bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual Simulated Childbirth Injuries Result in Slowed Recovery of Pudendal Nerve and Urethral Function
Authors: Jiang Hai‐Hong , Pan Hui Q. , Gustilo‐Ashby Marcus A. , Gill Bradley , Glaab Jonathan , Zaszczurynski Paul , Damaser Margot
Published: October 2008

Aims

Pelvic floor muscle trauma and pudendal nerve injury have been implicated in stress urinary incontinence (SUI) development after childbirth. In this study, we investigated how combinations of these injuries affect recovery.

Methods

Sixty‐seven female Sprague‐Dawley rats underwent vaginal distension (VD), pudendal nerve crush (PNC), PNC and VD (PNC + VD), pudendal nerve transection (PNT), or served as unmanipulated controls. Four days, 3 weeks, or 6 weeks after injury, we simultaneously recorded pudendal nerve motor branch potentials (PNMBP), external urethral sphincter electromyography (EUS EMG), and transurethral bladder pressure under urethane anesthesia. The presence of a guarding reflex (increased frequency and amplitude of PNMBP or EUS EMG activity) during leak point pressure (LPP) testing was determined.

Results

Controls consistently demonstrated a guarding reflex. Four days after VD, EUS EMG activity was eliminated, but PNMBP activity reflected the guarding reflex; EUS EMG activity recovered after 3 weeks. Four days after PNC, both EUS EMG and PNMBP activity were eliminated, but demonstrated significant recovery at 3 weeks. Four days after PNC + VD both EUS EMG and nerve activity were eliminated, and little recovery was observed after 3 weeks with significant recovery of the guarding reflex 6 weeks after injury. Little recovery was observed at all time points after PNT. LPP results mirrored the reduction in EUS EMG activity.

Conclusion

Functional recovery occurs more slowly after PNC + VD than after either PNC or VD alone. Future work will be aimed at testing methods to facilitate neuroregeneration and recovery after this clinically relevant dual injury. Neurourol. Urodynam. 28:229–235, 2009. © 2008 Wiley‐Liss, Inc.
Analysis of the stator/rotor‐contact in a two stators hybrid transducer type ultrasonic motor
Authors: Weerayuth Nantawatana , Seemann Wolfgang
Published: October 2008

This paper presents the procedure to understand the contact mechanism of the hybrid transducer type piezoelectric ultrasonic motor with two stators by using finite element analysis. First, the vibration mode of a stator will be calculated and analyzed using the commercial finite element program package ANSYS. The computed resonance frequencies of the stator will be presented in the frequency domain, in term of input admittance analysis. After that the distribution of the elliptic path of motion of a particle on the stator surface area will be studied. Finally, the contact condition between the stator and the rotor will be addressed in the computation. The normal displacement, normal velocity and tangential velocity of a point on stator surface area will be calculated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrical shape comparison by size theory
Authors: Frosini Patrizio
Published: October 2008

Size Theory allows us to compare shapes of topological spaces and manifolds with respect to properties described by real functions. The main tools used in Size Theory are some pseudo‐distances measuring the minimal changes of these real functions under the action of homeomorphisms. This method can be adapted to several different definitions of shape without changing its geometrical‐topological framework. Some new results about this approach to shape comparison are illustrated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast numerical solution of Boltzmann equation
Authors: Ibraghimov Ilghiz
Published: October 2008

In this work a new method is proposed for the solution of a spatially inhomogeneous Boltzmann equation. The key idea is to approximate the velocity space with multilinear tensors. This approach allows to solve huge numerical challenges with millions of space discretisations with the complexity of Navies‐Stocks solvers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On inverse crack problems in elastostatics
Authors: Ikehata Masaru , Itou Hiromichi
Published: October 2008

In solid mechanics, nondestructive testing has been an important technique in gathering information about unknown cracks, or defects in material. From a mathematical point of view, this is described as an inverse problem of partial differential equations, that is, the problem is to extract information about the location and shape of an unknown crack from the surface displacement field and traction on the boundary of the elastic material. By using the enclosure method introduced by Prof. Ikehata we can derive the extraction formula of an unknown linear crack from a single set of measured boundary data. Then, we need to have precise properties of a solution of the corresponding boundary value problem; for instance, an expansion formula around the crack tip. In this paper we consider the inverse problem concentrating on this point. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A preliminary study of the effect of the external stream structure on turbulent spots generation during by‐pass transition
Authors: Jonáš Pavel , Elsner Witold , Mazur Oton , Uruba Václav , Wysocki Marian
Published: October 2008

The investigation of turbulent spots production rate and average length at various FST turbulence length scales is worked on both the Narasimha's concept of the intermittency and the wavelet transform. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doubly nonlinear evolution equations with non‐monotone perturbations
Authors: Akagi Goro
Published: October 2008

The local (in time) existence of strong solutions to Cauchy problems for doubly nonlinear abstract evolution equations with non‐monotone perturbations in reflexive Banach spaces is proved under appropriate assumptions, which allow the case where solutions of the corresponding unperturbed problem may not be unique. To prove the existence, a couple of approximate problems are introduced and delicate limiting procedures are discussed by using various tools from convex analysis and the Kakutani‐Ky Fan fixed point theorem. Furthermore, an application of the preceding abstract theory to a nonlinear PDE is also given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of thermal hydraulics in an ADSS model
Authors: Prakash K. Arul , Kumar B. V. Rathish , Biswas G.
Published: October 2008

Accelerator Driven Sub‐critical nuclear reactor Systems (ADSS) are envisaged to enhance neutronics of reactors as well as safety physics. The spallation target module is the most innovative and key component for an ADSS. A conjugate heat transfer analysis is accomplished to mimic the physical operating condition of an ADSS in a more realistic way. The conduction equation of the beam window is solved in conjunction with the energy equation using the paradigm of domain decomposition parallelization method and the temperature distribution along the beam window is found. Finally, the thermal and mechanical stresses along the radial direction on the beam window is determined using temperature and pressure values. The stress values are found to increase with increasing Reynolds number (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two main utility‐sharing methods in joint businesses: A discussion
Authors: Amer Rafel , Carreras Francesc , Magaña Antonio
Published: October 2008

We compare two methods of sharing costs or profits among agents in cooperative games: the well–known proportional rule and the Shapley value. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An adaptive level set method for shock‐driven fluid‐structure interaction
Authors: Deiterding Ralf
Published: October 2008

The fluid‐structure interaction simulation of shock‐ and detonation‐loaded structures requires numerical methods that can cope with large deformations as well as local topology changes. A robust, level‐set‐based shock‐capturing fluid solver is described that allows coupling to any solid mechanics solver. As computational example, the elastic response of a thin steel panel, modeled with both shell and beam theory, to a shock wave in air is considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deformation of bilayer lipid membranes in bio‐inspired materials and systems
Authors: Vita Raffaella De , Stewart Iain W. , Leo Donald J.
Published: October 2008

Planar bilayer lipid membranes (BLMs) are currently employed to construct many bio‐inspired material systems and structures. In order to characterize the pressure effects on the equilibrium configurations of these biological membranes, a novel continuum model is proposed. The BLM is assumed to be a two‐layer Smectic A liquid crystal. The mean orientation of the amphiphilic molecules comprising the membrane is postulated to be perpendicular to the layers and each layer is idealized as a two dimensional liquid. Moreover, the BLM is modeled as a simply supported plate undergoing small deformations. It is subjected to a pressure load that acts perpendicularly to the layers. The equilibrium equations and boundary conditions are derived from the bulk elastic energy for Smectic A liquid crystals as described by de Gennes and Prost (1993) by using variational methods. The resulting fourth‐order linear partial differential equation is solved by employing cylindrical functions and the series solution is proved to be convergent. The solution is numerically computed for values of the model parameters that are reported in the literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pál‐type Birkhoff interpolation on nonuniformly distributed points
Authors: Dikshit H.P.
Published: October 2008

Regularity of certain problems of Pál‐type interpolation on non‐uniformly distributed points has been presented here. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hammering of gear wheels
Authors: Eberhard Peter , Ziegler Pascal
Published: October 2008

The dynamic behavior of gear trains is very often dominated by a rattling motion of teeth within the backlash. Because of the excited noise it is often referred to as gear hammering. It mainly originates from high dynamic loads of gas forces and auxiliary devices that usually exceed the nominal torque by far. Of course, the knowledge of the resulting contact forces is very important for the design. Since measurement of contact forces is complicated and expensive, the precise simulation of contact forces and the arising dynamic behavior of the complete gear trains is very important. Typically, gear wheels are modelled as rigid bodies, coupled by spring‐damper combinations. In this paper we show that this assumption may not hold for impact‐like contacts as they often occur in gear trains and may even be wrong for very compliant gear bodies as they are often used in gear trains. We present very detailed finite element analyses for impacts in a gear pair of a real gear train and compare the results to a rigid body model. The differences emerge from dynamic gear body effects, and an elastic description of the gear wheels is necessary to precisely simulate gear forces. In order to be able to use a fully elastic approach to simulate the contacts between gear wheels, a modal approach with a collision detection and a local force description is used. This approach allows simulations nearly as precise as finite element simulations but with a simulation time of more than a factor 1000 faster. This allows the transient simulation of many contacts and many rotations using a fully elastic model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical approximation of solutions to nonlinear inverse problems arising in olfaction experimentation
Authors: French D.A. , Kleene S.J.
Published: October 2008

Identification of detailed features of neuronal systems is an important challenge in the biosciences today. An interdisciplinary research team has been working to determine the distributions of ligand gated ion channels in frog olfactory cilia which are long thin processes that extend from the olfactory receptor neurons. Experiments involving ligand diffusion are performed leading to current data dependent on time. Mathematical models of the experiment are derived and solved numerically to obtain estimates of the spatial distributions of the ion channels along the length of a cilium from the data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Singular elliptic and parabolic problems and a class of free boundary problems
Authors: Guidotti Patrick
Published: October 2008

In this short contribution we report on some recently made progress in the analytical treatment of a class of Free Boundary Problems (FBPs) characterized by the initial onset of a phase. The analysis is motivated by a model problem arising in the description of case II diffusion in polymers. The main local well‐posedness and regularity theorem is obtained by means of fundamental results concerning the underlying singular elliptic and parabolic boundary value problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonance in viscous film flow over topography
Authors: Heining Christian , Wierschem Andreas , Bontozoglou Vasilis , Aksel Nuri , Uecker Hannes
Published: October 2008

We study viscous gravity‐driven films flowing over periodically undulated substrates. Linear analysis describes resonance in steady flow along small bottom corrugations for films of arbitrary thickness. Depending on the dimensionless film thickness we find different regimes for the resonance, which is associated with the interaction of the undulated film with capillary‐gravity waves traveling against the flow. Nonlinear terms produce higher harmonics resonance which in particular may lead to bistable resonance similar to that of the driven Duffing oscillator. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selection of steady states in planar Darcy convection
Authors: Karasözen B. , Tsybulin V. G.
Published: October 2008

The planar natural convection of incompressible fluid in a porous medium is considered. We study selection of steady states under temperature perturbations on the boundary. A selection map is introduced to analyze the selection of steady state from a continuous family of equilibria which exists under zero boundary conditions. The results of finite‐difference modeling for the rectangular enclosure are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Euler‐Maupertuis principle of least action as variational inequality
Authors: Leine R. I. , Aeberhard U.
Published: October 2008

Starting from Hamilton's Principle, the current paper discusses how we can derive the Euler‐Maupertuis Principle of Least Action in the context of non‐smooth dynamics. This variational principle allows us to directly obtain the space curve y (x) of a point‐mass in a potential field V (x, y) without referring to the temporal dynamics. This paper generalises the Euler‐Maupertuis Principle of Least Action to systems with impact by formulating the principle as a variational inequality. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A fully‐coupled nonlinear thermoelectromechanical model for piezolaminated smart structures
Authors: Lentzen Sven , Schmidt Rüdiger
Published: October 2008

In present engineering applications piezoelectric materials gain increasing importance in the development of smart structures; e.g., for shape and vibration control problems. Such structures exhibit a three‐way coupling effect between the mechanical, electrical and thermal quantities. In the majority of papers available in literature this coupling is taken into account only in the constitutive equations. It is however well known that truly coupled analysis should also be based on the interaction of the mechanical, thermal and electrostatic quantities in the field equations. Only in this way many physical effects can be taken into account; e.g., the strain rate dependant change of temperature due to mechanical loading. Furthermore most of the analyses conducted in this area are performed in the linear range of deformations assuming small strains, rotations and temperature changes. However smart technology is generally applied to thin walled structures and in many cases reported in literature the deflections are much larger than the thickness, which results into geometrically nonlinear behaviour, like e.g. the occurrence of stress stiffening which greatly affects the prediction of sensor voltage outputs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An approach to different voting rules from cooperative games with alternatives. Case study: the Catalonia Parliament
Authors: Carreras Francesc , Magaña Antonio
Published: October 2008

We apply simple games with alternatives to describe voting mechanisms used in parliamentary organizations. As a matter of example, we analyze the Catalonia Parliament. Special attention is paid to abstention, which is allowed in most voting rules but is not taken into account when a voting rule is modelled as a simple classical game. To measure the power of each voter in each game, the extended Shapley–Shubik index is considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of parallel eigensolvers for a discretized radiative transfer problem
Authors: Vasconcelos P. B. , Marques O. A.
Published: October 2008

In this work we consider the numerical computation of eigenpairs of integral operators associated to a radiative transfer problem. The target problem models the emission of photons in stellar atmospheres and is formulated in terms of a weakly singular Fredholm integral equation defined on a Banach space. We examine parallel, direct and iterative strategies for the eigensolution phase. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shock‐capturing schemes: high accuracy versus total‐variation boundedness
Authors: Marquina Antonio , Serna Susana
Published: October 2008

In this reseach work we analyze the total variation growth of some high order accurate reconstruction procedures used for the design of shock capturing schemes. This study allows to measure how oscillatory a high order accurate method is in terms of the basic elementary function chosen to increase the order of accuracy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On saturation effects in the Neumann boundary control of elliptic optimal control problems
Authors: Mateos Mariano , Rösch Arnd
Published: October 2008

A Neumann boundary control problem for a linear‐quadratic elliptic optimal control problem in a polygonal domain is investigated. The main goal is to show an optimal approximation order for discretized problems after a postprocessing process. It turns out that two saturation processes occur: The regularity of the boundary data of the adjoint state is limited if the largest angle of the polygon is at least 2π /3. Moreover, piecewise linear finite elements cannot guarantee the optimal order, if the largest angle of the polygon is greater than π /2. We will derive error estimates of order hσ with σ ∈ [3/2, 2] depending on the largest angle and properties of the finite elements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A wave‐type limit for the 3D Landau‐Lifshitz‐Gilbert equation
Authors: Melcher Christof
Published: October 2008

We present a general version of wave‐type limit for the micromagnetic Landau‐Lifshitz‐Gilbert equation in thin films previously encountered in joint work with A. Capella and F. Otto in the context of a reduced model for Néel wall motion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A connection‐theoretic approach to reduction of second‐order dynamical systems with symmetry
Authors: Mestdag T. , Crampin M.
Published: October 2008

We deal with reduction of Lagrangian systems that are invariant under the action of the symmetry group. Unlike the bulk of the literature we do not rely on methods coming from the calculus of variations. Our method is based on the geometrical analysis of regular Lagrangian systems, where solutions of the Euler‐Lagrange equations are interpreted as integral curves of the associated second‐order differential equation field. In particular, we explain so‐called Lagrange‐Poincaré reduction [1] and Routh reduction [3] from the viewpoint of that vector field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Derivative‐free optimization methods for surface structure determination of nanosystems
Authors: Meza J. C. , Garcia‐Lekue A. , Abramson M. A. , Dennis J. E.
Published: October 2008

Many properties of nanostructures depend on the atomic configuration at the surface. One common technique used for determining this surface structure is based on the low energy electron diffraction (LEED) method, which uses a high‐fidelity physics model to compare experimental results with spectra computed via a computer simulation. While this approach is highly effective, the computational cost of the simulations can be prohibitive for large systems. In this work, we propose the use of a direct search method in conjunction with an additive surrogate. This surrogate is constructed from a combination of a simplified physics model and an interpolation that is based on the differences between the simplified physics model and the full fidelity model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unstable periodic orbits in a Faraday disk dynamo
Authors: Moroz Irene M.
Published: October 2008

Hide et al [2] introduced a system of three nonlinear coupled ordinary differential equations to model a self‐exciting Faraday disk homopolar dynamo. Two examples of chaotic behaviour were shown by them. Moroz [4] performed a more extensive analysis of this dynamo model, including bifurcation transition diagrams and unstable periodic orbits for the two chaotic examples. We now use these unstable periodic orbits to identify a possible template for the chaotic attractor, using ideas from topology [1] and results from a corresponding analysis of the Lorenz attractor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A variational arbitrary Lagrangian‐Eulerian finite element formulation for standard dissipative solids at finite strains
Authors: Mosler J. , Ortiz M.
Published: October 2008

A novel Arbitrary Lagrangian‐Eulerian (ALE) finite element formulation for standard dissipative media at finite strains is presented. In contrast to previously published ALE approaches accounting for dissipative phenomena, the proposed scheme is fully variational. Consequently, no error estimates are necessary and thus, linearity of the problem and the corresponding Hilbert‐space are not required. Hence, the resulting Variational Arbitrary Lagrangian‐Eulerian (VALE) finite element method can be applied to highly nonlinear phenomena as well. In case of standard dissipative solids, so‐called variational constitutive updates provide a variational principle. Based on these updates, the deformation mapping follows from minimizing an incrementally defined (pseudo) potential, i.e., energy minimization is the overriding criterion that governs every aspect of the system. Therefore, it is natural to allow the variational principle to drive mesh adaption as well. Thus, in the present paper, the discretizations of the deformed as well as the undeformed configuration are optimized jointly by minimizing the respective incremental energy of the considered mechanical system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical linear stability on controlled solutions of Boussinesq Navier‐Stokes
Authors: Navarro María Cruz , Herrero Henar
Published: October 2008

A numerical linear stability analysis on optimally controlled solutions in a thermoconvective problem is presented. The thermoconvective problem is a stationary Boussinesq Navier‐Stokes with a gaussian heating at the bottom with a large horizontal temperature gradient. The numerical method is Chebyshev collocation. The optimal control permits to find a boundary condition such that the vorticity is minimized. For some values of the penalizing parameter the controlled solution is more stable than the corresponding uncontrolled one. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of the endolymph flow in a semicircular canal
Authors: Obrist Dominik
Published: October 2008

We present a concept for the simulation of the fluid flow in the semicircular canals of the inner ear. Based on the temporal dynamics of an idealized model configuration we formulate the governing equations and devise a strategy for their numerical solution. We analyze the proposed method and find a numerical instability. This instability is characterized by an error bound which can serve as a guideline for tuning the numerical method to the specific boundary conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Wachspress pentagonal patches
Authors: Choubey Nidhi , Dikshit H.P. , Ojha Aparajita
Published: October 2008

Wachspress quadrilateral patches have been recently studied from the point of view of applications to surface modelling in CAGD [1], [3], [4]. Some more applications for defining barycentric coordinates for arbitrary polygons have also been presented in [5] [9]. The purpose of the present paper is to introduce non‐negative Wachspress rational basis functions for surface modelling on pentagonal partitions. Interpolation formula for function values and directional derivatives at the vertices of pentagon has been presented. Conditions for C1– continuity of the composite surface have also been studied in the paper. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐local Dirichlet forms generated by pseudodifferential operators on compact abelian groups
Authors: Popescu Emil
Published: October 2008

Let Gi, 1 ≤ i ≤ n, be compact abelian groups and let Γi , 1 ≤ i ≤ n, be countable dual groups. We consider G = G1 ⊕ G2 ⊕ … ⊕ Gn and Γ = Γ1 ⊕ Γ2 ⊕ … ⊕ Γn . For 1 ≤ j ≤ n, let aj be a negative definite function on Γj and a (γ) = . For φ ∈ S (G), the set of all generalized trigonometrical polynomials on G, we define , where (γ) = aj (γj) (γ), 1 ≤ j ≤ n. Then is a Dirichlet form with the domain on L2 (G). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinearity management in optics
Authors: Porter Mason A. , Centurion Martin , Pu Ye , Kevrekidis P. G. , Frantezeskakis D. J. , Psaltis Demetri
Published: October 2008

We study nonlinearity management in optics by investigating the propagation of localized pulses and plane waves in a layered, cubically nonlinear (Kerr) medium that consists of alternating layers of glass and air. We show that such nonlinearity management delays the blow‐up/collapse of pulses and leads to a band structure of modulationally unstable regions for plane waves. We find excellent agreement between experiments, numerical simulations, and theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Can one hear shape?
Authors: Reuter Martin
Published: October 2008

The question “Can one hear the shape of a drum” has been asked in several contexts before (e.g., by Bers and Kac). It is a pictorial way of asking if the eigenvalues of the Laplacian on a given domain completely characterize its shape, in other words, if the spectrum is a complete shape descriptor (which it is not in general). Since the spectrum contains geometrical information and since it is an isometry invariant and therefore independent of the object's representation, parametrization, spatial position, and optionally of its size, it is well suited to be used as a fingerprint (Shape‐DNA) in contemporary computer graphics applications like database retrieval, quality assessment, and shape matching in fields like CAD, engineering or medicine. We will explain why isometry invariance is so important and point out future directions of research. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Instability mechanisms in buoyant‐thermocapillary liquid pools
Authors: Schoisswohl U. , Kuhlmann H. C.
Published: October 2008

A cylindrical volume of fluid, with a free surface on top, is heated by a parabolic heat flux from above. Two physical effects drive a flow: thermocapillary effects due to free‐surface temperature gradients introduced by the non‐uniform heat flux and buoyancy forces due to gravity. The basic axisymmetric flow is computed by finite volumes and its stability is investigated by a linear‐stability analysis. It is found that the critical stability boundaries and modes are similar to those known from the half‐zone model of crystal growth. For low Prandtl numbers the critical mode is steady and three‐dimensional. We find an asymptotic critical value in the limit of vanishing Prandtl number. For increasing Prandtl number the critical Reynolds number increases. Near unit Prandtl number no threshold could be found with the present computational limitations. For Prandtl numbers larger than unity, the critical mode is oscillatory and the critical Reynolds number decreases with the Prandtl number. We present evidence that the low‐ and high‐Prandtl‐number instabilities are essentially centrifugal respectively due to the hydrothermal‐wave mechanism. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale methods for stiff ODE: closure and consistency
Authors: Sharp Richard , Tsai Richard , Engquist Björn
Published: October 2008

We apply a Heterogeneous Multiscale Method style algorithm to highly oscillatory ODEs. The algorithm tracks the slow evolution of a system in a manner consistent with, but more efficient than methods that resolve the fast oscillations. An example is given where local time averages of the original system variables form a closed set of macroscopic variables. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On adaptive step‐size selections in gradient methods
Authors: Frassoldati Giacomo , Zanni Luca , Zanghirati Gaetano
Published: October 2008

In recent years several proposals for the step‐size selection have largely improved the gradient methods, in the case of both constrained and unconstrained nonlinear optimization. We introduce a new step‐size rule with some crucial properties. We design step‐size selection strategies where the new rule and a standard Barzilai‐Borwein (BB) rule can be adaptively alternated to get meaningful convergence rate improvements in comparison with other BB‐like gradient schemes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multi‐way decomposition of projected spectra obtained in protein NMR
Authors: Billeter Martin , Staykova Doroteya K. , Fredriksson Jonas , Bermel Wolfgang
Published: October 2008

Multidimensional nuclear magnetic resonance spectroscopy is a highly versatile tool in protein research. Experimental limitations prohibit spectra with ≥ 5 dimensions. However, similar information can be obtained by recording 2‐dimensional projections. A decomposition‐based approach for analyzing projections is presented and applied to a protein. The resulting resonance identification is a prerequisite for further characterization of structure, dynamics and interactions of proteins. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A nested dissection approach for sparse matrix partitioning
Authors: Boman Erik G.
Published: October 2008

We consider how to partition and distribute sparse matrices among processors to reduce communication cost in sparse matrix computations, in particular, sparse matrix‐vector multiplication. We consider 2d distributions, where the distribution is not constrained to just rows or columns. We present a new model and an algorithm based on vertex separators and nested dissection. Preliminary numerical results for sparse matrices from real applications indicate the new method performs consistently better than traditional 1d partitioning and is often also better than current 2d methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymmetric dynamic price competition with uncertainty
Authors: Ferreira Fernanda A. , Pinto Alberto A.
Published: October 2008

We consider a dynamic setting‐price duopoly model in which a dominant (leader) firm moves first and a subordinate (follower) firm moves second. We suppose that each firm has two different technologies, and uses one of them according to a certain probability distribution. The use of either one or the other technology affects the unitary production cost. We analyse the effect of the production costs uncertainty on the profits of the firms, for different values of the intercept demand parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient algorithm for perturbed shortest path problems
Authors: Grüne Lars , Junge Oliver
Published: October 2008

We present an efficient algorithm for perturbed shortest paths problems that arise, e.g., in dynamic games. Via a minmax version of Dijkstra's algorithm we compute piecewise constant upper and lower bounds on the upper value function of the game. Convergence of the bounds in the limit of vanishing cell diameter can be proved. The method is numerically demonstrated on a simple 2d dynamic game, the homicidal chauffeur. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Embedding quasi laminar 1D flame profiles to model turbulent premixed combustion with a joint PDF method
Authors: Hack Mathias Leander , Jenny Patrick
Published: October 2008

A new model for turbulent premixed combustion is presented which is based on a joint velocity composition probability density function (JPDF) method. The key idea is a scale separation approach. The method combines the model by Bray, Moss and Libby [1] (BML) for premixed combustion with the flamelet approach for nonpremixed combustion. Here, a Lagrangian formulation of the BML model is considered. The progress variable used by the BML model becomes a computational particle property and its value is triggered by the arrival of the flame front at the particle's position. Similar as in the flamelet approach we assume that the smallest eddies are not small enough to disturb the reactive diffusive flame structure. To resolve the (embedded) quasi laminar flame structure, a flame residence time is introduced. With that residence time, the evolution of the particle composition, including enthalpy, can be determined from precomputed laminar 1D flames. The main challenge with this approach is to model the probability that an embedded flamefront arrives at the particle location, which is necessary to close the chemical source term. Numerical experiments of a turbulent premixed flame show good agreement with experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accessibility of the matrix Riccati differential equation
Authors: Dirr G. , Helmke U.
Published: October 2008

A known result on the classification of transitive Lie group actions on complex Grassmann manifolds is exploited to derive a necessary and sufficient accessibility criterion for the complex matrix differential Riccati equation. We treat both cases, the symmetric as well as the non‐symmetric Riccati equation. Corresponding accessibility results for the real Riccati equation are also available, but not stated here. An application to the accessibility of generalized double bracket flows is given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of displacement washing of pulp fibers using orthogonal collocation on finite elements
Authors: Arora Shelly , Dhaliwal S.S. , Kukreja V.K.
Published: October 2008

Flow of fluid through packed bed of porous particles is modelled with the help of Peclet number (Pe) and Biot number (Bi). Packed bed is divided into three zones, flowing liquor, intrapore solute present in pores of particles and solute adsorbed on particle surface. Langmuir isotherm is used to describe the relationship between intrapore solute concentration and concentration of solute adsorbed on particle surface, whereas the bulk fluid concentration and the intrapore solute concentration are related by linear adsorption isotherm. Model predicted values are also compared with the experimental values. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluctuation measurements in the boundary layer of a supersonic flow
Authors: Lenz B. , Gaisbauer U. , Krämer E.
Published: October 2008

Fluctuation measurements were carried out via constant‐temperature hot‐wire anemometry inside the turbulent boundary layer of a flat plate and a compression ramp (deflexion angle: 11.5). The free‐stream Mach number was M = 2.54. Fluctuation profiles of the alternating quantities temperature, density and velocity were obtained under the assumption of low pressure fluctuations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reassignment of the Stockwell spectrogram
Authors: Liu Cheng , Zhu Hongmei
Published: October 2008

The recently developed Stockwell spectrogram provides a multi‐scale time‐frequency representation of a signal. Due to the Heisenberg's inequality, however, the unavoidable blurring of time and frequency information may conceal important signal structures. Here, we propose to use the reassignment method to improve the readability of the Stockwell representation. An numerical example is presented to illustrate its effectiveness in practice. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistic analysis of nonwoven properties based on a stochastic fiber lay‐down model
Authors: Marheineke Nicole
Published: October 2008

A quality measure for a nonwoven material is the relative variance of the fiber mass distribution. Using a stochastic fiber lay‐down model for the Monte‐Carlo simulations of nonwoven webs, the influence of the parameters of the nonwoven production process on the web quality is investigated via a design of experiments. The statistic results are confirmed by the asymptotic analysis (Chapman‐Enskog method) of the associated Fokker‐Planck equation for the hydrodynamic limit and the computation of the corresponding process functionals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Explicit solutions of the equation –div z = f under the constraint ∥z ∥∞ = 1
Authors: Milbers Zoja
Published: October 2008

We consider the eigenvalue problem for the 1‐Laplace operator and the corresponding variational problem. Since the underlying functionals are not differentiable, the derivation of the Euler‐Lagrange equation is highly nontrivial and involves methods of nonsmooth analysis. A remarkable fact is, that there are infinitely many functions f for which the equation –div z = f has to be satisfied. The purpose of the present work is the investigation of this equation. We show that in a square 2‐dimensional domain for each right hand side f there are infinitely many vector fields z satisfying the Euler‐Lagrange equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical study of 2‐D periodically‐forced internal flows
Authors: Olah Corina A.
Published: October 2008

We use a stabilized FEM with Gear time‐stepping to study periodically forced internal flows. The time‐periodically forced Navier‐Stokes equations always admit a time‐periodic solution but we show that this time‐periodic solution might not be stable, even in 2‐D. Numerical results are presented for a time‐periodic lid driven cavity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optische Uhren. Zeitmessung mit kalten Atomen und Laserlicht
Authors: Peik Ekkehard , Sterr Uwe
Published: October 2008

Optische Uhren nutzen die Anregung optischer Übergänge in neutralen Atomen oder Ionen. Deren Übergangsfrequenz liegt bei etwa 1015 Hz, also fünf Größenordnungen oberhalb der Gigahertz‐Schwingungen heutiger Atomuhren. Das erlaubt eine bis zu tausendmal präzisere Zeitmessung. Für die Genauigkeit ist es entscheidend, dass der Uhrenübergang eine schmale Linienbreite besitzt und seine Frequenz nicht verschoben wird. Dazu müssen die Atome oder Ionen möglichst ungestört und genau lokalisiert sein. Deshalb basiert ein Uhrentyp auf einem kalten Ion in einer Paul‐Falle, ein anderer Uhrentyp arbeitet mit vielen kalten Neutralatomen in optischen Gittern. Der Metrologie sollen optische Uhren zunächst als sekundäre Realisierung der Sekunde dienen. Derzeit ermöglichen sie bereits Frequenzmessungen mit 17 Stellen Genauigkeit.
Die Spintronik‐Jagd. Elektronenspins in Halbleiterbauelementen
Authors: Steinmüller Stephan , Lee Kiyoung , Bland Tony
Published: October 2008

Mikroelektronische Bauelemente der Zukunft könnten nicht mehr allein die Ladung des Elektrons als Informationsträger nutzen, sondern auch seinen Spin. Eine solche Spintronik würde die näher rückende Grenze der Miniaturisierung durchbrechen, die der konventionellen Mikroelektronik bei sehr kleinen Strukturen wegen unerwünschter Quanteneffekte und Wärmeleitungsproblemen droht. Die Spintronik ermöglicht zudem Bauelemente mit völlig neuen Funktionen. Dazu zählt die Spin‐Leuchtdiode, die zirkular polarisiertes Licht emittiert. Die große Herausforderung ist allerdings eine effektive Injektion spinpolarisierter Elektronen in etablierte Halbleitermaterialien. Dazu können diese mit verdünnten magnetischen Halbleitern kombiniert werden. Die Alternative ist die Kombination eines magnetischen Metalls mit einem Halbleitermaterial. Dieser Weg scheint derzeit schneller zur technisch realisierten Spintronik zu führen.
Die vielen Väter des Transistors. Meilensteine in der Geschichte des Festkörperverstärkers
Authors: Hillmer Hartmut
Published: October 2008

Vor hundert Jahren wurde der zweifache Physik‐Nobelpreisträger John Bardeen geboren, der zusammen mit William Shockley und Walter Brattain als Vater des Transistors gilt. Die Vorgeschichte des Festkörperverstärkers ist jedoch komplex. Zum Konzept des Feldeffekt‐Transistors leisteten deutsche Physiker zuvor in den zwanziger und dreißiger Jahren entscheidende Beiträge: Julius Edgar Lilienfeld, Oskar Heil und Heinrich Welker meldeten wichtige Patente an. Robert Pohl und Rudolf Hilsch bauten in Göttingen wahrscheinlich den ersten funktionsfähigen Festkörperverstärker auf Basis eines Kaliumbromid‐Kristalls. Welker und Herbert Franz Mataré arbeiteten 1946 im Auftrag von Westinghouse in Paris an Transistoren. Den ersten funktionsfähigen Germaniumtransistor realisierten jedoch Shockley, Bardeen und Brattain 1947 an den Bell Labs.
Individualismus aus Selbsterhaltungstrieb
Authors: Rempe Gerhard
Published: October 2008

Viele Phänomene wie Supraleitung und Magnetismus basieren auf Teilchenkorrelationen. Bisher wurden immer nur elastische Wechselwirkungen betrachtet. Mit ultrakalten Molekülen in einem optischen Gitter hat unsere Gruppe am Max‐Planck‐Institut für Quantenoptik in Garching gezeigt, dass Korrelationen auch durch eine inelastische Wechselwirkung zustande kommen können. Die bloße Möglichkeit, sich beim Stoß gegenseitig zu zerstören, führt zu einer regelmäßigen Anordnung der Moleküle und damit zu einer drastisch reduzierten Verlustrate.
Räumlich verschränkte Laserstrahlen
Authors: Bachor Hans‐A. , Morizur Jean François
Published: October 2008

Ein Lichtstrahl gilt geradezu als Definition einer geraden Linie. Doch wenn wir die genaue Position und die Richtung eines solchen Strahls messen wollen, setzt die Unschärferelation strikte Grenzen. Einem australisch‐französischen Forscherteam ist es gelungen, zwei Laserstrahlen räumlich miteinander zu verschränken. Damit lässt sich die Quantengrenze überwinden.
Am Rande des Schwarzen Lochs
Authors: Bührke Thomas
Published: October 2008

Einem internationalen Forscherteam ist es gelungen, ein leuchtendes Gebilde zu beobachten, dass sich am Rand des Schwarzen Lochs im Zentrum unserer Milchstraße befindet. Innerhalb der nächsten Jahre wird es technisch möglich sein, Eigenschaften des Schwarzen Lochs selbst und Effekte der Relativitätstheorie zu beobachten.
Behavior of Polymeric Matrices Containing Silver Inclusions, 2 – Oxidative Aging of Nanocomposite Ag/C:H and Ag/C:H:O Films
Authors: Hlídek Pavel , Biederman Hynek , Choukourov Andrei , Slavínská Danka
Published: October 2008

Nanocomposite Ag/C:H and Ag/C:H:O films were deposited by means of an unbalanced magnetron operated in a gas mixture of argon, hexane, and carbon dioxide. Infrared spectroscopy was employed to investigate the deposited layers in situ and to monitor film aging. Usual CH2/CH3 stretching and deformation bands dominate in the infrared spectra of as‐grown Ag/C:H films. Oxidation processes observed by FTIR as an evolution of absorption bands caused by hydroxyl, carbonyl, carboxylate, and carbonate groups depend considerably on the content of the metallic phase. It has been shown that the metallic particle surface is very important for the oxidation processes.

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Genome‐wide expression analysis of recently processed formalin‐fixed paraffin embedded human prostate tissues
Authors: Dunn Thomas A. , Fedor Helen , Isaacs William B. , De Marzo Angelo M. , Luo Jun
Published: October 2008

BACKGROUND

Formalin fixation and paraffin embedding (FFPE) is the standard practice to process surgical specimens in preparation for pathological evaluation. The FFPE procedure is known to introduce adverse effects on RNA quality and the ensuing RNA based expression analysis. However, the overall impact of the FFPE procedure alone on the reliability and accuracy of expression data, without influences from additional compromising factors introduced during long‐term storage, has not been vigorously assessed.

METHODS

The quality of RNA extracted from recently processed FFPE prostate tissues was examined. FFPE and frozen blocks were prepared from matched surgical specimens and processed in parallel for RNA extraction, two rounds of linear RNA amplification, and genome‐wide expression analysis. Expression ratios of prostate cancer versus benign prostatic hyperplasia (BPH) were compared between data derived from the paired FFPE tissues and frozen tissues.

RESULTS

RNA extracted from recently processed FFPE prostate tissues was of high quality and suitable for RNA expression analysis. An unbiased analysis of expression data revealed nearly 80% concordance between FFPE tissues and frozen tissues, in genome‐wide gene expression differences of cancer versus BPH, and across a wide spectrum of fold expression differences.

CONCLUSIONS

FFPE procedure itself does not lead to adverse effects on genome‐wide expression analysis. Prospective molecular archiving or modified long‐term storage conditions should be implemented to expand the utility of FFPE tissues without compromising standard surgical pathology routines. Prostate 69: 214–218, 2009. © 2008 Wiley–Liss, Inc.
Temporal changes in gene expression induced by sulforaphane in human prostate cancer cells
Authors: Bhamre Suvarna , Sahoo Debashis , Tibshirani Robert , Dill David L. , Brooks James D.
Published: October 2008

BACKGROUND

Prostate cancer is thought to arise as a result of oxidative stresses and induction of antioxidant electrophile defense (phase 2) enzymes has been proposed as a prostate cancer prevention strategy. The isothiocyanate sulforaphane, derived from cruciferous vegetables like broccoli, potently induces surrogate markers of phase 2 enzyme activity in prostate cells in vitro and in vivo. To better understand the temporal effects of sulforaphane and broccoli sprouts on gene expression in prostate cells, we carried out comprehensive transcriptome analysis using cDNA microarrays.

METHODS

Transcripts significantly modulated by sulforaphane over time were identified using StepMiner analysis. Ingenuity Pathway Analysis (IPA) was used to identify biological pathways, networks, and functions significantly altered by sulforaphane treatment.

RESULTS

StepMiner and IPA revealed significant changes in many transcripts associated with cell growth and cell cycle, as well as a significant number associated with cellular response to oxidative damage and stress. Comparison to an existing dataset suggested that sulforaphane blocked cell growth by inducing G2/M arrest. Cell growth assays and flow cytometry analysis confirmed that sulforaphane inhibited cell growth and induced cell cycle arrest.

CONCLUSIONS

Our data suggest that in prostate cells sulforaphane primarily induces cellular defenses and inhibits cell growth by causing G2/M phase arrest. Furthermore, based on the striking similarities in the gene expression patterns induced across experiments in these cells, sulforaphane appears to be the primary bioactive compound present in broccoli sprouts, suggesting that broccoli sprouts can serve as a suitable source for sulforaphane in intervention trials. Prostate 69: 181–190, 2009. © 2008 Wiley–Liss, Inc.