bluuebunny/crossref_metadata_2025 huggingface dataset:
Muscle response to leg lengthening during distraction osteogenesis
Authors: Thorey Fritz , Bruenger Jens , Windhagen Henning , Witte Frank
Published: October 2008

Continuous lengthening of intact muscles during distraction osteogenesis leads to an increase of sarcomeres and enhances the regeneration of tendons and blood vessels. A high distraction rate leads to an excessive leg and muscle lengthening and might cause damages of muscle fibers with fibrosis, necrosis, and muscle weakness. Complications like muscle contractures or atrophy after postoperative immobilization emphazize the importance of muscles and their function in the clinical outcome. In an animal model of distraction osteogenesis, 18 sheep were operated with an external fixator followed by 4 days latency, 21 days distraction (1.25 mm per day) and 51 days consolidation. The anatomical location (gastrocnemius, peroneus tertius, and first flexor digitorum longus muscle), dimension and occurrence of muscular defects were characterized histologically. The callus formation and leg axis was monitored by weekly X‐rays. Additionally, serum creatine kinase was analyzed during a distraction and consolidation period. Significant signs of muscle lesions in all three observed muscles can be found postoperatively, whereas normal callus formation and regular leg axis was observed radiologically. The peroneus tertius and first flexor digitorum longus muscles were found to have significantly more signs of fibrosis, inflammatory, and necrosis. Creatine kinase showed two peaks: 4 and 39 days postoperative as an indication of muscle damage and regeneration. The study implicates that muscle damages should be considered when a long‐distance distraction osteogenesis is planned. The surgeon should consider these muscle responses and individually discuss a two‐stage treatment or additional muscle tendon releases to minimize the risk of muscle damages. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 483–488, 2009
Land‐use and cover changes (1988–2002) around budongo forest reserve, NW Uganda: implications for forest and woodland sustainability
Authors: Mwavu E. N. , Witkowski E. T. F.
Published: October 2008

Land‐use and cover changes around Budongo Forest Reserve (BFR) were analysed from multi‐temporal LandSat images (1988 and 2002) and associated field‐based studies in 2003–2004. Three major land‐use and cover classes: forest/woodland, sugarcane plantations and grassland/shifting‐cultivation/settlements were clearly discriminated. The area under sugarcane cultivation increased over 17‐fold, from 690 ha in 1988 to 12729 ha in 2002, with a concomitant loss of about 4680 ha (8·2 per cent) of forest/woodland, mainly on the southern boundary of BFR. Land‐use and cover changes were a result of (a) agricultural expansion, (b) increasing human population, exacerbated by large influxes of refugees, (c) conflicts of interest and political interference in the management of BFR and (d) unclear land tenure. Agriculture is the main land‐use practice and source of income to local people, with commercial sugarcane and tobacco as the primary cash crops. Individual smallholder sugarcane plantations covered distances ranging from 30 to 1440 m along the BFR edge, with no buffer zone, resulting in direct conflicts between farmers and forest wild animals. There is an ever‐increasing need for more land for agricultural expansion, resulting in continued loss of forest/woodland on private/communal lands and encroachment into BFR. This unsustainable agricultural expansion and the local people's perception of BFR as an obstacle to agriculture, threatens the conservation of its threatened wild plants (e.g. Raphia farinifera) and the endangered chimpanzees. Therefore, their sustainable management for both development and conservation will require strong and incorruptible institutions that will seek a balance between resource exploitation and conservation. Copyright © 2008 John Wiley & Sons, Ltd.
Nitroxide‐Mediated Radical Polymerization of N‐tert‐Butylacrylamide
Authors: Gibbons Orla , Carroll William M. , Aldabbagh Fawaz , Zetterlund Per B. , Yamada Bunichiro
Published: October 2008

The nitroxide‐mediated polymerization of N‐tert‐butylacrylamide (TBAM) in DMF at 120 °C using SG1/DEPN and AIBN has been investigated. Linear growth in number‐average molecular weight ($\overline M _{\rm n}$) versus conversion and narrow molecular weight distributions (MWDs) with high livingness were obtained up to ≈8 000 g · mol−1. For higher molecular weights, the MWDs gradually became broader with low molecular weight tailing, and $\overline M _{\rm n}$ deviated downwards from theoretical values. Quantitative analyses of MWDs, along with specifically designed conventional radical polymerizations at 120 °C, were consistent with chain transfer to monomer limiting the attainable $\overline M _{\rm n}$. This finding can be equally applied to existing literature polymerizations of TBAM.

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Poly(methylenepyridinium)s by Poly(N‐alkylation) of Substituted Pyridines: Structural and Kinetic Study
Authors: Monmoton Sophie , Lefebvre Hervé , Costa‐Torro France , Fradet Alain
Published: October 2008

The solution polymerization of 4‐bromomethylpyridine (M1) and 3‐bromomethyl pyridine hydrobromides (M2) was studied by NMR spectroscopy. A mechanism involving a series of bimolecular reactions of the monomer, dimer, and higher oligomers closely fits with the experimental variations of bromomethyl end group concentrations with time. M1 presents a higher reactivity than M2 and an unusual behavior, since the oligomers are more reactive than the monomer. An explanation based on a mesomeric phenomenon is proposed. The influence of the anion on the solubility and thermal stability of the poly(methylenepyridinium)s were studied after various anion exchanges. Bis(trifluoromethylsulfonyl)imide anion (Tf2N) yielded the more stable and the more organosoluble polymers.

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Hyperbranched Poly[bis(alkylene)pyridinium]s
Authors: Monmoton Sophie , Lefebvre Hervé , Costa‐Torro France , Fradet Alain
Published: October 2008

3,5‐Bis(bromomethyl)pyridine hydrobromide and 3,5‐bis(bromobutyl)pyridine hydrobromide were synthesized from commercially available 3,5‐lutidine. The poly(N‐alkylation) of these monomers readily yielded new hyperbranched polyelectrolytes. The progress of reaction was followed by 1H NMR. A second‐order kinetic scheme fits the experimental data. Rate constants and activation parameters were determined, showing the higher reactivity of 3,5‐bis(bromomethyl)pyridine hydrobromide. This was explained by the electron‐attractive effect of pyridinium groups on the CH2Br end groups. The structures of the hyperbranched poly[3,5‐bis(alkylene)pyridinium]s were investigated by 1H and 13C NMR spectroscopy and a preliminary study of their properties is reported.

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Conditional loss of PTEN leads to skeletal abnormalities and lipoma formation
Authors: Hsieh Shu‐Chen , Chen Nien‐Tsu , Lo Su Hao
Published: October 2008

To understand the role of tumor suppressor PTEN in cartilage development, we have generated chondrocyte specific PTEN deletion mice using Col2a1Cre and PTENloxp/loxp mice. PTEN mutant mice are viable and fertile, nonetheless, develop kyphosis over time. Histological analyses show mutant vertebrae and intervertebral discs are larger and therefore the spines are longer than in control mice. In addition, the growth plates are thicker, invading trabecular bone areas are deeper, and marrow adipocyte populations are higher in PTEN mutant mice. Furthermore, the growth plates, not normally fused in mouse long bones, are fused in PTEN mutants. Intriguingly, PTEN mice develop lipomas and show abnormal accumulation of fat tissues along spines. Cell tracking assays have confirmed that lipomas and a portion of fat tissues were derived from Col2a1Cre PTENloxp/loxp cells. Further analyses have suggested that the phenotypes of PTEN mutant likely attribute to PTEN's negatively regulating role in PI3K/Akt pathway. © 2008 Wiley‐Liss, Inc.
c‐Fos accelerates hepatocyte conversion to a fibroblastoid phenotype through ERK‐mediated upregulation of paxillin‐Serine178 phosphorylation
Authors: Güller Meryem C. , André Jocelyne , Legrand Agnès , Setterblad Niclas , Mauviel Alain , Verrecchia Franck , Daniel Fanny , Bernuau Dominique
Published: October 2008

Transforming growth factor β (TGF‐β) exerts an important role in the late steps of carcinogenesis by cooperating with Ras to induce cell motility and tumor invasion. The transcription complex AP‐1 has been implicated in the regulation of genes involved in motility and invasion, by mechanisms not yet delineated. We utilized a model of immortalized human hepatocytes (IHH) overexpressing c‐Fos (IHH‐Fos) or not (IHH‐C) to investigate the role of c‐Fos on cell motility in response to a prolonged treatment with TGF‐β, EGF or a combination of both. Cotreatment with EGF and TGF‐β, but neither cytokine alone, induced the conversion of hepatocytes to a fibroblastoid phenotype and increased their motility in Boyden chambers. EGF/TGF‐β cotreatment induced a higher effect on ERK phosphorylation compared to TGF‐β treatment alone. It also induced an increase in total and phosphorylated Ser178 paxillin, a protein previously implicated in cell motility. This response was inhibited by two specific MEK inhibitors, indicating the involvement of the ERK pathway in paxillin activation. Overexpression of c‐Fos correlated with increased cell scattering and motility, higher levels of ERK activation and phospho Ser178 paxillin, increased levels of EGF receptor (EGF‐R) mRNA and higher EGF‐R phosphorylation levels following EGF/TGF‐β cotreatment. Conversely, siRNA‐mediated invalidation of c‐Fos delayed the appearance of fibroblastoid cells, decreased EGF‐R mRNA and downregulated ERK and Ser178 paxillin phosphorylations, indicating that c‐Fos activates hepatocyte motility through an EGF‐R/ERK/paxillin pathway. Since c‐Fos is frequently overexpressed in hepatocarcinomas, this newly identified mechanism might be involved in the progression of hepatic tumors in vivo. © 2008 Wiley‐Liss, Inc.
Involvement of motor pathways in corticobasal syndrome detected by diffusion tensor tractography
Authors: Boelmans Kai , Kaufmann Jörn , Bodammer Nils , Ebersbach Georg , Behlau Guido , Heinze Hans‐Jochen , Niehaus Ludwig
Published: October 2008

Corticobasal syndrome (CBS) is a progressive parkinsonian disease characterized by cortical and subcortical neuronal loss. Although motor disabilities are a core feature of CBS, the involvement of motor pathways in this condition has not been completely clarified. We used magnetic resonance diffusion tensor imaging (DTI) to study corticospinal and transcallosal motor projections in CBS, and applied fiber tractography to analyze the axonal integrity of white matter projections. Ten patients with CBS were compared with 10 age‐matched healthy controls. Fiber tracts were computed using a Monte‐Carlo simulation approach. Tract‐specific mean values of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were determined. CBS patients showed a reduction of corticospinal tract (CST) fibers on the first affected side with significantly increased ADC and reduced FA values. In the corpus callosum (CC), particularly in the posterior trunk, patients also had significantly reduced fiber projections, with a higher ADC and lower FA than controls. This pattern indicates changes of the white matter integrity in both CST and CC. Thus, magnetic resonance DTI can be used to assess motor pathway involvement in CBS patients. © 2008 Movement Disorder Society
The clinical impression of severity index for Parkinson's disease: International validation study
Authors: Martínez‐Martín Pablo , Rodríguez‐Blázquez Carmen , Forjaz Maria João , de Pedro Jesús
Published: October 2008

This study sought to provide further information about the psychometric properties of the Clinical Impression of Severity Index for Parkinson's Disease (CISI‐PD), in a large, international, cross‐culturally diverse sample. Six hundred and fourteen patients with PD participated in the study. Apart from the CISI‐PD, assessments were based on Hoehn & Yahr (HY) staging, the Scales for Outcomes in PD‐Motor (SCOPA‐M), ‐Cognition (SCOPA‐COG) and ‐Psychosocial (SCOPA‐PS), the Cumulative Illness Rating Scale‐Geriatrics, and the Hospital Anxiety and Depression Scale. The total CISI‐PD score displayed no floor or ceiling effects. Internal consistency was 0.81, the test–retest intraclass correlation coefficient was 0.84, and item homogeneity was 0.52. Exploratory and confirmatory factor analysis (CFI = 0.99, RMSEA = 0.07) confirmed CISI‐PD's unifactorial structure. The CISI‐PD showed adequate convergent validity with SCOPA‐COG and SCOPA‐M (rS = 0.46–0.85, respectively) and discriminative validity for HY stages and disease duration (P < 0.0001). In a multiple regression model, main CISI‐PD predictors were SCOPA‐M, disease duration, and depression. The results obtained were not only comparable to but also extended those yielded by the preliminary validation study, thus showing that the CISI‐PD is a valid instrument to measure clinical impression of severity in PD. Its simplicity and easy application make it an attractive and useful tool for clinical practice and research. © 2008 Movement Disorder Society
Bladder sensations during filling cystometry are different according to urodynamic diagnosis
Authors: Digesu G. Alessandro , Basra Ramandeep , Khullar Vik , Hendricken Caroline , Camarata Michelle , Kelleher Con
Published: October 2008

Purpose

To determine the position and character of bladder filling sensations in women undergoing urodynamic investigations.

Materials and Methods

Women with lower urinary tract symptoms referred to urodynamic clinics of two tertiary referral teaching hospitals were prospectively studied. During filling cystometry the women were asked to describe the bladder sensations at the first sensation of bladder filling, first desire to void, strong desire to void, maximum bladder capacity and if the woman felt urgency. Women were also asked to define the time that the voiding could be delayed and to indicate the position of each sensation on a body map. Women were classified into four groups according to urodynamic diagnosis: detrusor overactivity (DO), urodynamic stress incontinence (USI), co‐existing DO and USI (mixed) and inconclusive urodynamics; the latter was excluded from the study. Bladder sensations were compared between these groups using Chi squared and Kruskall–Wallis tests.

Results

Eighty‐two women were studied. Women with DO and mixed urodynamic diagnosis predominantly described the bladder sensations as being perineal or vaginal in origin, whereas those with USI felt the sensations suprapubically. The character of bladder sensation was not significantly different between the diagnostic groups and the intensity increased with larger bladder volume. The duration that women could delay voiding was significantly different between different urodynamic groups.

Conclusions

Bladder sensations experienced during cystometry are different in position and duration in relation to urodynamic diagnoses. This indicates that uniform descriptions of sensations during filling cystometry might not be appropriate to different urodynamic diagnoses. Neurourol. Urodynam. 28:191–196, 2009. © 2008 Wiley‐Liss, Inc.
Impact of urodynamic based incontinence diagnosis on quality of life in women
Authors: Haessler Alexandra L. , Nguyen John N. , Bhatia Narender N.
Published: October 2008

Aims

To characterize the effect of urodynamic diagnosis on degree of incontinence related bother and health related quality of life in a large, multi‐ethnic population of women.

Methods

Effects of multichannel urodynamic diagnosis, urethral competency, and other patient characteristics on abbreviated Urogenital Distress Inventory (UDI6) and Incontinence Impact Questionnaire (IIQ7) composite scores were analyzed retrospectively.

Results

Six hundred eleven patients were included. Mean UDI6 and IIQ7 scores were significantly higher among patients with mixed incontinence, detrusor overactivity, urinary stress incontinence with overactive bladder, and negative studies compared to those with stress incontinence without OAB. The relative composite UDI6 and IIQ7 mean scores did not significantly differ between the mixed incontinence, detrusor overactivity, stress incontinence with OAB and negative study groups. UDI6 and IIQ7 scores were significantly higher among stress incontinent patients with intrinsic sphincter deficiency, but similar among mixed incontinent patients with intrinsic sphincter deficiency.

Conclusion

Urodynamic diagnoses of detrusor overactivity, mixed incontinence, and stress incontinence with overactive bladder are associated with significantly worse incontinence related bother and health related quality of life when compared to those with stress incontinence without OAB. These conditions appear to have similar degree of impact on incontinence related bother and quality of life. Patients presenting with symptoms of incontinence can suffer a similar compromise in quality of life despite a negative MCUD study. Neurourol. Urodynam. 28:183–187, 2009. © 2008 Wiley‐Liss, Inc.
Cournot model with investments to change the market size
Authors: Pinto Alberto A. , Ferreira Fernanda A. , Ferreira Miguel , Oliveira Bruno M.P.M.
Published: October 2008

We present a new deterministic dynamical model on the market size of Cournot competitions, based on Nash equilibria of R&D investment strategies to increase the size of the market of the firms at every period of the game. We compute the unique Nash equilibrium for the second subgame and the profit functions for both firms. Adding uncertainty to the R&D investment strategies, we get a new stochastic dynamical model and we analyse the importance of the uncertainty to reverse the initial advantage of one firm with respect to the other. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stretching fields and lines in the transport dynamics of the Western Mediterranean
Authors: Hernández‐García E. , d'Ovidio F. , Fernández V. , García‐Ladona E. , Isern‐Fontanet J. , López C. , Mancho A.M. , Small D. , Wiggins S.
Published: October 2008

We summarize recent work on the location of Lagrangian structures in velocity fields obtained from realistic simulations and from satellite altimetry of the surface layers of the Mediterranean sea. Finite‐size Lyapunov exponents are found to be useful quantities to characterize stretching and compressing structures, and their implications for mixing. Direct calculation of hyperbolic points and their stable and unstable manifolds identifies ocean structures, and allows the use of the tools of lobe dynamics to characterize fluid transport. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An elastic beam approach to predictive vehicle motion planning
Authors: Hirsch Karina , Brandt Thorsten
Published: October 2008

Vehicle guidance systems are among the latest automotive developments. Examples are Adaptive Cruise Control (ACC), lane departure warning and active lane keeping. However, the rapid development of environmental sensor systems such as radar, lidar and video technologies in combination with data fusion of the single sensor signals enables further applications as for example lane changing assistance, collision avoidance or even autonomous driving.

For all of these functions, trajectories have to be planned and, depending on the application, to be communicated to the driver. Recently, methods originally developed in robotics as for example so‐called elastic bands are adapted for road vehicle applications. Here an virtual elastic beam is proposed to guide the vehicle. The beam is deflected by virtual potential fields generated by obstacles in the traffic space. In doing so, the elastic beam avoids obstacles and provides collision‐free trajectories, while its bending stiffness counteracts the curvature of the trajectory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equivalent governing equilibrium equations for nonlinear magnetoelastic solids
Authors: Bustamante Roger , Dorfmann Luis , Ogden Ray W.
Published: October 2008

Magneto‐sensitive elastomers are materials that rapidly and reversibly change their mechanical and magnetic properties in response to the application of a magnetic field. Typically, the magneto‐mechanical coupling is achieved and optimized by mixing, during the vulcanization process, nano or micron‐sized magnetizable particles with high magnetic saturation within a soft and highly elastic elastomeric matrix. Preferred materials are gels, resin, natural rubber, silicone rubber and nitrile rubber. The particles of choice are spherical or irregularly shaped carbonyl iron particles because of their high permeability, low remanent magnetization and high saturation magnetization. In this paper we provide an overview of different ways in which the equations of mechanical equilibrium of magneto‐sensitive materials can be written in the presence of magneto‐mechanical interactions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Supersonic turbulence as an agent of structure formation in space
Authors: Folini Doris , Walder Rolf , LeVeque R.J. , Favre J. M.
Published: October 2008

Supersonic turbulence is a main agent for structure formation in space, from stellar winds to wind‐blown bubbles, supernovae remnants, ‐ray bursts, and star‐formation in molecular clouds. Dissipation is mostly due to shocks. Under isothermal conditions, the density follows a log‐normal distribution whose variance grows with Mach number. The exact scaling is under debate. We focus on problems with not strictly periodic boundary conditions and present 2D and 3D numerical simulation of supersonic turbulence in plan‐parallel slabs. From dimensional analysis we derive scaling laws for the mean quantities under isothermal conditions. Simulations including spatially extended radiative cooling layers reveal a complex interplay between turbulence and RM‐ and RT‐unstable interfaces. Turbulent Mach numbers here are significantly reduced compared to the isothermal case and are of order 1. However, unstable interfaces between the different thermal component of the gas are equally able to produce structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A fast multiphase level set algorithm for solving the Chan‐Vese model
Authors: He Lin , Osher Stanley
Published: October 2008

In this work, we specifically solve the C‐V active contour model by multiphase level set methods. We first develop a fast algorithm based on calculating the variational energy of the C‐V model without the length term. We check whether the energy decreases or not when we move a point to another segmented region. Then we draw a connection between this algorithm and the topological derivative, a concept emerged from the shape optimization field. Furthermore, to include the length term of the C‐V model, a preprocessing step is taken by using nonlinear diffusion. Numerical experiments have demonstrated the efficiency and the robustness of our algorithm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of risk contribution in the Vasicek portfolio credit loss model
Authors: Huang Xinzheng , Oosterlee Cornelis W.
Published: October 2008

For the calculation of the VaR contribution in the Vasicek one‐factor portfolio credit loss model, two methods, namely the saddlepoint approximation and importance sampling, are very attractive in terms of accuracy, speed and robustness. We explore their connection with the Esscher transform. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time integration of inelastic material models exhibits an order reduction for higher‐order methods – can this be avoided?
Authors: Kuhn C. , Eidel B.
Published: October 2008

For the numerical treatment of inelastic material behavior within the finite element method a partitioned ansatz is standard in most of the software frameworks; the weak form of equilibrium is discretized in space and solved on a global level, whereas the initial value problem for the evolution equations of internal state variables is separately solved on a local, i.e. Gauss‐point level, where strains, derived from global displacements, serve as input, [1]. Applying higher order methods (p > 2) to the time integration of plasticity models an order reduction is reported where Runge‐Kutta schemes have shown hardly more than order two at best [2, 3]. In the present contribution, we analyze the reason for order reduction and in doing so, introduce an improved strain approximation and switching point detection which play a crucial role for the convergence order of multi‐stage methods used in this context. We apply Runge‐Kutta methods of Radau IIa class to the evolution equations of viscoelastic and elastoplastic material models and show ther improved performence in numerical examples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scalable algorithm for solving 3D contact problems with friction
Authors: Kučera Radek , Haslinger Jaroslav , Dostál Zdeněk
Published: October 2008

A scalable algorithm for solving contact problems with Coulomb friction is presented. It combines fixed point iterations with an augmented Lagrangian loop and an active set strategy. Numerical experiments indicate scalability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regularized total least squares based on the nonlinear Arnoldi method
Authors: Lampe Jörg , Voss Heinrich
Published: October 2008

A computational approach for solving regularized total least squares problems via a sequence of quadratic eigenvalue problems has recently been introduced by Sima, Van Huffel, and Golub. Combining this approach with the nonlinear Arnoldi method and reusing information from all previous quadratic eigenvalue problems, together with an early update of search spaces we arrive at a very efficient method for large regularized total least squares problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FronTier and applications to scientific and engineering problems
Authors: Bo Wurigen , Fix Brian , Glimm James , Li Xiaolin , Liu Xingtao , Samulyak R. , Wu Lingling
Published: October 2008

We report significant developments of the FronTier code and applications in science and engineering. The progress includes the extraction of an independent software library from the front tracking code, robust and accurate locally grid based method, applications to fluid mixing problem, fuel injection jet and fusion pellet injection in a magnetically confined plasma, among other problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discontinuous Galerkin relaxation algorithm for solute transport in porous media
Authors: Mahmood Mohammed Shuker
Published: October 2008

We consider a degenerate parabolic convection dominated equation which models the transport of contaminant in porous media. The numerical scheme is fulfilled by combining the DG – Discontinuous Galerkin Method with and an efficient relaxation algorithm that recently developed. Numerical results show the efficiency of our scheme. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mixing model providing statistics of the conditional scalar dissipation rate
Authors: Meyer D. W. , Jenny P.
Published: October 2008

Joint composition probability density function (PDF) methods are used for the numerical simulation of turbulent reactive flows. Here, other than in classical Reynolds averaged Navier–Stokes (RANS) or large eddy simulation (LES) approaches, the highly non‐linear chemical source term appears in closed form. On the other hand, mixing models are required for the closure of the molecular diffusion term. In the present work, the joint statistics of the scalar and the scalar dissipation rate provided by the parameterized scalar profile (PSP) mixing model are validated. The goal is to combine the PDF method with a flamelet approach, where the scalar dissipation rate plays a crucial role in determining the contribution of the chemical source term. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel method of control using chaotic dynamics in systems having many degrees‐of‐freedom
Authors: Li Yongtao , Tanaka Tai , Suemitsu Yoshikazu , Nara Shigetoshi
Published: October 2008

Chaotic dynamics in systems having many degrees of freedom are investigated from the viewpoint of harnessing chaos and is applied to complex control problems to indicate that chaotic dynamics has potential capabilities for complex control functions by simple rule(s). An important idea is that chaotic dynamics generated in these systems give us autonomous complex pattern dynamics itinerating through intermediate state points between embedded designed attractors in high‐dimensional state space. A key point is that, with the use of simple adaptive switching between a weakly chaotic regime and a strongly chaotic regime, complex problems can be solved. As an actual example, a two‐dimensional maze, where it should be noted that the set context is one of typical ill‐posed problems, is solved with the use of chaos in a recurrent neural network model. Our computer experiments show that the success rate over several hundreds trials is much better, at least, than that of a random number generator. Our functional simulations indicate that harnessing of chaos is one of essential ideas to approach mechanisms of brain functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive numerical components for PDE‐based simulations
Authors: Norris Boyana , McInnes Lois Curfman , Bhowmick Sanjukta , Li Li
Published: October 2008

Numerical simulations based on nonlinear partial differential equations (PDEs) using Newton‐based methods require the solution of large, sparse linear systems of equations at each nonlinear iteration. Typically in large‐scale parallel simulations such linear systems are solved by using preconditioned Krylov methods. In many cases, especially in time‐dependent problems, the attributes of the linear systems can change throughout the stimulation, potentially leading to varying times for solving the linear systems during different nonlinear iterations. We present an approach to characterizing the nonlinear and linear system solution and using the resulting application performance information to dynamically select linear solver methods, with the goal of reducing the total time to solution. We discuss the effect of these adaptive heuristics on fluid dynamics and radiation transport codes. We also introduce general component infrastructure to support dynamic algorithm selection and adaptation in applications involving the solution of nonlinear PDEs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling, analysis and simulation of case hardening of steel
Authors: Panizzi Lucia , Hömberg Dietmar , Fasano Antonio
Published: October 2008

A mathematical model for the gas carburizing in steel is presented. Carbon is dissolved in the surface layer of a low‐carbon steel part at a temperature sufficient to render the steel austenitic, followed by quenching to form a martensitic microstructure. We have a nonlinear evolution equation for the temperature, coupled with a nonlinear evolution equation for the carbon concentration, both coupled with two ordinary differential equations to describe the phase fractions. We present mathematical results concerning the well‐posedness of the model and finally present a simulation of the process using a finite element approximation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The composite mini element: a new mixed FEM for the Stokes equations on complicated domains
Authors: Peterseim Daniel , Sauter Stefan A.
Published: October 2008

We introduce a new finite element method, the composite mini element, for the mixed discretization of the Stokes equations on two and three‐dimensional domains that may contain a huge number of geometric details. Instead of a geometric resolution of the domain and the boundary condition by the finite element mesh the shape of the finite element functions is adapted to the geometric details. This approach allows low‐dimensional approximations even for problems with complicated geometric details such as holes or rough boundaries. It turns out that the method can be viewed as a coarse scale generalization of the classical mini element approach, i.e. it reduces the computational effort while the approximation quality depends linearly on the (coarse) mesh size in the usual way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sparsity of the average curvature information matrix
Authors: Frimannslund Lennart , Steihaug Trond
Published: October 2008

We present a theorem regarding the average curvature properties of partially separable functions which need not be differentiable or continuous. This has implications for derivative‐free optimization methods which make use of average curvature information to select the set of search directions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A quasi‐static approach for constrained systems in real‐time simulation
Authors: Burgermeister Bernhard , Arnold Martin , Eichberger Alex
Published: October 2008

Detailed multi‐body system models in applications like vehicle dynamics, robotics and bio‐mechanics are designed for accurate off‐line simulation. For real‐time applications simplified models are used. The presented quasi‐static solution method focuses on accelerated computation of the low frequency parts of the solution of the nonlinear equations of motion. The high frequency parts are eliminated by neglecting some of the inertia forces and torques. This reduces numerical stiffness and allows larger step‐sizes for the time‐integration.

The efficient and real‐time capable combination with existing highly efficient algorithms for multi‐body dynamics (𝒪(N) multi‐body formalisms) requires appropriate integration methods that are adapted to the special structure of the multi‐body formalism and solve the non‐linear constraints with a small, limited number of calculation steps. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum dynamics of ultrafast photoinduced processes in organic semiconductors: exciton dissociation at polymer heterojunctions
Authors: Burghardt Irene , Bittner Eric R. , Tamura Hiroyuki
Published: October 2008

A molecular‐level, quantum‐dynamical analysis of phonon‐driven exciton dissociation in semiconducting polymers is presented, using a linear vibronic coupling model in conjunction with a recently developed hierarchical chain representation. Quantum‐dynamical simulations in 20‐30 dimensions are carried out using efficient multiconfigurational techniques. The decay of the exciton towards a charge‐separated state is shown to be an ultrafast, coherent process of pronounced non‐equilibrium character, which cannot be modeled by conventional kinetic equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Betti numbers of random manifolds
Authors: Farber Michael , Kappeler Thomas
Published: October 2008

Betti numbers of configuration spaces of mechanical linkages (known also as polygon spaces) depend on a large number of parameters – the lengths of the bars of the linkage. Motivated by applications in topological robotics, statistical shape theory and molecular biology, we view these lengths as random variables and study asymptotic values of the average Betti numbers as the number of links n tends to infinity. We establish a surprising fact that for a reasonably ample class of sequences of probability measures the asymptotic values of the average Betti numbers are independent of the choice of the measure. The main results of the paper apply to planar linkages as well as for linkages in R3. We also prove results about higher moments of Betti numbers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the L2–discrepancies of van der Corput sequences
Authors: Faure Henri
Published: October 2008

We present a selection of results concerning the L2–discrepancies of the two classical generalizations of van der Corput sequences. Especially, we give very simple linear digit scramblings producing very small L2–discrepancies and we show that digitally shifted sequences are not a good choice to improve the star L2–discrepancy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seismic sources and waves using iterative operator splitting methods
Authors: Geiser Jürgen
Published: October 2008

In this paper, we discuss iterative operator‐splitting methods for wave equations motivated from a realistic problem in seismic sources and waves. The operator splitting methods are well‐known to solve such complicated multi‐dimensional and multi‐physical problems, while decomposing into simpler and computable equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy estimates for reaction‐diffusion processes of charged species
Authors: Glitzky Annegret
Published: October 2008

We consider electro‐reaction‐diffusion systems consisting of continuity equations for a finite number of species coupled with a Poisson equation. We take into account heterostructures, anisotropic materials and rather general statistical relations.

We investigate thermodynamic equilibria and prove for solutions to the evolution system the monotone and exponential decay of the free energy to its equilibrium value. Here the essential idea is an estimate of the free energy by the dissipation rate. The same properties are obtained for a fully implicit time discretized version of the problem. Moreover, we provide a space discretized scheme for the electro‐reaction‐diffusion system which is dissipative (the free energy decays monotonously). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of Rosenbrock‐type methods to a constitutive model of polymeric material
Authors: Hamkar Ahmad‐Wahadj , Hartmann Stefan
Published: October 2008

The consistent application of the time‐space discretization in the case of quasi‐static structural problems based on constitutive equations of evolutionary type yields after the finite element discretization to a system of differential‐algebraic‐equations (DAE). In order to carry out the time discretization, time‐adaptive Rosenbrock‐type methods are applied to the DAE‐system, which offer the possibility of a completely iteration‐less procedure. This presentation shows the behavior of a new global finite element approach and compares it to the classical implicit (iterative) procedure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extended flamelet model and improved interaction of chemistry and turbulence for modeling partially premixed combustion with a joint PDF method
Authors: Hegetschweiler Michael , Jenny Patrick
Published: October 2008

Turbulent combustion is commonly categorized into premixed, non‐premixed and partially premixed combustion. For nonpremixed combustion simulations the laminar flamelet concept proved to be very valuable while for the more complex case of partially premixed combustion this model shows considerable deficiencies. Here, the classical laminar flamelet approach is extended to the partially premixed combustion regime. For that, the joint statistics of mixture fraction, scalar dissipation rate and a progress variable, calculated with a joint probability density function (PDF) method, is used to get the statistics of the compositions and of the chemical energy source term from pre‐processed flame tables. This approach can be compared with the unsteady flamelet concept; the main differences consists of the way the progress variable evolution is computed and in the pre‐computed flame tables. The progress variable describes the point of time a fluid parcel is consumed by a flame front. The fluid parcels are represented by computational particles, which are used for PDF methods. The pre‐computed flame tables are computed from steady solutions 2D stabilized flames propagating into an unburnt mixture with varying mixture fraction. The corresponding position of a fluid particle in such a 2D laminar flame is determined by its mixture fraction and a burning time; both to be modeled for each computational particle in the PDF simulation. Numerical experiments of turbulent diffusion jet flames demonstrate that this approach can be employed for challenging test cases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a decoupling approach in inverse option pricing
Authors: Hein Torsten
Published: October 2008

We present a decoupling approach for the inverse problem of option pricing which separates the identification of term and smile structure into two subproblems. The determination of the smile structure is reduced to the case of purely price‐dependent options. For the identification of the term structure we suppose a Tikhonov regularization approach and present a convergence rates result including the special situation of at‐the‐money options. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A BE based finite element for crack propagation processes
Authors: Helldörfer Bastian , Kuhn Günther
Published: October 2008

A boundary element based finite macro element for the simulation of 3D crack propagation in the framework of linear elastic fracture mechanics is presented. While the major part of the numerical model is discretized with finite elements, a small domain containing the crack is meshed with boundary elements. By means of the Symmetric Galerkin BEM a stiffness formulation for the cracked BE domain is obtained which enables a direct FEM/BEM coupling. All necessary operations for the crack propagation are carried out within this boundary element based finite macro element and exploit the potential of the boundary integral formulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study groups in Denmark: A tale of three cities
Authors: Hjorth Poul G.
Published: October 2008

Since 1998 European Study Groups have been held in Denmark, and Danish companies from LEGO and NOVO to very small high‐tech firms have participated. Here, I briefly describe the history, the organization and the format of the Danish Study Groups, and highlight a few problem solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The vibrational behaviour of bladed disks with multiple coupling devices
Authors: Hohl A. , Panning L. , Siewert C. , Buerge A.
Published: October 2008

In turbomachinery applications turbine blades are subjected to high static and dynamic loads. Static loads are due to centrifugal stresses and thermal strains. Especially the dynamic excitation caused by fluctuating gas forces results in high vibration amplitudes which can lead to high cycle fatigue failures (HCF). Therefore, in practical applications, coupling devices like underplatform dampers, lacing wires and tip shrouds are installed to the structure. In case of blade vibrations the relative displacements between these coupling devices and the blades generate friction forces. The resulting energy dissipation provides additional damping to the structure. Furthermore, coupling devices, in particular tip shrouds, snubbers and lacing wires, increase the stiffness of the structure. Hence, they lead to a shift of the resonance frequencies.

So far, only effects of single coupling devices and the influencing properties have been examined. Within this paper the effect of multiple couplings is determined and compared with single couplings. The forced response of turbine bladings with multiple couplings is calculated under consideration of geometrical and mechanical parameters of the blading and contacts, respectively. The results are compared with the single coupled blading. Furthermore, a multiple coupled device with under‐platform damper and connecting pin is compared with respect to his effectiveness. Especially the influence on the resonance frequency and the achievable damping is analysed. The results of the simulation are verified by measurements at a two‐blade non‐rotating test rig with an underplatform damper and connecting pin. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lyapunov's second method in problems of the stability of solutions of systems with impulse effect
Authors: Ignatyev Alexander O.
Published: October 2008

A system of ordinary differential equations with impulse effect at fixed moments of time is considered. The system is assumed to have the zero solution. It is shown that the existence of a corresponding Lyapunov function is a necessary and sufficient condition for the uniform asymptotic stability of the zero solution. Restrictions on perturbations of the right‐hand sides of differential equations and impulse effects are obtained under which the uniform asymptotic stability of the zero solution of the ‘unperturbed’ system implies the uniform asymptotic stability of the zero solution of the ‘perturbed’ system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cosymmetric families of steady states in 3D convection of incompressible fluid in a porous medium
Authors: Tsybulin V. G. , Nemtsev A. D. , Karasözen B.
Published: October 2008

We consider three‐dimensional convection of an incompressible fluid saturated in a parallelepiped with a porous medium. A mimetic finite‐difference scheme for the Darcy convection problem in the primitive variables is developed. Two problems with different boundary conditions are considered to study scenarios of instability of the state of rest. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical method for soluble surfactants on moving interfaces
Authors: Khatri Shilpa , Tornberg Anna‐Karin
Published: October 2008

We present a numerical method modeling soluble surfactants on deforming interfaces. The method uses an explicit Eulerian discretization of the interface allowing the use of standard finite difference schemes to solve coupled time‐dependent differential equations for the concentration of surfactant on the interface and for the concentration of surfactant in the bulk. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and quantifying bifurcation diagrams of Chua's oscillator
Authors: Dittmar Jörg , Parlitz Ulrich
Published: October 2008

We present methods for evaluating bifurcation diagrams that were reconstructed from time series generated by the system of interest at different fixed parameter values. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vortex wake mitigation of an airfoil with winglets by active rudders
Authors: Schöll Robert , Hörnschemeyer Ralf , Henke Rolf
Published: October 2008

The wake vortex hazard and the required separation distances between aircraft at airports constitute an impediment to the growth of air traffic at major hubs. One approach to reduce separation distances is the exploitation of the inherent instability in vortex systems, leading to an accelerated breakdown. In this paper we show the impact of excitation by different control surfaces on the stability behavior of the wake of a rectangular wing with winglets. The experiment shows that the excitation through winglet rudders and ailerons yields the best results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A discontinuous Galerkin method for the Wigner‐Fokker‐Planck equation with a non‐polynomial approximation space
Authors: Sharp Richard , Gualdani Maria Pia , Gamba Irene
Published: October 2008

A discontinuous Galerkin approach to the Wigner‐Fokker‐Planck equation, a model for quantum devices including environmental effects, is proposed. Evaluation of a pseudo‐differential term is the main challenge. The approach can be applied to a variety of potential functions and uses general approximation spaces. Simulations using the method are in agreement with established analytic results and produce reasonable solutions for several potentials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)