, HONO, H2CO, and CO2. These are formed (except for the CO from the CH2CO photodissociation) in consecutive reactions of the accompanying H atoms and OH radicals from the HCNO and HCN reaction channels.
Multidimensional solid state NMR: A unique tool for the characterisation of complex materials
Authors: Spiess Hans Wolfgang 
Published: July 2012

AbstractA survey is given on new developments in multidimensional solid state NMR which evolves as an indispensable tool of materials characterisation. After a short introduction NMR is compared with other techniques, in particular X‐ray and neutron scattering. The unique information available by solid state NMR is demonstrated by specific examples of structural studies of chain conformation, advanced aspects of chain dynamics, phase separation and interfacial effects as well as non‐linear plastic deformation in polymers. Emphasis is placed on the new development of high resolution multiple quantum NMR spectroscopy of abundant nuclei in solids with first experimental examples on the location of hydrogen positions in organic solids, structure of inorganic glasses and chain order in polymer melts and elastomers.
The electrical conductivity of CoO: Experimental results and a new conductivity model
Authors: Lange F. , Martin M. 
Published: July 2012

AbstractThe electrical conductivity of the transition metal oxide Co1‐σO has been measured as a function of the oxygen activity and the temperature in the whole stability field of CoO using a very pure single crystal. The results are modelled in terms of a new conductivity model in which free electron holes as well as electron holes which are trapped by cation vacancies contribute to the conductivity. At low oxygen activities also electrons are considered. Within this model the following parameters are obtained: the two mass action constants,K1andK11, for the incorporation of oxygen and the formation of singly ionized vacancies, the mobilities of free and trapped electron holes,b0andb1, and the product of the electron mobility and the electronic mass action constant,Kebe. A microscopic interpretation of the model is made possible by translating the so‐called five‐frequency model for impurity diffusion to the conductivity problem. Then it is also possible to estimate the lifetime of the associate consisting of a doubly ionized vacancy and an electron hole, which is about twenty times larger than the residence time of an electron hole on a cation site.
Mechanism and rate constants for the reactions of Cl atoms with HOCl, CH3OCl and tert‐C4H9OCl
Authors: Kukui A. , Roggenbuck J. , Schindler R. N. 
Published: July 2012

AbstractReactions of Cl atoms with HOCl (1), CH3OCl (2) and C4H9OCl (3) have been investigated at 300 K using discharge flow LIF/MS technique. The mechanism and reaction rate constants were determined by monitoring absolute rates of hypochlorite and CI atom consumption together with the build‐up of reaction products. Based on the yields of CI2 and OH in (1a), Cl2 and CH3O in (2a) and Cl2 in (3a), as measured by MS/LIF, the reactions of Cl atom with the hypochlorites investigated in this work were found to proceed predominantly via the Cl atom abstraction channel with k1a/k1 = (0.96±0.05), k2a/k2 = (0.85 ± 0.06), k3a/k3 = (1.01 ±0.05).

The reaction rate constants were determined to be k1 = (2.28±0.09)·10−12, k2 = (6.0±0.2)·10−11, and k3 = (4.26±0.2)·10−11, all in units cm3·molecule−1·s−1. A reevaluation of the heat of formation of HOCl yielded ΔH0f (298 K) = −75.1 kJ·mol−1.
State‐resolved intramolecular dynamics in highly excited HOCl
Authors: Abel B. , Charvàt A. , Deppe S. F. , Hamann H. H. 
Published: July 2012

AbstractThe features and mechanisms of intramolecular energy redistribution (IVR) and state mixing of HOCl at chemically significant energies have been investigated using intra‐cavity laser absorption spectroscopy (ICLAS). These studies revealed that for the observed vibrational states up to about 75% of the dissociation energy E0 both strong and weak interactions (Fermi‐type, Coriolis) exist but producing only localized perturbations in the spectra. The 5v1 band, however, at about 85% of the dissociation threshold E0 (O‐Cl bond) has been found to be globally and strongly mixed with the 4v1 + 2v2 + v3 zero‐order vibrational state, and both states appeared in turn coupled to other background states by additional (weaker) interactions. The transfer from frequency to time domain led to the conclusion that this spectral signature is characteristic for efficient but nevertheless restricted intramolecular vibrational energy redistribution in the overtone spectrum of HOCl. The intramolecular dynamics of HOCl is compared to the dynamics of HCN and discussed in terms of low‐order interactions between zero‐order states (ZOS) grouped in different tiers.
Intramolecular dynamics and density of states for HN
Authors: Schmatz Stefan , Mladenović Mirjana 
Published: July 2012

AbstractThe rovibrational (J = 0–4) level structure of protonated nitrogen (HN+2) is investigated in detail for the CCSD(T) potential energy surface of Schmatz and Botschwina. The discrete variable representation (DVR) for the angular coordinate in conjunction with a distributed Gaussian basis set (DGB) for the radial degrees of freedom was used to perform the nuclear dynamics calculations. Both low lying and highly excited states are examined. The total number of bound states with J = 0 up to the first dissociation threshold at 44409 cm−1 is determined to be about 5000. We propose an empirical model for the level structure of HN+2 which incorporates Roe's suggestion for stretch‐bend coupling. The empirical numbers and densities of states agree well with the corresponding numerically exact quantum mechanical values for the given surface.
Stationary points of the potential surface for the reaction F− + CH3Cl → FCH3 + Cl−: Results of large‐scale coupled cluster calculations
Authors: Botschwina P. , Horn M. , Seeger S. , Oswald R. 
Published: July 2012

AbstractStationary points of the potential surface for the SN2 reaction F− + CH3Cl → FCH3 + Cl− have been investigated by large‐scale CCSD(T) calculations. The ion‐dipole complexes in the reactant and product channels have well depths of 15.8 and 9.6 kcal mol−1, respectively, and are separated by a small barrier of 3.3 ± 0.3 kcal mol−1. The molar reaction enthalpy at 298 K is obtained to be −31.5 kcal mol−1.