bluuebunny/crossref_metadata_2025 huggingface dataset:
Using simulation for teaching femoral arterial access: A multicentric collaboration
Authors: Gurm Hitinder S. , Sanz‐Guerrero Jorge , Johnson Daniel D. , Jensen Andrea , Seth Milan , Chetcuti Stanley J. , Lalonde Thomas , Greenbaum Adam , Dixon Simon R. , Shih Albert
Published: October 2015

Objective

To assess the impact of simulation training on complications associated with femoral arterial access obtained by first year cardiology fellows. Background: Prior studies demonstrate a higher incidence of arterial access related complications among patients undergoing invasive cardiac procedures.

Methods

First year cardiology fellows at four teaching hospitals in Michigan tracked their femoral access experience and any associated complications between July 2011 and June 2013. Fellows starting their academic training in July 2012 were first trained on a specially developed simulator before starting their rotation in the catheterization laboratory. The primary outcome was access proficiency, defined as five successful femoral access attempts without any complication or need to seek help from a more experienced team member.

Results

A total of 1,278 femoral access attempts were made by 21 fellows in 2011–2012 compared with 869 femoral access attempts made by 21 fellows in 2012–2013. There was a lower rate of access related complications in patients undergoing access attempts by first year fellows in year 2 compared with year 1 (2.1% versus 4.5%, P = 0.003) . The number of procedures to achieve procedural proficiency was significantly higher in year 1 compared with year 2 (median 20 versus 10, P = 0.007).

Conclusions

Incorporation of simulation in the training of first year fellows was associated with an improvement in proficiency and a clinically meaningful reduction in vascular complications. © 2015 Wiley Periodicals, Inc.
Enhancing the Oxygen Reduction Reaction Performance by Modifying the Surface of Platinum Nanoparticles
Authors: Cao Longsheng , Zhang Geng , Jiang Shangfeng , Tang Xuejun , Qin Xiaoping , Guo Xiaoqian , Shao Zhigang , Yi Baolian
Published: October 2015

The depressing oxygen reduction reaction (ORR) performance has impeded the commercialization of proton exchange membrane fuel cells. As a surface‐sensitive reaction, the surface structure of the electrocatalyst has a crucial impact on the ORR. Herein, Pt nanoparticle surfaces were modified with the aid of Ag, which was deposited on the surface of Pt nanoparticles and was etched away through cyclic voltammetry (CV). After surface modification, the step density of the Pt nanoparticles was observed to decrease, according to high‐resolution transmission electron microscopy images, which could contribute to the positive shift of the Pt 4f binding energy and the improved ability to prevent Pt from being oxidized, as seem by using X‐ray photoelectron spectroscopy. Furthermore, the peak potential increase for the surface metal‐oxide reduction during CV was consistent with the impact of the step density reduction. After surface modification, the Pt nanoparticles showed improved ORR performance, according to half‐cell tests. At the atomic scale, the decrease in the number of low‐coordination atoms on the surface steps, which exhibit stronger interactions with Oads/OHads compared with atoms on terraces, could lead to the enhanced ORR performance.
Gold‐Catalyzed Ring Expansion of Alkynyl Heterocycles through 1,2‐Migration of an Endocyclic Carbon–Heteroatom Bond
Authors: Chen Ming , Sun Ning , Xu Wei , Zhao Jidong , Wang Gaonan , Liu Yuanhong
Published: October 2015

A mild and efficient gold‐catalyzed oxidative ring‐expansion of a series of alkynyl heterocycles using pyridine‐N‐oxide as the oxidant has been developed, which affords highly valuable six‐ or seven‐membered heterocycles with wide functional group toleration. The reaction consists of a regioselective oxidation and a chemoselective migration of an endocyclic carbon–heteroatom bond (favored over CH migration) with the order of migratory aptitude for carbon–heteroatom bonds being CS>CN>CO. In the absence of an oxidant, polycyclic products are readily constructed through a ring‐expansion/Nazarov cyclization reaction sequence.
Finite difference diagonalization to simulate nuclear magnetic resonance diffusion experiments in porous media
Authors: Grombacher Denys , Nordin Matias
Published: October 2015

A finite difference approach for computing Laplacian eigenvalues and eigenvectors in discrete porous media is derived and used to approximately solve the Bloch–Torrey equations. Neumann, Dirichlet, and Robin boundary conditions are considered and applications to simulate nuclear magnetic resonance diffusion experiments are shown. The method is illustrated with MATLAB examples and computational tests in one and two dimensions and the extension to three dimensions is outlined. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 44A: 160–180, 2015.
Effects of Renal Impairment and Hepatic Impairment on the Pharmacokinetics of Hydrocodone After Administration of a Hydrocodone Extended‐Release Tablet Formulated With Abuse‐Deterrence Technology
Authors: Darwish Mona , Yang Ronghua , Tracewell William , Robertson Philmore , Bond Mary
Published: October 2015

Two open‐label, single‐dose, parallel‐group studies assessed effects of renal and hepatic impairment on the pharmacokinetics of a hydrocodone extended‐release (ER) formulation developed with the CIMA Abuse‐Deterrence Technology platform. Forty‐eight subjects with normal renal function or varying degrees of renal impairment received hydrocodone ER 45 mg (study 1); 16 subjects with normal hepatic function or moderate hepatic impairment received hydrocodone ER 15 mg (study 2). Blood samples were obtained predose and through 144 hours postdose. Mean maximum observed plasma hydrocodone concentration (Cmax) in subjects with normal renal function, mild, moderate, and severe impairment, and end‐stage renal disease was 28.6, 33.4, 42.4, 36.5, and 31.6 ng/mL, and mean area under the plasma hydrocodone concentration‐versus‐time curve from time 0 to infinity (AUC0–∞) was 565, 660, 973, 983, and 638 ng·h/mL, respectively. Incidence of adverse events was 57%, 38%, 44%, 33%, and 56%, respectively. Mean Cmax with normal hepatic function and moderate impairment was 10.1 and 13.0 ng/mL, and mean AUC0–∞ was 155 and 269 ng·h/mL, respectively. Incidence of adverse events was 38% in both groups. Altered systemic exposure in renally or hepatically impaired populations (up to ∼70% higher) should be considered when titrating to an effective dose of hydrocodone ER.
Elucidating the Structure of Chiral Molecules by using Amplified Vibrational Circular Dichroism: From Theory to Experimental Realization
Authors: Domingos Sérgio R. , Hartl František , Buma Wybren Jan , Woutersen Sander
Published: October 2015

The front cover artwork is provided by Dr. Sérgio Rosa Domingos, Prof. Wybren Jan Buma, and Prof. Sander Woutersen (University of Amsterdam, The Netherlands) as well as Prof. František Hartl (University of Reading, UK). The image shows a researcher/explorer highlighting a moiety within a large molecular system by using a flashlight, and in that way detecting the vibrational circular dichroism of that specific moiety. Read the full text of the article at 10.1002/cphc.201500551
Effects of size, neighbors, and site condition on tree growth in a subtropical evergreen and deciduous broad‐leaved mixed forest, China
Authors: Chi Xiulian , Tang Zhiyao , Xie Zongqiang , Guo Qiang , Zhang Mi , Ge Jielin , Xiong Gaoming , Fang Jingyun
Published: October 2015

Successful growth of a tree is the result of combined effects of biotic and abiotic factors. It is important to understand how biotic and abiotic factors affect changes in forest structure and dynamics under environmental fluctuations. In this study, we explored the effects of initial size [diameter at breast height (DBH)], neighborhood competition, and site condition on tree growth, based on a 3‐year monitoring of tree growth rate in a permanent plot (120 × 80 m) of montane Fagus engleriana–Cyclobalanopsis multiervis mixed forest on Mt. Shennongjia, China. We measured DBH increments every 6 months from October 2011 to October 2014 by field‐made dendrometers and calculated the mean annual growth rate over the 3 years for each individual tree. We also measured and calculated twelve soil properties and five topographic variables for 384 grids of 5 × 5 m. We defined two distance‐dependent neighborhood competition indices with and without considerations of phylogenetic relatedness between trees and tested for significant differences in growth rates among functional groups. On average, trees in this mixed montane forest grew 0.07 cm year−1 in DBH. Deciduous, canopy, and early‐successional species grew faster than evergreen, small‐statured, and late‐successional species, respectively. Growth rates increased with initial DBH, but were not significantly related to neighborhood competition and site condition for overall trees. Phylogenetic relatedness between trees did not influence the neighborhood competition. Different factors were found to influence tree growth rates of different functional groups: Initial DBH was the dominant factor for all tree groups; neighborhood competition within 5 m radius decreased growth rates of evergreen trees; and site condition tended to be more related to growth rates of fast‐growing trees (deciduous, canopy, pioneer, and early‐successional species) than the slow‐growing trees (evergreen, understory, and late‐successional species).
Crystal Structure and Spectroscopic Investigation of Bromofluoro‐ and Fluoroiodomethane
Authors: Feller Michael , Lux Karin , Kornath Andreas
Published: October 2015

The solid states of bromofluoromethane (BFM) and fluoroiodomethane (FIM) are characterized by X‐ray diffraction analysis and by Raman spectroscopy. The single crystals were obtained by crystallization in situ at low temperature. BFM and FIM crystallize in the space group I2/a and Abm2, respectively. The Raman spectra of both compounds were recorded in different aggregation states and at different temperatures. Quantum chemical calculations and the X‐ray diffraction data are considered to describe the noncovalent interactions of both compounds in the solid state. These interactions are discussed in the context of the σ‐hole concept.
Titanium Alkoxide Complexes as Catalysts for the Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides
Authors: Al‐Qaisi Feda'a , Streng Emilia , Tsarev Alexey , Nieger Martin , Repo Timo
Published: October 2015

Titanium alkoxides can catalyze efficient and selective synthesis of cyclic carbonates through CO2 insertion into epoxides when tetrabutylammonium bromide or iodide is used as a cocatalyst. Of the series of synthesized titanium alkoxides, the most active catalyst was one bearing an aliphatic bidentate alkoxide ligand, and it produced propylene carbonate under benign conditions (100 °C, 15 bar CO2, 3 h) with turnover frequencies of up to 116 h–1. The effect of reaction parameters such as pressure, temperature, and catalyst/cocatalyst molar ratio were also studied in order to optimize the catalytic system.
Deep Eutectic Mixtures: Promising Sustainable Solvents for Metal‐Catalysed and Metal‐Mediated Organic Reactions
Authors: García‐Álvarez Joaquín
Published: October 2015

This microreview is intended to cover the progress made in metal‐mediated and metal‐catalysed organic reactions performed in a new family of inexpensive, greener and biorenewable eutectic mixtures, the so‐called Deep Eutectic Solvents (DESs), as environmentally friendly reaction media. This ambitious research is focused on studies of particular interest in organometallic chemistry, in search of synthetic strategies able to optimise the overall process in an eco‐friendly manner. This microreview aims to provide an overview of the application of DESs in the fields of: (i) Ru‐ and Au‐catalysed isomerisation and cycloisomerisation of organic substrates, (ii) Cu‐catalysed click chemistry and C–C bond‐formation reactions, (iii) Pd‐catalysed cross‐coupling processes and Tsuji–Trost reactions, (iv) Rh‐catalysed hydrogenation and hydroformylation of alkenes, (v) addition of RMgX and RLi compounds to ketones, and (vi) regioselective ortho‐ and lateral lithiation of aryltetrahydrofurans.
Copper‐Catalysed Allylic Substitution Using 2,8,14,20‐Tetrapentylresorcinarenyl‐Substituted Imidazolium Salts
Authors: Kaloğlu Murat , Şahin Neslihan , Sémeril David , Brenner Eric , Matt Dominique , Özdemir İsmail , Kaya Cemal , Toupet Loïc
Published: October 2015

Unsymmetrical imidazolium salts, each having one nitrogen atom (N1) substituted by a cavity‐shaped TPR group (TPR = 2,8,14,20‐tetrapentylresorcinaren‐5‐yl), were tested in situ as proligands for the copper‐catalysed allylic arylation of cinnamyl bromide with arylmagnesium halides. The catalytic systems produced mixtures of linear (l) and branched (b) arylated compounds in variable proportions, with the b/l ratio being the highest (78:22) for the most crowded imidazolium salt used, namely that in which the second nitrogen atom (N2) was substituted by a mesityl group. An N‐heterocyclic carbene complex obtained from one of the imidazolium salts was characterised by an X‐ray diffraction study.
8‐Substituted, syn‐Configured Adenosine Derivatives as Potential Inhibitors of the Enzyme IspE from the Non‐Mevalonate Pathway of Isoprenoid Biosynthesis
Authors: Harder Michael , Schäfer Elisabeth , Kümin Tobias , Illarionov Boris , Bacher Adelbert , Fischer Markus , Diederich François , Bernet Bruno
Published: October 2015

The enzymes of the non‐mevalonate pathway for isoprenoid biosynthesis are attractive targets for drugs against various diseases, including malaria. We describe herein the structure‐based design, synthesis, conformational analysis, and biological evaluation of several 8‐brominated or 8‐aminated adenosine derivatives with different substituents at C(5′), targeting the ATP‐adenine binding site of the IspE protein from the non‐mevalonate pathway. An exhaustive conformational analysis of the adenosine derivatives both in solution and in the solid state confirmed the desired syn orientation of the adenine moiety. Despite this favorable pre‐organization for binding to the cofactor pocket, biological evaluation of the inhibitors showed only a very modest inhibitory activity.
One‐Pot Synthesis, Crystallization and Deracemization of Isoindolinones from Achiral Reactants
Authors: Steendam René R. E. , Kulka Michaël W. , Meekes Hugo , van Enckevort Willem J. P. , Raap Jan , Vlieg Elias , Rutjes Floris P. J. T.
Published: October 2015

The synthesis, crystallization, and complete solid‐state deracemization of isoindolinones was realized in one pot simply by grinding achiral reaction components in a suitable solvent with an achiral catalyst. Previously, this concept was applied to a reversible reaction, but herein we showed that it could also be used in combination with reactions in which product formation is irreversible. A controlled final configuration of the product was obtained by using small amounts of chiral additives or seed crystals of the product.
Verification of system identification utilizing shaking table tests of a full‐scale 4‐story steel building
Authors: Ikeda Yoshiki
Published: October 2015

This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full‐scale four‐story steel building at E‐Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single‐input‐four‐output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc–Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single‐input‐single‐output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent‐linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure. Copyright © 2015 John Wiley & Sons, Ltd.
Influence of the surface charge of PLGA nanoparticles on their in vitro genotoxicity, cytotoxicity, ROS production and endocytosis
Authors: Platel Anne , Carpentier Rodolphe , Becart Elodie , Mordacq Gwendoline , Betbeder Didier , Nesslany Fabrice
Published: October 2015

With the ongoing commercialization of nanotechnology products, human exposure to nanoparticles (NPs) is set to increase dramatically and an evaluation of their potential adverse effects is essential. Surface charge, among other physico‐chemicals parameters, is a key criterion that should be considered when using a definition for nanomaterials in a regulatory context. It has recently been recognized as an important factor in determining the toxicity of NPs; however, a complete understanding of the mechanisms involved is still lacking. In this context, the aim of the present study was to investigate the influence of the surface charge modification of NPs on in vitro toxicity assays. Poly(lactic‐co‐glycolic acid) (PLGA) nanoparticles bearing different surface charges, positive(+), neutral(n) or negative(−), were synthesized. In vitro genotoxicity assays (micronucleus and comet assays) coupled with an assessment of cytotoxicity, were performed in different cell lines (L5178Y mouse lymphoma cells, TK6 human B‐lymphoblastoid cells and 16HBE14o‐ human bronchial epithelial cells). Reactive oxygen species (ROS) production and endocytosis studies were also performed. Our results showed that PLGA(+) NPs were cytotoxic. They are endocytosed by the clathrin pathway and induced ROS in the three cell lines. They led to chromosomal aberrations without primary DNA damage in 16HBE14o‐ cells, suggesting that aneuploidy may be considered as an important biomarker when assessing the genotoxic potential of NPs. Moreover, 16HBE14o‐ cells seem to be more suitable for the in vitro screening of inhaled NPs than the regulatory L5178Y and TK6 cells. Copyright © 2015 John Wiley & Sons, Ltd.
Surface functionalization allowing repetitive use of optical sensors for real‐time detection of antibody‐bacteria interaction
Authors: Kutscher Marika , Rosenberger Manuel , Schmauss Bernhard , Meinel Lorenz , Lorenz Udo , Ohlsen Knut , Hellmann Ralf , Germershaus Oliver
Published: October 2015

In this study, sensor surface functionalization allowing the repetitive use of a sensing device was evaluated for antibody‐based detection of living bacteria using an optical planar Bragg grating sensor. To achieve regenerable immobilization of bacteria specific antibodies, the heterobifunctional cross‐linker N‐succinimidyl 3‐(2‐pyridyldithio) propionate (SPDP) was linked to an aminosilanized sensor surface and subsequently reduced to expose sulfhydryl groups enabling the covalent conjugation of SPDP‐activated antibodies via disulfide bonds. The immobilization of a capture antibody specific for Staphylococcus aureus on the sensor surface as well as specific binding of S. aureus could be monitored, highlighting the applicability of optical sensors for the specific detection of large biological structures. Reusability of bacteria saturated sensors was successfully demonstrated by cleaving the antibody along with bound bacteria through reduction of disulfide bonds and subsequent re‐functionalization with activated antibody, resulting in comparable sensitivity towards S. aureus.

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TNF‐α/TNFR2 Regulatory Axis Stimulates EphB2‐Mediated Neuroregeneration Via Activation of NF‐κB
Authors: Pozniak Paul D. , Darbinyan Armine , Khalili Kamel
Published: October 2015

HIV‐1 infected individuals are at high risk of developing HIV‐associated neurocognitive disorders (HAND) as HIV infection leads to neuronal injury and synaptic loss in the central nervous system (CNS). The neurotoxic effects of HIV‐1 are primarily a result of viral replication leading to the production of inflammatory chemokines and cytokines, including TNF‐α. Given an important role of TNF‐α in regulating synaptic plasticity, we investigated the effects of TNF‐α on the development of neuronal processes after mechanical injury, and we showed that TNF‐α treatment stimulates the regrowth of neuronal processes. To investigate transcriptional effects of TNF‐α on synaptic plasticity, we analyzed both human neurosphere and isolated neuronal cultures for the regulation of genes central to synaptic alterations during learning and memory. TNF‐α treatment upregulated Ephrin receptor B2 (EphB2), which is strongly involved in dendritic arborization and synaptic integrity. TNF‐α strongly activates the NF‐κB pathway, therefore, we propose that TNF‐α‐induced neurite regrowth occurs primarily through EphB2 signaling via stimulation of NF‐κB. EphB2 promoter activity increased with TNF‐α treatment and overexpression of NF‐κB. Direct binding of NF‐κB to the EphB2 promoter occurred in the ChIP assay, and site‐directed mutagenesis identified binding sites involved in TNF‐α‐induced EphB2 activation. TNF‐α induction of EphB2 was determined to occur specifically through TNF‐α receptor 2 (TNFR2) activation in human primary fetal neurons. Our observations provide a new avenue for the investigation on the impact of TNF‐α in the context of HIV‐1 neuronal cell damage as well as providing a potential therapeutic target in TNFR2 activation of EphB2. J. Cell. Physiol. 231: 1237–1248, 2016. © 2015 Wiley Periodicals, Inc.
Different Blood‐Borne Human Osteoclast Precursors Respond in Distinct Ways to IL‐17A
Authors: Sprangers Sara , Schoenmaker Ton , Cao Yixuan , Everts Vincent , de Vries Teun J.
Published: October 2015

Osteoclasts are bone‐degrading cells that are formed through fusion of their monocytic precursors. Three distinct subsets of monocytes have been identified in human peripheral blood: classical, intermediate, and non‐classical monocytes. They are known to play different roles in physiology and pathology, but their capacity to differentiate into osteoclasts and whether inflammatory cytokines influence this differentiation is unknown. We hypothesized that classical, intermediate, and non‐classical monocytes generate functionally different osteoclasts and that they respond in different ways to the inflammatory cytokine interleukin‐17A (IL‐17A). To investigate this, the different monocyte subsets were isolated from human peripheral blood and osteoclastogenesis was induced with the cytokines M‐CSF and RANKL, with or without IL‐17A. We found that all subsets are able to differentiate into osteoclasts in vitro, and that both osteoclastogenesis and subsequent bone resorption was distinctly affected by IL‐17A. Osteoclastogenesis and bone resorption by osteoclasts derived from classical monocytes remained unaffected by IL‐17A, while osteoclast formation from intermediate monocytes was inhibited by the cytokine. Surprisingly, bone resorption by osteoclasts derived from intermediate monocytes remained at similar levels as control cultures, indicating an increased bone resorbing activity by these osteoclasts. Limited numbers of osteoclasts were formed from non‐classical monocytes on bone and no bone resorption was detected, which suggest that these cells belong to a cell lineage different from the osteoclast. By providing more insight into osteoclast formation from human blood monocytes, this study contributes to the possible targeting of specific osteoclast precursors as a therapeutic approach for diseases associated with inflammatory bone loss. J. Cell. Physiol. 231: 1249–1260, 2016. © 2015 Wiley Periodicals, Inc.
What is “homology thinking” and what is it for?
Authors: Wagner Günter P.
Published: October 2015

In this paper I examine the thesis by Marc Ereshefsky that, in evolutionary biology, there is a third style of thinking, besides the well‐known “population thinking” and “tree thinking.” Ereshefsky proposes “homology thinking” as a third approach, focused on the transformation of organismal phenotypes. In this short commentary, I aim at identifying the underlying biological assumptions for homology thinking and how they can be put to work in a research program within evolutionary biology. I propose that homology thinking is based on three insights: 1) multicellular organisms consist of developmentally individualized parts (sub‐systems); 2) that developmental individuation entails evolutionary individuation, that is, variational quasi‐independence; and 3) these individuated body parts are inherited, though indirectly, and form lineages that are recognized as homologies. These facts support a research program focused on the modification and origination of individuated body parts that supplements and puts into perspective the population genetic and phylogenetic approaches to the study of evolution. J. Exp. Zool. (Mol. Dev. Evol.) 326B:3–8, 2016. © 2015 Wiley Periodicals, Inc.
Copper Price and Exchange Rate Dynamics in Zambia
Authors: Chipili Jonathan M.
Published: October 2015

The kwacha/US$ exchange rate has fluctuated widely with large changes attributed to the copper price booms and bursts due to the significant contribution of copper to the Zambian economy. Accordingly, the estimation results conducted in the cointegration framework over the period 1994q1–2012q4 reveal the existence of a long‐run equilibrium relationship between the real copper price and real kwacha/US$ exchange rate. These empirical results signify the importance of closely monitoring underlying developments in the copper price in order to design appropriate policy response to ensure that impulses to the copper price do not undermine the external competitiveness of the economy. Copyright © 2015 John Wiley & Sons, Ltd.
An inverse‐free ADI algorithm for computing Lagrangian invariant subspaces
Authors: Mehrmann Volker , Poloni Federico
Published: October 2015

The numerical computation of Lagrangian invariant subspaces of large‐scale Hamiltonian matrices is discussed in the context of the solution of Lyapunov equations. A new version of the low‐rank alternating direction implicit method is introduced, which, in order to avoid numerical difficulties with solutions that are of very large norm, uses an inverse‐free representation of the subspace and avoids inverses of ill‐conditioned matrices. It is shown that this prevents large growth of the elements of the solution that may destroy a low‐rank approximation of the solution. A partial error analysis is presented, and the behavior of the method is demonstrated via several numerical examples. Copyright © 2015 John Wiley & Sons, Ltd.
Variational Structural and Material Stability Analysis in Finite Electro‐Magneto‐Mechanics of Active Materials
Authors: Miehe Christian , Vallicotti Daniel
Published: October 2015

Soft matter electro‐elastic, magneto‐elastic and magneto‐electro‐elastic composites exhibit coupled material behavior at large strains. Examples are electro‐active polymers and magneto‐rheological elastomers, which respond by a deformation to applied electric or magnetic fields, and are used in advanced industrial environments as sensors and actuators. Polymer‐based magneto‐electro‐elastic composites are a new class of tailor‐made materials with promising future applications. Here, a magneto‐electric coupling effect is achieved as a homogenized macro‐response of the composite with electro‐active and magneto‐active constituents. These soft composite materials show different types of instability phenomena, which even might be exploited for future enhancement of their performance. This covers micro‐structural instabilities, such as buckling of micro‐fibers or particles, as well as material instabilities in the form of limit‐points in the local constitutive response. Here, the homogenization‐based scale bridging links long wavelength micro‐structural instabilities to material instabilities at the macro‐scale. This work outlines a comprehensive framework of an energy‐based homogenization in electro‐magneto‐mechanics, which allows a tracking of postcritical solution paths such as those related to pull‐in instabilities. Representative simulations demonstrate a tracking of inhomogenous composites, showing the development of postcritical zones in the microstructure and a possible instable homogenized material response. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Size Effects in Ferroelectric Materials using a Phase Field Model
Authors: Schrade David , Müller Ralf
Published: October 2015

An electro‐mechanically coupled phase field model for domain evolution in ferroelectric materials is presented. The inner length scale introduced by the model gives rise to size effects, especially in the context of the poling behavior of polycrystals. Such size effects are investigated by 2D numerical simulations for barium titanate polycrystals. Ferroelectric hysteresis curves and coercive fields are calculated for two different transition conditions for the order parameter at the grain boundaries. The results show that there is a significant size effect for the investigated polycrystal systems. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On molecular statics simulations of ferroelectric functional materials
Authors: Steinmann Paul , Endres Florian
Published: October 2015

The simulation of ferroelectric materials on the atomistic length scale is getting more and more important due to recent advancements in related manufacturing technologies. Therefore, we present an extended molecular statics algorithm in order to not only compute equilibrium configurations efficiently but also to consider the deformation of a discrete particle system due to macroscopic stress. Furthermore, we discuss the impact of mechanical stress and strain on the spontaneous polarization and the magnitude of the coercive field of a ferroelectric barium titanate system. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chirality transitions in frustrated ferromagnetic chains
Authors: Cicalese Marco
Published: October 2015

We consider the Γ‐limit, as the number of particles diverges, of the energy per particle of a one‐dimensional ferromagnetic/anti‐ferromag frustrated S1 (or S2) spin chain close to the helimagnet/ferromagnet transition point discussing the emergence of chirality transitions. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale hierarchical mechanics in soft tissues
Authors: Marino Michele , Vairo Giuseppe , Wriggers Peter
Published: October 2015

In this paper, the mechanics of soft tissues is modeled by introducing a novel polyconvex strain‐energy function able to include tissue structured hierarchical arrangement and by reducing model complexity via multiscale homogenization techniques. The case of arterial tissue is successfully addressed by obtaining a quantitative prediction of the age‐dependent alterations in aorta mechanics incorporating histological remodeling mechanisms and biochemical variations. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The fiber reorientation problem revisited in the context of Eshelbian micromechanics: theory and computations
Authors: Morin Claire , Avril Stéphane , Hellmich Christian
Published: October 2015

A multiscale micromechanical model for soft tissue is presented. This model accounts for the progressive stiffening of the mechanical response due to load‐induced microstructural rearrangements of the fibers within the microstructure. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational integrators of higher order for flexible multibody systems
Authors: Bartelt Matthias , Groß Michael
Published: October 2015

In this paper we present a time stepping scheme which is based on a variational integrator. This higher‐order time stepping scheme includes constraints and a viscoelastic material formulation. A variational integrator is structure‐preserving which results from using a discrete variational principle. Therefore, a variational integrator always takes the form of discrete EULER‐LAGRANGE equations or the equivalent position‐momentum equations. In this framework, we consider the motion of a flexible rope with non‐holonomic constraints by the LAGRANGE‐multiplier technique. The time stepping scheme is derived from a space‐time discretization of HAMILTON's principle. The space discretization is based on one‐dimensional linear LAGRANGE polynomials, whereas the time discretization is based on higher‐order polynomials and higher‐order quadrature rules. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Reproducible Excitation Mechanism for Analyzing Electric Guitars
Authors: Hanss Michael , Bestle Pascal , Eberhard Peter
Published: October 2015

This contribution presents the excitation mechanism of an experimental set‐up for measuring the structural behavior of an electric guitar body using Laser‐Doppler‐Vibrometers, to be compared to the generated sound. It is the aim of this investigation to gain insight into the influence on the sound of materials and designs of the large variety of commercially available electric guitars. The core of the experimental set‐up is the excitation mechanism, which has been developed to guarantee a well‐defined and absolute reproducible excitation of the guitar string in order to detect even small differences in sound. This mechanism has been constructed making use of the methods of multibody dynamics and optimization. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient amplification of maximum vibration amplitudes
Authors: Bonhage Marius , Hentschel Olaf Peter , Panning‐v. Scheidt Lars , Wallaschek Jörg
Published: October 2015

Many low damped structures as turbine blades or drill strings are exposed to high dynamical loads causing high vibration amplitudes. These applications comprise sub‐critical eigenfrequencies. Hereby, the lower eigenfrequencies have to be passed before reaching the operating point. Most investigations of vibration amplitudes caused by a resonance passage deal with the computation of single degree of freedom systems. Thereby, it has been shown that the stationary vibration response provides the highest possible amplitude. Further it can be stated that the maximum vibration response of the resonance passage decreases with an increasing sweep velocity [3]. Isolated modes of linear systems can be represented by single degree of freedom systems. Subsequently a mode shape can be described by the multiplication of the amplification function of the mode and the belonging eigenvector. There are only some recent works that deal with resonance passages of vicinal modes, e. g. [1].

In this paper the resonance passage of a three dimensional system with nearby modes is studied. To calculate the transient vibration response an analytical approach is used. It is shown that the maximum amplitude of the stationary vibration response is not the upper limit for the maximum amplitude of the resonance passage. Thus, the maximum amplitude may rise while the sweep velocity increases. Hence, regarding a multi degree of freedom system the maximum amplitude of the resonance passage can exceed the maximum amplitude of the stationary vibration response. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Active damping control for an underactuated multibody system
Authors: Burkhardt Markus , Morlock Merlin , Seifried Robert , Eberhard Peter
Published: October 2015

Light‐weight robots and manipulators stand out due to their very good weight‐to‐load ratio and a low energy consumption. Unfortunately, the light‐weight design yields a lower stiffness, which results in undesired elastic deformations, especially during high‐speed working motion. One way to limit these unwanted oscillations can be implemented with modifications of the command signals, e.g. by input shaping or pre‐computed feed‐forward control. However, a feedback control‐concept has the ability to provide a fast compensation of elastic deformations due to high‐speed working motions or in case of unwanted environment contact as well as in the presence of other external disturbances. In this contribution, an active damping control (ADC) for fast moving manipulators with significant structural elasticities is presented. This approach does not require additional actuators and it is suitable for a large variety of manipulators that exhibit structural vibrations. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling Elastic Bodies with an Enhanced Craig‐Bampton‐like Scheme
Authors: Eberhard Peter , Holzwarth Philip
Published: October 2015

Elastic multibody systems are widely used as description of mechanical systems that consist of separable components. These components are represented by elastic bodies that interact by the means of force and damping elements as well as boundary conditions. The description of the elasticity is usually provided by a linear finite‐element model. If the bodies are densely meshed, a large system of differential equations is obtained. The numerical effort can be reduced by model order reduction. This contribution presents reduction approaches that are especially well suited for the elastic multibody system framework. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Integrators for Thermo‐Viscoelastic Discrete Systems
Authors: Kern Dominik , Romero Ignacio , Groß Michael
Published: October 2015

Variational integrators are modern time‐integration schemes based on a discretization of the underlying variational principle. In this paper, Hamilton's principle is approximated by an action sum, whose vanishing variation results in discrete Euler‐Lagrange equations or, equivalently, in discrete evolution equations for the position and momentum. In order to include the viscous and thermal virtual work (mechanical and thermal virtual dissipation), Hamilton's principle is extended by D'Alembert terms, which account for the time evolution equation of the internal variable and Fourier's law.

From this variational formulation, variational integrators using different orders of approximation of the state variables as well as of the quadrature of the action integral are constructed and compared. A thermo‐viscoelastic double pendulum comprised of two discrete masses connected by generalized Maxwell elements, and subject to heat conduction between them serves as a discrete model problem. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Projection formulation of the cavitation problem in elastohydrodynamic lubrication contact
Authors: Krinner Andreas , Schindler Thorsten , Rixen Daniel
Published: October 2015

This contribution presents an alternative numerical method on how to find the cavitation region in elastohydrodynamic (EHD) lubrication using an augmented Lagrangian approach. A theoretical framework for the use of a projection formulation instead of a Linear Complementarity Problem (LCP) is given and the application to multibody systems with EHD contacts is shown. With this new formulation the cavitation condition can be covered by an additional algebraic equation. The projection formulation is applied to the steady‐state as well as to the dynamic, mass conservative treatment of the cavitation problem. A numerical verification is given for a rigid rotor with unbalance in an elastic bearing. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonexpansivity of the Newton's Cradle Impact Law
Authors: Leine Remco I. , Winandy Tom
Published: October 2015

The 3‐ball Newton's cradle is used as a stepping stone to divulge the structure of impact laws. A continuous cone‐wise linear impact law which maps the pre‐impact contact velocities to the post‐impact contact velocities is proposed for the 3‐ball Newton's cradle. The proposed impact law is kinematically, kinetically, and energetically consistent. It reproduces all the classical experimental outcomes. Moreover, the impact law has the mathematical property of being non‐expansive. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Back‐Transformation into Physical Configuration Space after Model Order Reduction onto a General Subspace
Authors: Lein Claudius , Beitelschmidt Michael
Published: October 2015

Model order reduction (MOR) techniques that project onto a general subspace are common practice. In Elastic Multi‐Body‐Dynamics (EMBD) distinct interface coordinates are required for the interconnection of the elastic structure and the multi‐body system. For that reason, a physical interpretation of the coordinates is mandatory, which is not the case for reduced order models in a general subspace. To make alternative MOR techniques accessible for EMBD, a back‐projection approach was introduced by [1]. Therein, the system is projected back onto the physical configuration space, which requires the inversion of the master partition of the projection matrix. But the procedure lacks of robustness and generality. A novel approach is introduced by generating additional master coordinates using sensor placement methods, e.g. the Effective‐Independence‐algorithm (EfI) [2]. By using a rank criterion for the automatic selection of additional coordinates, the improved back‐transformation performs properly and without damaging the reduced order model at a fairly small computational overhead, which is demonstrated at the example of a gear box housing. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error estimation approach for controlling the comunication step size for semi‐implicit co‐simulation methods
Authors: Meyer Tobias , Schweizer Bernhard
Published: October 2015

In this paper, an approach for controlling the macro‐step size in connection with co‐simulation methods [1, 2, 4] is suggested. The investigated step‐size controller is tailored for semi‐implicit co‐simulation techniques. Concretely, we consider predictor/corrector co‐simulation approaches [3]. By comparing variables from the predictor and the corrector step, an error estimator for the local error can be constructed. Making use of the estimated local error, a step‐size controller for the macro step‐size can be implemented. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An explicit approach for time‐optimal trajectory planning for kinematically redundant serial robots
Authors: Reiter Alexander , Springer Klemens , Gattringer Hubert , Müller Andreas
Published: October 2015

Kinematically redundant serial robots have become industrially important due their increased workspace and their inherent capability of null space motion resulting in remarkable adaptiveness to specific tasks compared to conventional, non‐redundant manipulators. Attempting to increase the cost‐effectiveness of industrial processes, introducing minimum‐time trajectories may yield economical advantages due to reduced motion cycle times. This contribution presents a method that uses joint space decomposition and analytic inverse kinematics as well as standard optimization techniques to obtain minimum‐time B‐spline joint trajectories along prescribed task space paths for kinematically redundant serial robots. It is shown that the present method was successfully applied to a planar manipulator. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Guideway based damping control of vehicle suspensions
Authors: Schiehlen Werner
Published: October 2015

The information on the routing of a road provided by a navigation system can be used by the driver of a vehicle with adaptive shock absorber to decide either for optimal comfort or optimal safety depending on the course of the guideway. However, the assessment criteria comfort and safety are with respect to the shock absorber in conflict with each other. In particular, maximal safety on a curvaceous road results in lower comfort. Thus, deciding on high safety means low comfort conveying a warning to the driver to reduce the speed. The methods applied in this paper originate from multibody dynamics, and they are extended by the stochastic road unevenness and the guideway curvature available to the driver from a navigation system using GPS data. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards effective mechanical properties of skeletal muscle tissue via homogenisation
Authors: Bleiler Christian , Ponte Castañeda Pedro , Röhrle Oliver
Published: October 2015

The constitutive modelling of skeletal muscle tissue in a continuum‐mechanical framework demands the consideration of many complex material characteristics. This complexity stems from the microscopic arrangement of different structural elements, such as, for example, sarcomeres and connective tissue. The former are responsible for the active contractile behaviour while the latter are mainly responsible for the passive stiffness of the muscle tissue. Thus, it is highly challenging to build appropriate macroscopic models based on phenomenological descriptions and yet cover most of the complex material behaviour. Strain‐energy functions have to be adapted for every significant material phenomena coming from experimental testing of muscle tissue. Another way to treat the modelling of active muscle tissue is to describe important parts of the heterogeneous microstructure and use homogenisation approaches to derive effective overall properties. This contribution aims to investigate and develop new homogenisation techniques for passive skeletal muscle tissue and is the first step towards the ultimate goal of developing a consistent framework that allows to derive macroscopic material properties for active muscle tissue based on microstructural characteristics. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A geometric approach to characterize rigidity in proteins
Authors: Budday Dominik , Leyendecker Sigrid , van den Bedem Henry
Published: October 2015

Kinematic analysis, in contrast to sophisticated molecular dynamics simulations, can provide high‐level insights into conformational diversity of proteins and other biomolecules, with broad implications for human health. Here, we model a protein as a kinematic linkage and present a new geometric method to characterize molecular rigidity. While existing combinatorial constraint counting is limited to generic structures, our geometric approach is also valid for non‐generic linkages. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Calculation of Fiber Orientation in Three‐Dimensional Arterial Walls
Authors: Fausten Simon , Balzani Daniel , Schröder Jörg
Published: October 2015

In this contribution an approach for the fiber reorientation in three‐dimensional arterial walls is presented. In detail the load‐bearing capacity of the tissue is increased by re orienting the fibers with respect to the principal stresses, cf. [1]. The improved fiber reorientation algorithm is combined with the polyconvex nonlinear anisotropic material model presented in [3]. The results of a three‐dimensional finite element simulation, where the reorientation approach is applied to a short segment of a patient‐specific arterial geometry, are presented. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)