bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐Pressure Picosecond Time‐Resolved Fluorescence Studies on the Excited Intramolecular Charge‐Transfer Kinetics of 4‐(9‐Anthrylmethyl)‐N,N‐Dimethylaniline in Alcohol
Authors: Hara Kimihiko , Bulgarevich Dmitry S. , Kajimoto Okitsugu 
Published: March 2014

AbstractPicosecond time‐resolved fluorescence spectroscopy has been used to examine the dynamic solvent effect on the excited intramolecular charge‐transfer (ICT)‐state formation in 4‐(9‐anthrylmethyl)‐N,N‐dimethylaniline (AMDMA) in linear alcohol solvents as a function of pressure. The non‐exponential population decay of the local excited (LE)‐state emission is analyzed by fitting to a double exponential function. As solvent viscosity increases, the rate of the ICT‐state formation of AMDMA becomes noticeably faster than the solvent relaxation time, which is gauged by the longitudinal relaxation time of the solvent (τL). The pressure effect on the ICT reaction of AMDMA in the excited state can be accounted for in terms of the pressure‐tuning effect of the solvent viscosity.In addition, the time‐dependent Stokes shift (TDSS) of the ICT emission is measured at high pressures.
Phase Diagrams with Asymptotic Transition Lines
Authors: Dunkel H. , Bärner K. , Zavadskii E.A. 
Published: March 2014

AbstractWhile linear and curved phase transition lines in P(T) or H(T) diagrams can be described by adding linear and quadratic terms in a joint expansion of the Landau coefficients a, b in terms of P–Pt and T–Tt where (Pt, Tt) is a critical point, a new class of phase diagram is obtained by allowing for bilinear, ϵ(P–Pt)(T–Tt), and higher product terms. In this contribution we relate these new expansion terms to some hitherto unexplained experimental P–T and H–T phase diagrams.
The Molecular Structure of Sodium Octanoate Micelles Studied by Molecular Dynamics Computer Experiments
Authors: Kuhn Hubert , Rehage Heinz 
Published: March 2014

AbstractIn this article we discuss the results of molecular dynamics simulations which were performed to get more information on the physical properties of sodium octanoate micelles. The calculations were based on the AMBER forcefield and we succeeded in simulating the dynamic features of the micelle for a period of 300 ps. The aggregate was surrounded by 870 water molecules and the simulation was performed in the isothermic‐isobaric constant NPT ensemble at a temperature of 300 K and a pressure of 105 Pa. From the results, thus obtained, it was possible to obtain some typical properties of the micelle. It turns out that the average radius of the micelle coincides pretty well with experimental results of small angle neutron scattering experiments. It was also possible to determine the actual conformations of monomers outside and inside the micelle. These data are in general agreement with nuclear magnetic resonance studies and with raman scattering experiments. On close inspection it was found that the micelle attains a slightly ellipsoidal shape.
Solvation and Counterion‐Distribution of Sodium Octanoate Micelles Studied by Molecular Dynamics Simulations
Authors: Kuhn H. , Rehage H. 
Published: March 2014

AbstractIn this publication we have studied molecular details of the solvent layer and the counterion distribution around sodium octanoate micelles. The results were obtained from computer experiments using molecular dynamics simulations. From the model it was possible to calculate the radial distribution functions, which give informations on the average distance between water molecules and the polar surfactant head groups. We observed different types of solvent layers. From these experiments it was also possible to calculate the number of hydrogen bonds between surrounding water molecules and the polar surfactant head groups. These results coincide well with experimental data and with other types of computer experiments. In analogy to water molecules it was also possible to get informations on the distribution of sodium counterions around the charged micelle. These results are in general agreement with experimental and theoretical data and they can be used to calculate Coulomb interactions and the net surface charge of the micellar aggregates.
Electron‐Energy‐Loss Spectroscopy of Spin‐Forbidden Transitions with Vibronic Resolution: The Lowest Triplet State of Fluorobenzenes
Authors: Swiderek P. , Schürfeld S. , Winterling H. 
Published: March 2014

AbstractLow‐energy electron‐energy‐loss spectra in the range of the lowest triplet state are presented for solid benzene, fluorobenzene, and p‐difluorobenzene deposited at a temperature of 30 K. Vibronic structure within the triplet bands of fluorobenzene and p‐difluorobenzene is observed for the first time. The spectrum of fluorobenzene closely resembles that of benzene, whereas p‐difluorobenzene shows characteristic differences. The spectra of all three molecules are dominated by pure progressions of the totally symmetric ring‐breathing vibrational modev1. In addition, less intense transitions to vibronic levels relating to the e2gmodes in benzene are observed and their assignment is given. The occurrence of e2gmodes in all three spectra underlines that the vibronic coupling pathways between the lowest and the second triplet state are similar in benzene and its derivatives. In p‐difluorobenzene a splitting of the extremely low frequency mode that relates to thev8(e2g) vibration in benzene is observed. This is in agreement with theoretical predictions of an asymmetric shape of the lowest triplet potential energy surface along a symmetry coordinate relating tov8in substituted benzenes.
Electronic Structure of Polymerized C60 Phases
Authors: Schulte Joachim , Böhm Michael C. , Schedel‐Niedrig Thomas , Schlögl Robert 
Published: March 2014

AbstractThe band structure and solid state electronic properties of three polymerized C60 phases are investigated by a crystal orbital (CO) approach based on an intermediate neglect of differential overlap (INDO) Hamiltonian. We have considered a one‐dimensional (1D) body‐centered orthorhombic phase as well as two 2D phases crystallizing in a body‐centered tetragonal and a rhombohedral lattice. The CO results derived for the polymerized C60 systems are correlated with electronic structure data of the isotropic body‐centered cubic van der Waals crystal. We analyze the energy bands ϵi(k), the associated electronic density of states (DOS) profiles as well as the atomic net charges and so‐called Wiberg bond indices which measure the strength of covalent bonds. The formation of intermolecular CC σ bonds leads to an enhanced alternation between formal double and single bonds on the soccerball. The dimensionality of the four C60 fullendes considered is discussed on the basis of the different quantities evaluated by the CO formalism. The theoretical results are supplemented by C 1s near‐edge X‐ray absorption fine structure (NEXAFS) spectra of polymerized and non‐polymerized C60 films before and after oxygen contamination.
Special Features of the Preliminary γ‐Irradiation Influence on Photoluminescence of Multi‐Component Silicate Glasses
Authors: Kasymdzhanov M.A. , Kasimova S.S. , Kurbanov S.S. , Khabibullaev P.K. 
Published: March 2014

AbstractIn multi‐component silicate glasses, under the UV‐excitation, time‐resolved luminescence spectra were observed. These spectra occupied the region of 350–700 nm. The dynamics of changes in radiation induced absorption and spectral‐kinetic characteristics of luminescence of γ‐irradiation glasses at the expiry of prolonged time were studied. It is assumed that the luminescence in these glasses is caused by quasi‐molecular compelxe centers which include the elements of base substance and impurity atom. These centers can appear in the glass both in the process of its melting and under the action of ionizing radiation. It is shown that, the centers of different origin are characterized by different spectral‐kinetic properties of their photoluminescence.
Ab Initio Modelling of Defects in Non‐Metallic Systems
Authors: Jones R. 
Published: March 2014

AbstractThe simplicity of density functional methods and the increasing availability of computer‐processing power have enabled ab initio modelling techniques to be applied to very large systems. Our own code, AIMPRO, enables the relaxation of clusters as large as 800 atoms while still maintaining full self‐consistency and a realistic basis. Moreover, the use of pseudopotentials means that applications to Ge clusters are no more time consuming than those built of C. An important thrust of our work has been the computation of accurate vibrational modes of defects and this has caught the attention of several prominent experimental groups with the consequence that joint studies of rather complicated defects have been successfully made. We outline the procedures used and discuss applications that have been made to a wide variety of non‐metallic systems such as vacancy defects in diamond, interstitial centres in silicon and carbon‐related defects in III–V materials.
Modelling Point Defects Diffusion and Interaction in Silicon: The Tight‐Binding Molecular Dynamics Approach
Authors: Colombo L. , Bongiorno A. 
Published: March 2014

AbstractIn this work we discuss the application of tight‐binding molecular dynamics to the study of migration of intrinsic point defects in c‐Si. In particular, we investigate self‐diffusion and formation of vacancy clusters. Furthermore, by means of Hartree‐Fock calculations, we present a quantitative picture for the chemical bond in silicon when point defects are present.
The Heat of Transport of Solute Atoms in Solid Argon
Authors: Jones Clive , Grout P.J. , Lidiard A.B. 
Published: March 2014

AbstractMolecular dynamics simulations of the solute migration by a vacancy have been made for a Lennard‐Jones model of solid argon. The results have been used to analyse the heat of transport, Q*, for solutes with masses corresponding to those of the noble gases. The theory shows that there are three contributions to Q*, coming from the fluxes of the kinetic energy, potential energy and a virial of the forces. Trends in the kinetic and potential terms are found with increasing mass of the solute atoms which it seems would be shown by solute atoms more generally. The molecular dynamics calculation is in the centre of mass frame and we give the necessary transformations to the required lattice frame.
Simulation of Electrical Properties of Grain Boundaries in Titanate Ceramics
Authors: Hagenbeck R. , Waser R. 
Published: March 2014

AbstractUsing a numerical simulation method, the electrostatic properties of grain boundaries in titanate ceramics (SrTiO3 and BaTiO3) are calculated by the combination of a defect chemistry model and the general potential equation. Based on these results and a simple three‐dimensional “brick‐wall‐model” of the ceramic microstructure, an equivalent network is developed for the ceramic body which consists of a great number of R C‐branches. Using this network it is possible to calculate the frequency dependence of the complex impedance of the ceramic. The results of the impedance simulation can be compared to experimental results. This comparison yields information about the charge transport across and along the grain boundaries and about the influence of the temperature, the bulk dopant concentrations, and the donor‐ or acceptor‐like grain boundary interface states on the electrical properties of the grain boundaries. By using the simulation technique one gets additional information to interpret and understand the experimental results and to model the physical and electrical behaviour of the grain boundaries which mainly determine the electrical characteristics of the ceramic.
First Principles Calculations of Solute‐Hole Interactions in the High Tc Oxyfluoride Superconductor Sr2CuO2F2
Authors: Mackrodt W.C. , Gotsis H.J. , Allan N.L. 
Published: March 2014

AbstractFirst principles periodic Hartree‐Fock calculations are reported of the electronic and magnetic structures and hole states in the T (La2CuO4) phases of Sr2CuO2F2, Sr2CuO2F2.5 and NaSrCuO2F2. Sr2CuO2F2 is predicted to be a highly ionic antiferromagnetic charge transfer insulator with Cu in a d9 ((dx2–y2)1) configuration. Holes are predicted to be highly localised spin polarons which destroy the AF ordering at concentrations of 0.5 per formula unit.
Nonlinear Charge Transport in Acceptor‐Doped Titanates
Authors: Vollmann M. , Weber U. , Waser R. 
Published: March 2014

AbstractThe field‐enhanced conductivity of grain boundary space charge depletion layers in acceptor‐doped SrTiO3ceramics was investigated by impedance analysis in the time domain. The dependence of the GB conductivity on the external applied electrical field are discussed and interpreted in terms of a Schottky diffusion model.
Studying the Environments of Ion‐Implanted Arsenic Defects in Amorphous and Recrystallised Silicon with Impurity EXAFS
Authors: Greaves G.N. , Dent A.J. , Derst G. , Kalbitzer S. , Müller G. 
Published: March 2014

AbstractWith recent developments in solid state detectors combined with X‐rays at glancing angles of incidence, Extended X‐ray Absorption Fine Structure (EXAFS) experiments on arsenic ion‐implanted into amorphous silicon surfaces have been obtained at dilutions down to 0.01 at%. Structural relaxation processes in both hydrogen‐containing and hydrogen‐free material have been examined, including the effects of single doping and of counterdoping. In addition the different careers of solid phase epitaxy and amorphisation have been followed from the standpoint of the arsenic environment. EXAFS has been used to establish the degree of crystallinity in the vicinity of arsenic impurities at each stage so that this can be compared with the overall extent of crystalline order in the ion‐implanted silicon.
Defects in Cubic Zirconia Studied by Mechanical Loss Spectroscopy
Authors: Weller M. , Lakki A. 
Published: March 2014

AbstractIn cubic Y2O3 (10–25 mol%) or CaO (14 and 17 mol%) stabilized ZrO2, oxygen vacancies are created as charge‐compensating defects. Mechanical loss (internal friction) measurements are performed on single crystals of cubic zirconia with various orientation at frequencies of f ≈︁ 1 Hz and 1 kHz, to study the local crystallographic structure of the defects. The mechanical spectra show a composite loss maximum at 400–600 K consisting of two overlapping submaxima: I and IA in ZrO2‐Y2O3; I' and I'A in ZrO2‐CaO. Submaxima I (I') are assigned to defect pairs of oxygen vacancies and impurity atoms forming elastic (and electric) dipoles. These are oriented parallel to <111>, with the vacancy on nearest neighbour sites (trigonal symmetry). Submaxima IA(I'A) are attributed to relaxation of vacancies within Y‐ (or Ca‐) clusters with various sizes and configurations corresponding to lower defect symmetry. The electrical conductivity (4 probe d.c. technique) decreases for concentrations ≥10mol% Y2O3, whereas the activation enthalpy increases with Y2O3 content. A high temperature peak C in ZrO2‐CaO around 1400 K (0.1 Hz) is probably due to local atomic jumps of cations.
Quantum Wells within Quantum Dots, a CdS/HgS Nanoheterostructure with Global and Local Confinement
Authors: Mews Alf , Eychmüller Alexander 
Published: March 2014

AbstractSemiconductor nanocrystals prepared by methods of wet chemistry are similar to MBE grown quantum dots where the mobility of the charge carriers is reduced to zero dimensionality. In this paper we summarize the physics of a unique system in which the charge carriers are locally confined within a heterogeneous quantum dot. With high resolution electron microscopy we will show that epitaxial growth ot atomic layer precision is possible by methods of solution chemistry leading to CdS quantum dots with embedded HgS quantum wells (QDQWs). The photophysics of this system is investigated by time‐correlated single photon counting, transient differential absorption and fluorescence line narrowing spectroscopies. The results reflect the very complex electronic structure of this new kind of matter which can be explained by an extended effective mass approach.
Investigation of the Pyrolysis and Crystallization of Lead Zirconate Titanate Ceramics Prepared via the Sol Gel Process
Authors: Brieger Jens , Merkle Rotraut , Bertagnolli Helmut , Müller Klaus 
Published: March 2014

AbstractThe sol gel process for the preparation of lead zirconate, lead titanate and lead zirconate titanate is studied by various experimental techniques, comprising solid state NMR methods, FT IR spectroscopy, DTA/TG and XRD. Two temperature ranges are examined that cover (i) the pyrolysis step from the solid gel to the amorphous oxide mixture and (ii) the calcination step from the amorphous state to the crystalline ceramics. 13C NMR and FT IR spectroscopy studies primarily are used to monitor the structural changes during the pyrolysis step. 207Pb NMR spectroscopy is employed to examine the development of the short range order at the lead nuclei over the whole temperature range. The latter studies clearly show that the observed changes in the short range order are accompanied by alterations in the long range order, as derived from the XRD data. In addition, 207Pb NMR experiments are performed on ceramic samples that were obtained via the sol gel or the mixed oxide route. It is demonstrated that these samples exhibit significant differences in the short range order, although the long range order was found to be the same, being independent of the actual preparation route.
Hydrogen Carbonate Inhibited and Induced Substitution Reactions of Labile Square‐Planar Diethylenetriaminepalladium(II) Complexes
Authors: Breet Ernst , van Eldik Rudi 
Published: March 2014

AbstractThe reaction of labile square‐planar diethylenetriaminepalladium(II) complexes with hydrogen carbonate ion was studied by stopped flow spectrophotometry as a function of [HCO−3] and [Cl−] and constant [Pd], ionic strength and temperature to investigate the substitution behaviour with a nucleophile capable of affecting the solution pH. The kinetic results significantly deviate from those for normal square‐planar substitution behaviour. The reaction comprises two consecutive equilibrations, which have complex kinetics compared to the simple two‐term rate law normally encountered, and which represent hydrogen carbonate inhibited and induced substitution reactions, respectively. The suggested mechanism and data treatment account for the observed deviating kinetics and provide alternative ways of obtaining formerly determined aquation and anation rate constants with comparable accuracy, even for complexes too labile to be monitored directly.
Shock Tube Study of the Reaction of Si Atoms with SiCl4
Authors: Kunz A. , Roth P. 
Published: March 2014

AbstractThe reaction of Si atoms with SiCl4 was studied behind reflected shock waves at temperatures between 1530 and 1800 K and pressures around 1.7 bar by applying atomic resonance absorption spectroscopy (ARAS) for time‐resolved measurement of Si atoms. The thermal decomposition of a few ppm Si2H6 was used as source for Si‐atoms. The presence of an excess of SiCl4 causes a fast consumption of Si atoms, which follows a pseudo‐first‐order rate law. The rate coefficient for the reaction of Si atoms with SiCl4magnified imagewas determined to be:k1 = 4.0±0.2×1013cm3 mol−1s−1with no observable temperature dependence in the temperature range of the present study.
Characterization of preclinical in vitro and in vivo ADME properties and prediction of human PK using a physiologically based pharmacokinetic model for YQA‐14, a new dopamine D3 receptor antagonist candidate for treatment of drug addiction
Authors: Liu Fei , Zhuang Xiaomei , Yang Cuiping , Li Zheng , Xiong Shan , Zhang Zhiwei , Li Jin , Lu Chuang , Zhang Zhenqing 
Published: March 2014

ABSTRACTYQA‐14 is a novel and selective dopamine D3 receptor antagonist, with potential for the treatment of drug addiction. However, earlier compounds in its structural class tend to have poor oral bioavailability. The objectives of this study were to characterize the preclinical absorption, distribution, metabolism and excretion (ADME) properties and pharmacokinetics (PK) of YQA‐14, then to simulate the clinical PK of YQA‐14 using a physiologically based pharmacokinetics (PBPK) model to assess the likelihood of developing YQA‐14 as a clinical candidate. For human PK prediction, PBPK models were first built in preclinical species, rats and dogs, for validation purposes. The model was then modified by input of human in vitro ADME data obtained from in vitro studies. The study data showed that YQA‐14 is a basic lipophilic compound, with rapid absorption (Tmax ~ 1 h) in both rats and dogs. Liver microsomal clearances and in vivo clearances were moderate in rats and dogs consistent with the moderate bioavailability observed in both species. The PBPK models built for rats and dogs simulated the observed PK data well in both species. The PBPK model refined with human data predicted that YQA‐14 would have a clearance of 8.0 ml/min/kg, a volume distribution of 1.7 l/kg and a bioavailability of 16.9%. These acceptable PK properties make YQA‐14 an improved candidate for further research and development as a potential dopamine D3R antagonism for the treatment of drug addiction in the clinic. Copyright © 2014 John Wiley & Sons, Ltd.
Fragmented proteins as food emulsion stabilizers: A theoretical study
Authors: Ettelaie Rammile , Zengin Adem , Lee Hazel 
Published: March 2014

ABSTRACTUsing a model based on the primary structure of αs1‐casein, the colloid stabilizing ability of fragmented protein and that of the intact chains are compared. We perform self consistent field (SCF) calculations to obtain the induced interaction potentials between the oil droplets, resulting from the overlap of adsorbed protein layers in each case. For the intact αs1‐casein, we confirm the known result, that the mediated interparticle interaction potential develops a deep attractive energy minimum at high salt concentrations and pH values close to the isoelectric point of the protein. The same does not occur for the appropriately fragmented systems, with improved emulsion stability predicted as a result, even at pH values close to pI. It is shown that this superior performance, for the case considered, is due to the diblock‐type behavior of one of the fragments. However, it is well known that αs1‐casein more closely resembles the less favorable triblock structure. However, it is also demonstrated that the presence of a “diblock” like fragment by itself may not always be enough to produce a better emulsion stabilizer. It is seen that the hydrolysis of some peptide bonds may indeed lead to a suitable polypeptide, but that this is displaced from the interface by the structurally less desirable ones, also generated by the fragmentation process. The displacement occurs due to the competitive adsorption between different fragments. The removal of the undesirable fragments from the solution is found to greatly enhance the predicted colloid stabilizing ability of the remaining polypeptide. © 2014 Wiley Periodicals, Inc. Biopolymers 101: 945–958, 2014.