bluuebunny/crossref_metadata_2025 huggingface dataset:
Formulation and Numerical Implementation of Ferroelectrics at Large Strains
Authors: Rosato Daniele , Miehe Christian
Published: November 2010

In recent years, an increasing interest has been shown in functional materials such as ferroelectric polymers. For such materials, viscous effects and electric polarizations cause hysteresis phenomena accompanied with possibly large remanent strains and rotations. Ferroelectric polymers have many attractive characteristics. They are light, inexpensive, fracture tolerant, and pliable. Furthermore, they can be manufactured into almost any conceivable shape and their properties can be tailored to suit a broad range of requirements. In this work, continuous and discrete variational formulations are exploited for the treatment of the non‐linear dissipative response of ferroelectric polymers under electrical loading. The point of departure is a general internal variable formulation that determines the hysteretic response of this class of materials in terms of an energy storage and a rate‐dependent dissipation function. The ferroelectric constitutive assumptions, which account for specific problems arising in the geometric nonlinear setting, are discussed. With regard to the choice of the internal variables, a critical factor is the kinematic assumptions. Here, we propose the multiplicative decomposition of the local deformation gradient into reversible and remanent parts, where the latter is characterized by a metric tensor. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of bainitic phase transformation
Authors: Schneidt Andreas , Mahnken Rolf
Published: November 2010

In this work, we present a macroscopic material model for simulation of austenite to bainite and of austenite to martensite transformations accompanied by transformation‐induced plasticity (TRIP), which is an important phenomenon in metal forming processes. In order to account for the incubation time the model considers nucleation of the bainite phase. When this quantity attains a barrier term, growth of bainite volume fraction is started. The model formulation allows for individual evolutions of upper and lower bainite. Furthermore, the numerical implementation of the constitutive equations into a finite element program is described. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FEM simulation of oxidation induced stresses in a simplified thermal barrier coating system
Authors: Seiler Philipp , Bäker Martin , Rösler Joachim
Published: November 2010

To study the behaviour of the complex failure mechanisms in thermal barrier coatings, a simplified model system is used to reduce the number of system parameters. The artificial system consists of a bond‐coat material (fast creeping Fecralloy or slow creeping MA956) as the substrate with a Y2O3 partially stabilized plasma sprayed zircon oxide TBC on top and a TGO between the two layers. A FEM simulation was developed to calculate the stress distribution inside the coating system. The simulation permits the identification of compression and tension areas which are established by the growth of the oxide layer and the stresses which occur during the heating and cooling processes. Full thermal cycles, including heating from RT to 1000°C, dwelling for 2 hours and cooling to RT, were simulated.

The stress distributions provide an insight into the possible failure mechanisms in the coating and allow to draw conclusions for optimizing real thermal barrier coating systems. It is shown that the failure mechanism depends on the creep properties of the bond‐coat. Therefore, optimizing the creep properties may adjust lifetime of the whole coating system. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of shear band formation in elastic material by energy relaxation
Authors: Trinh Bach Tuyet , Hackl Klaus
Published: November 2010

Following up the previous work, [1], a new approach to the problem of shear localization is proposed, based on energy minimization principles associated with micro‐structure developments. In this approach, two different material models are included. They represent the behaviour of material at very small strain and very large strain, respectively. Herein, shear bands are treated as the micro‐shearing of rank‐one laminates. The thickness of a shear band represented by its volume fraction is assumed to tend to zero while the strain inside the shear band tends to infinity. The existence of shear bands in the structure leads to an ill‐posed problem which can be solved by means of energy relaxation. The performance of the proposed energy relaxation is demonstrated through numerical simulation of a tension test under plane strain conditions. The presented numerical simulation shows that there is no mesh‐dependence. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multiphasic Model Describing the CO2 Injection Problem
Authors: Komarova Irina , Ehlers Wolfgang
Published: November 2010

According to the annual data, the portion of ejected carbon dioxide (CO2) into the atmosphere is much higher in comparison to other greenhouse gases. Therefore, the development of various scenarios in order to reduce the CO2 concentration in the atmosphere is nowadays a challenge and a relevant subject in research. The current investigation is dedicated to the modelling of a CO2 injection into a water‐saturated aquifer as the most capable reservoir, where its upward migration is blocked by a dense cap‐rock layer. The major part of the study is focused on two specific processes taking place in the stored reservoir: the phase transfer phenomenon of the supercritical CO2 which occurs under changeable surrounding conditions and the sequestration‐driven deformation of the solid skeleton acting under the pressure of the pumped CO2. For the numerical simulations within a continuum‐mechanical framework, a multiphasic model based on the Theory of Porous Media is introduced. Moreover, the main principles of developing a constitutive equation for the mass production term for the mass balance equation are discussed here. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application for generating characteristics of free and bonded systems
Authors: Buchacz Andrzej , Wrobel Andrzej
Published: November 2010

The present paper is the continuation of earlier publications with stack of piezoelectric plates. This work is an author's idea of application for generating characteristics of piezoelectric systems. The presented program, called Piezo3D, allows for generation a single piezoelectric plate graphs as well as complex, free and bonded systems. An additional advantage is the ability to obtain the 3D graphs, in which the characteristics of the test graph can be based not only on frequency, but also on other parameters such as the thickness of the plate. The application is written in the numerical software "Matlab". (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of heterogeneous dielectric elastomer actuators
Authors: Müller Ralf , Xu Bai‐Xiang , Gross Dietmar , Lyschik Mathias
Published: November 2010

Dielectric elastomer actuators, consisting of an elastomer film sandwiched between two compliant electrodes, are of increasing interests in application. Due to the nonlinearity, the nature of large deformation and the coupling of different physical fields, numerical investigations based on reasonable models are necessary. In the present work, the modeling and the numerical simulation of deformable dielectrics are discussed in a coupled electro‐mechanical framework. It shows how the Maxwell stress contributions can be implemented efficiently into a finite element method. For the purpose of improving the efficiency of the actuators, strategies to increase the electro‐mechanical coupling by a modified microstructure are discussed. The idea of introducing ceramic inclusions in soft elastomer is proposed, which can at the same time make use of the high relative dielectric constants of the ceramics and the large deformation of the soft elastomer. Numerical results confirm the improvement of the performance efficiency. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the number of grains in a polycrystal on the prediction of texture during rolling by using the Taylor approach
Authors: Jöchen Katja , Böhlke Thomas
Published: November 2010

The estimation of the texture in a sheet metal induced by rolling is an important issue for the accurate description of forming operations as, e.g., deep drawing. In this paper, we discuss the influence of the number of grains in the polycrystal on the prediction of the pole figures as well as on the α and β fiber in the orientation distribution function. For this study, we use the Taylor model as homogenization method where it is assumed that the macroscopic deformation of the polycrystal is identically transferred to each single crystal. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Dirichlet boundary conditions in second‐order FE2‐schemes
Authors: Sehlhorst Hans‐Georg , Düster Alexander , Jänicke Ralf , Diebels Stefan
Published: November 2010

In recent years FE2‐methods have become quite popular since they allow for accurate modeling of materials with inherent microstructures like, for example, foams, biological tissues, or cement paste. In FE2‐schemes of first‐order usually standard continua are applied on both, the micro‐ and the macroscale, whereas in FE2‐schemes of second‐order at least on the macroscale an extended continuum theory is considered. In both cases the scales are coupled by projection and homogenization rules. Due to the extended kinematics, second‐order schemes can capture higher‐order effects like, for example, size effects. In this contribution we discuss the projection of extended deformation modes when applying high‐order finite elements with hierarchic shape functions to discretize the microstructure. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelet‐based Methods for Multirate PDAEs
Authors: Winkler Renate
Published: November 2010

We present an adaptive envelope method for the transient simulation of problems with widely separated time scales. Typical applications are circuits where a periodic carrier signal is modulated by a slower signal. The presented method is specifically designed to work even in the case of steep gradients due to digital‐like signal structures. Using different independent variables for the slow and the fast time scales the original system is transformed to a hyperbolic multi‐rate differential‐algebraic system, from which the solution of the original system can be reconstructed. After discretising the slow time scale a periodic boundary value problems in the fast time scale has to be solved for each slow time step. These are solved by wavelet collocation using piecewise linear ansatz‐functions. To adapt the grid the solution is represented in terms of a hierarchical set of biorthogonal wavelets to detect the areas with rapidly changing solutions and to coarse or refine the grid. The performance of the method is illustrated by a circuit example. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation der Zeitabhängigkeit von Selbstorganisationsprozessen in gefüllten Gummiwerkstoffen
Authors: Ihlemann Jörn , Wulf Hans
Published: November 2010

Gefüllte Gummiwerkstoffe zeigen in mechanischen Belastungsversuchen ein sehr komplexes Verhalten. Dies gilt insbesondere auch für die Geschwindigkeitsabhängigkeit des Materialverhaltens. Die SOLP‐Theorie erklärt diese Ergebnisse mit einem auf molekularer Ebene ablaufenden, auf dem Zerfall und der Rekombination physikalischer Bindungen beruhenden Selbstorganisationsprozess. Der Überprüfung dieser Hypothese dient ein Simulationsprogramm, welches den Selbstorganisationsprozess nachbildet. Zunächst wird das dem Programm zugrunde liegende Modell vorgestellt. Im Anschluss daran werden Ergebnisse der Simulationen mit Messungen verglichen. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Variational Homogenization Approach to Electromechanical Hystereses Caused by Domain Wall Movement
Authors: Zäh Dominic , Rosato Daniele , Miehe Christian
Published: November 2010

In recent years, increasing interest in so‐called smart materials such as ferroelectric polymers and ceramics has been shown. Those materials are used in various actuators, sensors, and also in medical devices. In this paper, we outline a micro‐macro approach to the modeling of macroscopic hystereses which directly takes into account the microstructural evolution of electrically poled domains. To this end, an incremental variational formulation for a gradient‐type phase field model is developed and exploited for the simulation of electromechanically coupled problems. The formulation determines the hysteretic response of the material in terms of an energy‐enthalpy and a dissipation function which both depend on the microscopic remanent polarization treated as an order parameter. The gradient‐type balance law for the phase field can be considered as a generalization of Biot's equation for standard dissipative materials and may be related to the classical Ginzburg‐Landau equation. Furthermore, the variational formulation serves as natural starting point for a compact and symmetric finite element implementation of the coupled micromechanical problem covering the displacement, the electric potential, and the microscopic polarization vector. For this three‐field scenario we develop a variational‐based homogenization method which determines the overall macroscopic hysteretic properties of a polycrystalline aggregate. The proposed computational method can be used as a numerical laboratory for the improvement of microstructural properties. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localized Roll‐Solutions in the Ekman‐Couette‐System
Authors: Withalm Martin , Hoffmann Norbert P.
Published: November 2010

In the Ekman‐Couette‐System, where the usual Couette‐System is additionally rotated about its normal axis, localized single roll solutions have been known for some time. By varying different system parameters, a new localized solution emerging by saddle‐node bifurcations from these known solutions has now been found. This new solution is of the same localized nature like the old solution but with an additional roll. Further bifurcations lead then to an increasing number of rolls, still localized. This behavior is kind of analogous to the so called ‘homoclinic snaking’ which has recently been investigated in conjunction with the Swift‐Hohenberg equation and binary fluid convection. It might link the unstable localized single roll solutions with stable multi roll solutions or even with stable periodic roll solutions, which has to be shown yet. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Peculiarities of the surface and guided waves propagation in heterogeneous composites with nematic coatings
Authors: Zakharov Dmitry , Kaptsov Alexandr
Published: November 2010

Using the effective low frequency model of nematic medium we study the phase speeds and attenuations of the quasi‐Rayleigh and Love waves in composite made of elastic core with the peripheral coating, as well as the fundamental S0 and A0 Lamb modes in heterogeneous plates. The analytical and numerical analysis revealed two types of unusual resonance effects disturbing wave propagation. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of wall conductivity on turbulent channel flow under spanwise magnetic field
Authors: Krasnov Dmitry , Parepalli Prarthana , Zikanov Oleg , Boeck Thomas
Published: November 2010

The effect of wall conductivity on turbulence in electrically conducting fluid in the presence of a constant magnetic field is considered. A channel flow with a spanwise magnetic field is analyzed using high‐resolution direct numerical simulations performed for the case of low magnetic Reynolds number. It is found that the effect of suppression of wall‐normal momentum transfer and reduction of wall friction identified earlier for the flow with perfectly insulating walls is enhanced if the walls are electrically conducting. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Optimization of the Full Radiative Heat Transfer System
Authors: End Thomas
Published: November 2010

Solving the full radiative heat transfer equation, moderately discretized in space, time, frequency and direction, results in a tremendously huge system of equations. A common approach to avoid this problem is to use moment methods neglecting the directional dependence on radiation. Our approach, however, is to solve the full radiative heat transfer system with all dependencies and to optimize the heat distribution and the radiative flux, respectively, for a desired temperature function or desired radiative flux function. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pivot Tightening for the Interval Cholesky Method
Authors: Garloff Jürgen
Published: November 2010

The performance of the Cholesky decomposition in interval arithmetic is considered. In order to avoid the algorithm breaking down due to an interval pivot containing zero, a method is presented by which such a pivot can be tightened. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
hp‐Adaptivity in Two and Three Space‐Dimensions
Authors: Bürg Markus , Dörfler Willy
Published: November 2010

We present an hp‐adaptive refinement strategy for two and three space‐dimensions, which is based on the strategy presented in [2], and a convergence result for this strategy is stated. Then the refinement strategy is applied to some two‐ and three‐dimensional model problems. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis and Application of the Rational B‐Spline Finite Element Method in 2D
Authors: Klassen Markus , Müller Ralf , Mergheim Julia , Fischer Paul , Steinmann Paul
Published: November 2010

Non‐Uniform Rational B‐Splines (NURBS) are basis functions used in CAD software to describe exact geometric models. The implementation of these basis functions in the context of the Finite Element Analysis (FEA) is known as isogeometric analysis. The concept and definition of NURBS is briefly presented here. Since these functions are implemented as shape functions for the isogeometric analysis, the refinement strategies are discussed. The example of an infinite plate with circular hole serves as a benchmark. Finally, isogeometric analysis is applied to gradient elasticity since NURBS functions are of higher continuity and this is required in gradient elasticity. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Verification Tools for Reduced Derivatives Computed by a First‐Optimize‐Then‐Discretize Approach for Optimal Control Problems
Authors: Clever Debora
Published: November 2010

We give an overview about several verification tools to study consistency between discrete optimization problem and discrete derivatives when using independent discretization schemes for state and adjoint systems within the context of optimal control problems. We present strategies that detect impreciseness within a considered quantity without any additional effort. They are therefore a suitable tool to control the grid refinement within a multilevel setting. More detailed tools are useful to verify the problem implementation and to analyze the quantities discretization error order. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A State‐Space Implementation of Anti‐Causal Iterative Learning Control
Authors: Becker Urs , Damm Tobias
Published: November 2010

Iterative learning control is used to find input signals which match a previously generated output trajectory by repetitively correcting the inputs through the tracking errors. Using causal learning operators this only works up to a relative degree of one. We overcome this restriction with an anti‐causal approach following [1] and show a practical implementation in the state‐space with some examples. We also motivate the method as useful to determine inputs for simulations and test‐rigs. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controllable centrifugal pendulum
Authors: Ineichen Laurent
Published: November 2010

The combustion engine produces huge rotational periodic vibrations that could affect the acoustic comfort of the vehicle. An isolating device is placed after the engine and filters the oscillations in order to deliver a clean averaged torque to the rest of the drive train. The centrifugal pendulum is widely used even though its passive version can quench only one order of vibration.

We propose in [3] a design allowing to control the tuning of the pendulum. An actuator delivers an additional force that completes the centrifugal force. This is equivalent to changing the stiffness of a classical vibration absorber. In this paper, we apply to the stiffness an optimal feedback control on a neighbouring extremal path as defined in [1]. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Group‐Theoretic Approach to Parameter Identifiability of PDE Systems
Authors: Rieger Karl , Schlacher Kurt
Published: November 2010

The contribution is devoted to the parameter identifiability problem of (nonlinear) PDE systems. Especially, we discuss the (local) identifiability of parameters along a trajectory. The analysis relies on a coordinate‐free formulation for systems, including boundary conditions, and we motivate an approach by (Lie) transformation groups, whose success for PDE systems depends on a consequent extent to the accompanying boundary conditions. The (non‐)identifiability of parameters is related to the (non‐)existence of group generators, wherewith (local) conditions can be derived. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational homogenization for heterogeneous cohesive layers incorporating size effects
Authors: Hirschberger C. B.
Published: November 2010

A numerical framework is presented for the multiscale modelling of material layers that possess a both heterogeneous and microstructured mesostructure. The material layer is represented as a cohesive interface on the macro level, while on the meso level micromorphic representative volume elements are used. A computational homogenization approach for the cohesive material layers has been proposed to solve this nonlinear multiscale problem numerically. The present framework is particularly well suited for the modelling of damage and failure, as the micromorphic RVE is well known for its regularizing character. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling crack micro‐branching using finite elements with embedded strong discontinuities
Authors: Raina Arun , Linder Christian
Published: November 2010

The emphasis of this work lies in the development of a numerical method which is capable of representing the complex physical phenomena arising in the case of crack branching in brittle materials. In particular, the formation of crack micro‐branches needs to be accounted for when it comes to the prediction of the propagation pattern of crack macro‐branches which will ultimately lead to the failure of the material. This is achieved by numerically modeling the failure zones within the individual finite elements based on the concept of the embedded finite element method, where all the information with regard to the geometry of the failure zone is stored locally on the element level leading to a very efficient methodology capable of discretely resolving the failure zone. The main feature of the current work is the redundancy of the branching criterion based on crack tip velocity and that both, micro‐ as well as macro‐branches can be modeled. Whether a micro‐crack develops into a macro‐crack solely depends on the local state of the material as it is outlined based on the application of the proposed numerical scheme on a rectangular block with a pre‐existing notch set under tension. A comparison of the oscillatory behavior of the obtained crack tip velocity every time a micro‐crack develops with experimental results from the literature is provided. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of material failure by the discrete element method
Authors: Schneider Benjamin , Bischoff Manfred , Ramm Ekkehard
Published: November 2010

In this paper a two‐dimensional discrete element method with rigid, polygonal particles is used to model material failure of granular as well as quasi‐brittle materials. Different models for soft contact as well as cohesion between the particles are presented. The capabilities of the method are demonstrated simulating simplistic granular model materials as well as complex concrete specimens with an artificial microstructure. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly efficient purification of protein complexes from mammalian cells using a novel streptavidin‐binding peptide and hexahistidine tandem tag system: Application to Bruton's tyrosine kinase
Authors: Li Yifeng , Franklin Sarah , Zhang Michael J. , Vondriska Thomas M.
Published: November 2010

Tandem affinity purification (TAP) is a generic approach for the purification of protein complexes. The key advantage of TAP is the engineering of dual affinity tags that, when attached to the protein of interest, allow purification of the target protein along with its binding partners through two consecutive purification steps. The tandem tag used in the original method consists of two IgG‐binding units of protein A from Staphylococcus aureus (ProtA) and the calmodulin‐binding peptide (CBP), and it allows for recovery of 20–30% of the bait protein in yeast. When applied to higher eukaryotes, however, this classical TAP tag suffers from low yields. To improve protein recovery in systems other than yeast, we describe herein the development of a three‐tag system comprised of CBP, streptavidin‐binding peptide (SBP) and hexa‐histidine. We illustrate the application of this approach for the purification of human Bruton's tyrosine kinase (Btk), which results in highly efficient binding and elution of bait protein in both purification steps (>50% recovery). Combined with mass spectrometry for protein identification, this TAP strategy facilitated the first nonbiased analysis of Btk interacting proteins. The high efficiency of the SBP‐His6 purification allows for efficient recovery of protein complexes formed with a target protein of interest from a small amount of starting material, enhancing the ability to detect low abundance and transient interactions in eukaryotic cell systems.
Subunit arrangement in the dodecameric chloroplast small heat shock protein Hsp21
Authors: Lambert Wietske , Koeck Philip J.B. , Ahrman Emma , Purhonen Pasi , Cheng Kimberley , Elmlund Dominika , Hebert Hans , Emanuelsson Cecilia
Published: November 2010

Unfolding proteins are prevented from irreversible aggregation by small heat shock proteins (sHsps) through interactions that depend on a dynamic equilibrium between sHsp subunits and sHsp oligomers. A chloroplast‐localized sHsp, Hsp21, provides protection to client proteins to increase plant stress resistance. Structural information is lacking concerning the oligomeric conformation of this sHsp. We here present a structure model of Arabidopsis thaliana Hsp21, obtained by homology modeling, single‐particle electron microscopy, and lysine‐specific chemical crosslinking. The model shows that the Hsp21 subunits are arranged in two hexameric discs, similar to a cytosolic plant sHsp homolog that has been structurally determined after crystallization. However, the two hexameric discs of Hsp21 are rotated by 25° in relation to each other, suggesting a role for global dynamics in dodecamer function.
Antifatigue activity of the liposoluble fraction from Acanthopanax senticosus
Authors: Huang Lin‐Zhang , Huang Bao‐Kang , Liang Jie , Zheng Cheng‐Jian , Han Ting , Zhang Qiao‐Yan , Qin Lu‐Ping
Published: November 2010

The crude extract of Acanthopanax senticosus (AS) has been used extensively in Russia, China, Korea and Japan as an adaptogenic agent to fight against stress and fatigue. However, whether the liposoluble fraction possesses antifatigue activity or not is still unclear. A liposoluble fraction was administered orally to mice for 9 days. The swimming time to exhaustion was longer in the treatment groups (22.2 ± 3.3, 25.5 ± 4.8 min) than in the control group (13.7 ± 1.2 min, p < 0.05). The plasma TG (triglyceride) and BUN (blood urea nitrogen) levels in the high dose (500 mg/kg) groups were decreased significantly compared with the control group. Plasma lactate dehydrogenase (LDH) was lower in the treatment groups than in the control group. Chemical analysis from GC/MS revealed that the main components of the liposoluble fraction of AS were saturated fatty acid (12.98%), unsaturated fatty acid (33.13%), unsaturated alcohol (27.46%) and diolefine (15.76%). In conclusion, the liposoluble fraction enhanced the forced swimming capacity of mice by decreasing muscle damage, effectively preventing the increase in BUN concentration and increasing fat utilization. It is proposed that the antioxidant effect may be one of the antifatigue mechanisms of the liposoluble fraction of AS. Copyright © 2010 John Wiley & Sons, Ltd.
The semi‐geostrophic diagnosis of vertical motion. II: Results for an idealized baroclinic wave life cycle
Authors: Thorpe Alan J. , Pedder Mike A.
Published: November 2010

In this paper we apply the method of solution of the semi‐geostrophic (SG) omega equation developed in Part I to data generated from a numerical simulation of an idealized dry adiabatic frictionless baroclinic wave life cycle. The aim is to compare quantitatively the quasi‐geostrophic (QG) and SG solutions for the vertical motion, and to relate these to the model vertical motion field. This comparison allows an evaluation of how practical, and accurate, it would be to use such balance theories to estimate vertical motion from atmospheric data. It is found that the QG solution tends to overestimate both ascent and descent in the cyclone. This overestimation is due both to an overestimation of the forcing and to a poor treatment of the large horizontal gradients of static stability produced as the tropopause descends near the cyclone centre. As the SG theory more faithfully represents the Ertel‐Rossby potential vorticity (PV), the vertical motion which is implied by this distribution of PV is also quantitatively more similar to the model vertical motion than that produced by the QG theory. The PV distribution affects the vertical motion via the forcing and via explicit account of horizontal gradients of the local static stability distribution which appear in the differential operator in the omega equation. The residual between the vertical motion predicted by the SG, or any other balance, theory and that given by the model is produced partly by any inertia‐gravity wave activity and partly by inaccuracies in the assumed balance condition.
Planetary wave modes in the thermocline: Non‐Doppler‐shift mode, advective mode and Green mode
Authors: Liu Zhengyu
Published: November 2010

A quasi‐geostrophic theory is proposed for planetary waves in the extratropical thermocline. It is shown that planetary wave propagation, structure and stability can be affected significantly by the mean thermocline flow. One major planetary wave mode is the non‐Doppler‐shift mode, which resembles the first baroclinic mode and has a strong signature in both the sea surface height and the bottom of the thermocline. This mode propagates westward regardless of the mean flow. However, consistent with recent works, the westward propagation speed can be modestly enhanced by the mean flow. Another major planetary wave mode is the advective mode which bears some resemblance to the second baroclinic mode and has a strong signature in the upper thermocline temperature field.

In the region of strong westward thermocline flow and shear, such as the south‐western part of the North Pacific subtropical gyre, an unstable Green mode is produced by the coupling of the non‐Doppler‐shift mode and the advective mode. This unstable Green mode may have e‐folding times of a few years for a wave hundreds of kilometers in length. The structure of the Green mode contains the features of the second baroclinic mode with a strong signature in the upper‐thermocline. The Green mode always propagates westward. Finally, we discuss the relevance of our theory to recent observations.
Gravity‐wave drag produced by Madeira
Authors: Miranda Pedro M. A. , Ferreira João Jacinto , Thorpe Alan J.
Published: November 2010

The gravity‐wave drag exerted on the atmosphere by an isolated three‐dimensional mountain is here evaluated from observational data. The representation of such drag in numerical weather‐prediction models is known to be of considerable importance, and this study provides some rare field measurements for input and verification of parametrization schemes.

The results of a microbarograph experiment performed in the spring of 1993 on the Island of Madeira are presented. The data obtained with thermostatically adjusted microbarographs, located on the two sides of the island, are analysed in terms of the gravity‐wave drag produced by the mountain. The time series obtained show a high degree of coherency, consistent with the idea that they represent a mesoscale signal, not significantly affected by small‐scale perturbations. The pressure signal at each station shows a superposition of different oscillations including a 5–7 day synoptic oscillation, a 12‐hour tide and an irregular oscillation with an amplitude of about 2 hPa, which can be associated with gravity‐wave drag. The pressure differences across the island essentially contain the gravity‐wave drag signal, which somewhat surprisingly correlates rather well with linear estimates. The estimated drag has an average value similar to those observed in the PYREX experiment, despite the lower wind speeds typical of Madeira.
An improved fast radiative transfer model for assimilation of satellite radiance observations
Authors: Saunders R. , Matricardi M. , Brunel P.
Published: November 2010

To assimilate atmospheric and surface radiance measurements from satellites in a numerical weather prediction model, a fast radiative transfer model is required to compute radiances from the model first guess fields at every observation point. Such a model for satellite infrared and microwave radiance measurements is used operationally for the assimilation of TIROS operational vertical sounder radiances at the European Centre for Medium‐Range Weather Forecasts. An improved version of this model has been developed which requires ozone, in addition to temperature and water vapour, in the input profile and it has been generalized to compute radiances for other satellite radiometers using the same code. Instruments such as the high resolution infrared radiation sounder and the advanced microwave sounding unit on the National Oceanic and Atmospheric Administration polar orbiters, the METEOSAT water vapour imager and the Geostationary Operational Environmental Satellite infrared sounder have been simulated. It is demonstrated, by comparisons with line‐by‐line model computed radiances, that the fast model can reproduce the line‐by‐line model radiances for the TIROS operational vertical sounder stratospheric temperature sounding channels to an accuracy below the instrumental noise. The tropospheric, surface sensing, water vapour and ozone channel radiances cannot be predicted to such an accuracy, but still accurately enough for numerical weather prediction assimilation. A comparison of measured TIROS operational vertical sounder radiances with predicted values from numerical weather prediction model analyses gives larger differences than would be expected from the combination of the fast model and instrument related errors for most channels. The validity of the tangent linear approximation of the model gradient for typical radiance departures is also explored, with several examples, for the high resolution infrared radiation sounder/advanced microwave sounding unit instrument combination. The tangent‐linear approximation is valid for temperature but significant departures from linearity about the first guess profile are observed for water vapour and ozone. Cloud affected infrared radiances have a highly non‐linear response.
The effect of the iterative triple and quadruple cluster amplitudes on the adiabatic potential curve in the coupled cluster calculations of the ground electronic state of the Yb dimer
Authors: Mosyagin N. S. , Petrov A. N. , Titov A. V.
Published: November 2010

The dissociation energy, equilibrium internuclear distance, and spectroscopic constants for the 1Σ ground state of the Yb2 molecule are calculated. The relativistic effects are introduced through generalized relativistic effective core potentials with very high precision. The scalar relativistic coupled cluster method particularly well suited for closed‐shell van der Waals systems is used for the correlation treatment. Extensive generalized correlation basis sets were constructed and used. The relatively small corrections for high‐order cluster amplitudes and spin—orbit interactions are taken into account using smaller basis sets and the spin—orbit density functional theory. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Zinc selenide nanoclusters: Static dipole polarizability and electronic properties
Authors: Mohajeri Afshan , Alipour Mojtaba
Published: November 2010

The structural stability and electronic properties of stoichiometric zinc selenide (ZnSe) nanoclusters up to 20 atoms have been systematically investigated in the framework of density functional theory. The similarity function has been used to investigate the extent that the clusters are similar to the pure ZnSe or to each other. Energetically, the relative stability of ZnSe clusters at different sizes is studied by calculating the second‐order difference in total energy. The size evolution of several reactivity descriptors such as static dipole polarizability and chemical hardness has been determined for ZnSe clusters. In addition, the minimum polarizability principle and principle of maximum hardness are used to characterize the magic clusters. Moreover, it is shown that the differential mean polarizability can be also a useful quantity to characterize the stability of the studied clusters. It is found that there is a strong inverse correlation between the static dipole polarizability and the ionization potential of the ZnSe clusters. Similarly, the softness has also been shown to mostly correlate with the static dipole polarizability of these clusters. This work thus will have some important implications for the calculation of polarizability of ZnSe clusters in terms of the corresponding ionization potentials and softness. For each property, a comparison between studied clusters here and the zinc sulfide clusters from our recent article is presented. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Evaluation of the LTQ‐Orbitrap mass spectrometer for the analysis of polymerase chain reaction products
Authors: Manduzio Hélène , Ezan Eric , Fenaille François
Published: November 2010

We have investigated the potential and robustness of the off‐line coupling of polymerase chain reaction (PCR) with electrospray ionization mass spectrometry (ESI‐MS), for further applications in the screening of single‐nucleotide polymorphisms (SNPs). This was based on recently reported data demonstrating that anion‐exchange solid‐phase extraction was the most efficient technique for efficiently desalting PCR products, with a recovery of ∼70%. Results showed that this purification approach efficiently removes almost all the chemicals commonly added to PCR buffers. ESI‐MS analysis of a model 114‐bp PCR product performed on the LTQ‐Orbitrap instrument demonstrated that detection limits in the nM range along with an average mass measurement uncertainty of 9.15 ± 7.11 ppm can be routinely obtained using an external calibration. The PCR/ESI‐MS platform was able to detect just a few copies of a targeted oligonucleotide. However, it was shown that if two PCR products are present in a mixture in a ratio higher than 10 to 1, the lower abundance one might not be reproducibly detected. Applications to SNPs demonstrated that an LTQ‐Orbitrap with a resolution of 30 000 (at m/z 400) easily identified a single (A ↔ G) switch, i.e. a 16 Da difference, in binary mixtures of ∼ 35 kDa PCR products. Complementary experiments also showed that the combination of endonucleases and ESI‐MS could be used to confirm base composition and sequence, and thus to screen for unknown polymorphisms in specific sequences. For example, a single (T ↔ A) switch (9 Da mass difference) was successfully identified in a 114‐bp PCR product. Copyright © 2010 John Wiley & Sons, Ltd.
Study of plasma metabolic profiling and biomarkers of chronic unpredictable mild stress rats based on gas chromatography/mass spectrometry
Authors: Li Zhen‐Yu , Zheng Xing‐Yu , Gao Xiao‐Xia , Zhou Yu‐Zhi , Sun Hai‐Feng , Zhang Li‐Zeng , Guo Xiao‐Qing , Du Guan‐Hua , Qin Xue‐Mei
Published: November 2010

A metabolomic investigation of chronic unpredictable mild stress (CUMS) rats was carried out. Plasma obtained from Sprague‐Dawley (SD) rats treated by CUMS was analyzed using gas chromatography/mass spectrometry. Thirty‐seven metabolites were identified among the detected compounds. Subsequent data analysis using the t test and principal component analysis (PCA) revealed significant metabolic changes in the rats' plasma after CUMS treatment. Clear separation between the model and control group was achieved, and the level of twelve metabolites, including amino acids, sugar, organic acids and fatty acids, were significantly different between plasma samples from the controls and CUMS group. These observations suggested that the depressed state may be associated with perturbation of amino acid metabolism, energy metabolism and glycometabolism. The study suggested that the metabolomics approach could be used as a potential powerful tool to investigate the biochemical change in certain physiopathological conditions, such as depression, as an early diagnostic means. Copyright © 2010 John Wiley & Sons, Ltd.
On the limits of clustering in high dimensions via cost functions
Authors: Koepke Hoyt A. , Clarke Bertrand S.
Published: November 2010

This paper establishes a negative result for clustering: above a certain ratio of random noise to nonrandom information, it is impossible for a large class of cost functions to distinguish between two partitions of a data set. In particular, it is shown that as the dimension increases, the ability to distinguish an accurate partitioning from an inaccurate one is lost unless the informative components are both sufficiently numerous and sufficiently informative. We examine squared error cost functions in detail. More generally, it is seen that the VC‐dimension is an essential hypothesis for the class of cost functions to satisfy for an impossibility proof to be feasible. Separately, we provide bounds on the probabilistic behavior of cost functions that show how rapidly the ability to distinguish two clusterings decays. In two examples, one simulated and one with genomic data, bounds on the ability of squared‐error and other cost functions to distinguish between two partitions are computed. Thus, one should not rely on clustering results alone for high dimensional low sample size data and one should do feature selection. Copyright © 2010 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 4: 30–53 2011
Harderoporphyria due to homozygosity for coproporphyrinogen oxidase missense mutation H327R
Authors: Hasanoglu Alev , Balwani Manisha , Kasapkara Çiğdem S. , Ezgü Fatih S. , Okur İlyas , Tümer Leyla , Çakmak Alpay , Nazarenko Irina , Yu Chunli , Clavero Sonia , Bishop David F. , Desnick Robert J.
Published: November 2010

Hereditary coproporphyria (HCP) is an autosomal dominant acute hepatic porphyria due to the half‐normal activity of the heme biosynthetic enzyme, coproporphyrinogen oxidase (CPOX). The enzyme catalyzes the step‐wise oxidative decarboxylation of the heme precursor, coproporphyrinogen III, to protoporphyrinogen IX via a tricarboxylic intermediate, harderoporphyrinogen. In autosomal dominant HCP, the deficient enzymatic activity results primarily in the accumulation of coproporphyrin III. To date, only a few homozygous HCP patients have been described, most having Harderoporphyria, a rare variant due to specific CPOX mutations that alter enzyme residues D400–K404, most patients described to date having at least one K404E allele. Here, we describe a Turkish male infant, the product of a consanguineous union, who presented with the Harderoporphyria phenotype including neonatal hyperbilirubinemia, hemolytic anemia, hepatosplenomegaly, and skin lesions when exposed to UV light. He was homoallelic for the CPOX missense mutation, c.980A>G (p.H327R), and had massively increased urinary uroporphyrins I and III (9,250 and 2,910 μM, respectively) and coproporphyrins I and III (895 and 19,400 μM, respectively). The patient expired at 5 months of age from an apparent acute neurologic porphyric attack. Structural studies predicted that p.H327R interacts with residue W399 in the CPOX active site, thereby accounting for the Harderoporphyria phenotype.
Living on the verge: are roads a more suitable refuge for small mammals than streams in Mediterranean pastureland?
Authors: Sabino‐Marques Helena , Mira António
Published: November 2010

The retention of natural habitat corridors is a useful and practical conservation tool that can attenuate the effects of habitat loss and fragmentation on wildlife. Linear structures may contribute to the conservation of biodiversity by providing additional habitats for small fauna living in highly modified environments. We assessed the importance of road verges as refuge areas for small mammals, in highly intensified grazed pastures, within a Mediterranean landscape and compared the role of road verges as refuges with that of riparian galleries, which have been described as important shelter locations for small fauna. For this purpose, a small mammal trapping study was undertaken on two road verges and beside two small streams in southern Portugal. We captured 457 individuals of five different species, with Mus spretus the most common species captured, followed by Crocidura russula. Captures were 4.6‐fold higher immediately beside both roads and streams than 12 m away in the surrounding matrix. Individuals captured in the matrix presented a smaller body size and lower body condition, suggesting that this suboptimal habitat is occupied mainly by subadults. M. spretus was 46% more abundant by roads than by streams, while C. russula was present in similar numbers in both habitats. M. spretus individuals were larger near streams but exhibited no difference in body condition between habitats. C. russula had a better body condition and slightly higher body lengths at roadsides. Our results show that roadside verges in intensively grazed Mediterranean landscapes act as important refuges and constitute equally vital habitats for small mammals as do riparian vegetation strips in landscapes where other suitable habitats are scarce.