Channel opening duration in adult muscle nAChRs determined by activated external ACh binding site

We recorded currents through the cell membrane at single nAChR molecules, held at ACh or Epibatidine (Ebd) concentrations of 0.01, 0.1, 1, 10 or 100 μM. The measured current amplitudes had an absolutely fixed value of 15 pA. This was valid for different agonists at all concentrations. Binding an agonist at one or both sites in the ring of subunits allowed to open the channel, the site that initiated the opening determined the duration of the final opening of the channel. In addition, the current flow was continuously interrupted by < 3 μs shut times. The resolution of our records was optimized to reach 5 μs, but was insufficient to resolve an unknown proportion of shorter shut times. Therefore, measured durations of openings are overestimated, and cited in brackets: τo1 (3 μs) elicited by agonist-binding at the δ-site, τo2 and τo3 (40 and 183 μs) by binding at the ϵ-site, and τo4 (752 μs) by binding at the δ- and ϵ-site. Mono-liganded nAChRs trigger short bursts of 0.6 ms duration. Bi-liganded nAChRs generate long bursts that at low agonist concentrations last 12 ms. Above 10 μM ACh, long bursts are shortened, with 100 μM ACh, to 5 ms, and further at higher concentrations. While ACh was the main agonist, Ebd bound more effectively than ACh to the ϵ-site.

Lightning Return-Stroke Transmission Line Modelling Based on the Derivative of Heidler Function and CN Tower Data

One of the most important parameters in a lightning flash that is of interest to researchers is the lightning return-stroke current as it causes most of the destructions and disturbances in electrical and telecommunication networks. In most cases, the lightning return-stroke current can not be directly measured and current characteristics are determined from measured electric and magnetic fields through the use of lightning return-stroke models. The main objective of this work is the development of a lightning return-stroke model for an elevated object. Also, an important objective is the correlation of the wavefront parameters (peak, maximum rate of rise and risetime) of the return-stroke current with the wavefront parameters of its associated lightning electromagnetic pulse (LEMP), measured 2 km north of the tower. The developed field-current parameter relationships for CN Tower lightning return strokes are compared with those obtained from measurements conducted at the Peissenberg Tower in Germany. A 3-section transmission line (TL) model of the CN Tower, along with the derivative of the modified Heidler function, is used to simulate the measured current derivative signal. Then, the spatial-temporal distribution of the lightning current along the CN Tower and the lightning channel, during the lightning return-stroke phase, is determined. The presented model simulates the measured current derivative signal instead of the current as has been used by other researchers. The use of the derivative of the modified Heidler function to simulate the lightning current derivative proved to be superior than simulating the lightning current. For the quantitative assessment of the proposed model, a comparison between the simulated field, obtained through the usage of Maxwell’s equations and the simulated current, and the measured field is performed. The developed 3-section TL model based on the measured current derivative and the derivative of the modified Heidler function produced a simulated magnetic field that is much closer to the measured field in comparison with previous models. The developed field-current parameter relationships as well as the experimentally verified lightning return-stroke model can contribute to solving the inverse-source problem, one of the most challenging problems in lightning research, where the lightning current characteristics are estimated based on the characteristics of the measured LEMP.

Lightning Return-Stroke Transmission Line Modelling Based on the Derivative of Heidler Function and CN Tower Data

One of the most important parameters in a lightning flash that is of interest to researchers is the lightning return-stroke current as it causes most of the destructions and disturbances in electrical and telecommunication networks. In most cases, the lightning return-stroke current can not be directly measured and current characteristics are determined from measured electric and magnetic fields through the use of lightning return-stroke models. The main objective of this work is the development of a lightning return-stroke model for an elevated object. Also, an important objective is the correlation of the wavefront parameters (peak, maximum rate of rise and risetime) of the return-stroke current with the wavefront parameters of its associated lightning electromagnetic pulse (LEMP), measured 2 km north of the tower. The developed field-current parameter relationships for CN Tower lightning return strokes are compared with those obtained from measurements conducted at the Peissenberg Tower in Germany. A 3-section transmission line (TL) model of the CN Tower, along with the derivative of the modified Heidler function, is used to simulate the measured current derivative signal. Then, the spatial-temporal distribution of the lightning current along the CN Tower and the lightning channel, during the lightning return-stroke phase, is determined. The presented model simulates the measured current derivative signal instead of the current as has been used by other researchers. The use of the derivative of the modified Heidler function to simulate the lightning current derivative proved to be superior than simulating the lightning current. For the quantitative assessment of the proposed model, a comparison between the simulated field, obtained through the usage of Maxwell’s equations and the simulated current, and the measured field is performed. The developed 3-section TL model based on the measured current derivative and the derivative of the modified Heidler function produced a simulated magnetic field that is much closer to the measured field in comparison with previous models. The developed field-current parameter relationships as well as the experimentally verified lightning return-stroke model can contribute to solving the inverse-source problem, one of the most challenging problems in lightning research, where the lightning current characteristics are estimated based on the characteristics of the measured LEMP.

Monitoring and quantification of bioelectrochemical biofilms by means of OCT in novel and customized reactor-setups

&lt;p&gt;In the last 40 years, bioelectrochemical systems (BESs) have been increasingly discussed within the scope of debates about sustainable energy sources and production of value added chemicals independent of fossil sources. Since the produced current in microbial fuel cells as well as the turnover rates in microbial electrosynthesis cells are dependent on the biocatalysts&amp;#180; activity, control of the growing biofilm plays a major role in BESs. Moreover, the knowledge about the interplay between biofilm development and electrochemical parameters is crucial for optimizing these sytems.&lt;/p&gt; &lt;p&gt;In the last 3 years, various electroactive biofilms (anodic and cathodic) were cultivated and characterized in a versatile and house made lab-scale flow cell system as well as in a rotating disc biofilm contactor (RDBC). Both systems allow for control of substrate (liquid and gaseous), and nutritional conditions as well as hydrodynamics and other physical parameters. The monitoring of biofilm development was conducted non-invasively by means of optical coherence tomography (OCT). For cathodic biofilms, quantitative analysis of generated 3D OCT data sets revealed a correlation between substratum coverage and measured current density. The increase of substratum coverage led to a decrease of measured current density due to less abiotic redox processes on the cathode surface. A stable current density was achieved when a substratum coverage of 99 % was reached. Furthermore, calculated biofilm accumulation rates could also be correlated with the substratum coverage. The overall biofilm accumulation rate decreased when the substratum was fully covered. Both correlations support the hypothesis that the availability of electrons from the cathode surface is a limiting factor in microbial electrosynthesis.&lt;/p&gt; &lt;p&gt;A 10-liter RDBC was designed to continuously harvest biomass from the electrode to extract intracellularly stored products. In future, this approach could be applied for biotechnological processes. Additionally, the RDBC can be used to obtain reliable mass balances and turnover rates because of its larger scale.&lt;/p&gt;

Evolution Characteristics during Initial Stage of Triggered Lightning Based on Directly Measured Current

The initiation of a leader is an important lightning discharge process, but how an upward positive leader (UPL) initiates is still not fully understood. The evolution characteristics of a UPL during its initial stage was systematically studied based on directly measured current data of 14 triggered lightning events in 2019. It was found that the initial stage of triggered lightning can be divided into two types: a single initial process form and a multiple initial process form, with percentages of 64.29% and 35.71%, respectively. Compared with the former, the latter usually lasts longer, and the corresponding lightning is often triggered under a lower ground-level quasi-static electric field. In each initial process, precursor current pulses (PCPs), PCP clusters and initial precursor current pulse (IPCPs) are typical current waveforms, and the pulse durations and transferred charges of PCPs increase linearly with time. However, in the multiple initial process form, the pulse durations and transferred charges of PCPs will reduce significantly after each previous initial process and then continue to increase in the following initial process. In each initial process, when the pulse duration and transferred charge of a PCP increase to a certain extent, PCP clusters and IPCPs begin to appear. For the emergence of PCP clusters, the average values of the threshold are 3.48 μs and 19.53 μC, respectively. For the occurrence of IPCPs, the corresponding values are 4.69 μs and 27.23 μC, respectively. The average values of pulse durations and transferred charges of IPCPs are larger than those of PCP clusters. Compared with adjacent PCP clusters, IPCPs contain more pulses, with a critical range of 6–7. IPCPs also last longer, and have a critical range of 138–198 μs.

Fault Mechanism of Fiber Optical Current Transformer Based on Signal Processing Method

The fiber optical current transformer (FOCT) with sine wave modulation has been widely used in the DC transmission project, while its fault rate is much higher than that of an electromagnetic current transformer, which seriously threatens the safe operation of power grid. In order to investigate the fault mechanism of FOCT, the output signal model of the FOCT photodetector is established, and its basic methods of modulation and demodulation are analyzed to explore the influencing factors of the signal processing method used in the calculation of measured current. It is found that the reduction of the second harmonic component in the photodetector output is the root cause of FOCT fault, and the optical path, modulation signal amplitude, and measured current are important factors affecting the second harmonic component. The influencing law of three factors on the second harmonic component is calculated by simulation and the characteristic differences between them are given. Finally, the fault simulation test of FOCT light intensity and a modulation circuit were carried out in the laboratory, and the results verify the correctness of theoretical analysis. The research in this paper provides reference for fault analysis and reliability improvement of FOCT.

An Enhanced Fault Tolerant Control Against Current Sensor Failures in Induction Motor Drive by Applying Space Vector

In this paper, an enhanced active fault-tolerant control (FTC) is proposed to solve a current sensor failure in the induction motor drive (IMD) using two current sensors. The proposed FTC method applies only one observer to diagnose the faults and reconfigure the control signals by the space stator current. The diagnosis function is made up of a comparison algorithm between the measured current space vector and the estimated space vector. Then, incorrect feedback stator currents are replaced by the estimated values in the reconfiguration function. The amplitude of a healthy measured current is applied to adjusted the accuracy of estimated current signals. The IMD uses the field-oriented control (FOC) technique to control the speed and torque. The effectiveness in stabilizing the IMD system when a current sensor error occurs is verified by various simulations in the Matlab-Simulink environment This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.