Функциональная неднородность возникающая в результате электрического и механического взаимодействия между кардиомиоцитами в математической модели однородного волокна

2015 ◽  
Vol 10 (2) ◽  
pp. 436-454
Author(s):  
А.Г. Курсанов ◽  
A.G Kursanov
Keyword(s):  
Continuous Medium ◽  
Mechanical Activity ◽  
Mechanical Function ◽  
Electrical Excitation ◽  
Mechanical Interaction ◽  
Dynamic Adjustment ◽  
Calcium Activation ◽  
One Dimensional ◽  
Mechanical Coupling ◽  
Potential Development

We developed a mathematical model describing heart muscle strand as a one-dimensional continuous medium of cardiomyocytes, through which electrical excitation propagates and excites the cells for contraction. Intracellular excitation-contraction coupling is presented by means of our earlier published model describing mechanical function of the cardiomyocyte evoked by action potential development and calcium activation of cross-bridge formation. The whole strand model simulates also mechanical interaction between the cardiomyocytes in the tissue and accounts for both intracellular and intercellular electro-mechanical coupling and mechano-electric feedback mechanisms. Numerical experiments with the strand formed of initially identical cardiomyocytes revealed that electrical and mechanical interaction between the cells, as well as intracellular mechano-electric feedbacks caused pronounced nonuniformity of their behavior. Model analysis suggests that cooperative mechanisms of myofilament calcium activation play the key role in dynamic adjustment of electrical and mechanical activity of the interacting cardiomyocytes in the tissue.

DIFFERENTIAL EQUATIONS OF EQUILIBRIUM OF IDEALLY ELASTOPLASTIC CONTINUOUS MEDIUM FOR PLANE ONE-DIMENSIONAL DEFORMATION IN APPROXIMATION OF CLOSING EQUATIONS BY BIQUADRATIC FUNCTIONS

2021 ◽  
Vol 295 (2) ◽  
pp. 37-45
Author(s):  
S.V. Bakushev ◽  
Keyword(s):  
Differential Equations ◽  
Shear Deformation ◽  
Continuous Medium ◽  
Strain Tensor ◽  
Shear Deformations ◽  
One Dimensional ◽  
Volumetric Expansion ◽  
Fractional Rational Function ◽  
Secant Shear Modulus ◽  
Deformation Diagrams

The present article considers the construction of differential equations of equilibrium of geometrically and physically nonlinear ideally elastoplastic in relation to shear deformations of continuous medium under conditions of one-dimensional plane deformation, when the diagrams of volumetric and shear deformation are approximated by biquadratic functions. The construction of physical dependencies is based on calculating the secant moduli of volumetric and shear deformation. When approximating the graphs of the volumetric and shear deformation diagrams using two segments of parabolas, the secant shear modulus in the first segment is a linear function of the intensity of shear deformations; the secant modulus of volumetric expansion-contraction is a linear function of the first invariant of the strain tensor. In the second section of the diagrams of both volumetric and shear deformation, the secant shear modulus is a fractional (rational) function of the shear strain intensity; the secant modulus of volumetric expansion-compression is a fractional (rational) function of the first invariant of the strain tensor. Based on the assumption of independence, generally speaking, from each other of the volumetric and shear deformation diagrams, five main cases of physical dependences are considered, depending on the relative position of the break points of the graphs of the diagrams volumetric and shear deformation. On the basis of received physical equations, differential equations of equilibrium in displacements for continuous medium are derived under conditions of plane one-dimensional deformation. Differential equations of equilibrium in displacements constructed in the present article can be applied in determining stress and strain state of geometrically and physically nonlinear ideally elastoplastic in relation to shear deformations of continuous medium under conditions of plane one-dimensional deformation, closing equations of physical relations for which, based on experimental data, are approximated by biquadratic functions.

Isoproterenol induces release of atrial natriuretic peptide from rat atrium in vitro

1992 ◽  
Vol 262 (1) ◽  
pp. H285-H292 ◽  
Author(s):  
G. Agnoletti ◽  
A. Rodella ◽  
A. Cornacchiari ◽  
A. F. Panzali ◽  
P. Harris ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Mechanical Stimulation ◽  
The Other ◽  
Mechanical Activity ◽  
Mechanical Function ◽  
Rat Atria ◽  
Rat Atrium ◽  
Atrial Natriuretic

To investigate the mechanism underlying the release of atrial natriuretic peptide (ANP) in in vitro condition, isolated, superfused rat atria were subjected to adrenergic, chronotropic, and mechanical stimulation. First administration of isoproterenol (Iso; either 10(-9) or 10(-6) M) caused a release of ANP, which was transient. Subsequent increments in concentration of Iso always resulted in a much lower release of ANP, despite the increased effects on the mechanical function of the atria. Stretching of the atria resulted in a transient release of ANP. Subsequent increments in stretching were followed by decreasing release of ANP. The total score of ANP in atrial tissue after Iso and stretching was not measurably depleted. Pacing the atria with increasing frequency did not induce release of ANP. Depolarization with 40 mM KCl abolished the release of ANP in response to Iso but not the release induced by stretch. In the presence of low external Ca2+, which abolished mechanical activity, both Iso and stretch could still induce release of ANP. Propranolol abolished the release of ANP by Iso but not that induced by stretching. Prazosin did not affect the release by either stretch or Iso. Stretching the atria 20 min after administration of Iso did not cause any further release of ANP. On the other hand, adding Iso 20 min after stretching induced a release of ANP. It is concluded that Iso and stretch cause a transient release from isolated strips of atria. The amount of ANP released is not related to the dose of Iso or to the load applied. Mechanisms involved in the release mediated by the two stimuli are different.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Supercomputer model of dynamical dusty gas with intense momentum transfer between phases based on OpenFPM library

2021 ◽  
Vol 2099 (1) ◽  
pp. 012056
Author(s):  
Vitaliy Grigoryev ◽  
Olga Stoyanovskaya ◽  
Nikolay Snytnikov
Keyword(s):  
Continuous Medium ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Point Explosion ◽  
Vector Data ◽  
Sph Method ◽  
One Dimensional ◽  
Gas Dynamic ◽  
Plane Sound ◽  
Gas Dynamic Equations

Abstract The paper considers the solution of model gas-dynamic problems (propagation of plane sound wave, one-dimensional shock tube problem, three-dimensional problem of a point explosion in a continuous medium) in the case of a gas-dust medium. The interaction of dust and gas was taken into account using the IDIC method within the SPH method used to solve gas-dynamic equations. An important feature of the work is the use of the open computational package OpenFPM, which makes it easy to carry out parallel computations. The main advantage of this package is the ready-made (implemented by the authors of the package) and intuitive, automatically parallelizable vector data structures, the use of which is identical both in the case of calculations on a personal computer and in the case of using supercomputer resources. The paper analyzes the efficiency of parallelization of numerical solutions of the considered problems.

scholarly journals Bendy ARM 2.0: Continuum Arm Manipulator Refinement and Control for Assistive Technology

2018 ◽  
Author(s):  
Emily Swanson ◽  
Samantha Metevier ◽  
Kayla Sneller ◽  
Devin R. Berg
Keyword(s):  
Assistive Technology ◽  
Degrees Of Freedom ◽  
Structural Performance ◽  
Motion Processing ◽  
Mechanical Function ◽  
Continuum Robots ◽  
Mechanical Coupling ◽  
Technology Applications ◽  
And Control ◽  
Positional Control

Rigid link robots currently dominate the market for manipulators in assistive technology, though research on continuum robots for assistive technology has been developing over recent years. These types of robots have a continuous backbone that allows them to have infinite degrees of freedom, making them highly compliant, however this brings challenges in terms of modelling and control. Additionally, materials for this type of application require specific qualities. In this work, we attempt to address these problems while designing a continuum arm suitable for assistive technology applications. Bendy ARM 2.0 is a revised version of the first Bendy ARM robot to accomplish these goals. In its first iteration, Bendy ARM had limitations in its mechanical function, such as the structural performance of the backbone, which decreased the accuracy in positional control. Nitinol was tested as a new backbone material but failed during testing so a low density polyethylene was chosen. Cable conduits were added to help reduce the mechanical coupling between the proximal and distal segments of the manipulator. Motion processing units (MPU) are utilized to gather tilt angles and provide direction for automated movements. Due to the arms natural rotation, this data alone was not enough to consistently control and place the robot. With the information gathered, further consideration of backbone material and usage of MPU data is required for an automatable robot.

Analysis of One-Dimensional Thermal Consolidation of Saturated Soil with and without Thermo-Mechanical Coupling

2012 ◽  
Vol 594-597 ◽  
pp. 335-338
Author(s):  
Xue Shen ◽  
Rui Qian Wu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Saturated Porous Medium ◽  
Water Pressure ◽  
Saturated Soil ◽  
Excess Pore Water Pressure ◽  
One Dimensional ◽  
Mechanical Coupling ◽  
Thermal Consolidation ◽  
Excess Pore

Based on a one-dimensional thermal consolidation formulation with and without thermo-mechanical coupling of saturated porous medium, problems of one-dimensional thermal consolidation of saturated soil were investigated. For the condition with instantaneous constant surface temperature and uniform initial pore-pressure, analytical solutions of excess pore-water pressure and temperature increment were derived respectively by the method of finite Fourier transform and inverse transform. A relevant computer program was developed, and the excess pore-water pressure was compared in detail. The results show that the thermo-mechanical coupling item in the thermal consolidation equation can be ignored.

scholarly journals Electrical Excitation of Long-Range Surface Plasmons in PC/OLED Structure with Two Metal Nanolayers

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Valery Konopsky ◽  
Valery Prokhorov ◽  
Dmitry Lypenko ◽  
Artem Dmitriev ◽  
Elena Alieva ◽  
...  
Keyword(s):  
Surface Plasmons ◽  
Long Range ◽  
Light Emitting Diode ◽  
Electrical Excitation ◽  
Metal Electrodes ◽  
Light Emitting ◽  
One Dimensional ◽  
Organic Light Emitting Diode ◽  
Organic Light ◽  
A Current

AbstractA current-driven source of long-range surface plasmons (LRSPs) on a duplex metal nanolayer is reported. Electrical excitation of LRSPs was experimentally observed in a planar structure, where an organic light-emitting film was sandwiched between two metal nanolayers that served as electrodes. To achieve the LRSP propagation in these metal nanolayers at the interface with air, the light-emitting structure was bordered by a one-dimensional photonic crystal (PC) on the other side. The dispersion of the light emitted by such a hybrid PC/organic-light-emitting-diode structure (PC/OLED) comprising two thin metal electrodes was obtained, with a clearly identified LRSP resonance peak.

Effect of norepinephrine on contractility of isolated mesenteric lymphatics

1983 ◽  
Vol 244 (4) ◽  
pp. H479-H486 ◽  
Author(s):  
J. M. Allen ◽  
N. G. McHale ◽  
B. M. Rooney
Keyword(s):  
Action Potential ◽  
Lymphatic Vessels ◽  
Spontaneous Contraction ◽  
Mechanical Activity ◽  
Single Action ◽  
Potential Development ◽  
Sucrose Gap ◽  
Frequent Failure ◽  
Spontaneous Contractions ◽  
Evoked Contractions

Norepinephrine increases the spontaneous contraction frequency of isolated bovine lymphatic vessels but, paradoxically, reduces contraction force. In this investigation contractions were elicited by electrical stimulation, applied as field stimulation or across a sucrose gap. Evoked contractions were not reduced in force by concentrations of norepinephrine that have previously been shown to dramatically reduce contractility in spontaneously active vessels. However, at higher concentrations a beta-inhibitory component of the norepinephrine effect was often observed. Simultaneous recordings of electrical and mechanical activity from spontaneously active vessels showed that each spontaneous contraction was initiated by a single action potential. Norepinephrine significantly disrupted electrical activity causing increased action potential frequency, reduction in action potential amplitude, and frequent failure of full action potential development. We conclude that norepinephrine depresses the force of spontaneous contractions by disruption of spontaneous pacemaking rather than by any direct effect on vessel contractility.

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