Application Of Pulses Research Articles

Generation and applications of high-order harmonics and attosecond pulses in solids

Generation and applications of high-order harmonics and attosecond pulses in solids

Intelligent multi-parameter control of a rectangular pulse in a passively mode-locked fiber laser

Rectangular pulses with tunable width and intensity in fiber lasers are critical for the study of nonlinear pulse dynamics and applications of nanosecond laser sources. However, due to the complex nonlinear dynamics within the laser cavity, precisely controlling multiple parameters of the rectangular pulses in fiber lasers remains challenging. Here, we propose an approach for intelligently controlling the intensity and width of rectangular pulse using an improved particle swarm optimization (PSO) algorithm in a passively mode-locked fiber laser with a nonlinear polarization rotation (NPR) technique. By automatically adjusting the electronic polarization controller (EPC) and pump power, multiple parameters of the output rectangular pulse can be effectively tailored, and thus, to desirable ones. This enables the flexible setting of the intensity and width of the rectangular pulse within the permissible range in a passively mode-locked fiber laser. Our approach provides a promising way to meet the diverse demands of seed laser source in scientific and engineering fields.

Microstructure control of ultra-high-strength AlZnMgCu alloys fabricated by wire arc directed energy deposition: the role of variable polarity electric pulse

ABSTRACT In the manufacturing of large-scale ultra-high strength AlZnMgCu alloy components, wire arc directed energy deposition can be an efficient and flexible candidate. However, the fabricated AlZnMgCu alloys are faced with problems like coarse microstructures and high sensitivity to defects. Although metallurgical methods like micro-alloying and ceramic particle addition have shown considerable effects in microstructural control, pure process control methods that don’t affect the composition still lack investigation. This work proposed an effective control method by simply adding electric pulses during manufacturing. Results show that the application of pulses significantly reduces pore defects. A 2 Hz pulse can reduce the porosity by 65.7% to 0.122%. Low-frequency pulses effectively promote grain refinements. At 2 Hz, the deposited metal exhibited a mix of short columnar and fine equiaxed grains with a near-random orientation. Applying electric pulses leads to at least a 4.8% increase in UTS and a 225.0% increase in elongation.

Single-antenna super-resolution positioning with nonseparable toroidal pulses

The fundamental principle of satellite/node-based positioning involves triangulating the receiver’s coordinates through the intersection of spatial distances. Advancements in hybrid wireless networks have yielded high-precision positioning at decimeter-level (wavelength-level), approaching the resolution limits in free space. Here we present a 3D super-resolution positioning paradigm in free space by utilizing a kind of topologically structured pulses, toroidal electromagnetic pulses. We demonstrate that the space-time nonseparability and skyrmion topology inherent in toroidal pulses can be harnessed to achieve freespace microwave 3D positioning with super-resolution accuracy, reaching the centimeter level, using a single emitting antenna. This work opens up avenues for exploring the potential applications of topological electromagnetic pulses including but not limited to positioning, imaging and sensing technologies.

Safety and effectiveness of pulsed field ablation for pulmonary vein isolation in atrial fibrillation patients: a single centre experience

Abstract Introduction Atrial Fibrillation (AF) is the most frequent arrhythmia in the world with an exponentially increasing prevalence. Pulmonary veins (PV) are the primary triggering sites for AF and pulmonary veins isolation (PVI) is currently the standard therapy alongside pharmacological treatment and should be considered as first-line treatment. Pulsed-fieldablation (PFA) is a novel ablation modality that involves the application of electrical pulses causing cellular death, with preferential tissue specificity. Aim In this study, we evaluated the safety and efficacy of single-shot PFA in AF patients. Methods Single-center registry of consecutive patients undergoing PVI using the pentaspline PFA catheter (all with CARTO3D system v.7 and high-density mapping), between June 2022 and November 2023. Data on demographics, procedural characteristics, and electrocardiographic recurrence (assessed after a 3-month blanking period) were analyzed. Results 152 consecutive patients were included (63 ± 10 years, 57% male), with a mean CHA2DS2-VASc score of 2±1 points, median LVEF of 60% (IQR 59-65%), and a median CT-scan derived left atrial volume index of 56 mL/m2(IQR 44-69 mL/m2). A total of 40% had non-paroxysmal AF and a redo procedure was performed in 17% of patients. The median procedure time was 78 min (IQR 58-111 min) and fluoroscopy time was 11.6 min (IQR 8.2-15.6 min). Additionally, posterior wall isolation (PWI) was performed in 63 patients (41%). There were no esophageal complications, phrenic nerve injuries, cerebrovascular events, or procedure-related deaths. Two patients (1.3%) experienced acute cardiac tamponade, immediately treated with pericardiocentesis. Other complications were primarily vascular, in 5% of cases (4 femoral hematomas, 3 femoral pseudoaneurysms, 1 arteriovenous fistula). Over 293 (IQR 170 - 394) days of follow-up, considering electrocardiographic recurrence, 12% of patients had AF recurrence (5 with paroxysmal AF and 10 with persistent AF). These patients were older (69 ± 7y vs. 62 ± 11y, p=0.016), were more likely to undergo a redo procedure (33 vs. 8%, p=0.004), and had a higher percentage of posterior wall isolation (21 vs. 8%, p=0.038). Conclusions PFA for PVI wall ablation is safe and effective, with 100% intraprocedural technical success, a low rate of complications, and a high percentage of patients free from AF in the short-term.

Repeated CXCR4 Blockade by Plerixafor Attenuates Transplant Vasculopathy in Murine Aortic Allografts.

Plerixafor, a hematopoietic stem cell mobilization agent, increases the peripheral blood content of effector and regulatory T cells and may have beneficial effects on cardiac allograft vasculopathy. The aim of the current study was to evaluate its effects in a murine aortic allograft model using different application procedures. Allogeneic donor aorta grafts (n = 8/group) from C57BL/6 mice(H2b) were abdominally transplanted into CBA mice (H2k). Plerixafor application was performed either continuously for 14 d using abdominally implanted osmotic pumps (1 mg/kg/d) or i.p. with a single dose (1 and 5 mg/kg) on day 0 or pulsed injections of 1 mg/kg on days 0, 7, 14, and 21. Cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by Elastica-van-Gieson on day 30. Immunofluorescence and intragraft gene expression analysis were performed. On day 14, significantly fewer hematopoietic stem cells were found in the bone marrow of all plerixafor-treated mice. In the pulsed application group, significantly more hematopoietic stem cells were found in the peripheral blood on day 14 (0.045 ± 0.002%; p < 0.01 [pulsed]; versus 0.0068 ± 0.002% [control]) and also more regulatory T cells. PCR revealed lower inflammatory cytokines. The luminal occlusion was significantly reduced in the pulsed treated group (33.65 ± 8.84 versus 53.13 ± 12.41) going along with decreased neointimal CD4+ T cell and plasmacytoid dendritic cell infiltration, as well as less smooth muscle cell proliferation. The application of plerixafor attenuates chronic rejection in aortic allografts via immunomodulatory effects. Injection of repeated low-dose plerixafor is the most effective application form in the aortic transplant model.

Application of electric pulse and ultrasonic mufflers for increasing the degree of exhaust gas purification in car engines

The purpose of the article is to compare the efficiency of using electro-pulse and ultrasonic mufflers for cleaning exhaust gases from internal combustion engines of automobiles. The authors have developed full-size stands for conducting experiments with both types of mufflers on gasoline and diesel engines. Experimental studies have shown that electro-pulse mufflers are more effective in reducing the smoke of diesel engine exhausts, while ultrasonic mufflers are promising for cleaning exhaust gases from solid particles of gasoline engines. In the electro-pulse muffler, at the considered values of the angular velocity of the engine, the smoke indicators of the gas decreased to approximately 30%, while in the ultrasonic one, to 15%. The changes in the mass of the sold particles in the ultrasonic muffler of a diesel engine and a comparison with a gasoline engine show that ultrasonic mufflers have a lot of potential to stop solid particles from forming in the gas flow. In particular, the mass of the precipitated particles in a gasoline engine is 3 times greater than in a diesel engine. The alternative mufflers studied in the article allow for the purification of exhaust gases from solid particles, reducing their negative impact on the environment and giving impetus to the development of environmentally friendly motor transport.

Flupyradifurone activates DUM neuron nicotinic acetylcholine receptors and stimulates an increase in intracellular calcium through the ryanodine receptors

Insect neuronal nicotinic acetylcholine receptors (nAChRs) are transmembrane receptors that play a key role in the development and synaptic plasticity of both vertebrates and invertebrates, and are considered to be major targets of several insecticides. We used dorsal unpaired median (DUM) neurons, which are insect neurosecretory cells, to explore what type of nAChRs are involved in flupyradifurone's (FLU) mode of action, and to study the role of calcium release from intracellular stores in this process. Using whole-cell patch-clamp and fura-2-AM calcium imaging techniques, we found that inhibition of IP3Rs through application of 2-APB reduced FLU inward currents, but did not affect the intracellular calcium release induced by FLU. In contrast, inhibition of RyRs using ryanodine, led to reduction of intracellular calcium increase following FLU pulse application. These results suggested that FLU inward currents are likely due to a combination of the direct effects of FLU on DUM neuron nAChRs and the subsequent calcium release from RyRs.

Oxygen vacancies kinetics in TaO2−h/Ta2O5−x memristive interfaces

Abstract Oxygen vacancies (OV) are pervasive in metal oxides and play a pivotal role in the switching behaviour of oxide-based memristive devices. In this study we address OV dynamics in Pt/TaO 2 − h /Ta2O 5 − x /TaO 2 − y /Pt devices, through a combination of experiments and theoretical simulations, In particular, we focus on the RESET transition (from low to high resistance) induced by the application of electrical pulse(s), by choosing different initial OV profiles and studying their kinetics during the mentioned process. We demonstrate that by selecting specific OV profiles it is possible to tune the characteristic time-scale of the RESET. Finally, we show that the implementation of gradual RESETs, induced by applying many (small) successive pulses, allows estimating the activation energies involved in the OV electromigration process. Our results help paving the way for OV engineering aiming at optimizing key memristive figures such as switching speed or power consumption, which are highly relevant for neuromorphic or in-memory computing implementations.

Coupling Low-Frequency Ultrasound to a Crossflow Microfiltration Pilot: Effect of Ultrasonic Pulse Application on Sono-Microfiltration of Jackfruit Juice.

To reduce membrane fouling during the processing of highly pulpy fruit juices into clarified beverages, a crossflow Sono-Microfiltration (SMF) system was employed, strategically equipped with an ultrasonic probe for the direct application of low-frequency ultrasound (LFUS) to the juice just before the entrance to the ceramic membrane. Operating conditions were standardized, and the application of LFUS pulses in both corrective and preventive modes was investigated. The effect of SMF on the physicochemical properties and the total soluble phenol (TSP) content of the clarified juice was also evaluated. The distance of ultrasonic energy irradiation guided the selection of the LFUS probe. Amplitude conditions and ultrasonic pulses were more effective in the preventive mode and did not cause membrane damage, reducing the operation time of jackfruit juice by up to 50% and increasing permeability by up to 81%. The SMF did not alter the physicochemical parameters of the clarified juice, and the measured LFUS energy ranges did not affect the TSP concentration during the process. This study is the first to apply LFUS directly to the feed stream in a pilot-scale crossflow microfiltration system to reduce the fouling of ceramic membranes and maintain bioactive compounds in jackfruit juice.

Frequency and voltage-modulation multistable wave plate based on liquid crystals doped with silica nanoparticles

In this study, we demonstrate an all-range multistable liquid crystal (LC) wave plate. Its multistability arises from the formation of silica nanoparticle networks within the LC cell on the substrates, which stabilize LC molecules and induce varying phase retardation. Modulating the phase retardation of the LC wave plate can be achieved through the application of a DC pulse or by adjusting the frequency of the pulse. This multistable characteristic not only conserves energy but also enhances its versatility across diverse domains.

Evidence-Based Strategies for Warm Compress Therapy in Meibomian Gland Dysfunction.

Despite promising results from technological therapies like intense pulsed light application, warm compress therapy is a mainstay in meibomian gland dysfunction (MGD). However, applying warm compresses (WC) to the eyelids is palliative rather than curative and not always dispensed with specific instructions. The range of eyelid warming treatments available and lack of clear directives for use creates uncertainty for patients accustomed to explicit dosage information. This report examines data from clinical studies across the past 20years to identify effective protocols for three types of WC-hot towel, microwavable eye mask, and self-heating eye mask (EM). Literature search for studies on WC and MGD published between 2004 and 2023 in English was conducted. Studies wherein hot towel, microwavable EM, and self-heating EM were used in a treatment arm were included and those wherein they served only as control or were used in conjunction with another intervention were excluded. 20 resulting studies were separated into 3 groups: 5 on temperature profiles of WC, 6 with single application of WC, and 9 with repeated applications. Study methods and outcomes were tabulated, and a qualitative review was performed, attending to WC protocol and efficacy, as indicated by measures of tear film, meibomian gland health, and dry eye questionnaires. Data from the aforementioned studies revealed that each method can achieve target eyelid temperature of 40°C. A single application of WC-ranging from 5 to 20min-can significantly improve tear quality, while repeated applications significantly relieve symptoms associated with dry eyes from MGD and, in most studies, significantly improve meibomian gland health. Hot towels, however, require frequent reheating to maintain eyelid temperatures above 40°C, rendering them relatively ineffective in longitudinal studies. Microwavable EM retain heat well across 10min and were found to improve tear break-up time and/or meibomian gland score. Self-heating EM have variable activation times and were typically applied for longer periods, showing benefits akin to microwavable EM in short-term studies. Studies monitoring compliance indicate greater deviation from protocol with higher application frequencies or longer-term use. Evidence suggests superior heat retention and therapeutic effects on specific contributing factors in MGD (such as Demodex) with moist-heat compress. Considering decreased patience adherence to therapy with increased usage frequencies, and balancing needs to provide succinct instructions for various compress types, an advisable strategy is for patients to apply a moist-heat generating EM (microwavable or self-heating) to each eye for at least 10min, prepared according to manufacturer's instructions.

Ultrafast Acoustic Pulses Induced by Femtosecond Pulses and the Dynamics of Materials

Ultrafast acoustic pulses induced by a femtosecond laser can be considered as pure mechanical pressure pulses, excluding energy transitions of electrons caused by photons and thermal energy. This special issue discusses methods for controlling the dynamics of magnetic materials using ultrafast acoustic pulses and outlines the latest research trends. Additionally, it presents potential applications of acoustic pulses not only in magnetic materials but also in phase-transition materials.

Bandwidth modulation and pulse characterization of passively Q-switched erbium-doped fiber laser

We demonstrate the modulation of laser bandwidth by utilizing an ultranarrow tunable bandpass filter (UNTBF) in a passively Q-switched erbium-doped fiber laser. The passive Q-switch mechanism is enabled by using carbon nanotubes as saturable absorber at a Q-switched threshold of 35.5 mW. Based on spectral filtering effect introduced by the UNTBF, the 3 dB laser bandwidth can be tuned from 0.016 nm to 0.478 nm at a fixed pump power of 75.9 mW. The corresponding pulse behavior for each different bandwidth is characterized, and the results reveals that the pulse width can be as well tuned from 7.8 to 2.6 μs against the laser bandwidth, which agrees with the rule of time-bandwidth product. Correspondingly, the pulse repetition rate and the pulse energy vary from 16.23 kHz to 26.16 kHz and from 0.67 to 1.03 μJ respectively across the laser bandwidth. Further investigation of the pulse performance is performed against the pump power increment up to 107.2 mW. To the best of our knowledge, this is the first demonstration of spectrum bandwidth modulation in a passively Q-switched fiber laser, which can be useful for fully exploiting the possibilities of Q-switched pulse applications.

Modeling methods in overlapping electroporation treatments: Pulse number effects on tissue conductivity and ablation area

Irreversible electroporation (IRE) is a non-thermal tissue ablation technique that utilizes high-voltage pulses between electrode pairs to destroy tissue. Numerical models are essential for predicting treatment outcomes and aiding in treatment planning. This paper studies a nonlinear conductivity model (NC) and a multiparametric nonlinear conductivity model (MPNC) to investigate overlapping electroporation treatments using a three-needle electrode configuration. The NC model accounts for the effects of the electric field and temperature on tissue conductivity during multiple pulsed electric field applications. The MPNC model incorporates the influence of pulse number, alongside electric field and temperature, on tissue conductivity. Results indicate that in the MPNC model, tissue conductivity is significantly higher in regions where the electric field intensity is below the threshold for irreversible electroporation, with the maximum difference reaching 0.4S/m. In contrast, tissue conductivity is slightly lower in regions where the electric field intensity exceeds the IRE threshold. Additionally, the MPNC model predicts a smaller area of irreversible electroporation and a larger area of reversible electroporation, with these differences becoming more pronounced as the distance between electrode needles increases. These findings underscore the importance of considering pulse number effects in numerical models to enhance the accuracy of treatment planning for irreversible electroporation-based therapies.

A Model for Reversible Electroporation to Deliver Drugs into Diseased Tissues.

Drug delivery through electroporation could be highly beneficial for the treatment of different types of diseased tissues within the human body. In this work, a mathematical model of reversible tissue electroporation is presented for injecting drug into the diseased cells. The model emphasizes the tissue boundary where the drug is injected as a point source. In addition, the effect of drug loss at tissue boundaries through extracellular space is studied elaborately. Multiple pulses are applied to deliver a sufficient amount of drug into the targeted cells. The set of differential equations that model the physical circumstances are solved numerically. This model obtains a mass transfer coefficient (MTC), in terms of pore fraction coefficient and drug permeability that controls the drug transport from extracellular to intracellular space. The drug penetration throughout the tissue is captured for the application of different pulses. The boundary effects on drug concentration are highlighted in this study. The advocated model is able to perform homogeneous drug transport into the cells so that the affected tissue is treated completely. This model can be applied to optimize clinical experiments by avoiding the lengthy and costly in vivo and in vitro experiments.

Outstanding comprehensive energy storage performances in multiscale synergistic regulation-engineered (Bi0.5Na0.5)TiO3-based multilayer ceramics

Environmentally friendly dielectric ceramics with superior energy storage performances (ESP) are strongly demanded in pulsed power capacitor applications. Unfortunately, it is challenging to achieve simultaneously large recoverable energy density (Wrec), high Wrec/E (E as electric field) and broad operating temperature range in those ceramics. Herein we propose a multiscale synergistic regulation strategy to enhance comprehensive ESP of (Bi0.5Na0.5)TiO3 (BNT)-based ceramics. We introduce Ca(Zr0.8Ti0.2)O3 (CZT) into the BNT to increase atomic chaos and lattice distortion, which enhances relaxor behavior and lowers domain-switching barriers, thus effectively reducing remanent polarization. Besides, both suppressed oxygen vacancy and refined submicron grains improve extrinsic resistivity, which works synergistically with the enlarged intrinsic bandgap and multilayer structure design, producing substantially enhanced breakdown strength. Encouragingly, a very large Wrec of 13.4 J/cm3, an ultrahigh Wrec/E of 160 J/(kV∙m2), and a high efficiency η of 90.2 % are simultaneously achieved in the novel (Bi0.5Na0.5)TiO3-Ca(Zr0.8Ti0.2)O3 (BNT-CZT) multilayer ceramics, together with outstanding energy storage stability over a broad working temperature range (20–180 °C). The comprehensive ESP of our multilayer ceramics are superior to most of previously reported lead-free ones. This work provides a feasible pathway for substantially improving comprehensive ESP of lead-free ceramics, and also highlights advanced energy storage potential of the BNT-CZT for high-performance pulsed power applications.

Revealing Subsurface Damage Morphology and Patterns in areal Ultrashort Pulse Laser Machining of Glass

Material removal rates as well as surface and subsurface quality are key aspects for the industrial application of ultrashort pulse (USP) laser machining. However, revealing so-called subsurface damage (SSD) is challenging. The presented study visualizes and quantifies subsurface damage patterns in areal USP laser ablation of fused silica (FS) and glass N-BK7 (BK). For the first time, using high-resolution optical coherence tomography (OCT) as non-destructive and three-dimensional (3D) evaluation method, SSD morphologies of areal laser machining induced damages are analysed. Influences of laser wavelength, beam geometry and processed material are investigated. Discovered differences of damage morphologies and depth in FS and BK point out the relevance of selecting suitable process parameters. Based on the evaluation of volumetric OCT data, the authors were able to quantify damage morphologies using the surface texture ratio as well as power spectral density functions. One important finding for the quantification and comparability of damage depths in USP laser processing is the influence of applicable evaluation thresholds. In comparison to area thresholds of 0.001% being applicable to OCT measurements, more lenient thresholds of e.g. 1% commonly applied in destructive SSD measurement methods in average result in a reduction of measured damage depths by a factor of ~ 2. This potentially leads to an underestimation of damage depths depending on methods on thresholds used. The presented measurement and evaluation methods as well as gained process insights are important assets for the future optimization of low-damage USP laser micromachining of brittle materials. Moreover, the general applicability and relevance of OCT-based morphological damage analysis in laser material processing is shown.

Synthesis and Polymorph Manipulation of FeSe2 Monolayers.

Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe2 monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe2 monolayers predominantly display a 1T' structural polymorph at 5 K. Application of voltage pulses from an STM tip causes a local, reversible transition from the 1T' phase to the 1T phase. Density functional theory calculations suggest that this single-layer structural phase transition is accompanied by a magnetic transition from an antiferromagnetic to a ferromagnetic configuration. These results open new possibilities for creating functional magnetic devices with TMDC monolayers via polymorph engineering.

Electric Field Generated at the Millisecond Pulse-Polarized Interface Facilitates the Electrolytic Conversion of SO2 into H2S.

Interfacial electric field holds significant importance in determining both the polar molecular configuration and surface coverage during electrocatalysis. This study introduces a methodology leveraging the varying electric dipole moment of SO2 under distinct interfacial electric field strengths to enhance the selectivity of the SO2 electroreduction process. This approach presented the first attempt to utilize pulsed voltage application to the Au/PTFE membrane electrode for the control of the molecular configuration and coverage of SO2 on the electrode surface. Remarkably, the modulation of pulse duration resulted in a substantial inhibition of the hydrogen evolution reaction (HER) (FEH2 < 3%) under millisecond pulse conditions (ta = 10 ms, tc = 300 ms, Ea = -0.8 V (vs Hg/Hg2SO4), Ec = -1.8 V (vs Hg/Hg2SO4)), concomitant with a noteworthy enhancement in H2S selectivity (FEH2S > 97%). A comprehensive analysis, incorporating in situ Raman spectroscopy, electrochemical quartz crystal microbalance, COMSOL simulations, and DFT calculations, corroborated the increased selectivity of H2S products was primarily associated with the inherently large dipole moment of the SO2 molecule. The enhancement of the interfacial electric field induced by millisecond pulses was instrumental in amplifying SO2 coverage, activating SO2, facilitating the formation of the pivotal intermediate product *SOH, and effectively reducing the reaction energy barrier in the SO2 reduction process. These findings provide novel insights into the influences of ion and molecular transport dynamics, as well as the temporal intricacies of competitive pathways during the SO2 electroreduction process. Moreover, it underscores the intrinsic correlation between the electric dipole moment and surface-molecule interaction of the catalyst.