bluuebunny/crossref_metadata_2025_split huggingface dataset:
A valence bond study of the dioxygen molecule
Authors: Su Peifeng , Song Lingchun , Wu Wei , Hiberty Philippe C. , Shaik Sason 
Published: October 2006

AbstractThe dioxygen molecule has been the subject of valence bond (VB) studies since 1930s, as it was considered as the first “failure” of VB theory. The object of this article is to provide an unambiguous VB interpretation for the nature of chemical bonding of the molecule by means of modern VB computational methods, VBSCF, BOVB, and VBCI. It is shown that though the VBSCF method can not provide quantitative accuracy for the strongly electronegative and electron‐delocalized molecule because of the lack of dynamic correlation, it still gives a correct qualitative analysis for wave function of the molecule and provides intuitive insights into chemical bonding. An accurate quantitative description for the molecule requires higher levels of VB methods that incorporate dynamic correlation. The potential energy curves of the molecule are computed at the various VB levels. It is shown that there exists a small hump in the PECs of VBSCF for the ground state, as found in previous studies. However, higher levels of VB methods dissolve the hump. The BOVB and VBCI methods reproduce the dissociation energies and other physical properties of the ground state and the two lowest excited states in very good agreement with experiment and with sophisticated MO based methods, such as the MRCI method. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007
The Lewis legacy: The chemical bond—A territory and heartland of chemistry
Authors: Shaik Sason 
Published: October 2006

AbstractIs chemistry a science without a territory? I argue that “chemical bonding” has been a traditional chemical territory ever since the chemical community amalgamated in the seventeenth century, and even before. The modern charter of this territory is Gilbert Newton Lewis, who started the “electronic structure revolution in chemistry.” As a tribute to Lewis, I describe here three of his key papers from the years 1913, 1916, and 1923, and analyze them. Lewis has defined the quantum unit, the “electron pair bond,” for construction of a chemical universe, and in so doing he charted a vast chemical territory and affected most profoundly the mental map of chemistry for generations ahead. Nevertheless, not all is known about the chemical bond” the chemical territory is still teaming with new and exciting problems of in new materials, nanoparticles, quantum dots, metalloenzymes, bonding at surface‐vapor interfaces, and so on and so forth. © 2006 Wiley Periodicals, Inc.J Comput Chem, 2007
Chemical bonding: From Lewis to atoms in molecules
Authors: Bader R. F. W. , Hernández‐Trujillo J. , Cortés‐Guzmán F. 
Published: October 2006

AbstractThe Lewis electron pair concept and its role in bonding are recovered in the properties of the electron pair density and in the topology of the Laplacian of the electron density. These properties provide a bridge with the quantum mechanical description of bonding determined by the Feynman, Ehrenfest, and virial theorems, bonding being a consequence of the electrostatic forces acting within a molecular system. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007
Polyurethane Networks Modified with Octa(propylglycidyl ether) Polyhedral Oligomeric Silsesquioxane
Authors: Liu Yonghong , Ni Yong , Zheng Sixun 
Published: October 2006

AbstractSummary: OpePOSS was incorporated into polyurethane to make organic‐inorganic hybrid composites and nano‐composites containing up to 20 wt.‐% POSS were prepared. The formation of the hybrid polyurethane networks is ascribed to two principal cross‐linking reactions: i) the cross‐linking reaction between MOCA and the polyurethane prepolymer and ii) the inter‐component reaction between the PU networks and OpePOSS. The latter was confirmed by model compound reactions. TEM indicates that the POSS was homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the nanocomposites displayed increased glass transition temperatures compared to the control polyurethane. In terms of TGA, the nanocomposites displayed improved thermal stability. Tensile tests indicate that the organic‐inorganic hybrid networks were significantly reinforced with the inclusion of POSS. Contact angle measurements show that the organic‐inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity as well as a reduction in the surface free energy. The improvement in surface properties was ascribed to the presence of the POSS moiety in place of the polar component of polyurethane. XPS shows enrichment with Si‐containing moieties on the surfaces.Organic‐Inorganic Hybrid PU Networks.magnified imageOrganic‐Inorganic Hybrid PU Networks.
ESR Detection of Propagating Radical Species during RAFT‐Mediated Polymerization
Authors: Tonge Matthew P. , Calitz F. Malan , Sanderson Ronald D. 
Published: October 2006

AbstractSummary: ESR spectroscopy directly detected both propagating and intermediate radicals during RAFT‐mediated reactions of styrene and methyl acrylate. Their nature and concentrations during the initialization period were significantly different from those thereafter. The dominant radicals during the initialization period were initiator‐ and R‐group derived, and the intermediate radicals were both different and of lower concentration than during the subsequent steady state polymerization.
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Synthesis of Optically Active Photoresponsive Multifunctional Polymer Containing the Side‐Chain Azocarbazole Chromophore
Authors: Angiolini Luigi , Benelli Tiziana , Giorgini Loris , Mauriello Francesco , Salatelli Elisabetta 
Published: October 2006

AbstractSummary: A new optically active photochromic polymethacrylate containing the carbazole moiety, deriving from the chiral monomer (S)‐(4‐cyanophenyl)‐(3‐{9‐[2‐(2‐methacryloyloxypropanoyloxy)ethyl]carbazolyl})diazene [(S)‐MLECA] has been prepared and fully characterized with the aim to obtain a multifunctional derivative possessing at the same time chemical moieties suitable to NLO and optical storage, to chiroptical switches, and to photorefractive and photoconductive applications. Spectroscopic, thermal and chiroptical characterizations clearly indicate the occurrence of dipolar interactions between chromophores and the presence of an ordered chiral conformation of one prevailing helical handedness, at least for chain segments of the macromolecules.Structure of poly[(S)‐MLECA].magnified imageStructure of poly[(S)‐MLECA].
Fabrication of Robust High‐Quality ORMOCER® Inverse Opals
Authors: Lange Birger , Wagner Jürgen , Zentel Rudolf 
Published: October 2006

AbstractSummary: The nanostructuring of ORMOCER® to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER®. After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER® inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER® and high temperature stability up to 350 °C.ORMOCER® inverse opal annealed at 200 °C for 10 h.magnified imageORMOCER® inverse opal annealed at 200 °C for 10 h.
Synthesis, Microstructure, and Acidity of Poly(vinylphosphonic acid)
Authors: Bingöl Bahar , Meyer Wolfgang H. , Wagner Manfred , Wegner Gerhard 
Published: October 2006

AbstractSummary: Vinylphosphonic acid is polymerized at 80 °C by free radical polymerization to give a high‐molecular‐weight polymer ($\overline M _{\rm w}$ of 6.2 × 104) as determined by static light scattering. High‐resolution NMR spectroscopy is used to gain microstructure information. Information based on tetrad probabilities is utilized to deduce an almost atactic configuration. In addition, 13C NMR spectroscopy gives evidence for the presence of head‐to‐head and tail‐to‐tail links. Refined analysis of the 1H NMR spectra allows for the quantitative determination of the fraction of these links (23.5% of all links). Experimental evidence suggests that the polymerization proceeds via cyclopolymerization of the vinylphosphonic acid anhydride as an intermediate. Titration curves indicate that high‐molecular‐weight poly(vinylphosphonic acid) PVPA behaves as a monoprotic acid.Radical polymerization of vinylphosphonic acid proceeds by cyclopolymerization of its anhydride.magnified imageRadical polymerization of vinylphosphonic acid proceeds by cyclopolymerization of its anhydride.
On wave diffraction by a half‐plane with different face impedances
Authors: Castro L. P. , Kapanadze D. 
Published: October 2006

AbstractThe impedance wave diffraction problem by a half‐plane screen is revisited in view of its well‐posedness upon different impedance and wave parameters. The problem is analysed with the help of potential and pseudo‐differential operators. Seven conditions between the impedance and wave numbers are found under which the problem will be well‐posed in Bessel potential spaces. In addition, an improvement of the regularity of the solutions is shown for the previous seven conditions. Copyright © 2006 John Wiley & Sons, Ltd.
Local existence for the one‐dimensional Vlasov–Poisson system with infinite mass
Authors: Pankavich Stephen 
Published: October 2006

AbstractA collisionless plasma is modelled by the Vlasov–Poisson system in one dimension. We consider the situation in which mobile negative ions balance a fixed background of positive charge, which is independent of space and time, as ∣x∣ → ∞. Thus, the total positive charge and the total negative charge are both infinite. Smooth solutions with appropriate asymptotic behaviour are shown to exist locally in time, and criteria for the continuation of these solutions are established. Copyright © 2006 John Wiley & Sons, Ltd.
Numerical investigation on the failure criterion of normally consolidated clays
Authors: Tachibana Shinya , Iizuka Atsushi , Kawai Katsuyuki , Kobayashi Ichizou , Pipatpongsa Thirapong , Ohta Hideki 
Published: October 2006

AbstractIn this paper, a series of numerical simulations of conventional laboratory experiments on normally consolidated clays under undrained condition subject to uniaxial compression/extension loading at constant applied rate of strain in axisymmetric and plane strain conditions was performed in rectangular and octagonal modelled specimens in order to investigate failure behaviours of clays. The soil/water coupling finite element technique formulated under finite deformation theory based on the updated Lagrangean scheme were applied for the numerical simulations. Herein, the Cam‐clay material with von Mises type failure criterion, which is independent of the Lode angle, is used to describe constitutive behaviour. It can be seen that the stress states at failure of the specimens obtained from the numerical simulations do not show the von Mises shape on the π‐plane but rather more closely resembles the Lade–Duncan model, which is dependent of Lode angle. The result suggests that Lode angle dependence consistently observed in the laboratory at failure is not a constitutive behaviour but is instead a result influenced by applied boundary conditions and material imperfections. Copyright © 2006 John Wiley & Sons, Ltd.
Flexibility and complexity in periodic distribution problems
Authors: Francis Peter , Smilowitz Karen , Tzur Michal 
Published: October 2006

AbstractIn this paper, we explore trade‐offs between operational flexibility and operational complexity in periodic distribution problems. We consider the gains from operational flexibility in terms of vehicle routing costs and customer service benefits, as well as the costs of operational complexity in terms of modeling, solution methods, and implementation challenges for drivers and customers. The period vehicle routing problem (PVRP) is a variation of the classic vehicle routing problem in which delivery routes are constructed for a period of time; the PVRP with service choice (PVRP‐SC) extends the PVRP to allow service (visit) frequency to become a decision of the model. For the periodic distribution problems represented by PVRP and PVRP‐SC, we introduce operational flexibility levers and a set of quantitative measures to evaluate the trade‐offs between flexibility and complexity. We develop a Tabu Search heuristic to incorporate a range of operational flexibility options. We analyze the potential value and the increased operational complexity of the flexibility levers. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007
The strategic effects of a merger upon supplier interactions
Authors: Gilbert Stephen M. , Yu Gang , Xia Yusen 
Published: October 2006

AbstractWe consider how a merger between two naturally differentiated dealers affects their interactions with a common supplier and identify conditions under which the merger can increase or decrease the combined net worth of the two firms. Among other things, we find that the attractiveness of merging depends upon the extent to which end demand can be stimulated by either an upstream supplier or the dealers. Specifically, the greater the supplier's ability to invest in stimulating end demand, the more likely it is that the naturally differentiated firms will be better off operating independently than merging. On the other hand, if the greatest opportunities for stimulating demand are through the service that is provided by the dealers, then merging their operations will be more attractive. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007
A simplified pivoting strategy for symmetric tridiagonal matrices
Authors: Bunch James R. , Marcia Roummel F. 
Published: October 2006

AbstractThe pivoting strategy of Bunch and Marcia for solving systems involving symmetric indefinite tridiagonal matrices uses two different methods for solving 2 × 2 systems when a 2 × 2 pivot is chosen. In this paper, we eliminate this need for two methods by adding another criterion for choosing a 1 × 1 pivot. We demonstrate that all the results from the Bunch and Marcia pivoting strategy still hold. Copyright © 2006 John Wiley & Sons, Ltd.
Fully hierarchical divergence‐conforming basis functions on tetrahedral cells, with applications
Authors: Botha Matthys M. 
Published: October 2006

AbstractA new set of hierarchical, divergence‐conforming, vector basis functions on curvilinear tetrahedrons is presented. The basis can model both mixed‐ and full‐order polynomial spaces to arbitrary order, as defined by Raviart and Thomas, and Nédélec. Solenoidal‐ and non‐solenoidal components are separately represented on the element, except in the case of the mixed first‐order space, for which a decomposition procedure on the global, mesh‐wide level is presented. Therefore, the hierarchical aspect of the basis can be made to extend down to zero polynomial order. The basis can be used to model divergence‐conforming quantities, such as electromagnetic flux‐ and current density, fluid velocity, etc., within numerical methods such as the finite element method (FEM) or integral equation‐based methods. The basis is ideally suited to p‐adaptive analysis. The paper concludes with two example applications. The first is the FEM‐based solution of the linearized acoustic vector wave equation, where it is shown how the decomposition into solenoidal components and their complements can be used to stabilize the method at low frequencies. The second is the solution of the electric field, volume integral equation for electromagnetic scattering analysis, where the benefits of the decomposition are again demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.
Using Two Dimensional Sectional Distributions to Infer Three Dimensional Volumetric Distributions – Validation using Tomography
Authors: Gay S. L. , Morrison R. D. 
Published: October 2006

AbstractThe critical process parameter for mineral separation is the degree of mineral liberation achieved by comminution. The degree of liberation provides an upper limit of efficiency for any physical separation process. The standard approach to measuring mineral liberation uses mineralogical analysis based two‐dimensional sections of particles which may be acquired using a scanning electron microscope and back‐scatter electron analysis or from an analysis of an image acquired using an optical microscope.Over the last 100 years, mathematical techniques have been developed to use this two dimensional information to infer three‐dimensional information about the particles.  For mineral processing, a particle that contains more than one mineral (a composite particle) may appear to be liberated (contain only one mineral) when analysed using only its revealed particle section. The mathematical techniques used to interpret three‐dimensional information belong to a branch of mathematics called stereology.  However methods to obtain the full mineral liberation distribution of particles from particle sections are relatively new.To verify these adjustment methods, we require an experimental method which can accurately measure both sectional and three dimensional properties. Micro Cone Beam Tomography provides such a method for suitable particles and hence, provides a way to validate methods used to convert two‐dimensional measurements to three dimensional estimates.For this study ore particles from a well‐characterised sample were subjected to conventional mineralogical analysis (using particle sections) to estimate three‐dimensional properties of the particles.  A subset of these particles was analysed using a micro‐cone beam tomograph. This paper presents a comparison of the three‐dimensional properties predicted from measured two–dimensional sections with the measured three‐dimensional properties.
Advanced Statistical Analysis as a Novel Tool to Pneumatic Conveying Monitoring and Control Strategy Development
Authors: Romanowski Andrzej , Grudzien Krzysztof , Aykroyd Robert G. , Williams Richard A. 
Published: October 2006

AbstractBehaviour of powder flow in pneumatic conveying has been investigated for many years, though it still remains a challenging task both practically and theoretically, especially when considering monitoring and control issues. Better understanding of the gas‐solids flow structures can be beneficial for the design and operation of pneumatic transport installations. This paper covers a novel approach for providing the quantitative description in terms of parameter values useful for monitoring and control of this process with the use of Electrical Capacitance Tomography (ECT). The use of Bayesian statistics for analysis of ECT data allows the direct estimation of control parameters. This paper presents how this characteristic parameters estimation can be accomplished without the need for reconstruction and image post processing, which was a classical endeavour whenever tomography was applied. It is achieved using a ‘high‐level' statistical Bayesian modelling combined with a Markov chain Monte Carlo (MCMC) sampling algorithm. Advanced statistics is applied to data analysis for measurements coming from the part of phenomena present in the horizontal section of pneumatic conveyor during slug formation.
Mapping of Residual Oil and Water Saturation in Porous Media by Means of Digital X‐ray Laminography
Authors: Palchikov Eugene I. , Schemelinin Yury A. , Skripkin Anton G. , Mekhontsev Dmitry Yu. , Kondratiev Nikolay A. 
Published: October 2006

AbstractThe possibility of applying a digital X‐ray laminography method to the example of mapping the fluid distribution in porous media is studied. The study is performed on the basis of a system which models the process of oil displaced by water and gas as occurs in oil field development. Two methods of tomographic section recovery are discussed: geometric and algebraic, and their application for different specimen structures is made. It is shown that when scanning with steps of 25 μm, 100 μm, 250 μm, or 2 mm it is possible to determine the distribution of concentrations of heterogeneities for multiphase fluid inside a porous core sample layer, giving advantages compared to simple shadow pictures.
A Multi‐Path Ultrasonic Transit Time Flow Meter Using a Tomography Method for Gas Flow Velocity Profile Measurement
Authors: Kurniadi Deddy , Trisnobudi Amoranto 
Published: October 2006

AbstractA velocity profile is the distribution of velocities in the axial direction over a cross‐section of circular pipe. In this study, a new ultrasonic flow meter with a modified multi‐path configuration, namely, a tomographic ultrasonic flow meter is proposed for the measurement of the flow velocity profile. The flow meter consists of a set of transmitting transducers and a set of receiving transducers placed at different positions on the pipe surroundings. This configuration produces an ultrasonic path in various directions and positions for the flow detection. Transmitting transducers, in sequence, propagate the ultrasound wave to all receiving transducers, and the axial velocity in each ultrasonic path is measured. The average velocity is calculated by using the weighting method. Using the theoretical flow profiles, the tomographic ultrasonic flow meter is simulated in asymmetric flow and compared to both the diametrical and quadrature configurations. The filtered back projection method is employed to reconstruct a flow velocity profile. In the reconstruction process, the flow velocity obtained in each ultrasonic path is used as the projection data. An experiment is also performed in a circular pipe for measuring the air flow velocity profile, in order to validate the proposed flow meter.
Electrical transport properties of hot wall epitaxially grown para ‐sexiphenyl nano‐needles
Authors: Birendra Singh Th. , Hernandez‐Sosa G. , Neugebauer H. , Andreev A. , Sitter H. , Sariciftci N. S. 
Published: October 2006

AbstractHighly ordered anisotropic para ‐sexiphenyl (6P) films with nano‐needle structures, grown by hot wall epitaxy (HWE) on monocrystalline mica substrates, were prepared. The current–voltage (I–V) behaviour of gap‐type devices with current parallel and perpendicular to the needle axis was studied. From a space‐charge‐limited current (SCLC) regime in the I–V curves the charge carrier mobility was determined. When measured along the direction of needles, an effective charge carrier mobility as high as 14 cm2/Vs was obtained. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Progress in SWNT based, SAW driven charge pumps
Authors: Siegle Viktor , Ahlers Franz Josef , Roth Siegmar 
Published: October 2006

AbstractThe work presented gives a short overview of existing implementations for single electron pumps. A proposal by Talyanskii et al. [Phys. Rev. Lett. 87, 276802 (2001)] for a single walled carbon nanotube (SWNT) based device is discussed. SWNT is suggested to function as one‐dimensional channel for electrons, which are driven by the surface acoustic wave (SAW). The SAW is created on the surface of a piezoelectric by lithographically defined structures. This work addresses the details in manufacturing such a device. This work investigates the possibilities of growing SWNTs by chemical vapor deposition (CVD) on the surface of LiNbO3, which is known for its excellent piezoelectric properties. The results of this study are reported together with the progress in fabrication of such a device. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)