bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of redox and transport processes in a riparian wetland on stream water quality in the Fichtelgebirge region, southern Germany
Authors: Lischeid G. , Kolb A. , Alewell C. , Paul S.
Published: August 2006

Biologically mediated redox processes in the riparian zone, like denitrification, can have substantially beneficial impacts on stream water quality. The extent of these effects, however, depends greatly on the hydrological boundary conditions. The impact of hydrological processes on a wetland's nitrogen sink capacity was investigated in a forested riparian fen which is drained by a first‐order perennial stream. Here, we analysed the frequency distributions and time‐series of pH and nitrogen, silica, organic carbon and oxygen concentrations in throughfall, soil solution, groundwater and stream water, and the groundwater levels and stream discharges from a 3‐year period. During baseflow conditions, the stream was fed by discharging shallow, anoxic groundwater and by deep, oxic groundwater. Whereas the latter delivered considerable amounts of nitrogen (∼0·37 mg l−1) to the stream, the former was almost entirely depleted of nitrogen. During stormflow, near‐surface runoff in the upper 30 cm soil layer bypassed the denitrifying zone and added significant amounts to the nitrogen load of the stream. Nitrate‐nitrogen was close to 100% of deep groundwater and stream‐water nitrogen concentration. Stream‐water baseflow concentrations of nitrate, dissolved carbon and silica were about 1·6 mg l−1, 4 mg l−1 and 7·5 mg l−1 respectively, and >3 mg l−1, >10 mg l−1 and <4 mg l−1 respectively during discharge peaks. In addition to that macroscale bypassing effect, there was evidence for a corresponding microscale effect: Shallow groundwater sampled by soil suction cups indicated complete denitrification and lacked any seasonal signal of solute concentration, which was in contrast to piezometer samples from the same depth. Moreover, mean solute concentration in the piezometer samples resembled more that of suction‐cup samples from shallower depth than that of the same depth. We conclude that the soil solution cups sampled to a large extent the immobile soil‐water fraction. In contrast, the mobile fraction that was sampled by the piezometers exhibited substantially shorter residence time, thus being less exposed to denitrification, but predominating discharge of that layer to the stream. Consequently, assessing the nitrogen budget based on suction‐cup data tended to overestimate the nitrogen consumption in the riparian wetland. These effects are likely to become more important with the increased frequency and intensity of rainstorms that are expected due to climate change. Copyright © 2006 John Wiley & Sons, Ltd.
Hydrodynamics and geomorphic work of jökulhlaups (glacial outburst floods) from Kverkfjöll volcano, Iceland
Authors: Carrivick Jonathan L.
Published: August 2006

Jökulhlaups (glacial outburst floods) occur frequently within most glaciated regions of the world and cause rapid landscape change, infrastructure damage, and human disturbance. The largest jökulhlaups known to have occurred during the Holocene within Iceland drained from the northern margin of Vatnajökull and along the Jökulsá á Fjöllum. Some of these jökulhlaups originated from Kverkfjöll volcano and were routed through anastomosing, high gradient and hydraulically rough channels. Landforms and sediments preserved within these channels permit palaeoflow reconstructions.

Kverkfjöll jökulhlaups were reconstructed using palaeocompetence (point measurements), slope–area (one‐dimensional), and depth‐averaged two‐dimensional (2D) hydrodynamic modelling techniques. The increasing complexity of 2D modelling required a range of assumptions, but produced information on both spatial and temporal variations in jökulhlaup characteristics. The jökulhlaups were volcanically triggered, had a linear‐rise hydrograph and a peak discharge of 50 000–100 000 m3s−1, which attenuated by 50–75% within 25 km. Frontal flow velocities were ∼2 m s−1; but, as stage increased, velocities reached 5–15m s−1. Peak instantaneous shear stress and stream power reached 1 × 104N m−2and 1 × 105W m−2respectively.

Hydraulic parameters can be related to landform groups. A hierarchy of landforms is proposed, ranging from the highest energy zones (erosional gorges, scoured bedrock, cataracts, and spillways) to the lowest energy zones (of valley fills, bars, and slackwater deposits). Fluvial erosion of bedrock occurred in Kverkfjallarani above ∼3 m flow depth, ∼7m s−1flow velocity, ∼1 × 102N m−2shear stress, and 3 × 102W m−2stream power. Fluvial deposition occurred in Kverkfjallarani below ∼8 m flow depth, 11 m s−1flow velocity, 5 × 102N m−2shear stress, and 3 × 103W m−2stream power. Hence, erosional and depositional ‘envelopes’ have considerable overlap, probably due to transitional flow phenomena and the influence of upstream effects, such as hydraulic ponding and topographic constrictions, for example.

Holocene Kverkfjöll jökulhlaups achieved geomorphic work comparable to that of other late Pleistocene ‘megafloods’. This work was a result of steep channel gradients, topographic channel constrictions, and high hydraulic roughness, rather than to extreme peak discharges. The Kverkfjöll jökulhlaups have implications for landscape evolution in north‐central Iceland, for water‐sediment inputs into the North Atlantic, and for recognizing jökulhlaups in the rock record. 2D hydrodynamic modelling is likely to be important for hazard mitigation in similar landscapes and upon other glaciated volcanoes, because it only requires an input hydrograph and a digital elevation model to run a model, rather than suites of geomorphological evidence and field‐surveyed valley cross‐sections, for example. Copyright © 2006 John Wiley & Sons, Ltd.
Ocular phenotype in a mouse gene knockout model for infantile neuronal ceroid lipofuscinosis
Authors: Lei Bo , Tullis Gregory E. , Kirk Mark D. , Zhang Keqing , Katz Martin L.
Published: August 2006

Mutations in the human protein palmitoyl thioesterase‐1 (PPT‐1) gene result in an autosomal recessive neurodegenerative disorder designated neuronal ceroid lipofuscinosis (NCL), type CLN1, or infantile NCL. Among the symptoms of the CLN1 disease are accumulation of autofluorescent lysosomal storage bodies in neurons and other cell types, seizures, motor and cognitive decline, blindness, and premature death. Development of an effective therapy for this disorder will be greatly assisted by the availability of suitable animal models. A mouse PPT‐1 gene knockout model has recently been generated. Studies were performed to determine whether the mouse model exhibits ocular features of the human CLN1 disorder. A progressive accumulation of autofluorescent storage material in all layers of the retina was observed in the PPT‐1 knockout mice. Accompanying the storage body accumulation was a modest loss of cells with nuclei in the outer and inner nuclear layers. As indicated by electroretinogram (ERG) responses, retinal function was only mildly impaired at 4 months of age but was severely impaired by 8 months, despite only modest changes in retinal morphology. The pupillary light reflex (PLR), on the other hand, was exaggerated in the knockout mice. The apparent anomaly between the ERG and the PLR findings suggests that disease‐related PLR changes may be due to changes in extraocular signal processing. The pronounced ocular phenotype in the PPT‐1 knockout mice makes these animals a good model for testing therapeutic interventions for treatment of the human CLN1 disorder. © 2006 Wiley‐Liss, Inc.
Plant and fruit characteristics of cactus pear (Opuntia spp.) cultivars in South Africa
Authors: Oelofse Rachel M , Labuschagne Maryke T , Potgieter Johan P
Published: August 2006

The cultivation of cactus pear requires low input and is therefore conducive to a sustainable system that will increase the efficiency and economic viability of the small and medium‐sized farms of low‐income farmers. The aim of this study was to determine fruit and plant characteristics of the 10 most commonly grown cactus pear cultivars in South Africa under rain‐fed, subtropical conditions. Skinners Court favoured vegetative growth. The fruit of Gymno Carpo had below average total soluble sugars. Roedtan had high cladode yield, while producing fruit of good quality, especially high total soluble sugar values, and quantity. Turpin and Meyers proved to have the highest fruit yield, fruit mass, cladode yield and number of cladodes pruned per plant. These cultivars can therefore be planted for both fruit production and for harvesting of cladodes for animal feed. Copyright © 2006 Society of Chemical Industry
Source and changes of proteinase activities of Indian anchovy (Stolephorus spp.) during fish sauce fermentation
Authors: Siringan Patcharin , Raksakulthai Nongnuch , Yongsawatdigul Jirawat
Published: August 2006

Trypsin‐like proteinases exhibited the highest activity in viscera and muscle of Indian anchovy (Stolephorus spp.). The molecular weights (MWs) of proteinases in viscera were estimated to be 31, 35, 44, 49 and 57 kDa by activity staining in the presence of 4 mol L−1 NaCl. The MW of proteinase extracted from muscle was 56 kDa. This reflects that only one proteinase was extracted from muscle whereas five proteinases were extracted from viscera. Trypsin‐like, chymotrypsin‐like and cathepsin L‐like proteinases were found in commercial fish sauce samples throughout 12 months of fermentation, suggesting that these proteinases were stable at high salt concentrations (250–300 g kg−1 NaCl) and under acidic conditions (pH 5.2–5.8). In contrast, leucine aminopeptidase activity was detected only in the first month. The MWs of proteinases found in fish sauce after various fermentation periods were estimated to be 37, 47 and 53 kDa, which coincided with the MWs of proteinases found in Indian anchovy. Copyright © 2006 Society of Chemical Industry
A fast method for determining low‐molecular‐mass aliphatic carboxylic acids by high‐performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry
Authors: Käkölä Jaana , Alén Raimo
Published: August 2006

A fast quantitative high‐performance liquid chromatographic separation method with atmospheric pressure chemical ionization mass spectrometric detection (HPLC‐APCI‐MS) was developed for the determination of low‐molecular‐mass aliphatic mono‐ and dicarboxylic acids typically present in different industrial process waters. A mixture of glycolic, lactic, α‐glucoisosaccharinic, oxalic, maleic, fumaric, succinic, malic, glutaric, methylsuccinic, and adipic acids was separated using an RP chromatographic system. Adipic acid was used as an internal standard to calculate correlation coefficients for the acids studied. The chromatographic analysis of these acids was primarily carried out by means of gradient elution with an aqueous formic acid solution (0.15%, pH 2.5) and methanol using a modified C18 stationary phase. Good acid separation could be obtained for all acids by optimizing the chromatographic conditions. The method provides a simple sample preparation and faster analysis time compared to the traditional gas chromatographic methods, thus enabling almost real‐time monitoring of these acids. Finally, the method developed was applied to the analysis of a complex mixture of aliphatic hydroxy carboxylic acids, which are formed as alkaline degradation products of carbohydrates during wood delignification and are present in the cooking spent liquor (black liquor).
Engineered Bio‐Active Polysaccharides from Heparin
Authors: Guimond Scott E. , Turnbull Jeremy E. , Yates Edwin A.
Published: August 2006

Summary: Heparin, the well‐known anticoagulant polysaccharide, is also active in many other biological systems owing to its structural similarity to HS, but usually lacks selectivity because it is more highly sulfated. A series of straightforward chemical reactions (de‐O‐sulfation, de‐N‐sulfation and re‐N‐acetylation), carried out to partial or complete extent, were combined, resulting in a number of modified heparin polysaccharide derivatives with altered properties. These exhibited a range of abilities to promote cell signalling through the FGF/FGFR tyrosine kinase signalling system, in an in vitro cell assay with combinations of FGF‐1, ‐2, ‐3 and FGFR 1 and 3. One polysaccharide (N‐acetylated, 6‐O‐ and 2‐O‐sulfated heparin), with only a fraction (<10−3) of the anticoagulant activity of heparin (200 U · mg−1), promoted FGF‐2‐mediated angiogenesis (10‐fold) and therefore had an improved ratio of pro‐angiogenic activity to anticoagulant activity in excess of 104 compared to heparin. These results demonstrate that heparin‐derived polysaccharides can be engineered for selected activities and have potential in a wide range of medical, biotechnological and tissue‐engineering applications.

Effect of selected engineered heparin polysaccharides on angiogenesis.

magnified image

Effect of selected engineered heparin polysaccharides on angiogenesis.
Development of a Model Bladder Extracellular Matrix Combining Disulfide Cross‐Linked Hyaluronan with Decellularized Bladder Tissue
Authors: Brown Allison L. , Srokowski Elizabeth M. , Shu Xiao Z. , Prestwich Glenn D. , Woodhouse Kimberly A.
Published: August 2006

Summary: In this work we investigate the feasibility of modifying porcine‐derived BAM to include HA with a view to developing a model, artificial extracellular matrix for the study of bladder cell‐matrix interactions. HA‐DPTH was incorporated into BAM disks and then cross‐linked oxidatively to a disulfide containing hydrogel. Disks were seeded with bladder smooth muscle cells (BSMC) and UEC under three culture configurations and incubated for 3, 7, and 14 d. At each time point, matrix contraction was measured, and media supernatants assayed for cell‐secreted gelatinase activity. To evaluate cell adherence and organization, triple immunofluorescent labeling of cell nuclei, actin cytoskeleton, and focal contacts was performed. HA‐modified BAM exhibited a significant increase in matrix contraction and induced a higher level of cell‐secreted gelatinase activity compared to unmodified BAM. Immunofluorescent labeling demonstrated that BSMCs remained adherent to both scaffold types over time. The distribution and organization of the cytoskeleton and focal contacts did not appear to be altered by the presence of HA. Interestingly, cellular infiltration into modified BAM was evident by 7 d and continued beyond 14 d, while BSMCs seeded onto unmodified BAM remained localized to the surface out to 14 d, with minimal infiltration evident only at day 28. These differences in cell infiltration support the gelatinase activity results. Increases in cell migration and matrix proteolysis in the presence of HA may be contributing factors toward BAM remodeling leading to increased matrix contraction with time. The model ECM developed in this work will be utilized for future studies aimed at elucidating the mechanisms controlling key remodeling events associated with bladder repair.

Matrix contraction of cell‐seeded BAM scaffolds.

magnified image

Matrix contraction of cell‐seeded BAM scaffolds.
Water, Solute, and Segmental Dynamics in Polysaccharide Hydrogels
Authors: Cavalieri Francesca , Chiessi Ester , Finelli Ivana , Natali Francesca , Paradossi Gaio , Telling Mark F.
Published: August 2006

Summary: Polysaccharide hydrogels have found several applications in the food industry, in biomedicine, and cosmetics. The study of polysaccharide hydrogels offers a challenging scenario of intrinsic heterogeneities in the crosslinking density and large time and space ranges that characterize a number of dynamic processes entailing segmental motions, water diffusion, and small‐molecule diffusion. The understanding of such complex features is essential because of the extensive use of polysaccharidic moieties in the food industry, biomedical devices, and cosmetics. The study of phenomena occurring at the nanoscale to the mesoscale requires the combination of investigative tools to probe different time and distance scales and the structural characterization of the networks by established methodologies such as swelling and elastic modulus measurements. Elastic and quasielastic neutron scattering, and fluorescence recovery after photobleaching are emerging methodologies in this field. In this feature article we focus, somewhat arbitrarily, on these new approaches because other techniques, such as low‐resolution proton NMR relaxometry and rheology, have been already described thoroughly in the literature. Case examples of polysaccharide hydrogels studied by neutron scattering and fluorescence recovery are presented here as contributions to the comprehension of the dynamic behavior of physical and chemical hydrogels based on polysaccharides.

Quasielastic incoherent neutron scattering experiment on a Sephadex hydrogel sample at different temperatures.

magnified image

Quasielastic incoherent neutron scattering experiment on a Sephadex hydrogel sample at different temperatures.
A Reactive Flame Retardant as a Poly(propylene)‐Sized Glass Adhesion Promoter
Authors: Dvir Haim , Gottlieb Moshe
Published: August 2006

Summary: Contact‐mode AFM adhesion strength measurements were employed in order to investigate the capability of PBBMA FR as an adhesion promoter in PP composites. The reactive FR exhibited superior coupling properties in comparison to conventional coupling agents such as PP‐g‐ma introduced in reinforced PP composites.

AFM image showing the recess carved out by the AFM tip in a PBBMA layer deposited on glass treated with APS.

magnified image

AFM image showing the recess carved out by the AFM tip in a PBBMA layer deposited on glass treated with APS.
γ‐Radiation‐Induced Graft Copolymerization of Ethyl Acrylate onto Hydroxypropyl Methylcellulose
Authors: Wang Lili , Xu Yongshen
Published: August 2006

Summary: Graft copolymerization of EA onto water‐soluble HPMC was carried out using γ‐radiation using both simultaneous and preirradiation in an aqueous medium. The effects of radiation environment, radiation dose, monomer concentration, and reaction temperature on percentage of grafting (G) and grafting efficiency (GE) were investigated. For preirradiation, the observed values for G and GE were higher in air than in a nitrogen atmosphere. G and GE values are obviously higher for preirradiation; their maximum values were obtained for a radiation dose of 1.8 kGy. The grafting parameters increase for increasing monomer concentration up to 0.15 mol · L−1, where they reach their saturation values. In the case of preirradiation, the largest grafting parameters are obtained at 65 °C. The graft copolymers obtained were characterized by FTIR spectroscopy, TEM, SEM, and XRD methods. The method of irradiation significantly affects the mechanical properties of the grafted HPMC samples. Samples prepared by simultaneous irradiation show superior mechanical properties. In addition, the equilibrium humidity adsorption behaviors of the grafted copolymers were also studied, and the humidity resistance behavior of HPMC was enhanced through the grafting copolymerization.

Transmission electron micrograph of the HPMC‐g‐PEA water dispersion.

magnified image

Transmission electron micrograph of the HPMC‐g‐PEA water dispersion.
Effects of exercise and creatine on myosin heavy chain isoform composition in patients with Charcot–Marie–Tooth disease
Authors: Smith Cheryl A. , Chetlin Robert D. , Gutmann Laurie , Yeater Rachel A. , Alway Stephen E.
Published: August 2006

It is not known whether myosin heavy chain (MHC) content changes in response to exercise training or creatine supplementation in subjects with Charcot–Marie–Tooth disease (CMT). Based on previous data, we hypothesized that resistance exercise and creatine would increase the percentage of type I MHC composition in the vastus lateralis muscle and that myosin isoform changes would correlate with improved chair rise‐time in CMT subjects. To test this hypothesis, 18 CMT subjects were randomly assigned to either a placebo or creatine group. All subjects performed a 12‐week, home‐based, moderate‐intensity resistance training program. Chair rise‐time was measured before and after the training program. Muscle biopsies were obtained from the vastus lateralis before and after the 12‐week program. Gel electrophoresis showed a significant decrease (∼30%) in MHC type I in CMT subjects given creatine supplementation when compared with placebo. There was a nonsignificant increase in both MHC type IIa (∼23%) and MHC type IIx (∼7%) in CMT subjects given creatine. Reduced MHC type I content and increased MHC type IIa content correlated with faster chair rise‐times (i.e., improved muscle performance). The training‐induced change in MHC IIa content was inversely correlated with chair rise‐time in CMT subjects given creatine. When the two subject groups were combined, there was a linear, negative relationship between the change in MHC type IIa content and chair rise‐time after training and a positive relationship between the training‐induced change in MHC type I content and chair rise‐time. These data suggest that improved function (chair rise‐time) was associated with a lower level of MHC type I and increased MHC type IIa composition. Furthermore, the data are consistent with the hypothesis that creatine supplementation alters MHC composition in CMT patients undergoing resistance training and that MHC changes associated with creatine supplementation can improve muscle function. Muscle Nerve, 2006
Simultaneous price, location, and capacity decisions on a line of time‐sensitive customers
Authors: Dobson Gregory , Stavrulaki Euthemia
Published: August 2006

Consider a monopolist who sells a single product to time‐sensitive customers located on a line segment. Customers send their orders to the nearest distribution facility, where the firm processes (customizes) these orders on a first‐come, first‐served basis before delivering them. We examine how the monopolist would locate its facilities, set their capacities, and price the product offered to maximize profits. We explicitly model customers' waiting costs due to both shipping lead times and queueing congestion delays and allow each customer to self‐select whether she orders or not, based on her reservation price. We first analyze the single‐facility problem and derive a number of interesting insights regarding the optimal solution. We show, for instance, that the optimal capacity relates to the square root of the customer volume and that the optimal price relates additively to the capacity and transportation delay costs. We also compare our solutions to a similar problem without congestion effects. We then utilize our single‐facility results to treat the multi‐facility problem. We characterize the optimal policy for serving a fixed interval of customers from multiple facilities when customers are uniformly distributed on a line. We also show how as the length of the customer interval increases, the optimal policy relates to the single‐facility problem of maximizing expected profit per unit distance. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007
Comparison of fully implicit and IMPES formulations for simulation of water injection in fractured and unfractured media
Authors: Monteagudo J. E. P. , Firoozabadi A.
Published: August 2006

In this work, we compare the fully implicit (FI) and implicit pressure‐explicit saturation (IMPES) formulations for the simulation of water injection in fractured media. The system of partial differential equations is discretized within the discrete‐fracture framework using a control‐volume method. A unique feature of the methodology is that there is no need for the computation of matrix–fracture transfer terms.

The non‐linear system of equations resulting from the FI formulation is solved with state‐of‐the‐art Newton and tensor methods. Direct and Krylov iterative methods are employed to solve the system resulting from the Newton linearization. The performance of the FI and IMPES formulations is compared with numerical testing. Results show that the contrast between matrix and fracture properties affects the performance of both IMPES and FI formulations and that the tensor method outperforms all the Newton solvers for the near‐singular Jacobian matrix. Copyright © 2006 John Wiley & Sons, Ltd.
Allman's triangle, rotational DOF and partition of unity
Authors: Tian Rong , Yagawa Genki
Published: August 2006

A simplification of the 1984 Allman triangle (one of historically most important elements with rotational dofs) is presented. It is found that this old element takes a typical form of the partition of unity approximation. The Allman's rotation presented in the partition of unity form offers merits and convenience in formulation and practical applications. The stiffness matrix of the 1984 Allman triangle, which is originally computed from the linear strain triangular element (the 6 nodes quadratic triangle), can be obtained instead in a cheaper way from that of the constant strain triangular element. The constraint of the rotational terms during essential boundary treatment, which remains equivocal and ambiguous, is understood to be mandatory. The partition of unity notion enables a straightforward extension of the Allman's rotational dof to meshfree approximations. In numerical examples, we discuss suppression of spurious zero‐energy modes and patch tests. Standard benchmarks are carried out to assess performance of the newly formulated triangle and a meshfree approximation with the rotational dofs. Copyright © 2006 John Wiley & Sons, Ltd.
A projection semi‐implicit scheme for the coupling of an elastic structure with an incompressible fluid
Authors: Fernández M. A. , Gerbeau J.‐F. , Grandmont C.
Published: August 2006

We address the numerical simulation of fluid–structure systems involving an incompressible viscous fluid. This issue is particularly difficult to face when the fluid added‐mass acting on the structure is strong, as it happens in hemodynamics for example. Indeed, several works have shown that, in such situations, implicit coupling seems to be necessary in order to avoid numerical instabilities. Although significant improvements have been achieved during the last years, solving implicit coupling often exhibits a prohibitive computational cost. In this work, we introduce a semi‐implicit coupling scheme which remains stable for a reasonable range of the discretization parameters. The first idea consists in treating implicitly the added‐mass effect, whereas the other contributions (geometrical non‐linearities, viscous and convective effects) are treated explicitly. The second idea, relies on the fact that this kind of explicit–implicit splitting can be naturally performed using a Chorin–Temam projection scheme in the fluid. We prove (conditional) stability of the scheme for a fully discrete formulation. Several numerical experiments point out the efficiency of the present scheme compared to several implicit approaches. Copyright © 2006 John Wiley & Sons, Ltd.
Adaptive finite element methodology for tumour angiogenesis modelling
Authors: Peterson J. W. , Carey G. F. , Knezevic D. J. , Murray B. T.
Published: August 2006

In this paper, we consider an adaptive finite element approach for reliable, efficient solution of a class of continuum models for tumour‐induced angiogenesis. The ideas are demonstrated using an established three equation reaction/transport model that simulates aspects of tumour‐induced angiogenesis in a deterministic manner. The weak variational formulation and finite element approximation scheme for the model are developed, and a statistical approach for concurrent adaptive mesh refinement and coarsening is described. The appropriate form of the model and solution dependence on choice of parameters are explored. Computational results are presented for 1D, 2D and 3D geometry models. The effectiveness of the open‐source, parallel adaptive software library (LibMesh) that is being developed in the CFDLab at the University of Texas is also demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.
An alternative approach for numerical solutions of the Navier–Stokes equations
Authors: Chantasiriwan S.
Published: August 2006

Conventional approaches for solving the Navier–Stokes equations of incompressible fluid dynamics are the primitive‐variable approach and the vorticity–velocity approach. In this paper, an alternative approach is presented. In this approach, pressure and one of the velocity components are eliminated from the governing equations. The result is one higher‐order partial differential equation with one unknown for two‐dimensional problems or two higher‐order partial differential equations with two unknowns for three‐dimensional problems. A meshless collocation method based on radial basis functions for solving the Navier–Stokes equations using this approach is presented. The proposed method is used to solve a two‐ and a three‐dimensional test problem of which exact solutions are known. It is found that, with appropriate values of the method parameters, solutions of satisfactory accuracy can be obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Computational method of inverse elastostatics for anisotropic hyperelastic solids
Authors: Lu Jia , Zhou Xianlian , Raghavan Madhavan L.
Published: August 2006

The paper presents a computational method for predicting the initial geometry of a finitely deforming anisotropic elastic body from a given deformed state. The method is imperative for a class of problem in stress analysis, particularly in biomechanical applications. While the basic idea has been established elsewhere Comput. Methods Appl. Mech. Eng. 1996; 136:47–57; Int. J. Numer. Meth. Engng 1998; 43: 821–838), the implementation in general anisotropic solids is not a trivial exercise, but comes after a systematic development of Eulerian representations of constitutive equations. In this paper, we discuss the general representation in the context of fibrous hyperelastic solids, and provide explicit stress functions for some commonly used soft tissue models including the Fung model and the Holzapfel model. A three‐field mixed formulation is introduced to enforce quasi‐incompressibility constraints. The practical utility of this method is demonstrated using an example of aneurysm stress analysis. Copyright © 2006 John Wiley & Sons, Ltd.
Optimal layout design of three‐dimensional geometrically non‐linear structures using the element connectivity parameterization method
Authors: Yoon Gil Ho , Joung Young Soo , Kim Yoon Young
Published: August 2006

The topology design optimization of ‘three‐dimensional geometrically‐non‐linear’ continuum structures is still difficult not only because of the size of the problem but also because of the unstable continuum finite elements that arise during the optimization. To overcome these difficulties, the element connectivity parameterization (ECP) method with two implementation formulations is proposed. In ECP, structural layouts are represented by inter‐element connectivity, which is controlled by the stiffness of element‐connecting zero‐length links. Depending on the link location, ECP may be classified as an external ECP (E‐ECP) or an internal ECP (I‐ECP). In this paper, I‐ECP is newly developed to substantially enhance computational efficiency. The main idea in I‐ECP is to reduce system matrix size by eliminating some internal degrees of freedom associated with the links at voxel level. As for ECP implementation with commercial software, E‐ECP, developed earlier for two‐dimensional problems, is easier to use even for three‐dimensional problems because it requires only numerical analysis results for design sensitivity calculation. The characteristics of the I‐ECP and E‐ECP methods are compared, and these methods are validated with numerical examples. Copyright © 2006 John Wiley & Sons, Ltd.
Eight‐node Reissner–Mindlin plate element based on boundary interpolation using Timoshenko beam function
Authors: Zhang Hexin , Kuang J. S.
Published: August 2006

A new eight‐node Reissner–Mindlin plate element is developed with a special interpolation within the element. This special interpolation is an extension of the element boundary interpolation that employs Timoshenko beam function for the boundary segment interpolation. The element function can effectively capture the structural behaviours of thick plates and achieve high precision in the analysis of thick plates. Patch tests and numerical investigations are conducted. It can be seen that the proposed element successfully passes all the patch tests. The results of the numerical investigation show that the proposed element is free of the shear locking phenomenon and possesses a higher accuracy in the analyses, as compared to the earlier research in the literature. Copyright © 2006 John Wiley & Sons, Ltd.
Optimization control of bionics shell roofs subjected to snow skidding
Authors: Tesar Alexander , Melcer Jozef
Published: August 2006

Dynamic identification and optimization of bionics shell roofs subjected to the snow skidding is dealt with in present paper. The optimization control of structural geometry in order to induce the aimed snow skidding with reduction of dead weight snow loads is aimed. Theoretical, numerical and experimental in situ assessments based on wave approaches of the problem are presented. Structural application in situ on attractive shell roof made of laminated wood with optimization control suggested is presented. Copyright © 2006 John Wiley & Sons, Ltd.
A sinh transformation for evaluating two‐dimensional nearly singular boundary element integrals
Authors: Johnston Barbara M. , Johnston Peter R. , Elliott David
Published: August 2006

A new transformation technique is introduced for evaluating the two‐dimensional nearly singular integrals, which arise in the solution of Laplace's equation in three dimensions, using the boundary element method, when the source point is very close to the element of integration. The integrals are evaluated using (in a product fashion) a transformation which has recently been used to evaluate one‐dimensional near singular integrals. This sinh transformation method automatically takes into account the position of the projection of the source point onto the element and also the distance b between the source point and the element. The method is straightforward to implement and, when it is compared with a number of existing techniques for evaluating two‐dimensional near singular integrals, it is found that the sinh method is superior to the existing methods considered, both for potential integrals across the full range of b values considered (00.01. For smaller values of b, the use of the Lmethod is recommended for flux integrals. Copyright © 2006 John Wiley & Sons, Ltd.
Morphology based domain partitioning of multi‐phase materials: a preprocessor for multi‐scale modelling
Authors: Valiveti D. M. , Ghosh Somnath
Published: August 2006

This paper develops a microstructural morphology‐based domain partitioning method (MDP) as a comprehensive pre‐processor for multi‐scale simulation of heterogeneous multi‐phase materials. The MDP method systematically creates a multi‐scale image simulation–characterization methodology to enable domain partitioning that can delineate homogenizable regions from those where explicit representation of phases is necessary for analysis. The methods are strictly based on geometric features of the material morphology and do not use any mechanical response functions. The first step in this development simulates high‐resolution microstructural information from low resolution images of the domain and only a limited high resolution micrographs from optical or scanning electron microscopy. The second step uses quantitative characterization of these high resolution images with, e.g. phase distribution functions, to create effective metrics that can relate microstructural features to the material's physical behaviour. The third step invokes domain partitioning to demarcate regions corresponding to different length scales in a concurrent multi‐scale model. Partitioning criteria are defined in terms of descriptors of microstructural characteristics and these are used to adaptively create multi‐level domain partitions. The method developed is tested on a micrograph of a cast aluminium alloy A356. Copyright © 2006 John Wiley & Sons, Ltd.
Measurement of critical concentration for mesophase formation of chitosan derivatives in both aqueous and organic solutions
Authors: Dong Yan‐ming , Mao Wei , Wang Hui‐wu , Zhao Ya‐qing , Li Xiao‐jian , Bi Dan‐xia , Yang Liu‐lin , Ge Qiang , Fang Xueming
Published: August 2006

A novel chitosan derivative, acryloyl chitosan (AcCs), and two N‐maleoyl chitosans, MaCs‐1 and MaCs‐2, with different degrees of substitution were synthesized using completely deacetylated chitosan as raw material under different reaction conditions. AcCs is an amphiphilic chitosan derivative, but MaCs‐1 and MaCs‐2 are soluble in water and organic solvents respectively. The concentrated solutions of AcCs, MaCs‐1 and MaCs‐2 all demonstrated mesophases and were investigated using polarizing optical microscopy (POM). Circular dichroism (CD) was also employed for determining the critical concentration for mesophase formation. A broad peak in the visible light region of CD spectra had its origin in the appearance of the mesophase, and arose from the selective reflection of cholesteric helix pitches. The results of CD measurements agreed with those of POM. The critical concentration values for aqueous solutions were much lower than those for organic solutions, which was explained by the strong interactions between the chitosan derivatives and water. Copyright © 2006 Society of Chemical Industry
Surface activity and solubilization of a novel series of functional polyurethane surfactants
Authors: Dong Yang , Jin Yong , Wei Deqing
Published: August 2006

Functional polyurethane surfactants (di‐block and tri‐block) were synthesized by addition polymerization of 2,4‐toluenediisocyanate with poly(propylene oxide) and monoallyl‐end‐capped poly(ethylene oxide). The chemical structure of the polyurethane surfactants was confirmed by Fourier transform infrared and 1H NMR spectroscopy. These polymeric surfactants were found to have excellent surface activity. The lowest surface tension of polyurethane surfactant aqueous solutions could be reduced to 37.6 mN m−1. All the polyurethane surfactants synthesized had low critical micelle concentrations and could reduce the surface tension even at very low concentration levels (10−6–10−5 mol L−1). The solubilization of toluene in micelles of the synthesized polyurethane surfactants was studied using UV‐visible spectroscopy, and the results showed that they all exhibited good solubilization capacity. Possible solubilization positions of toluene in the micelles are conjectured. Copyright © 2006 Society of Chemical Industry
Decontamination of Surfaces by Low Pressure Plasma Discharges
Authors: Rossi François , Kylián Ondřej , Hasiwa Marina
Published: August 2006

Summary: Non‐equilibrium discharges in molecular gases and their mixtures have been extensively studied due to their applicability in different areas of surface treatment, cleaning and functionalization. In this paper, the feasibility of the use of low pressure discharges for sterilization and decontamination, i.e., a topic that has attracted great attention recently, is demonstrated and discussed using examples of bacterial spore sterilization and depyrogenation of bacterial endotoxins, as well as the elimination of protein films.

Image of spores used for sterilization, showing heavy stacking.

magnified image

Image of spores used for sterilization, showing heavy stacking.
Metallic TiO2
Authors: Sheppard L. R. , Bak T. , Nowotny J.
Published: August 2006

The present work reports the discovery of the effect of metallic‐type conduction for Nb‐doped TiO2 (0.65 at% Nb). This effect was attested by measurements of electrical conductivity at elevated temperatures (973–1223 K) in the gas phase of controlled oxygen activities. It is shown that the temperature coefficient of the mobility of electrons in reduced conditions is negative. This finding paves the way for the development of high‐efficiency photoelectrodes for photoelectrochemical hydrogen generation from water using solar energy with substantially reduced internal energy losses for charge transport. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rat lens aldose reductase inhibitory constituents of Nelumbo nucifera stamens
Authors: Lim Soon Sung , Jung Yu Jung , Hyun Sook Kyung , Lee Yeon Sil , Choi Jae Sue
Published: August 2006

Aldose reductase, the principal enzyme of the polyol pathway, has been shown to play an important role in the complications associated with diabetes. A methanol extract of the stamens of Nelumbo nucifera Gaertn. was shown to exert an inhibitory effect on rat lens aldose reductase (RLAR), and thus was fractionated using several organic solvents, including dichloromethane, ethyl acetate and n‐butanol. The ethyl acetate‐soluble fraction, which manifested potent RLAR‐inhibitory properties, was then purified further via repeated measures of silica gel and Sephadex LH‐20 column chromatography. Thirteen flavonoids: kaempferol (1) and seven of its glycosides (2–9), myricetin 3′,5′‐dimethylether 3‐O‐β‐d‐glucopyranoside (10), quercetin 3‐O‐β‐d‐glucopyranoside (11) and two isorhamnetin glycosides (12, 13) were isolated from N. nucifera, as well as four non‐flavonoid compounds: adenine (14), myo‐inositol (15), arbutin (16) and β‐sitosterol glucopyranoside (17). These compounds were all assessed with regard to their RLAR‐inhibitory properties. Among the isolated flavonoids, those harboring 3‐O‐α‐l‐rhamnopyranosyl‐(1→6)‐β‐d‐glucopyranoside groups in their C rings, including kaempferol 3‐O‐α‐l‐rhamnopyranosyl‐(1→6)‐β‐d‐glucopyranoside (5) and isorhamnetin 3‐O‐α‐l‐rhamnopyranosyl‐(1→6)‐β‐d‐glucopyranoside (13), were determined to exhibit the highest degree of rat lens aldose reductase inhibitory activity in vitro, evidencing IC50 values (concentration required for a 50% inhibition of enzyme activity) of 5.6 and 9.0 µm, respectively. Copyright © 2006 John Wiley & Sons, Ltd.
Identification and reduction of ion suppression effects on pharmacokinetic parameters by polyethylene glycol 400
Authors: Weaver Richard , Riley Rob J.
Published: August 2006

Ion suppression in mass spectrometry has been described recently in detail and should always be considered during analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS) in a drug metabolism and pharmacokinetics (DMPK) environment. At best, ion suppression leads to decreased sensitivity but at worst could lead to incorrectly determined pharmacokinetic (PK) parameters. Our investigations centred on polyethylene glycol (PEG 400), an excipient often used in pre‐clinical dosing vehicles. PEG was also found to be present in large quantities in the blood collection tubes used for pre‐clinical PK studies. Ion suppression was observed for many analytes, either due to the use of PEG in the dosing vehicle or in blood collection tubes. The elimination of large ion suppression effects was attained by simple chromatographic gradient changes and the use of alternative blood collection tubes. The effect of the above was to increase the detected plasma concentration levels, which resulted in a change in key PK parameters. Copyright © 2006 John Wiley & Sons, Ltd.
High‐throughput screening for multi‐class veterinary drug residues in animal muscle using liquid chromatography/tandem mass spectrometry with on‐line solid‐phase extraction
Authors: Tang Hubert Po‐on , Ho Clare , Lai Shirley Sau‐ling
Published: August 2006

A rapid qualitative method using on‐line column‐switching liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for screening 13 target veterinary drugs: four macrolides – erythromycin A, josamycin (leucomycin A3), kitasamycin (leucomycin A5), and tylosin A; six (fluoro)quinolones – ciprofloxacin, danofloxacin, enrofloxacin, flumequine, oxolinic acid, and sarafloxacin; and lincomycin, virginiamycin M1, and trimethoprim in different animal muscles. Clindamycin, norfloxacin, nalidixic acid, oleandomycin, ormetoprim, and roxithromycin were used as the internal standards. After simple deproteination and analyte extraction of muscle samples using acetonitrile, the supernatant was subjected to on‐line cleanup and direct analysis by LC/MS/MS. On‐line cleanup with an extraction cartridge packed with hydrophilic‐hydrophobic polymer sorbent followed by fast LC using a short C18 column resulted in a total analysis cycle of 6 min for 19 drugs. This screening method considerably reduced the time and the cost for the quantitative and confirmatory analyses. The application of a control point approach was also introduced and explained. Copyright © 2006 John Wiley & Sons, Ltd.
Determination of nicotine in mainstream smoke on the single puff level by liquid‐phase microextraction coupled to matrix‐assisted laser desorption/ionization Fourier transform mass spectrometry
Authors: Xie Jian‐Ping , Sun Shi‐Hao , Wang Hao‐Yang , Zong Yong‐Li , Nie Cong , Guo Yin‐Long
Published: August 2006

A method coupling liquid‐phase microextraction with matrix‐assisted laser desorption/ionization Fourier transform mass spectrometry (LPME/MALDI‐FTMS) was developed to measure the content of nicotine in mainstream smoke at the single puff level. Glycerol was utilized as a matrix additive in the sample preparation to improve the homogeneity of analyte distribution in a sample spot. Good repeatability of the MALDI‐MS signal (RSD <9%) was achieved by the method. Selective LPME facilitated the separation and purification of basic components from cigarette smoke. The LPME device was coupled to a smoking machine, and each puff of one cigarette could be gathered by this modified machine. The amount of nicotine in the mainstream smoke was measured at the single puff level by LPME/MALDI‐FTMS. The method was simple and selective and was sufficiently sensitive to detect nicotine in each puff of one cigarette. The method thus offered an alternative approach to the study of the formation mechanism of cigarette smoke constituents. Copyright © 2006 John Wiley & Sons, Ltd.
Market value effects of acquisitions involving internet firms: a resource‐based analysis
Authors: Uhlenbruck Klaus , Hitt Michael A. , Semadeni Matthew
Published: August 2006

While most prior research suggests that the average change in market value of acquiring firms varies closely around zero, recent research grounded in the resource‐based view and organizational learning theory identify positive returns to acquirers. We contribute to this literature by focusing on acquisitions of Internet firms and the potential for the transfer of scarce resources. We hypothesize that acquisitions made by offline firms of Internet firms and by Internet firms of other Internet firms lead to positive market valuation for the acquirer. Results of an event study of 798 acquisitions of Internet firms provided support for these predictions. We also find that prior alliances with online firms do not reduce the gains from such acquisitions to offline firms. Copyright © 2006 John Wiley & Sons, Ltd.