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In floating catalyst chemical vapor deposition (FCCVD), high-aspect-ratio carbon nanotubes (CNTs) are produced in the gas phase at high number concentrations and undergo collision and agglomeration, eventually giving rise to a macroscale aerogel, enabling functional material forms such as fibers or mats to be obtained directly from the synthesis process. The self-assembly behavior between high-aspect-ratio CNTs dictates the resulting morphology at the nanoscale and subsequently the bulk properties of the CNT product. Reorientation between CNTs after collision is a critical step that results in bundle formation and precedes aerogel formation. However, it has been challenging to study the phenomenon with existing methods as it spans multiple time and length scales. In this study, a physics-based semi-analytical model was developed to study the gas-phase reorientation dynamics of high-aspect-ratio CNTs and their bundles, with ±10% accuracy compared with mesoscale molecular dynamics simulations, but at <0.1% the computational cost. It was revealed that the reorientation time scale is dictated by the interplay among the van der Waals potential, drag, and the geometric configuration of CNTs upon collision. This then allows the time scale of reorientation (i.e., bundle formation) to be compared with other gas-phase dynamics in a typical FCCVD reactor and offers new insights into the self-assembly behavior of 1D nanoparticles in the gas phase.

This paper explores the interactions of both phase and amplitude in a network of N MEMS-Colpitts oscillators that are resistively coupled. The numerical simulations of the extensive networks of oscillators, required for emerging applications such as clock synchronization and neuromorphic computing, become computationally prohibitive as the number of oscillators increases. This complicates the design and evaluation of such systems, as understanding the effects of changes in coupling and design parameters can require many simulations. This study employs the method of multiple scales (MS) in combination with the harmonic balance method to convert the coupled differential equations governing the system of oscillators into a set of nonlinear evolution equations for the amplitude and phase of the oscillators. The amplitude and phase evolve on a timescale that is slow, commensurate with the damping in the system, compared with the fast timescale of the oscillation frequencies. The approach used in this study to describe the amplitude and phase dynamics offers significant computational efficiency (gains of 10× to 50× are shown) compared to direct numerical integration while maintaining an accurate representation of the response. The results of the presented simulations demonstrate the effect of coupling strength on the dynamics of the network, accounting for both phase and amplitude dynamics.

CsCdPO4adopts a periodic 3D Cd–P–O anionic network at room temperature. As the temperature increases above 440 K, thermal vibrations induced torsion and deformation within the PO4units are constrained by the 3D Cd–P–O network, which is critical for the unique periodic to incommensurately modulated long-range ordered phase transition. [Display omitted]

This investigation delves into the dynamic phase behavior of reservoir fluids during CO2huff-n-puff processes, a critical aspect of enhanced oil recovery. Utilizing numerical simulations, the study examines the formation and evolution of four key fluid phase zones, including a miscible-phase oil zone and two flanking miscible-phase condensate gas zones, shedding light on the intricate interactions between CO2and reservoir fluids. The research methodically addresses the spatial and temporal dynamics of these zones, providing a framework for understanding their evolution. It delves into the complex interplay of fluid properties and phase states, revealing the fundamental role of component migration in influencing phase behavior. This exploration not only uncovers the mechanisms driving fluid dynamics in the CO2huff-n-puff process but also emphasizes the broader implications for improving oil recovery strategies. By offering a comprehensive view of the factors governing phase behavior, the study contributes to the field's knowledge, suggesting avenues for future research and practical application in enhancing oil recovery efficiency.

Over the past two decades, the use of computational fluid dynamics (CFD) has witnessed widespread adoption as a pivotal approach for analyzing two-phase dynamics within membrane systems. The two-phase system typically arises from gas injection, aimed at improving membrane separation efficiency through improved mixing by mitigating the impact of concentration polarization (CP) and membrane fouling. While numerous CFD studies have contributed to this domain, an exhaustive and critical overview of the contemporary state of this field remains absent. To address this gap, this review comprehensively synthesizes the existing body of knowledge, outlining the theoretical underpinnings of the two-phase flow membrane system, accompanied by proper choice of CFD boundary conditions. In addition, this review investigates the extent to which current two-phase CFD models align with experimental findings, shedding light on applicability of these simulations in practical scenarios, while explores the current state-of-the-art of CFD modeling to capture the intricate interplay of gas injection dynamics and membrane behavior. Finally, research opportunities within CFD modeling of two-phase dynamics for membrane systems are outlined.

Conjugated ladder polymers (cLPs) represent an intriguing class of macromolecules, characterized by their multi‐stranded structure, with continuous fused π‐conjugated rings forming the backbone. Isotope substitution, such as deuteration and carbon‐13 labeling, offers unique approaches to address the significant challenges associated with elucidating the structure and solution phase dynamics of these polymers. For instance, selective deuteration can highlight parts of the polymer by controlling the scattering length density of specific molecular sections, thereby enhancing the contrast for neutron scattering experiments. In this context, deuteration of side‐chains in cLPs represents a promising approach to uncover the elusive polymer physics properties of their backbone. The synthesis of two distinct types of cLPs with perdeuterated side‐chains are reported here. During the synthesis, 13C isotope labeling was also employed to verify the low levels of defects in the synthesized polymers. Demonstrating these synthetic successes lays the foundation for rigorous characterization of the defects, conformation, and dynamics of cLPs.

Charge density waves are wave-like modulations of a material’s electron density that display collective amplitude and phase dynamics. The interaction with atomic impurities induces strong spatial heterogeneity of the charge-ordered phase. Direct real-space observation of phase excitation dynamics of such defect-induced charge modulation is absent. Here, by utilizing terahertz pump–probe spectroscopy in a scanning tunnelling microscope, we measure the ultrafast collective dynamics of the charge density wave in the transition metal dichalcogenide 2H-NbSe2with atomic spatial resolution. The tip-enhanced electric field of the terahertz pulses excites oscillations of the charge density wave that vary in magnitude and frequency on the scale of individual atomic impurities. Overlapping phase excitations originating from the randomly distributed atomic defects in the surface create this spatially structured response of the charge density wave. This ability to observe collective charge order dynamics with local probes makes it possible to study the dynamics of correlated materials at the intrinsic length scale of their underlying interactions.

In this work several computational approaches are tested for the two-phase simulation of the ELUBSYS bearing chamber in the high-speed regime−a four-equation Eulerian multifluid model, a steady-state Eulerian integral thin film (EITF) approach, a discrete parcel method (DPM) approach, and a simplified EITF-DPM coupled approach. While computationally expensive, the multifluid model captured the global liquid dynamics in the chamber and predicted that most of the oil is in the form of a thin film that flows on the stationary walls. The much more cost-efficient EITF approach achieved accurate results for the oil thickness distribution at the counter-current region but did not account for the large amounts of oil flowing out through the top vent. The DPM approach was used to assess the dispersed phase dynamics in both one-way and two-way coupling configurations, outlining a significant influence of the latter on the gas phase dynamics. Finally, the coupled EITFDPM approach was able to overcome some of the limitations observed by its individual counterparts by predicting a continuous film throughout the chamber circumference and a higher vent outflow, while still retaining most of the expected film distribution characteristics in the bearing chamber.

Unveiling molecular mechanisms that dominate protein phase dynamics has been a pressing need for deciphering the intricate intracellular modulation machinery. While ions and biomacromolecules have been widely recognized for modulating protein phase separations, effects of small molecules that essentially constitute the cytosolic chemical atmosphere on the protein phase behaviors are rarely understood. Herein, we report that vitamin C (VC), a key small molecule for maintaining a reductive intracellular atmosphere, drives reentrant phase transitions of myosin II/F-actin (actomyosin) cytoskeletons. The actomyosin bundle condensates dissemble in the low-VCregime and assemble in the high-VCregime in vitro or inside neuronal cells, through a concurrent myosin II protein aggregation–dissociation process with monotonic VCconcentration increase. Based on this finding, we employ in situ single-cell and single-vesicle electrochemistry to demonstrate the quantitative modulation of catecholamine transmitter vesicle exocytosis by intracellular VCatmosphere, i.e., exocytotic release amount increases in the low-VCregime and decreases in the high-VCregime. Furthermore, we show how VCregulates cytomembrane-vesicle fusion pore dynamics through counteractive or synergistic effects of actomyosin phase transitions and the intracellular free calcium level on membrane tensions. Our work uncovers the small molecule-based reversive protein phase regulatory mechanism, paving a new way to chemical neuromodulation and therapeutic repertoire expansion.

Control of cell proliferation is critical for the lymphocyte life cycle. However, little is known about how stage-specific alterations in cell cycle behavior drive proliferation dynamics during T cell development. Here, we employed in vivodual-nucleoside pulse labeling combined with the determination of DNA replication over time as well as fluorescent ubiquitination-based cell cycle indicator mice to establish a quantitative high-resolution map of cell cycle kinetics of thymocytes. We developed an agent-based mathematical model of T cell developmental dynamics. To generate the capacity for proliferative bursts, cell cycle acceleration followed a “stretch model” characterized by the simultaneous and proportional contraction of both G1 and S phases. Analysis of cell cycle phase dynamics during regeneration showed tailored adjustments of cell cycle phase dynamics. Taken together, our results highlight intrathymic cell cycle regulation as an adjustable system to maintain physiologic tissue homeostasis and foster our understanding of dysregulation of the T cell developmental program.

Due to the multifrequency coupling effect (m-FCE), precise modeling and effective stability assessment of an asymmetric grid-following converter (GFC)-based ac system are complex to achieve. Traditional small-signal modeling methods and recently reported order-reduction methods could establish multi-input and multioutput (MIMO) and equivalent single-input and single-output (SISO) models to characterize m-FCE effectively. However, revealing the physical implications of coupling components and the generation mechanism of m-FCE are still challenging. Meanwhile, although the amplitude and phase dynamics have been considered in the existing modeling, a concrete conclusion illustrating these dynamics’ impact on m-FCE is still missing. To fill the gaps, this article thoroughly considers the impacts of amplitude and phase dynamics and finds that phase dynamics form additional positive feedback loops to enhance m-FCE. Based on this cognition, an accurate complex circuit modeling framework is proposed. It reveals that m-FCE is generated by the admittance mismatching between conjugated responses and “chain reaction” among coupling components. The proposed method has two merits: 1) it is an SISO modeling approach and helps reduce analysis complexity and 2) its graphical form helps provide a deep physical insight into m-FCE. Simulations and experiments verified the correctness of the proposed method.

A new class of superfluids and superconductors with spatially periodic modulation of the superfluid density is arising1–12. It might be related to the supersolid phase of matter, in which the spontaneous breaking of gauge and translational symmetries leads to a spatially modulated macroscopic wavefunction13–16. This relation was recognized only in some cases1,2,5–9and there is the need for a universal property quantifying the differences between supersolids and ordinary matter, such as the superfluid fraction, which measures the reduction in superfluid stiffness resulting from the spatial modulation16–18. The superfluid fraction was introduced long ago16, but it has not yet been assessed experimentally. Here we demonstrate an innovative method to measure the superfluid fraction based on the Josephson effect, a ubiquitous phenomenon associated with the presence of a physical barrier between two superfluids or superconductors19, which might also be expected for supersolids20, owing to the spatial modulation. We demonstrate that individual cells of a supersolid can sustain Josephson oscillations and we show that, from the current–phase dynamics, we can derive directly the superfluid fraction. Our study of a cold-atom dipolar supersolid7reveals a relatively large sub-unity superfluid fraction that makes realistic the study of previously unknown phenomena such as partially quantized vortices and supercurrents16–18. Our results open a new direction of research that may unify the description of all supersolid-like systems.

Hydrodynamic dimension (HD) is the primary indicator of the size of bioconjugated particles and biomolecules. It is an important parameter in the study of solid–liquid two-phase dynamics. HD dynamic monitoring is crucial for precise and customized medical research as it enables the investigation of the continuous changes in the physicochemical characteristics of biomolecules in response to external stimuli. However, current HD measurements based on Brownian motion, such as dynamic light scattering (DLS), are inadequate for meeting the polydisperse sample demands of dynamic monitoring. In this paper, we propose MMQCM method samples of various types and HD dynamic monitoring. An alternating magnetic field of frequency ωmexcites biomolecule-magnetic bead particles (bioMBs) to generate magnetization motion, and the quartz crystal microbalance (QCM) senses this motion to provide HD dynamic monitoring. Specifically, the magnetization motion is modulated onto the thickness-shear oscillation of the QCM at the frequency ωq. By analysis of the frequency spectrum of the QCM output signal, the ratio of the magnitudes of the real and imaginary parts of the components at frequency ωq±2ωmis extracted to characterize the particle size. Using the MMQCM approach, we successfully evaluated the size of bioMBs with different biomolecule concentrations. The 30 min HD dynamic monitoring was implemented. An increase of ∼10 nm in size was observed upon biomolecular structural stretching. Subsequently, the size of bioMBs gradually reduced due to the continuous dissociation of biomolecules, with a total reduction of 20∼40 nm. This HD dynamic monitoring demonstrates that the release of biomolecules can be regulated by controlling the duration of magnetic stimulation, providing valuable insights and guidance for controlled drug release in personalized precision medicine.

Understanding the dynamics of phase boundaries in fluids requires quantitative knowledge about the microscale processes at the interface. We consider the sharp-interface motion of the compressible two-component flow and propose a heterogeneous multiscale method (HMM) to describe the flow fields accurately. The multiscale approach combines a hyperbolic system of balance laws on the continuum scale with molecular-dynamics (MD) simulations on the microscale level. Notably, the multiscale approach is necessary to compute the interface dynamics because there is—at present—no closed continuum-scale model. The basic HMM relies on a moving-mesh finite-volume method and has been introduced recently for the compressible one-component flow with phase transitions by Magiera and Rohde in (J Comput Phys 469: 111551, 2022). To overcome the numerical complexity of the MD microscale model, a deep neural network is employed as an efficient surrogate model. The entire approach is finally applied to simulate droplet dynamics for argon-methane mixtures in several space dimensions. To our knowledge, such compressible two-phase dynamics accounting for microscale phase-change transfer rates have not yet been computed.

A new method of obtaining directional modulation by implementing antenna array dynamics is proposed. An asymmetric switching feed structure is implemented in a two-element array that supports a static antenna pattern in a desired direction while adding sufficient complex modulation at other angles to mitigate the transfer of information. The dynamic antenna array feeds are calibrated to be in-phase, have a signal feed amplitude ratio of approximately 6.15 $\pm$ 0.1 dB through the design of an asymmetrical Wilkinson divider. The antenna system comprises of a two-state switching matrix using a double-pole double-throw (DPDT) RF switch. Secure communication capability is demonstrated in simulation and experiment by a 2.5 GHz two-element patch array. The communication system uses a 16-quadratic-amplitude modulation single-carrier signal transmitting 48 kb in a pseudorandom bit sequence at a rate of 4 Mb/s. The DPDT switch was controlled using a switching rate of 3 kHz. To isolate the effects of the phase dynamics, the communication system was operating at an signal-to-noise ratio of 33 dB, thus transmitting high power to all directions. A low bit error ratio (BER) of $ &lt; 10^{-3}$ is demonstrated at the desired transmission direction $\phi \leq |13^{\circ }|$, with higher BER outside this region. A measurement of a static antenna yielded BER $=0$ in all directions; thus, the bit errors and narrow $\pm 13^{\circ }$ information beamwidth were due exclusively to the antenna array dynamics. Performance metrics of this directional modulation technique are compared against previous literature for the reader. Further insights to spurious signals and mitigation are taken into consideration for the equipment and instrumentation of a narrowband signal to validate the technique as a viable “black-box” system implementation.

The structure and magnetic properties of the bimetallic borohydride-bridged dysprosocenium compound [{(η5-Cpttt)(η5-CpMe4t)Dy}2(μ:κ2:κ2-BH4)]+[B(C6F5)4]−([3Dy][B(C6F5)4]) are reported along with the solution-phase dynamics of the isostructural yttrium and lutetium analogues (Cptttis 1,2,4-tri(tert-butyl)cyclopentadienyl, CpMe4tis tetramethyl(tert-butyl)cyclopentadienyl). The synthesis of [3M][B(C6F5)4] was accomplished in the 2:1 stoichiometric reactions of [(η5-Cpttt)(η5-CpMe4t)Dy(BH4)] (2M) with [CPh3][B(C6F5)4], with the metallocenes 2Mobtained from reactions of the half-sandwich complexes [(η5-Cpttt)M(BH4)2(THF)] (1M) (M = Y, Dy, Lu) with NaCpMe4t. Crystallographic studies show significant lengthening of the M···B distance on moving through the series 1M, 2M, and 3M, with essentially linear {M···B···M} bridges in 3M. Multinuclear NMR spectroscopy indicates restricted rotation of the Cptttligands in 3Yand 3Luin solution. The single-molecule magnet (SMM) properties of [3M][B(C6F5)4] are characterized by Raman and Orbach processes, with an effective barrier of 533(18) cm–1and relaxation via the second-excited Kramers doublet. Although quantum tunneling of the magnetization (QTM) was not observed for [3M][B(C6F5)4], it was, surprisingly, found in its magnetically dilute version, which has a very similar barrier of Ueff= 499(21) cm–1. Consistent with this observation, slightly wider openings of the magnetic hysteresis loop at 2 K are found for [3M][B(C6F5)4] but not for the diluted analogue. The dynamic magnetic properties of the dysprosium SMMs and the role of exchange interactions in 3Dyare interpreted with the aid of multireference ab initio calculations.

The coupling between superconductors and oscillation cycles of light pulses, i.e., lightwave engineering, is an emerging control concept for superconducting quantum electronics. Although progress has been made towards terahertz-driven superconductivity and supercurrents, the interactions able to drive non-equilibrium pairing are still poorly understood, partially due to the lack of measurements of high-order correlation functions. In particular, the sensing of exotic collective modes that would uniquely characterize light-driven superconducting coherence, in a way analogous to the Meissner effect, is very challenging but much needed. Here we report the discovery of parametrically driven superconductivity by light-induced order-parameter collective oscillations in iron-based superconductors. The time-periodic relative phase dynamics between the coupled electron and hole bands drives the transition to a distinct parametric superconducting state out-of-equalibrium. This light-induced emergent coherence is characterized by a unique phase–amplitude collective mode with Floquet-like sidebands at twice the Higgs frequency. We measure non-perturbative, high-order correlations of this parametrically driven superconductivity by separating the terahertz-frequency multidimensional coherent spectra into pump–probe, Higgs mode and bi-Higgs frequency sideband peaks. We find that the higher-order bi-Higgs sidebands dominate above the critical field, which indicates the breakdown of susceptibility perturbative expansion in this parametric quantum matter.

Abstract: We present a class of one-dimensional systems of nonlinear parabolic equations for which the phase dynamics at large time can be described by an ODE with a Lipschitz vector field in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathbb R^n$$\end{document}. In the considered case of the Dirichlet boundary value problem, the sufficient conditions for a finite-dimensional reduction turn out to be much wider than the known conditions of this kind for a periodic situation.

A relativistic magneto-isolated vircator on the underlimit electron beam is studied. It contained two serial magnetic mirrors and a coaxial output of microwave radiation. Its 2.5-D particle-in-cell (PIC)-simulation is carried out. Space and phase dynamics of electrons are calculated. The mode is found at which several virtual cathodes (VCs) exist simultaneously in an electron beam, i.e., the multivircator mode is realized in the device. Spectral and power characteristics of the multivircator generation with two magnetic mirrors are calculated. The dependence of the average output microwave radiation and wave resistance of the radiation coaxial output is also calculated. The spectrogram of microwave radiation is provided.

Exploring the electronic structure and dynamic behavior of Mn(II) complexes reveals fascinating magnetic properties and prospective biomedical applications. In this study, we investigate the solvent phase dynamics of heptacoordinated Mn(II) complexes through ab initio molecular dynamics simulations and density functional theory (DFT) calculations with effectively varying temperatures. We observed that the complex with high stability ([Mn(pmpa)(H2O)2]) remains relatively rigid as the temperature increases to 90 °C, with only a minor change in its radial distribution functions (RDFs), compared to the RDF peaks at 25 °C. To elucidate the impact of halogens on the magnetic anisotropy of seven-coordinated Mn(II) complexes, we performed both DFT and multireference calculations. This shows that the zero-field splitting (ZFS) parameter Dfollows the order D(I)> D(Br)> D(Cl). We observed a significant increase in the D-value following the substitution of soft Se-donors in the equatorial position and heavier halogens in the axial position. The D-value of halogen derivatives of Se-analogues varies in the order of D(Cl) < D(I) < D(Br), deviating from the regular spectrochemical series with the discrepancy between the covalency of the Mn(II)–Se bond and the ligand field strength. We anticipate that this study will enhance our understanding of the solvent phase dynamics and structural aspects of ZFS in various Mn(II) complexes with different electronic environments.

Before large volumes of crystal poor rhyolites are mobilized as melt, they are extracted through the reduction of pore space within their corresponding crystal matrix (compaction). Petrological and mechanical models suggest that a significant fraction of this process occurs at intermediate melt fractions (ca. 0.3–0.6). The timescales associated with such extraction processes have important ramifications for volcanic hazards. However, it remains unclear how melt is redistributed at the grain‐scale and whether using continuum scale models for compaction is suitable to estimate extraction timescales at these melt fractions. To explore these issues, we develop and apply a two‐phase continuum model of compaction to two suites of analog phase separation experiments—one conducted at low and the other at high temperatures, T, and pressures, P. We characterize the ability of the crystal matrix to resist porosity change using parameterizations of granular phenomena and find that repacking explains both data sets well. A transition between compaction by repacking to melt‐enhanced grain boundary diffusion‐controlled creep near the maximum packing fraction of the mush may explain the difference in compaction rates inferred from high T + P experiments and measured in previous deformation experiments. When upscaling results to magmatic systems at intermediate melt fractions, repacking may provide an efficient mechanism to redistribute melt. Finally, outside nearly instantaneous force chain disruption events occasionally recorded in the low T + P experiments, melt loss is continuous, and two‐phase dynamics can be solved at the continuum scale with an effective matrix viscosity. Magma chambers in the continental crust are believed to be “mushy,” meaning they are reservoirs rich in both crystals and magma. The magma occupies the pore space between a connected network of crystals and the difference in density between crystal and magma leads to separation. During the separation process, the crystal networks behave like a sponge and magma percolates upward and is extracted as the pore space in the network of crystals closes. Magma collects atop the “sponge” and can potentially go on to feed volcanic eruptions at the Earth's surface. Therefore, how quickly it can separate has implications for monitoring volcanic hazards. When the porosity of the “sponge” is sufficiently low, the closing of pore space can only proceed if individual crystals are deformed (bent, for instance) and the process is slow. At larger porosities, however, the pore space can be closed by the sliding or rotation of crystals. We model this sliding process and compare our model to analog experiments and find that sliding may allow for this process to be efficient. Continuum model fits repacking experiments data of Hoyos et al. (2022) despite their stochastic natureAt intermediate melt fractions, mechanical repacking of particles may contribute significantly to the resistance of mushes to compactionParticle‐particle friction, rather than hydrodynamic effects, dominates viscous resistance associated with repacking Continuum model fits repacking experiments data of Hoyos et al. (2022) despite their stochastic nature At intermediate melt fractions, mechanical repacking of particles may contribute significantly to the resistance of mushes to compaction Particle‐particle friction, rather than hydrodynamic effects, dominates viscous resistance associated with repacking

The relationship between auroral, ground, and plasma sheet signatures in the late growth phase is crucial for understanding the sequence of events during a substorm expansion phase onset. Here we show conjugate ground‐auroral‐satellite observations of a substorm that occurred on 18 September 2021, between 04:45 and 05:00 UT, where four auroral activations were detected in the all‐sky imagers. An initial activation showed the brightening of an equatorward arc within the cutoff of the 630 nm emissions, indicating activity on closed field lines well inside the open‐closed field line boundary (OCFLB). During a second activation, auroral beads were observed on a brightening arc, equatorward and within the OCFLB, followed by the transformation from small‐scale to large‐scale vortices. The tail current sheet was highly disturbed during the auroral vortex evolution, including pressure and magnetic disturbances, an apparent broadening of a previously thin current sheet, and a breakdown of the frozen‐in condition. Our observations clearly show late growth phase dynamics, including arc brightenings, the formation of auroral beads, and auroral vortex development, can occur well in advance of fast Earthward flows in the tail. Indeed, it is only during that later activity that auroral breakup and strong Earthward flows, which we associate with magnetic reconnection further down the tail, are observed together with strong magnetic bays on the ground. The sequence of events is consistent with an inside‐to‐outside model at substorm expansion phase onset, most likely via a shear‐flow ballooning instability in the transition region from dipole to tail‐like fields in the near‐Earth plasma sheet. Substorm onset is associated with the explosive release of stored magnetic energy, which can be visualized as auroral activity in the ionosphere, magnetic‐field disturbances in the ground‐based magnetometers, and plasma sheet disturbances in the magnetosphere. Even though the processes that lead to energy storage are well known, the exact sequence of events and the triggering factors that lead to the release of this stored energy are poorly understood. In this study, we show conjugate auroral‐ground‐satellite observations of a substorm event that occurred on 18 September 2021. Four auroral activations were observed in the all‐sky imagers, all of which can be associated with plasma sheet disturbances observed in the satellites. Our observations show an initial activation and bead‐like structures on a brightening arc, followed by the formation and expansion of vortex‐like auroral forms, all of which can be associated with magnetic field and pressure fluctuations in the near‐Earth nightside magnetosphere on closed field lines. Auroral breakup and strong magnetic bays on the ground are only observed after the arrival of fast Earthward flows in the magnetosphere. Overall, this paper identifies disturbances in the near‐Earth plasma environment which are the counterparts to the evolving auroral forms seen leading up to the substorm expansion phase onset. Plasma sheet dynamical counterparts are reported for an evolving sequence of late growth phase auroral formsPlasma sheet current disruption and ion kinetic scale perturbations occur in advance of fast Earthward flows and magnetic reconnectionOne‐to‐one correspondence between plasma sheet disturbances and auroral forms implies ballooning instability in advance of auroral breakup Plasma sheet dynamical counterparts are reported for an evolving sequence of late growth phase auroral forms Plasma sheet current disruption and ion kinetic scale perturbations occur in advance of fast Earthward flows and magnetic reconnection One‐to‐one correspondence between plasma sheet disturbances and auroral forms implies ballooning instability in advance of auroral breakup

Clays and clay rocks are considered good natural and engineered barriers for deep geological disposal of nuclear waste worldwide. Metal corrosion and organic waste degradation in underground repositories generate significant amounts of gas that should be able to migrate through the multibarrier system to avoid potential pressure buildup, which could be compromising the integrity of the barriers and host rocks. The gas is expected to accumulate in larger pores and eventually form an interconnected network. Under such conditions, the migration of gas molecules takes place both in pore water films and gas-filled macropores. Therefore, mass fluxes depend on the distribution of gas molecules between the water-rich and gas-rich phases and their mobility in both compartments. Classical molecular dynamics (MD) simulations were employed to investigate the mobilities of He, H2, CO2, Ar, and CH4in a Na-montmorillonite mesopore as a function of the degree of saturation, as well as evaluate the hydrodynamic behavior of the pore fluid in partially saturated clays. The diffusivity of the gas molecules was determined by observing the asymptotic behavior of the mean square displacement in the gas-rich phase and at the gas–water interface. The partition coefficient and Gibbs free energy were analyzed to investigate the transfer of gas molecules between the gas-rich and water-rich phases by observing the molecular trajectories as they cross the vapor–liquid interface. The results revealed that the diffusion coefficient in the gas phase increased with increasing gas-filled pore width and converged asymptotically toward the diffusion coefficient in the bulk state. It could be shown that the diffusion coefficient of gas molecules dissolved in the water films remained constant as long as the interacting water surface was in the bulk-liquid-like phase. This behavior changes in very thin water films. It was observed that the partitioning coefficient of gas molecules at the solid–liquid interface is nearly the same as that in the bulk-liquid-like phase. Partitioning is observed to be strongly dependent on the temperature and gas molecular weights. In the second part of the study, nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate the mobility of gases in pressure-driven decoupled gas-phase dynamics (DGPD) and coupled gas and water phase dynamics (CGWPD) in a partially saturated Na-montmorillonite slit mesopore. The dynamic viscosity of the gas phase was calculated from NEMD simulations and indicated that the viscosity of the gas phase was almost the same in both methods (DGPD and CGWPD). The average slip length for gas molecules at the gas–water interface was also calculated, revealing that the slip-free boundary condition assumed in continuum models is generally invalid for microfluidics and that a slip boundary condition exists at the microscale for specific surface interactions. Finally, a Bosanquet-type equation was developed to predict the diffusion coefficient and dynamic viscosity of gas as a function of the average pore width, gas mean-free path, geometric factor, and thickness of the adsorbed water film.

The performance of feedforward control depends strongly on its ability to compensate for reproducible disturbances. The aim of this paper is to develop a systematic framework for artificial neural networks (ANN) for feedforward control. The method involves three aspects: a new criterion that emphasizes the closed-loop control objective, inclusion of preview to deal with delays and non-minimum phase dynamics, and enabling the use of an iterative learning algorithm to generate training data in view of addressing generalization errors. The approach is illustrated through simulations and experiments on an industrial flatbed printer.

We have investigated the theoretical constraints of the interactions between coupled cortical columns. Each cortical column consists of a set of neural populations where each population is modelled as a neural mass. The existence of semi-stable states within a cortical column is dependent on the type of interaction between the neuronal populations, i.e., the form of the synaptic kernels. Current-to-current coupling has been shown, in contrast to potential-to-current coupling, to create semi-stable states within a cortical column. The interaction between semi-stable states of the cortical columns is studied where we derive the dynamics for the collected activity. For small excitations the dynamics follow the Kuramoto model; however, in contrast to previous work we derive coupled equations between phase and amplitude dynamics with the possibility of defining connectivity as a stationary and dynamic variable. The turbulent flow of phase dynamics which occurs in networks of Kuramoto oscillators would indicate turbulent changes in dynamic connectivity for coupled cortical columns which is something that has been recorded in epileptic seizures. We used the results we derived to estimate a seizure propagationmodel which allowed for inversions using the Laplace assumption (Dynamic Causal Modelling). The seizure propagation model was trialed on simulated data, and future work will investigate the estimation of the connectivity matrix from empirical data. This model can be used to predict changes in seizure evolution after virtual changes in the connectivity network, something that could be of clinical use when applied to epilepsy surgical cases.

A CFD-DEM model is developed for chemical vapour deposition of silane in a fluidised bed reactor to investigate the effect of polydispersity on local phase dynamics, mass and heat transport, as well as the rate of Si deposition. Both gas-phase fines formation and heterogeneous deposition on the seed particle, as well as the scavenging effect for Si particle growth, are incorporated. The method is first validated against the experimentally measured Si deposition rate, percentage of fine production and minimum fluidisation velocity. Subsequently, the properties, primarily particle intermixing, fluidisation behaviour and bubble dynamics along with the deposition process, are analysed for several polydisperse beds under various operating conditions. The effect of polydispersity of the bed on a fraction of the bubble size, dense phase expansion and interchange coefficient between various phases is thoroughly investigated to establish a correlation with reactor performance. The results show that broad-Gaussian particle size distribution (PSD) exhibits excellent improvement in fluidisation behaviour, resulting in a high deposition rate, and minimum formation of Si fines.

A pair of relatively mild geomagnetic storms of February 3–4, 2022, resulted in the loss of 38 Starlink satellites. In this work we reconstruct a sequence of magnetospheric configurations during that event, based on the largest ever archive of historical data, a new magnetic field model, and the nearest‐neighbor method of mining the solar wind, magnetosphere, and ground activity data. The model is constructed as a combination of main modular framework, explicitly representing magnetic effects of principal current systems, and a high‐resolution superstructure, based on expanding the field of equatorial currents into a sum of quasi‐orthogonal harmonics, whose purpose is to correct residual inaccuracies of the modular component. In addition, the variable penetration of the interplanetary magnetic field (IMF) into the magnetosphere is taken into account in the form of a potential field, parameterized by the observed IMF components. Despite relatively modest intensity of the event in terms of Sym‐H peak values, surprisingly strong transient distortions of the global magnetic field are found. Whereas under quiet pre‐storm conditions the midnight segment of synchronous orbit and the dayside cusps mapped, respectively, to ∼67° and ∼77° of corrected latitude, at the peak of the storm their footpoints shifted equatorward to as low as ∼63° and ∼67°–68°, with formation of entangled flux‐rope‐like structures and magnetic neutral lines at distances R∼ 12–15 REon the nightside. At nearly the same time, a deep magnetic depression and, possibly, an island of reversed field polarity forms even closer, in the post‐dusk sector of geosynchronous orbit. In the beginning of February 2022, a relatively weak geomagnetic storm broke out, whose unexpected result was a premature demise of 38 Starlink satellites due to their abnormal drag in the upper atmosphere. This work analyses the concurrent distortions of the distant geomagnetic field, caused by the arrival of disturbed solar wind and interplanetary magnetic field. The storm‐time deformations of the Earth's magnetosphere are reconstructed by using an advanced magnetic field model, a huge database of past spacecraft and ground‐based observations covering the last 27 years, and novel methods of data mining. Strong distortions of the geomagnetic field during the storm culmination are revealed, that penetrated to unusually close distances up to the geosynchronous orbit. Dynamics of global geomagnetic connectivity during the ill‐famed storms of February 2022 is reconstructed via mining archived in situ dataA new hybrid model architecture is employed, combining flexible modular and high‐resolution components with added interplanetary magnetic field penetration effectDeep magnetic depression and possibly a neutral line formed in the post‐dusk sector around geosynchronous distance at the storm active phase Dynamics of global geomagnetic connectivity during the ill‐famed storms of February 2022 is reconstructed via mining archived in situ data A new hybrid model architecture is employed, combining flexible modular and high‐resolution components with added interplanetary magnetic field penetration effect Deep magnetic depression and possibly a neutral line formed in the post‐dusk sector around geosynchronous distance at the storm active phase