Monopolar Mode Research Articles

Stochastic Emission in Passively Fed Single-Emitter Porous-Media Ionic Liquid Ion Sources

Ionic liquid ion sources are a promising form of efficient thrust for power- and mass-constrained satellites. Flight performance requirements necessitate large arrays of emitters; however, the fundamental behaviors of the ion emission process are obscured by the simultaneous operation of multiple emitters. One such behavior is the stochastic nature of Taylor cone formation and ion emission from the emitter. To examine these phenomena, a single-emitter electrospray using a conventionally machined porous borosilicate emitter cone was operated using the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate. Repeated performance curves of the same emitter, measuring the emitter and extractor electrode currents as a function of the emitter voltage, vary significantly between tests. Ion current density spatial distribution maps of the plume and time-resolved emitter current and plume current while retarding potential energy analyzer sweeps are also presented. High-speed current measurements on a collector plate downstream of a different single-emitter electrospray were collected to examine the variation in the onset delay time of the Taylor cone. The onset delay time decreased with increasing emitter voltage and was effectively eliminated using bipolar switching. In monopolar mode, the onset delay rate was not sensitive to changes in the emitter voltage switching frequency across the range of tested values.

Incremental high power radiofrequency ablation with multi-electrodes for small hepatocellular carcinoma: a prospective study

Radiofrequency ablation (RFA) offers a minimally invasive treatment for small hepatocellular carcinoma (HCC), but it faces challenges such as high local recurrence rates. This prospective study, conducted from January 2020 to July 2022, evaluated a novel approach using a three-channel, dual radiofrequency (RF) generator with separable clustered electrodes to improve RFA’s efficacy and safety. The study employed a high-power, gradual, stepwise RFA method on HCCs (≤ 4 cm), utilizing real-time ultrasound-computed tomography (CT)/magnetic resonance imaging (MRI) fusion imaging. Involving 110 participants with 116 HCCs, the study reported no major complications. Local tumor progression (LTP) and intrahepatic remote recurrence (IRR) rates were low, with promising cumulative incidences at 1, 2, and 3 years for LTP (0.9%, 3.6%, 7.0%) and IRR (13.9%, 20.5%, 31.4%). Recurrence-free survival (RFS) rates were similarly encouraging: LTP (99.1%, 96.4%, 93.0%) and IRR (86.1%, 79.5%, 68.6%). This innovative gradual, incremental high-power RFA technique, featuring a dual switching monopolar mode and three electrodes, represents an effective and safer management option for small HCCs.Trial registrationclinicaltrial.gov identifier: NCT05397860, first registered on 26/05/2022.

A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation

Objective. Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full-head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation. Approach. Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar (TP), and partial TP modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve. Main results. The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities. Significance. Full-head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.

Effects of pulse shape on pitch sensitivity of cochlear implant users

Contemporary cochlear implants (CIs) use cathodic-leading symmetric biphasic (C-BP) pulses for electrical stimulation. It remains unclear whether asymmetric pulses emphasizing the anodic or cathodic phase may improve spectral and temporal coding with CIs. This study tested place- and temporal-pitch sensitivity with C-BP, anodic-centered triphasic (A-TP), and cathodic-centered triphasic (C-TP) pulse trains on apical, middle, and basal electrodes in 10 implanted ears. Virtual channel ranking (VCR) thresholds (for place-pitch sensitivity) were measured at both a low and a high pulse rate of 99 (Experiment 1) and 1000 (Experiment 2) pulses per second (pps), and amplitude modulation frequency ranking (AMFR) thresholds (for temporal-pitch sensitivity) were measured at a 1000-pps pulse rate in Experiment 3. All stimuli were presented in monopolar mode. Results of all experiments showed that detection thresholds, most comfortable levels (MCLs), VCR thresholds, and AMFR thresholds were higher on more basal electrodes. C-BP pulses had longer active phase duration and thus lower detection thresholds and MCLs than A-TP and C-TP pulses. Compared to C-TP pulses, A-TP pulses had lower detection thresholds at the 99-pps but not the 1000-pps pulse rate, and had lower MCLs at both pulse rates. A-TP pulses led to lower VCR thresholds than C-BP pulses, and in turn than C-TP pulses, at the 1000-pps pulse rate. However, pulse shape did not affect VCR thresholds at the 99-pps pulse rate (possibly due to the fixed temporal pitch) or AMFR thresholds at the 1000-pps pulse rate (where the overall high performance may have reduced the changes with different pulse shapes). Notably, stronger polarity effect on VCR thresholds (or more improvement in VCR with A-TP than with C-TP pulses) at the 1000-pps pulse rate was associated with stronger polarity effect on detection thresholds at the 99-pps pulse rate (consistent with more degeneration of auditory nerve peripheral processes). The results suggest that A-TP pulses may improve place-pitch sensitivity or spectral coding for CI users, especially in situations with peripheral process degeneration.

Simultaneous removal of turbidity, suspended solids and chemical oxygen demand from carwash effluent using aluminium electrodes in monopolar mode electrocoagulation

Simultaneous removal of turbidity, suspended solids and chemical oxygen demand from carwash effluent using aluminium electrodes in monopolar mode electrocoagulation

Electrocoagulation in treatment of municipal wastewater– life cycle impact assessment

The purpose of this study is investigation of electrocoagulation (EC) as a treatment of municipal wastewater, integrating life cycle impact assessment (LCIA) for assessing its environmental performance of investigated treatment. The study evaluated the effectiveness of EC in removing physico-chemical and microbial parameters using aluminum (Al) and iron (Fe) electrodes in monopolar and bipolar modes. Bipolar arrangement of Al(−)/Al/Al/Al(+) electrodes achieved the highest removals: 70% COD, 72% BOD5 followed by complete elimination of total phosphorous, turbidity and microbial parameters. This treatment was subject to investigation of the influence of reaction time (t = 10–60 min) on removals at higher current density (CD = 3.33 mA/cm2). In order to reduce energy consumption, the same reaction time range was used with a reduced CD = 2.33 mA/cm2. Following removal efficiencies obtained: 47–72% COD (higher CD) and 53–78% (lower CD); 69–75% BOD5 (higher CD) and 55–74% CD (lower CD); 12–21% NH4− (higher CD) and 7–22% NH4− (lower CD). Total P, NO3− and NO2− compounds showed the same removals regardless the CD. Decrease in current density did not influence removals of total suspended matter, turbidity, salinity as well as microbial parameters. The bipolar arrangement of Al(−)/Al/Al/Al(+) electrodes, assuming a lower CD = 2.33 mA/cm2 and t = 30 min, was assessed with the Recipe 2016Midpoint (H) and USEtox v.2 LCIA methods to explore the environmental justification of using EC for wastewater treatment. The LCIA results revealed that the EC process significantly reduces water eutrophication and toxicity for freshwater and marine ecosystems, but has higher impacts in global warming, fossil fuel consumption, human toxicity, acidification, and terrestrial ecotoxicity due to high energy consumption. This can be mainly explained by the assumption in the study that the EC precipitate is dispersed to agricultural soil without any pre-treatment and material recovery, along with relatively high energy consumption during the process.

Histological evaluation of monopolar and bipolar radiofrequency microneedling treatment in a porcine model.

Fractional radiofrequency microneedling (FRM) is widely used as an option for skin rejuvenation, however there is a lack of histological evidence for the various energy delivery systems available. The objective was to assess thermal denaturation of tissue and the wound healing response in monopolar mode versus bipolar mode. Histological analysis was performed to demonstrate the efficacy of automatic impedance feedback system in monopolar mode. In this study, the acute thermal effects caused by monopolar FRM treatment to the dorsal skin of pigs were assessed histologically by hematoxylin & eosin (H&E) staining. Then, one session of either monopolar or bipolar FRM was used to treat one or the other side of the pig using varying power levels and pulse widths. The acute and chronic tissue reactions were assessed using H&E, immunofluorescence, and western blot analysis at 0, 14, 30, and 90 days after treatment. The efficacy of the impedance feedback system was also monitored histologically. High-energy FRM treatment produced tissue loss and necrosis. The power level and pulse duration significantly affected the coagulation amount. Histopathology at 0, 14, 30, and 90 days showed that the skin tissue reaction was more pronounced for bipolar compared to monopolar FRM. Immunofluorescence showed the expression of TGF-β, Ki67, MMP3, and elastin increased dramatically with both modes, but were higher in the bipolar FRM treated side. The automatic impedance feedback system could effectively adjust the output energy. We found that bipolar FRM produced greater thermal effects, more collagen coagulation, and more pronounced molecular changes compared with monopolar mode in a porcine animal model.

Removal of textile pollutants by electrocoagulation using all bipolar and monopolar connection mode of iron and aluminum composite electrodes

Removal of textile pollutants by electrocoagulation using all bipolar and monopolar connection mode of iron and aluminum composite electrodes

Trajectory correction enables free-running chemical shift encoded imaging for accurate cardiac proton-density fat fraction quantification at 3T

BackgroundMetabolic diseases can negatively alter epicardial fat accumulation and composition, which can be probed using quantitative cardiac chemical shift encoded(CSE) MRI by mapping proton-density fat fraction (PDFF). To obtain motion-resolved high-resolution PDFF maps, we proposed a free-running cardiac CSE-MRI framework at 3T. To employ faster bipolar readout gradients, a correction for gradients imperfections was added using the gradient impulse response function (GIRF) and evaluated on intermediate images and PDFF quantification. MethodsTen minutes free-running cardiac 3D radial CSE-MRI acquisitions were compared in vitro and in vivo at 3T. Monopolar and bipolar readout gradients schemes provided 8 echoes (TE1/ΔTE = 1.16/1.96ms) and 13 echoes (TE1/ΔTE = 1.12/1.07ms), respectively. Bipolar-gradients free-running cardiac fat and water images and PDFF maps were reconstructed with or without GIRF-correction. PDFF values were evaluated in silico, in vitro on a fat/water phantom, and in vivo in 10 healthy volunteers and three diabetic patients. ResultsIn monopolar mode, fat-water swaps were demonstrated in silico and confirmed in vitro. Using bipolar readout gradients, PDFF quantification was reliable and accurate with GIRF correction with a mean bias of 0.03% in silico and 0.36% in vitro while it suffered from artifacts without correction, leading to a PDFF bias of 4.9% in vitro and swaps in vivo. Using bipolar readout gradients, in vivo PDFF of epicardial adipose tissue was significantly lower than in subcutaneous fat (80.4±7.1% vs 92.5±4.3%, P<0.0001). ConclusionAiming for an accurate PDFF quantification, high-resolution free-running cardiac CSE-MRI imaging proved to benefit from bipolar echoes with k-space trajectory correction at 3T. This free-breathing acquisition framework enables to investigate epicardial adipose tissue PDFF in metabolic diseases.

Energy-Efficient Power Management Interface With Adaptive HV Multimode Stimulation for Power-Sensor Integrated Patch-Type Systems.

An energy-efficient power management interface (PMI) with adaptive high-voltage (HV) stimulation capability is presented for patch-type healthcare devices where power management and sensor readout circuits are integrated. For efficient power supply, it proposes a multimode buck converter with an adaptive mode controller, delivering 95.6% peak power conversion efficiency and over 90% efficiency across a wide 4-440 mA output current range. For energy-efficient stimulation, a HV stimulation system is designed to perform mode-adaptive on/off control, where the charge pump (CP) is adopted for periodic power saving. The CP output is adaptively tuned to minimize the stimulator's power waste by utilizing a bio-impedance path in the sensor circuit. The stimulation core supports multimode functionality of current-/voltage-controlled stimulations with monopolar and bipolar modes, providing ten kinds of various stimulation waveform shape. For efficient system operation, battery interface circuits are included to monitor state-of-charge (SOC) conditions, and a device power adjustment scheme is proposed to provide SOC-based maximum 28% power reduced optimal operation of high-resolution and low-power. The power-sensor integrated circuits were fabricated in a 0.18-μm CMOS process, and the proposed schemes were experimentally verified. For system-level feasibility, a patch-type device prototype was manufactured, and both power and bio-signal interfaces were functionally demonstrated.

Ventilating noise barrier with slow wave propagation metamaterial

There has been rapid development of acoustic metamaterials over the past decades, which provide more flexible and effective alternatives to conventional acoustic applications in the field of noise insulation. Recent approaches resolve the conflict between noise insulation and ventilation with partially open meta-structures. Such a binary design eliminates the monopolar and dipolar modes, leading to a total reflection boundary. It holds huge potential in practical scenarios. More simple structures and a broader operating bandwidth are highly desirable to enhance its applicability. This work adopts a binary structure to tune the surface response: open areas with air and slow wave propagation layers with helical-structured metamaterial. These two phases alternate along the radial direction, forming a concentrically layered ventilating insulator. The numerically optimized metamaterial performs efficiently in a wide frequency band and has been validated through experiments.

Combining magnetoencephalography with telemetric streaming of intracranial recordings and deep brain stimulation—A feasibility study

Abstract The combination of subcortical Local Field Potential (LFP) recordings and stimulation with Magnetoencephalography (MEG) in Deep Brain Stimulation (DBS) patients enables the investigation of cortico-subcortical communication patterns and provides insights into DBS mechanisms. Until now, these recordings have been carried out in post-surgical patients with externalised leads. However, a new generation of telemetric stimulators makes it possible to record and stream LFP data in chronically implanted patients. Nevertheless, whether such streaming can be combined with MEG has not been tested. In the present study, we tested the most commonly implanted telemetric stimulator—Medtronic Percept PC with a phantom in three different MEG systems: two cryogenic scanners (CTF and MEGIN) and an experimental Optically Pumped Magnetometry (OPM)-based system. We found that when used in combination with the new SenSight segmented leads, Percept PC telemetric streaming only generates band-limited interference in the MEG at 123 Hz and harmonics. However, the “legacy streaming mode” used with older lead models generates multiple, dense artefact peaks in the physiological range of interest (below 50 Hz). The effect of stimulation on MEG critically depends on whether it is done in bipolar (between two contacts on the lead) or monopolar (between a lead contact and the stimulator case) mode. Monopolar DBS creates severe interference in the MEG as previously reported. However, we found that the OPM system is more resilient to this interference and could provide artefact-free measurements, at least for limited frequency ranges. A resting measurement in the MEGIN system from a Parkinson’s patient implanted with Percept PC and subthalamic SenSight leads revealed artefact patterns consistent with our phantom recordings. Moreover, analysis of LFP-MEG coherence in this patient showed oscillatory coherent networks consistent in their frequency and topography with those described in published group studies done with externalised leads. In conclusion, Percept PC telemetric streaming with SenSight leads is compatible with MEG. Furthermore, OPM sensors could provide additional new opportunities for studying DBS effects.

Hazards Of Monopolar Diathermy Plate In Surgery.

Respected Madam, I would like to draw attention to the hazard of severe skin burns from the using the monopolar diathermy plate electrode during surgical procedures. Diathermy operates in two modes. The monopolar mode where the current enters the patient’s body through an active electrode and exits via a grounding pad attached to the patient.(1) During a recent total abdominal hysterectomy with bilateral salpingo-oophorectomy of a 30-year-old lady with a complex mass, the grounding pad for the electro-cautery had been applied to the left foot, which was found to have third degree burns after completion of the procedure. Similarly, an elderly diabetic lady presented to our outpatient department with the history of a 32 days old non-healing lesion on her left thigh and a Pfannenstiel incision on her abdomen. She had undergone a complete abdominal hysterectomy in another health care centre. During the surgery, the grounding pad was placed on her left thigh which suffered partial thickness burns. According to the patient’s history, the lesion was coin sized at the beginning, but due to poor glycemic control, it continued to involve the surrounding healthy tissue, including the bone. She had previously undergone multiple debridements for the lesion and was advised hip disarticulation after a thorough assessment by the senior management at our department. Even though the procedure was carried out, she, unfortunately, could not survive a few days following the disarticulation. The reason for the burns was a loose application of the grounding pad to the skin of the patient resulting in heat generation and sparking at the site preventing the current to pass safely causing skin burns. To prevent this, the grounding pad should be firmly applied to the skin preferably with crepe bandage. Some other ways to help prevent such complications are adhesive grounding pads and utilization of diathermy machines alarm system.(1)Surgical briefing with the entire perioperative team is necessary so that each individual understands their role in preventing electrosurgical hazards.(2) In addition to this, case reporting of surgical burns to the national database is necessary for implementation of such preventive measures.(3)

Fault‐tolerant DC‐DC converter interconnected with energy storage device for bipolar distribution system: Working modes and optimizing control strategy

AbstractDC short‐circuit fault has become one of the major concerns in bipolar DC system operation under complicated conditions. Compared with conventional two‐port DC‐DC converter, fault‐tolerant DC‐DC converter with multiple external ports is evaluated as a preferential choice for high reliability, availability and flexibility required bipolar DC system due to its capability of fault reconfiguration. This article focuses on a type of fault‐tolerant DC‐DC converter interconnected with DC bus and integrated energy storage devices applied in bipolar DC system and theoretical analyses on transmitted power characteristics under bipolar mode and monopolar mode are also carried out in this article. For bipolar mode, the minimized‐peak‐current control strategy is proposed to reduce current stress on switching devices. As for monopolar mode and source‐port fault mode, the fault reconfiguration method and constant‐transmitted‐power control strategy are designed to eliminate fault impaction and achieve the constant transmitted power of output port connected with critical load, by means of power sharing between input port and normal output port or between the normal output ports. Furthermore, intersection of zero‐voltage‐switching (ZVS) operation area under different working modes is depicted with consideration of two optimizing control. Finally, the performance of the proposed fault reconfiguration method and optimizing control have been tested in PLECS environment and experimental prototype to verify the reliability and flexibility.

Clinical feasibility of radiofrequency ablation using novel adjustable separable electrodes with a multipurpose needle for treating small hepatocellular carcinomas: a prospective single center study

Background The novel separable clustered electrode system with two adjustable active tips (ICAEs) and a fine multipurpose needle (MPN) for in situ temperature monitoring and adjuvant agent injection was developed and validated in an animal study. The purpose of this study was to evaluate the technical efficacy and complication of the novel electrode system for patients who have small HCC. Methods In this prospective, single-center clinical trial, ten participants with 14 small (≤ 2 cm, BCLC 0-A) HCCs referred for RFA were enrolled. A novel electrode system consisting of two ICAEs and one MPN with a thermometer and side holes was used for RFA. The RF energy was delivered using a multichannel RF system combining bipolar and switching monopolar modes. Technical success, efficacy, and complications were evaluated on immediate and one-month follow-up CT. Results Technical success was achieved in 92.9% (13/14) of tumors. One participant withdrew consent after RFA, and technical efficacy was achieved in 91.7% (11/12) of tumors. None showed thermal injury to nontarget organs. All patients were discharged the day after RFA without major complications. The active electrode lengths were adjusted in 60% (6/10) of patients during the procedure to tailor the ablation zone (83.3%, n = 5) or treat two tumors with different sizes (16.7%, n = 1). MPN was capable of continuous temperature monitoring during all ablations (100%, 14/14). Conclusions RFA using a novel electrode system showed acceptable technical efficacy and safety in patients with small HCCs. Further comparative studies are needed for the investigation of the system’s potential benefits compared to conventional electrodes.

Thermal necrosis-aided dental implant removal: A rabbit model pilot study.

The significant advances in the materials and biological aspects of dental implants haven't completely eradicated the implant failures. The removal of osseointegrated but otherwise failed implants present several challenges including adjacent tissues damage and necessity of bone augmentation for reimplantation. Controlled thermal necrosis has emerged as an alternative technique to aid removal of osseointegrated dental implants with minimal to no defect to healthy bone or surrounding tissues. This study aimed to evaluate the thermal necrosis-aided implant removal method in a rabbit osseointegration model. A total of 8 male New Zealand rabbits were used in the study. Two dental implants were placed on each femur of the rabbits. Heating of the implants was performed after 7 weeks following the implantation. Heating was done by contacting the tip of an electrosurgey tool in monopolar mode at different power settings and contact durations (5W - 2 seconds, 5W - 10 seconds, and 10 W - 10 seconds). No heating was done on the control group. Implant stability right after implantation, before heat application and after heat application was determined using an Osstell™ Mentor Device. Following the removal of implants histological analyses were performed to determine the effects of heat application at cellular level. ISQ values of the 10W-10s group was significantly lower compared to the other groups (p<0.001). No indication of progressive necrosis or irreversible damage was observed in any of the groups. However, the percent of empty-apoptotic lacunae were statistically higher in the 5W-10s and the 10W-10s groups compared the control and the 5W-2s groups. Within the conditions of this study, we conclude that heat application with an electrosurgery tool using monopolar mode at 10W power for 10 seconds is optimal for reversing osseointegration with no extensive or progressive damage to the bone.

Electrochemical process for removing nitrate from drinking water by Taguchi model

The use of nitrogenous fertilizers, detergents, the food industry, the power industry, and nuclear fuels are all man-made causes of nitrate pollution. High nitrate levels in drinking water (>50 mg/L) cause blue baby syndrome (methemoglobinemia), particularly in children, as well as the development of carcinogenic nitrosamines. The goal of this applied-analytical research is to see how well a batch electrochemical (E) reactor with monopolar electrode mode can remove nitrate from urban drinking water. The effects of several operational factors on nitrate removal were investigated, including current density, electrode material, pH, and time. The efficacy of nitrate removal is investigated under various working conditions including current density (1–8 mA/cm2), electrode material (aluminum, copper, iron, steel, and zinc), pH (6–8), and time (5–40 min). The amount of nitrate in the body is measured using a process outlined in standard standards (4500-NO3-B). At comparable experimental circumstances, As–As anode–cathode electrodes generate the lowest nitrate removal (0.1%), whereas Zn–Cu anode–cathode electrodes provide the maximum nitrate removal (100%). Batch tests revealed that employing zinc–copper as the anode–cathode electrode configuration resulted in the most nitrate elimination. The increase in current density from 1 to 8 mA/cm2 at the optimal electrode and pH resulted in a 62%–100% improvement in nitrate removal. The increase in duration from 5 to 40 min at the optimal electrode and pH resulted in a 33%–100% increase in nitrate removal. The researchers discovered that increasing current density, electrolysis duration, and pH improved nitrate removal efficiency. As a result of batch tests, the electrochemical reactor seems to be effective in removing nitrate from drinking water and might be regarded a viable method for treating nitrate-polluted water. It was suggested that a bio- electrochemical reactor be investigated.

Optimal bipolar system positioning to provide information about the trapezius activity associated with scapular retraction during shoulder exercises for resistance training

Objective. Recently, the use of EMG biofeedback to make subjects aware of the stabilizer activation associated with scapular retraction during exercise has been of interest, and challenges related to EMG detection have been addressed. Whether there is an optimal bipolar positioning that discriminates the stabilizer activation with retraction from a neutral scapular position during resistance exercises is an open issue that we address here by simultaneously mapping different positions using high-density surface electromyography (HD-sEMG). Approach. Sixteen resistance-trained males performed five pulling exercises with and without scapular retraction, namely barbell rows, dumbbell rows, pull-downs at a lat machine, seated rows, and TRX (total resistance exercises) system rows. HD-sEMG was acquired in a monopolar mode from the medial and lower trapezius (8 × 4 electrodes and inter-electrode distance (ied): 10 mm) and different bipolar systems were simulated in terms of positioning, interelectrode distance, and orientation with respect to the spine: longitudinal with three ieds (20 mm, 30 mm, and 40 mm), one transversal, and two diagonals (ied: 20 mm), totalling six EMG sets. To identify the optimal electrode pair that was able to distinguish between the presence or absence of scapular retraction, we computed: (i) the root mean square (RMS) map for each condition and the difference between them, obtaining a differential RMS map per subject; and (ii) the intersection of cumulative maps, by summing the differential (binary) maps from all subjects. Main results. For the lower trapezius, the results revealed that the diagonal direction (45 degrees; ied: 20 mm) obtained the greater occurrence of intersecting segments within and between exercises than the other electrode configurations, showing low variability for the optimal positioning across exercises. Electrode configuration varied within and between the pulling exercises for the medial trapezius. Significance. This study allows us to identify an optimal bipolar positioning (consistent across subjects and exercises) for lower trapezius activity assessment, representing a guideline for electrode positioning when EMG biofeedback is adopted for selective activation of the lower trapezius during pulling exercises.

Broadband low-frequency sound absorption in open tunnels with deep sub-wavelength Mie resonators

We report both experimentally and numerically that near-perfect absorption of low-frequency sound is realized in an open tunnel embedded with two deep sub-wavelength (0.085 λ) Mie resonators. The resonators are composed of a multiple-cavity structure and an outer frame on three sides. In the eigenmode analysis, we obtain two types of monopolar Mie resonance modes (MMR I&amp;amp;II) in a single resonator around 250 Hz. The eigenfrequency of MMR I is mainly determined by the Helmholtz resonance of each cavity in the multiple-cavity structure, while that of MMR II is closely related to the coupling between the multiple-cavity structure and its outer frame, showing high performances of coupling and sound absorption. Based on the thermal viscous loss of sound energy in the channels created by the mutual coupling of MMR II of both Mie resonators with different diameters, the near-perfect sound absorption through the open tunnel is realized around 283 Hz. More interestingly, by increasing the number of Mie resonators in the tunnel, a broadband near-perfect sound absorption is observed, and the fractional bandwidth can reach about 0.25 and 0.46 for the tunnels with 6 and 13 resonators, The proposed deep sub-wavelength Mie resonator and its associated near-perfect sound absorptions have great potential applications in architectural acoustics and mechanical engineering.

Broadband ventilated meta-barrier based on the synergy of mode superposition and consecutive Fano resonances.

Sound insulation under ventilation conditions is an important issue in acoustic fields that has significant applications in various practical scenarios. The emergence of acoustic metasurfaces breaks the limitation of manipulating large-scale waves at subwavelength scales and enables a better ventilating capability, while there is still a problem that the bandwidth of previous studies is usually smaller than half an octave. Here, we design and experimentally implement a ventilated meta-barrier with subwavelength thickness capable of realizing broadband sound insulation while maintaining efficient ventilation. The underlying mechanism is the synergy of the consecutive Fano resonances and superposition of equal-strength monopolar mode of the gradient helical structure and dipolar mode of the central orifice, leading to an efficient blocking of approximately 90% of sound waves coming from various directions in the range from 1145 to 1815 Hz while preserving high-efficiency ventilation. The experiments are conducted to verify the effectiveness of the resulting device, which is in good agreement with the simulated results and theoretical predictions. Our design with functionality and flexibility opens up possibilities for the design of broadband ventilated acoustic devices and may find important application prospects in diverse fields such as noise control and architectural acoustics.