Weak Electric Currents Research Articles

Microbiome and antibiotic resistome in bioelectrochemical toilets for onsite treatment of fecal sludge

Effective management of fecal sludge (FS) is essential for preventing environmental and public health risks. Developing safe and efficient FS treatment technology is crucial for reducing the health risks of onsite sanitation systems. In this study, bioelectrochemical toilets (BETs) were developed to treat FS onsite. Compared with the open-circuit BETs (OC-BETs), BETs exhibited higher removal efficiencies for total organic carbon, total nitrogen, and total phosphorus. Specifically, the enhancements in removal efficiencies were 18.82 ± 1.73 %, 7.28 ± 0.32 %, and 11.41 ± 0.05 % for urine, and 19.28 ± 4.08 %, 21.65 ± 1.23 %, and 24.68 ± 0.95 % for feces, respectively. Microbiome analysis indicated that the dominant populations were affiliated with electroactive bacteria (Desulfuromonas and Pseudomonas) in the electrode biofilm of BETs. The species co-occurrence network showed that the electrode biofilm microbiome in BETs had more complex correlations than that in OC-BETs, suggesting that a weak electrical current enhanced the microbiome stability. The relative abundance of antibiotic resistance genes in BETs and OC-BETs reduced by 59.85 ± 1.32 % and 53.01 ± 2.81 % compared with the initial FS, respectively. These findings indicate that BETs are an alternative system for enhancing onsite treatment of fecal sludge and provide a theoretical foundation for the implementation of BETs.

A Phosphenotron Device for Sensoric Spatial Resolution of Phosphenes within the Visual Field Using Non-Invasive Transcranial Alternating Current Stimulation.

This study presents phosphenotron, a device for enhancing the sensory spatial resolution of phosphenes in the visual field (VF). The phosphenotron employs a non-invasive transcranial alternating current stimulation (NITACS) to modulate brain activity by applying weak electrical currents to the scalp or face. NITACS's unique application induces phosphenes, a phenomenon where light is perceived without external stimuli. Unlike previous invasive methods, NITACS offers a non-invasive approach to create these effects. The study focused on assessing the spatial resolution of NITACS-induced phosphenes, crucial for advancements in visual aid technology and neuroscience. Eight participants were subjected to NITACS using a novel electrode arrangement around the eye orbits. Results showed that NITACS could generate spatially defined phosphene patterns in the VF, varying among individuals but consistently appearing within their VF and remaining stable through multiple stimulations. The study established optimal parameters for vibrant phosphene induction without discomfort and identified electrode positions that altered phosphene locations within different VF regions. Receiver Operating characteristics analysis indicated a specificity of 70.7%, sensitivity of 73.9%, and a control trial accuracy of 98.4%. These findings suggest that NITACS is a promising, reliable method for non-invasive visual perception modulation through phosphene generation.

Simulation of a synchronized methodology for MR-based electromechanical property imaging during transcranial electrical stimulation

Introduction: Recent investigations into the biomechanics of the brain have unveiled alteration in tissue stiffness triggered by external stimuli. For instance, visual stimulation effects can be measured in elasticity images of the cortex generated by functional magnetic resonance elastography (MRE). Such a mechanical characterization method combined with non-invasive brain stimulation (NIBS), a technique that seeks to selectively modulate particular parts of the brain using weak electrical currents, has the potential to influence research on various neurological disorders. In this in silico study, we aimed to elucidate individual and interdependent aspects related to a synchronized biomechanical imaging and non-invasive brain stimulation methodology. Magnetic resonance electrical impedance tomography (MREIT) was incorporated to the pipeline, providing a promising way of evaluating NIBS-induced electrical current patterns in the brain while leveraging MRE and transcranial alternating current stimulation (tACS) experimental settings.Methods: A mouse head model was assembled using open-access atlases to include five anatomical structures: skin/subcutaneous tissue, skull, cerebrospinal fluid (CSF), brain white and grey matters. MRE, tACS, and MREIT experiments were simulated using Comsol Multiphysics with Matlab Livelink. Synthetic MRE and MREIT data were processed using the subzone non-linear inversion and harmonic Bz algorithm, respectively, to reconstruct images of the distributed complex shear modulus and electrical conductivity.Results and Discussion: Lorentz body forces arising from simultaneous MRE and tACS elicited elastic waves of negligible amplitude compared with the extrinsic actuation levels reported in the literature, which allowed accurate reconstructions of the complex shear modulus. Qualitative electrical conductivity maps retrieved by MREIT accurately delineated anatomical regions of the brain model and could be used to recover reasonably accurate distributions of tACS-induced currents. This multi-physics approach has potential for translation to human brain imaging, and may provide more possibilities for the characterization of brain function together than in isolation.

Influence of magnetotherapy on various systems of the body and on the process of wound healing in children with cleft lip and palate

In this article we present the results of magnetic therapy on the wound healing process in children with cleft lip and palate after cheiloplasty surgery. At the same time, there is an improvement in metabolic processes in tissues, which contributes to their proper nutrition and restoration.Inflammation and associated soft tissue swelling are eliminated. Locally, blood vessels dilate and blood supply improves. The pain is relieved.Magnetotherapy is a method of physiotherapy that uses magnetic fields of varying strengths and frequencies for the treatment, rehabilitation or prevention of diseases. To carry it out, stationary and portable devices have been developed. The principle is simple: one or more electromagnetic applicators are installed on certain areas of the body, or the patient is placed in a large-diameter magnetic chamber or on a special mattress. The method is based on the fact that a magnetic field affects electrically charged particles moving in the human body. They are found in biological fluids - blood, lymph, cytoplasm of cells. Under the influence of a magnet, weak electric currents arise in these environments. They cause many responses: metabolism, blood properties, the speed of transmission of nerve impulses change, microcirculation and the delivery of oxygen and micronutrients improve. This leads to the following effects: reduction of tissue swelling, suppression of the inflammatory process, local anesthesia, reduction of blood viscosity, normalization of blood pressure, acceleration of healing and tissue restoration, stimulation of the immune system.

Electrical impedance myography in healthy dogs: Normative values, repeatability, and the impact of age.

Convenient tools to assess canine skeletal muscle health would be useful for a variety of applications, including standard veterinary assessments of dog fitness, as well as studies of muscle deterioration due to age or disease. One technology that can be applied conveniently to awake dogs with minimal restraint is electrical impedance myography (EIM). In EIM, a weak electrical current is applied via surface electrodes to a muscle of interest and consequent impedance characteristics of the muscle are obtained, providing insight into muscle condition and composition. In this study, we assessed a total of 73 dogs (42 males and 31 females), of varied neutering status and breed, ages 0.6 to 13.5 years. We identified age-dependent reference values for the 100 kHz phase value in three pelvic limb muscles, caudal sartorius, cranial tibial, and gastrocnemius. While phase values were generally higher in males than females, the difference did not reach significance. In general, values declined on average with age at about 0.5 degrees/year, but with the decline being most substantial in the oldest dogs. Limited reproducibility assessment of the technique suggested good repeatability with variation in values between measurements being under 5%. These results show that EIM has the potential for the assessment of canine muscle health and may find value in aging muscle research.

Repetitive Anodal TDCS to the Frontal Cortex Increases the P300 during Working Memory Processing.

Transcranial direct current stimulation (TDCS) is a technique with which neuronal activity, and therefore potentially behavior, is modulated by applying weak electrical currents to the scalp. Application of TDCS to enhance working memory (WM) has shown promising but also contradictory results, and little emphasis has been placed on repeated stimulation protocols, in which effects are expected to be increased. We aimed to characterize potential behavioral and electrophysiological changes induced by TDCS during WM training and evaluate whether repetitive anodal TDCS has a greater modulatory impact on the processes underpinning WM than single-session stimulation. We examined the effects of single-session and repetitive anodal TDCS to the dorsolateral prefrontal cortex (DLPFC), targeting the frontal-parietal network, during a WM task in 20 healthy participants. TDCS had no significant impact on behavioral measures, including reaction time and accuracy. Analyzing the electrophysiological response, the P300 amplitude significantly increased following repetitive anodal TDCS, however, positively correlating with task performance. P300 changes were identified over the parietal cortex, which is known to engage with the frontal cortex during WM processing. These findings support the hypothesis that repetitive anodal TDCS modulates electrophysiological processes underlying WM.

Suppression of Motor Sequence Learning and Execution Through Anodal Cerebellar Transcranial Electrical Stimulation

Cerebellum (CB) and primary motor cortex (M1) have been associated with motor learning, with different putative roles. Modulation of task performance through application of transcranial direct current stimulation (TDCS) to brain structures provides causal evidence for their engagement in the task. Studies evaluating and comparing TDCS to these structures have provided conflicting results, however, likely due to varying paradigms and stimulation parameters. Here we applied TDCS to CB and M1 within the same experimental design, to enable direct comparison of their roles in motor sequence learning. We examined the effects of anodal TDCS during motor sequence learning in 60 healthy participants, randomly allocated to CB-TDCS, M1-TDCS, or Sham stimulation groups during a serial reaction time task. Key to the design was an equal number of repeated and random sequences. Reaction times (RTs) to implicitly learned and random sequences were compared between groups using ANOVAs and post hoc t-tests. A speed–accuracy trade-off was excluded by analogous analysis of accuracy scores. An interaction was observed between whether responses were to learned or random sequences and the stimulation group. Post hoc analyses revealed a preferential slowing of RTs to implicitly learned sequences in the group receiving CB-TDCS. Our findings provide evidence that CB function can be modulated through transcranial application of a weak electrical current, that the CB and M1 cortex perform separable functions in the task, and that the CB plays a specific role in motor sequence learning during implicit motor sequence learning.

Long-term effect of transcranial direct current stimulation in the treatment of chronic tinnitus: A randomized, placebo-controlled trial.

IntroductionTinnitus is an intrusive and chronic illness affecting a significant portion of the population, decreasing affected individuals’ quality of life and socioeconomic functioning. Transcranial Direct Current Stimulation (tDCS) is a non-invasive neuromodulatory method utilizing weak electrical currents to elicit short and long-term central nervous system changes. Several studies have proven its effect on tinnitus. We aimed to broaden the knowledge and provide data on the effect and its retention.MethodsIn the randomized, double-blinded, sham-controlled trial, 39 patients (active n = 19, sham n = 20) underwent bifrontal tDCS (anode over right dorsolateral prefrontal cortex (DLPFC), cathode left DLPFC, current of 1.5 mA, 20 min, 6 sessions in 2 weeks). Tinnitus Functional Index (TFI), Iowa Tinnitus Handicap Questionnaire (ITHQ), Beck Anxiety Inventory (BAI), Zung Self-Rating Depression Scale (SDS), and WHO-Quality of Life-BREF were employed in 4 evaluation points, including the follow-ups of 6 weeks and 6 months.ResultsWe reached a delayed, significant long-term improvement (p < 0.05) in auditory difficulties associated with tinnitus and noticed it even after 6 months compared to placebo. We also reached a short-term, negative effect in the psychological domain of WHO-Quality of Life-BREF (p < 0.05). Not all subdomains of TFI and ITHQ reached statistical significance during the data analysis, even though specific positive trends were noticed.ConclusionWe proved partial, positive, long-term effects of tDCS on tinnitus and short-term, negative, transient effect on a specific aspect of the general quality of life. We expanded upon the results of previous trials and provided data concerning the longevity and the precise effect of multiple sessions, bifrontal DLPFC tDCS. Our sample size (n = 39) was limited, which might have contributed to the lesser statistical power of the analyzed items.Clinical trial registration[www.ClinicalTrials.gov], identifier [NCT05437185].

Key factors in the cortical response to transcranial electrical Stimulations—A multi-scale modeling study

Transcranial electrode stimulation (tES), one of the techniques used to apply non-invasive brain stimulation (NIBS), modulates cortical activities by delivering weak electric currents through scalp-attached electrodes. This emerging technique has gained increasing attention recently; however, the results of tES vary greatly depending upon subjects and the stimulation paradigm, and its cellular mechanism remains unclear. In particular, there is a controversy over the factors that determine the cortical response to tES. Some studies have reported that the electric field's (EF) orientation is the determining factor, while others have demonstrated that the EF magnitude itself is the crucial factor. In this work, we conducted an in-depth investigation of cortical activity in two types of electrode montages used widely—the conventional (C)-tES and high-definition (HD)-tES—as well as two stimulation waveforms—direct current (DC) and alternating current (AC). To do so, we constructed a multi-scale model by coupling an anatomically realistic human head model and morphologically realistic multi-compartmental models of three types of cortical neurons (layer 2/3 pyramidal neuron, layer 4 basket cell, layer 5 pyramidal neuron). Then, we quantified the neuronal response to the C-/HD-tDCS/tACS and explored the relation between the electric field (EF) and the radial field's (RF: radial component of EF) magnitude and the cortical neurons' threshold. The EF tES induced depended upon the electrode montage, and the neuronal responses were correlated with the EF rather than the RF's magnitude. The electrode montages and stimulation waveforms caused a small difference in threshold, but the higher correlation between the EF's magnitude and the threshold was consistent. Further, we observed that the neurons' morphological features affected the degree of the correlation highly. Thus, the EF magnitude was a key factor in the responses of neurons with arborized axons. Our results demonstrate that the crucial factor in neuronal excitability depends upon the neuron models' morphological and biophysical properties. Hence, to predict the cellular targets of NIBS precisely, it is necessary to adopt more advanced neuron models that mimic realistic morphological and biophysical features of actual human cells.

High-voltage catfish immune to their own shocks

Malapterurus beniensis may look like a harmless catfish lounging on the bottom of a tank, but these creatures are far from benign. Packing a powerful 300 V electric shock, the fish usually reserve their pyrotechnics for stunning prey. ‘We always wear thick rubber gloves when handling the fish’, chuckles Stefan Schuster from the University of Bayreuth, Germany, admitting that he and Georg Welzel once tried holding a small catfish without gloves: ‘The shock was surprisingly strong and felt like touching an electric fence’, he recalls. But how do electric catfish withstand their self-administered shocks, which knock out the hearts and nervous systems of their victims? Do the catfish brace themselves to withstand their own electrical discharges, or are they somehow immune? Intrigued by the fish's electrical resilience, Schuster and Welzel obtained two of the shocking creatures to find out how they and their victims deal with an electric jolt.Turning the water to a slow flow to cajole the idle catfish off the bottom of the tank, Welzel gently brushed their tails with a paint brush to startle them into electrical action. But, when he scrutinised movies of the catfish's manoeuvres, they were completely unperturbed by their electric discharges. In contrast, goldfish swimming nearby went into a spasm, flinging their pectoral fins wide in addition to contracting their bodies, before recovering and going on their way. Even more surprisingly, the catfish were equally unconcerned when Welzel zapped the water with an electrofishing probe, never writhing nor twitching. ‘It was surprising that they were equally immune to external discharges that they could not prepare for and were designed specifically to paralyse fish’, Schuster recalls.The catfish's muscles were unaffected by high-voltage electric fields, but it still wasn't clear whether their brain and nervous system were also protected from the effects of electricity. The duo needed to find a way of startling the fish into releasing a bolt of electricity, after sensing the disturbance and processing it in the brain. They reasoned that if the catfish's nervous system was not protected from electric fields, then the speed and timing of the catfish's electrical discharge would be affected if the animal was sitting in an external electric field when startled. However, if the catfish's brain and nervous system were somehow protected, the presence of an external electric field would make no difference to their startled electrical outburst.‘We tested various visual and acoustic stimuli’, says Schuster, recalling how the pair eventually settled on a 300 Hz blast of sound, which reliably startled the fish into pulsing electrically. ‘We had to wear ear defenders’, Welzel laughs. Then, Welzel simultaneously gave the fish an external electric shock while startling them, in an attempt to get them to let their guard down. However, the catfish were completely impervious to the additional electric field, producing startled electric flashes that were indistinguishable from their usual shocking response. They were not steeling their nervous systems in preparation for the disruptive effects of their high-voltage pulses – they were somehow immune.‘Electric catfish show a remarkable degree of protection against high voltages’, says Welzel, who suspects that the extraordinary fish are insulated in some way against their own electric fields. And Schuster adds that the catfish's high-voltage resilience is even more paradoxical, as they are also exquisitely fine-tuned to the weak electric currents generated by the bodies of their prey. A conventional insulator would prevent the catfish from sensing their food, presenting Schuster and Welzel with another mystery to solve.

Immediate and after effects of transcranial direct-current stimulation in the mouse primary somatosensory cortex

Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique consisting in the application of weak electric currents on the scalp. Although previous studies have demonstrated the clinical value of tDCS for modulating sensory, motor, and cognitive functions, there are still huge gaps in the knowledge of the underlying physiological mechanisms. To define the immediate impact as well as the after effects of tDCS on sensory processing, we first performed electrophysiological recordings in primary somatosensory cortex (S1) of alert mice during and after administration of S1-tDCS, and followed up with immunohistochemical analysis of the stimulated brain regions. During the application of cathodal and anodal transcranial currents we observed polarity-specific bidirectional changes in the N1 component of the sensory-evoked potentials (SEPs) and associated gamma oscillations. On the other hand, 20 min of cathodal stimulation produced significant after-effects including a decreased SEP amplitude for up to 30 min, a power reduction in the 20–80 Hz range and a decrease in gamma event related synchronization (ERS). In contrast, no significant changes in SEP amplitude or power analysis were observed after anodal stimulation except for a significant increase in gamma ERS after tDCS cessation. The polarity-specific differences of these after effects were corroborated by immunohistochemical analysis, which revealed an unbalance of GAD 65–67 immunoreactivity between the stimulated versus non-stimulated S1 region only after cathodal tDCS. These results highlight the differences between immediate and after effects of tDCS, as well as the asymmetric after effects induced by anodal and cathodal stimulation.

High definition transcranial direct current stimulation (HD-tDCS): A systematic review on the treatment of neuropsychiatric disorders.

HD-tDCS (High-definition transcranial direct current stimulation) is a novel non-invasive brain stimulation (NIBS) technique based on the principle that when weak intensity electric currents are targeted on specific areas of the scalp, they cause underlying cortical stimulation. HD-tDCS shares its technical methodology with conventional tDCS (montage comprising of one anode and one cathode) except for a few modifications that are believed to have focal and longer-lasting neuromodulation effects. Although HD-tDCS is a recently available NIBS technique, impactful studies, case reports, and few controlled trials have been conducted in this context, facilitating an understanding of its neurobiological effects and the clinical translation of the same in health care set-up. The current article narratively reviews the mechanism of action of HD-tDCS, and it systematically examines the cognitive, clinical, and neurobiological effects of HD-tDCS in healthy volunteers as well as patients with neuropsychiatric conditions. Thus, this review attempts to explore the role of HD-tDCS in present-day practice and the future in the context of various neurological and psychiatric disorders.

Effects of Electrode Configurations and Injected Current Intensity on the Electrical Field of Transcranial Direct Current Stimulation: A Simulation Study.

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.

M66. FACILITATIVE EFFECTS OF TRANSCRANIAL DIRECT CURRENT STIMULATION ON SEMANTIC MEMORY EXAMINED BY TEXT-MINING ANALYSIS IN PATIENTS WITH SCHIZOPHRENIA

BackgroundTranscranial direct current stimulation (tDCS) is a neurophysiological therapy which modulates neural activities in the brain with weak electrical current. The beneficial effects of tDCS are relevant to positive and negative symptoms, as well as cognition and functional capacity in patients with schizophrenia (Narita et al, 2017). However, whether tDCS would improve higher-order cognition, e.g. semantic memory organization, has remained unclear. Recently, text-mining analyses have been proven to be effective to reveal semantic memory in patients with schizophrenia (Sung et al., 2012; Sumiyoshi et al., 2018). The purpose of the study was to investigate effects of tDCS to improve semantic memory, as evaluated by text-mining analyses of category fluency data, in patients with schizophrenia.MethodsTwenty-eight patients meeting DSM-5 criteria for schizophrenia entered the study. All subjects gave written informed consent, and the study was approved by the Ethical Committee of National Center of Neurology and Psychiatry and the Ethical Committee of Osaka university. Data from healthy control subjects (N=335) were also used. The tDCS was conducted according to the previous study (Narita et al., 2017). tDCS was administered twice a day in 5 consecutive days. The Brief Assessment of Cognition in Schizophrenia, (BACS) was administered at baseline and one month after the last tDCS session. Verbal outputs of the category fluency task in the BACS were submitted to the singular valued decomposition (SVD) analysis. Semantic memory structures were estimated by calculating cosine values (i.e. similarities) among frequent items in the six-dimensional solution. These values were compared between healthy controls vs. patients at baseline and follow-up using Pearson’s correlational coefficients.ResultsThe correlational coefficient for the frequent items (DOG, CAT, ELEPAHANT, GIRAFFE, LION, TIGER) between patients and healthy controls was considerably higher at the follow-up (r=0.58) compared to that at base line (r=0.12), reaching a marginal significance (p=0.058). A visual inspection for the cosine profiles of frequent items indicated that distinct clusters of Pet (DOG, CAT), Wild-Herbivorous (ELEPAHANT, GIRAFFE), and Wild-Carnivorous (LION, TIGER) in patients at follow-up, as in the case for healthy controls.DiscussionTo our knowledge, this is the first study reporting a facilitative effect of tDCS on higher-order of cognition in patients with schizophrenia. Semantic memory in the patients became structurally similar to that for healthy controls after administration of tDCS. Furthermore, animal names frequently produced were meaningfully clustered in patients at follow-up, similar to the pattern of healthy controls. These results may explain the efficacy of tDCS for improving other domains of cognitive function in patients with schizophrenia. We also could demonstrate that text-mining analysis is a powerful tool to elucidate higher-order cognition in people with mental disorders.ReferencesNarita, Z et al. 2017a. Front. Psychiatry, 8:184. doi: 10.3389/fpsyt.2017.00184.Sung, K. et al. 2012. J Int Neuropsychol Soc.,18, 565-57Sumiyoshi, C. et al. 2018. Front. Psychiatry, 9:87. doi: 10.3389/fpsyt.2018.00087

Fast Nondestructive Battery Diagnostics with MRI and Magnetometry: Detect State of Health, State of Charge, and Current Distributions

Rechargeable batteries are notoriously difficult to assess. We are presenting new battery assessment technology based on MRI and magnetometry techniques, which allow non-destructive scanning of rechargeable cells. The techniques are fast, can detect changes in the electrode chemistry that occur as the battery is charged and discharged, or sense a range of different defects at early stages. In particular, we can determine site-resolved state-of-charge (where charge is stored in the cell), current distributions, as well as tiny transient effects. The vision is to use a benchtop-type instrument, which could be deployed in a variety of ways. The aim is to improve safety and performance, help in predicting battery life, clarify failure modes, and aid in the development of next-generation cells. Both MRI and magnetometry provide complementary measurement modalities with their strengths and limitations. MRI allows sensitive state of charge determination in a localized manner, and magnetometry allows to detect extremely weak electrical currents, both DC and AC at the level of nA in principle. Both these techniques provide new opportunities for battery diagnostics and research and could help reducuing the development cycle for new batteries and determining obscure battery failure modes. Figure 1

Monitoring the mechanical response of early aged cement-mortar specimens using the Pressure Stimulated Currents technique

The time evolution of the electric signals emitted during uniaxial compression of prismatic cement mortar specimens is investigated in this study. The electric signals are recorded in the form of very weak electric currents, and their analysis is achieved in terms of the Pressure Stimulated Currents technique. The study is focused on the quantification of the role of the specimens’ age, i.e., the time interval between the production of the specimens and the implementation of the tests, on the intensity of these electric signals. In this context, four classes of specimens were tested, including specimens of ages equal to 3, 14, 28 and 90 days. It was concluded that for early ages the Pressure Stimulated Currents are quite stronger in comparison with those of mature specimens. There were no detectable differences between the specimens of ages 28 and 90 days, neither concerning the electric activity nor the mechanical response. Moreover, it was indicated that during loading, the electric activity is strongly intensified only after the mechanical response of the specimens abandons linearity, independently of the specimens’ age. Finally, it was concluded that the time evolution of the electric activity provides indicators that can be considered as pre-failure warnings, i.e., signals of upcoming fracture.

Electric and acoustic activity in notched fiber-reinforced concrete beams under three-point bending

An experimental study is presented, aiming to comparatively consider the electric and acoustic activity in fiber-reinforced concrete beams subjected to three-point bending. The study is part of an ongoing project attempting to detect phenomena considered as warning signals of upcoming catastrophic fracture, in case brittle materials are loaded mechanically at levels approaching the critical ones. A mature, well established monitoring tool (Acoustic Emissions) is used, in conjunction with a relatively new sensing technique, which is based on the detection of very weak electric currents (known as Pressure Stimulated Currents) produced during the various damage processes which precede (and lead to) the macroscopic fracture of brittle materials. In this direction, series of three-point bending tests with notched beam-shaped specimens made of concrete (either reinforced with metallic or plastic fibers or without any reinforcing agents) were implemented. It is concluded that, independently of the nature of the reinforcing fibers, both monitoring techniques employed in the experimental protocols (namely, the Acoustic Emissions and the Pressure Stimulated Currents) follow pretty faithfully the respective time evolution of the mechanical quantities and, what is more important, they provide well distinguishable features that can be considered as pre-failure indicators.

Beamforming Galvanic Coupling Signals for IoMT Implant-to-Relay Communication

Implants are poised to revolutionize personalized healthcare by monitoring and actuating physiological functions. Such implants operate under challenging constraints of the limited battery energy, heterogeneous tissue-dependent channel conditions, and human-safety regulations. To address these issues, we propose a new cross-layer protocol for galvanic coupled implants, wherein the weak electrical currents are used in place of classical radio frequency links. As the first step, we devise a method that allows multiple implants to communicate individual sensed data to each other through code division multiple access, combined with compressive sensing method to lower the transmission time and save energy, as well as delegates the computational burden of dispreading and decoding only to the on-body surface relays. Then, we devise a distributed beamforming approach that allows coordinated transmissions from the implants to the relays by considering the specific tissue path chosen and tissue heating-related safety constraints. We then proceed to implement distributed beamforming on a phantom of human tissue and prove an increase in received signal strength and a decrease in BER due to constructive interference of the signals of each implant. Our contributions are twofold: First, we devise a collision-free protocol that prevents undue interference at neighboring implants, especially for multiple deployments. Second, this is the first application of near-field distributed beamforming in human tissue. Simulation results reveal significant improvement in the network lifetime for implants of up to 79% compared to the galvanic coupled links without beamforming. In addition, the implementation of phantom tissue proves improved communication metrics when beamforming is used.

Charge transfer equilibrium in surface barrier discharge: continuous current and negative ion-driven ionisation wave

Sensitive measurements of very weak electrical currents in sinusoidally driven surface barrier discharge in atmospheric air are reported for discharge arrangements with and without liquid covering the top electrode. The transferred charge of the low-power discharge is carefully quantified and it is shown that after the complete voltage period the total charge balance is approaching zero. This rather obvious result is mechanically assumed in the literature, yet it is experimentally not understood in detail. We show that continuous and pulsed micro-ampere currents measured during the negative polarity are responsible for the gradual renewal of the charge transfer equilibrium abruptly distorted by strong electrical pulses caused by positive streamers during the opposite half-period. Using synchronised ICCD imaging we reveal that weak continuous current is caused by slowly expanding surface discharges stemming from previously established cathode spots. The expansion is caused by a surface ionisation wave. Based on the experimental evidence, supported by the theoretical results found in literature, we conclude that an expanding negative ion cloud is responsible for the electric field enhancement at its forefront which is sufficient to ionise the surrounding air.

Body-Guided Galvanic Coupling Communication for Secure Biometric Data

In a world dominated by the wearable IoT devices, malicious security threats have become a common concern in system design. Guided by this notion, we propose a secure transmission system through body-guided channels using Galvanic Coupling (GC). The GC-method injects weak electrical current into human tissue, primarily propagating through the skin. The proposed design provides impermeability to malicious attacks, (e.g. side-channel sniffing) when sending biometric data, as the body behaves as a natural waveguide. The following contributions are: 1) the analytical formulation and empirical verification of a 3D tissue equivalent circuit model for GC-signal propagation of the human arm-wrist-palm channel; 2) the simulation study of numerous modulation schemes, drawn from the validated results of the GC-channel model; 3) the design and implementation of a transceiver prototype using optimal communication parameters (modulation, frequency, power) for transmission on a dielectrically equivalent tissue phantom; and 4) through the experimental trials, we demonstrate the eavesdropping susceptibility of the GC-signals, and similar body communication techniques, over-the-air and while in direct contact with the medium. The performance results of the GC-transceiver prototype yield a bit error rate of 10−6 with a transmit power of −2 dBm, in addition to over 7 $\times$ reduction of signal radiation outside the body compared to capacitive coupling.