bluuebunny/crossref_metadata_2025 huggingface dataset:
Rainfall trends in the KwaZulu‐Natal Drakensberg region of South Africa during the twentieth century
Authors: Nel Werner
Published: December 2008

This study assesses long‐term rainfall records in the KwaZulu‐Natal Drakensberg, South Africa's most valuable source of surface runoff. Records from 11 stations covering the Drakensberg region in South Africa indicate that no statistically significant trend in interannual variability existed during the last half of the twentieth century. Annual rainfall in the Drakensberg is highly seasonal, and analysis of monthly rainfall indicates an increase in the variability of the distribution of monthly rainfall and the strengthening of rainfall seasonality in the Drakensberg through a significant decrease in autumn rainfall. The El Niño/Southern Oscillation (ENSO) influences summer rainfall variability of the KwaZulu‐Natal Drakensberg, and a strong correlation also exists between summer rainfall and the Southern Oscillation Index (SOI) for preceding periods. This correlation between summer rainfall and ENSO events suggests that changes in the frequency and intensity of the ENSO should affect the rainfall in the Drakensberg. The lagged correlation between summer rainfall in the Drakensberg and the SOI could be used as an indicator for seasonal forecasting. Copyright © 2008 Royal Meteorological Society
Summer daily precipitation variability over the East Anglian region of Great Britain
Authors: Neal Robert A. , Phillips Ian D.
Published: December 2008

Daily precipitation totals for five consecutive summers (1994–1998) were obtained for 136 stations in East Anglia to explore geographic variations in rainfall. S‐mode principal components analysis (PCA) was used to identify the main spatial modes of variability in the region's precipitation field. The components were interpreted physically by examining synoptic charts and the British Isles' circulation variables for the days with high PC scores. Whilst seven principal components have eigenvalues greater than 1, and collectively explain 86.3% of the variance, only the first 5 PCs have well defined rainfall patterns that can be attributed to specific circulation patterns. The most dominant pattern (PC 1) shows a gradient between wetter conditions in NE Norfolk and drier conditions in Cambridgeshire and Essex, which is favoured by a cyclonic northerly airflow. PC 2 is almost as dominant, and shows a west to east decay in rainfall totals that is typically associated with active zonal W–SW flows. PC 3 sees the highest totals occurring in Essex. Wetter conditions in the south of East Anglia tend to occur when areas of low pressure follow a southerly track along the English Channel and southern North Sea. PC 4 shows a maximum in convective activity that occurs furthest inland in SE Cambridgeshire and west Suffolk, with the convection being triggered or accentuated by the East Anglian Heights (the highest land in East Anglia). PC 5 shows the rainfall distribution under a cyclonic N–NW, whereby showers generated over The Wash penetrate inland and produce the most rainfall in west Norfolk. Finally, a summer precipitation regionalization was derived by applying agglomerative hierarchical cluster analysis to the loadings of PCs 1–7. It is concluded that a location's precipitation climatology is more strongly determined by the orientation of the nearest coastline rather than simply the site's distance from the North Sea. Copyright © 2008 Royal Meteorological Society
The role of surgical margin status in retroperitoneal sarcoma
Authors: Anaya Daniel A. , Lev Dina C. , Pollock Raphael E.
Published: December 2008

Retroperitoneal sarcomas (RPS) represent approximately 15% of all soft tissue sarcomas (STS). Clinical and prognostic features as well as oncologic outcomes are well known in this group of patients. Post‐operative margin status specifically, is a major predictor of local and distant recurrence and survival. The purpose of this review is to define complete resection as it applies to RPS and evaluate its effect on future outcomes in these patients. J. Surg. Oncol. 2008;98:607–610. © 2008 Wiley‐Liss, Inc.
Multimodality management of desmoid tumors: How important is a negative surgical margin?
Authors: Melis Marcovalerio , Zager Jonathan S. , Sondak Vernon K.
Published: December 2008

Desmoid tumors are rare, locally invasive mesenchymal tumors without metastatic potential. Their clinical behavior is heterogeneous and characteristically unpredictable; outcomes are influenced by anatomic location, proximity to vital organs, association with familial adenomatous polyposis. Surgery is the main treatment modality, but the significance of positive resection margins remains controversial since they may not increase the risk of recurrence: in this setting re‐resection, adjuvant radiation or close clinical follow‐up could all be appropriate options. We reviewed the current evidence for multimodality therapy of desmoids, with a focus on the importance of resection margins, and present our own algorithm for treatment. J. Surg. Oncol. 2008;98:594–602. © 2008 Wiley‐Liss, Inc.
Margin status after breast‐conserving treatment of breast cancer: How much free margin is enough?
Authors: von Smitten Karl
Published: December 2008

In breast conserving surgery the margins of the specimen have to be tumor free. There is no universal agreement on the width of the tumor free margin. The width has some impact on recurrence rate, and at least 5 mm seems to be preferred and this is especially important in extensive intraductal component. In ductal cancer in situ the free margin should be at least 5 mm, preferably 10 mm. Oncoplastic surgery is beneficial for reaching adequate margins. J. Surg. Oncol. 2008;98:585–587. © 2008 Wiley‐Liss, Inc.
Ultrafast exciton relaxation dynamics in silicon quantum dots
Authors: Cimpean C. , Groenewegen V. , Kuntermann V. , Sommer A. , Kryschi C.
Published: December 2008

The photoluminescence properties of silicon quantum dots may be tailored by surface states via efficient coupling to resonant bulk states. Therefore various wet‐chemistry procedures were developed to fabricate silicon quantum dots with adjustable sizes and surface properties. While the energy gap of the Si core is tuned by the size, resonant electronic surface states may be attained by varying the structure and chemical composition of the grafting. The strength of electronic couplings between surface and bulk states determines the timescale of both photo‐induced electron transfer from excited surface states to conduction band states and capture of conduction band electrons by surface states. Whereas the origin of photoluminescence and therewith the quantum dot size distribution may be elucidated by stationary luminescence spectroscopy, ultrafast optical spectroscopy techniques, for instance the femtosecond transient absorption spectroscopy, allow to monitor photo‐induced electron transfer between surface and bulk states and carrier trapping on the subpicosecond timescale.
Femtosecond laser near field ablation
Authors: Plech A. , Leiderer P. , Boneberg J.
Published: December 2008

The high field strength of femtosecond laser pulses leads to nonlinear effects during the interaction with condensed matter. One such effect is the ablation process, which can be initiated below the threshold of common thermal ablation if the excitation pulses are sufficiently short. This effect leads to structure formation, which is anisotropic because of the polarization properties of the near field and can result in pattern sizes below the resolution limit of light. These effects are explored by temporally resolved scattering methods and by post‐mortem analysis to show the non‐thermal and anisotropic nature of this process. The near‐field distribution of plasmon modes can be tailored to a large extent in order to obtain control of the pattern formation.
Ultrafast laser written active devices
Authors: Ams M. , Marshall G.D. , Dekker P. , Piper J.A. , Withford M.J.
Published: December 2008

Direct‐write optical waveguide device fabrication is probably the most widely studied application of femtosecond laser micromachining in transparent dielectrics at the present time. Devices such as buried waveguides, power splitters, couplers, gratings, optical amplifiers and laser oscillators have all been demonstrated. This paper reviews the application of the femtosecond laser direct‐write technique to the fabrication of active waveguide devices in bulk glass materials.
Structural Analysis of Proteinaceous Components in Byssal Threads of the Mussel Mytilus galloprovincialis
Authors: Hagenau Anja , Scheidt Holger A. , Serpell Louise , Huster Daniel , Scheibel Thomas
Published: December 2008

The mussel byssus is a unique holdfast structure employed by marine mussels to colonize diverse substrates. The byssus consists of extracellular threads with mainly proteinaceous components. Individual threads reveal high tensile strength at their distal end and high elasticity in their proximal portion. Our studies show that proteins of the distal part are oriented along the thread axis and are well‐ordered with a high β‐structural content. In contrast, proteins of the proximal part are less ordered and are not as well‐oriented with primarily α‐helical structure. The detected differences in the structural features of the proteins along a byssus thread are likely an important basis for its gradual mechanical properties.

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Gas Diffusion in Anisotropic Nonhomogeneous Polymers
Authors: Grisafi Steven
Published: December 2008

In an effort to address the situation of gas diffusion in polymers that undergo swelling during the absorption process, two mass flux constitutive relations, independent of Fick's law, are evaluated. Both mass flux relations utilize the mass diffusivity as a tensor quantity. The diffusivity tensor considered can be a function of both time and spatial coordinates. For the case of one‐dimensional diffusion, approximations are found relating the diffusivity, when it is considered to be time varying and a function of position in the polymer, to the constant diffusivity assumed by Fick's law and its predicted concentration profile. Analyzing a case of oxygen absorption by glassy poly(ethylene terephthalate) shows a time‐dependent diffusivity with negligible spatial variation.

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Repair of DNA lesions associated with triplex‐forming oligonucleotides
Authors: Chin Joanna Y. , Glazer Peter M.
Published: December 2008

Triplex‐forming oligonucleotides (TFOs) are gene targeting tools that can bind in the major groove of duplex DNA in a sequence‐specific manner. When bound to DNA, TFOs can inhibit gene expression, can position DNA‐reactive agents to specific locations in the genome, or can induce targeted mutagenesis and recombination. There is evidence that third strand binding, alone or with an associated cross‐link, is recognized and metabolized by DNA repair factors, particularly the nucleotide excision repair pathway. This review examines the evidence for DNA repair of triplex‐associated lesions. © 2008 Wiley‐Liss, Inc.
From delocalized lipophilic cations to hypoxia: Blocking tumor cell mitochondrial function leads to therapeutic gain with glycolytic inhibitors
Authors: Kurtoglu Metin , Lampidis Theodore J.
Published: December 2008

An unexpected similarity between cancer and cardiac muscle cells in their sensitivity to anthracyclines and delocalized lipophilic cations (DLC) prompted a series of studies in which it was shown that the positive charge of these compounds is central to their selective accumulation and toxicity in these two distinct cell types. An initial finding to explain this phenomenon was that cancer and cardiac muscle cells exhibit high negative plasma membrane potentials resulting in increased uptake of these agents. However, thep‐glycoprotein efflux pump was shown to be another factor underlying differential accumulation of these compounds, since it recognizes positively charged drugs and thereby actively reduces their intracellular concentrations. The delocalized positive charge and lipophilicity of DLCs leads to their retention and inhibition of ATP synthesis in mitochondria. Years later it was realized that cancer cells in the hypoxic portions of solid tumors were similar to those treated with DLCs in relying mainly on anaerobic metabolism for survival and could thus be targeted with a glycolytic inhibitor, 2‐deoxy‐D‐glucose (2‐DG). This hypothesis has lead to a Phase I clinical trial in which 2‐DG is used to selectively kill the hypoxic tumor cell population which are resistant to standard chemotherapy or radiation.
Vitamin E analogues as mitochondria‐targeting compounds: From the bench to the bedside?
Authors: Zhao Yan , Neuzil Jiri , Wu Kun
Published: December 2008

Despite considerable effort focusing on designing and finding efficient anti‐cancer drugs over the last decade, little progress has been achieved, in particular in case of highly recalcitrant malignancies. Also, since there is a trend suggesting that deaths from cancers may be more frequent than from cardiovascular diseases, it is important to look for novel efficient and selective therapeutic approaches to gradually start winning the battle with cancer. Redox‐silent vitamin E analogues, epitomised by α‐tocopheryl succinate, give some hope in the quest for drugs with such properties. Thus far, these agents have been successfully tested in experimental animals with different types of cancer, showing high efficacy against malignancies including HER2‐positive breast carcinomas or malignant mesotheliomas. Further research will provide additional, necessary data to launch clinical trials, possibly in near future, translating into development of innovative anti‐cancer drugs acting by targeting mitochondria selectively in cancer cells.
Resveratrol analog‐3,5,4′‐trimethoxy‐trans‐stilbene inhibits invasion of human lung adenocarcinoma cells by suppressing the MAPK pathway and decreasing matrix metalloproteinase‐2 expression
Authors: Yang Ya‐Ting , Weng Chia‐Jui , Ho Chi‐Tang , Yen Gow‐Chin
Published: December 2008

Resveratrol (3,5,4′‐trihydroxystilbene) is a natural polyphenol that presents various physiological activities. It has been reported that the methylated derivatives of resveratrol show better potential antifungal and antiproliferative activities than resveratrol. In the present study, we investigated the inhibitory effect of 3,5,4′‐trimethoxy‐trans‐stilbene (MR‐3), a methylated derivative of resveratrol, on the invasion of A549 cells (a human lung adenocarcinoma cell line). We found that treatment with MR‐3 at the concentration of 5 μM resulted in antiadhesive, antimigratory, and antiinvasive activities on A549 cells through the suppression of matrix metalloproteinase (MMP)‐2 protein expression and transcriptional levels in a time‐dependent manner. The suppression of MMP‐2 expression by MR‐3 led to an inhibition of A549 cell invasion by inactivating phosphorylation of SAPK/c‐Jun N‐terminal kinase (JNK) and p38 MAPK signaling pathways. A time‐dependent inhibition of protein levels for p65, c‐Jun, and c‐Fos in the nucleus by MR‐3 treatment was also observed. In conclusion, our data demonstrate that the antiinvasive effects of MR‐3 on A549 cells are likely mediated through the inhibition of phosphorylation of JNK and p38, as well as a reduction in the protein levels of nuclear factor‐kappa B (NF‐κB) and activator protein‐1 (AP‐1) in the nucleus, ultimately leading to downregulation of MMP‐2 expression.
Vertical dynamic response of a rigid foundation embedded in a poroelastic soil layer
Authors: Cai Y. Q. , Hu X. Q. , Xu C. J. , Hong Z. S.
Published: December 2008

A simplified analytical method is presented for the vertical dynamic analysis of a rigid, massive, cylindrical foundation embedded in a poroelastic soil layer. The foundation is subjected to a time‐harmonic vertical loading and is perfectly bonded to the surrounding soil in the vertical direction. The soil underlying the foundation base is represented by a single‐layered poroelastic soil based on rigid bedrock while the soil at the side of the foundation is modeled as an independent poroelastic layer composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory and its governing equations are solved by the use of Hankel integral transform. The contact surface between the foundation base and the soil is smooth and fully permeable. The dynamic interaction problem is solved following standard numerical procedures. The accuracy of the present solution is verified by comparisons with the well‐known solutions obtained from other approaches for both the elastodynamic interaction problem and poroelastodynamic interaction problem. Numerical results for the vertical dynamic impedance and response factor of the foundation are presented to demonstrate the influence of nondimensional frequency of excitation, soil layer thickness, poroelastic material parameters, depth ratio and mass ratio on the dynamic response of a rigid foundation embedded in a poroelastic soil layer. Copyright © 2008 John Wiley & Sons, Ltd.
Symmetries and solutions of reaction‐diffusion‐convection equations with power diffusivities
Authors: Cherniha Roman , Pliukhin Oleksii
Published: December 2008

New Q‐conditional symmetries for two classes of reaction‐diffusion‐convection equations with power diffusivities are derived. The symmetries obtained for constructing exact solutions of the relevant nonlinear equations are successfully applied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling dissipative effects in anisotropic materials by means of evolving generalized structural tensors
Authors: Ehret Alexander E. , Itskov Mikhail
Published: December 2008

In this work, an anisotropic dissipative model is proposed as an extension of a recently presented polyconvex anisotropic strain‐energy function for fiber‐reinforced materials. This thermodynamically consistent model is able to describe different softening phenomena and includes residual deformations. The so‐called preconditioning behavior of a soft biological tissue sample is considered as a numerical example. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical approximation of the Smagorinsky model by a two‐level method
Authors: Borggaard Jeff , Iliescu Traian , Lee Hyesuk , Roop John Paul , Son Hyunjin
Published: December 2008

A two‐level method for discretizing the Smagorinsky model for the numerical simulation of turbulent flows is proposed. In the two‐level algorithm, the solution to the fully nonlinear coarse mesh problem is utilized in a single‐step linear fine mesh problem. When modeling parameters are chosen appropriately, the error in the two‐level algorithm is comparable to the error in solving the fully nonlinear problem on the fine mesh. We provide an a priori error estimate for the two‐level method, which yields appropriate scalings between the coarse and fine mesh‐sizes (H and h, respectively), and the radius of the spatial filter used in the Smagorinsky model (δ). In addition, we provide an algorithm in which a coarse mesh correction is performed to further enhance the accuracy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bugs, errors, and unexpected results in computer algebra packages
Authors: Krämer Walter
Published: December 2008

The following is a citation from the description and aims of the Dagstuhl Seminar on Algebraic and Numerical Algorithms and Computer‐assisted Proofs:

In contrast, most algorithms in computer algebra are ‘never failing’, that is they are proved to provide a solution for any input, and the maximum computing time for this is estimated a priori.

The focus of this contribution is the reliability of the computer algebra system Maple. We will show that ‘never failing’ algorithms may be the theory but concerning actual implementations such a statement seems not to be drawn from life. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Path integrals as analysis on path space by time slicing approximation
Authors: Kumano‐go Naoto , Fujiwara Daisuke
Published: December 2008

This is a survey of our papers [3, 4]. We give a fairly general class of functionals on a path space so that Feynman path integral has a mathematically rigorous meaning. More precisely, for any functional belonging to our class, the time slicing approximation of Feynman path integral converges uniformly on compact subsets of the configuration space. Our class of functionals is closed under addition, multiplication, translation, real linear transformation and functional differentiation. The invariance under translation and orthogonal transformation, the interchange of the order with Riemann‐Stieltjes integrals and some limits, the semiclassical approximation, the integration by parts and the Taylor expansion formula with respect to functional differentiation, and the fundamental theorem of calculus hold in Feynman path integral. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical phenomena in evolving networks: Ferromagnetic phase transition in evolving network of stochastic cellular automata
Authors: Makowiec Danuta
Published: December 2008

It is shown by MC simulations that ferromagnetic system modeled by cellular automata with synchronously rewired interconnections changes critically when preference in rewiring is added – the system becomes resistant against stochastic noise. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The LANS‐alpha turbulence model in primitive‐equation ocean modeling
Authors: Petersen Mark R. , Hecht Matthew W. , Holm Darryl D. , Wingate Beth A.
Published: December 2008

The Lagrangian‐Averaged Navier‐Stokes alpha (LANS‐α) and Leray turbulence parameterizations are demonstrated in a primitive‐equation ocean model using an idealized channel domain. For LANS‐α, turbulence statistics such as kinetic energy, eddy kinetic energy, and temperature profiles resemble doubled‐resolution statistics with the standard model. In a North Atlantic domain with realistic topography, the Leray model increases eddy activity. The LANS‐α and Leray models show great promise to improve heat transport and temperature distributions in global ocean‐climate simulations, as these processes depend on better resolution of eddies near the grid‐scale. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A functional iteration for the quantum drift–diffusion model: existence analysis and numerical approximation
Authors: Falco Carlo de , Jerome Joseph W. , Sacco Riccardo
Published: December 2008

This communication describes a functional iteration technique, denoted Generalized Gummel Map (GGM), for the solution of the Quantum Drift–Diffusion (QDD) model. The assumptions needed to establish existence of a fixed point for the GGM are described and their plausibility is assessed via physical arguments supported by one–dimensional numerical experiments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tensor product methods for stochastic problems
Authors: Zander Elmar , Matthies H. G.
Published: December 2008

In the solution of stochastic partial differential equations (SPDEs) the generally already large dimension N of the algebraic system resulting from the spatial part of the problem is blown up by the huge number of degrees of freedom P coming from the stochastic part. The number of degrees of freedom of the full system will be NP, which poses severe demands on memory and processor time. We present a method how to approximate the system by a data‐sparse tensor product (based on the Karhunen‐Loève decomposition with M terms), which uses only memory in the order of M (N + P), and how to keep this representation also inside the iterative solvers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Continuous workspace analysis for parallel cable‐driven Stewart‐Gough platforms
Authors: Bruckmann Tobias , Mikelsons Lars , Schramm Dieter , Hiller Manfred
Published: December 2008

Parallel cable‐driven Stewart‐Gough platforms consist of a end‐effector which is connected to the machine frame by motor driven cables. Since cables can transmit only tension forces, at leastm=n+ 1 cables are needed to tense a system havingndegrees‐of‐freedom. This results in a kinematical redundancy and leads to a (m–n)‐dimensional solution space for the cable force distribution. For this reason, performing a workspace analysis requires advanced methods and is time consuming. However, reliable and robust algorithms are demanded to calculate the workspace for a given parameter set (winch positions and platform anchor points). Discrete methods are widely used to analyze the workspace. Singularities as well as cable collisions inside the workspace of a cable‐driven Stewart‐Gough platform are possible [1]. Therefore discrete methods may deliver wrong results due to the fact that intermediate points on the discrete calculation grids are neglected. In this paper, another approach is presented. The use of intervals avoids the problems described above and leads to reliable results. In the following the basic ideas of this continuous workspace analysis are shown. For practical application, e.g. in robotics, even more important is the parameter synthesis, i.d. the process of designing a robot for a predefined workspace. However, the workspace geometries are very complex and not intuitive in general. Here, the analysis methods are also extended for synthesis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape derivatives without taking the shape derivative
Authors: Ito K. , Kunisch K. , Peichl G.
Published: December 2008

A general framework for calculating shape derivatives for optimization problems with partial differential equations as constraints is presented. Exploiting the structure of the cost functional the proposed technique allows to obtain the shape derivative of the cost without the necessity to involve the shape derivative of the state variable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The characteristic Chern type classes and integrability of multidimensional differential systems on Riemannian manifolds
Authors: Prykarpatsky Anatoliy K. , Bogolubov Nikolai N.
Published: December 2008

The differential‐geometric properties of generalized de Rham‐Hodge complexes naturally related with integrable multidimensional differential systems of M. Gromov type are analyzed. The geometric structure of Chern type characteristic classes are studied, special differential invariants of the Chern type are constructed. The integrability of multi‐dimensional nonlinear differential systems on Riemannian manifolds is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence oflow Mach numbers on thenumerical dissipation of Godunov‐typeschemes: a comparison between Roeand HLLscheme
Authors: Rieper Felix
Published: December 2008

Upwind schemes for the Euler equations face three kinds of problems in the low Mach number regime: The stiffness due to the presence of fast acoustic and slow entropy and shear waves can be overcome – at least for steady problems – by preconditioning the physical equations, see for example [1, 2]. Secondly, the 𝒪(M2)‐pressure variations get lost in the O(1)‐global pressure due to finite precision arithmetics. This cancellation problem was dealt with in [3]. The third problem originates in the numerical viscosity of the upwind schemes and is – in the author's view of the matter – not fully understood to date. Asymptotic analyses of the upwind schemes such as [4] suggest that the pressure field will completely degenerate, producing variations of the wrong order of magnitude. Our numerical andanalytical results give a more precise picture of the problem and are – at least in parts – contradicting the established view. We will prove in this paper that complete Riemann solvers such as Roe's behave completely different to incomplete Riemann solvers such as HLL in the low Mach number regime. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling laboratory data from clinical trials
Authors: Rosenkranz Gerd
Published: December 2008

Laboratory data from clinical trials are considered precursors of potential organ dysfunctions. The routine analysis of these data focusses on the occurrence of extremely high or low values relative to normal ranges, the change of these incidences compared to baseline, or the worst values from each individual patient. However, only rarely is an attempt made to model the dynamics of the measurements over time. In this paper we propose to model laboratory measurements by stochastic processes, specifically by Ornstein‐Uhlenbeck processes. The aim is to estimate parameters of these processes in order to characterize a potential effect of drugs or other medical treatments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aspects of sensitivity analysis using the level‐set method in structural optimization
Authors: Rotthaus Monika , Barthold Franz‐Joseph
Published: December 2008

The level‐set method is very common for modelling structural optimization problems, e.g. multi‐material structures. Essentially two different approaches are known. The first method describes the shape by an implicit function formulation. The weak form is expressed as a Heaviside function of this implicit function and the optimization problem is solved by an iterative procedure. This method is applied to topology optimization by e.g. Belytschko et al. [1]. The second approach is based on the combination of the shape derivative and the level‐set method for front propagation, which has been devised by Osher and Sethian [2]. Allaire et. al. [3] use the shape derivative for the minimization problem to compute the advection velocity in the Hamilton‐Jacobi equation. The Hamilton‐Jacobi equation can be solved numerically by an explicit first order upwind scheme on a Cartesian grid. We propose a new numerical method for shape optimization of multi‐material structures. This approach is based on the level‐set method combined with the variational sensitivity analysis, see Barthold [4]. The aim of the present contribution is to point out the essential aspects of this combination and to compare it with the two methods mentioned above. Furthermore the sensitivity of multi‐material structures in terms of various design parameters is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An atomic interaction‐based continuum model for computational multiscale contact mechanics
Authors: Sauer Roger A. , Li Shaofan
Published: December 2008

A computational multiscale contact mechanics model is presented which describes the interaction between deformable solids based on the interaction of individual atoms or molecules. The contact model is formulated in the framework of large deformation continuum mechanics and combines the approaches of molecular modelling [1] and continuum contact mechanics [2]. In the following a brief overview of the contact model is given. Further details can be found in [3], [4] and [5]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrically nonlinear finite‐shell elements with magnetostrictive layers
Authors: Lentzen Sven , Schmidt Rüdiger
Published: December 2008

In this paper a geometrically nonlinear composite shell element with integrated magnetostrictive layers is presented. Three translational and two rotational nodal degrees of freedom are used for the first‐order transverse shear approximation. The finite element is used in order to investigate shape and stability control problems of structures with magnetostrictive actuator layers in the range of large deformations. The numerical approximations to this static problem are obtained using the total Lagrangian formulation for the moderate rotation shell theory. The aforementioned finite element is used to numerically investigate the actuation behaviour of the integrated magnetostrictive layers. Since the magnetic field is prescribed, the coupled magnetoelastic problem turns into a decoupled problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cahn‐Hilliard inpainting and the Willmore functional
Authors: Burger Martin , Chu Shun‐Yin , Markowich Peter , Schönlieb Carola‐Bibiane
Published: December 2008

The Cahn‐Hilliard equation has its origin in material sciences and serves as a model for phase separation and phase coarsening in binary alloys. A new approach in the class of fourth order inpainting algorithms is inpainting of binary images using the Cahn‐Hilliard equation. Like solutions of the Cahn‐Hilliard equation converging to two main values during the phase separation process, the grayvalues inside the missing part of the image are oriented towards the binary states black and white. We present stability/instability results for solutions of the Cahn‐Hilliard equation and their connection to the Willmore functional. In particular we will consider the Willmore functional as a quantity to find the optimal scale of the inpainting result. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact local nonreflecting boundary conditions for time‐dependent multiple scattering
Authors: Grote Marcus J. , Sim Imbo
Published: December 2008

In [2, 3] a nonreflecting boundary condition(NBC) for time‐dependent multiple scattering was derived, which is local in time but nonlocal in space. Here, based on a high‐order local nonreflecting boundary condition (NBC) for single scattering [4], we seek a local NBC for time‐dependent multiple scattering, which is completely local both in space and time. To do so, we first develop a high order representation formula for a purely outgoing wave field, given its values and those of certain auxiliary functions needed for the artificial boundary condition. By combining that representation formula with a decomposition of the total scattered field into purely outgoing contributions, we obtain the first exact, completely local, NBC for time‐dependent multiple scattering. The accuracy and stability of this local NBC is evaluated by coupling it to standard finite element and finite difference methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Singularities for dynamical arrest in disordered systems
Authors: Sperl Matthias
Published: December 2008

It will be shown how attraction and repulsion among interacting particles can lead to rich dynamical scenarios including glass transitions, gel transitions, and glass‐glass transitions. The transition diagram is explained by the topologically stable singularities of the Aℓ hierarchy. These singularities arise from the microscopic equations of motion and allow for asymptotic solutions. Close to glass‐glass transitions asymptotic solutions are identified in results from computer simulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fatigue life investigation using non‐destructive testing methods
Authors: Stanković Z. , Bruhns O.T.
Published: December 2008

Experimental investigations of the fatigue life prediction of two different specimen forms made from steel 42CrMo4 are described. The fatigue load is defined as a cyclic loading with constant and non constant amplitudes in tension range and with different stress ratios. This loading range leads to a high cyclic fatigue behaviour of both specimens. During the test, the growth of the fatigue crack is monitored using two different non‐destructive methods, namely acoustic emission and the electric resistance. The acoustic emission is used for detecting sound waves as a result of dissipation of elastic energy during microcracks and cracks growth, as well as for the detection of the place of crack initiation. The electric resistance is used for the monitoring and quantitative investigation of the crack growth. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some Bregman distances between financial diffusion processes
Authors: Stummer Wolfgang
Published: December 2008

We introduce Bregman distances between general probability measures, and discuss some link with Csiszar divergences. From this, we derive bounds on particular Bregman distances between non–lognormally distributed financial diffusion processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact solution for a Stefan problem with convective boundary condition and density jump
Authors: Tarzia Domingo A.
Published: December 2008

We consider the solidification of a semi‐infinite material which is initially at its liquid phase at a uniform temperature Ti. Suddenly at time t > 0 the fixed face x = 0 is submitted to a convective cooling condition with a time‐dependent heat transfer coefficient of the type H (t) = ht–1/2 (h > 0) The bulk temperature of the liquid at a large distance from the solid‐liquid interface is T∞, a constant temperature such that T∞ < Tf < Ti where Tf is the freezing temperature. We also consider the density jump between the two phases. We obtain that the corresponding phase‐change (solidification) process has an explicit solution of a similarity type for the temperature of both phases and the solid‐liquid interface, if and only if the coefficient h is large enough, that is where kl and αl are the conductivity and diffusion coefficients of the initial liquid phase. Moreover, when h ≤ h0 we only have a heat conduction problem for the initial liquid phase and the corresponding change of phase does not occur. We do the mathematical analysis of a problem which was presented in S.M. Zubair – M.A. Chaudhry, Wärme‐und‐Stoffübertragung, 30 (1994), 77‐81 and we generalized the results obtained in D.A. Tarzia, MAT‐Serie A, 8 (2004), 21‐27 when the density jump between the two phases was neglected. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some remarks on index of matrix singular integral operators in non‐smooth domains
Authors: Vasilyev V.B.
Published: December 2008

On manifolds with non‐smooth boundaries the Mikhlin‐Calderon‐Zygmund operators with a matrix symbol are considered. The Noetherian property conditions (wave factorization) and reduction to Atiyah‐Singer theorem are described. These results were obtained through joint work with I.V. Scherbenko. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lattice‐Boltzmann model for dissolution phenomena
Authors: Verhaeghe Frederik , Arnout Sander , Blanpain Bart , Wollants Patrick
Published: December 2008

We briefly review the modelling of complex dissolution phenomena using a lattice Boltzmann formulation. The model can describe both diffusion‐ and reaction‐controlled dissolution of arbitrarily shaped solid phases, possibly giving rise to thermosolutal natural convection. Applications of the model are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weak solutions and attractors for motion equations for an objective model of viscoelastic medium
Authors: Vorotnikov Dmitry , Zvyagin Victor
Published: December 2008

We study the boundary value problem for the equations of motion of incompressible viscoelastic medium with an objective constitutive law of Jeffreys kind. We show existence of global weak solutions for any initial data and construct their minimal uniform trajectory attractor and uniform global attractor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On gradient methods for maximum entropy regularizing retrieval of atmospheric aerosol particle size distribution function
Authors: Wang Yanfei , Kuenzer Claudia
Published: December 2008

The determination of the aerosol particle size distribution function using the particle spectrum extinction equation is an ill‐posed integral equation of the first kind, since as is known, we are often faced with limited or insufficient observations in remote sensing and the observations are contaminated. Physically, the particle size distribution is always nonnegative, and we are often faced with incomplete data. Therefore, the concept of maximum entropy from information theory and statistic mechanics can be used to counteract this problem of missing or erroneous data. Therefore, in this paper, we study the maximum entropy based regularization model and gradient methods for solving the corresponding optimization problem. Numerical tests are made for synthetic aerosol data to show the efficiency and feasibility of the proposed algorithms. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Invariant tori in perturbed three vortex motion
Authors: Blackmore Denis , Ting Lu , Knio Omar
Published: December 2008

The motion of three point vortices in an ideal fluid in a plane comprises a Hamiltonian dynamical system – one that is completely integrable, so it exhibits numerous periodic orbits, and quasiperiodic orbits on invariant tori. Certain perturbations of three vortex dynamics, such as three vortex motion in a half‐plane, are also Hamiltonian, but not completely integrable. Yet these perturbed systems may still have periodic trajectories and invariant tori close to those for the unperturbed dynamics.

Extending recent work by the authors [4], invariant 2‐tori approximating those for the unperturbed system are located and analyzed using a combination of classical analysis, asymptotics, and Hamiltonian methods. It is shown that the results and approximation methods used are applicable to several perturbations of three vortex dynamics such as three vortices in a half‐plane, the restricted four vortex problem in the plane, and three coaxial vortex rings in 3‐space. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decision diagrams for the approximate analysis of Markov models
Authors: Ciardo Gianfranco
Published: December 2008

Decision diagrams of various types can be used to encode the exact state space and transition rate matrix of large Markov models. However, the exact solution of such models still requires to store at least one real vector with one entry per reachable state, a formidable limitation to the practical use of these encodings. Thus, we discuss automatic techniques for the approximate computation of performance measures when the Markov model can be compactly encoded but not exactly solved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear programming approaches in the multidisciplinary design optimization of a sailing yacht keel fin
Authors: Campana Emilio F. , Fasano Giovanni , Peri Daniele , Pinto Antonio
Published: December 2008

We consider the use of global optimization techniques for the minimization of a nonconvex function, arising from a Multidisciplinary Design Optimization problem of a ship. In ship design different disciplines must be often coupled, encompassing hydrodynamic and structural problems. This scenario requires the use of specific multidisciplinary formulations, where standard mathematical programming methods could be unsuitable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topological and dynamical properties of genetic and social networks
Authors: Liò Pietro
Published: December 2008

Theoretical investigations of complex systems have provided statistical methodologies for the analysis of topological and dynamical properties of biological networks. We have compared the topology and cluster structures of the genes in plasmids and of the transcriptional network from three different studies on S. pombe cell cycle. The topology of the plasmid genes provides insights into the ecology of gene diffusion among bacterial species. We have used a phase and a clustering related parameters to gauge the level of inter‐connectivity around nodes in a transcriptional network. The analysis reveals genetic relationships at the boundaries of different cell cycle events. In human networks topological changes occur because of risk awareness, trust estimation i.e. the perception of the state of the other individuals (nodes). We found that this effect introduces a much richer dynamics. We show that for finite average network connectivity, there is always a value of risk perception that stops the epidemics. For scale‐free networks with diverging input connectivity, a linear perception cannot stop the epidemics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanics of complex bodies: comments on the unified modeling of active substructures
Authors: Mariano Paolo Maria
Published: December 2008

Basic issues of the general model‐building framework of the mechanics of complex bodies are discussed. Attention is focused on the representation of the material elements, the conditions for the existence of ground states of elastic complex bodies and their consequences on the interpretation of the nature of the various balance laws occurring. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On dispersive stability of Hamiltonian systems on lattices
Authors: Patz Carsten
Published: December 2008

We study the long‐time dynamics of oscillations in lattices of infinitely many particles interacting via certain non‐linear potentials. The aim is to proof dispersive stability of such Hamiltonian systems analogously to results known for PDEs. To do so we first recapitulate the dynamics of linear Hamiltonian systems on an infinite chain and give optimal decay rates based on the dispersion relation. Based on this we proof that if the non‐linearity is weak enough, the non‐linear system shows a similar behaviour like its linearization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical modeling of active structural acoustic control
Authors: Ringwelski Stefan , Gabbert Ulrich
Published: December 2008

Since the reduction of disturbing noise is highly important in industrial and civil engineering, much research and development has been done in this field over the past decades. The application of smart structures provides a way to reduce unwanted noise radiation. A smart structure is an integrated system consisting of the passive base structure attached with actuators and sensors. Piezoelectric ceramics are widely used as sensors and actuators, because they can easily be bonded on or imbedded into conventional structures. An often used concept for noise reduction is active structural acoustic control (ASAC). This concept means that the noise radiation will be reduced by minimizing or changing the vibrational behavior of a structure using additional actuator forces. The development and industrial use of smart structures for ASAC requires efficient and reliable simulation and design tools. Usually the design process of smart structures is based on numerical methods. In order to verify numerical techniques, the paper presents an analytical reference solution for an ASAC system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Returns of Eastern European financial markets:α ‐stable distributions, measures of risk
Authors: Serbinenko Anna , Emmenegger Jean‐François
Published: December 2008

The daily returns of financial market indices of nineteen Eastern European countries are modelled, linear trend or ARMA(p, q) for the levels and GARCH(p ′, q ′) for the residuals. For the non Gaussian residuals ‐stable distributions are proposed. Then, risk measures, like the STARR and the R‐ratio are used to analyse the risk in the cases of Gaussian and ‐stable distribution models of the residuals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The equilibrium shape of an elastic developable Möbius strip
Authors: Starostin E.L. , van der Heijden G.H.M.
Published: December 2008

A variational geometrical approach is applied to find the characteristic shape of the Möbius strip made of an inextensible rectangular sheet. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element discretization of parabolic‐elliptic interface problems
Authors: Stiemer Marcus
Published: December 2008

We consider mixed boundary value problems for partial differential equations which are parabolic in one part of the underlying domain and elliptic in another part. Such problems arise in eddy current simulations in electromagnetics. A fully discrete scheme for the numerical solution of such problems is presented. Particularly, adaptivity in space and time is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary integral equations and maximum modulus estimates for the Stokes system
Authors: Varnhorn Werner
Published: December 2008

A maximum modulus estimate for the Stokes system in bounded domains of ℝn (n ≥ 2) is established via methods of hydrodynamical potential theory. The method is based on the unique solvability of the boundary integral equations' system resulting from the double layer potential ansatz together with a projection onto the normal field on the boundary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)