Pulse Period Research Articles

Determination of the splitting function by signal spectrum

In modern telecommunication, spread spectrum techniques often used. Special case of spread spectrum – spectrum splitting. This technique is characterized by signals whose energy is concentrated in two or more spaced portions of the spectrum. If there is a modulating subcarrier in modulation function, and this subcarrier is shorter then duration of transmitted information symbols by a multiplicity factor, then this function provide spectrum splitting. The frequency of this subcarrier called subcarrier frequency, and function of this subcarrier called subcarrier frequency function or splitting function. The main problem of this article is the ability to determine by which split function the original spectrum of the unknown signal has obtained, because during the analysis it is necessary to understand general patterns of the signal formation. The article discusses various signals with spectrum splitting. There is an overview of the methods of spectrum splitting obtained for different types of modulation (phase, amplitude, frequency) and some splitting functions (harmonic, meander and functions of periodic triangular pulses). The spectrums of the signals obtained by different splitting functions are studied and conclusions has drawn on how to determine the splitting function and the type of modulation for the spectrum splitting of an unknown signal.

Influence of periodic pulse intake on the ventilation efficiency of positive pressure explosion-proof robot

The ventilation work is an important step to be completed before the start of the positive pressure explosion-proof robot. The existing explosion-proof technology uses constant pressure inflation, which will cause explosive gas to accumulate in the corner area of the cavity for a long time. In order to solve this problem, a ventilation method with periodic pulse intake is proposed. Based on the finite element method, the cleaning and ventilation process of the positive pressure explosion-proof robot is simulated and analyzed. The concentration of explosive gas in the robot cavity with time under constant pressure intake and pulse intake with different periods and amplitudes is compared. The simulation results show that the pulse intake is beneficial to the ventilation of the corner position. The period and amplitude of the pulse intake has an effect on the ventilation efficiency, when the period is the same, the greater the amplitude of the pulse intake, the higher the ventilation efficiency; when the amplitude is the same, the smaller the period of the pulse intake, the higher the ventilation efficiency. After experimental verification, the validity of the simulation results is proved. This study helps to improve the ventilation efficiency of positive-pressure explosion-proof robots and provides guidance for practical applications.

Study of controlled pulsed illumination (CPI) efficiency in the homogeneous UV-LED/S2O82− process for the removal of organic dye from contaminated water

The present investigation aims to shed light on the efficiency of the irradiation-based advanced oxidation processes using controlled pulsed illumination (CPI) in a homogeneous process. A more in-depth emphasis has been applied considering the ultraviolet-light emitting diodes/persulfate (LED/S2O82−) system. Irradiation-driven processes can present unexpected behaviour under a pulsed irradiation compered to continuous irradiation. This behaviour can be explained by Parrando's paradox concept. The removal efficiency of organic dyes under a continuous illumination source was compared to the CPI system employing a pulsed UV-LED/S2O82− photoreactor to explore CPI performance. The efficiency of the pulsed UV-LED/PS method was investigated using three organic dyes as model pollutants and duty cycle and pulse period as parameters of the pulsed irradiation source. The duty cycle and pulse period have a crucial impact on the pulsed system efficiencies, which were studied in the values of 10 %, 25 %, 50 %, 75 %, 90 %, and 99 % for pulse periods from 1 ms (ms) to a few hundred ms in the current study. For all experiments, the electrical energy consumption (EEO) values were calculated, and the CPI values were compared to the continuous illumination values. According to the results, duty cycles and pulse periods of (10 %, 800 ms), (10 %, 1 ms), and (10 %, 800 ms), with the EEO amounts of 58.29, 120.65, and 29.62 kWh per order showed the best performance for the removal of organic dyes, respect to continuous irradiation and other CPI experiments in terms of saving energy. Besides, the game theory and the collision hypothesis were scrutinized to justify the achieved results.

Periodic superradiance in an Er:YSO crystal

We observed periodic optical pulses from an Er:YSO crystal during irradiating with a continuous-wave excitation laser. We refer to this phenomenon as “periodic superradiance.” This periodicity can be understood qualitatively by a simple model, in which a cyclic process of a continuous supply of population inversion and a sudden burst of superradiance is repeated. The excitation power dependences of peak interval and the pulse area can be interpreted with our simple model. In addition, the linewidth of superradiance is much narrower than an inhomogeneous broadening in a crystal. This result suggests that only Er3+ ions in a specific environment are involved in superradiance. Published by the American Physical Society 2024

Cluster Neuronal Firing Induced by Uniform Pulses of High-Frequency Stimulation on Axons in Rat Hippocampus.

High-frequency stimulation (HFS) of electrical pulse sequences has been used in various neuromodulation techniques to treat certain disorders. Here, we test the hypothesis that HFS sequences with purely periodic pulses could directly generate non-uniform firing in directly stimulated neurons. In vivo experiments were conducted in the rat hippocampal CA1 region. A stimulation electrode was placed on the alveus fibers, and a recording electrode array was inserted into the CA1 region upstream of the stimulation site. Antidromic-HFS (A-HFS) of 100 Hz pulses was applied to the alveus to antidromically activate the soma of pyramidal neurons around the recording site. By minimizing the interferences of population spikes, the evoked unit spikes of individual pyramidal neurons were obtained during A-HFS. Additionally, a computational model of pyramidal neuron was used to simulate the neuronal responses to A-HFS, revealing possible mechanisms underlying the different firing patterns. Of the total 54 pyramidal neurons recorded during 2-min 100 Hz A-HFS, 38 (70%) neurons fired in a cluster pattern with alternating periods of intensive spikes and silence. The remaining 16 (30%) neurons fired in a non-cluster pattern with regular spikes. Modeling simulations showed that under the situation of HFS-induced intermittent block, conduction failure and generation failure of action potentials along the axons resulted in the cluster and non-cluster firing. Sustained axonal A-HFS with periodic pulses can induce non-uniform firing in directly stimulated neurons. This finding provides new evidence for the nonlinear dynamics of neuronal firing, even under uniform stimulation.

Influence of strong laser field on nuclear <i>α</i> decay

With the development of pulse amplification and compression technology, the peak power of the pulse has been improved by several orders of magnitude, and it is possible for the ultra strong laser field to affect nuclei directly. The <i>α</i> decay, as one of the most major forms in nuclear reaction, is a critical research topic in nuclear physics. According to the theory of Gamow model explaining nuclear <i>α</i> decay in quantum mechanics, double folding model solving nuclear potential energy, and cluster model describing atomic nucleus, we present a complete set of solutions for the half-life of nuclear <i>α</i> decay to study the influence of ultra strong laser field on nuclear <i>α</i> decay. These half-lives of <i>α</i> decay of different nuclei from medium to heavy in the absence of laser field are obtained, which accord well with the experimental data. Subsequently, we introduce the effects of ultra strong laser field into our theoretical method to achieve the variations of the half-life of nuclear <i>α</i> decay. Considering that the optical period of the laser pulse is much longer than the theoretical tunneling time and the Lorentz force is much smaller than the Coulomb force, the laser field is treated as an electrostatic field. The results show that the half-life of nuclear <i>α</i> decay will reduce about 0.1% by the strong laser field with a peak power density of about 1.0×10<sup>26</sup> W/cm<sup>2</sup>, demonstrating that the half-life of nuclear <i>α</i> decay is effectively affected by the strong laser field. Furthermore, the influences of the nuclear parameters, e.g. total quantum number <i>G</i> describing <i>α</i> particle orbits, and <i>α</i> decay reaction energy <i>Q</i><sub><i>α</i></sub>, on the variations of these half-lives of <i>α</i> decay of different nuclei are discussed with the help of the calculation results. The dependence of the half-lives of nuclear <i>α</i> decay on the laser peak power density is also explained correspondingly. In summary, we provide a more accurate method of calculating the half-life of nuclear <i>α</i> decay, which is used to study the influences of ultra strong laser field on these half-lives of nuclear <i>α</i> decay of different nuclei. With the further construction of strong laser devices, more interesting phenomena and results will be found from the experiment on the atomic nucleus under strong laser field.

Broadband dual-comb hyperspectral imaging and adaptable spectroscopy with programmable frequency combs

We explore the advantages of a free-form dual-comb spectroscopy (DCS) platform based on time-programmable frequency combs for real-time, penalty-free apodized scanning. In traditional DCS, the fundamental spectral point spacing, which equals the comb repetition rate, can be excessively fine for many applications. While fine point spacing is not itself problematic, it comes with the penalty of excess acquisition time. Post-processing apodization (windowing) can be applied to tailor the resolution to the sample, but only with a deadtime penalty proportional to the degree of apodization. The excess acquisition time remains. With free-form DCS, this deadtime is avoided by programming a real-time apodization pattern that dynamically reverses the pulse periods between the dual frequency combs. In this way, one can tailor the spectrometer’s resolution and update rate to different applications without penalty. We show the operation of a free-form DCS system where the spectral resolution is varied from the intrinsic fine 160 MHz up to 822 GHz by applying tailored real-time apodization. Because there is no deadtime penalty, the spectral signal-to-noise ratio increases linearly with resolution by 5000× over this range, as opposed to the square root increase observed for post-processing apodization in traditional DCS. We explore the flexibility to change resolution and update rate to perform hyperspectral imaging at slow camera frame rates, where the penalty-free apodization allows for optimal use of each frame. We obtain dual-comb hyperspectral movies at a 20 Hz spectrum update rate with broad optical spectral coverage of over 10 THz.

An economical single-shot pulse picker without nonlinear effect and dispersion.

An economical and stable single-shot pulse picker design without dispersion, nonlinear effect, and limitation on wavelength is proposed. This design is composed of a periodic pulse blocker (PPB), a control unit, and a mechanical shutter. It has successfully beenapplied to the commercial high-fluence femtosecond laser with 11-mm beam diameter, 2-mJ pulse energy, and 1-kHz repetition rate. Significantly, by incorporating commercial optical choppers equipped with custom-designed chopper blades in the PPB, this design can accommodate lasers with fluences reaching 610 mJ/cm2 and the standard 1kHz repetition rate typical of high-fluence lasers. Furthermore, the proposed design provides a cost-effective substitute compared to using electro-optic modulators or acousto-optic modulators.

Cu TSV Filling with Cetyltrimethyl Ammonium Cations (CTA+) and Br-

Through silicon via (TSV) technology is essential for the three-dimensional packaging of electronic devices. After creating high-aspect-ratio vias, Cu electrodeposition is performed to achieve defect-free Cu interconnection. The most important purpose of electrodeposition process is to fill the features without any defects, and this process is called superfilling, superconformal deposition, or bottom-up filling. Since TSV is a key component for the packaging of semiconductor devices, various research on the electrodeposition process for TSV filling have been studied. Defect-free TSV filling can be achieved by introducing appropriate organic/inorganic additives into the electrolyte and the filling performance can be promoted by pulse reverse electrodeposition.1-3 Generally, it has been reported that Cu bottom-up filling at TSVs can be obtained by three-additive combinations (suppressor, accelerator, and leveler) or by using a single suppressor. Tetronic 701 is the most representative suppressor in a single-additive filling method, which was based on S-shaped negative differential resistance (S-NDR) behavior.4-6 In the case of three-additive systems, various levelers that contained ammonium functional groups, a polymeric suppressor, and an accelerator have been researched.7,8 Furthermore, it has been reported that halide ions (Br- and I-) can act as levelers for inducing Cu bottom-up filling at TSVs.9,10 This study investigated the effects of cetyltrimethyl ammonium cation (CTA+) and halide ion on TSV filling in the presence of an accelerator and polymeric suppressor. The influences of two halide ions, Cl- and Br-, on the adsorption of CTA+ and their convection dependency were studied. This presentation will introduce the electrochemical behaviors of halide ions and CTA+ and defect-free filling using the optimum combination of these additives. References M. Hayase, and K. Otsubo. "Copper deep via filling with selective accelerator deactivation by a reverse pulse" J. Electrochem. Soc.,157, D628 (2010).Q.S. Zhu, X. Zhang, C.Z. Liu, and H.Y. Liu. "Effect of reverse pulse on additives adsorption and copper filling for through silicon via" J. Electrochem. Soc.,166, D3006 (2019)Q.S. Zhu, A. Toda, Y. Zhang, T. Itoh, and R. Maeda. "Void-free copper filling of through silicon via by periodic pulse reverse electrodeposition" J. Electrochem. Soc.,161, D263 (2014)T. P. Moffat, and D. Josell. "Extreme bottom-up superfilling of through-silicon-vias by damascene processing: suppressor disruption, positive feedback and turing patterns" J. Electrochem. Soc.,159, D208 (2012)D. Joell, and T. P. Moffat. "Superconformal copper deposition in through silicon vias by suppression-breakdown." J. Electrochem. Soc.,165, D23 (2018)M. Dong, Y. Zhang, T. Hang, and M. Li. "Structural effect of inhibitors on adsorption and desorption behaviors during copper electroplating for through-silicon vias." Electrochim Acta372 (2021)M. J. Kim, Y. Seo, J. H. Oh, Y. Lee, H. C. Kim, Y. G. Kim, and J. J. Kim. "Communication—halide ions in teg-based levelers affecting TSV filling performance." J. Electrochem. Soc.,163, D185 (2016)V. Q. Dinh, K. Kondo, V. H. Hoang, and T. Hirato. "Communication—Bottom-up TSV filling using sulfonated diallyl dimethyl ammonium bromide copolymer as a leveler." J. Electrochem. Soc.,166, D505 (2019)M. J. Kim, H. C. Kim, and J. J. Kim. "The influences of iodide ion on Cu electrodeposition and TSV filling." J. Electrochem. Soc.,163, D434 (2016)M. Sung, Y. Yoon, J. Hong, M. J. Kim, and J. J. Kim. "Bromide ion as a leveler for high-speed TSV filling." J. Electrochem. Soc., 166, D546 (2019) Figure 1

Effects of rotational component of ground motions on seismic responses of asymmetric base-isolated structures

Asymmetric base-isolated structures installed on lead rubber bearings (LRBs) and laminated rubber bearings (LNRs) may suffer severe torsion due to the presence of the eccentricity ratio of the isolation system (eb/r). It is also recognized that the rotational component of ground motions can markedly increase torsional responses in structures, which may further amplify the adverse effect of torsion on asymmetric structures. Therefore, understanding how these rotational motions affect asymmetric base-isolated structures on LRBs and LNRs is crucial. Surprisingly, existing literature overlooks the impact of the structural parameter (eb/r) and the ground motion’s pulse period (Tp) on these effects. To fill this gap, numerical analyses are conducted on typical U-shaped planar asymmetric base-isolated structures. These structures, having 5 and 8 stories, are examined using MATLAB programming. Firstly, the translational and rotational responses of the selected cases under coupled rotational and translational components of ground motions are compared with those under the translational components. The responses are also compared to those of the associated, asymmetric fixed-base structures. Then, the role of eb/r in amplifying the negative effect of rotational excitations on selected cases is examined by varying eb/r from 0 to 0.3. The study compares the responses of selected cases subjected to coupled rotational and translational components of fourteen pulse-type ground motions (with Tp ranging from 0.728 to 8.043 s) to those subjected only to the translational components. The results reveal that seismic isolation effectively mitigates the adverse effects of the rotational component of ground motions on asymmetric structures. While rotational components can increase torsion in asymmetric base-isolated structures, the adverse effects are relatively minor and are not exacerbated by eb/r. However, when facing pulse-type ground motions with substantial Tp values, these structures exhibit at least a 200% increase in maximum interstory rotation and a 28% increase in maximum isolator displacement. These increases significantly exceed those observed for the structure subjected to non-pulse-type ground motions. Consequently, structural engineers should take these findings into account when designing and evaluating asymmetric base-isolated structures installed on LRBs and LNRs, particularly in regions where pulse-type ground motions are typical.

Synchrotron X-ray operando study and multiphysics modelling of the solidification dynamics of intermetallic phases under electromagnetic pulses

In this paper, we used synchrotron X-ray radiography and tomography to study systematically and in operando conditions the growth dynamics of the primary Al3Ni intermetallic phases in an Al-15wt%Ni alloy in the solidification process with magnetic pulses of up to 1.5 T. The real-time observations clearly revealed the growth dynamics of the intermetallics in time scale from millisecond to minutes, including phase growth instability, side branching, fragmentation and orientation alignment under different magnetic pulse fluxes. A multiphysics numerical model was also developed to calculate the alternating and cyclic Lorentz forces and stresses acting on the Al3Ni phases and the nearby melt due to the applied pulses. Combining the results of the operando experiments and modelling, for the first time, the differential forces between the growing Al3Ni phases and the nearby melt were quantified. The forces can create slip dislocations at the growing crystal front which can further develop into nm and µm crystal steps for initiating phase branching. Furthermore, the magnitudes of the shear stresses are strongly related to the size, morphological and geometric features of the growing Al3Ni phases. Dependent on the magnitude of the shear stresses, phase fragmentation could occur in a single pulse period or in multiple pulse periods via fatigue mechanism. This systematic research work elucidate some of the long-time debated hypotheses concerning intermetallic phases growth instability and phase fragmentation in pulse magnetic fields. The research establishes a robust theoretical framework for quantitative understanding of the intermetallic phase growth dynamics in solidification under pulse magnetic fields.

Increasing marsh bird abundance in coastal wetlands of the Great Lakes, 2011–2021, likely caused by increasing water levels

Abstract Wetlands of the Laurentian Great Lakes of North America (i.e., lakes Superior, Michigan, Huron, Erie, and Ontario) provide critical habitat for marsh birds. We used 11 years (2011–2021) of data collected by the Great Lakes Coastal Wetland Monitoring Program at 1,962 point-count locations in 792 wetlands to quantify the first-ever annual abundance indices and trends of 18 marsh-breeding bird species in coastal wetlands throughout the entire Great Lakes. Nine species (50%) increased by 8–37% per year across all of the Great Lakes combined, whereas none decreased. Twelve species (67%) increased by 5–50% per year in at least 1 of the 5 Great Lakes, whereas only 3 species (17%) decreased by 2–10% per year in at least 1 of the lakes. There were more positive trends among lakes and species (n = 34, 48%) than negative trends (n = 5, 7%). These large increases are welcomed because most of the species are of conservation concern in the Great Lakes. Trends were likely caused by long-term, cyclical fluctuations in Great Lakes water levels. Lake levels increased over most of the study, which inundated vegetation and increased open water-vegetation interspersion and open water extent, all of which are known to positively influence abundance of most of the increasing species and negatively influence abundance of all of the decreasing species. Coastal wetlands may be more important for marsh birds than once thought if they provide high-lake-level-induced population pulses for species of conservation concern. Coastal wetland protection and restoration are of utmost importance to safeguard this process. Future climate projections show increases in lake levels over the coming decades, which will cause “coastal squeeze” of many wetlands if they are unable to migrate landward fast enough to keep pace. If this happens, less habitat will be available to support periodic pulses in marsh bird abundance, which appear to be important for regional population dynamics. Actions that allow landward migration of coastal wetlands during increasing lake levels by removing or preventing barriers to movement, such as shoreline hardening, will be useful for maintaining marsh bird breeding habitat in the Great Lakes.

Statistical analysis of plasma thermodynamic behavior based on laser deep penetration welding of TC4 titanium alloy

The laser-induced plasma is an important characteristic that affects the welding process and weld quality. The plasma plume erupting velocity and temperature are the two critical parameters of plasma thermodynamic behavior. In this paper, a kind of passive dual-probe device was proposed to measure the erupting velocity of the plasma plume, and the feasibility of the method was demonstrated. The temperature distribution of the plasma plume was also investigated. The experimental results showed that for the reason of the state of the keyhole was different, the MPV at the beginning of the laser pulse period increased from 14 m/s to 26 m/s with the peak power increased from 1980 W to 2520 and from 4 m/s to 25 m/s with the peak power increased from 1200 W to 1500 in the pulse laser welding process, while the MPV decreased from 20 m/s to 11 m/s with the laser power increase from 1200 W to 1500 W in the continuous laser welding process. The MPT decreased with the increase of height in pulse laser welding process; but in the continuous laser welding process, the plasma plume was heated by absorbing the laser energy and a hot core occurred in the plasma plume, the MPT first increased and then decreased with the increase of probe height.

Automated parameterization of velocity pulses in near‐fault ground motions

AbstractProper parameterization of near‐fault ground motions is of critical importance in earthquake engineering, and this process is traditionally performed by directly fitting an analytical pulse model to the original motion. Yet such a process is usually limited by the trial‐and‐error procedure, which is strongly dependent on the initial guesses and may converge to local rather than global minimums. In this study, we propose a progressive (step‐by‐step) iterative approach that can achieve a fully automated parameterization of the velocity pulse contained in near‐fault motions. Assuming that a velocity pulse can be characterized by a pulse model with four key parameters, the approach is conducted by iteratively matching the pulse model to the smoothed ground motion, and the parameterized pulse is analytically derived by best fitting to the smoothed motion not only in the time domain but also in the spectral domain. Specifically, the velocity time history of interest is initially smoothed by a moving average filter so that the low‐frequency content can be filtered out of the original motion, from which the pulse amplitude as well as its epoch is accordingly determined. The coherent velocity pulse is then progressively extracted by performing the nonlinear least‐square‐fitting of the pulse model to the filtered low‐frequency content, during which the remaining parameters, that is, the pulse period, the number of cycles and the phase of the pulse, are estimated successively. Finally, the above procedure is applied repeatedly to the original ground motion by changing an empirical factor controlling the extent of smoothing of the motion so that convergence to local minimums that frequently occurs in the trial‐and‐error procedure could be largely avoided, and best match of the spectrum of the extracted pulse to that of the original motion can be acquired. Fitting quality of the velocity pulses is examined by comparing with existing methods. Prospective applications of the proposed procedure include the stochastic simulations of near‐fault ground motions and parametric investigations of the influence of velocity pulses on various engineered structures.

Site‐specific response spectra developed by considering near‐fault motion with finite‐fault simulation in Taiwan

AbstractA new methodology is proposed for developing a scenario‐based site‐specific response spectrum (RS) considering near‐fault effects in Taiwan. First, source parameters, together with reference rock site conditions, are defined according to the available geological and geophysical information at a target site close to a potential active fault in northern Taiwan. Secondly, the scenario‐based response spectrum for a reference rock site condition is developed theoretically through an empirical approach by using a ground motion prediction equation (GMPE). The effect of the pulse period and the occurrence probability of near‐fault pulse‐like ground motion on RS is evaluated by using the ground motion simulation (GMS) technique, in which the stochastic finite‐fault simulation method is validated and applied for evaluating velocity pulse. Third, site‐specific site amplification is incorporated into RS through a site transfer function calculated from the measured horizontal‐to‐vertical Fourier spectral ratio through the microtremor (MHVR) of the target site. Finally, the design spectrum of the target site is compared with the derived site‐specific RS to evaluate the impact of the neighbor fault on the structure of the target site.

Acoustic emission characteristics of micro-discharges in initial pulsed PEO process on 60% SiCp/Al composite

The initial discharge process of pulsed plasma electrolytic oxidation (PEO) on the 60% SiCp/2009 aluminum metal matrix composite (Al MMC) in silicate solution was monitored by acoustic emission (AE) technique. Parameters and correlations of AE signals on the Al MMC sample and under water were analyzed, and their generation mechanism was discussed. It was found that the peak amplitudes of AE signals and AE hits during the pulse time quickly increased with the increase of micro-discharge intensity, and the absolute energy of AE signals improved several orders of magnitude. Moreover, different from the peak amplitude, duration and rise time, the duration and count had a strong correlation. Elastic stress waves resulted from the microjet of plasma bubble collapse, the inner-surface friction inside discharge channel, the expansion-shrinkage process of plasma bubbles and micro-crack propagation during rapid solidification of melt are sources of AE signals on the Al MMC sample during the pulse time. However, the expansion-shrinkage process of plasma bubbles plays a key role in the generation of underwater AE signals. In the pause time of one pulse period, the bursting and moving of vapor bubbles result in weak AE signals. It is demonstrated that the AE technique can effectively characterize the features of micro-discharges within a pulse period.

In silico optical modulation of spiral wave trajectories in cardiac tissue

Life-threatening cardiac arrhythmias such as ventricular tachycardia and fibrillation are common precursors to sudden cardiac death. They are associated with the occurrence of abnormal electrical spiral waves in the heart that rotate at a high frequency. In severe cases, arrhythmias are combated with a clinical method called defibrillation, which involves administering a single global high-voltage shock to the heart to reset all its activity and restore sinus rhythm. Despite its high efficiency in controlling arrhythmias, defibrillation is associated with several negative side effects that render the method suboptimal. The best approach to optimize this therapeutic technique is to deepen our understanding of the dynamics of spiral waves. Here, we use computational cardiac optogenetics to study and control the dynamics of a single spiral wave in a two-dimensional, electrophysiologically detailed, light-sensitive model of a mouse ventricle. First, we illuminate the domain globally by applying a sequence of periodic optical pulses with different frequencies in the sub-threshold regime where no excitation wave is induced. In doing so, we obtain epicycloidal, hypocycloidal, and resonant drift trajectories of the spiral wave core. Then, to effectively control the wave dynamics, we use a method called resonant feedback pacing. In this approach, each global optical pulse is applied when the measuring electrode positioned on the domain registers a predefined value of the membrane voltage. This enables us to steer the spiral wave in a desired direction determined by the position of the electrode. Our study thus provides valuable mechanistic insights into the success or failure of global optical stimulation in executing efficient arrhythmia control.

Failure Probability-Based Dynamic Instability Evaluation of the Long Span Steel Arch Bridge Subjected to Earthquake Excitations

Instability is one of the major failure modes of long span arch bridges, and its possibility of occurrence will be increased as triggered by earthquake excitations. However, the randomness of each ground motion causes the difficulty in achieving a reliable assessment of the safety of the bridges in regard to its stability issue based on certain time history analysis. Therefore, a failure probability-based instability evaluation method and corresponding instability damage index are proposed in this study to solve this problem, converting the deterministic analysis of a ground motion into a probability analysis of a group of random ground motions. The results find that the input direction, the velocity pulse and the pulse period of the ground motion have a significant impact on the stability of the bridge, while seismic moment and PGV/PGA ratio do not. The fragility curves show that the bridge has more than 60% probability of slight instability when input PGA reaches 0.2 g, 50% probability of moderate instability when input PGA reaches 0.6 g, and 20% probability of collapse when input PGA reaches 1.0 g. Moreover, when the PGA approaches 1.0 g, it is discovered that the velocity pulse and the pulse period can increase the chance of the occurrence of bridge instability by 20%–30%.

A dynamic electrochemiluminescence system for continuous on-line measurements based on potential stepping pulse strategy

A dynamic electrochemiluminescence (ECL) detection system combining flow injection analysis with a potential stepping pulse strategy was developed. It contains a flow injection unit that carrying the sample solution flow through a specially designed ECL detection cell continuously, ensuring the valid renew of the test solution and thus is favorable for continuous on-line measurements. This dynamic ECL analytical system based on potential stepping pulse strategy is very efficient and time-saving. Taking the ruthenium(II) tris(bipyridine) (Ru(bpy)32+)-tripropylamine (TPA) system as an example, the ECL responses to step pulse potentials and pulse period, as well as the sample flow rate were examined. Under optimized experimental parameters, the proposed protocol was further successfully applied for the continuous detection of TPA, and malachite green based on its inhibitory effect on the ECL of Ru(bpy)32+-TPA system with a limit of detection of 17.77 nM. The relative standard deviation of 97 cycles measurements was only 0.46 % under ideal conditions. The results indicate that this system could provide reproducible and reliable ECL signals. As a versatile and efficient ECL detection protocol, it has a broad prospect of application.

P53 and p21 dynamics encode single-cell DNA damage levels, fine-tuning proliferation and shaping population heterogeneity

Cells must accurately and quickly detect DNA damage through a set of checkpoint mechanisms that enable repair and control proliferation. Heterogeneous levels of cellular stress and noisy signaling processes can lead to phenotypic variability but little is known about their role in underlying proliferation heterogeneity. Here we study two previously published single cell datasets and find that cells encode heterogeneous levels of endogenous and exogenous DNA damage to shape proliferation heterogeneity at the population level. Using a comprehensive time series analysis of short- and long-term signaling dynamics of p53 and p21, we show that DNA damage levels are quantitatively translated into p53 and p21 signal parameters in a gradual manner. Analyzing instantaneous proliferation and signaling differences among equally-radiated cells, we identify time-localized changes in the period of p53 pulses that drive cells out of a low proliferative state. Our findings suggest a novel role of the p53-p21 network in quantitatively encoding DNA damage strength and fine-tuning proliferation trajectories.