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PLoS Computational Biology Feb 2021Axonal connections are widely regarded as faithful transmitters of neuronal signals with fixed delays. The reasoning behind this is that extracellular potentials caused...
Axonal connections are widely regarded as faithful transmitters of neuronal signals with fixed delays. The reasoning behind this is that extracellular potentials caused by spikes travelling along axons are too small to have an effect on other axons. Here we devise a computational framework that allows us to study the effect of extracellular potentials generated by spike volleys in axonal fibre bundles on axonal transmission delays. We demonstrate that, although the extracellular potentials generated by single spikes are of the order of microvolts, the collective extracellular potential generated by spike volleys can reach several millivolts. As a consequence, the resulting depolarisation of the axonal membranes increases the velocity of spikes, and therefore reduces axonal delays between brain areas. Driving a neural mass model with such spike volleys, we further demonstrate that only ephaptic coupling can explain the reduction of stimulus latencies with increased stimulus intensities, as observed in many psychological experiments.
Topics: Action Potentials; Animals; Axons; Biophysical Phenomena; Computational Biology; Computer Simulation; Extracellular Space; Humans; Models, Neurological; Nerve Fibers, Myelinated; Synaptic Transmission; White Matter
PubMed: 33556058
DOI: 10.1371/journal.pcbi.1007858 -
Journal of the American Chemical Society Feb 2020We describe a new catalytic strategy to transcend the energetic limitations of visible light by electrochemically priming a photocatalyst prior to excitation. This new...
We describe a new catalytic strategy to transcend the energetic limitations of visible light by electrochemically priming a photocatalyst prior to excitation. This new catalytic system is able to productively engage aryl chlorides with reduction potentials hundreds of millivolts beyond the potential of Na in productive radical coupling reactions. The aryl radicals produced via this strategy can be leveraged for both carbon-carbon and carbon-heteroatom bond-forming reactions. Through direct comparison, we illustrate the reactivity and selectivity advantages of this approach relative to electrolysis and photoredox catalysis.
Topics: Catalysis; Chlorides; Electrons; Oxidation-Reduction; Photochemical Processes
PubMed: 31951393
DOI: 10.1021/jacs.9b12328 -
ACS Central Science Dec 2021Extreme fast charging (XFC), with a recharging time of 15 min, is the key to the mainstream adoption of battery electric vehicles. Lithium metal, in the meantime, has...
Extreme fast charging (XFC), with a recharging time of 15 min, is the key to the mainstream adoption of battery electric vehicles. Lithium metal, in the meantime, has re-emerged as the ultimate anode because of its ultrahigh specific capacity and low electrochemical potential. However, the low lithium-ion concentration near the lithium electrode surface can result in uncontrolled dendrite growth aggravated by high plating current densities. Here, we reveal the beneficial effects of an adaptively enhanced internal electric field in a constant voltage charging mode in XFC via a molecular understanding of the electrolyte-electrode interfaces. With the same charging time and capacity, the increased electric field stress in dozens of millivolts, compared with that in a constant current mode, can facilitate Li migrating toward the negatively charged lithium electrode, mitigating Li depletion at the interface and thereby suppressing dendrites. In addition, more NO ions are involved in the solvation sheath that is constructed on the lithium electrode surface, leading to the nitride-enriched solid electrolyte interphase and thus favoring lower barriers for Li transport. On the basis of these merits, the Li||LiTiO battery runs steadily for 550 cycles with charging current peaks up to 27 mA cm, and the Li||S full cells exhibit extended life-spans charged within 12 min.
PubMed: 34963895
DOI: 10.1021/acscentsci.1c01014 -
Scientific Reports May 2023Artificial electronic synapses are commonly used to simulate biological synapses to realize various learning functions, regarded as one of the key technologies in the...
Artificial electronic synapses are commonly used to simulate biological synapses to realize various learning functions, regarded as one of the key technologies in the next generation of neurological computation. This work used a simple spin coating technique to fabricate polyimide (PI):graphene quantum dots(GQDs) memristor structure. As a result, the devices exhibit remarkably stable exponentially decaying postsynaptic suppression current over time, as interpreted in the spike-timing-dependent plasticity phenomenon. Furthermore, with the increase of the applied electrical signal over time, the conductance of the electrical synapse gradually changes, and the electronic synapse also shows plasticity dependence on the amplitude and frequency of the pulse applied. In particular, the devices with the structure of Ag/PI:GQDs/ITO prepared in this study can produce a stable response to the stimulation of electrical signals between millivolt to volt, showing not only high sensitivity but also a wide range of "feelings", which makes the electronic synapses take a step forwards to emulate biological synapses. Meanwhile, the electronic conduction mechanisms of the device are also studied and expounded in detail. The findings in this work lay a foundation for developing brain-like neuromorphic modeling in artificial intelligence.
PubMed: 37210533
DOI: 10.1038/s41598-023-35183-8 -
Angewandte Chemie (International Ed. in... Feb 2020The design of solid-state reference electrodes without a liquid junction is important to allow miniature and cost-effective electrochemical sensors. To address this, a...
The design of solid-state reference electrodes without a liquid junction is important to allow miniature and cost-effective electrochemical sensors. To address this, a pulse control is proposed using an Ag/AgI element as reliable solid-state reference electrode. It involves the local release of iodide by a cathodic current that is immediately followed by an electromotive force (EMF) measurement that serves as the reference potential. The recapture of iodide ions is achieved by potentiostatic control. This results in intermittent potential values that are reproducible to less than one millivolt (SD=0.27 mV, n=50). The ionic strength is shown to influence the activity coefficient of released iodide in accordance with the extended Debye-Hückel equation, resulting in a predictable change of the potential reading. The principle is applied to potentiometric potassium detection with a valinomycin-based ion-selective electrode (ISE), demonstrating a completely solid-state sensor configuration.
PubMed: 31714666
DOI: 10.1002/anie.201912651 -
Science (New York, N.Y.) May 2024The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we...
The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (>90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino-silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane-treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.
PubMed: 38753792
DOI: 10.1126/science.ado2302 -
Sensors (Basel, Switzerland) Jul 2023Piezoresistive pressure sensors exhibit inherent nonlinearity and sensitivity to ambient temperature, requiring multidimensional compensation to achieve accurate...
Piezoresistive pressure sensors exhibit inherent nonlinearity and sensitivity to ambient temperature, requiring multidimensional compensation to achieve accurate measurements. However, recent studies on software compensation mainly focused on developing advanced and intricate algorithms while neglecting the importance of calibration data and the limitation of computing resources. This paper aims to present a novel compensation method which generates more data by learning the calibration process of pressure sensors and uses a larger dataset instead of more complex models to improve the compensation effect. This method is performed by the proposed aquila optimizer optimized mixed polynomial kernel extreme learning machine (AO-MPKELM) algorithm. We conducted a detailed calibration experiment to assess the quality of the generated data and evaluate the performance of the proposed method through ablation analysis. The results demonstrate a high level of consistency between the generated and real data, with a maximum voltage deviation of only 0.71 millivolts. When using a bilinear interpolation algorithm for compensation, extra generated data can help reduce measurement errors by 78.95%, ultimately achieving 0.03% full-scale (FS) accuracy. These findings prove the proposed method is valid for high-accuracy measurements and has superior engineering applicability.
Topics: Temperature; Algorithms; Calibration
PubMed: 37448016
DOI: 10.3390/s23136167 -
Polymers May 2023The demand for multi-functional elastomers is increasing, as they offer a range of desirable properties such as reinforcement, mechanical stretchability, magnetic...
The demand for multi-functional elastomers is increasing, as they offer a range of desirable properties such as reinforcement, mechanical stretchability, magnetic sensitivity, strain sensing, and energy harvesting capabilities. The excellent durability of these composites is the key factor behind their promising multi-functionality. In this study, various composites based on multi-wall carbon nanotubes (MWCNT), clay minerals (MT-Clay), electrolyte iron particles (EIP), and their hybrids were used to fabricate these devices using silicone rubber as the elastomeric matrix. The mechanical performance of these composites was evaluated, with their compressive moduli, which was found to be 1.73 MPa for the control sample, 3.9 MPa for MWCNT composites at 3 per hundred parts of rubber (phr), 2.2 MPa for MT-Clay composites (8 phr), 3.2 MPa for EIP composites (80 phr), and 4.1 MPa for hybrid composites (80 phr). After evaluating the mechanical performance, the composites were assessed for industrial use based on their improved properties. The deviation from their experimental performance was studied using various theoretical models such as the Guth-Gold Smallwood model and the Halpin-Tsai model. Finally, a piezo-electric energy harvesting device was fabricated using the aforementioned composites, and their output voltages were measured. The MWCNT composites showed the highest output voltage of approximately 2 milli-volt (mV), indicating their potential for this application. Lastly, magnetic sensitivity and stress relaxation tests were performed on the hybrid and EIP composites, with the hybrid composite demonstrating better magnetic sensitivity and stress relaxation. Overall, this study provides guidance on achieving promising mechanical properties in such materials and their suitability for various applications, such as energy harvesting and magnetic sensitivity.
PubMed: 37242867
DOI: 10.3390/polym15102287 -
Investigative Ophthalmology & Visual... Mar 2023The purpose of this study was to compare 24-hour intraocular pressure (IOP) related fluctuations monitoring between 2 groups of visual field progression rates in...
PURPOSE
The purpose of this study was to compare 24-hour intraocular pressure (IOP) related fluctuations monitoring between 2 groups of visual field progression rates in patients with open angle glaucoma (OAG).
METHODS
Cross-sectional study performed at Bordeaux University Hospital. Twenty-four-hour monitoring was performed using a contact lens sensor (CLS; Triggerfish; SENSIMED, Etagnières, Switzerland). Progression rate was calculated using a linear regression of the mean deviation (MD) parameter of the visual field test (Octopus; HAAG-STREIT, Switzerland). Patients were allocated into two groups: group 1 with an MD progression rate <-0.5 dB/year and group 2 with an MD progression rate ≥-0.5 dB/year. An automatic signal-processing program was developed and a frequency filtering of the monitoring by wavelet transform analysis was used to compare the output signal between the two groups. A multivariate classifier was performed for prediction of the faster progression group.
RESULTS
Fifty-four eyes of 54 patients were included. The mean progression rate was -1.09 ± 0.60 dB/year in group 1 (n = 22) and -0.12 ± 0.13 dB/year in group 2 (n = 32). Twenty-four-hour magnitude and absolute area under the monitoring curve were significantly higher in group 1 than in group 2 (group 1: 343.1 ± 62.3 millivolts [mVs] and 8.28 ± 2.10 mVs, respectively, group 2: 274.0 ± 75.0 mV and 6.82 ± 2.70 mVs respectively, P < 0.05). Magnitude and area under the wavelet curve for short frequency periods ranging from 60 to 220 minutes were also significantly higher in group 1 (P < 0.05).
CONCLUSIONS
The 24-hour IOP related fluctuations characteristics, as assessed by a CLS, may act as a risk factor for progression in OAG. In association with other predictive factors of glaucoma progression, the CLS may help adjust treatment strategy earlier.
Topics: Humans; Intraocular Pressure; Glaucoma, Open-Angle; Cross-Sectional Studies; Glaucoma; Contact Lenses
PubMed: 36862120
DOI: 10.1167/iovs.64.3.3 -
Advanced Materials (Deerfield Beach,... May 2024Integration of molecular switching units into complex electronic circuits is considered to be the next step towards the realization of novel logic and memory devices....
Integration of molecular switching units into complex electronic circuits is considered to be the next step towards the realization of novel logic and memory devices. Here, we report on an ordered 2D network of neighboring ternary switching units represented by triazatruxene (TAT) molecules organized in a honeycomb lattice on a Ag(111) surface. Using low-temperature scanning tunneling microscopy, we are able to control the bonding configurations of individual TAT molecules within the lattice, realizing up to 12 distinct states per molecule. The switching between those states shows a particularly strong bias dependence ranging from tens of millivolts to volts. Based on a single TAT molecule as a fundamental building block, we then explore the low-bias switching behavior in units consisting of two and more interacting TAT molecules purposefully defined by the high-bias switching within the honeycomb lattice. we demonstrate the possibility to realize up to 9 and 19 distinguishable states in a dyad and a tetrad of coupled switching units, respectively. The switching dynamics can be triggered and accessed by single-point measurements on a single molecule. High experimental control over the desired state, owing to hierarchical switching and pronounced switching directionality, as well as the observed full reversibility, makes this system particularly appealing, paving the way to design complex molecule-based memory systems. This article is protected by copyright. All rights reserved.
PubMed: 38749066
DOI: 10.1002/adma.202401662