Electrode Position Research Articles

How the Number and Distance of Electrodes Change the Induced Electric Field in the Cortex during Multichannel tDCS.

Multichannel transcranial direct current stimulation (tDCS) is a promising approach to target neuromodulation of neural networks by making use of variable number of electrodes and distances to facilitate/inhibit specific connectivity patterns. Optimization of the electric field (EF) spatial distribution through computational models can provide a more accurate definition of the stimulation settings that are more effective. In this study, we investigate the effect of increasing the number of cathodes around a central anode placed over the target. We demonstrate that anode-cathode distance has the largest influence in the EF and using more than 3 cathodes did not result in considerable changes in the EF magnitude and direction. This could be relevant for simultaneous tDCS-electroencephalography (EEG) applications, by saving electrode positions for EEG acquisition. Clinical Relevance- This study demonstrates that distance between electrodes is more relevant than electrode number in determining the electric field distribution, and that a highly-focused stimulation can be equally effective with fewer electrodes.

On the Graphical Analysis of the Impedance Response of Passive Electrodes

The analysis of the capacitive behavior of a passive electrode is often a difficult subject because the response obtained by electrochemical impedance spectroscopy (EIS) is characterized by a non-ideal behavior that we try to model by using a constant phase element (CPE) or a Young impedance [1, 2]. In doing so, both the contribution of the double layer and the effects of the current and potential distributions due to the geometry of the electrode are usually neglected.In the case of the contribution of the double layer, such an approximation can be verified a posteriori when data analysis is performed assuming that each of the contributions is a capacitance and that the double layer capacitance, the value of which is usually in the range 10 to 50 µF cm-2, is at least one order of magnitude larger than the value of the impedance of the passive film. However, this simplified approach is often invalid since both the impedance of passive film and the double layer relaxation usually exhibit a non-ideal behavior, thus resulting in the use of CPEs to account for the distribution of dielectric properties of the interface as well as experimental factors (position of the reference electrode, adsorption of impurities...).We present in this work, a new method that uses the graphical analysis of the experimental data in the different frequency ranges (Figure 1), including the low-frequency domain, in order to determine the values of the capacitances without resorting to fitting procedures involving complex functions. This analysis, which is based on the electrical description of the interface, allows the determination of the thickness of a thin layer at the interface, independently of the use of a CPE to describe the distribution of time constants [3]. This will be first demonstrated on synthetic data and then used for the determination of thickness of the oxide film formed on Al electrode.In a second part, we will show that this analysis can be extended to more complicated cases, including when frequency dispersion is observed in the high frequency domain [4]. In that case, the ohmic impedance needs to be properly estimated and then corrected on the experimental results before any data analysis.

Reference Electrodes in PEM Water Electrolysis – a Review and Experimental Investigation of Oxygen and Hydrogen Evolution Reaction Kinetics

Membrane electrode assemblies (MEA) and specifically the anode catalyst are of particular interest in PEM water electrolysis (WE) research as they are considered key components for the capital expenditure and operating expenditure of a PEMWE system (1). An effective method to understand the operation of the MEA is to apply diagnostic tools during the operation of the electrolysis cell. Previous studies in this regard have been mainly limited to the total cell voltage. However, the individual electrode behavior cannot be investigated in the standard setup. To improve the MEA design, the individual electrode behavior is crucial. This can be captured by using a reference electrode (RE).In this work, a salt bridge is used for the first time as RE concept for polarization curves and electrochemical impedance spectroscopy (EIS). The implementation is shown in figure 1.a. Via a porous transport layer impregnated with Nafion, the reference electrode can access the ionic potential of the catalyst layer under investigation. This isolates the kinetic overvoltage from other cell voltage contributions such as ohmic membrane losses, see figure 1.b. The experiments in this study include polarization curves with conventional materials and operating conditions. In addition, EIS is performed to test the applicability of the measurement method in RE operation. Exemplary results are shown in Figure 1.c.In addition, a previous analysis of RE from fuel and electrolytic cells is presented and a classification by electrode type and positioning is made. The key results are subsequently summarized. First, a distinction is made according to the principle behavior of the electrode or its possible configurations. The principal electrode behavior includes the dynamic hydrogen electrode (DHE), the quasireference electrodes, external REs and other configurations. Concrete concepts follow from this. For example, the DHE can be implemented with two platinum wires. By applying a current in the microampere range, the hydrogen evolution reaction takes place in the presence of water. The platinum wire in hydrogen atmosphere becomes the RE (2). Quasireference electrodes are very commonly used with ionic liquids. They are often metal wires (3). A platinum wire is used in a recent work for recording individual electrochemical impedance spectra of anode and cathode (4). Any type of RE can be used as an external RE, such as the silver-silver chloride electrode. Another possibility is to create a free-standing catalyst strip by laser ablation of the MEA. This strip can be used as a reversible electrode to measure the voltage difference with the active catalyst layer participating in the reaction (5).In addition to the behavior of the electrode, a subdivision is made into the position of the RE. In order to separate the potential of one of the two electrodes from the total potential, the measurement can be made as close as possible to the electrode under investigation. This can be implemented by a direct measurement in the catalyst layer (6) or a special geometry of the active area (7). Alternatively, the potential can be measured at the membrane and a correction of the ohmic membrane losses can be used to infer the electrode potential to be investigated. Here, too, two implementations are possible. On the one hand, the RE can be positioned between two membrane halves (4). On the other hand, the membrane can be contacted outside the active area (8).One requirement chosen for the presented concept is the applicability of the RE independent of the geometry of the MEA. Furthermore, the RE should be insensitive to misalignment of the catalyst layers. The exact alignment of the anodic and cathodic catalyst layers is challenging and even small deviations lead to a shift of the potential in the membrane (8). For the two reasons mentioned above, the concept of salt bridge with external RE is used in the direct approach at the electrode.References The national hydrogen strategy (Juni 2020).M. V. Lauritzen, P. He, A. P. Young, S. Knights, V. Colbow and P. Beattie, Journal of New Materials for Electrochemical Systems, 10(3), 143–145 (2007).G. Inzelt, A. Lewenstam, F. Scholz and F. G. K. Baucke, Editors, Handbook of reference electrodes, Springer, Berlin (2013).A. Hartig-Weiß, M. Bernt, A. Siebel and H. A. Gasteiger, J. Electrochem. Soc., 168(11), 114511 (2021).D. Gerteisen, J Appl Electrochem, 37(12), 1447–1454 (2007).E. Brightman, J. Dodwell, N. van Dijk and G. Hinds, Electrochemistry Communications, 52, 1–4 (2015).A. A. Kulikovsky and P. Berg, J. Electrochem. Soc., 162(8), F843-F848 (2015).G. Li and P. G. Pickup, Electrochimica Acta, 49(24), 4119–4126 (2004). Figure 1

Deconvoluting CO2 Electroreduction Membrane-Electrode-Assembly Performance Via Five-Electrode Setup

For CO2 electrolysis, a zero-gap or membrane-electrode-assembly (MEA) configuration is desirable for lowering internal resistances and enabling the use of dilute supporting electrolytes for operation at industrially relevant current densities (>100 mA cm-2). However, to rationally optimize individual electrolyzer components, the contributions that cell components (cathode, anode, and membrane) have on the total cell voltage and internal resistance need to be deconvoluted. Moreover, deconvolution techniques can provide operando snapshots of electrode dynamics and component potentials to help assess component degradation for accelerated stability testing protocols1.In this work, we present a technique for the complete deconvolution of the cell voltage and internal resistances through a five-electrode setup. Unlike similar methods1-3, three additional reference electrodes are introduced: two quasi-reference electrodes on each side of the MEA and one fritted reference electrode in the supporting electrolyte, fed to the anode, for validation of quasi-reference electrode potentials before and after testing. Furthermore, the technique presented in this work was optimized for ease of implementation for a standard test setup for laboratory-scale CO2 electrolysis without requiring modifications to the electrochemical cell endplates or a multi-channel potentiostat.Using this five-electrode setup, a significant membrane impedance at both high and low frequencies is identified for a CO2 reduction MEA employing an anion exchange membrane. As shown via electrochemical impedance spectroscopy (EIS) (Fig. 1b), the membrane accounts for about 40% of the total cell impedance at high frequencies. Notably, the membrane also exhibits a low-frequency impedance attributed to concentration gradients across the membrane4. As an initial validation check, the individual EIS spectra of each component were summed to obtain the measured full cell EIS spectra, albeit with an introduction of measurement noise (Fig. 1b, d).To further validate the setup, the corners of the cathode and anode electrodes were cut asymmetrically to assess sensitivity towards edge effects from electrode misalignment reported for a similar technique (Fig. 1a,c)2. We demonstrate that the membrane impedance can be reversed by deliberately introducing this edge effect (Fig. 1b,d). In this reversed configuration, the measured membrane impedance is flipped due to the apparent reference electrode positions being swapped. Moreover, in this configuration the user inadvertently measures the cathode and anode through the membrane, thereby convoluting the signal. This is of significant concern for directly measuring the cathode mass transport dynamics measured at low frequency (<100 Hz) as the membrane has its own characteristic low-frequency impedance. We will present these results and discuss the application of this method towards catalyst layer optimization, diagnosing a working CO2 reduction MEA employing a cation exchange membrane and comparing the performance of zero-gap and hot-pressed MEA configurations.References O. Sorsa, J. Nieminen, P. Kauranen, and T. Kallio, J. Electrochem. Soc., 166, F1326–F1336 (2019) https://iopscience.iop.org/article/10.1149/2.0461916jes.R. Zeng, R. C. T. Slade, and J. R. Varcoe, Electrochim. Acta, 56, 607–619 (2010) http://dx.doi.org/10.1016/j.electacta.2010.08.032.D. Salvatore and C. P. Berlinguette, ACS Energy Lett., 5, 215–220 (2020) https://pubs.acs.org/doi/10.1021/acsenergylett.9b02356.A. Kozmai et al., Membranes (Basel)., 11, 1–17 (2021). AcknowledgementThis work was supported by the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy under award no. DE-EE0009287.0001 Figure 1

Assessing the Placement of the Cochlear Slim Perimodiolar Electrode Array by Trans Impedance Matrix Analysis: A Temporal Bone Study.

New cochlear implant (CI) electrode arrays provide softer insertion dynamics; however, due to their high flexibility, the possibilities of fold-overs or intraoperative displacements must be taken into account. The position of each individual electrode can only be determined by using high-resolution computed tomography or cone-beam CT. The trans-impedance matrix test (TIM) is an electrophysiological method based on electric field imaging that can provide images of electrode position and electrode folding. Objective: In this experimental research, we evaluated the result of TIM as a method of monitoring cochlear insertion for a precurved slim modiolar electrode array in fresh human temporal bones by analyzing the transimpedance matrix patterns and their correlation with electrode position using high-resolution computed tomography. Material and Methods: Sixteen slim modiolar electrode arrays were inserted into eight fresh Human Temporal Bones. Eight electrodes were inserted according to the correct methodology of insertion, and eight were intentionally folded over. After all insertions, a trans-impedance matrix analysis and a Cone Beam CT (CBCT) were performed in each temporal bone. Results: If we correlated the TIM patterns with the radiological electrode position, we observed that better electrode intracochlear positions indicated more “homogeneous” TIM patterns (intracochlear voltage dropped monotonically as the distance between stimulation and recording contact increased, both toward the apex and toward the base). A correlation where fold-over was detected in the TIM results was found in all eight temporal bone radiological findings. Conclusions: Trans-Impedance Matrix patterns were correlated with the radiological CI electrode position. When a tip fold-over appeared, a matrix with a secondary ridge in addition to the primary ridge was observed in all cases. TIM can be an effective method in the control of electrode positioning.

Effects of tonotopic matching and spatial cues on segregation of competing speech in simulations of bilateral cochlear implants.

In the clinical fitting of cochlear implants (CIs), the lowest input acoustic frequency is typically much lower than the characteristic frequency associated with the most apical electrode position, due to the limited electrode insertion depth. For bilateral CI users, electrode positions may differ across ears. However, the same acoustic-to-electrode frequency allocation table (FAT) is typically assigned to both ears. As such, bilateral CI users may experience both intra-aural frequency mismatch within each ear and inter-aural mismatch across ears. This inter-aural mismatch may limit the ability of bilateral CI users to take advantage of spatial cues when attempting to segregate competing speech. Adjusting the FAT to tonotopically match the electrode position in each ear (i.e., increasing the low acoustic input frequency) is theorized to reduce this inter-aural mismatch. Unfortunately, this approach may also introduce the loss of acoustic information below the modified input acoustic frequency. The present study explored the trade-off between reduced inter-aural frequency mismatch and low-frequency information loss for segregation of competing speech. Normal-hearing participants were tested while listening to acoustic simulations of bilateral CIs. Speech reception thresholds (SRTs) were measured for target sentences produced by a male talker in the presence of two different male talkers. Masker speech was either co-located with or spatially separated from the target speech. The bilateral CI simulations were produced by 16-channel sinewave vocoders; the simulated insertion depth was fixed in one ear and varied in the other ear, resulting in an inter-aural mismatch of 0, 2, or 6 mm in terms of cochlear place. Two FAT conditions were compared: 1) clinical (200–8000 Hz in both ears), or 2) matched to the simulated insertion depth in each ear. Results showed that SRTs were significantly lower with the matched than with the clinical FAT, regardless of the insertion depth or spatial configuration of the masker speech. The largest improvement in SRTs with the matched FAT was observed when the inter-aural mismatch was largest (6 mm). These results suggest that minimizing inter-aural mismatch with tonotopically matched FATs may benefit bilateral CI users’ ability to segregate competing speech despite substantial low-frequency information loss in ears with shallow insertion depths.

Pilot study of a new type of machine vision-assisted stereotactic neurosurgery for EVD placement.

The usage of machine vision technologies for image-based analysis and inspection is increasing. With the advent of the ability to process high-dimension data instantly, the possibilities of machine vision multiply exponentially. Robots now use this technology to assist in surgery. The aim of this study is to explore the efficacy of Surgical Navigation Robot NaoTrac (Brain Navi Biotechnology Co., Ltd.), which utilizes machine vision-inspired technology for patient registration and stereotactic external ventricular drainage (EVD) by the robotic arm. Preoperative and postoperative computed tomography (CT) scans were acquired for each case. The surgeons planned the targets and trajectories with the preoperative CT images. The postoperative CT images were utilized in the accuracy measurements. All 14 cases had cerebrospinal fluid drained through the catheter. The NaoTrac placed the catheter into the frontal horn in one attempt in 13 cases and was able to drain CSF in 12 cases. Not a single case had any bleeding or intraoperative complications. The average time spent on the patient registration was 142.8s. The mean target deviation was 1.68mm, and the mean angular deviation was 1.99°, all within the accepted tolerance for minimal tissue damage. The results of this report demonstrate that machine vision-inspired patient registration is feasible and fast. NaoTrac has demonstrated its accuracy and safety in performing frameless catheter placement in 13 clinical cases. Other stereotactic neurosurgical operations such as stereotactic biopsy, depth electrode placement, deep brain stimulation electrode positioning, and neuroendoscopy may also be benefited from the assistance of NaoTrac.

Utility of Postoperative Imaging Software for Deep Brain Stimulation Targeting in Patients with Movement Disorders

The objective of this study was to evaluate the accuracy of the SureTune3 postoperative imaging software in determining the location of a deep brain stimulation (DBS) electrode based on clinical outcomes and the adverse effects (AEs) observed. Twenty-six consecutive patients with Parkinson disease (n= 17), essential tremor (n= 8), and dystonia (n= 1) who underwent bilateral DBS surgery (52 electrodes) were included in this study. Presurgical assessments were performed in all patients prior to surgery and at 3 and 6months after surgery, using quality-of-life and clinical scales in each case. The SureTune3 software was used to evaluate the anatomical positioning of the DBS electrodes. Following DBS surgery, motor and quality-of-life improvement was observed in all patients. Different AEs were detected in 12 patients, in 10 of whom (83.3%) SureTune3 related the symptoms to the positioning of an electrode. A clinical association was observed with SureTune3 for 48 of 52 (92.3%) electrodes, whereas no association was found between the AEs or clinical outcomes and the SureTune3 reconstructions for 4 of 52 electrodes (7.7%) from 4 different patients. In 2 patients, the contact chosen was modified based on the SureTune3 data, and in 2 cases, the software helped determine that second electrode replacement surgery was necessary. The anatomical position of electrodes analyzed with SureTune3 software was strongly correlated with both the AEs and clinical outcomes. Thus, SureTune3 may be useful in clinical practice, and it could help improve stimulation parameters and influence decisions to undertake electrode replacement surgery.

A simple procedure to produce bio-mimic brick-and-mortar microstructure in commercially pure Ti

The extremely high fracture toughness of nacre is known to arise from its brick-and-mortar microstructure and has inspired the development of metals, metallic glasses and composites with similar bio-mimic microstructures. Although various approaches have been proposed to produce materials with a brick-and-mortar microstructure, including powder metallurgy, electro deposition, spray deposition, etc., the production of large-scale samples remains to be a challenge. In this research, we present a simple way to produce large samples of commercially pure Ti with a brick-and-mortar microstructure, which includes a pre-heat-treatment followed by deformation in the single-phase temperature region and subsequent annealing. EBSD characterization shows a layered microstructure in the produced samples resembling a brick-and-mortar structure.

Photocatalytic water splitting on Cu2SnS3 photoelectrode: Effects of Cu/Sn composite ratio on the photoelectrochemical performance

Solar hydrogen production from water splitting has been regarded as one of the most promising energy alternatives to fossil fuel because of environmentally friendly nature and abundant water resources. Copper tin sulfide (Cu2SnS3, CTS), a non-toxic p-type semiconductor composed of abundant elements in the earth crust has been employed for photoelectrochemical (PEC) water splitting. The CTS photoelectrodes were prepared by the electrodeposition (ED) of Cu and Sn ions with different Coulomb charge, followed by heating at 560 °C in the presence of solid sulfur. The morphology and crystal structures of the CTS have been characterized by SEM-EDX, XRD, Raman spectroscopies and electrochemical measurement. The CTS photoelectrode with different Cu/Sn composition has a monoclinic structure, and it exhibits optical absorption from visible-light to infrared light having a bandgap of ca. 0.90 eV. The Pt-In2S3/CTS photoelectrode was demonstrated to generate H2 by the photocatalytic water splitting under solar light irradiation. Moreover, it was found that the PEC properties strongly depend on the Cu/Sn composite ratio of CTS, and the Sn-rich CTS exhibited the high PEC water splitting to produce H2.

Design of multi-pad electrotactile system envisioned as a feedback channel for supernumerary robotic limbs.

Providing real-time haptic feedback is an important, but still not sufficiently explored aspect of the use of supernumerary robotic limbs (SRLs). We present a multi-pad electrode for conveying multi-modal proprioceptive and sensory information from SRL to the user's thigh and propose a method for stimuli calibration. Within two pilot tests, we investigated return electrode configuration and active electrode discrimination in three healthy subjects to select the appropriate electrode pad topology. Based on the obtained results and anthropometric data from the literature, the electrode was designed to have three branches of 10 pads and two additional pads that can be displaced over/under the electrode branches. The electrode was designed to be connected to the stimulator that allows full multiplexing so that specific branches can serve as a common return electrode. To define the procedure for application of this system, the sensation, localization, and discomfort thresholds applicable for the novel electrode were determined and analyzed in 10 subjects. The results showed no overlaps between the three thresholds for individual pads, with significantly different average values, suggesting that the selected electrode positioning and design provide a good active range of useful current amplitude. The results of the subsequent analysis suggested that the stimuli intensity level of 200% of the sensation threshold is the most probable value of the localization threshold. Furthermore, this level ensures a low chance (i.e., 0.7%) of reaching the discomfort. We believe that envisioned electrotactile system could serve as a high bandwidth feedback channel that can be easily set up to provide proprioceptive and sensory feedback from supernumerary limbs.

Insertion Guidance Based on Impedance Measurements of a Cochlear Electrode Array.

The cochlear implantable neuromodulator provides substantial auditory perception to those with severe or profound impaired hearing. Correct electrode array positioning in the cochlea is one of the important factors for quality hearing, and misplacement may lead to additional injury to the cochlea. Visual inspection of the progress of electrode insertion is limited and mainly relies on the surgeon's tactile skills, and there is a need to detect in real-time the electrode array position in the cochlea during insertion. The available clinical measurement presently provides very limited information. Impedance measurement may be used to assist with the insertion of the electrode array. Using computational modeling of the cochlea, and its local tissue layers merging with the associated neuromodulator electrode array parameters, the impedance variations at different insertion depths and the proximities to the cochlea walls have been analyzed. In this study, an anatomical computational model of the temporal region of a patient is used to derive the relationship between impedance variations and the electrode proximity to the cochlea wall and electrode insertion depth. The aim was to examine whether the use of electrode impedance variations can be an effective marker of electrode proximity and electrode insertion depth. The proposed anatomical model simulates the quasi-static electrode impedance variations at different selected points but at considerable computation cost. A much less computationally intensive geometric model (~1/30) provided comparative impedance measurements with differences of <2%. Both use finite element analysis over the entire cross-section area of the scala tympani. It is shown that the magnitude of the impedance varies with both electrode insertion depth and electrode proximity to the adjacent anatomical layers (e.g., cochlea wall). In particular, there is a 1,400% increase when the electrode array is moved very close to the cochlea wall. This may help the surgeon to find the optimal electrode position within the scala tympani by observation of such impedance characteristics. The misplacement of the electrode array within the scala tympani may be eliminated by using the impedance variation metric during electrode array insertion if the results are validated with an experimental study.

Mapping Inter-individual Functional Connectivity Variability in TMS Targets for Major Depressive Disorder.

Transcranial magnetic stimulation (TMS) is an emerging alternative to existing treatments for major depressive disorder (MDD). The effects of TMS on both brain physiology and therapeutic outcomes are known to be highly variable from subject to subject, however. Proposed reasons for this variability include individual differences in neurophysiology, in cortical geometry, and in brain connectivity. Standard approaches to TMS target site definition tend to focus on coordinates or landmarks within the individual brain regions implicated in MDD, such as the dorsolateral prefrontal cortex (dlPFC) and orbitofrontal cortex (OFC). Additionally considering the network connectivity of these sites (i.e., the wider set of brain regions that may be mono- or poly-synaptically activated by TMS stimulation) has the potential to improve subject-specificity of TMS targeting and, in turn, improve treatment outcomes. In this study, we looked at the functional connectivity (FC) of dlPFC and OFC TMS targets, based on induced electrical field (E-field) maps, estimated using the SimNIBS library. We hypothesized that individual differences in spontaneous functional brain dynamics would contribute more to downstream network engagement than individual differences in cortical geometry (i.e., E-field variability). We generated individualized E-field maps on the cortical surface for 121 subjects (67 female) from the Human Connectome Project database using tetrahedral head models generated from T1- and T2-weighted MR images. F3 and Fp1 electrode positions were used to target the left dlPFC and left OFC, respectively. We analyzed inter-subject variability in the shape and location of these TMS target E-field patterns, their FC, and the major functional networks to which they belong. Our results revealed the key differences in TMS target FC between the dlPFC and OFC, and also how this connectivity varies across subjects. Three major functional networks were targeted across the dlPFC and OFC: the ventral attention, fronto-parietal and default-mode networks in the dlPFC, and the fronto-parietal and default mode networks in the OFC. Inter-subject variability in cortical geometry and in FC was high. Our analyses showed that the use of normative neuroimaging reference data (group-average or representative FC and subject E-field) allows prediction of which networks are targeted, but fails to accurately quantify the relative loading of TMS targeting on each of the principal networks. Our results characterize the FC patterns of canonical therapeutic TMS targets, and the key dimensions of their variability across subjects. The high inter-individual variability in cortical geometry and FC, leading to high variability in distributions of targeted brain networks, may account for the high levels of variability in physiological and therapeutic TMS outcomes. These insights should, we hope, prove useful as part of the broader effort by the psychiatry, neurology, and neuroimaging communities to help improve and refine TMS therapy, through a better understanding of the technology and its neurophysiological effects.

Investigation on the binary ionization choices for large conjugated amines during electrospray ionization.

Generally, amines form protonated cations ([M + H]+ ) in positive polarity during electrospray ionization (ESI). However, it was found that large conjugated amines (LCAs) had binary ionization choices of generating either radical cations (M•+ ) or [M + H]+ during ESI. Investigation on the mechanism would further our understanding of ESI. In this work, the binary ionization behavior of LCAs was reported and studied. Internal factors (functional groups and sizes of conjugated systems) and external factors (solvent type, flow rate, and electrode position) were systematically investigated and discussed. For the internal factors, electron-donating groups and large conjugated structures of LCAs were conducive to the generation of M•+ . For the external factors, aprotic solvent, higher flow rate, and shorter distance from the electrode to the spray cone facilitated the formation of M•+ but hampered the generation of [M + H]+ . The present study illustrated that the formations of M•+ and [M + H]+ for LCAs were two independent processes. The M•+ cations of LCAs were formed on the surface of the electrode through electrochemical oxidation, whereas the [M + H]+ cations were generated following the typical ESI evolution process. By regulating the external factors, the ionization results of LCAs could be well modulated.

The Relation of Cochlear Implant Electrode Array Type and Position on Continued Hearing Preservation.

To analyze the relationship of electrode array (EA) type and position on hearing preservation longevity following cochlear implantation. Retrospective chart review. Tertiary referral center. Adult cochlear implant recipients between 2013 and 2019 with hearing preserved postoperatively and postoperative CT scans. CT scan analysis of EA position. Stepwise regression to determine influence of EA position, EA type, and patient demographics on postoperative low frequency hearing. Low frequency pure tone average (LFPTA), LFPTA shift, angular insertion depth, base insertion depth, scalar position, mean perimodiolar distance. Of 792 cochlear implant recipients, 121 had preoperative LFPTA <80 dB HL with 60 of the 121 (49.6%) implanted with straight, 32 (26.4%) with precurved, styletted, and 29 (24.0%) implanted precurved, nonstyletted EA. Mean follow up was 28.6 months (range 1-103). There was no statistically significant difference in activation, 6- and 12-month, and last follow-up LFPTA (125, 250, and 500 Hz) shift based on EA type (straight p = 0.302, precurved, styletted p = 0.52, precurved, nonstyletted p = 0.77). Preoperative LFPTA and age of implantation were significant predictors of LFPTA shift at activation, accounting for 30.8% of variance ( F [2, 113] = 26.603, p < 0.0001). LFPTA shift at activation, scalar position, and base insertion depth were significant predictors of variability and accounted for 39.1% of variance in LFPTA shift at 6 months ( F [3, 87] = 20.269, p < 0.0001). Only LFPTA shift at 12 months was found to be a significant predictor of LFPTA shift at last follow up, accounting for 41.0% of variance ( F [1, 48] = 32.653, p < 0.0001). Patients had excellent long-term residual hearing regardless of EA type. Age, preoperative acoustic hearing, and base insertion depth may predict short term preservation, while 12-month outcomes significantly predicted long-term hearing preservation.

A Feature-Fused Convolutional Neural Network for Emotion Recognition From Multichannel EEG Signals

Automatic emotion recognition based on multichannel electroencephalogram (EEG) data is a fundamental but challenging problem. Some previous researches ignore the correlation information of brain activity among the inter-channel and inter-frequency bands, which may provide potential information related to emotional states. In this work, we propose a 3-D feature construction method based on spatial-spectral information. First, power values per channel are arranged into a 2-D spatial feature representation according to the position of electrodes. Then, features from different frequency bands are arranged into a 3-D integration feature tensor to capture their complementary information. Simultaneously, we propose a novel framework based on feature fusion modules and dilated bottleneck-based convolutional neural networks (DBCN) which builds a more discriminative model to process the 3-D features for EEG emotion recognition. Both participant-dependent and participant-independent protocols are conducted to evaluate the performance of the proposed DBCN on the DEAP benchmark datasets. Mean 2-class classification accuracies of 89.67% / 90.93% (for participant-dependent) and 79.45% / 83.98% (for participant-independent) were respectively achieved for arousal / valence. These results suggest the proposed method based on the integration of spatial and spectral information could be extended to the assessment of mood disorder and human-computer interaction (HCI) applications.

Review of the effectiveness of neuromuscular electrical stimulation in the treatment of dysphagia - an update.

Background: Neuromuscular electrical stimulation (NMES) has been used as a treatment option in the therapy of dysphagia for several years. In a previous review of the literature, it was concluded that NMES might be a valuable adjunct in patients with dysphagia and in patients with vocal fold paresis. However, due to different stimulation protocols, electrode positioning and various underlying pathological conditions, it was difficult to compare the studies which were identified and it was concluded that more empirical data is needed to fully understand the benefits provided by NMES. The purpose of this systematic review is, therefore, to evaluate recent studies regarding a potential effectiveness of transcutaneous NMES applied to the anterior neck as a treatment for dysphagia considering these different aspects.Method: For this systematic review, a selective literature research in PubMed has been carried out on 5th May 2021 using the terms electrical stimulation AND dysphagia and screened for inclusion criteria by two reviewers in Rayyan. The search resulted in 62 hits.Results: Studies were excluded due to their publication language; because they did not meet inclusion criteria; because the topical focus was a different one; or because they did not qualify as level 2 studies. Eighteen studies were identified with varying patient groups, stimulation protocols, electrode placement and therapy settings. However, 16 studies have reported of beneficial outcomes in relation with NMES.Discussion: The purpose of this systematic review was to evaluate the most recent studies regarding a potential effectiveness of NMES as a treatment for oropharyngeal dysphagia considering different aspects. It could generally be concluded that there is a considerable amount of level 2 studies which suggest that NMES is an effective treatment option, especially when combined with TDT for patients with dysphagia after stroke and patients with Parkinson’s disease, or with different kinds of brain injuries. Further research is still necessary in order to clarify which stimulation protocols, parameters and therapy settings are most beneficial for certain patient groups and degrees of impairment.

Circular Nonuniform Electric Field Gel Electrophoresis for the Separation and Concentration of Nanoparticles.

A circular nonuniform electric field strategy coupled with gel electrophoresis was proposed to control the precise separation and efficient concentration of nano- and microparticles. The circular nonuniform electric field has the feature of exponential increase in the electric field intensity along the radius, working with three functional zones of migration, acceleration, and concentration. The distribution form of electric field lines is regulated in functional zones to control the migration behaviors of particles for separation and concentration by altering the relative position of the ring electrode (outside) and rodlike electrode (inner). The circular nonuniform electric field promotes the target-type and high-precision separation of nanoparticles based on the difference in charge-to-size ratio. The concentration multiple of nanoparticles is also controlled randomly with the alternation of radius, taking advantage of vertical extrusion and concentric converging of the migration path. This work provides a brand new insight into the simultaneous separation and concentration of particles and is promising for developing a versatile tool for the separation and preparation of various samples instead of conventional methods.

Grouting Effect Detection within the Floor of a Coal Seam Using 3D Electric Resistivity Tomography (ERT) with Arbitrary Electrode Positions

To prevent the occurrence of water inrush from the working face floor, explorations of water-rich floors are necessary. For a working face with a regular shape, a water-rich floor can be detected by laying electrodes and cables around the working face. However, the rectangular working face develops an irregular shape, and the exploration of water in irregular working faces is a difficulty in the study of 3D electric resistivity tomography (ERT). In this paper, an unconventional dipole–dipole array is used for data acquisition and the potential of a non-grid point electrode is replaced by the potential of the surrounding electrode, which identifies a water-rich floor using 3D ERT with arbitrary electrode positions. Taking the 8826 irregular working face of the Baizhuang coal mine as an example, the working face is explored by 3D ERT, the anomalous area is delineated, and targeted grouting is carried out in the anomalous area. After grouting, the grouting effect is detected by 3D ERT, and the safe mining of the working face is ensured. The results show that grouting effect detection within the floor of a coal seam using 3D electric resistivity tomography (ERT) with arbitrary electrode positions could be applied to solving the problem of water-rich exploration of floors in irregular working faces.

Thermal ablation effects on rotors that characterize functional re-entry cardiac arrhythmia.

Thermal ablation is a well-established successful treatment for cardiac arrhythmia, but it still presents limitations that require further studies and developments. In the rotor-driven functional re-entry arrhythmia, tissue heterogeneity results on the generation of spiral/scroll waves and wave break dynamics that may cause dangerous sustainable fibrillation. The selection of the target region to perform thermal ablation to mitigate this type of arrhythmia is challenging, since it considerably affects the local electrophysiology dynamics. This work deals with the numerical simulation of the thermal ablation of a cardiac muscle tissue and its effects on the dynamics of rotor-driven functional re-entry arrhythmia. A non-homogeneous two-dimensional rectangular region is used in the present numerical analysis, where radiofrequency ablation is performed. The electrophysiology problem for the propagation of the action potential in the cardiac tissue is simulated with the Fenton-Karma model. Thermal damage caused to the tissue by the radiofrequency heating is modeled by the Arrhenius equation. The effects of size and position of a heterogeneous region in the original muscle tissue were first analyzed, in order to verify the possible existence of the functional re-entry arrhythmia during the time period considered in the simulations. For each case that exhibited re-entry arrhythmia, six different ablation procedures were analyzed, depending on the position of the radiofrequency electrode and heating time. The obtained results revealed the effects of different model parameters on the existence and possible mitigation of the functional re-entry arrhythmia.