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1.
Waste Manag ; 118: 677-687, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33011545

RESUMO

A multi-analytical methodology is implemented to characterize several sieving fractions of industrial samples of Black Mass (BM) powders originating from the thermo-mechanical treatment of cylindrical and prismatic-type spent nickel metal-hydride (Ni-MH) batteries. Elemental analyses of 17 elements (including C and O) indicate that the elemental composition of the powders (greater than93 %wt) does not depend on the battery type nor on the sieving fraction. XRD analyses evidence several phases (including Ni, NiO, CeO2 and C) but their quantification is not possible. Beyond these standard characterisations, magnetic susceptibility measurements demonstrate that the amount of metallic nickel versus nickel oxide increases with the sieving fraction, and that powders from prismatic-type batteries contain twice as much metallic nickel than cylindrical ones. Thanks to statistical analysis (based on clustering algorithms) of an electron probe µ-analysis (EPMA) compositional map, the complete methodology allows us to propose a full phase distribution for the BM particles. Three types of particles are identified and quantified. They originate from the partial oxidation of the battery components (anode active mass, anode current collector, cathode active mass and cathode current collector). The whole picture highlights the joint importance of battery ageing mechanisms, thermal deactivation and BM sieving steps on powder composition.


Assuntos
Metais , Níquel , Fontes de Energia Elétrica , Eletrodos , Pós
2.
Nat Commun ; 11(1): 5075, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033245

RESUMO

Nickel-iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel-iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel-iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies.


Assuntos
Desulfotomaculum/metabolismo , Hidróxidos/metabolismo , Níquel/metabolismo , Oxigênio/metabolismo , Corrosão , Teoria da Densidade Funcional , Eletroquímica , Eletrodos , Análise Espectral Raman , Espectroscopia por Absorção de Raios X
3.
Artigo em Inglês | MEDLINE | ID: mdl-33017924

RESUMO

The EEG has showed that contains relevant information about recognition of emotional states. It is important to analyze the EEG signals to understand the emotional states not only from a time series approach but also determining the importance of the generating process of these signals, the location of electrodes and the relationship between the EEG signals. From the EEG signals of each emotional state, a functional connectivity measurement was used to construct adjacency matrices: lagged phase synchronization (LPS), averaging adjacency matrices we built a prototype network for each emotion. Based on these networks, we extracted a set node features seeking to understand their behavior and the relationship between them. We found through the strength and degree, the group of representative electrodes for each emotional state, finding differences from intensity of measurement and the spatial location of these electrodes. In addition, analyzing the cluster coefficient, degree, and strength, we find differences between the networks from the spatial patterns associated with the electrodes with the highest coefficient. This analysis can also gain evidence from the connectivity elements shared between emotional states, allowing to cluster emotions and concluding about the relationship of emotions from EEG perspective.


Assuntos
Eletroencefalografia , Emoções , Terapia Comportamental , Eletrodos
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 116-119, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33017944

RESUMO

Many prior studies on EEG-based emotion recognition did not consider the spatial-temporal relationships among brain regions and across time. In this paper, we propose a Regionally-Operated Domain Adversarial Network (RODAN), to learn spatial-temporal relationships that correlate between brain regions and time. Moreover, we incorporate the attention mechanism to enable cross-domain learning to capture both spatial-temporal relationships among the EEG electrodes and an adversarial mechanism to reduce the domain shift in EEG signals. To evaluate the performance of RODAN, we conduct subject-dependent, subject-independent, and subject-biased experiments on both DEAP and SEED-IV data sets, which yield encouraging results. In addition, we also discuss the biased sampling issue often observed in EEG-based emotion recognition and present an unbiased benchmark for both DEAP and SEED-IV.


Assuntos
Eletroencefalografia , Emoções , Encéfalo , Eletrodos , Aprendizagem
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 225-231, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33017970

RESUMO

Upper gastrointestinal (GI) disorders are highly prevalent, with gastroparesis (GP) and functional dyspepsia (FD) affecting 3% and 10% of the US population, respectively. Despite overlapping symptoms, differing etiologies of GP and FD have distinct optimal treatments, thus making their management a challenge. One such cause, that of gastric slow wave abnormalities, affects the electromechanical coordination of pacemaker cells and smooth muscle cells in propelling food through the GI tract. Abnormalities in gastric slow wave initiation location and propagation patterns can be treated with novel pacing technologies but are challenging to identify with traditional spectral analyses from cutaneous recordings due to their occurrence at the normal slow wave frequency. This work advances our previous work in developing a 3D convolutional neural network to process multi-electrode cutaneous recordings and successfully classify, in silico, normal versus abnormal slow wave location and propagation patterns. Here, we use transfer learning to build a method that is robust to heterogeneity in both the location of the abnormal initiation on the stomach surface as well as the recording start times with respect to slow wave cycles. We find that by starting with training lowest-complexity models and building complexity in training sets, transfer learning one model to the next, the final network exhibits, on average, 80% classification accuracy in all but the most challenging spatial abnormality location, and below 5% Type-I error probabilities across all locations.


Assuntos
Dispepsia , Gastroparesia , Simulação por Computador , Eletrodos , Gastroparesia/diagnóstico , Humanos
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 430-433, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018020

RESUMO

In this paper, we review several advances in different fields that provide new potential for brain-computer interfaces enabled by directly interfacing biological neural networks with electrodes, including recent successes with liquid injected conductive channels and mesh electronics supported by 3D scaffolds. Based on this review, it is clear that the success of biological neural connectivity is dependent on the precision and density of the inserted electrodes. In order to better understand the dynamics of this relationship, we propose a simple impedance-based electrode connectivity model, based on which we perform a simulation of the impact of both electrode density and electrode precision on the amount of information lost as part of the connection. Although the examples illustrated are more informative rather than conclusive, the fundamental takeaway from this work is that electrode density is a substantially important parameter while electrode precision is necessarily helpful.


Assuntos
Interfaces Cérebro-Computador , Condutividade Elétrica , Impedância Elétrica , Eletrodos , Eletrônica
7.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 837-840, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018115

RESUMO

Gastric motility is in part coordinated by bio-electrical slow waves. The wavefront orientation of the slow wave contains vital physiological information about the motility condition of the gastrointestinal system. Dysmotility was shown to be associated with dysrhythmic propagation of the slow wave. The most commonly used method to detect wavefront orientation is computationally expensive because of the involvement of activation time identification. The information of local directionality contained in bipolar slow wave recordings could be used to detect the wavefront orientation. An algorithm called bipolar direction detection was developed to utilize the information contained in the bipolar slow wave recordings. Bipolar recordings were constructed by subtracting the unipolar in vivo recordings of directional electrode pairs. Then, time delay information was used to detect the wavefront direction. The algorithm was verified using synthetic data and validated using experimental data. Ten high-resolution in vivo slow wave signals from 5 pigs were recorded for a duration of 2 minutes. The performance was compared against the semi-automated approach, resulting in an average angle error of 20° for the experimental data. The algorithm was able to detect slow wave wavefront orientation with minimal errors rapidly.Clinical relevance-The ability to rapidly detect slow wave propagation direction will enable effective analysis of large data sets, through which we can obtain a better understanding of functional motility disorders and help with diagnosis and treatment.


Assuntos
Transtorno Bipolar , Estômago , Algoritmos , Animais , Transtorno Bipolar/diagnóstico , Eletrodos , Reprodução , Suínos
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1448-1451, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018263

RESUMO

In Electrical Impedance Tomography (EIT) the coaxial cables used to connect the electrodes to the electronics have long been a concern due to their impact on system performance. Driving the shield of the cable is useful, since it mitigates the shunt capacitance. However, this approach introduces complexity and, sometimes, stability issues. Using "active electrodes", i.e. placing the front end of the electronics at the electrode end of the cables, is also helpful but can introduce packaging and hygiene problems. In this paper, a new type of high-precision current source is described and its performance is studied when driving loads through a coaxial cable. This new current source adjusts its current output to compensate for current lost in any shunt impedance to ground, including the shunt losses in the cable. Experimental results for frequencies up to 1 MHz are provided, comparing performance with resistive and complex loads connected without a cable, with 1 m of RG-174 coaxial cable with a driven shield, and 1 m of RG-174 coaxial cable with a grounded shield. The results for all 3 cases are similar, demonstrating that the source can provide satisfactory performance with a grounded-shield cable.


Assuntos
Tomografia Computadorizada por Raios X , Tomografia , Impedância Elétrica , Eletrodos , Equipamentos de Proteção
9.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1452-1456, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018264

RESUMO

A novel method for measuring the shunt impedance of current sources in Electrical Impedance Tomography (EIT) systems is introduced. In an EIT system, electrical currents with theoretical sum of zero, are applied to the body and any mismatch between the currents results in current going through an extra grounded electrode. Since the N - 1 current patterns applied in an N-electrode EIT system are orthogonal to each other, by introducing an additional linearly- independent current pattern, a system of linear equations can be established from which the unknown shunt impedances can be calculated. The framework of the proposed scheme is introduced and its effectiveness is validated through both simulation and practical implementation. The experimental results show that by measuring the shunt impedances with the proposed method and using those values to adjust the current sources, the current passing through the grounded electrode is significantly reduced.


Assuntos
Tomografia Computadorizada por Raios X , Tomografia , Algoritmos , Impedância Elétrica , Eletrodos
10.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 1457-1460, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018265

RESUMO

Electrical impedance tomography (EIT) creates images of the internal conductivity, normally using only body surface electrodes. There has been little investigation of internal electrodes, however an internal electrode position promises to increase sensitivity in the most central regions of the chest to improve impedance imaging of the inner regions of the lung and heart. This paper investigates EIT sensitivity in simulation with various internal electrode positions. Results show in increased sensitivity in internal regions which is promising for imaging pulsatile activity within the heart.


Assuntos
Algoritmos , Tomografia , Impedância Elétrica , Eletrodos , Tomografia Computadorizada por Raios X
11.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2023-2026, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018401

RESUMO

Microwave ablation has become a common treatment method for liver cancers. Unfortunately, microwave ablation success is correlated with clinician's ability for proper electrode placement and assess ablative margins, requiring accurate imaging of liver tumors and ablated zones. Conventionally, ultrasound and computed tomography are utilized for this purpose, yet both have their respective drawbacks. As an alternate approach, electrode displacement elastography offers promise but is still plagued by decorrelation artifacts reducing lesion depiction and visualization. A recent filtering method, namely dictionary representation, has improved contrast-to-noise ratios without reducing delineation contrast. As a supplement to this recent work, this paper evaluates adaptations on this initial dictionary-learning algorithm and applies them to an EDE phantom and 15 in-vivo patient datasets. Two new adaptations of dictionary representations were evaluated, namely a combined dictionary and magnitude-based dictionary representation. When comparing numerical results, the combined dictionary representation algorithm outperforms the previous developed dictionary representation in signal-to-noise (1.54 dB) and contrast-to-noise (0.67 dB) ratios, while a magnitude dictionary representation produces higher noise levels, but improves visualized strain tensor resolution.


Assuntos
Técnicas de Imagem por Elasticidade , Neoplasias Hepáticas , Eletrodos , Humanos , Neoplasias Hepáticas/diagnóstico por imagem , Imagens de Fantasmas
12.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2221-2226, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018449

RESUMO

Single-cell dielectrophoretic movement and dielectrophoretic deformation of monocyte cells were interrogated applying 20 Vpp, 50 kHz to 1 MHz signal in the 3D carbon electrode array. Heterogeneity of the monocyte population is shown in terms of the crossover frequencies, translational movement, and deformation index of the cells. The results presented that crossover range for monocytes was 100 kHz - 200 kHz, the translational movement of the cells was rapidly altered when the initial positions of the cells were in the negative dielectrophoretic region. Finally, the deformation index of the monocyte population varied from 0.5 to 1.5.


Assuntos
Carbono , Monócitos , Eletrodos , Eletroforese
13.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2500-2503, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018514

RESUMO

The cellular morphology is a vital biological characteristic for determining explicit information about its physiological state. Monitoring real-time cell shape is of great importance in infectious pathogen detection. Here, we designed a highly sensitive coplanar electrode sensing system and merged it with planar electrodes for simultaneous impedance signals in two dimensions. We simulated the proposed design in this study for the detection of different single cell pathogens based on their morphology. The optimized design has a great potential to monitor and characterize different bacteria based on their sizes and shapes. In this report, spherical and rod shaped particles were used to illustrate the device performance. This simple and extremely sensitive modified electrode design is very promising for bacterial detection and will serve as a future guiding tool for discriminating different morphologies of singular cells.


Assuntos
Impedância Elétrica , Eletrodos , Citometria de Fluxo
14.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2622-2625, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018544

RESUMO

Respiratory rate (RR), which is an essential observation for prediagnosis, can be obtained indirectly from the electrocardiogram (ECG), the so-called ECG-derived respiration (EDR). In this paper, we compared embroidered electrodes with gel electrodes on their performance in capturing EDR signals and analysed which frequency feature best estimates RR. Data were collected from 9 healthy subjects. Results reveal that (1) embroidered electrodes performed similarly to gel electrodes (P = 0.077), (2) using the median frequency of the obtained EDR signals is significantly better (P = 0.01) than the counting methods in the time domain. The obtained results are relevant for the future development of textile-based sensors.


Assuntos
Eletrocardiografia , Taxa Respiratória , Eletrodos , Respiração , Têxteis
15.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2885-2888, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018609

RESUMO

Human Machine Interfaces (HMIs) can provide critical support and improve daily task functionality for prosthesis users or social interaction for patients with locked-in syndrome using an assistive communication device. One goal in the development of sophisticated HMIs is to reduce the cognitive load (CL) they place on the user to promote the use of the technology. Electroencephalogram (EEG)-derived measures collected with wired wet-electrode systems have been used to assess CL in laboratory environments and have demonstrated acceptable test-retest reliability. Assessment of CL during real-world unconstrained HMI operation, however, requires the use of a wireless dry-electrode EEG system which provides easier electrode application and untethered movement. However, the test-retest reliability of wireless dry-electrode systems to quantify CL has not been explored. Ensuring the consistent capture of CL-related signals across multiple sessions is critical if these devices are to be used to assess how improvements in HMIs affect CL. Therefore, the current study used a wireless dry-electrode EEG system to compare Evoked Response Potential (ERP) features of a simple auditory oddball task to measure CL during two separate testing sessions a week apart. ERPs of 11 subjects were recorded while participants performed a virtual task at two difficulty levels. A significant correlation was found between the P300 component of the ERPs and subjective ratings of CL during both testing sessions. Furthermore, there was a statistically significant test-retest reliability for this same ERP feature and similar signal-to-noise ratios (SNRs) across sessions.Clinical Relevance- This is an initial step in validating wireless dry-electrode EEG systems to assess cognitive load across multiple sessions. The evidence presented is critical if dry-wireless EEG systems are to be used to identify aspects of HMIs that reduce CL in clinical and real-life environments. Assessing CL in unconstrained environments can better inform clinicians and technology developers in their design of future HMIs.


Assuntos
Eletroencefalografia , Potenciais Evocados , Cognição , Eletrodos , Humanos , Reprodutibilidade dos Testes
16.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2934-2937, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018621

RESUMO

Bioelectronic neural interfaces that deliver adaptive therapeutic stimulation in an intelligent manner must be able to sense and stimulate activity within the same nerve. Existing minimally-invasive peripheral neural interfaces can provide a read-out of the aggregate level of activity via electrical recordings of nerve activity, but these recordings are limited in terms of their specificity. Computational simulations can provide fine-grained insight into the contributions of different neural populations to the extracellular recording, but integration of the signals from individual nerve fibers requires knowledge of spread of current in the complex (heterogenous, anisotropic) extracellular space. We have developed a model which uses the open-source EIDORS package for extracellular stimulation and recording in the pelvic nerve. The pelvic nerve is the primary source of autonomic innervation to the pelvic organs, and a prime target for electrical stimulation to treat a variety of voiding disorders. We simulated recordings of spontaneous and electrically-evoked activity using biophysical models for myelinated and unmyelinated axons. As expected, stimulus thresholds depended strongly on both fibre type and electrode-fibre distance. In conclusion, EIDORS can be used to accurately simulate extracellular recording in complex, heterogenous neural geometries.


Assuntos
Axônios , Nervos Periféricos , Estimulação Elétrica , Eletrodos , Fibras Nervosas
17.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3293-3296, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018708

RESUMO

It is still a challenge to delay the onset of fatigue on muscle contraction induced by Functional Electrical Stimulation (FES). We explored the use of two stimulation methods with the same total area, single electrode stimulation (SES), and spatially distributed electrical stimulation (SDSS) during isometric knee extension with spinal cord injured (SCI) volunteers. We applied stimulation on the left and right quadriceps of two SCI participants with both methods and recorded isometric force and evoked electromyography (eEMG). We calculated the force-time integral (FTI) and eEMG-time integral (eTI) for each stimulation series and used a linear regression as a measure of decay ratio. Moreover, we also estimated the contribution from each channel from eEMG.


Assuntos
Terapia por Estimulação Elétrica , Traumatismos da Medula Espinal , Eletrodos , Humanos , Contração Muscular , Fadiga Muscular , Traumatismos da Medula Espinal/terapia
18.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3436-3439, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018742

RESUMO

To meet the dimensional requirements for bioelectronic medicine, new packaging solutions are needed that could enable small, light-weight and flexible implants. For protecting the implantable electronics against biofluids, recently various atomic layer deposited (ALD) coatings have been proposed with high barrier properties. Before implantation, however, the protective coating should be evaluated for any defects which could otherwise lead to leakage and device failure. In these cases, the conventional helium leak test method can no longer be used due to the millimeter size of the implant. Therefore, an in-situ sensing platform is needed that could evaluate the coating and justify the implantation of the final device. In this work, we explore the possibility of using the CMOS bulk for such a platform. Towards this aim, as a proof of concept, test chips were made in a standard 6-metal 0.18 µm CMOS process and for the connection to the bulk, a p+ diffusion was used. A group of samples was then coated with an ALD multilayer. For coating evaluation, off-chip DC current leakage and impedance measurements were carried out in saline between the CMOS bulk and a platinum reference electrode. Results were compared between non-coated and coated chips that clearly demonstrated the potential of using the bulk as a sensing platform for coating evaluations. This novel approach could pave the way towards an all integrated in-situ hermeticity test, currently missing in mm-size implants.


Assuntos
Metais , Próteses e Implantes , Eletrodos
19.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3444-3447, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018744

RESUMO

Peripheral nerve interfaces (PNIs) allow us to extract motor, sensory and autonomic information from the nervous system and use it as control signals in neuroprosthetic and neuromodulation systems. Recent efforts have aimed to improve the recording selectivity of PNIs, including by using spatiotemporal patterns from multi-contact nerve cuff electrodes as input to a convolutional neural network (CNN). Before such a methodology can be translated to humans, its performance in chronic implantation scenarios must be evaluated. We investigated the performance of a CNN-based selective recording approach in the presence of encapsulation tissue, a common immune response to the implantation of a neural interface. This factor was simulated using anatomically accurate computational models of a rat sciatic nerve and nerve cuff electrode. Performance over time was examined in three conditions: training the CNN at baseline only, supervised retraining with explicitly labeled data at periodic intervals, and a semi-supervised self-learning approach. The periodic recalibration approach demonstrated the best results, with an average F1-score of 0.96 ± 0.04, 0.89 ± 0.08, and 0.80 ± 0.08 for SNRs of -5 dB, -10 dB, and -15 dB, respectively, across all time points. Thus, the periodic recalibration approach may be an effective solution to compensate for changes in signal recordings seen over time as a result of encapsulation tissue. The self-learning approach, in which a network is retrained periodically using predicted labels, generally showed degradation in classification performance over time, even as the frequency of training was increased, attributed to an eventual accumulation of mislabeled training data.


Assuntos
Redes Neurais de Computação , Nervo Isquiático , Animais , Eletrodos , Humanos , Ratos , Razão Sinal-Ruído
20.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3517-3520, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018762

RESUMO

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technology that modulates the excitability of the brain by delivering weak electric currents to the brain via scalp electrodes. Electrode configuration and injected current intensity are two important parameters in the tDCS design. This simulation study examined three commercially available electrode configurations, i.e. conventional low definition rectangular pad, high-definition Disc, and high-definition 4 x 1 with different electrode distances and different injected current intensity. Simulation results show that increasing the injected current intensity of HD-tDCS mainly increases the electrical field strength for all configurations. Both Disc and 4 x 1 high definition tDCS (HD-tDCS) have better focality than the conventional low-definition rectangular pad. Increasing the inter-electrode distance in HD-tDCS enlarges the electrical field strength and the depth of stimulation but reduces the focality. In motor rehabilitation, a trade-off needs to be made in the tDCS design to allow the electrical field reaching the white matter to facilitate the usage of the cortico-spinal tract without influencing other undesirable regions in the brain.


Assuntos
Estimulação Transcraniana por Corrente Contínua , Substância Branca , Encéfalo , Eletrodos , Injeções
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