bluuebunny/crossref_metadata_2025 huggingface dataset:
A mouse model to evaluate the interface between skin and a percutaneous device
Authors: Isenhath S. N. , Fukano Y. , Usui M. L. , Underwood R. A. , Irvin C. A. , Marshall A. J. , Hauch K. D. , Ratner B. D. , Fleckman P. , Olerud J. E.
Published: June 2007

Percutaneous medical devices are integral in the management and treatment of disease. The space created between the skin and the device becomes a haven for bacterial invasion and biofilm formation and results in infection. We hypothesize that sealing this space via integration of the skin into the device will create a barrier against bacterial invasion. The purpose of this study was to develop an animal model in which the interaction between skin and biomaterials can be evaluated. Porous poly(2‐hydroxyethyl methacrylate) [poly(HEMA)] rods were implanted for 7 days in the dorsal skin of C57 BL/6 mice. The porous poly(HEMA) rods were surface‐modified with carbonyldiimidazole (CDI) or CDI plus laminin 5; unmodified rods served as control. Implant sites were sealed with 2‐octyl cyanoacrylate; corn pads and adhesive dressings were tested for stabilization of implants. All rods remained intact for the duration of the study. There was histological evidence of both epidermal and dermal integration into all poly(HEMA) rods regardless of treatment. This in vivo model permits examination of the implant/skin interface and will be useful for future studies designed to facilitate skin cell attachment where percutaneous devices penetrate the skin. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Combination of ascorbate and growth factor (TGF β‐3) in thermo‐reversible hydrogel constructs embedded with rabbit chondrocytes for neocartilage formation
Authors: Choi Seong‐Jun , Na Kun , Kim Sungwon , Woo Dae Gyun , Sun Bo Kyung , Chung Hyung‐Min , Park Keun‐Hong
Published: June 2007

This study evaluated the potential of using poly(NiPAAm‐co‐AAc) as an injectable drug delivery carrier and a cell therapeutic agent in the form of a supporting matrix for the chondrogenic differentiation of rabbit chondrocytes. In particular, rabbit chondrocytes were embedded in hydrogels containing a combination of ascorbate and transforming growth factor β‐3 (TGF β‐3). Hydrogel constructs containing embedded cells either without ascorbate or a combination of ascorbate and TGF β‐3 were used as controls to determine the effects of ascorbate and TGF β‐3 on chondrogenic differentiation. The level of cartilage associated ECM proteins was examined using immunohistochemical staining for collagen type II as well as by Safranin‐O and Alcian blue (GAG) staining. The results showed that ascorbate is an important factor for preparing cartilage constructs because of its action on chondrocyte phenotype modulation and proliferation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Material dependent differences in inflammatory gene expression by giant cells during the foreign body reaction
Authors: Luttikhuizen D.T. , Dankers P.Y.W. , Harmsen M.C. , van Luyn M.J.A.
Published: June 2007

Multinucleated giant cells (GCs) are often observed in the foreign body reaction against implanted materials. The in vivo function of GCs in this inflammatory process remains to be elucidated. GCs degrade collagen implants in rats and may also orchestrate the inflammatory process via the expression and secretion of modulators, such as cytokines and chemokines. In this study, we show that the gene expression of PMN chemoattractants, CXCL1/KC and CXCL2/MIP‐2, is high in GCs micro‐dissected from explanted Dacron, cross‐linked collagen (HDSC), and bioactive ureido‐pyrimidinone functionalized oligocaprolactone (bioactive PCLdiUPy). Conversely, the gene expression levels of TGFβ and pro‐angiogenic mediators VEGF and FGF were found to be low in these GCs as compared with the expression levels in total explants. GCs in bioactive PCLdiUPy displayed high cytokine and angiogenic mediator expression compared with GCs isolated from the two other studied materials, whereas chemokine gene expression in GCs isolated form HDSC was low. Thus, GCs adopt their expression profile in response to the material that is encountered. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Collagen stiffness regulates cellular contraction and matrix remodeling gene expression
Authors: Karamichos D. , Brown R.A. , Mudera V.
Published: June 2007

Cell‐level mechanical and 3D spatial cues are essential to the organization and architecture of new tissues that form during growth, repair or in bioreactors. Fibroblast‐seeded 3D collagen constructs have been used as bioartifical extracellular matrix (ECM) providing a 3D environment to embedded resident cells. As cells attach to scaffold fibrils, they generate quantifiable contractile forces which depend on cell type, cell attachment, cell density, growth factors, and matrix stiffness. The aim of this study was to quantify the cytomechanical and molecular responses of human dermal (HDF) and neonatal foreskin fibroblasts (HNFF) seeded in constructs of increased stiffness. We also tested the effect of blocking early attachment using serum starvation on these outputs. Constructs were placed under uniaxial strains of 0–10% to increase scaffold stiffness, prior to gel contraction, and force generation was monitored using a tensional culture force monitor (t‐CFM). Increased matrix stiffness reduced generation of quantifiable cellular force (up to 70%) over 24 h in both cell types and delayed the onset of measurable contraction (upto sevenfold). The delay of measurable force generation was cell lineage dependent but not FCS dependent. Gene expression of MMP‐2, TIMP‐2, and collagen type III expression in HDFs were significantly upregulated in constructs of increased stiffness. HNFFs did not show any significant changes in these gene expressions indicating a lineage specific response. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
COMP mutations: Domain‐dependent relationship between abnormal chondrocyte trafficking and clinical PSACH and MED phenotypes
Authors: Chen Tung‐Ling L. , Posey Karen L. , Hecht Jacqueline T. , Vertel Barbara M.
Published: June 2007

Mutations in cartilage oligomeric matrix protein (COMP) produce clinical phenotypes ranging from the severe end of the spectrum, pseudoachondroplasia (PSACH), which is a dwarfing condition, to a mild condition, multiple epiphyseal dysplasia (MED). Patient chondrocytes have a unique morphology characterized by distended rER cisternae containing lamellar deposits of COMP and other extracellular matrix proteins. It has been difficult to determine why different mutations give rise to variable clinical phenotypes. Using our in vitro cell system, we previously demonstrated that the most common PSACH mutation, D469del, severely impedes trafficking of COMP and type IX collagen in chondrocytic cells, consistent with observations from patient cells. Here, we hypothesize that PSACH and MED mutations variably affect the cellular trafficking behavior of COMP and that the extent of defective trafficking correlates with clinical phenotype. Twelve different recombinant COMP mutations were expressed in rat chondrosarcoma cells and the percent cells with ER‐retained COMP was assessed. For mutations in type 3 (T3) repeats, trafficking defects correlated with clinical phenotype; PSACH mutations had more cells retaining mutant COMP, while MED mutations had fewer. In contrast, the cellular trafficking pattern observed for mutations in the C‐terminal globular domain (CTD) was not predictive of clinical phenotype. The results demonstrate that different COMP mutations in the T3 repeat domain have variable effects on intracellular transport, which correlate with clinical severity, while CTD mutations do not show such a correlation. These findings suggest that other unidentified factors contribute to the effect of the CTD mutations. J. Cell. Biochem. 103: 778–787, 2008. © 2007 Wiley‐Liss, Inc.
Benchmarking approximate density functional theory for s/d excitation energies in 3d transition metal cations
Authors: Schultz Nathan E. , Zhao Yan , Truhlar Donald G.
Published: June 2007

Holthausen has recently provided a comprehensive study of density functional theory for calculating the s/d excitation energies of the 3d transition metal cations. This study did not include the effects of scalar relativistic effects, and we show here that the inclusion of scalar relativistic effects significantly alters the conclusions of the study. We find, contrary to the previous study, that local functionals are more accurate for the excitation energies of 3d transition method cations than hybrid functionals. The most accurate functionals, of the 38 tested, are SLYP, PBE, BP86, PBELYP, and PW91. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
pyVib, a computer program for the analysis of infrared and Raman optical activity
Authors: Zerara Mohamed
Published: June 2007

A new program called pyVib has been developed as a tool for the analysis of Gaussian (Gaussian 03, Gaussian Inc., Pittsburgh, PA) outputs of vibrational absorption (IR), Raman as well as vibrational optical activity (VOA) spectra calculations. This program has been designed to help the computational chemistry practitioner in the task of analyzing and visualizing molecular vibrations and cross sections. In particular, the analysis of absorption and scattering cross sections can be done using new tools such as group coupling matrices (GCMs) and atomic contribution patterns (ACPs) as either 2D or 3D representations, respectively (Hug, Chem Phys 2001, 264, 53). It reads the Hessian, the atomic polar tensors (APTs), the atomic axial tensors (AATs) (Nafie, J Chem Phys 1983, 79, 4950), and the gradients of the various polarizability tensors involved in VOA calculations and stored in Gaussian fchk ascii files. pyVib is capable of picking suitably chosen atoms or group of atoms for evaluating the contribution of each atom or defined groups of atoms to the calculated VOA scattered intensities. All the results generated by pyVib can be visualized in real‐time but can also be transferred to text editors and electronic spreadsheets, which facilitate a detailed subsequent analysis and the visualization by other graphical user interfaces (GUIs).

This program is coded in Python and used the visualization toolkit (VTK) library. It is freely available under the terms of the general GNU public license (GPL) for Linux platforms. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Interval Tournaments
Authors: Brown David E. , Busch Arthur H. , Lundgren J. Richard
Published: June 2007

A tournament is an orientation of a complete graph. A directed graph is an interval digraph if for each vertex v there corresponds an ordered pair of intervals (Sv, Tv) such that u → v if and only if Su ∩ Tv ≠ ∅︁. A bipartite graph is an interval bigraph if to each vertex there corresponds an interval such that vertices are adjacent if and only if their corresponding intervals intersect and each vertex belongs to a different partite set. We use the equivalence of the models for interval digraphs and interval bigraphs to characterize tournaments that are interval digraphs via forbidden subtournaments and prove that a tournament on n vertices is an interval digraph if and only if it has a transitive (n − 1)‐subtournament. We also characterize the obstructions to the existence of a transitive subtournament of order n − 1 in a tournament of order n. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 72–81, 2007
The crossing number of K11 is 100
Authors: Pan Shengjun , Richter R. Bruce
Published: June 2007

The crossing number of Kn is known for n ⩽ 10. We develop several simple counting properties that we shall exploit in showing by computer that cr(K11 = 100, which implies that cr(K12) = 150. We also determine the numbers of non‐isomorphic optimal drawings of K9 and K10. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 128–134, 2007
Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb2+ ions
Authors: Firdoussi Ahlam El , Lafitte Marie , Tortajada Jeanine , Kone Omar , Salpin Jean‐Yves
Published: June 2007

Electrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)m− H]+ ions (m = 1–2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)n]2+ are also observed. Our study shows that MS/MS experiments have to be performed to differentiate Pb2+‐coordinated disaccharides. Upon collision, [Pb(disaccharide) − H]+ species mainly dissociate according to glycosidic bond cleavage and cross‐ring cleavages, leading to the elimination of CnH2nOn neutrals (n = 2–4). The various fragmentation processes allow the position of the glycosidic bond to be unambiguously located. Distinction between glc‐glc and glc‐fru disaccharides also appears straightforward. Furthermore, for homodimers of D‐glucose our data demonstrate that the anomericity of the glycosidic bond can be characterized for the 1 → n linkages (n = 2, 4, 6). Consequently, Pb2+ cationization combined with tandem mass spectrometry appears particularly useful to identify underivatized disaccharides. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of extracellular osmolarity and mechanical stimulation on gene expression of intervertebral disc cells
Authors: Wuertz K. , Urban J.P.G. , Klasen J. , Ignatius A. , Wilke H.‐J. , Claes L. , Neidlinger‐Wilke C.
Published: June 2007

Intervertebral discs (IVD) have a higher extracellular osmolarity than most other tissues; moreover their osmolarity changes by around 25% during each diurnal cycle. In this study, changes in aggrecan, collagen I and collagen II expression of IVD cells were examined after exposure to osmotic environment alterations or mechanical stimulation under different osmotic conditions. Human and bovine IVD cells seeded in three‐dimensional (3D) collagen type I matrices were cultured under hypo‐osmotic (300 mOsm), iso‐osmotic (400 mOsm), or hyperosmotic (500 mOsm) conditions. Osmolarity‐induced changes in gene expression of IVD cells were measured after 5 days. Load‐induced changes in gene expression under the different osmotic conditions were measured after application of hydrostatic pressure (0.25 MPa, 0.1 Hz, 30 min) or cyclic strain (4%, 1 Hz, 24 h). The results showed that IVD cells respond strongly to changes in the osmotic environment by altering mRNA expression. Human cells cultured over 5 days increased expression of aggrecan and collagen II in both nucleus and annulus cells under increasing osmolarity. In contrast, collagen I expression was inhibited at high osmolarity in both cell types. Mechanically induced alterations in gene expression appear to have only modest effects on matrix protein expression, but the same stimulus partly resulted in an inhibition or stimulation of gene expression, depending on the osmotic conditions. This study showed that the osmotic environment does not only have an appreciable effect on gene expression but also affects responses to mechanical stimuli. This suggests that the osmotic conditions cannot be ignored when examining physiological and pathological behavior of IVD cells. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1513–1522, 2007
Reactivity of tert‐butylperoxyl radical with manganese(III), cobalt(II), and nickel(II) salicylidene Schiff base chelates
Authors: Tavadyan Levon A. , Tonikyan Hakob Gh. , Musaelyan Makich V. , Barsegyan Aram E. , Minasyan Seyran H. , Sorenson John R. J.
Published: June 2007

Salicylidene Schiff base chelates (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminomanganese(III) chloride, (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminocobalt(II), N,N′‐bis(salicylidene)‐ethylenediaminocobalt(II), N,N′‐bis(salicylidene)ethylenediaminonickel(II), and N,N′‐bis(salicylidene)ethylenediaminoaquacobalt(II), as well as (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)1,2‐cyclohexanediamine, were kinetically examined as antioxidants in the scavenging of tert‐butylperoxyl radical (tert‐butylOO•). Absolute rate constants and corresponding Arrhenius parameters were determined for reactions of tert‐butylOO• with these chelates in the temperature range −52.5 to −11°C. High reactivity of tert‐butylOO• with Mn(III) and Co(II) salicylidene Schiff base chelates was established using a kinetic electron paramagnetic resonance method. These salicylidene Schiff base chelates react in a 1:1 stoichiometric fashion with tert‐butylOO• without free radical formation. Ultraviolet–visible spectrophotometry and differential pulse voltammetry established that the rapid removal rate of tert‐butylOO• by these chelates is the result of Mn(III) oxidation to Mn(IV) and Co(II) oxidation to Co(III) by tert‐butylOO•. It is concluded that removal of alkylperoxyl radical by Mn(III) and Co(II) salicylidene Schiff base chelates may partially account for their biological activities. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 431–439, 2007
The use of the IKP method for evaluating the kinetic parameters and the conversion function of the thermal decomposition of NaHCO3 from nonisothermal thermogravimetric data
Authors: Janković Bojan , Adnađević Borivoj
Published: June 2007

Three linear isoconversional methods (Friedman, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose) and the invariant kinetic parameters (IKP) method were used in order to examine the kinetics of the nonisothermal decomposition of a sodium bicarbonate (NaHCO3). The objective of the paper is to show the usefulness of the IKP method to determine both the kinetic parameters and the kinetic model of the investigated process. The activation energy (Ea) value obtained by the IKP method is in good agreement with the values obtained by isoconversional methods. The IKP method associated with the criterion of coincidence of kinetic parameters for all heating rates led us to the following kinetic triplet: Ea = 95.5 kJ mol−1, A = 2.65 × 1010 min−1, and conversion function f(α) = (1 − α) (first‐order reaction model, F1). © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 462–471, 2007
The kinetics of complex formation between Ti(IV) and hydrogen peroxide
Authors: O'Sullivan Daniel W. , Tyree Michael
Published: June 2007

The kinetics of the formation of the titanium‐peroxide [TiO2+2] complex from the reaction of Ti(IV)OSO4 with hydrogen peroxide and the hydrolysis of hydroxymethyl hydroperoxide (HMHP) were examined to determine whether Ti(IV)OSO4 could be used to distinguish between hydrogen peroxide and HMHP in mixed solutions. Stopped‐flow analysis coupled to UV‐vis spectroscopy was used to examine the reaction kinetics at various temperatures. The molar absorptivity (ε) of the [TiO2+2] complex was found to be 679.5 ± 20.8 L mol−1 cm−1 at 405 nm. The reaction between hydrogen peroxide and Ti(IV)OSO4 was first order with respect to both Ti(IV)OSO4 and H2O2 with a rate constant of 5.70 ± 0.18 × 104 M−1 s−1 at 25°C, and an activation energy, Ea = 40.5 ± 1.9 kJ mol−1. The rate constant for the hydrolysis of HMHP was 4.3 × 10−3 s−1 at pH 8.5. Since the rate of complex formation between Ti(IV)OSO4 and hydrogen peroxide is much faster than the rate of hydrolysis of HMHP, the Ti(IV)OSO4 reaction coupled to time‐dependent UV‐vis spectroscopic measurements can be used to distinguish between hydrogen peroxide and HMHP in solution. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 457–461, 2007
Picosecond Raman induced Stokes and anti-Stokes lasing in fine-grained Ba(Sn,Zr,Mg,Ta)O3 crystalline ceramics with the cubic perovskite structure
Authors: Kaminskii A A , Tanaka N , Eichler H J , Rhee H , Ueda K , Takaichi K , Shirakawa A , Tokurakawa M , Kintaka Y , Kuretake S , Sakabe Y
Published: June 2007

We report on the first observation of the Raman induced Stokes and anti-Stokes nonlinear χ(3)-lasing in crystalline ``cubic'' Ba(Sn,Zr,Mg,Ta)O3 ceramics of the E- and Z-types. We believe that these isotropic transparent oxide materials are also promising host-ceramics for lanthanide and transition-metal lasants.
Charged Polymers via Controlled Radical Polymerization and their Implications for Gene Delivery
Authors: Heath William H. , Senyurt Askim F. , Layman John , Long Timothy E.
Published: June 2007

Non‐viral gene delivery agents are notorious for their poor nucleic acid transfection efficiency and relatively high cell cytotoxicity. Thus, many investigators are exploring the important parameters involved in charged polymer‐mediated gene delivery, such as chemical composition, molecular weight, structural architecture, surface charge, etc. It is important to develop clear structure‐property relationships in order to design successful nucleic acid delivery agents for gene therapy. To elucidate these relationships, well‐defined materials are necessary. Controlled radical polymerization methods offer a facile route to systematically produce well‐defined, structurally distinct gene delivery agents. The use of charged polymers prepared via controlled radical polymerizations to elucidate transfection mechanisms or develop new delivery vectors will be reviewed herein.

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New Results on the Collapse Transition(s) of Flexible Homopolymers
Authors: Paul Wolfgang , Rampf Federica , Strauch Thomas , Binder Kurt
Published: June 2007

Summary:We analyze the collapse transition of flexible homopolymer chains in the bond‐fluctuation model employing the Wang‐Landau Monte Carlo algorithm. The coil‐globule transition is followed by a first order transition into a solid state occurring in the collapsed globule. In the thermodynamic limit (chain length to infinity) the topology of the phase diagram depends on the range of the attractive interaction between the monomers. For sufficiently large interaction range anormalbehaviour of a continuous coil‐globule transition at the Θ‐temperature followed by a crystallization transition at lower temperature is observed. For short interaction range the first‐order transition asymptotically can pre‐empt the coil‐globule transition such that a first‐order collapse from a random‐coil into a crystalline globule occurs. This vanishing of the liquid globule state is similar to the vanishing of the vapour‐liquid coexistence found for colloidal suspensions interacting by a short‐ ranged attraction.
Monte Carlo Computer Simulation of a Single Semi‐Flexible Macromolecule at a Plane Surface
Authors: Ivanov Victor A. , Martemyanova Julia A.
Published: June 2007

Summary: The properties of a single semiflexible mushroom chain at a plane surface with a long‐ranged attracting potential are studied by means of lattice Monte Carlo computer simulation using the bond fluctuation model, configurational bias algorithm for chain re‐growing and the Wang‐Landau sampling technique. We present the diagram of states in variables temperature T vs. strength of the adsorption potential, εw, for a quite short semiflexible chain consisting of N = 64 monomer units. The diagram of states consists of the regions of a coil, liquid globule, solid isotropic globule, adsorbed coil and cylinder‐like liquid‐crystalline globule. At low values of the adsorption strength εw the coil–globule and the subsequent liquid–solid globule transitions are observed upon decreasing temperature below the adsorption transition point. At high values of εw these two transitions change into a single transition from an adsorbed coil to a cylinder‐like liquid‐crystalline solid globule. We conclude that for a semiflexible chain the presence of a plane attracting surface favors the formation of a globule with internal liquid‐crystalline ordering of bonds.
Polymer Brushes on Flat and Curved Substrates: Scaling Concepts and Computer Simulations
Authors: Dimitrov Dimitar , Milchev Andrey , Binder Kurt
Published: June 2007

Summary:The scaling concepts for isolated flexible macromolecules in good solvent grafted with one chain end to a flat surface (“polymer mushrooms”) as well as for layers of many overlapping end‐grafted chain molecules (“polymer brushes”) are introduced. Monte Carlo attempts to test these concepts are briefly reviewed. Then the extension of these concepts to polymer brushes grafted to the interior of a cylinder surface is discussed. Molecular Dynamics results on chain average linear dimensions in the direction normal to the grafting surface and in axial direction are described, as well as distribution functions for the density of end monomers and of all monomers of the chains. It is argued that under typical conditions reachable in either simulation or experiment the data fall in a crossover regime, where no simple power‐laws (as derived from the scaling description) hold. Moreover, extensions of the Daoud‐Cotton blob picture to the cylinder geometry, implying that each chain in such a cylindrical brush is confined into a conical sector, are invalid; thus, chain ends in densely filled cylinders are not restricted to stay in the “hemicylinder” containing the grafting site of the chain.
Simulation of Copolymer Bottle‐Brushes
Authors: Hsu Hsiao‐Ping , Paul Wolfgang , Binder Kurt
Published: June 2007

Summary:The structure of bottle‐brush polymers with a rigid backbone and flexible side chains is studied in three dimensions, varying the grafting density, the side chain length, and the solvent quality. Some preliminary results of theoretical scaling considerations for one‐component bottle‐brush polymers in a good solvent are compared with Monte Carlo simulations of a simple lattice model. For the simulations a variant of the pruned‐enriched Rosenbluth method (PERM) allowing for simultaneous growth of all side chains in the Monte Carlo sampling is employed. For a symmetrical binary (A,B) bottle‐brush polymer, where two types (A,B) of flexible side chains are grafted with one chain end to the backbone in an alternating way, varying repulsive binary interactions between unlike monomers and the solvent quality, it is found that phase separation into anA‐rich part of the cylindrical molecule and aB‐rich part can occur only locally. Long range order (in the direction of the backbone) does not occur, and hence the transition from the randomly mixed state of the bottle‐brush to the phase‐separated structure is strongly rounded, in contrast to the corresponding mean field predictions of a sharp transition to a “Janus cylinder” phase‐separated structure. This lack of a phase transition can be understood from an analogy with spin models in one dimension. By estimating the correlation length for this phase separation along the backbone as a function of side chain length and solvent quality, we present strong evidence that no sharp phase transition occurs.
New Results in Weak Segregation Limit Theory of Block Copolymers
Authors: Kuchanov Semion
Published: June 2007

Summary:Some theoretical results recently obtained in papers with participation of the author in the field of statistical thermodynamics of block copolymers are briefly discussed.
Molecular Dynamic Simulation of Side‐Chain Liquid Crystalline Elastomer Under Load
Authors: Darinskii Anatoly A. , Zarembo Anna , Balabaev Nikolai K.
Published: June 2007

Summary:We present a molecular dynamic simulation of a side chain liquid crystalline elastomer (LCE) under load. The LCE is composed of a flexible tetrafunctional diamond like network with rod‐like mesogens attached to the network. As a precursor of the LC elastomer a flexible polymer network in a low molecular liquid‐crystal (LC) solvent was used. The phase behavior of the LCE under uniaxial stretching up to the deformations ofλ = 1.5 and 2.0 at different densities was studied. As in the non‐stretched case upon density increase an isotropic to nematic phase transition occurs. However, in contrast to thermotropic side chain LC elastomers the stress induced shift transition is not observed. The stretching slightly increases the anisotropy of translational diffusion of mesogens in the nematic state. The stress‐strain dependence for LCE both in the isotropic and the nematic states is obtained. Elastic modulus increases at high values of order parameter.
Charged Semi‐Permeable Shell with Encapsulated Polyions: Concentration Profile, Surface Potential, and Electrostatic Pressure
Authors: Tsekov Roumen , Vinogradova Olga I.
Published: June 2007

Summary: We study theoretically the electrostatic equilibrium for a charged shell filled with a suspension of polyions (e.g., colloids, polyelectrolytes, etc.) and immersed in an infinite salt‐free reservoir. The shell is impermeable for polyions, but allows free diffusion of counterions. From the solution of the linearized Poisson‐Boltzmann equation we obtain the distribution of the potential and concentration profiles for polyions. We then derive explicit formulas for the electrostatic pressure exerted by the shell. If the overall charge of the filled shell has the same sign as the surface alone the pressure on the shell increases with increase of the surface charge density. Otherwise the surface charge density suppresses the electro‐osmotic pressure due to the electrostatic attraction between the oppositely charged polyions and shell.
Polyamine‐mediated regulation of protein acetylation in murine skin and tumors
Authors: Wei Gang , Hobbs Cheryl A. , DeFeo Karen , Hayes Candace S. , Gilmour Susan K.
Published: June 2007

Overexpression of ornithine decarboxylase (ODC), resulting in increased polyamine metabolism, is a common feature of epithelial tumors. Polyamines play a complex role in promoting tumor development, affecting diverse cellular processes, including gene expression. One way polyamines may affect gene expression is to modulate the multiprotein complexes comprised of transcription factors and coregulatory factors that alter chromatin structure by acetylating/deacetylating nearby histones. We have capitalized on ODC‐overexpressing cultured cells and K6/ODC and ODC/Ras transgenic mouse models, in which ODC overexpression is targeted to hair follicles, to evaluate the influence of polyamines on the acetylation of histones and other proteins. ODC overexpression was found to alter intrinsic histone acetyltransferase (HAT) and deacetylase activities and histone acetylation patterns. The high HAT activity exhibited by ODC transgenic mouse skin and tumors might be partly attributed to enhanced p300/creb‐binding protein (CBP)‐associated HAT activity and increased levels of Tat interactive protein, 60 kDa (Tip60) HAT protein isoforms. Altered association of Tip60 with E2F1 and a subset of newly identified Tip60‐interacting transcription factors was detected in ODC mouse skin and tumors, implying novel polyamine modulation of Tip60‐regulated gene expression. Polyamine effects on HAT enzymes also influence the acetylation status of nonhistone proteins. Overexpression of ODC in skin serves as a novel stimulus for acetylation of the tumor suppressor protein, p53—a target of both p300/CBP and Tip60—with concomitant increased binding to, and increased transcription of, a downstream target gene. The future challenge will be to elucidate the multiple mechanisms by which polyamines influence enzymes that regulate protein acetylation and gene transcription to promote cancer. © 2007 Wiley‐Liss, Inc.
Explicit solutions of the one‐dimensional Vlasov–Poisson system with infinite mass
Authors: Pankavich Stephen
Published: June 2007

A collisionless plasma is modelled by the Vlasov–Poisson system in one dimension. A fixed background of positive charge, dependent only upon velocity, is assumed and the situation in which the mobile negative ions balance the positive charge as |x| → ∞ is considered. Thus, the total positive charge and the total negative charge are infinite. In this paper, the charge density of the system is shown to be compactly supported. More importantly, both the electric field and the number density are determined explicitly for large values of |x|. Copyright © 2007 John Wiley & Sons, Ltd.
Riccati equation‐based generalization of Dawson's integral function
Authors: Messina R. , Jivulescu M. A. , Messina A. , Napoli A.
Published: June 2007

A new generalization of Dawson's integral function based on the link between a Riccati nonlinear differential equation and a second‐order ordinary differential equation is reported. The MacLaurin expansion of this generalized function is built up and to this end an explicit formula for a generic cofactor of a triangular matrix is deduced. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative analysis of mitochondrial RNA in goat–sheep cloned embryos
Authors: Ma Li‐Bing , Yang Li , Zhang Yong , Cao Jun‐Wei , Hua Song , Li Ji‐Xia
Published: June 2007

Mitochondria are the key generators of cellular ATP, and contain extranuclear genome‐mitochondrial DNA (mtDNA). In the process of nuclear transfer (NT), heteroplasmic sources of mtDNA from a donor cell and a recipient oocyte are mixed in the cytoplasm of the reconstituted embryo. Previous studies showed inconsistent patterns of mtDNA inheritance in offspring and early fetuses generated through interspecies NT. The quantitative analysis of mitochondrial RNA (mtRNA) in interspecies cloned embryos is useful for better understanding the fate of two types of mitochondria. The components of nicotinamide adenine dinucleotide (NADH) dehydrogenase were coded by both nuclear DNA (nDNA) and mtDNA. The Subunit 1 (ND‐1) is one of seven NADH dehydrogenase subunits coded by mtDNA. In present study, using real‐time and reverse‐transcription PCR, the copy number of species‐specific ND‐1 mRNA was examined in goat–sheep cloned embryos of various developmental stages, and was applied to evaluate the expression pattern of species‐specific mtDNA. The results of showed that (1) the expression of mtDNA derived from goat fetal fibroblast (GFF) decreased from 1‐cell stage (immediately after fused) to 2‐cell stage, and could not be detected from 4‐cell stage onward to blastocyst stage; (2) the expression of mtDNA derived from sheep oocyte was roughly constant from 1‐cell stage to the 8‐cell stage, increased gradually from 16‐cell stage, and sharply at morula and blastocyst stage. Moreover, we strongly argued a mechanism, that is GFF‐derived mitochondria were degraded for the depression of bioenergetic functions, and then selectively eliminated during the embryogenesis of goat‐sheep cloned embryos. Mol. Reprod. Dev. 75: 33–39, 2008. © 2007 Wiley‐Liss, Inc.
Bifurcation and instability modelling by a multimechanism elasto‐plastic model
Authors: Hamadi Kamel , Modaressi‐Farahmand Razavi Arézou , Darve Félix
Published: June 2007

The bifurcation and instability conditions in geomechanics are closely related to the elasto‐plastic behaviour. In this paper the potential of a multimechanism elasto‐plastic model to predict various modes of failure is examined. First, a brief overview for the essential aspects of the constitutive model and the development of the elasto‐plastic constitutive matrix for this model are presented. Then, numerical simulations of different drained and undrained paths in the axisymmetric and plane‐strain conditions for the Hostun sand are illustrated. These examples confirm the capacity of the model to reproduce instability and strain localization phenomena. The
obtained response is in agreement with experimental observations, theoretical developments and numerical analyses existing in the literature. Copyright © 2007 John Wiley & Sons, Ltd.
The impact of manufacturer rebates on supply chain profits
Authors: Chen Xin , Li Chung‐Lun , Rhee Byong‐Duk , Simchi‐Levi David
Published: June 2007

Manufacturer rebates are commonly used as price discount tools for attracting end customers. In this study, we consider a two‐stage supply chain with a manufacturer and a retailer, where a single seasonal product faces uncertain and price‐sensitive demand. We characterize the impact of a manufacturer rebate on the expected profits of both the manufacturer and the retailer. We show that unless all of the customers claim the rebate, the rebate always benefits the manufacturer. Our results thus imply that “mail‐in rebates,” where some customers end up not claiming the rebate, particularly when the size of the rebate is relatively small, always benefit the manufacturer. On the other hand, an “instant rebate,” such as the one offered in the automotive industry where every customer redeems the rebate on the spot when he/she purchases a car, does not necessarily benefit the manufacturer. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007
In vivo MRI using positive‐contrast techniques in detection of cells labeled with superparamagnetic iron oxide nanoparticles
Authors: Liu Wei , Dahnke Hannes , Jordan E. Kay , Schaeffter Tobias , Frank Joseph A.
Published: June 2007

Positive‐contrast techniques are being developed to increase the detection of magnetically labeled cells in tissues. We evaluated a post‐processing positive‐contrast technique, susceptibility‐gradient mapping (SGM), and compared this approach with two pulse sequences, a gradient‐compensation‐based “White Marker” technique and an off‐resonance‐based approach, inversion recovery on‐resonance water suppression (IRON), for the detection of superparamagnetic iron oxide (SPIO) nanoparticle‐labeled C6 glioma cells implanted in the flanks of nude rats. The SGM, White Marker and IRON positive‐contrast images were acquired when the labeled C6 glioma tumors were ∼5 mm (small), ∼10 mm (medium) and ∼20 mm (large) in diameter along the largest dimension to evaluate their sensitivity to the dilution of the SPIO nanoparticles as the tumor cells proliferated. In vivo MRI demonstrated that all three positive‐contrast techniques can produce hyperintensities in areas around the labeled flank tumors against a dark background. The number of positive voxels detected around small and medium tumors was significantly greater with the SGM technique than with the White Marker and IRON techniques. For large tumors, the SGM resulted in a similar number of positive voxels to the White Marker technique, and the IRON approach failed to generate positive‐contrast images with a 200 Hz suppression band. This study also reveals that hemorrhage appears as hyperintensities on positive‐contrast images and may interfere with the detection of SPIO‐labeled cells. Published in 2007 by John Wiley & Sons, Ltd.
Robust capacity expansion of network flows
Authors: Ordóñez Fernando , Zhao Jiamin
Published: June 2007

We consider the problem of expanding arc capacities in a network subject to demand and travel time uncertainty. We propose a robust optimization approach to obtain capacity expansion solutions that are insensitive to this uncertainty. Our results show that, under reasonable assumptions for network flow applications, such robust solutions can be computed by solving tractable conic linear problems. For example, the robust solution for a multicommodity flow problem is obtained by solving a linear program if the problem has a single source and sink per commodity and the uncertainty in demand and travel time is given by independent bounded polyhedral sets. Preliminary computational results show that the robust solution is attractive, as it can reduce the worst case cost by more than 20%, while incurring a 5% loss in optimality when compared to the optimal solution of a representative scenario. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 136–145 2007
On stochastic programs over trees with partially dependent arc capacities
Authors: Shi Ning , Cheung Raymond K. , Song Haiqing
Published: June 2007

We study the new problem of stochastic programs over trees with dependent random arc capacities. This problem can be used as a subproblem in decomposition methods that solve multi‐stage networks with independent random arc capacities and random travel times. An efficient algorithm is provided to compute the expected total cost. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 157–163 2007
Multiterminal resilience for series‐parallel networks
Authors: Farley Toni R. , Colbourn Charles J.
Published: June 2007

Network resilience measures the average two‐terminal reliability (connectedness) of a network. Multiterminal resilience extends this measure to any k vertices; it is the average k‐terminal reliability of a network. This generalizes two well‐studied network connectedness measures. Calculating multiterminal resilience on general networks encompasses all‐terminal reliability and thus is NP‐hard. Multiterminal resilience is examined on undirected series‐parallel networks, and an efficient (polynomial time) algorithm is developed for calculating the resilience for every k. Applications in mobile ad hoc and sensor networks are outlined. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 164–172 2007
Matching preclusion for some interconnection networks
Authors: Cheng Eddie , Lipták László
Published: June 2007

The matching preclusion number of a graph is the minimum number of edges whose deletion results in a graph that has neither perfect matchings nor almost‐perfect matchings. In this paper, we find this number for various classes of interconnection networks and classify all the optimal solutions. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 173–180 2007
A highly accurate collocation Trefftz method for solving the Laplace equation in the doubly connected domains
Authors: Liu Chein‐Shan
Published: June 2007

A highly accurate new solver is developed to deal with the Dirichlet problems for the 2D Laplace equation in the doubly connected domains. We introduce two circular artificial boundaries determined uniquely by the physical problem domain, and derive a Dirichlet to Dirichlet mapping on these two circles, which are exact boundary conditions described by the first kind Fredholm integral equations. As a direct result, we obtain a modified Trefftz method equipped with two characteristic length factors, ensuring that the new solver is stable because the condition number can be greatly reduced. Then, the collocation method is used to derive a linear equations system to determine the unknown coefficients. The new method possesses several advantages: mesh‐free, singularity‐free, non‐illposedness, semi‐analyticity of solution, efficiency, accuracy, and stability. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
A family of conservative finite difference schemes for the dynamical von Karman plate equations
Authors: Bilbao Stefan
Published: June 2007

Numerical methods for nonlinear plate dynamics play an important role across many disciplines. In this article, the focus is on numerical stability for numerical methods for the von Karman system, through the use of energy‐conserving methods. It is shown that one may take advantage of structure particular to the system to construct numerical methods, which are provably numerically stable, and for which computer implementation is simplified. Numerical results are presented. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Approximation and eigenvalue extrapolation of biharmonic eigenvalue problem by nonconforming finite element methods
Authors: Jia Shanghui , Xie Hehu , Yin Xiaobo , Gao Shaoqin
Published: June 2007

In this paper, we analyze the biharmonic eigenvalue problem by two nonconforming finite elements, Q and E Q. We obtain full order convergence rate of the eigenvalue approximations for the biharmonic eigenvalue problem based on asymptotic error expansions for these two nonconforming finite elements. Using the technique of eigenvalue error expansion, the technique of integral identities, and the extrapolation method, we can improve the accuracy of the eigenvalue approximations. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Integration of high‐risk human papillomavirus: a key event in cervical carcinogenesis?
Authors: Pett M , Coleman N
Published: June 2007

An important occurrence in cervical carcinogenesis is deregulated expression of the high‐risk human papillomavirus (HR‐HPV) oncogenes E6 and E7. Several risk factors for cervical neoplastic progression are likely to contribute to viral oncogene deregulation, particularly integration of HR‐HPV into the host genome. Integration represents a by‐product of viral infection that is detected in almost 90% of cervical carcinomas. The mechanism of integration is not fully understood, although there is a clear predilection for chromosomal common fragile sites, most likely due to their accessibility for insertion of foreign DNA. Recent work has suggested that an important intermediate stage in cervical carcinogenesis is characterized by transcriptionally silent HR‐HPV integrants, which co‐exist with viral episomes in infected cells. As episome‐derived E2 protein inhibits integrant transcription, clearance of episomes (eg by host innate immunity) is associated with loss of integrant silencing and integrant selection. The process of integration and subsequent clonal selection of integrants can therefore be considered as two independent and biologically distinct events. Indeed, integrated HPV may be viewed as selectable because it represents a form of the virus that is resistant to host mechanisms of viral clearance, enabling infected cells to maintain viral oncogene expression and avoid cell death. Care should be taken in interpreting studies of HPV integration frequency in clinical samples, as the techniques used have assessed either the presence of integrated viral DNA or evidence of transcriptional activity from integrants, but not both. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Methylation of tumor‐suppressor genes in neuroblastoma: The RASSF1A gene is almost always methylated in primary tumors
Authors: Michalowski Mariana Bohns , de Fraipont Florence , Plantaz Dominique , Michelland Sylvie , Combaret Valérie , Favrot Marie‐Christine
Published: June 2007

Background

Currently, the best characterized genetic aberration in neuroblastoma (NB) is MYCN amplification, which has been clearly related to prognosis. In the present study, we investigated whether specific epigenetic alterations are associated with stage of disease.

Procedure

Sixty‐two NBs (45 primary tumors and 17 NBs at relapse) were studied in terms of the methylation status of 19 genes (p15INK4a, p16INK4a, p14ARF, APC, RB1, RASSF1A, BLU, FHIT, RARβ, INI1, TIMP3, NF2, MGMT, DAPK, FLIP, ECAD, CASP8, and the receptors DcR1 and DcR2).

Results

At diagnosis, we found hypermethylation of RASSF1A in 93% of these tumors, hypermethylation of TIMP3 in 51%, of CASP8 in 38%, of BLU in 34%, of DcR2 in 25%, and of DcR1 in 11%. All 17 tumors tested at relapse showed hypermethylation of RASSF1A (100%), while 10 showed hypermethylation of TIMP3 (59%), six of CASP8 (35%), five of DcR2 (29%), four of BLU (24%), and three of DcR1 (18%). Hypermethylation was related to clinical stage; NBs at stages 1, 2, and 4s were less frequently methylated than stages 3 and 4 disease (P = 0.002).

Conclusion

These results from our series indicate that hypermethylation of tumor‐suppressor genes may be important in the development and evolution of NB. These epigenetic alterations could be used as a marker of the disease and genes regulating methylation should be considered as possible therapeutic targets in NB. Pediatr Blood Cancer 2008;50:29–32. © 2007 Wiley‐Liss, Inc.
Reducing irinotecan‐associated diarrhea in children
Authors: Wagner Lars M. , Crews Kristine R. , Stewart Clinton F. , Rodriguez‐Galindo Carlos , McNall‐Knapp Rene Y. , Albritton Karen , Pappo Alberto S. , Furman Wayne L.
Published: June 2007

Irinotecan is increasingly being used in pediatric oncology. Amelioration of diarrhea associated with protracted irinotecan administration may reduce morbidity and improve dose intensity. In this review, we discuss what is known about the pathogenesis of this toxicity as well as potential predisposing genetic factors. We comprehensively summarize the literature regarding available prevention and treatment strategies, and report data on the use of cephalosporin prophylaxis in 51 patients treated on various pediatric trials. This approach is feasible in children and allows for tolerance of higher doses of protracted irinotecan. Pediatr Blood Cancer 2008; 50:201–207. © 2007 Wiley‐Liss, Inc.