bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential fatigue of paralyzed thenar muscles by stimuli of different intensities
Authors: Godfrey Sharlene , Butler Jane E. , Griffin Lisa , Thomas Christine K. 
Published: October 2002

AbstractMuscles paralyzed by injury or disease fatigue excessively when stimulated. This study examined whether the first few paralyzed thenar motor units recruited by electrical stimulation of the median nerve were more fatigue resistant than the total thenar motor unit population. The paralyzed thenar muscles of four subjects with chronic cervical spinal cord injury were fatigued by a 2‐min intermittent 40‐HZ protocol on 2 days. One experiment involved submaximal stimulation, the other supramaximal stimulation. These stimuli resulted in activation of part and all of the thenar muscles, respectively. Relative force loss, force–time integral decline, and slowing of half‐relaxation time were always significantly less when only part rather than all of the muscles was fatigued. The part of the paralyzed muscles that was activated was also relatively fatigue resistant compared with control single thenar motor units. Thus, a reversal of recruitment order from fatigable to fatigue‐resistant units cannot explain the extreme fatigability of paralyzed muscles. Use of submaximal stimulation during functional electrical stimulation may therefore help to reduce muscle fatigue because it recruits the more fatigue‐resistant units. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 122–131, 2002
Partial conduction blocks in N‐hexane neuropathy
Authors: Pastore Carlos , Izura Virginia , Marhuenda Dolores , Prieto María‐José , Roel José , Cardona Antonio 
Published: October 2002

AbstractNerve conduction blocks, defined by a significant reduction in amplitude or area of the compound muscle action potential at proximal compared with distal sites of stimulation, have been described in glue‐sniffers and in workers with industrial exposure at an early stage of n‐hexane neuropathy. The frequency with which this focal conduction anomaly appears is described and discussed in the case of a very homogeneous group of 10 young workers diagnosed with n‐hexane polyneuropathy. Partial conduction blocks occurred in only two workers and may have been related to the intensity and duration of toxic exposure. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 132–135, 2002
Note on “deterministic inventory lot‐size models under inflation with shortages and deterioration for fluctuating demand” by Yang et al.
Authors: Skouri K. , Papachristos S. 
Published: October 2002

AbstractIn a recent paper Yang et al. extended the lot‐size models to allow for inflation and fluctuating demand. For this model they proved that the optimal replenishment schedule exists and is unique. They also proposed an algorithm to find the optimal policy. The present paper provides examples, which show that the optimal replenishment schedule and consequently the overall optimal policy may not exist. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 527–529, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10022
Activin and bone morphogenetic proteins are present in perinatal sensory neuron target tissues that induce neuropeptides
Authors: Hall Alison K. , Burke Rebecca M. , Anand Malini , Dinsio Kyl J. 
Published: October 2002

AbstractPrevious studies have shown that sensory target tissues induce neuropeptides in naïve sensory neurons, and that activin and bone morphogenetic proteins (BMPs) are capable of inducing neuropeptides associated with nociception in embryonic sensory neurons in vitro. The goal of the present study was to learn if these ligands were available in native sensory neuron target tissues at correct developmental periods to play this inductive role in vivo. Sensory neurons initially contact their peripheral target tissues and begin to express neuropeptides during late embryogenesis, and we demonstrate that activin and BMPs are present in the embryo and neonate to regulate sensory neuron differentiation. Native embryonic and neonatal target tissues were analyzed by immunoblot and immunohistochemical studies using ligand‐specific antibodies. Although activin was easily solubilized, BMPs were detected only after high salt extraction, suggesting that BMPs were bound to extracellular moieties and were capable of acting only locally in native tissues. One inhibitor, noggin, was present in both embryonic skin and muscle. In combination, these data suggest that neuronal differentiation is unlikely to be regulated by simple expression of ligand, but that the functional availability of ligand is a critical component confering biological activity. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 52–60, 2002
On the formulation of closest‐point projection algorithms in elastoplasticity—part II: Globally convergent schemes
Authors: Pérez‐Foguet A. , Armero F. 
Published: October 2002

AbstractThis paper presents the formulation of numerical algorithms for the solution of the closest‐point projection equations that appear in typical implementations of return mapping algorithms in elastoplasticity. The main motivation behind this work is to avoid the poor global convergence properties of a straight application of a Newton scheme in the solution of these equations, the so‐called Newton‐CPPM. The mathematical structure behind the closest‐point projection equations identified in Part I of this work delineates clearly different strategies for the successful solution of these equations. In particular, primal and dual closest‐point projection algorithms are proposed, in non‐augmented and augmented Lagrangian versions for the imposition of the consistency condition. The primal algorithms involve a direct solution of the original closest‐point projection equations, whereas the dual schemes involve a two‐level structure by which the original system of equations is staggered, with the imposition of the consistency condition driving alone the iterative process. Newton schemes in combination with appropriate line search strategies are considered, resulting in the desired asymptotically quadratic local rate of convergence and the sought global convergence character of the iterative schemes. These properties, together with the computational performance of the different schemes, are evaluated through representative numerical examples involving different models of finite‐strain plasticity. In particular, the avoidance of the large regions of no convergence in the trial state observed in the standard Newton‐CPPM is clearly illustrated. Copyright © 2001 John Wiley & Sons, Ltd.
On the computation of stress fields on polygonal domains with V‐notches
Authors: Helsing Johan , Jonsson Anders 
Published: October 2002

AbstractThe interior stress problem is solved numerically for a single‐edge notched specimen under uniaxial load. The algorithm is based on a modification of a Fredholm second‐kind integral equation with compact operators due to Muskhelishvili. Several singular basis functions for each of the seven corners in the geometry enable high uniform resolution of the stress field with a modest number of discretization points. As a consequence, notch stress intensity factors can be computed directly from the solution. This is an improvement over other procedures where the stress field is not resolved in the corners and where notch stress intensity factors are computed in a roundabout way via a path‐independent integral. Numerical examples illustrate the superior stability and economy of the new scheme. Copyright © 2001 John Wiley & Sons, Ltd.
Multifrontal incomplete factorization for indefinite and complex symmetric systems
Authors: Qu Yong , Fish Jacob 
Published: October 2002

AbstractA new class of preconditioners based on the adaptive threshold incomplete multifrontal factorization for indefinite and complex symmetric systems is developed. Numerical experiments consisting of the 3D Helmholtz equations, fluid–structure interaction and localization problems demonstrate the excellent performance of the preconditioner. Copyright © 2001 John Wiley & Sons, Ltd.
Hierarchical model adaptivity in finite element analysis for non‐linear plate problems
Authors: Fu Kang 
Published: October 2002

AbstractBased on the polynomial series expansion of kinematic fields throughout the thickness of a plate, hierarchical models are constructed by selected truncations. The models are formulated with the three‐dimensional second Piola–Kirchhoff stress and Green–Lagrange strain at large deformation. The adaptivity of the models in the framework of finite element method is devised for not only the compatible combination of the elements of different models but also the evolution of the models in an element when the function of its interested property changes during analysis procedures. The key idea in the method is to meet the continuity requirement of the primary displacement field by fixing a set of common active hierarchical expansion degrees of freedom for each node, which may be shared by the elements of different models. The von Mises criterion is used here to describe material plasticity. Unilateral contact phenomena are examined on the upper and/or lower surfaces of the plates by using a penalty method. Friction effects are taken into account with a regularized Coulomb law. Examples on the numerical simulation of sheet metal forming and the analysis of a cracked plate are included to illustrate the advantage of this new strategy. Copyright © 2001 John Wiley & Sons, Ltd.
Second‐order optimal control algorithm for complex systems
Authors: Kaplan Matthew L. , Heegaard Jean H. 
Published: October 2002

AbstractThe solution to large‐scale optimal control problems, characterized by complex dynamics and extended time periods, is often computationally demanding. We present a solution algorithm with favourable local convergence properties as a way to reduce simulation times. This method is based on using a trapezoidal direct collocation to convert the differential equations into algebraic constraints. The resulting constrained minimization problem is then solved with an augmented Lagrangian formulation to accommodate both equality and inequality constraints. In contrast to the prevalent optimal control software implementations, we calculate analytical first and second derivatives. We then apply a generalized Newton method to the augmented Lagrangian formulation, solving for all unknowns simultaneously. The computational costs of the Hessian formation and matrix solution remain manageable as the system size increases due to the sparsity of all tensor quantities. Likewise, the total iterations for convergence scale well due to the local quadratic convergence of the generalized Newton method. We demonstrate the method with an inverted pendulum problem and a neuromuscular control problem with complex dynamics and 18 forcing functions. The optimal control solutions are successfully found. In both examples, we obtain quadratic convergence rates in the neighbourhood of the solution. Copyright © 2002 John Wiley & Sons, Ltd.
Dual‐mixed p and hp finite elements for elastic membrane problems
Authors: Bertóti E. 
Published: October 2002

AbstractA complementary energy‐based, dimensionally reduced plate model using a two‐field dual–mixed variational principle of non‐symmetric stresses and rotations is derived. Both the membrane and bending equilibrium equations, expressed in terms of non‐symmetric mid‐surface stress components, are satisfied a priori introducing first‐order stress functions. It is pointed out that (i) the membrane‐, shear‐ and bending energies of the plate written in terms of first‐order stress functions are decoupled, (ii) although unmodified 3‐D constitutive equations are applied, the energy parts do not contain the 1/(1‐2ν) term for isotropic, linearly elastic materials. These facts mean that the finite element formulation based on the present plate model should be free from shear locking when the thickness tends to zero and free from incompressibility locking when the Poisson ratio ν converges to 0.5, irrespective of low‐order h‐, or higher‐order p elements are used.Curvilinear dual‐mixed hp finite elements with higher‐order stress approximation and continuous surface tractions are developed and presented for the membrane (2‐D elasticity) problem. In this case the formulation requires the approximation of three independent variables: two components of a first‐order stress function vector and a scalar rotation. Numerical performance of three quadrilateral dual–mixed elements is presented and compared to displacement‐based hp finite elements when the Poisson ratio converges to the incompressible limit of 0.5. The numerical results show that, as expected, the dual–mixed elements developed in this paper are free from locking in the energy norm as well as in the stress computations, for both h‐ and p‐extensions. Copyright © 2001 John Wiley & Sons, Ltd.
Geometrically non‐linear damage interface based on regularized strong discontinuity
Authors: Larsson Ragnar , Jansson Niklas 
Published: October 2002

AbstractThe contribution of this paper concerns the fracture modelling of an interface with a fixed internal material surface in the context of geometrically non‐linear kinematics. Typical applications are composite laminates and adhesive/frictional joints in general. In the model development, a key feature is the concept of regularized strong discontinuity, which provides a regular deformation gradient within the interface. The deformation gradient within the interface is formulated in a multiplicative structure with a continuous part and a discontinuous part, whereby the interface deformation is interpreted as a transformation between the material damaged configuration and the actual spatial configuration. In analogy with the continuum formulation of hyper‐inelasticity, a constitutive framework is defined for the relation between the induced material traction and the displacement jump vector, which are defined on the material damaged interface configuration. Within this framework, a simple, but yet still representative, model for the delamination problem is proposed on the basis of a damage–plasticity coupling for the interface. The model is calibrated analytically in the large deformation context with respect to energy dissipation in mode I so that a predefined amount of fracture energy is dissipated. The paper is concluded with a couple of numerical examples that display the properties of the interface. Copyright © 2002 John Wiley & Sons, Ltd.
Topology design of structures using a dual algorithm and a constraint on the perimeter
Authors: Jog C. S. 
Published: October 2002

AbstractDual optimization algorithms are well suited for the topology design of continuum structures in discrete variables, since in these problems the number of constraints is small in comparison to the number of design variables. The ‘raw’ dual algorithm, which was originally proposed for the minimum compliance design problem, worked well when a perimeter constraint was added in addition to the volume constraint. However, if the perimeter constraint was gradually relaxed by increasing the upper bound on the allowable perimeter, the algorithm tended to behave erratically. Recently, a simple strategy has been suggested which modifies the raw dual algorithm to make it more robust in the absence of the perimeter constraint; in particular the problem of checkerboarding which is frequently observed with the use of lower‐order finite elements is eliminated. In this work, we show how the perimeter constraint can be incorporated in this improved algorithm, so that it not only provides a designer with a control over the topology, but also generates good topologies irrespective of the value of the upper bound on the perimeter. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of general quadrilateral orthotropic thick plates with arbitrary boundary conditions by the Rayleigh–Ritz method
Authors: Saadatpour M. M. , Azhari M. , Bradford M. A. 
Published: October 2002

AbstractA numerical method is developed for the analysis of general quadrilateral, moderately thick orthotropic plates having arbitrary boundary conditions. The procedure is based on the application of the Rayleigh–Ritz method in conjunction with the Reissner–Mindlin thick plate theory. A set of complete polynomials in terms of natural co‐ordinates comprising of boundary and domain terms, which satisfy the boundary conditions, is deployed as the basic functions to approximate the real displacement field. The generalized displacements and the eigenvalues are determined by imposing the principle of stationary potential energy. Although the procedure has the ability to solve problems involving thick quadrilateral plates, the numerical examples presented are mostly for skew plates. The results herein are compared with their counterparts determined by other investigators. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐linear dynamic behaviour of flexible marine pipes and risers
Authors: Yazdchi M. , Crisfield M. A. 
Published: October 2002

AbstractThis paper describes the way in which hydrostatic and hydrodynamic forces can be added to the conventional static and inertia forces for the non‐linear analysis of 3D flexible pipes and riser systems. Emphasis is placed on elements that use the Reissner–Simo beam theory or a related co‐rotational approach. Copyright © 2002 John Wiley & Sons, Ltd.
Numerical investigation of quenching for a nonlinear diffusion equation with a singular Neumann boundary condition
Authors: Christov C. I. , Deng K. 
Published: October 2002

AbstractFor a nonlinear diffusion equation with a singular Neumann boundary condition, we devise a difference scheme which represents faithfully the properties of the original continuous boundary value problem. We use non‐uniform mesh in order to adequately represent the spatial behavior of the quenching solution near the boundary. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 429–440, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10013
Least‐squares mixed finite element methods for the incompressible Navier‐Stokes equations
Authors: Gu Haiming , Wu Xiaonan 
Published: October 2002

AbstractLeast‐squares mixed finite element schemes are formulated to solve the evolutionary Navier‐Stokes equations and the convergence is analyzed. We recast the Navier‐Stokes equations as a first‐order system by introducing a vorticity flux variable, and show that a least‐squares principle based on L2 norms applied to this system yields optimal discretization error estimates. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 441–453, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10015
Chromosomal imbalances of primary and metastatic lung adenocarcinomas
Authors: Goeze Almut , Schlüns Karsten , Wolf Guenter , Thäsler Zsuzsanna , Petersen Simone , Petersen Iver 
Published: October 2002

AbstractComparative genomic hybridization (CGH) was used to screen 83 lung adenocarcinomas of 60 patients for chromosomal imbalances. The most common alteration was DNA overrepresentation on chromosome 1q, with a peak incidence at 1q22–q23 in 73% of the primary tumours, followed by DNA overrepresentation on chromosomes 8q and 20q, and deletions on chromosomes 3p, 4q, 6q, 9p, 9q, and 13q, in at least 60%. The generation of a difference histogram of metastasizing versus non‐metastasizing tumours and a case‐by‐case histogram for the comparison of 23 paired samples of primary tumours and corresponding metastases suggested that deletions on chromosomes 3p12–p14, 3p22–p24, 4p13–15.1, 4q21‐qter, 6q21‐qter, 8p, 10q, 14q21, 17p12–p13, 20p12, and 21q, and overrepresentations on chromosomes 1q21–q25, 7q11.2, 9q34, 11q12–q13, 14q11–q13, and 17q25 are associated with the metastatic phenotype. In contrast, losses on chromosome 19 and gains on 3p, 4q, 5p, and 6q were preferentially found in non‐metastasizng tumours. The analysis of the paired samples revealed considerable chromosomal instability, but indicated a clonal relationship in each case. The primary tumours often showed additional deletions, suggesting that loss of function mutations are critical in the initial phase of tumour dissemination, whereas the metastases preferentially acquired DNA gains, probably modulating the metastatic phenotype. The primary data from this study (ratio profiles, clinicopathological parameters, histograms) are also available at http://amba.charite.de/cgh. Copyright © 2001 John Wiley & Sons, Ltd.
Inter‐observer variation in the histopathological diagnosis of clinically suspicious pigmented skin lesions
Authors: Brochez Lieve , Verhaeghe Evelien , Grosshans Edouard , Haneke Eckhart , Piérard Gérald , Ruiter Dirk , Naeyaert Jean‐Marie 
Published: October 2002

AbstractWhen a biopsy is taken of a suspicious pigmented skin lesion, histological examination is expected to establish the definitive diagnosis. This study evaluated the inter‐observer variation of 20 pathologists in the histological diagnosis of a randomly selected set of suspicious pigmented skin lesions (PSLs), by comparing their diagnoses to a reference diagnosis. Overall sensitivity for melanoma was 87%, ranging from 55% to 100% between the observers. Sensitivity was significantly lower for thin (Breslow thickness <1 mm) than for thick melanomas (83% versus 97%, p=0.005). Overall melanoma specificity was 94%, ranging from 83% to 100% between observers. Dysplastic naevus was the most important source of false‐positive diagnoses, mainly in situ melanomas. Positive and negative predictive values in the given test set were 75% and 97%, respectively. In the case of melanoma, there was quite some variation in measured Breslow thickness. This would have led to a different therapeutic approach in 12% of the readings. Some of the variation seemed to be due to a different interpretation of the presence of a co‐existent naevus. In 9% (3/35) of the readings, participants did not agree on the presence of ulceration. These results reflect a tendency to overdiagnose mainly thin melanomas in general histopathological practice. They also demonstrate variation in the assessment of major prognostic factors of melanoma. Copyright © 2002 John Wiley & Sons, Ltd.
FHIT expression in clear cell renal carcinomas: versatility of protein levels and correlation with survival
Authors: Ramp U. , Caliskan E. , Ebert T. , Karagiannidis C. , Willers R. , Gabbert H. E. , Gerharz C. D. 
Published: October 2002

AbstractClear cell renal cell carcinomas (RCCs) are characterized by a deletion of chromosome 3p, which might result in the inactivation of the FHIT (fragile histidine triad) gene, a putative tumour suppressor gene. To explore the relevance of FHIT aberrations for tumour progression and prognosis in clear cell RCCs, FHIT protein expression was analysed in formalin‐fixed tissue from 149 clear cell RCCs by immunohistochemistry. FHIT protein expression was found to be markedly reduced in all RCCs, when compared with adjacent non‐neoplastic tubule epithelia. Although remaining below the FHIT levels of normal tubule epithelia, a significant increase of FHIT expression became evident from well (G1) to poorly (G3) differentiated clear cell RCCs (p=0.0001) and from low (pT1) to advanced (pT3) tumour stages (p=0.001). The log‐rank test demonstrated a significant inverse correlation (p=0.0074) between FHIT expression and tumour aggressiveness as indicated by patient survival. Cox regression analysis revealed that FHIT expression is an independent prognostic parameter (p=0.0139) in clear cell RCCs. In conclusion, clear cell RCCs show a marked reduction of FHIT protein expression when compared with their putative cells of origin. In contrast to other tumour types, however, loss of FHIT protein expression is significantly less pronounced in poorly differentiated RCCs or advanced tumour stages. This versatility of FHIT expression during tumour progression suggests a role for reversible mechanisms of FHIT inactivation during the initiation and progression of clear cell RCCs. Copyright © 2002 John Wiley & Sons, Ltd.