Range Of Pulse Widths Research Articles

Enhanced Dye-Sensitized Mechanosensation Utilizing Pulsed and Digitally Modulated Light.

The generation of pressure perturbations in matter stimulated by pulsed light is a method widely recognized as the photoacoustic or light-induced thermoelastic effect. In a series of psychophysical experiments, the robustness of the tactile perception generated with a variety of light sources is examined: a diverging pulsed laser used for photoacoustic tomography optical parameter oscillation (OPO), a miniature diode laser (MDL), and a commercial digital light processing (DLP) projector. It is demonstrated that participants can accurately detect, categorically describe the sensations, and discern the direction of pulsed light travel. High detection accuracy is reported as follows: (d' = 4.95 (OPO); d' = 2.78 (modulated MDL); d' = 2.99 (DLP)) of the stimulus on glabrous skin coated with a thin layer of dye absorber. For all light sources, the predominant sensation is felt as vibration at the distal phalanx (i.e., fingertip, 55.21-57.29%) and the proximal phalanx (41.67-44.79%). At the fingertip, thermal sensations are perceived less frequently than mechanical ones. Moreover, these haptic effects are preserved under a wide range of pulse widths, spot sizes, optical energies, and wavelengths of the light sources. This form of sensory stimulation demonstrates a generalizable non-contact, non-optogenetic, in situ activation of the mechanosensorysystem.

Numerical study on the effect of actuation parameters on the formation characteristics of metal droplets in magnetohydrodynamic drop-on-demand (DOD) jetting

Numerical simulations have investigated the effects of electromagnetic drive waveform amplitude and pulse width on the state of metal droplet generation during drop-on-demand printing of molten metal aluminum by electromagnetic drive. It indicates that positive and negative pulses of magnetohydrodynamic(MHD) actuation applied to the molten metal in the crucible can form a so-called “push-pull” effect, which is the main mechanism affecting droplet generation and breakup. The positive pressure pulse causes the liquid metal to be extruded outward, and the negative pressure pulse promotes the fluid retraction at the nozzle to promoting the thinning of the liquid bridge and the generation of liquid droplets. With the increase in the amplitude of the applied current, the ejected molten aluminum from the crucible experiences three states: no droplet, single droplet, and droplet with satellite droplets. In the single drop state, the droplet formation time is shortened as the current peak increases and the droplet volume increases with the increase of pulse width. The energy conversion and force changes during droplet formation and falling are analyzed. When the peak kinetic energy of the ejected molten metal exceeds its surface energy, the jet breaks up and generates a single droplet. For the actuation with constant amplitude and duration for positive pulses, extending the duration of negative pulses weakens the "pull" effect, leading to a transition from the generation of a single droplet to multiple droplets. The numerical simulation results provide information on the current amplitude, pulse width, and Weber number range necessary for stable single droplet generation.

Realizing enhanced lithotripsy efficiency using 700 W peak power thulium-doped fiber laser

Despite its widespread use in laser lithotripsy, the Ho:YAG solid-state laser suffers from limited parameter combinations, poor beam quality, and low photoelectric conversion efficiency. The development of 2.0 μm fiber laser technology has positioned the thulium-doped fiber laser (TFL) as a superior alternative to the Ho:YAG laser in lithotripsy. The TFL excels because of its high-water absorption coefficient, all-fiber structure and pump modulation flexibility. However, the peak power reported for TFL in lithotripsy remains at most 500 W. This study presented a quasi-continuous wave (QCW) TFL featuring a wide tunable range of pulse width and pulse repetition rates, and a peak power of 700 W to realize enhanced ablation efficiency. A high-speed camera was used to acquire the laser-induced cavitation bubble images for the analysis of the interaction mechanism of a high peak power QCW TFL pulse with water and stones. While the synergistic action of photothermal and photomechanical effects constituted the mechanism of TFL lithotripsy, the laser-induced bubble channel was a prerequisite for TFL noncontact effective lithotripsy, with bubble length and width markedly influencing stone ablation rates. Ablation experiments on uric acid and calcium oxalate monohydrate stones conducted with various parameter combinations at a peak power of 700 W yielded rates of 8.9 mg/s for uric acid stones and 7.5 mg/s for calcium oxalate monohydrate stones. A comparison with prior findings confirmed that a high peak power TFL could notably improve stone ablation rates.

Maps of Membrane Pore Dynamics From Picosecond to Millisecond Pulse Durations.

Electroporation occurs when cells are exposed to an electric pulse of sufficient intensity E0 and pulse duration τ. Many studies have attempted to develop universal scaling laws to predict membrane pore dynamics for pulsed electric fields (PEFs) of different durations; however, the differences in pore dynamics across these parameters makes this difficult both experimentally and numerically. This study uses the asymptotic Smoluchowski equation (ASME) to quantify the number of pores, average pore radius, and fractional pore area (FPA) during exposure to PEFs with durations from hundreds of picoseconds to a millisecond. We highlight pulse parameter regimes that favor increases in pore radius and number and show that the FPA is dominated by the number of pores formed on the cell membrane. Furthermore, the number of pores and the FPA depend almost entirely on E0 for τ exceeding the charging time of the cell and both E0 and τ for τ shorter than the charging time. Finally, the maps of pore number, average radius, and FPA demonstrate that a universal scaling law for pore dynamics across a wide range of pulse durations does not exist, although certain scaling behaviors may be valuable over narrow regimes. Practically, these maps provide a guideline for selecting PEF parameters to achieve desired membrane permeabilization.

An Isolated Gate-Drive Method for Series MOSFETs in a Wide Adjustable Pulsewidth Range

An Isolated Gate-Drive Method for Series MOSFETs in a Wide Adjustable Pulsewidth Range

Simulation study of protoacoustics as a real-time in-line dosimetry tool for FLASH proton therapy.

Applying ultra-high dose rates to radiation therapy, otherwise known as FLASH, has been shown to be just as effective while sparing more normal tissue compared to conventional radiation therapy. However, there is a need for a dosimeter that is able to detect such high instantaneous dose, particularly in vivo. To fulfill this need, protoacoustics is introduced, which is an in vivo range verification method with submillimeter accuracy. The purpose of this work is to demonstrate the feasibility of using protoacoustics as a method of in vivo real-time monitoring during FLASH proton therapy and investigating the resulting protoacoustic signal when dose per pulse and pulsewidth are varied through multiple simulation studies. The dose distribution of a proton pencil beam was calculated through a Monte Carlo toolbox, TOPAS. Next, the k-Wave toolbox in MATLAB was used for performing protoacoustic simulations, where the initial proton dose deposition was inputted to model acoustic propagations, which were also used for reconstructions. Simulations involving the manipulation of the dose per pulse and pulsewidth were performed, and the temporal and spatial resolution for protoacoustic reconstructions were investigated as well. A 3D reconstruction was performed with a multiple beam spot profile to investigate the spatial resolution as well as determine the feasibility of 3D imaging with protoacoustics. Our results showed consistent linearity in the increasing dose-per-pulse, even up to rates considered for FLASH. The simulations and reconstructions were performed for a range of pulsewidths from 0.1 to 10μs. The results show the characteristics of the proton beam after convolving the protoacoustic signal with the varying pulsewidths. 3D reconstruction was successfully performed with each beam being distinguishable using an 8cm×8cm planar array. These simulation results show that measurements using protoacoustics has the potential for in vivo dosimetry in FLASH therapy during patient treatments in real time. Through this simulation study, the use of protoacoustics in FLASH therapy was verified and explored through observations of varying parameters, such as the dose per pulse and pulsewidth. 2D and 3D reconstructions were also completed. This study shows the significance of using protoacoustics and provides necessary information, which can further be explored in clinical settings.

Pulse duration dependent optical nonlinearities of Bi2Se3 thin films.

Topological insulators, such as the Bi2Se3 material, exhibit significant optical nonlinearities. This work investigates the impact of the pulse duration on the nonlinear optical responses of Bi2Se3 layers. Scanning electron microscopy studies have been performed to reveal the crystalline structure of the samples. The nonlinear optical performance has been investigated for a wide range of pulse durations, from 400 fs to 10 ps, using 1030 nm laser excitation. The nonlinear absorption coefficients recorded in this study range from -1.45 x10-7 m/W to -4.86 x10-7 m/W. The influence of two different mechanisms on optical nonlinearities was observed and discussed. Identical experimental conditions have been employed throughout the studies allowing a direct comparison of the results.

Development of a current controlled stimulation setup for investigating the effect of electrical currents on implant infections caused by biofilms

Abstract Introduction: Biofilms are bacterial communities that transform into a state enclosed in an extracellular polymeric substance, which makes them less susceptible to antibiotics. Those bacterial formations often develop on metal implants and cause chronic infections. Due to the severely reduced impact of antibiotics against biofilms, the effect of electric stimulation (on its own and in combination with antimicrobials) needs to be further observed, as available studies indicate a positive effect. Methods: Therefore, this work examined the development of a six-channel current-controlled stimulation setup, which enables further in vitro research on the effects of electric stimulation on biofilms. The setup controls the desired stimulation current through the load to counteract electrochemical processes, which constantly change its resistive and capacitive properties. Results: Each channel of the stimulator is able to operate within an amplitude range of 50 μA to 1 mA, a frequency range of 0 Hz to 1 kHz, and a pulse width range of 50 μs to 1 ms. The current control provides a sufficient rise time of 3.3 μs for three different stimulation modes: constant direct current (DC), pulsed DC, and biphasic-pulsed alternating current (AC). Furthermore, a graphical user interface enables the user to regulate and observe the stimulation on a computer to which the stimulator device is connected. Conclusion: The achieved variety of stimulation parameters in one device makes it possible to analyze the effect of different stimulation paradigms on biofilms and therefore enables more in vitro research which is inevitable to develop a sufficient treatment for patients with biofilm-infected implants.

A Magnetic Isolation Multichannel Driver With a Wide Range of Pulsewidths for Pulse Generators

A Magnetic Isolation Multichannel Driver With a Wide Range of Pulsewidths for Pulse Generators

Evaluation of electric phrenic nerve stimulation patterns for mechanical ventilation: a pilot study

Diaphragm atrophy is a common side effect of mechanical ventilation and results in prolonged weaning. Electric phrenic nerve stimulation presents a possibility to avoid diaphragm atrophy by keeping the diaphragm conditioned in sedated patients. There is a need of further investigation on how to set stimulation parameters to achieve sufficient ventilation. A prototype system is presented with a systematic evaluation for stimulation pattern adjustments. The main indicator for efficient stimulation was the tidal volume. The evaluation was performed in two pig models. As a major finding, the results for biphasic pulses were more consistent than for alternating pulses. The tidal volume increased for a range of pulse frequency and pulse width until reaching a plateau at 80–120 Hz and 0.15 ms. Furthermore, the generated tidal volume and the stimulation pulse frequency were significantly correlated (0.42–0.84, p<0.001). The results show which stimulation parameter combinations generate the highest tidal volume. We established a guideline on how to set stimulation parameters. The guideline is helpful for future clinical applications of phrenic nerve stimulation.

Fine-Tunable Emission Pulse Generation Circuit Based on p-Type Low-Temperature Poly-Si Thin-Film Transistors for Active Matrix Organic Light-Emitting Diode Displays

Active matrix organic light-emitting diode (AMOLED) displays have deployed the compensation techniques to cope with the luminance non-uniformity issues caused by variations on electrical characteristics of thin-film transistors (TFTs). While some compensation circuits require control signals of longer pulse widths than a line time, the luminance control as well as the higher bit depth representation have been also accomplished by adjusting the pulse widths. A proposed EM pulse generation circuit consists of 11 p-type low-temperature poly-Si (LTPS) TFTs and a one coupling capacitor. While previous tunable circuits could address pulse widths of either even or odd multiples of a line time, the proposed circuit can generate any multiples by changing phases of additional clock signals. In particular, the internal inverter is implemented with a load connected to the output of a previous stage’s inverter to reduce the power consumption over pulse widths. The coupling capacitor is also connected between two adjacent stages through one TFT, eliminating coupling noises on the output pulses. The proposed EM circuit is simulated at a line time of 3.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> s for a 120 Hz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{3840}$</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{2160}$</tex-math> </inline-formula> display. The results ensure that pulse widths from three to 2160 lines are generated successfully without coupling noises and the small variation on power consumption from 1.23 to 0.33 mW is achieved at 30 stages for the whole range of pulse widths, compared to the large range from 1.26 to 76.91 mW with the inverter of a diode-connected load.

Graphene/MoS2/SiOx memristive synapses for linear weight update

Memristors for neuromorphic computing have gained prominence over the years for implementing synapses and neurons due to their nano-scale footprint and reduced complexity. Several demonstrations show two-dimensional (2D) materials as a promising platform for the realization of transparent, flexible, ultra-thin memristive synapses. However, unsupervised learning in a spiking neural network (SNN) facilitated by linearity and symmetry in synaptic weight update has not been explored thoroughly using the 2D materials platform. Here, we demonstrate that graphene/MoS2/SiOx/Ni synapses exhibit ideal linearity and symmetry when subjected to identical input pulses, which is essential for their role in online training of neural networks. The linearity in weight update holds for a range of pulse width, amplitude and number of applied pulses. Our work illustrates that the mechanism of switching in MoS2-based synapses is through conductive filaments governed by Poole-Frenkel emission. We demonstrate that the graphene/MoS2/SiOx/Ni synapses, when integrated with a MoS2-based leaky integrate-and-fire neuron, can control the spiking of the neuron efficiently. This work establishes 2D MoS2 as a viable platform for all-memristive SNNs.

Sub-Nanosecond Switching of Si:HfO2 Ferroelectric Field-Effect Transistor.

The discovery of ferroelectric doped HfO2 enabled the emergence of scalable and CMOS-compatible ferroelectric field-effect transistor (FeFET) technology which has the potential to meet the growing need for fast, low-power, low-cost, and high-density nonvolatile memory, and neuromorphic devices. Although HfO2 FeFETs have been widely studied in the past few years, their fundamental switching speed is yet to be explored. Importantly, the shortest polarization time demonstrated to date in HfO2-based FeFET was ∼10 ns. Here, we report that a single subnanosecond pulse can fully switch HfO2-based FeFET. We also study the polarization switching kinetics across 11 orders of magnitude in time (300 ps to 8 s) and find a remarkably steep time-voltage relation, which is captured by the classical nucleation theory across this wide range of pulse widths. These results demonstrate the high-speed capabilities of FeFETs and help better understand their fundamental polarization switching speed limits and switching kinetics.

Artificial neural network-based rapid predictor of biological nerve fiber activation for DBS applications

Objective. Computational models are powerful tools that can enable the optimization of deep brain stimulation (DBS). To enhance the clinical practicality of these models, their computational expense and required technical expertise must be minimized. An important aspect of DBS models is the prediction of neural activation in response to electrical stimulation. Existing rapid predictors of activation simplify implementation and reduce prediction runtime, but at the expense of accuracy. We sought to address this issue by leveraging the speed and generalization abilities of artificial neural networks (ANNs) to create a novel predictor of neural fiber activation in response to DBS. Approach. We developed six variations of an ANN-based predictor to predict the response of individual, myelinated axons to extracellular electrical stimulation. ANNs were trained using datasets generated from a finite-element model of an implanted DBS system together with multi-compartment cable models of axons. We evaluated the ANN-based predictors using three white matter pathways derived from group-averaged connectome data within a patient-specific tissue conductivity field, comparing both predicted stimulus activation thresholds and pathway recruitment across a clinically relevant range of stimulus amplitudes and pulse widths. Main results. The top-performing ANN could predict the thresholds of axons with a mean absolute error (MAE) of 0.037 V, and pathway recruitment with an MAE of 0.079%, across all parameters. The ANNs reduced the time required to predict the thresholds of 288 axons by four to five orders of magnitude when compared to multi-compartment cable models. Significance. We demonstrated that ANNs can be fast, accurate, and robust predictors of neural activation in response to DBS.

Detection rate of fast radio bursts in the Milky Way with BURSTT

ABSTRACT Fast radio bursts (FRBs) are intense bursts of radio emission with durations of milliseconds. Although researchers have found them happening frequently all over the sky, they are still in the dark to understand what causes the phenomena because the existing radio observatories have encountered certain challenges during the discovery of FRB progenitors. The construction of Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is being proposed to solve these challenges. We simulate mock Galactic FRB-like events by applying a range of spatial distributions, pulse widths, and luminosity functions (LFs). The effect of turbulent interstellar medium (ISM) on the detectability of FRB-like events within the Milky Way plane is considered to estimate the dispersion measure and pulse scattering of mock events. We evaluate the fraction of FRB-like events in the Milky Way that are detectable by BURSTT and compare the result with those by Survey for Transient Astronomical Radio Emission 2 (STARE2) and Galactic Radio Explorer (GReX). We find that BURSTT could increase the detection rate by more than two orders of magnitude compared with STARE2 and GReX, depending on the slope of LF of the events. We also investigate the influence of the specifications of BURSTT on its detection improvement. This leads to the fact that greatly higher sensitivity and improved coverage of the Milky Way plane have significant effects on the detection improvement of BURSTT. We find that the upgraded version of BURSTT, BURSTT-2048 could increase the detection rate of faint Galactic FRB-like events by a factor of 3.

Raman gain control in optical fibers with orbital-angular-momentum-induced chirality of light.

Stimulated Raman scattering is a particularly robust nonlinearity, occurring in virtually every material because its spectral linewidth and associated frequency shift do not typically depend on phases or directions (i.e. wavevectors) of the interacting light beams. In amorphous materials such as glass fibers, Raman bandwidths are large, enabling its use as a broadband gain element. This ubiquity makes it a versatile means for achieving optical amplification or realizing lasers over a large range of pulsewidths at user-defined colors. However, this ease of deploying the effect also presents itself as a stubborn source of noise in fiber-based quantum sources or parasitic emission in fiber lasers. Here, we show that orbital angular momentum carrying light beams experiencing spin-orbit interactions yield novel phase-matching criteria for Raman scattering. This enables tailoring its spectral shape (by over half the Raman shift in a given material) as well as strength (by ∼ 100×) simply by controlling light's topological charge - a capability of utility across the multitude of applications where modulating Raman scattering is desired.

Long single pulse NQR for broad resonance lines

This paper describes the experimental application of long single pulses to strongly inhomogeneously broadened NQR spectral lines, where the pulse length significantly exceeds the transverse relaxation time. A63Cu NQR resonance in the mineral covellite (CuS) was used as an exemplar for study in this specific regime, which was motivated by the requirement to obtain useful signals in very large volume applications having radiofrequency power limitations. In this study, signal transients that followed the application of the long single pulses were measured over a large range of radiofrequency field strength and pulse width. The results indicate effective generation of signal amplitudes. This is in contrast to previously reported studies involving long pulses applied to relatively narrow resonances. The results are found to be well described by simulations of the modified Bloch equations.

Acousto-optically driven lensless single-shot ultrafast optical imaging

Driven by many applications in a wide span of scientific fields, a myriad of advanced ultrafast imaging techniques have emerged in the last decade, featuring record-high imaging speeds above a trillion-frame-per-second with long sequence depths. Although bringing remarkable insights into various ultrafast phenomena, their application out of a laboratory environment is however limited in most cases, either by the cost, complexity of the operation or by heavy data processing. We then report a versatile single-shot imaging technique combining sequentially timed all-optical mapping photography (STAMP) with acousto-optics programmable dispersive filtering (AOPDF) and digital in-line holography (DIH). On the one hand, a high degree of simplicity is reached through the AOPDF, which enables full control over the acquisition parameters via an electrically driven phase and amplitude spectro-temporal tailoring of the imaging pulses. Here, contrary to most single-shot techniques, the frame rate, exposure time, and frame intensities can be independently adjusted in a wide range of pulse durations and chirp values without resorting to complex shaping stages, making the system remarkably agile and user-friendly. On the other hand, the use of DIH, which does not require any reference beam, allows to achieve an even higher technical simplicity by allowing its lensless operation but also for reconstructing the object on a wide depth of field, contrary to classical techniques that only provide images in a single plane. The imaging speed of the system as well as its flexibility are demonstrated by visualizing ultrashort events on both the picosecond and nanosecond timescales. The virtues and limitations as well as the potential improvements of this on-demand ultrafast imaging method are critically discussed.

Modular multilevel TMS device with wide output range and ultrabrief pulse capability for sound reduction

Objective. This article presents a novel transcranial magnetic stimulation (TMS) pulse generator with a wide range of pulse shape, amplitude, and width. Approach. Based on a modular multilevel TMS (MM-TMS) topology we had proposed previously, we realized the first such device operating at full TMS energy levels. It consists of ten cascaded H-bridge modules, each implemented with insulated-gate bipolar transistors, enabling both novel high-amplitude ultrabrief pulses as well as pulses with conventional amplitude and duration. The MM-TMS device can output pulses including up to 21 voltage levels with a step size of up to 1100 V, allowing relatively flexible generation of various pulse waveforms and sequences. The circuit further allows charging the energy storage capacitor on each of the ten cascaded modules with a conventional TMS power supply. Main results. The MM-TMS device can output peak coil voltages and currents of 11 kV and 10 kA, respectively, enabling suprathreshold ultrabrief pulses (>8.25 μs active electric field phase). Further, the MM-TMS device can generate a wide range of near-rectangular monophasic and biphasic pulses, as well as more complex staircase-approximated sinusoidal, polyphasic, and amplitude-modulated pulses. At matched estimated stimulation strength, briefer pulses emit less sound, which could enable quieter TMS. Finally, the MM-TMS device can instantaneously increase or decrease the amplitude from one pulse to the next in discrete steps by adding or removing modules in series, which enables rapid pulse sequences and paired-pulse protocols with variable pulse shapes and amplitudes. Significance. The MM-TMS device allows unprecedented control of the pulse characteristics which could enable novel protocols and quieter pulses.

Control Strategies for Flight Stability of Trajectory Correction Projectile with Air-Ducts Structure

Aiming at the controllability of spin-stabilized projectile trajectory correction, a new two-dimensional trajectory correction projectile model with a controllable air-ducts structure suitable for the spin-stabilized projectile is proposed in this paper. Furthermore, control strategies of the projectile in the corrected configuration are studied to ensure a stable flight. The correction scheme of the projectile is innovated on the basis of the ram air control mechanism. The air-ducts structure is designed inside the projectile body, and the internal air valve is used to control the lateral air-jet to achieve trajectory correction of the projectile. This is a new two-dimensional trajectory correction scheme with a relatively simple control method. Firstly, the correction mechanism of the new air-ducts structure projectile is analyzed. Secondly, based on the dynamic equation of the projectile, the key parameters of the impulse air valve control, including the safe range of the working pulse width and frequency, are calculated, and the corresponding control strategies are proposed. Finally, the flow field of the projectile in the corrected configuration of the terminal trajectory is numerically simulated, and aerodynamic parameters of the projectile are obtained. Through stability conditions established in this paper and combined with aerodynamic parameters, the validity of the proposed projectile stable flight control strategies is confirmed. The innovations of this paper include: (1) a proposed new aerodynamic configuration model with the air-ducts structure for the spin-stabilized projectile and (2) proposed innovative stable flight control strategies of the corrected configuration projectile. The numerical simulation results show that, compared with the reference projectile without air-ducts structure, the lateral force of the air-ducts structure projectile can produce a radial correction effect on the moving projectile. The simulation results of control strategies indicate that the control strategies can ensure stable flight of the corrected configuration projectile under different conditions.