bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving multigrid performance for unstructured mesh drift–diffusion simulations on 147,000 cores
Authors: Lin Paul T. 
Published: May 2012

SUMMARYThis study considers the scaling of three algebraic multigrid aggregation schemes for a finite element discretization of a drift–diffusion system, specifically the drift–diffusion model for semiconductor devices. The approach is more general and can be applied to other systems of partial differential equations. After discretization on unstructured meshes, a fully coupled multigrid preconditioned Newton–Krylov solution method is employed. The choice of aggregation scheme for generating coarser levels has a significant impact on the performance and scalability of the multigrid preconditioner. For the test cases considered, the uncoupled aggregation scheme, which aggregates/combines the immediate neighbors, followed by repartitioning and data redistribution for the coarser level matrices on a subset of the Message Passing Interface (MPI) processes, outperformed the two other approaches, including the baseline aggressive coarsening scheme. Scaling results are presented up to 147,456 cores on an IBM Blue Gene/P platform. A comparison of the scaling of a multigrid V‐cycle and W‐cycle is provided. Results for 65,536 cores demonstrate that a factor of 3.5 × reduction in time between the uncoupled aggregation and baseline aggressive coarsening scheme can be obtained by significantly reducing the iteration count due to the increased number of multigrid levels and the generation of better quality aggregates. Copyright © 2012 John Wiley & Sons, Ltd.
A domain decomposition method for a two‐phase transport model of polymer electrolyte fuel cell containing micro‐porous layer
Authors: Sun Pengtao 
Published: May 2012

SUMMARYIn this paper, a nonlinear Dirichlet–Robin iteration‐by‐subdomain domain decomposition method is studied for a multidimensional, multiphysics, and multiphase model of polymer electrolyte fuel cell (PEFC) containing micro‐porous layer (MPL). Across the interface of gas diffusion layer and MPL in PEFC, it is well known that the capillary pressure is continuous, whereas liquid saturation is discontinuous, by which the liquid‐water removal in the porous electrodes can be significantly enhanced. We design a type of non‐overlapping domain decomposition method to deal with water transport in such multi‐layer diffusion media, where Kirchhoff transformation and its inverse techniques are employed to conquer the discontinuous and degenerate water diffusivity in the coexisting single‐phase and two‐phase regions. In addition, the conservation equations of mass, momentum, charge, and hydrogen and oxygen transport are also solved by the combined finite element–upwind finite volume method (FEM/FVM) to overcome the dominated convection effect in gas channels. Numerical simulations demonstrate that the presented techniques are effective in obtaining a fast and convergent nonlinear iteration for such a 3D PEFC model within around 50 steps, in contrast with the oscillatory and nonconvergent iteration conducted by standard FEM/FVM. A series of numerical convergence tests are also carried out to verify the efficiency and accuracy of the present numerical techniques. Copyright © 2012 John Wiley & Sons, Ltd.
Enriched space–time finite element method: a new paradigm for multiscaling from elastodynamics to molecular dynamics
Authors: Yang Ye , Chirputkar Shardool , Alpert David N. , Eason Thomas , Spottswood Stephen , Qian Dong 
Published: May 2012

SUMMARYThe main objective of this paper is to present an enriched version of the space–time FEM method to incorporate multiple temporal scale features with a focus on dynamics problems. The method is established by integrating the basic framework of the space–time discontinuous Galerkin method with the extended finite element method. Two versions of the method have been developed: one at the continuum scale (elastodynamics) and the other focuses on the dynamics at the molecular level. After an initial outline of the formulation, we explore the incorporation of different types of enrichments based on the length scale of interest. The effects of both continuous and discontinuous enrichments are demonstrated through numerical examples involving wave propagations and dynamic fracture in harmonic lattice. The robustness of the method is evaluated in terms of convergence and the ability to capture the fine scale features. It is shown that the enriched space–time FEM leads to an improvement in the convergence properties over the traditional space–time FEM for problems with multiple temporal features. It is also highly effective in integrating atomistic with continuum representations with a coupled framework. Copyright © 2012 John Wiley & Sons, Ltd.
A fast method for solving microstructural problems defined by digital images: a space Lippmann–Schwinger scheme
Authors: Yvonnet Julien 
Published: May 2012

SUMMARYA fast numerical method is proposed to solve thermomechanical problems over periodic microstructures whose geometries are provided by experimental techniques, such as X‐ray microtomography images. In such configuration, the phase properties are defined over regular grids of voxels. To overcome the limitations of calculations on such fine models, an iterative scheme is proposed, avoiding the construction and storage of finite element matrices. Equilibrium equations are written in the form of a Lippmann–Schwinger integral equation, which can be solved iteratively. Unlike previous algorithms based on the Fourier transform, the present scheme strictly operates in the real‐space domain and removes the numerical Fourier and inverse Fourier transforms at each iteration. For this purpose, the linear operator related to the Lippmann–Schwinger equation is constructed numerically by means of transformation tensors in the real‐space domain. The convergence and accuracy of the method are evaluated through examples in both steady‐state thermics and linear elasticity problems. Computational times are found to scale linearly with the number of degrees of freedom, and parallel computations can be carried out straightforwardly. The method is also illustrated on many examples involving complex microstructures, including a problem defined by a microtomography image. Copyright © 2012 John Wiley & Sons, Ltd.
Toll‐like receptor‐4 agonist inhibits motility and invasion of hepatoblastoma HepG2 cells in vitro
Authors: Hsiao Chih‐Cheng , Kao Ying‐Hsien , Huang Shun‐Chen , Chuang Jiin‐Haur 
Published: May 2012

AbstractBackgroundExpression of toll‐like receptor‐4 (TLR4) on tumor cells is known to mediate innate immune responses that influence tumor cell growth and migration. This study aimed to characterize TLR4 expression and elucidate its functional significance in human hepatoblastoma (HB) cells.ProcedureImmunohistochemistry (IHC) was used to determine TLR4 expression level and its distribution pattern in HB liver tissues. Transcripts of tumor necrosis factor (TNF)‐α, interleukin (IL)‐8, matrix metalloproteinase (MMP)‐2, MMP‐13, tissue inhibitor of metalloproteinases (TIMP)‐1, and TIMP‐2 in HB HepG2 cells with lipopolysacharide (LPS) treatment were measured by quantitative PCR. Soluble cytokines and peptides in conditioned media were measured by ELISA. MMP‐2 activity was determined by using gelatin zymography. Cell motility and invasiveness was determined using wound healing migration and Matrigel invasion assays, respectively.ResultsTLR4 IHC staining demonstrated that TLR4 overexpression in HB liver tissues dramatically vanished after chemotherapy. In vitro study using an HB cell line, HepG2, showed that TLR4 agonist, LPS, significantly decreased transcripts of IL‐8 and TNF‐α, but did not affect MMP‐13 mRNA level. By contrast, LPS only down‐regulated IL‐8 production and MMP‐2 gelatinolytic activity. The latter might be in part due to the increased levels of MMP‐2/TIMP‐2 complex in conditioned media, thus leading to the decreased motility and invasiveness of HepG2 cells.ConclusionsHB cells overexpress TLR4, whereas TLR4 agonistic treatment inhibits migration and invasion of HB HepG2 cells. These findings suggest that TLR4 signaling pathway is a potential therapeutic target for control of HB tumor progression. Pediatr Blood Cancer 2013;60:248–253. © 2012 Wiley Periodicals, Inc.
Current issues and controversies in the classification of pediatric hepatocellular tumors
Authors: López‐Terrada Dolores , Zimmermann Arthur 
Published: May 2012

AbstractSystematic histopathologic examination of hepatoblastoma specimens from patients enrolled in therapeutic protocols has allowed the identification of clinically relevant histologic subtypes that are being incorporated into risk stratification systems. Genetic and molecular studies have documented recurrent chromosomal abnormalities and aberrant activation of developmental, and oncogenic signaling pathways in hepatoblastoma. Molecular profiling has also identified molecular subclasses and gene signatures that could be used to stratify hepatoblastoma patients. Future international collaboration is needed to develop consensus pathology classifications, and to progressively incorporate genetic and molecular biomarkers into therapeutic pediatric liver tumors protocols. Pediatr Blood Cancer 2012; 59: 780–784. © 2012 Wiley Periodicals, Inc.
Socioeconomic disparities in the quality of life in children with cancer or brain tumors: the mediating role of family factors
Authors: Litzelman Kristin , Barker Emily , Catrine Kristine , Puccetti Diane , Possin Peggy , Witt Whitney P. 
Published: May 2012

AbstractObjectiveThis study aimed to determine if and to what extent (i) socioeconomic disparities exist in the health‐related quality of life (QOL) of children with cancer or brain tumors and healthy children; and (ii) family functioning and burden mediate the relationship between socioeconomic status and children's QOL.MethodsIn this cross‐sectional study, parents of children ages 2–18 with (n = 71) and without (n = 135) cancer or brain tumors completed in‐person interviewer‐assisted surveys assessing sociodemographics (including income and parental education), child QOL (measure: PedsQL), family functioning (measure: Family Adaptability and Cohesion Evaluation Scale IV) and burden (measure: Impact on the Family Scale). For children with cancer, clinical characteristics were captured through medical record abstraction. Multiple linear regression was used to determine the relationship between income and child QOL; the interaction between group status and income was assessed. Staged multivariate regression models were used to assess the role of family factors in this relationship among children with cancer.ResultsIn multivariate analyses, the effect of income differed by cancer status; lower income was associated with worse QOL in children with cancer but not among healthy children. Among children with cancer, this relationship was significantly attenuated by family burden.ConclusionsSignificant socioeconomic disparities exist in the QOL of children with cancer. Family factors partially explain the relationship between low income and poor QOL outcomes among these children. Lower‐income families may have fewer resources to cope with their child's cancer. Increased support, monitoring, and referrals to reduce burden for these families may lead to improved QOL in children with cancer. Copyright © 2012 John Wiley & Sons, Ltd.
Deposition and Characterisation of Plasma Polymerised Allyl Methacrylate Based Coatings
Authors: Kakaroglou Alexandros , Scheltjens Gill , Nisol Bernard , De Graeve Iris , Van Assche Guy , Van Mele Bruno , Willem Rudolph , Biesemans Monique , Reniers François , Terryn Herman 
Published: May 2012

AbstractAllyl methacrylate (AMA) was deposited on aluminium using atmospheric dielectric barrier discharge plasma. AMA posseses two CC bonds which have very different reactivities and the efficiency of the plasma on polymerising the two different kinds of double bonds was evaluated. The Fourier transform infrared spectra and the nuclear magnetic resonance spectra of the plasma coatings were compared with those of conventionally synthesised poly(AMA). The influence of the monomer feed on the ester, the vinyl and the allyl functionalities of the coatings were investigated. Plasma coatings showed lower concentration of non‐reacted allyl groups than conventional poly(AMA) suggesting a more cross‐linked network. Pull‐off adhesion tests were performed after the deposition of the a topcoat to evaluate the potential use of the AMA based coatings as adhesion promoter. magnified image
Practical Amine Functionalization of Multi‐Walled Carbon Nanotubes for Effective Interfacial Bonding
Authors: Chen Zhiqiang , Dai Xiujuan J. , Lamb Peter R. , de Celis Leal David R. , Fox Bronwyn L. , Chen Ying , du Plessis Johan , Field Matthew , Wang Xungai 
Published: May 2012

AbstractImproved methods of functionalizing the surfaces of multi‐walled carbon nanotubes (MWCNTs) have been investigated. It is shown that a level of primary amines of 2.3%, higher than previously reported for any nitrogen‐containing gas plasma treatment, can be achieved using a mixture of N2 and H2, which is preferable to using NH3. Even higher levels (3.5%) of primary amines can be achieved by coating the MWCNTs with a thin layer of plasma polymerized heptylamine. In both cases, the highest levels were achieved using a combined continuous plus pulsed plasma mode which was superior to either continuous wave or pulsed wave alone. The integrity of the MWCNT structure is maintained by the plasma treatments, and the functionalized surface improves the dispersion of the MWCNTs and their interfacial bonding with epoxy, giving superior nanoindentation performance of the composites. magnified image
Grain and grain boundary effects in Ca2+ doped BiFeO3 multiferroic ceramics
Authors: Tirupathi Patri , Chandra Amreesh 
Published: May 2012

AbstractThe present work reports the analysis of temperature‐dependent electrical and conductivity studies on Ca2+ doped BiFeO3 multiferroic ceramics in the temperature range of 300–600 K. The effect of Ca2+ doping on the impedance and modulus behavior of BiFeO3 lattice is discussed. The observed changes as a function of increasing Ca2+ concentration have been explained using the change in crystal unit cell. It is also shown that the microstructure changes significantly as a function of Ca2+ concentration. The grain and grain boundary effects in determining the impedance behavior is also reported in the paper.
Spatial coherence of a polariton condensate in 1D acoustic lattice
Authors: Tsyplyatyev O. , Whittaker D. M. 
Published: May 2012

AbstractSeveral mechanisms are discussed which could determine the spatial coherence of a polariton condensate confined to a one dimensional wire. The mechanisms considered are polariton–polariton interactions, disorder scattering and non‐equilibrium occupation of finite momentum modes. For each case, the shape of the resulting spatial coherence function g(1)(x) is analysed. The results are compared with the experimental data on a polariton condensate in an acoustic lattice from E. A. Cerda‐Mendez et al. [Phys. Rev. Lett. 105, 116402 (2010)]. It is concluded that the shape of g(1)(x) can only be explained by non‐equilibrium effects, and that ∼10 modes are occupied in the experimental system.
Hepatitis E virus: neutralizing sites, diagnosis, and protective immunity
Authors: Zhang Jun , Li Shao‐Wei , Wu Ting , Zhao Qinjian , Ng Mun‐Hon , Xia Ning‐Shao 
Published: May 2012

SUMMARYThere have been increased attentions on HEV and its associated diseases in recent years as a result of an increased number of reports on autochthonous patients from many developed countries. Vaccine development and better disease management are expected from protective immunity with increased knowledge on the pathogenesis and virology of HEV. This review summarizes the current understanding of the HEV virology, the key neutralization sites (epitopes) on the surface of the viral capsid, the host humoral immune responses for HEV infection, and the protective immunity conferred by natural infection and vaccination. Recombinant VLPs were prepared to mimic the protective and neutralizing epitopes on the virion surface, thus being capable of eliciting protective immunity when injected to nonhuman primates or human volunteers during preclinical tests and clinical trials. Four markers—viral RNA, anti‐HEV IgM, anti‐HEV IgG, and low avidity of anti‐HEV IgG—are important in the diagnosis of HEV infection, particularly for patients presenting with acute hepatitis symptoms. This toolbox of genomic and immunological assays is valuable in furthering our understanding of the time course of HEV infection and the subsequent hepatitis during preclinical and clinical development of an efficacious vaccine. Two vaccine candidates had shown good tolerability, high immunogenicity, and high efficacy against symptomatic and/or asymptomatic HEV infection. One of them has been licensed in China recently. However, many issues need to be resolved before new technological progresses can benefit the people who need them most. Copyright © 2012 John Wiley & Sons, Ltd.
A theory of spatial system archetypes
Authors: BenDor Todd K. , Kaza Nikhil 
Published: May 2012

AbstractHistoric reference behavior and archetypes of system structure are key tools for creating rigorous system dynamics (SD) models. Modelers often delineate causal relationships by employing common archetypes of dynamic system structure, which produce behaviors such as growth and decline, oscillation, and complex combinations thereof. We extend archetypes to spatial‐dynamic models, focusing on structural archetypes that exhibit changing spatial patterns in two‐dimensional landscapes. Although many fields employ spatial modeling techniques, analogy‐based, causally focused system archetypes remain confined to non‐spatial SD models. We draw on spatial analysis literature to explore the influence of space on dynamic relationships and archetypes, including methods for articulating “space” and expressing feedback. We offer simple examples of spatial system archetypes and explore network structures for spatially extending SD models. By doing this, we argue for spatial modeling techniques that parallel the learn‐by‐analogy environment that archetypes have promoted in aspatial SD research. Copyright © 2012 System Dynamics Society.
SDRP: a secure distributed revocation protocol for vehicular environments
Authors: Chaib Noureddine , Lagraa Nasreddine , Yagoubi Mohamed Bachir , Lakas Abderrahmane 
Published: May 2012

AbstractSecure routing protocols that are based only on cryptographic techniques cannot guarantee security against all attacks. Among solutions that have been proposed to enhance the security in vehicular networks are the distributed revocation protocols, which provide vehicles with the ability to quickly detect and avoid malicious attacks. However, most of the proposed revocation protocols are vulnerable to colluding attacks conducted by malicious nodes, a situation which results in denial of service. In this work, we propose a new and robust distributed revocation protocol for vehicular ad hoc networks, called Secure Distributed Revocation Protocol (SDRP), with the main objective to exclude misbehaving nodes conducting or not a colluding attack from the routing operation in VANET. We present an evaluation analysis of SDRP on the basis of the simulation results and show that our scheme provides a high detection rate of misbehaving nodes with a low rate of false positives even in the presence of a large number of attackers. Copyright © 2012 John Wiley & Sons, Ltd.
Mapping out the integration of the components of pedagogical content knowledge (PCK): Examples from high school biology classrooms
Authors: Park Soonhye , Chen Ying‐Chih 
Published: May 2012

AbstractThis study explored the nature of the integration of the five components of pedagogical content knowledge (PCK): (a) Orientations toward Teaching Science, (b) Knowledge of Student Understanding, (c) Knowledge of Instructional Strategies and Representations, (d) Knowledge of Science Curriculum, and (e) Knowledge of Assessment of Science Learning. Given the topic and context specificity of PCK, this investigation was conducted in the context of the photosynthesis and heredity instruction of four teachers who were working at the same high school with the same curricular materials. Data sources included classroom observations, semi‐structured interviews, lesson plans, instructional materials, and students' work samples. Data were analyzed through three different approaches: (a) in‐depth analysis of explicit PCK, (b) enumerative approach, and (c) the constant comparative method. Data analysis indicated five salient features of the integration of the PCK components: (a) the integration of the components was idiosyncratic and topic‐specific; (b) Knowledge of Student Understanding and Knowledge of Instructional Strategies and Representations were central in the integration; (c) Knowledge of Science Curriculum and Knowledge of Assessment of Science Learning had most limited connection with other components; (d) Knowledge of Assessment of Science Learning was more often connected with Knowledge of Student Understanding and Knowledge of Instructional Strategies and Representations than with the other components; and (e) Didactic Orientations toward Teaching Science directed Knowledge of Instructional Strategies and Representations inhibiting its connection with other components. This study highlights that the quality of PCK depends on the coherence among the components as well as the strength of individual components. From a methodological perspective, this study demonstrates the possibility to make PCK more visible and accessible by using a PCK Map, a pictorial representation of the interactions of the PCK components. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 922–941, 2012
Polycystic ovaries at ultrasound: normal variant or silent polycystic ovary syndrome?
Authors: Catteau‐Jonard S. , Bancquart J. , Poncelet E. , Lefebvre‐Maunoury C. , Robin G. , Dewailly D. 
Published: May 2012

AbstractObjectiveIt is not known whether polycystic ovaries (PCO) are an ovarian appearance without pathological meaning or whether they share with polycystic ovary syndrome (PCOS) the same ovarian follicle abnormality. There are few studies including strictly selected women with PCO but without other criteria of PCOS. In order to address these issues, we compared hormonal, metabolic and ultrasound parameters obtained from patients with PCO only, patients with PCOS and controls.MethodsThis was a comparative analysis including three age‐matched groups of 95 patients, who were included consecutively in a database: controls, patients with sonographic PCO but no symptoms (PCO group) and patients with PCOS. A clinical examination, fasting serum sampling and pelvic ultrasound examination were performed between cycle days 2 and 5 and results were compared between groups.ResultsThe median serum anti‐Mullerian hormone (AMH) level in the PCO group was intermediate between that in controls and that in the PCOS group (33.6 pmol/L, 19.8 pmol/L and 63.3 pmol/L, respectively), the differences being significant after adjustment for follicle number (P < 0.05), while the mean androgen serum level in the PCO group was similar to that in the control group and significantly lower than that in the PCOS group (P < 0.05) (median serum testosterone levels: 0.90 nmol/L, 0.79 nmol/L and 1.39 nmol/L; median androstenedione levels: 5.25 nmol/L, 4.37 nmol/L and 6.09 nmol/L, respectively). Body mass index, waist circumference and insulin levels had no effect on these differences.ConclusionPCO is an abnormal condition, affected women showing no evidence of hyperandrogenism but having higher AMH serum levels compared with controls, suggesting a granulosa cell abnormality in PCO similar to that observed in PCOS. The absence of hyperandrogenism in PCO does not seem linked to the metabolic status. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.