scholarly journals The strain-generated electrical potential in cartilaginous tissues: a role for piezoelectricity

2021 ◽  
Vol 13 (1) ◽  
pp. 91-100
Author(s):  
Philip Poillot ◽  
Christine L. Le Maitre ◽  
Jacques M. Huyghe
Keyword(s):  
Physiological Response ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Electrical Potential ◽  
Evidence Base ◽  
Piezoelectric Response ◽  
Mechanical Forces ◽  
Streaming Potentials ◽  
Cartilaginous Tissues ◽  
Electrical Potentials

AbstractThe strain-generated potential (SGP) is a well-established mechanism in cartilaginous tissues whereby mechanical forces generate electrical potentials. In articular cartilage (AC) and the intervertebral disc (IVD), studies on the SGP have focused on fluid- and ionic-driven effects, namely Donnan, diffusion and streaming potentials. However, recent evidence has indicated a direct coupling between strain and electrical potential. Piezoelectricity is one such mechanism whereby deformation of most biological structures, like collagen, can directly generate an electrical potential. In this review, the SGP in AC and the IVD will be revisited in light of piezoelectricity and mechanotransduction. While the evidence base for physiologically significant piezoelectric responses in tissue is lacking, difficulties in quantifying the physiological response and imperfect measurement techniques may have underestimated the property. Hindering our understanding of the SGP further, numerical models to-date have negated ferroelectric effects in the SGP and have utilised classic Donnan theory that, as evidence argues, may be oversimplified. Moreover, changes in the SGP with degeneration due to an altered extracellular matrix (ECM) indicate that the significance of ionic-driven mechanisms may diminish relative to the piezoelectric response. The SGP, and these mechanisms behind it, are finally discussed in relation to the cell response.

Analysis of Solute Transport in Cartilaginous Tissue Under Dynamic Unconfined Compression

2003 ◽  
Author(s):  
Hai Yao ◽  
Wei Yong Gu
Keyword(s):  
Dynamic Compression ◽  
Electrical Potential ◽  
Loading Frequency ◽  
Mechanical Forces ◽  
The Finite Element Method ◽  
Unconfined Compression ◽  
Cartilage Sample ◽  
Cartilaginous Tissues ◽  
Transduction Mechanisms ◽  
Theoretical Analyses

Transport of fluid and solutes through the extracellular matrix plays a key role in the nutrition and growth of cartilaginous tissues that lack blood supply. It has been found that the mechanical loading can alter the transport rates of solutes within cartilage [Bonassar, 2000; O’Hara, 1990; Quinn, 2002]. Dynamic compression may enhance the transport of large solutes (e.g., growth factors) within the tissue. Many theoretical analyses have been reported in literature on the transport of fluid and solutes, as well as physical signals (stress, strain, pressure, concentrations, and electrical potential) in cartilage under unconfined compression [Armstrong, 1984; Levenston, 1999; Mow, 2002]. However, little is known as to how the tissue fixed charge density (FCD) affects the transport of fluid and neutral solutes (e.g., glucose and IGF-1) in cartilage sample in dynamic compression. In this study, we numerically analyzed the transport of fluid and solutes, as well as the mechano-electrochemical signals within the cartilage sample in dynamic unconfined compression, using the finite element method (FEM). The objective of this study was to investigate the effects of FCD, loading frequency, and loading platens (permeable vs. impermeable) on the transport of fluid, ions, and neutral solutes within cartilage. This study is essential for the understanding of tissue nutrition and signal transduction mechanisms in cartilage subjected to mechanical forces.

Leakage Flow Investigations on a Through-Wall Crack Related to Thermal Fatigue of Nuclear Power Plant Piping

2017 ◽  
Author(s):  
Stefan Schmid ◽  
Rudi Kulenovic ◽  
Eckart Laurien
Keyword(s):  
Experimental Data ◽  
Nuclear Power ◽  
Numerical Models ◽  
Measurement Techniques ◽  
Experimental Investigations ◽  
Leakage Flow ◽  
Test Rig ◽  
Reduced Pressure ◽  
Flow Rates ◽  
Set Up

For the validation of empirical models to calculate leakage flow rates in through-wall cracks of piping, reliable experimental data are essential. In this context, the Leakage Flow (LF) test rig was built up at the IKE for measurements of leakage flow rates with reduced pressure (maximum 1 MPA) and temperature (maximum 170 °C) compared to real plant conditions. The design of the test rig enables experimental investigations of through-wall cracks with different geometries and orientations by means of circular blank sheets with integrated cracks which are installed in the tubular test section of the test rig. In the paper, the experimental LF set-up and used measurement techniques are explained in detail. Furthermore, first leakage flow measurement results for one through-wall crack geometry and different imposed fluid pressures at ambient temperature conditions are presented and discussed. As an additional aspect the experimental data are used for the determination of the flow resistance of the investigated leak channel. Finally, the experimental results are compared with numerical results of WinLeck calculations to prove specifically in WinLeck implemented numerical models.

Understanding the electrical behavior of the action potential in terms of elementary electrical sources

2015 ◽  
Vol 39 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Javier Rodriguez-Falces
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Present Report ◽  
Electrical Potential ◽  
Ionic Currents ◽  
New Approach ◽  
Electrical Potentials ◽  
Proposed Model ◽  
Ionic Mechanisms ◽  
Human Electrophysiology

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However, this model is unsuitably complex for teaching purposes. In addition, the Hodgkin and Huxley approach describes the shape of the action potential only in terms of ionic currents, i.e., it is unable to explain the electrical significance of the action potential or describe the electrical field arising from this source using basic concepts of electromagnetic theory. The goal of the present report was to propose a new model to describe the electrical behaviour of the action potential in terms of elementary electrical sources (in particular, dipoles). The efficacy of this model was tested through a closed-book written exam. The proposed model increased the ability of students to appreciate the distributed character of the action potential and also to recognize that this source spreads out along the fiber as function of space. In addition, the new approach allowed students to realize that the amplitude and sign of the extracellular electrical potential arising from the action potential are determined by the spatial derivative of this intracellular source. The proposed model, which incorporates intuitive graphical representations, has improved students' understanding of the electrical potentials generated by bioelectrical sources and has heightened their interest in bioelectricity.

2-D and 3-D resistivity image reconstruction using crosshole data

Geophysics ◽  
1992 ◽  
Vol 57 (10) ◽  
pp. 1270-1281 ◽  
Author(s):  
Hiromasa Shima
Keyword(s):  
Field Test ◽  
Numerical Models ◽  
Electrical Potential ◽  
Nonlinear Least Squares ◽  
Three Dimensions ◽  
Inversion Method ◽  
Good Resolution ◽  
Inversion Algorithm ◽  
Linear Inversion ◽  
Resistivity Model

Theoretical changes in the distribution of electrical potential near subsurface resistivity anomalies have been studied using two resistivity models. The results suggest that the greatest response from such anomalies can be observed with buried electrodes, and that the resistivity model of a volume between boreholes can be accurately reconstructed by using crosshole data. The distributive properties of crosshole electrical potential data obtained by the pole‐pole array method have also been examined using the calculated partial derivative of the observed apparent resistivity with respect to a small cell within a given volume. The results show that for optimum two‐dimensional (2-D) and three‐dimensional (3-D) target imaging, in‐line data and crossline data should be combined, and an area outside the zone of exploration should be included in the analysis. In this paper, the 2-D and 3-D resistivity images presented are reconstructed from crosshole data by the combination of two inversion algorithms. The first algorithm uses the alpha center method for forward modeling and reconstructs a resistivity model by a nonlinear least‐squares inversion. Alpha centers express a continuously varying resistivity model, and the distribution of the electrical potential from the model can be calculated quickly. An initial general model is determined by the resistivity backprojection technique (RBPT) prior to the first inversion step. The second process uses finite elements and a linear inversion algorithm to improve the resolution of the resistivity model created by the first step. Simple 2-D and 3-D numerical models are discussed to illustrate the inversion method used in processing. Data from several field studies are also presented to demonstrate the capabilities of using crosshole resistivity exploration techniques. The numerical experiments show that by using the combined reconstruction algorithm, thin conductive layers can be imaged with good resolution for 2-D and 3-D cases. The integration of finite‐element computations is shown to improve the image obtained by the alpha center inversion process for 3-D applications. The first field test uses horizontal galleries to evaluate complex 2-D features of a zinc mine. The second field test illustrates the use of three boreholes at a dam site to investigate base rock features and define the distribution of an altered zone in three dimensions.

Tooth Movement

1991 ◽  
Vol 2 (4) ◽  
pp. 411-450 ◽  
Author(s):  
Zeev Davidovitch
Keyword(s):  
Alveolar Bone ◽  
Tooth Movement ◽  
Bone Cells ◽  
Biological Response ◽  
Mechanical Forces ◽  
Clinical Environment ◽  
Isolated Cells ◽  
Streaming Potentials ◽  
Pdl Cells ◽  
New Findings

This article reviews the evolution of concepts regarding the biological foundation of force-induced tooth movement. Nineteenth century hypotheses proposed two mechanisms: application of pressure and tension to the periodontal ligament (PDL), and bending of the alveolar bone. Histologic investigations in the early and middle years of the 20th century revealed that both phenomena actually occur concomitantly, and that cells, as well as extracellular components of the PDL and alveolar bone, participate in the response to applied mechanical forces, which ultimately results in remodeling activities. Experiments with isolated cells in culture demonstrated that shape distortion might lead to cellular activation, either by opening plasma membrane ion channels, or by crystallizing cytoskeletal filaments. Mechanical distortion of collagenous matrices, mineralized or non-mineralized, may, on the other hand, evoke the development of bioelectric phenomena (stress-generated potentials and streaming potentials) that are capable of stimulating cells by altering the electric charge on their membrane or their fluid envelope. In intact animals, mechanical perturbations on the order of about 1 min/d are apparently sufficient to cause profound osteogenic responses, perhaps due to matrix proteoglycan-related "strain memory". Enzymatically isolated human PDL cells respond biochemically to mechanical and chemical signals. The latter include endocrines, autocrines, and paracrines. Histochemical and immunohistochemical studies showed that during the early places of tooth movement, PDL fluids are shifted, and cells and matrix are distorted. Vasoactive neurotransmitters are released from periodontal nerve terminals, causing leukocytes to migrate out of adjacent capillaries. Cytokines and growth factors are secreted by these cells, stimulating PDL cells and alveolar bone lining cells to remodel their related matrices. This remodeling activity facilitates movement of teeth into areas in which bone had been resorbed. This emerging information suggests that in the living mammal, many cell types are involved in the biological response to applied mechanical stress to teeth, and thereby to bone. Essentially, cells of the nervous, immune, and endocrine systems become involved in the activation and response of PDL and alveolar bone cells to applied stresses. This fact implies that research in the area of the biological response to force application to teeth should be sufficiently broad to include explorations of possible associations between physical, cellular, and molecular phenomena. The goals of this investigative field should continue to expound on fundamental principles, particularly on extrapolating new findings to the clinical environment, where millions of patients are subjected annually to applications of mechanical forces to their teeth for long periods of time in an effort to improve their position in the oral cavity. Recently developed research tools such as cell culture techniques and immunologic probes, are the best hope for enhancing this development.

Advances and benefits of fractal models to predict streaming potentials in partially saturated porous media

2021 ◽  
Author(s):  
Damien Jougnot ◽  
Luong Duy Thanh ◽  
Mariangeles Soldi ◽  
Jan Vinogradov ◽  
Luis Guarracino
Keyword(s):  
Porous Media ◽  
Fractal Theory ◽  
Electrical Potential ◽  
Streaming Potential ◽  
Excess Charge ◽  
Distribution Law ◽  
Distribution Models ◽  
Streaming Potentials ◽  
Fractal Models ◽  
Partially Saturated Porous Media

<p>Understanding streaming potential generation in porous media is of high interest for hydrological and reservoir studies as it allows to relate water fluxes to measurable electrical potential distributions in subsurface geological settings. The evolution of streaming potential <span>stems</span> from electrokinetic coupling between water and electrical fluxes due to the presence of an electrical double layer at the interface between the mineral and the pore water. Two different approaches can be used to model and interpret the generation of the streaming potential in porous media: the classical coupling coefficient approach based on the Helmholtz-Smoluchowski equation, and the effective excess charge density. Recent studies based on both approaches use a mathematical up-scaling procedure that employs the so-called fractal theory. In these studies, the porous medium is represented by a bundle of tortuous capillaries characterized by a fractal capillary-size distribution law. The electrokinetic coupling between the fluid flow and electric current is obtained by averaging the processes that take place in a single capillary. In most cases, closed-form expressions for the electrokinetic parameters are obtained in terms of macroscopic hydraulic variables like permeability, saturation and porosity. In this presentation we propose a review of the existing fractal distribution models that predict the streaming potential in porous media and discuss their benefits compared against other published models.</p>

The Effect of External Potassium Ions on the Electrical Potential Measured Across the Gills of the Teleost, Dormitator Maculatus

1974 ◽  
Vol 61 (2) ◽  
pp. 277-283
Author(s):  
DAVID H. EVANS ◽  
JEFFREY C. CARRIER ◽  
MARGARET B. BOGAN
Keyword(s):  
Sea Water ◽  
Electrical Potential ◽  
Potassium Ions ◽  
Sodium Efflux ◽  
Electrical Potentials ◽  
External Potassium ◽  
Potassium Influx ◽  
Sodium Extrusion ◽  
Sufficient Magnitude ◽  
Stimulation Of

1. A technique has been developed for the measurement of electrical potentials (TGP's) across the gills of free-swimming, Dormitator maculatus. 2. Transfer of fish to various KCl solutions is correlated with changes in the TGP, which are not of sufficient magnitude to account for the known potassium stimulation of sodium efflux from this species. 3. Transfer to potassium-free sea water results in little or no change in TGP while previous results have shown that such a transfer is correlated with a 22% reduction of sodium efflux. 4. Transfer to fresh water results in a reduction of TGP from +17 mV (inside positive) to -36 mV which is sufficient to account for the instantaneous reduction in sodium efflux previously shown for this species. 5. It is concluded that while changes in TGP can account for the ‘Na-free effect’ in D. maculatus they cannot account for the potassium effects on sodium extrusion. This supports the previous conclusion that sodium efflux and potassium influx are chemically linked in this species.

scholarly journals A Carbon Nanotube Packed Bed Electrode for Small Molecule Electrosorption: An Electrochemical and Chromatographic Approach for Process Description

2020 ◽  
Vol 10 (3) ◽  
pp. 1133
Author(s):  
Tatjana Trunzer ◽  
Timothy Stummvoll ◽  
Melanie Porzenheim ◽  
Paula Fraga-García ◽  
Sonja Berensmeier
Keyword(s):  
Structural Changes ◽  
Aqueous Media ◽  
Electrical Potential ◽  
Packed Bed ◽  
Electrical Potentials ◽  
Packed Bed Electrode ◽  
Through Flow ◽  
Multi Walled Carbon Nanotubes ◽  
Electrochemical Double Layer ◽  
Walled Carbon Nanotubes

Triggering the interaction of nanomaterials with molecules by means of electrical potentials in aqueous media remains challenging, especially if 3D through-flow systems are used as electrodes, as in potential-controlled liquid chromatography (PCC). In this paper, multi-walled carbon nanotubes (MWCNTs) function as a particulate packed bed electrode in order to study the system’s response to various applied potentials and electrolyte compositions. The process principle was analyzed using chronoamperometry and cyclic voltammetry. Applying an electrical potential to the hydrophilic MWCNTs induces the presence of both capacitive and faradaic currents. This leads, over time, to a degradation of the electrode due to structural changes of the MWCNT matrix and an increase in redox reactions on the surface. The role of the electrochemical double layer (EDL) is highlighted as a main player in the process, directly influencing the adsorption capability of the electrode. The EDL rearrangement time and coverage radius depend on the composition of the mobile phase and on the potential applied. The capacity of the electrode for the target (maleic acid) increases at high positive potentials (+800 mV vs. Ag/AgCl), while the presence of electrolytes leads to a capacity decrease. Our research enhances the understanding of capacitive through-flow cells.

scholarly journals Remote Measurements of Horizontal Eddy Diffusivity

2005 ◽  
Vol 22 (9) ◽  
pp. 1373-1380 ◽  
Author(s):  
Darek J. Bogucki ◽  
Burton H. Jones ◽  
Mary-Elena Carr
Keyword(s):  
Numerical Models ◽  
Measurement Techniques ◽  
Rapid Assessment ◽  
Digital Camera ◽  
Eddy Diffusivity ◽  
Direct Measurements ◽  
Remote Measurements ◽  
Rgb Images ◽  
Speed Fluctuations

Abstract The rate of horizontal diffusivity or lateral dispersion is key to understanding the dispersion of tracers and contaminants in the ocean, and it is an elusive, yet crucial, parameter in numerical models of circulation. However, the difficulty of parameterizing horizontal mixing is exacerbated in the shallow coastal ocean, which points to the need for more direct measurements. Here, a novel and inexpensive approach to remotely measure the rate of horizontal diffusivity is proposed. Current shipboard measurement techniques require repeated surveys and are thus time consuming and labor intensive. Furthermore, intensive in situ sampling is generally impractical for routine coastal management or for rapid assessment in the case of emergencies. A remote approach is particularly useful in shallow coastal regions or those with complex bathymetry. A time series of images from a dye-release experiment was obtained with a standard three-megapixel digital camera from a helicopter that hovered over the study area. The red–green–blue (RGB) images were then 1) analyzed to distinguish the dye from the ambient color of the water and adjacent land features, 2) orthorectified, and 3) analyzed to obtain advection and diffusion rates of the thin subsurface dye layer. A horizontal current of the order of 6 cm s−1 was found. The estimated horizontal eddy diffusivity rate for scales of O(10 m) in the harbor was 0.1 m2 s−1. The dye diffusivity and advection rate that are calculated from the images are consistent with independent calculations based on in situ measurements of current speed fluctuations.

scholarly journals Modeling of the Onset, Propagation, and Interaction of Multiple Cracks Generated From Corrosion Pits by Using Peridynamics

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Dennj De Meo ◽  
Luigi Russo ◽  
Erkan Oterkus
Keyword(s):  
Structural Damage ◽  
Crack Nucleation ◽  
Numerical Models ◽  
Measurement Techniques ◽  
High Stress ◽  
Numerical Approach ◽  
Multiple Cracks ◽  
Numerical Instabilities ◽  
Corrosion Pits ◽  
Crack Transition

High stress regions around corrosion pits can lead to crack nucleation and propagation. In fact, in many engineering applications, corrosion pits act as precursor to cracking, but prediction of structural damage has been hindered by lack of understanding of the process by which a crack develops from a pit and limitations in visualization and measurement techniques. An experimental approach able to accurately quantify the stress and strain field around corrosion pits is still lacking. In this regard, numerical modeling can be helpful. Several numerical models, usually based on finite element method (FEM), are available for predicting the evolution of long cracks. However, the methodology for dealing with the nucleation of damage is less well developed, and, often, numerical instabilities arise during the simulation of crack propagation. Moreover, the popular assumption that the crack has the same depth as the pit at the point of transition and by implication initiates at the pit base has no intrinsic foundation. A numerical approach is required to model nucleation and propagation of cracks without being affected by any numerical instability and without assuming crack initiation from the base of the pit. This is achieved in the present study, where peridynamics (PD) theory is used in order to overcome the major shortcomings of the currently available numerical approaches. Pit-to-crack transition phenomenon is modeled, and nonconventional and more effective numerical frameworks that can be helpful in failure analysis and in the design of new fracture-resistant and corrosion-resistant materials are presented.

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