Current-clamp Research Articles

Influence of Object Physical Properties Instability on Edge Current Method Sensitivity

The article contains results of a study of the eddy current transducer signal parameters from artificial defects against the background of the influence of stray parameters simulated on specially manufactured samples exposed to various external influences. The authors studied the added voltage change of eddy current prob depending on factors affecting the electromagnetic properties of steels. The results of the study were the determination of optimal excitation parameters and threshold values for discrimination levels of phase, amplitude and dynamic parameters when detuning from stray factors. The authors modeled stray parameters of eddy current testing in the form of temperature effects, effects of chemical reagents and plastic deformation of the surface layer. The researchers assessed the distribution of the temperature field, the time of chemical reactions and the composition of the reagents, as well as the geometric parameters of the deformable surface layer of the samples and their effect on eddy current prob added voltage. For the research, artificial defects were made in the form of thin cuts with an opening width of 0.2 mm, located in the stray parameter zone. The geometric dimensions of artificial defects were determined by the requirements for the amplitude of the transducer signals, which should not exceed the change in amplitude under the influence of a stray parameter on the time base, relative to the zero-value installed in the sample area not subject to the influence of external factors. The obtained results of the hodograph analysis when scanning with a clamp-on eddy current transducer made it possible to propose recommendations for detuning from stray parameters of various nature. This was done in order to increase the detectability of defects on objects with significant heterogeneity of the surface structure in the eddy current testing zones.

A NIR-II Photoacoustic Probe for High Spatial Quantitative Imaging of Tumor Nitric Oxide in Vivo.

Nitric oxide (NO) exhibits both pro- and anti-tumor effects. Therefore, real-time in vivo imaging and quantification of tumor NO dynamics are essential for understanding the conflicting roles of NO played in pathophysiology. The current molecular probes, however, cannot provide high-resolution imaging in deep tissues, making them unsuitable for these purposes. Herein, we designed a photoacoustic probe with an absorption maximum beyond 1000 nm for high spatial quantitative imaging of in vivo tumor NO dynamics. The probe exhibits remarkable sensitivity, selective ratiometric response behavior, and good tumor-targeting abilities, facilitating ratiometric imaging of tumor NO throughout tumor progression in a micron-resolution level. Using the probe as the imaging agent, we successfully quantified NO dynamics in tumor, liver and kidney. We have pinpointed an essential concentration threshold of around 80 nmol/cm3 for NO, which plays a crucial role in the "double-edged-sword" function of NO in tumors. Furthermore, we revealed a reciprocal relationship between the NO concentration in tumors and that in the liver, providing initial insights into the possible NO-mediated communication between tumor and the liver. We believe that the probe will help resolve conflicting aspects of NO biology and guide the design of imaging agents for tumor diagnosis and anti-cancer drug screening.

A NIR‐II Photoacoustic Probe for High Spatial Quantitative Imaging of Tumor Nitric Oxide in Vivo

AbstractNitric oxide (NO) exhibits both pro‐ and anti‐tumor effects. Therefore, real‐time in vivo imaging and quantification of tumor NO dynamics are essential for understanding the conflicting roles of NO played in pathophysiology. The current molecular probes, however, cannot provide high‐resolution imaging in deep tissues, making them unsuitable for these purposes. Herein, we designed a photoacoustic probe with an absorption maximum beyond 1000 nm for high spatial quantitative imaging of in vivo tumor NO dynamics. The probe exhibits remarkable sensitivity, selective ratiometric response behavior, and good tumor‐targeting abilities, facilitating ratiometric imaging of tumor NO throughout tumor progression in a micron‐resolution level. Using the probe as the imaging agent, we successfully quantified NO dynamics in tumor, liver and kidney. We have pinpointed an essential concentration threshold of around 80 nmol/cm3 for NO, which plays a crucial role in the “double‐edged‐sword” function of NO in tumors. Furthermore, we revealed a reciprocal relationship between the NO concentration in tumors and that in the liver, providing initial insights into the possible NO‐mediated communication between tumor and the liver. We believe that the probe will help resolve conflicting aspects of NO biology and guide the design of imaging agents for tumor diagnosis and anti‐cancer drug screening.

A novel coreless current sensing mechanism for two-wire power cord

In the development of smart home products, energy monitoring, and control systems, there is a significant need for precise and reliable electric current measurement. Most domestic appliances, whether residential or commercial, are powered by power cords with two wires. A reliable and accurate current probe would be required to detect current in two-wire power cables. Existing current sensors for two-wire power cables are complex, bulky (they use a magnetic core), and need full access to the power cord. In this paper a coreless, contactless current probe that requires only limited access of the space around the two-wire power cable is proposed. The sensor unit presented here measures the current accurately even for certain types of misalignments of the power cord. This makes the current measurement less sensitive to minor mechanical displacements, radius of the conductors, and the overall insulation thickness of power cord. In the proposed current probe, one-of-a-kind and highly reliable arrangement of magnetic field sensors, are used to measure the magnetic flux density caused by the current passing in the power cord. The current is computed using a derived mathematical formula which is expressed in terms of the voltage outputs of the magnetic sensors. To provide a clear understanding of the measurement process, an analysis using the Finite Element Method (FEM) is performed. The functionality of the proposed current probe is theoretically tested. Considering different sources of errors, an accuracy of less than 1.5% is obtained.

Participation of calcium-permeable AMPA receptors in the regulation of epileptiform activity of hippocampal neurons.

Epileptiform activity is the most striking result of hyperexcitation of a group of neurons that can occur in different brain regions and then spread to other sites. Later it was shown that these rhythms have a cellular correlate in vitro called paroxysmal depolarization shift (PDS). In 13-15 DIV neuron-glial cell culture, inhibition of the GABA(A) receptors induces bursts of action potential in the form of clasters PDS and oscillations of intracellular Ca2+ concentration ([Ca2+]i). We demonstrate that GABAergic neurons expressing calcium-permeable AMPA receptors (CP-AMPARs) as well as Kv7-type potassium channels regulate hippocampal glutamatergic neurons' excitability during epileptiform activity in culture. A combination of whole-cell patch-clamp in current clamp mode and calcium imaging microscopy was used to simultaneously register membrane potential and [Ca2+]i level. To identify GABAergic cell cultures were fixed and stained with antibodies against glutamate decarboxylase GAD 65/67 and neuron-specific enolase (NSE) after vital [Ca2+]i imaging. It was shown that CP-AMPARs are involved in the regulation of the PDS clusters and [Ca2+]i pulses accompanied them. Activation of CP-AMPARs of GABAergic neurons is thought to cause the release of GABA, which activates the GABA(B) receptors of other GABAergic interneurons. It is assumed that activation of these GABA(B) receptors leads to the release of beta-gamma subunits of Gi protein, which activate potassium channels, resulting in hyperpolarization and inhibition of these interneurons. The latter causes disinhibition of glutamatergic neurons, the targets of these interneurons. In turn, the CP-AMPAR antagonist, NASPM, has the opposite effect. Measurement of membrane potential in GABAergic neurons by the patch-clamp method in whole-cell configuration demonstrated that NASPM suppresses hyperpolarization in clusters and individual PDSs. It is believed that Kv7-type potassium channels are involved in the control of hyperpolarization during epileptiform activity. The blocker of Kv7 channels, XE 991, mimicked the effect of the CP-AMPARs antagonist on PDS clusters. Both drugs increased the duration of the PDS cluster. In turn, the Kv7 activator, retigabine, decreased the duration of the PDS cluster and Ca2+ pulse. In addition, retigabine led to deep posthyperpolarization at the end of the PDS cluster. The Kv7 channel is believed to be involved in the formation of PDS, as the channel blocker reduced the rate of hyperpolarization in the PDS almost three times. Thus, GABAergic neurons expressing CP-AMPARs, regulate the membrane potential of innervated glutamatergic neurons by modulating the activity of postsynaptic potassium channels of other GABAergic neurons.

Utilizing Text-Generative AI for Creating Oral Reading Fluency Probes

Oral reading fluency probes are essential for reading assessment, intervention, and progress monitoring. Due to the limited options for choosing oral reading fluency probes, it is important to utilize all available resources such as generative artificial intelligence (AI) like ChatGPT to create oral reading fluency probes. The purpose of this article is to describe how to use AI through ChatGPT to create customizable reading passages comparable with that of oral reading fluency probes. Using readability estimates, the ChatGPT-generated passages can be tailored to suit for specific grade levels, similar to how current publishers design oral reading fluency probes for the market. The implication of ChatGPT-generated passages is that researchers and practitioners alike could use ChatGPT to be able to create a seemingly unlimited amount of reading passages tailored to the skill level and interests of the learner for intervention material and potentially assessment material, while reducing cost and time investment.

Single shot detection of alterations across multiple ionic currents from assimilation of cell membrane dynamics

The dysfunction of ion channels is a causative factor in a variety of neurological diseases, thereby defining the implicated channels as key drug targets. The detection of functional changes in multiple specific ionic currents currently presents a challenge, particularly when the neurological causes are either a priori unknown, or are unexpected. Traditional patch clamp electrophysiology is a powerful tool in this regard but is low throughput. Here, we introduce a single-shot method for detecting alterations amongst a range of ion channel types from subtle changes in membrane voltage in response to a short chaotically driven current clamp protocol. We used data assimilation to estimate the parameters of individual ion channels and from these we reconstructed ionic currents which exhibit significantly lower error than the parameter estimates. Such reconstructed currents thereby become sensitive predictors of functional alterations in biological ion channels. The technique correctly predicted which ionic current was altered, and by approximately how much, following pharmacological blockade of BK, SK, A-type K+ and HCN channels in hippocampal CA1 neurons. We anticipate this assay technique could aid in the detection of functional changes in specific ionic currents during drug screening, as well as in research targeting ion channel dysfunction.

Unique fluorescent probe for the recognition of late apoptosis via translocation from plasma membrane to nucleus

Cell apoptosis is a crucial physiological process playing central roles in key biological and pathological activities. However, the current fluorescent probes for the detection of late apoptosis were “off–on” probes, which were facilely interfered by false positive signals caused by inhomogeneous staining and other factors. Herein, a unique fluorescent probe (NPn) discriminating late apoptosis from early apoptosis and heathy status with two different sets of fluorescent signals have been prepared, to overcome the possible false positive signals. NPn was designed impermeable to biomembranes and simultaneously with high affinity to DNA/RNA, which localized on the plasma membranes of living and early apoptotic cells, while relocated to the nucleus in late apoptotic cells. The hydrophilic amine unit and small ion radius were responsive for its membrane impermeability, which was confirmed with two control molecules without amine group. Using the probe, we have successfully evaluated the cell apoptosis induced by ultraviolet irradiation, rotenone, colchicine, and paclitaxel, demonstrating its potential application in biological researches.

Adaptive edge finishing process on distorted features through robot-assisted computer vision

Robotic deburring has emerged as a transformative solution in finishing processes, offering independence from operator influence to enhance product quality and reduce production costs. To do this, contour tracking is key to ensuring cutting tool contact and obtaining chamfers within narrow tolerances, especially on high added-value parts such as aeronautical turbomachinery. The persistent challenge involves accommodating workpiece variability, including deformations and burrs. Current probe positioning methods lack insights into burr morphology, while optical systems often require expensive scanners, resulting in time-intensive point cloud generation. Therefore, this paper presents an innovative industrial computer vision approach for adaptive deburring of functional edges. By processing the detected contour deviation signal, the proposed method generates tailored toolpaths based on real-time part conditions. The primary contribution lies in its ability to swiftly detect edges and burrs, dynamically adjusting machining toolpaths and conditions based on their dimensions, all through the rapid analysis of a simple image. This approach optimizes deburring operations, directing the cutting tool precisely where it is needed. Consequently, the default NC programming was enhanced with two new sub-programs tailored for deburring with conical tools—one for primary burr removal and another for uniform chamfering of distorted edges. The developed methodology can be easily applied in various industrial environments, offering a rapid and efficient means to improve chamfering of workpieces with variable contours. This research not only presents a practical solution for robotic deburring but also contributes to the advancement of adaptive manufacturing systems.

In-vivo integration of soft neural probes through high-resolution printing of liquid electronics on the cranium

Current soft neural probes are still operated by bulky, rigid electronics mounted to a body, which deteriorate the integrity of the device to biological systems and restrict the free behavior of a subject. We report a soft, conformable neural interface system that can monitor the single-unit activities of neurons with long-term stability. The system implements soft neural probes in the brain, and their subsidiary electronics which are directly printed on the cranial surface. The high-resolution printing of liquid metals forms soft neural probes with a cellular-scale diameter and adaptable lengths. Also, the printing of liquid metal-based circuits and interconnections along the curvature of the cranium enables the conformal integration of electronics to the body, and the cranial circuit delivers neural signals to a smartphone wirelessly. In the in-vivo studies using mice, the system demonstrates long-term recording (33 weeks) of neural activities in arbitrary brain regions. In T-maze behavioral tests, the system shows the behavior-induced activation of neurons in multiple brain regions.

In vitro modulator responsiveness of 655 CFTR variants found in people with cystic fibrosis

BackgroundIn 2017, the US Food and Drug Administration initiated expansion of drug labels for the treatment of cystic fibrosis (CF) to include CF transmembrane conductance regulator (CFTR) gene variants based on in vitro functional studies. This study aims to identify CFTR variants that result in increased chloride (Cl−) transport function by the CFTR protein after treatment with the CFTR modulator combination elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA). These data may benefit people with CF (pwCF) who are not currently eligible for modulator therapies. MethodsPlasmid DNA encoding 655 CFTR variants and wild-type (WT) CFTR were transfected into Fisher Rat Thyroid cells that do not natively express CFTR. After 24 h of incubation with control or TEZ and ELX, and acute addition of IVA, CFTR function was assessed using the transepithelial current clamp conductance assay. Each variant's forskolin/cAMP-induced baseline Cl− transport activity, responsiveness to IVA alone, and responsiveness to the TEZ/ELX/IVA combination were measured in three different laboratories. Western blots were conducted to evaluate CFTR protein maturation and complement the functional data. Results and conclusions253 variants not currently approved for CFTR modulator therapy showed low baseline activity (<10 % of normal CFTR Cl− transport activity). For 152 of these variants, treatment with ELX/TEZ/IVA improved the Cl− transport activity by ≥10 % of normal CFTR function, which is suggestive of clinical benefit. ELX/TEZ/IVA increased CFTR function by ≥10 percentage points for an additional 140 unapproved variants with ≥10 % but <50 % of normal CFTR function at baseline. These findings significantly expand the number of rare CFTR variants for which ELX/TEZ/IVA treatment should result in clinical benefit.

A selective chromo-fluorogenic chemosensor for visual detection of solution and vapor phase of sarin, tabun mimics diethyl chlorophosphate, diethyl cyanophosphonate

The abuse of nerve agents has become a severe threat to peaceful modern civilization. Hence, it is of paramount importance to the scientific communities to detect and degrade them for a modern society. In the present contribution, we have introduced a selective chromo-fluorogenic probe (AMP) based on neutral red dye for visual detection of the solution and vapor phase of sarin & tabun mimics, namely diethyl chlorophosphate (DCP) and diethyl cyanophosphonate (DCNP), respectively. A ratiometric UV–visible absorption spectral change with colorimetric visualization from yellow to bright pink is observed in the presence of both mimics. A “turn-off” photoluminescence from yellow color to non-fluorescence is observed in the presence of both mimics. The spectral and chromo-fluorgenic behavior is reversed in the presence of triethylamine (TEA). The sensitivity of AMP towards the detection of targeted analytes is recorded in the μM range. Additionally, filter paper-based strips are fabricated for the actual applicability of the current probe to identify trace amounts of both analytes in the presence of various types of analogous target analytes. The vapor phase sensing and two types of soil analysis are also employed to check the sensor's potential in real-life applications. The present report has revealed prompt, sensitive, selective, in-situ, accurate sample detectors of sarin & tabun gas in actual threatening situations.

Analytical model of eddy current bobbin coil probe responses at support plates in steam generator and heat exchanger tubes

The steam generators (SGs) of CANadian Deuterium Uranium nuclear reactors require periodic inspections to ensure their safe operation. Eddy current (EC) testing is the primary method by which the SG tubes are inspected. Many conditions in the SG tubes affect the EC response, such as fretting, pitting, cracking, as well as tube expansion, and the presence of tubesheet and support structures. When two or more of these parameters overlap, the EC signals from degradation induced wall losses are frequently difficult to interpret because these wall loss signals are often distorted due to interference with background signal variations. In this paper, a novel analytical model that describes the impedance of a bobbin coil with a plate encircling an arbitrary number of cylindrical conductors is developed. The model is validated against finite element method modelling and experiment. This model can be used to simulate the main probe response, while inspecting SG tubes near the tubesheet and support structures and thereby, provides the potential to separate out smaller flaw responses.

A Small-Molecule Ratiometric Photoacoustic Probe for the High-Spatiotemporal-Resolution Imaging of Copper(II) Dynamics in the Mouse Brain.

Copper dysmetabolism is associated with various neurodegenerative disorders, making high-spatiotemporal-resolution imaging of Cu2+ in the brain essential for understanding the underlying pathophysiological processes. Nevertheless, the current probes encounter obstacles in crossing the blood-brain barrier (BBB) and providing high-spatial-resolution in deep tissues. Herein, we present a photoacoustic probe capable of imaging Cu2+ dynamics in the mouse brain with high-spatiotemporal-resolution. The probe demonstrates selective ratiometric and reversible responses to Cu2+ , while also efficiently crossing the BBB. Using the probe as the imaging agent, we successfully visualized Cu2+ in the brain of Parkinson's disease (PD) model mouse with a remarkable micron-level resolution. The imaging results revealed a significant increase in Cu2+ levels in the cerebral cortex as PD progresses, highlighting the close association between Cu2+ alternations in the region and the disease. We also demonstrated that the probe can be used to monitor changes in Cu2+ distribution in the PD model mouse brain during L-dopa intervention. Mechanism studies suggest that the copper dyshomeostasis in the PD mouse brain was dominated by the expression levels of divalent metal transporter 1. The application of our probe in imaging Cu2+ dynamics in the mouse brain offers valuable insights into the copper-related molecular mechanisms underlying neurodegenerative diseases.

A Small‐Molecule Ratiometric Photoacoustic Probe for the High‐Spatiotemporal‐Resolution Imaging of Copper(II) Dynamics in the Mouse Brain

AbstractCopper dysmetabolism is associated with various neurodegenerative disorders, making high‐spatiotemporal‐resolution imaging of Cu2+ in the brain essential for understanding the underlying pathophysiological processes. Nevertheless, the current probes encounter obstacles in crossing the blood–brain barrier (BBB) and providing high‐spatial‐resolution in deep tissues. Herein, we present a photoacoustic probe capable of imaging Cu2+ dynamics in the mouse brain with high‐spatiotemporal‐resolution. The probe demonstrates selective ratiometric and reversible responses to Cu2+, while also efficiently crossing the BBB. Using the probe as the imaging agent, we successfully visualized Cu2+ in the brain of Parkinson's disease (PD) model mouse with a remarkable micron‐level resolution. The imaging results revealed a significant increase in Cu2+ levels in the cerebral cortex as PD progresses, highlighting the close association between Cu2+ alternations in the region and the disease. We also demonstrated that the probe can be used to monitor changes in Cu2+ distribution in the PD model mouse brain during L‐dopa intervention. Mechanism studies suggest that the copper dyshomeostasis in the PD mouse brain was dominated by the expression levels of divalent metal transporter 1. The application of our probe in imaging Cu2+ dynamics in the mouse brain offers valuable insights into the copper‐related molecular mechanisms underlying neurodegenerative diseases.

Nano-positive up negative down in binary oxide ferroelectrics

Ferroelectric HfO2 and ZrO2-based materials are promising candidates for next-generation ferroelectric devices, but their characterization is challenging due to complex factors such as crystal phases, degradation mechanisms, and local inhomogeneities. In this work, we propose a novel nanosized positive-up-negative-down (PUND) method to assess the ferroelectric response of doped-HfO2. This method is based on actual current probing and is immune to most electrostatic artifacts that plague other electrical atomic force microscopy (AFM) techniques. We demonstrate the PUND method’s ability to induce ferroelectric switching in Si-doped HfO2 and investigate the distinctive PUND response obtained for individual grains. We also extract the polarization charge based on a direct estimate of the tip–sample contact area. The proposed PUND method is a significant innovation as it is a method to combine the high spatial resolution of AFM with the immunity to electrostatic artifacts of current probing. This makes it a powerful tool for studying ferroelectric materials at the nanoscale, where local inhomogeneities and other effects can have a significant impact on their behavior. The PUND method is also notable for its ability to extract polarization charge based on a direct estimate of the tip–sample contact area. This is a significant improvement over previous methods, which often relied on indirect or approximate estimates of the contact area. Overall, the PUND method is a novel and innovative technique that offers significant advantages for the characterization of ferroelectric materials at the nanoscale. It is expected to have a major impact on the research and development of next-generation ferroelectric devices.

Advancing eddy current detection probes with magnetoelectric composite Materials: Enhancing crack detection in conductive materials

Eddy current testing (ECT) is a non-destructive method widely employed for detecting cracks in various conductive materials. However, the applicability of detection probes in low-frequency settings is limited by their sensitivity and size. This study introduces a novel magnetic detection probe for ECT, utilizing dual-magnetoelectric (ME) composites in a differential noise cancellation mode to enhance detection capabilities at low frequencies (kHz). Our investigation demonstrates the superior performance of the proposed detection probe compared to traditional copper coils. Through numerical analysis of the ME detection probe's voltage output, we establish its efficacy in identifying small defects or cracks in conductive materials. Furthermore, this research explores a crucial factor for accurately estimating crack length and depth in system analysis applications. The study significantly contributes to the field of magnetism and magnetic materials, paving the way for the development of more effective and versatile crack detection techniques.

Characteristics of an AC rotating gliding arc discharge in NH3 and air atmospheres

Plasmas have emerged as a promising technology for the utilization of NH3 as a carbon-free fuel for direct plasmas-assisted combustion and hydrogen production. This study aims to explore the electrical and optical emission characteristics of the rotating gliding arc (RGA) discharge in NH3 and air swirling flows over a wide range of nominal power inputs. The electrical characteristics were measured using voltage–current probes, while a spectrometer was employed to assess the spectral characteristics. Additionally, a synchronized high-speed camera equipped with a dual-scope objective was utilized to capture transient phenomena of the arc in the optical emission spectrum. Both the spark-type and glow-type discharges were observed in RGA. Interestingly, the spark-type discharge frequency exhibited a non-monotonic variation with increasing nominal power inputs for both NH3 and air, while the glow-type discharge frequency displayed a monotonous upward trend. Regarding the spectral emission characteristics in NH3, a dramatic transition of the arc emission spectrum from Hα to NH2* was observed as nominal power inputs increased. The Hα and NH2* emissions that are dominated in the spark-type and glow-type discharges, respectively, and the intensity ratio of Hα and NH2* emission shows evident correlations with discharge current and electric field strength. In summary, this study represents the first investigation into the electrical and spectral characteristics of RGA in NH3.

Point projection radiography of electromagnetically accelerated flyer plates with an external X-pinch driver.

A platform for flyer plate benchmarking experiments has been developed, with an external X-pinch driver for point projection radiography. The experiments were performed using CEPAGE, a low inductance pulsed power machine at First Light Fusion (2 MA, 1.4 µs), with a new vacuum transmission line and flyer load hardware designed specifically to give a line of sight for radiography. A broadband 10-20keV x-ray source was produced by a portable X-pinch driver (140kA, 350ns) [Strucka etal., Matter Radiat. Extremes 7, 016901 (2021)] and was used to image the flyer. Radiography compliments the pre-existing diagnostic suite, which consists of current probes, velocimetry, and side-on optical probing of the impact shock transmitted into a transparent sample. The platform allows for significant insights into the 2D and 3D nature of the flyer launch, such as deformation and instability formation. It was used to diagnose a 10 × 9 × 1mm3 aluminum flyer, which reached a peak velocity of 4.2 km s-1 before impact with a poly(methylmethacrylate) sample. The experimental configuration, on-shot source characterization, and the results from two flyer plate experiments on CEPAGE are discussed.

A MODEL OF THE MAGNETIC FIELD OF A CRACK SURROUNDED BY A UNIFORM EDDY CURRENT

Eddy current probes with uniform eddy currents, which are increasingly often used in practice, use the measurement of various components of the magnetic field of a defect arising when the current flows around surface cracks. The patterns of formation of components of the magnetic field strength of the defect that are orthogonal to the surface of the tested object (normal) Hn, as well as parallel to the plane of the crack (tangential) Ht are quite obvious and allow us to establish that their extreme values arise in the plane of the crack above its ends and center, respectively. At the same time, there does not exist a satisfactory model of the mechanism of formation of the axial component Hx, directed perpendicular to the crack plane. Both experiments and numerical calculations show the complex character of the function Hx. It has 4 regions with different directions in the vicinity of the crack, and its four extrema arise at a certain distance from the plane of the crack and are shifted relative to the axis of symmetry. The lack of a simple model of the formation of the function Hx makes it difficult to understand the functioning and develop appropriate eddy current transducers. The present paper addresses this problem.