bluuebunny/crossref_metadata_2025 huggingface dataset:
Averaging in non‐linear advective transport problems
Authors: Heijnekamp J. J. , Krol M. S. , Verhulst F.
Published: November 2005

Advective transport in a tidal basin is modelled by a non‐linear parabolic equation with initial‐boundary values. The model includes small effects such as diffusion, the reststream, reaction effects and sources. For a given periodic flow field, the long‐time behaviour of the solutions is approximated by using the averaging method. We show the existence of a periodic solution and we demonstrate the asymptotic validity of the approximations for all time using maximum principles.
About the concept of measure‐valued solutions to distributed parameter systems
Authors: Roubíček Tomáš , Hoffmann Karl‐Heinz
Published: November 2005

The measure‐valued (mv) solutions are commonly defined in the literature simply by putting Young measures into the respective partial differential equations. Here a few examples of mv‐solutions to evolution problems (conservation laws, fluid dynamics and a so‐called backward‐forward heat problem) are re‐investigated to show that such definitions are not satisfactorily selective, i.e. they admit (sometimes surprisingly) many mv‐solutions apparently without any physical sense. Then an attempt for a selective definition in the case of the backward‐forward heat problem is made, resulting to a certain evolution variational inequality.
On a kinetic model for shallow water waves
Authors: Struckmeier Jens
Published: November 2005

The system of shallow water waves is one of the classical examples for non‐linear, two‐dimensional conservation laws. The paper investigates a simple kinetic equation depending on a parameter ϵ which leads for ϵ → 0 to the system of shallow water waves. The corresponding ‘equilibrium’ distribution function has a compact support which depends on the eigenvalues of the hyperbolic system. It is shown that this kind of kinetic approach is restricted to a special class of non‐linear conservation laws. The kinetic model is used to develop a simple particle method for the numerical solution of shallow water waves. The particle method can be implemented in a straightforward way and produces in test examples sufficiently accurate results.
A new system of boundary integral equations for plates with free edges
Authors: Giroire Jean , Nédélec Jean‐Claude
Published: November 2005

We present a new system of boundary integral equations for the free‐edge plate. This system expresses an abstract symmetric variational problem posed on the boundary of the plate. In order to obtain this abstract problem, we must set the exterior boundary value problem corresponding to the free‐edge plate in a framework of weighted Sobolev spaces. Finally, we take care of the hypersingular kernels appearing in our system of BIEs, by using an abstract technique of integration by parts.
Linear symmetric hyperbolic systems with characteristic boundary
Authors: Secchi Paolo
Published: November 2005

The author studies the mixed problem for the linear symmetric hyperbolic systems with maximally non‐negative and characteristic boundary condition. Existence of a unique solution is proved inside a suitable class of functions of weighted Sobolev type which takes account of the loss of regularity in the normal direction to the characteristic boundary.
Characterization of proteoglycan depletion in articular cartilage using two‐dimensional time domain nuclear magnetic resonance
Authors: Lattanzio Pierre‐Jean , Marshall K. Wayne , Damyanovich Andrei Z. , Peemoeller Hartwig
Published: November 2005

In vitro proteoglycan (PG) depletion in the 20–40% range (enzymatic PG depletion of normal cartilage in the early osteoarthritis (OA) PG depletion range) was investigated in articular cartilage using 2D time domain NMR relaxation techniques. Spin–lattice relaxation times were measured at low fields (T1ρ) and at high fields (T1) using nonselective and selective excitation pulse sequences. The short relaxation time magnetization components in T1ρ (∼8% signal) and nonselective T1 (∼5% signal) experiments were significantly altered with PG degradation. In addition, a magnetization component (∼5% signal) with a “fast ” T1 ∼ 7 ms was observed in the T1 experiment involving selective excitation. This fast T1 was at least 10 times shorter than the short T1 in the nonselective experiment and was associated with a strong magnetization exchange mechanism between collagen and PG. The results suggest that T1ρ and T1 (nonselective and selective) relaxation based MRI techniques, which focus on the short relaxation time magnetization components, have the potential of detecting molecular abnormalities associated with early OA earlier than single, long relaxation time component approaches. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Inducing coordination in supply chains through linear reward schemes
Authors: Golany Boaz , Rothblum Uriel G.
Published: November 2005

Decentralized decision‐making in supply chain management is quite common, and often inevitable, due to the magnitude of the chain, its geographical dispersion, and the number of agents that play a role in it. But, decentralized decision‐making is known to result in inefficient Nash equilibrium outcomes, and optimal outcomes that maximize the sum of the utilities of all agents need not be Nash equilibria. In this paper we demonstrate through several examples of supply chain models how linear reward/penalty schemes can be implemented so that a given optimal solution becomes a Nash equilibrium. The examples represent both vertical and horizontal coordination issues. The techniques we employ build on a general framework for the use of linear reward/penalty schemes to induce stability in given optimal solutions and should be useful to other multi‐agent operations management settings. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006
Numerical calculation of invariant manifolds for maps
Authors: Fuming Ma , Küpper Tassilo
Published: November 2005

Many processes in the sciences and in engineering are modelled by dynamical systems and—in discretized version—by nonlinear maps. To understand the often complicated dynamical behaviour it is a well established tool to use the concept of invariant manifolds of the system. In this way it is often possible to reduce the dimension of the system considerably. In this paper we propose a new method to calculate numerically invariant manifolds near fixed points of maps. We prove convergence of our procedure and provide an error estimation. Finally, the application of the method is illustrated by examples.
On the use of periodicity properties for the efficient numerical solution of certain Markov chains
Authors: Bonhoure François , Dallery Yves , Stewart William J.
Published: November 2005

Markov chains with periodic graphs arise frequently in a wide range of modelling experiments. Application areas range from flexible manufacturing systems in which pallets are treated in a cyclic manner to computer communication networks. The primary goal of this paper is to show how advantage may be taken of this property to reduce the amount of computer memory and computation time needed to compute stationary probability vectors of periodic Markov chains. After reviewing some basic properties of Markov chains whose associated graph is periodic, we introduce a ‘reduced scheme’ in which only a subset of the probability vector need be computed. We consider the effect of the application of both direct and iterative methods to the original Markov chain (permuted to normal periodic form) as well as to the reduced system. We show how the periodicity of the Markov chain may be efficiently computed as the chain itself is being generated. Finally, some numerical experiments to illustrate the theory, are presented.
Improved SSOR and incomplete Cholesky solution of linear equations on shared memory and distributed memory parallel computers
Authors: Joubert Wayne , Oppe Thomas
Published: November 2005

In this paper two new implementations of SSOR and incomplete factorization preconditioners are given, for shared memory and distributed memory parallel computers respectively. These new implementations give increased solution speeds for matrix problems such as those arising from discretized partial differential equations with natural ordering of the grid points, for which it is well‐known that the standard implementation of these preconditioners is difficult to parallelize effectively. For shared memory machines, a new technique is presented here which decreases the number of synchronization points in each preconditioning step and thus allows better parallel speedups. For distributed memory machines, an implementation based on block cyclic reduction is given which circumvents the problem of idle processors during the preconditioning phase. Descriptions of the implementations are given, and numerical comparisons are given for a model diffusion problem on the Cray Y‐MP and the CM‐2 Connection Machine.
ILUT: A dual threshold incomplete LU factorization
Authors: Saad Yousef
Published: November 2005

In this paper we describe an Incomplete LU factorization technique based on a strategy which combines two heuristics. This ILUT factorization extends the usual ILU(O) factorization without using the concept of level of fill‐in. There are two traditional ways of developing incomplete factorization preconditioners. The first uses a symbolic factorization approach in which a level of fill is attributed to each fill‐in element using only the graph of the matrix. Then each fill‐in that is introduced is dropped whenever its level of fill exceeds a certain threshold. The second class of methods consists of techniques derived from modifications of a given direct solver by including a dropoff rule, based on the numerical size of the fill‐ins introduced, traditionally referred to as threshold preconditioners. The first type of approach may not be reliable for indefinite problems, since it does not consider numerical values. The second is often far more expensive than the standard ILU(O). The strategy we propose is a compromise between these two extremes.
On the convergence behavior of the restarted GMRES algorithm for solving nonsymmetric linear systems
Authors: Joubert Wayne
Published: November 2005

The solution of nonsymmetric systems of linear equations continues to be a difficult problem. A main algorithm for solving nonsymmetric problems is restarted GMRES. The algorithm is based on restarting full GMRES every s iterations, for some integer s>0. This paper considers the impact of the restart frequency s on the convergence and work requirements of the method. It is shown that a good choice of this parameter can lead to reduced solution time, while an improper choice may hinder or preclude convergence. An adaptive procedure is also presented for determining automatically when to restart. The results of numerical experiments are presented.
A parallel version of the preconditioned conjugate gradient method for boundary element equations
Authors: Pester Matthias , Rjasanow Sergej
Published: November 2005

The parallel version of precondition techniques is developed for matrices arising from the Galerkin boundary element method for two‐dimensional domains with Dirichlet boundary conditions. Results were obtained for implementations on a transputer network as well as on an nCUBE‐2 parallel computer showing that iterative solution methods are very well suited for a MIMD computer. A comparison of numerical results for iterative and direct solution methods is presented and underlines the superiority of iterative methods for large systems.
On the stability of the incomplete Cholesky decomposition for a singular perturbed problem, where the coefficient matrix is not an M‐matrix
Authors: Sauter Stefan A.
Published: November 2005

The incomplete Cholesky decomposition is known as an excellent smoother in a multigrid iteration and as a preconditioner for the conjugate gradient method. However, the existence of the decomposition is only ensured if the system matrix is an M‐matrix. It is well‐known that finite element methods usually do not lead to M‐matrices. In contrast to this restricting fact, numerical experiments show that, even in cases where the system matrix is not an M‐matrix the behaviour of the incomplete Cholesky decomposition apparently does not depend on the structure of the grid. In this paper the behaviour of the method is investigated theoretically for a model problem, where the M‐matrix condition is violated systematically by a suitable perturbation. It is shown that in this example the stability of the incomplete Cholesky decomposition is independent of the perturbation and that the analysis of the smoothing property can be carried through. This can be considered as a generalization of the results for the so called square‐grid triangulation, as has been established by Wittum in [12] and [11].
Matrix shapes invariant under the symmetric QR algorithm
Authors: Arbenz Peter , Golub Gene H.
Published: November 2005

The QR algorithm is a basic algorithm for computing the eigenvalues of dense matrices. For efficiency reasons it is prerequisite that the algorithm is applied only after the original matrix has been reduced to a matrix of a particular shape, most notably Hessenberg and tridiagonal, which is preserved during the iterative process. In certain circumstances a reduction to another matrix shape may be advantageous. In this paper, we identify which zero patterns of symmetric matrices are preserved under the QR algorithm.
Approximate solutions and eigenvalue bounds from Krylov subspaces
Authors: Paige Chris C. , Parlett Beresford N. , van der Vorst Henk A.
Published: November 2005

Approximations to the solution of a large sparse symmetric system of equations are considered. The conjugate gradient and minimum residual approximations are studied without reference to their computation. Several different bases for the associated Krylov subspace are used, including the usual Lanczos basis. The zeros of the iteration polynomial for the minimum residual approximation (harmonic Ritz values) are characterized in several ways and, in addition, attractive convergence properties are established. The connection of these harmonic Ritz values to Lehmann's optimal intervals for eigenvalues of the original matrix appears to be new.
Trust regions based on conic functions in linear and nonlinear programming
Authors: Nazareth J. L.
Published: November 2005

An optimization method is developed based on ellipsoidal trust regions that are defined by conic functions. It provides a powerful unifying theory from which can be derived a variety of interesting and potentially useful optimization algorithms, in particular, conjugate‐gradient‐like algorithms for nonlinear minimization and Karmarkar‐like interior‐point algorithms for linear programming.
Dynamical analysis of numerical systems
Authors: Batterson Steve
Published: November 2005

For many years techniques from numerical analysis have been applied fruitfully to the study of dynamical systems. In this paper it is shown that the theory of dynamical systems may be applied to certain computational problems. In particular the question of global convergence of various QR algorithms can be reduced to the study of certain vector iterations derived from Schur forms of matrices. The technique is illustrated in determining the convergence behavior of normal Hessenberg matrices under the Francis and multishift QR iterations.
A comparison result for multisplittings and waveform relaxation methods
Authors: Frommer Andreas , Pohl Bert
Published: November 2005

We show that certain multisplitting iterative methods based on overlapping blocks yield faster convergence than corresponding nonoverlapping block iterations, provided the coefficient matrix is an M‐matrix. This result can be used to compare variants of the waveform relaxation algorithm for solving initial value problems. The methods under consideration use the same discretization technique, but are based on multisplittings with different overlaps. Numerical experiments on the Intel iPSC/860 hypercube are included.
The RSCG algorithm on distributed memory architectures
Authors: Freitag Lori , Ortega James
Published: November 2005

In this paper, we demonstrate the scalability of the Reduced System Conjugate Gradient (RSCG) algorithm on distributed memory architectures. We present speed‐up results obtained on the Intel iPSC/860 that compare one‐, two‐, and three‐dimensional decompositions of the domain for both positive definite and positive semidefinite test problems. We develop a model for the RSCG algorithm to analyze computational and communication costs. The model is validated using experimental data and then used to examine and predict behavior of the RSCG algorithm as a function of architecture parameters including communication latency and transmission times and memory access costs.
Some remarks on the Barrier Lemma and 𝒦‐monotonicity
Authors: Marek I.
Published: November 2005

An abstract version of the well known Barrier Lemma is presented and some of its generalizations are shown for bounded linear and some unbounded densely defined linear monotone operators in some partially ordered Banach spaces. 𝒦‐monotonicity of generally unbounded operators is characterized. Some applications of constructing error bounds for approximately solving equations governed by bounded linear operators are established.
Implicit Cholesky algorithms for singular values and vectors of triangular matrices
Authors: Vince Fernando K. , Parlett Beresford N.
Published: November 2005

The implicit Cholesky algorithm has been developed by several authors during the last 10 years but under different names. We identify the algorithm with a special version of Rutishauser's LR algorithm. Intermediate quantities in the transformation furnish several attractive approximations to the smallest singular value.

The paper extols the advantages of using shifts with the algorithm. The nonorthogonal transformations improve accuracy.
Finite element analysis of mixing phenomena in tangential twin‐screw extruders for non‐Newtonian fluids
Authors: Sastrohartono T. , Kwon T. H.
Published: November 2005

A flow analysis of non‐Newtonian fluids inside co‐rotating tangential twin‐screw extruders is presented with the emphasis on mixing phenomena. A new simplified approach was proposed in modelling the flow, i.e. the flow in twin‐screw extruders was considered as a sequence of flows in two regions: (i) the translation region (T‐region), similar to a single‐screw extruder; and (ii) the mixing region (M‐region), representing the central part of twin‐screw extruders. The flow has been assumed to be isothermal, steady‐state and creeping. Furthermore, it was assumed that the velocity field does not change significantly in one co‐ordinate (i.e. the down‐channel direction in the case of the T‐region and the axial direction in the case of the M‐region) as compared with the other co‐ordinate directions. Accordingly, a quasi‐three‐dimensional finite element method has been developed to analyse the flows in both regions. The mixing mechanisms inside the T ‐ and M‐regions were analysed and the inter‐channel mixing in the M‐region was quantified. The residence time distribution and performance characteristic of a single screw with a self‐wiping profile were also calculated.
Progress in mixed Eulerian‐Lagrangian finite element simulation of forming processes
Authors: Huétink J. , Vreede P. T. , van der Lugt J.
Published: November 2005

A review is given of a mixed Eulerian‐Lagrangian finite element method for simulation of forming processes. This method permits incremental adaptation of nodal point locations independently from the actual material displacements. Hence numerical difficulties due to large element distortions, as may occur when the updated Lagrange method is applied, can be avoided. Movement of (free) surfaces can be taken into account by adapting nodal surface points in a way that they remain on the surface. Hardening and other deformation path dependent properties are determined by incremental treatment of convective terms. A local and a weighed global smoothing procedure is introduced in order to avoid numerical instabilities and numerical diffusion. Prediction of contact phenomena such as gap openning and/or closing and sliding with friction is accomplished by a special contact element. The method is demonstrated by simulations of an upsetting process and a wire drawing process.
A method of finite element tearing and interconnecting and its parallel solution algorithm
Authors: Farhat Charbel , Roux Francois‐Xavier
Published: November 2005

A novel domain decomposition approach for the parallel finite element solution of equilibrium equations is presented. The spatial domain is partitioned into a set of totally disconnected subdomains, each assigned to an individual processor. Lagrange multipliers are introduced to enforce compatibility at the interface nodes. In the static case, each floating subdomain induces a local singularity that is resolved in two phases. First, the rigid body modes are eliminated in parallel from each local problem and a direct scheme is applied concurrently to all subdomains in order to recover each partial local solution. Next, the contributions of these modes are related to the Lagrange multipliers through an orthogonality condition. A parallel conjugate projected gradient algorithm is developed for the solution of the coupled system of local rigid modes components and Lagrange multipliers, which completes the solution of the problem. When implemented on local memory multiprocessors, this proposed method of tearing and interconnecting requires less interprocessor communications than the classical method of substructuring. It is also suitable for parallel/vector computers with shared memory. Moreover, unlike parallel direct solvers, it exhibits a degree of parallelism that is not limited by the bandwidth of the finite element system of equations.
Parallel/vector improvements of the frontal method
Authors: Lesoinne M. , Farhat C. , Geradin M.
Published: November 2005

We present, discuss, and report on the performance of two combined parallel/vector frontal algorithms which have been incorporated in a production finite element code. Two parallelization strategies are described. The first approach is algebra driven and is recommended for the solution of problems with a large bandwidth on a coarse grain configuration. The second strategy is targeted for finer grain systems; it blends the first one with a substructuring technique that is based on a careful partitioning of the finite element mesh into a series of subdomains. Using only 4 IBM 3090/VF processors, the proposed algorithms are shown to deliver speed‐ups as high as 17 with respect to a serial non‐vectorized frontal solver.
Solution of large displacement contact problems with friction using Newton's method for generalized equations
Authors: Klarbring Anders , Bjöourkman Gunnar
Published: November 2005

This work is concerned with the formulation and numerical realization of large displacement contact problems with friction. A restricted class of contact problems is treated, where the deformation of one of the contacting bodies is prescribed. The formulation utilizes a particular convected co‐ordinate chart to define, firstly, tangential components for all potential contact points and, secondly, the notion of incremental tangential displacement. By writing the discretized problem as a generalized equation in the sense of Robinson it is made clear how Newton's method may be extended to this kind of non‐differentiable problems. The proposed algorithm is verified by several numerical examples.
Cellular automata simulation of flow around chains of cylinders
Authors: Eissler Werner , Drtina Peter , Frohn Arnold
Published: November 2005

The simulation of flows around single cylinders, tandem cylinders and infinite chains of cylinders with the lattice gas method is presented. The effects of the ratio of the cylinder diameter to channel width and different outflow boundary conditions are discussed. Results obtained applying different lattice gas models are given. Drag coefficient, wake length and Strouhal number are compared with experimental data. The agreement between numerical and experimental results is satisfactory.
A stabilized 9‐node non‐linear shell element
Authors: Kebari H. , Cassell A. C.
Published: November 2005

A non‐linear 9‐node stress resultant shell finite element with six degrees of freedom per node is formulated. The material non‐linearity is based on an implicit integration scheme using the von Mises yield criterion and linear isotropic bardening. The small strain geometric non‐linearity is formulated using the polar decomposition theorem of continuum mechanics via a corotational updated Lagrangian method, which represents finite rotations with accuracy. Reduced integration is used to remove locking and calculate the stresses at their optimal stress accuracy points. A practical procedure is employed to stabilize the troublesome spurious zero energy modes. A number of tests covering the non‐linear material and geometry ranges and buckling show the good performance of the new element.
Genuinely resultant shell finite elements accounting for geometric and material non‐linearity
Authors: Chróścielewski J. , Makowski J. , Stumpf H.
Published: November 2005

A general theoretical framework is presented for the fully non‐linear analysis of shells by the finite element method. The governing equations are derived exclusively in terms of resulting quantities through a logical and straightforward descent from three‐dimensional continuum mechanics without appealing to simplifying assumptions (hence the name genuinely resultant). As a result, the underlying theory is statically and geometrically exact, and it naturally includes small strain and finite strain problems of thin as well as thick shells. The underlying mathematical structure and the variational formulation of the theory are examined. This appears to be crucial for the development of computational procedures employing the Newton‐Kantorovich linearization process and the Galerkin type discretization method. The treatment of finite rotations through an arbitrary parametrization of the rotation group and the interpolation procedure of SO(3)‐valued functions underlying the construction of finite element basis are other issues studied in this paper. A numerical analysis is presented in order to assess the effectiveness of the proposed formulation. Small strain problems as well as finite strain deformation of rubber‐like shells undergoing finite rotations are considered. Special attention is devoted to the assessment of the relevance of the drilling degree‐of‐freedom and highly non‐uniform through‐the‐thickness deformation in the case of shells made of incompressible material.
Design and Optimization of airfoils in non‐stalling incompressible flow with a prescribed range of the angle of attack
Authors: Elizarov A. M. , Fokin D. A.
Published: November 2005

A simple and reliable method of aerodynamic design of airfoils is proposed for a given range of the angle of attack. The method is based on the solution of a new inverse boundary‐value problem of aerohydrodynamics. In the problem the initial velocity distributions are given along the contour of the required airfoil as a function of the are co‐ordinate for extreme values of the angle of attack from a fixed range. We justify a method of choice of these distributions which guarantees a non‐stalling flow around the airfoil. The problem of airfoil optimization is also considered. Results of numerical calculations are presented.
Diffusion problems using transient discrete source superposition
Authors: Walker S. P.
Published: November 2005

Discrete source superposition techniques seek sets of discrete, singular source strengths which satisfy the boundary conditions of a particular problem, and, necessarily, the governing differential equation. The sum of the fields produced by such sources thus provides an approximation to the required solution. In many respects these techniques are a special case of conventional boundary integral equation methods, where density distributions of smeared sources are sought. In this paper an attempt is made to extend the discrete source superposition technique to transient problems. The example addressed is the transient diffusion equation. The method developed does seem to have sòme promise. It is found that even coarse spatial discretization can yield quite accurate results, and that surprisingly large timesteps can be employed and accuracy maintained. Further, although no direct comparisons are made, the absence of spatial integrations indicates that the computational effort per timestep is likely to be less than for conventional BIE.
Noncovalent synthesis of supramolecular dendritic architectures in water
Authors: Broeren Maarten A. C. , Linhardt Jeffrey G. , Malda Hinke , de Waal Bas F. M. , Versteegen Ron M. , Meijer Joris T. , Löwik Dennis W. P. M. , van Hest Jan C. M. , van Genderen Marcel H. P. , Meijer E. W.
Published: November 2005

Water‐soluble guest–host complexes are prepared in a two‐step process. For this a new, polydisperse ethylene glycol containing guest molecule is synthesized that is soluble in both chloroform and water. This guest is able to bind to urea–adamantyl‐modified poly(propylene imine) dendrimers in chloroform in a noncovalent manner. When the chloroform is slowly evaporated and D2O is added, the hydrophobic dendrimer is solubilized in water. This is not possible when the hydrophobic dendrimer is directly added to the hydrophilic guests in water. When the unmodified poly(ethylene glycol) starting material is used, no solubilization occurs, and this indicates that the urea–acetic acid head group is necessary to solubilize the dendrimer. Approximately 26 guests are required for solubilization of the dendrimer. A lower number of guests results in aggregation and precipitation of the dendrimer. A monodisperse guest molecule has been used in NMR studies to show that the guest molecule binds with its acidic head group to the periphery of the dendrimer. This methodology opens the way to functional dendrimer aggregates in aqueous media. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6431–6437, 2005
Synthesis, polymerization, and effects on the flame retardancy of boron‐containing styrenic monomers
Authors: Martín C. , Hunt B. J. , Ebdon J. R. , Ronda J. C. , Cádiz V.
Published: November 2005

A boron‐containing styrenic monomer, 5‐benzyl‐2‐phenyl‐5‐(4‐vinylbenzyl)‐[1,3,2]‐dioxaborinane, was synthesized to study the influence of boron on the properties of the homopolymer and copolymer with styrene. A similar monomer without boron was also prepared and polymerized so that the properties of its polymer could be compared with the aforementioned boron‐containing polymers. These monomers were characterized by elemental analysis, mass spectrometry, Fourier transform infrared, and 1H and 13C NMR. The thermal degradation of boron‐containing styrenic polymers was studied by means of Fourier transform infrared, which showed the presence of boric acid as char. The flame‐retardant effect was assessed by the measurement of the limiting oxygen indices and char yields during heating in nitrogen and air. The boron‐containing polymers had higher limiting oxygen indices and gave greater yields of char than those without boron. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem43: 6419–6430, 2005
Reactions of Me2Si(2‐Me‐4,5‐BenzInd)Zr(Cl)(NEt2) and Me2Si(2‐Me‐4,5‐BenzInd)ZrCl2 (BenzInd = benzindenyl) with trimethylaluminum and methylaluminumoxane: Correlation of spectroscopy and propene polymerizations
Authors: Seraidaris Tanja , Löfgren Barbro , Helaja Tuulamari , Vanne Tiina , Mäkelä‐Vaarne Nora
Published: November 2005

The activity of metallocene/methylaluminumoxane (MAO) catalysts in olefin polymerization is highly dependent on both the alkylation and activation of the complexes. The leaving ligands have an important role in the complex activation, influencing the activity of the system. The aim of this work was to study the reactions of complexes Me2Si(2‐Me‐4,5‐BenzInd)2ZrCl2 (A; BenzInd = benzindenyl) and Me2Si(2‐Me‐4,5‐BenzInd)2Zr(Cl)(NEt2) (B) with trimethylaluminum (TMA) and MAO. The reaction kinetics and products were studied by both ultraviolet–visible and NMR spectroscopy. In addition, the polymerization behavior of the different species was investigated in propene polymerizations. Complex B was more easily monomethylated by TMA than complex A and resulted in L2Zr(Me)(NR2)‐type species. Monomethylation of the complexes before polymerization enhanced the polymerization activity of both complexes. When complexes A and B reacted with MAO, similar cationic species were formed, giving equal polymerization activities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6455–6464, 2005
Polymerization of n‐hexyl isocyanate with CpTiCl2(OR) (R = functional group or macromolecular chain): A route to ω‐functionalized and block copolymers and terpolymers of n‐hexyl isocyanate
Authors: Mourmouris Stylianos , Kostakis Konstantinos , Pitsikalis Marinos , Hadjichristidis Nikos
Published: November 2005

Well‐defined ω‐cholesteryl poly(n‐hexyl isocyanate) (PHIC–Chol), as well as diblock copolymers of n‐hexyl isocyanate (HIC) with styrene, PS‐b‐PHIC [PS = polystyrene; PHIC = poly(n‐hexyl isocyanate)], and triblock terpolymers with styrene and isoprene, PS‐b‐PI‐b‐PHIC and PI‐b‐PS‐b‐PHIC (PI = polyisoprene), were synthesized with CpTiCl2(OR) (R = cholesteryl group, PS, or PS‐b‐PI) complexes. The synthetic strategy involved the reaction of the precursor complex CpTiCl3 with cholesterol or the suitable ω‐hydroxy homopolymer or block copolymer, followed by the polymerization of HIC. The ω‐hydroxy polymers were prepared by the anionic polymerization of the corresponding monomers and the reaction of the living chains with ethylene oxide. The reaction sequence was monitored by size exclusion chromatography, and the final products were characterized by size exclusion chromatography (light scattering and refractive‐index detectors), nuclear magnetic resonance spectroscopy, and, in the case of PHIC–Chol, differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6503–6514, 2005
Relation between thermal conductivity and molecular alignment direction of free‐standing film aligned with rubbing method
Authors: Kato Takashi , Nagahara Takatoshi , Agari Yasuyuki , Ochi Mitsukazu
Published: November 2005

The liquid crystal acryl compounds, in which the molecular directions were aligned by the rubbing method, were polymerized by UV irradiation, to provide the free‐standing aligned films of 200‐μm thickness. The relation between the thermal conductivity and the aligned molecular direction of the films was investigated. The homogeneous film showed the largest magnitude of the thermal conductivity at the direction along the molecular long axis (0.69 W/m K). This was 3.6 times greater than that of poly(methyl methacrylate). The thermal conductivity was dependent on the rotation angle and the concentration of the homogeneous molecular long axis fractions in the networks. These relations were investigated with the twisted film. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3591–3599, 2005
Compatibilization level effects on the structure and mechanical properties of rubber‐modified polyamide‐6/clay nanocomposites
Authors: González I. , Eguiazábal J. I. , Nazábal J.
Published: November 2005

Exfoliated polyamide‐6 (PA6)/organically modified montmorillonite clay (OMMT) nanocomposites (PNs) were modified with partially maleinized styrene–ethylene/butadiene–styrene triblock copolymers (SEBS) at three maleinization levels in an attempt to link in these materials high toughness with appropriate small‐strain and fracture tensile properties. OMMT stayed only in the PA6 matrix, and no preferential location in the matrix/rubber interphase was observed. The increased dispersed phase size upon the addition of OMMT was attributed to interactions between maleic anhydride (MA) functionalized SEBS and the surfactant of OMMT. The rubber particle size generally decreased when the MA content of SEBS increased, and this indicated compatibilization. The subsequent good adhesion led to tough nanocomposites across a wide range of both strain rates and fracture modes. As the critical interparticle distance (τc) decreased with the MA content, and the other parameters that could influence the surface‐to‐surface mean interparticle distance did not change, it is proposed that in these PNs higher adhesion leads to a smaller τc value. Finally, the presence in the matrix of a nanostructured clay makes the rubber content necessary for the toughness jump to increase and τc to decrease. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3611–3620, 2005
Atomic branching in molecules
Authors: Estrada Ernesto , Rodríguez‐Velázquez Juan A. , Randić Milan
Published: November 2005

A graph theoretic measure of extended atomic branching is defined that accounts for the effects of all atoms in the molecule, giving higher weight to the nearest neighbors. It is based on the counting of all substructures in which an atom takes part in a molecule. We prove a theorem that permits the exact calculation of this measure based on the eigenvalues and eigenvectors of the adjacency matrix of the graph representing a molecule. The definition of this measure within the context of the Hückel molecular orbital (HMO) and its calculation for benzenoid hydrocarbons are also studied. We show that the extended atomic branching can be defined using any real symmetric matrix, as well as any Hermitian (self‐adjoint) matrix, which permits its calculation in topological, geometrical, and quantum chemical contexts. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Reactivity of acetonyl anion with nitroaromatics: an atmospheric pressure chemical ionization study
Authors: Song Yishu , Chen Hao , Cooks R. Graham
Published: November 2005

Nucleophilic attack by the acetonyl anion (CH3COCH) on highly electron‐deficient nitroaromatics such as trinitrotoluene (TNT) results in the carbon‐bonded anionic σ‐complexes (Meisenheimer complexes). The complexes are generated at atmospheric pressure with relatively low internal energy and do not dissociate under atmospheric pressure chemical ionization conditions, but can be dissociated upon collisional activation to produce characteristic nitrobenzyl‐substituted acetonyl anions via elimination of HNO2. Further fragmentation produces deprotonated nitrotoluene anions through the loss of CH2CO, while loss of CH2COCH3 and CH3COCH3 yields nitroaromatic molecular anions and their H‐loss counterparts. Hydrogen/deuterium (H/D) scrambling is observed in the fragmentation products of the [TNT · CD3COCD2]− complex to extents which vary for different fragmentation pathways. Selective Meisenheimer complex formation, together with its distinctive fragmentation pattern, supplies a highly discriminatory method for detection of TNT and related compounds. Copyright © 2005 John Wiley & Sons, Ltd.
Method for the elucidation of the elemental composition of low molecular mass chemicals using exact masses of product ions and neutral losses: application to environmental chemicals measured by liquid chromatography with hybrid quadrupole/time‐of‐flight mass spectrometry
Authors: Suzuki Shigeru , Ishii Tetsuko , Yasuhara Akio , Sakai Shinichi
Published: November 2005

A method for elucidating the elemental compositions of low molecular weight chemicals, based primarily on mass measurements made using liquid chromatography (LC) with time‐of‐flight mass spectrometry (TOFMS) and quadrupole/time‐of‐flight mass spectrometry (LC/QTOFMS), was developed and tested for 113 chemicals of environmental interest with molecular masses up to ∼400 Da. As the algorithm incorporating the method is not affected by differences in the instrument used, or by the ionization method and other ionization conditions, the method is useful not only for LC/TOFMS, but also for all kinds of mass spectra measured with higher accuracy and precision (uncertainties of a few mDa) employing all ionization methods and on‐line separation techniques. The method involves calculating candidate compositions for intact ionized molecules (ionized forms of the sample molecule that have lost or gained no more than a proton, i.e., [M+H]+ or [M–H]−) as well as for fragment ions and corresponding neutral losses, and eliminating those atomic compositions for the molecules that are inconsistent with the corresponding candidate compositions of fragment ions and neutral losses. Candidate compositions were calculated for the measured masses of the intact ionized molecules and of the fragment ions and corresponding neutral losses, using mass uncertainties of 2 and 5 mDa, respectively. Compositions proposed for the ionized molecule that did not correspond to the sum of the compositions of a candidate fragment ion and its corresponding neutral loss were discarded. One, 2–5, 6–10, 11–20, and >20 candidate compositions were found for 65%, 39%, 1%, 1%, and 0%, respectively, for the 124 ionized molecules formed from the 113 chemicals tested (both positive and negative ions were obtained from 11 of the chemicals). However, no candidate composition was found for 2% of the test cases (i.e., 3 chemicals), for each of which the measured mass of one of the product ions was in error by 5–6.7 mDa. Copyright © 2005 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization mass spectrometry of taxanes
Authors: Armirotti Andrea , Benatti Umberto , Miele Mariangela , Damonte Gianluca
Published: November 2005

Taxanes are biologically active compounds that have been extensively used in pharmacology for their powerful anticancer properties. High specificity and low level sensitivity for analysis of these compounds have been obtained with reversed‐phase high‐pressure liquid chromatography/mass spectrometry (RP‐HPLC/MS), but the number of applications of matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) for low molecular weight analytes is rapidly growing. A new MALDI‐MS approach for the rapid screening of a variety of taxanes and a tandem mass spectrometric (MS/MS) analysis of the most important and diagnostic taxane fragmentation pathways are proposed. A solid‐phase extraction method followed by preliminary quantification is also reported. Copyright © 2005 John Wiley & Sons, Ltd.
Evolution in software systems: foundations of the SPE classification scheme
Authors: Cook Stephen , Harrison Rachel , Lehman Meir M. , Wernick Paul
Published: November 2005

The SPE taxonomy of evolving software systems, first proposed by Lehman in 1980, is re‐examined in this work. The primary concepts of software evolution are related to generic theories of evolution, particularly Dawkins' concept of a replicator, to the hermeneutic tradition in philosophy and to Kuhn's concept of paradigm. These concepts provide the foundations that are needed for understanding the phenomenon of software evolution and for refining the definitions of the SPE categories. In particular, this work argues that a software system should be defined as of type P if its controlling stakeholders have made a strategic decision that the system must comply with a single paradigm in its representation of domain knowledge. The proposed refinement of SPE is expected to provide a more productive basis for developing testable hypotheses and models about possible differences in the evolution of E‐ and P‐type systems than is provided by the original scheme. Copyright © 2005 John Wiley & Sons, Ltd.
Use of the Vacuum Extractor by Midwives—What Has Changed in the Last Decade?
Authors: Clark P. Annie
Published: November 2005

This article provides an update on use of vacuum extraction by certified nurse‐midwives (CNMs) and certified midwives (CMs). Research findings from the last decade relevant to the training and use of vacuum extractors are reviewed along with professional guidelines and legal implications.
The National Practitioner Data Bank: Information for and About Midwifery
Authors: Jevitt Cecilia , Schuiling Kerri Durnell , Summers Lisa
Published: November 2005

The National Practitioner Data Bank (NPDB), mandated by federal legislation in 1986, serves as a mechanism to protect the public from unsafe practitioners who attempt to avoid discovery of prior negligent behavior or malpractice record(s) by moving from state to state. Reporting to the NPDB about malpractice payments on behalf of nurse‐midwives began in 1990. Reporting of providers excluded from Medicare and Medicaid program participation began in September 1999. Practitioners who were already in an excluded status at that time were reported. Reports of adverse action against a nurse‐midwife can be submitted to the NPDB by a state licensure board, a governmental agency, hospitals, health maintenance organizations, or other health care organizations. Reporting of licensing actions and clinical privilege actions are not required, although these may be voluntarily reported. The NPDB received 484 reports about nurse‐midwives from September 1, 1999, to March 31, 2005. Of the 484 reports, 375 have an obstetric malpractice code. The median claim payment made on behalf of nurse‐midwives during this period is $225,000. Although limited, the NPDB is the only systematic national source of nurse‐midwifery malpractice data collection.
Majority Norms, Multiculturalism, and Gender Equality
Authors: SONG SARAH
Published: November 2005

Although many scholars have discussed the conflict that can arise between multiculturalism and gender equality, both critics and defenders of multiculturalism have largely overlooked a variety of interactive dynamics between majority and minority cultures that have important implications for the theory and practice of multiculturalism. Examining cases in the U.S. context, this essay argues for an interactive view of the dilemmas of gender and culture that is attentive to interconnections between majority and minority cultures. What is of particular concern for debates on multiculturalism is that the mainstream legal and normative frameworks within which minority claims for accommodation are evaluated have themselves been informed by patriarchal norms, which in turn have offered support for gender hierarchies within minority cultures. The interactive view defended here suggests the need to scrutinize both minority and majority norms and practices in evaluating the claims of minority cultures.
Using Geographic Information Systems to Study Interstate Competition
Authors: BERRY WILLIAM D. , BAYBECK BRADY
Published: November 2005

Scholars have proposed two distinct explanations for why policies diffuse across American states: (1) policymakers learn by observing the experiences of nearby states, and (2) states seek a competitive economic advantage over other states. The most common empirical approach for studying interstate influence is modeling an indicator of a state's policy choice as a function of its neighbors' policies, with each neighbor weighted equally. This can appropriately specify one form of learning model, but it does not adequately test for interstate competition: when a policy diffuses due to competition, states' responses to other states vary depending on the size and location of specific populations. We illustrate with two substantive applications how geographic information systems (GIS) can be used to test for interstate competition. We find that lottery adoptions diffuse due to competition—rather than to learning—but find no evidence of competition in state choices about welfare benefits. Our empirical approach can also be applied to competition among nations and local jurisdictions.