bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic oxygen‐enhanced MRI reflects diffusing capacity of the lung
Authors: Ohno Yoshiharu , Hatabu Hiroto , Takenaka Daisuke , Van Cauteren Marc , Fujii Masahiko , Sugimura Kazuro
Published: October 2002

The purpose of this study was to demonstrate the feasibility of dynamic oxygen‐enhanced MRI in a clinical setting. We hypothesized that dynamic oxygen enhancement can reflect the regional diffusing capacity of the lung. Ten patients with pulmonary emphysema and seven healthy volunteers were examined with a respiratory‐synchronized inversion recovery single‐shot turbo spin‐echo sequence (TR = 3200–5000 ms, TE = 16 ms, TI = 720 ms, ETS = 4 ms) following 100% oxygen inhalation, using a 1.5 T whole‐body scanner. Maximum mean relative enhancement ratios calculated by averaging six defined regions of interest (ROIs) in both lungs were statistically compared between healthy volunteers and patients, and were correlated with diffusing lung capacity (%DLCO). In patients with pulmonary emphysema, maximum mean relative enhancement ratios were significantly decreased compared to those in healthy volunteers (P = 0.0008). Maximum mean relative enhancement ratio had excellent correlation with % DLC0 (r2 = 0.83). Dynamic oxygen‐enhanced MRI may reflect the diffusing capacity of the lung; therefore, imaging of oxygen enhancement with MRI may provide maps of the diffusing capacity. Magn Reson Med 47:1139–1144, 2002. © 2002 Wiley‐Liss, Inc.
Reconstruction of MR images from data acquired on an arbitrary k‐space trajectory using the same‐image weight
Authors: Qian Yongxian , Lin Jiarui , Jin Deqin
Published: October 2002

A sampling density compensation function denoted “same‐image (SI) weight” is proposed to reconstruct MR images from the data acquired on an arbitrary k‐space trajectory. An equation for the SI weight is established on the SI criterion and an iterative scheme is developed to find the weight. The SI weight is then used to reconstruct images from the data calculated on a random trajectory in a numerical phantom case and from the data acquired on interleaved spirals in an in vivo experiment, respectively. In addition, Pipe and Menon's weight (MRM 1999;41:179–186) is also used in the reconstructions to make a comparison. The images obtained with the SI weight were found to be slightly more accurate than those obtained with Pipe's weight. Magn Reson Med 48:306–311, 2002. © 2002 Wiley‐Liss, Inc.
Neuromuscular diseases and disorders of the alimentary system
Authors: Chaudhry Vinay , Umapathi T. , Ravich William J.
Published: October 2002

This review outlines the relationship and interaction between neuromuscular diseases and disorders of the alimentary system. Neuromuscular manifestations of gastrointestinal and hepatobiliary diseases are first considered. Such diseases may cause neuromuscular disorders by leading to nutritional deficiency or by more direct mechanisms. The pathogenesis, clinical features, and treatment of these various neuromuscular manifestations are discussed. The impact of disorders of nerve, neuromuscular transmission, and muscle on the alimentary system is then reviewed. The main sequelae are impaired deglutition and gastrointestinal dysmotility. The management of these complications is considered. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
Severe exacerbation of hepatitis C–associated vasculitic neuropathy following treatment with interferon alpha: A case report and literature review
Authors: Boonyapisit Kanokwan , Katirji Bashar
Published: October 2002

Vasculitic neuropathy may occur in association with chronic hepatitis C infection. Interferon alpha (IFNα), an effective treatment for chronic hepatitis C, can precipitate or worsen autoimmune diseases. We report a patient with chronic hepatitis C and mild indolent vasculitic sensorimotor peripheral polyneuropathy, who developed severe mononeuropathy multiplex soon after IFNα was initiated, and review the literature on worsening vasculitic neuropathy after IFNα treatment for chronic hepatitis C. Care should be taken after starting patient with chronic hepatitis C–associated vasculitic neuropathy on IFNα, as there is evidence that IFNα may exacerbate the neuropathy. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
Severe sensory ataxia and demyelinating polyneuropathy with IgM anti‐GM2 and GalNAc‐GD1A antibodies
Authors: Lopate Glenn , Choksi Rati , Pestronk Alan
Published: October 2002

Several polyneuropathy syndromes have been described with polyclonal serum immunoglobulin G (IgG) or immunoglobulin M (IgM) binding to gangliosides GM2 and GalNAc‐GD1a that contain the terminal trisaccharide moiety GalNAc(β1‐4)Gal(α2‐3)NeuAc. We describe the clinical and electrodiagnostic features in two patients with serum IgM monoclonal anti‐GM2 and anti‐GalNAc‐GD1a antibodies. These patients had slowly progressive, panmodal sensory loss with severe sensory ataxia. Electrodiagnostic testing showed demyelinating features. Prominent improvement in gait ataxia occurred after treatment with human immune globulin but not after other immunomodulating therapies. Enzyme‐linked immunoabsorbent assay and thin‐layer chromatography demonstrate that the patient's serum monoclonal IgM bound to gangliosides GM2 and GalNac‐GD1a but not to gangliosides without the GalNAc(β1‐4)Gal(α2‐3)NeuAc moiety. This neuropathy differs from previously reported neuropathy syndromes associated with polyclonal GM2 and GalNAc‐GD1a antibodies and from other chronic demyelinating polyneuropathies. We conclude that a distinct syndrome of chronic demyelinating neuropathy with sensory ataxia, unresponsive to corticosteroids, is associated with monoclonal IgM binding to gangliosides with a terminal GalNAc(β1‐4)Gal(α2‐3)NeuAc trisaccharide moiety. Diagnosis of this syndrome is important to direct appropriate treatment. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002
IGF‐I, IGF‐II, and IGF‐receptor‐1 transcript and IGF‐II protein expression in myostatin knockout mice tissues
Authors: Kocamis Hakan , Gahr Scott A. , Batelli Lori , Hubbs Ann F. , Killefer John
Published: October 2002

Semiquantitative reverse transcriptase–polymerase chain reaction (RT‐PCR) and immunohistochemistry were performed to demonstrate whether a correlation exists between insulin‐like growth factors (IGFs)—positive regulators of growth—and myostatin, a negative regulator of muscle growth. IGF‐I, ‐II, and IGF–receptor‐1 (IGF‐R1) mRNA and IGF‐II protein expressions were determined in control and myostatin knockout mice tissues. IGF‐I gene expressions were similar between control and knockout mice tissues, whereas IGF‐II mRNA levels were significantly higher in myostatin knockout mice kidney and soleus muscles than those of control mice (P < .01). IGF‐R1 mRNA levels from control mice heart (P < .05) and kidney (P < .01) were significantly higher than in myostatin knockout mice, whereas levels were lower in pectoralis muscle of control mice than knockout mice (P < .01). The strongly IGF‐II–positive cells in soleus muscle were more common in myostatin knockout mice and were seen in a few foci in control mice. IGF–II immunoreactivity in both control and myostatin knockout mice kidneys was localized to the epithelium of renal tubules and collecting ducts. Reciprocal changes in the expression of myostatin and IGF‐II and IGF‐R1 may underlie normal growth of skeletal muscle and other organs in mammals, and the changes in these tissues associated with disease. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 55–63, 2002
Improvement of dy/dy dystrophic diaphragm by 3,4‐diaminopyridine
Authors: Van Lunteren Erik , Moyer Michelle
Published: October 2002

Concerns have been raised that inotropic agents may worsen function of dystrophic muscle due to structural fragility. Studies tested the hypothesis that force increments elicited by potassium (K+) channel blockade can be maintained during the course of repetitive stimulation. In vitro twitch force of dy/dy dystrophic mouse diaphragm was significantly lower than normal (796 versus 1271 g/cm2). 3,4‐Diaminopyridine (DAP) increased twitch force of dystrophic diaphragm by 111 ± 12% (P < .0001) and increased force at stimulation frequencies of 5–50 Hz by 41–77%. During fatigue‐inducing stimulation, force augmentation by DAP was well maintained in dystrophic muscle throughout 25 Hz (P = .0047) and 50 Hz (P = .0059) stimulation. These findings indicate that the K+ channel blocker DAP augments the force of dystrophic muscle to values close to that of normal muscle over a range of stimulation frequencies. Furthermore, these functional increments can be achieved without causing force to eventually deteriorate below that of untreated dystrophic muscle during fatiguing stimulation. It is possible that DAP may be useful for the clinical management of a variety of disorders causing muscle weakness. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 71–78, 2002
Diagnostic accuracy of electrodiagnostic testing in the evaluation of weakness
Authors: Nardin Rachel A. , Rutkove Seward B. , Raynor Elizabeth M.
Published: October 2002

Electrodiagnostic testing is often used in the evaluation of patients presenting with weakness, but the diagnostic accuracy of the test in this setting is unknown. We prospectively identified 100 patients presenting to our electromyography (EMG) laboratory with the chief complaint of weakness, and compared their referring diagnosis with the electrophysiological diagnosis reached after electrodiagnostic testing. We reviewed each patient's medical record 9 months after EMG to yield a final diagnosis. Electrodiagnostic testing led to a single diagnosis in 79% of the cases; in 31%, this diagnosis was unsuspected by the referring clinician. Adequate follow‐up was available for 79% of the patients. The electrodiagnostic testing resulted in a single, correct diagnosis in 73% of the patients and provided more than one possible diagnosis, one of which was correct, in an additional 18%, for an overall diagnostic accuracy of 91% in this group of patients presenting with weakness. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 201–205, 2002
Robust ship scheduling with multiple time windows
Authors: Christiansen Marielle , Fagerholt Kjetil
Published: October 2002

We present a ship scheduling problem concerned with the pickup and delivery of bulk cargoes within given time windows. As the ports are closed for service at night and during weekends, the wide time windows can be regarded as multiple time windows. Another issue is that the loading/discharging times of cargoes may take several days. This means that a ship will stay idle much of the time in port, and the total time at port will depend on the ship's arrival time. Ship scheduling is associated with uncertainty due to bad weather at sea and unpredictable service times in ports. Our objective is to make robust schedules that are less likely to result in ships staying idle in ports during the weekend, and impose penalty costs for arrivals at risky times (i.e., close to weekends). A set partitioning approach is proposed to solve the problem. The columns correspond to feasible ship schedules that are found a priori. They are generated taking the uncertainty and multiple time windows into account. The computational results show that we can increase the robustness of the schedules at the sacrifice of increased transportation costs. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 611–625, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10033
Recovery of song preferences after excitotoxic HVC lesion in female canaries
Authors: Halle F. , Gahr M. , Pieneman A. W. , Kreutzer M.
Published: October 2002

The courtship solicitation display (CSD) of the female canary is a model to study estrogen dependent auditory preferences for male songs. The forebrain auditory‐vocal nucleus, HVC, is part of the circuit that determines such preferences. To further develop this model we show that bilateral excitotoxic lesions of the medial part of HVC involving between 18–60% of the bilateral nucleus are behaviorally effective while complete unilateral lesions are not. Further, we show that animals recover their song preferences over a period of several months after the lesion. This functional recovery does not involve anatomical recovery of the HVC. Even 9 months after the lesion, the HVC size of these females was similar to that of females sacrificed 2 days after the lesion and thus was 40 ± 8% smaller compared to normal females. Further, ipsilaterally, the lesion procedure transiently disturbed the neurochemistry, such as GAD‐mRNA expression, in the part of HVC that did not undergo cell death. These results suggest that the integrity of the lateral part of at least one HVC is required to perform CSD in response to relevant auditory stimuli. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 1–13, 2002
On the equivalence of the time domain differential quadrature method and the dissipative Runge–Kutta collocation method
Authors: Fung T. C.
Published: October 2002

Numerical solutions for initial value problems can be evaluated accurately and efficiently by the differential quadrature method. Unconditionally stable higher order accurate time step integration algorithms can be constructed systematically from this framework. It has been observed that highly accurate numerical results can also be obtained for non‐linear problems. In this paper, it is shown that the algorithms are in fact related to the well‐established implicit Runge–Kutta methods. Through this relation, new implicit Runge–Kutta methods with controllable numerical dissipation are derived. Among them, the non‐dissipative and asymptotically annihilating algorithms correspond to the Gauss methods and the Radau IIA methods, respectively. Other dissipative algorithms between these two extreme cases are shown to be B‐stable (or algebraically stable) as well and the order of accuracy is the same as the corresponding Radau IIA method. Through the equivalence, it can be inferred that the differential quadrature method also enjoys the same stability and accuracy properties. Copyright © 2001 John Wiley & Sons, Ltd.
Polynomial approximation of shape function gradients from element geometries
Authors: Dohrmann C. R. , Rashid M. M.
Published: October 2002

A method is presented for the polynomial approximation of shape function gradients based solely on the geometry of finite element boundaries. The method is founded on a least squares approach which leads to an integration scheme satisfying a necessary condition for convergence. In its simplest form the method reduces to the well‐known uniform strain approach for finite elements. The method is applicable to a broad class of problems such as connecting dissimilar meshes, mesh adaptivity and transitioning, and the construction of finite elements with variable topologies. Finite elements based on the polynomial approximations are shown to pass patch tests of various orders. In contrast to standard elements, higher‐order patch tests are passed without the need for nodes internal to element boundaries. Less sensitivity to volumetric locking under plane strain conditions is demonstrated through comparisons with a standard element formulation. Copyright © 2001 John Wiley & Sons, Ltd.
Finite element buckling analysis of rotationally periodic laminated composite shells
Authors: Xiang Zhihai , Xue Mingde , Liu Yinghua , Cen Zhangzhi
Published: October 2002

A finite element (FE) buckling analysis of rotationally periodic laminated composite shells is performed in this paper. Because the buckling mode of such structures is characterized as rotationally periodic, a corresponding FE buckling analysis scheme is proposed to reduce the computational expenses. Moreover, a new kind of relative degrees‐of‐freedom element is developed, which can be connected to other solid elements with ease and can yield satisfactory results with a relatively coarse FE mesh. Numerical results of two laminated cylindrical shells subjected to lateral pressure are compared with theoretical ones. The good agreement of them shows the validity of this new computational strategy. Finally, a practical structure is analysed to demonstrate the advantage of this method. Copyright © 2001 John Wiley & Sons, Ltd.
Numerical simulation of Lamb wave scattering in semi‐infinite plates
Authors: Galán José M. , Abascal Ramón
Published: October 2002

A finite element formulation is applied to study Lamb wave scattering in homogeneous and sandwich isotropic plates. Dispersion curves are calculated in a simple and automatic way by solving a quadratic eigenproblem. A meshing criterion to obtain accurate results with linear and quadratic elements is provided. An absorbing boundary condition for semi‐infinite plates is derived from this formulation by means of a truncated normal mode expansion technique, where the finite element eigenvectors are used instead of the analytical expressions for the normal modes. This non‐reflecting boundary condition is directly applicable to study Lamb wave reflection by simple obstacles such as a flat edge. In order to tackle Lamb wave diffraction problems by defects with more complex geometries, a hybrid boundary element‐finite element formulation is developed. The validity and accuracy of both formulations are checked thoroughly with a series of test problems studied by other researchers. Copyright © 2001 John Wiley & Sons, Ltd.
Higher‐order responses of three‐dimensional elastic plate structures and their numerical illustration by p‐FEM
Authors: Dauge Monique , Rössle Andreas , Yosibash Zohar
Published: October 2002

The displacements of three‐dimensional linearly elastic plate domains can be expanded as a compound power‐series asymptotics, when the thickness parameter ε tends to zero. The leading term u0 in this expansion is the well‐known Kirchhoff–Love displacement field, which is the solution to the limit case when ε→0. Herein, we focus our discussion on plate domains with either clamped or free lateral boundary conditions, and characterize the loading conditions for which the leading term vanishes. In these situations the first non‐zero term uk in the expansion appears for k=2, 3 or 4 and is denoted as higher‐order response of order 2,3 or 4, respectively. We provide herein explicit loading conditions under which higher order responses in three‐dimensional plate structures are visible, and demonstrate the mathematical analysis by numerical simulation using the p‐version finite element method. Owing to the need for highly accurate results and ‘needle elements’ (having extremely large aspect ratio up to 10000), a p‐version finite element analysis is mandatory for obtaining reliable and highly accurate results. Copyright © 2001 John Wiley & Sons, Ltd.
Tetrahedral mesh improvement via optimization of the element condition number
Authors: Freitag Lori A. , Knupp Patrick M.
Published: October 2002

We present a new shape measure for tetrahedral elements that is optimal in that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. Using this shape measure, we formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst‐quality element in the mesh. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement methods. We show that a combined optimization approach that uses both objective functions obtains the best‐quality meshes for several complex geometries. Copyright © 2001 John Wiley & Sons, Ltd.
A canonical form return mapping algorithm for rate independent plasticity
Authors: Keavey M. A.
Published: October 2002

A canonical form for the representation of elastic predictor radial return plasticity algorithms is presented which is deceptive in its simplicity. Iterative application of the corrector is in a form used universally in the solution of ordinary differential equations and substitution of different yield functions and state variable evolution equations is trivial. The consistency condition is maintained by an additional constraint equation via what is, in effect, a Lagrange multiplier. A consistent material Jacobian may be obtained automatically by applying partial elimination to the same set of equations. The process is numerical and requires no additional algebraic manipulation. To demonstrate the validity of such a simple technique, existing, apparently more complex, formulations are derived through the simple expedient of static condensation. As a practical example of the application of the method, a standard von Mises plasticity model is implemented and results are presented for two standard benchmarks that test quadratic convergence for large increments. Copyright © 2001 John Wiley & Sons, Ltd.
Finite element evaluation of mixed mode stress intensity factors in functionally graded materials
Authors: Kim Jeong‐Ho , Paulino Glaucio H.
Published: October 2002

This paper is directed towards finite element computation of fracture parameters in functionally graded material (FGM) assemblages of arbitrary geometry with stationary cracks. Graded finite elements are developed where the elastic moduli are smooth functions of spatial co‐ordinates which are integrated into the element stiffness matrix. In particular, stress intensity factors for mode I and mixed‐mode two‐dimensional problems are evaluated and compared through three different approaches tailored for FGMs: path‐independent J*k‐integral, modified crack‐closure integral method, and displacement correlation technique. The accuracy of these methods is discussed based on comparison with available theoretical, experimental or numerical solutions. Copyright © 2001 John Wiley & Sons, Ltd.
Mixed‐enhanced formulation for geometrically linear axisymmetric problems
Authors: Kasper E. P. , Taylor R. L.
Published: October 2002

A four‐noded quadrilateral axisymmetric formulation in the context of a mixed‐enhanced method is presented. The strain field is represented by two sets of element parameters, which results in enhanced performance and coarse mesh accuracy in bending dominated problems and locking‐free response in the near incompressible limit. The mixed fields presented are such that variational stress recovery is permissible. In addition, the formulation is cast such that the mixed parameters are obtained explicitly yielding finite element arrays with the proper rank using standard order quadrature. In this paper our attention is restricted to the area of geometrically linear problems in solid mechanics. Representative simulations show favourable performance of the formulation. Copyright © 2002 John Wiley & Sons, Ltd.
A plasticity based model and an adaptive algorithm for finite element analysis of reinforced concrete panels
Authors: Pravida J. , Wunderlich W.
Published: October 2002

This paper deals with an adaptive finite element procedure for the analysis of plain and reinforced concrete panels in a state of plane stress. Therefore, we will present a plasticity based model for plain concrete which captures the two failure modes of concrete within one formulation. In spite of a simple formulation the model is capable to describe the different mechanisms for tensile failure as well as for compression fracture. To restrict the time discretization error and the spatial discretization error to certain tolerances, the constitutive model is embedded in an adaptive algorithm which controls the size of the incremental load steps and leads to a hierarchical mesh refinement if necessary. The application of the model will be shown by various numerical examples. Copyright © 2002 John Wiley & Sons, Ltd.
Mesh generation in curvilinear domains using high‐order elements
Authors: Sherwin S. J. , Peiró J.
Published: October 2002

The ability to construct suitable computational meshes is currently a significant limiting factor in the development of compact high‐order algorithms in very complex geometries. Compact high‐order algorithms such as spectral element or p‐type finite element techniques offer the potential of high accuracy if the solution is smooth and a well‐behaved mapping exists between the local sub‐domains and a standard region. In this paper we address the problem of coupling high‐order algorithms with unstructured mesh generation and CAD representation techniques. We present three complementary strategies to alleviate the problem of generation of elemental regions with singular elemental mappings. The first strategy investigates the influence of an anisometric parametric surface representation on the quality of high‐order unstructured meshes. We show that a straightforward splitting of a standard linear mesh for use in a high‐order method can lead to the generation of distorted, possibly invalid, meshes even for simple computational domains such as cubes. The second strategy uses hybrid meshes applying prismatic elements near curvilinear boundaries. In the third and final strategy we investigate the use of curvature driven surface discretization to incorporate higher‐order information about the surface into the mesh generation. Using the computational reconstruction of the arterial bypass graft as an example computational domain we demonstrate how the combination of all three strategies leads to a valid high‐order discretization of the computational domain. Copyright © 2001 John Wiley & Sons, Ltd.
Remeshing for metal forming simulations—Part II: Three‐dimensional hexahedral mesh generation
Authors: Kwak Dae‐Young , Im Yong‐Taek
Published: October 2002

In the present study, a hexahedral mesh generator was developed for remeshing in three‐dimensional metal forming simulations. It is based on the master grid approach and octree‐based refinement scheme to generate uniformly sized or locally refined hexahedral mesh system. In particular, for refined hexahedral mesh generation, the modified Laplacian mesh smoothing scheme mentioned in the two‐dimensional study (Part I) was used to improve the mesh quality while also minimizing the loss of element size conditions. In order to investigate the applicability and effectiveness of the developed hexahedral mesh generator, several three‐dimensional metal forming simulations were carried out using uniformly sized hexahedral mesh systems. Also, a comparative study of indentation analyses was conducted to check the computational efficiency of locally refined hexahedral mesh systems. In particular, for specification of refinement conditions, distributions of effective strain‐rate gradient and posteriori error values based on a Z2 error estimator were used. From this study, it is construed that the developed hexahedral mesh generator can be effectively used for three‐dimensional metal forming simulations. Copyright © 2002 John Wiley & Sons, Ltd.
On a wildland fire model with radiation
Authors: Asensio M. I. , Ferragut L.
Published: October 2002

The 2‐D simplified wildland fire model presented here is based on conservation laws and takes into account radiation as the dominant thermal transfer mechanism, as well as convection, which represents the effect of the wind and the slope. The non‐dimensional equations are obtained using the Frank–Kamenestkii change of variables. The existence of weak solutions of the non‐linear reaction diffusion problem obtained is established as a particular case of more general existence results using a compactness method. The uniqueness of the weak solution is shown for a given initial data and fixed parameters of the equations. The approximate solution is obtained using a mixed finite element method. This preserves the continuity of the flux through the inter‐element boundaries and allows to represent high gradients in the solution. Semi‐discrete error estimation is presented. The convective term is solved by a splitting technique using Godunov's method. The numerical examples show the efficiency of the algorithm in capturing the fire front, even for critical values of the parameters. Copyright © 2002 John Wiley & Sons, Ltd.
QuickTrace: a fast algorithm to detect contact
Authors: Bruneel Herman C. J. , De Rycke Igor
Published: October 2002

QuickTrace is a new, fast contact detection algorithm. It searches for contact typically between a tool, modelled by some kind of geometrical surface facets, and deforming material. Contact is searched for at material surface points called contact nodes. A contact node is in contact with a facet when the contact node is inside of the tool and the negative outer normal on the material surface at the contact node ‘leaves’ the tool surface through that facet. When multiple facets are intersected, only the closest facet to the contact node should be considered. From this definition of contact, the penetration depth results automatically as a by‐product.

In QuickTrace, the m facets of the tool are packaged in boxes that are hierarchically ordered in a search tree with an average depth of log4 m. The computational complexity for one contact search is proportional to this average depth. So, for n contact nodes the computational complexity is O(n log4 m). This places QuickTrace amongst the best performing contact detection algorithms. At the same time there are no approximations or tricks involved and the contact detection is absolutely correct. The algorithm can easily be extended to material–material or tool–tool contact. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐planar 3D crack growth by the extended finite element and level sets—Part I: Mechanical model
Authors: Moës N. , Gravouil A. , Belytschko T.
Published: October 2002

A methodology for solving three‐dimensional crack problems with geometries that are independent of the mesh is described. The method is based on the extended finite element method, in which the crack discontinuity is introduced as a Heaviside step function via a partition of unity. In addition, branch functions are introduced for all elements containing the crack front. The branch functions include asymptotic near‐tip fields that improve the accuracy of the method. The crack geometry is described by two signed distance functions, which in turn can be defined by nodal values. Consequently, no explicit representation of the crack is needed. Examples for three‐dimensional elastostatic problems are given and compared to analytic and benchmark solutions. The method is readily extendable to inelastic fracture problems. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐planar 3D crack growth by the extended finite element and level sets—Part II: Level set update
Authors: Gravouil A. , Moës N. , Belytschko T.
Published: October 2002

We present a level set method for treating the growth of non‐planar three‐dimensional cracks.The crack is defined by two almost‐orthogonal level sets (signed distance functions). One of them describes the crack as a two‐dimensional surface in a three‐dimensional space, and the second is used to describe the one‐dimensional crack front, which is the intersection of the two level sets. A Hamilton–Jacobi equation is used to update the level sets. A velocity extension is developed that preserves the old crack surface and can accurately generate the growing surface. The technique is coupled with the extended finite element method which approximates the displacement field with a discontinuous partition of unity. This displacement field is constructed directly in terms of the level sets, so the discretization by finite elements requires no explicit representation of the crack surface. Numerical experiments show the robustness of the method, both in accuracy and in treating cracks with significant changes in topology. Copyright © 2002 John Wiley & Sons, Ltd.
A numerical upscaling method for an elliptic equation with heterogeneous tensorial coefficients
Authors: Luce Robert , Perez Sylvie
Published: October 2002

The aim of this paper is to develop a new numerical method to determine the effective permeability on a coarse scale level of problems with strongly heterogeneous tensorial coefficients defined on a fine scale. This method stems from a primal–dual mixed formulation and the upscaled permeability is obtained by imposing the continuity of the numerical flux across the lines of discontinuities. Moreover, a finite volume scheme is built to numerically solve elliptic equations with this kind of coefficients. Finally, the method is illustrated by several numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd.
An improved unsteady, unstructured, artificial compressibility, finite volume scheme for viscous incompressible flows: Part II. Application
Authors: Malan A. G. , Lewis R. W. , Nithiarasu P.
Published: October 2002

In Part I of this paper, a preconditioned artificial compressibility scheme was developed for modelling laminar steady‐state and transient, incompressible flows for a wide range of Reynolds and Rayleigh numbers. In this part, several examples of laminar incompressible problems are solved and discussed. The influence of various AC parameters on robustness and convergence rates are assessed for a complex category of problems. It is shown that the scheme developed in Part I is an accurate, robust and easy to use method for solving incompressible laminar flow problems over a wide range of flow regimes. Copyright © 2002 John Wiley & Sons, Ltd.
Sandwich shell finite element for dynamic explicit analysis
Authors: Tabiei Ala , Tanov Romil
Published: October 2002

The contribution of this paper consists of new development of transverse shear stresses through the thickness and finding an expression for the critical time step for explicit time integration of layered shells. This work presents the finite element (FE) formulation and implementation of a higher‐order shear deformable shell element for dynamic explicit analysis of composite and sandwich shells. The formulation is developed using a displacement‐based third‐order shear deformation shell theory. Using the differential equilibrium equations and the interlayer requirements, special treatment is developed for the transverse shear, resulting in a continuous, piecewise quartic distribution of the transverse shear stresses through the shell thickness. Expressions are developed for the critical time step of the explicit time integration for orthotropic homogeneous and layered shells based on the developed third‐order formulation. To assess the performance of the present shell element, it is implemented in the general non‐linear explicit dynamic FE code DYNA3D. Several problems are solved and results are presented and compared to other theoretical and numerical results. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling three‐dimensional piece‐wise homogeneous domains using the α‐shape‐based natural element method
Authors: Cueto E. , Calvo B. , Doblaré M.
Published: October 2002

In this paper, the application of the natural element method (NEM) to the numerical analysis of two‐ and three‐dimensional piece‐wise homogeneous domains is presented. The NEM differs from other meshless methods in its capability to accurately reproduce essential boundary conditions along convex boundaries. The α‐shape‐based extension of this method (α‐NEM) generalizes this behaviour to non‐convex domains, enables us to construct models entirely in terms of the initial cloud of points and allows us to simulate material discontinuities in a straightforward manner. In the following sections, simple and effective algorithms are presented for the construction of α‐shapes in domains composed of various materials. Examples are presented in two‐ and three‐dimensional cases in the context of linear elastostatics showing good performance even with the simple numerical quadrature used. Copyright © 2002 John Wiley & Sons, Ltd.
Derived data structure algorithms for unstructured finite element meshes
Authors: Waltz Jacob
Published: October 2002

A set of derived data structure algorithms for unstructured finite element meshes is presented. Both serial and parallel algorithms are described for each data structure. Colouring groups for the elements are used to facilitate parallelization on shared memory architectures. Scaling studies indicate that the parallel algorithms are most efficient when the number of elements per processor is on the order of 106 or higher, and overall efficiencies of 60–70% are achieved down to 0.5×106 elements per processor. Although the meshes under consideration are tetrahedral, the algorithms are general in nature and can be extended to arbitrary element types with minimal effort. Copyright © 2002 John Wiley & Sons, Ltd.
An algorithm coupling the OSRC and FEM for the computation of an approximate scattered acoustic field by a non‐convex body
Authors: Antoine X.
Published: October 2002

This paper describes a new formulation to solve the acoustic scattering problem by a non‐convex structure. The presented hybrid algorithms connect the on‐surface radiation condition method to accelerate the calculations with a two‐dimensional finite element method to treat the non‐convex part of the domain. This allows the problem of truncating the computational domain to be overcome. The variational formulations associated with a Dirichlet or a Neumann boundary condition are considered. Finally, we give some numerical results on a model test case to illustrate the improvement of accuracy of the new algorithm compared to a pure OSRC approach. Copyright © 2002 John Wiley & Sons, Ltd.
Adaptive moving mesh methods for simulating one‐dimensional groundwater problems with sharp moving fronts
Authors: Huang Weizhang , Zheng Li , Zhan Xiaoyong
Published: October 2002

Accurate modelling of groundwater flow and transport with sharp moving fronts often involves high computational cost, when a fixed/uniform mesh is used. In this paper, we investigate the modelling of groundwater problems using a particular adaptive mesh method called the moving mesh partial differential equation approach. With this approach, the mesh is dynamically relocated through a partial differential equation to capture the evolving sharp fronts with a relatively small number of grid points. The mesh movement and physical system modelling are realized by solving the mesh movement and physical partial differential equations alternately. The method is applied to the modelling of a range of groundwater problems, including advection dominated chemical transport and reaction, non‐linear infiltration in soil, and the coupling of density dependent flow and transport. Numerical results demonstrate that sharp moving fronts can be accurately and efficiently captured by the moving mesh approach. Also addressed are important implementation strategies, e.g. the construction of the monitor function based on the interpolation error, control of mesh concentration, and two‐layer mesh movement. Copyright © 2002 John Wiley & Sons, Ltd.
A new variable‐order singular boundary element for two‐dimensional stress analysis
Authors: Lim K. M. , Lee K. H. , Tay A. A. O. , Zhou W.
Published: October 2002

A new variable‐order singular boundary element for two‐dimensional stress analysis is developed. This element is an extension of the basic three‐node quadratic boundary element with the shape functions enriched with variable‐order singular displacement and traction fields which are obtained from an asymptotic singularity analysis. Both the variable order of the singularity and the polar profile of the singular fields are incorporated into the singular element to enhance its accuracy. The enriched shape functions are also formulated such that the stress intensity factors appear as nodal unknowns at the singular node thereby enabling direct calculation instead of through indirect extrapolation or contour‐integral methods. Numerical examples involving crack, notch and corner problems in homogeneous materials and bimaterial systems show the singular element's great versatility and accuracy in solving a wide range of problems with various orders of singularities. The stress intensity factors which are obtained agree very well with those reported in the literature. Copyright © 2002 John Wiley & Sons, Ltd.
Hyaluronan expression in differentiated thyroid carcinoma
Authors: Böhm Jan , Niskanen Leo , Tammi Raija , Tammi Markku , Eskelinen Matti , Pirinen Risto , Hollmen Sinikka , Alhava Esko , Kosma Veli‐Matti
Published: October 2002

The extracellular polysaccharide hyaluronan (HA) controls cell migration, differentiation, and proliferation, and is supposed to contribute to the spreading of several human cancers. Little is known about the role of HA in the development and progression of differentiated thyroid carcinoma (DTC). The expression and prognostic value of HA were therefore evaluated in 204 consecutive patients with DTC. A biotinylated affinity probe specific for HA was applied to paraffin‐embedded tumour samples to assay the expression of HA in carcinoma cells and in intra/peritumoural stroma. In a majority of the samples, a high percentage (≥90%) of normal thyroid follicle epithelial cells were HA‐positive. This high percentage was also found in 80 (47%) papillary carcinomas, but only in seven (21%) follicular carcinomas (p=0.004). Age (>60 years) of the patients was significantly associated with a low percentage of HA‐positive cancer cells (p=0.013). Cancer cell‐associated HA correlated significantly with the percentage of cells expressing total CD44 and its isoforms containing exons v3 and v6 (r=0.223–0.289, p<0.001 for all). The tumour stroma was always positive for HA. Stromal staining intensity did not differ markedly between papillary and follicular carcinomas. A strong stromal HA staining intensity was related to distant metastases (p=0.044), high pTNM stage (p=0.024), old age (>60 years) (p=0.043), and cancer‐related mortality (p=0.001). In a log‐rank univariate survival analysis, strong stromal HA staining intensity was related to DTC mortality (p=0.0007). Cancer cell‐associated HA expression did not significantly correlate with patient survival. In Cox's multivariate survival analysis, age (>60 years, p=0.0164), gender (p=0.0251), and pTNM stage (p=0.0121) were significant independent prognostic factors for DTC‐related death. These results suggest that strong stromal HA staining intensity is related to progression and unfavourable outcome in DTC patients, while the clinical factors remain more powerful in predicting DTC‐related death. Copyright © 2001 John Wiley & Sons, Ltd.
Expression of frizzled‐related protein and Wnt‐signalling molecules in invasive human breast tumours
Authors: Wong Sze Chuen Cesar , Lo Siu Fong Elena , Lee King Chung , Yam Judy W. P. , Chan John K. C. , Wendy Hsiao W. L.
Published: October 2002

Frizzled‐related protein (Frp) is a new family of secreted proteins that contain a region homologous to the extracellular cysteine‐rich domain (CRD) of the frizzled family proteins. The role of Frp protein is far from clear. To explore the role of Frp and its relationship to the Wnt‐signalling pathway in breast cancer, in situ hybridization and immunohistochemical analyses of Frp, Wnt‐1, APC, β‐catenin, and its target genes c‐myc and cyclin D1 were conducted in 70 specimens of invasive ductal carcinomas of the human breast. Frp mRNA was down‐regulated in 62 and elevated in eight tumour specimens, compared with adjacent normal tissues. In the course of tumour progression, however, Frp mRNA steadily increased in both tumour and the adjacent tissues. Interestingly, the number of cases with axillary lymph node metastasis was significantly lower in the group with elevated Frp than in the group with decreased Frp, suggesting that Frp may contribute as a prognostic factor in invasive breast cancer. Wnt‐1, a gene implicated in human breast cancer, was markedly elevated in grade 1 tumours, but declined as tumour grade declined. The level of Wnt‐1 was linearly correlated with its downstream target β‐catenin (p<0.05), but was inversely correlated with Frp (p<0.05), suggesting a possible negative regulatory role of Frp with regard to Wnt‐1. APC was inversely correlated with β‐catenin (p<0.05). β‐catenin, a key transcriptional activator responsible for the activation of both c‐myc and cyclin D1 in colorectal tumours, was detected at high levels in the plasma membranes of cells in normal tissue. In tumour masses, however, β‐catenin lost its tight association with the membrane and diffused into the cytoplasm. Surprisingly, it clearly did not penetrate the nuclei, despite the fact that both c‐myc and cyclin D1 were markedly elevated in all tumour tissues. As revealed in this study, Wnt‐1/β‐catenin plays very different roles in the oncogenesis of breast and colon cancers. This first systemic analysis of the Frp and the Wnt‐signalling pathway in human breast cancer provides a springboard for further work on the role of Frp in the development of breast cancer. Copyright © 2001 John Wiley & Sons, Ltd.
APC mutations in synovial sarcoma
Authors: Saito Tsuyoshi , Oda Yoshinao , Sakamoto Akio , Kawaguchi Ken‐ichi , Tanaka Kazuhiro , Matsuda Shuichi , Tamiya Sadafumi , Iwamoto Yukihide , Tsuneyoshi Masazumi
Published: October 2002

It has previously been demonstrated that accumulated β‐catenin serves as an oncoprotein in synovial sarcoma and results in a poor overall survival rate, but the frequency of β‐catenin mutation was quite low (8.2%). The present study, using essentially the same study group of cases, screened for genetic alterations in the mutation cluster region (MCR) of the APC gene in 49 cases of synovial sarcoma. SSCP analysis followed by DNA direct sequencing revealed five missense APC mutations in four cases of synovial sarcoma (8.2%). The mutational sites comprised one case each at codons 1299 (GCT to ACT, Ala to Thr), 1412 (GGA to AGA, Gly to Arg), and 1414 (GTA to ATA, Val to Ile), in addition to one case with double point mutations at codon 1398 (AGT to AAT, Ser to Asn) and at codon 1413 (ATG to ATA, Met to Ile), together with β‐catenin mutation at codon 32 (GAC to TAC, Asp to Tyr). All four cases with APC mutations were histologically of the monophasic fibrous type and showed β‐catenin accumulation. All three cases with APC mutations available for follow‐up data were long survivors. This study provides the first evidence that APC mutations also occur in the field of sarcoma, especially in synovial sarcoma. Copyright © 2002 John Wiley & Sons, Ltd.
Correlation between localization, age, and chromosomal imbalances in ependymal tumours as detected by CGH
Authors: Jeuken Judith W. M. , Sprenger Sandra H. E. , Gilhuis Job , Teepen Hans L. J. M. , Grotenhuis Andre J. , Wesseling Pieter
Published: October 2002

Ependymal tumours (ETs) are gliomas that arise from the ependymal lining of the cerebral ventricles and from the remnants of the central canal of the spinal cord. Both clinical and genetic studies suggest that distinct genetic subtypes of ETs exist, the subtypes being correlated with patient age and/or tumour site. In the present study, the tumour genome of 20 ETs (15 adult and five paediatric cases) was screened for chromosomal imbalances by comparative genomic hybridization (CGH). The most frequently detected imbalances were −22q (75%), −10q (65%), −21 (50%), −16p (50%), −1p (45%), +4q (45%), −10p (45%), −2q (40%), −6 (40%), −19 (40%), −2p (35%), −3p (35%), and −16q (35%). Comparison of the chromosomal imbalances detected in ETs with those previously reported in oligodendroglial and astrocytic tumours revealed that in this respect ETs show similarities to these other gliomas. By combining these results with those of a recent study of Zheng et al. and Hirose et al., it was found that although ETs from different sites and from adult and paediatric patients show overlap at the CGH level, some chromosomal imbalances occur predominantly in a certain category. In adult patients, spinal ETs relatively often showed +2, +7, +12, and −14q; infratentorial ETs −22; and supratentorial ETs −9. In addition, in posterior fossa ETs, −6 and +9 were much more frequent in adults than in children. It is concluded that the genetic background of ETs is complex and partly determined by tumour site, histopathological subtype, and age of the patient. Copyright © 2002 John Wiley & Sons, Ltd.