bluuebunny/crossref_metadata_2025_split huggingface dataset:
Confocal imaging of biofilm formation process using fluoroprobed Escherichia coli and fluoro‐stained exopolysaccharide
Authors: Maeyama Ryo , Mizunoe Yoshimitsu , Anderson James M. , Tanaka Masao , Matsuda Takehisa 
Published: June 2004

AbstractWe developed a novel method of evaluating biofilm architecture on a synthetic material using green fluorescent protein‐expressing Escherichia coli and red fluorescence staining of exopolysaccharides. Confocal laser scanning microscopy observation revealed the time course of the change in the in situ three‐dimensional structural features of biofilm on a polyurethane film without structural destruction: initially adhered cells are grown to form cellular aggregates and secrete exopolysaccharides. These cells were spottily distributed on the surface at an early incubation time but fused to form a vertically grown biofilm with incubation time. Fluorescence intensity, which is a measure of the number of cells, determined using a fluorometer and biofilm thickness determined from confocal laser scanning microscopy vertical images were found to be effective for quantification of time‐dependent growth of biofilms. The curli (surface‐located fibers specifically binding to fibronectin and laminin)–producing Escherichia coli strain, YMel, significantly proliferated on fibronectin‐coated polyurethane, whereas the curli‐deficient isogenic mutant, YMel‐1, did not. The understanding of biofilm architecture in molecular and morphological events and new fluorescence microscopic techniques may help in the logical surface design of biomaterials with a high antibacterial potential. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 274–282, 2004
Hyaluronic acid grafting mitigates calcification of glutaraldehyde‐fixed bovine pericardium
Authors: Ohri Rachit , Hahn Sei K. , Hoffman Allan S. , Stayton Patrick S. , Giachelli Cecilia M. 
Published: June 2004

AbstractPathologic calcification is the leading cause of the clinical failure of glutaraldehyde‐fixed bovine pericardium used in bioprosthetic valves. A novel surface modification of glutaraldehyde fixed bovine pericardium was carried out with high molecular weight hyaluronic acid (HA). HA was chemically modified with adipic dihydrazide (ADH) to introduce hydrazide functional groups onto the HA backbone. Glutaraldehyde‐fixed bovine pericardium (GFBP) was modified by grafting this HA to the free aldehyde groups on the tissue via the hydrazide groups. Following a 2‐week subcutaneous implantation in osteopontin (OPN)‐null mice, the calcification of HA‐modified bovine pericardium was drastically reduced (by 84.5%) compared to positive controls (tissue without HA‐modification) (p = 0.005). The calcification‐mitigating effect of HA surface modification was also confirmed by microscopic analysis of explanted tissue stained with Alizarin Red S for calcium. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 328–334, 2004
Redox regulation of glial inflammatory response to lipopolysaccharide and interferonγ
Authors: Pawate Siddharama , Shen Qin , Fan Fan , Bhat Narayan R. 
Published: June 2004

AbstractAstrocytes and microglia, the two immune‐regulatory cells of the central nervous system (CNS), are activated by a variety of pathogens and cytokines to elicit rapid transcriptional responses. This program of activation is initiated by a set of intracellular signaling cascades that includes mitogen‐activated protein kinase (MAPK), nuclear factor (NF) κB, and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways. This study defines the critical role that NADPH oxidase(Phox)‐derived reactive oxygen species (ROS) play in lipopolysaccharide (LPS)‐ and interferon (IFN)γ‐induced signaling cascades leading to gene expression in glial cells. Treatment of rat microglia and astrocytes with LPS and IFNγ resulted in a rapid activation of Phox and the release of ROS followed by an induction of inducible nitric oxide synthase (iNOS) expression. iNOS induction was blocked by inhibitors of Phox, i.e., diphenylene iodonium chloride (DPI) and 4‐(2‐aminoethyl) benzenesulfonylfluoride (AEBSF), suggesting an involvement of ROS signaling in iNOS gene expression. Exogenous catalase but not superoxide dismutase suppressed the basal activity and completely blocked induced levels of NO/iNOS, suggesting that hydrogen peroxide is the ROS involved. Phox inhibitors and catalase also suppressed LPS/IFNγ‐induced expression of cytokines, i.e., interleukin (IL)‐1, IL‐6, and tumor necrosis factor (TNF)α and blocked LPS activation of MAP kinases (i.e., p38 MAPK, c‐Jun N‐terminal kinase and extracellular signal‐regulated kinase), NFκB, and IFNγ‐induced STAT1 phosphorylation. A microglial cell line stably transfected with a mutant form of Phox subunit, i.e., p47phox W(193)R, and primary astrocytes derived from Phox‐deficient mice showed attenuated ROS production and induction of iNOS in response to LPS/IFNγ, further strengthening the notion that Phox‐derived ROS are crucial for proinflammatory gene expression in glial cells. © 2004 Wiley‐Liss, Inc.
The impact of winter ice retreat on Antarctic winter sea‐ice extent and links to the atmospheric meridional circulation
Authors: Harangozo S. A. 
Published: June 2004

Abstract15 years of weekly Antarctic ice extent and 10 m winds from numerical meteorological reanalyses have been used to test the hypothesis that the Antarctic final winter ice extent (FWE) is brought about by ice retreats as much as by advances, and that both are strongly affected by the meridional (north–south) component of the atmospheric circulation. This hypothesis is found to be correct and it is shown that extensive FWE fails to occur when total winter retreat is anomalously large. This is the case even in the coldest Antarctic regions. Retreats reduce the time available for advance, notably when they are substantial, with the ice cover taking up to several weeks to recover. Systematic changes in the meridional winds between retreats and advance are also detected in all regions; retreats are consistently associated with northerly winds supporting ice compaction and ice drift. The results agree with Antarctic case studies.Close similarities are found between several Antarctic and sub‐Arctic regions in terms of the prevalence of retreat in some winters, its impact on the FWE and its relationship to the meridional atmospheric circulation. The study also reveals a more complex picture of the atmospheric circulation during sub‐monthly ice retreats and advances. In particular, retreats in some Pacific regions are, on average, associated with anomalous anticyclonic circulations. This helps to explain why evidence of strong cyclone–ice extent relationships has not been found previously. A meteorological explanation is also sought for total retreat in winter being small in a winter of limited ice extent in the Bellingshausen Sea despite this being the mildest Antarctic region. In such cases, limited winter ice extent is attended by reduced advance caused by ice compaction due to northerly winds and waves and also anomalously high air temperatures. Reduced advance then limits opportunities for retreat to take place compared with winters with more advance and sea ice reaching lower latitudes. Overall, the results point to sub‐monthly ice–atmospheric circulation interactions largely determining the winter ice extent throughout much of the Antarctic. Copyright © 2004 Royal Meteorological Society
North Atlantic oscillation influence on precipitation, river flow and water resources in the Iberian Peninsula
Authors: Trigo Ricardo M. , Pozo‐Vázquez David , Osborn Timothy J. , Castro‐Díez Yolanda , Gámiz‐Fortis Sonia , Esteban‐Parra María Jesus 
Published: June 2004

AbstractThe Iberian Peninsula precipitation and river flow regimes are characterized by large values of inter‐annual variability, with large disparities between wet and dry years, especially in southern Iberia. This situation is a major problem for water resources management in general, and for the production of hydroelectricity in particular. Hydroelectric production represents, in an average year of precipitation, 20% of the total Spanish electricity production (and 35% for Portuguese production). Its absolute value, however, can vary by a factor of three between wet and dry years. We have assessed the impact of the North Atlantic oscillation (NAO) on winter precipitation and river flow regimes for the three main international Iberian river basins, namely the Douro (north), the Tejo (centre) and the Guadiana (south). Results show that the large inter‐annual variability in the flows of these three rivers is largely modulated by the NAO phenomenon. Throughout most of the 20th century, the January‐to‐March river flow is better correlated with the December to February (DJF) NAO index than is the simultaneous (DJF) river flow. Correlation values for the period 1973–98 are highly significant (−0.76 for Douro, −0.77 for Tejo and −0.79 for Guadiana), being consistently of higher magnitude than those obtained over previous decades. This impact of the NAO on winter river flow was quantified in terms of total Spanish potential hydroelectricity production. The important control exerted by the NAO and the recent positive trend in the NAO index contribute to a significant decrease in the available flow. This reduction represents an important hazard for the two Iberian economies because of its negative impact on water‐dependent resources, such as intensive agriculture and hydroelectric power production. Copyright © 2004 Royal Meteorological Society
Climate signature of solar irradiance variations: analysis of long‐term instrumental, historical, and proxy data
Authors: Lohmann Gerrit , Rimbu Norel , Dima Mihai 
Published: June 2004

AbstractThe signature of solar irradiance variations on decadal‐to‐centennial climate variability is analysed by means of statistical analysis of long‐term instrumental, historical, and proxy data sets. Solar variations associated with the Schwabe, Hale, and Gleissberg cycles are detected by their spatial patterns in sea‐surface temperature and sea‐level pressure. Different statistical methods for instrumental and proxy data show that the mode related to solar irradiance fluctuations on multi‐decadal time scales (Gleissberg cycle) is distinct from the Atlantic multi‐decadal mode associated with ocean circulation changes. From this, one can infer the degree to which solar variability has contributed to long‐term temperature variations during the instrumental and pre‐instrumental era. Copyright © 2004 Royal Meteorological Society
Energy transfer effects during the multichannel decomposition of ethanol
Authors: Tsang Wing 
Published: June 2004

AbstractRate constants and expressions for the initial processes in the decomposition of ethanol have been derived on the basis of existing experimental and estimated results. Energy transfer effects on the multichannel decomposition processes have been determined through the solution of the master equation and on the basis of exponential‐down and step‐ladder collisional transition models. The predominant (lower threshold) channel is unaffected by the presence of the upper channels and results for the two transition models can be brought into correspondence by using a somewhat higher value for the step‐size down parameter in the step‐ladder model. For the upper channels and with an exponential‐down model, the logarithms of the ratio of the rate constants between perturbed and unperturbed systems can be captured by a sigmoidal shaped curve. In the case of the step‐ladder model, the logarithms of this ratio decreases monotonically. Initially, differences between the two models are small (after adjusting the step‐size down parameter). The results are compared with the recent simulations of Marinov. The order of magnitude differences in rate constants have been traced to the inclusion in the present study of experimental results pertaining to decomposition and the reverse combination processes in addition to the proper treatment of energy transfer effects during multichannel decompositions. Some observations regarding the parameterization of this type of pressure dependent data for use in simulations are presented. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:456–465, 2004.
Unusual kinetic role of a water‐soluble iron(III) porphyrin catalyst in the oxidation of 2,4,6‐trichlorophenol by hydrogen peroxide
Authors: Lente Gábor , Espenson James H. 
Published: June 2004

AbstractThe oxidation of 2,4,6‐trichlorophenol (TCP) to 2,6‐dichloro‐1,4‐benzoquinone (DCQ) by hydrogen peroxide using iron(III) meso‐tetra(4‐sulfonatophenyl) porphine chloride, Fe(TPPS)Cl, as a catalyst was studied with stopped‐flow UV–vis spectrophotometry and potentiometry using a chloride ion selective electrode. The observations are interpreted by a three‐step kinetic model: the initial reaction of the catalyst with the oxidant (Fe(TPPS)+ + H2O2 → Cat′) produces an active intermediate, which oxidizes the substrate (Cat′ + TCP → Fe(TPPS)+ + DCQ + Cl−) in the second step. The third step is the transformation of the catalyst into a much less active form (Cat′ → Cat″) and is responsible for the unusual kinetic phenomena observed in the system. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:449–455, 2004.
Non‐local damage model with evolving internal length
Authors: Pijaudier‐Cabot Gilles , Haidar Khalil , Dubé Jean‐François 
Published: June 2004

AbstractA modified non‐local damage model with evolving internal length, inspired from micromechanics, is developed. It is shown in particular that the non‐local influence between two points in the damaged material depends on the value of damage at each of these points. The resulting weight function is non‐symmetric and truncated. Finite element results and strain localization analysis on a one‐dimensional problem are presented and compared to those of the original non‐local damage model. It is shown that in the course of damage localization, the incremental strain profiles expand according to the modified non‐local model, instead of shrinking according to the original constitutive relation. Comparisons with experimental data on model materials with controlled porosity are also discussed. Acoustic emission analyses provide results with which the theoretical model is consistent qualitatively. This model also opens the path for durability mechanics analyses, where it has been demonstrated that the internal length in the non‐local model should evolve with environmentally induced damage. Copyright © 2004 John Wiley & Sons, Ltd.
Discrete vs smeared crack models for concrete fracture: bridging the gap
Authors: Borst René de , Remmers Joris J. C. , Needleman Alan , Abellan Marie‐Angèle 
Published: June 2004

AbstractDiscrete and smeared crack models for concrete fracture are discussed in a historical perspective. It is argued that these two computational approaches, originally conceived as very different, can be brought together by exploiting the partition‐of‐unity property of finite element shape functions. The cohesive segments method, which exploits this partition‐of‐unity property, exhibits advantages of both the discrete and smeared crack approaches, and is capable of describing the transition from distributed micro‐cracking to a dominant crack. The versatility of the cohesive methodology is shown by incorporating water diffusion and ion transport into the formulation. Copyright © 2004 John Wiley & Sons, Ltd.
A model updating strategy of non‐linear vibrating structures
Authors: Kerschen G. , Golinval J. C. 
Published: June 2004

AbstractThe objective of this paper is to present a model updating strategy of non‐linear vibrating structures. Because modal analysis is no longer helpful in non‐linear structural dynamics, a special attention is devoted to the features extracted from the proper orthogonal decomposition and one of its non‐linear generalizations based on auto‐associative neural networks. The efficiency of the proposed procedure is illustrated using simulated data from a three‐dimensional portal frame. Copyright © 2004 John Wiley & Sons, Ltd.
Gradient method for inverse heat conduction problem in nanoscale
Authors: Kim Sun K. , Daniel Isaac M. 
Published: June 2004

AbstractAn inverse heat conduction problem for nanoscale structures was studied. The conduction phenomenon is modelled using the Boltzmann transport equation. Phonon‐mediated heat conduction in one dimension is considered. One boundary, where temperature observation takes place, is subject to a known boundary condition and the other boundary is exposed to an unknown temperature. The gradient method is employed to solve the described inverse problem. The sensitivity, adjoint and gradient equations are derived. Sample results are presented and discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical analysis of Augmented Lagrangian algorithms in complementary elastoplasticity
Authors: Contrafatto L. , Ventura G. 
Published: June 2004

AbstractThe main subject of the paper is the investigation of Augmented Lagrangian algorithms and update formulas in the solution of elastoplastic problems. A stress rate formulation for elastoplastic models with internal variables and its finite increment form is employed to state the mechanical problem. In this formulation the Augmented Lagrangian is used to enforce the constraint of plastic admissibility directly on the stresses and thermodynamic forces. This is not a limitation of the Augmented Lagrangian approach, and the same framework can be built on more classical displacement formulations as well. The meaning and the derivation of various first and second order Lagrangian multipliers update formulas and iterative schemes is shown. A new diagonal iteration algorithm and the introduction of a scale factor for the Augmented Lagrangian term are proposed. Numerical examples compare the efficiency of several forms of Augmented Lagrangian algorithms and illustrate the influence of the scale factor and of the penalty parameter. Copyright © 2004 John Wiley & Sons, Ltd.
A mesh free approach using radial basis functions and parallel domain decomposition for solving three‐dimensional diffusion equations
Authors: Ingber M. S. , Chen C. S. , Tanski J. A. 
Published: June 2004

AbstractThe analysis of transient heat conduction problems in large, complex computational domains is a problem of interest in many technological applications including electronic cooling, encapsulation using functionally graded composite materials, and cryogenics. In many of these applications, the domains may be multiply connected and contain moving boundaries making it desirable to consider meshless methods of analysis. The method of fundamental solutions along with a parallel domain decomposition method is developed for the solution of three‐dimensional parabolic differential equations. In the current approach, time is discretized using the generalized trapezoidal rule transforming the original parabolic partial differential equation into a sequence of non‐homogeneous modified Helmholtz equations. An approximate particular solution is derived using polyharmonic splines. Interfacial conditions between subdomains are satisfied using a Schwarz Neumann–Neumann iteration scheme. Outside of the first time step where zero initial flux is assumed, the initial estimates for the interfacial flux is given from the converged solution obtained during the previous time step. This significantly reduces the number of iterations required to meet the convergence criterion. The accuracy of the method of fundamental solutions approach is demonstrated through two benchmark problems. The parallel efficiency of the domain decomposition method is evaluated by considering cases with 8, 27, and 64 subdomains. Copyright 2004 © John Wiley & Sons, Ltd.
A geometry projection method for shape optimization
Authors: Norato J. , Haber R. , Tortorelli D. , Bendsøe M. P. 
Published: June 2004

AbstractWe present a new method for shape optimization that uses an analytical description of the varying design geometry as the control in the optimization problem. A straightforward filtering technique projects the design geometry onto a fictitious analysis domain to support simplified response and sensitivity analysis. However, the analytical geometry model is referenced directly for all purely geometric calculations. The method thus combines the advantages of direct geometry representations with the simplified analysis procedures that are possible with fictitious domain analysis methods, such as the material distribution methods commonly used in topology optimization. The projected geometry measure converges to the indicator function of the analytical geometry model in the limit of numerical mesh refinement. Consequently, optimal designs obtained with the new method converge to solutions of well‐defined continuum optimization problems in the limit of mesh refinement. This property is confirmed in example computations for minimum compliance design of an elastic structure subject to a volume constraint and for minimum volume design subject to a maximum stress constraint. Copyright © 2004 John Wiley & Sons, Ltd.
Finite element formulation for modelling large deformations in elasto‐viscoplastic polycrystals
Authors: Matouš Karel , Maniatty Antoinette M. 
Published: June 2004

AbstractAnisotropic, elasto‐viscoplastic behaviour in polycrystalline materials is modelled using a new, updated Lagrangian formulation based on a three‐field form of the Hu‐Washizu variational principle to create a stable finite element method in the context of nearly incompressible behaviour. The meso‐scale is characterized by a representative volume element, which contains grains governed by single crystal behaviour. A new, fully implicit, two‐level, backward Euler integration scheme together with an efficient finite element formulation, including consistent linearization, is presented. The proposed finite element model is capable of predicting non‐homogeneous meso‐fields, which, for example, may impact subsequent recrystallization. Finally, simple deformations involving an aluminium alloy are considered in order to demonstrate the algorithm. Copyright © 2004 John Wiley & Sons, Ltd.
A simple boundary element method for problems of potential in non‐homogeneous media
Authors: Sutradhar Alok , Paulino Glaucio H. 
Published: June 2004

AbstractA simple boundary element method for solving potential problems in non‐homogeneous media is presented. A physical parameter (e.g. heat conductivity, permeability, permittivity, resistivity, magnetic permeability) has a spatial distribution that varies with one or more co‐ordinates. For certain classes of material variations the non‐homogeneous problem can be transformed to known homogeneous problems such as those governed by the Laplace, Helmholtz and modified Helmholtz equations. A three‐dimensional Galerkin boundary element method implementation is presented for these cases. However, the present development is not restricted to Galerkin schemes and can be readily extended to other boundary integral methods such as standard collocation. A few test examples are given to verify the proposed formulation. The paper is supplemented by an Appendix, which presents an ABAQUS user‐subroutine for graded finite elements. The results from the finite element simulations are used for comparison with the present boundary element solutions. Copyright © 2004 John Wiley & Sons, Ltd.