bluuebunny/crossref_metadata_2025_split huggingface dataset:
An upwind finite element scheme for high‐Reynolds‐number flows
Authors: Tabata Masahisa , Fujima Shoichi 
Published: August 2005

AbstractA new upwind finite element scheme for the incompressible Navier‐Stokes equations at high Reynolds number is presented. The idea of the upwind technique is based on the choice of upwind and downwind points. This scheme can approximate the convection term to third‐order accuracy when these points are located at suitable positions. From the practical viewpoint of computation, the algorithm of the pressure Poisson equation procedure is adopted in the framework of the finite element method. Numerical results of flow problems in a cavity and past a circular cylinder show excellent dependence of the solutions on the Reynolds number. The influence of rounding errors causing Karman vortex shedding is also discussed in the latter problem.
A linearized Riemann solver for the steady supersonic Euler equations
Authors: Toro Eleuterio F. , Chou Cheng‐Chiang 
Published: August 2005

AbstractA very simple linearization of the solution to the Riemann problem for the steady supersonic Euler equations is presented. When used locally in conjunction with the Godunov method, computing savings by a factor of about four relative to the use of exact Riemann solvers can be achieved. For severe flow regimes, however, the linearization loses accuracy and robustness. We then propose the use of a Riemann solver adaptation procedure. This retains the accuracy and robustness of the exact Riemann solver and the computational efficiency of the cheap linearized Riemann solver. Numerical results for two‐ and three‐dimensional test problems are presented.
Role for CXCR2 and CXCL1 on glia in multiple sclerosis
Authors: Omari Kakuri M. , John Gareth , Lango Richard , Raine Cedric S. 
Published: August 2005

AbstractAs part of a need to understand myelin repair mechanisms, molecular pathways underlying oligodendrocyte behavior and central nervous system (CNS) remyelination are currently key topics in multiple sclerosis (MS). In the present study, we report expression of a chemoattractant receptor of the immune system, the chemokine receptor, CXCR2, on normal and proliferating oligodendrocytes in active MS lesions. Proliferating oligodendrocytes were occasionally associated with reactive astrocytes positive for CXCL1 (GRO‐α), the ligand for CXCR2. CXCL1 expression was not seen on astrocytes in control and normal CNS tissue, while CXCR2 expression was constitutive on oligodendrocytes. At the functional level, following stimulation with the proinflammatory cytokine, interleukin‐1β (IL‐1β), we found high‐level synthesis of CXCL1 by human fetal astrocytes in vitro. In contrast, human oligodendrocytes in culture expressed the receptor, CXCR2, constitutively. We propose that the concurrence of CXCR2 on oligodendrocytes and induced CXCL1 on hypertrophic astrocytes in MS provides a novel mechanism for recruitment of oligodendrocytes to areas of damage, an essential prerequisite for lesion repair in this devastating human condition. © 2005 Wiley‐Liss, Inc.
Cell sheet detachment affects the extracellular matrix: A surface science study comparing thermal liftoff, enzymatic, and mechanical methods
Authors: Canavan Heather E. , Cheng Xuanhong , Graham Daniel J. , Ratner Buddy D. , Castner David G. 
Published: August 2005

AbstractThis work compares the removal of bovine aortic endothelial cell (BAEC) monolayers via 1) low‐temperature liftoff from a “smart polymer,” plasma polymerized poly(N‐isopropyl acrylamide) (ppNIPAM), 2) enzymatic digestion, and 3) mechanical dissociation from ppNIPAM surfaces. We examine the surfaces after cell removal by using X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), immunostaining, and cell adhesion assay. Immunoassay results indicate that low‐temperature liftoff nondestructively harvests the cell sheet and most of the underlying extracellular matrix (ECM), whereas enzymatic digestion and mechanical dissociation are damaging to both the cells and ECM. XPS results indicate that amide and alcohol groups attributed to proteins in the ECM are present on postliftoff surfaces. Principal component analysis (PCA) of ToF‐SIMS data indicates that molecular ion fragments of amino acids are present on postliftoff surfaces. Finally, a cell adhesion assay seeding new cells on surfaces from which an initial layer of cells was removed via each of the three methods indicates that liftoff and mechanical dissociation leave behind surfaces that better promote cell adhesion. We conclude that the removal of BAEC cells via low‐temperature liftoff from ppNIPAM‐treated surfaces is less damaging to the ECM proteins remaining at the surface than the other methods. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Chitosan–alginate as scaffolding material for cartilage tissue engineering
Authors: Li Zhensheng , Zhang Miqin 
Published: August 2005

AbstractTissue compatibility of chitosan–alginate scaffolds was studied in vitro in terms of cell morphology, proliferation, and functionality using HTB‐94 cells. The scaffold has an interconnected 3D porous structure, and was fabricated by thermally induced phase separation followed by freeze drying. Cell proliferation on the chitosan–alginate scaffold was found to be faster than on a pure chitosan scaffold. After cell culture for 2 weeks in vitro, the cells on the chitosan scaffold gradually assumed a fibroblast‐like morphology while the cells on the chitosan–alginate scaffold retained their spherical morphology throughout the period of study. SDS‐PAGE electrophoresis and Western blot assays for proteins extracted from cells grown on scaffolds indicated that production of cartilage‐specific collagen type II, a marker for chondrocytic phenotype, increased from week 2 to week 3 on the chitosan–alginate scaffold but decreased on the chitosan scaffold. This study suggested that chitosan–alginate scaffolds promote cell proliferation, enhance phenotype expression of HTB‐94 chondrocytes, and may potentially serve as an improved alternative to chitosan scaffolds for cartilage tissue engineering. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
The effect of hyaluronic acid with different molecular weights on collagen crosslink synthesis in cultured chondrocytes embedded in collagen gels
Authors: Abe Masashi , Takahashi Masaaki , Nagano Akira 
Published: August 2005

AbstractHyaluronic acid (HA) is a component of the extracellular matrix of cartilage and has various effects on three‐dimensional cultured chondrocytes. We measured Pyridinoline (Pyr), which is a crosslink of collagen in cultured chondrocyte–collagen composites treated with HA of different molecular weights to investigate the effects of the various molecular weights on collagen crosslink synthesis. The control group was collagen gel without cells; group N was treated without HA; and the others were treated with HA with an average molecular weight of 2.3 ×106 Da (group H), 8.0 ×105 Da (group M), and 2.3 ×104 Da (group L). In the control group, the Pyr content decreased, at week 4, being one‐tenth that of preculture levels. In groups H and M, it was significantly greater than that in groups L and N at week 4. Pyr/hydroxyproline, which indicates the concentration of Pyr per collagen, decreased greatly in the control group at week 3. In groups H and M, it was significantly higher than that in groups L and N at week 4 and increased to 80 and 76% of normal rabbit articular cartilage, respectively. The concentration of Pyr per collagen in cultured chondrocyte–collagen composites was similar to that of normal articular cartilage in vivo, and higher molecular weight HA may have a greater effect on the maturation of collagen in the composite. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Processing of radial fast spin‐echo data for obtaining T2 estimates from a single k‐space data set
Authors: Altbach Maria I. , Bilgin Ali , Li Zhiqiang , Clarkson Eric W. , Trouard Theodore P. , Gmitro Arthur F. 
Published: August 2005

AbstractRadially acquired fast spin‐echo data can be processed to obtain T2‐weighted images and a T2 map from a single k‐space data set. The general approach is to use data at a specific TE (or narrow TE range) in the center of k‐space and data at other TE values in the outer part of k‐space. With this method high‐resolution T2‐weighted images and T2 maps are obtained in a time efficient manner. The mixing of TE data, however, introduces errors in the T2‐weighted images and T2 maps that affect the accuracy of the T2 estimates. In this work, various k‐space data processing methods for reconstructing T2‐weighted images and T2 maps from a single radial fast spin‐echo k‐space data set are analyzed in terms of the accuracy of T2 estimates. The analysis is focused on the effect of image artifacts, object dependency, and noise on the T2 estimates. Results are presented in computer‐generated phantoms and in vivo. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
19F MR imaging of ventilation and diffusion in excised lungs
Authors: Jacob Richard E. , Chang Yulin V. , Choong Cliff K. , Bierhals Andy , Zheng Hu Ding , Zheng Jie , Yablonskiy Dmitriy A. , Woods Jason C. , Gierada David S. , Conradi Mark S. 
Published: August 2005

AbstractPerfluorinated gases, particularly C2F6, are potentially suitable alternatives to hyperpolarized noble gases for pulmonary airspace spin density and diffusion MRI. This work focuses mainly on 19F imaging of C2F6 gas in healthy and emphysematous explanted lungs, avoiding regulatory issues of human in vivo measurements. Three‐dimensional gradient echo and spin echo spin density images of human lungs can be made in 10 s with adequate signal‐to‐noise, demonstrating the feasibility for breathing dynamics to be captured during a succession of short breath holds. As expected, the spin echo images have much smaller susceptibility artifacts than the gradient echo images. 19F and 3He images of the same lungs are compared. The apparent diffusion coefficient (ADC) of C2F6 is sensitive to restrictions imposed by the lung microstructure: the average ADC is measured to be 0.018 cm2/s in healthy lungs versus 0.031 cm2/s in emphysematous lungs at a diffusion time Δ = 2.2 ms. The low free diffusivity of pure C2F6 (D0 = 0.033 cm2/s) places it in a regime where the ADC measurement allows the surface‐to‐volume ratio to be determined in each voxel, a potentially valuable quantitative characterization of regional lung tissue destruction in emphysema. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Chronic inflammatory demyelinating polyradiculoneuropathy with tumefactive central demyelination
Authors: Krivickas Lisa S. , Hochberg Fred H. , Freeman Stefanie 
Published: August 2005

AbstractA 46‐year‐old man with a 1‐year history of distal paresthesias and mild distal weakness subacutely developed paralysis of the left hand. Electrodiagnostic evaluation revealed a demyelinating peripheral neuropathy that met criteria for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Magnetic resonance imaging of the brain revealed a mass that enhanced with contrast, but revealed focal myelin loss with intense macrophage activity and axonal preservation on biopsy. The mass and hand weakness improved following steroid therapy. The combination of CIDP and central demyelination with mass effect broadens the spectrum of demyelinating disease in association with CIDP. Muscle Nerve, 2005
On Garg's solution of Biot's equations for wave propagation in a one‐dimensional fluid‐saturated elastic porous solid
Authors: Hong S. J. , Sandhu Ranbir S. , Wolfe William E. 
Published: August 2005

AbstractGarg's approximate analytical solutions of Biot's equations for wave propagation in a fluid‐saturated elastic porous solid of infinite extent subjected to a velocity boundary condition of a Heaviside function at one end are examined for small and large drag. Garg's approximations were apparently introduced to facilitate exact inversion of Laplace transforms of certain quantities. The approximate solutions are compared with carefully evaluated numerical inverses of the Laplace transform solutions for different soils with widely varying properties. It is seen that for most soils (clays, silts and, sands) the error in Garg's approximate solutions in insignificant, and the solutions can be used as benchmarks for verifying numerical analysis procedures such as finite element codes.
Material instability for drained and undrained behaviour. Part 2: Combined uniform deformation and shear‐band generation
Authors: Molenkamp F. 
Published: August 2005

AbstractTo increase the insight into the phenomenon of liquefaction a theoretical study has been performed of material instability for undrained behaviour. Material instability concerns the instability of an equilibrium state of an infinite homogeneous solid for both uniform deformation and shear‐band generation. In a companion paper shear‐band generation has been considered. In this paper the case of uniform deformation is elaborated and combined with the previous results. It can be concluded that instability occurs sooner for increasing contraction and decreasing drainage. For zero plastic volume change and decreasing drainage the mode of instability changes from drained shear‐band generation to undrained uniform deformation. For contractant materials the instability of undrained behaviour is mainly due to uniform deformation.
Numerical analysis of sedimentation and consolidation by the moving finite element method
Authors: Shodja Hossein M. , Feldkamp Joseph R. 
Published: August 2005

AbstractTraditionally, sedimentation and self‐weight consolidation have been viewed as physically distinct processes requiring separate treatment. Relatively recently, Pane and Schiffman1 and also Philip and Smiles2 have suggested that the two processes may be described by a single partial differential equation, essentially that of Gibson et al.3 The former suggests a modification of Terzaghi's effective stress principle while the paper by Philip and Smiles suggests that a suitable modelling of material properties is sufficient. We have adopted the latter approach by allowing for the compressibility of the material in question to change abruptly from finite values to infinity in the so‐called transition region which delineates that portion of space where effective stress is zero from that where effective stress in non‐zero. This procedure gives rise to serious difficulties when trying to solve the governing partial differential equation numerically. These difficulties are circumvented by using a relatively new numerical technique known as the Moving Finite Element (MFE) method. The MFE method is especially effective in solving problems having solutions that characteristically exhibit shock‐like structure. The modelling of sedimentation and self‐weight consolidation from a single governing model is an ideal candidate for MFE due to the abrupt, almost discontinuous change in void ratio displayed in the transition region.
Thermodynamical approach for CamClay‐family models with Roscoe‐type dilatancy rules
Authors: Modaressi Hormoz , Laloui Lyesse , Aubry Denis 
Published: August 2005

AbstractThe CamClay model has been extensively used in numerous research programmes for constitutive modelling in Soil Mechanics during the past quarter of a century. Several derivations of this model are now available and routinely used for numerical simulations in the geomechanical engineering field. However, to the authors' knowledge the thermodynamical basis of this model in its original form has never been established, at least in a modern thermodynamics framework. The thermodynamics principle proposed by Ziegler is very expedient for this purpose as the non‐associated flow rule may be considered. This approach is applied to the CamClay model with the Roscoe dilatancy rule. A dissipation function and free energy are specified in terms of kinematic variables (i.e. state and internal variables), and the material response is derived entirely from these functions.
Influence of subsurface fractures on surface deformation of an elastic half‐space
Authors: Wang G. , Dusseault M. B. , Pindera J. T. , Rothenburg L. 
Published: August 2005

AbstractThe paper presents a solution for calculation of the surface uplift field of a semi‐infinite elastic solid embedded with a pressurized elliptical crack oriented at any angle, and at any depth. The results presented are those for a uniform pressure loading on the crack face, simulating a static pressurized hydraulic fracture, but the mathematical technique developed can be extended directly to non‐uniform normal loads or general shear loads in the form of a polynomial up to the third order. The result of a special case of the new solution, where the crack is penny shaped and parallel to the free surface, is compared with results from Sun's solution and from experiments which were designed and performed by the authors. The experiments involved pressurization of a penny‐shaped crack in a polyurethane material which is linear elastic under low stresses, and measurement of surface deformation by holographic interferometry and Fizeau interferometry. The correspondence between theory and experiment is excellent.
Non‐linear structural analysis by dynamic relaxation
Authors: Brew J. S. , Brotton D. M. 
Published: August 2005

AbstractDynamic relaxation, an iterative method for use with digital computers, is described and is shown to be suitable for the solution of a system of linear equations and in particular for such problems derived from structural frame analysis. It is further shown that the method may be modified to include non‐linear equations relating to these problems.Some specific examples of linear and non‐linear solutions are given and comparisons are made with another computer method which performs the same tasks.
Calculation of eigenvalues of the Helmholtz equation by an integral equation
Authors: de Mey G. 
Published: August 2005

AbstractA method is presented to calculate the eigenvalues of the Helmholtz equation Δ2ø + k2ø = 0 in a two‐dimensional area when ø vanishes on the boundary. The method is based on an integral equation, which can be easily solved numerically. Results obtained for circular and rectangular geometries are also given and compared to the exact values.
Automatic generation of triangular grid: I—subdivision of a general polygon into convex subregions. II—triangulation of convex polygons
Authors: Bykat A. 
Published: August 2005

AbstractOne of the integral parts of any finite element procedure is the subdivision of a finite dimensional region into a finite number of non‐overlapping subregions. An algorithm for subdivision of 2‐dimensional polygons into triangular subregions is presented here. The algorithm consists conceptually of two steps. In the first step the region is subdivided into convex subregions; In the second step the convex subregions are further subdivided into triangular elements.
Mixed finite element formulation for geometrically non‐linear analysis of shells of revolution
Authors: Tottenham H. , Barony S. Y. 
Published: August 2005

AbstractA Finite Element formulation for the axisymmetrical analysis of rotational shells with geometric non‐linearity is developed, using a mixed finite element model of a curved rotational shell type, the two global components of displacement (ur, uz) and the two stress couples (Mr, MtH) being the free and independent unknowns of the problem. The prescribed geometry at every nodal circle comprises the co‐ordinates and meridional slope angle and curvature. Newton‐Raphson Iteration is used in solving the non‐linear system of equations. Circular plates and a spherical cap are used as examples to test the formulation; good results were achieved which are presented graphically in comparison to the analytical solution.
A finite element method for Burgers' equation in hydrodynamics
Authors: Arminjon Paul , Beauchamp Cladue 
Published: August 2005

AbstractA Finite Element Method using rectangular elements is applied to solve Burgers' non‐linear equation in one space dimension. The non‐linear algebraic equations thus obtained are solved by an iteration which is equivalent to the generalized Newton method. Numerical experiments indicate that the order of accuracy is equal to 2. In two space dimensions, the method is more efficient than other methods we have tested.
Hybrid stress finite element analysis of bending of a plate with a through flaw
Authors: Rhee H. C. , Atluri S. N. 
Published: August 2005

AbstractA hybrid stress finite element procedure for the solution of bending stress intensity factors of a plate with a through‐the‐thickness crack is presented. Reissner's sixth‐order plate theory including the effects of transverse shear deformation is used. The dominant singular crack tip stress field is embedded in the crack tip singular elements and only regular polynomial functions are assumed in the far field elements. The stress intensity factors can be calculated directly from the crack tip singular stress solution functions. The effects of the plate thickness, the ratio between the crack size and the inplane dimension of the plate, and the singular element size on the stress intensity factor solution are investigated.The effects of the explicit enforcement of traction‐free conditions along crack surfaces, which are the natural boundary conditions in the present hybrid stress finite element model, are also investigated. The numerical results of bending of a plate with a straight central crack compare favourably with analytical solutions. It is also found that the explicit enforcement of traction‐free conditions along crack surfaces is mandatory to obtain meaningful results for the Mode I type of bending stress intensity factor.
Dual analysis of plane stress problems by commonly based finite elements
Authors: Harvey John W. 
Published: August 2005

AbstractFinite element models for linear elastic plane stress problems which provide, alternatively, a completely compatible displacement field or a precisely equilibrated stress field are developed. The basis for both models is a biquintic interpolation polynomial representing Airy's stress function over a triangular region. The polynomial coefficients are modified and grouped to establish compatibility while retaining equilibrium within each element. Nodal kinematic parameters are selected and matched to the stress function for the compatible (modified stiffness) model, while nodal stress function parameters are chosen for the equilibrium (modified flexibility) model. Constraints on the global freedoms, enforced by Lagrange multipliers, are introduced to augment nodal connectivity in establishing interelement compatibility in the ‘stiffness’ model and uniform stress transmission in the ‘flexibility’ model. Appropriate boundary conditions are formed for each model. Numerical solutions are obtained and assessed.
Added mass computations by integral equation methods
Authors: Ousset Y. , Sayhi M. N. 
Published: August 2005

AbstractThis paper presents boundary integral equation procedures for calculating the added mass matrix required to determine hydroelastic vibrational modes of tanks or immersed structures. The liquid is assumed inviscid and incompressible and no surface waves are admitted. Two symmetric variational formulations of the boundary integral equation are derived, including the free surface condition and possible conditions of symmetry. These are approximated by a curved finite element method and numerical results are presented for an axisymmetric tank, immersed cantilever plates and a three‐dimensional fuel storage container.