External Pulse Research Articles

Non-existence of causal, standard classical electrodynamics with point charged particle

Abstract The existence of consistent, standard and causal theory of point charged particle (for example electron) interacting with electromagnetic field was the subject of many investigations. This problem is often stated as the description of the system of electromagnetic pulse of radiation interacting with single point charged particle (for example electron). The correct theory should give the causal particle trajectory for any electromagnetic pulse of radiation. Up to now no such theory was formulated. We show that for certain electromagnetic pulse of radiation and point particle being initially at rest, there does not exist a causal and physical particle trajectory that satisfies energy and momentum conservation. This shows that the causal, standard electrodynamics of scalar point particles, valid for all possible external pulses, does not exist.

Femtosecond-Laser-Enabled Geometric Microengineering of PZT Films for Boosted Piezoelectric Response and Rainfall Monitoring Demonstration.

Geometric microengineering of the active layer in a piezoelectric sensor has emerged as a hot topic to improve performance but meets challenges due to the brittle nature of piezoelectric ceramics. Here, we demonstrate that fs-laser-induced compressive stress leads to film bulging in the nanoscale and forms various shapes of nanostructures, including nanobumps, nanovolcanoes, and nanocaves on Pb1.1Zr0.52Ti0.48O3 (PZT) films, in a single-step, mask-free, large-scale, and rapid fashion. Highly reproducible 3D profiles of the nanostructures are finely controlled by carefully adjusting the laser energy density around the ablation threshold. Evaluation of piezoelectric response to external pressure pulses shows that the PZT films patterned with 450 nm high nanobumps exhibit a 30% increase in output voltage compared to flat PZT films. In a rainfall monitoring test, the PZT films patterned with 450 nm high nanobumps show a significantly enhanced response with varying rain droplet volumes and falling frequencies. Geometric microengineering of PZT films using a femtosecond laser direct writing route provides a guideline for material design in a wide range of microsensor applications.

Spray characteristics and combustion mechanism influence on combustion stability of UDMH/NTO pre-combustor under external excitation

To study the combustion stability of liquid rocket engines with hypergolic propellant more comprehensively, external pressure pulse excitation was applied to the UDMH (unsymmetrical dimethylhydrazine)/NTO (methylhydrazine) pre-combustor. The effects of pressure pulse intensity, spray characteristics (droplet diameter and spray cone angle), and combustion mechanism on combustion stability characteristic frequencies and attenuation characteristics after excitation were investigated. The simulation results show that all operation conditions capture the first three longitudinal frequencies of the pre-combustor, and all factors have a greater impact on frequencies with higher orders. Increasing the pulse intensity and reducing the droplet diameter are not conducive to combustion stability. The influence of the spray cone angle on the combustion stability is not monotonous. The pre-combustor has good stability when the spray cone angle is 70°. Different combustion mechanisms have a significant effect on the results before and after pressure pulses, and considering a more complete combustion process may increase the attenuation time in the pre-combustor. The obtained rules can provide a reference for the design and simulation of hypergolic liquid rocket engines, which is beneficial for predicting and evaluating the combustion stability of liquid rocket engines.

Preventing technique-related complications in spinal cord stimulation trials: The Dural Substitute Confetti technique. A retrospective monocentric analysis.

Spinal Cord Stimulation (SCS) is an established therapy for chronic pain, employing screening trials to identify suitable candidates before implantation. However, complications arising from both technique and medical factors present challenges to this practice. This study introduces the Dural Substitute Confetti technique, which addresses technique-related complications during SCS implantation by preventing scar-induced lead migration or breakage and reducing operating times. We conducted a retrospective analysis on 174 patients treated with SCS trials from 2017 to 2022 at our institution. Of these, 85.1% proceeded to permanent implantation. During trial surgery, synthetic dural substitutes (DS) were used to protect leads, which remained connected to an external pulse generator (EPG) for 20-28 days (mean 21.4 days). Utilizing the DS Confetti technique, leads were easily dissected from the DS during the second surgery and connected to an internal pulse generator (IPG). We compared complications and surgical times before and after the introduction of this technique in 2017. Following the complete SCS trial, patients experienced over 50% pain relief, with an implant-to-trial ratio of 85.1% and a mean follow-up of 52 months. No technique-related complications occurred during the trial period post-2017, while the pre-2017 group had a 3.9% lead migration rate due to scarring, necessitating re-implantation. The average surgery duration decreased from 54 min pre-2017 to 32 min post-2017. Medical-related complications included infections (2.1%) and wound dehiscence (1.3%). The DS Confetti technique prevents scar adhesion formation during screening trials, thereby facilitating and expediting the definitive SCS implantation. Additionally, it may also reduce the risk of lead migration and iatrogenic damage, potentially lowering technique-related complications.

Ion-migration-induced synaptic plasticity in high ion-storable fluorine graphdiyne for information processing

Neuromorphic devices encounter constraints associated with complementary metal–oxide–semiconductor technology, such as intricate electronics and high power consumption. Recently, solid polymer electrolytes (SPE) have gained attention in electronic devices for constructing artificial synapses, primarily due to their low-voltage operation enabled by ion-assisted signal transmission. This study presents a two-terminal artificial synapse fabricated using fluorine graphdiyne (F-GDY) synthesized through chemical vapor deposition and ion-doped SPE. The device architecture consists of Au/SPE/F-GDY/Si, which operates by ion migration induced by external potential pulses. Electrical measurements are conducted to depict the synaptic plasticity of the devices. Among devices employing different ion-doped SPEs (Li-SPE, Na-SPE, K-SPE, and Ca-SPE), the one utilizing Li-SPE demonstrates the highest synaptic weight. This is attributed to the superior Li+ ion storage capacity of F-GDY. Hence, Li-SPE/F-GDY was chosen for in-depth examinations of synaptic activity presenting long-term potentiation, short-term depression, and pair-pulse facilitation. The device has good durability and stability and can respond to low action potential with power consumption at the pJ level. Furthermore, Modified National Institute of Standards and Technology simulations reveal its learning and pattern recognition capability with 91.3 % accuracy after 10 training epochs. Finally, flexible substrate-based SPE/F-GDY devices integrated with gate electrodes were fabricated to record physiological signals, showing promise for in-sensing applications. This work shows the potential of F-GDY/Li-SPE devices for low-power neuromorphic computing, though real-time parallel processing and multimodal integration (e.g., visual, auditory) remain unexplored. Even so, the biocompatibility and efficient ion-assisted transmission of F-GDY suggest promising future applications in these areas.

Numerical assessments of geometry, proximity and multi-electrode effects on electroporation in mitochondria and the endoplasmic reticulum to nanosecond electric pulses

Most simulations of electric field driven bioeffects have considered spherical cellular geometries or probed symmetrical structures for simplicity. This work assesses cellular transmembrane potential build-up and electroporation in a Jurkat cell that includes the endoplasmic reticulum (ER) and mitochondria, both of which have complex shapes, in response to external nanosecond electric pulses. The simulations are based on a time-domain nodal analysis that incorporates membrane poration utilizing the Smoluchowski model with angular-dependent changes in membrane conductivity. Consistent with prior experimental reports, the simulations show that the ER requires the largest electric field for electroporation, while the inner mitochondrial membrane (IMM) is the easiest membrane to porate. Our results suggest that the experimentally observed increase in intracellular calcium could be due to a calcium induced calcium release (CICR) process that is initiated by outer cell membrane breakdown. Repeated pulsing and/or using multiple electrodes are shown to create a stronger poration. The role of mutual coupling, screening, and proximity effects in bringing about electric field modifications is also probed. Finally, while including greater geometric details might refine predictions, the qualitative trends are expected to remain.

Entrainment and multi-stability of the p53 oscillator in human cells

The tumor suppressor p53 responds to cellular stress and activates transcription programs critical for regulating cell fate. DNA damage triggers oscillations in p53 levels with a robust period. Guided by the theory of synchronization and entrainment, we developed a mathematical model and experimental system to test the ability of the p53 oscillator to entrain to external drug pulses of various periods and strengths. We found that the p53 oscillator can be locked and entrained to a wide range of entrainment modes. External periods far from p53's natural oscillations increased the heterogeneity between individual cells whereas stronger inputs reduced it. Single-cell measurements allowed deriving the phase response curves (PRCs) and multiple Arnold tongues of p53. In addition, multi-stability and non-linear behaviors were mathematically predicted and experimentally detected, including mode hopping, period doubling, and chaos. Our work revealed critical dynamical properties of the p53 oscillator and provided insights into understanding and controlling it. Arecord of this paper's transparent peer review process is included in the supplemental information.

Optimizing Control of a Hybrid Quantum System of Nitrogen-Vacancy Centers and Superconducting Transmon Qubits

Abstract The control of hybrid quantum systems via the application of external fields is rapidly evolving field of research for the development of quantum applications and technologies. We model and optimize the dynamics of a hybrid quantum system consists of two non-local ensembles of nitrogen-vacancy centers and a superconducting transmon qubit mediated by two transmission line resonators. We apply a set of optimized time-dependent external driving field to enhance the system performance to function as a high fidelity state-to-state transfer. The Hamiltonian of the externally driven transmission line resonators is modelled by considering the non-linear transmons. The numerical simulation of the system is done using the optimized parameters of the external fields. By applying the optimized pulses, we have increased the fidelity of the state transfer from 0.7 to 1.0 within 100 ns. By varying the full wave half maxima value (FWHM) of the Gaussian pulse, it result in decreasing the amplitude of the fast oscillating states of the transmon and nitrogen-vacancy ensembles. These optimized external pulses also created a strong coupling between the components of under-consideration physical quantum system, which will eventually increase the fidelity of the system in a relatively faster time.

Adaptive Nonsingular Fast Terminal Sliding Mode Control for Shape Memory Alloy Actuated System

Due to its high power-to-weight ratio, low weight, and silent operation, shape memory alloy (SMA) is widely used as a muscle-like soft actuator in intelligent bionic robot systems. However, hysteresis nonlinearity and multi-valued mapping behavior can severely impact trajectory tracking accuracy. This paper proposes an adaptive nonsingular fast terminal sliding mode control (ANFTSMC) scheme aimed at enhancing position tracking performance in SMA-actuated systems by addressing hysteresis nonlinearity, uncertain dynamics, and external disturbances. Firstly, a simplified third-order actuator model is developed and a variable gain extended state observer (VGESO) is employed to estimate unmodeled dynamics and external disturbances within finite time. Secondly, a novel nonsingular fast terminal sliding mode control (NFTSMC) law is designed to overcome singularity issues, reduce chattering, and guarantee finite-time convergence of the system states. Finally, the ANFTSMC scheme, integrating NFTSMC with VGESO, is proposed to achieve precise position tracking for the prosthetic hand. The convergence of the closed-loop control system is validated using Lyapunov’s stability theory. Experimental results demonstrate that the external pulse disturbance error of ANFTSMC is 8.19°, compared to 19.21° for the comparative method. Furthermore, the maximum absolute error for ANFTSMC is 0.63°, whereas the comparative method shows a maximum absolute error of 1.03°. These results underscore the superior performance of the proposed ANFTSMC algorithm.

Inertial Confinement Fusion Propulsion for the Massive Ra World Ship Model – Part 2

A strategy for sending humans around other stars will be to acquire the ability to construct large World Ships which are of order ~1011-1012 tons in mass, ~100 km in length and host large populations of millions of people over many generations of lifetime. This paper presents such a concept but driven by inertial confinement fusion engines utilising very large pellets of order 230 g in mass augmented with 4.85 kg/pellet of expellant propellant for increased mass flow rate and thrust generation. A mission architecture is constructed for a 1 million population carrying capacity growing to 10 million, based on an original 1984 published model which achieved a cruise speed of 1,500 km/s or 0.5% for a 1,000 year trip time. Calculations show that propulsion of such a vast construction will require hundreds of engines operating in parallel thrust mode and at moderately high pulse frequency for an elongated burn time of order half a century. The purpose of this study was to examine whether it was possible to drive an interstellar world ship using ICF engines using similar assumptions to a 1984 study for a Mk2A design. The conclusion of this study is that although an architecture does appear to be possible, there are practical reasons why it may be better to pursue alternative propulsion methods for this specific application such as via external nuclear pulse propulsion as adopted for the original studies. This paper is a follow-up to an earlier one which discussed some of the assumptions of the study. Keywords: World Ships, Interstellar Studies, Fusion Propulsion

Investigation of the dynamics of transverse oscillations of a vertical rod under gravity, friction, and thermal expansion

The paper considers the mathematical formulation of the problem of transverse oscillations of a vertical rod under gravity, friction and external pulse effect, leading to thermal expansion of the rod. The dynamics of the system under consideration corresponds to the behavior of a fuel element (FE) in a pulsed reactor and is related to the dynamic stability of the processes occurring in it.The FE dynamics is described by inhomogeneous linear differential equation of the fourth order with non-constant coefficients. Initial boundary conditions are not smooth since they correspond to the instant heating of the part of the FE surface exposed to neutron pulse radiation. The general solution of the homogeneous linear equation can be found using the concept of generalized functions expressed as a series expansion in terms of coordinate eigenfunctions dependent on p parameter. The p parameter is related with the FE mass and at some certain values results in bifurcation points of the boundary value problem for eigenfunctions. The partial solution can be found in several ways: using the Fourier transform, the method of Green's function, and in terms of series expansion by eigenfunctions.Eigenfunction expansion coefficients in an explicit form have been obtained and the numerical solution accuracy has been estimated for some important particular cases. The results of the obtained exact solutions appear to be very close to the results of the ANSYS numerical estimations. In the future the obtained exact solutions will be used as input data to simulate self-consistent system dynamics of more than 400 FE. Therefore, the advantage of the exact solution in practical use is that its calculation is much faster as compared with the finite element method done with ANSYS.

Amplification characteristics of N+2 lasing at multiple wavelengths generated by polarization-modulated femtosecond laser fields.

Multiple gain routes complicate the amplification behaviors of N2+ lasing. A direct comparison of the amplification processes of various lasing lines of N2+ is still lacking to date, mainly because the efficient generation of different lasing lines requires different experimental conditions. In this work, to overcome the limitation, we use an intense polarization-modulated femtosecond laser pulse to simultaneously produce high-intensity N2+ lasing signals at 391 nm and 428 nm, permitting us readily performing their time-domain characterizations. Our results show that the primary amplification of 428-nm lasing is always retarded by a few picoseconds with respect to the probe pulse while the amplification of 391-nm lasing can be basically completed within the probe pulse duration at a relatively high gas pressure, and besides, the time duration of the former sustains several times longer than that of the latter. These observations indicate the non-negligible contribution of the initial electronic coherence established by the pump laser, apart from the external triggering pulse. For the 391-nm lasing, the seed amplification and superradiance can fiercely interplay within the probe pulse duration. However, for the 428-nm lasing, its amplification is in essence Raman-assisted superfluorescence due to the lacking of the initial electronic coherence and a direct triggering pulse. Our findings not only shed light on the physics of N2+ lasing but also promote the relevant studies on the collective emissions in the cascaded multi-level molecular ion system.

Dynamical behavior of memristive Hopfield neural network under pulsed current excitation

This paper investigates the effect of pulsed currents and multi-piecewise memristor on dynamic behavior of memristive Hopfield neural network (HNN). Firstly, a four-neuron HNN model is constructed by using the traditional memristor as the connecting synapse and its dynamic behavior is analyzed. Secondly, the traditional memristor in the HNN is replaced with a multi-piecewise memristor, and external pulse currents are applied to the model. The system exhibits rich dynamical behavior by introducing varying numbers of pulse current stimuli and adjusting the parameters of the multi-piecewise memristor. Experimental results demonstrate that the number of attractors in the system changes when pulse currents are applied, and after a period of chaotic behavior, the system eventually exhibits periodic activity. Furthermore, adjusting the parameters of the multi-piecewise memristor can generate multiple scroll attractors in the system. Finally, the experimental results were verified by Multisim.

Peripheral Nerve Stimulation in Postoperative Analgesia: A Narrative Review.

Recent research has shown the effectiveness of peripheral nerve stimulators (PNS) in managing chronic pain conditions. Ongoing studies aim to explore its potential application in treating acute postoperative pain states. The purpose of this systematic review is to assess the role of PNS in providing relief for postoperative pain. Clinical studies investigating the use of peripheral nerve stimulators (PNS) for analgesia following various surgeries, such as total knee arthroplasty, anterior cruciate ligament repair, ankle arthroplasty, rotator cuff repair, hallux valgus correction, and extremity amputation, have shown promising results. Lead placement locations include the brachial plexus, sciatic, femoral, tibial, genicular, perineal, sural, radial, median, and ulnar nerves. These studies consistently report clinically significant reductions in pain scores, and some even indicate a decrease in opioid consumption following PNS for postoperative pain. PNS involves the subcutaneous placement of electrode leads to target peripheral nerve(s) followed by delivery of an electric current via an external pulse generator. While the precise mechanism is not fully understood, the theory posits that PNS modulates electrical stimulation, hindering the signaling of nociceptive pain. PNS presents itself as an alternative to opioid therapy, holding promise to address the opioid epidemic by offering a nonpharmacologic approach for both acute and chronic pain states.

The estimation of pore size distribution of electroporated MCF-7 cell membrane

ABSTRACT The size of the pores created by external electrical pulses is important for molecule delivery into the cell. The size of pores and their distribution on the cell membrane determine the efficiency of molecule transport into the cell. There are very few studies visualizing the presence of electropores. In this study, we aimed to investigate the size distribution of electropores that were created by high intensity and short duration electrical pulses on MCF-7 cell membrane. Scanning Electron Microscopy (SEM) was used to visualize and characterize the membrane pores created by the external electric field. Structural changes on the surface of the electroporated cell membrane was observed by Atomic Force Microscopy (AFM). The size distribution of pore sizes was obtained by measuring the radius of 500 electropores. SEM imaging showed non-uniform patterning. The average radius of the electropores was 12 nm, 51.60% of pores were distributed within the range of 5 to 10 nm, and 81% of pores had radius below 15 nm. These results showed that microsecond (µs) high intensity electrical pulses cause the creation of heterogeneous nanopores on the cell membrane.

High repetition rate coherent terahertz synchrotron radiation via self-amplified energy modulation

Coherent terahertz (THz) radiation sources based on a storage ring hold a significant future for generating high average power terahertz radiation, as the electron beam possesses a high revolution frequency. We propose a novel scheme to generate a high repetition rate coherent THz radiation leveraging the energy modulation self-amplification technology. In this scheme, utilizing the interaction of external intensity-modulated laser pulses with the electron beam can lead to a customized manipulation of the electron beam, such as a periodic longitudinal density modulation with a submillimeter scale for coherent THz radiation. Positively, it can propel the repetition rate when the peak power requirement of an external laser system is decreased. Thus, we employ a self-modulation method to enhance the initial weak energy modulation induced by the laser directly. In the meanwhile, the use of self-modulation can bypass the limitation that the bandwidth of a long modulator should be smaller than that of the external wideband laser source, which is necessary to shape the intensity envelope flexibly. The one-dimensional analytical description of electron longitudinal dynamic during the self-modulation process is given, which confirms the effective enhancement of the modulation at THz band. Three-dimensional time-dependent simulation results based on the parameters of Hefei light source-II show that the coherent THz radiation pulses with a repetition rate of 10 kHz can be generated. Published by the American Physical Society 2024

On-chip spiking neural networks based on add-drop ring microresonators and electrically reconfigurable phase-change material photonic switches

We propose and numerically demonstrate a photonic computing primitive designed for integrated spiking neural networks (SNNs) based on add-drop ring microresonators (ADRMRs) and electrically reconfigurable phase-change material (PCM) photonic switches. In this neuromorphic system, the passive silicon-based ADRMR, equipped with a power-tunable auxiliary light, effectively demonstrates nonlinearity-induced dual neural dynamics encompassing spiking response and synaptic plasticity that can generate single-wavelength optical neural spikes with synaptic weight. By cascading these ADRMRs with different resonant wavelengths, weighted multiple-wavelength spikes can be feasibly output from the ADRMR-based hardware arrays when external wavelength-addressable optical pulses are injected; subsequently, the cumulative power of these weighted output spikes is utilized to ascertain the activation status of the reconfigurable PCM photonic switches. Moreover, the reconfigurable mechanism driving the interconversion of the PCMs between the resonant-bonded crystalline states and the covalent-bonded amorphous states is achieved through precise thermal modulation. Drawing from the thermal properties, an innovative thermodynamic leaky integrate-and-firing (TLIF) neuron system is proposed. With the TLIF neuron system as the fundamental unit, a fully connected SNN is constructed to complete a classic deep learning task: the recognition of handwritten digit patterns. The simulation results reveal that the exemplary SNN can effectively recognize 10 numbers directly in the optical domain by employing the surrogate gradient algorithm. The theoretical verification of our architecture paves a whole new path for integrated photonic SNNs, with the potential to advance the field of neuromorphic photonic systems and enable more efficient spiking information processing.

Research on vibration characteristics of rocket engine flow pipeline

PurposeAbnormal vibrations often occur in the liquid oxygen kerosene transmission pipelines of rocket engines, which seriously threaten their safety. Improper handling can result in failed rocket launches and significant economic losses. Therefore, this paper aims to examine vibrations in transmission pipelines.Design/methodology/approachIn this study, a three-dimensional high-pressure pipeline model composed of corrugated pipes, multi-section bent pipes, and other auxiliary structures was established. The fluid–solid coupling method was used to analyse vibration characteristics of the pipeline under various external excitations. The simulation results were visualised using MATLAB, and their validity was verified via a thermal test.FindingsIn this study, the vibration mechanism of a complex high-pressure pipeline was examined via a visualisation method. The results showed that the low-frequency vibration of the pipe was caused by fluid self-excited pressure pulsation, whereas the vibration of the engine system caused a high-frequency vibration of the pipeline. The excitation of external pressure pulses did not significantly affect the vibrations of the pipelines. The visualisation results indicated that the severe vibration position of the pipeline thermal test is mainly concentrated between the inlet and outlet and between the two bellows.Practical implicationsThe results of this study aid in understanding the causes of abnormal vibrations in rocket engine pipelines.Originality/valueThe causes of different vibration frequencies in the complex pipelines of rocket engines and the propagation characteristics of external vibration excitation were obtained.

Method of instantaneous signal synchronization of measuring pulse generators

The synchronization methods used in the pulse generators of the G5 measuring group in the external trigger mode are analyzed. The factors determining the error in the formation of time intervals in this mode have been studied. It is shown that the main source of errors in the formation of time intervals during external triggering of measuring pulse generators is the variation in the position of the clock generator reference pulses relative to the external trigger pulses. An analytical review of synchronization methods based on the sampling of time intervals by a multi-tap delay line as a pulse signal propagates along it is carried out. The method of instantaneous synchronization of output pulses is proposed, using sampling of the period of the reference pulses of the clock generator with a multi-tap delay line and fixing the position of the edge of the external trigger pulse within the period of the reference frequency by triggers that control the multiplexer, which connects the output of the multi-tap delay line to the output of the device, at which the edge of the next reference clock pulse generator lags by a minimum time from the front of the external trigger pulse. A device is presented that makes it possible to implement the proposed solution. The simulation of the device was carried out, illustrating the details of its functioning. Jitter was assessed on a prototype device using an integrated 5-tap delay line with a total delay of 20 ns. The method can be applied in measuring pulse generators and belongs to the field of pulse technology.

Optical Manipulation of Bipolarons in a System with Nonlinear Electron-Phonon Coupling.

We investigate full quantum mechanical evolution of two electrons nonlinearly coupled to quantum phonons and simulate the dynamical response of the system subject to a short spatially uniform optical pulse that couples to dipole-active vibrational modes. Nonlinear electron-phonon coupling can either soften or stiffen the phonon frequency in the presence of electron density. In the former case, an external optical pulse tuned just below the phonon frequency generates attraction between electrons and leads to a long-lived bound state even after the optical pulse is switched off. It originates from a dynamical modification of the self-trapping potential that induces a metastable state. By increasing the pulse frequency, the attractive electron-electron interaction changes to repulsive. Two sequential optical pulses with different frequencies can switch between attractive and repulsive interaction. Finally, we show that the pulse-induced binding of electrons is shown to be efficient also for weakly dispersive optical phonons, in the presence anharmonic phonon spectrum and in two dimensions.