Fast Modes Research Articles (Page 1)

Impact of high irradiance and short exposure times on the polymerization kinetics of sculptable and flowable bulk-fill composites.

Modeling of fermentative polyhydroxyalkanoate production from Cerbera odollam oil using Monod-based and multi-scale kinetic models.

PurposeRecently, there has been a revived interest in system neuroscience causation models, driven by their unique capability to unravel complex relationships in multi-scale brain networks. In this paper, we present a novel method that leverages causal dynamics to achieve effective fMRI-based subject and task fingerprinting.MethodsBy applying an implicit-explicit discretization scheme, we develop a two-timescale linear state-space model. Through data-driven identification of its parameters, the model captures causal signatures, including directed interactions among brain regions from a spatial perspective, and disentangled fast and slow dynamic modes of brain activity from a temporal perspective. These causal signatures are then integrated with: (i) a modal decomposition and projection method for model-based subject identification, and (ii) a Graph Neural Network (GNN) framework for learning-based task classification. Furthermore, we introduce the concept of the brain reachability landscape as a novel visualization tool, which quantitatively characterizes the maximum possible activation levels of brain regions under various fMRI tasks.ResultsWe evaluate the proposed approach using the Human Connectome Project dataset and demonstrate its advantage over non-causality-based methods. The obtained causal signatures are visualized and demonstrate clear biological relevance with established understandings of brain function.ConclusionWe verified the feasibility and effectiveness of utilizing brain causal signatures for subject and task fingerprinting. Additionally, our work paves the way for further studies on causal fingerprints with potential applications in both healthy controls and neurodegenerative diseases.

Abstract The first close flyby of Ganymede by Juno on 2021 June 7 provided a unique opportunity to visit the previously unexplored wake and magnetopause regions. During the flyby, the Juno Waves instrument recorded traces of the existence of electrostatic solitary waves (ESWs) in the wake and magnetopause boundary. The flyby detected the presence of H2 + and H3 + ions in Ganymede’s wake for the first time, indicating that the wake is dominated by water products from the surface of Ganymede. The conditions for the occurrence of ESWs and double layers in the wake region and the associated existence domains (in parameter space) are explored in this paper. A magnetized fluid plasma is introduced to model Ganymede’s wake conditions, comprising of warm H+, O+, and H3 + ions and an electron beam, in addition to a non-Maxwellian background of suprathermal electrons. We have explored in particular the role of the third ion component H3 + on the properties of ESWs. Different acoustic modes are predicted and used as basis for our analysis, namely identified as one slow and two fast ion-acoustic modes and a higher-frequency electron-acoustic mode. Nonlinear analysis shows that the model may support the existence of positive and negative potential ion-acoustic solitons and double layers depending on the number density and on the temperature of H3 + ions. The theoretical prediction is correlated with observed ESWs in Ganymede’s wake.

Vertical-cavity surface-emitting lasers (VCSELs) are essential in modern optoelectronic systems, driving applications in high-speed optical communications, 3D sensing, and LiDAR. While significant progress has been made in improving VCSEL performance, the role of cavity geometry in optimizing key optical characteristics remains insufficiently explored. This study systematically examines how distinct cavity geometries—circular, square, D-shaped, mushroom-shaped, and pentagonal—affect both the static and dynamic properties of broad-area VCSELs. We analyze their effects on optical power, multimode behavior, beam profile, spatial coherence, and polarization dynamics. Our results show that breaking the continuous rotational symmetry of the cavity effectively increases gain utilization and power, changes the multimode lasing characteristics, shapes the beam, and modifies the polarization. Notably, the pentagonal VCSEL exhibits more than twice the optical power density of its circular counterpart. It also supports the highest number of modes and the fastest mode dynamics, driven by strong mode interaction. These properties make it a strong candidate for high-speed entropy generation. Mushroom-shaped VCSELs demonstrate high power and low spatial coherence, making them ideal for speckle-free imaging and illumination applications. Meanwhile, D-shaped VCSELs provide the most stable polarization and controllable multimode behavior with high power, showcasing their potential for applications that require stable and low-coherence light sources. This study offers a comprehensive analysis of the impact of cavity geometry on VCSEL performance, which provides insights for optimizing VCSEL designs tailored to diverse applications that require distinct properties with broad applicability to advanced imaging, sensing, optical coherence tomography, high-speed communication, and other photonic technologies.

Abstract In this work, we employ the set of ideal expanding magnetohydrodynamic (MHD) equations within the Expanding Box Model (EBM) framework to theoretically characterize the effects of radial solar wind expansion on its characteristic linear MHD waves. Through the analytical derivation of dispersion relations by a first-order expansion of the MHD-EBM equations, we explore the changes in wave propagation across a range of heliocentric distances on the linear magnetohydrodynamic modes: the Alfvén mode and the fast and slow magnetosonic modes, as obtained from the ideal MHD-EBM equations. Our findings reveal a spatial dependence in the derived dispersion relations that aligns with both the literature and the traditional ideal MHD case in the non-expanding limit, thereby helping to bridge the gap between theory and observation in solar wind dynamics. We observe a general decrease in wave frequencies as the plasma expands farther from the Sun. This decrease is reflected in the dispersion relations through the radial decrease of both the Alfvén and sound speeds, which decrease proportionally to 1/R and 1/R γ−1, respectively, where γ is the plasma polytropic index. The fast magnetosonic mode frequency and phase speed are significantly affected by the polytropic index value. We consider three models for the polytropic index evolution in the expanding solar wind: a constant (quasi-adiabatic) case, a radially decreasing profile in the outer heliosphere, and a model incorporating thermodynamic heating effects. Notably, we find that in the case of a decreasing polytropic index, the fast magnetosonic mode experiences an acceleration in the distant heliosphere, highlighting the significant influence of expansion on solar wind dynamics.

Microscopic Current Sheets and Fast Tearing Modes in Plasma Turbulence

Acoustic emission (AE) damage location methods rely strongly on the estimation of wave arrival times. These arrival times corresponding to the fast symmetric modes are generally susceptible to noise. In contrast, the subsequent antisymmetric modes with higher out-of-plane energy could provide relatively accurate arrival times through time–frequency analysis, which still has inherent errors. Aiming at more effective damage location of large-scale plate-like structures under noise interference, an A0 mode arrival time difference (A0-delta-T) deep learning framework was developed by integrating continuous wavelet transform (CWT), position embedding multihead self-attention long short-term memory (PE-MHSA-LSTM) network, and genetic algorithm (GA). For data preprocessing, CWT extracted coefficients at the dominant frequency of A0 mode. Then, a PE-MHSA-LSTM model was trained to identify the A0-delta-T of the sensor pair from corresponding CWT coefficients feature segments. GA was utilized to optimize the error function related to A0-delta-T and estimate the damage source location. The experiment conducted on a large-scale steel plate specimen demonstrated that the proposed framework could achieve a reliable performance of AE source location at various noise levels. Such a robust noise resistance highlighted its potential for field applications in engineering structures.

Abstract We study the effect of the solar cycle on various magnetohydrodynamic (MHD) fluctuation modes using the linear mode decomposition technique developed by G. P. Zank et al. We decompose various MHD modes, including propagating modes: Alfvén (forward and backward), fast (forward and backward), and slow (forward and backward) modes, as well as nonpropagating structures: entropy and magnetic island modes, from solar wind intervals during both the minimum and maximum phases of solar cycle 23. We find that the amplitudes of different modes corresponding to fluctuations in density, magnetic field, and velocity vary over the solar cycle, with larger amplitudes observed during the solar maximum compared to the solar minimum. The fluctuating energy of these modes is ∼1.5–4.5 times larger during the solar maximum. The frequency spectrum shows that the entropy mode exhibits the largest fluctuating power among density fluctuations, surpassing the contributions of fast and slow magnetosonic modes during both solar maximum and minimum intervals. For magnetic field fluctuations, the dominant contributors are the magnetic island mode, followed by the Alfvén modes. The Alfvén modes dominate the overall velocity fluctuations. This study provides observational evidence for the influence of the solar cycle on linear MHD modes.

Decrypting gene-spliced like and fast kinetic energy storage modes of Na/Mg dual doped manganese oxides cathode for high-performance aqueous zinc-ion batteries

Abstract The stability of weakly collisional plasmas is well represented by linear theory, and the generated waves play an essential role in the thermodynamics of these systems. The velocity distribution functions (VDFs) characterizing kinetic particle behavior are commonly represented as a sum of anisotropic bi-Maxwellians. A three bi-Maxwellian model is commonly applied for the ions, assuming that the VDF consists of a proton core, a proton beam, and a single He (α) particle population, each with its own density, bulk velocity, and anisotropic temperature. Resolving a secondary α-beam component was generally not possible due to instrumental limitations. The Solar Orbiter Solar Wind Analyser Proton and Alpha Sensor (SWA-PAS) resolves velocity space with sufficient coverage and accuracy to consistently characterize secondary α populations. This design makes the SWA-PAS ideal for examining the effects of α-particle beams on the plasma’s kinetic stability. We test the wave signatures observed in the magnetic field power spectrum at ion scales and compare them to the predictions from linear plasma theory, Doppler-shifted into the spacecraft reference frame. We find that taking into account the α-particle beam component is necessary to predict the coherent wave signatures in the observed power spectra, emphasizing the importance of separating the α-particle populations as is traditionally done for protons. Moreover, we demonstrate that the drifts of beam components are responsible for the majority of the modes that propagate in the oblique direction to the magnetic field, while their temperature anisotropies are the primary source of parallel fast magnetosonic modes.

We study the linear theory of magnetohydrodynamic (MHD) waves, namely, the Alfvén and the fast and slow magnetosonic modes in a rotating Hall-MHD plasma with the effects of the obliqueness of the external magnetic field and the Coriolis force and show that these waves can be coupled either by the influence of the Coriolis force or the Hall effects. To this end, we derive a general form of the linear dispersion relation for these coupled modes by the combined influence of the Coriolis force and the Hall effects and analyze numerically their characteristics in three different plasma-β regimes: β∼1, β>1, and β<1, including some particular cases. We show that while the coupling between the Alfvén and the fast magnetosonic modes is strong in the low-β(β≲1) regime and the wave dispersion appears in the form of a thumb curve, in the high-β (β>1) regime, the strong coupling can occur between the Alfvén and the slow magnetosonic modes and the dispersion appears in the form of a teardrop curve. Switching of the coupling in the regime of β∼1 can occur, i.e., instead of a thumb curve, a teardrop curve appears when the obliqueness of propagation and rotational angle are close to 70° or more (but less than 90°). Implications of our results to solar and fusion plasmas are briefly discussed.

This paper offers a thorough mathematical analysis of the propagation of acoustic-gravity waves (AGWs) in a stratified ocean, utilizing the framework of small-amplitude water wave theory. The dispersion relation that governs acoustic-gravity modes is derived, accompanied by an in-depth exploration of two distinct types of modes: barotropic (fast modes) and baroclinic (slow modes). The study examines three distinct AGW propagation scenarios for each mode type, namely, across both layers, solely in the upper layer and exclusively in the lower layer alone. In addition, it investigates how the position, frequency, and density ratio of the interface between the two layers affect various flow characteristics. The primary observation lies in the shift of cutoff frequencies of the different AGW modes as the parameters change, which are essential in time-domain simulations. Simulations showing how the individual AGW modes influence a frequency-domain Gaussian pulse are provided. A near-zero-movement portion of the pulse, emphasizing a near-blocking supported by an almost zero slope of the dispersion curve, is evident, along with a portion of the pulse moving in the direction of the internal wave along the interface. A comparison with the incompressible ocean is shown by juxtaposing it with the compressible one and reveals faster propagation both at the surface and interface for the incompressible ocean.

Adaptive Smooth Control via Nonsingular Fast Terminal Sliding Modes for Distributed Space Telescope Demonstration Mission by CubeSat Formation Flying

Recent research on the use of heptazine-based polymeric carbon nitride materials as potential photocatalysts for hydrogen evolution has made significant progress. However, the impact of the water cluster's size on the time-dependent photochemical mechanisms during the water splitting process of heptazine-water clusters remains largely unexplored. Here, we present a Landau-Zener trajectory surface hopping dynamics calculation for heptazine-(H2O)4 clusters at the ADC(2) level. The electron-driven proton transfer (EDPT) mechanism reaction from water to hydrogen-bonded heptazine-water clusters was confirmed using this method, yielding a heptazinyl radical and an OH biradical as products. The calculated quantum yield of the EDPT for the heptazine-(H2O)4 complex was 6.5%, which was slightly lower than that of the heptazine-H2O complex (9%), suggesting that increasing the water cluster size does not significantly enhance the efficiency of hydrogen transfer. Interestingly, our results show that the de-excitation of the heptazine-water complex from the excited state to the ground state via the EDPT process follows both fast and slow decay modes, which govern population relaxation and facilitate the photochemical water splitting reaction. This newly identified differential decay behavior offers valuable insights that could help deepen our understanding of the EDPT process, potentially improving the efficiency of water splitting under sunlight.

To assess the efficiency and safety of the MultiCut Solo® morcellator in patients undergoing holmium laser enucleation of the prostate (HoLEP), and to analyze the influence of device settings, surgeon experience, and blade reuse on morcellation outcomes. This prospective, multicenter, observational study included 232 patients undergoing HoLEP from January to September 2023 across two high-volume centers in Madrid, Spain. Three morcellation settings were evaluated: reduction, fast, and slow modes. Data on morcellation efficiency (g/min), surgeon experience (expert vs. trainee), and blade use frequency (0-10) were collected. Efficiency and complication rates were compared across groups. Statistical analysis was performed using Student's t-tests and Pearson's correlation. A total of 326 morcellation instances were analyzed. Mean global morcellation efficiency was 14.5g/min (SD ± 7.6), with reduction, fast, and slow modes yielding 16.7, 12.5, and 8.5g/min, respectively. Surgeons' experience showed a non-significant trend toward higher efficiency (15.2 vs. 13.1g/min, p = 0.051). Blade reuse up to 10 times did not significantly affect performance. Bladder perforation occurred in 1.29% of cases, and hematuria requiring temporary morcellation suspension in 3.88%. Obstruction occurred in 31.47% of cases, but disassembly was only required in 8.19%. The MultiCut Solo® morcellator demonstrated high efficiency and a favorable safety profile. Efficiency was consistent across surgeon experience levels and was not significantly impacted by blade reuse within the manufacturer's recommended lifespan. These findings suggest that the device is effective and user-friendly, even in the early learning curve, and represents a valuable tool for tissue morcellation in HoLEP procedures.

Adherent cells have long been known to display two modes during migration: a faster mode that is persistent in direction and a slower one where they turn. Compared to the persistent mode, the turns are less studied. Here we develop a simple yet effective protocol to isolate the turns quantitatively. With the protocol, we study different adherent cells in different morphological states and find that, during turns, the cells behave as rotors with constant turning rates but random turning directions. To perform tactic motion, the cells bias the sign of turning towards the stimuli. Our results clarify the bimodal kinematics of adherent cell migration. Compared to the rotational-diffusion-based turning dynamics, which has been widely implemented, our data reveal a distinct picture, where turns are governed by a deterministic angular velocity. Published by the American Physical Society 2025

Freight mode choice and the resulting inventory implications significantly influence a product’s carbon footprint. This paper investigates mode selection under a voluntary carbon emissions constraint. Slower modes such as inland waterways and ocean freight are less expensive and emit less greenhouse gas (GHG), but they require higher inventory levels due to longer lead times. In contrast, faster modes like less-than-truckload (LTL) shipping reduce inventory needs but incur higher transportation costs and emissions. Mode choice thus involves trade-offs between transport cost, inventory holding, lead time uncertainty, and GHG emissions from transportation and warehousing. This paper develops a comprehensive inventory-transportation model under the stochastic demand and lead time to evaluate these trade-offs and guide sustainable freight decisions. The model is a practical toolbox that enables managers to evaluate how freight mode choice and inventory policy affect costs and emissions under different operational scenarios and carbon constraints.

Covalent adaptable networks (CANs) are polymer networks that engage in chemical reactions. Their dynamic covalent linkages permit topology fluctuations, making them processable. Here, we demonstrate the reaction-controlled terminal relaxation of unentangled CANs by using a mesoscopic coarse-grained single-chain model based on Gaussian strands. The association dynamics is incorporated to reproduce the features of reversible or bond-exchange reactions in CANs. With this model, the dependence of terminal relaxation on cross-ink density [i.e., the number of associated stickers (Nas) for this model] is comparatively studied for dissociative and associative CANs, in terms of stress-relaxation behavior, plateau modulus, as well as terminal relaxation times. Both dissociative and associative model CANs exhibit plateau moduli and exponential terminal relaxations. Their slow and fast relaxation modes are of different Nas dependences, inducing the stress-relaxation curves to undergo a change in shape with Nas. The temperature dependence of terminal relaxation is also examined for both model CANs by considering the kinetics of intrinsic reaction and segmental motion. The engagement of segmental motion forces the horizontal shift factor of time-temperature superposition (TTS) to depart from the Arrhenius-like equation. For dissociative model CANs, the shape of stress-relaxation curve changes with temperature, causing the TTS principle not to hold.

A hydroelastic wave–current interaction model with a deformable bottom is developed to study the effect of following current on the surface and deformable bottom based on the linearized theory of water waves in a three-dimensional channel. The deformable bottom is modeled as an elastic thin plate theory and Green's function of the interaction between wave–current and the deformable bottom is derived using the fundamental source potentials. The progressive wave behavior of the slow-mode is analyzed through a comparison of the current bottom deflection results with previously published linear and nonlinear analytical results from other calculations. The generalized expansion formula in the presence of current velocity has been derived based on the Fourier sine and cosine series and the associated orthogonal mode-coupling relations for finite and semi-infinite channels of finite depth. The obtained expansion formula is applied to two classical boundary value problems: (a) forced motion and (b) wave reflection by an impermeable wall with limited width and length, which will play a significant role in the analysis of wave–current interaction with a deformable bottom arising in ocean engineering problems. In addition, free oscillations in the presence of current are derived, and the effect of current velocity over several numerical results in fast and slow modes is compared.