Automatic Registration of the Nascence and Propagation of Cracks in Electrically Conductive Materials

A correlation is established between the length of the propagating crack in electrically conductive flat specimens and the change in the field of electric potentials over the surface of the specimen when an electric current is passed through it. The experimental data correspond to the analytical solution in a two-dimensional formulation obtained by means of a conformal mapping. Work can be attributed to the field of converting mechanical values into electrical ones. This transformation simplifies the process of recording mechanical processes and provides a convenient form of their control. The work is aimed at automatic control of the process of fracture of electrically conductive materials.

Quantitative simulations of ratchet potential in a dusty plasma ratchet

Using a dusty plasma ratchet, one can realize the rectification of charged dust particle in a plasma. To obtain the ratchet potential dominating the rectification, here, we perform quantitative simulations based on a two-dimensional fluid model of capacitively coupled plasma. Plasma parameters are firstly calculated in two typical cross sections of the dusty plasma ratchet which cut vertically the saw channel at different azimuthal positions. The balance positions of charged dust particle in the two cross sections then can be found exactly. The electric potentials at the two balance positions have different values. Using interpolation in term of a double-sine function from previous experimental measurement, an asymmetrical ratchet potential along the saw channel is finally obtained. The asymmetrical orientation of the ratchet potential depends on discharge conditions. Quantitative simulations further reproduce our previous experimental phenomena such as the rectification of dust particle in the dusty plasma ratchet.

Simulating Epileptic Seizures using the Bidomain Model

Epileptic seizures are due to excessive and synchronous neural activity. Extensive modelling of seizures has been done on the neuronal level, but it remains a challenge to scale these models up to whole brain models. Measurements of the brain’s activity over several spatiotemporal scales follow a power-law distribution in terms of frequency. During normal brain activity, the power-law exponent is often found to be around 2 for frequencies between a few Hz and up to 150 Hz, but is higher during seizures and for higher frequencies. The Bidomain model has been used with success in modelling the electrical activity of the heart, but has been explored far less in the context of the brain. This study extends previous models of epileptic seizures on the neuronal level to the whole brain using the Bidomain model. Our approach is evaluated in terms of power-law distributions. The electric potentials were simulated in 7 idealized 2D models and 3 MRI-derived 3D patient-specific models. Computed electric potentials were found to follow power-law distribtions with slopes ranging from 2 to 5 for frequencies greater than 10-30 Hz.

Spatio-temporal analysis the results of solving the inverse problem of electrocardiography

The results of the development and testing an algorithm for the physiological interpretation the results of solving the inverse problem of electrocardiography are presented. The solution to the inverse problem of electrocardiography is the distributions of equivalent current sources on the quasi-epicardium, restored from the electric potentials created by the heart on the surface of the chest. The developed algorithms are based on the space-time analysis of the distributions of equivalent current sources on the quasi-epicardium. The development and testing of the algorithm was carried out using a simulation model of the electrical activity of the heart based on cellular automata. The efficiency of the algorithm has been demonstrated when simulating the electrical activity of the heart in normal conditions, as well as in the presence of pathological changes in the myocardium in the form of areas with delayed conduction of excitation.

On the Role of Electrostatic Repulsion in Topological Defect-Driven Membrane Fission

Within a modified Langevin Poisson–Boltzmann model of electric double layers, we derived an analytical expression for osmotic pressure between two charged surfaces. The orientational ordering of the water dipoles as well as the space dependencies of electric potentials, electric fields, and osmotic pressure between two charged spheres were taken into account in the model. Thus, we were able to capture the interaction between the parent cell and connected daughter vesicle or the interactions between neighbouring beads in necklace-like membrane protrusions. The predicted repulsion between them can facilitate the topological antidefect-driven fission of membrane daughter vesicles and the fission of beads of undulated membrane protrusions.

Differential programming enabled functional imaging with Lorentz transmission electron microscopy

Lorentz transmission electron microscopy is an advanced characterization technique that enables the simultaneous imaging of both the microstructure and functional properties of materials. Information such as magnetization and electric potentials is carried by the phase of the electron wave, and is lost during image acquisition. Various methods have been proposed to retrieve the phase of the electron wavefunction using intensities of the acquired images, most of which work only in the small defocus limit. Imaging at strong defoci not only carries more quantitative phase information, but is essential to the study of weak magnetic and electrostatic fields at the nanoscale. In this work we develop a method based on differentiable programming to solve the inverse problem of phase retrieval. We show that our method maintains a high spatial resolution and robustness against noise even at the upper defocus limit of the microscope. More importantly, our proposed method can go beyond recovering just the phase information. We demonstrate this by retrieving the electron-optical parameters of the contrast transfer function alongside the electron exit wavefunction.

Energetic Ion Precipitation in Jupiter’s Polar Auroral Region Observed by Juno/JEDI

<p>Remote observations clearly show that soft X-ray emissions at Jupiter concentrate poleward of the main oval forming a so-called “hot spot” (Gladstone et al., 2002; Dunn et al., 2016). One hypothesis proposes that the X-rays are likely produced from precipitating energetic heavy ions that become fully stripped via interactions in Jupiter’s upper atmosphere; however, the details regarding the ion source and acceleration mechanism(s) of the soft X-ray (~2 keV) component is still an active area of research. NASA’s Juno mission – a Jupiter polar orbiting spacecraft – is shedding light onto this mystery with in situ observations of the energetic particle environment over the poles, and coordinated observing campaigns with Earth-orbiting X-ray observatories, e.g., Chandra and XMM-Newton. Recent ideas supported by Juno data include: 1) pitch angle scattering of energetic ions via electromagnetic ion cyclotron waves in the outer magnetosphere (Yao et al., 2021); and 2) acceleration of ions to several MeV over Jupiter’s poles via field-aligned electric potentials (Clark et al., 2017; Haggerty et al., 2017; Clark et al., 2020; Yao et al., 2021). New techniques have been recently developed to push the capabilities of Juno’s Jupiter Energetic particle Detector Instrument (JEDI) to measure the > 10 MeV ions (Westlake et al., 2019; Kollmann et al., 2020). In this presentation, we utilize these techniques to characterize the precipitating fluxes of > 10 MeV ions over Jupiter’s polar region with the goal of better understanding the sources of Jupiter’s X-ray auroral emissions.</p>

Numerical Simulation of Electric Field Distribution around an Instrumented Total Hip Stem

Presently, total joint replacement (TJR) is a standard procedure in orthopedic surgery. Adequate osseointegration of the implant components still remains a clinical issue. However, active stimulation of bone tissue to enhance bone ongrowth at the implant surfaces has not been widely investigated so far. For the last several years, invasive electromagnetically induced osseotherapy has been employed in clinical practice, e.g., for the treatment of avascular necrosis, femoral neck fractures, and pseudarthrosis. In the present study, the approach of exploiting the electric stimulation effect was transferred to the field of TJR. Therefore, a commercially available total hip stem was instrumented with an electrode on its surface in order to generate an electric field supporting the regeneration of the surrounding bone tissue. The objective was to conduct numerical simulations validated by experimental investigations as a proof of concept for an instrumented electro-stimulative total hip stem. The results revealed that the calculated electric field around a total hip stem fulfills the requirements to stimulate adjacent bone tissue when using clinically applied electric voltages. The derived numerical and experimental data of electric potentials and corresponding electric fields are encouraging for the implementation of active electrical stimulation in uncemented total hip stems to enhance their osseointegration.

THE STUDY OF ENTROPY INDICATORS OF THE DAILY DYNAMICS OF THE STATISTICAL ELECTRICAL POTENTIAL OF BIOACTIVE POINTS OF THE SKIN OF ANIMALS IN NORMAL, UNDER STRESS AND AFTER STRESS

В данной статье приведены значения суточной динамики статических электрических потенциалов (СЭП) аурикулярных биологически активных точек (БАТ) животных в норме, при стрессе и после снятия стресса. Определены значения энтропии СЭП БАТ как в норме и при стрессе, и после стресса. Показано , что показатели энтропии СЭП БАТ у контрольных групп животных ниже, чем у опытных групп. Повышение показателей энтропии СЭП БАТ у животных при стрессе свидетельствует о разрегулированности суточных ритмов. This article presents the values of the daily dynamics of static electric potentials (SEP) of auricular biologically active points (BAP) of animals in normal conditions, under stress and after stress relief. The values of the entropy of the BOT SEP are determined both in normal and under stress, and after stress. It is shown that the entropy indicators of the BOT BOT in the control groups of animals are lower than in the experimental groups. An increase in the entropy of the SEP BAT in animals under stress indicates a lack of regulation of daily rhythms.