scholarly journals Programmable viscoelasticity in protein-RNA condensates with disordered sticker-spacer polypeptides

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ibraheem Alshareedah ◽  
Mahdi Muhammad Moosa ◽  
Matthew Pham ◽  
Davit A. Potoyan ◽  
Priya R. Banerjee
Keyword(s):  
Optical Tweezers ◽  
Material Properties ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Rna Sequences ◽  
Microscopic Scale ◽  
Maxwell Fluids ◽  
Molecular Determinants ◽  
Subcellular Processes ◽  
Liquid Liquid Phase Separation

AbstractLiquid-liquid phase separation of multivalent proteins and RNAs drives the formation of biomolecular condensates that facilitate membrane-free compartmentalization of subcellular processes. With recent advances, it is becoming increasingly clear that biomolecular condensates are network fluids with time-dependent material properties. Here, employing microrheology with optical tweezers, we reveal molecular determinants that govern the viscoelastic behavior of condensates formed by multivalent Arg/Gly-rich sticker-spacer polypeptides and RNA. These condensates behave as Maxwell fluids with an elastically-dominant rheological response at shorter timescales and a liquid-like behavior at longer timescales. The viscous and elastic regimes of these condensates can be tuned by the polypeptide and RNA sequences as well as their mixture compositions. Our results establish a quantitative link between the sequence- and structure-encoded biomolecular interactions at the microscopic scale and the rheological properties of the resulting condensates at the mesoscale, enabling a route to systematically probe and rationally engineer biomolecular condensates with programmable mechanics.

scholarly journals Thermo-Viscoelastic Response of 3D Braided Composites Based on a Novel FsMsFE Method

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 271
Author(s):  
Jun-Jun Zhai ◽  
Xiang-Xia Kong ◽  
Lu-Chen Wang
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Structural Parameters ◽  
Thermal Relaxation ◽  
Viscoelastic Behavior ◽  
Unit Cell ◽  
Time Dependent ◽  
3D Braided Composites ◽  
Equivalent Time ◽  
Representative Unit Cell

A homogenization-based five-step multi-scale finite element (FsMsFE) simulation framework is developed to describe the time-temperature-dependent viscoelastic behavior of 3D braided four-directional composites. The current analysis was performed via three-scale finite element models, the fiber/matrix (microscopic) representative unit cell (RUC) model, the yarn/matrix (mesoscopic) representative unit cell model, and the macroscopic solid model with homogeneous property. Coupling the time-temperature equivalence principle, multi-phase finite element approach, Laplace transformation and Prony series fitting technology, the character of the stress relaxation behaviors at three scales subject to variation in temperature is investigated, and the equivalent time-dependent thermal expansion coefficients (TTEC), the equivalent time-dependent thermal relaxation modulus (TTRM) under micro-scale and meso-scale were predicted. Furthermore, the impacts of temperature, structural parameters and relaxation time on the time-dependent thermo-viscoelastic properties of 3D braided four-directional composites were studied.

scholarly journals 3D Plotting of Silica/Collagen Xerogel Granules in an Alginate Matrix for Tissue-Engineered Bone Implants

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 830
Author(s):  
Sina Rößler ◽  
Andreas Brückner ◽  
Iris Kruppke ◽  
Hans-Peter Wiesmann ◽  
Thomas Hanke ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Bone Regeneration ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Viscoelastic Behavior ◽  
Matrix Phase ◽  
Patient Specific ◽  
Active Player ◽  
Alginate Concentration ◽  
Alginate Matrix

Today, materials designed for bone regeneration are requested to be degradable and resorbable, bioactive, porous, and osteoconductive, as well as to be an active player in the bone-remodeling process. Multiphasic silica/collagen Xerogels were shown, earlier, to meet these requirements. The aim of the present study was to use these excellent material properties of silica/collagen Xerogels and to process them by additive manufacturing, in this case 3D plotting, to generate implants matching patient specific shapes of fractures or lesions. The concept is to have Xerogel granules as active major components embedded, to a large proportion, in a matrix that binds the granules in the scaffold. By using viscoelastic alginate as matrix, pastes of Xerogel granules were processed via 3D plotting. Moreover, alginate concentration was shown to be the key to a high content of irregularly shaped Xerogel granules embedded in a minimum of matrix phase. Both the alginate matrix and Xerogel granules were also shown to influence viscoelastic behavior of the paste, as well as the dimensionally stability of the scaffolds. In conclusion, 3D plotting of Xerogel granules was successfully established by using viscoelastic properties of alginate as matrix phase.

Application of a Viscoelastic Model for Polyester Mooring

2010 ◽  
Author(s):  
J. W. Kim ◽  
J. H. Kyoung ◽  
A. Sablok
Keyword(s):  
Material Properties ◽  
Viscoelastic Model ◽  
Practical Method ◽  
Time Dependent ◽  
Mooring Line ◽  
New Model ◽  
Global Performance ◽  
Excitation Period ◽  
Linear Viscoelastic ◽  
Floating Platforms

A new practical method to simulate time-dependent material properties of polyester mooring line is proposed. The time-dependent material properties of polyester rope are modeled with a standard linear solid (SLS) model, which is one of the simplest forms of a linear viscoelastic model. The viscoelastic model simulates most of the mechanical properties of polyester rope such as creep, strain-stress hysteresis and excitation period-dependent stiffness. The strain rate-stress relation of the SLS model has been re-formulated to a stretch-tension relation, which is more suitable for implementation into global performance and mooring analyses tools for floating platforms. The new model has been implemented to a time-domain global performance analysis software and applied to simulate motion of a spar platform with chain-polyester-chain mooring system. The new model provides accurate platform offset without any approximation on the mean environmental load and can simulate the transient effect due to the loss of a mooring line during storm conditions, which has not been possible to simulate using existing dual-stiffness models.

scholarly journals Time-Dependent Material Properties of Shotcrete: Experimental and Numerical Study

Materials ◽  
2017 ◽  
Vol 10 (9) ◽  
pp. 1067 ◽  
Author(s):  
Matthias Neuner ◽  
Tobias Cordes ◽  
Martin Drexel ◽  
Günter Hofstetter
Keyword(s):  
Material Properties ◽  
Numerical Study ◽  
Time Dependent

scholarly journals Impact of Enzymatic Degradation on the Material Properties of Poly(Ethylene Terephthalate)

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3885
Author(s):  
Teresa Menzel ◽  
Sebastian Weigert ◽  
Andreas Gagsteiger ◽  
Yannik Eich ◽  
Sebastian Sittl ◽  
...  
Keyword(s):  
Material Properties ◽  
Enzymatic Degradation ◽  
Ethylene Terephthalate ◽  
Compact Tension ◽  
Time Dependent ◽  
Material Failure ◽  
Near Surface ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
The Impact

With macroscopic litter and its degradation into secondary microplastic as a major source of environmental pollution, one key challenge is understanding the pathways from macro- to microplastic by abiotic and biotic environmental impact. So far, little is known about the impact of biota on material properties. This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-PET) and the degrading enzyme PETase from Ideonella sakaiensis. Compact tension (CT) specimens were incubated in an enzymatic solution and thermally and mechanically characterized. A time-dependent study up to 96 h revealed the formation of steadily growing colloidal structures. After 96 h incubation, high amounts of BHET dimer were found in a near-surface layer, affecting crack propagation and leading to faster material failure. The results of this pilot study show that enzymatic activity accelerates embrittlement and favors fragmentation. We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation.

Measurement of Residual Strains As a Parameter of Matrix Cracking in CFRP Laminates

2020 ◽  
Author(s):  
M. J. Mohammad Fikry ◽  
Shinji Ogihara ◽  
Vladimir Vinogradov
Keyword(s):  
Viscoelastic Behavior ◽  
Matrix Cracking ◽  
Time Dependent ◽  
Strain Gauges ◽  
Recovery Test ◽  
Cfrp Laminates ◽  
Matrix Cracks ◽  
Theoretical Predictions ◽  
Residual Strains ◽  
Good Agreement

Abstract Matrix cracking in CFRP laminates results in degradation of mechanical properties of the material and appearance of residual strains. In this study, the residual strains investigated are experimentally and analytically for CFRP [0/756]s laminates. The strain gauges were used in this study to measure the strains. Due to very small residual strains at the unloading condition, the residual strains were also measured at different stress levels for laminates with different crack densities and are compared with theoretical predictions. Time-dependent viscoelastic behavior of the material is also considered to accurately measure the residual strains due to the occurrence of matrix cracks. This was done by using the strain recovery test when the loads were stopped for 1–1.5 hours during unloading and the strain changes during these times were recorded. The experimental results of the residual strains are in reasonably good agreement with the theoretical predictions. The fiber non-linearity properties of the laminates may cause some experimental data to shift above the analytical line.

scholarly journals Effect of Preservation Period on the Viscoelastic Material Properties of Soft Tissues With Implications for Liver Transplantation

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Sina Ocal ◽  
M. Umut Ozcan ◽  
Ipek Basdogan ◽  
Cagatay Basdogan
Keyword(s):  
Liver Transplantation ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Soft Tissues ◽  
Excitation Frequency ◽  
Viscoelastic Model ◽  
Relaxation Modulus ◽  
Bovine Liver ◽  
Dynamic Responses ◽  
Time Dependent

The liver harvested from a donor must be preserved and transported to a suitable recipient immediately for a successful liver transplantation. In this process, the preservation period is the most critical, since it is the longest and most tissue damage occurs during this period due to the reduced blood supply to the harvested liver and the change in its temperature. We investigate the effect of preservation period on the dynamic material properties of bovine liver using a viscoelastic model derived from both impact and ramp and hold experiments. First, we measure the storage and loss moduli of bovine liver as a function of excitation frequency using an impact hammer. Second, its time-dependent relaxation modulus is measured separately through ramp and hold experiments performed by a compression device. Third, a Maxwell solid model that successfully imitates the frequency- and time-dependent dynamic responses of bovine liver is developed to estimate the optimum viscoelastic material coefficients by minimizing the error between the experimental data and the corresponding values generated by the model. Finally, the variation in the viscoelastic material coefficients of bovine liver are investigated as a function of preservation period for the liver samples tested 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 36 h, and 48 h after harvesting. The results of our experiments performed with three animals show that the liver tissue becomes stiffer and more viscous as it spends more time in the preservation cycle.

Evaluation of the Temperature Effect on the Viscoelastic Responses of Flexible Risers

2019 ◽  
Author(s):  
Junpeng Liu ◽  
Jinsheng Ma ◽  
Murilo Augusto Vaz ◽  
Menglan Duan
Keyword(s):  
Material Properties ◽  
Global Analysis ◽  
Viscoelastic Behavior ◽  
Step Test ◽  
Nonlinear Material ◽  
Polymer Layer ◽  
Axial Stiffness ◽  
Loading Frequency ◽  
Flexible Risers ◽  
Improved Model

Abstract Mechanical behavior of flexible risers can be challenging due largely to its complex design generating strong nonlinear problems. Nonlinear material properties, as one of them, from polymer layers dominate the overall viscoelastic responses of flexible risers which may play an inevitable role on the global analysis in deepwater application. An alternative to predict the viscoelastic behavior comprising of the time domain and the frequency domain has been proposed recently by the authors (Liu and Vaz, 2016). Given the fact that polymeric material properties are temperature-dependent and that the temperature profiles in flexile risers vary continuously in both axial and radial direction, the temperature of the internal hydrocarbons must affect the viscoelastic responses. However, such phenomenon dose not draw much attention in previous studies. This paper presents an improved model for overcoming some drawbacks in the proposed model involving assumption of steady temperature distribution in polymer layer and no gap appearance between the adjacent layers. The computing method of model is developed by using a step by step test approach. Consequently, some important parameters like equivalent axial stiffness, contact pressure or gap between the near layers, and force-deformation relationship can be observed. Parametric studies are conducted on the axisymmetric viscoelastic behavior of flexible risers to study the role of input temperature and loading frequency. Results show that equivalent axial stiffness given by the improved model is smaller than before. It can also be found that the gap between metal layer and polymer layer appear easily and increases as time goes on.

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