bluuebunny/crossref_metadata_2025_split huggingface dataset:
Partition of unity for localization in implicit a posteriori finite element error control for linear elasticity
Authors: Carstensen Carsten , Thiele Jan 
Published: May 2007

AbstractThe partition of unity for localization in adaptive finite element method (FEM) for elliptic partial differential equations has been proposed in Carstensen and Funken (SIAM J. Sci. Comput. 2000; 21: 1465–1484) and is applied therein to the Laplace problem. A direct adaptation to linear elasticity in this paper yields a first estimator ηL based on patch‐oriented local‐weighted interface problems. The global Korn inequality with a constant CKorn yields reliability for any finite element approximation uh to the exact displacement u. In order to localize this inequality further and so to involve the global constant CKorn directly in the local computations, we deduce a new error estimator µL. The latter estimator is based on local‐weighted interface problems with rigid body motions (RBM) as a kernel and so leads to effective estimates only if RBM are included in the local FE test functions. Therefore, the excluded first‐order FEM has to be enlarged by RBM, which leads to a partition of unit method (PUM) with RBM, called P1+RBM or to second‐order FEMs, called P2 FEM. For P1+RBM and P2 FEM (or even higher‐order schemes) one obtains the sharper reliability estimate . Efficiency holds in the strict sense of .The local‐weighted interface problems behind the implicit error estimators ηL and µL are usually not exactly solvable and are rather approximated by some FEM on a refined mesh and/or with a higher‐order FEM. The computable approximations are shown to be reliable in the sense of . The oscillations are known functions of the given data and higher‐order terms if the data are smooth for first‐order FEM.The mathematical proofs are based on weighted Korn inequalities and inverse estimates combined with standard arguments. The numerical experiments for uniform and adapted FEM on benchmarks such as an L‐shape problem, Cook's membrane, or a slit problem validate the theoretical estimates and also concern numerical bounds for CKorn and the locking phenomena. Copyright © 2007 John Wiley & Sons, Ltd.
Stochastic convergence acceleration through basis enrichment of polynomial chaos expansions
Authors: Ghosh Debraj , Ghanem Roger 
Published: May 2007

AbstractGiven their mathematical structure, methods for computational stochastic analysis based on orthogonal approximations and projection schemes are well positioned to draw on developments from deterministic approximation theory. This is demonstrated in the present paper by extending basis enrichment from deterministic analysis to stochastic procedures involving the polynomial chaos decomposition. This enrichment is observed to have a significant effect on the efficiency and performance of these stochastic approximations in the presence of non‐continuous dependence of the solution on the stochastic parameters. In particular, given the polynomial structure of these approximations, the severe degradation in performance observed in the neighbourhood of such discontinuities is effectively mitigated. An enrichment of the polynomial chaos decomposition is proposed in this paper that can capture the behaviour of such non‐smooth functions by integrating a priori knowledge about their behaviour. The proposed enrichment scheme is applied to a random eigenvalue problem where the smoothness of the functional dependence between the random eigenvalues and the random system parameters is controlled by the spacing between the eigenvalues. It is observed that through judicious selection of enrichment functions, the spectrum of such a random system can be more efficiently characterized, even for systems with closely spaced eigenvalues. Copyright © 2007 John Wiley & Sons, Ltd.
An FMM for periodic boundary value problems for cracks for Helmholtz' equation in 2D
Authors: Otani Yoshihiro , Nishimura Naoshi 
Published: May 2007

AbstractThis paper presents an FMM (fast multipole method) for periodic boundary value problems for Helmholtz' equation in 2D. The periodic Green function is an important ingredient in our formulation, which is computed efficiently with the help of the Fourier analysis. We validate the proposed method by comparing the obtained numerical results with those computed with the conventional approach. We then apply the proposed method to the analysis of scattering problems for periodic array of cracks and plot the energy transmittance vs wave numbers. The stopband and related phenomena are observed clearly. Copyright © 2007 John Wiley & Sons, Ltd.
On the computation of steady‐state compressible flows using a discontinuous Galerkin method
Authors: Luo Hong , Baum Joseph D. , Löhner Rainald 
Published: May 2007

AbstractComputation of compressible steady‐state flows using a high‐order discontinuous Galerkin finite element method is presented in this paper. An accurate representation of the boundary normals based on the definition of the geometries is used for imposing solid wall boundary conditions for curved geometries. Particular attention is given to the impact and importance of slope limiters on the solution accuracy for flows with strong discontinuities. A physics‐based shock detector is introduced to effectively make a distinction between a smooth extremum and a shock wave. A recently developed, fast, low‐storage p‐multigrid method is used for solving the governing compressible Euler equations to obtain steady‐state solutions. The method is applied to compute a variety of compressible flow problems on unstructured grids. Numerical experiments for a wide range of flow conditions in both 2D and 3D configurations are presented to demonstrate the accuracy of the developed discontinuous Galerkin method for computing compressible steady‐state flows. Copyright © 2007 John Wiley & Sons, Ltd.
A new neural network‐based model for hysteretic behavior of materials
Authors: Yun Gun Jin , Ghaboussi Jamshid , Elnashai Amr S. 
Published: May 2007

AbstractCyclic behavior of materials is complex and difficult to model. A combination of hardening rules in classical plasticity is one possibility for modeling this complex material behavior. Neural network (NN) constitutive models have been shown in the past to have the capability of modeling complex material behavior directly from the results of material tests. In this paper, we propose a novel approach for NN‐based modeling of the cyclic behavior of materials. The proposed NN material model uses new internal variables that facilitate the learning of the hysteretic behavior of materials. The same approach can also be used in modeling of the hysteretic behavior of structural systems or structural components under cyclic loadings. The proposed model is shown to be superior to the earlier versions of NN material models. Although the earlier versions of the NN material models were effective in capturing the multi‐axial material behavior, they were only tested under cyclic uni‐axial state of stress. The proposed NN material model is capable of learning the hysteretic behavior of materials under even non‐uniform stress state in multi‐dimensional stress space. The performance of the proposed model is demonstrated through a series of examples using actual experimental data and simulated testing data. Copyright © 2007 John Wiley & Sons, Ltd.
Preparation and characterization of polytetrafluoroethylene‐polyacrylate core–shell nanoparticles
Authors: Cui Xuejun , Zhong Shuangling , Zhang Haitao , Gu Qiang , Li Junfeng , Wang Hongyan 
Published: May 2007

AbstractPolytetrafluoroethylene (PTFE)‐polyacrylate core–shell nanoparticles were produced by using PTFE micropowder and acrylate via seeded emulsion polymerization in the presence of fluorosurfactant. The properties of emulsion under various polymerization conditions were investigated and optimized. The chemical composition of the PTFE‐polyacrylate nanoparticles was characterized by Fourier‐transform infrared spectrometry (FTIR). The particle size and core–shell structure of the resulting PTFE‐polyacrylate nanoparticles were confirmed by transmission electron microscopy (TEM). Wettability of the PTFE‐polyacrylate core–shell particles was higher than the pristine PTFE. The formation of this kind of PTFE‐polyacrylate core–shell nanoparticles could improve the compatibility of PTFE with other materials because PTFE is covered by polyacrylate shell, which make them promising in various fields. Copyright © 2007 John Wiley & Sons, Ltd.
Photo‐stabilization of EPDM–clay nanocomposites: effect of antioxidant on the preparation and durability
Authors: Lonkar Sunil P. , Kumar A. Pratheep , Singh Raj Pal 
Published: May 2007

AbstractThe present study is to examine the photo‐stabilization effect of an antioxidant on the photo‐oxidation of ethylene‐propylene‐diene monomer (EPDM)–clay nanocomposites. During the preparation of EPDM–clay nanocomposites via melt processing antioxidants are usually incorporated along with clay, which allows phenolic antioxidant molecules to get adsorbed onto acidic clay platelets and their interaction with metallic impurities reduces the stabilizing efficiency of the antioxidant. The nanocomposites were obtained by solution dispersion followed by melt compounding of EPDM and organophilic montmorillonite (OMMT). The samples were characterized by conventional tools such as X‐ray diffraction (XRD), Fourier Transform Infra Red (FT‐IR) spectroscopy, and thermo‐gravimetric analysis (TGA). It was found, upon photo‐irradiation (λ > 290 nm) studies by following the changes in functional groups and surface morphology, that photo‐degradation was lowered by the antioxidant and the efficiency of the antioxidant could be improved by initial incorporation of antioxidant in the EPDM matrix. In EPDM–clay nanocomposites, a stabilizing activity of the antioxidant was observed above some threshold concentration of the antioxidant. The relationship between the nanoclay reinforcement and stabilizing efficiency in terms of photo‐oxidation and surface morphology for their applicability are discussed. The methodology adopted for this study is also justified through our observation. Copyright © 2007 John Wiley & Sons, Ltd.
Drug related problems with Antiparkinsonian agents: consumer Internet reports versus published data
Authors: Schröder Sabrina , Zöllner York Francis , Schaefer Marion 
Published: May 2007

AbstractPurposeThere is currently a lack of detailed information concerning drug related problems in the outpatient treatment of Parkinson's disease.MethodsProblems associated with drug treatment communicated anonymously in Parkinson's disease online forums were therefore retrospectively searched and documented for 1 year.ResultsBased on postings concerning 12 drugs for the treatment of Parkinson's disease, a total of 238 drug related problems were identified and categorised using the Problem Intervention Documentation (PI‐Doc). Of these, 153 were adverse drug reactions. Adverse drug reactions associated with the skin were relatively common, but central effects such as cognitive or psychiatric changes, effects on the sleep/waking system and other problems like headache and dizziness accounted for the highest percentage of adverse events. A comparison with data from scientific literature revealed a number of differences. This means that an analysis of online forums detected a number of drug related problems that were otherwise largely invisible. These were mainly associated with the qualitative aspects of treatment such as medication handling, dosage and individual problems concerning adverse events. In addition, the described method of identifying and classifying drug related problems in Internet forums may also be seen as a contribution to the international discussion about consumer reports and pharmacovigilance. The information about adverse drug reactions given by Internet users can be seen as a valuable adjunct to clinical trial data and as being very timely with regard to the event itself.ConclusionOnline forums may be considered as a suitable source of observational information to complement data from randomised clinical trials. Copyright © 2007 John Wiley & Sons, Ltd.
Use of anxiolytic or hypnotic drugs and total mortality in a general middle‐aged population
Authors: Hausken Anne Margrethe , Skurtveit Svetlana , Tverdal Aage 
Published: May 2007

AbstractPurposeThe aim of the study was to evaluate the effect of the consumption of anxiolytic or hypnotic drugs on total mortality in a general population.MethodsWe followed a cohort of 7225 men and 7726 women aged 40–42 years who underwent health surveys in 1985–1989 in two Norwegian counties, with respect to deaths. Mean follow‐up period was 18 years. The subjects were categorised according to frequency of anxiolytic or hypnotic drug use during the last month: daily, every week, less than every week and not used during the last month.ResultsThe proportion of anxiolytic or hypnotic drug users was 6.6% among men and 16.2% among women. Altogether 402 men and 290 women died. There was an increase in risk of death with an increase in frequency of use. Crude hazard ratios for men and women daily using anxiolytics or hypnotics were 3.1 (95%CI 2.0, 4.8) and 2.7 (1.9, 4.0), respectively, as compared with non‐users last month. After adjusting painkiller use and smoking the hazard ratios were lowered, being 2.4 (1.5–4.0) (men) and 2.1 (1.4–3.2) (women). After additional adjustments for other possible confounders the hazard ratios were further attenuated to 1.5 (0.9–2.7) for men and 1.7 (1.1–2.6) for women.ConclusionsDaily users of anxiolytic or hypnotic drugs in our study showed higher crude mortality than non‐users. However, after adjusting lifestyle and socio‐economic variables the difference was markedly reduced suggesting that the remaining excess mortality is due to residual confounding. Copyright © 2007 John Wiley & Sons, Ltd.
Low dielectric constant nanocomposite thin films based on silica nanoparticle and organic thermosets
Authors: Lin Qinghuang , Cohen Stephen A. , Gignac Lynne , Herbst Brian , Klaus David , Simonyi Eva , Hedrick Jeffrey , Warlaumont John , Lee Hae‐Jeong , Wu Wen‐li 
Published: May 2007

AbstractLow dielectric constant (low‐k) nanocomposite thin films have been prepared by spin coating and thermal cure of solution mixtures of one of two organic low‐k thermoset prepolymers and a silica nanoparticle with an average diameter of about 8 nm. The electrical, the mechanical, and the thermomechanical properties of these low‐k nanocomposite thin films have been characterized with 4‐point probe electrical measurements, nanoindentation measurements with an atomic force microscope, and specular X‐ray reflectivity. Addition of the silica nanoparticle to the low‐k organic thermosets enhances both the modulus and the hardness and reduces the coefficient of thermal expansion of the resultant nanocomposite thin films. The enhancements in the modulus of the nanocomposite thin films are less than those predicted by the Halpin‐Tsai equations, presumably due to the relatively poor interfacial adhesion and/or the aggregation of the hydrophilic silica nanoparticles in the hydrophobic organic thermoset matrices. The addition of the silica nanoparticle to the low‐k organic thermoset matrices increases the relative dielectric constant of the resultant nanocomposite thin films. The relative dielectric constant of the nanocomposite thin films has been found to agree fairly well with an additive formula based on the Debye equation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1482–1493, 2007
Finite element method parametric study on scratch behavior of polymers
Authors: Jiang H. , Lim G. T. , Reddy J. N. , Whitcomb J. D. , Sue H.‐J. 
Published: May 2007

AbstractParametric studies were performed using finite element analysis (FEA) to learn how material and surface properties of polypropylene (PP) affect scratch behavior. Three‐dimensional FEA modeling of scratching on a PP substrate with a spherical‐tipped indenter is presented. Three different loading conditions, that is constant scratch depth, constant normal load, and linearly increasing normal load, are adopted for this parametric study. From the FEA findings, it is learned that Poisson's ratio has a negligible effect on scratch performance, whereas raising the coefficient of adhesive friction induces a significantly larger residual scratch depth and tangential force on the scratch tip. Increasing the Young's modulus of a material does not necessarily improve its overall scratch performance. On the other hand, modifying the yield stress of a material has a major impact on scratch resistance as a higher yield stress reduces the residual scratch depth. From this numerical effort, it is concluded that the yield stress and coefficient of adhesive friction are the most critical parameters to influence the scratch performance of a material. Analyses also suggest that the general trend in the parametric effect of the above four parameters on scratch behavior is independent of the applied normal load level. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1435–1447, 2007
Antiinflammatory activity of an herbal preparation (HemoHIM) in rats
Authors: Jo Sung Kee , Lee Hae June , Kim Se Ra , Kim Jong Choon , Bae Chun Sik , Jung Uhee , Park Hae Ran , Jang Jong Sik , Kim Sung Ho 
Published: May 2007

AbstractThis study evaluated a new herbal preparation, HemoHIM, for its antiinflammatory activity against carrageenan‐induced edema, the formation of granulation tissues by cotton pellet and experimental colitis by 2,4,6‐trinitrobenzene sulfonic acid (TNBS). The HemoHIM was prepared by adding its ethanol‐insoluble polysaccharide fraction to the total water extract of Angelica Radix, Cnidii Rhizoma and Paeonia Radix. The preparation (4 mg of solids/mL of drinking water, p.o., 50–100 mg/kg of body weight, i.p.) produced a dose‐related inhibition of carrageenan‐induced paw edema and cotton pellet‐induced granuloma in rats. In addition, HemoHIM also reduced the degree of TNBS‐induced colitis and improved the gross and histological changes such as thickening, dilatation, ulceration, and infiltration by polymorphonuclear leukocytes and multiple erosive lesions. These results demonstrate that the HemoHIM has a potent antiinflammatory effect. Copyright © 2007 John Wiley & Sons, Ltd.
Antitumor activity of crude polysaccharides isolated from Solanum nigrum Linne on U14 cervical carcinoma bearing mice
Authors: Li Jian , Li Qingwang , Feng Tao , Zhang Tao , Li Kun , Zhao Rui , Han Zengsheng , Gao Dawei 
Published: May 2007

AbstractSolanum nigrum Linne (SNL) has been used in traditional Chinese medicine for centuries because of its diuretic and antipyretic effects. The present study examined the effect of the crude polysaccharides isolated from Solanum nigrum Linne (SNL‐P) on tumor growth. SNL‐P had a significant growth inhibition effect on cervical cancer (U14) of tumor‐bearing mice. Further analysis of the tumor inhibition mechanism indicated that the number of apoptotic tumor cells increased significantly, the expression of Bax increased and the expression of Bcl‐2 and mutant p53 decreased dramatically in cervical cancer sections after oral administration of SNL‐P for 12 days. Moreover, SNL‐P treatment decreased the level of blood serum TNF‐α. These results indicated that the tumor growth inhibition of SNL‐P administration might correlate with the reduction of TNF‐α level of blood serum, which resulted in a massive necrosis in tumor tissues and the up‐regulation of Bax and down‐regulation of Bcl‐2 and mutant p53 gene expression, which triggered apoptosis in tumor cells. These findings demonstrated that the SNL‐P is a potential antitumor agent. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of 30 elements in colorectal biopsies by sector field inductively coupled plasma mass spectrometry: method development and preliminary baseline levels
Authors: Bocca Beatrice , Lamazza Antonella , Pino Anna , De Masi Ercole , Iacomino Maura , Mattei Daniela , Rahimi Siavash , Fiori Enrico , Schillaci Alberto , Alimonti Alessandro , Forte Giovanni 
Published: May 2007

AbstractAn analytical procedure applicable to restricted sample sizes was developed and applied to the analysis of 30 chemical elements in colorectal biopsies of healthy patients. Acidic microwave digestion processed ≤10 mg of tissue at 80°C in 15‐mL polystyrene liners. The digests were diluted to a volume of 2 mL with high‐purity water and directly analyzed by sector field inductively coupled plasma mass spectrometry without further specimen handling. A careful selection of isotopes and instrumental resolution permitted the quantification in a single analytical sequence both of the elements present at parts per trillion and of those at parts per million. The accuracy calculated on BCR 184 ranged from 93.3–110%, the recoveries of the biopsy material was in the range 95.2–105%, the precision was <10%, and the blank levels were much below those expected in biopsy samples. The metal concentrations (on a dry‐weight basis) in colorectal normal tissue showed a large range of variation: Ag, Au, Be, Bi, Co, Li, Sb, Tl, V, W and Zr were below 50 ng g−1; As, Ba, Cd, Cr, Cs, Hg, Mo, Ni, Pb, Se and Sn were distributed from 100 to 500 ng g−1; Al, Cu, Fe, Mn, Sr and Zn were from a few µg g−1 to 100 µg g−1; and Ca and Mg were at a level of 1000 µg g−1. These data represent the first attempt to achieve an elemental profile in the colorectal mucosa of healthy patients as baseline level measurements for studies focused on the imbalance of chemical elements in diseased mucosa. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization by high‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight mass spectrometry of the lipid fraction of Spirulina platensis pressurized ethanol extract
Authors: Herrero Miguel , Vicente María J. , Cifuentes Alejandro , Ibáñez Elena 
Published: May 2007

AbstractMicroalgae have been suggested as a potential source for new functional ingredients, making possible the development of new functional foods from natural origin. Among the natural ingredients, polyunsaturated fatty acids (PUFAs) have generally been identified as an interesting group of compounds with biological activity, mainly related to their anti‐inflammatory properties. In this regard, the use of environmentally friendly extraction procedures (e.g. pressurized liquid extraction, PLE) to obtain such natural ingredients is also becoming necessary. In this work, an exhaustive characterization of the lipid fraction of a pressurized ethanolic extract of the microalga Spirulina platensis is carried out. To achieve this objective high‐performance liquid chromatography (HPLC) coupled to quadrupole time‐of‐flight mass spectrometry (QTOF‐MS) is employed. The use of the QTOF analyzer allows the selection and isolation of precursor ions as well as providing the high efficiency, sensitivity and mass accuracy required. By means of this powerful hyphenated technique, it was possible to identify several polar lipids in an extract of S. platensis (some of them, to our knowledge, described for the first time in this work), including four free fatty acids, four monogalactosyl monoacylglycerols, three phosphatidylglycerols and two sulfoquinovosyl diacylglycerols. Copyright © 2007 John Wiley & Sons, Ltd.