Acquisition Of Currents Research Articles

Investigating different carbon-based target materials: Can we improve ionization in HiPIMS for the deposition of diamondlike carbon films?

Investigating different carbon-based target materials: Can we improve ionization in HiPIMS for the deposition of diamondlike carbon films?

Phase Current Reconstruction Method With an Improved Direct Torque Control of SRM Drive for Electric Transportation Applications

Acquisition of the accurate phase currents is indispensable for the control and protection of switched reluctance motor (SRM) drives for electric transportation applications. Existing phase current reconstruction techniques for SRM are implemented under the current control techniques, which generate large torque pulsations. Therefore, the direct torque control (DTC) method can be adopted to minimize torque pulsations and to enhance transient performance in electrified vehicles. However, the existing current estimation methods cannot be applied to DTC strategies due to the simultaneous conduction of all phases at any switching instant. Furthermore, it offers a lower torque per ampere ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ) ratio and draws a high source current. This article addresses the aforementioned concerns by proposing a cost-effective phase current reconstruction method with an improved DTC strategy for a 4-kW four-phase SRM drive. This method employs a 16-sector partition method with a new voltage vector selection by detecting zero-current regions of each phase. As a result, the long-tail currents can be avoided, thereby limiting the simultaneous conduction of all phases. The simulation and test results show that the proposed DTC has minimal torque pulsations, high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ratio, low converter losses, and lower source current ripple in comparison to the existing DTC schemes under various operating conditions. Also, the proposed phase current estimation method effectively reconstructs the phase currents under both steady-state and transient operating conditions.

Online Glucose Analysis System With High Precision and Wide Detection Range for Fermentation Monitoring

Online glucose monitoring during the fermentation process is critical for evaluating the microbial metabolism state and reaction course, achieving precise process control for industrial efficiency enhancement. However, the fast, wide-range and highly accurate test technique always presents a challenge for state-of-the-art analytical instruments. In this work, we proposed an online glucose analysis system based on a homemade screen-printed enzymatic biosensor chip composed of Prussian blue nanocubes with a high sensitivity of 83.404 mA mM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . To match the detection behavior of this chip, a specific signal conversion system was designed to realize the highly precise acquisition and treatment of nA-level currents by integrating hardware acquisition circuits and Kalman filtering algorithms. Focusing on the continuous change in glucose concentration during fermentation, an adaptive injection strategy for the sampling volume was proposed to achieve an ultrawide linear range from 1 g/L to 180 g/L. The results show that the online analytical system exhibits excellent detection performance with high accuracy and low relative error of detection (<2%) during the fermentation of sophorolipid and ethanol compared to high performance liquid chromatography and commercial analyzers.

A compact low-noise broadband digital picoammeter architecture

Abstract A low-noise (⩽4 fA/√Hz), broadband (⩾100 kHz) compact architecture and related operation solutions are proposed for portable and low-cost time-domain acquisition of currents with effective resolution in the order of 1 pA and below. The front-end architecture is based on an integrating-differentiating scheme to achieve the optimal performance in terms of input-referred equivalent noise, but it overcomes the typical noise/bandwidth trade-off by making the sampling frequency of the A/D conversion independent from the rate at which the analog front-end is reset. In order to strongly mitigate the main drawback, i.e., the introduction in the system of an inherent time-variance, a Track-and-Hold circuit synchronized with the reset is exploited. For validation purposes, a dual-channel prototype was implemented in a low-cost CMOS technology. The prototype is characterized by standard figures of merit and is experimentally validated by two simple case studies, which are typical of practical applications.

Research on Urban Power Grid Harmonic Source Location Based on Harmonic Transmission

Based on the analysis of parameter identification of harmonic state estimation and harmonic source localization on fundamental theory, urban power grid harmonic transmission model is established, and by using harmonic transmission rule, preliminary determine the harmonic source area, effectively reduce the dimension of harmonic state estimation and calculation workload. Then using intelligent methods and data reliability security strategy, automatic identification and acquisition of harmonic currents, improve the quality of data, effectively prevent the harmonic current of nonlinear and measurement noise vector's influence on the harmonic state estimation. Finally, a case is given to prove the correctness and feasibility of the theory in this paper.

Synchronized Measurements-Based Algorithm for Short Transmission Line Fault Analysis

A new numerical algorithm for the analysis of single line to ground faults on short overhead transmission lines is presented in this paper. It is based upon synchronized sampling at two line ports, and an accurate fault model including the arcing phenomena and tower footing resistance at the fault point. The core of the algorithm is an efficient nonrecursive parameter estimation method. A dynamic arc model is included in the fault model to represent the arc’s interaction with the external power network. The algorithm accurately estimates the arc voltage amplitude, tower footing resistance, and the fault location, simultaneously. The algorithm is derived in the time domain, and is based on the synchronized acquisition of currents and voltages at both line terminals. Case studies based on simulated data are presented to demonstrate the effectiveness of the new method. In particular, the sensitivity of the proposed algorithm to synchronization errors, harmonics, line capacitance, and fault resistance were explored with lumped, distributed, transposed, and untransposed line models.

Railway Transportation Efficiency Improvement: Loco Health Assessment by Time Domain Data Analysis to Support Condition Based Maintenance Implementation

Health estimate of loco mechanical transmission components usually implies the on-board installation of fit-to-purpose devices and the use of specific protocols for data acquisition. In this paper the authors present a different approach, based on the acquisition and post-processing of the stator currents of an induction traction motor, easy to be measured and already monitored by standard on-board automation systems. The use of a PWM inverter for the electrical drive of the traction unit introduces harmonics in the stator currents, and an analogous effect is due to the presence, for instance, of a bearing fault. For this reason, the authors have paid great attention to the choice of a reliable de-noising technique for the removal of the harmonic content due to the electronic conversion unit. The so cleaned stator current time series have been then processed by the Independent Component Analysis (ICA) method, in order to identify some current “features” able to predict motor condition. On the basis of a huge amount of data deriving from a laboratory test campaign, the author present and discuss in the paper the results of their study.

Sequential acquisition of cacophony calcium currents, sodium channels and voltage‐dependent potassium currents affects spike shape and dendrite growth during postembryonic maturation of an identified Drosophila motoneuron

During metamorphosis the CNS undergoes profound changes to accommodate the switch from larval to adult behaviors. In Drosophila and other holometabolous insects, adult neurons differentiate either from respecified larval neurons, newly born neurons, or are born embryonically but remain developmentally arrested until differentiation during pupal life. This study addresses the latter in the identified Drosophila flight motoneuron 5. In situ patch-clamp recordings, intracellular dye fills and immunocytochemistry address the interplay between dendritic shape, excitability and ionic current development. During pupal life, changes in excitability and spike shape correspond to a stereotyped, progressive appearance of voltage-gated ion channels. High-voltage-activated calcium current is the first current to appear at pupal stage P4, prior to the onset of dendrite growth. This is followed by voltage-gated sodium as well as transient potassium channel expression, when first dendrites grow, and sodium-dependent action potentials can be evoked by somatic current injection. Sustained potassium current appears later than transient potassium current. During the early stages of rapid dendritic growth, sodium-dependent action potentials are broadened by a calcium component. Narrowing of spike shape coincides with sequential increases in transient and sustained potassium currents during stages when dendritic growth ceases. Targeted RNAi knockdown of pupal calcium current significantly reduces dendritic growth. These data indicate that the stereotyped sequential acquisition of different voltage-gated ion channels affects spike shape and excitability such that activity-dependent calcium influx serves as a partner of genetic programs during critical stages of motoneuron dendrite growth.

Detection of interturn faults in PMSMs with different winding configurations

Interturn faults in permanent magnet synchronous motors (PMSMs) may develop fast into more severe faults such as coil-to-coil, phase-to-phase and phase-to-ground short circuits. These faults are very destructive and may irreversibly damage the PMSM. Therefore, it is highly desirable to develop suitable methods for the early detection of such faults. The effects of interturn faults are visible in both the stator currents and the zero-sequence voltage component (ZSVC) spectra. By designing appropriate fault diagnosis schemes based on the analysis of the harmonic content of such electric variables it is possible to detect short circuit faults in its early stage. However, the stator winding configuration of the PMSM deeply impacts the harmonic content of both spectra. This paper studies the effects of different stator winding configurations in both the stator currents and the ZSVC spectra of healthy and faulty machines. Results presented may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and/or the ZSVC harmonic components.

Measurement-Based Load Modeling Using Transfer Functions for Dynamic Simulations

Measurement-based load modeling is a promising approach to reliably represent load behavior in dynamic simulations of large power systems. This paper presents a methodology that starts with the acquisition of voltages and currents from power quality monitoring systems and highlights the issues associated with selecting, processing and resampling the data to estimate the relationship between the power deviations as a function of the voltage deviations. The load model mathematical structure chosen is a second-order transfer function, whose parameters are estimated using a genetic algorithm (GA) as the optimization technique that minimizes the error between the real data that are measured and the data that are simulated with the proposed models. Some insights were achieved regarding the appropriate search space choice.

Influence of the Stator Windings Configuration in the Currents and Zero-Sequence Voltage Harmonics in Permanent Magnet Synchronous Motors With Demagnetization Faults

Demagnetization faults in permanent magnet synchronous motors may generate specific fault harmonic frequencies in the stator currents and the zero-sequence voltage component (ZSVC) spectra. Hence, by analyzing the stator currents or/and the ZSVC spectra it is possible to develop fault diagnosis schemes to detect such faults. In order to have a broad view of such effects, a representative set of stator windings configurations must be considered. By analyzing different stator windings configurations this paper shows that the amplitude of the harmonic frequencies of both the stator currents and the ZSVC spectrato be analyzed are significantly influenced by the stator windings configuration. It is also proved that depending on the winding configuration, new harmonic components may emerge in both spectra. The results presented in this paper may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and the ZSVC harmonic components.

A Compact Remote Monitoring System for a Three-Phase 10-kVA Energy-Efficient Switchable Distribution Transformer

Remote monitoring has been implemented in many areas. This paper introduces its specific application to a three-phase 10-kVA energy-efficient switchable distribution transformer. A designed embedded system and embedded Ethernet have been implemented to achieve a compact remote condition monitoring for the transformer. The embedded system performs acquisition of voltages, currents, and temperatures, controls the switching devices that connect the tappings of the transformer, and processes acquired data. Client and server applications were developed through the use of embedded Ethernet to enable remote monitoring through a local area network (LAN). Some protocols were developed as parts of software development of the whole system. Experimentation was done by applying the remote monitoring system to the transformer connected to three-phase variable supply voltage and load. Results of the experimentation by using a LAN available in the school revealed that the system can handle remote monitoring and control tasks for the transformer.

Gipc3 mutations associated with audiogenic seizures and sensorineural hearing loss in mouse and human

Sensorineural hearing loss affects the quality of life and communication of millions of people, but the underlying molecular mechanisms remain elusive. Here, we identify mutations in Gipc3 underlying progressive sensorineural hearing loss (age-related hearing loss 5, ahl5) and audiogenic seizures (juvenile audiogenic monogenic seizure 1, jams1) in mice and autosomal recessive deafness DFNB15 and DFNB95 in humans. Gipc3 localizes to inner ear sensory hair cells and spiral ganglion. A missense mutation in the PDZ domain has an attenuating effect on mechanotransduction and the acquisition of mature inner hair cell potassium currents. Magnitude and temporal progression of wave I amplitude of afferent neurons correlate with susceptibility and resistance to audiogenic seizures. The Gipc3343A allele disrupts the structure of the stereocilia bundle and affects long-term function of auditory hair cells and spiral ganglion neurons. Our study suggests a pivotal role of Gipc3 in acoustic signal acquisition and propagation in cochlear hair cells.

Expression of BK‐type calcium‐activated potassium channel splice variants during chick cochlear development

The appearance of large-conductance, calcium-activated potassium (BK) current is a hallmark of functional maturation in auditory hair cells. Acquisition of this fast-activating current enables high-frequency, graded receptor potentials in all vertebrates and an electrical tuning mechanism in nonmammals. The gene encoding BK alpha subunits is highly alternatively spliced, and the resulting variations in channel isoforms may contribute to functional diversity at the onset of hearing. We examined the tissue specificity of nine BK alpha alternative exons and investigated changes in expression during chick cochlear development using quantitative polymerase chain reaction (qPCR). Each alternative was widely expressed in several tissues except for an insert near the C-terminus Ca(2+) sensing domain, which appeared brain-specific. The only alternative form in the membrane-bound core of the channel was expressed in brain and muscle but was undetected in cochlea. Of the remaining variants, three increased in expression prior to the onset of hearing and acquisition of BK currents. These three variants cause decreased Ca(2+) sensitivity or increased intracellular retention, traits that would not easily explain the advent of calcium-sensitive currents at embryonic day (E)18-19. Expression levels of other variants were mature and stable by E15, days before currents were acquired. Surface expression of C-terminal isoforms was examined using patch-clamp electrophysiology and immunocytochemistry. C-terminal variants that exhibit robust surface expression appeared in the membrane at E18, even though transcripts were unchanged during development starting from E12. These results indicate that delays in protein synthesis and trafficking/scaffolding of channel subunits underlie the late acquisition of BK currents in cochlear hair cells.

Developmental expression of BK channels in chick cochlear hair cells

BackgroundCochlear hair cells are high-frequency sensory receptors. At the onset of hearing, hair cells acquire fast, calcium-activated potassium (BK) currents, turning immature spiking cells into functional receptors. In non-mammalian vertebrates, the number and kinetics of BK channels are varied systematically along the frequency-axis of the cochlea giving rise to an intrinsic electrical tuning mechanism. The processes that control the appearance and heterogeneity of hair cell BK currents remain unclear.ResultsQuantitative PCR results showed a non-monotonic increase in BK α subunit expression throughout embryonic development of the chick auditory organ (i.e. basilar papilla). Expression peaked near embryonic day (E) 19 with six times the transcript level of E11 sensory epithelia. The steady increase in gene expression from E11 to E19 could not explain the sudden acquisition of currents at E18-19, implicating post-transcriptional mechanisms. Protein expression also preceded function but progressed in a sequence from diffuse cytoplasmic staining at early ages to punctate membrane-bound clusters at E18. Electrophysiology data confirmed a continued refinement of BK trafficking from E18 to E20, indicating a translocation of BK clusters from supranuclear to subnuclear domains over this critical developmental age.ConclusionsGene products encoding BK α subunits are detected up to 8 days before the acquisition of anti-BK clusters and functional BK currents. Therefore, post-transcriptional mechanisms seem to play a key role in the delayed emergence of calcium-sensitive currents. We suggest that regulation of translation and trafficking of functional α subunits, near voltage-gated calcium channels, leads to functional BK currents at the onset of hearing.

Possibilities of multivariate curve resolution and partial least squares in the resolution of coeluted peaks in liquid chromatography with electrochemical detection

Two different strategies are compared for the resolution of coeluted peaks in liquid chromatography with electrochemical detection. The first is voltammetric detection (VD) for the acquisition of currents as a function of potential and time with multivariate curve resolution by alternating least squares (MCR-ALS) for data analysis and quantification. The second is amperometric detection (AD), i.e. recording currents as a function of time for a fixed potential and calibration by partial least squares (PLS). Both approaches are used to analyse a model mixture of pyrocatechol, dopamine and epinephrine. The results show that for high analyte concentrations VD-MCR-ALS provides accurate quantification with minimal effort (a single injection of the sample and each standard). However, at lower concentrations the excessive proportion of noise and the predominance of the capacitive contribution decrease the performance of VD-MCR-ALS, thus making AD-PLS preferable as its greater accuracy counters the more time-consuming calibration, which involves the injection of a large number of mixtures of different composition.

Regulation of Ca2+-dependent Desensitization in the Vanilloid Receptor TRPV1 by Calcineurin and cAMP-dependent Protein Kinase

The vanilloid receptor TRPV1 is a polymodal nonselective cation channel of nociceptive sensory neurons involved in the perception of inflammatory pain. TRPV1 exhibits desensitization in a Ca2+-dependent manner upon repeated activation by capsaicin or protons. The cAMP-dependent protein kinase (PKA) decreases desensitization of TRPV1 by directly phosphorylating the channel presumably at sites Ser116 and Thr370. In the present study we investigated the influence of protein phosphatase 2B (calcineurin) on Ca2+-dependent desensitization of capsaicin- and proton-activated currents. By using site-directed mutagenesis, we generated point mutations at PKA and protein kinase C consensus sites and studied wild type (WT) and mutant channels transiently expressed in HEK293t or HeLa cells under whole cell voltage clamp. We found that intracellular application of the cyclosporin A.cyclophilin A complex (CsA.CyP), a specific inhibitor of calcineurin, significantly decreased desensitization of capsaicin- or proton-activated TRPV1-WT currents. This effect was similar to that obtained by extracellular application of forskolin (FSK), an indirect activator of PKA. Simultaneous applications of CsA.CyP and FSK in varying concentrations suggested that these substances acted independently from each other. In mutation T370A, application of CsA.CyP did not reduce desensitization of capsaicin-activated currents as compared with WT and to mutant channels S116A and T144A. In a double mutation at candidate protein kinase C phosphorylation sites, application of CsA.CyP or FSK decreased desensitization of capsaicin-activated currents similar to WT channels. We conclude that Ca2+-dependent desensitization of TRPV1 might be in part regulated through channel dephosphorylation by calcineurin and channel phosphorylation by PKA possibly involving Thr370 as a key amino acid residue.

A Coplanar-Waveguide System for Cells Exposure During Electrophysiological Recordings

In order to investigate the biological effects of microwave electromagnetic (EM) fields as those emitted from mobile telecommunication equipment, a suitable exposure system has been designed. The system is specific for real-time acquisition of membrane ionic currents in a biological cell, i.e., patch-clamp recordings. Both numerical and experimental characterizations are considered, in terms of EM field and specific absorption rate (SAR) distribution in the Petri dish containing the biological target. Results show a good efficiency of the system in terms of SAR induced in the sample by incident input power.

Neurotrophic factors modulate hair cells and their potassium currents in chick otocyst explants.

Neurotrophins, retinoids and their receptors are present in the sensory epithelia of the inner ear during development. We show that these factors modulate the proliferation of hair cells and their K+-currents when the embryonic day 3 (ED 3) presumptive inner ear (i.e. otocyst) is maintained in organ culture. All trans-retinoic acid (RA) increases hair cell differentiation and enhances the acquisition of outward currents, including a delayed rectifier and a fast activating, transient type, voltage-gated potassium current. In contrast, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) decrease ionic current activity, and the addition of RA with the neurotrophins enhances this inhibitory response in an age-dependent manner. We measured the total number of cells per explant over time to determine precisely when and how these factors inhibit explant growth. We found that high concentrations of BDNF and NT-3 administered together, and low concentrations of both neurotrophins combined and administered with RA suppress otocyst cell numbers after 24 h in vitro. This suppressive response is induced by RA and NT-3, not by RA and BDNF. The suppressive or inhibitory influence of NT-3 and RA is the result of NT-3 binding to the low affinity receptor, p75NTR, not the result of RA increasing mRNA levels for the high affinity receptor, trkC. However, trk may act with p75NTR, as disruption of trk signalling alleviates the inhibitory response induced by NT-3 and RA. Our data suggest that various combinations and/or concentration gradients of these factors can differentially regulate inner ear development and hair cell excitability.

Identification of G protein-coupled receptors by RNase H-mediated hybrid depletion using Xenopus laevis oocytes as expression system

A method has been developed for rapidly identifying putative G protein-coupled receptors isolated initially as small cDNA fragments, following reverse transcription and polymerase chain reaction (PCR) amplification of mRNA. The method is based upon the use of synthetic oligonucleotides deduced from the sequence of the amplified receptor fragments, to direct a RNase H-mediated specific degradation of hybrids formed between the oligonucleotides and the corresponding receptor-encoding mRNA. Loss of an agonist-dependent receptor response in the Xenopus laevis oocyte expression system identifies the amplified receptor fragment. Taking in vitro synthesised serotonin HT 2-receptor (SR)-encoding mRNA as a model, it was shown that following incubation with RNase H and SR antisense oligonucleotides, injection of this message no longer caused the acquisition of agonist-dependent membrane currents in voltage-clamped oocytes. In contrast, when corresponding sense oligonucleotides were used, the serotonin-evoked membrane responses in oocytes were acquired as normal. The method should allow the identification of receptors which can functionally be expressed and measured in Xenopus oocytes.