scholarly journals Viscoelastic Material Properties of the Myocardium and Cardiac Jelly in the Looping Chick Heart

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Jiang Yao ◽  
Victor D. Varner ◽  
Lauren L. Brilli ◽  
Jonathan M. Young ◽  
Larry A. Taber ◽  
...  
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Constitutive Relations ◽  
Computational Method ◽  
Heart Tube ◽  
Embryonic Tissues ◽  
Strain Energy Density Function ◽  
Modeling Techniques ◽  
Chick Heart ◽  
Intact Heart

Accurate material properties of developing embryonic tissues are a crucial factor in studies of the mechanics of morphogenesis. In the present work, we characterize the viscoelastic material properties of the looping heart tube in the chick embryo through nonlinear finite element modeling and microindentation experiments. Both hysteresis and ramp-hold experiments were performed on the intact heart and isolated cardiac jelly (extracellular matrix). An inverse computational method was used to determine the constitutive relations for the myocardium and cardiac jelly. With both layers assumed to be quasilinear viscoelastic, material coefficients for an Ogden type strain-energy density function combined with Prony series of two terms or less were determined by fitting numerical results from a simplified model of a heart segment to experimental data. The experimental and modeling techniques can be applied generally for determining viscoelastic material properties of embryonic tissues.

Viscoelastic Material Properties of the Hamburger-Hamilton Stage 12 Chick Heart

2008 ◽  
Author(s):  
Jiang Yao ◽  
Victor D. Varner ◽  
Renato Perucchio ◽  
Larry A. Taber
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Early Stage ◽  
Biological Tissues ◽  
Heart Tissue ◽  
Nonlinear Finite Element ◽  
Nonlinear Finite Element Method ◽  
Cardiac Looping ◽  
Chick Heart

Mechanical force is believed to play a significant role in regulating the morphogenetic process of cardiac looping. To better understand this process, it is crucial to determine the material properties of the early chick heart. It is well known that biological tissues are viscoelastic, however previous data on early stage embryonic heart tissue shows a hyperelastic behavior only [1] and currently, only late stage heart tissues have been quantified using viscoelastic properties [2]. The objective of this study is to use microindentation and nonlinear finite element method (FEM) to characterize the viscoelastic material properties of stage 12 chick heart during cardiac looping.

Material Properties and Residual Stress in the Stage 12 Chick Heart During Cardiac Looping

2004 ◽  
Vol 126 (6) ◽  
pp. 823-830 ◽  
Author(s):  
Evan A. Zamir ◽  
Larry A. Taber
Keyword(s):  
Residual Stress ◽  
Computational Models ◽  
Constitutive Relations ◽  
Surface Displacement ◽  
Computational Method ◽  
Cardiac Looping ◽  
Curved Tube ◽  
Chick Heart ◽  
Matrix Compartment ◽  
Force Displacement

During the morphogenetic process of cardiac looping, the initially straight cardiac tube bends and twists into a curved tube. The biophysical mechanisms that drive looping remain unknown, but the process clearly involves mechanical forces. Hence, it is important to determine mechanical properties of the early heart, which is a muscle-wrapped tube consisting primarily of a thin outer layer of myocardium surrounding a thick extracellular matrix compartment known as cardiac jelly. In this work, we used microindentation experiments and finite element modeling, combined with an inverse computational method, to determine constitutive relations for the myocardium and cardiac jelly at the outer curvature of stage 12 chick hearts. Material coefficients for exponential strain-energy density functions were found by fitting force-displacement and surface displacement data near the indenter. Residual stress in the myocardium also was estimated. These results should be useful for computational models of the looping heart.

Properties of Mouse Cutaneous Rapidly Adapting Afferents: Relationship to Skin Viscoelasticity

2004 ◽  
Vol 92 (2) ◽  
pp. 1236-1240 ◽  
Author(s):  
P. Grigg ◽  
D. R. Robichaud ◽  
Z. Del Prete
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Mechanical Response ◽  
Loss Modulus ◽  
Multiple Logistic Regression Analysis ◽  
Rate Of Change ◽  
Volterra Model ◽  
Lower Sensitivity ◽  
Dynamic Stimuli

When skin is stretched, stimuli experienced by a cutaneous mechanoreceptor neuron are transmitted to the nerve ending through the skin. In these experiments, we tested the hypothesis that the viscoelastic response of the skin influences the dynamic response of cutaneous rapidly adapting (RA) neurons. Cutaneous RA afferent neurons were recorded in 3 species of mice (Tsk, Pallid, and C57BL6) whose skin has different viscoelastic properties. Isolated samples of skin and nerve were stimulated mechanically with a dynamic stretch stimulus, which followed a pseudo Gaussian waveform with a bandwidth of 0–60 Hz. The mechanical response of the skin was measured as were responses of single RA cutaneous mechanoreceptor neurons. For each neuron, the strength of association between spike responses and the dynamic and static components of stimuli were determined with multiple logistic regression analysis. The viscoelastic material properties of each skin sample were determined indirectly, by creating a nonlinear (Wiener–Volterra) model of the stress–strain relationship, and using the model to predict the complex compliance (i.e., the viscoelastic material properties). The dynamic sensitivity of RA mechanoreceptor neurons in mouse hairy skin was weakly related to the viscoelastic properties of the skin. Loss modulus and phase angle were lower (indicating a decreased viscous component of response) in Tsk and Pallid than in C57BL6 mice. However, RA mechanoreceptor neurons in Tsk and Pallid skin did not differ from those in C57 skin with regard to their sensitivity to the rate of change of stress or to the rate of change of incremental strain energy. They did have a decreased sensitivity to the rate of change of tensile strain. Thus the skin samples with lower dynamic mechanical response contained neurons with a somewhat lower sensitivity to dynamic stimuli.

Theoretical Meso-Model of Al2O3/ZrO2 Ceramic Response under Compression

2014 ◽  
Vol 601 ◽  
pp. 92-95
Author(s):  
Tomasz Sadowski ◽  
Liviu Marsavina
Keyword(s):  
Grain Boundary ◽  
Material Properties ◽  
Mechanical Model ◽  
Constitutive Relations ◽  
Ceramic Composites ◽  
Theoretical Modeling ◽  
Polycrystalline Structure ◽  
Two Phase

This paper presents theoretical modeling of two-phase ceramic composites subjected to compression. The meso-mechanical model allows for inclusion of all microdefects in the polycrystalline structure that exists at the grain boundary interfaces and inside the grains. The constitutive relations for the Al2O3/ZrO2composite with the gradual degradation of the material properties due to different defects development were formulated.

scholarly journals Viscoelastic Characterization of Peripapillary Sclera: Material Properties by Quadrant in Rabbit and Monkey Eyes

2003 ◽  
Vol 125 (1) ◽  
pp. 124-131 ◽  
Author(s):  
J. Crawford Downs ◽  
J-K. Francis Suh ◽  
Kevin A. Thomas ◽  
Anthony J. Bellezza ◽  
Claude F. Burgoyne ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Viscoelastic Material ◽  
Optic Nerve Head ◽  
Material Properties ◽  
Uniaxial Stress ◽  
Species Group ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

In this report we characterize the viscoelastic material properties of peripapillary sclera from the four quadrants surrounding the optic nerve head in both rabbit and monkey eyes. Scleral tensile specimens harvested from each quadrant were subjected to uniaxial stress relaxation and tensile ramp to failure tests. Linear viscoelastic theory, coupled with a spectral reduced relaxation function, was employed to characterize the viscoelastic properties of the tissues. We detected no differences in the stress-strain curves of specimens from the four quadrants surrounding the optic nerve head (ONH) below a strain of 4 percent in either the rabbit or monkey. While the peripapillary sclera from monkey eyes is significantly stiffer (both instantaneously and in equilibrium) and relaxes more slowly than that from rabbits, we detected no differences in the viscoelastic material properties (tested at strains of 0–1 percent) of sclera from the four quadrants surrounding the ONH within either species group.

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.

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