bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of material properties of cancellous bone using multiscale FEM
Authors: Ilic S. , Hackl K. , Gilbert R.
Published: August 2008

Cancellous bone is a spongy type of bone with voids filled by blood marrow. Without much loss of generality it can be modeled as a material with periodic microstructure where overall parameters can be calculated using homogenization methods. Here the multiscale finite element method is applied and the assumed representative volume element (RVE) is a cube with solid frame and fluid core. From the point of view of the finite element method the RVE is a combination of solid and shell elements. As the acoustic excitation is considered, a complex stiffness matrix and complex displacements appear in the solution of the problem. Calculation of overall properties is repeated for different geometries of the solid frame. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of the conditional moments method to multi‐layered anisotropic shells
Authors: Müller Wolfgang H. , Nazarenko Lidija , Wille Ralf
Published: August 2008

In this paper the so‐called Conditional Moments Method (CMM) is explained, which allows investigating the stress‐strain state of stochastic composites under externally applied loads. This technique is used to determine effective (homogenized) material properties and, in particular, preparatory measures are taken, which eventually will allow to assess the deformation behavior of tires. The tire shells are modeled as a rubber matrix strengthened by metal or cord fibers. For this reason general CMM results will be specialized to the case of ellipsoidal inclusions of arbitrary aspect ratios in a matrix of various stiffness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A generalization of Cahn‐Hilliard inpainting for grayvalue images
Authors: Burger Martin , He Lin , Markowich Peter , Schönlieb Carola‐Bibiane
Published: August 2008

The Cahn‐Hilliard equation has its origin in material sciences and serves as a model for phase separation and phase coarsening in binary alloys. A new approach in the class of fourth order inpainting algorithms is inpainting of binary images using the Cahn‐Hilliard equation. We will present a generalization of this fourth order approach for grayvalue images. This is realized by using subgradients of the total variation functional within the flow, which leads to structure inpainting with smooth curvature of level sets. We will present some numerical examples for this approach and analytic results concerning existence and convergence of solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mathematical model for lifetime prediction of lacquer‐paint coatings in sea water
Authors: Shevchuk Victor A. , Shevchuk Pavlo R.
Published: August 2008

Main features of the mechanism of lacquer‐paint coatings destruction in sea water have been revealed. On this basis, a mathematical model has been developed and boundary value problems of mathematical physics have been formulated to calculate the determining processes on characteristic stages of coatings in sea water. The theoretical evaluation of coatings longevity depending on physical characteristics of the system has been made. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reliable safety analysis with continuous‐time models
Authors: Lin Youdong , Stadtherr Mark A.
Published: August 2008

Using a recently developed method for the guaranteed solution of interval‐valued ODE problems, we extend the regiontransition approach for process safety analysis to continuous‐time models. This makes it possible to identify, with certainty, regions of operating space that are safe, unsafe, or lead to off‐spec product. The analysis can be done in the presence of uncertain model parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical valuation of options under Kou's model
Authors: Toivanen Jari
Published: August 2008

Numerical methods are developed for pricing European and American options under Kou's jump‐diffusion model which assumes the price of the underlying asset to behave like a geometrical Brownian motion with a drift and jumps whose size is log‐double‐exponentially distributed. The price of a European option is given by a partial integro‐differential equation (PIDE) while American options lead to a linear complementarity problem (LCP) with the same operator. Spatial differential operators are discretized using finite differences on nonuniform grids and time stepping is performed using the implicit Rannacher scheme. For the evaluation of the integral term easy to implement recursion formulas are derived which have optimal computational cost. When pricing European options the resulting dense linear systems are solved using a stationary iteration. Also for pricing American options similar iterations can be employed. A numerical experiment demonstrates that the described method is very efficient as accurate option prices can be computed in a few milliseconds on a PC. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On linear programming bounds for nets
Authors: Schmid Wolfgang Ch. , Trinker Horst
Published: August 2008

It is well known that there are close connections between low‐discrepancy point sets and sequences on the one hand, and certain combinatorial and algebraic structures on the other hand. E. g., Niederreiter [1] showed the equivalence between (t, t + 2, s)‐nets and orthogonal arrays of strength 2. Some years later this was generalized and made precise in the work of Lawrence [2] as well as Mullen and Schmid [3] by introducing ordered orthogonal arrays. This large class of combinatorial structures yields both new constructions and bounds for the existence of nets and sequences.

The linear programming bound for ordered orthogonal arrays was first derived by Martin and Stinson [4]. As in the case of error‐correcting codes and orthogonal arrays, it yields a very strong bound for ordered orthogonal arrays, and consequently for nets and sequences.

Solving linear programming problems in exact arithmetics is very time‐consuming. Using different approaches to reduce the computing time, we have calculated the linear programming bound for a wide parameter range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Matching and stabilization of discrete mechanical systems
Authors: Bloch Anthony M. , Leok Melvin , Marsden Jerrold E. , Zenkov Dmitry V.
Published: August 2008

Controlled Lagrangian and matching techniques are developed for the stabilization of equilibria of discrete mechanical systems with symmetry as well as broken symmetry. Interesting new phenomena arise in the controlled Lagrangian approach in the discrete context that are not present in the continuous theory. Specifically, a nonconservative force that is necessary for matching in the discrete setting is introduced. The paper also discusses digital and model predictive controllers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stable deep‐water waves propagating in one and two dimensions
Authors: Henderson Diane , Segur Harvey
Published: August 2008

Deep‐water, narrow‐banded wavetrains of uniform amplitude propagating in one horizontal dimension were shown to be unstable to small perturbations with nearly the same frequency and direction about 40 years ago. More recently, interactions of two narrow‐banded wavetrains of uniform amplitude propagating in arbitrary directions were shown to be similarly unstable. In both cases, the instabilities have been described by either a single nonlinear Schrödinger (NLS) equation or by two coupled NLS equations. However, the inclusion in these equations of any amount of damping (of a particular type) stabilizes the instabilities. Experiments show that the evolution of perturbed wavetrains in both cases is more accurately described by the NLS models that include damping when the amplitudes are small or moderate. When the amplitude of either the underlying waves or the perturbations is large, neither the undamped NLS model nor the damped NLS model accurately predicts the observed behaviour, which includes frequency downshifting. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical eigenmode analysis of an acoustic‐duct system by CFD‐OLTF and comparison against experiment
Authors: Neunert Urban , Kopitz Jan , Sattelmayer Thomas , Polifke Wolfgang
Published: August 2008

In this contribution, a novel approach to determine acoustic eigenmodes in duct systems is presented. The approach combines Computational fluid dynamics, classical Network models of duct acoustics and the Nyquist criterion known from control theory, and is therefore called CNN‐method. The method has been applied to a geometrically simple, but aero‐acoustically non‐trivial configuration – i.e. a sudden change in cross‐sectional area connecting two ducts with non‐zero mean flow – and validated against experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal operation for a river fishway
Authors: Alvarez‐Vázquez L.J. , Martínez A. , Vázquez‐Méndez M.E. , Vilar M.
Published: August 2008

In this paper we present an optimal control problem related to the optimal management of a vertical slot fishway. We introduce the mathematical statement of the environmental problem, we derive an optimality condition for characterizing its optimal solutions, and we give an optimization algorithm for their numerical computation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse problems related to ion channels
Authors: Arning Kattrin , Burger Martin , Eisenberg Robert S. , Engl Heinz W. , He Lin
Published: August 2008

Ion channels are proteins with a hole down theirmiddle that allow ions to move across otherwise impermeable cellmembranes, thereby controlling many important physiological functions. The transport process of the ions can be described using the Poisson‐Nernst‐Plank equations, a system of coupled nonlinear partial differential equations. Based on this model we derive a simplified surrogate model that captures the main features of the associated current‐voltage curves of the ion channel. This surrogate model is then used to identify individual channel parameters based on current data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic spatial price equilibrium problem: regularity results and computational procedure
Authors: Barbagallo Annamaria
Published: August 2008

In this paper we consider the dynamic spatial price equilibrium problem and the associated evolutionary variational inequality. In particular the regularity of equilibrium solutions is studied and a method for solving the dynamic spatial price equilibrium problem is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subcritical instability of liquid metal channel flow in the presence of a spanwise magnetic field
Authors: Boeck Thomas , Krasnov Dmitry , Rossi Maurice , Zikanov Oleg
Published: August 2008

The linear and nonlinear evolution of perturbations is investigated in a magnetohydrodynamic channel flow with electrically insulating walls. The applied magnetic field is parallel to the walls and orthogonal to the stream. Linear optimal perturbations and their maximum amplifications over finite time intervals are computed using a scheme based on the direct and adjoint governing equations. It is shown that dominant optimal perturbations are no more the classical streamwise modes and how the flow is two‐dimenzionalized for high enough Hartmann numbers. For fixed Reynolds and Hartmann numbers, direct numerical simulations are applied to investigate how the transition to turbulence is affected by the magnetic field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence and multiplicity of solutions for elliptic problems with indefinite discontinuous nonlinearities
Authors: Calahorrano Marco
Published: August 2008

In this paper we study the critical points for a locally Lipschitz functional that in some sense will be solutions of an elliptic problem with indefinite discontinuous nonlinearities. We should mention that our results were inspired by the work of Ambrosetti‐Badiale [3], Arcoya‐Calahorrano [5], Alama‐Tarantello [1] and Chang [8]. For the problem studied in [3] we introduce indefinite nonlinearities as in [1] and [6]. To obtain the existence and multiplicity of solutions we use the critical points theory developed by Chang. Applications for Plasma Physics are considered with nonlinearities that change sign. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptives quadratures and fractional IDEs: Applications in image processing
Authors: Cuesta E.
Published: August 2008

In this paper we show adaptive time discretizations of a fractional integro–differential equation ∂αtu = Δu + f, where A is a linear operator in a complex Banach space X and ∂αt stands for the fractional time derivative, for 1 < α < 2. Some numerical illustrations are provided showing practical applications where the computational cost is one of drawbacks, e.g., some problems related to images processing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constructive approximations of spherical functions
Authors: Ganesh M. , Mhaskar H. N.
Published: August 2008

Approximation of functions on the sphere arises in almost all applications modeling data collected on the surface of the earth and for reconstruction of various processes in spherical coordinates. Constructive approximation of high dimensional spherical functions are useful for approximation of processes of several variables on a compact subset of a Euclidean space by mapping the data onto the unit sphere of a space having one higher dimension, avoiding the boundary effect of the set. Interpolation operators on the circle and periodic domains (based on a class of basis functions and data values) are essential for many high performance simulations. These operators are represented by analytical summation formulas that can be computed very efficiently using the fast Fourier transform. This work is concerned with construction of a similar class of interpolation and quasi‐interpolation operators on the unit sphere in ℝq , for q = 3, 4, 5, · · ·, using a new class of basis functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐order ADI method for stream‐function vorticity equations
Authors: Karaa Samir
Published: August 2008

Many recent works have demonstrated the efficiency of high‐order compact (HOC) difference schemes on the stream‐function and vorticity formulation of 2‐D incompressible Navier‐Stokes equations. HOC discretizations induce cross spatial derivatives which are treated explicitly in most ADI schemes. Recently, Karaa and Zhang proposed a fourth‐order ADImethod for solving convection‐diffusion problems efficiently. In this work, we extend this method to the solution of incompressible Navier‐Stokes equations. The driven flow in a square cavity is used as a model problem and numerical results are compared with other results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel methods of pulse wave diagnostics based on compression of a superficial artery
Authors: Kizilova Natalya
Published: August 2008

Pulse wave propagation and reflection in the branching systems of viscoelastic tubes and complex resistances as a model of arterial vasculature is considered. Axisymmetric wave motion of a viscous incompressible liquid in the system is investigated in application to the pressure and flow wave propagation in the system. Expression for the input admittance of the system taking into account wave reflection at the end of the tube is obtained. The dependence of the input admittance on the geometrical and mechanical parameters of the system is investigated. It is shown that the parameters of the pressure wave (the modules and phases of different harmonics) at the inlet of the system give information on the state (normal or pathological) of the inner organs. It is shown that after a proper compression (slight or deep) some harmonics can be amplified while the others are attenuated. Based on the theory of resonant harmonics of different inner organs the novel method of pulse wave palpation is proposed. The results are compared to some other methods as separation of the pressure wave into the forward and backward components, estimation of the parameters of the reflected wave and wave‐intensity analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A variational approach to optimal control problems for elastic body motions
Authors: Kostin G. , Saurin V.
Published: August 2008

The initial‐boundary problem for the linear theory of elasticity is considered. Based on the method of integrodifferential relations a new dynamical variational principle in which displacement, stress, and momentum functions are varied is proposed and discussed. To minimize the nonnegative functional under initial, boundary, and partial differential constraints arising in this approach a regular algorithm for approximation of the unknown functions is worked out. The algorithm gives us the possibility to estimate explicitly the local and integral quality of obtained numerical solutions. An effective numerical method for the optimization problems of controlled motions of elastic bodies with quadratic objective functionals is developed. As example, the 3D problems of optimal longitudinal motions of a rectilinear elastic prism with a quadratic cross section are considered for the terminal total mechanical energy to be minimized. The numerical results and their error estimates are presented and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An application of parabolic H‐measures
Authors: Antonić Nenad , Lazar Martin
Published: August 2008

A new, parabolic variant of H‐measures, as well as its application to the advection‐diffusion equation is presented. By the means of localisation property, the strong compactness for gradients of solutions is obtained in the case of variable coefficients. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DNA supercoiling modeling of nucleosome and viral spooling
Authors: Maggioni Francesca , Ricca Renzo L.
Published: August 2008

New kinematic equations are used to model DNA supercoiling. These equations govern the simultaneous production of multiple folding and coiling of a filament in space by diffeomorphism of a reference curve. Here we show how to use these equations to model regions of highly localized filament coiling, where mechanisms of proteic coding or viral spooling are important. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the interconnection structures of discretized port Hamiltonian systems
Authors: Eberard D. , Maschke B.M. , van der Schaft A.J.
Published: August 2008

For numerical simulation and control design purposes, a mixed‐finite element method [3] preserving the port Hamiltonian structure of the system has been developed [2]. This method was successfully applied for 1D systems. In this paper, we shall suggest some generalization of this result to higher dimensional spatial domain (3D) using Whitney forms as Galerkin base. The discretization procedure is illustrated on Maxwell's equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Verifying all eigenpairs in symmetric positive definite generalized eigenvalue problem
Authors: Miyajima Shinya , Ogita Takeshi , Oishi Shin'ichi
Published: August 2008

A fast method for enclosing all eigenpairs in symmetric positive definite generalized eigenvalue problem is proposed. Firstly theorems on verifying all eigenvalues are presented. Next a theorem on verifying all eigenvectors is presented. The proposed method is developed based on these theorems. Numerical results are presented showing the efficiency of the proposed method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fractional amplitude and phase dynamics in super‐diffusive reaction–diffusion systems
Authors: Nec Y. , Nepomnyashchy A.A. , Golovin A.A.
Published: August 2008

Study of weakly non‐linear dynamics of a reaction–super‐diffusion system near a Hopf bifurcation by means of fractional analogues of complex Ginzburg‐Landau and Kuramoto‐Sivashinsky equations is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error estimates for an Euler implicit‐mixed finite element scheme for reactive transport in saturated/unsaturated soil
Authors: Radu Florin A. , Pop Iuliu S. , Attinger Sabine , Knabner Peter
Published: August 2008

We present convergence results for a fully discrete scheme based on the mixed finite element (MFE) method and an one‐step Euler implicit (EI) method for simulating reactive solute transport in saturated/unsaturated soil. The results considered the low regularity of the solution of the degenerate parabolic equation describing the water flow in porous media. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of tear propagation in soft hydrated biological tissue
Authors: Rempler Hans‐Uwe , Ehlers Wolfgang
Published: August 2008

We present a method for the numerical simulation of tear propagations in soft hydrated biological tissues. The tissue is modelled using the Theory of Porous Media (TPM) which allows the description of multi‐component continua with internal interaction. For the numerical treatment of the tearing mechanism, the Extended Finite Element Method (XFEM) is applied. Discontinuities resulting from the tearing are numerically described by a vector level‐set function. Volume changes due to the tear propagation are taken into account with a formulation of internal fluid flow towards the additional volume. Therein, fluid flow is regarded as an internal Neumann boundary. A numerical example shows the pressure development and fluid flow during a mode 1 tearing experiment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mixed finite element formulation for piezoelectric shells
Authors: Schulz Katrin , Klinkel Sven
Published: August 2008

A finite element formulation to analyze piezoelectric shell problems is presented. A reference surface of the shell is modelled with a four node element. Each node possesses six mechanical degrees of freedom, three displacements and three rotations, and one electric degree of freedom, which is the difference of the electric potential in thickness direction. The formulation is based on the mixed field variational principle of Hu‐Washizu. The independent fields are displacements u, electric potential φ, strains E, electric field E, stresses S and dielectric displacements D. The mixed formulation allows an interpolation of the strains and the electric field in thickness direction. Accordingly a three‐dimensional material law is incorporated in the variational formulation. It is remarked that no simplification regarding the constitutive law is assumed. The formulation allows the consideration of arbitrary constitutive relations. The normal zero stress condition and the normal zero dielectric displacement condition are enforced by the independent stress and dielectric displacement fields. They are defined as zero in thickness direction. The present shell element fulfills the important patch tests: the in‐plane, bending and shear test. Some numerical examples demonstrate the applicability of the present piezoelectric shell element. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accelerating the coarse time‐stepper for a lattice Boltzmann model
Authors: Vandekerckhove Christophe , Roose Dirk
Published: August 2008

The equation‐free framework for multiscale computing is built around the central idea of a coarse time‐stepper, which is an approximate time integrator for the macroscopic variables when only a microscopic simulator is available. In a previous paper, we studied the accuracy and stability of the coarse time‐stepper when the microscopic simulator is a lattice Boltzmann model for one‐dimensional diffusion. In this paper, we rely on these results to show how the coarse time‐stepper can be accelerated using the recently proposed teleprojective method or the multistep state extrapolation method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A variational formulation of nonlocalmaterials withmicrostructure based on dual macro‐ and micro‐balances
Authors: Welschinger Fabian , Zimmermann Dominik , Miehe Christian
Published: August 2008

We investigate a variational setting of nonlocal materials with microstructure and outline aspects of its numerical implementation. Thereby, the current state of the evolving microstructure is described by independent global degrees in addition to the macroscopic displacement field, so‐called order parameters. Focussing on standard‐dissipative materials, the constitutive response is governed by two fundamental functions for the energy storage and the dissipation. Based on these functions, a global dissipation postulate is introduced. Its exploitation constitutes a global variation formulation of nonlocal materials, which can be related to a minimization principle. Following this methodology, we end up with coupled macro‐ and microscopic field equations and corresponding boundary conditions. On the numerical side, we consider the weak counterpart of these coupled field equations and obtain after linearization a fully coupled system for increments of the displacement and the order parameters. Due to the underlying variational structure, this system of equations is symmetric. In order to show the capability of the proposed setting, we specify the above outlined scenario to a model problem of isotropic damage mechanics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DNS of laminar separation nubble flows with free‐stream fluctuations
Authors: Wissink Jan G. , Rodi Wolfgang
Published: August 2008

A series of Direct Numerical Simulations (DNS) of Laminar Separation Bubble (LSB) flow in the presence of external disturbances has been performed. In all simulations, the primary mechanism for the transition to turbulence was found to be a two‐dimensional Kelvin‐Helmholtz (KH) instability of the separated shear layer that was triggered by the external fluctuation(s). The KH instability caused the shear layer to roll up. Inside the rolled up shear layer, entrained disturbances triggered elliptic instabilities which led to a rapid transition to fully three‐dimensional (3D) turbulence. In the simulations with inflow oscillations the streamwise variation of the location of transition was found to decrease with the amplitude of the inflow oscillation. In the simulations with free‐stream turbulence the size of the separation bubble – measured by the shape factor – was found to drastically decrease with increasing free‐stream turbulence level. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and properties of new derivatives of poly[9‐(2,3‐epoxypropyl)carbazole]
Authors: Malinauskas Tadas , Vilionskiene Ingrida , Grazulevicius Juozas V , Getautis Vytautas , Reina Jose A , Sidaravicius Jonas
Published: August 2008

BACKGROUND: Carbazole derivatives are well known to exhibit interesting electro‐ and photo‐active properties due to their hole‐transporting ability, strong absorption in the ultraviolet spectral region and blue‐light emission. One of the most widely studied materials among carbazole‐containing oligomers is poly[9‐(2,3‐epoxypropyl)carbazole] (PEPK). The main field of application of this oligomer is electrophotographic microfilming. It is also used for the manufacture of multicolour slides and in the photothermoplastic recording of information. Unfortunately, due to its high ionization potential, which reaches 5.86 eV, the possibilities of application of this compound in optoelectronic devices are rather limited.

RESULTS: PEPK‐based charge transporting oligomers, incorporating hydrazone moieties, are reported. The oligomers were prepared by chemical modification of PEPK. The materials obtained were examined using various techniques including differential scanning calorimetry and ultraviolet, infrared and NMR spectroscopy. Electron photoemission spectra of layers of the synthesized oligomers showed ionization potentials (Ip) in the range 5.4–5.5 eV.

CONCLUSION: The synthesized oligomers possess a larger π‐conjugated system and show ionization potentials of ca 5.4 eV. Therefore, they are more suitable for use in optoelectronic devices with quicker photoresponse than unmodified PEPK. Copyright © 2008 Society of Chemical Industry
Nonionic detergent phase extraction for the proteomic analysis of heart membrane proteins using label‐free LC‐MS
Authors: Donoghue Pamela M. , Hughes Chris , Vissers Johannes P. C. , Langridge James I. , Dunn Michael J.
Published: August 2008

Heart diseases resulting in heart failure are among the leading causes of morbidity and mortality in the Western world and can result from either systemic disease (e.g., hypertensive heart disease, ischemic heart disease) or specific heart muscle disease (e.g., dilated cardiomyopathy/DCM). Subproteome analysis of such disease subsets affords a reduction in sample complexity, potentially revealing biomarkers of cardiac failure that would otherwise remain undiscovered in proteome wide studies. Label‐free nanoscale LC‐MS has been applied in this study to validate a Triton X‐114‐based phase enrichment method for cardiac membrane proteins. Annotation of the subcellular location combined with GRAVY score analysis indicates a clear separation between soluble and membrane‐bound proteins with an enrichment of over 62% for this protein subset. LC‐MS allowed confident identification and annotation of hydrophobic proteins in this control sample pilot study and demonstrates the power of the proposed technique to extract integral membrane‐bound proteins. This approach should be applicable to a wider scale study of disease‐associated changes in the cardiac membrane subproteome.
Adapting the stretched sample method from tissue profiling to imaging
Authors: Zimmerman Tyler A. , Monroe Eric B. , Sweedler Jonathan V.
Published: August 2008

The characterization and localization of peptides and proteins in tissues provides information that aids in understanding their function and in characterizing disease states. Over the past decades, the use of MS for the profiling and imaging of biological compounds from tissues has evolved into a powerful modality to accomplish these studies. One recently described sampling approach, the stretched sample method (Monroe, E. B. et al.., Anal. Chem. 2006, 78, 6826–6832), places a tissue section onto an array of glass beads embedded on a Parafilm M membrane. When the membrane is stretched, it separates the tissue section into thousands of cell‐sized pieces for tissue profiling by MALDI‐MS. The physical separation between beads eliminates analyte redistribution during matrix application and allows long analyte extraction periods without loss of spatial resolution. Here, we enhance this sampling approach by introducing algorithms that enable the reconstruction of ion images from these stretched samples. As the first step, a sample‐tailored data acquisition method is devised to obtain mass spectra exclusively from the beads, thereby reducing the time, instrument resources, and data handling required for such MS imaging (MSI) experiments. Next, an image reconstruction algorithm matches data acquired from the stretched sample to the initial bead locations. The efficacy of this method is demonstrated using peptide‐coated beads with known peptide distributions and appears well‐suited to the MSI of heterogeneous tissue samples.
Effect of Plasma Exposure on the Chemistry and Morphology of Aerosol‐Assisted, Plasma‐Deposited Coatings
Authors: Twomey Barry , Rahman Mahfujur , Byrne Gerry , Hynes Alan , O'Hare Lesley‐Ann , O'Neill Liam , Dowling Denis
Published: August 2008

This study reports on the effect on the morphology and chemistry of atmospheric pressure plasma deposited nm‐thick coatings (21 ± 3 nm) as the level of exposure to the plasma is systematically altered. Coatings were deposited by directly injecting hexamethyldisiloxane, polydimethylsiloxane or tetramethyldisiloxane liquid precursors through a nebulizer into a helium/oxygen atmospheric pressure plasma. An increase in the level of the precursor was found to be associated with a decrease in the concentration of methyl functional groups in the coating and to an increase of the SiO crosslinking, as demonstrated using surface energy and XPS analysis. This resulted in an increase in the coating refractive index, and in a reduction of the number of surface particulates, as well as of surface roughness.

magnified image
Unmethylated E‐Cadherin gene expression is significantly associated with metastatic human prostate cancer cells in bone
Authors: Saha Baisakhi , Kaur Pavinder , Tsao‐Wei Denice , Naritoku Wesley Y. , Groshen Susan , Datar Ram H. , Jones Lawrence W. , Imam S. Ashraf
Published: August 2008

BACKGROUND

The concurrent determination of methylation status of E‐cadherin gene and E‐cadherin protein expression remains scant in metastatic prostate cancer cells in bone, the most prevalent site for metastatic growth. Therefore, the study was undertaken to ascertain the methylation status of E‐cadherin gene, a most frequent and known epigenetic mechanism of its regulation, and the protein expression in prostate tissue biopsy specimen.

METHODS

The methylation of E‐cadherin gene was determined by methylation specific‐PCR and the protein expression by immunohistochemical method in the consecutive sections of each prostate tissue biopsy specimen.

RESULTS

The unmethylated E‐cadherin gene and homogeneous E‐cadherin protein expression was significantly associated with BPH as compared to the primary prostate carcinoma (Fisher's Exact P < 0.001). A significant association was observed between the concurrent methylated gene and markedly reduced expression of the protein in the primary prostate cancer cells as compared to the BPH cells, suggesting methylation‐dependent regulation of the gene expression in these cases. In contrast to the primary cancer, a highly significant increase in the frequency of metastatic prostate cancer cells in bone exhibited the concurrent expression of unmethylated gene and homogeneous protein (Fisher's Exact P < 0.001).

CONCLUSIONS

The study clearly demonstrated a significant association of the concurrent expression of unmethylated E‐cadherin gene and E‐cadherin protein with metastatic prostate cancer cells in bone, and that its expression may have a role in the intercellular adhesion in the formation of metastatic lesions in bone. Prostate 68: 1681–1688, 2008. © 2008 Wiley‐Liss, Inc.
Neonicotinoids—from zero to hero in insecticide chemistry
Authors: Jeschke Peter , Nauen Ralf
Published: August 2008

In recent years, neonicotinoids have been the fastest‐growing class of insecticides in modern crop protection, with widespread use against a broad spectrum of sucking and certain chewing pests. As potent agonists, they act selectively on insect nicotinic acetylcholine receptors, their molecular target site. The discovery of neonicotinoids can be considered as a milestone in insecticide research and facilitates greatly the understanding of the functional properties of insect nicotinic acetylcholine receptors. Because of the relatively low risk for non‐target organisms and environment, the high target specificity of neonicotinoid insecticides and their versatility in application methods, this important class has to be maintained globally for integrated pest management strategies and insect resistance management programmes. This review comprehensively describes particularly the origin, structure and bonding as well as associated properties of neonicotinoid insecticides. Copyright © 2008 Society of Chemical Industry
Is thermal conductivity time‐dependent?
Authors: Hüttner Bernd
Published: August 2008

The question whether thermal conductivity may be time dependent on short time scales is investigated and answered in the affirmative. For this purpose, we make use of a classical relation between the Brownian mean displacement and the thermal conductivity. Interestingly, the transition from the time dependent regime to stationary behaviour is in the vicinity of Allen's temperature relaxation time. Calculation of the electronic temperature, when the new time dependent thermal conductivity is used, shows an improvement in the results derived by means of the two‐temperature model. Furthermore, the Wiedemann–Franz law is not valid in the time regime investigated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiconducting P3HT microstructures: fibres and tubes obtained from macroporous silicon template
Authors: Palacios R. , Formentín P. , Trifonov T. , Estrada M. , Alcubilla R. , Pallarés J. , Marsal L. F.
Published: August 2008

Microtubes and microfibres composed of poly(3‐hexylthiophene) (P3HT) were fabricated by melt‐assisted templates using ordered macroporous silicon. We have studied the influence of the pore depth and the template type on the microstructure fabrication, where the templates were membranes or structures opened only at one end. Current– voltage (I–V) measurements demostrated that the resistivity of these P3HT microstructures was in the same order as that of homogeneous films, which allows them to be used in electronic devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Combined Virtual Screening 2D and 3D QSAR Methodology for the Selection of New Anticonvulsant Candidates from a Natural Product Library
Authors: Gavernet Luciana , Talevi Alan , Castro Eduardo A. , Bruno‐Blanch Luis E.
Published: August 2008

A virtual screening methodology combining a discriminant function (df) based on Dragon 2D‐descriptors, general ADME filters, and a pharmacophore identified through superposition of rigid analogs was applied in order to identify new anticonvulsant agents among 10 903 natural products. Fifty‐six compounds were selected from the application of this df, Lipinski's rule‐of‐five and other criteria for prediction of oral bioavailability, and the optimal value of log P for a compound to diffuse passively through the blood–brain barrier. Seven of these compounds were removed because they did not belong to descriptor space defined by the training set. The remaining 49 compounds were fitted to the pharmacophore structural constrains, selecting 7 structures with RMS distance value below 0.2. Systematic conformational analysis was performed to find the global minimum conformation, using the PM3 base included in Hyperchem 6.03. The global minimum conformations were further refined at a 6‐31G** level with Gaussian 03. Restricted optimization was then performed to determine the energy difference between the energy minimum conformation and the active conformation defined by the pharmacophore, retaining those structures whose energy differences were below 7 kcal/mol. Four new potential anticonvulsants which fulfill the df and the pharmacophore requisites were selected. One of these structures, 2‐(4,6‐dimethyl‐1‐benzofuran‐3‐yl)acetic acid, was acquired and assayed in the MES and Rotorod tests, confirming anticonvulsant activity in mice at 30 and 100 mg/kg (0.5 and 4 h, i.p.) and absence of neurotoxicity at the tested doses.
Plasma phospholipids implicated in the matrix effect observed in liquid chromatography/tandem mass spectrometry bioanalysis: evaluation of the use of colloidal silica in combination with divalent or trivalent cations for the selective removal of phospholipids from plasma
Authors: Wu Steven T. , Schoener Dale , Jemal Mohammed
Published: August 2008

The feasibility of the use of colloidal silica in combination with a number of divalent or trivalent cations for the removal of plasma phospholipids was evaluated by sequentially adding the two reagents (i.e., colloidal silica and a cation) directly to blank plasma samples or plasma samples spiked with analytes. Three representative plasma phospholipids were monitored to determine the efficiency of the phospholipids removal under different reagent combinations. The recovery of each spiked analyte was also monitored under each condition in order to determine if any of the analyte was removed along with the phospholipids. By optimizing the amounts of the reagents used and the sequence of the addition of the reagents, quantitative and reproducible removal of the phospholipids was achieved. Using the finally selected lanthanum cation, the removal of phospholipids was achieved with minimal concomitant loss of the ten investigated analytes which were carefully selected to incorporate functional groups that could potentially interact with the added reagents and hence could be removed along with the phospholipids. Copyright © 2008 John Wiley & Sons, Ltd.
Checking hazard regression models using pseudo‐observations
Authors: Perme Maja Pohar , Andersen Per Kragh
Published: August 2008

Graphical methods for model diagnostics are an essential part of the model fitting procedure. However, in survival analysis, the plotting is always hampered by the presence of censoring. Although model specific solutions do exist and are commonly used, we present a more general approach that covers all the models using the same framework. The pseudo‐observations enable us to calculate residuals for each individual at each time point regardless of censoring and provide methods for simultaneously checking all the assumptions of both the Cox and the additive model. We introduce methods for single as well as multiple covariate cases and complement them with corresponding goodness‐of‐fit tests. The methods are illustrated on simulated as well as real data examples. Copyright © 2008 John Wiley & Sons, Ltd.
Enhancement of Radiation Cytotoxicity in Breast‐Cancer Cells by Localized Attachment of Gold Nanoparticles
Authors: Kong Tao , Zeng Jie , Wang Xiaoping , Yang Xiaoyan , Yang Jing , McQuarrie Steve , McEwan Alexander , Roa Wilson , Chen Jie , Xing James Z.
Published: August 2008

Gold nanoparticles (GNPs) and modified GNPs having two kinds of functional molecules, cysteamine (AET) and thioglucose (Glu), are synthesized. Cell uptake and radiation cytotoxicity enhancement in a breast‐cancer cell line (MCF‐7) versus a nonmalignant breast‐cell line (MCF‐10A) are studied. Transmission electron microscopy (TEM) results show that cancer cells take up functional Glu‐GNPs significantly more than naked GNPs. The TEM results also indicate that AET‐capped GNPs are mostly bound to the MCF‐7 cell membrane, while Glu‐GNPs enter the cells and are distributed in the cytoplasm. After MCF‐7 cell uptake of Glu‐GNPs, or binding of AET‐GNPs, the in vitro cytotoxicity effects are observed at 24, 48, and 72 hours. The results show that these functional GNPs have little or no toxicity to these cells. To validate the enhanced killing effect on cancer cells, various forms of radiation are applied such as 200 kVp X‐rays and γ‐rays, to the cells, both with and without functional GNPs. By comparison with irradiation alone, the results show that GNPs significantly enhance cancer killing.
Positive and Negative ZnO Micropatterning on Functionalized Polymer Surfaces
Authors: Yang Peng , Zou Shengli , Yang Wantai
Published: August 2008

Patterned ZnO deposition on substrates has received increasing attention because of its great potential in photocatalysis, energy conversion, and electro‐optical techniques. Chemical solution growth is especially promising for organic substrates due to its very mild reaction conditions. Here this method is used on functionality‐patterned polymer surfaces in order to fabricate positive and negative ZnO micropatterns. A ZnO film made of arrayed rods, typically 500–750 nm in diameter and 2.5 µm in length, is selectively obtained on sulfated and hydroxylated regions of biaxially oriented poly(propylene), giving rise to positive patterns. For reactive polyesters such as poly(ethylene terephthalate), the ZnO rods selectively remain on the unmodified original regions, creating negative patterns. Unlike complex photolithography procedures, the irradiation and patterning processes do not require the use of positive or negative photoresists, and possible damage from acidic solutions on the underlying substrate during the chemical etching process is avoided. The process thus proves to be a simple, creditable, and low‐cost method, which could be easily applied on a variety of inert and reactive polymer surfaces.
Biomimetic Synthesis of Gold Nanocrystals Using a Reducing Amphiphile
Authors: Gonzaga Ferdinand , Singh Sherdeep , Brook Michael A.
Published: August 2008

The first synthesis of a chelating and reactive surfactant derived from citric acid and a short silicone as hydrophobic tail is described. Aqueous solutions of this reactive amphiphile spontaneously induce gold ion reduction, particle nucleation, and further direct crystal growth. The process, both pH and light dependent, occurs through lipid‐directed assembly of metal ions, their reduction and subsequent lipid‐directed growth to yield ultrathin (approximately 7 nm thick) quasi two‐dimensional gold nanocrystals.
An ApoA‐I Mimetic Peptide High‐Density‐Lipoprotein‐Based MRI Contrast Agent for Atherosclerotic Plaque Composition Detection
Authors: Cormode David P. , Briley‐Saebo Karen C. , Mulder Willem J. M. , Aguinaldo Juan Gilberto S. , Barazza Alessandra , Ma Yanqing , Fisher Edward A. , Fayad Zahi A.
Published: August 2008

Cardiovascular disease is one of the prime causes of mortality throughout the world and there is a need for targeted and effective contrast agents to allow noninvasive imaging of the cholesterol‐rich atherosclerotic plaques in arteries. A new, fully synthetic, high‐density lipoprotein (HDL)‐mimicking MRI contrast agent is developed, which enhances macrophage‐rich areas of plaque in a mouse model of atherosclerosis by 94%. Confirmation of the targeting of this nanoparticulate agent is achieved using confocal microscopy by tracking a fluorescent lipid incorporated into the nanoparticle.
Embedding and knotting of flat compact surfaces in 3-space
Authors: Røgen Peter
Published: August 2008

In 3-space, any compact surface with nonempty boundary is isotopic to a flat (zero Gaussian curvature) surface and two such flat surfaces are isotopic through flat surfaces if and only if they are isotopic through ordinary surfaces. Hereby the isotopy classes of flat surfaces are in one-to-one correspondence with the isotopy classes of ordinary surfaces which have no constraint in their curvature. Applied to Seifert surfaces we get: Any simple closed space curve can be deformed until it bounds a flat orientable surface.
Preservation of Hand Function Using Muscle Perforator Flaps
Authors: Hallock Geoffrey G.
Published: August 2008

Adequate soft tissue coverage is imperative after any interventions performed to maximize or preserve hand function. Although this can most simply be achieved by primary closure or a skin graft if possible, often a vascularized flap will be preferable, especially if a later secondary procedure is planned. Even moderately sized skin deficits of the upper extremity, and especially if involving the hand itself, can be better covered using a free tissue transfer. Many reasonable options in this regard are available. Muscle perforator flaps, as a relatively new variant of a fasciocutaneous flap, have unique attributes, including availability, diversity, accessibility, large size, and lengthy vascular pedicle, and since no muscle need be included, donor site function is preserved. As is shown here in a series of nine muscle perforator flaps in eight patients, these represent yet another alternative that should be considered if selection of a free flap is indicated to maintain hand function.
Exploring the Immunotoxicity of Carbon Nanotubes
Authors: Yu Yanmei , Zhang Qiu , Mu Qingxin , Zhang Bin , Yan Bing
Published: August 2008

Mass production of carbon nanotubes (CNTs) and their applications in nanomedicine lead to the increased exposure risk of nanomaterials to human beings. Although reports on toxicity of nanomaterials are rapidly growing, there is still a lack of knowledge on the potential toxicity of such materials to immune systems. This article reviews some existing studies assessing carbon nanotubes’ toxicity to immune system and provides the potential mechanistic explanation.
CONTACT METRIC (κ,μ)-SPACES AS BI-LEGENDRIAN MANIFOLDS
Authors: MONTANO BENIAMINO CAPPELLETTI , TERLIZZI LUIGIA DI
Published: August 2008

We describe a contact metric manifold whose Reeb vector field belongs to the (κ,μ)-nullity distribution as a bi-Legendrian manifold and we study its canonical bi-Legendrian structure. Then we characterize contact metric (κ,μ)-spaces in terms of a canonical connection which can be naturally defined on them.