Depolarization Process Research Articles

Effect of transition metal ions on the dielectric properties of chromium potassium phosphates

Potassium ions are important for developing electrode materials because they have similar properties to lithium and sodium ions. Mixed chromium phosphates (KMIICr(PO4)2) with substituted MII sites using divalent elements (M = Ni, Co, Cu) were synthesized using a solid-state reaction method. The samples were analyzed using various techniques such as powder X-ray diffraction, Fourier transform infrared, Raman, and electron paramagnetic resonance spectroscopy. The proposed phosphates had a monoclinic phase structure with a P21/n space group, and they contained large tunnels occupied by K+ cations. The dielectric properties showed that the Ni-based phosphates had slower dielectric relaxation, while the Co and Cu-based phosphates had quicker polarization and depolarization processes. Additionally, the resistance of the grains decreased from Ni to Co to Cu-based phosphates, indicating easier charge movement in each material, consistent with the increase in conductive losses and a.c. conductivity when changing the MII ions.

Unraveling Thermal Depolarization Phenomena in Biphasic Polarized Calcium Phosphate Catalyst

AbstractPermanently polarized biphasic calcium phosphate composed of hydroxyapatite and brushite (pp‐HAp/Bru), which is prepared by applying the thermally stimulated polarization treatment to calcined HAp, is used as a sustainable catalyst to transform CO2 into value‐added products. In this work, the stability of pp‐HAp/Bru is studied from structural, electrical, and catalytic perspectives, applying a thermal depolarization process with temperatures (Td) ranging from 200 to 1000 °C. Results show that the Bru phase is not stable when Td ≤ 400 °C, while the structure of the HAp refines and transforms into Bru when Td ≥ 600 °C. Besides, the electrical resistance and capacitance of the pp‐HAp/Bru increase with Td, evidencing the progressive electrical depolarization of the material. Thermal depolarization also influences the specific orientation of the OH– ions, which is partially lost (≈50%). All such changes affect the catalytic efficiency of pp‐HAp/Bru, which is proven using a reaction that transforms CO2 gas into acetic acid and formic acid. Results show that the total reaction yield linearly decreases with increasing Td. Based on such observations, a simple process is designed that allows the reconstitution of the structure and restores the activity of such green catalysts.

Expert system-based application for fatal ventricular arrhythmia risk level estimation based on QT-Interval prolongation

There is an overwhelming number of medications that can affect the morphology of the beating heart by delaying the ventricular depolarization and repolarization processes, resulting in an elongated QT interval. This circumstance, in turn, can lead to ventricular arrhythmias, which can result in the patient’s death, as was overwhelmingly the case at the beginning of the coronavirus pandemic. In this regard, this document presents an innovative expert system-based application devoted to estimating the level of risk of fatal ventricular arrhythmia as a consequence of QT prolonging treatments. For this purpose, the use of a fuzzy rule-based system has been considered for the decision-making process, establishing three different risk levels regarding the QT interval obtained from an electrocardiogram, its evolution from a basal electrocardiogram, and other significant clinical information of the patient such as age, sex, among others. This novel expert system-based application has been designed by considering the criteria of several specialist physicians from four different Spanish private and public hospitals. The proposed application can be especially important in primary health care centers, where the absence of specialists is remarkable because it provides clinical staff with a powerful tool for estimating the level of risk of fatal ventricular arrhythmia with 96.5% accuracy when comparing its decisions to those of specialist physicians, which could imply a significant reduction in the risk of death due to fatal ventricular arrhythmias in patients with QT prolonging treatment. In this respect, the developed application is currently used in some primary health care centers in Spain.

Chirality-Dependent Dynamic Evolution for Trions in Monolayer WS2.

Monolayer transition metal dichalcogenides exhibit valley-dependent excitonic characters with a large binding energy, acting as the building block for future optoelectronic functionalities. Herein, combined with pump-probe ultrafast transient transmission spectroscopy and theoretical simulations, we reveal the chirality-dependent trion dynamics in h-BN encapsulated monolayer tungsten disulfide. By resonantly pumping trions in a single valley and monitoring their temporal evolution, we identify the temperature-dependent competition between two relaxation channels driven by chirality-dependent scattering processes. At room temperature, the phonon-assisted upconversion process predominates, converting excited trions to excitons within the same valley on a sub-picosecond (ps) time scale. As temperature decreases, this process becomes less efficient, while alternative channels, notably valley depolarization process for trions, assume importance, leading to an increase of trion density in the unpumped valley within a ps time scale. Our time-resolved valley-contrast results provide a comprehensive insight into trion dynamics in 2D materials, thereby advancing the development of novel valleytronic devices.

ПОТЕНЦИАЛ ИСПОЛЬЗОВАНИЯ ДИНАМИКИ ЭЛЕКТРОКАРДИОГРАФИЧЕСКИХ ПОКАЗАТЕЛЕЙ ПРИ ВЫЯВЛЕНИИ КАРДИОТОКСИЧНОСТИ ЧЕРЕЗ 12 МЕСЯЦЕВ ПОСЛЕ ОКОНЧАНИЯ ХИМИОТЕРАПИИ РАКА МОЛОЧНОЙ ЖЕЛЕЗЫ ДОКСОРУБИЦИНОМ

Background. Changes in electrocardiographic parameters of the heart, reflecting the processes of depolarization and repolarization of the myocardium, can be signs of early cardiotoxicity (CT). Aim. To study changes in electrocardiographic parameters of the myocardium in patients with verified breast cancer 12 months after the end of chemotherapy with doxorubicin. Material and methods. The study included 100 patients with a confirmed diagnosis of breast cancer who were treated at the health care institution “Grodno University Clinic” (Grodno, Belarus). A number of electrocardiographic parameters of the myocardium were measured in patients before and 12 months after the end of chemotherapy using electrocardiography and 24-hour Holter monitoring. Results. A statistically significant increase in electrocardiographic parameters of depolarization and repolarization was revealed (P, P-Q, Tpeak-Tend, Q-Tc / QRS, Q-Tc - p<0.007; p<0.001; p=0.042; p=0.009; p<0.001, respectively) before and 12 months after the end of chemotherapy. A change in the time and total number of episodes of sinus tachycardia and supraventricular extrasystoles was also noted (p=0.029, p=0.026 and p=0.002). The Tpeak-Tend indicator changed statistically significantly in the CT+ subgroup (p=0.032) after 12 months. The dynamics of the Q-Tc indicator before and 12 months after the end of chemotherapy was observed in almost all patients. However, in the CT+ subgroup, an increase in Q-Tc was recorded statistically significantly more often compared to the CT- subgroup (p <0.005). Conclusion. During chemotherapy with doxorubicin, an increase in Tpeak-Tend and Q-Tc was observed. An especially significant increase in these indicators was noted in the CT+ subgroup. The number and duration of sinus tachycardia episodes as well as the number of supraventricular extrasystoles also increased. This may correlate with the relationship between chemotherapy with doxorubicin and the dynamics of electrocardiographic parameters.

Comparative study of thermodynamic & kinetic parameters measuring techniques in lithium-ion batteries

Quantitative analysis of the aging process of lithium-ion batteries by using electrochemical thermodynamic and kinetic parameters such as electrochemical potential, Li stoichiometry, and Li inventory loss is a key research topic in the development of Li-ion battery for electric vehicles and smart grids. It is generally known the above parameters can be acquired through the analysis of Electromotive Force (EMF) or Open-Circuit Voltage (OCV) curves. In this work, we proposed and applied five EMF measurement techniques to obtain the EMF-SoC relationships in LFP/Gr single-layer laminated pouch cells at different temperatures and States of Health (SoH), and comprehensively examined them from the viewpoints of eight evaluation dimensions. A Python program, named Degradation Modes Analysis (DMA), is used to diagnose the thermodynamic degradation modes of the battery automatically. Furthermore, electrochemical kinetic parameters were also extracted along with the depolarization process. For faster and more accurate aging diagnosis, we recommend an optimal blend of short relaxation time GITT (Short-Rest-GITT) and extrapolated EMF (Extrap-EMF) to reach the most precise EMF measurements and gain the most comprehensive information about battery thermodynamics and kinetics at the same time.

Dynamic symmetrization in a memristive HR neuron

AbstractThe significance of neuronal discharge symmetry lies in its reflection of the stability and orderliness within the neuron's activity. This symmetry is correlated with various issues, including the biophysical properties within neurons, network structures, and synaptic transmission. Memristors are highly analogous to neuronal synapses due to their unique memory properties, allowing them to emulate biological neural synapses. In this work, a memristor is employed into the Hindmarsh‐Rose (HR) neuron as a synapse for the construction of a memristive HR neuron. Accompanied with the introducing of the absolute value and signum function, the derived neurons exhibit complex coexisting symmetric firing patterns. The phenomenon of symmetric firing can effectively simulate the depolarization and hyperpolarization processes of neurons, providing a new approach to study the diversity of the brain.

Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers

The lowest energy states in transition metal dichalcogenide (TMD) monolayers follow valley selection rules, which have attracted vast interest due to the possibility of encoding and processing of quantum information. However, these quantum states are strongly affected by temperature-dependent intervalley scattering leading to complete valley depolarization, which hampers practical applications at room temperature. Therefore, for achieving clear and robust valley polarization in TMD monolayers one needs to suppress parasitic depolarization processes, which is the central challenge in the growing field of valleytronics. Here, in electron-doping experiments on TMD monolayers, we show that strong doping levels beyond 1013 cm−2 can induce 61% and 37% valley contrast at room temperature in tungsten diselenide and molybdenum diselenide monolayers, respectively. Our findings demonstrate that charged excitons in TMD monolayers hold the potential for the development of efficient valleytronic devices functional at 300 K.

Suppression of Pulsed Dynamic Nuclear Polarization by Many-Body Spin Dynamics.

We study a mechanism by which nuclear hyperpolarization due to the polarization transfer from a microwave-pulse-controlled electron spin is suppressed. From analytical and numerical calculations of the unitary dynamics of multiple nuclear spins, we uncover that, combined with the formation of the dark state within a cluster of nuclei, coherent higher-order nuclear spin dynamics impose limits on the efficiency of the polarization transfer even in the absence of mundane depolarization processes such as nuclear spin diffusion and relaxation. Furthermore, we show that the influence of the dark state can be partly mitigated by introducing a disentangling operation. Our analysis is applied to the nuclear polarizations observed in ^{13}C nuclei coupled with a single nitrogen-vacancy center in diamond [Randall etal., Science 374, 1474 (2021)SCIEAS0036-807510.1126/science.abk0603]. Our Letter sheds light on collective engineering of nuclear spins as well as future designs of pulsed dynamic nuclear polarization protocols.

Body Surface Potential Mapping during Ventricular Depolarization in Athletes with Prolonged PQ Interval after Exercise.

Prolongation of the PQ interval, generally associated with an atrioventricular conduction delay, may be related to changes in intraventricular impulse spreading. To assess, using body surface potential mapping (BSPM), the process of ventricular depolarization in athletes with prolonged PQ intervals at rest and after exercise. The study included 7 cross-country skiers with a PQ interval of more than 200 ms (Prolonged-PQ group) and 7 with a PQ interval of less than 200 ms (Normal-PQ group). The BSPM from 64 unipolar torso leads was performed before (Pre-Ex) and after the bicycle exercise test (Post-Ex). Body surface equipotential maps were analyzed during ventricular depolarization. The significance level was 5%. Compared to Normal-PQ athletes, the first and second periods of the stable position of cardiac potentials on the torso surface were longer, and the formation of the "saddle" potential distribution occurred later, at Pre-Ex, in Prolonged-PQ athletes. At Post-Ex, the Prolonged-PQ group showed a shortening of the first and second periods of stable potential distributions and a decrease in appearance time of the "saddle" phenomenon relative to Pre-Ex (to the values near to those of the Normal-PQ group). Additionally, at Post-Ex, the first inversion of potential distributions and the total duration of ventricular depolarization in Prolonged-PQ athletes decreased compared to Pre-Ex and with similar values in Normal-PQ athletes. Compared to Normal-PQ athletes, the second inversion was longer at Pre-Ex and Post-Ex in Prolonged-PQ athletes. Prolonged-PQ athletes had significant differences in the temporal characteristics of BSPM during ventricular depolarization both at rest and after exercise as compared to Normal-PQ athletes.

Social Depolarization: Blume–Capel Model

This study belongs to an emerging area of research seeking ways to depolarize societies in the short run (around events such as elections) as well as in a sustainable fashion. We approach the depolarization process with a model of three homophilic groups (US Democrats, Republicans, and Independents interacting in the context of upcoming federal elections). We expand a previous polarization model, which assumed that each individual interacts with all other individuals in its group with mean-field interactions. We add a depolarization field, which is analogous to the Blume–Capel model’s crystal field. There are currently numerous depolarization efforts around the world, some of which act in ways similar to this depolarization field. We find that for low values of the depolarization field, the system continues to be polarized. When the depolarization field is increased, the polarization decreases.

Improving insulation properties of epoxy filled with surface fluorinated polystyrene nanospheres

<sec>Epoxy resin nanocomposites are widely used in the field of electrical insulation packaging. It is of great significance to regulate the dielectric and insulation properties of composite materials by introducing nano-filler to meet special application requirements. This work proposes a chemical copolymerization method, fluorinated polystyrene nanospheres are synthesized through an addition reaction as filler, and finally the epoxy nanocomposites are prepared. The polystyrene nanospheres have a uniform size and good compatibility with the epoxy resin. The introducing of nanospheres reduces the dielectric constant of the epoxy resin composite material and increases the breakdown strength simultaneously. Although the dielectric loss increases, the composites’ imaginary part remains below 0.04 within 1 MHz frequency. In particular, the fluorinated polystyrene/epoxy composite with a mass fraction of 2% exhibits a decrease in dielectric constant and DC conductivity, while the AC breakdown strength and DC breakdown strength increase by 12.6% and 6%, respectively.</sec><sec>The results of the pulse electro-acoustic method indicate that the charge injection of the epoxy resin filled with non-fluorinated polystyrene nanospheres is evident, while the introduction of fluorinated nanospheres significantly reduces the charge injection level. Calculations based on the depolarization process reveal that the introduction of fillers leads to an increase in trap density and depth of energy levels in the composites. Notably, the epoxy resin filled with fluorinated fillers has the deepest trap levels, providing an explanation for the improved insulation breakdown performance. The research can provide guidance for regulating dielectric properties of epoxy composites and material synthesis for the application of electrical insulation packaging <b>.</b> </sec>

Multilevel Mathematical Model of Epileptic Seizures

The paper presents novel developed modular mathematical model of epileptic seizures, obtained by combining and modifying existing models of epilepsy, which for the first time makes it possible to simulate the dynamics of seizure onset, propagation and termination simultaneously at the cellular and regional levels of brain organization. At the level of individual cells, the dynamics of AMPA receptor trafficking, changes in the concentrations of intra- and extracellular ions, membrane depolarization, and other biophysical processes responsible for the development of ictal activity were calculated. Local field potentials of brain regions were modeled at the regional level taking into account cellular processes and the large-scale structure of the brain network. It is shown that the dynamics of submodels used in the structure of the multilevel model corresponds to the dynamics of the original models, the authors of which validated them with experimental data. The theoretical justification of the connections between submodels was given.

CineECG repolarization gradients predict acute hemodynamical response in CRT patients

Abstract Background Cardiac resynchronization therapy (CRT) is widely used for patients with conduction disorders and heart failure. The proportion of the CRT-non-responders can exceed 30%, which warrants search for new approaches to optimize the CRT device implantation and follow-up. CineECG is a novel cardiac anatomy-based ECG modality proposed for better visualization of the myocardial depolarization and repolarization processes. This method yielded promising results in patients with sinus rhythm but has not been tested in ventricular pacing. Purpose The aim of the present study was to evaluate CineECG-derived mean temporo-spatial isochrone (TSI) trajectory in different pacing protocols and test its association with acute hemodynamical responses in CRT patients. Methods CineECG uses a generic heart/torso model to construct the average electrical pathway within the cardiac anatomy from the 12 lead ECG. CineECG and invasive hemodynamical parameters were tested in 15 patients undergoing multisite CRT system implantation. ECG recording and hemodynamical measurements were performed simultaneously, while the patients were undergoing 4-6 biventricular pacing protocols with the same interventricular pacing delay (30 ms) and different left ventricular (LV) lead localizations (apical, basal, multisite). LV dP/dt max was tested for association with the parameters of standard ECG (QRS duration, QT duration, Tpeak-Tend duration) and CineECG pathway parameters. The latter pathway directions were computed for QRS and ST-T intervals for anteroposterior (X), left-to-right (Y), and apicobasal (Z) directions. Results Biventricular protocols did not differ between each other in LV dP/dt. In univariate linear regression analysis, LV dP/dt max was associated with QRS and ST-T pathway directions (Figure 1 - table). The left-to-right (Y) and apicobasal (Z) ST-T pathway directions remained independent predictors of LV dP/dt max in multivariate linear regression analysis with the adjustment for a pacing protocol [regression coefficient 571.6 (319.3 – 823.8), p<0.001; regression coefficient -406.9 (-636.7 – -177.2), p=0.001, respectively]. Optimal repolarization sequences associated with better acute hemodynamic responses assessed by LV dP/dt max were from right to left and from base to apex (Figure 2). Conclusion CineECG repolarization pathway gradients in the left-to-right and apicobasal directions outperform temporal ECG parameters and predict the acute hemodynamical response in biventricular pacing protocols in CRT patients.

Rational Design of an Air-Stable, High-Spin Diradical with Diazapyrene.

Stable carbon-based polyradicals exhibiting strong spin-spin coupling and slow depolarization processes are particularly attractive functional materials. A new molecular motif synthesized by a convenient method that allows the integration of stable, high-spin radicals to (hetero)aromatic polycycles has been developed, as illustrated by a non-Kekulé diradical showing a triplet ground state with long persistency (τ1/2 ≈31 h) in air. Compared to the widely used 1,3-phenylene, the newly designed (diaza)pyrene-4,10-diyl moiety is for the first time demonstrated to confer ferromagnetic (FM) spin coupling, allowing delocalized non-disjoint SOMOs. With the X-ray crystallography unambiguously proving the diradical structure, the triplet ground state was thoroughly characterized. A large ΔES-T of 1.1 kcal/mol, proving the strong FM coupling effect, was revealed consistently by superconducting quantum interference device (SQUID) measurements and variable-temperature electron paramagnetic resonance (EPR) spectroscopy, while the zero-field splitting and triplet nutation characters were examined by continuous-wave and pulsed EPR spectroscopy. A millisecond spin-lattice relaxation time was also detected. The current study not only offers a new molecular motif enabling FM coupling between carbon-based spins, but more importantly presents a general method for installing stable polyradicals into functional π-systems.

Rational Design of an Air‐Stable, High‐Spin Diradical with Diazapyrene

AbstractStable carbon‐based polyradicals exhibiting strong spin‐spin coupling and slow depolarization processes are particularly attractive functional materials. A new molecular motif synthesized by a convenient method that allows the integration of stable, high‐spin radicals to (hetero)aromatic polycycles has been developed, as illustrated by a non‐Kekulé diradical showing a triplet ground state with long persistency (τ1/2≈31 h) in air. Compared to the widely used 1,3‐phenylene, the newly designed (diaza)pyrene‐4,10‐diyl moiety is for the first time demonstrated to confer ferromagnetic (FM) spin coupling, allowing delocalized non‐disjoint SOMOs. With the X‐ray crystallography unambiguously proving the diradical structure, the triplet ground state was thoroughly characterized. A large ΔES‐T of 1.1 kcal/mol, proving the strong FM coupling effect, was revealed consistently by superconducting quantum interference device (SQUID) measurements and variable‐temperature electron paramagnetic resonance (EPR) spectroscopy, while the zero‐field splitting and triplet nutation characters were examined by continuous‐wave and pulsed EPR spectroscopy. A millisecond spin‐lattice relaxation time was also detected. The current study not only offers a new molecular motif enabling FM coupling between carbon‐based spins, but more importantly presents a general method for installing stable polyradicals into functional π‐systems.

A Kpc-scale radio polarization study of PG BL Lacs with the uGMRT

ABSTRACT We present here uGMRT band 4 (∼650 MHz) polarization images of 8 BL Lac objects belonging to the Palomar-Green (PG) ‘blazar’ sample. A large fraction of the sources ($\sim 63~{{\ \rm per\ cent}}$) reveal core-halo radio structures with most of the polarization detected in the inner core-jet regions. PG1101 + 385 and PG2254 + 075 exhibit a ‘spine-sheath structure’ in polarization. The core-halo and ‘spine-sheath’ structures are consistent with the Unified Scheme suggestion that BL Lacs are the pole-on beamed counterparts of Fanaroff–Riley (FR) type I radio galaxies. PG1418 + 546 and PG0851 + 203 (OJ287) show the presence of terminal hotspots similar to FR type II radio galaxies. They were also found to be low-spectrally peaked BL Lacs, supportive of the ‘blazar envelope’ scenario for BL Lacs and quasars. Fractional polarization ranges from 1 to 13 per cent in the cores and 2 to 26 per cent in the inner jets/lobes of the sample BL Lacs. Compared to the varied radio morphology of quasars from the PG ‘blazar’ sample, the BL Lacs appear to be less diverse. A comparison of the inferred core magnetic (B-) field structures on arcsec- (kpc-) scales w.r.t. the Very Long Baseline Interferometry jet direction does not reveal any preferred orientation, suggesting that if large-scale ordered B-fields exist, they do so on scales smaller than probed by the current observations. However, the presence of polarized emission on arcsec-scales suggests that any mixing of thermal plasma with the synchrotron emitting plasma is insufficient to fully depolarize the emission via the internal depolarization process.

THE IMPACT OF SEX ON METABOLIC AND FUNCTIONAL ABNORMALITIES, INDUCED BY HIGH-FRUCTOSE-DIET IN RATS

Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors, which manifestation may be different for men and women. Changes in sex hormone levels in men and women during lifespan contribute to increased cardiometabolic risk. Data of clinical researches suggest that transition from normal glucose tolerance to dysglycemia lead to more adverse differences in cardiometabolic risk factors in women than in men, suggesting an important impact of sex on the development of metabolic abnormalities. A significant increase in risk may be due to the sex differences in manifestation of some components of metabolic syndrome, but accurate reasons of these discrepancies need future investigations. The aim of this study was to determine the differences in impairment of glucose, lipid metabolism and cardiovascular systems function between male and female rats with different levels of estrogen sufficiency. Materials and Methods. MetS was modelled in male and female rats with different levels of estrogens by chronic (for 8 weeks) intake of fructose (high-fructose diet - HFD) with drinking water at a concentration 200 g/L. Estrogens deficiency was reproduced by bilateral ovariectomy. Experimental rats were divided into five groups: control males (n=6), control females (n=6), males with HFD (n=6), sham-operated females with intact ovaries and HFD (n=6), ovariectomized (OVX) females with HFD (n=6). Glucose homeostasis was assessed by basal glycemia, glycemia during the intra-abdominal glucose tolerance test and fructosamine level. Insulin sensitivity was determined using intra-abdominal insulin tolerance test. Body weight gain, visceral fats, level of total cholesterol, triglycerides, levels of estradiol and testosterone in blood serum were determined. At the end of the study, electrocardiograms were recorded in three standard leads from the limbs. Data are presented as mean ± standard error of mean (SEM). Results. It was established that HFD have not been induced metabolic abnormalities in female rats with intact ovaries. HFD, independently of sex, led to the development of insulin resistance and significant increase in fructosamine level in blood serum of rats. Ovariectomized females with HFD had greater intensity of body weight gain, significantly higher levels of relative mass of fats, more pronounced alterations of lipid metabolism with increased total cholesterol and significantly higher levels of triglycerides, than HFD-treated male rats. However, impairment of glucose tolerance, induced by HFD, was more pronounced in male than in OVX female rats. We found the decline testosterone levels and slight increase in estradiol levels in male rats with HFD. OVX females with HFD had a moderate significant increase in testosterone levels and dramatically decrease in estradiol concentration as result of bilateral ovariectomy. HFD, independently from sex, induced the development of sinus tachycardia in experimental animals. Metabolic abnormalities, induced by HFD, in OVX female rats led to more pronounced disturbances of heart depolarization and repolarization processes and development of diastolic dysfunction compare to HFD-treated males. Conclusions. We revealed that sex and estrogens levels have a great impact on the impairment of glucose and lipid metabolism and cardiovascular systems function, induced by high-fructose diet in rats. The obtained data justifies the necessity to take into account sex and estrogens sufficiency in the development of gender-specific prevention and treatment of metabolic syndrome.

ELECTRICAL ACTIVITY OF THE HUMAN HEART DURING THE PERIOD OF VENTRICULAR DEPOLARIZATION UNDER ACUTE NORMOBARIC HYPOXIA

Background. The effect of acute hypoxia on the human heart leads to deterioration of the heart function, this is reflected in an increase of the heterogeneity of the depolarization process, which is difficult to reveal when using a traditional ECG.
 Purpose. To investigate the electrical activity of the heart during the ventricular depolarization on the thorax surface under the exposure of acute normobaric hypoxia using multichannel ECG mapping.
 Material and methods. The electrical activity of the heart in apparently healthy young men (20±1 years) was studied during ventricular depolarization under exposure of acute normobaric hypoxia using cardioelectrotopography. Unipolar ECGs were recorded from 64 electrodes on the surface of the chest, simultaneously with bipolar ECGs in limb leads and the amplitudes of R and S waves from the surface electrodes localized in positions V1 and V5 of the traditional ECG were evaluated.
 Results. It was revealed that during hypoxia, in comparison with the initial state, the pattern of distribution and the spatio-temporal dynamics of positive and negative cardiac potentials reflecting the sequence of myocardial activation on the torso surface did not change significantly and were typical for the period of ventricular depolarization of the healthy person. A decrease in the amplitudes of the maximum extrema of cardiac electric potentials, the amplitudes of the SV1 and RV5 waves at hypoxic exposure was revealed: the amplitude of the maximum decreased from 1.88±0.58 mV in the initial state to 1.83±0.55 mV at hypoxia, the minimum – from -2.08±0.76 mV to -1.85±0.73 mV, the SV1 wave from -1.28±0.25 mV to -1.17±0.18 mV, RV5 wave from 1.21±0.25 mV to 1.05±0.29 mV, respectively, while the duration of ventricular depolarization did not change statistically significantly.
 Conclusion. Under hypoxic exposure, the examined persons showed a significant decrease in the amplitudes of the maximum extrema of the electric field of the heart, a direct correlation between changes in the amplitudes of the positive extremum and the RV5 wave, with practically unchanged duration of ventricular depolarization and dynamics of the distribution of cardioelectric potentials.

Dipolar Energy as an Electrical Power Source: Dipole Rotation in Solids Enables a New Source for the Triboelectric Generator

Herein, the concept of triboelectric generators using dipolar polarization energy as an electrical power source is introduced. Dipolar polarization energy is stored in dielectric films by rubbing, and is conveyed to external circuits for use during the depolarization process. Pyromellitic dianhydride‐4,4’‐oxydianiline polyimide films are used as a possible candidate for triboelectric generators, where polarization is formed by rubbing owing to the orientational alignment of polar molecular groups. The current–voltage measurements are used to evaluate the equivalent‐circuit parameters of the generator. The current source is 0.07 nA at 30 °C, which is enhanced to 0.13 nA at 110 °C. It is indicated in these results that the depolarization process proceeds in a short time at higher temperatures, causing an increase in the current. Consequently, the maximum power increases from 18 nW (30 °C) to 33 nW (110 °C). The enhancement of the output power at higher temperatures well supports the idea of using dipolar polarization energy as a power source of triboelectric generators.