Effect of annealing time and pressure on electrical activation and surface morphology of Mg-implanted GaN annealed at 1300 °C in ultra-high-pressure nitrogen ambient

We performed an isothermal annealing study on Mg-implanted GaN at 1300 °C in an ultra-high-pressure (1 GPa) nitrogen ambient. Annealing for more than 30 min resulted in a high acceptor activation ratio and a low compensation ratio that were comparable to those obtained with annealing at 1400 °C for 5 min. We also performed annealing at 1300 °C in a reduced nitrogen pressure of 300 MPa which makes us possible to expand inner diameter of annealing equipment in the future. High electrical activation, similar to one obtained by annealing at 1 GPa, was successfully obtained.

Increase of activation efficiency of hardening backfilling mixture components by application mining and metallurgical wastes

The main operation associated with the preparation of mining and metallurgical wastes for use as a hardening mixture and backfilling of mined-out space is their crushing and activation. Improving the activation processes is an urgent task, since their use can significantly increase the strength of the filling mass or reduce the consumption of the binder while maintaining its strength characteristics. For the efficient operation of mining enterprises, including ferrous metallurgy mines, it is necessary to provide highquality binders for the preparation of hardening mixtures for filling man-made voids formed during underground mining of solid mineral deposits. It has been established that the use of vibration, mechanical and electrical activation of the components of the hardening backfill mixture at mining enterprises leads to an increase in the activity of substandard materials by up to 10–40% for each apparatus. In particular, the enrichment of inert materials on a vibrating screen ГВ-1,2/3,2, Ukraine, increases the activity by 15– 20%. It has been substantiated that the activation of binders (blast-furnace granular slags) in a vertical vibrating mill МВВ-0,7, Ukraine, and a disintegrator ДУ-65 company “Disintegrator”, Estonia, increases the activity of the binder by 20–25%, when the active class of fractions 0.074 mm – by 55% is released versus 40% in ball mills. The recommended vibratory conveying installations increase the activity of the components of the hardening backfill mixture by 10–15%. The use of vibro-gravity transport installations ensures the supply of the filling mixture at a distance 15–20 times higher than the height of the vertical stack.

Enabling comprehensive optogenetic studies of mouse hearts by simultaneous opto-electrical panoramic mapping and stimulation

During the last decade, cardiac optogenetics has turned into an essential tool for investigating cardiac function in general and for assessing functional interactions between different myocardial cell types in particular. To advance exploitation of the unique research opportunities offered by this method, we develop a panoramic opto-electrical measurement and stimulation (POEMS) system for mouse hearts. The core of the experimental platform is composed of 294 optical fibers and 64 electrodes that form a cup which embraces the entire ventricular surface of mouse hearts and enables straightforward ‘drop&go’ experimentation. The flexible assignment of fibers and electrodes to recording or stimulation tasks permits a precise tailoring of experiments to the specific requirements of individual optogenetic constructs thereby avoiding spectral congestion. Validation experiments with hearts from transgenic animals expressing the optogenetic voltage reporters ASAP1 and ArcLight-Q239 demonstrate concordance of simultaneously recorded panoramic optical and electrical activation maps. The feasibility of single fiber optical stimulation is proven with hearts expressing the optogenetic voltage actuator ReaChR. Adaptation of the POEMS system to larger hearts and incorporation of additional sensors can be achieved by redesigning the system-core accordingly.

Symmetry reduction in a hyperpolarization-activated homotetrameric ion channel

Plants obtain nutrients from the soil via transmembrane transporters and channels in their root hairs, from which ions radially transport in towards the xylem for distribution across the plant body. We determined structures of the hyperpolarization-activated channel AKT1 from Arabidopsis thaliana, which mediates K+ uptake from the soil into plant roots. These structures of AtAKT1 embedded in lipid nanodiscs show that the channel undergoes a reduction of C4 to C2 symmetry, possibly to regulate its electrical activation.

3-Dimensional ventricular electrical activation pattern assessed from a novel high-frequency electrocardiographic imaging technique: principles and clinical importance

The study introduces and validates a novel high-frequency (100–400 Hz bandwidth, 2 kHz sampling frequency) electrocardiographic imaging (HFECGI) technique that measures intramural ventricular electrical activation. Ex-vivo experiments and clinical measurements were employed. Ex-vivo, two pig hearts were suspended in a human-torso shaped tank using surface tank electrodes, epicardial electrode sock, and plunge electrodes. We compared conventional epicardial electrocardiographic imaging (ECGI) with intramural activation by HFECGI and verified with sock and plunge electrodes. Clinical importance of HFECGI measurements was performed on 14 patients with variable conduction abnormalities. From 3 × 4 needle and 108 sock electrodes, 256 torso or 184 body surface electrodes records, transmural activation times, sock epicardial activation times, ECGI-derived activation times, and high-frequency activation times were computed. The ex-vivo transmural measurements showed that HFECGI measures intramural electrical activation, and ECGI-HFECGI activation times differences indicate endo-to-epi or epi-to-endo conduction direction. HFECGI-derived volumetric dyssynchrony was significantly lower than epicardial ECGI dyssynchrony. HFECGI dyssynchrony was able to distinguish between intraventricular conduction disturbance and bundle branch block patients.

Electroactivation of media in agricultural technologies as a way to intensify production processes

The monograph examines the scientific foundations, methodological approaches and applied aspects of the electroactivation of air and water solutions for their direct use in various technological processes of agricultural production. The results of numerous experimental studies of the authors and other researchers conducted over several years to substantiate the parameters and operating modes of electrotechnological installations for the electrical activation of various media are presented. It is intended for undergraduates, postgraduates, engineers and researchers who study and deal with issues of electrical technology, in particular, the development of electroactivators and the use of electroactivation processes in various areas of agricultural production and processing of agricultural products.

Signal Analysis For Cardiac Electrical Activation Studies

The aim of this study is to determine if some of the characteristics of reconstructed unipolar electrograms from the noncontact mapping system can be used to detect epicardial and to differentiate it from endocardial electrical activation in a canine heart. This would help the electrophysiologist know where exactly the origin of ventricular tachycardia or the critical point in tissue is located. Following this, arrhythmia can be successfully treated by ablating that part of the tissue of the heart. Virtual electrograms were recorded while pacing the right ventricle of an open-chest dog at multiple endocardial and epicardial sites using the commercially available noncontact mapping system (EnSite Array™ Catheter 3000). The endocardial and epicardial paced virtual electrograms from the juxtaposing sites allow for analyzing systematically the differences in their morphologies. Maximal dV / dt, area under the depolarization curve and latency extracted from unipolar electrograms demonstrated significant difference between epicardial and endocardial pacing sites with a p-value of less than 0.01 in all three cases. The above features were fed to a linear discriminant analysis based classifier and high classification accuracy was achieved. Therefore, reliable criteria can be proposed to allow for discrimination of an endocardial versus epicardial origin of electrical activation. And also the endocardial and epicardial paced virtual electrograms from the juxtaposing sites allows for an estimate of the transfer function of the myocardium in different positions of the right ventricles of a canine heart. The transfer function estimation will aid in better mathematical modeling of myocardium and could be a sensitive measure of myocardial homogeneity and arrhythmic foci localization.Another study was done on a human heart. This study was to evaluate the ability of virtual electrograms to predict abnormal bipolar electrograms. We tested the hypothesis of maxdV/dt, filtering and optimized DSM threshold. This allows better identification of abnormal myocardial substrate traditionally defined by contact bipolar mapping in human RVOT.

Signal Analysis For Cardiac Electrical Activation Studies

The aim of this study is to determine if some of the characteristics of reconstructed unipolar electrograms from the noncontact mapping system can be used to detect epicardial and to differentiate it from endocardial electrical activation in a canine heart. This would help the electrophysiologist know where exactly the origin of ventricular tachycardia or the critical point in tissue is located. Following this, arrhythmia can be successfully treated by ablating that part of the tissue of the heart. Virtual electrograms were recorded while pacing the right ventricle of an open-chest dog at multiple endocardial and epicardial sites using the commercially available noncontact mapping system (EnSite Array™ Catheter 3000). The endocardial and epicardial paced virtual electrograms from the juxtaposing sites allow for analyzing systematically the differences in their morphologies. Maximal dV / dt, area under the depolarization curve and latency extracted from unipolar electrograms demonstrated significant difference between epicardial and endocardial pacing sites with a p-value of less than 0.01 in all three cases. The above features were fed to a linear discriminant analysis based classifier and high classification accuracy was achieved. Therefore, reliable criteria can be proposed to allow for discrimination of an endocardial versus epicardial origin of electrical activation. And also the endocardial and epicardial paced virtual electrograms from the juxtaposing sites allows for an estimate of the transfer function of the myocardium in different positions of the right ventricles of a canine heart. The transfer function estimation will aid in better mathematical modeling of myocardium and could be a sensitive measure of myocardial homogeneity and arrhythmic foci localization.Another study was done on a human heart. This study was to evaluate the ability of virtual electrograms to predict abnormal bipolar electrograms. We tested the hypothesis of maxdV/dt, filtering and optimized DSM threshold. This allows better identification of abnormal myocardial substrate traditionally defined by contact bipolar mapping in human RVOT.