scholarly journals Magneto-Mechanical Coupling in Magneto-Active Elastomers

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 434
Author(s):  
Philipp Metsch ◽  
Dirk Romeis ◽  
Karl A. Kalina ◽  
Alexander Raßloff ◽  
Marina Saphiannikova ◽  
...  
Keyword(s):  
Particle Interaction ◽  
Helical Structures ◽  
Systematic Comparison ◽  
Mechanical Coupling ◽  
Basic Assumptions ◽  
Modeling Approaches ◽  
Model Predictions ◽  
Interaction Approach ◽  
Remarkable Agreement

In the present work, the magneto-mechanical coupling in magneto-active elastomers is investigated from two different modeling perspectives: a micro-continuum and a particle–interaction approach. Since both strategies differ significantly in their basic assumptions and the resolution of the problem under investigation, they are introduced in a concise manner and their capabilities are illustrated by means of representative examples. To motivate the application of these strategies within a hybrid multiscale framework for magneto-active elastomers, their interchangeability is then examined in a systematic comparison of the model predictions with regard to the magneto-deformation of chain-like helical structures in an elastomer surrounding. The presented results show a remarkable agreement of both modeling approaches and help to provide an improved understanding of the interactions in magneto-active elastomers with chain-like microstructures.

scholarly journals Die Kastanie im Engadin – oder was halten Baumarten von modellierten Potenzialgebieten? Chestnut in the Engadine – what do tree species think about model predictions?

2008 ◽  
Vol 159 (10) ◽  
pp. 326-335 ◽  
Author(s):  
Niklaus E. Zimmermann ◽  
Harald Bugmann
Keyword(s):  
Tree Species ◽  
Expert Knowledge ◽  
Forest Succession ◽  
Future Climate ◽  
Sensitivity Analyses ◽  
Climate Projections ◽  
Distribution Models ◽  
Modeling Approaches ◽  
Model Predictions ◽  
National Analysis

New IPCC climate projections suggest drastic changes in future climate. We discuss two commonly used modeling approaches, statistical distribution models and dynamic forest succession models, as they are suitable for assessing expected effects of climate change on the tree species distribution in Switzerland and for assisting management decisions in forestry. We discuss the basic assumptions and the strengths and weaknesses of the two approaches, without an understanding of which it is impossible to fully judge the outcome of modeling exercises. We give an overview of results from applying these two modeling approaches in Switzerland and in the Alps and discuss their appropriate use. We believe that these models are an important basis for decision making in the face of highly uncertain development of future climate. Nonetheless, models do not represent an exact copy of reality. Plausibility analyses are necessary in order to assess the results' usefulness and precision. Sensitivity analyses and a critical comparison of model results with expert knowledge of current forests, long measurement time series and other data are important. Also, dialog with practitioners and managers is not only important for checking the plausibility of model predictions under current conditions, but may also serve to improve the evaluation of future projections. We propose to apply models to the whole of Switzerland and to many tree species. Such a concerted national analysis may serve the adaptive management of forests and may strengthen dialog between researchers and practitioners.

scholarly journals An Interface–Particle Interaction Approach for Evaluation of the Co-Encapsulation Efficiency of Cells in a Flow-Focusing Droplet Generator

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3774
Author(s):  
Mohammad Yaghoobi ◽  
Mohammad Said Saidi ◽  
Sepehr Ghadami ◽  
Navid Kashaninejad
Keyword(s):  
Point Of Care ◽  
Particle Interaction ◽  
Cell Encapsulation ◽  
Surface Tension Force ◽  
Extensive Literature ◽  
The Finite Element Method ◽  
Proposed Model ◽  
Highly Sensitive ◽  
Passive Technique ◽  
Interaction Approach

Droplet-based microfluidics offers significant advantages, such as high throughput and scalability, making platforms based on this technology ideal candidates for point-of-care (POC) testing and clinical diagnosis. However, the efficiency of co-encapsulation in droplets is suboptimal, limiting the applicability of such platforms for the biosensing applications. The homogeneity of the bioanalytes in the droplets is an unsolved problem. While there is extensive literature on the experimental setups and active methods used to increase the efficiency of such platforms, passive techniques have received less attention, and their fundamentals have not been fully explored. Here, we develop a novel passive technique for investigating cell encapsulation using the finite element method (FEM). The level set method was used to track the interfaces of forming droplets. The effects of walls and the droplet interfaces on relatively large cells were calculated to track them more accurately during encapsulation. The static surface tension force was used to account for the effects of the interfaces on cells. The results revealed that the pairing efficiency is highly sensitive to the standard deviation (SD) of the distance between the cells in the entrance channel. The pairing efficiency prediction error of our model differed by less than 5% from previous experiments. The proposed model can be used to evaluate the performance of droplet-based microfluidic devices to ensure higher precision for co-encapsulation of cells.

Photomechanics of Light-Activated Shape Memory Polymers

2008 ◽  
Author(s):  
Kevin N. Long ◽  
Timothy F. Scott ◽  
H. Jerry Qi ◽  
Martin L. Dunn
Keyword(s):  
Shape Memory ◽  
Mechanical Response ◽  
Irradiation Time ◽  
Shape Memory Polymer ◽  
Polymer System ◽  
Shape Memory Polymers ◽  
Model Parameters ◽  
Model Framework ◽  
Mechanical Coupling ◽  
Model Predictions

Photomechanical shape memory polymers are an exciting class of materials that are able to store a temporary shape and recover their original shape when stimulated by light. In this work we develop a model to simulate the photomechanical behavior of light-activated shape memory polymers. To the best of our knowledge this is the first theoretical model developed to describe this exciting class of active materials. Our model incorporates the interplay among four aspects of the underlying physical phenomena: light propagation, photo-chemistry, chemical-mechanical coupling, and mechanical response. The model framework is applied to a recently developed photo-induced shape memory polymer system [1, 2]. We describe a suite of experiments used to guide the modeling efforts, calibrate the model parameters, and then validate model predictions. Regarding the latter, we measure and then simulate the photo-induced bending behavior of shape memory polymer samples; model predictions are in good agreement with measurements. We use the model to then explore the effect of important photomechanical parameters (applied strain magnitude, irradiation time and intensity, and photoabsorber concentration) on material response with a view toward the design of novel actuator materials and structures.

scholarly journals The Fitness Landscape of HIV-1 Gag: Advanced Modeling Approaches and Validation of Model Predictions by In Vitro Testing

2014 ◽  
Vol 10 (8) ◽  
pp. e1003776 ◽  
Author(s):  
Jaclyn K. Mann ◽  
John P. Barton ◽  
Andrew L. Ferguson ◽  
Saleha Omarjee ◽  
Bruce D. Walker ◽  
...  
Keyword(s):  
Fitness Landscape ◽  
In Vitro Testing ◽  
Modeling Approaches ◽  
Model Predictions ◽  
Hiv 1

scholarly journals Multiphysics modeling of porous ferrogels at finite strains

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Philipp Gebhart ◽  
Abdolhamid Attaran ◽  
Thomas Wallmersperger
Keyword(s):  
Variational Principles ◽  
Particle Interaction ◽  
Material Behavior ◽  
Shape Effect ◽  
Material Response ◽  
Modeling Approaches ◽  
Multiple Length Scales ◽  
Main Emphasis ◽  
Hydrogel Matrix ◽  
The Hierarchical Structure

Abstract Porous ferrogels are a new class of magnetoactive composite materials that consist of a polymeric hydrogel matrix with embedded magnetizable particles. The mutual particle interaction within the soft elastic matrix enables ferrogels to deform and alter their material characteristics upon magnetic stimulation. Due to these unique properties, ferrogels have attracted significant attention for potential uses in a variety of engineering applications, especially in biomedical engineering and microfluidics. Therefore, it is crucial to develop precise mathematical models capturing the complex material behavior of ferrogels, which spans over multiple length scales. The aim of this work is to present suitable modeling approaches for porous ferrogels. Following the hierarchical structure of scales, we present modeling frameworks for two different scenarios: (i) the modeling of ferrogels at the macroscale level and (ii) the modeling of ferrogels at the microscale level. Regarding the constitutive modeling of ferrogels, we limit our attention to locally nondissipative isotropic material response. For both modeling approaches, we provide comprehensive variational principles and briefly discuss relevant ingredients of a stable finite element implementation. In each section, numerical simulations are outlined in order to demonstrate the capabilities and relevant features of each modeling approach. Main emphasis of the numerical studies lies on the investigation of the macroscopic shape effect as well as on the characterization of the magnetomechanical material response of ferrogels with random monodisperse microstructures.

Studies of a Defective Measles Virus

1968 ◽  
Vol 26 ◽  
pp. 208-209
Author(s):  
R. M. McCombs ◽  
M. Benyesh-Melnick ◽  
J. P. Brunschwig
Keyword(s):  
Inclusion Bodies ◽  
Measles Virus ◽  
Giant Cells ◽  
Helical Structures ◽  
Thin Sections ◽  
Virus Particles ◽  
Extracellular Virus ◽  
Culture Cells ◽  
Infected Cells ◽  
Eosinophilic Inclusions

Measles virus is an agent that is capable of replicating in a number of different culture cells and generally causes the formation of multinucleated giant cells. As a result of infection, virus is released from the cells into the culture fluids and reinfection can be initiated by this cell-free virus. The extracellular virus has been examined by negative staining with phosphotungstic acid and has been shown to be a rather pleomorphic particle with a diameter of about 140 mμ. However, no such virus particles have been detected in thin sections of the infected cells. Rather, the only virus-induced structures present in the giant cells are eosinophilic inclusions (intracytoplasmic or intranuclear). These inclusion bodies have been shown to contain helical structures, resembling the nucleocapsid observed in negatively stained preparations.

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