Electrical Excitation Research Articles

A first-principle study on the pressure-dependent structural, electronic, and optical properties of 4-Hydrazine Benzene Sulfonamide

This study utilizes first-principle density functional theory (DFT) to explore the high-pressure behavior of 4-hydrazine benzene sulfonamide. Our investigation, spanning pressures from 0 to 300[Formula: see text]GPa, delves into diverse properties of the crystal (C6H9N3O2S), encompassing the crystal structure, band gap, density of states, permittivity, and conductivity. Under increasing pressure, intriguing observations emerge. Distortions in the molecular structure manifest notably at 70, 130, and 270[Formula: see text]GPa, accompanied by distinctive anisotropic behavior in lattice constants. Notably, our scrutiny of the band gap and density of states exposes a transition from a semiconductor to a metallic state and back to a semiconductor state, illuminating the profound influence of pressure on the material’s electronic structure. At 0[Formula: see text]GPa, the real part of permittivity registers negative values within the 15.6–20.2[Formula: see text]eV energy range, suggesting the crystal’s inability to propagate light and its manifestation of metallic reflection properties. Conversely, at 270[Formula: see text]GPa, the imaginary part of permittivity indicates metallic characteristics within the electronic structure, alongside a substantial energy loss in the crystal’s real part of conductivity. Moreover, the imaginary part of conductivity unveils pronounced energy conversion between the driving electric field and current excitation, hinting at structural instability under this extreme pressure. This research contributes vital insights into the behavior of hydrocarbons under high pressure, filling crucial gaps in our understanding of their properties.

Iontolysis using an electrically excited solid source of aqueous copper ions compatible with bacterial gene quantification

Iontolysis was demonstrated as a feasible low-voltage and low-frequency technique for bacterial DNA extraction. This was achieved through mild electrical excitation (3 Vpp with a 0.5 VDC offset at 5 Hz sinusoidal signal) of submerged copper thin films serving as a solid source for releasing aqueous copper ions into the bacterial sample upon electrical stimulation. The technique achieved approximately 40 % of the lysing efficiency of bead beating after 5 min. The electrical power consumption per Escherichia coli K12 bacterial sample was approximately 25 mW, making it suitable for use with existing portable analyzers. Its compatibility with the existing intercalating fluorescent dye gene quantification technique was demonstrated with high linearity (R2 = 0.97). Notably, it suggested the minimal presence of interfering species that may have been generated from the iontolysis byproducts. This compatibility is essential for existing bacterial gene quantification techniques to leverage the low electrical power consumption, simplicity of design and manufacturing, and ease of storage and shipping of the proposed iontolysis.

Manipulating CNT Films with Atomic Precision for Absorption Effectiveness–Enhanced Electromagnetic Interference Shielding and Adaptive Infrared Camouflage

AbstractPromoting advanced functional films that integrate protective behaviors for synergetic radar, infrared (IR), and visible light is confronted with extreme challenges. The effective integration of shielding capacity and IR camouflage into single‐component carbon films remains an enormous challenge because of limited conductivity and high IR absorption. In this work, carbon nanotube (CNT) films with excellent electromagnetic interference (EMI) shielding, switchable IR camouflage, and energy conversion are obtained via a (FCCVD) method and subsequent defect engineering strategies induced by temperature (Strategy I) and N/S co‐doping (Strategy II). Wherein the effect on the electronic configuration as well as multi‐spectra performance is deeply explored. Ascribing to the synergistic effects of strategies, defective CNT films present superior EMI shielding effectiveness (SE) with a high absorption effectiveness ratio of 86.9%, and a large span of emissivity (0.479), which provides the necessary condition for various application scenarios. Under the applied electric field excitation, the IR radiation of CNT films can adapt to rapidly changing surroundings, such as low‐high/high‐low temperatures. Besides, the desirable energy conversion performance and de‐icing can be achieved. This work supplies a feasible strategy for designing EM absorption, adaptive IR camouflage, and energy conversion to confront multiband surveillance.

Magnetic Field Analysis and Development of Disk Axial–Radial Hybrid Excitation Generator for Range Extenders in Extended-Range Electric Vehicles

Magnetic Field Analysis and Development of Disk Axial–Radial Hybrid Excitation Generator for Range Extenders in Extended-Range Electric Vehicles

A comparison of Algebraic Multigrid Bidomain solvers on hybrid CPU–GPU architectures

The numerical simulation of cardiac electrophysiology is a highly challenging problem in scientific computing. The Bidomain system is the most complete mathematical model of cardiac bioelectrical activity. It consists of an elliptic and a parabolic partial differential equation (PDE), of reaction–diffusion type, describing the spread of electrical excitation in the cardiac tissue. The two PDEs are coupled with a stiff system of ordinary differential equations (ODEs), representing ionic currents through the cardiac membrane. Developing efficient and scalable preconditioners for the linear systems arising from the discretization of such computationally challenging model is crucial in order to reduce the computational costs required by the numerical simulations of cardiac electrophysiology. In this work, focusing on the Bidomain system as a model problem, we have benchmarked two popular implementations of the Algebraic Multigrid (AMG) preconditioner embedded in the PETSc library and we have studied the performance on the calibration of specific parameters. We have conducted our analysis on modern HPC architectures, performing scalability tests on multi-core and multi-GPUs settings. The results have shown that, for our problem, although scalability is verified on CPUs, GPUs are the optimal choice, since they yield the best performance in terms of solution time.

Transient targeting of hypothalamic orexin neurons alleviates seizures in a mouse model of epilepsy

Lateral hypothalamic (LH) hypocretin/orexin neurons (HONs) control brain-wide electrical excitation. Abnormally high excitation produces epileptic seizures, which affect millions of people and need better treatments. HON population activity spikes from minute to minute, but the role of this in seizures is unknown. Here, we describe correlative and causal links between HON activity spikes and seizures. Applying temporally-targeted HON recordings and optogenetic silencing to a male mouse model of acute epilepsy, we found that pre-seizure HON activity predicts and controls the electrophysiology and behavioral pathology of subsequent seizures. No such links were detected for HON activity during seizures. Having thus defined the time window where HONs influence seizures, we targeted it with LH deep brain stimulation (DBS), which inhibited HON population activity, and produced seizure protection. Collectively, these results uncover a feature of brain activity linked to seizures, and demonstrate a proof-of-concept treatment that controls this feature and alleviates epilepsy.

Multiscale Fabrication Process Optimization of DFB Cavities for Organic Laser Diodes.

In the context of the quest for the Organic Laser Diode, we present the multiscale fabrication process optimization of mixed-order distributed-feedback micro-cavities integrated in nanosecond-short electrical pulse-ready organic light-emitting diodes (OLEDs). We combine ultra-short pulsed electrical excitation and laser micro-cavities. This requires the integration of a highly resolved DFB micro-cavity with an OLED stack and with microwave electrodes. In a second challenge, we tune the cavity resonance precisely to the electroluminescence peak of the organic laser gain medium. This requires precise micro-cavity fabrication performed using e-beam lithography to pattern gratings with a precision in the nanometer scale. Optimal DFB micro-cavities are obtained with 300 nm thick hydrogen silsesquioxane negative-tone e-beam resist on 50 nm thin indium tin oxide anode exposed with a charge quantity per area (i.e., dose) of 620 µC/cm2, developed over 40 min in tetramethylammonium hydroxide diluted in water. We show that the integration of the DFB micro-cavity does not hinder the pulsed electrical operability of the device, which exhibits a peak current density as high as 14 kA/cm2.

Enhancement of Optical Gain in Colloidal CdSe/CdS/ZnS Quantum Dots through Nanosecond Optical Pumping.

Optical gain and lasing in colloidal nanocrystals are often hindered by sub-nanosecond rapid Auger non-radiative recombination, especially under continuous wave optical or electrical excitation. This study demonstrates amplified spontaneous emission (ASE) from CdSe/CdS/ZnS quantum dot (QD) solids through prolonged pulsed optical pumping over 10 ns. The incorporation of CdS and ZnS double shells on CdSe QDs effectively decelerates the Auger process in multiexcitonic states by extending the electron wave function and enhancing dielectric screening. Furthermore, we engineer smooth, densely packed QD solid films that efficiently guide the optical mode, achieving substantial net gain values under nanosecond pumping. The proposed approach helps observe ASE with gain thresholds of 0.84 and 1.5 mJ/cm2 under optical pumping pulse widths of 6 and 15 ns, respectively. This advancement can promote continuous pumping in colloidal QD gain systems, opening new avenues for optoelectronic applications.

Redefining left bundle branch block from high-density electroanatomical mapping

BackgroundThe existing ECG criteria for diagnosing left bundle branch block (LBBB) are insufficient to distinguish between true and false blocks accurately. MethodsWe hypothesized that the notch width of the QRS complex in the lateral leads (I, avL, V5, V6) on the LBBB-like ECG could further confirm the diagnosis of true complete left bundle branch block (t-LBBB). We conducted high-density, three-dimensional electroanatomical mapping in the cardiac chambers of 37 patients scheduled to undergo CRT. These patients' preoperative electrocardiograms met the ACC/AHA/HRS guidelines for the diagnosis of complete LBBB. If the left bundle branch potential could be mapped from the base of the heart to the apex on the left ventricular septum, it was defined as a false complete left bundle branch block (f-LBBB). Otherwise, it was categorized as a t-LBBB. We conducted a comparative analysis between the two groups, considering the clinical characteristics, real-time correspondence between the spread of ventricular electrical excitation and the QRS wave, QRS notch width of the lateral leads (I, avL, V5, V6), and the notch width/left ventricular end-diastolic diameter (Nw/LVd) ratio. We performed the ROC correlation analysis of Nw/LVd and t-LBBB to determine the sensitivity and specificity for diagnostic authenticity. ResultsTwenty-five patients were included in the t-LBBB group, while 12 patients were assigned to the f-LBBB group. Within the t-LBBB group, the first peak of the QRS notch correlated with the depolarization of the right ventricle and septum, the trough corresponded to the depolarization of the left ventricle across the left ventricle, and the second peak aligned with the depolarization of the left ventricular free wall. In contrast, within the f-LBBB group, the first peak coincided with the depolarization of the right ventricle and a majority of the left ventricle, the second peak occurred due to the depolarization of the latest, locally-activated myocardium in the left ventricle, and the trough was a result of delayed activation of the left ventricle that did not align with the usual peak timing. The QRS notch width (45.2 ± 12.3 ms vs. 52.5 ± 9.2 ms, P < 0.05) and the Nw/LVd ratio (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05) were compared between the two groups. After conducting the ROC correlation analysis, a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using Nw/LVd were obtained. ConclusionBy utilizing the current diagnostic criteria for LBBB, an increased Nw/LVd value can enhance the effectiveness of diagnosing LBBB.

Selection of power supply scheme for controlled excitation converters in traction electric motors of single-phase DC electric locomotives

The article focuses on the development of an effective design and algorithms for automatic control of singlephase DC electric locomotives according to the laws of constant traction force and power without switching electrical devices within power electric circuits. Methods of mathematical modelling for electromagnetic, electromechanical, and mechanical processes by MatLab, Simulink, and SimPowerSystems software were used to address this problem. The nonlinearities of the magnetisation curve were taken into account, along with the influence of eddy currents from the coils of the main and additional poles in traction motors. Structural and parametric synthesis of a power electrical circuit and control algorithms by controlled bridge IGBT converters were used in the simulation. The object of the research was an electrotechnical complex, including a 9840 kW three-stack electric locomotive 3ES5K “Ermak”. On the basis of the research results, it is recommended to use a power electrical circuit with two reversible converters for each of the three sections on the electric locomotive. These converters provide power to four 820 kW traction motors and a group power supply for controlled bridge IGBT converters shunting the field coils for axial traction control. The calculations confirmed the applicability of a scheme for individual control of traction electric motors and excitation currents, ensuring a smooth increase in the traction force of an electric locomotive. The developed algorithm of axial traction control ensures a smooth increase in this force and creates the optimal conditions for coupling the wheels of an electric locomotive with rails. These solutions can be used in the manufacture and modernisation of new and existing electric locomotives

Multifunctional optoelectronic memristor based on CeO2/MoS2 heterojunction for advanced artificial synapses and bionic visual system with nociceptive sensing

The emerging intelligent nanodevices make the artificial visual system a reality. Memristors, as artificial synapses equipped with the advantages of high parallelism and low power consumption, hold considerable promise for developing biological visual systems. In this study, an optoelectronic memristor composed of Ag/CeO2/MoS2/ITO is proposed, which actualizes neural synapse functions such as short/long-term plasticity by adjusting electrical excitation, and short/long-term learning and memory conversion is realized with the assistance of a letter “NANO” pattern of 50 devices. Moreover, light is capable of replacing voltage to induce advanced synaptic functions including short/long-term memory and learning-forgetting-relearning. In particular, the device benefits from the ability to produce significantly distinguishable photoconductive effects for multi-wavelengths (620, 580, and 520 nm) and exhibits memory properties for different wavelengths. A human visual system that is able to sense, memory, and color recognition of the “traffic signal” image is implemented on a 7 × 7 optoelectronic memristor array constructed with multi-wavelength modulation. Finally, an artificial visual system with pain-sensing capability is presented, where the four key features of human visual nociceptors, namely “threshold”, “no-adaption”, “relaxation” and “nociceptive sensitization”. This work provides a strategy to integrate sensing, memory, and visual pain devices for electronic eyes and humanoid robots in the future.

Triplet dynamics reveal loss pathways in multi-resonance thermally activated delayed fluorescence emitters.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials are of interest for light-emitting applications due to their narrow emission bandwidths and high photoluminescence quantum yields. Whilst there have been numerous examples of multi-resonance molecules exhibiting efficient TADF, the photophysics and mechanism of TADF in multi-resonance emitters have not been investigated to the same extent as the more conventional spatially separated donor-acceptor TADF materials, limiting the development of MR-TADF devices. Here we study the photophysics of a multi-resonance TADF material, OQAO(mes)2, using transient absorption spectroscopy to spectrally resolve the triplet population(s). We identify multiple triplet populations with distinct spectral contributions, and resolve the dynamics between them. Unlike conventional donor-acceptor TADF materials that have previously been studied, we find these triplet states are not formed in equilibrium, instead exhibiting a slow evolution from a high-energy triplet to a low-energy triplet. Delayed fluorescence predominantly reflects the lifetime of the high-energy triplet state, indicating that the formation of the low-energy triplet is a loss pathway for TADF. We also find that greater amounts of the low-energy triplet are formed in a higher dielectric environment, which leads to less delayed fluorescence. These triplet dynamics have significant implications for TADF in devices, as depending on the identity of the triplet formed by electrical excitation, there will either be a significant barrier to TADF, or a competing nonradiative decay pathway.

Alignment transport between ultracold polar molecules.

We propose an array of ultracold polar molecules as a platform to study alignment transport between molecules. We envision a polar molecule being aligned with an intense off-resonant laser field whose alignment migrates to a nearby molecule due to dipole-dipole interactions. Our results show that the transport of the alignment is due to a complex interplay between electric field-driven excitations and dipole-dipole interactions. All mechanisms for alignment transfer are elucidated and analyzed. Using NaCs as a prototype molecule, we find that the time for alignment transfer is (10 μs), which makes the phenomena readily observable in the lab.

Switchable ultra-broadband absorption and polarization conversion terahertz metasurface

Metasurfaces can realize flexible modulation of electromagnetic waves at the wavelength level. However, the reported functions of metasurface are usually fixed and cannot be changed, once its structural design is completed. The designed metasurface cannot meet the requirements for flexible regulation of terahertz waves. We find that the phase change material of vanadium dioxide can achieve a transition from insulating state to metallic state through thermal, electrical, or light excitation, and the phase transition of this material is reversible. Therefore, using vanadium dioxide to form a composite metasurface can achieve dynamic modulation of terahertz waves. In this study, we propose a terahertz metasurface with switchable broadband absorption and polarization conversion. The proposed metasurface is composed of a 9-layer structure stacked from bottom to top with a combination pattern of different dielectric layers. By adjusting the conductivity of vanadium dioxide, the designed metasurface can achieve flexible switching between terahertz wave absorption function and polarization conversion function. When the vanadium dioxide is in the metal state, the designed metasurface behaves as a broadband absorber with an absorption rate of more than 90% in a range of 6.32–18.06 THz and a relative bandwidth of 96.3%. When the vanadium dioxide is in the insulated state, the designed structure acts as a polarization converter in a frequency range of 2.41–3.42 THz, 4.78–7.48 THz, and 9.53–9.73 THz, respectively, with a polarization conversion rate of over 90%. We believe that this metasurface structure will have good applications in the fields of terahertz wave detection, terahertz switches, terahertz filtering, terahertz communication, and terahertz sensing.

Manipulating metastability: Quenched control of topological defects in multiferroics

The topological properties of quasiparticles, such as skyrmions and vortices, have the potential to offer extraordinary metastability through topological protection, and drive motion with minimal electrical current excitation. This has promising implications for future applications in spintronics. Skyrmions frequently appear either in lattice form or as separate, isolated quasiparticles [Y. Tokura and N. Kanazawa, Chemical Reviews 121, 2857–2897 (2021)]. Magnetic ferroelectrics, a subset of multiferroics that exhibit magnetically induced ferroelectricity, possess intriguing characteristics like magnetic (electric) field-controlled ferroelectric (magnetic) responses. Previous research based on Landau theory indicated the potential to stabilize metastable phases in multiferroic barium hexaferrite [Karpov et al., Phys. Rev. B 100, 054432 (2019)]. We have successfully stabilized these meta-stable phases through magnetic quenching of hexaferrite nanoparticles, leading to the creation of compelling topological structures. The structural changes in individual BaFe12O19 nanocrystals were scrutinized using Bragg coherent diffractive imaging, granting us insight into the emergent topological structures in field-quenched multiferroics. Additionally, we explored why these structures are energetically preferable for the formation of metastable topological structures [Karpov et al., Nature Communications 8, 280 (2017) and Karpov et al., Phys. Rev. B 100, 054432 (2019)].

The measurement of the E2 nuclear resonance effects in kaonic atoms at DAΦNE: The KAMEO proposal

KAMEO (Kaonic Atoms Measuring Nuclear Resonance Effects Ob-servables) is a proposal for an experiment aiming to perform the first consistent measurement of the E2 nuclear resonance effects in kaonic molybdenum A=94,96,98,100 isotopes. The E2 nuclear resonance mixes atomic states, due to the electrical quadrupole excitation of nuclear rotational states. It occurs in atoms having the energy of a nuclear excitation state closely matching an atomic de-excitation state energy, and affects the rates of X-ray atomic transitions matching the energy of the resonance. The measurement E2 nuclear resonance effect in KMO isotopes allows the study of the strong kaon-nucleus interaction in a rotational excited nuclear state. Moreover, the effect enables the K- to access an inner atomic level not easily reachable by the kaon normal cascade, due to the nuclear absorption. The KAMEO proposed apparatus consists of 4 enriched Mo A=94,96,98,100 isotope strips, exposed to the kaons produced by the DAφNE collider, for kaonic atoms formation, with a high-purity germanium detector, cooled with liquid nitrogen, used to measure the X-ray atomic transitions. The DAφNE collider is located at the National Laboratories of Frascati (LNF-INFN), in Italy. It is already suited for kaonic atoms measurement by the SIDDHARTA-2 collaboration.

Design and Analysis of Inductive Power Transfer System for Electric Machine Excitation

Design and Analysis of Inductive Power Transfer System for Electric Machine Excitation

Design and Test of an Intraoral Electrode Grid for Tongue High-Density Electromyography.

Tongue motor function is crucial in a wide range of basic activities and its impairment affects quality of life. The electrophysiological assessment of the tongue relies primarily on needle electromyography, which is limited by its invasiveness and inability to capture the concurrent activity of the different tongue muscles. This work aimed at developing an intraoral grid for high-density surface electromyography (HDsEMG) to non-invasively map the electrical excitation of tongue muscles. We developed a grid of 4×8 electrodes deposited over an adhesive 8- μ m thick polyurethane membrane. The testing protocol was conducted on 7 healthy participants and included functional tasks (vowels articulation and tongue movements) aimed at activating different regions of the tongue. The electrical stability of contact was assessed by measuring electrode-tongue impedances before and after the tasks. The spatial amplitude distribution of global EMG and single motor unit action potentials (MUAPs) was characterized. Electrode-tongue impedance magnitude showed no significant changes in the pre-post comparison ( 58±46 k Ω vs. 67±58 k Ω at 50Hz). Contact stability was confirmed by the quality of the signals that allowed to quantify spatiotemporal characteristics of muscle activation during the different tasks. The analysis of the spatial distribution of individual MUAPs amplitude showed that they were confined to relatively small areas on the tongue surface (range: 0.5cm2 -3.9cm [Formula: see text]. A variety of different spatiotemporal MUAP patterns, likely due to the presence of different muscle compartments with different fiber orientations, were observed. Our results demonstrate that the developed electrode grid enables HDsEMG acquisition from the tongue during functional tasks, thus opening new possibilities in tongue muscle assessment both at global and single motor unit level.

Intracellular Dynamics of Human Cardiac Ventricular Myocyte: ORd Model

Human heart is elegantly articulated to mechanically contract in response to electrical excitation. Cardiac electrical activity may be described as a multiscale process from sub-cellular to cellular to tissue level. Ion movement at the cellular level through ion channels results in an action potential that propagates as an electrical wave in tissue. A first-principles-based mathematical description of the cellular-level dynamics of cardiac electrophysiological behavior provides a better understanding of the functioning of the heart. The mathematical models describing cellular dynamics often involve a coupled system of ordinary differential equations (ODEs) with variables including transmembrane voltage, ion concentrations and ion channel gating variables, whose evolution describes activation/inactivation of ion channels. In this study we discuss a mathematical model of the human ventricular myocyte (O’Hara–Rudy model), defined as a system of 41 ODEs, with variables involving membrane voltage, 29 gating variables describing activation of Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] channels, 11 variables describing ion concentrations and Ca[Formula: see text] related flux. Runge–Kutta method with variable order and variable time step was adopted to solve the system numerically. We discuss the action potential (AP) profile of a healthy human ventricular myocyte and corresponding dominant ionic currents. We present a phase plot that describes the change in voltage and its rate as the system evolves over time. The phase plot seems to provide more details of the underlying events than the AP curve.

Electroluminescence and temperature-dependent time-resolved photoluminescence of monolithically integrated triple-wavelength InGaN-based LED

Here, we propose a monolithically integrated triple-wavelength InGaN-based LED structure and conduct comprehensive research on its emission dynamics under electrical and optical excitation. Through experimental and numerical analyses, a carrier transport and a recombination process can be manipulated in bandgap-engineered multiple quantum wells (MQWs), thus realizing the manipulation of emission properties. A rational triple-wavelength LED structure is heteroepitaxially grown, which shows excellent color stability versus injected currents. Furthermore, utilizing the temperature-dependent time-resolved photoluminescence (TRPL), triple-wavelength peaks display different TRPL decay behaviors. Especially, an anomalous three-stage decay phenomenon is found for a low-energy peak measured at 10 K, accompanied by a decay profile transition with the increasing temperature. The underlying mechanisms are revealed and correlated with carrier localization, interaction between different QWs, and competition between radiative and nonradiative recombination.