bluuebunny/crossref_metadata_2025 huggingface dataset:
Mikrostrukturelle und mechanische Eigenschaften von laserstrahlgeschweißtem Magnesiumfeinblech AZ31‐HP mit und ohne Zusatzwerkstoffe
Authors: Ventzke V. , Riekehr S. , Koçak M.
Published: July 2008

Gegenstand dieses Manuskripts sind Untersuchungen an einem gewalzten Mg‐Magnesiumfeinblech der Dicke 2,5 mm aus AZ31‐HP, welches in Stumpfstoßausführung mit und ohne Zusatzwerkstoffe laserstrahlgeschweißt wurde. Als Zusatzwerkstoffe wurden AZ31X und AZ61A‐F in Spulendrahtform mit einem Durchmesser von 1,2 mm verwendet. Die mikrostrukturellen und mechanischen Eigenschaften der unterschiedlich laserstrahlgeschweißten Magnesiumlegierung AZ31‐HP wurden untersucht und miteinander verglichen. Die Ergebnisse zeigen, dass das Feinblech AZ31‐HP mit oder auch ohne Zusatzwerkstoffe ohne Heißrissbildung laserstrahlschweißbar ist. Die an der ohne Zusatzdraht geschweißten Verbindung ermittelten Eigenschaften wie Festigkeit, Duktilität, Mikrohärte und Bruchzähigkeit wurden weder durch AZ31X noch durch AZ61A‐F beeinflusst, lediglich geringe Zn‐Verluste werden mit den Zusatzdrähten ausgeglichen sowie die Nahtform verbessert. Die Werte für Zugfestigkeit, Dehngrenze und Mikrohärte sind für die Laserstrahlschweißverbindungen und des Grundwerkstoffs nahezu gleich. Bedingt durch die Gefügeheterogenität in den Fügezonen und durch die nahtgeometrischen Kerben sind die Schweißverbindungen im Vergleich zum Grundwerkstoff durch eine deutlich niedrigere Duktilität gekennzeichnet. Sowohl der Grundwerkstoff als auch die Laserstrahlschweißnähte zeigten stabile Rissausbreitung, wobei die Bruchzähigkeit des Grundwerkstoffs etwas niedriger war als die der Schweißnähte.
Cytochrome P450 1B1 expression in rat esophageal tumorigenesis promoted by gastric and duodenal reflux
Authors: Devlin Andrea H. , McIlroy Marie , McKeen Hayley D. , Bonde Pramode , Menezes A.A. Carlos , Swarbrick Christine J. , Robson Tracy , Hirst David G. , Campbell F. Charles , McGuigan James A. , McKeown Stephanie R.
Published: July 2008

Cytochrome P450 1B1 (CYP1B1) mRNA is constitutively expressed in most normal extra‐hepatic tissues; however the protein is not detectable in these tissues but is expressed in a wide variety of tumors. CYP1B1 is responsible for the activation of a number of carcinogens present in tobacco smoke and food. A surgical model of rat esophageal tumorigenesis, promoted by gastric or duodenal reflux was used to determine CYP1B1 expression in premalignant esophageal tissue. Immunohistochemistry was performed using a modified amplified fluorescein tyramide protocol. CYP1B1 was not observed in normal esophageal mucosa, submucosa, or muscularis mucosa. Animals exposed to gastric reflux developed mild hyperplasia. Varying degrees of hyperplasia were observed in the duodenal reflux group. All regions of hyperplasia showed moderate or strong CYP1B1 immunoreactivity. Duodenal reflux induced a small number of premalignant changes: immunoreactivity was absent from the epithelium of squamous dysplasia (0/10), Barrett's esophagus (0/7), and majority of dysplastic Barrett's esophagus (1/4). Moderate or strong immunoreactivity was observed in the majority (7/8) of squamous cell carcinomas (SCCs) in situ. Immunoreactivity was also observed in the lamina propria and submucosa in association with inflammation, regardless of the severity of inflammation. The expression of CYP1B1 in hyperplasia, SCCs in situ, or in association with inflammation may increase the production of carcinogenic metabolites, which may promote esophageal tumorigenesis. © 2008 Wiley‐Liss, Inc.
Calcium and calcium sensing receptor modulates the expression of thymidylate synthase, NAD(P)H:quinone oxidoreductase 1 and survivin in human colon carcinoma cells: Promotion of cytotoxic response to mitomycin C and fluorouracil
Authors: Liu Guangming , Hu Xin , Varani James , Chakrabarty Subhas
Published: July 2008

Ca2+ and the cell‐surface calcium sensing receptor (CaSR) constitute a novel and robust ligand/receptor system in regulating the proliferation and differentiation of colonic epithelial cells. Here we show that activation of CaSR by extracellular Ca2+ (or CaSR agonists) enhanced the sensitivity of human colon carcinoma cells to mitomycin C (MMC) and fluorouracil (5‐FU). Activation of CaSR up‐regulated the expression of MMC activating enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO‐1) and down‐regulated the expression of 5‐FU target, thymidylate synthase (TS) and the anti‐apoptotic protein survivin. Cells that were resistant to drugs expressed little or no CaSR but abundant amount of survivin. Disruption of CaSR expression by shRNA targeting the CaSR abrogated these modulating effects of CaSR activation on the expression of NQO1, TS, survivin and cytotoxic response to drugs. It is concluded that activation of CaSR can enhance colon cancer cell sensitivity to MMC and 5‐FU and can modulate the expression of molecules involved in the cellular responses to these cytotoxic drugs. © 2008 Wiley‐Liss, Inc.
Suicidal and death ideation in Parkinson's disease
Authors: Nazem Sarra , Siderowf Andrew D. , Duda John E. , Brown Gregory K. , Ten Have Tom , Stern Matthew B. , Weintraub Daniel
Published: July 2008

Parkinson's disease (PD) is a chronic, disabling illness affecting primarily the elderly and is associated with a high prevalence of depression. Although these are known risk factors for suicidal and death ideation, little is known about the prevalence and correlates of such ideation in PD. A convenience sample of 116 outpatients with idiopathic PD at two movement disorders centers were administered a modified Paykel Scale for suicidal and death ideation, as well as an extensive psychiatric, neuropsychological, and neurological battery. Univariate and multivariate logistic regression models were used to determine the correlates of suicidal or death ideation. Current death ideation (28%) or suicide ideation (11%) were present in 30% of the sample, and 4% had a lifetime suicide attempt. On univariate logistic regression analysis, increasing severity of depression (odds ratio = 2.92, 95% CI 2.01–4.24, P < 0.001), impulse control disorder (ICD) behaviors sometime during PD (odds ratio = 6.08, 95% CI 1.90–19.49, P = 0.002), and psychosis (odds ratio = 2.45, 95% CI 1.05–5.69, P = 0.04) were associated with either ideation. On multivariate logistic regression analysis, only increasing severity of depressive symptoms (odds ratio = 2.76, 95% CI 1.88–4.07, P < 0.001) predicted suicidal or death ideation. In conclusion, active suicidal or death ideation occurs in up to one‐third of PD patients. Comorbid psychiatric disorders, more than PD‐related disease variables, are associated with this ideation, highlighting the need for a comprehensive approach to the clinical care of PD patients. © 2008 Movement Disorder Society
Striatal dopamine transporter imaging correlates with depressive symptoms and tower of London task performance in Parkinson's disease
Authors: Rektorova Irena , Srovnalova Hana , Kubikova Radka , Prasek Jiri
Published: July 2008

We studied whether the 123I‐FP‐CIT uptake in the striatum correlates with depressive symptoms and cognitive performance in patients with Parkinson's disease (PD). Twenty patients with PD without major depression and/or dementia (mean age 61.7 ± 12.7 years) underwent the 123I‐FP‐CIT SPECT. Depressive symptoms and cognitive performance were assessed in the ON state. The ratios of striatal to occipital binding for the entire striatum, putamina, and putamen to the caudate (put/caud) index were calculated in the basal ganglia. The association between neuropsychiatric measures and dopamine transporter (DAT) availability was calculated; multiple regression analysis was used to assess association with age and disease duration. We found significant correlations between Montgomery and Asberg Depression Rating Scale (MARDS) and Tower of London (TOL) task scores and 123I‐FP‐CIT uptake in various striatal ROIs. Multiple regression analysis confirmed the significant relationship between TOL performance and put/caud ratio (P = 0.001) and to age (P = 0.001), and between MADRS and left striatal (P = 0.005) and putaminal DAT availability (P = 0.003). Our pilot study results demonstrate that imaging with 123I‐FP‐CIT SPECT appears to be sensitive for detecting dopaminergic deficit associated with mild depressive symptoms and specific cognitive dysfunction in patients with PD, yet without a current depressive episode and/or dementia. © 2008 Movement Disorder Society
Hand reconstruction with lobulated combined flaps based on the circumflex scapular pedicle
Authors: Gao Weiyang , Hong Jianjun , Li Zhijie , Chen Xinglong
Published: July 2008

Repair of multiple soft tissue defects on hand often pose a difficult problem to the reconstructive surgeons with employing a limited number of reliable flaps and recipient vessels. This report is to explore the feasibility and advantage of the treatment of multiple soft tissue defects on hand with combined island flaps based on branches of the circumflex scapular system. From 2002 to 2006, nine patients had transfer of the scapular lobulated combined flaps based on the transverse branch, ascending branch, and descending branch of the circumflex scapular vascular pedicle for coverage of soft‐tissue defects over injured hands. Follow‐up ranged from 6 months to 24 months with average 12.1 months' all of nine flaps completely survived without complications. Arterial insufficiency was found in one flap because of the pedicle compression in the subcutaneous tunnel. The blood supply to flap was restored after the compression was released. All transferred flaps showed good appearance without significantly swelling and congestion. Two flaps underwent secondary debulking surgery. At 6 months postoperatively, partial protective sensation (S1) was restored in the flaps. The donor sites were directly closed in six cases. Skin grafts were used to cover the donor sites in other three cases. All of donor sites healed without complications. Our report shows that the management of multiple soft tissue defects on hand in complex hand injuries with lobulated flaps of circumflex scapular system can obtain good results for its good appearance and low donor site complications. It is probably the optimal surgical intervention for these injuries. © 2008 Wiley‐Liss, Inc. Microsurgery, 2008.
Polynomial and analytic stabilization of a wave equation coupled with an Euler–Bernoulli beam
Authors: Ammari Kaïs , Nicaise Serge
Published: July 2008

We consider a stabilization problem for a model arising in the control of noise. We prove that in the case where the control zone does not satisfy the geometric control condition, B.L.R. (see Bardos et al. SIAM J. Control Optim. 1992; 30:1024–1065), we have a polynomial stability result for all regular initial data. Moreover, we give a precise estimate on the analyticity of reachable functions where we have an exponential stability. Copyright © 2008 John Wiley & Sons, Ltd.
Scattering of an incident acoustic wave by an infinite elastic cylinder in a shallow sea
Authors: Lee Doo‐Sung
Published: July 2008

The scattering of sound waves by an isotropic elastic circular cylinder of infinite extent in a water of finite depth is investigated taking into account the shear waves that can exist in addition to compressional waves in scatterers of solid material. The axis of the cylinder is parallel to the water level.

The reflected and transmitted energies are plotted for the various values of the radius of the cylinder, and the farfield scattered pressure is obtained for various depth and presented in a graphical form. Copyright © 2008 John Wiley & Sons, Ltd.
Notes on ferromagnetic p‐spin and REM
Authors: Barra Adriano
Published: July 2008

In this paper we apply some of the recent mathematical techniques (mainly based on interpolation) developed in the spin glass theory to the ferromagnetic p‐spin model. We introduce two Hamiltonians and derive their thermodynamics. This is a second step toward an alternative and rigorous formulation of the statistical mechanics of simple systems on lattice. A first step has been performed in J. Stat. Phys. (2007; arXiv:0712.1344) where the techniques have been tested on the two‐body Ising model. For completeness the adaptation of the well‐known random energy model to the context of the ferromagnetism is presented. At the end a discussion on the extension of these techniques to Gaussian‐disordered p‐spin models is also briefly outlined. Copyright © 2008 John Wiley & Sons, Ltd.
A boundary obstacle problem for the Mindlin–Timoshenko system
Authors: Araruna F. D. , Feitosa A. J. R. , Oliveira M. L.
Published: July 2008

We consider the dynamical one‐dimensional Mindlin–Timoshenko model for beams. We study the existence of solutions for a contact problem associated with the Mindlin–Timoshenko system. We also analyze how its energy decays exponentially to zero as time goes to infinity. Copyright © 2008 John Wiley & Sons, Ltd.
Multi‐dimensional inhomogeneity indicators and the force on uncharged spheres in electric fields
Authors: Langemann Dirk
Published: July 2008

Uncharged droplets on outdoor high‐voltage equipment suffer a non‐vanishing total force in non‐homogeneous electric fields. Here, the model problem of a spherical test body is considered in arbitrary dimensions. A series expansion of inhomogeneity indicators is proven, which approximates the total force in local terms of the undisturbed electric field. The proof uses the ideas of generalized spherical harmonics without referring to the particular choice of the orthonormal system. The fast converging series expansion establishes a relationship between the solutions of two partial differential equations on different domains. Copyright © 2008 John Wiley & Sons, Ltd.
In vivoassessment of herb–drug interactions: Possible utility of a pharmacogenetic approach?
Authors: Tomlinson Brian , Hu Miao , Lee Vivian W. Y.
Published: July 2008

Herbal medicines are frequently used in combination with conventional drugs and interactions are likely to be more common than those which manifest clinically. Pharmacokinetic interactions mediated by drug‐metabolizing enzymes or transporters are involved in many herb–drug interactions. Polymorphisms in the genes for these enzymes and transporters may influence the interactions mediated through these pathways. Herb–drug interactions can be identifiedin vivousing the herbs with individual probe drugs or drugs with a narrow therapeutic index. A probe drug cocktail approach offers a more efficient screening procedure. If potential interactions are studied in subject groups with different genotypes, more definitive information can be obtained. The selection of genotype groups to study should depend not only on the major enzymes or transporters involved in the disposition of a drug, but also on alternate pathways which may become more important in subjects with reduced activity in the primary pathway, and the pathways for pharmacodynamic effects should also be considered for some drugs. Some genotypes may only be found in certain ethnic groups. Currently, the pharmacogenetic approach has been used mainly to study drug–drug interactions so there is considerable potential to extend this to the study of herb–drug interactionsin vivo.
Comparison of delphinidin, quercetin and (–)‐epigallocatechin‐3‐gallate as inhibitors of the EGFR and the ErbB2 receptor phosphorylation
Authors: Fridrich Diana , Teller Nicole , Esselen Melanie , Pahlke Gudrun , Marko Doris
Published: July 2008

In the present study, delphinidin was found to suppress the phosphorylation of the epidermal growth factor receptor (EGFR) within human tumour cells (human colon carcinoma cell line (HT29), human vulva carcinoma cell line (A431)), albeit less effective than the flavonol quercetin. The higher potency of quercetin was also observed downstream on the level of the mitogen‐activated protein kinase (MAPK) cascade. In addition, delphinidin, quercetin and (–)‐epigallocatechin‐3‐gallate (EGCG) were found to suppress the phosphorylation of the ErbB2 receptor, with delphinidin exhibiting the strongest inhibitory properties. Their potency to suppress the ErbB2 receptor phosphorylation can be summarised as delphinidin > EGCG > quercetin. The effectiveness of delphinidin against the EGFR and the ErbB2 receptor was comparable, indicating a broader spectrum of activity against receptor tyrosine kinases. At low micromolar concentrations delphinidin showed some preference towards the ErbB2 receptor. In summary, quercetin and delphinidin appear to differ in their activity profile towards the ErbB receptor family members. Whereas quercetin was most effective against the EGFR, delphinidin exhibited some preference towards the ErbB2 receptor.
Saturation transfer double‐difference NMR spectroscopy using a dual solenoid microcoil difference probe
Authors: Bergeron Scott J. , Henry Ian D. , Santini Robert E. , Aghdasi Abdollah , Raftery Daniel
Published: July 2008

An experiment designed to collect a saturation transfer double difference (STDD) NMR spectrum using a solenoid microcoil NMR difference probe is reported. STDD‐NMR allows the investigation of ligand‐biomolecule binding, with moderate concentration requirements for unlabeled molecular targets and the ability to discern binding events in the presence of non‐binding ligands. The NMR difference probe acquires the signals from two different samples at once, and cancels common signals automatically through a mechanism of switching between parallel excitation and serial acquisition of the sample signals. STDD spectra were acquired on a system consisting of human serum albumin and two ligands, octanoic acid and glucose. The non‐binding ligand, glucose, was cancelled internally through phase cycling, while the protein signal was subtracted automatically by the difference probe. The proton NMR resonance signal from octanoic acid remained in the double difference spectrum. This work demonstrates that the double difference can be performed both internally and automatically through the utilization of the solenoid microcoil NMR difference probe and STDD‐NMR pulse sequence, resulting in a clean signal from the binding ligand with good protein background subtraction and an overall favorable result when compared to the conventional approach. Copyright © 2008 John Wiley & Sons, Ltd.
Structural determination of flavonoids from Sorphora flavescens
Authors: Ma Xiao‐Chi , Xin Xiu‐Lan , Zhang Bao‐Jing , Li Feng‐Yun , Liu Ke‐Xin , Guo De‐An
Published: July 2008

Eight flavonoids were isolated from Sophora flavescens. Among them, three prenylflavanones: (2S)‐6[2(3‐hydroxyisopropyl)‐5‐methyl‐4‐hexenyl]‐5‐methoxy‐7,2′, 4′‐trihydroxyflavanone (1), (2S)‐5, 4′‐dimethoxy‐8‐lavandulyl‐7, 2′‐dihydroxy flavanone (2) and (2S)‐8‐(5‐hydroxy‐2‐isopropenyl‐5‐methylhexyl)‐7‐methoxy‐5,2′, 4′‐trihydroxyflavanone (3) are new compounds. Their chemical structures were determined by spectral methods including 2D NMR. Copyright © 2008 John Wiley & Sons, Ltd.
Assessment of blood volume, vessel size, and the expression of angiogenic factors in two rat glioma models: a longitudinal in vivo and ex vivo study
Authors: Valable Samuel , Lemasson Benjamin , Farion Régine , Beaumont Marine , Segebarth Christoph , Remy Chantal , Barbier Emmanuel L.
Published: July 2008

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

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

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

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

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

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

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

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

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

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

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

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

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

We consider the problem of optimal design of nano‐scale heat conducting systems using topology optimization techniques. At such small scales the empirical Fourier's law of heat conduction no longer captures the underlying physical phenomena because the mean‐free path of the heat carriers, phonons in our case, becomes comparable with, or even larger than, the feature sizes of considered material distributions. A more accurate model at nano‐scales is given by kinetic theory, which provides a compromise between the inaccurate Fourier's law and precise, but too computationally expensive, atomistic simulations.

We analyze the resulting optimal control problem in a continuous setting, briefly describing the computational approach to the problem based on discontinuous Galerkin methods, algebraic multigrid preconditioned generalized minimal residual method, and a gradient‐based mathematical programming algorithm. Numerical experiments with our implementation of the proposed numerical scheme are reported. Copyright © 2008 John Wiley & Sons, Ltd.
Crack identification by ‘arrival time’ using XFEM and a genetic algorithm
Authors: Rabinovich Daniel , Givoli Dan , Vigdergauz Shmuel
Published: July 2008

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

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

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

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

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

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

Nach Jahren der Freude über die Entzifferung des menschlichen Genoms rückt nun die individualisierte Genom‐Sequenzierung in den Mittelpunkt des Interesses. Dabei zündet die ohnehin rasante Genom‐Sequenzierung den Turbo.
A Rapid and effective method for RNA extraction from different tissues of grapevine and other woody plants
Authors: Gambino Giorgio , Perrone Irene , Gribaudo Ivana
Published: July 2008

Introduction – RNA quality and integrity are critical for many studies in plant molecular biology. High‐quality RNA extraction from grapevine and other woody plants is problematic due to the presence of polysaccharides, polyphenolics and other compounds that bind or co‐precipitate with the RNA.

Objective – To develop an optimised cetyltrimethylammonium bromide (CTAB)‐based protocol, to reduce the time and cost of extraction without reducing quality and yield of RNA extracted from polysaccharide‐rich tissues of several plants.

Methodology – Several changes were introduced to the original CTAB protocol. All centrifugation steps were carried out at 4°C, the sample weight was decreased and the concentrations of PVP‐40 and LiCl were increased reducing incubation time prior to RNA precipitation. This rapid CTAB protocol was compared with six different RNA extraction methods from three grapevine tissues, namely, in vitro plantlets, and leaves and mature canes from actively growing field vines.

Results – The rapid CTAB method gave high‐quality RNA in only 3 h at low cost with efficiency equal to or higher than that obtained with other time‐consuming and expensive protocols. The procedure was applied to RNA extraction from other grapevine tissues and other woody species including olive, lemon, poplar, chestnut, apple, pear, peach, cherry, apricot, plum and kiwi fruit. RNA of high quality could be isolated from all tissues and from all species.

Conclusion – The study has shown that the improvement of a CTAB‐based protocol allows the rapid isolation of high‐quality RNA from grapevine and many woody species. Copyright © 2008 John Wiley & Sons, Ltd.
Safety assessment of food and herbal products containing hepatotoxic pyrrolizidine alkaloids: interlaboratory consistency and the importance ofN‐oxide determination
Authors: Cao Yu , Colegate Steven M. , Edgar John A.
Published: July 2008

Introduction – Two recent mass spectrometry‐based reports concerningSenecio scandensyielded remarkably dissimilar pyrrolizidine alkaloid constituents. In both studies, and in a related analysis ofSenecio scandensandTussilago farfarausing micellar electrokinetic chromatography, the presence of hazardousN‐oxides of the alkaloids was either not considered or was inadequately considered. This raises concerns about the effectiveness of the methodologies used in these, and similar, studies in assessing the pyrrolizidine alkaloid content and the safety of food, food supplements and medicines for human use.

Objective – To highlight essential analytical requirements for confident assessment of pyrrolizidine alkaloid‐related safety of food and herbal products for human use.

Methodology – Direct infusion‐ESI MS and HPLC‐ESI MS were used to analyse samples derived from liquid–liquid partitioning experiments and from strong cation exchange, solid‐phase extraction of pyrrolizidine alkaloids and theirN‐oxides.

Results – A simple solvent partitioning experiment using pure senecionine and senecionine‐N‐oxide, two constituents reported in one of the mass spectrometry‐based studies ofS.scandens, clearly demonstrated the inadequacy of the reported method to detect and quantitate hazardous pyrrolizidine alkaloidN‐oxide components. A preliminary LCMS analysis of commercially‐prepared extracts of comfrey roots (Symphytum officinaleandS.uplandicums. l.) was used as a model to highlight the analytical importance ofN‐oxides in the safety assessment of pyrrolizidine alkaloid‐containing medicinal herbs.

Conclusions – This study highlighted significant differences in the reported identification of pyrrolizidine alkaloids from the same plant species, and clearly demonstrated the inadequacy of some procedures to includeN‐oxides in the assessment of pyrrolizidine alkaloid‐related safety of food and herbal products. Copyright © 2008 John Wiley & Sons, Ltd.
Influence of the extraction mode on the yield of hyperoside, vitexin and vitexin‐2′′‐O‐rhamnoside from Crataegus monogyna Jacq. (hawthorn)
Authors: Martino Emanuela , Collina Simona , Rossi Daniela , Bazzoni Deborah , Gaggeri Raffaella , Bracco Francesco , Azzolina Ornella
Published: July 2008

Introduction – The extract of Crataegus monogyna shows sedative, hypotensive, vasodilator and cardio‐tonic actions. Although several papers dealing with the extraction of metabolites from Crataegus have been published, the plant productivity in terms of bioactive compounds is not easily understandable as yet.

Objective – To investigate the influence of the extraction mode on the yield of bioactive compounds from Crataegus monogyna Jacq. in order to evaluate plant productivity.

Methodology – Samples were prepared by extraction of powdered material obtained from top branches, flowers and leaves. Soxhlet extraction, maceration and ultrasound‐ and microwave‐assisted extraction at different experimental conditions were investigated for the exhaustive extraction of hyperoside, vitexin and vitexin‐2′′‐O‐rhamnoside. The phytocomponents were identified and quantified by HPLC‐UV/PAD, comparing HPLC retention times and UV spectra of individual peaks with those of the standards analysed under the same conditions.

Results – An easy‐to‐use HPLC isocratic method suitable for the quantification of hyperoside, vitexin and vitexin‐2′′‐O‐rhamnoside in raw plant extracts was developed. The optimised HPLC methodology was applied to evaluate different extraction procedures. The ultrasound and microwave‐assisted extraction protocols showed higher extraction efficiency than the others. In particular, the optimised microwave protocol gave rise to the highest extraction efficiency with high reproducibility.

Conclusions – A microwave protocol combined with isocratic HPLC analysis is proposed for the rapid screening of plant materials collected in different environmental conditions in order to evaluate the productivity of Crataegus monogyna Jacq. and to find out the best ecological conditions to cultivate hawthorn in Northern Italy. Copyright © 2008 John Wiley & Sons, Ltd.