bluuebunny/crossref_metadata_2025_split huggingface dataset:
First‐pass dynamic contrast‐enhanced MRI with extravasating contrast reagent: evidence for human myocardial capillary recruitment in adenosine‐induced hyperemia
Authors: Li Xin , Springer Charles S. , Jerosch‐Herold Michael 
Published: August 2008

AbstractHuman myocardial 1H2O T1‐weighted dynamic contrast‐enhanced MRI data were acquired during the brief first‐pass period after injection of a very small gadolinium diethylenetriaminepenta‐acetate (GdDTPA2−) dose. The shutter‐speed pharmacokinetic effects of both transendothelial and transcytolemmal equilibrium water exchange processes were investigated. Our results indicate that even for such a short acquisition window and relatively large pseudo‐first‐order rate constant (Ktrans) for plasma/interstitium contrast reagent (CR) transfer the kinetics of these water exchange processes cannot be treated as infinitely fast or slow. However, neither the intracellular water molecule lifetime (τi) nor its intravascular counterpart (τb) are among the parameters most influential in analysis of the noisy data typically associated with the cardiac perfusion application. Thus, the actual values of water exchange kinetic rate constants are relatively indeterminate as this experiment is usually conducted. Combining the Ktrans evaluations with independently determined flow (F) values allows us to estimate CR permeability coefficient surface area product (PCRS) values. The fact that the PCRS magnitudes almost equal the Ktrans values confirms that GdDTPA2− extravasation in resting human myocardial muscle is indeed permeation‐limited and supports the validity of the Ktrans and PCRS estimations. Nevertheless the model analysis is most consistent with the results if PCRS is not assumed to be constant with changing flow. The capillary blood volume fraction (vb) is a sensitive parameter in the analysis. We also compared resting and hyperemic cardiac conditions, the latter resulting from the volume flow increase induced by adenosine arteriolar vasodilation. We found that the PCRS value increases with flow probably mostly because of an S increase associated with capillary recruitment. The vb values also increased in hyperemia and showed a flow‐dependence with a clearly identifiable component due to capillary recruitment. Copyright © 2008 John Wiley & Sons, Ltd.
Effective condition number of Trefftz methods for biharmonic equations with crack singularities
Authors: Li Zi‐Cai , Lu Tzon‐Tzer , Wei Yimin 
Published: August 2008

AbstractThe paper presents the new stability analysis for the collocation Trefftz method (CTM) for biharmonic equations, based on the new effective condition number Cond_eff. The Trefftz method is a special spectral method with the particular solutions as admissible functions, and it has been widely used in engineering. Three crack models in Li et al. (Eng. Anal. Boundary Elements 2004; 28:79–96; Trefftz and Collocation Methods. WIT Publishers: Southampton, Boston, 2008) are considered, and the bounds of Cond_eff and the traditional condition number Cond are derived, to give the polynomial and the exponential growth rates, respectively. The stability analysis explains well the numerical experiments. Hence, the new Cond_eff is more advantageous than Cond. Besides since the bounds of Cond_eff and Cond involve the estimation of the minimal singular value σmin of the discrete matrix F, and since the estimation of σmin is challenging and difficult, the proof for lower bounds of σmin in this paper is important and intriguing. Copyright © 2008 John Wiley & Sons, Ltd.
Two classes of multisecant methods for nonlinear acceleration
Authors: Fang Haw‐ren , Saad Yousef 
Published: August 2008

AbstractMany applications in science and engineering lead to models that require solving large‐scale fixed point problems, or equivalently, systems of nonlinear equations. Several successful techniques for handling such problems are based on quasi‐Newton methods that implicitly update the approximate Jacobian or inverse Jacobian to satisfy a certain secant condition.We present two classes of multisecant methods which allow to take into account a variable number of secant equations at each iteration. The first is the Broyden‐like class, of which Broyden's family is a subclass, and Anderson mixing is a particular member. The second class is that of the nonlinear Eirola–Nevanlinna‐type methods.This work was motivated by a problem in electronic structure calculations, whereby a fixed point iteration, known as the self‐consistent field (SCF) iteration, is accelerated by various strategies termed ‘mixing’. Copyright © 2008 John Wiley & Sons, Ltd.
On parallel multisplitting methods for symmetric positive semidefinite linear systems
Authors: Cao Guangxi , Song Yongzhong 
Published: August 2008

AbstractIn this paper we propose some parallel multisplitting methods for solving consistent symmetric positive semidefinite linear systems, based on modified diagonally compensated reduction. The semiconvergence of the parallel multisplitting method is discussed. The results here generalize some known results for the nonsingular linear systems to the singular systems. Copyright © 2008 John Wiley & Sons, Ltd.
Modeling shear bands in J2 plasticity using a two‐scale formulation via embedded strong discontinuity modes
Authors: D'hers Sebastián , Dvorkin Eduardo N. 
Published: August 2008

AbstractA new two‐scale finite element formulation was developed for modeling J2 plastic deformation processes (2D) in which shear band localizations take place. The formulation is based on the use of embedded strong discontinuity modes, which are triggered using a stress‐based criterion. The new formulation does not require a specific mesh refinement to model the localization phenomena and provides mesh‐independent results. The shear bands constitutive behavior is derived from the continuum properties without the introduction of any ad hoc physical law. Copyright © 2008 John Wiley & Sons, Ltd.
Pointwise supercloseness of tensor‐product block finite elements
Authors: Liu Jinghong , Zhu Qiding 
Published: August 2008

AbstractIn this article, we first introduce interpolation operator of projection type in three dimensions, from which we then derive weak estimates for tensor‐product block finite elements of degree m ≥ 1. Finally, using estimates for the discrete Green's function and the discrete derivative Green's function, we prove that both of the gradient and the function value of the finite element solution uh and the corresponding interpolant Πmu of projection type and degree m are superclose in the pointwise sense of the L∞‐norm. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Preparation and properties of natural rubber composites reinforced with pretreated carbon nanotubes
Authors: Sui G. , Zhong W. H. , Yang X. P. , Yu Y. H. , Zhao S. H. 
Published: August 2008

AbstractIn order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)‐reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcanization characteristics, and physical and mechanical properties of the CNT/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR composite. Through the addition of the CNTs treated using acid bath followed by ball milling with HRH (hydrated silica, resorcinol, and hexamethylene tetramine) bonding systems, the crystallization melting peak in differential scanning calorimetry (DSC) curves of NR weakened and the curing rate of NR slightly decreased. Meanwhile, the over‐curing reversion of CNT/NR nanocomposites was alleviated. The dispersion of the treated CNTs in the rubber matrix and interfacial bonding between them were rather good. The mechanical properties of the CNT‐reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR composite. At the same time, the CNT/NR nanocomposites exhibited better rebound resilience and dynamic compression properties. The storage modulus of the CNT/NR nanocomposites greatly exceeds that of neat NR and CB/NR composites under all temperature regions. The thermal stability of NR was also obviously improved with the addition of the treated CNTs. Copyright © 2008 John Wiley & Sons, Ltd.
Pt/SiO2 as addition to multilayer SPSU/PTFE composite membrane for fuel cells
Authors: Wang L. , Yi B. L. , Zhang H. M. , Xing D. M. 
Published: August 2008

AbstractA multilayer composite membrane was prepared by reinforcing sulfonated polysulfone (SPSU) with porous polytetrafluoroethylene (PTFE), and adding Pt/SiO2–Nafion® membranes on both sides of the SPSU/PTFE membrane to self‐humidify and protect the inside membrane. The ex situ Fenton test and open circuit voltage (OCV) accelerated test show that the composite membrane has better stability than the initial membrane because of the protection of the outside Pt/SiO2–Nafion layers. The composite membrane has similar performance to that of NRE‐212 under the fully humidified condition and better performance than NRE‐212 without humidifying. The self‐humidifying membrane shows great potential for use in low humidifying conditions. Copyright © 2008 John Wiley & Sons, Ltd.
Lipase‐catalyzed polymerization of L‐lactide in ionic liquids
Authors: Yoshizawa‐Fujita Masahiro , Saito Chihiro , Takeoka Yuko , Rikukawa Masahiro 
Published: August 2008

AbstractLipase‐catalyzed polymerizations of L‐lactide were carried out in four kinds of ionic liquids (ILs) in order to investigate the effect of ILs on the conversion, molecular weight, and yield of the obtained poly(lactide) (PLLA). PLLA could be synthesized in ILs of 1‐butyl‐3‐methylimidazolium ([C4mim]) except in [C4mim][N(CN)2]. While the number‐average molecular weight (Mn) of the PLLA obtained in [C4mim][PF6] was below 4000 g mol−1 and the yield was below 10%, the Mn and yield of the PLLA obtained in [C4mim][BF4] reached 55000 g mol−1 and 35%, respectively. The Mn values of PLLAs in the ILs were clearly higher than those of PLLAs obtained in bulk and in toluene (<44000 g mol−1). The polymerization in the ILs proceeds even at lower temperatures as compared with that in bulk. The effect of lipase content on the Mn of PLLA was also investigated. When [C4mim][BF4] was used as the solvent, the highest Mn was obtained at a lipase content of 10 wt%. In the case of [C4mim][NTf2], the most suitable lipase content depended on the polymerization temperature. [C4mim][BF4] was suitable to obtain higher molecular weight PLLA and higher polymer yield at lower lipase contents. Copyright © 2008 John Wiley & Sons, Ltd.
Overexpression of TFAP2C in invasive breast cancer correlates with a poorer response to anti‐hormone therapy and reduced patient survival
Authors: Gee JMW , Eloranta JJ , Ibbitt JC , Robertson JFR , Ellis IO , Williams T , Nicholson RI , Hurst HC 
Published: August 2008

AbstractThe AP‐2γ transcription factor encoded by the TFAP2C gene is a member of a family of homologous DNA binding proteins that play essential roles during vertebrate embryogenesis but show a restricted pattern of expression in the adult. Elevated expression of the AP‐2α and AP‐2γ family members has been associated with a number of neoplasms, particularly breast cancer. Here we present an exploratory immunohistochemical study of an archival primary breast tumour series (n = 75) with parallel clinicopathological data using a new, well‐characterized antibody to AP‐2γ. Heterogeneous, exclusively nuclear expression of AP‐2γ was found in the epithelial and myoepithelial compartments of normal breast and within tumour epithelial cells. In the breast cancer series, the most notable association was a correlation between elevated levels of AP‐2γ and shortened patient survival (p = 0.0009*). This relationship was also conserved in ER‐positive and ErbB2‐negative patients; sub‐groups generally considered to have a relatively good prognosis. When patient data for survival and duration of treatment response on anti‐hormone therapy were examined by multivariate analysis, AP‐2γ was revealed in this study to be an independent predictor of outcome for both survival (p = 0.005) and response to anti‐hormone therapy (p = 0.046). Studies using in vitro models confirmed that while tamoxifen response is associated with lower levels of AP‐2γ, acquisition of resistance to this and other anti‐hormone measures (eg faslodex or oestrogen deprivation) is associated with high levels of nuclear AP‐2γ. Together these data suggest that elevated tumour AP‐2γ expression can contribute to the failure of cells to growth arrest following anti‐hormone treatment and lead to sustained growth and poorer patient outcome. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Role of Necl‐5 in the pathophysiology of colorectal lesions induced by dimethylhydrazine and/or dextran sodium sulphate
Authors: Abe A , Fukui H , Fujii S , Kono T , Mukawa K , Yoshitake N , Sekikawa A , Ichikawa K , Tomita S , Yamagishi H , Imai Y , Shinoda M , Ishizaki H , Tanaka‐Okamoto M , Kubota K , Miyoshi J , Takai Y , Fujimori T 
Published: August 2008

AbstractNecl‐5 is an immunoglobulin‐like molecule that was originally identified as a poliovirus receptor. Although Necl‐5 expression is often up‐regulated in cancer cells, its pathophysiological significance in the development of cancer remains unclear. We investigated the roles of Necl‐5 in the development of colitis‐associated neoplasia. Necl‐5‐deficient mice were generated and treated with dimethylhydrazine (DMH) and/or dextran sodium sulphate (DSS) to induce colitis and its associated neoplasias. Colon tissues were examined for histology, Ki‐67 expression by immunohistochemistry and K‐ras gene mutation. Colon tumours occurred significantly less frequently in heterozygous (Necl‐5+/−) or homozygous Necl‐5‐deficient (Necl‐5−/−) mice than in wild‐type (WT) mice with DMH/DSS treatment. Total ulcer index and inflammatory cell infiltration were significantly lower in Necl‐5−/− mice than in WT mice with DSS alone or DMH/DSS treatment. Colon tumours in both WT and Necl‐5−/− mice showed high cell proliferation ability but lacked K‐ras mutation. The total Ki‐67 labelling index in non‐neoplastic colon epithelium was significantly higher in WT (45.9 ± 0.94) than in Necl‐5+/− (34.3 ± 1.40) or Necl‐5−/− (27.7 ± 1.15) mice with DMH/DSS treatment (p < 0.001). Necl‐5 plays a role in the development of colitis‐associated cancer by up‐regulating colonic mucosal cell proliferation. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
SAHA induces caspase‐independent, autophagic cell death of endometrial stromal sarcoma cells by influencing the mTOR pathway
Authors: Hrzenjak A , Kremser M‐L , Strohmeier B , Moinfar F , Zatloukal K , Denk H 
Published: August 2008

AbstractEndometrial stromal sarcomas are rare and molecular mechanisms involved in their pathogenesis are poorly understood. Covalent modifications of histone proteins, in particular de/acetylation of lysine residues, play an important role in the regulation of gene transcription in normal and neoplastic cells, but there are only limited data about these processes in solid mesenchymal tumours. We treated endometrial stromal sarcoma cells (ESS‐1) and non‐malignant human endometrial stromal cells (HESCs) with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor. SAHA was able to mediate the cell cycle and expression of genes related to the malignant phenotype of endometrial stromal tumours, eg p21WAF1 and HDAC7. SAHA led to dose‐dependent differentiation and death of ESS‐1 cells but not of HESCs. Exposure of HESCs to SAHA resulted only in slightly decreased cell proliferation. SAHA also increased the p21WAF1 expression and caused significant changes in the cell cycle by inhibiting the G1/S transition in ESS‐1 cells. Recovery experiments indicated that these changes became irreversible when the tumour cells were treated with SAHA for longer than 24 h. In our experimental system, not apoptotic but autophagic processes were responsible for the cell death. Monodansyl cadaverine accumulation in treated ESS‐1 cells and decreased expression of the mTOR and phospho‐S6 ribosomal protein (S6rp) additionally supported this observation. Taken together, our study indicates that HDACs might be considered as potential drug targets in the therapy of stromal sarcomas and that SAHA might be a promising therapeutic agent for endometrial stromal sarcoma. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Insulin‐like growth factor‐1 receptor acts as a growth regulator in synovial sarcoma
Authors: Friedrichs N , Küchler J , Endl E , Koch A , Czerwitzki J , Wurst P , Metzger D , Schulte JH , Holst MI , Heukamp LC , Larsson O , Tanaka S , Kawai A , Wardelmann E , Buettner R , Pietsch T , Hartmann W 
Published: August 2008

AbstractSynovial sarcomas account for 5–10% of all soft tissue sarcomas and the majority of synovial sarcomas display characteristic t(X;18) translocations that result in enhanced transcription of the insulin‐like growth factor‐2 (IGF‐2) gene. IGF‐2 is an essential fetal mitogen involved in the pathogenesis of different tumours, leading to cellular proliferation and inhibition of apoptosis. Here we asked whether activation of IGF signalling is of functional importance in synovial sarcomas. We screened human synovial sarcomas for expression of IGF‐2 and the phosphorylated IGF‐1 receptor (IGF‐1R), which mainly mediates the proliferative and anti‐apoptotic effects of IGF‐2. Since both the phosphatidylinositol 3′‐kinase (PI3K)–AKT pathway and the MAPK signalling cascade are known to be involved in the transmission of IGF‐1R signals, expression of phosphorylated (p)‐AKT and p‐p44/42 MAPK was additionally assessed. All tumours expressed IGF‐2 and 78% showed an activated IGF‐1R. All tumours were found to express p‐AKT and 92% showed expression of activated p44/42 MAPK. To analyse the functional and potential therapeutic relevance of IGF‐1R signalling, synovial sarcoma cell lines were treated with the IGF‐1R inhibitor NVP‐AEW541. Growth was impaired by the IGF‐1R antagonist, which was consistently accompanied by a dose‐dependent reduction of phosphorylation of AKT and p44/42 MAPK. Functionally, inhibition of the receptor led to increased apoptosis and diminished mitotic activity. Concurrent exposure of selected cells to NVP‐AEW541 and conventional chemotherapeutic agents resulted in positive interactions. Finally, synovial sarcoma cell migration was found to be dependent on signals transmitted by the IGF‐1R. In summary, our data show that the IGF‐1R might represent a promising therapeutic target in synovial sarcomas. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Number‐average molecular weight of branched polymers from SEC with viscosity detection and universal calibration
Authors: Netopilík Miloš , Podešva Jiří , Lokaj Jan , Kratochvíl Pavel 
Published: August 2008

AbstractBACKGROUND: Number‐average molecular weight, M̄n, is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size‐exclusion chromatography (SEC) using on‐line viscometric detection and assuming the validity of the universal calibration concept.RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on‐line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M̄n and weight‐average molecular weight, M̄w. Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules.CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η]M, on elution volume, can differ in values of [η]M from those obtained for narrow molecular weight standards by 10–15%. The method studied is helpful for the determination of M̄n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers. Copyright © 2008 Society of Chemical Industry
Synthesis and characterization of fast responsive thermo‐ and pH‐sensitive poly[(N,N‐diethylacrylamide)‐co‐(acrylic acid)] hydrogels
Authors: Liu Hongliang , Liu Mingzhu , Jin Shuping , Chen Shilan 
Published: August 2008

AbstractBACKGROUND: A considerable amount of research has been focused on smart hydrogels that can respond to external environmental stimuli, especially temperature and pH. In this study, fast responsive thermo‐ and pH‐sensitive poly[(N,N‐diethylacrylamide)‐co‐(acrylic acid)] hydrogels were prepared by free radical copolymerization in aqueous solution using poly(ethylene glycol) (PEG) as a pore‐forming agent.RESULTS: Swelling studies showed that the hydrogels produced had both temperature and pH sensitivity. The deswelling kinetics at high temperature demonstrated that the shrinking rates were influenced by the addition of the pore‐forming agent and the amount of acrylic acid in the initial total monomers. The deswelling curves in low‐buffer solutions had two stages. Pulsatile swelling studies indicated that the PEG‐modified hydrogels were superior to the normal ones. These different swelling properties were further confirmed by the results of scanning electron microscopy.CONCLUSION: Such fast responsive thermo‐ and pH‐sensitive hydrogels are expected to be useful in biomedical fields for stimuli‐responsive drug delivery systems. Copyright © 2008 Society of Chemical Industry
Computational (MP2 and DFT) modeling of the substrate/inhibitor interaction with the LDH active pocket in the gas phase and aqueous solution: bimolecular charged (pyruvate/oxamate–guanidinium cation) and neutral adducts (pyruvic/oxamic acids–guanidine)
Authors: Raczyńska Ewa D. , Makowski Mariusz , Hallmann Magorzata , Duczmal Kinga 
Published: August 2008

AbstractTwo types of bimolecular adducts were studied for the substrate and inhibitor of lactate dehydrogenase (LDH), one type of adducts between ionic species,α‐keto‐carboxylates (pyruvate and oxamate) and the guanidinium cation, and the other type of adducts between neutral species,α‐ketocarboxylic (pyruvic and oxamic) acids and guanidine. Calculations were performed in the gas phase and aqueous solution using the MP2 and PCM methods and the 6‐31++G** basis set. Application of the DFT(B3LYP) and PCM methods led to similar results. A change of the adducts' preference was observed when proceeding from the gas phase to aqueous solution. This change is in good agreement with the acidity–basicity scales in both phases. Formation constant (KHB) for adduct between neutral species is greater for pyruvic than for oxamic acid in the gas phase, whereas a reverse situation takes place in aqueous solution, where theKHBvalue for adduct between ionic species is smaller for pyruvate than for oxamate. The water molecules favor interactions of more polar oxamate with the guanidinium cation. Stronger interaction with this cation, a model of the arginine fragment of the LDH pocket, suggests that oxamate (inhibitor of LDH) has stronger binding properties in aqueous solution than pyruvate (substrate of LDH). Copyright © 2008 John Wiley & Sons, Ltd.