bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age‐related changes in Brain T1 are correlated with iron concentration
Authors: Ogg Robert J. , Steen R. Grant 
Published: March 2007

AbstractAge‐related changes in brain T1 from 115 healthy subjects (range, 4.5–71.9 yr) were analyzed in relation to published regional brain iron concentration in cortex, caudate, putamen, and frontal white matter. The relaxation rate in these struc tures was linear with respect to iron concentration (P < 0.001). The iron relaxivity, k1 (s−1/mg iron/g wet weight), was much higher in cortex (5.5) and white matter (6.1) than in caudate (1.7) and putamen (1.0). These results are consistent with evidence that iron is an important factor in determining the relaxation properties of brain tissue. Iron relaxivity may reflect regional differences in the physical state of brain iron or in the interaction of brain iron with tissue water.
Effects of acute normovolemic hemodilution onT2* ‐ weighted images of rat brain
Authors: Lin Weili , Paczynski Richard P. , Celik Azim , Hsu Chung Y. , Powers William J. 
Published: March 2007

AbstractAcute normovolemic hernodilution (HD) was induced in anesthetized rats to assess the effect of changes in hematocrit (Hct) on signal intensity inT2*‐weighted magnetic resonance (MR) images. Other relevant physiological parameters were maintained invariant. Two degrees of HD were induced: mild (Hct reduced from 42.6 ± 2.2% to 33.4 ± 2.1%) and moderate (Hct reduced from 44.6 ± 2.7% to 26.2 ± 1.7%). A two‐dimensional gradient‐echo sequence was used to monitor signal changes with high temporal resolution before, during, and after HD protocols. The time course of signal intensity change was closely related to that of changes in Hct. Corresponding changes in R2* (ΔR2*) with respect to the pre‐HD state were calculated for the brain parenchyma. Average ΔR2* values of −0.24 ± 0.06 s−1and −0.40 ± 0.07 s−1were obtained for the mild and moderate HD groups, respectively, during the final 2 min of MR imaging (proximal to correlative measurements of Hct). MR measured ΔR2* values were in close agreement with the expected changes inR2* predicted from theory when the measured changes in Hct were used as independent variables. These data are in good agreement with the current understanding of the effects of changes in the intravascular concentration of deoxyhemoglobin on induced magnetic susceptibility and hold promise for quantitative measurement of brain oxygenationin vivo.
Quantitative magnetic resonance imaging in the assessment of degenerative disc disease
Authors: Antoniou John , Pike G. Bruce , Steffen Thomas , Baramki Hani , Poole A. Robin , Aebi Max , Alini Mauro 
Published: March 2007

AbstractUnderstanding degenerative intervertebral disc diseases hinges on the ability to objectively and noninvasively assess the disc matrix composition and integrity. The potential of quantitative magnetic resonance imaging to meet these demands was evaluated. Analyzing the T1 and T2 signal patterns in the nucleus pulposus with increasing Thompson morphological grade revealed a significant reduction related to grade. This significant decrease in T1 and T2 in the nucleus pulposus with grade 4 degeneration and the corresponding low correlation coefficients with respect to the content of individual matrix molecules suggest that matrix integrity plays an important and distinct role in determining T1 and T2 signal. Similarly, the significant increase in magnetization transfer in the nucleus pulposus observed in grade 4 degeneration did not correlate with the changes in molecular content in these highly degenerated discs. Again, this lack of correlation clearly indicates that the tissue integrity and matrix composition independently contribute to the magnetization transfer signal. This study presents the first clear evidence that quantitative magnetic resonance analysis reflects not only the disc matrix composition, but also the structural integrity of the matrix of the disc.
Spatial localization combining projection presaturation with a two‐dimensional excitation pulse
Authors: Lawrence Keith St. , Lee Ting‐Yim , Henkelman Mark 
Published: March 2007

AbstractSingle‐shot spatial localization of short T1 nuclei was achieved by outer volume suppression with projection presaturation followed by selective excitation of the desired volume with a two‐dimensional (2D) pulse. After the projection, presaturation with a 2D pulse avoided signal contamination from magnetization regrowth in the outer volume, whereas preceding the 2D pulse with projection presaturation reduced any unwanted excitation in the outer volume caused by the 2D pulse. The improvement in outer volume suppression achieved by combining these two techniques was demonstrated by images collected after the application of projection presaturation alone, a 2D pulse alone, and the two combined.
Variational h‐adaption in finite deformation elasticity and plasticity
Authors: Mosler J. , Ortiz M. 
Published: March 2007

AbstractWe ropose a variational h‐adaption strategy in which the evolution of the mesh is driven directly by the governing minimum principle. This minimum principle is the principle of minimum potential energy in the case of elastostatics; and a minimum principle for the incremental static problem of elasto‐viscoplasticity. In particular, the mesh is refined locally when the resulting energy or incremental pseudo‐energy released exceeds a certain threshold value. In order to avoid global recomputes, we estimate the local energy released by mesh refinement by means of a lower bound obtained by relaxing a local patch of elements. This bound can be computed locally, which reduces the complexity of the refinement algorithm to O(N). We also demonstrate how variational h‐refinement can be combined with variational r‐refinement to obtain a variational hr‐refinement algorithm. Because of the strict variational nature of the h‐refinement algorithm, the resulting meshes are anisotropic and outperform other refinement strategies based on aspect ratio or other purely geometrical measures of mesh quality. The versatility and rate of convergence of the resulting approach are illustrated by means of selected numerical examples. Copyright © 2007 John Wiley & Sons, Ltd.
Accurate eight‐node hexahedral element
Authors: Fredriksson Magnus , Ottosen Niels Saabye 
Published: March 2007

AbstractBased on the assumed strain method, an eight‐node hexahedral element is proposed. Consistent choice of the fundamental element stiffness guarantees convergence and fulfillment of the patch test a priori. In conjunction with a γ‐projection operator, the higher order strain field becomes orthogonal to rigid body and linear displacement fields. The higher order strain field in question is carefully selected to preserve correct rank for the element stiffness matrix, also for distorted elements. Volumetric locking is also removed effectively. By considerations of the bending energy, improved accuracy is obtained even for coarse element meshes. The choice of local co‐ordinate system aligned with the principal axes of inertia makes it possible to improve the performance even for distorted elements. The strain‐driven format obtained is well suited for materials with non‐linear stress–strain relations. Several numerical examples are presented where the excellent performance of the proposed eight‐node hexahedral is verified. Copyright © 2007 John Wiley & Sons, Ltd.
Mesh deformation based on fully stressed design: the method and 2‐D examples
Authors: Hsu Su‐Yuen , Chang Chau‐Lyan 
Published: March 2007

AbstractMesh deformation in response to redefined boundary geometry is a frequently encountered task in shape optimization and analysis of fluid–structure interaction. We propose a simple and concise method for deforming meshes defined with three‐node triangular or four‐node tetrahedral elements. The mesh deformation method is suitable for large boundary movement. The approach requires two consecutive linear elastic finite element analyses of an isotropic continuum using a prescribed displacement at the mesh boundaries. The first analysis is performed with homogeneous elastic property and the second with inhomogeneous elastic property. The fully stressed design is employed with a vanishing Poisson ratio and a proposed form of equivalent strain (modified Tresca equivalent strain) to calculate, from the strain result of the first analysis, an element‐specific Young's modulus for the second analysis. The theoretical aspect of the proposed method, its convenient numerical implementation using a typical linear elastic finite element code in conjunction with very minor extra coding for data processing, and results for examples of large deformation of 2‐D meshes are presented in this paper. Copyright © 2007 John Wiley & Sons, Ltd.
Two‐scale method for shear bands: thermal effects and variable bandwidth
Authors: Areias Pedro M. A. , Belytschko Ted 
Published: March 2007

AbstractA method for the analysis of shear bands using local partition of unity is developed in the framework of the extended finite element method (XFEM). Enrichments are introduced for both the displacement field and the thermal field. The shear band width is determined by minimizing the plastic work. A coupled finite strain thermo‐elastoplastic constitutive law is used. The enrichment is injected into the mesh when the material law becomes unstable. The criterion based on a complete stability analysis for materials in the finite strain regime including heat conduction, strain hardening, strain rate hardening and thermal softening is presented. A mixed continuous quadrilateral element is employed. The method is applied to the Nesterenko experiments, which exhibit multiple propagating shear bands and other problems. Copyright © 2007 John Wiley & Sons, Ltd.
Locking‐free finite elements for shear deformable orthotropic thin‐walled beams
Authors: Minghini F. , Tullini N. , Laudiero F. 
Published: March 2007

AbstractNumerical models for finite element analyses of assemblages of thin‐walled open‐section profiles are presented. The assumed kinematical model is based on Timoshenko–Reissner theory so as to take shear strain effects of non‐uniform bending and torsion into account. Hence, strain elastic‐energy coupling terms arise between bending in the two principal planes and between bending and torsion. The adopted model holds for both isotropic and orthotropic beams. Several displacement interpolation fields are compared with the available numerical examples. In particular, some shape functions are obtained from ‘modified’ Hermitian polynomials that produce a locking‐free Timoshenko beam element. Analogously, numerical interpolation for torsional rotation and cross‐section warping are proposed resorting to one Hermitian and six Lagrangian formulation. Analyses of beams with mono‐symmetric and non‐symmetric cross‐sections are performed to verify convergence rate and accuracy of the proposed formulations, especially in the presence of coupling terms due to shear deformations, pointing out the decay length of end effects. Profiles made of both isotropic and fibre‐reinforced plastic materials are considered. The presented beam models are compared with results given by plate‐shell models. Copyright © 2007 John Wiley & Sons, Ltd.
Boundary recovery after 3D Delaunay tetrahedralization without adding extra nodes
Authors: Liu Jianfei , Chen Bin , Chen Yongqiang 
Published: March 2007

AbstractIn this paper, we investigate boundary recovery, the problem that has troubled researchers ever since Delaunay‐based methods were applied to generate mesh. There are a number of algorithms for boundary recovery already and most of them depend heavily on adding extra nodes. In this paper, we make an effort to seek a method to recover boundaries without using extra nodes.It was noted that some previous algorithms imposed artificial boundary constraints on a meshing problem at the recovering stage; we first try to discard these artificial constraints and thus make things easier. Then a new method is proposed by which the boundaries can be recovered by means of two operations: (1) creating a segment in the mesh and (2) removing a segment from the mesh. Both operations are special cases of a general local transformation called small polyhedron reconnection operation. The method works well when coupled with the sphere‐packing method proposed by the first author. If the mesh sizing function is suitable, a good configuration of nodes will be created accordingly by the sphere‐packing method and the boundary can be recovered by the local transformation presented here without inserting extra nodes. Copyright © 2007 John Wiley & Sons, Ltd.
High quality baseline for high efficiency, Cu(In1−x,Gax)Se2 solar cells
Authors: Jackson Philip , Würz Roland , Rau Uwe , Mattheis Julian , Kurth Matthias , Schlötzer Thomas , Bilger Gerhard , Werner Jürgen H. 
Published: March 2007

AbstractWe report on the progress that we have made in the quality of our baseline process for the production of high efficiency soda lime glass/Mo/Cu(In,Ga)Se2 (CIGS)/CdS/i‐ZnO/ZnO:Al/MgF2 solar cells. The enhancement of the average performance level has enabled us to reach conversion efficiencies of up to 19·3% (internal measurement). The new quality initiative uses process control, optical and electrical modelling, and the critical revision of all process steps as tools for the attainment of the 19% efficiency level. Our experiments show that the compositional process window for CIGS solar cells that have an efficiency of η ≈ 19% is very wide. Accordingly, we suggest that an efficiency of 19·0–19·5% is achievable in the following compositional process windows: 0·69 ≤ Cu/(Ga + In) ≤ 0·98 and 0·21 ≤ Ga/(Ga + In) ≤ 0·38. In addition, our results show that large CIGS grains are not a necessary requirement for high efficiencies up to 19%. These findings and the partly lacking ability to correlate certain aspects of our progress with experimental parameters lead us to the conclusion that there are still some important process variables undiscovered. From this conclusion and from the evaluation of the available data we infer that there is a potential for the enhancement of CIGS solar cell efficiencies beyond 20%. Copyright © 2007 John Wiley & Sons, Ltd.
Antiviral triterpenoids from the medicinal plant Schefflera heptaphylla
Authors: Li Yaolan , Jiang Renwang , Ooi Linda S. M. , But Paul P. H. , Ooi Vincent E. C. 
Published: March 2007

AbstractSchefflera heptaphylla (L.) Frodin is a principal ingredient of an herbal tea formulation widely used for the treatment of common cold in southern China. An extract of the long leafstalk of the compound leaf of S. heptaphylla exhibited the most potent antiviral activity against respiratory syncytial virus (RSV). Further antiviral‐guided fractionation and isolation of the leafstalk extract of S. heptaphylla led to obtain two highly active pure triterpenoids, namely 3α‐hydroxylup‐20(29)‐ene‐23,28‐dioic acid and 3‐epi‐betulinic acid 3‐O‐sulfate, together with an inactive saponin, 3α‐hydroxylup‐20(29)‐ene‐23,28‐dioic acid 28‐O‐α‐l‐rhamnopyranosyl‐(1→4)‐O‐β‐d‐glucopyranosyl‐(1→6)‐β‐d‐glucopyranoside. An antiviral assay using a cytopathic effect (CPE) reduction method showed that the two triterpenoids possessed broader antiviral activity against respiratory syncytial virus (RSV) with a similar 50% inhibition concentration (IC50) value of 6.25 µg/mL, influenza A (H1N1) virus with IC50 values of 25 and 31.3 µg/mL, Coxsackie B3 (Cox B3) virus with IC50 values of 12.5 and 20 µg/mL and herpes simplex virus type 1 (HSV‐1) with IC50 values of 18.8 and 25 µg/mL, respectively, whereas the saponin did not have antiviral activity against these four viruses at a concentration of 100 µg/mL. Copyright © 2007 John Wiley & Sons, Ltd.
Antimutagenic effect of broccoli flower head by the ames salmonella reverse mutation assay
Authors: S. Murugan S. , P. Balakrishnamurthy , J. Mathew Y. 
Published: March 2007

AbstractA study was performed to investigate the antimutagenic effect of broccoli flower head by the Ames Salmonella reverse mutation assay. Broccoli flower head being the most highly edible part in the plant was analysed for its antimutagenic effect. Without isolating the phytomolecules, the crude ethanol extract of broccoli flower head was tested for suppressing the mutagenic effect induced by certain chemical mutagens. Three strains – TA 98, TA102 and TA 1535 were used in the study. The tester strains were challenged with their respective mutagens. These were challenged with the ethanol extract of broccoli flower head at concentrations of 23 and 46 mg/plate. The plates were incubated for 72 h and the revertant colonies were counted. The crude extract did not prove to be promutagenic. The ethanol extract of the broccoli flower head at 46 mg/plate suppressed the mutagenic effect induced by the corresponding positive mutagens on all the three tester strains used in this study. The crude extract of broccoli flower head alone was not cytotoxic even at the maximum concentration tested (46 mg/plate). In conclusion, the ethanol extract of broccoli at 46 mg/plate suggests their diverse antimutagenic potential against the mutagenic chemicals employed in this study. Copyright © 2007 John Wiley & Sons, Ltd.
Antibacterial activity of ergosterol peroxide against Mycobacterium tuberculosis: dependence upon system and medium employed
Authors: Duarte Noélia , Ferreira Maria‐José U. , Martins Marta , Viveiros Miguel , Amaral Leonard 
Published: March 2007

AbstractErgosterol peroxide, cycloart‐23‐en‐3β,25‐diol, vanillin and 4‐hydroxybenzaldehyde have been isolated and characterized from a crude methanol extract of Euphorbia lagascae. Previous studies have shown contradictory results about the antibacterial activity of ergosterol peroxide against Mycobacterium tuberculosis. In order to clarify this question, the activity of this compound was tested against Mycobacterium tuberculosis H37Rv ATCC 27294 strain using two different systems: BACTEC 460TB (Bactec 460) and BACTEC MGIT 960 system (Bactec 960). The results obtained show that significant activity was demonstrable only with the Bactec 460 system. The lack of activity noted with the Bactec 960 system appears to be due to the much faster growth rate of the organism in the medium of this system as opposed to that of the Bactec 460 system. Ergosterol peroxide is also shown by the current study to be devoid of any activity against an antibiotic sensitive ATCC strain of Staphylococcus aureus. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of a diterpenoid from Salvia cinnabarina on arterial blood pressure in rats
Authors: Alfieri Alessio , Maione Francesco , Bisio Angela , Romussi Giovanni , Mascolo Nicola , Cicala Carla 
Published: March 2007

AbstractThe effect of a diterpenoid isolated from Salvia cinnabarina, 3,4‐seicosopimar‐4(18),7,15‐triene‐3‐oic acid (SCB), on arterial blood pressure was evaluated in anaesthetized rats. Male Wistar rats, anaesthetized with urethane (sol. 10% p/v; 10 mL/kg), underwent surgery for continuous monitoring of arterial blood pressure. After preliminary experiments to evaluate the dose response (3, 10 and 30 mg/kg i.v.) of SCB, a dose of 3 mg/kg was chosen for all successive experiments. On different groups of rats treated with the ganglion‐blocking agent chlorisondamine (2.5 mg/kg i.p.) the effect of SCB (3 mg/kg i.v.) was evaluated before and following an infusion of the nitric oxide synthase inhibitor l‐NAME (0.3 mg/kg/min i.v.). Intravenous administration of SCB at doses of 3, 10 and 30 mg/kg led to a fall in mean arterial blood pressure (MABP) of 14.75 ± 1.44 mmHg, 36.60 ± 31.40 mmHg and 31.40 ± 6.28 mmHg, respectively (n = 4–5), that was not modified by treatment of the rat with chlorisondamine nor with l‐NAME. The results demonstrate a hypotensive effect of SCB – due to a peripheral mechanism but independent of endothelial nitric oxide release. Copyright © 2007 John Wiley & Sons, Ltd.
In Vitro cytotoxicity of some medicinal plants from Georgian Amaryllidaceae
Authors: Jokhadze Malkhaz , Eristavi Lina , Kutchukhidze Jumber , Chariot Alain , Angenot Luc , Tits Monique , Jansen Olivia , Frédérich Michel 
Published: March 2007

AbstractUsing an ethnomedical data approach, some Georgian plants, which are used in Georgian traditional medicine for cancer or non‐cancer diseases, were collected and evaluated for cytotoxic activity. The cytotoxic effect of the methanol extracts of species from the genera Galanthus and Leucojum was evaluated in vitro on three human cell lines (Hela, ephitheloid cervix carcinoma; HCT‐116, colon carcinoma; HL‐60, acute myeloid leukaemia). Cell type cytotoxic specificity was observed for some extracts. Overall, the HCT‐116 cells were much more sensitive to most of the extracts than were the other cell lines. Plants that showed pronounced cytotoxic activity will be further evaluated for the possible isolation of active antitumour compounds. Copyright © 2007 John Wiley & Sons, Ltd.
Robust H∞ control for a class of nonlinear stochastic systems with mixed time delay
Authors: Liu Yurong , Wang Zidong , Liu Xiaohui 
Published: March 2007

AbstractThis paper is concerned with the problem of robust H∞ control for a class of uncertain nonlinear Itô‐type stochastic systems with mixed time delays. The parameter uncertainties are assumed to be norm bounded, the mixed time delays comprise both the discrete and distributed delays, and the sector nonlinearities appear in both the system states and delayed states. The problem addressed is the design of a linear state feedback controller such that, in the simultaneous presence of parameter uncertainties, system nonlinearities and mixed time delays, the resulting closed‐loop system is asymptotically stable in the mean square and also achieves a prescribed H∞ disturbance rejection attenuation level. By using the Lyapunov stability theory and the Itô differential rule, some new techniques are developed to derive the sufficient conditions guaranteeing the existence of the desired feedback controllers. A unified linear matrix inequality is proposed to deal with the problem under consideration and a numerical example is exploited to show the usefulness of the results obtained. Copyright © 2007 John Wiley & Sons, Ltd.
Interval estimation for individual categories in cumulative logit models
Authors: Rajeswaran Jeevanantham , Blackstone Eugene H. 
Published: March 2007

AbstractWe derive and compute confidence intervals for probabilities of categories for ordinal responses in cumulative logit link models using frequentist, Bayesian, and bootstrap approaches. The three approaches are evaluated by their coverage probabilities and are illustrated for longitudinal assessment of graded heart valve prosthesis regurgitation following aortic valve replacement. Copyright © 2007 John Wiley & Sons, Ltd.