bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of blood volume, vessel size, and the expression of angiogenic factors in two rat glioma models: a longitudinal in vivo and ex vivo study
Authors: Valable Samuel , Lemasson Benjamin , Farion Régine , Beaumont Marine , Segebarth Christoph , Remy Chantal , Barbier Emmanuel L. 
Published: July 2008

AbstractAssessment of angiogenesis may help to determine tumor grade and therapy follow‐up. In vivo imaging methods for non‐invasively monitoring microvasculature evolution are therefore of major interest for tumor management. MRI evaluation of blood volume fraction (BVf) and vessel size index (VSI) was applied to assess the evolution of tumor microvasculature in two rat models of glioma (C6 and RG2). The results show that repeated MRI of BVf and VSI – which involves repeated injection of an iron‐based MR contrast agent – does not affect either the physiological status of the animals or the accuracy of the MR estimates of the microvascular parameters. The MR measurements were found to correlate well with those obtained from histology. They indicate that microvascular evolution differs significantly between the two glioma models, in good agreement with expression of angiogenic factors (vascular endothelial growth factor, angiopoietin‐2) and with activities of matrix metalloproteinases, also assessed in this study. These MRI methods thus provide considerable potential for assessing the response of gliomas to anti‐angiogenic and anti‐vascular agents, in preclinical studies as well as in the clinic. Furthermore, as differences between the fate of tumor microvasculature may underlie differences in therapeutic response, there is a need for preclinical study of several tumor models. Copyright © 2008 John Wiley & Sons, Ltd.
Diffusion tensor quantification of the macrostructure and microstructure of human midsagittal corpus callosum across the lifespan
Authors: Hasan Khader M. , Ewing‐Cobbs Linda , Kramer Larry A. , Fletcher Jack M. , Narayana Ponnada A. 
Published: July 2008

AbstractThe midsagittal cross‐sectional area of the human corpus callosum (CC) has been used by many researchers as a marker of development, natural aging, and neurodegenerative and acquired pathologies. The availability of non‐invasive MRI methods for quantifying the macrostructural and microstructural organization of the CC would help to clarify the CC contribution to behavior and cognition in both health and disease. In this report, we extended and validated the ability of a recently described semi‐automated diffusion tensor imaging tissue segmentation method to utilize the high orientation contrast of the CC on diffusion tensor imaging. Using a cohort of healthy right‐handed children and adults aged 7–59 years, we show gender‐independent non‐linear (quadratic) and strongly correlated growth trends in the CC area and the corresponding diffusion tensor fractional anisotropy (r = 0.67; P < 1 × 10−10). Our results provide preliminary evidence that diffusion tensor anisotropy in the living CC may be related to the number of small myelinated fibers. Copyright © 2008 John Wiley & Sons, Ltd.
ODDLS: A new unstructured mesh finite element method for the analysis of free surface flow problems
Authors: Garcia‐Espinosa Julio , Valls Aleix , Oñate Eugenio 
Published: July 2008

AbstractThis paper introduces a new stabilized finite element method based on the finite calculus (Comput. Methods Appl. Mech. Eng.1998;151:233–267) and arbitrary Lagrangian–Eulerian techniques (Comput. Methods Appl. Mech. Eng.1998;155:235–249) for the solution to free surface problems. The main innovation of this method is the application of an overlapping domain decomposition concept in the statement of the problem. The aim is to increase the accuracy in the capture of the free surface as well as in the resolution of the governing equations in the interface between the two fluids. Free surface capturing is based on the solution to a level set equation. The Navier–Stokes equations are solved using an iterative monolithic predictor–corrector algorithm (Encyclopedia of Computational Mechanics. Wiley: New York, 2004), where the correction step is based on imposing the divergence‐free condition in the velocity field by means of the solution to a scalar equation for the pressure. Examples of application of the ODDLS formulation (for overlapping domain decomposition level set) to the analysis of different free surface flow problems are presented. Copyright © 2008 John Wiley & Sons, Ltd.
Centroidal Voronoi tessellation‐based finite element superconvergence
Authors: Huang Yunqing , Qin Hengfeng , Wang Desheng 
Published: July 2008

AbstractIn this article, a finding on finite element superconvergence is reported. The Laplacian operator with Dirichlet boundary condition is considered. The linear finite element solutions have an O(h2+α)(α≈0.5)‐superconvergence in l2 norm at nodes on an almost equilateral triangular mesh generated based on centroidal Voronoi tessellation, for an arbitrary 2D bounded domain. Extensive numerical examples are presented to demonstrate the superconvergence property. Copyright © 2008 John Wiley & Sons, Ltd.
An a posteriori error estimator for the mimetic finite difference approximation of elliptic problems
Authors: Beirão da Veiga Lourenço , Manzini Gianmarco 
Published: July 2008

AbstractWe present an a posteriori error indicator for the mimetic finite difference approximation of elliptic problems in the mixed form. We show that this estimator is reliable and efficient with respect to an energy‐type error comprising both flux and pressure. Its performance is investigated by numerically solving the diffusion equation on computational domains with different shapes, different permeability tensors, and different types of computational meshes. Copyright © 2008 John Wiley & Sons, Ltd.
Strongly orthotropic continuum mechanics and finite element treatment
Authors: Kellermann D. C. , Furukawa T. , Kelly D. W. 
Published: July 2008

AbstractDespite successful application to orthotropic analysis, any Lagrangian strain tensor that is symmetric can be classified as an isotropic metric, while the infinitely orthotropic case can be accurately dealt with using one‐dimensional elements, structural tensors or kinematic constraints. In this paper, we present a strongly orthotropic continuum mechanics basis that models the exact kinematic behavior of the intermediary class of materials and also show its application to multi‐axial media and treatment using the finite element method. By asserting that mechanistic strain metrics must be material property dependent and satisfy equilibrium, we are able to derive a novel orthotropic linear strain tensor that is asymmetric and thus capable of describing all levels of orthotropy, while maintaining generality to the well‐established isotropic approach. Subsequently formulated are a material principal rotation tensor, extended orthotropic compliance tensor and an extended Mohr's plot for strain relying on an additional metric denoted as aspectual strain. Using the developed finite element formulation, it is shown that identical stress results to conventional theory for an orthotropic linear problem are predicted, while offering a more informative analysis. A second numerical example demonstrates the unique capability of this approach to solve the erroneous response of strongly orthotropic materials under trellis shear as compared with a number of conventional and contemporary approaches and thus its ability to produce kinematically exact results. Copyright © 2008 John Wiley & Sons, Ltd.
A smeared‐embedded mesh‐corrected damage model for tensile cracking
Authors: Cervera M. 
Published: July 2008

AbstractTraditional smeared orthotropic models display an unacceptable dependence of the solution on the alignment of the mesh, which usually manifests as stress locking. A solution for this drawback is proposed in this paper by adopting the concept of embedded inelastic strains, rather than displacement jumps, and by linking the structure of the inelastic strain to the geometry of the cracked element. The resulting model, applicable to linear 3‐noded triangles, is formulated as a non‐symmetric orthotropic local damage constitutive model, with the softening modulus regularized according to the material fracture energy and the element size. Analytical and numerical results show that this approach is effective in removing the locking problem as well as efficient from the computational point of view. Copyright © 2008 John Wiley & Sons, Ltd.
A boundary element numerical scheme for the two‐dimensional convection–diffusion equation
Authors: Romero Luis M. , Benitez Francisco G. 
Published: July 2008

AbstractIn this study, the theoretical and numerical fundamentals of BIEM techniques for the two‐dimensional convection–diffusion problem are presented. After an extended presentation of the basic integral formulation, the discretizing and iterative processes for its resolution are introduced. Interesting remarks on general expressions versus previously published particularized results are worth mentioning. A numerical solution scheme is provided, which has been completely developed and designed to the physical problem posed. A novel scheme based in the simultaneous solving of the potential and the gradient of the potential boundary integral equations is included. A diversity of problems is tested to prove the possibilities of the method. Copyright © 2008 John Wiley & Sons, Ltd.
Eight‐node membrane element with drilling degrees of freedom for analysis of in‐plane stiffness of thick floor plates
Authors: Zhang Hexin , Kuang J. S. 
Published: July 2008

AbstractThe development of eight‐node arbitrary quadrilateral membrane elements with drilling degrees of freedom is presented using the compatible displacement interpolation within the element. The element is considered to develop specifically for analysing the in‐plane stiffness of thick floor plates in building systems, particularly the transfer plates in tall buildings as well as pile caps. With a new set of shape functions and following the displacement‐based element procedure, the element stiffness and force vector are derived and nodal displacements are obtained after solving the simultaneous equations; the element stresses are then determined. A wide range of patch tests is conducted to evaluate the consistency and stability of the proposed element. The test results show very good agreement with the exact solutions of the beam theory. Numerical investigations are carried out, showing that the analyses using the proposed elements provide better results than those from the existing methods. Copyright © 2008 John Wiley & Sons, Ltd.
Optimization‐based stability analysis of structures under unilateral constraints
Authors: Kanno Yoshihiro , Ohsaki Makoto 
Published: July 2008

AbstractThis paper discusses an optimization‐based technique for determining the stability of a given equilibrium point of the unilaterally constrained structural system, which is subjected to the static load. We deal with the three problems in mechanics sharing the common mathematical properties: (i) structures containing no‐compression cables; (ii) frictionless contacts; and (iii) elastic–plastic trusses with non‐negative hardening. It is shown that the stability of a given equilibrium point of these structures can be determined by solving a maximization problem of a convex function over a convex set. On the basis of the difference of convex functions optimization, we propose an algorithm to solve the stability determination problem, at each iteration of which a second‐order cone programming problem is to be solved. The problems presented are solved for various structures to determine the stability of given equilibrium points. Copyright © 2008 John Wiley & Sons, Ltd.
Enhanced blending elements for XFEM applied to linear elastic fracture mechanics
Authors: Tarancón J. E. , Vercher A. , Giner E. , Fuenmayor F. J. 
Published: July 2008

AbstractThe application of the extended finite element method (XFEM) to fracture mechanics problems enables one to obtain accurate solutions more efficiently than with the standard finite element method. A component can be modelled without the need to build a mesh that matches the crack geometry, and thus remeshing as the crack grows is unnecessary. In the XFEM approach, the interpolation on certain elements is enriched with functions that make it feasible to represent the crack tip asymptotic displacement fields by using a local partition of unity method. However, the enrichment is only partial in the blending elements connecting the enriched zone with the rest of the mesh, and consequently pathological terms appear in the interpolation, which lead to increased error. In this study we propose enhancing the blending elements by adding hierarchical shape functions where appropriate; this permits compensating for the unwanted terms in the interpolation. This technique is an extension of the study of Chessa et al. (Int. J. Numer. Meth. Engng. 2003; 57:1015–1038) to fracture mechanics problems. The numerical results show that the proposed enhancement always results in greater accuracy. Moreover, enhancing the blending elements makes it possible to recover the convergence rate that is decreased when the degrees of freedom gathering technique is used to improve the condition number of the stiffness matrix. Copyright © 2008 John Wiley & Sons, Ltd.
Numerical analysis of an elasto‐piezoelectric problem with damage
Authors: Fernández José R. , Martínez Rebeca , Stavroulakis Georgios E. 
Published: July 2008

AbstractIn this paper, we analyze an algorithm for the quasistatic evolution of the mechanical state of an elasto‐piezoelectric body with damage. Both damage, caused by the development and the growth of internal microcracks, and piezoelectric effects, are included in the model. The mechanical problem is expressed as an elliptic system for the displacement field coupled with a non‐linear parabolic partial differential equation for the damage field and a linear partial differential equation for the electric potential. The variational formulation leads to a coupled system composed of two linear variational equations for the displacement field and the electric potential, and a non‐linear parabolic variational equation for the damage field. The existence of a unique weak solution is stated. Then, a fully discrete scheme is introduced by using the finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Error estimates are derived on the approximate solutions, from which the linear convergence of the algorithm is deduced under suitable regularity conditions. Finally, some numerical simulations are performed, in one, two and three dimensions, to demonstrate the accuracy of the scheme and the behaviour of the solution. Copyright © 2008 John Wiley & Sons, Ltd.
A wideband fast multipole algorithm for two‐dimensional volume integral equations
Authors: Nakashima N. , Tateiba M. 
Published: July 2008

AbstractThis paper describes a wideband fast multipole algorithm (FMA) for the computation of two‐dimensional volume integral equations. Our previous paper presented the wideband FMA by switching between the diagonal and non‐diagonal forms according to cell size and required accuracy. In order to improve the efficiency of the algorithm, we use interpolation and filtering techniques. Moreover, we introduce a simple and efficient way to store sequences of the special functions and their discrete Fourier transforms. Numerical examples show that the computational and memory complexities are reduced from O(N2) to O(N), where N is the number of square elements followed by the discretization of the volume integral equations. The computation results show very good agreement with the analytical solutions. We present some numerical results for the computation of scattering from a cylindrical object with sharp edges and a Gaussian‐like inhomogeneous cylinder. Copyright © 2008 John Wiley & Sons, Ltd.
Topology optimization for nano‐scale heat transfer
Authors: Evgrafov A. , Maute K. , Yang R. G. , Dunn M. L. 
Published: July 2008

AbstractWe consider the problem of optimal design of nano‐scale heat conducting systems using topology optimization techniques. At such small scales the empirical Fourier's law of heat conduction no longer captures the underlying physical phenomena because the mean‐free path of the heat carriers, phonons in our case, becomes comparable with, or even larger than, the feature sizes of considered material distributions. A more accurate model at nano‐scales is given by kinetic theory, which provides a compromise between the inaccurate Fourier's law and precise, but too computationally expensive, atomistic simulations.We analyze the resulting optimal control problem in a continuous setting, briefly describing the computational approach to the problem based on discontinuous Galerkin methods, algebraic multigrid preconditioned generalized minimal residual method, and a gradient‐based mathematical programming algorithm. Numerical experiments with our implementation of the proposed numerical scheme are reported. Copyright © 2008 John Wiley & Sons, Ltd.
Crack identification by ‘arrival time’ using XFEM and a genetic algorithm
Authors: Rabinovich Daniel , Givoli Dan , Vigdergauz Shmuel 
Published: July 2008

AbstractA computational framework is developed in which cracks in two‐dimensional structures are identified, in conjunction with non‐destructive testing of specimens. As opposed to a previous study by the authors, which was based on time‐harmonic excitation with a single frequency, here the transient response of the structure to a short‐duration signal is measured along part of the external boundary. Crack detection is performed using the solution of an inverse time‐dependent problem. It is shown that the arrival time of the input signal to the points of measurement is a good criterion for crack identification in the time domain. The inverse problem of identification is solved using a genetic algorithm, while each forward problem is solved by the time‐dependent extended finite element method (XFEM). The XFEM scheme is efficient in that it allows the use of a single regular mesh for a large number of forward time response problems with different crack geometries. Numerical examples involving a crack in a flat membrane are presented. Identification based on ‘arrival time’ is shown to perform better than that based on time‐harmonic response. Copyright © 2008 John Wiley & Sons, Ltd.
A high‐order finite difference method for 1D nonhomogeneous heat equations
Authors: Lin Yuan , Gao Xuejun , Xiao MingQing 
Published: July 2008

AbstractIn this article a sixth‐order approximation method (in both temporal and spatial variables) for solving nonhomogeneous heat equations is proposed. We first develop a sixth‐order finite difference approximation scheme for a two‐point boundary value problem, and then heat equation is approximated by a system of ODEs defined on spatial grid points. The ODE system is discretized to a Sylvester matrix equation via boundary value method. The obtained algebraic system is solved by a modified Bartels‐Stewart method. The proposed approach is unconditionally stable. Numerical results are provided to illustrate the accuracy and efficiency of our approximation method along with comparisons with those generated by the standard second‐order Crank‐Nicolson scheme as well as Sun‐Zhang's recent fourth‐order method. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
A fully Galerkin method for the damped generalized regularized long‐wave (DGRLW) equation
Authors: Achouri Talha , Ayadi Mekki , Omrani Khaled 
Published: July 2008

AbstractIn this article, a fully discrete Galerkin scheme based on a nonlinear Crank–Nicolson method to approximate the solution of the DGRLW equation is constructed. Some a priori bounds are proved as well as error estimates. Then, a linearized modification scheme by an extrapolation method is discussed. The two schemes are time second order convergence. The last part is devoted to some numerical results. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
A new polynomial sequence as a guide to numerical solutions for applied‐physics‐related partial differential equations under Dirichlet‐Newman‐type exogenous boundary conditions
Authors: Mahmoud Karem B. Ben 
Published: July 2008

AbstractIn this article, a new set of polynomials is proposed as a new tool for solving bivaried partial differential equation related with some appropriated applied physics problems. A concrete formulation of canonical expressions, with respect to more common boundary conditions, is yielded out of the recently established Boubaker polynomials. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Benigne Prostata‐Hyperplasie und Benignes Prostata‐Syndrom. Die Krankheit des alten Mannes
Authors: Orth Matthias 
Published: July 2008

AbstractDie BPH oder besser das BPS ist eine sehr häufige Erkrankung des Mannes in der zweiten Lebenshälfte. Aufgrund der sehr heterogenen Symptome und Beeinträchtigung der Patienten durch das BPS steht vor einer Therapie immer eine ausreichende Diagnostik. Diese quantifiziert die Beschwerden, ermittelt deren Ursachen und schließt andere Erkrankungen wie das Prostatakarzinom mit hoher Sicherheit aus. Bei entsprechender Klinik stehen mit α‐Blockern und 5α‐Reduktasehemmern Medikamente mit guter Wirksamkeit zur Verfügung. Aufgrund der Nebenwirkungen und der Progredienz der Erkrankung sollte die Indikation zur Pharmakotherapie in regelmäßigen Abständen hinterfragt werden. Alternativen zur Pharmakotherapie bei geringer Symptomatik können Phytopharmaka sein, bei ausgeprägter Symptomatik muss allerdings oft chirurgisch interveniert werden.
Neuer Auftrieb in der Telomerase‐Forschung
Authors: Zündorf Ilse , Dingermann Theo 
Published: July 2008

AbstractUnsere linearen Chromosomen haben ein großes Problem: Bei jeder Replikationsrunde der DNA verkürzen sich ihre Enden um ca. 50 bis 100 Basenpaare. Zwar betrifft das vermeintlich “unwichtige” Sequenz‐Bereiche, die so genannten Telomere. Allerdings bedeutet die Verkürzung der Telomere auch eine Alterung der Zelle. Sind die Enden irgendwann zu kurz, stirbt die Zelle. Deshalb ist das Enzym, das Telomere wieder verlängern kann, die Telomerase, eine wichtige Ausstattung unsterblicher Krebszellen.
Führt das individuelle Genom zur individuellen Therapie?
Authors: Winckler Thomas 
Published: July 2008

AbstractNach Jahren der Freude über die Entzifferung des menschlichen Genoms rückt nun die individualisierte Genom‐Sequenzierung in den Mittelpunkt des Interesses. Dabei zündet die ohnehin rasante Genom‐Sequenzierung den Turbo.