bluuebunny/crossref_metadata_2025_split huggingface dataset:
Initial exploration of tribological performance of novel triazine derivatives in water
Authors: Sheng Liping , Li Fenfang , Fan Chengkai 
Published: April 2009

AbstractTwo novel ashless and non‐phosphorus triazine derivatives, 2,4,6‐tri‐[N‐hydroxyethyl‐amino‐methylenesulfanyl]‐s‐triazine and 2,4,6‐tri‐[N,N‐bishydroxyethyl‐amino‐methylenesulfanyl]‐s‐triazine, were synthesised and their structures were analysed through elemental analysis. Their tribological behaviours in water were evaluated with a four‐ball machine, and the results indicate that their wear resistance and load‐carrying properties were excellent. The chemical features of the worn steel surface were observed and examined by means of inverted metallurgical microscopy and energy dispersive X‐ray spectroscopy. The analytical results of typical elements on the worn steel surface demonstrated, during the lubricating process, that the additives reacted with counter‐face metal and generated a boundary lubricating and protecting film containing elements of S, N and others, which contributes to improve the tribological properties of the test fluid. Copyright © 2009 John Wiley & Sons, Ltd.
Structural elucidation and NMR spectral assignment of three new furostanol saponins from the roots of Tupistra chinensis
Authors: Guo Zhiyong , Zou Kun , Wang Junzhi , Liu Chuang , Tang Zichun , Yang Chunyan 
Published: April 2009

AbstractThree new furostanol saponins (1–3) were isolated from the roots of Tupistra chinensis (T. chinensis). And their structures were elucidated on the basis of NMR and mass spectrometry (MS) spectral analysis. Copyright © 2009 John Wiley & Sons, Ltd.
Optimal control problem for nonstationary Schrödinger equation
Authors: Yildiz Bunyamin , Kilicoglu Oguz , Yagubov G. 
Published: April 2009

AbstractIn this study we investigate an optimal control problem for the nonstationary Schrödinger equation; the questions needed to correctly identify the optimal control problem were answered, and the existence and uniqueness of the solution and the necessary and sufficient conditions for the solution were investigated. We consider the initial situation as control for the controlled system. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Numerical solution of nonlinear Schrödinger equation by using time‐space pseudo‐spectral method
Authors: Dehghan Mehdi , Taleei Ameneh 
Published: April 2009

AbstractIn this article, a time‐space pseudo‐spectral method is proposed for the numerical solution of nonlinear Schrödinger equation. The employed method is based on Chebyshev‐Gauss‐Lobbato quadrature points. Using the pseudo‐spectral differentiation matrices the problem is reduced to a system of nonlinear algebraic equations. However, this method is basically a spectral method, but a subdomain‐in‐time algorithm is used which yields a smaller nonlinear system to study long‐time numerical behavior. Because the time‐space pseudo‐spectral method has spectral accuracy, we present numerical experiments which show high accuracy of this method for the variant nonlinear Schrödinger equations and also particular attention is paid to the conserved quantities as an indicator of the accuracy. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010
The role of the museum shop in extending the visitor experience
Authors: Kent Tony 
Published: April 2009

Abstract

The aim of the research is to assess the role of the museum shop in extending the learning experience in the museum. The research is situated in the theoretical framework of museum experiences and learning. It acknowledges environmental influences on learning, and of consumption sites that synthesise leisure and consumption and create memorable sensory experiences that engage customers.

The exploratory approach uses mixed methods to examine visitors' knowledge and experience of museums and their shops. The first phase of the research was undertaken with in‐depth interviews to scope the experience of museum shops and their contribution to learning. The second phase was undertaken with visitors to the Imperial War Museum (IMW) in London through a convenience sample which elicited 150 responses to a semi‐structured questionnaire. The research demonstrates the significance of the museum shop as a destination for museum visitors, and its role in creating experiences that can supplement the museum's educational priorities and a return to the everyday world of familiar objects.

Copyright © 2009 John Wiley & Sons, Ltd.
Synthesis and characterization of new optically active polymers carrying calix[4]arene and amino acid units in the main chain and their binding properties towards toxic heavy metals
Authors: Hajipour Abdol‐Reza , Habibi Sakineh , Ruoho Arnold E 
Published: April 2009

AbstractBACKGROUND: A series of novel optically active polymers containing upper rim calix[4]arene was prepared from the polycondensation reaction of calix diamine derivative 2 with two optically active diacid chlorides.RESULTS: The optically active compounds were prepared from the reaction of a pyromellitic dianhydride with two chiral amino acids. The optically active polymers were obtained in a yield of 80–86% and had an inherent viscosity of 0.20–0.26 dL g−1. The polymers were characterized using Fourier transform infrared and 1H NMR spectroscopy and elemental analysis. Studies of the complexation of the polymers towards some alkali metal and toxic transition metal cations were performed using solid–liquid sorption procedures and comparisons made with the starting monomer.CONCLUSION: It is evident from the complexation studies that the polymers investigated are good polymeric ionophores for alkali metal cations like Na+ and K+, for Ag+ and for toxic heavy metal cations such as Cu2+, Co2+, Cd2+ and Hg2+. These polymers are good candidates for use in chiral stationary phases for separation of enantiomers in ionic media, as well for removing metal ions. Copyright © 2009 Society of Chemical Industry
Photo‐crosslinking of poly[ethene‐stat‐(methacrylic acid)] functionalised with maleimide side groups
Authors: Schmeling Nadine , Hunger Katharina , Engler Gernot , Breiten Benjamin , Rölling Patrick , Mixa Alexander , Staudt Claudia , Kleinermanns Karl 
Published: April 2009

AbstractBACKGROUND: Photo‐crosslinkable polymers are well known and commercially applied as photoresists. But so far they have not been applied as membrane materials for separation processes. They would offer certain advantages in membrane fabrication over conventional crosslinked polymer materials. Therefore, in this work, a poly[ethene‐stat‐(methacrylic acid)] (PEMAA) which is a potential membrane polymer for different separation problems was functionalised with photo‐crosslinkable maleimide side groups.RESULTS: It has been shown that PEMAA can be used as basic polymer material and a conversion with 3‐hydroxypropylmaleimide is possible in order to obtain a photo‐crosslinkable polymer. Investigation of the crosslinking mechanism was performed using stationary infrared and UV‐visible spectroscopy as well as nanosecond transient spectroscopy absorption measurements of a rotating film. Intense transient absorption of the maleimide‐esterified PEMAA occurs at 250 nm in the film pointing to maleimide anion formation and crosslinking via an ionic dimerisation mechanism.CONCLUSION: It is found that crosslinking reactions can be observed spectroscopically in situ using a maleimide‐functionalised PEMAA. Furthermore, experiments can be performed in the liquid phase (polymer in solution) as well as in the solid phase (polymer film) using a rotating polymer film sample. Maleimide anion formation and crosslinking via an ionic dimerisation mechanism can be investigated by variation of the polymer structure as well as the structure of the maleimide side groups. Copyright © 2009 Society of Chemical Industry
Polydimethylsiloxane/silica composites incorporating pyrite powders for actuation elements
Authors: Cazacu Maria , Ignat Mircea , Racles Carmen , Vlad Angelica , Alexandru Mihaela , Zarnescu George 
Published: April 2009

AbstractBACKGROUND: Among polymers, elastomers can achieve very large deformations and deliver relatively high forces when an electric field is applied to them. In addition, a number of active components, such as carbon black, multi‐walled nanotubes or metallic powders, can be used to obtain increased effects. One elastomer used as a host for these active fillers is polydimethylsiloxane.RESULTS: Pyrite powders were physically incorporated in a polymeric matrix consisting of interconnected polydimethylsiloxane/silica networks. The mixtures were processed as films by casting on a Teflon substrate before crosslinking. The films thus formed were investigated from the point of view of their mechanical behaviour and were tested as active elements in an actuation system.CONCLUSION: Electromechanical tests of the polymeric membranes under investigation revealed a very good behaviour for applications in nano‐ and micro‐actuation. Some of the prepared films showed significant displacements at reasonable voltages (i.e. 56 000 nm at 460 V or 1000 nm at 6 V). Sensitivities between 2.608 and 333.33 nm V−1 were obtained in inverse dependence on the Young's modulus values. Copyright © 2009 Society of Chemical Industry
The effect of β‐methylation on the conformation of α, β‐dehydrophenylalanine: a DFT study
Authors: Broda Małgorzata A. , Buczek Aneta , Siodłak Dawid , Rzeszotarska Barbara 
Published: April 2009

AbstractDehydroamino acids are non‐coded amino acids that offer unique conformational properties. Dehydrophenylalanine (ΔPhe) is most commonly used to modify bioactive peptides to constrain the topography of the phenyl ring in the side chain, which commonly serves as a pharmacophore. The Ramachandran maps (in the gas phase and in CHCl3 mimicking environments) of ΔPhe analogues with methyl groups at the β position of the side chain as well as at the C‐terminal amide were calculated using the B3LYP/6‐31 + G** method. Unexpectedly, β‐methylation alone results in an increase of conformational freedom of the affected ΔPhe residue. However, further modification by introducing an additional methyl group at C‐terminal methyl amide results in a steric crowding that fixes the torsion angle ψ of all conformers to the value 123°, regardless of the Z or E position of the phenyl ring. The number of conformers is reduced and the accessible conformational space of the residues is very limited. In particular, (Z)‐Δ(βMe)Phe with the tertiary C‐terminal amide can be classified as the amino acid derivative that has a single conformational state as it seems to adopt only the β conformation. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.
Regioselective and sequential reactivity of activated 2,5‐diketopiperazines
Authors: Farran Daniel , Echalier Delphine , Martinez Jean , Dewynter Georges 
Published: April 2009

AbstractThe electrophilic reactivity of Boc‐DKPs has been studied. Thanks to Boc activation, the opening ability of carbonyl lactam groups is enhanced. According to experimental conditions, this enabled the synthesis of Boc‐amino acid derivatives or original dipeptides via a regioselective and sequential way. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.
Spanning the Hilbert space with an even tempered Gaussian basis set
Authors: Cherkes Ira , Klaiman Shachar , Moiseyev Nimrod 
Published: April 2009

AbstractIn this work we show how and why the well‐known Gaussian even‐tempered basis spans the Hilbert space evenly. This basis is thought to be chosen based mainly on empirical results. However as shown here it can also be deduced based on rigorous numerical ground using a Gram‐Schmidt orthogonalization procedure. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Efficient calculation of the exchange in the Fourier representation of HF‐LCAO‐CO equations for 1D periodic systems
Authors: Fripiat Joseph G. , Delhalle Joseph 
Published: April 2009

AbstractRecent advances in the preparation of quasi‐1D nano‐objects motivate further the development of suitable theoretical models for the calculation of their properties (structural, electronic, etc.). Hartree–Fock crystal orbital‐based methodologies and beyond, in spite of their cost, provide a consistent basis for calculations on systems exhibiting periodicity in one direction. One of the often reported drawbacks is the difficulty to deal with the long‐range contributions (Coulomb and exchange). In this contribution, it shown that the Fourier representation of the HF‐LCAO‐CO equations is an appropriate framework to effectively compute the exchange contributions in GTO basis sets. A numerical example illustrates the efficiency of the proposed procedure. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
The leaky aquifer function revisited
Authors: Temme Nico M. 
Published: April 2009

AbstractThis article discusses the leaky aquifer function considered in a recent article by Frank Harris in the Journal of Computational and Applied Mathematics (2008). We describe the properties of an integral representing this function and give details on how to compute this function with a single algorithm for a wide range of the parameters. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Intermediate Hamiltonian Hilbert space coupled cluster method: Theory and pilot application
Authors: Eliav Ephraim , Borschevsky Anastasia , Shamasundar K. R. , Pal Sourav , Kaldor Uzi 
Published: April 2009

AbstractThe intermediate Hamiltonian state universal (Hilbert‐space) coupled‐cluster method is presented, using a formalism similar to that developed for the valence universal (Fock‐space) approach. The method is expected to be applicable to many states not accessible by traditional multiroot multireference all‐order size‐extensive approaches. A pilot application to excited states of atomic beryllium shows good convergence and agreement with experiment and full CI values. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Numerical orbital Fourier space approach to polymer band‐structure calculations
Authors: Talman J. D. , Delhalle J. , Fripiat J. G. 
Published: April 2009

AbstractThe periodic symmetry of polymer chains can be applied via Bloch functions to polymer band structure calculations (Delhalle and Harris, Phys Rev B 1985, 31, 6755). The possibility of replacing Gaussian orbitals with numerically defined orbitals in this approach is discussed. Two modifications of the theory to overcome problems with the cancellation of divergent terms are described. Result for a LiH chain are compared with analytic Gaussian orbital results. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
An ab initio analysis of charge redistribution upon isomerization of retinal in rhodopsin and bacteriorhodopsin
Authors: Corn Brittany , Malinovskaya Svetlana A. 
Published: April 2009

AbstractIn the framework of quantum‐chemical methods (RHF, MP2, and DFT), we study the reaction of photoinduced isomerization of biological molecules—retinal in rhodopsin (Rh) and bacteriorhodopsin (BRh)—the key intermediates in the vision process. The charge redistribution in the retinal chromophore of these biological molecules as the mechanism of the photoinduced isomerization is investigated. The results of the Mulliken, Löwdin, Natural Bond, and ESP population analyses are compared and validated. We demonstrate that the isomerization reaction is accompanied by the substantial charge relocation within the isomerization region with the electron localization on C11 for the retinal in Rh and C14 for the retinal in BRh. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Exact mathematical treatment of the modifications of finite‐dimensional quantum systems
Authors: Živković Tomislav P. 
Published: April 2009

AbstractLow rank modification (LRM) is a new mathematical formalism by which one can express eigenvalues and eigenstates of the modified system B in terms of the eigenvalues and eigenstates of the original system A. In this respect, LRM is similar to a standard perturbation expansion, which also expresses eigenvalues and eigenstates of the perturbed system B in terms of the eigenvalues and eigenstates of the unperturbed system A. However, unlike perturbation expansion, LRM produces correct results however strong the “perturbation” of the original system A. LRM is here applied to finite n‐dimensional systems A and B that are described by generalized n × n eigenvalue equations. In the LRM approach, modified system B is described by a ρ × ρ matrix equation, where ρ is the dimension of the space affected by the “modification” of the original system A. In mathematical terms, ρ is the rank of the operators that describe this modification. In many important cases, ρ << n, which results in the substantial numerical efficiency of the LRM approach. The method is illustrated with two examples. In the first example, LRM is applied to the vibrational isotope effect within the harmonic approximation. In particular, out‐of‐plane vibrations of benzene (H,D)‐isotopomers are analyzed in this way. In the second example, LRM is applied to some problems in a solid state physics. LRM provides a new mathematical treatment of all those features that break translational symmetry of a solid, such as point defects, the surface of a solid, etc. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Effects of local Coulomb potentials on acid and base protonation–deprotonation rates and equilibria
Authors: Smuczyńska Sylwia , Simons Jack 
Published: April 2009

AbstractAb initio electronic structure methods, even when performed at a very modest level, applied to the energy profiles for deprotonation of an organic acid or of a protonated amine in the presence of proximal charged groups yield data that suggest the following: 1. The proton affinity of an amine tethered to a surface can be altered substantially by the presence of proximal positively charged groups. 2. Barriers (above the thermodynamic energy requirement) along the amine protonation–deprotonation pathway arise when positive charges are tethered nearby. 3. A competition between the attractive intrinsic NH bonding potential and the repulsive Coulomb potential between the departing proton and the proximal positive charges is the primary source of the above two results. 4. There is much less change in the equilibrium constant K or the deprotonation and protonation rate constants k1 and k−1 for an organic acid tethered to a surface when in the presence of proximal negative charges. 5. The attractive intrinsic OH bonding potential and the attractive Coulomb potential between the proton and the proximal and nascent negative charges act in concert in the organic acid case. So, unlike the amine example, there is no competition between the dominant potentials and, as a result, no pronounced barriers occur along the reaction path. The relevance of these findings to acid–base properties of surfaces and nanoparticles are discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Application of the method of increments to the adsorption of H2S on graphene
Authors: Paulus Beate , Rosciszewski Krzysztof 
Published: April 2009

AbstractThe method of increments is applied to the adsorption energy of H2S on a graphene layer using a CCSD(T) correlation treatment. We determine the incremental expansion for the correlation contribution to the adsorption energy in terms of localized orbitals of the molecule and the surface. The changes in the correlation energy of the molecule and the individual localized surface orbitals are repulsive and small, the major contributions arise from the joint correlation of molecule and surface orbitals. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
A numerical study of the asymptotic convergence characteristics of partial averaged and reweighted Fourier path integral methods
Authors: Kunikeev Sharif , Freeman David L. , Doll J. D. 
Published: April 2009

AbstractThe asymptotic convergence characteristics with respect to the number of included path variables of the partial average and reweighted Fourier path integral methods are numerically compared using a Gaussian fit to the one‐dimensional Lennard‐Jones potential. Using harmonic inversion to determine the parameters of the Gaussian fit potential appropriate for neon, the energy eigenvalues and thermodynamic properties of the Gaussian fit and the Lennard‐Jones interaction agree to better than 1%. Using Monte Carlo methods to study the Gaussian fit potential, the systematic error associated with the truncation of the number of path variables is found to be larger for the reweighted method than the partial average method for the same number of path variables actually used. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Spheroidal confinement of a single electron and of the hydrogen atom, the H and HeH++ molecular ions with arbitrary nuclear positions along the major axis
Authors: Cruz Salvador A. , Colín‐Rodríguez Ricardo 
Published: April 2009

AbstractEvidence is given on the usefulness of the variational method to explore the nonseparable Schroedinger problem for the energy evolution of one‐electron atoms and diatomic molecular ions confined by a hard prolate spheroidal cavity when the nuclear positions do not coincide with the foci. In this work, we study explicity the case of the hydrogen atom (H) and the H and HeH++ under the aforementioned confinement conditions and obtain variationally the energy evolution as a function of nuclear positions along the major axis of a confining spheroid of fixed size and eccentricity. The particular case of an electron (e−) under the same confinement conditions is also addressed using the same methodology. Our calculations are restricted to the ground states of H (1sσ), HeH++ (1sσ), e−(1sσ) and the ground‐state (1sσg) and first excited state (2pσu) of H. It is shown that a simple LCAO Dickinson‐type variational ansatz wavefunction adapted for the confinement case of all systems treated in this work provides very rewarding results for the energy dependence on the size and shape of the confining cavity when compared with corresponding available exact calculations. For e− as well as for H, H and HeH++ with “on‐focus” nuclear positions excellent general quantitative agreement is observed. For the “off‐focus” case, moderate quantitative agreement is obtained with available accurate B‐spline variational calculations for H. For the molecular systems with “off‐focus” nuclear positions, the results of this work are the first of this kind. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Few sketches on connections between the Riccati and Ermakov–Milne–Pinney equations
Authors: Kryachko Eugene S. 
Published: April 2009

AbstractIn this work, we focus on some connections that exist between the Riccati and Ermakov–Milne–Pinney equations, particularly those which are established via the Schrödinger equation. Some formulas that express the general solution of the Riccati and Schrödinger equations in terms of a particular solution of the Riccati equation are obtained. It is shown that the difference between the general and particular solutions of the normal Riccati equation satisfies the Ermakov–Milne–Pinney equation with λ = −1/4. The formulas derived in this work are discussed in view of their quantum chemical applications, especially related to the WKB approach that is applied to describe the semiclassical behavior of molecules. This discussion is illustrated by a simple model of quantum harmonic oscillator. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009