bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of inducible nitric oxide synthase prevents graft injury after transplantation of livers from rats after cardiac death
Authors: Shi Yanjun , Rehman Hasibur , Wright Gary L. , Zhong Zhi
Published: October 2010

This study investigated the roles of inducible nitric oxide synthase (iNOS) in the failure of rat liver grafts from cardiac death donors (GCDD). Livers were explanted after 30-minute aorta clamping and implanted after 4-hour storage in University of Wisconsin solution. The iNOS expression increased slightly in grafts from non–cardiac death donors (GNCDD) but markedly in GCDD. Serum nitrite and nitrate and hepatic 3-nitrotyrosine adducts, indicators of NO and peroxynitrite production, respectively, were substantially higher after transplantation of GCDD than GNCDD. Production of reactive nitrogen species (RNS) was largely blocked by 1400W (N-[1-naphthyl]ethylenediamine dihydrochloride; 5 μM), a specific iNOS inhibitor. Alanine aminotransferase release, bilirubin, necrosis, and apoptosis were 6.4-fold, 6.5-fold, 2.3-fold, and 2.7-fold higher, respectively, after transplantation of GCDD than GNCDD. The inhibitor 1400W effectively blocked these alterations and also increased survival of GCDD to 80% from 33%. Increased RNS production and failure of GCDD were associated with activation of c-Jun-N-terminal kinase (JNK), an effect that was blocked by inhibition of iNOS. Inhibition of JNK also improved the outcome after transplantation of GCDD. Together, the data indicate that iNOS increases substantially in GCDD, leading to RNS overproduction, JNK activation, and more severe graft injury. Inhibitors of iNOS are suggested as effective therapies to improve the outcome after transplantation of GCDD. Liver Transpl 16:1267-1277, 2010. © 2010 AASLD.
Reactive oxygen species mediate human hepatocyte injury during hypoxia/reoxygenation
Authors: Bhogal Ricky Harminder , Curbishley Stuart M. , Weston Christopher J. , Adams David H. , Afford Simon C.
Published: October 2010

Increasing evidence shows that reactive oxygen species (ROS) may be critical mediators of liver damage during the relative hypoxia of ischemia/reperfusion injury (IRI) associated with transplant surgery or of the tissue microenvironment created as a result of chronic hepatic inflammation or infection. Much work has been focused on Kupffer cells or liver resident macrophages with respect to the generation of ROS during IRI. However, little is known about the contribution of endogenous hepatocyte ROS production or its potential impact on the parenchymal cell death associated with IRI and chronic hepatic inflammation. For the first time, we show that human hepatocytes isolated from nondiseased liver tissue and human hepatocytes isolated from diseased liver tissue exhibit marked differences in ROS production in response to hypoxia/reoxygenation (H-R). Furthermore, several different antioxidants are able to abrogate hepatocyte ROS–induced cell death during hypoxia and H-R. These data provide clear evidence that endogenous ROS production by mitochondria and nicotinamide adenine dinucleotide phosphate oxidase drives human hepatocyte apoptosis and necrosis during hypoxia and H-R and may therefore play an important role in any hepatic diseases characterized by a relatively hypoxic liver microenvironment. In conclusion, these data strongly suggest that hepatocytes and hepatocyte-derived ROS are active participants driving hepatic inflammation. These novel findings highlight important functional/metabolic differences between hepatocytes isolated from normal donor livers, hepatocytes isolated from normal resected tissue obtained during surgery for malignant neoplasms, and hepatocytes isolated from livers with end-stage disease. Furthermore, the targeting of hepatocyte ROS generation with antioxidants may offer therapeutic potential for the adjunctive treatment of IRI and chronic inflammatory liver diseases. Liver Transpl 16:1303-1313, 2010. © 2010 AASLD.
Effect of Sterilization on Non‐woven Polyethylene Terephthalate Fiber Structures for Vascular Grafts
Authors: Dimitrievska Sashka , Petit Alain , Doillon Charles J. , Epure Laura , Ajji Abdellah , Yahia L'Hocine , Bureau Martin N.
Published: October 2010

Non‐woven polyethylene terephthalate (PET) fibers produced via melt blowing and compounded into a 6 mm diameter 3D tubular scaffold were developed with artery matching mechanical properties. This work compares the effects of ethylene oxide (EtO) and low temperature plasma (LTP) sterilization on PET surface chemistry and biocompatibility. As seen through X‐ray photoelectron spectroscopy (XPS) analysis, LTP sterilization led to an increase in overall oxygen content and the creation of new hydroxyl groups. EtO sterilization induced alkylation of the PET polymer. The in vitro cytotoxicity showed similar fibroblastic viability on LTP‐ and EtO‐treated PET fibers. However, TNF‐α release levels, indicative of macrophage activation, were significantly higher when macrophages were incubated on EtO‐treated PET fibers. Subcutaneous mice implantation revealed an inflammatory response with foreign body reaction to PET grafts independent of the sterilization procedure.

magnified image
Polyelectrolyte Multilayer Nanofilms Used as Thin Materials for Cell Mechano‐Sensitivity Studies
Authors: Boudou Thomas , Crouzier Thomas , Nicolas Claire , Ren Kefeng , Picart Catherine
Published: October 2010

Three types of multilayer films made from poly(L‐lysine)/hyaluronan, chitosan/hyaluronan, and poly(allylamine hydrochloride)/poly(L‐glutamic acid), were used to investigate the interplay between film mechano–chemical properties and cell adhesion. We showed that C2C12 myoblast adhesion and proliferation depended on the extent of film cross‐linking for all films whatever their internal chemistry. Cell spreading areas were found to correlate with the film's stiffness and to be distributed over a unique curve. Immuno‐staining of the cytoskeletal components revealed the formation of F‐actin stress fibers and vinculin plaques only on stiff films. Finally, we compared our results with previous studies performed on polyacrylamide and PDMS gels, two recognized materials for mechano‐sensitivity studies. We found that the effect of substrate stiffness on cell spreading is material‐dependent.

magnified image
Influence of water vapour on high temperature oxidation of steels used in petroleum refinery heaters
Authors: Sultan A. , Karakaya İ. , Erdoğan M.
Published: October 2010

The oxidation behaviours of three different steels used in the construction of petroleum refinery heaters were investigated by thermogravimetric analysis (TGA) technique. C‐5, P‐11 and P‐22 steel samples were tested in two different environments: air and CO2 + 2H2O + 7.52N2, a gas composition which simulates the combustion products of natural gas, at 450 and 500 °C. P‐22 steel had the best oxidation resistance at both temperatures in air. In CO2 + 2H2O + 7.52N2 environment, the oxidations of all the steels were accelerated and C‐5 exhibited better oxidation resistance than P‐22 and P‐11.

Analyses of oxidation products by optical microscopy, SEM‐EDX and XRD were carried out to correlate TGA results to oxide composition and morphology. The lower oxidation rate of P‐22 in air was explained with reference to the formation of a protective Cr‐containing oxide layer between the steel and the iron oxide scale. The higher oxidation rates of chromium containing steels in CO2 + 2H2O + 7.52N2 environment were attributed to the depletion of protective Cr‐containing oxide scale, which was deduced from the lower Cr content of this layer than that formed in air oxidation, as a result of probably faster oxidation of Cr even inside the steel. Therefore, the oxidation mechanisms of FeCr alloys with intermediate Cr contents at higher temperatures could also be valid for steels with low chromium contents such as P‐22 (2.25%) even at 450 and 500 °C.
Effect of sodium silicate pretreatment on phosphate layer: Morphology and corrosion resistance behavior
Authors: Wang J. , Zhou W. , Du Y.
Published: October 2010

Phosphating is a widely adopted treatment in industry for many purposes. In this paper, carbon steel was pretreated with sodium silicate before phosphating. X‐ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements were used to evaluate the pretreatment effect by sodium silicate on the phosphating layer. The results demonstrate that the phosphate layer pretreated by sodium silicate has a better corrosion resistance as compared with the un‐pretreated ones. More compact and uniform coatings composed of finer crystals were obtained with the pretreatment of sodium silicate.
Corrosion in alkanolamine used for acid gas removal: From natural gas processing to CO2 capture
Authors: Kittel J. , Fleury E. , Vuillemin B. , Gonzalez S. , Ropital F. , Oltra R.
Published: October 2010

The aim of this paper is to review some of the parameters influencing the corrosivity of alkanolamine solvents used for natural gas purification or for CO2 capture. In the light of literature data and of new experimental results, the influences of temperature and of acid gas loading are discussed. These two parameters appear to have a strong impact on corrosion rates of carbon steel, with extrapolated corrosion rates of several tens of mm/year for the highest temperature and acid gas loading condition.

It is then proposed to discuss about similarities and differences between natural gas processing and CO2 capture from flue gas. For both applications, alkanolamine processes are used. Still, differences can be found in operating parameters. The most significant gap concerns the lean amine sections. In acid gas treatment, the regeneration of the solvent is often performed down to zero loading. Under these conditions, an extremely low corrosivity of the lean solvent is expected. On the contrary, CO2 capture from flue gas requires only a partial stripping of the CO2 in the regeneration section, due to energy efficiency reasons. Then, the lean solvent still contains some acid gas, and subsequently a higher corrosivity.

Finally, the general principles for material selection for the different parts of acid gas removal units are discussed, considering both cases of natural gas processing or CO2 capture.
Effect of atmosphere composition on the oxidation behavior of MCrAlY coatings
Authors: Song P. , Subanovic M. , Toscano J. , Naumenko D. , Quadakkers W. J.
Published: October 2010

In the present work the effect of atmosphere composition on the growth rate and adherence of the alumina scales was studied using free‐standing MCrAlY‐coatings and TBC‐specimens with MCrAlY‐bondcoats. The exposures comprised isothermal and cyclic exposures in laboratory air and Ar‐H2‐H2O at 1100 °C.

It is shown that minor Zr‐addition to the bondcoat results in enhanced scale growth and internal oxidation. This effect is independent of the atmosphere composition. As a consequence of the rapid oxide formation the times to TBC failure on the Zr‐containing bondcoat in both atmospheres were much shorter compared to those with Zr‐free bondcoat. In the latter case the formation of a thin compact alumina TGO was slower in H2/H2O than in air resulting in significantly longer TBC‐lifetime in the former atmosphere.
Internal surface protection of gas turbine blade by Si‐aluminide coating
Authors: Firouzi A. , Shirvani K.
Published: October 2010

A laboratory‐scale slurry silicoaluminizing process has been developed to apply coating into cooling passageways of a first‐stage gas turbine blade. Analytical techniques for characterizing the coatings comprised optical microscopy, SEM, EDS, and XRD. The results of metallographic examinations demonstrated that acceptable coatings had been formed in almost all of the passageways. The amounts of Al and Si in the topcoat were found to be in the ranges of 24–26 wt% and 4.5–6 wt%, respectively. The heat treated coating consisted largely of β‐NiAl phase as the coating matrix with uniform distribution of <2 µm‐size precipitates. In addition, oxidation and hot corrosion performance of the coatings were investigated by cyclic exposure to 1100 °C and the furnace method using a mixture of sodium sulfate‐40 wt% sodium vanadate‐10 wt% sodium chloride at 780 °C, respectively. It was found that the presence of Si in the coating improves both oxidation and hot corrosion Type II properties.
Thermoresponsive Copolymer Cryogel Possessing Molecular Memory: Synthesis, Energetics of Collapse and Interaction with Ligands
Authors: Burova Tatiana V. , Grinberg Natalia V. , Kalinina Elena V. , Ivanov Roman V. , Lozinsky Vladimir I. , Alvarez‐Lorenzo Carmen , Grinberg Valerij Y.
Published: October 2010

An imprinted thermoresponsive cryogel of copolymer of N‐isopropylacrylamide and N‐[3‐(N,N′‐dimethylamino)propyl]acrylamide was synthesized in a frozen (−10 °C) aqueous medium in presence of a molecular template, the drug substance ibuprofen. A reversible volume phase transition upon heating (thermotropic collapse) of the swollen cryogel was studied by high‐sensitivity differential scanning calorimetry. In the absence of ligands, the transition temperature, enthalpy, and width were 82.5 °C, 9.8 J · g−1 and 32.2 °C, respectively. Significant changes in the transition parameters were observed in presence of the template ligand (ibuprofen): with increasing ligand concentration the transition temperature decreased down to 30 °C, the enthalpy passed through a minimum, and the transition width notably reduced. The binding constants of ibuprofen by the cryogel subchains in the collapsed and swollen states were 119 and 5 M−1, respectively. This implies a preferential binding of ibuprofen by the shrunken cryogel. The excess absorption of ibuprofen by the cryogel related to its collapse amounted to 0.327 mmol · g−1 while for all other ligands that were structural analogs of ibuprofen this parameter did not exceed 0.016 mmol · g−1. Consequently, the imprinted cryogel possessed a selective molecular memory toward the template ligand.

magnified image
Multifunctional Porous Poly(vinylidene fluoride)‐graft‐Poly(butyl methacrylate) with Good Li+ Ion Conductivity
Authors: Samanta Sanjoy , Chatterjee Dhruba P. , Layek Rama K. , Nandi Arun K.
Published: October 2010

PnBMA is grafted on PVDF using ATRP in NMP solution at 90 °C and characterized by means of 1D and 2D NMR. 19F NMR spectra clearly reveal that the attack occurs on the head‐head >CF2 groups. Cast PB films show a honeycomb‐patterned porous microstructure, and the “breath‐figure” model is used to explain pore formation. FT‐IR spectra suggest a supramolecular interaction between >CO groups of PnBMA and >CF2 groups of PVDF. Storage modulus, loss modulus and stress at break decrease with graft conversion, but the strain at break increases significantly. The toughness of the copolymers also increases dramatically (882%). The porous materials can be applied as solid‐state electrolytes (Li+‐doped) with good ionic conductivity (10−5 S · cm−1).

magnified image
Synthesis, Crystallization, and Enzymatic Degradation of the Biodegradable Polyester Poly(ethylene azelate)
Authors: Papageorgiou George Z. , Bikiaris Dimitrios N. , Achilias Dimitris S. , Karagiannidis Nikitas
Published: October 2010

Poly(ethylene azelate) (PEAz) was synthesized and its melting behavior was studied with DSC and Step Scan DSC. The equilibrium melting point of PEAz was found 62 °C and the heat of fusion of 100% crystalline polymer was estimated at 160 J · g−1. Polarized light microscopy showed mixed birefringence. From isothermal crystallization DSC study, after self‐nucleation, crystallization rates were estimated. The Lauritzen–Hoffman plots showed crystallization regime I to II and II to III transition at 34 and 19 °C respectively. Non‐isothermal crystallization was studied. The activation energy was calculated applying the isoconversional method of Friedman. Chemical hydrolysis of PEAz was very slow, while enzymatic hydrolysis showed comparable rates with PCL.

magnified image
A Highly Efficient Polymerizable Photoinitiator Comprising Benzophenone, Thio Moieties, and N‐Arylmaleimide
Authors: Wei Jun , Wang Baozong
Published: October 2010

A novel, highly efficient, polymerizable, thio‐containing photoinitiator, 4‐maleimido‐4'‐thiophenylbenzophenone (MTBP), was synthesized by directly introducing maleimide to benzophenone moieties. Three polymerizable photoinitiators with different location or number of maleimide substituents, together with the bare benzophenone, were chosen to evaluate the photoefficiency of MTBP. Photopolymerization studies indicate that polymerizable photoinitiator with single maleimide substituent directly linking to benzophenone moieties is more efficient for photopolymerization of vinyl monomers than those with indirect or double maleimide substituents. As for the photopolymerization of 1,6‐hexanediol diacrylate, MTBP show surprisingly high efficiency, and the final conversion runs up to 95.94%.

magnified image
Superamphiphobic Web of PTFEMA Fibers via Simple Electrospinning Without Functionalization
Authors: Choi Gyoung‐Rin , Park Joonsik , Ha Jong‐Wook , Kim Wan‐Doo , Lim Hyuneui
Published: October 2010

This paper reports on a web of superamphiphobic fluoro‐compound fibers that forms as a result of a typical electrospinning method without any additional treatment. An electrospun web of poly(2,2,2‐trifluoroethyl methacrylate) fibers exhibits superamphiphobicity when the water and hexadecane contact angles both exceed 150°. The morphology of a web is modulated by changing the polymer solution concentration from 24 to 30 wt.‐% with other fixed processing conditions. The fiber diameter length depends mainly on the polymer concentration. A web formed from a 26 wt.‐% solution has the smallest and most uniform fiber diameter; it also has the highest robustness parameter on wetting, thus the highest water and hexadecane contact angles. This result offers the possibility of simple industrial production of an amphiphobic surface.

magnified image
Analysis of the large‐n limit of multiple orthogonal polynomials and non‐intersecting Brownian motions
Authors: Alonso L. Martínez , Medina E.
Published: October 2010

In this work, we use the connection between families of multiple orthogonal polynomials with respect to a certain set of weights and random matrix models with external sources to determine the eigenvalue density and its support in the large‐n limit. These results are also applied to a model of non‐intersecting Brownian motions starting from a fix point. Copyright © 2010 John Wiley & Sons, Ltd.
Aroma WaterLOGSY: a fast and sensitive screening tool for drug discovery
Authors: Hu Jun , Eriksson Per‐Olof , Kern Gunther
Published: October 2010

One‐dimensional NMR spectroscopy has proven to be a powerful technique for screening compound libraries in drug discovery. We report a novel water ligand‐observed gradient spectroscopy (WaterLOGSY) pulse sequence, named Aroma WaterLOGSY, that selectively detects aromatic WaterLOGSY signals from compounds or ligands. In the Aroma WaterLOGSY, water magnetization is untouched after water excitation and utilizes the whole period of the remaining pulse sequence to relax back to the + z direction. Due to the phase cycling design, the water magnetization is allowed to relax for the period of two full scans before it gets inverted again. Therefore, the recycle delay can be significantly shortened. Within similar experimental time, Aroma WaterLOGSY shows approximately two times higher sensitivity than the standard scheme. This method also allows the use of non‐deuterated reagents, thereby accelerating experimental set‐up time for ligand‐binding studies. Copyright © 2010 John Wiley & Sons, Ltd.
Polystyrene microsphere–ferritin conjugates: A robust phantom for correlation of relaxivity and size distribution
Authors: Sukerkar Preeti A. , Rezvi Uzma G. , MacRenaris Keith W. , Patel Pinal C. , Wood John C. , Meade Thomas J.
Published: October 2010

In vivo iron load must be monitored to prevent complications from iron overload diseases such as hemochromatosis or transfusion‐dependent anemias. While liver biopsy is the gold standard for determining in vivo iron load, MRI offers a noninvasive approach. MR phantoms have been reported that estimate iron concentration in the liver and mimic relaxation characteristics of in vivo deposits of hemosiderin. None of these phantoms take into account the size distribution of hemosiderin, which varies from patient to patient based on iron load. We synthesized stable and reproducible microsphere‐ferritin conjugates (ferribeads) of different sizes that are easily characterized for several parameters that are necessary for modeling such as iron content and bead fraction. T1s and T2s were measured on a 1.41‐T low‐resolution NMR spectrometer and followed a size‐dependent trend. Ferribeads imaged at 4.7 and 14.1 T showed that signal intensities are dependent on the distribution of ferritin around the bead rather than the iron concentration alone. These particles can be used to study the effects of particle size, ferritin distribution, and bead fraction on proton relaxation and may be of use in mimicking hemosiderin in a phantom for estimating iron concentration. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Estimation of tensors and tensor‐derived measures in diffusional kurtosis imaging
Authors: Tabesh Ali , Jensen Jens H. , Ardekani Babak A. , Helpern Joseph A.
Published: October 2010

This article presents two related advancements to the diffusional kurtosis imaging estimation framework to increase its robustness to noise, motion, and imaging artifacts. The first advancement substantially improves the estimation of diffusion and kurtosis tensors parameterizing the diffusional kurtosis imaging model. Rather than utilizing conventional unconstrained least squares methods, the tensor estimation problem is formulated as linearly constrained linear least squares, where the constraints ensure physically and/or biologically plausible tensor estimates. The exact solution to the constrained problem is found via convex quadratic programming methods or, alternatively, an approximate solution is determined through a fast heuristic algorithm. The computationally more demanding quadratic programming‐based method is more flexible, allowing for an arbitrary number of diffusion weightings and different gradient sets for each diffusion weighting. The heuristic algorithm is suitable for real‐time settings such as on clinical scanners, where run time is crucial. The advantage offered by the proposed constrained algorithms is demonstrated using in vivo human brain images. The proposed constrained methods allow for shorter scan times and/or higher spatial resolution for a given fidelity of the diffusional kurtosis imaging parametric maps. The second advancement increases the efficiency and accuracy of the estimation of mean and radial kurtoses by applying exact closed‐form formulae. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Vascular therapy for radiation cystitis
Authors: Soler Roberto , Vianello Alberto , Füllhase Claudius , Wang Zhan , Atala Anthony , Soker Shay , Yoo James J. , KoudyWilliam James
Published: October 2010

Purpose

The underlying pathology of radiation cystitis is cellular and vascular damage followed by increased fibrosis and inflammation. This study was to determine if neovascular‐promoting therapy could reduce the pathological changes in the bladder wall associated with pelvic irradiation.

Methods

Adult female Lewis inbred rats were irradiated with a single dose of 20 Gy directed at their bladder. Four weeks later, 30 rats were divided equally into one of three treatment groups for bladder wall injection of: (1) PBS (Control); (2) PBS containing 50 ng vascular endothelial growth factor (VEGF165); or (3) PBS containing 1 × 106 rat endothelial cells (EC). Age‐matched non‐irradiated rats (n = 10) served as untreated controls. At either 1.5 or 3 months following radiation, bladders were analyzed for collagen deposition using Masson's Trichrome staining of collagen and muscle and vascularization using Von Willebrand factor staining of ECs. Quantitative‐PCR was used to examine markers of angiogenesis, hypoxia, and fibrosis.

Results

The collagen/muscle ratio was doubled in the control group 3 months post‐irradiation (P < 0.05 vs. non‐irradiated bladders). Both ECs and VEGF inhibited increases in collagen content (P < 0.05 vs. control). Similarly, irradiation reduced bladder wall vessel counts compared to non‐irradiated controls (P < 0.05) and both ECs and VEGF maintained vessel counts similar to that of non‐irradiated controls (P < 0.05). PCR analysis showed a higher expression of neovascular markers (CD31, KDR) in the EC and VEGF groups compared to non‐irradiated controls (P < 0.05).

Conclusions

Angiogenesis therapy may be useful in the prevention and/or treatment of the underlying pathology of radiation cystitis. Neurourol. Urodynam. 30:428–434, 2011. © 2010 Wiley‐Liss, Inc.
Decomposing inventory routing problems with approximate value functions
Authors: Toriello Alejandro , Nemhauser George , Savelsbergh Martin
Published: October 2010

We present a time decomposition for inventory routing problems. The methodology is based on valuing inventory with a concave piecewise linear function and then combining solutions to single‐period subproblems using dynamic programming techniques. Computational experiments show that the resulting value function accurately captures the inventory's value, and solving the multiperiod problem as a sequence of single‐period subproblems drastically decreases computational time without sacrificing solution quality. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010
Approximation results for min‐max path cover problems in vehicle routing
Authors: Xu Zhou , Xu Liang , Li Chung‐Lun
Published: October 2010

This article studies a min‐max path cover problem, which is to determine a set of paths for k capacitated vehicles to service all the customers in a given weighted graph so that the largest path cost is minimized. The problem has wide applications in vehicle routing, especially when the minimization of the latest service completion time is a critical performance measure. We have analyzed four typical variants of this problem, where the vehicles have either unlimited or limited capacities, and they start from either a given depot or any depot of a given depot set. We have developed approximation algorithms for these four variants, which achieve approximation ratios of max{3 ‐ 2/k,2}, 5, max{5 ‐ 2/k,4}, and 7, respectively. We have also analyzed the approximation hardness of these variants by showing that, unless P = NP, it is impossible for them to achieve approximation ratios less than 4/3, 3/2, 3/2, and 2, respectively. We have further extended the techniques and results developed for this problem to other min‐max vehicle routing problems.© 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010
Hybrid‐Trefftz stress element for bounded and unbounded poroelastic media
Authors: de Freitas J. A. Teixeira , Moldovan I. D.
Published: October 2010

The equations that govern the dynamic response of saturated porous media are first discretized in time to define the boundary value problem that supports the formulation of the hybrid‐Trefftz stress element. The (total) stress and pore pressure fields are directly approximated under the condition of locally satisfying the domain conditions of the problem. The solid displacement and the outward normal component of the seepage displacement are approximated independently on the boundary of the element. Unbounded domains are modelled using either unbounded elements that locally satisfy the Sommerfeld condition or absorbing boundary elements that enforce that condition in weak form. As the finite element equations are derived from first‐principles, the associated energy statements are recovered and the sufficient conditions for the existence and uniqueness of the solutions are stated. The performance of the element is illustrated with the time domain response of a biphasic unbounded domain to show the quality of the modelling that can be attained for the stress, pressure, displacement and seepage fields using a high‐order, wavelet‐based time integration procedure. Copyright © 2010 John Wiley & Sons, Ltd.
Coupling finite elements and finite volumes by Lagrange multipliers for explicit dynamic fluid–structure interaction
Authors: Casadei Folco , Leconte Nicolas
Published: October 2010

This paper proposes a strategy for coupling a Finite Element description of structures with a Finite Volume (FV) description of fluids by means of the Lagrange multipliers method, for the numerical simulation of Fluid–Structure Interaction problems in fast transient dynamics. The structural domain uses the classical explicit Central Difference (CD) time integration scheme, while in the fluid domain a node‐centered Finite Volume scheme is adopted, which achieves second‐order accuracy in space and in time by a predictor–corrector algorithm combined with a MUSCL‐like technique. The FV time marching scheme is suitably adapted to enable ‘strong’ coupling with the CD scheme via Lagrange multipliers. Numerical examples illustrate the effectiveness of the proposed procedure. Copyright © 2010 John Wiley & Sons, Ltd.
Efficient non‐linear model reduction via a least‐squares Petrov–Galerkin projection and compressive tensor approximations
Authors: Carlberg Kevin , Bou‐Mosleh Charbel , Farhat Charbel
Published: October 2010

A Petrov–Galerkin projection method is proposed for reducing the dimension of a discrete non‐linear static or dynamic computational model in view of enabling its processing in real time. The right reduced‐order basis is chosen to be invariant and is constructed using the Proper Orthogonal Decomposition method. The left reduced‐order basis is selected to minimize the two‐norm of the residual arising at each Newton iteration. Thus, this basis is iteration‐dependent, enables capturing of non‐linearities, and leads to the globally convergent Gauss–Newton method. To avoid the significant computational cost of assembling the reduced‐order operators, the residual and action of the Jacobian on the right reduced‐order basis are each approximated by the product of an invariant, large‐scale matrix, and an iteration‐dependent, smaller one. The invariant matrix is computed using a data compression procedure that meets proposed consistency requirements. The iteration‐dependent matrix is computed to enable the least‐squares reconstruction of some entries of the approximated quantities. The results obtained for the solution of a turbulent flow problem and several non‐linear structural dynamics problems highlight the merit of the proposed consistency requirements. They also demonstrate the potential of this method to significantly reduce the computational cost associated with high‐dimensional non‐linear models while retaining their accuracy. Copyright © 2010 John Wiley & Sons, Ltd.
Finite element modelling of saturated porous media at finite strains under dynamic conditions with compressible constituents
Authors: Gajo A. , Denzer R.
Published: October 2010

Two finite element formulations are proposed to analyse the dynamic conditions of saturated porous media at large strains with compressible solid and fluid constituents. Unlike similar works published in the literature, the proposed formulations are based on a recently proposed hyperelastic framework in which the compressibility of the solid and fluid constituents is fully taken into account when geometrical non‐linear effects are relevant on both micro‐ and macroscales. The first formulation leads to a three‐field finite element method (FEM), which is suitable for analysing high‐frequency dynamic problems, whereas the second is a simplification of the first, leading to a two‐field FEM, in which some inertial effects of the pore fluid are disregarded, hence the second formulation is suitable for studying low‐frequency problems. A fully Lagrangian approach is considered, hence all terms are expressed with reference to the material setting; the balance equations for the pore fluid are also expressed in terms of the chemical potential and the mass flux of the pore fluid in order to take the compressibility of the fluid into account. To improve the numerical response in the case of wave propagation, a discontinuous Galerkin FEM in the time domain is applied to the three‐field formulation. The results are compared with analytical and semi‐analytical solutions, highlighting the different effects of the discontinuous Galerkin method on the longitudinal waves of the first and second kind. Copyright © 2010 John Wiley & Sons, Ltd.
Optimal component mode synthesis for medium frequency problem
Authors: Herran Mathieu , Nélias Daniel , Combescure Alain , Chalons Hervé
Published: October 2010

The component mode synthesis (CMS) with fixed interface (denoted Craig–Bampton) method uses a combination of static and dynamic modes. The usual definition of this CMS leads to a coupling between static and dynamic modes which are not orthogonal with respect to the stiffness matrix. This type of basis is not well suited for dynamic explicit computations, because the resulting mass matrix is not diagonal. If one keeps the same basis mode set but uses an orthogonalization process with respect to the mass matrix, the quality of the reduced Craig–Bampton system is kept but the basis vectors are combined differently. The aim of this paper is to propose a new way to control the accuracy of the reduced dynamic system for a specific frequency domain. Thus a new CMS is defined in order to be accurate in the medium frequency range. Copyright © 2010 John Wiley & Sons, Ltd.
Multiscale XFEM‐modelling and simulation of the inelastic material behaviour of textile‐reinforced polymers
Authors: Kästner M. , Haasemann G. , Ulbricht V.
Published: October 2010

This paper addresses the multiscale simulation of fibre‐reinforced polymers. The considered composite materials exhibit a hierarchical material structure with three distinct length scales—micro, meso and macro. This feature of the morphology allows for the application of homogenization techniques based on a representative volume element (RVE) that is entirely typical for the local, periodic material structure. The effective macroscopic material behaviour of the composite can be predicted from the properties of the individual constituents and the geometric arrangement of the reinforcing fibres based on the simulation of the material behaviour in the RVE.

The heterogeneous material structure in an RVE is modelled by the eXtended finite element method (XFEM). To this, two special element types, called X‐element and 2X‐element, are derived. They can represent one or two material interfaces within the element domain. For an efficient modelling process, an automated model generation procedure that determines the required element types, locates the material interfaces and performs the subdivision of the X‐elements into tetrahedral integration domains has been developed. Problems related to a consistent interface approximation and a continuous displacement field are discussed.

In the generated RVE models, a viscoplastic material model accounts for the inelastic material behaviour of the polymeric matrix, whereas the glass‐fibres are assumed to have a linear elastic stress–strain behaviour. Using periodic displacement boundary conditions, effective stress–strain curves are computed for glass‐fibre‐reinforced polypropylene with unidirectional and woven arrangements of the reinforcing fibres. Copyright © 2010 John Wiley & Sons, Ltd.
GPU accelerated lattice Boltzmann model for shallow water flow and mass transport
Authors: Tubbs Kevin R. , Tsai Frank T.‐C.
Published: October 2010

A lattice Boltzmann method (LBM) for solving the shallow water equations (SWEs) and the advection–dispersion equation is developed and implemented on graphics processing unit (GPU)‐based architectures. A generalized lattice Boltzmann equation (GLBE) with a multiple‐relaxation‐time (MRT) collision method is used to simulate shallow water flow. A two‐relaxation‐time (TRT) method with two speed‐of‐sound techniques is used to solve the advection–dispersion equation. The proposed LBM is implemented to an NVIDIA®Computing Processor in a single GPU workstation. GPU computing is performed using the Jacket GPU engine for MATLAB®and CUDA. In the numerical examples, the MRT‐LBM model and the TRT‐LBM model are verified and show excellent agreement to exact solutions. The MRT outperforms the single‐relaxation‐time (SRT) collision operator in terms of stability and accuracy when the SRT parameter is close to the stability limit of 0.5. Mass transport with velocity‐dependent dispersion in shallow water flow is simulated by combining the MRT‐LBM model and the TRT‐LBM model. GPU performance with CUDA code shows an order of magnitude higher than MATLAB‐Jacket code. Moreover, the GPU parallel performance increases as the grid size increases. The results indicate the promise of the GPU‐accelerated LBM for modeling mass transport phenomena in shallow water flows. Copyright © 2010 John Wiley & Sons, Ltd.
A cure for crime? Psycho‐pharmaceuticals and crime trends
Authors: Marcotte Dave E. , Markowitz Sara
Published: October 2010

In this paper we consider possible links between the diffusion of new pharmaceuticals used for treating mental illness and crime rates. We describe recent trends in crime and review the evidence showing that mental illness is a clear risk factor both for criminal behavior and victimization. We summarize the development of a number of new pharmaceutical therapies for the treatment of mental illness that came into wide use during the “great American crime decline.” We examine limited international data, as well as more detailed American data, to assess the relationship between rates of prescriptions of psychotropic drugs and crime rates, while controlling for other factors that may explain trends in crime rates. Using state‐level variation in the rates that various drug therapies disperse within populations to identify impacts on crime rates, we find some evidence that the expansion of psychiatric drugs is associated with decreased violent crime rates, but not property crime rates. We find no robust impacts on homicide rates and no effects on arrest rates. Further, the magnitudes of the estimated effects of expanded drug treatment on violent crime are small. Our estimates imply that about 5 percent of the decline in crime during the period of our study was due to expanded mental health treatment. © 2010 by the Association for Public Policy Analysis and Management.
P‐15 functionalized porous microspheres as biomimetic habitats for bone tissue engineering applications
Authors: Garkhal Kalpna , Mittal Anupama , Verma Shalini , Kumar Neeraj
Published: October 2010

Poly(L‐lactide‐co‐ε‐caprolactone) (PLCL, 75/25) solid and porous microspheres (MS) were prepared using solvent evaporation and gas foaming method, respectively. These MS were characterized for particle size, surface morphology, porosity, and surface area. Porous MS were modified by P‐15 peptide using carbodiimide coupling method. These unmodified solid and P‐15‐modified/‐unmodified porous MS were further evaluated for MG‐63 proliferation, cell alignment, collagen type I expression, and matrix mineralization for 21 days. In vitro cell culture studies of P‐15 functionalized porous MS exhibited enhanced cell viability, increased formation of actin filament bundles and collagen type I expression as compared to solid MS and 2D (polystyrene 24 well plate), and maintained the mineralization potential of MG‐63 cells. The results suggests P‐15‐modified porous PLCL MS were able to grow the cells with proper cell functionality and hold potential to be used as an injectable cell carrier for bone tissue engineering applications. Copyright © 2010 John Wiley & Sons, Ltd.
Interaction of luminescent dyes with noble metal nanoparticles in organic–inorganic glasses for future luminescent materials
Authors: Reisfeld Renata , Levchenko Viktoria , Saraidarov Tsiala
Published: October 2010

Organic–inorganic glasses (ormocers) incorporated by fluorescent dyes absorbing in the solar spectrum are important as new materials for luminescent solar concentrators. We present here how the fluorescence efficiencies of the new fluorescent ormocers can be enhanced by additions of noble metal—silver nanoparticles (NPs). The preparation of the ormocer and various size silver NPs is described. The film of hybrid inorganic–organic matrix consists of silica, diurethane‐siloxane, and polyvinyl‐butyral matches optically to the glass substrate. The film has high‐mechanical stability, and is photostable and atmosphere‐resistant. The fluorescence of the system doped by a model dye Rhodamine‐123, without and with presence of the silver NPs, was measured. The increase of the luminescence intensity was observed and attributed to the interaction of the excited levels of the dyes with silver plasmons. Copyright © 2010 John Wiley & Sons, Ltd.
Alcoholics show reduced telomere length in the oesophagus
Authors: Aida Junko , Yokoyama Akira , Izumiyama Naotaka , Nakamura Ken‐ichi , Ishikawa Naoshi , Poon Steven S , Fujiwara Mutsunori , Sawabe Motoji , Matsuura Masaaki , Arai Tomio , Takubo Kaiyo
Published: October 2010

Telomeres are repetitive G‐rich DNA sequences located at the ends of chromosomes. Chromosomal and genomic instability due to telomere dysfunction plays an important role in carcinogenesis. To study telomere shortening in the oesophageal epithelium of alcoholics, we measured the telomere lengths of basal and parabasal cells in comparison with those of non‐alcoholics using Q‐FISH and our original software, Tissue Telo, and also assessed histological inflammation. Telomeres in basal cells were significantly shorter in alcoholics than in age‐matched normal controls. Prominent histological findings of chronic inflammation were not evident in either alcoholics or non‐alcoholics. Our finding that telomeres in the oesophageal epithelium are shorter in alcoholics than in non‐alcoholics indicates that telomere shortening may be associated with the frequent occurrence of squamous cell carcinoma in alcoholics. Further studies to clarify the reason for the large annual loss of telomere length with rapid turnover or lower telomerase activity in the oesophageal epithelium of alcoholics will be necessary. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Synthesis of double‐hydrophilic poly(methylacrylic acid)–poly(ethylene glycol)–poly(methylacrylic acid) triblock copolymers and their micelle formation
Authors: Liu Ren , Tao Youhua , Zhu Ye , Chen Mingqing , Yang Cheng , Liu Xiaoya
Published: October 2010

The aim of the work reported was to synthesize a series of double‐hydrophilic poly(methacrylic acid)‐block‐poly(ethylene glycol)‐block‐poly(methacrylic acid) (PMAA‐b‐PEG‐b‐PMAA) triblock copolymers and to study their self‐assembly behavior. These copolymeric self‐assembly systems are expected to be potential candidates for applications as carriers of hydrophilic drugs. Bromo‐terminated difunctional PEG macroinitiators were used to synthesize well‐defined triblock copolymers of poly(tert‐butyl methacrylate)‐block‐poly(ethylene glycol)‐block‐poly(tert‐butyl methacrylate) via reversible‐deactivation radical polymerization. After the removal of the tert‐butyl group by hydrolysis, double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers were obtained. pH‐sensitive spherical micelles with a core–corona structure were fabricated by self‐assembly of the double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers at lower solution pH. Transmission electron microscopy and laser light scattering studies showed the micelles were of nanometric scale with narrow size distribution. Solution pH and micelle concentration strongly influenced the hydrodynamic radius of the spherical micelles (48–310 nm). A possible reason for the formation of the micelles is proposed. Copyright © 2010 Society of Chemical Industry
Synthesis and characterization of water‐soluble polypyrrole/multi‐walled carbon nanotube composites
Authors: Lin Yen‐Wen , Wu Tzong‐Ming
Published: October 2010

Water‐soluble polypyrrole (PPy)/multi‐walled carbon nanotube (MWCNT) composites were prepared by mixing chemically modified MWCNTs carrying carboxylic groups (c‐MWCNTs) and sulfonated PPy (SPPy) aqueous colloids in solution. Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy were used to characterize the structure and morphology of the resulting composites. Raman and X‐ray photoelectron spectra demonstrate the presence of electrostatic interactions between the radical species of the SPPy and the carboxylic acid species of the c‐MWCNTs. The addition of c‐MWCNTs into SPPy efficiently enhances its thermal stability and electrical conductivity. Owing to the doping effect and one‐dimensional linear structure of the c‐MWCNTs, the conductivity of SPPy/c‐MWCNT composites at room temperature is increased by two orders of magnitude by the introduction of 5 wt% c‐MWCNTs into the SPPy matrix. Copyright © 2010 Society of Chemical Industry
Effect of Low‐pressure Microwave Plasma Discharges on the Surface of Vulcanized Rubbers Before Bonding with a Silicone Sheet
Authors: Moreno‐Couranjou Maryline , Choquet Patrick , Guillot Jerôme , Frache Gilles , Audinot Jean‐Nicolas
Published: October 2010

In this work, the surface of vulcanized rubbers was treated by a low‐pressure microwave plasma process to enhance the adhesion with a silicone adhesive. The plasma reactor was fed with nitrogen, oxygen or synthetic air. Scanning electron microscopy and atomic force microscopy observations associated with X‐ray photoelectron spectroscopy, laser desorption/ionization time‐of‐flight mass spectrometry, secondary ion mass spectroscopy and surface energy measurements showed how the plasma gas treatment can affect the morphology and the chemistry of the rubber surface. The adhesion performances of the treated samples were evaluated using 90°‐peel tests. Correlations between the plasma surface modifications and the adhesion properties are reported.

magnified image
Reliability of the de Morton mobility index (DEMMI) in an older acute medical population
Authors: de Morton Natalie A. , Davidson Megan , Keating Jennifer L.
Published: October 2010

Background. The de Morton Mobility Index (DEMMI) is an instrument that accurately measures the mobility of older people across clinical settings. Purpose. To report the multiple reliability studies conducted during the development and validation of the DEMMI. Methods. Intra‐rater and inter‐rater reliability studies were conducted for the DEMMI in two independent samples (development and validation samples) of older acute medical patients (aged 65 years or older). Inter‐rater reliability studies were conducted between the test developer (a physiotherapist) and another experienced physiotherapist. Order of assessor administration was randomized by a coin toss. Patients who were fatigued after the first assessment were excluded from the inter‐rater reliability study. Intra‐rater reliability studies included participants with ‘unchanged’ mobility status between hospital admission and discharge. Scale reliability estimates were expressed as the minimal detectable change with 90% confidence (MDC90). Item reliability was calculated using Kappa statistics and absolute percentage agreement. Results. The MDC90 for the DEMMI development sample was 9.51 points (95% confidence interval [95% CI], 5.04–13.32; n = 21) and 7.84 (95% CI, 4.34–11.65; n = 16) on the 100‐point interval DEMMI scale for the inter‐rater and intra‐rater reliability studies, respectively. Similar estimates were obtained for the DEMMI validation samples of 8.90 (95% CI, 6.34–12.69; n = 35) and 13.28 points (95% CI, 8.08–20.87; n = 19). Items were not excluded from the DEMMI based on the results of item reliability. Conclusion. Reliability estimates for the DEMMI were consistent across independent samples of older acute medical patients using different reliability study methodology. Error represents approximately 9% of the DEMMI scale width. Copyright © 2010 John Wiley & Sons, Ltd.