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We report on successful 10 Gb/s transmission of a message hidden in a chaotic optical phase over more than 100 km of an installed fiber optic network. This represents the best performance to date for so-called optical chaos communication, a physical layer oriented optical data encryption technique. Such performances was achieved through the use of a recently developed electro-optic nonlinear delay phase dynamics, inspired from differential phase modulation techniques. The setup appears as a superior alternative to the most popular architectures, i.e., the ones involving laser rate equations subjected to delayed feedback. It is compatible with standard dispersion compensation techniques and optical amplification, as shown by two field experiments over installed fiber optic networks. [ABSTRACT FROM PUBLISHER]

We have studied a time response of electromagnetically induced transparency (EIT) in a rubidium vapor to a rapid variation of optical phase. We have observed a very fast growth of the absorption when the phase of the optical field has been abruptly changed, followed by a slow return to the level of steady-state absorption. The recovery time decreases with increasing optical power. A simple theoretical analysis shows that under our experimental conditions the low power limit of the recovery time is determined by the ground relaxation time. In our case it is defined by a time-of-flight of rubidium atoms through laser beam. The obtained value of the ground state relaxation time is in a good agreement with result of direct measurements by 'relaxation in the dark' method. Our technique based on phase dynamics in EIT can be used for investigation of the ground state relaxation and the fast control of EIT. [ABSTRACT FROM AUTHOR]

Synaptically coupled neurons show in-phase or antiphase synchrony depending on the chemical and dynamical nature of the synapse. Deterministic theory helps predict the phase differences between two phase-locked oscillators when the coupling is weak. In the presence of noise, however, deterministic theory faces difficulty when the coexistence of multiple stable oscillatory solutions occurs. We analyze the solution structure of two coupled neuronal oscillators for parameter values between a subcritical Hopf bifurcation point and a saddle node point of the periodic branch that bifurcates from the Hopf point, where a rich variety of coexisting solutions including asymmetric localized oscillations occurs. We construct these solutions via a multiscale analysis and explore the general bifurcation scenario using the λ-ω model. We show for both excitatory and inhibitory synapses that noise causes important changes in the phase and amplitude dynamics of such coupled neuronal oscillators when multiple oscillatory solutions coexist. Mixed-mode oscillations occur when distinct bistable solutions are randomly visited. The phase difference between the coupled oscillators in the localized solution, coexisting with in-phase or antiphase solutions, is clearly represented in the stochastic phase dynamics. [ABSTRACT FROM AUTHOR]

One of the most sensitive methods for determining the presence and character of coupling between two oscillators is based on the modeling of their phase dynamics. This method is applicable if the observed oscillations are not synchronous and the length of available time series is no less than 50 characteristic periods. Now it is established that the method can be applied to still shorter time series with a length of 20 to 50 periods, provided that the estimated phase coherence coefficient (measuring the degree of synchronization) does not exceed a certain threshold dependent on the time series length and the frequency detuning. This result expands the possibilities of detecting the coupling between oscillatory systems under conditions of nonstationary signals and deficient data. [ABSTRACT FROM AUTHOR]

Source activity was extracted from resting-state magnetoencephalography data of 103 subjects aged 18–60 years. The directionality of information flow was computed from the regional time courses using delay symbolic transfer entropy and phase entropy. The analysis yielded a dynamic source connectivity profile, disentangling the direction, strength, and time delay of the underlying causal interactions, producing independent time delays for cross-frequency amplitude-to-amplitude and phase-to-phase coupling. The computation of the dominant intrinsic coupling mode (DoCM) allowed me to estimate the probability distribution of the DoCM independently of phase and amplitude. The results support earlier observations of a posterior-to-anterior information flow for phase dynamics in {α1, α2, β, γ} and an opposite flow (anterior to posterior) in θ. Amplitude dynamics reveal posterior-to-anterior information flow in {α1, α2, γ}, a sensory-motor β-oriented pattern, and an anterior-to-posterior pattern in {δ, θ}. The DoCM between intra- and cross-frequency couplings (CFC) are reported here for the first time and independently for amplitude and phase; in both domains {δ, θ, α1}, frequencies are the main contributors to DoCM. Finally, a novel brain age index (BAI) is introduced, defined as the ratio of the probability distribution of inter- over intra-frequency couplings. This ratio shows a universal age trajectory: a rapid rise from the end of adolescence, reaching a peak in adulthood, and declining slowly thereafter. The universal pattern is seen in the BAI of each frequency studied and for both amplitude and phase domains. No such universal age dependence was previously reported. [ABSTRACT FROM AUTHOR]

Based on a developed and experimentally tested model, self-oscillatory lasing regimes have been studied for a Class A four-frequency gas ring laser with linear coupling of elliptically polarized counter-propagating waves. In the self-oscillatory regime, switching of the intensities, polarization states, and phase differences of the counter-propagating waves is observed, and also a polarization-phase dynamics effect involving displacement of the intensity switching point (with respect to detuning), due to the phase shift as a result of an ellipticity different from zero. [ABSTRACT FROM AUTHOR]

We demonstrate in numerical experiments that estimators of strength and directionality of coupling between oscillators based on modeling of their phase dynamics [D. A. Smirnov and B. P. Bezruchko, Phys. Rev. E 68, 046209 (2003)] are widely applicable. Namely, although the expressions for the estimators and their confidence bands are derived for linear uncoupled oscillators under the influence of independent sources of Gaussian white noise, they turn out to allow reliable characterization of coupling from relatively short time series for different properties of noise, significant phase nonlinearity of the oscillators, and nonvanishing coupling between them. We apply the estimators to analyze a two-channel human intracranial epileptic electroencephalogram (EEG) recording with the purpose of epileptic focus localization. [ABSTRACT FROM AUTHOR]

Complex-valued Hopfield networks which possess the energy function are analyzed. The dynamics of the network with certain forms of an activation function is decomposable into the dynamics of the amplitude and phase of each neuron. Then the phase dynamics is described as a coupled system of phase oscillators with a pair-wise sinusoidal interaction. Therefore its phase synchronization mechanism is useful for the area-wide offset control of the traffic signals. The computer simulations show the effectiveness under the various traffic conditions. [ABSTRACT FROM AUTHOR]

We describe the phase dynamics of a timing extraction system based on direct optical injection locking of a multifrequency oscillator employing an InGaAs/InP heterojunction bipolar phototransistor. We present a general model for the locking range, jitter transfer function, and output phase noise. The model is confirmed by a series of locking experiments. We consider first fundamental timing extraction, that is, a 10-GHz oscillator extracting the clock from a 10-Gbit/s data stream. Second, we address superharmonic timing extraction where 40-Gbit/s data lock the fourth harmonic of the 10-GHz oscillator. In the superharmonic timing extraction case, a clock is extracted at 40 GHz as well as its subharmonics at 10, 20, and 30 GHz. [ABSTRACT FROM PUBLISHER]

Nonphotic entrainment of an overt sleep-wake rhythm and a circadian pacemaker-driving temperature/melatonin rhythm suggests existence of feedback mechanisms in the human circadian system. In this study, the authors constructed a phase dynamics model that consisted of two oscillators driving temperature/melatonin and sleep-wake rhythms, and an additional oscillator generating an overt sleep-wake rhythm. The feedback mechanism was implemented by modifying couplings between the constituent oscillators according to the history of correlations between them. The model successfully simulated the behavior of human circadian rhythms in response to forced rest-activity schedules under free-run situations: the sleep-wake rhythm is reentrained with the circadian pacemaker after release from the schedule, there is a critical period for the schedule to fully entrain the sleep-wake rhythm, and the forced rest-activity schedule can entrain the circadian pacemaker with the aid of exercise. The behavior of human circadian rhythms was reproduced with variations in only a few model parameters. Because conventional models are unable to reproduce the experimental results concerned here, it was suggested that the feedback mechanisms included in this model underlie nonphotic entrainment of human circadian rhythms. [ABSTRACT FROM AUTHOR]

Here, we study the upper critical solution temperature triggered phase transition of thermally responsive poly(ethylene glycol)-block-poly(ethylene glycol) methyl ether acrylate-co-poly(ethylene glycol) phenyl ether acrylate-block-polystyrene nanoassemblies in isopropanol. To gain mechanistic insight into the organic solution-phase dynamics of the upper critical solution temperature polymer, we leverage variable temperature liquid-cell transmission electron microscopy correlated with variable temperature liquid resonant soft X-ray scattering. Heating above the upper critical solution temperature triggers a reduction in particle size and a morphological transition from a spherical core shell particle with a complex, multiphase core to a micelle with a uniform core and Gaussian polymer chains attached to the surface. These correlated solution phase methods, coupled with mass spectral validation and modeling, provide unique insight into these thermoresponsive materials. Moreover, we detail a generalizable workflow for studying complex, solution-phase nanomaterials via correlative methods. The inclusion of an upper critical solution temperature (UCST) block in multiblock copolymer amphiphiles can enable temperature triggered nanoscale morphological transitions, but there are limited studies probing the actual UCST transition. Here, the authors couple variable temperature liquid-cell transmission electron microscopy and variable temperature liquid resonant soft X-ray scattering to study UCST polymeric nanostructures. [ABSTRACT FROM AUTHOR]

A relativistic magnetically isolated vircator with a magnetic mirror on a prelimit electron beam is proposed. Its computer simulation has been carried out. The phase dynamics of an electron beam in a vircator has been studied. It is shown that a number of virtual cathodes appear in the beam after the beam is reflected from the magnetic mirror. The output microwave characteristics are calculated: the average power and the spectral composition of generation, containing a set of narrow spectral lines and their harmonics. The effect of the mirror ratio on the average output power and on the frequencies of the spectral lines is studied. It is found that the power increases with the growth of the mirror ratio. The frequencies of some spectral lines increase with the mirror ratio, while the frequencies of other lines do not depend on this ratio. [ABSTRACT FROM AUTHOR]

We study the dynamics of a swarmalator model with higher harmonic phase coupling. We analyze stability, bifurcation, and structural properties of several novel attracting states, including the formation of spatial clusters with distinct phases, and single spatial clusters with a small number of distinct phases. We use mean-field (centroid) dynamics to analytically determine intercluster distance. We also find states with two large clusters along with a small number of swarmalators that are trapped between the two clusters and vacillate (waver) between them. In the case of a single vacillator we use a mean-field reduction to reduce the dynamics to two dimensions, which enables a detailed bifurcation analysis. We show excellent agreement between our reduced two-dimensional model and the dynamics and bifurcations of the full swarmalator model. [ABSTRACT FROM AUTHOR]

Metal halide perovskites are widely used in the preparation of photodetectors (PDs) due to their excellent photoelectric properties, tunable band gap, low cost, and rapid processing in solutions. Although 3D perovskite PDs exhibit exceptional performance, their practical applications are limited due to instability issues. Conversely, 2D perovskite PDs are gaining popularity due to their superior environmental stability. To produce efficient and stable perovskite‐based PDs, it is crucial to control the film formation process to achieve high‐quality perovskite films. This paper examines the impacts of perovskite film preparation process and crystallinity on the photoelectric properties of PDs and presents important observations regarding the crystallization and phase dynamics that occur during perovskite film formation. These insights have practical implications on the design and preparation of high‐performance and stable metal halide perovskite photodetectors, particularly in the domains of optical communications and imaging. They offer valuable guidance for next researchers and developers seeking to improve the functionality and marketability of photodetectors using perovskite films. [ABSTRACT FROM AUTHOR]

We experimentally investigate the forced synchronization of a self-excited chaotic thermoacoustic oscillator with two natural frequencies, f1 and f2. On increasing the forcing amplitude, xf, at a fixed forcing frequency, ff, we find two different types of synchronization: (i) ff/f1 = 1: 1 or 2: 1 chaos-destroying synchronization (CDS), and (ii) phase synchronization of chaos (PSC). En route to 1: 1 CDS, the system transitions from an unforced chaotic state (CH1,2) to a forced chaotic state (CH1,2,f), then to a two-frequency quasiperiodic state where chaos is destroyed (T²2,f), and finally to a phase-locked period-1 state (P1f). The route to 2: 1 CDS is similar, but the quasiperiodic state hosts a doubled torus (2T²2,f) that transforms into a phase-locked period-2 orbit (P2f) when CDS occurs. En route to PSC, the system transitions to a forced chaotic state (CH1,2,f) followed by a phase-locked chaotic state, where f1, f2 and ff still coexist but their phase difference remains bounded. We find that the maximum reduction in thermoacoustic amplitude occurs near the onset of CDS, and that the critical xf required for the onset of CDS does not vary significantly with ff. We then use two unidirectionally coupled Anishchenko-Astakhov oscillators to phenomenologically model the experimental synchronization dynamics, including (i) the route to 1: 1 CDS, (ii) various phase dynamics, such as phase drifting, slipping and locking, and (iii) the thermoacoustic amplitude variations in the ff/f1-xf plane. This study extends the applicability of open-loop control further to a chaotic thermoacoustic system, demonstrating (i) the feasibility of using an existing actuation strategy to weaken aperiodic thermoacoustic oscillations, and (ii) the possibility of developing new active suppression strategies based on both established and emerging methods of chaos control. [ABSTRACT FROM AUTHOR]

We study the collective behaviors of the fractional Kuramoto model (FKM) proposed in [16] with general interaction network topologies and present a new hybrid fractional Kuramoto (HFKM) model for synchronization. Here, our proposed HFKM model consists of continuous evolution processes and a sequence of discrete processes. The continuous dynamics between discrete times is governed by the fractional Kuramoto (FKM) model, whereas a sequence of discrete processes governs the reinitialization of data by deleting past memory of phase dynamics except for the current state and changing interaction network topologies. For the proposed models, we provide sufficient conditions for the emergence of practical synchronization for nonidentical oscillators and phase synchronization for identical oscillators, respectively. This improves the earlier work [16] on the slow relaxation of the FKM model. [ABSTRACT FROM AUTHOR]

Microfluidic technology applied for the controlled production of double emulsions has gained significant interest in biomedicine and material synthesis. The precise regulation of emulsion size depends on the in-depth study of the formation mechanism. A ternary multiple-relaxation-time lattice Boltzmann model with robust stability and multiphase accuracy is established and applied to investigate the formation mechanism of double emulsions within a flow-focusing microchannel. Integrated with the regularized and convective boundary conditions, the present model proves adept at simulating the complex multiphase flow behavior in microchannels under various properties and operation parameters. Extensive validations involving static and dynamic cases demonstrate the model accuracy in capturing three-phase interactions and multiphase flow fields while also significantly enhancing stability and accommodating a broader range of viscosity ratios. Our systematic investigation involves the influence of flow rate, viscosity ratio, interfacial tension ratio, and orifice section size on the formation of double emulsions. The results show the impact of flow rate on flow patterns and inner phase volume, revealing an expanded operation range of the dripping pattern brought by the increased outer phase flow rate. Notably, two distinct droplet formation mechanisms, i.e., shear mode and squeeze mode, are identified across a wide range of viscosity ratios. Additionally, the investigation of interfacial tension ratios focuses on assessing the effect of various interfacial tension combinations, while alterations in orifice width reveal its significant impact on shear strength and dispersed phase dynamics. This work deepens the understanding of double emulsion mechanics and offers a versatile platform for future research. [ABSTRACT FROM AUTHOR]

A rigorous methodology that combines a fully quantum mechanical treatment of a small system with a classical trajectory description of a large number of degrees of freedom is discussed in connection with the mechanism of decoherence. The need for mean field approximations in traditional quantum-classical calculations is removed by abandoning the delocalized wavefunction description of the quantum particle in favor of Feynman's formulation, which is based on local paths. The effects of the environment enter the quantum-classical path integral (QCPI) expression in terms of phase factors along classical trajectories, whose number grows exponentially with the number of time steps. It is argued that memory loss allows termination of trajectory branching and that the main contribution to decoherence arises from a single classical trajectory (from each sampled initial condition). Exploiting these ideas allows a dramatic reduction in the required number of trajectories, making QCPI calculations feasible. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The Kadomstev-Petviashvili (KP) equation is a wellknown modulation equation normally derived by starting with the trivial state and an appropriate dispersion relation. In this paper, it is shown that the KP equation is also the relevant modulation equation for bifurcation from periodic travelling waves when the wave action flux has a critical point. Moreover, the emergent KP equation arises in a universal form, with the coefficients determined by the components of the conservation of wave action. The theory is derived for a general class of partial differential equations generated by a Lagrangian using phase modulation. The theory extends to any space dimension and time, but the emphasis in the paper is on the case of 3 + 1. Motivated by light bullets and quantum vortex dynamics, the theory is illustrated by showing how defocusing NLS in 3 + 1 bifurcates to KP in 3 + 1 at criticality. The generalization to N >3 is also discussed. [ABSTRACT FROM AUTHOR]

We have simulated a chain of sinoatrial pacemaker cells connected via gap junctions. To study the dynamics we introduce a phase of oscillations and show that Burgers equation is adequate to describe the phase dynamics in the sinoatrial node. We show that the propagating action potential bears properties of either trigger waves, or phase waves, which depends upon its wave number. We propose a definition of the safety factor that is applicable to the oscillatory tissue of the sinoatrial node and show that the maximum of the safety factor relates to the boundary case separating phase waves and trigger waves. [ABSTRACT FROM AUTHOR]

High temperature Mössbauer spectroscopy has been used for studying “in situ” the phase dynamics of the silicon rich part of the binary Fe-Si system. In particular the rate and mechanism of the transformation of the so-called zeta-alpha phase of iron disilicide to the zeta-beta phase is of special interest, since there still remains uncertainty about the stability and the structure of the phase in this system which influence material properties such as compressive strength and disintegration. In the present work the phase transition from the zeta-alpha phase to the zeta-beta phase is followed by a time sequence of Mössbauer spectra recorded every three hours at a fixed temperature around 800 K. The exponential precipitation rate is analysed and the exponent calculated. Samples with differing degree of impurities have been studied and the effect of aluminium impurities on the rate of the transition will be discussed. The Debye temperature of the two phases was determined from series of Mössbauer spectra recorded at temperatures between 300 and 800 K. [ABSTRACT FROM AUTHOR]

Synchronization is common in both nature and human physiology, often used to illustrate nonlinear dynamics. Interestingly, one can initiate their comprehension of this phenomenon from pure linear systems. In this Tutorial, we begin with a theoretical exploration of coupled oscillators' dynamic behavior, enabling us to discern and contrast the unique attributes of dissipative coupling as opposed to commonly observed coherent coupling. We then examine synchronization in two dissipative coupled linear systems: one with two pendulums mutually linked via the Lenz effect and the other with two RLC oscillators coupled via a resistor. This Tutorial is designed to serve as a concise starting point for researchers interested in exploring synchronization phenomena using a simplified model driven solely by dissipative coupling. [ABSTRACT FROM AUTHOR]

This paper presents an approach for developing an experimentally validated dynamic multisegment model to simulate human flight-phase dynamics and multijoint control. Modeling and experimental techniques were integrated to systematically examine the contribution of multiple error sources to the accuracy of the model and to determine the complexity of a model that adequately emulates the dynamic behavior at the total-body and multijoint levels during flight. The accuracy of the model and of the experimental data was assessed using an inverse dynamics simulation of flight-phase motion for two representative cases: (i) a physical model released from a bar and (ii) a gymnast performing a layout dismount from a bar. Multijoint models with varying numbers of segments were assessed in order to determine the complexity of the model that adequately simulates the flight-phase task. A five-segment model was found to adequately simulate the layout dismount performed by the gymnast. The error introduced during modeling and digitizing contributed to an apparent violation of the conservation law manifested as large external forces acting on the nonactuated joints. These results demonstrate the need to reduce sources of error prior to testing hypotheses regarding feedforward and feedback components of the multijoint control system. The proposed approach for quantifying sources of error provides a crucial step that is required in the development of experimentally based dynamic models designed to examine and test hypotheses regarding multijoint control logic. [ABSTRACT FROM AUTHOR]

Abstract. Schoner [Schoner G (1995) Ecol Psychol 7: 291 314] argued that the relative phase dynamics of rhythmic interlimb coordination may be attributed to the timing level in that the stability properties of the relative phase are largely independent of dynamical principles operating at the goal level, such as those related to the maintenance of a particular amplitude or target position. Yet, according to the coupling functions in the coupled oscillator model proposed by Haken et al. [Haken H, Kelso JAS, Bunz H (1985) Biol Cybern 51:347 356], the effect of frequency on the stability properties of relative phase is either wholly or partially mediated by frequency-induced changes in amplitude, implying that the relative phase dynamics strongly depends on spatial factors. In order to distinguish between these contrasting interpretations of the organizational principles underwriting the phase dynamics of interlimb coordination, an experiment was conducted in which the effects of frequency and amplitude on the stability of relative phase were separated. Six subjects performed both in-phase and antiphase coordination patterns at seven different frequencies and three different amplitudes. Two measures of pattern stability were used, the standard deviation of relative phase and the exponent of the relaxation process following phasic perturbations of relative phase. According to both measures, pattern stability decreased with increasing frequency, whereas the amplitude manipulation only had a significant effect on the standard deviation of relative phase. This result was interpreted to imply that the organizational principles at the... [ABSTRACT FROM AUTHOR]

A two-dimensional D-shaped cylinder and heaving foil were mounted in tandem and used to simulate the main body and tail, respectively, of a natural swimmer. Thrust/drag measurements of the force on the foil and particle image velocimetry measurements of the flow downstream of the swimming system were conducted at a Reynolds number of about $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}10^4$ in a water channel with a constant free stream current speed. Two main sets of measurements were conducted: one set with the swimming system locked at a fixed streamwise location in the water channel as the heave frequency of the foil was varied; the other set with the system freely swimming to a desired set-point position from different upstream and downstream locations. When the freely swimming system reached and maintained its set-point position, so that its swimming speed matched that of the current, the oscillation frequency of the heaving foil corresponded to a Strouhal number of 0.36. Phase portraits of the measured thrust/drag forces reveal limit cycle oscillations for all swimming cases studied, which suggests that self-regulation drives the selection of this Strouhal number. No coupling was observed between the vortices shed by the D-shaped cylinder and the self-selected frequency of the heaving foil during free swimming. An examination of the ratio of the phase-locking indices for the input heaving motion of the foil and the coupled fluidic thrust/drag response reveals that it approaches a value of 0.5 over time when the freely swimming system is released from rest and allowed to achieve steady-state cruising. The jet produced by the freely swimming foil was inclined at an angle of approximately $4^\circ $ with respect to the direction of the mean flow. [ABSTRACT FROM PUBLISHER]

Benzophenone is a prototype molecule for photochemistry in the triplet state through its high triplet yield and reactivity. We have investigated its dynamics of triplet formation under the isolated gas phase conditions via femtosecond and nanosecond time resolved photoelectron spectroscopy. This represents the complete evolution from the excitation in S2 to the final decay of T1 to the ground state S0. We have found that the triplet formation can be described almost as a direct process in preparing T1, the lowest reacting triplet state, from the S1 state after S2→ S1 internal conversion. The molecule was also deposited by a pick-up technique on cold argon clusters providing a soft relaxation medium without evaporation of the molecule and the mechanism was identical. This cluster technique is a model for medium influenced electronic relaxation and provides a continuous transition from the isolated gas phase to the relaxation dynamics in solution. [ABSTRACT FROM AUTHOR]

The rate of conversion during gasification of char particles depends on the type of reagents, the concentration of reactants, and reactor temperature, among many other parameters; however, the overall conversion depends on the residence time distribution (RTD) of the particles in the reactor. The objective of the present work is to investigate the influence of gasifying agents, their concentration, and reactor wall temperature on the RTD of the char particles. The aim also includes studying the effect of mean residence time on the overall char conversion during gasification of Victorian brown coal in an entrained flow reactor. Two gasifying reagents, namely, CO2 and H2O, are selected in the present study. A discrete particle model (DPM) is coupled with computational fluid dynamics (CFD) to simulate the solid phase dynamics. Gasification is modelled using a lumped approach. The mean residence time of the solid char particles, determined using three different methods, is observed to increase with the CO2 concentration and wall temperature but decrease in the H2O environment. The longer residence time leads to higher overall char conversion in a CO2 environment despite the higher reactivity of H2O compared to CO2 as a gasifying reagent. [ABSTRACT FROM AUTHOR]

Introduction: The relationship between brain activity and respiration is recently attracting increasing attention, despite being studied for a long time. Respiratory modulation was evidenced in both single-cell activity and field potentials. Among EEG and intracranial measurements, the effect of respiration was prevailingly studied on amplitude/power in all frequency bands. Methods: Since phases of EEG oscillations received less attention, we applied our previously published carrier frequency (CF) mathematical model of human alpha oscillations on a group of 10 young healthy participants in wake and drowsy states, using a 14-channel average reference montage. Since our approach allows for a more precise calculation of CF phase shifts (CFPS) than any individual Fourier component, by using a 2-s moving Fourier window, we validated the new method and studied, for the first time, temporal waveforms CFPS (t) and their oscillatory content through FFT (CFPS (t)). Results: Although not appearing equally in all channel pairs and every subject, a clear peak in the respiratory frequency region, 0.21–0.26 Hz, was observed (max at 0.22 Hz). When five channel pairs with the most prominent group averaged amplitudes at 0.22 Hz were plotted in both states, topographic distributions changed significantly—from longitudinal, connecting frontal and posterior channels in the wake state to topographically split two separate regions—frontal and posterior in the drowsy state. In addition, in the drowsy state, 0.22-Hz amplitudes decreased for all pairs, while statistically significant reduction was obtained for 20/91 (22%) pairs. Discussion: These results potentially evidence, for the first time, the respiratory frequency modulation of alpha phase shifts, as well as the significant impact of wakeful consciousness on the observed oscillations. [ABSTRACT FROM AUTHOR]

This article presents a study of the dynamics of n-alkyl cyanides (CnH2n+1CN with n = 1–5) in the 0–450 cm−1 spectral region as a function of alkyl chain length. The spectra were measured using femtosecond optical Kerr effect (OKE) spectroscopy. The OKE spectra are characterized by a broad band in the 0–150 cm−1 region arising mainly from intermolecular modes and by narrow bands in the 150–450 cm−1 region arising from intramolecular modes. The intramolecular bands in the OKE spectra are in good agreement with the bands in simulated spectra obtained from density functional theory calculations. For cyanide molecules with long alkyl chains (n = 3–5), a low frequency intramolecular band associated with a torsional vibrational mode overlaps with the intermolecular band. Applying multicomponent line-shape analysis to the broad low-frequency band allowed us to obtain the intermolecular component of the band. We find the frequency and amplitude of the intermolecular band decrease with increasing chain length. Based on previous theoretical studies of the OKE spectrum of methyl cyanide and OKE reorientational studies of n-alkyl cyanides, we show that the dependence of the frequency of the intermolecular band on alkyl chain length is consistent with the band being primarily due to the hindered rotational motion of the molecules in the extended configuration about an axis perpendicular to the long axis of the molecule. The dependence of the amplitude of the intermolecular band on alkyl chain length is a mass effect associated with suppression of the collision-induced contribution to the intermolecular band. [ABSTRACT FROM AUTHOR]

Feedforward control with model inversion is a widely-used solution for high-precision output tracking. However, because inverting a non-minimum phase model generates unbounded control input, model-inversion only applies to limited types of systems. This paper presents a new non-parametric pseudo-inversion approach to design bounded optimal control input with desirable properties for arbitrary types of systems. Closed-form equations are presented for the batch (full preview) and recursive (limited preview) implementations of this approach, and its performance is compared against existing pseudo-inversion methods in benchmark numerical examples. Furthermore, the practical implementation of the proposed method is demonstrated by designing a feedforward controller for a commercial 3-Dimensional (3D) printer. The results show that the proposed approach effectively compensates for the structural vibrations of the printer, preventing layer-shifting errors that usually happen during high-speed printing. [ABSTRACT FROM AUTHOR]

We use the spatial map of the logarithm of past estimated released earthquake energies as input of fully convolutional networks (FCN) to forecast future earthquakes. This model is applied to California and compared with an elaborated version of the epidemic type aftershock sequence (ETAS) model. Our long-term earthquake forecast simulations show that the FCN model is close to the ETAS model in forecasting earthquakes with |$M \ge 3.0,\,\,4.0,\,\,{\rm{and\,\,}}5.0$| according to the Molchan diagram. Moreover, training and implementing the FCN model is 2000–4000 times faster than calibrating the ETAS model and generating its probabilistic forecasts. The FCN model is straightforward in terms of its neural network structure and feature engineering. It does not require extensive knowledge of statistical seismology or the analysis of earthquake catalogue completeness. Using the earthquake catalogue with |$M \ge 0$| as FCN input can enhance the model's performance in some time–magnitude forecasting windows. [ABSTRACT FROM AUTHOR]

We study a family of structure-preserving deterministic numerical schemes for Lindblad equations. This family of schemes has a simple form and can systemically achieve arbitrary high-order accuracy in theory. Moreover, these schemes can also overcome the non-physical issues that arise from many traditional numerical schemes. Due to their preservation of physical nature, these schemes can be straightforwardly used as backbones for further developing randomized and quantum algorithms in simulating Lindblad equations. In this work, we systematically study this family of structure-preserving deterministic schemes and perform a detailed error analysis, which is validated through numerical examples. [ABSTRACT FROM AUTHOR]

The conformational dynamics of the pyrene excimer play a critical role in its unique fluorescence properties. Yet, the influence of multiple local minima on its excited-state behavior remains underexplored. Using a combination of time-dependent density functional theory (TD-DFT) and unsupervised machine learning analysis, we have identified and characterized a diverse set of stable excimer geometries in the first excited state. Our analysis reveals that rapid structural reorganization towards the most stable stacked-twisted conformer dominates the excimer's photophysics, outcompeting radiative relaxation. This conformer, which is primarily responsible for the characteristic red-shifted, structureless fluorescence emission, reconciles experimental observations of long fluorescence lifetimes and emission profiles. These findings provide new insights into the excited-state dynamics of excimers. They may inform the design of excimer-based materials in fields ranging from organic electronics to molecular sensing. [ABSTRACT FROM AUTHOR]

The microstructure of hypereutectic Al-Si alloys is crucial in determining their mechanical properties and overall performance in engineering applications. This paper investigates the effect of a rotating magnetic field (RMF) and eutectic front velocity on the microstructure of hypereutectic Al-18 wt.% Si alloy. The hypereutectic samples were solidified using five different front velocities (0.02, 0.05, 0.09, 0.2, and 0.4 mm/s) with an average temperature gradient (G) of 8 K/mm in a crystallizer equipped with an RMF inductor. The samples were solidified into two sections. The first section solidified without stirring, while the second section solidified with stirring using RMF at an induction (B) of 7.2 mT. The length, angular orientation of eutectic Si lamellas, and interlamellar distances were measured in both the non-stirred and the stirred sections to evaluate the impact of RMF and front velocity on the eutectic structure. The results revealed that the application of RMF and the increase in front velocity during solidification led to the significant refinement of the eutectic structure. These findings highlight the potential of RMF and front velocity manipulation to enhance the microstructure of hypereutectic Al-Si alloys, with practical implications for the development of high-performance materials. [ABSTRACT FROM AUTHOR]

Satellite-based precipitation products (SPPs) are essential for climate monitoring, especially in regions with sparse observational data. This study compares the performance of the latest version (V07B) and its predecessor (V06B) of the Integrated Multi-satellitE Retrievals for GPM (IMERG) across South America and the adjacent oceans. It focuses on evaluating their accuracy under different precipitation regimes in Brazil using 22 years of IMERG Final data (2000–2021), aggregated into seasonal totals (summer, autumn, winter, and spring). The observations used for the evaluation were organized into 0.1° × 0.1° grid points to match IMERG's spatial resolution. The analysis was restricted to grid points containing at least one rain gauge, and in cases where multiple gauges were present within a grid point the average value was used. The evaluation metrics included the Root Mean Square Error (RMSE) and categorical indices. The results reveal that while both versions effectively capture major precipitation systems such as the mesoscale convective system (MCS), South Atlantic Convergence Zone (SACZ), and Intertropical Convergence Zone (ITCZ), significant discrepancies emerge in high-rainfall areas, particularly over oceans and tropical zones. Over the continent, however, these discrepancies are reduced due to the correction of observations in the final version of IMERG. A comprehensive analysis of the RMSE across Brazil, both as a whole and within the five analyzed regions, without differentiating precipitation classes, demonstrates that version V07B effectively reduces errors compared to version V06B. The analysis of statistical indices across Brazil's five regions highlights distinct performance patterns between IMERG versions V06B and V07B, driven by regional and seasonal precipitation characteristics. V07B demonstrates a superior performance, particularly in regions with intense rainfall (R1, R2, and R5), showing a reduced RMSE and improved categorical indices. These advancements are linked to V07B's reduced overestimation in cold-top cloud regions, although both versions consistently overestimate at rain/no-rain thresholds and for light rainfall. However, in regions prone to underestimation, such as the interior of the Northeastern region (R3) during winter, and the northeastern coast (R4) during winter and spring, V07B exacerbates these issues, highlighting challenges in accurately estimating precipitation from warm-top cloud systems. This study concludes that while V07B exhibits notable advancements, further enhancements are needed to improve accuracy in underperforming regions, specifically those influenced by warm-cloud precipitation systems. [ABSTRACT FROM AUTHOR]

The Earth's inner core (IC) is known to exhibit heterogeneous structures with their origins still unknown. From the onset of nucleation, the IC can grow via sedimentation and compaction of iron crystals freezing out from the fluid outer core. Previous studies of IC growth have shown entrapment of fluid within the solid matrix, and unstable density profiles in 1D can appear depending on the efficiency of fluid percolation. In this study, we perform simulations of IC growth in spherical geometries (assuming axisymmetry). We find that it is possible for the IC to develop large‐scale convective flows under certain conditions and, in some instances, produce small‐scale heterogeneites close to the IC boundary. Assuming representative values for the physical properties of the Earth's IC, we show that it is possible for the IC to exhibit compaction‐driven convection today. Plain Language Summary: The Earth's inner core is a solid body composed primarily of an iron‐nickel alloy, formed from crystallization of the fluid outer core over time. Seismologists studying its structure have found some peculiarities such as elastic properties that depend on direction, but figuring out the cause of these peculiarities have been challenging. One theory is the presence of fluids trapped within the solid body of the inner core during its growth, giving rise to its anomalous structure and seismic velocities. In this study, we model the growth of the inner core in 3D spherical geometry (assuming cylindrical symmetry) to investigate the distribution of fluids in the interior. We observe that under certain conditions, instabilities can develop across different scales in the interior which redistribute the fluids within. Taking certain representative values of the properties of the Earth's core, it is possible that instabilities are present in the inner core today. Key Points: For the first time we simulate inner core growth via compaction and melt migration in spherical geometry (assuming axisymmetry)The inner core can develop convective flows under certain parameter ranges to create internal structural heterogeneitiesAssuming values of relevant physical parameters, the Earth's inner core can be expected to exhibit compaction‐driven convection today [ABSTRACT FROM AUTHOR]

Gap dynamics are driving many important processes in the development of temperate forest ecosystems. What remains largely unknown is how often the regeneration processes initialized by endogenous mortality of dominant and co-dominant canopy trees take place. We conducted a study in the high mountain forests of the Central Western Carpathians, naturally dominated by the Norway spruce. Based on the repeated forest inventories in two localities, we quantified the structure and amount of deadwood, as well as the associated mortality of standing dead canopy trees. We determined the basic specific gravity of wood and anatomical changes in the initial phase of wood decomposition. The approach for estimating the rate of gap formation and the number of canopy trees per unit area needed for intentional gap formation was formulated based on residence time analysis of three localities. The initial phase of gap formation (standing dead tree in the first decay class) had a narrow range of residence values, with a 90–95% probability that gap age was less than 10 or 13 years. Correspondingly, a relatively constant absolute number of 12 and 13 canopy spruce trees per hectare died standing in 10 years, with a mean diameter reaching 50–58 cm. Maximum diameters trees (70–80 cm) were represented by 1–4 stems per hectare. The values of the wood-specific gravity of standing trees were around 0.370–0.380 g.cm−3, and varied from 0.302 to 0.523 g.cm−3. Microscopically, our results point out that gap formation is a continuous long-lasting process, starting while canopy trees are living. We observed early signs of wood degradation and bacteria, possibly associated with bark beetles, that induce a strong effect when attacking living trees with vigorous defenses. New information about the initial phase of gap formation has provided a basis for the objective proposal of intervals and intensities of interventions, designed to promote a diversified structure and the long-term ecological stability of the mountain spruce stands in changing climate conditions. [ABSTRACT FROM AUTHOR]

Cr-doped V2O3 thin film shows a huge resistivity change with controlled epitaxial strain at room temperature as a result of a gradual Mott metal-insulator phase transition with strain. This novel piezoresistive transduction principle makes Cr-doped V2O3 thin film an appealing piezoresistive material. To investigate the piezoresistivity of Cr-doped V2O3 thin film for implementation in MEMS sensor applications, the resistance change of differently orientated Cr-doped V2O3 thin film piezoresistors with external strain change was measured. With a longitudinal gauge factor of 222 and a transversal gauge factor of 217 at room temperature, isotropic piezoresistivity coefficients were discovered. This results in a significant orientation-independent resistance change with stress for Cr-doped V2O3 thin film piezoresistors, potentially useful for new sensor applications. To demonstrate the integration of this new piezoresistive material in sensor applications, a micromachined pressure sensor with Cr-doped V2O3 thin film piezoresistors was designed, fabricated and characterized. At 20 °C, a sensitivity, offset, temperature coefficient of sensitivity and temperature coefficient of offset of 21.81 mV/V/bar, -25.73 mV/V, -0.076 mV/V/bar/°C and 0.182 mV/V/°C, respectively, were measured. This work paves the way for further research on this promising piezoresistive transduction principle for use in MEMS sensor applications. [ABSTRACT FROM AUTHOR]

Introduction: Negative pressure breathing is breathing with decreased pressure in the respiratory tract without lowering pressure acting on the torso. We lowered pressure only during inspiration (NPBin). NPBin is used to increase venous return to the heart and is considered as a countermeasure against redistribution of body fluids toward the head during spaceflight. Aims of our study were: to obtain quantitative information on NPBin-induced changes in parameters of circulation and respiration in healthy human at various rarefactions; to identify main processes involved in cardiorespiratory response to NPBin. Methods: Cardiorespiratory response to 25 min of NPBin were studied, rarefaction ranged from −10 to −25 cmH2O. Parameters of systemic, cerebral, and peripheral hemodynamics, as well as respiratory and gas exchange parameters, were measured with non-invasive methods (Finometer, impedance cardiography, rheoencephalography, transcranial Doppler ultrasonography, laser Doppler flowmetry, capillaroscopy). Concentrations of endothelin-1, atrial and brain natriuretic peptides precursors in venous blood, O2 and CO2 tensions in arterialized capillary blood were measured. Results: Tidal volume increased, respiratory rate decreased under NPBin with no significant changes in minute ventilation. Group averaged, respiratory rate and tidal volume changed approximately twice relative to their values observed under normal breathing. Despite the decrease in respiratory rate (up to 2-3 breaths/min), the results indicate CO2 wash-out. Changes in respiratory and gas exchange parameters were virtually independent of rarefaction level. Synchronous with breathing oscillations of circulatory parameters increased in amplitude under NPBin, while values of the parameters averaged over NPBin period changed little. Amplitude of oscillations in parameters associated with arteries virtually did not change with increasing rarefaction. Inspiration under NPBin reduced left ventricle stroke volume and arterial blood pressure, increased heart rate. Head blood filling decreased during inspiration under NPBin, the decrease increased almost linearly with increasing rarefaction. Parameters returned to their initial values after the end of inspiration. Peak-to-peak amplitude of oscillations under NPBin ranged: stroke volume 17–25 mL, mean arterial pressure 7–9 mmHg, heart rate 14–18 bpm. Peripheral hemodynamics responded to NPBin little. Conclusion: Changes in stroke volume and central venous pressure during inspiration under NPBin appear to be the major phenomena mediating the effects of NPBin on the cardiorespiratory system. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have been powering portable electronic devices and electric vehicles for over three decades. However, growing concerns regarding the limited availability of lithium resources and the subsequent surge in costs have prompted the exploration of alternative energy storage systems beyond LIBs. Among these alternatives, sodium-based batteries, with their similar intercalation chemistry, have emerged as the most promising alternative due to their cost-effectiveness and the abundance of sodium reserves in nature. Developing sodium-ion batteries (SIBs) that possess high energy density, long lifespan, and high-rate capability necessitates a comprehensive understanding of the reaction mechanisms, especially the intricate chemistry involved in cathode materials. In this review, we delve into the reaction mechanisms of the most commonly used cathode materials for SIBs, which include layered transition-metal oxides, polyanionic compounds, Prussian blue analogues, etc. We also highlight the specific physicochemical properties that have been uncovered through the application of advanced operando characterization techniques. Building upon the insights gained from this comprehensive review, we put forth future perspectives on the development of novel cathode materials for SIBs. By leveraging the extensive knowledge generated, we aspire to pave the way for further advancements in sodium-ion battery technology. [ABSTRACT FROM AUTHOR]

Cortical signals have been shown to track acoustic and linguistic properties of continuous speech. This phenomenon has been measured in both children and adults, reflecting speech understanding by adults as well as cognitive functions such as attention and prediction. Furthermore, atypical low-frequency cortical tracking of speech is found in children with phonological difficulties (developmental dyslexia). Accordingly, low-frequency cortical signals may play a critical role in language acquisition. A recent investigation with infants Attaheri et al., 2022 [1] probed cortical tracking mechanisms at the ages of 4, 7 and 11 months as participants listened to sung speech. Results from temporal response function (TRF), phase-amplitude coupling (PAC) and dynamic theta-delta power (PSD) analyses indicated speech envelope tracking and stimulus-related power (PSD) for delta and theta neural signals. Furthermore, delta- and theta-driven PAC was found at all ages, with theta phases displaying stronger PAC with high-frequency amplitudes than delta. The present study tests whether these previous findings replicate in the second half of the full cohort of infants (N = 122) who were participating in this longitudinal study (first half: N = 61, (1); second half: N = 61). In addition to demonstrating good replication, we investigate whether cortical tracking in the first year of life predicts later language acquisition for the full cohort (122 infants recruited, 113 retained) using both infant-led and parent-estimated measures and multivariate and univariate analyses. Increased delta cortical tracking in the univariate analyses, increased ~2Hz PSD power and stronger theta-gamma PAC in both multivariate and univariate analyses were related to better language outcomes using both infant-led and parent-estimated measures. By contrast, increased ~4Hz PSD power in the multi-variate analyses, increased delta-beta PAC and a higher theta/delta power ratio in the multi-variate analyses were related to worse language outcomes. The data are interpreted within a "Temporal Sampling" framework for developmental language trajectories. [ABSTRACT FROM AUTHOR]

Despite the extensive history of investigation, characterization and diagnostics of giftedness is still a point of debate. The lack of understanding of the phenomenon affects the identification process of gifted children, development of targeted educational programs and state of research in the field of gifted education. In the current systematic review, we seek to delineate the specific aspects in which gifted children differ from their typically developing peers in cognitive abilities, psychophysiology and psychological characteristics. Secondly, we aim to document the prevalence and criteria of intelligence tests used to assess gifted children and adolescents. We reviewed 104 articles from more than 25 countries that examined a total of 77,705 children ages 5–18 years. Results reveal a discernible trend toward adopting more culturally appropriate measures for assessing giftedness in children. Findings highlight that gifted children generally outperform their peers in several cognitive domains such as verbal working memory, inhibition, geometric problem solving, attention-switching and elemental information processing, showcasing an accuracy-reaction time trade-off. Psychophysiological assessments demonstrate heightened and accelerated brain activity during complex effortful cognitive processes. Psychological and behavioral measures reveal that gifted children score higher on tests measuring intrinsic motivation, self-efficacy, and openness to experience; as well as achieving higher grades in school and employing better problem-solving strategies. Our systematic review can be beneficial in educational and research contexts, giving directions in assessment of giftedness and designing future research. [ABSTRACT FROM AUTHOR]