bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of spin compartment in arterial spin labeling MRI
Authors: Liu Peiying , Uh Jinsoo , Lu Hanzhang
Published: August 2010

A major difference between arterial‐spin‐labeling MRI and gold‐standard radiotracer blood flow methods is that the compartment localization of the labeled spins in the arterial‐spin‐labeling image is often ambiguous, which may affect the quantification of cerebral blood flow. In this study, we aim to probe whether the spins are located in the vascular system or tissue by using T2 of the arterial‐spin‐labeling signal as a marker. We combined two recently developed techniques, pseudo‐continuous arterial spin labeling and T2‐Relaxation‐Under‐Spin‐Tagging, to determine the T2 of the labeled spins at multiple postlabeling delay times. Our data suggest that the labeled spins first showed the T2 of arterial blood followed by gradually approaching and stabilizing at the tissue T2. The T2 values did not decrease further toward the venous T2. By fitting the experimental data to a two‐compartment model, we estimated gray matter cerebral blood flow, arterial transit time, and tissue transit time to be 74.0 ± 10.7 mL/100g/min (mean ± SD, N = 10), 938 ± 156 msec, and 1901 ± 181 msec, respectively. The arterial blood volume was calculated to be 1.18 ± 0.21 mL/100 g. A postlabeling delay time of 2 s is sufficient to allow the spins to completely enter the tissue space for gray matter but not for white matter. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Novel spherical phantoms for Q‐ball imaging under in vivo conditions
Authors: Moussavi‐Biugui Amir , Stieltjes Bram , Fritzsche Klaus , Semmler Wolfhard , Laun Frederik B.
Published: August 2010

For the validation of complex diffusion imaging techniques like q‐ball imaging that aim to resolve multiple fiber directions, appropriate phantoms are highly desirable. However, previous q‐ball imaging phantoms had diffusion anisotropies well below those of in vivo white matter. In this work, fiber phantoms of well‐defined geometry are presented. The fibers are wound on a spherical spindle yielding high packing densities and consequently high diffusion anisotropies (fractional anisotropy 0.93 ± 0.02 at b = 500 s/mm2). Phantoms with 90° and 45° crossing angle were constructed both with two crossing types. In the “stacked” crossing, two fiber strings were wound consecutively to simulate two touching fibers, in the “interleaved” crossing, fibers were wound alternately. The stacked crossing allows the alteration of partial volumes, whereas the interleaved crossing provides constant partial volumes, allowing e.g. the easy alteration of the SNR by varying the slice thickness. Exemplary q‐ball imaging validation measurements using different b‐values and slice thicknesses are presented. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Accelerated cardiac magnetic resonance imaging in the mouse using an eight‐channel array at 9.4 Tesla
Authors: Schneider Jürgen E. , Lanz Titus , Barnes Hannah , Stork Lee‐Anne , Bohl Steffen , Lygate Craig A. , Ordidge Roger J. , Neubauer Stefan
Published: August 2010

MRI has become an important tool to noninvasively assess global and regional cardiac function, infarct size, or myocardial blood flow in surgically or genetically modified mouse models of human heart disease. Constraints on scan time due to sensitivity to general anesthesia in hemodynamically compromised mice frequently limit the number of parameters available in one imaging session. Parallel imaging techniques to reduce acquisition times require coil arrays, which are technically challenging to design at ultrahigh magnetic field strengths. This work validates the use of an eight‐channel volume phased‐array coil for cardiac MRI in mice at 9.4 T. Two‐ and three‐dimensional sequences were combined with parallel imaging techniques and used to quantify global cardiac function, T1‐relaxation times and infarct sizes. Furthermore, the rapid acquisition of functional cine‐data allowed for the first time in mice measurement of left‐ventricular peak filling and ejection rates under intravenous infusion of dobutamine. The results demonstrate that a threefold accelerated data acquisition is generally feasible without compromising the accuracy of the results. This strategy may eventually pave the way for routine, multiparametric phenotyping of mouse hearts in vivo within one imaging session of tolerable duration. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Effect of shoulder angle on the activation pattern of the elbow extensors during a submaximal isometric fatiguing contraction
Authors: Davidson Andrew W. , Rice Charles L.
Published: August 2010

The aim of this study was to examine the effect of shoulder angle on the electromyographic (EMG) activation pattern of the elbow extensors during a fatiguing contraction. Ten young men (23.5 ± 1.7) were tested on two occasions with the elbow angle at 90° and the shoulder at either 0° or 90° of flexion. EMG was recorded by fine wire electrodes inserted into the lateral, medial, and long heads of the triceps brachii and the anconeus. An EMG‐torque relationship was determined prior to a sustained isometric contraction at 20% of maximum voluntary contraction (MVC) until target failure. Endurance time was shorter, and postfatigue MVC torque was lower at 90° (40.4 ± 12.7 Nm) versus 0° (47.9 ± 14.7 Nm) of flexion. EMG activity of the long head during the final 10% of the fatiguing contraction was significantly greater at 90° versus 0° with no effect of shoulder angle on any other muscle portions. The findings suggest that measures from one muscle portion of the elbow extensors are not representative of the whole group, and the relative activation of the two‐joint long head was changed depending on shoulder angle during a fatigue task. Muscle Nerve, 2010
Permissive environment for B‐cell maturation in myositis muscle in the absence of B‐cell follicles
Authors: Salajegheh Mohammad , Pinkus Jack L. , Amato Anthony A. , Morehouse Chris , Jallal Bahija , Yao Yihong , Greenberg Steven A.
Published: August 2010

Myositis muscle contains antigen‐matured B‐cells and plasma cells. Myositis muscle biopsy specimens were examined for nodular collections of T‐cells, B‐cells, myeloid dendritic cells, plasma cells, and follicular dendritic cells. Immunoglobulin and B‐cell–activating factor (BAFF) transcripts were quantitated. Laser‐capture microdissection was used to isolate single plasma cells, and their immunoglobulin transcripts were sequenced. Dense inflammatory infiltrates contained histological elements of ectopic lymphoid tissue but not B‐cell follicles. Immunoglobulin transcript sequence analysis demonstrated spatially distributed, clonally related B‐cells and plasma cells, suggesting local maturation of B‐cells into plasma cells in myositis muscle. Regions of dense cellular infiltrates in myositis muscle are sometimes areas of B‐cell maturation into antibody‐producing plasma cells. An atypical lymphoid histology, lacking concentrated collections of germinal‐center–like B‐cell follicles, is capable of antigen‐stimulated clonal maturation of antibody‐producing plasma cells. Muscle Nerve, 2010
Natural history of exertional rhabdomyolysis: A population‐based analysis
Authors: Alpers Joshua P. , Jones Lyell K.
Published: September 2010

Exertional rhabdomyolysis is a potentially catastrophic syndrome with an incidence and rate of recurrence that are unknown. In this study patients with rhabdomyolysis were identified retrospectively from the Wilford Hall Medical Center records. A population‐based analysis was performed on exertional rhabdomyolysis patients enrolled in basic military training. A retrospective cohort was analyzed for rate and risks of recurrence. Of 177 rhabdomyolysis patients, 63 were exertional in mechanism. The rate of renal failure was lower in exertional rhabdomyolysis patients (odds ratio 0.45, 95% confidence interval 0.22–0.95, P = 0.04). There were 44 cases of exertional rhabdomyolysis from a population of 198,399 total military trainees over the study period, or 22.2 cases per 100,000 per year. A cohort of 22 exertional rhabdomyolysis patients was followed for a mean of 31.2 months, with only 1 recurrence (recurrence risk of 0.08% per person per year). Exertional rhabdomyolysis is associated with lower rates of complications than other causes of rhabdomyolysis. Among young, physically active patients, the incidence of exertional rhabdomyolysis is low, as is the risk of recurrence. Muscle Nerve, 2010
Probabilistic muscle characterization using quantitative electromyography: Application to facioscapulohumeral muscular dystrophy
Authors: Pino Lou Joseph , Stashuk Daniel W. , Podnar Simon
Published: August 2010

Based on quantitative electromyography, a muscle can be categorized as normal or affected by a neuromuscular disorder. The objective of this work was to compare the utility of probabilistic to conventional means and outlier methods of categorization of myopathic and normal muscles. Various sets of motor unit potential (MUP) features detected in biceps brachii muscles of control subjects and patients with facioscapulohumeral muscular dystrophy were used to categorize them as normal or myopathic based on conventional means and outlier categorization (CMC) as well as a new probabilistic muscle categorization (PMC). The sensitivity, specificity, and accuracy provided by each categorization method were compared. The categorizations made using PMC were significantly more accurate (by at least 10%) compared with CMC (P < 10−10) for muscles evaluated in this study. Area, duration, and thickness were highly discriminative MUP features. Muscle Nerve, 2010
A novel SOD1 mutation in a young amyotrophic lateral sclerosis patient with a very slowly progressive clinical course
Authors: Georgoulopoulou Eleni , Gellera Cinzia , Bragato Cinzia , Sola Patrizia , Chiari Annalisa , Bernabei Chiara , Mandrioli Jessica
Published: August 2010

Approximately 10% of amyotrophic lateral sclerosis (ALS) cases are familial, and the Cu/Zn superoxide dismutase (SOD1) gene mutation accounts for 20% of them. More than 100 SOD1 mutations have been described, some with peculiar phenotypes. Moreover, mutations in the SOD1 gene have been described in apparently sporadic ALS cases. We report a new mutation (D11Y) in the Cu/Zn superoxide dismutase gene in a patient with ALS and an unusually slow disease progression. Muscle Nerve, 2010
Compound muscle action potential and motor function in children with spinal muscular atrophy
Authors: Lewelt Aga , Krosschell Kristin J. , Scott Charles , Sakonju Ai , Kissel John T. , Crawford Thomas O. , Acsadi Gyula , D'anjou Guy , Elsheikh Bakri , Reyna Sandra P. , Schroth Mary K. , Maczulski Jo Anne , Stoddard Gregory J. , Elovic Elie , Swoboda Kathryn J.
Published: August 2010

Reliable outcome measures that reflect the underlying disease process and correlate with motor function in children with SMA are needed for clinical trials. Maximum ulnar compound muscle action potential (CMAP) data were collected at two visits over a 4–6‐week period in children with SMA types II and III, 2–17 years of age, at four academic centers. Primary functional outcome measures included the Modified Hammersmith Functional Motor Scale (MHFMS) and MHFMS‐Extend. CMAP negative peak amplitude and area showed excellent discrimination between the ambulatory and non‐ambulatory SMA cohorts (ROC = 0.88). CMAP had excellent test–retest reliability (ICC = 0.96–0.97, n = 64) and moderate to strong correlation with the MHFMS and MHFMS‐Extend (r = 0.61–0.73, n = 68, P < 0.001). Maximum ulnar CMAP amplitude and area is a feasible, valid, and reliable outcome measure for use in pediatric multicenter clinical trials in SMA. CMAP correlates well with motor function and has potential value as a relevant surrogate for disease status. Muscle Nerve, 2010
Three‐dimensional inverse analyses of a deep excavation in Chicago clays
Authors: Hashash Youssef M. A. , Song Hwayeon , Osouli Abdolreza
Published: August 2010

Numerical models are commonly used to estimate excavation‐induced ground movements. Two‐dimensional (2D) plain strain assumption is typically used for the simulation of deep excavations which might not be suitable for excavations where three‐dimensional (3D) effects dominate the ground response. This paper adapts an inverse analysis algorithm to learn soil behavior from field measurements using a 3D model representation of an excavation. The paper describes numerical issues related to this development including the generation of the 3D model mesh from laser scan images of the excavation. The inverse analysis to extract the soil behavior in 3D is presented. The model captures the measured wall deflections. Although settlements were not sufficiently measured, the predicted settlements around the excavation site reflected strong 3D effects and were consistent with empirical correlations. Copyright © 2010 John Wiley & Sons, Ltd.
Modeling of dynamic cohesive fracture propagation in porous saturated media
Authors: Khoei A. R. , Barani O. R. , Mofid M.
Published: August 2010

In this paper, a mathematical model is presented for the analysis of dynamic fracture propagation in the saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double‐nodded zero‐thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The crack is automatically detected and propagated perpendicular to the maximum effective stress. The spatial discretization is continuously updated during the crack propagation. Numerical examples from the hydraulic fracturing test and the concrete gravity dam show the capability of the model to simulate dynamic fracture propagation. The comparison is performed between the quasi‐static and fully dynamic solutions, and the performance of two analyses is investigated on the values of crack length and crack mouth opening. Copyright © 2010 John Wiley & Sons, Ltd.
Prediction of blast fragmentation using multivariate analysis procedures
Authors: Hudaverdi T. , Kulatilake P. H. S. W. , Kuzu C.
Published: August 2010

An extensive multivariate analysis procedure for prediction of blast fragmentation distribution is presented. Several blasts performed in various mines and rock formations in the world are brought together and evaluated. Blast design parameters, the modulus of elasticity, in situ block size are considered to perform multivariate analysis. The hierarchical cluster analysis is used to separate the blasts data into different groups of similarity. Group memberships were checked by the discriminant analysis. The multivariate regression analysis was applied to develop prediction equations for the estimation of the mean particle size of muckpiles. Two different prediction equations were developed based on the rock stiffness. Validation of the proposed equations on various mines is presented and the capability of the prediction equations was compared with one of the most applied fragmentation distribution models appearing in the blasting literature. Prediction capability of the proposed models was found to be strong. Diversity of the blasts data used is one of the most important aspects of the developed models. The models are not complex and suitable for practical use at mines. Copyright © 2010 John Wiley & Sons, Ltd.
Degradation of rock fracture asperities in unloading, reloading, and reversal
Authors: Asadollahi Pooyan , Tonon Fulvio
Published: August 2010

Among the constitutive models for rock fractures developed over the years, Barton's empirical model has been widely used. Although Barton's failure criterion predicts peak shear strength of rock fractures with acceptable precision, it has some limitations in estimating the peak shear displacement, post‐peak shear strength, dilation, and surface degradation. The first author modified Barton's original model in order to address these limitations.

Barton proposed his model for degradation of fracture asperities in unloading, reloading, and shear displacement reversal based on just one cyclic direct shear test. In this study, a database of results of 18 cyclic direct shear tests available in the literature was collected and analyzed. Modifications were made to Barton's original model (in terms of fracture cyclic shearing) to make it consistent with the modified model proposed by the first author. Copyright © 2010 John Wiley & Sons, Ltd.
Isogeometric finite element data structures based on Bézier extraction of NURBS
Authors: Borden Michael J. , Scott Michael A. , Evans John A. , Hughes Thomas J. R.
Published: August 2010

We present the B'ezier extraction operator and isogeometric Bézier elements for non‐uniform rational B‐Spline (NURBS)‐based isogeometric analysis. The Bézier extraction operator allows numerical integration of smooth functions to be performed on C0 Bézier elements. We show how the Bézier extraction operator is computed for NURBS. We then show that the extraction operator and Bézier elements provide an element structure for isogeometric analysis that can be easily incorporated into existing finite element codes, without any changes to element form and assembly algorithms, and standard data processing arrays. All significant changes may be implemented in a shape function subroutine. Copyright © 2010 John Wiley & Sons, Ltd.
A system‐level model reduction technique for the efficient simulation of flexible multibody systems
Authors: Heirman Gert H. K. , Naets Frank , Desmet Wim
Published: August 2010

Flexible multibody systems are governed by sets of non‐linear differential‐algebraic equations (DAE). The number of degrees of freedom (DOFs) required for accurate body flexibility modeling, as well as the presence of the algebraic constraint equations limit the simulation speed. Body‐level model reduction and general‐purpose system‐level model reduction techniques do not result in optimal model dimension reduction and do not necessarily transform the DAE‐set into a cheaper to solve set of ordinary differential equations, as opposed to model reduction techniques, such as Global Modal Parameterization (GMP), which are based on describing the system motion by the contribution of its dominant (configuration‐dependent) system‐level modal patterns. Their use as a simulation tool has not been thoroughly investigated. This paper investigates the influence of the modal content of the configuration‐dependent mode set on the simulation accuracy through numerical experiments. By including the dynamically excited eigenmodes and static deformation patterns for DOFs in which the system is externally loaded, the system can be accurately represented by a very limited number of DOFs. Phenomena such as mode veering and mode crossing, in which the modal content of eigenmodes rapidly varies, can be expected to be problematic for such a description, which is confirmed with numerical experiments. Copyright © 2010 John Wiley & Sons, Ltd.
An efficient framework for fluid–structure interaction using the lattice Boltzmann method and immersed moving boundaries
Authors: Owen D. R. J. , Leonardi C. R. , Feng Y. T.
Published: August 2010

This paper presents a serial computational framework that hydrodynamically couples the lattice Boltzmann method (LBM) and the discrete element method (DEM) for the solution of particle suspension problems in two and three dimensions. The single‐relaxation‐time Bhatnagar–Gross–Krook (LBGK) form of the lattice Boltzmann equation is employed with an immersed moving boundary method for the fluid–structure interaction. Similar algorithms have been previously reported in the literature, however, this work deliberately utilizes solution options that minimize the computational overheads of the framework to facilitate simulations of multibody structural fields in large fluid domains. In particular, mixed boundary conditions are employed which combine the simple bounce‐back technique with the immersed moving boundary method, and the relatively inexpensive D3Q15 lattice is employed for 3D solutions. The fundamentals of the LBM are briefly discussed followed by a review of the coupling techniques available for FSI using the LBM. Options for mapping solid obstacles to the LBM grid are presented and an algorithm for automatic, dynamic subcycling of the two explicit solution schemes is outlined. The LBM–DEM framework is then validated and benchmarked against previously published LBM results, with comments made where appropriate on the comparative accuracy and convergence characteristics. Finally, a multi‐particle suspension simulation is presented to qualitatively assess the performance of the framework when a large number of dynamic contacts exist. Copyright © 2010 John Wiley & Sons, Ltd.
A thin plate formulation without rotation DOFs based on the radial point interpolation method and triangular cells
Authors: Cui X. Y. , Liu G. R. , Li G. Y. , Zhang G. Y.
Published: August 2010

A formulation for thin plates with only the deflection as nodal variables has been proposed using the generalized gradient smoothing technique and the radial point interpolation method (RPIM). The deflection fields are approximated using the RPIM shape functions which possess the Kronecker Delta property for easy impositions of essential boundary conditions. Three types of smoothing domains, which are also serving as the numerical integrations domains, are constructed based on the background three‐node triangular cells and the generalized gradient smoothing operation is performed over each of them to obtain the smoothed curvatures. The generalized smoothed Galerkin weak form is then used to create the discretized system equations. The essential boundary conditions of rotations are imposed in the process of constructing the curvature field, and the translation boundary conditions are imposed as in the standard FEM. A number of numerical examples, including both static and free vibration analysis, are studied using the present methods and the numerical results are compared with the analytical ones and those in the open literatures. The results show that the present formulation can obtain very stable and accurate solutions, even for the extremely irregular background cells. Copyright © 2010 John Wiley & Sons, Ltd.
Reliable second‐order hexahedral elements for explicit methods in nonlinear solid dynamics
Authors: Danielson Kent T. , O'Daniel James L.
Published: August 2010

Second‐order hexahedral elements are common in static and implicit dynamic finite element codes for nonlinear solid mechanics. Although probably not as popular as first‐order elements, they can perform better in many circumstances, particularly for modeling curved shapes and bending without artificial hourglass control or incompatible modes. Nevertheless, second‐order brick elements are not contained in typical explicit solid dynamic programs and unsuccessful attempts to develop reliable ones have been reported. In this paper, 27‐node formulations, one for compressible and one for nearly incompressible materials, are presented and evaluated using non‐uniform row summation mass lumping in a wide range of nonlinear example problems. The performance is assessed in standard benchmark problems and in large practical applications using various hyperelastic and inelastic material models and involving very large strains/deformations, severe distortions, and contact‐impact. Comparisons are also made with several first‐order elements and other second‐order hexahedral formulations. The offered elements are the only second‐order ones that performed satisfactorily in all examples, and performed generally at least as well as mass lumped first‐order bricks. It is shown that the row summation lumping is vital for robust performance and selection of Lagrange over serendipity elements and high‐order quadrature rules are more crucial with explicit than with static/implicit methods. Whereas the reliable performance is frequently attained at significant computational expense compared with some first‐order brick types, these elements are shown to be computationally competitive in flexure and with other first‐order elements. These second‐order elements are shown to be viable for large practical applications, especially using today's parallel computers. Published in 2010 by John Wiley & Sons, Ltd.
Codf‐evolutions on polycrystalline orientation continua obtained by fast geometric estimates of plastic slip
Authors: Miehe C. , Frankenreiter I. , Rosato D.
Published: August 2010

This paper presents a framework for the modeling of evolving crystal orientation distribution functions (codf) and orientation averages of polycrystalline aggregates undergoing finite deformations. The method is designed for fast estimates of the polycrystalline deformation textures in metals. It bases on the Taylor approach of rigid polycrystal plasticity, where the decision of slip‐activity in the local crystalline grains is based on a geometric argument. This approach allows a purely kinematic estimate of codf evolution completely independent of the hardening response of the single crystal grains. The investigation starts with a precise description of a deforming orientation continuum. This concerns the general geometric setup as well as details of the parameterization of rotations in terms of Rodrigues vectors. We then outline Lagrangian and Eulerian geometric settings of crystal fraction conservation laws and discuss the details of their discretization. An important aspect is the definition of orientation averages. This homogenization over the orientation space is an important ingredient of a multiscale modeling of evolving anisotropy. It is shown that the discrete evaluation of orientation averages does not need the explicit computation of codf. The core of the proposed method is a fast update algorithm for rate‐independent rigid crystal plasticity that directly determines the current Rodrigues vectors. We show for several deformation modes of polycrystalline aggregates that the proposed geometric estimates predict the codf evolution and overall anisotropy very well in the range of large strains. The new method is extremely robust and suitable for multiscale methods for the description of evolving anisotropy in polycrystals. Copyright © 2010 John Wiley & Sons, Ltd.
Advanced fully coupled thermo‐mechanical plate elements for multilayered structures subjected to mechanical and thermal loading
Authors: Nali P. , Carrera E. , Calvi A.
Published: August 2010

This paper presents a hierarchical modeling for the analysis of multilayered structures subjected to mechanical and thermal loadings. The principle of virtual displacement is applied in the framework of the Carrera unified formulation to obtain a complete family of plate finite elements. The order of the variable description through the plate‐thickness direction can be set in the range from one to four. The results in the form of tables and graphs are given to validate the proposed elements. Pure mechanical and fully coupled thermo‐mechanical cases studies are proposed. The application of Fourier's law is not required since the plate‐thickness temperature profile is automatically obtained in the framework of the proposed approach. The numerical results are obtained through the MUL2 academic code. Copyright © 2010 John Wiley & Sons, Ltd.
Dynamics of clusters of charged particulates in electromagnetic fields
Authors: Zohdi T. I.
Published: August 2010

The dynamics of rigid clusters of charged particulates is the subject of this work. The work ascertains what properties of the cluster control its dynamic response to an external electromagnetic field. A primary focus is on the role of the distribution of the charges within the cluster and the effects of the Lorentz force on the overall body's linear and angular momentum. The presentation contains a derivation of the equations governing a charged cluster's dynamics and development of corresponding numerical methods for the simulation. Numerical examples are presented, along with comparisons to qualitative analytical results, where possible. Copyright © 2010 John Wiley & Sons, Ltd.
A fracture framework for Euler–Bernoulli beams based on a full discontinuous Galerkin formulation/extrinsic cohesive law combination
Authors: Becker G. , Noels L.
Published: August 2010

A new full Discontinuous Galerkin discretization of Euler–Bernoulli beam is presented. The main interest of this framework is its ability to simulate fracture problems by inserting a cohesive zone model in the formulation. With a classical Continuous Galerkin method, the use of the cohesive zone model is difficult because inserting a cohesive element between bulk elements is not straightforward. On one hand if the cohesive element is inserted at the beginning of the simulation, there is a modification of the structure stiffness and on the other hand inserting the cohesive element during the simulation requires modification of the mesh during computation. These drawbacks are avoided with the presented formulation as the structure is discretized in a stable and consistent way with full discontinuous elements and inserting cohesive elements during the simulation becomes straightforward. A new cohesive law based on the resultant stresses (bending moment and membrane) of the thin structure discretization is also presented. This model allows propagating fracture while avoiding through‐the‐thickness integration of the cohesive law. Tests are performed to show that the proposed model releases, during the fracture process, an energy quantity equal to the fracture energy for any combination of tension‐bending loadings. Copyright © 2010 John Wiley & Sons, Ltd.
Automation of finite element formulations for large deformation contact problems
Authors: Lengiewicz Jakub , Korelc Jože , Stupkiewicz Stanisław
Published: August 2010

The aim of this paper is to present a general method for automation of finite element formulations of large deformation contact problems. A new automatic‐differentiation‐based notation is introduced that represents a bridge between the classical mathematical notation of contact mechanics and the actual computer implementation of contact finite elements. Automation of derivation of the required formulas (e.g. element residual and tangent matrix) combined with automatic code generation makes the finite element implementation possible at a moderate effort. Accordingly, several 3D contact formulations have been implemented in this work, including penalty and augmented Lagrangian treatments of contact constraints, and several contact smoothing techniques. A typical benchmark problem could thus be executed in an objective way leading to a comprehensive study of the efficiency and the accuracy of various formulations of 3D contact finite elements. Copyright © 2010 John Wiley & Sons, Ltd.
Harmonic enrichment functions: A unified treatment of multiple, intersecting and branched cracks in the extended finite element method
Authors: Mousavi S. E. , Grinspun E. , Sukumar N.
Published: August 2010

A unifying procedure to numerically compute enrichment functions for elastic fracture problems with the extended finite element method is presented. Within each element that is intersected by a crack, the enrichment function for the crack is obtained via the solution of the Laplace equation with Dirichlet and vanishing Neumann boundary conditions. A single algorithm emanates for the enrichment field for multiple cracks as well as intersecting and branched cracks, without recourse to special cases, which provides flexibility over the existing approaches in which each case is treated separately. Numerical integration is rendered to be simple—there is no need for partitioning of the finite elements into conforming subdivisions for the integration of discontinuous or weakly singular kernels. Stress intensity factor computations for different crack configurations are presented to demonstrate the accuracy and versatility of the proposed technique. Copyright © 2010 John Wiley & Sons, Ltd.
Marketing a new African God: Pentecostalism and material salvation in Ghana
Authors: Bonsu Samuel K. , Belk Russell W.
Published: August 2010

Pentecostalism is an American creation that has been exported to various parts of the world. Its message of hope is produced and promoted by churches that are led by religious entrepreneurial salespeople who create value for customers through the use of marketing techniques that facilitate the blending of the local and the global; the sacred and the profane. Its success in Africa has been attributed to the African penchant for connecting every human experience to the religious. Using the marketing strategic framework of target market and four Ps as an organization tool, we draw on a year‐long ethnography in Kumasi, Ghana, to suggest that Pentecostalism in Ghana is marketed as an effective route to material success without risk to postmortem salvation. While the effective blend of the sacred and the profane allows for open public discourse, it fails to deliver on its promise of economic salvation for the poor. In fact, it causes the condition of the poor to deteriorate even further through application of its fundamental requirement: give and God will bless you according to the extent of your giving. We conclude that the new African Pentecostalism and its open embrace of contemporary consumption and materialism have arrested local religiosity and imposed an “economic imperialism” that impregnates every human experience with a commercial character.

Copyright © 2010 John Wiley & Sons, Ltd.
Low‐order multi‐rate linear time‐invariant decentralized trackers using the new observer‐based sub‐optimal method for unknown sampled‐data nonlinear time‐delay system with closed‐loop decoupling
Authors: Hu N. T. , Tsai J. S. H. , Guo S. M. , Shieh L. S. , Chen Y.
Published: August 2010

This paper presents the low‐order multi‐rate linear time‐invariant decentralized trackers using the new observer‐based sub‐optimal method for a class of unknown sampled‐data nonlinear time‐delay system with closed‐loop decoupling. For the unknown sampled‐data nonlinear time‐delay system, we assume that the inner time delay is clearly known. Under this prerequisite, the appropriate (low‐) order decentralized linear observer for the unknown sampled‐data nonlinear system is determined by the off‐line observer/Kalman filter identification (OKID) method with artificial delay input and actual delay output. Then, the above observer has been further improved based on the proposed new observer‐based sub‐optimal approach. Sequentially, the decentralized tracker with the high gain property is proposed, so that the closed‐loop system has the decoupling property. The proposed approach constructs complete mathematics method including the concept of optimal control theory and state‐matching digital redesign technique and is quite useful for the complicated interconnected large‐scale sampled‐data nonlinear time‐delay system with unknown system equation. Copyright © 2010 John Wiley & Sons, Ltd.
Haemolytic uraemic syndrome in a patient with acute lymphoblastic leukaemia
Authors: Clarke Rachel T. , Mitchell Chris
Published: August 2010

We describe a patient diagnosed with haemolytic uraemic syndrome (HUS) during long‐term maintenance therapy for childhood acute lymphoblastic leukaemia (ALL). He rapidly developed renal failure, hypertension and profound thrombocytopenia. Despite suffering a large intracerebral haemorrhage, he made a full recovery without residual neurological or renal deficit. His case raises the question of whether ALL or its treatments predispose an individual to developing HUS. Pediatr Blood Cancer. 2010;55:1402–1405. © 2010 Wiley‐Liss, Inc.
Initial testing (stage 1) of the Akt inhibitor GSK690693 by the pediatric preclinical testing program
Authors: Carol Hernan , Morton Christopher L. , Gorlick Richard , Kolb E. Anders , Keir Stephen T. , Reynolds C. Patrick , Kang Min H. , Maris John M. , Billups Catherine , Smith Malcolm A. , Houghton Peter J. , Lock Richard B.
Published: August 2010

Background

GSK690693 is a small molecule ATP‐competitive inhibitor of the pro‐survival kinase Akt. Since Akt regulates multiple downstream targets including transcription factors, glycogen synthase 3, the pro‐apoptotic protein Bad, as well as MDM2 and mTORC1, it was tested against the in vitro and in vivo panels of the Pediatric Preclinical Testing Program (PPTP).

Procedures

GSK690693 was tested in vitro at concentrations from 1 nM to 10 µM, and against the in vivo panel of xenografts at a dose of 30 mg/kg daily × 5 for 6 consecutive weeks. Three measures of in vivo antitumor activity were used: (1) an objective response measure modeled after the clinical setting; (2) a treated to control (T/C) tumor volume measure; and (3) a time to event measure based on the median event‐free survival (EFS) of treated and control animals for each xenograft.

Results

GSK690693 inhibited cell growth in vitro with IC50 values between 6.5 nM and >10 µM. In vivo, GSK690693 significantly increased EFS in 11 of 34 (32%) solid tumor xenografts, most notably in all 6 osteosarcoma models, but not in any of the 8 ALL xenografts tested. No objective responses were observed and only one solid tumor met EFS T/C criteria for intermediate activity.

Conclusions

GSK690693 demonstrated broad activity in vitro, however our results against both the solid tumor and ALL PPTP in vivo panels demonstrate that, as single agent at the dose and schedule used, GSK690693 has only modest antitumor activity. Pediatr Blood Cancer. 2010;55:1329–1337. © 2010 Wiley‐Liss, Inc.
Clinical significance of serum vascular endothelial growth factor, endostatin, and leptin levels in children with lymphoma
Authors: Okur Fatma Visal , Karadeniz Ceyda , Buyukpamukcu Munevver , Oguz Aynur , Yucel Aysegul , Cinaz Peyami , Emir Suna , Varan Ali
Published: August 2010

Background

A number of clinical studies conducted in adults have demonstrated the prognostic significance of angiogenic factors in malignancies, however, only a limited number of studies have been conducted in children. The aim of this study was to determine serum vascular endothelial growth factor (VEGF), endostatin, and leptin levels in children with lymphoma and to investigate whether these factors provide prognostic information.

Procedure

Serum samples from 36 children with lymphoma (non‐Hodgkin lymphoma (NHL) N = 21, Hodgkin lymphoma (HL) N = 15) were collected at diagnosis and during remission. Serum samples were also collected from 18 healthy children as the control group. Serum VEGF and endostatin levels were quantified by using enzyme‐linked immunosorbent assay (ELISA) and serum leptin by immunoradiometric assay.

Results

The serum VEGF levels were found elevated in patients compared to controls (P = 0.033), while endostatin and leptin levels were lower in patients than in controls (endostatin, 43.9 ± 5.8 ng/ml vs. 123.6 ± 13.5 ng/ml, P < 0.001; leptin, 5 ± 1.5 ng/ml vs. 6.7 ± 1.2 ng/ml, P = 0.013). VEGF levels declined (pre, 151.6 ± 55.9 pg/ml vs. post, 16.2 ± 7.9 pg/ml, P = 0.041), while endostatin and leptin levels increased in patients who achieved remission (33 of 36 patients) when compared to pre‐treatment levels (endostatin pre, 43.1 ± 5.9 ng/ml vs. post, 65.9 ± 6.8 ng/ml, P = 0.047; leptin, pre, 5.3 ± 1.6 ng/ml vs. post, 9.8 ± 2.7 ng/ml, P = 0.012). Serum VEGF, endostatin, and leptin levels were not predictive of survival.

Conclusion

Serial measurement of serum VEGF, endostatin, and leptin levels could potentially be used to predict response to treatment or progressive disease in children with lymphoma. Pediatr Blood Cancer. 2010;55:1272–1277. © 2010 Wiley‐Liss, Inc.
Oncolytic virotherapy reaches adolescence
Authors: Hammill Adrienne M. , Conner Joseph , Cripe Timothy P.
Published: August 2010

Lytic viruses kill cells as a consequence of their normal replication life cycle. The idea of harnessing viruses to kill cancer cells arose over a century ago, before viruses were even discovered, from medical case reports of infections associated with cancer remissions. Since then, there has been no shortage of hype, hope, or fear regarding the prospect of oncolytic virotherapy for cancer. Early developments in the field included encouraging antitumor efficacy both in animal studies in the 1920s–1940s and in human clinical trials in the 1950s–1970s. Despite its long‐standing history, oncolytic virotherapy was an idea ahead of its time. Without needed advances in molecular biology, virology, immunology, and clinical research ethics, early clinical trials resulted in infectious complications and were fraught with controversial research conduct, so that enthusiasm in the medical community waned. Oncolytic virotherapy is now experiencing a major growth spurt, having sustained numerous laboratory advances and undergone multiple encouraging adult clinical trials, and is now witnessing the emergence of pediatric trials. Here we review the history and salient biology of the field, including preclinical and clinical data, with a special emphasis on those agents now being tested in pediatric cancer patients. Pediatr Blood Cancer. 2010;55:1253–1263. © 2010 Wiley‐Liss, Inc.
Management of sialoblastoma with surgery and brachytherapy
Authors: Shan Xiao‐Feng , Cai Zhi‐Gang , Zhang Jian‐Guo , Zhang Jie , Gao Yan , Yu Guang‐Yan
Published: August 2010

Sialoblastoma is a rare congenital or perinatal salivary gland tumor with significant variability in histological appearance and biological behavior. We reported one case of sialoblastoma occurring in the parotid gland of an 18‐month‐old female. The tumor was excised with negative margins, and the sacrificed facial nerve was reconstructed with great auricular nerve graft. The tumor recurred 6 months after operation and was treated with 125I seed implant brachytherapy. No recurrence was found after 21 months of follow‐up. Pediatr Blood Cancer. 2010;55:1427–1430. © 2010 Wiley‐Liss, Inc.
Opposing effects of nanoclay on viscoelastic response of reactive phenoxy/poly (trimethylene terephthalate) blends: Clay‐induced transreactions versus percolated network formation
Authors: Seyfi Javad , Jafari Seyed‐Hassan , Khonakdar Hossein Ali
Published: August 2010

The role of nanofillers in reactive blends, which are compatibilized via interchange/exchange reactions, in particular transesterification reactions, is still a challenge. In this study, effects of clay on viscoelastic response of reactive melt intercalated phenoxy/poly (trimethylene terephthalate) blends are investigated. Using rheological plots, it was found that at low clay contents, clay‐induced transreactions could cause an unexpectedly enhanced viscous response. But higher clay contents lead to an enhancement in elastic behavior by inducing the formation of a percolated network. The observed opposing effects of clay particles on viscoelastic response were further examined by stress relaxation analysis, which verified the enhanced viscous response at low clay contents. The effect of interaction between the silicate layers and the blend matrix is also probed by using two different organo‐modifiers. Viscoelastic behavior of samples was also studied by dynamic mechanical analysis, and the results corroborated our findings from rheological measurements. Based on loss modulus data, the improved dynamic homogeneity of nanocomposites is attributed to the enhanced transreactions and stronger hydrogen bonds between the blend components. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers
Surface‐modified sisal fiber‐reinforced eco‐friendly composites: Mechanical, thermal, and diffusion studies
Authors: P.A. Sreekumar , Joseph Kuruvilla , G. Unnikrishnan , Thomas Sabu
Published: August 2010

To improve the fiber/matrix interaction, sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100°C, permanganate treatment, benzoylation, and silanization. Polyester composites were fabricated using compression molding. Tensile and flexural properties increased for every treated fiber‐reinforced composites with a reduction in the impact strength. This is attributed to the improved interfacial adhesion between fiber and polyester matrix. An increase in thermal stability was observed for the treated fiber‐reinforced composites especially at lower temperature. Significant reduction in water uptake occurred for the treated fiber‐reinforced composites at 30°C and 90°C. Scanning electron micrograph studies have been used to substantiate the above observations. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers
In‐plane thermal conductivity modeling of carbon‐filled liquid crystal polymer–based resins
Authors: Adams Tayloria N.G. , Olson Tamara R. , King Julia A. , Keith Jason M.
Published: August 2010

Adding conductive carbon fillers to insulating thermoplastic resins increases composite electrical and thermal conductivity. In this study, varying amounts of three different carbons (carbon black, synthetic graphite particles, and carbon fiber) were added to Vectra A950RX liquid crystal polymer. The in‐plane thermal conductivity of the resulting single filler composites was tested. The results showed that adding synthetic graphite particles caused the largest increase in the in‐plane thermal conductivity of the composite. The composites were modeled using ellipsoidal inclusion problems to predict the effective in‐plane thermal conductivities at varying volume fractions with only physical property data of the constituents. The synthetic graphite and carbon black were modeled using the average field approximation with ellipsoidal inclusions and the model showed good agreement with the experimental data. The carbon fiber polymer composite was modeled using an assemblage of coated ellipsoids and the model showed good agreement with the experimental data. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers
Mechanical and thermal properties of compatibilized composites of LDPE and esterified unbleached wood pulp
Authors: Sailaja R.R.N. , Deepthi M.V.
Published: August 2010

Wood pulp has been esterified and blended with low density polyethylene (LDPE) along with LDPE grafted maleic anhydride as compatibilizer. The mechanical and thermal properties of the blends were measured and compared with neat LDPE. The mechanical properties improved due to the addition of compatibilizer. In all cases, an optimal compatibilizer content was observed. Scanning electron microscopy (SEM) revealed better adhesion between LDPE and treated wood pulp. SEM micrographs showed ductile fracture morphology for lower loadings of esterified wood pulp while for higher loadings, the specimen exhibited predominantly brittle fracture. Thermal analysis revealed that weight loss is higher for compatibilized composites. The obtained experimental results were analyzed using predictive theories which indicated better interaction between the LDPE and treated wood pulp. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers
Multi‐scale hybrid composites‐based carbon nanotubes
Authors: Wang Yongkun , Xu Zhiwei , Chen Li , Jiao Yanan , Wu Xiaoqing
Published: August 2010

Since the carbon nanotubes (CNTs) have been discovered, there has been a marked increase in the scientific literature dealing with multi‐scale composites. The multi‐scale hybrid composites with CNTs could endow the composites with some superior mechanical properties, such as improving the tensile performance, modest increasing compressive and flexural properties, and significantly enhancing interlaminar, interfacial and fracture strength. In addition, composites with CNTs can also develop the functional properties. A small quantity of CNTs can significantly increase the electrical properties of composites and lower the coefficient of thermal expansion of composites. The purpose of this work is to review the available literature in mechanical and functional properties of multi‐scale hybrid composites manufactured using CNTs. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers