DC Level Research Articles

Zero-average Bias Bidirectional Single-electron Current Generation in a Hybrid Turnstile

Hybrid turnstiles have proven to generate accurate single-electron currents. The usual operation consists of applying a periodic modulation to a capacitively coupled gate electrode and requires a nonzero DC source-drain bias voltage. Under this operation, a current of the same magnitude and opposite direction can be generated by flipping the polarity of the bias. Here, we demonstrate that accurate single-electron currents can be generated under zero average bias voltage. We achieve this by applying an extra periodic modulation with twice the frequency of the gate signal and zero DC level to the source electrode. This creates a time interval, which is otherwise zero, between the crossings of tunnelling thresholds that enable single-electron tunnelling. Furthermore, we show that within this operation the current direction can be reversed by only shifting the phase of the source signal.

Line‐transient enhancement techniques for multi‐path hybrid DC–DC converter with <1% output overshoot/undershoot

This letter presents two transient enhancement techniques for multi-path switched-capacitor-inductor (MP-SCI) hybrid DC–DC converters to eliminate the line-transient-induced voltage coupling to the converter output. Since the existing input-feedforward method is hard to apply to the MP-SCI converter, the proposed techniques tackle the intrinsic hard-charging property with the MP-SCI topology, preventing the line-coupling current through topology operation reconfiguration and power-switch modulation. The proposed controller also achieves adaptive line-transition detection and automatic flying-capacitor voltage balancing, ensuring a fast line regulation feature. Implemented with an MP-SCI topology for a 9 to 14 V-input to 5 V-output conversion, the proposed control techniques provide an output (VOUT) overshoot and undershoot as low as 0.5% of the output DC level under a 3-V input voltage step. From the simulation, the corresponding output variation reduction can be more than 94% when compared with the existing MP-SCI operations. Besides, the proposed controller is compatible with a voltage-mode (VM) V2 pulse-width modulation (PWM) function, achieving a fast load-transient recovery in six switching cycles and a VOUT variation of 75 mV at a 5 V DC level under a 0-to-3 A load step. The peak conversion efficiency can be as high as 95.5%, and the targeted load current delivery is up to 3 A.

High current efficiency fast transient gain-boosted single-stage bulk-driven OTA with enhanced input stage suitable for heavy capacitive loads

This article presents a 0.5 V operated, bulk-driven subthreshold OTA with up to 30 nF capacitive load driving capability. The input stage utilizing three unmatched pseudo-differential pairs is biased with two DC level shifters, especially bulk-driven flipped voltage followers in a direct and cross-coupled connection, exhibiting superior performance to existing bulk-driven OTAs. The input transconductance stage with local common-mode feedback (LCMFB) followed by partial positive feedback (PPF) contributes a large dynamic output current using three-successive amplification. As a result, the proposed OTA provides 24.2 times higher effective input core transconductance, 2.62 times higher DC gain, and 11.5 times more slew rate than a conventional class-A BD OTA with PPF at 5% lower static power. The post-layout results of the proposed OTA for a 10 nF capacitive load using UMC 0.18-µm technology in Cadence Virtuoso-XL yield a DC gain of 124.6 dB, a UGF of 183.47 kHz, a PM of 89.98°, and greater figures of merit (FOM) for small- and large-signal performance than the state-of-the-art bulk-driven OTAs.

Abstract 2635: Inhibiting deoxycytidine kinase significantly inhibits tumor growth in xenograft models of castration resistant prostate cancer

Abstract Mammalian cells synthesis deoxyribonucleoside triphosphate (dNTP) precursors for DNA replication via the de novo pathway (DNP), and to a lesser extent, via the nucleoside salvage pathway (NSP). Evidence suggests that rapid tumor cell growth associated with increased dNTP needs results in elevated NSP activity. As deoxycytidine kinase (dCK) is the rate-limiting enzyme of the NSP, and the only enzyme that can supply cells with all dNTP precursors for DNA replication, dCK has been implicated as a promising therapeutic target. Data from the Cancer Cell Line Encyclopedia demonstrated that most human cancer cell lines have elevated dCK gene expression (2- to 17-fold) therefore suggesting selective susceptibility of tumor cells to dCK inhibition. Accordingly, a potent first-in-class oral dCK inhibitor, TRE-515, was evaluated as a single agent in two human castration-resistant prostate cancer (CRPC) models. In the first CRPC model, C4-2, TRE-515 was administered intraperitoneally once a day for eight consecutive days (50 mg/kg, QDx8). TRE-515 significantly inhibited tumor growth (50.7%, p=0.021, relative to vehicle control), with 50% of the TRE-15 treated tumors regressing during the eight-day treatment window. In a repeat C4-2 study, TRE-515 monotherapy trended toward tumor growth inhibition, (53.7%, p=0.061, relative to vehicle control). A second CRPC model, 22Rv1, was then selected as it has been shown to carry DNP mutations, suggesting enhanced sensitivity to dCK inhibition. In this study, TRE-515 was dosed orally two times a day for 28 days (75 mg/kg, BIDx28) and plasma deoxycytidine (dC) concentrations (a substrate for dCK) were measured 7 hours after the morning dose on day 21. TRE-515 alone significantly inhibited tumor growth (49.9%, p=0.0004, relative to vehicle control), and growth inhibition was associated with a 77% increase in plasma dC levels (p<0.0001), relative to vehicle control, consistent with TRE-515 inhibitory activities on dCK. These data are in agreement with a previously reported study on target enzyme inhibition by TRE-515 which employed a clinically validated PET probe imaging of dCK. Taking together these results support the therapeutic potential for TRE-515 to selectively inhibit cancer cells that rely on dCK for DNA synthesis and rapid malignant proliferation. As such, TRE-515 is currently being evaluated in a phase 1 open-label, dose escalation study in solid tumors (NCT #05055609). Citation Format: Caius G. Radu, Kenneth A. Schultz, Katharina Lückerath, H Michael Shepard, Johannes Czernin. Inhibiting deoxycytidine kinase significantly inhibits tumor growth in xenograft models of castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2635.

Four-quadrant multiplier using the floating-bulk technique for rail-to-rail input range and insensitivity to different input dc levels

Four-quadrant multiplier using the floating-bulk technique for rail-to-rail input range and insensitivity to different input dc levels

Measurements and Analysis of Partial Discharges at HVDC Voltage with AC Components

This paper presents the methodology for phase-resolved partial discharge measurements in HVDC systems with a DC voltage containing trace AC harmonics or a DC voltage ripple. The measurement result of partial discharges is an indicator of the current condition of the high-voltage power devices’ insulation system. The voltage waveforms in HVDC systems are not ideal DC, because different disturbances occurring naturally in these systems can affect the DC voltage. The AC harmonics related to the AC source voltage, and the voltage ripples provided by the power converter topology, can be found in the HVDC voltage. This paper proposes a novel approach to partial discharge measurement in DC networks. The synchronization to the particular AC harmonics appearing in DC voltage was applied to the PD measurements. The analyses were performed on the model sample containing a void inclusion, which was placed between electrodes fed by the DC voltages with the imposed chosen AC harmonics. Two scenarios were analyzed at a constant DC level: one with a variable AC magnitude and the second with a variable frequency of an AC source adjusted to the harmonics: 50, 150, 300, and 350 Hz. It was observed that the superimposed AC voltage component resulted in an intensification of PDs.

Development of a Multichannel Bioinstrumentation System for Human-Computer Interface Applications

A multi-channel measurement system used to measure electrocardiogram (ECG), electroencephalogram (EEG), electromyogram (EMG) and electrooculogram (EOG) biosignals has been designed and prototyped. The designed system has 16 configurable measurement channels. Of the 16 channels the developed system has, 8 have been designed for EEG, 2 for EMG, 2 for EOG, 1 for ECG measurements, the remaining 3 have been reserved as backup channels. In circuit design, biosignal amplifier design principles have been applied by taking into account the characteristics of the biosignal to be measured for each channel, such as bandwidth, frequency, amplitude, noise level. Modules such as instrumentation amplifier, filter, DC suppression unit, amplifier, DC level determination unit, analog-digital converter, optical isolation unit, power supply have been designed to perform biosignal measurements through these channels. Biosignals measured by the developed system can be shifted to the desired threshold level with the help of the analog output reference voltage, converted to digital data 10-bit resolution and transferred to the computer environment in real time. The data transferred to the computer can be used in C#, Excel, MATLAB, and LabVIEW platforms. The novelty of the developed system is that any of the four desired biosignal types can be measured from any channel. In addition, another feature of the system is that it can work with real-time data without being dependent on the databases serving for human-computer interface applications. In experimental studies with some researchers for the performance tests of the system, ECG, EEG, EMG and EOG signals have been recorded with different module configurations, and signal processing stages were carried out to be used for human-computer applications.

A Novel Multiphase Interleaved DC-DC Boost Converter with Reduced Input Current Ripple for Renewable Energy Application

This paper presents a new multiphase boost converter with improved input current ripple characteristics. The low input current ripple is important due to its effect on the converter’s efficiency and upstream dc bus noise level. It will further affect other devices connected to the same bus. Furthermore, for battery-connected systems such as renewable energy systems, the low current ripple increases the battery life. The method in this research uses split inductance and capacitance configuration as an input filter. The input filter helps compensating for the rippled converter topology, it reduces conduction-switching noise without affecting transient response, and it minimizes the physical size. Therefore, in this new topology, the use of smaller sized components directly influences the converter's size. Interleaved is used for improved heat distribution on the physical circuit board while retaining the benefits of a multiphase converter. Additionally, the low current ripple implies using smaller sized components that directly affect the size of the converter. A three-phase example of the proposed boost converter will be described, along with the derivation of its state space equations. Compared with the standard three-phase boost, the proposed converter can reduce the input current ripple and the output current ripple by 21% and 43%, respectively.

Optimizing DC restoration in Kramers-Kronig optical single-sideband receivers.

Kramers-Kronig optical single-sideband receivers remove the signal-signal beat interference (SSBI) that occurs when detecting a signal that has electrical signals mapped onto its optical field at the transmitter; such signals support electronic dispersion compensation without the need for a coherent receiver. To use the full range of the analog-to-digital converter's (ADC) range, it is best to a.c.-couple the photocurrent, to remove its DC content; however, the DC must be restored digitally before the KK algorithm is applied. Recent publications have concentrated on perfectly determining the restored DC's required level from the signal, with a view this is optimal for lowering error rates. In this paper, we investigate signal-signal beat interference (SSBI) cancellation in a single photodiode receiver using Kramers-Kronig receiver algorithm, with large variations in optical carrier-to-signal power ratio (CSPR) and DC offset level. Through simulations and experiments, we find a strategy to optimize the signal quality without the need of an extensive search for the DC offset value. We also find that a theoretically perfect determination of the original DC level does not provide best signal quality especially for low CSPRs; in order to achieve maximum cancellation of signal-signal beat interference, the level of the restored DC has an optimum value that depends on the optical CSPR. We define a digital CSPR, which is the value of the CSPR in the digital domain after DC restoration. Our measurements show that we simply need to bias the signal upwards and make the minimum signal above zero by 0.1% of the r.m.s. signal amplitude when the optical CSPR is low. For higher values of optical CSPR, the optimal digital CSPR is about 2-dB lower than the optical CSPR, and the optimal DC offset can be calculated from this digital CSPR. We find that the boundary between our low optical CSPR region and high optical CSPR region depends on the noise level in the system.

Reduced Auxiliary Circuit Switch Nine-Level Inverter for Renewable Energy Applications

Multilevel Inverters (MLI) created a milestone due to increasing demand in high power medium voltage applications. To decrease the harmonics content and stress across power semiconductor devices, multilevel inverters are used. In this paper, a nine-level inverter is presented with a auxiliary circuit that requires a minimum number of power devices compared to the traditional MLI topologies. The suggested nine-level inverter's control circuitry is controlled by an ATmega8 microcontroller in this study. Opto-isolators with galvanic isolation supply the triggering pulses to operate switches. A nine-level inverter to power 100 W load is implemented using two proposed auxiliary circuits for renewable energy applications. The presented nine-level inverter's control switches are driven using a DC level shifting method. The suggested inverter's functionality and feasibility are confirmed by the experimental and simulation findings.

Assessment of Female University Students’ Digital Competence: Potential Implications for Higher Education in Africa

This study assessed the digital skills of female university students and the implications for higher education in Africa. A descriptive survey was used to sample 100 female university students from four African countries (Nigeria, Rwanda, South Africa, and Uganda). The instrument used was the digital competence survey. Two research questions and two hypotheses were postulated and tested. According to the study's findings, most female university students in Nigeria and South Africa have expert and advanced levels of information and digital literacy, communication and collaboration, digital content creation, and safety.On the other hand, Uganda was mainly found at the basic or no levels, whereas Rwanda was mostly found at the intermediate levels. The chi-square analysis reveals a significant difference between the ages of female university students and their DC levels (χ2 =.000; p < 0.05). A significant difference exists between female university students’ program of study and their levels of DC (χ2 = .000; p < 0.05). Students also faced challenges such as a lack of ICT tools, insufficient knowledge and skills, data issues, and poor internet connectivity. The implications of these findings for African higher education institutions suggest that female students, particularly in Rwanda and Uganda, require training to be digitally competent and compete globally with their peers. As a result, we recommend that students from different programs of study with less demand in technology be allowed to take compulsory electives in technology courses while older female students are given adequate support.

Reliability and Cost-Oriented Analysis, Comparison and Selection of Multi-Level MVdc Converters

DC technology has gained considerable interest in the medium voltage applications due to the benefits over the AC counterpart. However, to utilize the full capacity of this development, the selection of a suitable power electronic converter topology is a key aspect. From the pool of voltage source converters (VSC's), it is unclear which topology is suitable for multi-megawatt applications at medium voltage dc (MVdc) levels. To address this, the paper proposes a selection guideline based on reliability and optimum redundancy levels of VSCs for MVdc applications. This will be combined with other functional factors such as operational efficiency and return-on-investment. Three candidate multi-level topologies namely three-level neutral point clamped converter (3L-NPC), modular multi-level converter (MMC) and cascaded 3L-NPC (which is being used for the first MVdc link in the U.K.) have been evaluated over two-level-VSC from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 10 kV to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 50 kV. Results show that with the increase of MVdc voltage level MMC shows better performance whereas at low MVdc voltage levels 3L-NPC is the prominent topology.

A Reconfigurable Differential-to-Single-Ended Autonomous Current Adaptation Buffer Amplifier Suitable for Biomedical Applications.

A reconfigurable differential-to-single-ended autonomous current adaptation buffer amplifier (ACABA) is proposed. The ACABA, based on floating-gate technologies, is a capacitive circuit, of which output DC level and bandwidth can be adjusted by programming charges on floating nodes. The gain is variable by switching different amounts of capacitors without altering the output DC level. Without extra sensing and control circuitries, the current consumption of the proposed ACABA increases spontaneously when the input signal is fast or large, achieving a high slew rate. The supply current dwindles back to the low quiescent level autonomously when the output voltage reaches equilibrium. Therefore, the proposed ACABA is power-efficient and suitable for processing physiological signals. A prototype ACABA has been designed and fabricated in a [Formula: see text] CMOS process occupying an area of [Formula: see text]. When loaded by a [Formula: see text] capacitor, it consumes [Formula: see text] to achieve a unity-gain bandwidth of [Formula: see text] with a measured IIP2 value of [Formula: see text] and a slew rate of [Formula: see text].

Development of Fast charging system with ZVS integrated with Fuzzy controller-based Hybrid renewable energy source

Climate change is a growing concern due to greenhouse gas emission and transportation has increased the requirement for various energy sources with limiting and less pollution. But with the establishment of more electric vehicles on the road, charging EV’s will be difficult if the grid is used. When many numbers of electric vehicles are integrated to the grid, it will inevitably have a huge effect on its function and control. Hence, there is a requirement for an effective charging system for electric vehicles using renewable energy sources. Solar energy is renewable and green, but the volatile nature of energy from the Photo-Voltaic (PV) system and dynamic charging requirement of electric vehicles has added new problems to the effective charging of EV from these sources. The Solar powered charging station with battery storage system is a better solution for this problem. The power is transferred from the AC grid to the DC link when there is a depletion of power from solar. This paper deals with DC level 1 fast charger to charge an electric vehicle with phase shifted full bridge converter as a main charging topology which is able to deliver the load of 50KW to charge the electric vehicle. To maintain a constant voltage at the output of the boost converter connected to the solar panel, a fuzzy controller is also developed in the proposed system

Wireless power transfer system prototype with a wide input power range rectifier and power‐optimized waveforms

AbstractThis paper describes a wireless power transfer (WPT) system operating at 2.4 GHz, which is based on waveform optimization technique and a wide input power range rectifier. This latter consists of an RF‐to‐dc power conversion circuit based on circulators. The waveform optimization is then applied in order to enhance the power conversion efficiency at very low input power levels. The proposed WPT system was prototyped and tested in open and closed loop configurations with different types of obstacles placed between the transmitter and the receiver. The generation of power‐optimized waveforms and the control process in the closed loop configuration were carried out using software‐defined radio. The obtained experimental results validate the wide input power behavior of the two proposed WPT systems especially when dealing with very low input power levels and relatively dynamic environments. In fact, for the two WPT systems featured a distance of 1 m and a transmitted power of 50mw, dc power levels of about 38 and 11 μW are harvested in the cases of no obstacle and low attenuation obstacle respectively.

Neural Spike Detection Circuit with Amplification Method using Input DC Level Control

Neural Spike Detection Circuit with Amplification Method using Input DC Level Control

Rapamycin treated tol-dendritic cells derived from BM-MSCs reversed graft rejection in a rat liver transplantation model by inducing CD8+CD45RC−Treg

ObjectiveTo investigate the influence of tolerance dendritic cells (tolDCs), generated from Bone marrow mesenchymal stem cells (BM-MSCs) treated with rapamycin (Rapa) on liver allograft survival in a rat acute liver transplantation model. MethodsDifferent GM-CSF induction project was used to obtain immature DCs (imDCs), mature DCs (matDCs) or tolDCs from BM-MSCs. First, MLR was performed to analyze the activity of tolDCs on polyclonaly stimulated total T cells. Then, co-cultured imDCs, matDCs and tolDCs with CD8+T cells isolated by magnetic activated cell sorting to analyze the influence on its regulatory characteristic. Last, the established rat acute liver transplantation model were adoptive transfused with imDCs, matDCs or tolDCs isolated by anti-CD11c immunomagnetic beads. The phenotype of DC cells and level of CD8+Treg in the culture system and in vivo, the expression of CD8 and CD45RC in the tissues were analyzed by flow cytometry and immunohistochemistry, respectively. ResultsThe loGM-CSF plus IL-4 decreased the costimulatory molecules of CD80/86 and MHC class II of DCs comparison with hiGM-CSF from BM-MSCs no matter whether stimulation by LPS (P<0.05). Rapa treated not only reduced the expression of CD80/86 and MHC class II but also down-regulated the expression of CD11c after LPS stimulation which was more obviously in tolDCs by loGM-CSF project (P<0.05). Moreover, tolDCs displayed a rather higher level of IL-10 and low level of IL-12p70 than others (P<0.01), which shown a rather lower stimulative effect on the proliferation of T cells comparison with matDCs and imDCs. Co-cultured with CD8+Treg showed an improvement on induction of CD8+TCR+CD45RC−T cells (CD8+Treg) in ex vivo. The rats transfused with tolDCs has a delayed survival benefits with high level of CD8+Tregs (P<0.01) and high expression of CD45RC in liver tissue (P<0.01) and spleen when comparison with other groups. The infused tolDCs improved a mean survival time (MST) of 32 days comparison with a MTS of 9.5 days and 15.75 days displayed by rat that per-infused with matDCs and imDCs, respectively. ConclusionRapa modified tolDCs derived from BM-MSCs reversed graft rejection by improve tolerance characteristics of CD8+CD45RC−Treg in acute liver rat transplantation.

Dynamics of hole injection from p-GaN drain of a hybrid drain embedded GIT

The addition of a p-GaN drain to a conventional gate-injection transistor (GIT), forming the so-called hybrid drain embedded GIT, is crucial in the suppression of the dynamic Rdson. The DC leakage due to hole injection is limited to around 10 nA/mm at 600 V (25 °C). However, an injected hole current of several amperes (W = 210 mm) has been observed during the hard switching event. To reconcile this difference over 6 orders of magnitude, a TCAD study is carried out to understand the dynamics of the hole injection and what leads to the difference between the static and the transient current. According to the scenario played out by the present simulation model, the high concentration of carbon, intentionally doped to control the vertical leakage, plays a crucial role in limiting the hole injection current to its DC level, while under fast switching, the hole injection current can be very high due to a lag in response on the part of the carbon trap.

THE ROLE OF QUALITY OF LIFE IN MELATONIN CONTENT AS A REGULATOR OF DEFENSE AND AGGRESSION FACTORS IN GASTROESOPHAGEAL REFLUX DISEASE PATIENTS WITH SLEEP APNEA SYNDROME

The aim of the study: to study the effect of the quality of life on the melatonin content, and at the same time to assess the state of the factors of aggression and protection of the esophageal mucosa in patients with GERD without comorbidities and with concomitant obstructive sleep apnea/hypopnea syndrome (OSAHS).&#x0D; Methods. 45 patients were taken for the study. 23 of them had GERD concomitant COPD, 22 were with isolated GERD with a non-erosive form.&#x0D; Melatonin levels were determined using the enzyme immunoassay method (ELIZA). Quality of life was assessed using the SF-36 questionnaire. Antioxidant protection of the mucous membrane (protection factor) – was assessed by the activity of superoxide dismutase (SOD). SOD activity in blood serum was determined by calorimetric method. Determination of the DC level was carried out in the blood by the spectrofluorimetric method.&#x0D; Results. The study showed that in patients with GERD with concomitant COPD, there is a significant decrease in the indicators of antioxidant activity and melatonin, both with indicators from the control group and with indicators of patients with GERD without comorbidity.&#x0D; At the same time, in patients with GERD without comorbidities, an increase in the level of DC was observed in comparison with the control group and patients with GERD with concomitant pathology and acidity of gastric juice.&#x0D; When analyzing the indicators of QOL in patients with GERD with concomitant pathology, there is a significantly more pronounced decrease in mental health, role emotional functioning and vitality.&#x0D; Conclusions. It has been established that in patients with GERD in the stage of exacerbation of the disease, there is a statistically significant decrease in QOL indicators with a high degree of reliability, manifesting itself in patients without combined pathology in the spectrum of indicators of the physical component of health, and in patients with GERD with concomitant obstructive sleep syndrome – in the spectrum of the psychological component quality of life.&#x0D; It has been shown that with a decrease in QOL in patients with GERD, the level of melatonin decreases, the decrease in which more clearly increases in patients with concomitant obstructive sleep apnea.&#x0D; Simultaneously with a drop in the level of melatonin in patients with GERD without associated pathology, the aggression factor increases with a high degree of certainty - that is, a decrease in the pH of gastric juice and an increase in the content of DC, while in patients with GERD with concomitant sleep apnea syndrome, the factor decreases with a high degree of certainty. Protection of the esophageal mucosa – (that is, a decrease in SOD activity), which must be taken into account when treating this category of patients.

Analysis of Distribution Grid, Power Loss Reduction and Fault Detection in 33 Bus System using Optimization

We have to design a system model in MATLAB 2015A software. In this analysis micro-grid 33 bus system data Power generation source are used PV these are provide constant DC outcome then these outcome improving to dc level, used dc to dc convertor. DC/DC convertor output to connect three phase invertor system. In this invertor gate pulse control using FACT- VSC device with fuzzy logic, VSC provide fixed pulse with constant duty cycle. Our proposed system optimization of 33 bus system data power loss, faulty bus and DG placement in term of stability index.