Evaluation of a low-cost and low-noise active dry electrode for long-term biopotential recording

Wet Ag/AgCl electrodes, although very popular in clinical diagnosis, are not appropriate for expanding applications of wearable biopotential recording systems which are used repetitively and for a long time. Here, the development of a low-cost and low-noise active dry electrode is presented. The performance of the new electrodes was assessed for recording electrocardiogram (ECG) and electroencephalogram (EEG) in comparison with that of typical gel-based electrodes in a series of long-term recording experiments. The ECG signal recorded by these electrodes was well comparable with usual Ag/AgCl electrodes with a correlation up to 99.5% and mean power line noise below 6.0 μVRMS. The active electrodes were also used to measure alpha wave and steady state visual evoked potential by recording EEG. The recorded signals were comparable in quality with signals recorded by standard gel electrodes, suggesting that the designed electrodes can be employed in EEG-based rehabilitation systems and brain-computer interface applications. The mean power line noise in EEG signals recorded by the active electrodes (1.3 μVRMS) was statistically lower than when conventional gold cup electrodes were used (2.0 μVRMS) with a significant level of 0.05, and the new electrodes appeared to be more resistant to the electromagnetic interferences. These results suggest that the developed low-cost electrodes can be used to develop wearable monitoring systems for long-term biopotential recording

The Impact of Task-Based Language Teaching on the Development of Iranian EFL Learners’ ESP Reading Comprehension Skills

The present study primarily aimed at investigating the effect of Task-Based Language Teaching (TBLT) on development of the Iranian EFL learners’ ESP Reading Comprehension Skills. Moreover, it was aimed at investigating the probable difference between the TBLT-instructed students of Law and Mechanical Engineering with respect to their ESP reading skills, on the one hand, and the probable difference between TBLT-instructed males and females, on the other. In so doing, four groups of 25 participants (including two experimental groups and two control ones) were selected through cluster random sampling from among ESP students majoring in Law and Mechanical Engineering. After a four-week instruction treatment, the post-test was conducted to the participants. The results of the data analysis revealed that the experimental groups significantly performed better than the control groups in the post-test with respect to their reading comprehension scores. Furthermore, the results of independent samples t-test indicated that TBLT has been more effective on the Mechanical Engineering students than the Law students. Finally, the findings of the study were indicative of the fact that TBLT was more effective on females’ reading comprehension rather than on males’. Consequently, it can be concluded that TBLT can have a positive effect on students’ ESP reading ability. The findings of this study can be employed in different areas of second/foreign language teaching and learning to facilitate and improve the process of language learning.

Development of a Assistive Human-Computer device Based On Electro-Oculogram for Disabled People

Objective: In the study, a novel wearable miniaturized human computer interface system was designed and implemented. It allowed disabled people, who are not able to move their limbs voluntarily and speech overtly, to express their intentions and feelings just by moving their eyes. Materials & Methods: The developed system that is installed on a pair of glasses, records the electrooculogram signal and transfers the digitized data wirelessly to a laptop. Realtime analysis of the signals allows users to utilize two high performance graphical user interfaces a keypad and a game, just by their eye movements. The performance of the developed system was tested on six normal people, who typed a total number of 1071 characters successfully, to evaluate accuracy and rate of typing. It was also tested by four people with quadriplegia and cerebral palsy who performed a computer game by using their eye movements. Results: According to results of the experiments on normal people, the accuracy of recognizing the user's intention was obtained 94.1% and the average rate of communication was 7.72 characters per minute. Evaluating the usability of the system for disabled people showed that they were able to perform the computer game using their eyes. The percentage of success was evaluated as an average of 58.7%. Conclusion: The proposed system recorded and processed elecrooculogram signals with appropriate quality. The final prototype of the system was 2.6 cm× 4.5 cm in size and weighted only 15 grams. The total power consumption was measured as 123 mW. The designed keypad provided selection of each character by minimum eye movements. The system assures high performance for communication as well as high level of mobility and comfort for everyday use

Harvesting of energy from Human Walking with a piezoelectric transducer to supply a medical instrument

Abstract Introduction: Nowadays, the advanced technology of designing electronic circuits in very small size and with very low power consumption has led to development of wearable and implantable medical devices. However, the electronic circuits need power supply that is usually provided by relatively large and heavy batteries. The discharged batteries have to replaced or recharged for long time operation of electronic circuits. A new promising approach to overcome these limitations is harvesting the required power from the human body itself. Materials and Methods: In this paper, a harvesting system which implements a high performance piezoelectric transducer in the shoe was developed and evaluated for supplying the power required by a basic electronic circuit as a model of a wearable medical device. Results: The developed system was able to harvest 0.8mw of steady power with the use of only one piezoelectric transducer. The power was used to supply a basic micro-controller based electronic system steadily without the need for any batteries. Conclusion: The results demonstrate that low power monitoring or rehabilitation instruments may be supplied without batteries by harvesting the available energy in the walking process. Keywords: Energy harvesting, Human walking, Piezoelectric Transducer, Wearable Medical Device

An Arbitrary Waveform Wearable Neuro-stimulator System for Neurophysiology Research on Freely Behaving Animals

Portable wireless neuro-stimulators have been developed to facilitate long-term cognitive and behavioral studies on the central nervous system in freely moving animals. These stimulators can provide precisely controllable input(s) to the nervous system, without distracting the animal attention with cables connected to its body. In this study, a low power backpack neuro-stimulator was developed for animal brain researches that can provides arbitrary stimulus waveforms for the stimulation, while it is small and light weight to be used for small animals including rats. The system consists of a controller that uses an RF link to program and activate a small and light microprocessor-based stimulator. A Howland current source was implemented to produce precise current controlled arbitrary waveform stimulations. The system was optimized for ultra-low power consumption and small size. The stimulator was first tested for its electrical specifications. Then its performance was evaluated in a rat experiment when electrical stimulation of medial longitudinal fasciculus induced circling behavior. The stimulator is capable of delivering programmed stimulations up to ± 2 mA with adjusting steps of 1 μA, accuracy of 0.7% and compliance of 6 V. The stimulator is 15 mm × 20 mm × 40 mm in size, weights 13.5 g without battery and consumes a total power of only 5.l mW. In the experiment, the rat could easily carry the stimulator and demonstrated the circling behavior for 0.1 ms current pulses of above 400 μA. The developed system has a competitive size and weight, whereas providing a wide range of operation and the flexibility of generating arbitrary stimulation patterns ideal for long-term experiments in the field of cognitive and neuroscience research

Computational Insights into The Neuroprotective Action of Riluzole on 3-Acetylpyridine-Induced Ataxia in Rats

Objective: Intra-peritoneal administration of riluzole has been shown to preserve the membrane properties and firing characteristics of Purkinje neurons in a rat model of cerebellar ataxia induced by 3-acetylpyridine (3-AP). However, the exact mechanism(s) by which riluzole restores the normal electrophysiological properties of Purkinje neurons is not completely understood. Changes in the conductance of several ion channels, including the BK channels, have been proposed as a neuro protective target of riluzole. In this study, the possible cellular effects of riluzole on Purkinje cells from 3-AP-induced ataxic rats that could be responsible for its neuro protective action have been investigated by computer simulations.Materials and Methods: This is a computational stimulation study. The simulation environment enabled a change in the properties of the specific ion channels as the possible mechanism of action of riluzole. This allowed us to study the resulted changes in the firing activity of Purkinje cells without concerns about its other effects and interfering parameters in the experiments. Simulations were performed in the NEURON environment (Version 7.1) in a time step of 25 μs; analyses were conducted using MATLAB r2010a (The Mathworks). Data were given as mean ± SEM. Statistical analyses were performed by the student’s t test, and differences were considered significant if p<0.05.Results: The computational findings demonstrated that modulation of an individual ion channel current, as suggested by previous experimental studies, should not be considered as the only possible target for the neuro protective effects of riluzole to restore the normal firing activity of Purkinje cells from ataxic rats.Conclusion: Changes in the conductance of several potassium channels, including voltage-gated potassium (Kv1, Kv4) and big Ca2+-activated K+ (BK) channels may be responsible for the neuro protective effect of riluzole against 3-AP induced alterations in the firing properties of Purkinje cells in a rat model of ataxia

Design and implementation of a portable impedance cardiography system for noninvasive stroke volume monitoring

Measurement of the stroke volume (SV) and its changes over time can be very helpful for diagnosis of dysfunctions in the blood circulatory system and monitoring their treatments. Impedance cardiography (ICG) is a simple method of measuring the SV based on changes in the instantaneous mean impedance of the thorax. This method has received much attention in the last two decades because it is noninvasive, easy to be used, and applicable for continuous monitoring of SV as well as other hemodynamic parameters. The aim of this study was to develop a low-cost portable ICG system with high accuracy for monitoring SV. The proposed wireless system uses a tetrapolar configuration to measure the impedance of the thorax at 50 kHz. The system consists of carefully designed precise voltage-controlled current source, biopotential recorder, and demodulator. The measured impedance was analyzed on a computer to determine SV. After evaluating the system's electronic performance, its accuracy was assessed by comparing its measurements with the values obtained from Doppler echocardiography (DE) on 5 participants. The implemented ICG system can noninvasively provide a continuous measure of SV. The signal to noise ratio of the system was measured above 50 dB. The experiments revealed that a strong correlation (r = 0.89) exists between the measurements by the developed system and DE (P < 0.05). ICG as the sixth vital sign can be measured simply and reliably by the developed system, but more detailed validation studies should be conducted to evaluate the system performance. There is a good promise to upgrade the system to a commercial version domestically for clinical use in the future

Automated Multi-Wavelength Quality Assessment of Photoplethysmography Signals Using Modulation Spectrum Shape Features

Photoplethysmography (PPG) is used to measure blood volume changes in the microvascular bed of tissue. Information about these changes along time can be used for estimation of various physiological parameters, such as heart rate variability, arterial stiffness, and blood pressure, to name a few. As a result, PPG has become a popular biological modality and is widely used in wearable health devices. However, accurate measurement of various physiological parameters requires good-quality PPG signals. Therefore, various signal quality indexes (SQIs) for PPG signals have been proposed. These metrics have usually been based on statistical, frequency, and/or template analyses. The modulation spectrogram representation, however, captures the second-order periodicities of a signal and has been shown to provide useful quality cues for electrocardiograms and speech signals. In this work, we propose a new PPG quality metric based on properties of the modulation spectrum. The proposed metric is tested using data collected from subjects while they performed various activity tasks contaminating the PPG signals. Experiments on this multi-wavelength PPG dataset show the combination of proposed and benchmark measures significantly outperforming several benchmark SQIs with improvements of 21.3% BACC (balanced accuracy) for green, 21.6% BACC for red, and 19.0% BACC for infrared wavelengths, respectively, for PPG quality detection tasks. The proposed metrics also generalize for cross-wavelength PPG quality detection tasks

A Smart Textile Band Achieves High-Quality Electrocardiograms in Unrestrained Horses

Electrocardiography (ECG) is an essential tool in assessing equine health and fitness. However, standard ECG devices are expensive and rely on the use of adhesive electrodes, which may become detached and are associated with reduced ECG quality over time. Smart textile electrodes composed of stainless-steel fibers have previously been shown to be a suitable alternative in horses at rest and during exercise. The objective of this study was to compare ECG quality using a smart textile girth band knit with silver and carbon yarns to standard adhesive silver/silver chloride (Ag/AgCl) electrodes. Simultaneous three-lead ECGs were recorded using a smart textile band and Ag/AgCl electrodes in 22 healthy, mixed-breed horses that were unrestrained in stalls. ECGs were compared using the following quality metrics: Kurtosis (k) value, Kurtosis signal quality index (kSQI), percentage of motion artifacts (%MA), peak signal amplitude, and heart rate (HR). Two-way ANOVA with Tukey’s multiple comparison tests was conducted to compare each metric. No significant differences were found in any of the assessed metrics between the smart textile band and Ag/AgCl electrodes, with the exception of peak amplitude. Kurtosis and kSQI values were excellent for both methods (textile mean k = 21.8 ± 6.1, median kSQI = 0.98 [0.92–1.0]; Ag/AgCl k = 21.2 ± 7.6, kSQI = 0.99 [0.97–1.0]) with <0.5% (<1 min) of the recording being corrupted by MAs for both. This study demonstrates that smart textiles are a practical and reliable alternative to the standard electrodes typically used in ECG monitoring of horses