bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collisional Deactivation of O2(1Δg) by Solvent Molecules. Comparative Experiments with 16O2 and 18O2
Authors: Schmidt Reinhard , Afshari Ebrahim 
Published: March 2014

AbstractPhosphorescence spectra of natural singlet oxygen 16O2(1Δg) and its heavier isotope 18O2(1Δg) have been recorded in several O2(1Δg) weakly deactivating solvents. Lifetimes of singlet oxygen were determined for both isotopes in 21 solvents. From these data rate constants kXY of deactivation of singlet oxygen by terminal oscillators X—Y of the solvent molecules are calculated revealing a graduated isotope effect of 1.0 ≤ 16kXY/18kXY ≤ 1.9. The unexpectedly low isotope effect points to the important role of overtone excitations of X—Y during O2(1Δg) deactivation. A modified collisional deactivation model including overtone excitation of the energy accepting oscillator reproduces the experimental findings: the tremendeous graduation of kXY of almost 5 orders of magnitude, the heavy atom effect, the O2 isotope effect and the very weak temperature effect on kXY.
Absorption and fluorescence of pyrylium salts
Authors: Haucke Günter , Czerney Peter , Cebulla Frank 
Published: March 2014

AbstractAbsorption and fluorescence of donor‐substituted pyrylium compounds are studied in order to get information of the x‐ and y‐chromophore system and of the role of structural and solvent effects. The experimental results are in accordance with the assumption that the absorption and fluorescence behaviour can be rationalized in terms of intramolecular radiative and non‐radiative charge transfer (charge shift) processes.
Water oxidation at polycrystalline OSX2 electrodes
Authors: Schwarzlose T. , Fiechter S. , Jaegermann W. 
Published: March 2014

AbstractPolycristalline OsX2 (X = S, Se, Te) powders have been synthesized and electrochemically investigated as pressed discs with respect to water oxidation. Complementary the electrodes were analyzed by ex‐situ X‐ray photoelectron spectroscopy (XPS). OsS2 was identified as oxygen evolution catalyst whereas OsTe2 was completely decomposed. The difference in catalytic behavior is related to differences in the XP valence band spectra and discussed in terms of electronic states involved in charge transfer.
The dynamics of a quantal reservoir coupled to classical modes: A mixed‐mode approach to dissociating molecules
Authors: Yurtsever Ersin , Uzer Turgay 
Published: March 2014

AbstractWe have analyzed a three‐mode model system to study quantum effects in a dissociative process. An algorithm which combines Hamilton's and time‐dependent Schroedinger equations in an SCF manner is applied. Large differences in the qualitative behaviour of trajectories are observed which suggests a chaotic nature. The monitoring of the energy transfer or trajectories themselves by interactive computer graphics can be used to forecast possibilities of dissociation. It is also noted that the initial conditions strongly affect the dissociation process. We compare fully classical calculations with these mixed mode results, and analyze the reasons behind disparities.
Electrical conductivity and thermodynamic properties of liquid Na3+δSb alloys
Authors: Heyer H. , Egan J. J. , Freyland W. 
Published: March 2014

AbstractThe melting point of the intermetallic compound Na3Sb was measured and found to be 1015°C. Partial molar Gibbs energies of Na in liquid NaSb alloys were determined at 1030°C for alloy compositions between xNa = 0.71 and xNa = 0.78 using an emf technique employing CaF2 as a solid electrolyte. A special cell design was used and is described in detail. The electrical conductivity of NaSb alloys was also measured at 1030°C over a composition range from xNa = 0.71 to xNa = 0.77. A sealed cell was used for these measurements where the composition of the alloy is accurately controlled by coulometric titration. Results showed that the alloys are liquid semiconductors. The thermodynamic and electrical properties are quantitatively explained by a model previously proposed by Carl Wagner, and pertinent equations are given. The correspondence with the predictions of electrical transport in disordered liquid semiconductors is discussed.
pH dependent raman spectra of nicotinic acid – spectra of aqueous solutions and surface enhanced raman spectra on silver electrodes
Authors: Barthelmes J. , Pofahl G. , Plieth W. 
Published: March 2014

AbstractRaman spectra of nicotinic acid have been measured in aqueous solutions in the pH‐range between 1.0 and 12.5. Raman band assignments between 500 cm−1 and 1750 cm−1 are carried out by referring to the compound's solid state Raman spectrum and to spectra of related molecules. Changes of the Raman spectra with solution pH are correlated to the structure change of the nicotinic acid molecule. The surface enhanced Raman spectra (SERS) of nicotinic acid (NA) on a polycrystalline silver electrode are reported in the range 500–1750 cm−1 as a function of pH and applied potential. The results are presented in order to determine the type of adsorbed species (anion, cation, zwitterion). Therefore the SER spectra are compared with the pH dependent solution spectra of NA. These investigations show – in the presence of a non specifically adsorbing electrolyte (0.1 mol l−1 Na2SO4) – the nicotinate anion as the only surface active species detectable within the pH range of 1.4 to 12.5. A detailed analysis of the SER spectra reveals, that the anion exhibits two different molecular orientations towards the metal electrode, a presumably planar alignment dominating at low and medium pH values and a perpendicular one at low proton concentrations. In the intermediate range both orientations exist side by side. The ratio of planar to perpendicular oriented molecules depends on applied potential and increases with growing cathodic polarisation.
Ionic Fragmentation and Ion‐Pair Formation in Chlorine Dioxide
Authors: Rockland U. , Baumgärtel H. , Rühl E. , Lösking O. , Müller H.S.P. , Willner H. 
Published: March 2014

AbstractIonic fragmentation and ion‐pair formation in chlorine dioxide (OClO) are reported. Photoionization efficiency curves of OClO+, ClO+, O2+, Cl+, O+, as well as of O− and Cl− are measured in the energy regime between 10 eV and 21 eV using monochromatized synchrotron radiation. Appearance potentials are obtained from photoionization efficiency curves which are used to derive photofragmentation mechanisms. These include the formation of electronically excited fragments as well as multiparticle formation. The occurrence of O+2 is interpreted as evidence for rearrangement processes of the chlorine dioxide cation prior to dissociation. This finding is compared to photofragmentation of electronically excited neutral OClO. Ion‐pair formation of photoexcited OClO leads to formation of O− and Cl−. The importance of highly excited Rydberg states and direct processes leading to ion‐pair formation is discussed.
Solute and Solvent Dependencies of Intermolecular Interactions in Different Density Regions in Supercritical Fluids. A Generalization of the Three‐Density‐Region Solvation Mechanism
Authors: Sun Ya‐Ping , Bunker Christopher E. 
Published: March 2014

AbstractPyrene, 6‐propionyl‐2‐(N,N‐dimethylamino)naphthalene (PRODAN) and ethyl p‐(N,N‐diethylamino)benzoate (DEAEB) are used as fluorescent probes to study solute‐solvent interactions in supercritical fluoroform, carbon dioxide, and ethane as functions of density and temperature. The Py values, solvatochromic shifts of fluorescence spectra, and dual fluorescence from the locally excited singlet state and twisted intramolecular charge transfer state are strongly fluid density dependent. While the intensities of solvent effects are different for different probes and different fluids, the density dependencies of spectroscopic responses of the probes follow a characteristic pattern. The results are in strong support of the three‐density‐region solvation mechanism.
A Study about the Reactions of NH2 (X̃2B1) Radicals with Unsaturated Hydrocarbons in the Gas Phase
Authors: Hennig G. , Wagner H.G.G. 
Published: March 2014

AbstractThe reactions of NH2(X̃2B1) with the hydrocarbons ethene (1), propene (2) and acetylene (3) were investigated behind incident shock waves at temperatures between 1500 K and 2000 K. The decay of NH2 was measured by laser absorption. NH2 was formed by the thermal decomposition of hydrazine. The following rate constants were obtained for the temperature range mentioned:

These measurements extend the results obtained at low temperatures by Bosco et al. (240 K–460 K) and by Khe and Lesclaux (300 K–500 K) into the range of interest for combustion processes.The apparent energies of activation correlate well with the ionisation potentials of the unsaturated hydrocarbons and can therefore be used for the extrapolation to the addition reactions of the higher alkenes. For the reaction of propene with NH2 a contribution of an abstraction reaction channel besides electrophilic addition cannot be excluded at high temperatures.
Accurate Calculation of NMR Chemical Shifts
Authors: Gauss Jürgen 
Published: March 2014

AbstractAn overview over currently available methods for the calculation of NMR chemical shifts is given. After a brief discussion of the basis aspects, i.e. definition of the shielding tensor and gauge‐origin problem in the calculation of magnetic properties, recently developed methods for calculating NMR chemical shifts based on electron‐correlated quantum chemical approaches will be discussed. The importance of electron correlation effects for the accurate determination of absolute shielding constants and relative shifts is demonstrated and the accuracy of various approaches assessed by a careful comparison with experiment, before a few representative applications will be presented. In case of the carboranes C2B3H5 and C2B3H7, electron‐correlated calculations were essential to resolve discrepancies between SCF calculations and experiment, while for the vinyl‐substituted vinyl cations CH2 = C+ –CH = CHCH3 correlated NMR chemical shift calculations – but not the SCF calculations – allow the unequivocal assignment of the measured 13C signals to the Z and E isomers formed in superacid solutions. Finally, an outlook with respect to pending problems in the area of NMR chemical shift calculations is given.
Structure Investigations of Liquid Chloroform by Statistical‐Mechanical Calculations and Reverse Monte Carlo Simulation
Authors: Bertagnolli H. , Goller K. , Zweier H. 
Published: March 2014

AbstractThe structure of liquid Chloroform at 298 K is determined with Reverse Monte Carlo simulations. Three independent neutron and one X‐ray scattering experiments are fitted simultaneously to obtain higher evidence in the structural results. The structure is described in form of atom pair correlation and angular distribution functions. Furthermore, the atom pair correlation functions are used to calculate a probability that gives the spatial correlation of atoms of neighbouring molecules around a center molecule. The results are compared with Molecular Dynamics simulations of chloroform from literature and a very good agreement between both methods is found. The aim to reproduce experimental results with statistical mechanical calculations based on site‐site Ornstein Zernike (SSOZ or R1SM) theory in combination with the HNC closure fails. The comparison between statistical mechanical calculations and simulations reveals the unability of the SSOZ theory to describe the short range order of liquid chloroform. SSOZ theory predicts correlations of the hydrogen atom at short distances which clearly are not possible in the real liquid.
Thermodynamic Testing of Equations of State of Dense Simple Liquids
Authors: Randzio Stanisław L. , Deiters Ulrich K. 
Published: March 2014

AbstractThe isobaric thermal expansivities (αp) of n‐hexane and of methane measured over large pressure and temperature ranges have been proposed as a thermodynamic property test for theoretical and semi‐empirical equations of state for simple liquids at high densities. The correlation equations for αp(p, T) and the coordinates of the crossing point of isotherms of αp are given for both substances. A number of selected equations of state with various modifications of the attractive and repulsive contribution to the pressure have been tested with respect to their ability to reproduce the proposed test property. The analysis has revealed that at high densities the equations of state with modified repulsive term reproduce the test property better than the equations with modified attractive term. A reproduction of the most characteristic feature of the test property, the crossing of isotherms of αp can be only obtained with equations in which the repulsion term is made softer than the simple rigid‐sphere term R T/(Vm – b). The best reproduction of the test property was obtained with the soft‐sphere equation constructed on 8–4 Lennard‐Jones intermolecular pair potential. The anisotropy in molecular shape of n‐hexane and methane has only a little influence on the results of testing.
An Ab Initio Study of Alkali Halide Clusters with an Alkali Excess: M13X12, [M13X12]+, [M14X12]+, [M14X12]2+, and [M23X22]+
Authors: Ochsenfeld Christian , Ahlrichs Reinhart 
Published: March 2014

AbstractThe alkali‐excess system [M13X12]+ and the corresponding excess‐electron cluster M13X12 are studied with ab initio methods. Selected reaction energies of cationic alkali‐excess clusters, especially of [M23X22]+, are reported using results for the stoichiometric cluster M10X10 and a comparison between sodium chloride and lithium fluoride is presented. Finally, a fully internal anion defect and an edge defect location are investigated for the clusters [Na14Cl12]2+ and [Na14Cl12]+, to resolve previous discrepancies in the literature.
The High Pressure Range of the Addition of OH to C2H2 and C2H4
Authors: Fulle D. , Hamann H.F. , Hippler H. , Jänsch C.P. 
Published: March 2014

AbstractThe kinetics of the bimolecular reactions OH+C2H2+M ⟺ C2H2OH+M (1) and OH+C2H4+M ⟺ C2H4OH+M (2) have been investigated over an extended pressure (1–130 bar) and temperature (300–800 K) range. The OH radicals have been generated by laser flash photolysis of suited precursors and their decays have been measured by saturated laser‐induced fluorescence (SLIF) under pseudo‐first‐order conditions. The pressure dependences have been analyzed by constructing falloff curves at fixed temperatures leading to reliable extrapolations towards the high pressure limiting rate constants k∞. In the given temperature range these rate constants are represented as k1,∞ = 3.8×10−11 exp (–910 K/T) cm3 molecule−1 s−1 and as k2,∞ = 1.0×10−11 cm3 molecule−1 s−1. At temperatures above 700 K biexponential decay curves have been obtained. The chemical equilibria of reactions (1) and (2) could be determined. By a third law analysis the equilibrium constants have been evaluated with reaction enthalpies for the addition complex C2H2OH of δIHo1 (O K) = ‐(146 ± 10) kJ/mol and for C2H4OH of δIHo2 (O K) = ‐(123 ± 6) kJ/mol, respectively. The two equilibrium constants are given by K1,eq = (5.4±2.2)×10−2 (T/K)−1.7±0.2 exp ((17560±1200) K/T) bar−1 and K2,eq = 2.1 × 10−2 (T/K)−95±0.1 × exp ((14780±720) K/T) bar−1, respectively.
Kinetic Study of the Fe(bpy)2+3 +S2O2−8 Reaction in Solvent Mixtures
Authors: Matamoros‐Fontenla M.S. , Pérez P. , López P. , Prado‐Gotor R. , de la Vega R. , Sánchez F. 
Published: March 2014

AbstractThe kinetics of the oxidation of Fe(bpy)2+3 by S2O2−8 have been studied in water and different water‐cosolvent mixtures. The cosolvents used were methanol t‐butyl alcohol, ethane 1,2‐diol and glycerol. The results are explained assuming an additional component of the reorganization free energy of the solvent in the mixtures, caused by dynamics of the changes in the composition of the (at least) innermost solvation shells of the reactants produced by the electron transfer. A quantitative estimation of this component is attempted.
Vapour Pressures at Eight Temperatures of Mixtures of Di‐n‐Propylether + Ethanol, or +1‐Butanol – Thermodynamic Description of Mixtures of Di‐n‐Propylether + Alkanol According to the ERAS Model
Authors: Garriga R. , Pérez P. , Gracia M. 
Published: March 2014

AbstractVapour pressures of di‐n‐propylether with ethanol and with 1‐butanol were measured at eight temperatures between 278.15 and 323.15 K by a static method. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by Barker's method. Mixtures containing ethanol show azeotropy with a minimum boiling temperature. GE, HE, and VE, at 298.15 K, of mixtures of di‐n‐propylether + methanol, + ethanol, + 1‐propanol, + 2‐propanol, and + 1‐butanol are compared with predictions of the ERAS model observing that the model reproduces acceptably the experimental behaviour.
Correlation Times and Quadrupole Coupling Constants in Liquid N‐Methylformamide and N‐Methylacetamide
Authors: Seipelt C.G. , Zeidler M.D. 
Published: March 2014

AbstractLongitudinal 1H, 13C and 15N nmr relaxation rates were measured in the liquid phase for N‐methylformamide (NMF) over the temperature range 228–328 K and for N‐methylacetamide (NMA) over the range 300–378 K. Rotational correlation times were determined for the formyl C‐H and the N‐H bonds. The motion of both molecules is anisotopic, particularly that of N‐methylacetamide. The activation energies are 5.6 kJ/mol for C‐H and 19.7 kJ/mol for N‐H in NMF and 20.4–22.5 kJ/mol for N‐H in NMA. Quadrupole coupling constants were determined by relaxation measurements for the nuclei 14N and 2H. The quadrupole coupling constant for the amide deuteron in NMF is temperature dependent and varies from 193 to 206 kHz. For NMA this quadrupole coupling constant falls into the range 178 to 238 kHz. The quadrupole coupling constant for the formyl 2H in NMF (151–169 kHz) is temperature independet while for the 14N (NMF: 1.85–2.40 MHz; NMA: 1.65–2.45 MHz) it is temperature dependent.
Theoretical Studies of the Relative Cross Sections and Transition State Spectroscopy of Cl+Na2(3 ≤ v″ ≤ 19) → [NaNaCl]‡ *→ NaCl+Na*
Authors: Wang Ming‐Liang , Han Ke‐Li , He Guo‐Zhong , Lou Nan‐Quan 
Published: March 2014

AbstractQuasiclassical trajectory method (QCT) has been used to investigate the effect of vibrational excitation on the relative cross section for the reaction Cl+Na2(v″). The calculated results are in good agreement with the experimental data, which show the increase of the cross section with increasing vibrational excitation. Furthermore, the spectroscopy of transition state in this reaction has been predicted out using QCT method based on LEPS potential energy surface.
Structure and Electrochemical Properties of the Cathode/Electrolyte Interface in the Planar SOFC
Authors: Kuznecov M. , Otschik P. , Eichler K. , Schaffrath W. 
Published: March 2014

AbstractThe electrochemical behaviour of the cathode/electrolyte interface which is formed between screen printed Lao0.8Sr0.2MNO3‐cathode and ZrO2+8%Y2O3 electrolyte was investigated. The impedance of the cathode/electrolyte interface was calculated as a function of (I) the oxygen exchange velocity between cathode material and atmosphere, (II) interface microstructure and (III) the oxygen vacancies diffusion coefficient. A very good agreement between calculated and measured impedance spectra was achieved. The influence of the porosity of the cathode on the impedance is discussed.
Spectroscopic Anomalies in the 4‐Aryl‐2,2‐Difluoro‐6‐Methyl‐1,3,2‐Dioxaborine Series
Authors: Görlitz Gunter , Hartmann Horst , Kossanyi Jean , Valat Pierre , Wintgens Véronique 
Published: March 2014

AbstractThe spectroscopic properties of 4‐methyl‐6‐phenyl‐2,2‐difluoro‐1,3,2‐dioxaborine 1 and of several of its derivatives 2–5 substituted in para position on the phenyl ring or bearing an alkylene chain between their carbo‐cyclic and heterocyclic rings have been studied in solution of different polarities and in the solid state. In solution, an important intramolecular charge transfer (ICT) process is characterized in the excited state. This charge transfer occurs in a planar configuration of the molecules, as demonstrated by comparison of the data obtained for 1 and 3 with those of the rigid molecules 6 and 7, respectively. The singlet excited state of molecules 1–5 is typical of species having a free rotating substituent and for which the small fluorescence quantum yield and lifetime increase when a planar configuration can be stabilized by electron‐donor substitution. The low fluorescence quantum yield found for molecules 1 and 2, with respect to molecules 3–5, has been attributed to an important deactivation channel resulting from the rapid free rotation of the phenyl moiety of the molecule and not to an efficient intersystem crossing to the triplet excited state, as this process has a quantum yield lower than 0.01. Theoretical calculations lead to a low oscillator strength for molecules 1 and 2 which are more stable with a planar configuration, while a significant higher oscillator strength is calculated for compounds 3 and 4 substituted with electron‐donating groups. The singlet excited state of compounds 4 and 5 might be stabilized by the formation of a twisted species. In the solid state, the molecules are shown by X‐ray analysis to be planar and packed in such a way that two molecules lie head‐to‐tail in two parallel planes separated from each other by ca. 360 pm. As a result, this proximity enables the development of a ground state charge transfer. This charge transfer species has been confirmed by increasing the concentration of compound 2 in dichloromethane solution, giving rise to a new fluorescence band in the long wavelength region.
Neck Circumference Is Not Associated With Subclinical Atherosclerosis in Retired National Football League Players
Authors: Pokharel Yashashwi , Macedo Francisco Y. , Nambi Vijay , Martin Seth S. , Nasir Khurram , Wong Nathan D. , Boone Jeffrey , Roberts Arthur J. , Ballantyne Christie M. , Virani Salim S. 
Published: March 2014

ABSTRACTBackgroundNeck circumference (NC) is associated with metabolic syndrome (MetS) in the general population. It is not known if NC is associated with MetS and subclinical atherosclerosis in retired National Football League (NFL) players.HypothesisWe hypothesized that NC is associated with MetS and subclinical atherosclerosis (assessed as coronary artery calcium [CAC] and carotid artery plaque [CAP]) in retired NFL players.MethodsNC was measured midway between the midcervical spine and midanterior neck in 845 retired NFL players. CAC presence was defined as total CAC score >0. CAP was defined as carotid plaque of at least 50% greater than that of the surrounding vessel wall, with a minimal thickness of at least 1.2 mm on carotid ultrasound. Logistic regression analysis was used for the association of NC with CAC or CAP.ResultsOf the participants, 21% had MetS. CAC and CAP were present in 62% and 56%, respectively. Those with MetS had a higher median NC than those without MetS (17 vs 16 inches, P < 0.0001). NC was not associated with the presence of CAC or CAP in an unadjusted model and after adjusting for age, race, and cardiometabolic risk factors (odds ratio [OR]: 1.11, 95% confidence interval [CI]: 0.94–1.31 for CAC; OR: 0.96, 95% CI: 0.82–1.12 for CAP per 1‐standard deviation increase in NC [3.8 inches]). The results were similar when the predictor variable was NC indexed to body mass index.ConclusionsIn retired NFL players with a high prevalence of CAC and CAP, NC was not associated with coronary or carotid subclinical atherosclerosis. NC may not be the most appropriate risk marker for atherosclerosis.