scholarly journals Stress generation, relaxation and size control in confined tumor growth

2019 ◽  
Author(s):  
H. Yan ◽  
D. Ramirez-Guerrero ◽  
J. Lowengrub ◽  
M. Wu
Keyword(s):  
Stress Relaxation ◽  
Malignant Tumors ◽  
Size Control ◽  
Maxwell Model ◽  
Stress Generation ◽  
Current Position ◽  
Volumetric Growth ◽  
Differential Growth ◽  
Elastic Stresses ◽  
Mechanical Feedback

Experiments on tumor spheroids have shown that compressive stress from their environment can reversibly decrease tumor expansion rates and final sizes. Stress release experiments show that nonuniform anisotropic elastic stresses can be distributed throughout. The elastic stresses are maintained by structural proteins and adhesive molecules, and can be actively relaxed by a variety of biophysical processes. In this letter, we present a new continuum model to investigate how the instantaneous elastic moduli and active stress relaxation, in conjunction with mechanical feedback machinery within cells, regulate the sizes of and stress distributions within growing tumors in the presence of external physical confinement and gradients of growth-promoting chemical fields. We introduce an adaptive reference map that relates the current position with the reference position but adapts to the current position in the Eulerian frame (lab coordinates) via relaxation. This type of stress relaxation is similar to but simpler than the classical Maxwell model of viscoelasticity. By fitting the model to experimental data from two independent studies of tumor spheroid growth, treating the tumors as incompressible, neo-Hookean elastic materials, we find that the rates of stress relaxation of tumor tissues can be comparable to volumetric growth rates. Our study provides insight on how the biophysical properties of the tumor and host microenvironment, mechanical feedback control and diffusion-limited differential growth act in concert to regulate spatial patterns of stress and growth. When the tumor is stiffer than the host, our model predicts tumors are more able to change their size and mechanical state autonomously, which may help to explain why increased tumor stiffness is an established hallmark of malignant tumors.PACS numbers: 46.15.Cc,62.20.mt,68.55.at,87.19.1x,87.19.R-

scholarly journals Stress generation, relaxation and size control in confined tumor growth

2021 ◽  
Vol 17 (12) ◽  
pp. e1009701
Author(s):  
Huaming Yan ◽  
Daniel Ramirez-Guerrero ◽  
John Lowengrub ◽  
Min Wu
Keyword(s):  
Stress Relaxation ◽  
Cell Density ◽  
Malignant Tumors ◽  
Size Control ◽  
Stress Generation ◽  
Current Position ◽  
Volumetric Growth ◽  
Differential Growth ◽  
Elastic Stresses ◽  
Control Feedback

Experiments on tumor spheroids have shown that compressive stress from their environment can reversibly decrease tumor expansion rates and final sizes. Stress release experiments show that nonuniform anisotropic elastic stresses can be distributed throughout. The elastic stresses are maintained by structural proteins and adhesive molecules, and can be actively relaxed by a variety of biophysical processes. In this paper, we present a new continuum model to investigate how the growth-induced elastic stresses and active stress relaxation, in conjunction with cell size control feedback machinery, regulate the cell density and stress distributions within growing tumors as well as the tumor sizes in the presence of external physical confinement and gradients of growth-promoting chemical fields. We introduce an adaptive reference map that relates the current position with the reference position but adapts to the current position in the Eulerian frame (lab coordinates) via relaxation. This type of stress relaxation is similar to but simpler than the classical Maxwell model of viscoelasticity in its formulation. By fitting the model to experimental data from two independent studies of tumor spheroid growth and their cell density distributions, treating the tumors as incompressible, neo-Hookean elastic materials, we find that the rates of stress relaxation of tumor tissues can be comparable to volumetric growth rates. Our study provides insight on how the biophysical properties of the tumor and host microenvironment, mechanical feedback control and diffusion-limited differential growth act in concert to regulate spatial patterns of stress and growth. When the tumor is stiffer than the host, our model predicts tumors are more able to change their size and mechanical state autonomously, which may help to explain why increased tumor stiffness is an established hallmark of malignant tumors.

scholarly journals Xyloglucan Remodeling Defines Auxin-Dependent Differential Tissue Expansion in Plants

2021 ◽  
Vol 22 (17) ◽  
pp. 9222 ◽  
Author(s):  
Silvia Melina Velasquez ◽  
Xiaoyuan Guo ◽  
Marçal Gallemi ◽  
Bibek Aryal ◽  
Peter Venhuizen ◽  
...  
Keyword(s):  
Cell Wall ◽  
Growth Control ◽  
Size Control ◽  
Tissue Expansion ◽  
Major Type ◽  
Hypocotyl Growth ◽  
Differential Growth ◽  
Rigid Cell Wall ◽  
Molecular Complexity ◽  
Genetic Interference

Size control is a fundamental question in biology, showing incremental complexity in plants, whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Our results indicate that auxin-reliant growth programs affect the molecular complexity of xyloglucans, the major type of cell wall hemicellulose in eudicots. Auxin-dependent induction and repression of growth coincide with reduced and enhanced molecular complexity of xyloglucans, respectively. In agreement with a proposed function in growth control, genetic interference with xyloglucan side decorations distinctly modulates auxin-dependent differential growth rates. Our work proposes that auxin-dependent growth programs have a spatially defined effect on xyloglucan’s molecular structure, which in turn affects cell wall mechanics and specifies differential, gravitropic hypocotyl growth.

scholarly journals Experimental Study and Simulation of the Stress Relaxation Characteristics of Machine-Harvested Seed Cotton

2021 ◽  
Vol 11 (21) ◽  
pp. 9959
Author(s):  
Jun Wang ◽  
Hongwen Zhang ◽  
Lei Wang ◽  
Ximei Wei ◽  
Meng Wang ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Stress Relaxation ◽  
Moisture Content ◽  
Cross Section ◽  
Testing Machine ◽  
Maxwell Model ◽  
Maximum Error ◽  
Virtual Prototype ◽  
Seed Cotton ◽  
Relaxation Characteristics

Seed cotton compression molding solves the inconvenience of seed cotton transportation and storage after mechanical harvesting. Stress relaxation is closely related to the performance of the compressed seed cotton. In this study, an electronic universal testing machine with a homemade compression device was used to study the stress relaxation characteristics of machine-harvested seed cotton. The stress relaxation model of machine-harvested seed cotton was established, the influence of test factors on the response indexes was analyzed and, finally, stress relaxation characteristics of machine-harvested seed cotton were simulated. Results show that machine-harvested seed cotton stress relaxation characteristics can be described by the five-element Maxwell model. The equilibrium elastic modulus is negatively correlated with moisture content and cross-section dimensions, and the equilibrium elastic modulus is positively correlated with trash content and compression density. The rapid decay time and the residual stress ratio are negatively correlated with moisture content and compression density, but the influence of trash content and cross-section dimensions are limited. The stress relaxation process of machine-harvested seed cotton was simulated using virtual prototype technology, and the maximum error between the experimental and simulated values was obtained as 4.96%. The feasibility of the virtual prototype technique for the viscoelastic simulation of biomaterials was demonstrated.

Stress and Microstructural Evolution of Lpcvd Polysilicon Thin Films During High Temperature Annealing

1996 ◽  
Vol 441 ◽  
Author(s):  
Chia-Liang Yu ◽  
Paul A. Flinn ◽  
Seok-Hee Lee ◽  
John C. Bravman
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Stress Relaxation ◽  
Deposition Temperature ◽  
Stress Generation ◽  
Deformation Model ◽  
Silicon Thin Films ◽  
Compressive Stresses ◽  
Polysilicon Films ◽  
Curvature Measurements

AbstractThe mechanisms of stress generation and stress relaxation of LPCVD silicon thin films were studied using high temperature wafer curvature measurements. The stresses generated during depositions are measured as functions of deposition temperature and microstructure. Amorphous silicon deposited with a compressive stress shows a large stress change toward tensile during crystallization. The stress relaxation of polysilicon films deposited with tensile stresses can be described by a deformation model from Ashby and Frost [1]. The polysilicon films deposited with compressive stresses have hydrogen incorporated during deposition and shows hydrogen evolution during thermal cycles.

Stress relaxation modelling of polymethylmethacrylate bone cement

2002 ◽  
Vol 216 (3) ◽  
pp. 195-199 ◽  
Author(s):  
O R Eden ◽  
A J C Lee ◽  
R M Hooper
Keyword(s):  
Stress Relaxation ◽  
Bone Cement ◽  
Load Transfer ◽  
Femoral Stem ◽  
Maxwell Model ◽  
Mechanical Tests ◽  
Hip Joints ◽  
Four Point Bending ◽  
Pmma Bone Cement ◽  
Double Exponential

This paper describes tests that were carried out to model the stress relaxation behaviour of polymethylmethacrylate (PMMA) bone cement. Stress relaxation of bone cement is believed to be a significant factor in the mechanism of load transfer in the femoral stem of a polished, collarless taper-fit replacement hip joints. It is therefore important that this condition and its implications are understood. Stress relaxation was carried out on PMMA samples of varying age in four-point bending configuration. It was shown that the samples stiffened with age and that the amount of stress relaxation reduced as the samples aged. The experimental results of the stress relaxation were accurately modelled on the double exponential of the Maxwell model so that long-term predictions of the stress condition could be made from short-term mechanical tests.

scholarly journals Volumetric finite-element modelling of biological growth

Open Biology ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 190057 ◽  
Author(s):  
Richard Kennaway ◽  
Enrico Coen
Keyword(s):  
Finite Element ◽  
Finite Element Modelling ◽  
Shape Change ◽  
Growth Patterns ◽  
Three Dimensions ◽  
Volumetric Growth ◽  
Differential Growth ◽  
Element Modelling ◽  
Wide Range ◽  
Polarity Field

Differential growth is the driver of tissue morphogenesis in plants, and also plays a fundamental role in animal development. Although the contributions of growth to shape change have been captured through modelling tissue sheets or isotropic volumes, a framework for modelling both isotropic and anisotropic volumetric growth in three dimensions over large changes in size and shape has been lacking. Here, we describe an approach based on finite-element modelling of continuous volumetric structures, and apply it to a range of forms and growth patterns, providing mathematical validation for examples that admit analytic solution. We show that a major difference between sheet and bulk tissues is that the growth of bulk tissue is more constrained, reducing the possibility of tissue conflict resolution through deformations such as buckling. Tissue sheets or cylinders may be generated from bulk shapes through anisotropic specified growth, oriented by a polarity field. A second polarity field, orthogonal to the first, allows sheets with varying lengths and widths to be generated, as illustrated by the wide range of leaf shapes observed in nature. The framework we describe thus provides a key tool for developing hypotheses for plant morphogenesis and is also applicable to other tissues that deform through differential growth or contraction.

Mechanical Properties of Hulless Barley Stem with Different Moisture Contents

2019 ◽  
Vol 15 (1-2) ◽  
Author(s):  
Jia-hui Chen ◽  
Nan Zhao ◽  
Nan Fu ◽  
Dong Li ◽  
Li-jun Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Moisture Content ◽  
Loss Modulus ◽  
Maxwell Model ◽  
Creep Tests ◽  
Hulless Barley ◽  
Dynamic Mechanical ◽  
Moisture Contents ◽  
Study Results

AbstractMechanical properties of hulless barley stems with different moisture contents (10.23%–43.14%) were investigated by using temperature sweep, frequency sweep, stress relaxation and creep tests of dynamic mechanical analyzer (DMA) in this study. Results showed a significant dependence of storage modulus, loss modulus and tan delta on moisture content. The data from stress relaxation and creep was fitted by using generalized Maxwell model and Burgers model. 5-element Maxwell model was better for describing relaxation behaviors of hulless barely stem compared with the 3-element Maxwell model. The peak values of loss modulus and tan delta both occurred at a low temperature when moisture content increased. The dynamic mechanical properties can provide useful information for the harvesting and processing of huless barely stem.

The Stress-Relaxation Behavior of Rice as a Function of Time, Moisture and Temperature

2017 ◽  
Vol 13 (2) ◽  
Author(s):  
Pan Wang ◽  
Li-jun Wang ◽  
Dong Li ◽  
Zhi-gang Huang ◽  
Benu Adhikari ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Moisture Content ◽  
Master Curve ◽  
Superposition Principle ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Linear Viscoelastic ◽  
Single Rice

Abstract: Stress-relaxation behavior of single rice kernel was studied using a dynamic mechanical analyzer (DMA) in compression mode. The relaxation modulus was measured in a moisture content range of 12–30 % on dry basis (d.b.) and a temperature range of 25–80°C. A constant stain value of 1 % (within the linear viscoelastic range) was selected during the stress-relaxation tests. The relaxation modulus was found to decrease as the temperature and moisture increased. A master curve of relaxation modulus as a function of temperature and moisture content was generated using the time–moisture–temperature superposition principle. Results showed that the generalized Maxwell model satisfactorily fitted the experimental data of the stress-relaxation behavior and the master curve of relaxation modulus (R2> 0.997). By shifting the temperature curves horizontally, the activation energy of the stress relaxation was obtained which significantly decreased with increase in the moisture content.

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