rss_2.0Journal of Electrical Bioimpedance FeedSciendo RSS Feed for Journal of Electrical Bioimpedance of Electrical Bioimpedance Feed growth monitoring in a tetrapolar electrode configuration<abstract> <title style='display:none'>Abstract</title> <p>There are various methods for cell growth monitoring. However, most of these methods have drawbacks, such as being invasive, not providing real-time results, or being costly. In this study, we present an alternate method of cell growth monitoring, which is low-cost, non-invasive, real-time, and uses Electrical Impedance Spectro-scopy (EIS). In this work, commercially available culture plates were fitted with custom tetrapolar electrodes, and mouse cells were cultured on them. The variation of culture media impedance, resulting from cell growth, proliferation and other metabolic activities, was recorded over a period of seven days. The results demonstrated an initial increase in impedance corresponding with the cell growth phase, followed by a decrease during the cell death (apoptosis) phase, as confirmed by microscope images. Overall, the results show that our method to monitor cell growth using tetrapolar electrodes is promising and can be further refined for related applications.</p> </abstract>ARTICLEtrue as an alternative tool for subjective, visual scoring of a prevalent ham quality defect<abstract> <title style='display:none'>Abstract</title> <p>The detection of meat quality defects can involve both subjective and objective methods. PSE-like meat is linked to a common pork defect and can be caused by rapid post-mortem damage of muscle fibers. This damage can again be linked to various factors, such as a low ultimate pH or a higher slaughter weight. PSE-like defects are characterized by discoloration, structural damage, and excessive moisture loss. However, the lack of suitable instrument-based methods makes the detection of PSE-like defects difficult, and subjective methods typically suffer from poorer reproducibility. The objective of this study was to establish how subjective visual evaluation correlates with electrical impedance spectroscopy and with traditional quality parameters. To do so, visual scoring was performed together with measurements of bioimpedance, color, and pH in two ham muscles (Adductor, Semimembranosus) for 136 animals 24-hours post-mortem. When comparing with visual scoring, Pearson correlation analysis shows the strongest correlation for bioimpedance (<italic>P<sub>y</sub></italic>, r = −0.46, R<sup>2</sup> = 21%), followed by pH<sub>u</sub> (r = 0.44, R<sup>2</sup> = 19%). When using all five quality measures, i.e., <italic>P<sub>y</sub></italic>, pH<sub>u</sub>, and CIELAB <italic>L</italic><sup>*</sup> <italic>a</italic><sup>*</sup> <italic>b</italic><sup>*</sup>, the multivariate regression model had a prediction error of 0.76 for the visual scores. This was close to the error describing the subjective bias of visual scoring, more specifically the prediction error between the two observers (0.85). In all, <italic>P<sub>y</sub></italic> showed the strongest correlation among instrument-based quality tests and alone may be used for predicting pork ham structural defects, i.e., as an instrument-based alternative for subjective, visual scoring. However, an instrument that combines <italic>P<sub>y</sub></italic> with pH and/or <italic>L</italic>*<italic>a</italic>*<italic>b</italic>* would improve the prediction of PSE-like quality defects.</p> </abstract>ARTICLEtrue learning-enhanced gesture recognition through impedance signal analysis<abstract> <title style='display:none'>Abstract</title> <p>Gesture recognition is a crucial aspect in the advancement of virtual reality, healthcare, and human-computer interaction, and requires innovative methodologies to meet the increasing demands for precision. This paper presents a novel approach that combines Impedance Signal Spectrum Analysis (ISSA) with machine learning to improve gesture recognition precision. A diverse dataset that included participants from various demographic backgrounds (five individuals) who were each executing a range of predefined gestures. The predefined gestures were designed to encompass a broad spectrum of hand movements, including intricate and subtle variations, to challenge the robustness of the proposed methodology. The machine learning model using the K-Nearest Neighbors (KNN), Gradient Boosting Machine (GBM), Naive Bayes (NB), Logistic Regression (LR), Random Forest (RF), and Support Vector Machine (SVM) algorithms demonstrated notable precision in performance evaluations. The individual accuracy values for each algorithm are as follows: KNN, 86%; GBM, 86%; NB, 84%; LR, 89%; RF, 87%; and SVM, 87%. These results emphasize the importance of impedance features in the refinement of gesture recognition. The adaptability of the model was confirmed under different conditions, highlighting its broad applicability.</p> </abstract>ARTICLEtrue protocol development: Implementing systematic contextual memory to enhance real-time fMRI neurofeedback<abstract> <title style='display:none'>Abstract</title> <sec> <title style='display:none'>Objective</title> <p>The goal of this study was to explore the development and implementation of a protocol for real-time fMRI neurofeedback (rtfMRI-nf) and to assess the potential for enhancing the selective brain activation using stimuli from Virtual Reality (VR). In this study we focused on two specific brain regions, supplementary motor area (SMA) and right inferior frontal gyrus (rIFG). Publications by other study groups have suggested impaired function in these specific brain regions in patients with the diagnoses Attention Deficit Hyperactivity Disorder (ADHD) and Tourette’s Syndrome (TS). This study explored the development of a protocol to investigate if attention and contextual memory may be used to systematically strengthen the procedure of rtfMRI-nf.</p> </sec> <sec> <title style='display:none'>Methods</title> <p>We used open-science software and platforms for rtfMRI-nf and for developing a simulated repetition of the rtfMRI-nf brain training in VR. We conducted seven exploratory tests in which we updated the protocol at each step. During rtfMRI-nf, MRI images are analyzed live while a person is undergoing an MRI scan, and the results are simultaneously shown to the person in the MRI-scanner. By focusing the analysis on specific regions of the brain, this procedure can be used to help the person strengthen conscious control of these regions. The VR simulation of the same experience involved a walk through the hospital toward the MRI scanner where the training sessions were conducted, as well as a subsequent simulated repetition of the MRI training. The VR simulation was a 2D projection of the experience.</p> <p>The seven exploratory tests involved 19 volunteers. Through this exploration, methods for aiming within the brain (e.g. masks/algorithms for coordinate-system control) and calculations for the analyses (e.g. calculations based on connectivity versus activity) were updated by the project team throughout the project. The final procedure involved three initial rounds of rtfMRI-nf for learning brain strategies. Then, the volunteers were provided with VR headsets and given instructions for one week of use. Afterward, a new session with three rounds of rtfMRI-nf was conducted.</p> </sec> <sec> <title style='display:none'>Results</title> <p>Through our exploration of the indirect effect parameters – brain region activity (directed oxygenated blood flow), connectivity (degree of correlated activity in different regions), and neurofeedback score – the volunteers tended to increase activity in the reinforced brain regions through our seven tests. Updates of procedures and analyses were always conducted between pilots, and never within. The VR simulated repetition was tested in pilot 7, but the role of the VR contribution in this setting is unclear due to underpowered testing.</p> </sec> <sec> <title style='display:none'>Conclusion</title> <p>This proof-of-concept protocol implies how rtfMRI-nf may be used to selectively train two brain regions (SMA and rIFG). The method may likely be adapted to train any given region in the brain, but readers are advised to update and adapt the procedure to experimental needs.</p> </sec> </abstract>ARTICLEtrue study of a locally developed six electrode focused impedance method<abstract> <title style='display:none'>Abstract</title> <p>The Focused Impedance Method (FIM) is a new technique of electrical bioimpedance measurements in the human body. The idea originated in Bangladesh and provides an opportunity for localized measurement of bioimpedance down to reasonable depths from the body surface using skin surface electrodes. This has potential applications for physiological studies of targeted organs in the body and in detecting or diagnosing diseases and disorders. FIM is based on the age-old Tetra-Polar Impedance Measurement (TPIM) but provides a few significant improvements.</p> <p>Technology must be developed indigenously to obtain long-term benefits, particularly in Low and Medium Income countries (LMIC). This paper presents an experimental sensitivity study of the six-electrode version of the Focused Impedance method (FIM-6) with the circuit and phantom indigenously designed in Nepal. The work involved sensitivity studies of both FIM-6 and TPIM with the necessary circuit blocks developed through experimental validation. The sensitivity studies were performed on a simple 2D phantom with different electrode arrangements for FIM-6 and linear TPIM. A cylindrical object was placed at different positions for this study. The FIM-6 gave a high sensitivity in the central part, which remained almost constant within a small region that may be termed as the focused region. On the other hand, TPIM results fell off sharply away from the central point, making it unsuitable for practical measurements on target organs. Besides, there were areas with large negative sensitivities in TPIM, which were much smaller in FIM. The results obtained through this work clearly show the improvement offered by FIM over TPIM.</p> </abstract>ARTICLEtrue between dual indirect methods for assessing fat percentage<abstract> <title style='display:none'>Abstract</title> <p>In the last decades there is a growing interest in the evaluation of human body composition for being an important part of the integral assessment of individuals. Its use has been extended to different disciplines associated with health care (medicine, nutrition, physiotherapy), and to sports and population fields. Specifically, fat percentage can be related to innumerable diseases. However, there are discrepancies in the results of fat percentage measurement measured by different methods.</p> <sec> <title style='display:none'>Objective</title> <p>To evaluate the concordance between two low-cost and easily accessible double indirect methods, which have been used indistinctly in different studies where access to more accurate methods is not available, and to determine fat percentage and its relationship with age, sex, body mass index (BMI), waist circumference, level of physical activity and sedentary hours.</p> </sec> <sec> <title style='display:none'>Materials and Method</title> <p>Twenty-four persons between 18 and 38 years and 28 between 39 and 59 years from a university community were evaluated. Calculations were made: BMI, fat % was estimated by anthropometry with a digital adipometer (Skyndex System I USA) and by Electrical Bioimpedance Analysis – BIA (Biody Expert ZM II FRA), physical activity level and sedentary hours were determined with the short IPAQ questionnaire. Pearson's correlation coefficient, Bland &amp; Altman's graphical method and Lin's concordance correlation index were calculated. The significance level p&lt;0.05 was estimated.</p> </sec> <sec> <title style='display:none'>Results</title> <p>The fat percentage by anthropometry was: 30.5% ±8.5 (18–38 years) 35.0% ±6.7 (39–59 years); by BIA 27.0% ±7.3 (18–38 years) and 29.2% ±7.0 (39–59 years). Both techniques showed good correlation, but low degree of concordance (Lin index less than 0.9) except for the group of young persons with moderate level of physical activity (0.95).</p> </sec> <sec> <title style='display:none'>Conclusions</title> <p>The doubly indirect methods used in the study showed strong correlation, but low concordance, so their use is not recommended indistinctly for the follow-up of a particular case. According to the study data for this specific population in young people with moderate physical activity, follow-up could be performed with either of the two methods.</p> </sec> </abstract>ARTICLEtrue A non-invasive method for neuromonitoring<abstract> <title style='display:none'>Abstract</title> <p>In neurocritical care, the gold standard method is intracranial pressure (ICP) monitoring for the patient's lifesaving. Since it is an invasive method, it is desirable to use an alternative, noninvasive technique. The computerized real-time invasive cerebral blood flow (CBF) autoregulation (AR) monitoring calculates the status of CBF AR, called the pressure reactivity index (PRx). Studies documented that the electrical impedance of the head (Rheoencephalography – REG) can detect the status of CBF AR (REGx) and ICP noninvasively. We aimed to test REG to reflect ICP and CBF AR.</p> <p>For nineteen healthy subjects we recorded bipolar bifrontal and bitemporal REG derivations and arm bioimpedance pulses with a 200 Hz sampling rate. The challenges were a 30-second breath-holding and head-down-tilt (HDT – Trendelenburg) position. Data were stored and processed offline. REG pulse wave morphology and REGx were calculated.</p> <p>The most relevant finding was the significant morphological change of the REG pulse waveform (2<sup>nd</sup> peak increase) during the HDT position. Breath-holding caused REG amplitude increase, but it was not significant. REGx in male and female group averages have similar trends during HDT by indicating the active status of CBF AR.</p> <p>The morphological change of REG pulse wave during HDT position was identical to ICP waveform change during increased ICP, reflecting decreased intracranial compliance. A correlation study between ICP and REG was initiated in neurocritical care patients. The noninvasive REG monitoring would also be useful in space research as well as in military medicine during the transport of wounded service members as well as for fighter pilots to indicate the loss of CBF and consciousness.</p> </abstract>ARTICLEtrue of the effect of several moisturizing creams using the low frequency electrical susceptance approach<abstract> <title style='display:none'>Abstract</title> <p>Moisturizers are cosmetic compounds designed to increase the moisture content of the skin. There are many types of these products in the market making it difficult for consumers to select the most effective moisturizer according to their age and gender. Hence, the aim of this study was to evaluate the effects of different moisturizers on skin hydration as well as to figure out any dependencies of the effects of these products on age or gender-related differences. We investigated the short-term moisturizing effects of five different skin moisturizers on 60 participants by using a low frequency electrical instrument. Skin surface susceptance was recorded and compared before and after the application of moisturizers. Statistically significant differences were observed in the moisturizing effect among different types of products. However, with respect to gender and age differences, there were insignificant differences in the effects of the moisturizers. Results of this study suggest that some types of moisturizers that exist in the markets are not as effective as required, which calls for a further evaluation of the moisturizers before entering markets and offering them for sale. In addition, findings suggest that gender or age differences are perhaps not important to consider in the application of moisturizers.</p> </abstract>ARTICLEtrue bioimpedance in the era of artificial intelligence needle electrical bioimpedance to provide information on needle tip relationship to target nerve prior to local anesthetic deposition in peripheral nerve block (USgPNB) procedures<abstract> <title style='display:none'>Abstract</title> <p>Ultrasound guided peripheral nerve block (USgPNB) refers to anaesthetic techniques to deposit local anesthetic next to nerves, permitting painful surgery without necessitating general anesthesia. Needle tip position prior to local anesthetic deposition is a key determinant of block success and safety. Nerve puncture and intra-neural injection of local anesthetic can cause permanent nerve injury. Currently ultrasound guidance is not sufficiently sensitive to reliably detect needle to nerve proximity. Feedback with bioimpedance data from the smart needle tip might provide the anesthetist with information as to the relationship between the needle tip and the target nerve prior to local anesthetic deposition.</p> <p>Bioimpedance using a smart needle integrated with a two-electrode impedance sensor has been developed to determine needle to nerve proximity during USgPNB. Having obtained all necessary ethical and regulatory approvals, <italic>in vivo</italic> data on brachial plexus, vagus, femoral and sciatic nerves were obtained from seven pig models using the smart needle bioimpedance system. The excision and histological analysis of above peripheral nerves and observation of the architecture and structure of nerves by means of histology allow the calculation of the ratios of connective tissue to neural tissue to determine the influence of this variable on absolute impedance. The ratio results give extra clinical data and explain the hetrogeneity of impedance data in the pig models and the hypothesis that connective tissue with intra-neural fat has higher impedance than neural tissue.</p> </abstract>ARTICLEtrue of physiological concentrations of GABA using dielectric spectroscopy - A pilot study<abstract> <title style='display:none'>Abstract</title> <p>Gamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter that is present at a relatively low level throughout the normal adult human brain. Abnormal GABA levels are found in people with neurodegenerative disorders such as Parkinson’s disease, epilepsy, schizophrenia, depression, and others. Being able to measure the GABA concentration would be beneficial for patient groups with fluctuating GABA levels for better diagnosis and treatment. In this study, we explore the feasibility of using dielectric relaxation spectroscopy for the detection of GABA concentrations within a physiological range, with the perspective of miniaturization and use during implantation. Utilizing machine learning techniques, we were able to differentiate GABA concentrations down to 5 μm. This work investigates a novel use of dielectric relaxation spectroscopy, to assess if physiological GABA concentrations can be detected through permittivity measurements.</p> </abstract>ARTICLEtrue phase angle correlates with pre-operative markers in total joint arthroplasty<abstract> <title style='display:none'>Abstract</title> <sec> <title style='display:none'>Background</title> <p>Bioimpedance derived whole body phase angle (ϕ), a measure of cellular integrity, has been identified as an independent marker of morbidity and mortality in many medical and surgical specialties. While similar measures of water homeostasis like extracellular edema (EE) have been associated with pre-operative risk, ϕ has not been studied in orthopaedics, despite potential to serve as a pre-operative marker. This study aims to identify relationships between ϕ, EE, and body composition metrics, laboratory values, patient reported outcomes, and comorbidities.</p> </sec> <sec> <title style='display:none'>Methods</title> <p>Multi-frequency bioimpedance analysis (BIA) records, laboratory values, and patient reported outcomes of adult patients presenting to an academic arthroplasty clinic were retrospectively reviewed. Correlation coefficients between ϕ, EE, and reviewed information were conducted.</p> </sec> <sec> <title style='display:none'>Results</title> <p>ϕ was significantly correlated (p&lt;0.001) most positively with measures of lean tissue such as skeletal muscle mass (r=0.48), appendicular skeletal muscle index (r=0.39), lean body mass (r=0.43), and dry lean mass (r=0.47), while it held negative correlations (p&lt;0.001) with age (r= -0.55), and body fat mass (r= -0.11). ϕ was not correlated with body mass index (BMI, p = 0.204). In contrast, EE demonstrated its strongest positive correlations (p&lt;0.001) with body fat mass (r=0.32), age (r=0.50), and BMI (r=0.26), and its strongest negative correlations (p&lt;0.001) with serum albumin (r= -0.37) and total protein (r= -0.23).</p> </sec> <sec> <title style='display:none'>Conclusions</title> <p>Based on their associations with markers of health and fitness, BIA determined ϕ and EE demonstrate relationships to markers currently implemented in orthopaedic practice. This likely indicates that ϕ has potential as a comprehensive surrogate for several commonly used markers to quantify pre-operative risk. In the future, ϕ may aid in developing risk-stratifications for intervention and prevention of complications.</p> </sec> </abstract>ARTICLEtrue biomedical engineering: Leveraging Hjorth features for electroencephalography signal analysis<abstract> <title style='display:none'>Abstract</title> <p>Biomedical engineering stands at the forefront of medical innovation, with electroencephalography (EEG) signal analysis providing critical insights into neural functions. This paper delves into the utilization of EEG signals within the MILimbEEG dataset to explore their potential for machine learning-based task recognition and diagnosis. Capturing the brain’s electrical activity through electrodes 1 to 16, the signals are recorded in the time-domain in microvolts. An advanced feature extraction methodology harnessing Hjorth Parameters—namely Activity, Mobility, and Complexity—is employed to analyze the acquired signals. Through correlation analysis and examination of clustering behaviors, the study presents a comprehensive discussion on the emergent patterns within the data. The findings underscore the potential of integrating these features into machine learning algorithms for enhanced diagnostic precision and task recognition in biomedical applications. This exploration paves the way for future research where such signal processing techniques could revolutionize the efficiency and accuracy of biomedical engineering diagnostics.</p> </abstract>ARTICLEtrue knowledge-based peak current mode control of electrosurgical generators for improved output power regulation<abstract> <title style='display:none'>Abstract</title> <p>Electrosurgical generators (ESG) are widely used in medical procedures to cut and coagulate tissue. Accurate control of the output power is crucial for surgical success, but can be challenging to achieve. In this paper, a novel expert knowledge-based peak current mode controller (EK-PCMC) is proposed to regulate the output power of an ESG. The EK-PCMC leverages expert knowledge to adapt to changes in tissue impedance during surgical procedures. We compared the performance of the EK-PCMC with the classical peak current mode controller (PCMC) and fuzzy PID controller. The results demonstrate that the EK-PCMC significantly outperformed the PCMC, reducing the integral square error (ISE) and integral absolute error (IAE) by a factor of 3.88 and 4.86, respectively. In addition, the EK-PCMC outperformed the fuzzy PID controller in terms of transient response and steady-state performance. Our study highlights the effectiveness of the proposed EK-PCMC in improving the regulation of the output power of an ESG and improving surgical outcomes.</p> </abstract>ARTICLEtrue layer classification by feedforward neural network in bioelectrical impedance spectroscopy<abstract> <title style='display:none'>Abstract</title> <p>Conductivity change in skin layers has been classified by source indicator <italic>o<sup>k</sup></italic> (<italic>k</italic>=1: Stratum corneum, <italic>k</italic>=2: Epidermis, <italic>k</italic>=3: Dermis, <italic>k</italic>=4: Fat, and <italic>k</italic>=5: Stratum corneum + Epidermis) trained from feedforward neural network (FNN) in bioelectrical impedance spectroscopy (BIS). In BIS studies, treating the skin as a bulk, limits the differentiation of conductivity changes in individual skin layers, however skin layer classification using FNN shows promise in accurately categorizing skin layers, which is essential for predicting source indicators <italic>o<sup>k</sup></italic> and initiating skin dielectric characteristics diagnosis. The <italic>o<sup>k</sup></italic> is trained by three main conceptual points which are (i) implementing FNN for predicting <italic>k</italic> in conductivity change, (ii) profiling four impedance inputs <italic>α<sub>ξ</sub></italic> consisting of magnitude input <italic>α</italic>|<sub><italic>z</italic></sub>|, phase angle input <italic>α<sub>θ</sub></italic>, resistance input <italic>α<sub>R</sub></italic>, and reactance input <italic>α<sub>x</sub></italic> for filtering nonessential input, and (iii) selecting low and high frequency pair <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_joeb-2023-0004_ieq_001.png"/><mml:math xmlns:mml="" display="inline"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msubsup><mml:mi>f</mml:mi><mml:mi>r</mml:mi><mml:mrow><mml:mi>l</mml:mi><mml:mi>h</mml:mi></mml:mrow></mml:msubsup></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math><tex-math>$$(f_{r}^{lh})$$</tex-math></alternatives></inline-formula> by distribution of relaxation time (DRT) for eliminating parasitic noise effect. The training data set of FNN is generated to obtain the <italic>α<sub>ξ</sub></italic> ∈ <italic><bold>R</bold></italic><sup>10×17×10</sup> by 10,200 cases by simulation under configuration and measurement parameters. The trained skin layer classification is validated through experiments with porcine skin under various sodium chloride (NaCl) solutions <italic>C<sub>NaCl</sub></italic> = {15, 20, 25, 30, 35}[mM] in the dermis layer. FNN successfully classified conductivity change in the dermis layer from experiment with accuracy of 90.6% for the bipolar set-up at <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_joeb-2023-0004_ieq_002.png"/><mml:math xmlns:mml="" display="inline"><mml:mrow><mml:msubsup><mml:mi>f</mml:mi><mml:mn>6</mml:mn><mml:mrow><mml:mi>l</mml:mi><mml:mi>h</mml:mi></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>10</mml:mn><mml:mtext> </mml:mtext><mml:mo>&amp;</mml:mo><mml:mn>100</mml:mn><mml:mtext> </mml:mtext><mml:mo stretchy="false">[</mml:mo><mml:mtext>kHz]</mml:mtext></mml:mrow></mml:math><tex-math>$$f_{6}^{lh}=10\,\And 100\,{\rm{[kHz]}}$$</tex-math></alternatives></inline-formula> and with the same accuracy for the tetrapolar at <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_joeb-2023-0004_ieq_003.png"/><mml:math xmlns:mml="" display="inline"><mml:mrow><mml:msubsup><mml:mi>f</mml:mi><mml:mn>8</mml:mn><mml:mrow><mml:mi>l</mml:mi><mml:mi>h</mml:mi></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>35</mml:mn><mml:mtext> </mml:mtext><mml:mo>&amp;</mml:mo><mml:mn>100</mml:mn><mml:mtext> </mml:mtext><mml:mo stretchy="false">[</mml:mo><mml:mtext>kHz]</mml:mtext></mml:mrow></mml:math><tex-math>$$f_{8}^{lh}=35\,\And 100\,{\rm{[kHz]}}$$</tex-math></alternatives></inline-formula>. The measurement noise and systematic error in the experimental results are minimized by the proposed method using the feature extraction based on <italic>α<sub>ξ</sub></italic> at <inline-formula><alternatives><inline-graphic xmlns:xlink="" xlink:href="graphic/j_joeb-2023-0004_ieq_004.png"/><mml:math xmlns:mml="" display="inline"><mml:mrow><mml:msubsup><mml:mi>f</mml:mi><mml:mi>r</mml:mi><mml:mrow><mml:mi>l</mml:mi><mml:mi>h</mml:mi></mml:mrow></mml:msubsup></mml:mrow></mml:math><tex-math>$$f_{r}^{lh}$$</tex-math></alternatives></inline-formula>.</p> </abstract>ARTICLEtrue fresh look at sports PSM-systems<abstract> <title style='display:none'>Abstract</title> <p>The aim of the proposed study is to reveal the correlations between the dynamics of Respiratory Rate (RR) and Heart Rate (HR) during intermittent physical work at maximum power on a cycle ergometer. The stage of investigating the General functional athlete readiness (GFAR) was conducted using the sports standard “R-Engine” and the cycle ergometer in 16 volunteers (10 men, 6 women) whose average age was 21±1.17 years. To determine the athletic potential of the volunteers in this study, we used our own Coefficient of Anaerobic Capacity (CANAC Q, beats). Continuous registration of the heart rate and respiratory rate of volunteers in the maximum power sports test was performed by the “RheoCardioMonitor” system with a module of the athlete functional readiness based on the method of Transthoracic electrical impedance rheography (TEIRG). The degree of correlation of functional indicators (M, HRM, GFAR) with CANAC Q in all experimental series of the study group as a whole (n=80) was at a very high level, which confirmed the effectiveness of using the Coefficient of Anaerobic Capacity (CANAC Q) in assessing the general functional athlete readiness of the volunteers. CANAC Q is measured in “beats” of the heart and is recorded very accurately using the method of transthoracic electrical impedance rheography (TEIRG). For this reason, as a promising sports PSM-system, CANAC Q can replace the methods for determining the functional athlete readiness by blood lactate concentration and maximum oxygen consumption.</p> </abstract>ARTICLEtrue detection using mercaptopropionic acid and cysteamine for electrodes surface modification<abstract><title style='display:none'>Abstract</title><p>Gold electrodes are often not suitable for dopamine measurements as dopamine creates a non-conducting polymer layer on the surface of the electrodes, which leads to increased amount of electrode passivity with the gradual increase in voltammograms measurement. This work presents the impedance spectroscopy and cyclic-voltammetry comparative study for dopamine detection with two modifications for the surface of Au electrodes; cysteamine and mercaptopropionic acid for thermally bonded and ultrasonically welded microfluidic chips, respectively. The effects of optimized tubing selection, bonding techniques, and cleaning methods of the devices with KOH solution played crucial role for improvements in dopamine detection, which are observed in the results. Furthermore, comparison for the modification with unmodified chips, and finding the unknown concentration of dopamine solution using flow injection techniques, is also illustrated.</p></abstract>ARTICLEtrue activity responses for quantitative assessment of felt pain<abstract><title style='display:none'>Abstract</title><p>Accurate assessment of experienced pain is a well-known problem in the clinical practices. Therefore, a proper method for pain detection is highly desirable. Electrodermal activity (EDA) is known as a measure of the sympathetic nervous system activity, which changes during various mental stresses. As pain causes mental stress, EDA measures may reflect the felt pain. This study aims to evaluate changes in skin conductance responses (SCRs), skin potential responses (SPRs), and skin susceptance responses (SSRs) simultaneously as a result of sequences of electrical (painful) stimuli with different intensities. EDA responses as results of painful stimuli were recorded from 40 healthy volunteers. The stimuli with three different intensities were produced by using an electrical stimulator. EDA responses significantly changed (increased) with respect to the intensity of the stimuli. Both SCRs and SSRs showed linear relationship with the painful stimuli. It was found that the EDA responses, particularly SCRs (<italic>p</italic> &lt; 0.001) and SSRs (<italic>p</italic> = 0.001) were linearly affected by the intensity of the painful stimuli. EDA responses, in particular SCRs, may be used as a useful indicator for assessment of experienced pain in clinical settings.</p></abstract>ARTICLEtrue memristor bridge circuit realized with human skin<abstract><title style='display:none'>Abstract</title><p>It has been demonstrated before that human skin can be modeled as a memristor (memory resistor). Here we realize a memristor bridge by applying two voltages of opposite signs at two different skin sites. By this setup it is possible to use human skin as a frequency doubler and half-wave rectifier which is an application of the non-linear electrical properties of human skin. The corresponding electrical measurements are non-linear since these are affected by the applied stimulus itself.</p></abstract>ARTICLEtrue single differential equation description of membrane properties underlying the action potential and the axon electric field<abstract><title style='display:none'>Abstract</title><p>In a succession of articles published over 65 years ago, Sir Alan Lloyd Hodgkin and Sir Andrew Fielding Huxley established what now forms our physical understanding of excitation in nerve, and how the axon conducts the action potential. They uniquely quantified the movement of ions in the nerve cell during the action potential, and demonstrated that the action potential is the result of a depolarizing event across the cell membrane. They confirmed that a complete depolarization event is followed by an abrupt increase in voltage that propagates longitudinally along the axon, accompanied by considerable increases in membrane conductance. In an elegant theoretical framework, they rigorously described fundamental properties of the Na<sup>+</sup> and K<sup>+</sup> conductances intrinsic to the action potential.</p><p>Notwithstanding the elegance of Hodgkin and Huxley’s incisive and explicative series of discoveries, their model is mathematically complex, relies on no small number of stochastic factors, and has no analytical solution. Solving for the membrane action potential and the ionic currents requires integrations approximated using numerical methods. In this article I present an analytical formalism of the nerve action potential, <italic>V<sub>m</sub></italic> and that of the accompanying cell membrane electric field, <italic>E<sub>m</sub></italic>. To conclude, I present a novel description of <italic>V<sub>m</sub></italic> in terms of a single, nonlinear differential equation. This is an original stand-alone article: the major contribution is the latter, and how this description coincides with the cell membrane electric field. This work has necessitated unifying information from two preceding papers [1,2], each being concerned with the development of closed-form descriptions of the nerve action potential, <italic>V<sub>m</sub></italic>.</p></abstract>ARTICLEtrue