Low-amplitude Pulses Research Articles

Adaptive Escape of Pseudomonas aeruginosa by Application of Low-Amplitude Electric Pulses.

Marine antibiofouling using low-amplitude electric pulses (EP) is an energy-efficient and eco-friendly approach, but potential mechanisms for preventing biofouling remain unclear. In the present study, the 3D adhesion dynamics of a model microorganism─Pseudomonas aeruginosa (PAO1)─under low-amplitude cathodic EP were examined as a function of applying voltage and its duration (td). The results demonstrated that adhered bacteria escaped from the electrode surface even when EP was removed. The escaped bacteria ratio, induction period of escape, and duration of the detachment were influenced profoundly by EP amplitude but slightly by td when td ≥ 5 min. The acceleration of escaped PAO1 from the surface indicated that their flagellar motor was powered by EP. Particularly, EP enabled swimming bacteria to have adaptive motions that were sustainable and regulated by the gene rsmA. As a result, they had less accumulation near the surface. The propulsion of adhered bacteria and adaptive escape of swimming bacteria were enhanced in response to low-amplitude EP. Hence, low-amplitude and short-duration EP is promising for sustainable antibiofouling applications.

Electrical pulse stimulation parameters modulate N2a neuronal differentiation

Electrical pulse stimulation has been used to enhance the differentiation or proliferation of neuronal progenitor cells in tissue engineering and cancer treatment. Therefore, a comprehensive investigation of the effects caused by its parameters is crucial for improvements in those fields. We propose a study of pulse parameters, to allow the control of N2a cell line fate and behavior. We have focused on designing an experimental setup that allows for the knowledge and control over the environment and the stimulation signals applied. To map the effects of the stimulation on N2a cells, their morphology and the cellular and molecular reactions induced by the pulse stimulation have been analyzed. Immunofluorescence, rt-PCR and western blot analysis have been carried out for this purpose, as well as cell counting. Our results show that low-amplitude electrical pulse stimulation promotes proliferation of N2a cells, whilst amplitudes in the range 250 mV/mm–500 mV/mm induce differentiation. Amplitudes higher than 750 mV/mm produce cell damage at low frequencies. For high frequencies, large amplitudes are needed to cause cell death. An inverse relation has been found between cell density and pulse-induced neuronal differentiation. The best condition for neuronal differentiation was found to be 500 mV/mm at 100 Hz. These findings have been confirmed by up-regulation of the Neurod1 gene. Our preliminary study of the molecular effects of electrical pulse stimulation on N2a offers premonitory clues of the PI3K/Akt/GSK-3β pathway implications on the neuronal differentiation process through ES. In general, we have successfully mapped the sensitivity of N2a cells to electrical pulse stimulation parameters.

Sub-10 nm HfZrO ferroelectric synapse with multiple layers and different ratios for neuromorphic computing

To break the von Neumann bottleneck, emerging non-volatile memories have gained extensive attention in hardware implementing neuromorphic computing. The device scaling with low operating voltage is of great importance for delivering a high-integrating and energy-efficient neuromorphic system. In this paper, we fabricated sub-10 nm ferroelectric capacitors based on HfZrO (HZO) film with varying HfO and ZrO components. Compared to the conventional HZO capacitors (a constant component of 1:1), the varying component ferroelectric capacitors show similar remnant polarization but a lower coercive electric field (Ec). This enables the partial domain switching processed at a lower pulse amplitude and width, which is essential for emulating typical synaptic features. In the MNIST recognition task, the accuracy of sub-10 nm ferroelectric artificial synapse can approach ∼85.83%. Our findings may provide great potential for developing next-generation neuromorphic computing-based ultra-scaled ferroelectric artificial synapses.

Анализ действия детонационного генератора низкоамплитудных импульсов давления регулируемой длительности

The paper presents results of the analysis conducted on the action of the low-amplitude pressure pulse detonation generator with adjustable duration, where the detonation wave affects the controlled compressible medium and propagates in the direction from the medium subjected to the shock wave compression. Analytical expressions are provided for a simple model of the process under study to calculate the pressure pulse amplitude-time characteristics on the compressible medium with the charge detonation product plane-symmetric flow and the compressible inert medium. The paper considers a scheme of experimental (laboratory) assembly. In its cylindrical channel, the detonation product quasi-one-dimensional effect on the controlled environment is realized. Results of registering dynamics of pressure alterations in the controlled environment were obtained. When comparing calculation and experiment results, the reasons causing their discrepancy were identified. If the assembly body is made of steel not subjected to heat treatment, then it becomes possible to use it five times (at least) with charges of the bulk explosives based on the hexogen with generating controlled pressure pulses of several kilobars in the condensed organic materials with duration of at least tens of microseconds. In this case, the pressure rise time at the pulse leading edge reaches approximately ten microseconds.

Machine learning techniques for β/γ discrimination in phoswich detectors

Particle discrimination technology is widely used in multiple fields. Phoswich detectors are detectors based on pulse shape discrimination technology that combine two or more scintillators with different time characteristics to achieve particle discrimination. This study focuses on a phoswich detector composed of BGO/EJ-260 and uses machine learning algorithms to classify pulses to achieve β/γ classification. Experiments were conducted using the 137Cs radioactive source and three different models were trained: Gaussian mixture model, support vector machine, and convolutional neural network. The classification capabilities of the three models were tested and the results were discussed. The calculation results show that all three models achieved pulse data classification and accurately marked most pulses to the correct category. The classification ability of low-amplitude pulses by the Gaussian mixture model and support vector machine is limited by data processing, while the convolutional neural network model avoids this problem. For higher amplitude pulses, all three models showed that high classification accuracy, with the convolutional neural network model achieving a classification accuracy of 96.1% in the training set, achieves the expected goal.

FOXO nuclear shuttling dynamics are stimulus-dependent and correspond with cell fate.

FOXO transcription factors are regulators of cellular homeostasis linked to increased lifespan and tumor suppression. FOXOs are activated by diverse cell stresses including serum starvation and oxidative stress. FOXO activity is regulated through posttranslational modifications that control shuttling of FOXO proteins to the nucleus. In the nucleus, FOXOs up-regulate genes in multiple, often conflicting pathways, including cell-cycle arrest and apoptosis. How cells control FOXO activity to ensure the proper response for a given stress is an open question. Using quantitative immunofluorescence and live-cell imaging, we found that the dynamics of FOXO nuclear shuttling is stimulus-dependent and corresponds with cell fate. H2O2 treatment leads to an all-or-none response where some cells show no nuclear FOXO accumulation, while other cells show a strong nuclear FOXO signal. The time that FOXO remains in the nucleus increases with the dose and is linked with cell death. In contrast, serum starvation causes low-amplitude pulses of nuclear FOXO and predominantly results in cell-cycle arrest. The accumulation of FOXO in the nucleus is linked with low AKT activity for both H2O2 and serum starvation. Our findings suggest the dynamics of FOXO nuclear shuttling is one way in which the FOXO pathway dictates different cellular outcomes.

High amplitude pulses on the same charge condition efficiently elicit bipolar cell-mediated retinal ganglion cell responses in the degenerate retina.

Retinal pigmentosa (RP) patients lose vision due to the loss of photoreceptors. Retinal prostheses bypass the dead photoreceptors by electrically stimulating surviving retinal neurons, such as bipolar cells or retinal ganglion cells (RGCs). In previous studies, stimulus charge has been mainly optimized to maximize the RGC response to electrical stimulation. This study aimed to investigate the effect of amplitude and duration even under the same charge condition on eliciting RGC spikes in the wild-type and degenerate retinas. Wild-type (WT) Sprague-Dawley rats were used as the normal retinal model, and Pde6b knockout rats were used as a retinal degeneration (RD) model. Electrically-evoked RGC spikes were recorded from isolated rat retinas using an 8 8 multielectrode array. The same charge was maintained (10 or 20 nC), and electrical stimulation was applied to WT and RD retinas, adjusting the amplitude and duration of the 1st phase of biphasic pulses. In the pulse modulation of the 1st phase, high amplitude (short duration) pulses induced more RGC spikes than low amplitude (long duration) pulses. Both WT and RD retinas showed a significant reduction in the number of RGC spikes upon stimulation with lower amplitude (longer duration) pulses. In clinical trials where stimulus charges are delivered to the degenerate retina of blind patients, high amplitude (short duration) pulses would help elicit more RGC spikes.

Characterization of Preliminary Breakdown Pulse Trains in Negative Cloud-To-Ground Flashes Recorded during A Rainy Season in The Bogota Savannah, Colombia

Lightning-generated electric field measurement is used to characterize cloud-to-ground (CG) flashes. Prior to the first return stroke (FRS), these signals sometimes exhibit a pulse train, known as preliminary breakdown pulses (PBP), whose study provides information about the first event that originate the breakdown process inside the cloud. Considering that characteristics of PBPs may change according to geographical conditions, in this work, six parameters (temporal and magnitude) associated with 69 trains identified in negative CG flashes that occurred in the Bogota savannah, Colombia were analyzed. The signatures were recorded in 2017 using a fast response antenna (10 MHz bandwidth), a 100 ns sampling time and a window of 500 ms. Among the most relevant results, it was found that the train duration ( ) varied from 0.5 ms up to 5.2 ms with arithmetic mean (AM) of 1.74 ms, while the time interval between the peak of the train and the FRS (PBP-FRS) had an AM and a geometric mean (GM) of 35.7 ms and 10.2 ms, respectively. On the other hand, the ratio between the peak value of the PBP and its FRS ( ) exhibited an AM of 0.7 and a GM of 0.56. It was concluded that PBP train starts with low amplitude pulses, later increases its magnitude in the central region and decreases at the end. Furthermore, bipolar pulses with similar polarity to that of the FRS were identified at the beginning and in the middle of the train, while unipolar pulses were observed at the end of the signatures.

Prolonged inhibition of bladder function is evoked by low-amplitude electrical stimulation of the saphenous nerve in urethane-anesthetized rats.

To better understand the effects of saphenous nerve (SN) stimulation on bladder function, we investigated the duration of electrical stimulation as a key variable in eliciting urodynamic changes. SN stimulation is a novel approach to electrically modulating bladder function. In previous animal studies, bladder-inhibitory responses were evoked by low-amplitude (25 μA) stimulus pulses applied in short-duration (10min) trials and at frequencies between 10 and 20 Hz. Experiments were performed in urethane-anesthetized rats that were separated into three groups: intravesical saline infusion + SN stimulation (group A), intravesical 0.1% acetic acid infusion + SN stimulation (group B), and intravesical saline infusion + no SN stimulation (group C). Changes in bladder function- basal bladder pressure (P base ), contraction amplitude (ΔP), and inter-contraction interval (T ICI )-were measured in response to stimulation trials applied for different durations (10, 20, and 40 min). Trials were also repeated at frequencies of 10 and 20 Hz. In group A, longer-duration (40 min) stimulation trials applied at 10Hz evoked overflow incontinence (OI) episodes that were characterized by significant changes in P base (122.7 ± 9.1%, p=0.026), ΔP (-60.8 ± 12.8%, p=0.044), and T ICI (-43.2 ± 13.0%, p=0.031). Stimulation-evoked OI was observed in 5 of 8 animals and lasted for 56.5 ± 10.7min. In contrast, no significant changes in bladder function were observed in either group B or group C. Our findings show that longer-duration trials consisting of electrical pulses applied at 10Hz are important stimulation parameters that elicit inhibitory bladder responses in anesthetized rodents.

Low intensity stimulation of aortic baroreceptor afferent fibers as a potential therapeutic alternative for hypertension treatment

Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits, but neuromodulation of aortic baroreceptor afferents remains unexplored for potential translation into the clinic. Published studies have used supramaximal stimulations, which are unphysiological and energy inefficient. The objective of the present study was to identify optimal low-charge nerve stimulation parameters that would provide a clinically-relevant (20–30 mmHg) decrease in mean arterial pressure (MAP) in anesthetized spontaneously hypertensive rats. Stimulations of 20 s were delivered to the left aortic depressor nerve (ADN) of these rats using low ranges of pulse amplitudes (≤ 0.6 mA), widths (≤ 0.5 ms) and frequencies (≤ 5 Hz). We also assessed the effects of continuous (20 s) versus intermittent (5 s ON/3 s OFF and 5 s ON/3 s OFF for 20 s) stimulation on MAP, heart rate (HR), mesenteric (MVR) and femoral (FVR) vascular resistance using low (5 Hz) and high (15 Hz) frequencies. Lower pulse amplitudes (0.2 mA) produced 9 ± 2 to 18 ± 2 mmHg decreases in MAP. Higher pulse amplitudes (0.4 mA) produced a median MAP reduction of 28 ± 4 mmHg at 0.2 ms and 5 Hz, with no added benefit seen above 0.4 mA. Continuous and intermittent low frequency stimulation at 0.4 mA and 0.2 ms produced similar sustained decreases in MAP, HR, MVR and FVR. Continuous high frequency stimulation at 0.4 mA and 0.2 ms produced larger reductions in MAP, HR, MVR and FVR compared with all low frequency and/or intermittent high frequency stimulations. We conclude from these findings that “low intensity intermittent” electrical stimulation is an effective alternate way for neuromodulation of the aortic baroreceptor afferents and to evoke a required restoration of MAP levels in spontaneously hypertensive rats. This approach enables low energy consumption and markedly lowers the excessive decreases in MAP and hemodynamic disturbances elicited by continuous high-charge injection protocols.

Sound production and mechanism in the cryptic cusk-eel Parophidion vassali.

This study investigates the sounds and the anatomy of the sound-producing organ in the male and female sand-dwelling cusk-eel Parophidion vassali. Although both sexes have similar external phenotype, they can be distinguished by their sonic apparatus and sounds. As in many Ophioidei, Parophidion vassali presents a panel of highly derived characters. Fish possess three pairs of sonic muscles, and males have mineralized swimbladder caps on which inserts the ventral sonic muscle, a neural arch that pivots, a stretchable swimbladder fenestra, an osseous swimbladder plate and a rounded pressure-release membrane in the caudal swimbladder. Females, however, do not possess anterior swimbladder caps, a swimbladder fenestra and the caudal rounded membrane. Males possess the unusual ability to produce sounds starting with a set of low amplitude pulses followed by a second set with higher amplitudes clearly dividing each sound unit into two parts. Females do not vary their sound amplitude in this way: they produce shorter sounds and pulse periods but with a higher peak frequency. Morphology and sound features support the sound-producing mechanism is based on a rebound system (i.e. quick backward snap of the anterior swimbladder). Based on features of the sounds from tank recordings, we have putatively identified the sound of male Parophidion vassali at sea. As these species are ecologically cryptic, we hope this work will allow assessment and clarify the distribution of their populations.

Microalgae Improve the Photosynthetic Performance of Rice Seedlings (Oryza sativa L.) under Physiological Conditions and Cadmium Stress

The aim of this study was to assess the impact of the microalgae Chlorella vulgaris on the rice seedlings at physiological conditions and under cadmium (Cd) stress. We examined the effects of C. vulgaris in the nutrient solution on rice seedlings grown hydroponically in the presence and the absence of 150 μM CdCl2, using the low (77 K) temperature and pulse amplitude modulated (PAM) chlorophyll fluorescence, P700 photooxidation measurements, photochemical activities of both photosystems, kinetic parameters of oxygen evolution, oxidative stress markers (MDA, H2O2 and proline), pigment content, growth parameters and Cd accumulation. Data revealed that the application C. vulgaris not only stimulates growth and improves the functions of photosynthetic apparatus under physiological conditions, but also reduces the toxic effect of Cd on rice seedlings. Furthermore, the presence of the green microalgae in the nutrient solution of the rice seedlings during Cd exposure, significantly improved the growth, photochemical activities of both photosystems, the kinetic parameters of the oxygen-evolving reactions, pigment content and decreased lipid peroxidation, H2O2 and proline content. Data showed that the alleviation of Cd-induced effects in rice seedlings is a result of the Cd sorption by microalgae, as well as the reduced Cd accumulation in the roots and its translocation from the roots to the shoots.

Spectral-temporal patterned supercontinuum generation and pulse compression with tunable sub-terahertz repetition rate

We report on the generation of a spectral-temporal patterned supercontinuum (SC) that is a train of ultrashort pulse bunches with an ultra-broadband spectrum changing from pulse to pulse in a controllable manner. The SC is attained in a highly nonlinear silica fiber pumped by a specially designed mode-locked fiber laser that can generate homogeneous soliton molecules (SMs) consisting of similar high-amplitude dissipative solitons and heterogeneous SMs consisting of interleaved high- and low-amplitude pulses. The temporal distance between the spectrally broadened pulses can be adjusted in a wide range from 5 to 170 ps by tuning the laser. The SC spans from 1350 to beyond 1700 nm. It is formed by Raman-shifted solitons in the long-wavelength region and dispersive waves in the short-wavelength region, whose wavelength shift regularly varies from pulse to pulse depending on the amplitudes of the pump pulses. By selecting different parts of the SC spectrum it is possible to obtain different patterned optical pulse trains. It was shown that the pulse duration in the SMs can be decreased below 100 fs due to soliton-effect compression directly in the highly-nonlinear fiber.

Wing movements underlying sound production in calling, rivalry, and courtship songs of the cricket Gryllus bimaculatus (DeGeer)

We recorded the wing movements and sound signals during the production of calling, rivalry, and courtship song in the bispotted field cricket Gryllus bimaculatus. Recordings confirm that salient sound pulses during calling and rivalry song are generated during the closing movements of the wings. Wing movements for calling and rivalry song start from an elevated wing position and are performed with a very similar opening-closing movement, indicating that both types of songs may be generated by the same neuronal network. Wing movements for courtship song start from a low wing position; rapid closing movements generate high-frequency ticks and low-amplitude wing oscillations lead to low–amplitude pulses, generated during the opening and closing movements with a carrier frequency corresponding to the calling song. The two types of wing movements underlying courtship song indicate a different motor control as compared to calling song and may represent an early evolutionary phenotype.

Pulse Oximetry Waveform Represents an Earlier Ventricular Contraction in Relation to the Intraarterial Blood Pressure Tracing and Electrocardiogram on Multichannel Monitors: A Case Series.

Multichannel patient monitors apparently display the electrocardiogram, intra-arterial blood pressure, and pulse oximetry waveforms in synchrony during sinus cardiac rhythm. We recorded 20 events of a premature cardiac contraction on multichannel monitors from 10 patients. Interestingly, during premature cardiac contraction, the low-amplitude arterial trace was aligned with the premature electrocardiogram, but the low-amplitude pulse oximetry plethysmograph was aligned with the next normal electrocardiogram and arterial tracing. In conclusion, the pulse oximetry plethysmograph tracing is offset by 1 ventricular depolarization on the electrocardiogram (QRS) and the arterial tracing on multichannel monitors.

Electrocardiogram Findings Associated With Malignant Pericardial Effusion and Cardiac Tamponade.

Electrocardiogram Findings Associated With Malignant Pericardial Effusion and Cardiac Tamponade.

Stability characteristics of different aerofoil flows at [formula omitted] and the implications for aerofoil self-noise

Three compressible-flow direct numerical simulations (DNS) of aerofoils were conducted at a chord based Reynolds number of Rec=150,000: a Controlled-Diffusion (CD) aerofoil at two incidences and an untripped NACA 6512-63 aerofoil at 0∘ angle of attack (AoA). The aim of the simulations was to help improve the understanding of the generation mechanisms of aerofoil self-noise. To this end, the time-averaged flows around the aerofoils were investigated using a multi-dimensional global stability analysis based on the response to very low-amplitude hydrodynamic initial pulses. For the CD aerofoil at 5∘ AoA and the untripped NACA 6512-63 aerfoil at 0∘ AoA, the base flows are found to be globally unstable and an acoustic feedback loop occurs regardless of the perturbation locations. For the CD aerofoil at a slightly higher incidence (8∘ AoA) where a laminar separation bubble appears at the leading edge and a turbulent attached boundary layer is present at the trailing edge, the initial perturbations decay with time for all initial pulse locations indicating that the base flow is globally stable. The results confirm that for cases where a laminar separation bubble is present on the aerofoil suction side at the trailing edge, independent of whether tones in the DNS exist or not, an unstable feedback loop exists. The laminar separation bubble at the aerofoil trailing edge on the suction side seems to be the only required prerequisite for triggering the acoustic feedback loop.

On linear and nonlinear acoustics in stratified variable-area ducts and atmospheres and Lighthill's proposition

Abstract

Experimental and Simulation Study on the Ignition Criterion of JHL‐3 under Non‐Shock Loading

AbstractThe non‐shock ignition of explosives can bring huge accidental disasters, so it is meaningful to study the conditions under which explosives ignite. The safety performance of JHL‐3, a polymer‐bonded explosive (PBX), under low amplitude and long pulse load has been analyzed based on experiment and simulation from a macro perspective, and the load criterion for ignition of JHL‐3 is given. First, JHL‐3 was loaded under confining pressure by the modified separated Hopkinson pressure bar. By observing whether the explosives ignite at different pulses whose width and amplitude can be changed by changing the length and initial speed of the striker, we find that the greater the loading pressure, the shorter the loading time required for the ignition of JHL‐3. According to the experimental results, the relationship between the amplitude and width of the loading pulse at which the JHL‐3 is ignited is fitted. Then, load JHL‐3 of different densities under the same conditions to analyze the influence of density on the ignition sensitivity of JHL‐3. The experimental results show that the sensitivity is highest when the density is between 1.7–1.75 g/cm3. Finally, based on the Uintah Computational Framework (UCF), the experiment is simulated by the coupling algorithm (MPMICE) of material point method (MPM) and implicit continuous‐fluid Eulerian (ICE). JHL‐3 is modeled by the Visco‐Scram model, and the WSB model is used as a reaction model to simulate the combustion behavior of the explosive after ignition. The simulation results closely match the experimental results, further verifying the accuracy of the ignition criterion. The ignition criterion can predict the ignition of explosives under non‐shock loading conditions, which has a guiding effect on the storage, transportation, and packaging of explosives.

Modeling of vortex dynamics in HTSs with defects under the impact of pulsed magnetic field

By means of the Monte Carlo method, a numerical study of the vortex system in a high-temperature superconductor under the impact of pulses of magnetic field has been conducted. Various shapes and amplitudes of pulses have been considered. Samples with random and regular distributions of three different numbers of defects have been compared from the viewpoint of efficiency of flux trapping. The low-temperature behavior of vortices and their penetration into samples have been shown to be independent of the pulse shape but strongly dependent of the type of pinning distribution. Saturating dependences of density of trapped magnetic flux on the pulse amplitude have been obtained. The samples with random pinning demonstrated higher efficiency of flux trapping at lower pulse amplitudes, and the samples with a triangular lattice of defects—at higher amplitudes. If the amplitude exceeded the saturation field of both samples, the trapped field was almost equal. The increasing number of defects has lead to an increase in trapped field within the considered range of concentrations.