DC Level Research Articles

Characterization of lipid peroxidation processes and antioxidant defense in parturients with COVID-19

Aim. The aim of the study was to investigate the functional state of the «lipid peroxidation - antioxidant defense» system in the peripheral blood of parturients with mild and severe COVID-19.Materials and methods. This casecontrol study examined 95 parturients with confirmed COVID-19 diagnosis in the third trimester, divided into two groups based on the severity of the disease. Group 1a included parturients with severe COVID-19 (community-acquired pneumonia, n=48), while group 1b consisted of patients with mild COVID-19 (acute respiratory viral infection, n=47). The control group was composed of 45 parturients without a prior or current diagnosis of COVID-19. The average age of women in the study groups was 23.9±0.50 years, and 24.4±0.60 years in the control group (p>0.05). Peripheral venous blood served as the material for the study. Spectrophotometric methods were used to examine the concentrations of primary (diene conjugates - DC) and final (active thiobarbituric acid products - TBARS) products of lipoperoxidation. The content of 8-isoprostane, total antioxidant capacity of plasma components, and phospholipase A2 were investigated using enzymelinked immunosorbent assay (ELISA).Results. Study showed that parturients with severe COVID-19 had increased levels of phospholipase A2 by 2.1 times (p<0.001), oxidative stress markers: diene conjugate concentrations by 1.94 times (p><0.001), TBARS by 2.2 times (p><0.001), and 8-isoprostane by more than 2 times (p><0.001), along with a simultaneous decrease in the total antioxidant capacity of blood plasma components by 1.7 times (p><0.001) compared to the control group. In the group of parturients with mild COVID-19, the studied indicators changed less significantly. Conclusion. The study established the pathogenetic role of SARS-CoV-2 in disrupting the functional system of «lipid peroxidation - antioxidant defense» and the development of oxidative stress in parturients who had COVID-19 in the third trimester. A dependency of oxidative stress marker concentrations in peripheral blood on the severity of COVID-19 was identified. It was shown that COVID-19 in the third trimester of pregnancy is associated with high levels of phospholipase A2, an imbalance in the prooxidant-antioxidant system, characterized by a reduction in the level of total antioxidant capacity and an increase in oxidative modification products of biomolecules, expressed by the growth of DC, TBARS, and 8-isoprostane levels, leading to oxidative stress correlated with the severity of lung damage. Key words: COVID-19, parturients, lipid peroxidation, antioxidant defense, oxidative stress> ˂ 0.001), oxidative stress markers: diene conjugate concentrations by 1.94 times (p ˂ 0.001), TBARS by 2.2 times (p ˂ 0.001), and 8-isoprostane by more than 2 times (p ˂ 0.001), along with a simultaneous decrease in the total antioxidant capacity of blood plasma components by 1.7 times (p ˂ 0.001) compared to the control group. In the group of parturients with mild COVID-19, the studied indicators changed less significantly.Conclusion. The study established the pathogenetic role of SARS-CoV-2 in disrupting the functional system of «lipid peroxidation - antioxidant defense» and the development of oxidative stress in parturients who had COVID-19 in the third trimester. A dependency of oxidative stress marker concentrations in peripheral blood on the severity of COVID-19 was identified. It was shown that COVID-19 in the third trimester of pregnancy is associated with high levels of phospholipase A2, an imbalance in the prooxidant-antioxidant system, characterized by a reduction in the level of total antioxidant capacity and an increase in oxidative modification products of biomolecules, expressed by the growth of DC, TBARS, and 8-isoprostane levels, leading to oxidative stress correlated with the severity of lung damage.

Reimagining E-mobility: A holistic business model for the electric vehicle charging ecosystem

Nowadays business has shifted from product-centric to customer-centric due to the industrial revolution. As a result, the customer’s problem and experience need to be studied and inspected thoroughly to find solutions. Charging stations implementing different charging technologies are reinforced in various topographical locations. Varied charging methods, including AC slow charging, AC fast charging, DC level 1 charging, DC level 2 charging, wireless charging is implemented so far to reduce the charging time. Various business models are established and reported by researchers to support the EV ecosystem. This paper presents one such business model for an electric vehicle (EV) charging system. Design Thinking is one of the problem-solving approaches discussed here. How to tackle the charging issues by implementing different technologies is also discussed. Different phases of Design Thinking are used to find the possible solution to the problems faced by customers. Different groups of customers’ problems and how the proposed solution can fulfil a major group of customers’ needs are discussed here.

A 0.67 μV-IIRN super-T Ω-Z IN 17.5 μW/Ch Active Electrode With In-Channel Boosted CMRR for Distributed EEG Monitoring.

We present the design, development, and experimental characterization of an active electrode (AE) IC for wearable ambulatory EEG recording. The proposed architecture features in-AE double common-mode (CM) rejection, making the recording's CMRR independent of typically-significant AE-to-AE gain variations. Thanks to being DC coupled and needless of chopper stabilization for flicker noise suppression, the architecture yields a super-T Ω input impedance. Such a large input impedance makes the AE's CMRR practically immune to electrode-skin interface impedance variations across different recording channels, a critical feature for dry-electrode ambulatory systems. Signal quantization and serialization are also performed in-AE, which enables a distributed system in which all AEs use a single data bus for data/command communication to the backend module, thus significantly improving the system's scalability. Additionally, the presented AE hosts auxiliary modules for (i) detection of an unstable electrode-skin connection through continuous interface impedance monitoring, (ii) dynamic measurement and adjustment of input DC level, and (iii) a CM feedback loop for further CMRR enhancement. The article also presents the development of printed (extrusion) tattoo electrodes and their experimental characterization results with the proposed AE architecture. Besides bio-compatibility, low-cost, pattern flexibility, and quick fabrication process, the printed electrodes offer a very stable electrode-skin connection, conform to scalp shape, and exhibit consistent performance under various bending curvatures. Analog circuit blocks of the presented AE architecture are designed and fabricated using a standard 180 nm CMOS technology, and the [Formula: see text] IC is integrated with off-chip low-power digital modules on a PCB to form the AE. Our measurement results show a CMRR of 82.2 dB (at 60 Hz), amplification voltage gain of 52.8 dB, a bandwidth of 0.2-400 Hz, ±500 mV input DC offset tolerance, An input impedance [Formula: see text], and 0.67 μV RMS integrated input referred noise (0.5-100 Hz), while consuming 17.5 μW per channel. All auxiliary modules are tested experimentally, and the entire system is validated in-vivo, for both ECG and EEG recording.

Automatic Electric Vehicle Charging Station

Our Automatic Electric Vehicle Charging station is a autonomous power supply unit which works without the need for human attendants. The system is designed to facilitate the existing power grid infrastructure. The system employs the Raspberry Pi as our primary controller board and hosts the User Interface on the LCD Display mounted on the Charger Housing. The Pi Board interfaces with our custom Pilot PCB to communicate with the Electric Vehicle Battery Management Systems to negotiate the charging speed, capacity of the car battery and perform safety checks. The user can choose AC level 1, 2 or DC level 3 charging. The system uses a 30A relay circuit to isolate the battery from the power supply until all the necessary checks and payment processes are completed. RazorPay is our real time Payment gateway for payment transactions. Once the user has completed the formalities the charging process will begin. We also have a charging monitoring system developed that will help users track the battery charge percentage and charging time remaining on the LCD display. The station has emergency Kill Switches and Emergency Stop buttons mounted on the housing to address safety concerns that arise on the advert of damaged high power output utilities, when engaged the entire system will kill all the power inputs from the grid so that any fault can be safely repaired without risk of electrocution. For our implementation and testing we have built a 18650 NMC chemistry 3S5P Battery pack with a 3S BMS. The unit utilizes level 3 AC charging SAE (Society of Automotive Engineering) standards to ensure the safety and quality of the service.

Synergistic Therapeutic Effects and Immunoregulatory Mechanism of Maxing Shigan Decoction Combined with Sijunzi Decoction on Viral Pneumonia in Mice.

Influenza is defined in traditional Chinese medicine (TCM) as an epidemic febrile illness and is usually treated with herbal compound formulas under the guidance of the "Qu Xie and Fu Zheng" theories. Ma Xing Shi Gan Tang (MXSGD) is a prominent remedy for clearing heat and detoxifying toxins in the clinical treatment of influenza in TCM, playing the role of "Qu Xie." Si Jun Zi Tang (SJZD) is recognized as one of the "Fu Zheng" formulas for strengthening the spleen and nourishing the stomach, with immunomodulatory effects. In this study, we followed the principles of "Qu Xie and Fu Zheng" to explore the effects of MXSGD combined with SJZD on viral pneumonia and its mechanism. Results showed that the couse of MXSGD and SJZD was effective in reducing the mortality rates and severity of lung pathology in lethally infected FM1 mice compared to the use of either drug alone. Moreover, further research demonstrated that the combined use suppressed TLRs and NLRP3 inflammatory signaling pathways at 4 dpi while promoting them at 7 dpi. At 10 dpi, there was a significant increase in CD11c+ and CD103+ DCs in the lungs. Together, SJZD improved the therapeutic effectiveness of MXSGD in treating influenza virus pneumonia than when used alone. MXSGD and SJZD exhibit synergistic effects in the treatment of influenza, as evidenced by the inhibition of TLR7 and NLRP3 inflammatory pathways early in the infection and facilitation of the response later. They also increase CD11c+ and CD103+ DC levels, as well as balancing Th1/Th2 cytokines.

Development of a low-cost, compact, wireless, 16 - channel biopotential data acquisition, signal conditioning and arbitrary waveform stimulator.

The health and fitness of the human body rely heavily on physiological parameters. These parameters can be measured using various tools such as ECG, EMG, EEG, EOG, among others, to obtain real-time physiological data. Analysing the bio-signals obtained from these measurements can provide valuable information that can be used to improve health-care in terms of observation, diagnosis, and treatment. In bio-signal pattern recognition applications, more channels provide multiple information simultaneously. Different biosignal acquisition devices are available in the market, most of which are designed for specific signals like ECG, EMG, EEG etc The gain of the amplifiers and frequency of the filters are designed as per the targeted signals; due to which one device cannot be used for other signals. Also, most of the systems are wired system which is not comfortable for animal studies. In this paper, a low-cost, compact, wireless, 16 channel biopotential data acquisition system with integrated electrical stimulator is designed and implemented. There are several novel and flexible design approaches were incorporated in the proposed design like (1) It has user selectable digital filter in each channel based on the signal frequencies like ECG, EMG, EEG, EOG. The same system will be used to acquire different signals simultaneously. (2) It has variable gain with a configurable analog bandpass filter. (3) It can acquire signals from 4 patients simultaneously. (4) The system is capable to acquire signal from both two-electrode as well as three-electrode configurations. (5) It has integrated stimulator with trapezoidal, charge-balanced, biphasic stimulus output with near zero DC level and user selectable pulse duration or frequency of the stimulus. The developed system has the ability to acquire and transmit data wirelessly in real-time at a high transfer rate. To validate the performance of the system, tests were conducted on the acquired signals using a simulator.

Design, implementation and empirical analysis of a cascaded hybrid MPPT controller for grid tied solar photovoltaic systems under partial shaded conditions

Solar Photovoltaic (PV) system based power generation is going to become the major power source in the following few decades. Because of the advantages such as reliability, cleanliness, feasibility in small scale to medium scale power generation etc., Solar Photovoltaic (PV) based power generation is developing very rapidly. Hybrid MPPT control methods are essential to track and achieve maximum power generation from solar PV systems under normal and Partially Shaded Conditions (PSC). The proposed Hybrid Grey Wolf Optimization (GWO) algorithm with Adaptive Neuro-Fuzzy Inference System (ANFIS) will effectively tracks the Maximum Power Point when compared to the conventional hybrid MPPT methods. Luo converter is employed as DC-DC converter to convert the variable DC output from solar panel into a nominal DC level. The Luo converter output is given to a single phase Voltage Source Inverter (VSI) and the inverter is connected to grid. The Arithmetic Optimization Algorithm (AOA) tuned Fractional order Proportional Integral controller (FOPI) is adopted to maintain the stability of the grid connected inverter. The tracking efficiency of the proposed system is maintained around 98 % even under different irradiance conditions with very less convergence time of 0.016 s.

A Reconfigurable Analog Baseband for Multistandard Wireless Receivers in 22-nm CMOS

This paper presents a low noise, and high linearity reconfigurable receiver (RX) analog baseband (ABB) with tunable bandwidth (BW) and gain for multi-standard applications. The designed ABB consists of a programmable gain amplifier (PGA) and a second-order active RC low-pass filter (LPF) with cutoff frequency range from 0.7 MHz–10 MHz, whereas the gain could be tuned between 0 dB and 49 dB. The proposed ABB is implemented in 22 nm CMOS process. The post-simulation results show that the current consumption is 3.36 mA from 1 V supply and the area occupies 571×328 μm 2. The ABB achieves 42.8 dBm in-band third-order harmonic intercept point (IIP3). The spurious-free dynamic range (SFDR) and in-band total harmonic distortion (THD) is 83.2 dBc and is -83.1 dB, respectively. The input referred in-band integrated noise (IRN) is 144.8 μVrms . A digital DCOC is used to calibrate the output DC level.

A reconfigurable floating-gate-transistor-capacitor filter for analog signal processing

This paper introduces a fully reconfigurable floating-gate-transistor-capacitor (FGT-C) filter that exhibits compactness and power efficiency. The proposed filter incorporates a biquadratic section, enabling the generation of lowpass (LP) and bandpass (BP) outputs with adjustable filter parameters, including gains, natural frequency, quality factor, and DC levels for input and output signals. Moreover, the FGT-C filter topology demonstrates a modular structure, facilitating easy cascading and scalability of the biquadratic sections to implement high-order frequency responses. A prototype chip has been fabricated in the 0.35 μm CMOS process, where each biquadratic section occupies an area of 0.0313 mm2. The chip measurements were conducted with a supply voltage of 1.8 V and both output voltage levels programmed at 0.9 V. The biquadratic FGT-C filter exhibits a power consumption of 118.4 nW and achieves a spurious free dynamic range of 43 dB in a 10 kHz bandwidth setting. It is suitable for low-power analog signal processing in large-scale field programmable analog arrays.

Real-time implementation of sliding mode controller for standalone microgrid systems for voltage and frequency stabilization

This paper presents for stabilizing the output voltage and frequency of the hybrid source microgrid system (HSMG) and standalone solar photovoltaic microgrid system (SAPV), under varying source and loading conditions. An HSMG system consists of a solar, wind and battery system incorporated with a solar boost converter, wind rectifier/boost converter and bidirectional converter, respectively. These different dc level outputs are applied to the multiple input dc–dc converter for obtaining the constant dc level and then converted into three-phase power with suitable inverters. The source-side converters are designed to obtain the maximum output irrespective of the input conditions with PI controllers. The multiple input dc–dc converter controls the dc link voltage with the well-designed proportional, proportional integral, proportional integral derivative controller. The three-phase inverter is premeditated to obtain the constant voltage and frequency even under varying load patterns. The tuning of the PID controller is incorporated with Ziegler Nichols’s technique to reduce the frequency deviation and steady-state error. A SAPV microgrid system is developed with a high-capacity solar system incorporated with two-stage power conversion. Stage 1 and 2 are constant dc/constant ac obtained using suitable converters incorporated with an adaptive controller. The sliding mode controller (SMC) is an adaptive controller that performs better in dynamic operations. In this work, SMC maximizes the solar output and stabilizes the DC voltage using an appropriate PWM pulse to the boost converters. Also, the output voltage and frequency are maintained constant during the different operating situations. All simulations are carried out in MATLAB. PID and SMC controllers are implemented to the HSMG and SAPV microgrid systems in the OPAL-RT environment to validate the results in real-time applications respectively. The different operating conditions are tested for both the systems and the results prove that the chosen controllers are more suitable for these applications.

A common-mode suppression structure for absolute optical encoders

In traditional absolute optical encoders, the DC levels of the absolute code output signals are easily influenced by factors such as light intensity and temperature, leading to fluctuations in the duty cycles and errors in reading absolute code information. This paper presents a novel common-mode suppression structure for the readout of absolute code signals. By eliminating the common-mode component of the signals, the structure effectively suppresses common-mode interference and ensures that the duty cycles of the output signals remain close to the ideal value of 50%. To verify the effectiveness of the proposed common-mode suppression structure for absolute optical encoders, a photonic readout chip based on a 0.35μm CMOS process was designed, and good common-mode suppression effects can be achieved by combining the differential-distributed code disk. Test results show that when the LED’s normal operating current is 3.5 mA, the output duty cycle error is less than ±4%, which reduces 50% compared to the traditional structure. Under a variation of ±1 mA in LED operating current, the corresponding changes in output duty cycles remain within 5%. Similarly, when the temperature shifts from 25 °C to 125 °C, the changes in output duty cycles are contained within 3% It can be seen that this structure can suppress most of the common-mode interference caused by external factors, ensuring the stability of the output signals and reducing the bit error rate of the absolute code signals.

Discontinuous PWM Strategy with Frequency Modulation for Vibration Reduction in Asynchronous Machines

The aim of this paper is to present our research into the reduction of vibrations in induction motors. The use of power inverters results in the generation of electrical harmonics, which increase the level of the mechanical vibrations of electrical machines. To reduce these harmonics, we present a discontinuous pulse-width modulation (PWM) control strategy based on carrier-wave modulation applied to multilevel inverters. Using the proposed modulation technique, the amplitude of the electrical harmonics is reduced, as compared to other conventional techniques. These current harmonics produce the MMF (magnetomotive force) harmonics in the air gap, which are one of the main sources of vibrations. The control strategy makes it possible to vary the electrical spectrum at the output of a multilevel inverter by modifying a control parameter of the carrier wave in the PWM, thus avoiding the natural frequencies of mechanical resonance. The proposed technique also has the feature of attenuating the total harmonics distortion of the voltage of the multilevel inverters, as well as the achievement of a higher RMS value of the output voltage for the same DC level. Laboratory results for an induction motor with different modulation strategies, applied in a multilevel inverter and compared to the strategy presented, are attached.

Differential rectification technique in a three-phase coil based angle sensor

A technique of differential rectification is proposed for three-phase coil based inductive angle sensors so that the amplitude difference between any two of the amplitudes of three-phase coils is output for further signal processing. A 3-to-6 multiplexer, a low pass filter, and a 6-to-2 multiplexer are designed for the proposed technique, which is used for differential rectification, turning rectified signals into DC levels, and transmitting DC levels to the output of differential rectifiers, respectively. This differential rectification could suppress 3rd harmonic noise and common-mode noise, in order to improve the accuracy of angle calculation. The circuit of the proposed differential rectifier is given and simulation results shown in this manuscript verify the proposed circuit is feasible for three-phase coil based inductive angle sensors.

Examination of Trapping Effects on Single-Event Transients in GaN HEMTs

The effect of various trapping centers on single event-transients (SETs) in GaN high-electron-mobility transistors (HEMTs) are examined via calibrated technology computer aided design (TCAD) simulations. A single-channel, Schottky-gate HEMT computational model is developed and validated with static characteristics and single-photon absorption laser data. Simulations of SETs show that a two-dimensional electron gas (2DEG) enhancement effect occurs, which leads to additional collected charge in excess of the generated charge. The origins of this effect are examined and shown to result from an increase in occupation rate of the surface donor traps as the influx of charge is developed in the charge track. Variations in trap characteristics are then introduced and their effect on internal charge collection processes examined. It is further shown the SET response is dominated by the properties of the surface donor traps (i.e., energy level and density) such that the SET drain current closely follows the transient decay of occupation rate back to the original DC level.

Self-excited MEMS Oscillator using an Electrostatic Cantilever

In this paper, we propose a new use of an electrostatic MEMS cantilever structure as a voltage-controlled oscillator (VCO). A cantilever made of plated gold is accompanied with a drive electrode to turn on the contact switch upon voltage application. The electrical interconnection is arranged to discharge the cantilever when it is brought into contact with the switch, thereby promptly losing the electrostatic force and opening the contact switch again. As a result, the electrostatic cantilever spontaneously repeats the electrostatic pull-in and release at a frequency determined by the DC level of the applied voltage. A metallic cantilever of 500 μm long, 8 μm wide, and 12 μm thick is experimentally confirmed to work as an VCO in the frequency range between 8.4 kHz and 10.7 kHz controlled by the DC voltage between 160V and 180V.

Review of Discrete Fourier Transform During Dynamic Phasor Estimation and the Design of Synchrophasor Units

In a large and complex interconnected power system, the measurement of synchronized bus voltage and line current plays a vital role in the monitoring and precise control of various sophisticated electrical equipment for secure and reliable operation. Phasor measurement units (PMUs) are incorporated into a wide area of the power system to extract the different signals of synchronized phasors. In this paper, the capacity of the PMU phasor estimation algorithm is explored based on discrete Fourier transform (DFT) under different sampling frequency rates during various dynamic scenarios in accordance with the IEEE C37.118.1a-2014 standard. Furthermore, the performance of the DFT algorithm varies according to the phase angle and dynamic parameters such as frequency, frequency ramp rates, modulation frequency, harmonic levels, step change, decaying dc, and noise levels. The simulation results reveal that accuracy of the phasor estimation algorithm based on DFT can be achieved at high sampling frequency rates. Furthermore, the results of DFT-based phasor estimation are compared with Shank’s estimation method (SEM) and the least-squares estimation method (LEM). The presented method is best suited to PMU algorithms development based on DFT for better visualization of the smart electric grid.

Compensation for Dynamic Subdivision Error When the Grating Displacement Sensor Code Disk is Stained

When the code disk of a displacement sensor gains dust or other impurities, its moiré fringe signal will deviate from the standard range, which increases subdivision error. In this study, a high-speed A/D converter was used to collect the moiré fringe signal of a sensor in real time and to extract the characteristic points. The center point trajectory of the moiré fringe signal Lissajous figure was calculated, and the amplitude values of the two moiré fringe signals were determined according to characteristic points. The moiré fringe signals according to the center point trajectory and signal amplitudes were then normalized. Error compensation of the dc level and amplitude of moiré fringe signals was realized, so as to improve the dynamic subdivision accuracy of moiré fringe signals when the code disk was stained. Experiments showed that, when the reading head was in the stained area of the code disk, the subdivision error of moiré fringe signals was reduced from the peak value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$37.2^{\prime \prime }$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.6^{\prime \prime }$ </tex-math></inline-formula> , and the accuracy of the sensor can be improved using this algorithm for both different resolutions and different stains, which greatly improved the ability of the displacement sensor to adapt to a harsh environment.

PROGRAMACIÓN DE INTERFAZ GRÁFICA EN APP DESIGNER DEL MATLAB PARA REPRESENTAR LA SERIE DE FOURIER EN CURSO INTRODUCTORIO DE TELECOMUNICACIONES

This article describes the procedure for the implementation of a graphical user interface using the App Designer development environment of the Matlab software and its Toolbox Signal Processing and Symbolic Math, which allowed obtaining the Fourier Series coefficients for seven periodic signals followed by a graphical representation in the domain of time and frequency through pulses. Likewise, this &#x0D; interface was implemented using various components such as Drop Down, Button, Knob, Axes, among others, which allowed the choice of the number of sinusoidal components used in the decomposition, as well as the choice of the type of signal, its amplitude, frequency, DC level and duration time of the same. Therefore, this implementation complements the teaching-learning process developed remotely for a topic in the Telecommunications I course of the 6th academic semester of the Electronic Engineering Degree at Ricardo Palma University. Finally, the graphical results are presented for the case of four choices of periodic signals, with different amplitudes, frequencies and DC levels; as well as the numerical results in terms of the mean square error, showing a lower value for the triangular signal despite using a reduced number of sinusoidal components

Peripheral and regional blood bloodstreams lipid peroxidation comparative analysis in women with pelvic venous disorder.

Pelvic venous disorder (PVD) in women is a polyetiological multifactorial disease characterized by a high prevalence (up to 80%), a high risk of infertility, and a progressive recurrent course. Morphological changes of the venous bed occur in PVD, contributing to retrograde blood flow and pelvic phlebohypertension. It is occur due to dynamic hypervolemia and hypertension long-term exposure on the venous wall. However, PVD pathogenesis analysis only from venous hemodynamic disorders position does not explain all mechanisms of the disease development and does not contribute to the treatment measures effectiveness. Currently oxidative stress reactions are considered as the most important markers of the pathological process. The aim of our work was a comparative analysis of lipid peroxidation-antioxidant defense component changes in the peripheral and regional blood flow in women with primary pelvic venous disorder depending on the disease stage. The study involved 137 women of reproductive age (mean age 37.4±9.1 years old) with diagnosed primary PVD divided into 3 groups according to the pathological process stages (stages I, II, III). Data from 30 practically healthy women (mean age 33.5±6.3 years old) were used as controls. Spectrophotometric, fluorometric, immunoassay and statistical methods were used. In patients with PVD stage I in peripheral bloodstream were higher values of SOD and GPO activity; in the regional bloodstream were higher levels of TBARs, SOD, catalase, GPO and lower GSH. In PVD stage II the peripheral bloodstream showed elevated levels of DC, GSH and SOD reduced levels; the regional bloodstream showed higher levels of DC, TBARs, GPO and GSH reduced levels relative to controls. PVD stage III was characterized by: higher levels of DC and TBARs and lower levels of SOD and GSH in the peripheral bloodstream; higher levels of DC, TBARs and lower levels of GSH and catalase in the regional bloodstream compared with control. Thus, the results of our study showed no significant differences in the LPO-AOD system between peripheral and regional bloodstreams in patients with PVD depending on the disease stage. However, negative changes in the redox balance in the regional bloodstream were earlier and were already registered at the first stage of the disease. It is likely that control of antioxidant insufficiency in patients with PVD should be an important component of preventive measures in the early stages and pathogenetic treatment in the pathological process progression, particularly in stage III of the disease.

A Fully-Differential CMOS Instrumentation Amplifier for Bioimpedance-Based IoT Medical Devices

The implementation of a fully-differential (FD) instrumentation amplifier (IA), based on indirect current feedback (ICF) and aimed to electrical impedance measurements in an Internet of Things (IoT) biomedical scenario, is presented. The IA consists of two FD transconductors, to process the input signal and feed back the output signal, a summing stage, used to add both contributions and generate the correcting current feedback signal, and a common-mode feedback network, which controls the DC level at the output nodes of the circuit. The transconductors are formed by a voltage-to-current conversion resistor and two voltage buffers, which are based on a super source follower cell in order to improve the overall response of the circuit. As a result, a compact single-stage structure, suitable for achieving a high bandwidth and a low power consumption, is obtained. The FD ICF IA has been designed and fabricated in 180 nm CMOS technology to operate with a 1.8-V supply and provide a nominal gain of 4 V/V. Experimental results show a voltage gain of 3.78 ± 0.06 V/V, a BW of 5.83 MHz, a CMRR at DC around 70 dB, a DC current consumption of 266.4 μA and a silicon area occupation of 0.0304 mm2.