Understanding cytoskeletal avalanches using mechanical stability analysis

Eukaryotic cells are mechanically supported by a polymer network called the cytoskeleton, which consumes chemical energy to dynamically remodel its structure. Recent experiments in vivo have revealed that this remodeling occasionally happens through anomalously large displacements, reminiscent of earthquakes or avalanches. These cytoskeletal avalanches might indicate that the cytoskeleton’s structural response to a changing cellular environment is highly sensitive, and they are therefore of significant biological interest. However, the physics underlying “cytoquakes” is poorly understood. Here, we use agent-based simulations of cytoskeletal self-organization to study fluctuations in the network’s mechanical energy. We robustly observe non-Gaussian statistics and asymmetrically large rates of energy release compared to accumulation in a minimal cytoskeletal model. The large events of energy release are found to correlate with large, collective displacements of the cytoskeletal filaments. We also find that the changes in the localization of tension and the projections of the network motion onto the vibrational normal modes are asymmetrically distributed for energy release and accumulation. These results imply an avalanche-like process of slow energy storage punctuated by fast, large events of energy release involving a collective network rearrangement. We further show that mechanical instability precedes cytoquake occurrence through a machine-learning model that dynamically forecasts cytoquakes using the vibrational spectrum as input. Our results provide a connection between the cytoquake phenomenon and the network’s mechanical energy and can help guide future investigations of the cytoskeleton’s structural susceptibility.

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Dielectric Elastomers for Direct Wind-to-Electricity Power Generation

Volume 1: Active Materials, Mechanics and Behavior; Modeling, Simulation and Control ◽

10.1115/smasis2009-1335 ◽

2009 ◽

Cited By ~ 5

Author(s):

Paul Brochu ◽

Wei Yuan ◽

Han Zhang ◽

Qibing Pei

Keyword(s):

Mechanical Stability ◽

Mechanical Energy ◽

Polymer Network ◽

Single Layer ◽

Energy Conversion Efficiency ◽

Operational Reliability ◽

Dielectric Elastomer ◽

Low Energy ◽

Interpenetrating Polymer Network ◽

Comparative Results

We present a universal dielectric elastomer energy generator that can be scaled to match the requirements of the energy source. The design couples mechanical energy directly into an out of plane deflection that deforms the film. Cycling the generator between high and low strain states while applying a bias electric field switches the device between high and low energy states; charge that is injected at low energy can then be extracted at a higher potential. We present an analysis of the energy generation capacity and mechanical stability of the device and demonstrate its scalability via a compact, low energy/low deflection device and a larger, higher energy device. We demonstrate the capability of generating approximately 40 mJ per cycle in a single layer device with an active elastomer volume of only 0.57 cm3 and a maximum observed energy conversion efficiency of over 55%. We use recently developed advances in dielectric elastomer technology including interpenetrating polymer network films and carbon nanotube electrodes to improve operational reliability and present comparative results that demonstrate an increase in lifetime by several orders of magnitude over prestrained VHB acrylic films with carbon grease electrodes.

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Mechanical Stability of Hybrid Corrugated Sandwich Plates under Fluid-Structure-Thermal Coupling for Novel Thermal Protection Systems

Applied Sciences ◽

10.3390/app10082790 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2790

Author(s):

Wenzheng Zhuang ◽

Chao Yang ◽

Zhigang Wu

Keyword(s):

Mechanical Stability ◽

Thermal Protection ◽

Element Model ◽

Parameter Study ◽

The Novel ◽

Thermal Coupling ◽

Mechanical Instability ◽

Fluid Structure ◽

Thermal Protection Systems ◽

Protection Systems

Hybrid corrugated sandwich (HCS) plates have become a promising candidate for novel thermal protection systems (TPS) due to their multi-functionality of load bearing and thermal protection. For hypersonic vehicles, the novel TPS that performs some structural functions is a potential method of saving weight, which is significant in reducing expensive design/manufacture cost. Considering the novel TPS exposed to severe thermal and aerodynamic environments, the mechanical stability of the HCS plates under fluid-structure-thermal coupling is crucial for preliminary design of the TPS. In this paper, an innovative layerwise finite element model of the HCS plates is presented, and coupled fluid-structure-thermal analysis is performed with a parameter study. The proposed method is validated to be accurate and efficient against commercial software simulation. Results have shown that the mechanical instability of the HCS plates can be induced by fluid-structure coupling and further accelerated by thermal effect. The influences of geometric parameters on thermal buckling and dynamic stability present opposite tendencies, indicating a tradeoff is required for the TPS design. The present analytical model and numerical results provide design guidance in the practical application of the novel TPS.

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Marker for the pre-clinical development of bone substitute materials

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2017-0151 ◽

2017 ◽

Vol 3 (2) ◽

pp. 711-715

Author(s):

Michael de Wild ◽

Simon Zimmermann ◽

Marcel Obrecht ◽

Michel Dard

Keyword(s):

Bone Graft ◽

Mechanical Stability ◽

Clinical Performance ◽

Ex Vivo ◽

Region Of Interest ◽

Defect Site ◽

Novel Approach ◽

Bone Substitute Materials ◽

Clinical Experiments

AbstractThin mechanically stable Ti-cages have been developed for the in-vivo application as X-ray and histology markers for the optimized evaluation of pre-clinical performance of bone graft materials. A metallic frame defines the region of interest during histological investigations and supports the identification of the defect site. This standardization of the procedure enhances the quality of pre-clinical experiments. Different models of thin metallic frameworks were designed and produced out of titanium by additive manufacturing (Selective Laser Melting). The productibility, the mechanical stability, the handling and suitability of several frame geometries were tested during surgery in artificial and in ex-vivo bone before a series of cages was preclinically investigated in the female Göttingen minipigs model. With our novel approach, a flexible process was established that can be adapted to the requirements of any specific animal model and bone graft testing.

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Impact of mechanical stability on the progress of bone ongrowth on the frame surfaces of a titanium-coated PEEK cage and a 3D porous titanium alloy cage: in vivo analysis using CT color mapping

European Spine Journal ◽

10.1007/s00586-020-06673-4 ◽

2021 ◽

Author(s):

Takahiro Makino ◽

Shota Takaneka ◽

Yusuke Sakai ◽

Hideki Yoshikawa ◽

Takashi Kaito

Keyword(s):

Titanium Alloy ◽

Mechanical Stability ◽

Porous Titanium ◽

Peek Cage ◽

Color Mapping ◽

In Vivo Analysis

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Partial Decellularization for Segmental Tracheal Scaffold Tissue Engineering: A Preliminary Study in Rabbits

Biomolecules ◽

10.3390/biom11060866 ◽

2021 ◽

Vol 11 (6) ◽

pp. 866

Author(s):

Luong Huu Dang ◽

Yuan Tseng ◽

How Tseng ◽

Shih-Han Hung

Keyword(s):

Mechanical Stability ◽

Vital Staining ◽

Potential Method ◽

Term Survival ◽

Long Term Survival ◽

Cartilage Cells ◽

Preliminary Study ◽

Epithelial Layers

In this study, we developed a new procedure for the rapid partial decellularization of the harvested trachea. Partial decellularization was performed using a combination of detergent and sonication to completely remove the epithelial layers outside of the cartilage ring. The post-decellularized tracheal segments were assessed with vital staining, which showed that the core cartilage cells remarkably remained intact while the cells outside of the cartilage were no longer viable. The ability of the decellularized tracheal segments to evade immune rejection was evaluated through heterotopic implantation of the segments into the chest muscle of rabbits without any immunosuppressive therapy, which demonstrated no evidence of severe rejection or tissue necrosis under H&E staining, as well as the mechanical stability under stress-pressure testing. Finally, orthotopic transplantation of partially decellularized trachea with no immunosuppression treatment resulted in 2 months of survival in two rabbits and one long-term survival (2 years) in one rabbit. Through evaluations of posttransplantation histology and endoscopy, we confirmed that our partial decellularization method could be a potential method of producing low-immunogenic cartilage scaffolds with viable, functional core cartilage cells that can achieve long-term survival after in vivo transplantation.

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Adipose and Muscle Cell Co-Culture System: A Novel In Vitro Tool to Mimic the In Vivo Cellular Environment

Biology ◽

10.3390/biology10010006 ◽

2020 ◽

Vol 10 (1) ◽

pp. 6

Author(s):

Palaniselvam Kuppusamy ◽

Dahye Kim ◽

Ilavenil Soundharrajan ◽

Inho Hwang ◽

Ki Choon Choi

Keyword(s):

Drug Development ◽

Culture System ◽

Cell Types ◽

Culture Cell ◽

In Vitro Techniques ◽

Culture Systems ◽

Complex Interactions ◽

Cellular Environment

A co-culture system allows researchers to investigate the complex interactions between two cell types under various environments, such as those that promote differentiation and growth as well as those that mimic healthy and diseased states, in vitro. In this paper, we review the most common co-culture systems for myocytes and adipocytes. The in vitro techniques mimic the in vivo environment and are used to investigate the causal relationships between different cell lines. Here, we briefly discuss mono-culture and co-culture cell systems and their applicability to the study of communication between two or more cell types, including adipocytes and myocytes. Also, we provide details about the different types of co-culture systems and their applicability to the study of metabolic disease, drug development, and the role of secretory factors in cell signaling cascades. Therefore, this review provides details about the co-culture systems used to study the complex interactions between adipose and muscle cells in various environments, such as those that promote cell differentiation and growth and those used for drug development.

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Properties of a bovine collagen type I membrane for guided bone regeneration applications

e-Polymers ◽

10.1515/epoly-2021-0021 ◽

2021 ◽

Vol 21 (1) ◽

pp. 210-221

Author(s):

Igor S. Brum ◽

Carlos N. Elias ◽

Jorge J. de Carvalho ◽

Jorge L. S. Pires ◽

Mario J. S. Pereira ◽

...

Keyword(s):

Bone Regeneration ◽

Collagen Type ◽

Mechanical Stability ◽

Collagen Type I ◽

Guided Bone Regeneration ◽

Bone Volume ◽

Male Rats ◽

Toxicity Tests ◽

Type I

Abstract Dental implant treatment requires an available bone volume in the implantation site to ensure the implant’s mechanical stability. When the bone volume is insufficient, one must resort to surgical means such as guided bone regeneration (GBR). In GBR surgery, bone grafts and membranes are used. The objective of this work is to manufacture and characterize the in vitro and in vivo properties of resorbable collagen type I membranes (Green Membrane®) for GBR. Membrane surface morphology was characterized by SEM and roughness was measured using an interferometric noncontact 3D system. In vivo skin sensitization and toxicity tests have been performed on Wistar rats. Bone defects were prepared in 24 adult male rats, filled with biomaterials (Blue Bone® and Bio Oss®) and covered with collagen membranes to maintain the mechanical stability of the site for bone regeneration. The incisions were closed with simple stitches; and 60 days after the surgery, the animals were euthanized. Results showed that the analyzed membrane was homogeneous, with collagen fiber webs and open pores. It had no sign of cytotoxicity and the cells at the insertion site showed no bone morphological changes. There was no tissue reaction and no statistical difference between Blue Bone® and Bio Oss® groups. The proposed membrane has no cytotoxicity and displays a biocompatibility profile that makes it suitable for GBR.

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Experimental travelling waves identification in mechanical structures

Mathematics and Mechanics of Solids ◽

10.1177/1081286517732825 ◽

2017 ◽

Vol 24 (1) ◽

pp. 152-167

Author(s):

Izhak Bucher ◽

Ran Gabai ◽

Harel Plat ◽

Amit Dolev ◽

Eyal Setter

Keyword(s):

Energy Flux ◽

Power Flow ◽

Reactive Power ◽

Mechanical Energy ◽

Travelling Waves ◽

Electrical Power ◽

Normal Modes ◽

Standing Waves ◽

Amplitude Curve ◽

Physical Point

Vibrations are often represented as a sum of standing waves in space, i.e. normal modes of vibration. While this can be mathematically accurate, the representation as travelling waves can be compact and more appropriate from a physical point of view, in particular when the energy flux along the structure is meaningful. The quantification of travelling waves assists in computing the energy being transferred and propagated along a structure. It can provide local as well as global information about the structure through which the mechanical energy flows. Presented in this paper is a new method to quantify the fraction of mechanical power being transmitted in a vibration cycle at a specific direction in space using measured data. It is shown that the method can detect local defects causing slight non-uniformity of the energy flux. Equivalence is being made with the electrical power factor and electromagnetic standing waves ratio, commonly employed in such cases. Other methods to perform experiment based wave identification in one-dimension are compared with the power flow based identification. Including a signal processing approach that fits an ellipse to the complex amplitude curve and Hilbert transform for obtaining the local phase and amplitude. A new representation of the active and reactive power flow is developed and its relationship to standing waves ratio is demonstrated analytically and experimentally.

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