bluuebunny/crossref_metadata_2025_split huggingface dataset:
The biomarker potential of cell‐free microRNA from cerebrospinal fluid in Parkinsonian Syndromes
Authors: Starhof Charlotte , Hejl Anne‐Mette , Heegaard Niels H.H. , Carlsen Anting L. , Burton Mark , Lilje Berit , Winge Kristian 
Published: December 2018

ABSTRACTBackground: MicroRNAs are small noncoding RNAs involved in the post‐transcriptional regulation of protein synthesis. Extracellular microRNAs are accessible in a stable form in biofluids.Objectives: The aim was to identify individual microRNAs and/or subsets of microRNAs in CSF with biomarker potential and thus identify specific putative pathophysiological pathways.Methods: In a two‐step exploratory study design of PD, MSA, PSP, and controls, we initially profiled CSF microRNAs in a pilot cohort (n = 40) by screening for 372 microRNAs. Subsequently, we attempted to validate findings in an independent study cohort in CSF (n = 118) and ethylenediaminetetraacetic acid plasma (n = 114). This study cohort encompassed 46 microRNAs, of which 26 were singled out from the pilot cohort, and an additional 20 microRNAs were added based on previous publications. The most accurate diagnostic microRNA classifiers were identified in a multivariable logistic regression model adjusted for age and sex.Results: A set of three microRNAs in CSF discriminated PD and MSA from controls with good diagnostic accuracy by receiver operating characteristics curve evaluation. The microRNAs were for PD versus controls: miR‐7‐5p, miR‐331‐5p, and miR‐145‐5p (area under the curve = 0.88) and MSA versus controls: miR‐7‐5p, miR‐34c‐3p, and miR‐let‐7b‐5p (area under the curve = 0.87). The classifier that best distinguished MSA and PD consisted of two microRNAs: miR‐9‐3p and miR‐106b‐5p (area under the curve = 0.73). A single microRNA, miR‐106b‐5p, provided the best discrimination between PD and PSP (area under the curve = 0.85) in the CSF.Conclusions: Levels of specific trios of CSF‐microRNAs discriminate well between α‐synucleinopathies (PD and MSA) and controls. The results need to be validated in larger, independent cohorts. © 2018 International Parkinson and Movement Disorder Society
The Early Life History of the Guadalupe Bass: Lessons for Culturing a Threatened Species
Authors: Prangnell David I , Matthews Michael D 
Published: December 2018

Abstract
Guadalupe Bass Micropterus treculii fingerlings are produced at the A. E. Wood State Fish Hatchery in San Marcos, Texas, and stocked into streams draining the Edwards Plateau in central Texas as part of a conservation program to restore threatened populations and combat hybridization with Smallmouth Bass M. dolomieu. Despite an intensive conservation effort, much of the early life history (including morphological development and first feeding characteristics) required for the intensive production of Guadalupe Bass is unreported in the mainstream literature. A better understanding of this critical period may improve culture practices, fingerling production, and management efforts. We documented spawning and early developmental characteristics and milestones over a temperature range of 20–24°C and the prey composition of Guadalupe Bass in a hatchery setting. Eggs and fry were photographed under a microscope and observed in culture tanks and ponds from initial stocking to fingerling harvest. A dominant-male, polygynous spawning structure was confirmed. Egg incubation (28–29 growing degree-days), larval development, yolk depletion, swim-up, and life stage transition proceeded faster at higher temperature. Eggs (mean diameter, 2.1 mm), fry (mean hatchling TL, 4.7 mm), and yolk reserves (mean hatchling yolk volume, 2.02 μL) were larger than reported for Largemouth Bass M. salmoides. Normally developed fry commenced exogenous feeding on a variety of zooplankton soon after swim-up (120–144 h posthatch and 6.95–8.05 mm TL at 23.4°C), while yolk was still present, and consumed progressively larger aquatic invertebrates over time. Swim-up fry with a range in gape width of 0.75–0.89 mm readily consumed brine shrimp Artemia spp. nauplii as first feed. Guadalupe Bass appear to be a relatively pliable species, and current culture practices are generally sound. The observations presented can be used to refine culture and management practices.
Lightweight construction with two‐dimensional cellular solids in additive manufacturing
Authors: Großmann Alexander , Mittelstedt Christian 
Published: December 2018

AbstractAdditive manufacturing delivers a high degree of manufacturing freedom. New applications such as structural integration of cellular structures are enabled by this technology. However, the manufacturing process bears some challenges, that need to be investigated. This contribution focusses on manufacturing, elastic properties and lightweight degree assessment of two dimensional cellular solids. To get a high lightweight degree at a given stiffness one must be aware of the structure's geometry and the amount of material used in a representative volume element. Even though this can be obtained by simple geometric considerations little research has been conducted on that aspect.In this work we deliver exact solutions for the so called relative density, which denotes the volume fraction of material used in a representative volume element, which is crucial to assess the lightweight degree. Furthermore an approach in order to realize the corresponding structures by a powder bed based additive manufacturing process will be presented.
Fiber‐based modeling of muscles in the musculoskeletal system
Authors: Gfrerer Michael , Simeon Bernd 
Published: December 2018

AbstractThe aim of this contribution is to present a fiber‐based modeling approach for the behavior of muscles within the musculoskeletal system. We represent the skeletal system as a rigid multibody system which is actuated by muscles. Each muscle is represented by one 1D cable with variable cross section undergoing large deformation and strains. We employ a incompressible Kelvin‐Voigt material for the passive behavior and a active stress law found in the literature. We incorporate contact between the muscles and the rigid bodies within a finite element framework by the penalty method. We apply our framework to conduct a forward simulation of a simple upper limb model.
Complex Falk‐Langemeyer Method
Authors: Hari Vjeran 
Published: December 2018

AbstractThe known Falk‐Langemeyer method for the simultaneous diagonalization of two positive definite symmetric matrices is generalized to work with complex matrices. It is shown that the derived method is well defined for the Hermitian matrices which make a definite pair. Special attention is paid to the stability of the formulas for the computational parameters when the pivot submatrices are close to being proportional. Numerical tests indicate the high relative accuracy of the method provided that both matrices are definite and well‐behaved, i.e. if they can be well‐scaled symmetrically.
Impact of particle boundary conditions on the collision rates of inclusions around a single bubble rising in liquid metal
Authors: May Ronja , Gruy Frédéric , Fröhlich Jochen 
Published: December 2018

AbstractIn the presented flow simulations a spherical argon gas bubble rises in stagnant liquid metal with initially homogeneously distributed spherical aluminium oxide particles of small inertia. Depending on their relative position to the bubble particles are subjected to different fluid forces and show different collision behaviour. The contribution presents Direct Numerical Simulations with the bubble being geometrically resolved and the inclusions represented as point particles. In the community, the boundary condition at the particle surface is discussed controversially. To elucidate its potential influence, two extreme cases are simulated, one with full no‐slip condition, the other one with full slip condition. It is found that the influence of this change on the result is very small.
Homogenized material properties for cross‐laminated timber
Authors: Furtmüller Thomas , Adam Christoph , Giger Benjamin 
Published: December 2018

AbstractIn this contribution the coefficients of the elastic stiffness tensor of a generalized shell section for cross‐laminated timber (CLT) slabs are derived by application of a numerical homogenization scheme based on a repeating unit cell (RUC). In an example it is shown that a finite shell element model with those homogenized shell stiffness parameters predicts closely the modal properties of a CLT slab, thus, verifying the accuracy of the applied homogenization procedure for this type of structural members.
Energy‐momentum consistent time integration scheme for non‐linear electro‐elastodynamics
Authors: Janz Alexander , Betsch Peter , Franke Marlon , Ortigosa Rogelio 
Published: December 2018

AbstractIn this work we present a new approach to the design of energy‐momentum (EM) consistent algorithms inspired by the structure of polyconvex internal energy functions (see [1]) and tailor‐made for the consistent space‐time discretization of electro‐active polymers (EAPs). A Hu‐Washizu‐type mixed variational framework with a novel cascade form of kinematic constraints [2] along with the concept of partitioned discrete derivatives leads to a structure‐preserving time integrator, which shows superior numerical stability and robustness. This work can be seen as an extension of [1] to mixed formulations in the sense of [2].
Gradient‐Enhancement of a Rock Model Applied to Numerical Simulations of Tunnel Advance
Authors: Schreter Magdalena , Neuner Matthias , Hofstetter Günter 
Published: December 2018

AbstractRock is classified as a frictional cohesive material characterized by nonlinear stress‐strain relations including softening leading to structural failure. To describe the mechanical behavior of rock comprising the accumulation of irreversible strains, strain hardening, and the degradation of stiffness and strength, an isotropic damage plasticity model for intact rock and rock mass was proposed in [1]. In the context of numerical simulations of tunneling, considering strain softening of rock allows to predict the formation of shear bands emanating from the tunnel surface due to the excavation process, which is crucial for engineers to forecast potentially dangerous situations related to failure. To ensure objective results in the softening regime upon mesh refinement, in the aforementioned rock model the concept of the crack band approach by Bažant and Oh was adopted. As a remedy of known deficiencies related to this regularization approach, the rock model is extended by the over‐nonlocal implicit gradient‐enhancement proposed in [2]. Accordingly, a nonlocal field of the damage‐driving variable, implicitly defined as the solution of a Helmholtz‐like partial differential equation, is introduced yielding a fully coupled system of second‐order PDEs. In the present contribution, the over‐nonlocal gradient enhancement of the rock model is presented and applied together with a linear‐elastic material model for shotcrete to finite element simulations of a deep tunnel constructed by the New Austrian Tunneling Method. Based on this real example, objectivity of the results with respect to the finite element discretization is discussed.
Some remarks on parametric excitation in circulatory systems
Authors: Karev Artem , DeBroeck Lara , Hagedorn Peter 
Published: December 2018

AbstractDynamical systems with time‐periodic coefficients, i.e. with parametric excitation, have been studied in different fields for over a hundred years. It is well known that the presence of parametric excitation acts mostly destabilizing, leading to the emergence of instability regions depending on the amplitude and frequency of excitation. However, most of the work is done on systems with synchronous parametric excitation, while there are only few papers dealing with out‐of‐phase time‐periodicity. At the same time little to no research in this context is done on systems containing gyroscopic or circulatory terms. The present paper demonstrates different approaches for stability assessment of time‐periodic systems featuring nonconservative terms. In particular, out‐of‐phase parametric excitation as well as circulatory forces are considered in an example which is treated analytically and numerically. The derived stability boundaries show that the interaction of both features leads to the occurrence of rather unexpected resonance areas. The results extend the understanding of the influence of parametric excitation and encourage study of more general systems.
On anisotropy evolution in finite strain plasticity
Authors: Kaiser Tobias , Lu Jia , Menzel Andreas , Papadopoulos Panayiotis 
Published: December 2018

AbstractMotivated by the experimental investigations on cold rolled sheet metal presented in [1], this contribution focuses on a specific modelling approach to capture the evolution of (plastic) material symmetry groups that is induced by finite plastic deformation processes. The ensuing developments are based on the general theoretical framework by Lu and Papadopoulos with regard to evolving material symmetries proposed in [2, 3]. In particular, we elaborate a specific form of the evolution equation for the structural tensor that characterises the respective material symmetry group and show that the simulation results are in good accordance with the experimental findings.
Willmore Flow of Networks
Authors: Garcke Harald , Menzel Julia , Pluda Alessandra 
Published: December 2018

AbstractWe consider networks of curves in the plane moving according to the L2 –gradient flow of the elastic energy. We prove short time existence in the case of networks composed of three curves that are required to meet at one or two triple junctions. As a variation of the result we additionally impose that they form angles of 120 degrees at the triple junction(s).
An energy based peridynamic state‐based failure criterion
Authors: Willberg Christian , Rädel Martin 
Published: December 2018

AbstractThe paper presents a verification and convergence study of an enhanced energy based failure model based on Foster et al. [2]. The failure model has been implemented in the open source software Peridigm. The study is performed with a virtual double cantilever beam test. To verify the implementation an energy release rate is virtually measured and compared with the input data. Time and load of the crack initiation are used as the convergence criteria.
Phase‐field modelling of fracture in heterogeneous materials
Authors: Hansen‐Dörr Arne C. , Gude Maik , Böhm Robert , Kästner Markus 
Published: December 2018

AbstractIn this contribution, we apply a phase‐field model to simulate fracture processes in heterogeneous materials. The local material structure is modelled in a diffuse manner, e.g. by a local reduction of the fracture toughness. In order to obtain a physically meaningful crack propagation, the interaction between the length scales of the diffuse microstructure and the regularised crack are studied. We employ a local correction of the fracture toughness assigned to the interface domain. The method is verified in several numerical benchmark problems and applied to simulate fracture processes in heterogeneous materials.
Optimal control of resources for species survival
Authors: Mazari Idriss , Nadin Grégoire , Privat Yannick 
Published: December 2018

AbstractConsider a species whose population density solves the steady diffusive logistic equation in a heterogeneous environment modeled with the help of a spatially non constant coefficient standing for a resources distribution in a given box. We look at maximizing the total population size with respect to resources distribution, under some biologically relevant constraints. Assuming that the diffusion rate of the species is large enough, we prove that any optimal configuration is the characteristic function of a domain standing for the resources location. Moreover, we highlight that optimal configurations look concentrated whenever the diffusion rate is large enough. In the one‐dimensional case, this problem is deeply analyzed, and for large diffusion rates, all optimal configurations are exhibited.
Comparative study of worm‐like chain models for collagen molecules
Authors: Hillgärtner Markus , Linka Kevin , Itskov Mikhail 
Published: December 2018

AbstractCollagen is the main structural protein in various biological tissues and of high interest for microstructural multi‐scale models due to its load bearing functionality. The worm‐like chain (WLC) model [4] with its approximation [6] is a widely used approach for the modeling of DNA, which has a helical structure similar to tropocollagen. However, the classical WLC is suitable only for the entropic deformation regime of collagen. By modeling the extension behavior, it fails to give accurate predictions when the helical structure of the molecule starts twisting under higher loads.The twistable worm‐like chain [3] and its special case referred to as the extensible worm‐like chain [7] aim to include the mechanical coupling between bond stretching and twist of the helix using a twist‐stretch coupling term, leading to more accurate predictions in the energetic regime. This contribution discusses different variations and coupling terms describing the molecular behavior behind the transition state between the entropic and energetic regime. Experimental data of the literature [1] are used to make a quantitative comparison of the discussed models and their applicability.
Efficient and reliable phase‐field simulation of brittle fracture using a nonsmooth multigrid solution scheme
Authors: Kienle Daniel , Gräser Carsten , Sander Oliver , Keip Marc‐André 
Published: December 2018

AbstractIn the last decades the phase‐field approach to fracture [1–3] has gained wide popularity due to advantages such as straight‐forward modeling of complex crack patterns and crack branching while allowing standard finite‐element discretizations. Time‐discrete phase‐field models of brittle fracture are typically formulated in terms of biconvex minimization problems for which a standard monolithic Newton‐Raphson scheme usually fails to converge. Solutions can be found by using operator‐splitting methods [2] or predictor‐corrector schemes [4]. Such methods come at the cost of high computational efforts. Furthermore, models incorporating the thermodynamically consistent local irreversibility of the damage phase‐field contain nonsmooth terms [2]. To improve the stability and to reduce the computational costs originating from the biconvexity and the nonsmoothness of the energy functional, we employ a nonsmooth multigrid method that can solve such problems roughly in the time of one equivalent linear problem [5] and which has been shown to be globally convergent [5]. We will demonstrate the computational speed of the proposed solution scheme by means of a classical benchmark problem of brittle fracture.
Efficient numerical simulations of drug delivery in multi‐component brain tissue
Authors: Wagner Arndt , Fink Davina , Ehlers Wolfgang 
Published: December 2018

AbstractIn this contribution, we discuss the problem‐specific application of suitable model‐reduction techniques to obtain an efficient numerical simulation of therapeutic infusion processes within multi‐component brain tissues. Therefore, the required set up is reviewed to apply the method of proper orthogonal decomposition (POD) in a combination with the discrete‐empirical‐interpolation method (DEIM) to a multi‐component brain‐tissue model based on the Theory of Porous Media (TPM). It appears that the required computation time for simulations can be reduced significantly. In this regard, an exemplary clinical issue (choice of the optimal infusion pressure) is discussed in terms of efficiency, accuracy, boundary‐value variations and clinical applicability.
Sensitivity Analysis of Nonlinear Structural Response regarding Geometry and External Loads
Authors: Liedmann Jan , Barthold Franz‐Joseph 
Published: December 2018

AbstractThis paper is concerned with response sensitivity analysis of elastoplastic structures regarding geometric shape and external load parameters. Additionally to classic shape optimization, sensitivity information has to be computed concerning external load parameters. Due to the path dependent material behavior, variations of history variables have to be provided likewise. The analytical derivation of sensitivities is based on an enhanced kinematic concept that allows a strict separation of physical and geometrical quantities. With this approach it is possible to compute the structural response and response sensitivity simultaneously within a finite element framework. The main base equations are briefly described and the accuracy of the algorithm is demonstrated in an academic example.
On an accurate and fast regularization approach to thermodynamic based topology optimization
Authors: Jantos Dustin Roman , Hackl Klaus , Junker Philipp 
Published: December 2018

AbstractIn our previous works [1–3], we introduced a variational approach derived from thermodynamical principles, i.e. Hamilton's principle for dissipative processes. The Hamilton principle directly yields evolution equations providing an iterative update scheme for the design variables of the problem, requiring no additional (mathematical) minimization algorithms.We enhance our approach to reduce the calculation effort and improve the overall results: we introduce a regularization by penalizing the gradient of the density field, which gives us a well‐posed optimization problem. The strong form of the stationary condition results in a parabolic partial differential equation (PDE) which is solved by a finite difference method requiring minimal calculation effort. The regularization yields mesh‐independent results without checkerboarding. No additional filtering techniques are introduced and the complexity of the structure can be controlled a priori by a numerical parameter introduced along with the gradient penalization.
An efficient reduced computational method for nonlinear homogenization problems: the Hashin–Shtrikman type Finite Element method (HSFE)
Authors: Cavaliere Fabiola , Wulfinghoff Stephan , Reese Stefanie 
Published: December 2018

AbstractThis contribution is dedicated to a numerically efficient homogenization method for nonlinear microstructures (HSFE), which combines the small computational effort of the Hashin‐Shtrikman type approach with the accuracy of full‐field finite element solutions. The key point of the method is a model order reduction scheme based on data‐clustering, which leads to a significant reduction of computational time. The derivation of the analytical tangent operator realises the coupling between the microscopic and macroscopic scale. The presented approach is tested in the context of small strains by a numerical example, where a nonlinear RVE is attached to each integration point of a 2D macrostructure. A comparison to the FE‐simulations shows that the global‐ and local‐responses are well captured by the HSFE method.
Possibilistic and stochastic analysis using for rubber‐like materials
Authors: Penner Eduard , Caylak Ismail , Dridger Alex , Mahnken Rolf 
Published: December 2018

AbstractIn many engineering applications the material behavior, e.g. hyperelasticity, is described by an appropriate mathematical model. However, those become uncertain due to different types of uncertainty such as variation in the manufacturing process, measurement errors and missing or incomplete information on material properties. This contribution presents a framework for an uncertain nonlinear elastic material model at large deformations. As a key idea uncertainties of a material are described by correlated uncertain parameters, which are modeled in the first case as possibilistic and in the second case as random variables.