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It is crucial to deeply understand how the interlayer interaction acts on controlling the structural and electronic properties of shifted patterns of bilayer phosphorene. A comprehensive first-principles study on the bilayer phosphorene through relative translation along different directions has revealed that there is a direct correlation between the potential energy surface and the interlayer equilibrium distance. The shorter the interlayer distance, the lower the potential energy surface. The shifted patterns with the most stable state, the metastable state, and the transition state (with energy barrier of ∼1.3 meV/atom) were found associated with the AB, the A δ, and the TS stacking configurations, respectively. The high energy barriers, on the other hand, are ∼9.3 meV/atom at the AA stacking configuration along the zigzag pathway, ∼5.3 meV/atom at the AB′ stacking configuration along the armchair pathway, and ∼11.2 meV/atom at the AA′ stacking configuration along the diagonal pathway, respectively. The character of electronic bandgap with respect to the shifting shows an anisotropic behavior (with the value of 0.69–1.22 eV). A transition from the indirect to the direct bandgap occurs under the shifting, implying a tunable bandgap by stacking engineering. Furthermore, the orbital hybridization at the interfacial region induces a redistribution of the net charge (∼0.002–0.011 e) associated with the relative shifting between layers, leading to a strong polarization with stripe-like electron depletion near the lone pairs and accumulation in the middle of the interfacial region. It is expected that such interesting findings will provide a fundamental reference to deeply understand and analyze the complex local structural and electronic properties of twisted bilayer phosphorene and will make the shifted patterns of bilayer phosphorene promising for nanoelectronics as versatile shiftronics materials. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations are routinely performed of biomolecules in solution, because this is their native environment. However, the structures used in such simulations are often obtained with X-ray crystallography, which provides the atomic coordinates of the biomolecule in a crystal environment. With the advent of free electron lasers and time-resolved techniques, X-ray crystallography can now also access metastable states that are intermediates in a biochemical process. Such experiments provide additional data, which can be used, for example, to optimize MD force fields. Doing so requires that the simulation of the biomolecule is also performed in the crystal environment. However, in contrast to simulations of biomolecules in solution, setting up a crystal is challenging. In particular, because not all solvent molecules are resolved in X-ray crystallography, adding a suitable number of solvent molecules, such that the properties of the crystallographic unit cell are preserved in the simulation, can be difficult and typically is a trial-and-error based procedure requiring manual interventions. Such interventions preclude high throughput applications. To overcome this bottleneck, we introduce gmXtal, a tool for setting up crystal simulations for MD simulations with GROMACS. With the information from the protein data bank (rcsb.org) gmXtal automatically (i) builds the crystallographic unit cell; (ii) sets the protonation of titratable residues; (iii) builds missing residues that were not resolved experimentally; and (iv) adds an appropriate number of solvent molecules to the system. gmXtal is available as a standalone tool https://gitlab.com/pbuslaev/gmxtal. [ABSTRACT FROM AUTHOR]

We study the gravitational tidal response of D1D5, Top Star and (1,0,n) strata horizonless geometries. We find that the tidal interactions in fuzzball geometries, unlike in the case of black holes, exhibits a sequence of resonant peaks associated to the existence of metastable bound states. The spectrum of resonant frequencies is computed by semianalytical and numerical methods. [ABSTRACT FROM AUTHOR]

Results of XRD and TEM studies of a metastable phase state in Fe73Ti5B19O3 and Fe55Ti16B27O2 films, which is formed upon magnetron deposition under preset conditions, and of the evolution of the state in the course of subsequent annealing at 500 °C for 1, 5, and 9 h and experimental data on the magnetic microstructure and magnetic properties are reported. The annealed films were found to be characterized by a nanocrystalline structure, which is represented by two crystalline phases, namely, the ferromagnetic solid solution αFe(Ti), and nonferromagnetic boride FenB. The Ti content in the films determines the grain size of the αFe(Ti) phase, whereas the content of B localized within the grain boundaries determines the ratio of the volume fractions of amorphous and nanocrystalline phases in the structure. In contrast to the ferromagnetic Fe73Ti5B19O3 films, the Fe55Ti16B27O2 films are superparamagnets both in the deposited state and after annealing at 500 °C for 1 and 5 h because of the higher volume fraction of the amorphous phase in the structure. The 9 h annealing of the Fe55Ti16B27O2 films transfers them into the ferromagnets owing to the development of the amorphous phase crystallization, increase in the content of nanocrystalline ferromagnetic phase αFe(Ti) grains, and realization of exchange interaction between them. [ABSTRACT FROM AUTHOR]

We present the fabrication of a MoS2−xSex thin film from a co-sputtering process using MoS2 and MoSe2 commercial targets with 99.9% purity. The sputtering of the MoS2 and MoSe2 was carried out using a straight and low-cost magnetron radio frequency sputtering recipe to achieve a MoS2−xSex phase with x = 1 and sharp interface formation as confirmed by Raman spectroscopy, time-of-flight secondary ion mass spectroscopy, and cross-sectional scanning electron microscopy. The sulfur and selenium atoms prefer to distribute randomly at the octahedral geometry of molybdenum inside the MoS2−xSex thin film, indicated by a blue shift in the A1g and E1g vibrational modes at 355 cm−1 and 255 cm−1, respectively. This work is complemented by computing the thermodynamic stability of a MoS2−xSex phase whereby density functional theory up to a maximum selenium concentration of 33.33 at.% in both a Janus-like and random distribution. Although the Janus-like and the random structures are in the same metastable state, the Janus-like structure is hindered by an energy barrier below selenium concentrations of 8 at.%. This research highlights the potential of transition metal dichalcogenides in mixed phases and the need for further exploration employing low-energy, large-scale methods to improve the materials' fabrication and target latent applications of such structures. [ABSTRACT FROM AUTHOR]

The extractant-assisted transport of metal ions from aqueous to organic environments by liquid--liquid extraction has been widely used to separate and recover critical elements on an industrial scale. While current efforts focus on designing better extractants and optimizing process conditions, the mechanism that underlies ionic transport remains poorly understood. Here, we report a nonequilibrium process in the bulk aqueous phase that influences interfacial ion transport: the formation of metastable ion--extractant precipitates away from the liquid--liquid interface, separated from it by a depletion region without precipitates. Although the precipitate is soluble in the organic phase, the depletion region separates the two and ions are sequestered in a long-lived metastable state. Since precipitation removes extractants from the aqueous phase, even extractants that are sparingly soluble in water will continue to be withdrawn from the organic phase to feed the aqueous precipitation process. Solute concentrations in both phases and the aqueous pH influence the temporal evolution of the process and ionic partitioning between the precipitate and organic phase. Aqueous ion--extractant precipitation during liquid--liquid extraction provides a reaction path that can influence the extraction kinetics, which plays an important role in designing advanced processes to separate rare earths and other minerals. [ABSTRACT FROM AUTHOR]

This study aims to investigate the hydrogen embrittlement susceptibility of Cu-containing Fe–Cr–Ni austenitic stainless steels to examine the feasibility of Ni substitution in the steel used under a hydrogen atmosphere. The susceptibility to hydrogen embrittlement increased with replacement of Ni with Cu in N-free steels, while a complicated tendency appeared in N-added steels. Cu improved the austenite stability more effectively than Ni, but it promoted H diffusion and increased the adsorbed H content. Additionally, increase of Cu accelerated planar slip during tensile deformation, causing stress concentration and the accelerating H-induced cracks near the grain boundaries. In the metastable state, partial replacement of Ni with Cu improved hydrogen embrittlement resistance by suppressing the martensitic transformation. However, excessive replacement in stable steels resulted in the deterioration of hydrogen embrittlement resistance. • Increase of Cu/Ni ratio promoted the hydrogen diffusion. • Cu improved the austenite stability effectively than Ni. • Solute Cu promoted planar slip to induce stress localization. [ABSTRACT FROM AUTHOR]

Subcritical pipe flow transition has received a great deal of attention over the past decades, as it constitutes a quintessential bifurcation process between two metastable fluid states: the laminar and turbulent solutions. Coherent lower-branch structures, forming flow states that facilitate between these two attracting equilibria, have been proposed that together form an edge manifold in phase space separating relaminarizing from transitioning perturbations. Typically, direct numerical simulations or low-dimensional model equations have been used to study this edge manifold with bisection methods. In the article by Kaszás & Haller (J. Fluid Mech., vol. 979, 2024, A48), an effective nonlinear invariant-manifold technique has been applied to extract a low-dimensional, global representation of the phase-space dynamics directly from simulation data. It allows the computation of the intersection of the edge manifold with a low-dimensional surface that is strikingly accurate in predicting the long-term dynamics of perturbations about the lower-branch solution and thus provides an accessible parameterization of the edge manifold for subcritical pipe flow transition. [ABSTRACT FROM AUTHOR]

This study introduces an innovative outdoor nephelometer system designed to monitor the dynamic hygroscopic behavior of aerosols in ambient air. Field measurements conducted in the Pearl River Delta region of China unveil significant roles of relative humidity (RH) swings on aerosol phase states. Highlighting the occurrence of aerosol crystallization in the afternoon followed by gradual deliquescence as RH increases, particularly when minimum afternoon RH drops below 35%, with no such behavior observed when it exceeds 40%. Emphasizing that aerosol phase states are shaped not only by RH and chemical composition but also by their RH history, illustrating that RH levels of 70% in the morning or evening may correspond to fully dissolved metastable or partially dissolved metastable states of ambient aerosols. These findings underscore the need to account for RH history when predicting aerosol phase states and have broader implications for comprehending aerosol behavior and its atmospheric impacts. Plain Language Summary: This research introduces a new device to study how tiny particles called atmospheric aerosols in the air behave when they encounter moisture. We tested it in a region of China and discovered that relative humidity fluctuations from morning to evening impact significantly on phase state of atmospheric aerosols. In the afternoon, some of the particles might become solid, like tiny crystals, and later turn into liquid gradually as humidity increases. This phenomenon occurs when the afternoon minimum relative humidity is low, below 35%, but does not take place when it exceeds 40%. Suggesting that relative humidity history matters for aerosol phase. For example, relative humidity of 70% in the morning or evening, particles may be in a liquid or semi‐liquid state. This study helps us understand phase changes of atmospheric particles and their effects on our environment. Key Points: Innovative outdoor nephelometer system was developed to monitor aerosol hygroscopic behavior in ambient airAerosol crystallization in the afternoon followed by gradual deliquescence observedRelative humidity history plays significant roles in determining aerosol phase state [ABSTRACT FROM AUTHOR]

We describe a new Fortran computer program to solve the system of equations for the NH 4+ –Na + –Ca 2+ –K + –Mg 2+ –SO 42- –NO 3- –Cl - –H 2 O system, based on the algorithms of ISORROPIA II. Specifically, the code solves the system of equations describing the "forward" (gas + aerosol input) metastable state but with algorithm improvements and corrections. These algorithm changes allow the code to deliver more accurate solution results in formal evaluations of accuracy of the roots of the systems of equations, while reducing processing time in practical applications by about 50 %. The improved solution performance results from several implementation improvements relative to the original ISORROPIA algorithms. These improvements include (i) the use of the "interpolate, truncate and project" (ITP) root-finding approach rather than bisection, (ii) the allowance of search interval endpoints as valid roots at the onset of a search, (iii) the use of a more accurate method to solve polynomial subsystems of equations, (iv) the elimination of negative concentrations during iterative solutions, (v) corrections for mass conservation enforcement, and (vi) several code structure improvements. The new code may be run in either a "vectorization" mode wherein a global convergence criterion is used across multiple tests within the same chemical subspace or a "by case-by-case" mode wherein individual test cases are solved with the same convergence criteria. The latter approach was found to be more efficient on the compiler tested here, but users of the code are recommended to test both options on their own systems. The new code has been constructed to explicitly conserve the input mass for all species considered in the solver and is provided as open-source Fortran shareware. [ABSTRACT FROM AUTHOR]

A novel class of protein misfolding characterized by either the formation of non-native noncovalent lasso entanglements in the misfolded structure or loss of native entanglements has been predicted to exist and found circumstantial support through biochemical assays and limited-proteolysis mass spectrometry data. Here, we examine whether it is possible to design small molecule compounds that can bind to specific folding intermediates and thereby avoid these misfolded states in computer simulations under idealized conditions (perfect drug-binding specificity, zero promiscuity, and a smooth energy landscape). Studying two proteins, type III chloramphenicol acetyltransferase (CAT-III) and D-alanyl-D-alanine ligase B (DDLB), that were previously suggested to form soluble misfolded states through a mechanism involving a failure-to-form of native entanglements, we explore two different drug design strategies using coarse-grained structure-based models. The first strategy, in which the native entanglement is stabilized by drug binding, failed to decrease misfolding because it formed an alternative entanglement at a nearby region. The second strategy, in which a small molecule was designed to bind to a non-native tertiary structure and thereby destabilize the native entanglement, succeeded in decreasing misfolding and increasing the native state population. This strategy worked because destabilizing the entanglement loop provided more time for the threading segment to position itself correctly to be wrapped by the loop to form the native entanglement. Further, we computationally identified several FDA-approved drugs with the potential to bind these intermediate states and rescue misfolding in these proteins. This study suggests it is possible for small molecule drugs to prevent protein misfolding of this type. Author summary: A variety of diseases are caused by protein misfolding. Therefore, the recent evidence suggesting there is an entire unexplored class of protein misfolding that may be widespread opens the possibility they contribute to disease and may be therapeutic targets. Here, we bypass the question of what diseases such misfolding may contribute to and ask whether it is even possible to restore proper folding and function to proteins that misfold in this manner. We tried the most obvious strategy first: in the computer simulations we created a drug that binds to the folded, native entanglement. The rationale being that this would thermodynamically stabilize the native state relative to misfolded states, and thereby shift the population of molecules to the folded states. But thermodynamic reasoning neglects the folding pathways and kinetics connecting metastable states on the energy landscape, and this strategy had the unintended consequence of slowing down native state formation by stabilizing the entanglement loop without the threading segment piercing it, resulting in the loss of the native entanglement and formation of a non-native entanglement. Building on this observation, we took a different route, and designed a drug that would delay formation of the entanglement loop allowing more time for the threading segment to position itself and allow proper folding of the native entanglement. While this study was carried out using coarse-grained structure-based models, the results indicate it is possible in principle for drugs to be designed to avoid such misfolding and suggest our second design strategy is more likely to work in future experiments. [ABSTRACT FROM AUTHOR]

We study the effect of chain rigidity on tailoring the nanoparticle locations for neutral and selective particles embedded in the lamellar morphology formed by semiflexible diblock copolymer chains using self-consistent field calculations. The nanoparticles are modeled through a cavity function, and the semiflexible chains are represented by the continuous Kratsky-Porod chain model. In general situation, the nanoparticles prefer to stay at the interface in order to reduce the interface areas and thus the system free energy. However, the particle distribution at the domain center is subtle, and the underlying physics is intrinsically different depending on the polymer flexibility. In the case of flexible chains, the entropy just contributes a constant shift to the free energy when the nanoparticles move around the domain center indicating that the local metastable state if appears at the domain center is wholly attributed to the local minimum in the enthalpy. If the polymers are rigid, the variation of the particle distribution at the domain center has a close relation with the polymer rigidity and nanoparticle size. In the case of strongly rigid polymers with small nanoparticles, a nearly uniform particle distribution at the domain center is observed, while in other cases, a local enhancement of particle distribution there is found. In contrast to the case of flexible chains, further analysis reveals the crucial role of entropy in controlling the shape of particle distributions at the phase domain. Specifically, the local metastable state appears in the domain center is determined by the large entropy there which arises from the weak coupling of bond orientations that allows the polymer chains to be relatively relaxed. When the particle becomes selective, its distribution in the phase domain exhibits a shift almost uniformly rather than changes its profile, and the underlying physics still holds. In all, our study establishes a strong coupling between the chain rigidity and effect of entropy. [ABSTRACT FROM AUTHOR]

The investigation of photo‐induced effects is profoundly influenced by the characteristics of photo‐excitation sources. In this study, we present a comprehensive analysis of the structures of two photoinduced linkage isomers (PLI) in a ruthenium nitrosyl complex, trans‐[Ru(py)4F(NO)](ClO4)2, following irradiation with both pulsed and continuous wave (CW) light sources under low temperature conditions. The X‐ray (photo)diffraction analysis shows that the resulting PLI generated from the two types of irradiation sources, an isonitrosyl configuration of the nitrosyl ligand in the so‐called metastable state MS1, and a side‐on configuration of the nitrosyl ligand in the metastable state MS2, are identical. In‐situ optical absorption spectroscopy was employed during CW and pulsed irradiation, enabling the monitoring of the population process of these PLI. The results obtained from the infrared spectroscopic analysis after pulsed irradiation give insight into the population mechanism illustrating that the generation of the isonitrosyl MS1 occurs through a two‐step process, via the second PLI, the side‐on configuration MS2. [ABSTRACT FROM AUTHOR]

We developed a radio frequency discharge apparatus for He gas to investigate the spin states of metastable helium (He*) interacting with solid-state surfaces. Our apparatus consisted of a stainless steel vacuum chamber, in which a coil produced He* by discharging introduced He gas. The spin states of the He* were detected using optical pumping and probing techniques. The chamber was designed to accommodate various solid-state samples. We measured the He* polarization produced at a dielectric prism surface by total internal reflection of the circularly polarized pumping light. Our apparatus can be used to investigate possible spin transfer from various solid surfaces to He* atoms. [ABSTRACT FROM AUTHOR]

In this article we prove the existence of a new family of periodic solutions for discrete, nonlinear Schrödinger equations subject to spatially localized driving and damping. They provide an alternate description of the metastable behavior in such lattice systems which agrees with previous predictions for the evolution of metastable states while providing more accurate approximations to these states. We analyze the stability of these breathers, finding a very small positive eigenvalue whose eigenvector lies almost tangent to the surface of the cylinder formed by the family of breathers. This causes solutions to slide along the cylinder without leaving its neighborhood for very long times. [ABSTRACT FROM AUTHOR]

Boron, an element of captivating chemical intricacy, has been surrounded by controversies ever since its discovery in 1808. The complexities of boron stem from its unique position between metals and insulators in the Periodic Table. Recent computational studies have shed light on some of the stable boron allotropes. However, the demand for multifunctionality necessitates the need to go beyond the stable phases into the realm of metastability and explore the potentially vast but elusive metastable phases of boron. Traditional search for stable phases of materials has focused on identifying materials with the lowest enthalpy. Here, we introduce a workflow that uses reinforcement learning coupled with decision trees, such as Monte Carlo tree search, to search for stable and metastable boron phases, with enthalpy as the objective. We discover new boron metastable phases and construct a phase diagram that locates their phase space (T, P) at different levels of metastability (ΔG) from the ground state and provides useful information on the domains of relative stability of the various stable and metastable boron phases. [ABSTRACT FROM AUTHOR]

The search for low-energy antideuterons in cosmic rays allows the addressing of fundamental physics problems testing for the presence of primordial antimatter and the nature of Dark Matter. The PHeSCAMI (Pressurized Helium Scintillating Calorimeter for AntiMatter Identification) project aims to exploit the long-living metastable states of the helium target for the identification of low-energy antideuterons in cosmic rays. A space-based pressurized helium calorimeter would provide a characteristic identification signature based on the coincident detection of a prompt scintillation signal emitted by the antideuteron energy loss during the slowing-down phase in the gas, and the (≈µs) delayed scintillation signal provided by the charged pions produced in the subsequent annihilation. The performance of a high-pressure (200-bar) helium scintillator prototype, tested in the INFN-TIFPA laboratory, will be summarized. [ABSTRACT FROM AUTHOR]

To understand protein folding mechanisms from molecular dynamics (MD) simulations, it is important to explore not only folded/unfolded states but also representative intermediate structures on the conformational landscape. Here, we propose a novel approach to construct the landscape using the uniform manifold approximation and projection (UMAP) method, which reduces the dimensionality without losing data-point proximity. In the approach, native contact likelihood is used as feature variables rather than the conventional Cartesian coordinates or dihedral angles of protein structures. We tested the performance of UMAP for coarse-grained MD simulation trajectories of B1 domain in protein G and observed on-pathway transient structures and other metastable states on the UMAP conformational landscape. In contrast, these structures were not clearly distinguished on the dimensionality reduced landscape using principal component analysis or time-lagged independent component analysis. This approach is also useful to obtain dynamical information through Markov state modeling and would be applicable to large-scale conformational changes in many other biomacromolecules. [ABSTRACT FROM AUTHOR]

The transient negative-ion resonances found in scattering experiments are important intermediates in many chemical processes. These metastable states correspond to the continuum part of the Hamiltonian of the projectile–target composite system. Usual bound-state electronic structure methods are not applicable for these. In this work, we develop a subspace-projection method in connection with an electron propagator (EP) defined in terms of a complete-active-space self-consistent-field initial state. The target Hamiltonian ( H ̂) is perturbed by a complex absorbing potential (CAP) for the analytical continuation of the spectrum of H ̂ to complex eigenvalues associated with the continuum states. The resonance is identified as a pole of the EP, which is stable with respect to variations in the strength of the CAP. The projection into a small subspace reduces the size of the complex matrices to be diagonalized, minimizes the computational cost, and affords some insight into the orbitals that are likely to play some role in the capture of the projectile. Two molecular ( Π g 2 N 2 − and 2Π CO−) and an atomic shaperesonance (2P Be−) are investigated using this method. The position and width of the resonances are in good agreement with the previously reported values. [ABSTRACT FROM AUTHOR]

CO is one of the important molecules in dense molecular clouds, and its dissociation induced by cosmic ray heavy ions is a fundamental process for molecular breaking up and rearrangement in astronomical networks. Extensive laboratory simulations are required to understand molecular evolution in astrophysical contexts. Here, we investigate the CO dissociation induced by 1 keV/u Ar2+ using cold target recoil ion momentum spectroscopy. Kinetic energy release for double electron capture Ar2++CO→Ar0+C++O+ and transfer ionization Ar2++CO→Ar++C++O++e− was obtained. The dissociation mechanisms are attributed to different KER distributions. The autoionization process is identified below the CO2+ double ionization threshold.

After reviewing the peculiar thermodynamics and statistical mechanics of self-gravitating systems, we consider the case of a “binary star” consisting of two particles of size a in gravitational interaction in a box of radius R. The caloric curve of this system displays a region of negative specific heat in the microcanonical ensemble, which is replaced by a first-order phase transition in the canonical ensemble. The free energy viewed as a thermodynamic potential exhibits two local minima that correspond to two metastable states separated by an unstable maximum forming a barrier of potential. By introducing a Langevin equation to model the interaction of the particles with the thermal bath, we study the random transitions of the system between a “dilute” state, where the particles are well separated, and a “condensed” state, where the particles are bound together. We show that the evolution of the system is given by a Fokker–Planck equation in energy space and that the lifetime of a metastable state is given by the Kramers formula involving the barrier of free energy. This is a particular case of the theory developed in a previous paper (Chavanis, 2005) for N Brownian particles in gravitational interaction associated with the canonical ensemble. In the case of a binary star (N=2), all the quantities can be calculated exactly analytically. We compare these results with those obtained in the mean field limit N→+∞.

Path sampling approaches have become invaluable tools to explore the mechanisms and dynamics of the so-called rare events that are characterized by transitions between metastable states separated by sizable free energy barriers. Their practical application, in particular to ever more complex molecular systems, is, however, not entirely trivial. Focusing on replica exchange transition interface sampling (RETIS) and forward flux sampling (FFS), we discuss a range of analysis tools that can be used to assess the quality and convergence of such simulations, which is crucial to obtain reliable results. The basic ideas of a step-wise evaluation are exemplified for the study of nucleation in several systems with different complexities, providing a general guide for the critical assessment of RETIS and FFS simulations. [ABSTRACT FROM AUTHOR]

Absorption of slow moving electrons by neutral ground state nucleobases has been known to produce resonance metastable states. There are indications that such metastable states may play a key role in DNA/RNA damage. Therefore, herein, we present an ab initio non-Hermitian investigation of the resonance positions and decay rates for the low lying shape-type states of the uracil anion. In addition, we calculate the complex transition dipoles between these resonance states. We employ the resonance via Padé (RVP) method to calculate these complex properties from real stabilization curves by analytical dilation into the complex plane. This method has already been successfully applied to many small molecular systems, and herein, we present the first application of RVP to a medium-sized system. The presented resonance energies are optimized with respect to the size of the basis set and compared with previous theoretical studies and experimental findings. Complex transition dipoles between the shape-type resonances are computed using the optimal basis set. The ability to calculate ab initio energies and lifetimes of biologically relevant systems paves the way for studying reactions of such systems in which autoionization takes place, while the ability to also calculate their complex transition dipoles opens the door for studying photo-induced dynamics of such biological molecules. [ABSTRACT FROM AUTHOR]

Finding a low dimensional representation of data from long-timescale trajectories of biomolecular processes, such as protein folding or ligand–receptor binding, is of fundamental importance, and kinetic models, such as Markov modeling, have proven useful in describing the kinetics of these systems. Recently, an unsupervised machine learning technique called VAMPNet was introduced to learn the low dimensional representation and the linear dynamical model in an end-to-end manner. VAMPNet is based on the variational approach for Markov processes and relies on neural networks to learn the coarse-grained dynamics. In this paper, we combine VAMPNet and graph neural networks to generate an end-to-end framework to efficiently learn high-level dynamics and metastable states from the long-timescale molecular dynamics trajectories. This method bears the advantages of graph representation learning and uses graph message passing operations to generate an embedding for each datapoint, which is used in the VAMPNet to generate a coarse-grained dynamical model. This type of molecular representation results in a higher resolution and a more interpretable Markov model than the standard VAMPNet, enabling a more detailed kinetic study of the biomolecular processes. Our GraphVAMPNet approach is also enhanced with an attention mechanism to find the important residues for classification into different metastable states. [ABSTRACT FROM AUTHOR]

The kinetics of a dynamical system dominated by two metastable states is examined from the perspective of the activated-dynamics reactive flux formalism, Markov state eigenvalue spectral decomposition, and committor-based transition path theory. Analysis shows that the different theoretical formulations are consistent, clarifying the significance of the inherent microscopic lag-times that are implicated, and that the most meaningful one-dimensional reaction coordinate in the region of the transition state is along the gradient of the committor in the multidimensional subspace of collective variables. It is shown that the familiar reactive flux activated dynamics formalism provides an effective route to calculate the transition rate in the case of a narrow sharp barrier but much less so in the case of a broad flat barrier. In this case, the standard reactive flux correlation function decays very slowly to the plateau value that corresponds to the transmission coefficient. Treating the committor function as a reaction coordinate does not alleviate all issues caused by the slow relaxation of the reactive flux correlation function. A more efficient activated dynamics simulation algorithm may be achieved from a modified reactive flux weighted by the committor. Simulation results on simple systems are used to illustrate the various conceptual points. [ABSTRACT FROM AUTHOR]

Geometric and electronic structures of a corannulene ( C 20 H 10) intercalated bilayer graphene are investigated in terms of the molecular conformation using density functional theory. Our calculations indicate that the electronic structure of bilayer graphene is tunable by controlling the molecular conformation of corannulene. Holes and electrons coexist on the upper and lower layers of graphene, which are situated at the convex region and edge of corannulene when it has the bowl conformation. In contrast, bilayer graphene has a tiny gap of 4.7 meV at the K point owing to the substantial interaction between graphene and corannulene when corannulene has flat conformation. Electron and hole redistribution in bilayer graphene intercalating corannulene indicated the possibility of all carbon p-n border at an interface between corannulene with convex and concave arrangements. The intercalation substantially decreases the energy difference between the ground state bowl conformation and the metastable state flat conformation by approximately 400 meV. Accordingly, the two-dimensional nano-spacing between the graphene layers changes the molecular conformation of corannulene from a bowl to a flat structure at 139 MPa. [ABSTRACT FROM AUTHOR]

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong A1Π ← X1Σ+ transition around 227 nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden a3Π ← X1Σ+ transition around 367 nm, which has a recoil limit in the µK range. We here report on the spectroscopic characterization of the lowest rotational levels in the a3Π state of AlF for v = 0–8 using a jet-cooled, pulsed molecular beam. An accidental AC Stark shift is observed on the a3Π0, v = 4 ← X1Σ+, v = 4 band. By using time-delayed ionization for state-selective detection of the molecules in the metastable a3Π state at different points along the molecular beam, the radiative lifetime of the a3Π1, v = 0, J = 1 level is experimentally determined as τ = 1.89 ± 0.15 ms. A laser/radio frequency multiple resonance ionization scheme is employed to determine the hyperfine splittings in the a3Π1, v = 5 level. The experimentally derived hyperfine parameters are compared to the outcome of quantum chemistry calculations. A spectral line with a width of 1.27 kHz is recorded between hyperfine levels in the a3Π, v = 0 state. These measurements benchmark the electronic potential of the a3Π state and yield accurate values for the photon scattering rate and for the elements of the Franck–Condon matrix of the a3Π–X1Σ+ system. [ABSTRACT FROM AUTHOR]

It is generally not straightforward to apply molecular-thermodynamic theories to fluids with short-ranged attractive forces between their constituent molecules (or particles). This especially applies to perturbation theories, which, for short-ranged attractive fluids, typically must be extended to high order or may not converge at all. Here, we show that a recent first-order perturbation theory, the uv-theory, holds promise for describing such fluids. As a case study, we apply the uv-theory to a fluid with pair interactions defined by the Lennard-Jones spline potential, which is a short-ranged version of the LJ potential that is known to provide a challenge for equation-of-state development. The results of the uv-theory are compared to those of third-order Barker–Henderson and fourth-order Weeks–Chandler–Andersen perturbation theories, which are implemented using Monte Carlo simulation results for the respective perturbation terms. Theoretical predictions are compared to an extensive dataset of molecular simulation results from this (and previous) work, including vapor–liquid equilibria, first- and second-order derivative properties, the critical region, and metastable states. The uv-theory proves superior for all properties examined. An especially accurate description of metastable vapor and liquid states is obtained, which might prove valuable for future applications of the equation-of-state model to inhomogeneous phases or nucleation processes. Although the uv-theory is analytic, it accurately describes molecular simulation results for both the critical point and the binodal up to at least 99% of the critical temperature. This suggests that the difficulties typically encountered in describing the vapor–liquid critical region are only to a small extent caused by non-analyticity. [ABSTRACT FROM AUTHOR]

The complex absorbing potential equation-of-motion coupled-cluster (CAP-EOM-CC) method is routinely used to investigate metastable electronic states in small molecules. However, the requirement of evaluating eigenvalue trajectories presents a barrier to larger simulations, as each point corresponding to a different value of the CAP strength parameter requires a unique eigenvalue calculation. Here, we present a new implementation of CAP-EOM-CCSD that uses a subspace projection scheme to evaluate resonance positions and widths at the overall cost of a single electronic structure calculation. We analyze the performance of the projected CAP-EOM-CC scheme against the conventional scheme, where the CAP is incorporated starting from the Hartree–Fock level, for various small and medium sized molecules, and investigate its sensitivity to various parameters. Finally, we report resonance parameters for a set of molecules commonly used for benchmarking CAP-based methods, and we report estimates of resonance energies and widths for 1- and 2-cyanonaphtalene, molecules that were recently detected in the interstellar medium. [ABSTRACT FROM AUTHOR]

We have examined the structure of supercooled liquid D2O as a function of temperature between 185 and 255 K using pulsed laser heating to rapidly heat and cool the sample on a nanosecond timescale. The liquid structure can be represented as a linear combination of two structural motifs, with a transition between them described by a logistic function centered at 218 K with a width of 10 K. The relaxation to a metastable state, which occurred prior to crystallization, exhibited nonexponential kinetics with a rate that was dependent on the initial structural configuration. When the temperature is scaled by the temperature of maximum density, which is an isostructural point of the isotopologues, the structural transition and the non-equilibrium relaxation kinetics of D2O agree remarkably well with those for H2O. [ABSTRACT FROM AUTHOR]

Metastable phases of the photoswitchable molecular magnet K0.3Co[Fe(CN)6]0.77 ⋅ nH2O in sub-micrometer particles have been structurally investigated by synchrotron powder x-ray diffraction (PXRD) measurements. The K0.3Co[Fe(CN)6]0.77 ⋅ nH2O bulk compound (studied here with a sample having average particle size of 500 nm) undergoes a charge transfer coupled spin transition (CTCST), where spin configurations change between a paramagnetic CoII (S = 3/2) –FeIII (S = 1/2) high-temperature (HT) state and a diamagnetic CoIII (S = 0) –FeII (S = 0) low-temperature (LT) state. The bulk compound exhibits a unique intermediate (IM) phase, which corresponds to a mixture of HT and LT spin states that depend on the cooling rate. Several hidden metastable HT states emerge as a function of thermal and photo stimuli, namely: (1) a quench (Q) state generated from the HT state by flash cooling, (2) a LTPX state obtained by photoexcitation from the LT state derived by thermal relaxation from the Q state, and (3) an IMPX state accessed by photo-irradiation from the IM state. A sample with a smaller particle size, 135 nm, is investigated for which the particles are on the scale of the coherent LT domains in the IM phase within the larger 500 nm sample. PXRD studies under controlled thermal and/or optical excitations have clarified that the reduction of the particle size profoundly affects the structural changes associated with the CTCST. The unusual IM state is also observed as segregated domains in the 135 nm particle, but the collective structural transformations are more hindered in small particles. The volume change decreases to 2%–3%, almost half the value found for 500 nm particles (5%–8%), even though the linear thermal expansion coefficients are larger for the smaller particles. Furthermore, photoexcitation from the IM and LT states does not turn into single phases in the smaller particles, presumably because of the multiple interfaces and/or internal stress generated by the coexistence of small CoII–FeIII and CoIII–FeII domains in the lattice. Since the reduced particle size limits cooperativity and domain growth in the lattice, CTCST in the small particle sample becomes less sensitive to external stimuli. [ABSTRACT FROM AUTHOR]

Understanding the behavior of a complex gene regulatory network is a fundamental but challenging task in systems biology. How to reduce the large number of degrees of freedom of a specific network and identify its main biological pathway is the key issue. In this paper, we utilized the transition path theory (TPT) and Markov state modeling (MSM) framework to numerically study two typical cell fate decision processes: the lysis–lysogeny transition and stem cell development. The application of TPT to the lysis–lysogeny decision-making system reveals that the competitions of CI and Cro dimer binding play the major role in determining the cell fates. We also quantified the transition rates from the lysogeny to lysis state under different conditions. The overall computational results are consistent with biological intuitions but with more detailed information. For the stem cell developmental system, we applied the MSM to reduce the original dynamics to a moderate-size Markov chain. Further spectral analysis showed that the reduced system exhibits nine metastable states, which correspond to the refinement of the five known typical cell types in development. We further investigated the dominant transition pathways corresponding to the cell differentiation, reprogramming, and trans-differentiation. A similar approach can be applied to study other biological systems. [ABSTRACT FROM AUTHOR]

While the search for topological triplet-pairing superconductivity has remained a challenge, recent developments in optically stabilizing metastable superconducting states suggest a new route to realizing this elusive phase. Here, we devise a testable theory of competing superconducting orders that permits ultrafast switching to an opposite-parity superconducting phase in centrosymmetric crystals with strong spin-orbit coupling. Using both microscopic and phenomenological models, we show that dynamical inversion symmetry breaking with a tailored light pulse can induce odd-parity (spin triplet) order parameter oscillations in a conventional even-parity (spin singlet) superconductor, which when driven strongly can send the system to a competing minimum in its free energy landscape. Our results provide new guiding principles for engineering unconventional electronic phases using light, suggesting a fundamentally non-equilibrium route toward realizing topological superconductivity. S. Gassner et al. propose using light pulses to drive a centrosymmetric s-wave superconductor with strong spin-orbit coupling into a metastable triplet p-wave superconductor with non-trivial topology. The two superconducting orders must be closely competing in equilibrium and the light pulse must break a generalized, dynamic form of inversion symmetry. [ABSTRACT FROM AUTHOR]

Lithium- and manganese-rich layered oxide cathode materials have attracted extensive interest because of their high energy density. However, the rapid capacity fading and serve voltage decay over cycling make the waste management and recycling of key components indispensable. Herein, we report a facile concentrated solar radiation strategy for the direct recycling of Lithium- and manganese-rich cathodes, which enables the recovery of capacity and effectively improves its electrochemical stability. The phase change from layered to spinel on the particle surface and metastable state structure of cycled material provides the precondition for photocatalytic reaction and thermal reconstruction during concentrated solar radiation processing. The inducement of partial inverse spinel phase is identified after concentrated solar radiation treatment, which strongly enhances the redox activity of transition metal cations and oxygen anion, and reversibility of lattice structure. This study sheds new light on the reparation of spent cathode materials and designing high-performance compositions to mitigate structural degradation. Rapid capacity decay and voltage drop hinder lithium- and manganese-rich cathode material (LMRO) development. Here, the authors apply concentrated solar radiation arrays on cycled LMRO electrodes, inducing inverse spinel phase to boost redox activity and reversibility, yielding enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

The Guaymas Basin, Gulf of California is a hydrothermally active sediment-covered oceanic spreading center in the early stages of rifting. Hot-spring fluids were collected from its southern trough in 1998, 2003, and 2008 and analyzed for the concentration and isotopic composition of organic and inorganic aqueous species to assess subseafloor geochemical processes. Fluids discharged from the seafloor through hydrothermal edifices with measured temperatures of 91 to 317 °C. In general, fluids exiting larger structures were characterized by higher temperatures than fluids venting from smaller structures. Measured pH (25 °C) ranged from 5.7 to 7.1. Endmember fluids were characterized by near-zero concentrations of Mg and SO 4 , depletions in Na, and enrichments in K, Ca, and Cl relative to seawater, reflecting extensive interaction with sediment during circulation. Thermal maturation of sedimentary organic matter resulted in the addition of abundant ΣNH 4 +, ΣCO 2 , CH 4 , short-chain n -alkanes, and carboxylic acids to solution. Organic compounds added to fluids during recharge pass through high temperature deep-seated reaction zones and reach high levels of thermal maturity while others may be added by entrainment of lower temperature sedimentary pore fluids in hydrothermal upflow zones. The relative abundance of many organic compounds mobilized during hydrothermal alteration is consistent with metastable states of thermodynamic equilibrium that likely record subseafloor temperature conditions. The isotope composition of low molecular weight hydrocarbons and elevated concentrations of dissolved Cl suggest that temperatures may have exceeded the two-phase boundary for seawater and subsequently cooled before discharging at the seafloor. Periods of high temperature fluid-sediment or fluid-rock interaction followed by cooling may provide a mechanism for the aqueous mobilization and concentration of sulfide-forming metals in subseafloor mineral deposits. Fluid compositions have remained constant at the southern trough of Guaymas Basin for at least 26 years, indicating decadal stability in the physical and chemical conditions in subseafloor environments as well as the km-scale regional recharge zones containing unaltered sediment. [ABSTRACT FROM AUTHOR]

A central challenge in the study of intrinsically disordered proteins is the characterization of the mechanisms by which they bind their physiological interaction partners. Here, we utilize a deep learning–based Markov state modeling approach to characterize the folding-upon-binding pathways observed in a long timescale molecular dynamics simulation of a disordered region of the measles virus nucleoprotein NTAIL reversibly binding the X domain of the measles virus phosphoprotein complex. We find that folding-upon-binding predominantly occurs via two distinct encounter complexes that are differentiated by the binding orientation, helical content, and conformational heterogeneity of NTAIL. We observe that folding-upon-binding predominantly proceeds through a multi-step induced fit mechanism with several intermediates and do not find evidence for the existence of canonical conformational selection pathways. We observe four kinetically separated native-like bound states that interconvert on timescales of eighty to five hundred nanoseconds. These bound states share a core set of native intermolecular contacts and stable NTAIL helices and are differentiated by a sequential formation of native and non-native contacts and additional helical turns. Our analyses provide an atomic resolution structural description of intermediate states in a folding-upon-binding pathway and elucidate the nature of the kinetic barriers between metastable states in a dynamic and heterogenous, or “fuzzy”, protein complex. [ABSTRACT FROM AUTHOR]

The problem of computing the rate of diffusion-aided activated barrier crossings between metastable states is one of broad relevance in physical sciences. The transition path formalism aims to compute the rate of these events by analysing the statistical properties of the transition path between the two metastable regions concerned. In this paper, we show that the transition path process is a unique solution to an associated stochastic differential equation, with a discontinuous and singular drift term. The singularity arises from a local time contribution, which accounts for the fluctuations at the boundaries of the metastable regions. The presence of fluctuations at the local time scale calls for an excursion theoretic consideration of barrier crossing events. We show that the rate of such events, as computed from excursion theory, factorizes into a local time term and an excursion measure term, which bears empirical similarity to the transition state theory rate expression. Since excursion theory makes no assumption about the presence of a transition state in the potential energy landscape, the mathematical structure underlying this factorization ought to be general. We hence expect excursion theory (and local times) to provide some physical and mathematical insights in generic barrier crossing problems. [ABSTRACT FROM AUTHOR]

This study investigates the dynamic modeling of a spherical vapor bubble in an infinite liquid. Initially, the liquid is in a state of saturation, but then, there is a change in ambient pressure. Unlike previous studies that assumed vapor saturation, our model fully considers the metastable fluid state of subcooled vapor and superheated liquid. The theoretical model is based on the state equation of vapor and the kinetic theory of gases, allowing the visualization of the effects of superheating and subcooling on the bubble pressure and the phase transition rate. The accuracy of the numerical solutions for the bubble collapse and growth is confirmed by experimental results using water as the working fluid. Two approaches of heat transfer simplification are validated in the numerical solution, and an adhesion coefficient within the range of 0.1–1 is recommended for the calculation. Additionally, this study provides insights into how the metastable fluid state affects the bubble pressure and phase transition, especially in the early stages of bubble collapse. Furthermore, the conservation of vapor mass inside the bubble is also demonstrated. [ABSTRACT FROM AUTHOR]

Aggregation‐induced emission (AIE) is a phenomenon where a molecule that is weakly or non‐luminescent in a diluted solution becomes highly emissive when aggregated. AIE luminogens (AIEgens) hold promise in diverse applications like bioimaging, chemical sensing, and optoelectronics. Investigation in AIE luminescence is also critical for understanding aggregation kinetics as the aggregation process is an essential component of AIE emission. Experimental investigation of AIEgen aggregation is challenging due to the fast timescale of the aggregation and the amorphous aggregate structures. Computer simulations such as molecular dynamics (MD) simulation provide a valuable approach to complement experiments with atomic‐level knowledge to study the fast dynamics of aggregation processes. However, individual simulations still struggle to systematically elucidate heterogeneous kinetics of the formation of amorphous AIEgen aggregates. Kinetic network models (KNMs), constructed from an ensemble of MD simulations, hold great potential in addressing this challenge. In these models, dynamic processes are modeled as a series of Markovian transitions occurring among metastable conformational states at discrete time intervals. In this perspective article, we first review previous studies to characterize the AIEgen aggregation kinetics and their limitations. We then introduce KNMs as a promising approach to elucidate the complex kinetics of aggregations to address these limitations. More importantly, we discuss our perspective on linking the output of KNMs to experimental observations of time‐resolved AIE luminescence. We expect that this approach can validate the computational predictions and provide great insights into the aggregation kinetics for AIEgen aggregates. These insights will facilitate the rational design of improved AIEgens in their applications in biology and materials sciences. [ABSTRACT FROM AUTHOR]

Proposed as initial activation experiments for photonuclear research with -quanta at energies MeV are those using a source of backward Compton scattered laser radiation on accelerated electrons, which is currently under development. These experiments are crucial both for refining the techniques of tuning and monitoring such -beams, and for investigating the excitation of pygmy and giant resonances in nuclei at near the threshold of the () reactions, as well as the multiplicity of photoneutrons during the de-excitation of E1 giant resonances at above the threshold of the () reactions. [ABSTRACT FROM AUTHOR]

We combine synchrotron-based infrared absorption and Raman scattering spectroscopies with diamond anvil cell techniques and first-principles calculations to explore the properties of hafnia under compression. We find that pressure drives HfO2:7%Y from the mixed monoclinic (P21=c) + antipolar orthorhombic (Pbca) phase to pure antipolar orthorhombic (Pbca) phase at approximately 6.3 GPa. This transformation is irreversible, meaning that upon release, the material is kinetically trapped in the Pbca metastable state at 300 K. Compression also drives polar orthorhombic (Pca21) hafnia into the tetragonal (P42=nmc) phase, although the latter is not metastable upon release. These results are unified by an analysis of the energy landscape. The fact that pressure allows us to stabilize targeted metastable structures with less Y stabilizer is important to preserving the flat phonon band physics of pure HfO2. [ABSTRACT FROM AUTHOR]

The interplay between superconductivity and magnetism has been a subject of significant interest for decades. While extensive research has focused on modifying the superconducting state through a magnetic domain as an independent variable, the manipulation of magnetic domains by the superconducting state has been relatively unexplored, primarily due to their higher stiffness compared to the energy associated with superconducting vortices. In this Letter, we demonstrate the manipulation of magnetic domains by thermally activated superconducting vortices in a ferromagnet/superconductor hybrid. We observe a reversible domain transition between metastable magnetic stripes and bubbles in a Nb/CeRu2Ga2B hybrid induced by vortex motion and the trapped field within the Nb superconducting film. The comparable Curie and superconducting critical temperatures and the presence of magnetic metastable states enable the magnetic domain changes driven by superconducting vortices in this hybrid system. [ABSTRACT FROM AUTHOR]

Absorption of stellar X-ray and extreme ultraviolet (EUV) radiation in the upper atmosphere of close-in exoplanets can give rise to hydrodynamic outflows, which may lead to the gradual shedding of their primordial light element envelopes. Excess absorption by neutral helium atoms in the metastable 23S state [He I(2 3S)], at ~10 830 Å, has recently emerged as a viable diagnostic of atmospheric escape. Here we present a public add-on module to the 1D photoionization hydrodynamic code ATES, designed to calculate the He I(2 3S) transmission probability for a broad range of planetary parameters. By relaxing the isothermal outflow assumption, the code enables a self-consistent assessment of the He I(2 3S) absorption depth along with the atmospheric mass-loss rate and the outflow temperature profile, which strongly affects the recombination rate of He II into He I(2 3S). We investigate how the transit signal can be expected to depend upon known system parameters, including host spectral type, orbital distance, and planet gravity. At variance with previous studies, which identified K-type stars as favorable hosts, we conclude that late M dwarfs with Neptune-sized planets orbiting at ~0.05–0.1 AU can be expected to yield the strongest transit signal, well in excess of 30% for near-cosmological He-to-H abundances. More generally, we show that the physics that regulates the population and depletion of the metastable state, combined with geometrical effects, can yield somewhat counterintuitive results, such as a nonmonotonic dependence of the transit depth on orbital distance. These are compounded by a strong degeneracy between the stellar EUV flux intensity and the atmospheric He-to-H abundance, both of which are highly uncertain. Compared with spectroscopy data, now available for over 40 systems, our modeling suggests either that a large fraction of the targets have helium-depleted envelopes or that the input stellar EUV spectra are systematically overestimated. The updated code and transmission probability module are available publicly as an online repository. [ABSTRACT FROM AUTHOR]

Photochemistry can significantly affect the ionospheric status. Adopting a comprehensive photochemical scheme with 60 reactions, primarily based on the recent systematic study of ion chemistry by Richards in 2011, we revised the open-source SAMI2 (Sami2 is another model of the ionosphere) model to SAMI2−ph. The scheme includes both ground state and metastable/vibrational excited compositions (e.g., N(2D), N2(ν), and O2(ν)) and associated reactions, which can remarkably affect the ionospheric electron density. The model accuracy is tested using the most widely used ionospheric data foF2 derived from mid-latitude ionosonde stations. The correlation coefficients are larger for SAMI2−ph than for SAMI2. In addition, the linear slope k is significantly closer to 1 than the default run for the NmF2 comparisons. The smaller RMSE and b indicate that the modified model provides a reasonably good match with the ionosonde NmF2 measurements. The above results demonstrate that the model with the chosen photochemical scheme performs better than the original SAMI2 at mid-latitude. [ABSTRACT FROM AUTHOR]

Topologically non-trivial magnetization configurations in ferromagnetic materials on the nanoscale, such as hopfions, skyrmions, and vortices, have attracted considerable attention of researchers during the last few years. In this article, by applying the theory of micromagnetism, I demonstrate that the toroidal hopfion magnetization configuration is a metastable state of a thick cylindrical ferromagnetic nanodot or a nanowire of a finite radius. The existence of this state is a result of the competition among exchange, magnetostatic, and magnetic anisotropy energies. The Dzyaloshinskii–Moriya exchange interaction and surface magnetic anisotropy are of second importance for the hopfion stabilization. The toroidal hopfion metastable magnetization configuration may be reached in the process of remagnetizing the sample by applying an external magnetic field along the cylindrical axis. [ABSTRACT FROM AUTHOR]

Stochastic systems often exhibit multiple viable metastable states that are long-lived. Over very long timescales, fluctuations may push the system to transition between them, drastically changing its macroscopic configuration. In realistic systems, these transitions can happen via multiple physical mechanisms, corresponding to multiple distinct transition channels for a pair of states. In this paper, we use the fact that the transition path ensemble is equivalent to the invariant measure of a gradient flow in pathspace, which can be efficiently sampled via metadynamics. We demonstrate how this pathspace metadynamics, previously restricted to reversible molecular dynamics, is in fact very generally applicable to metastable stochastic systems, including irreversible and time-dependent ones, and allows rigorous estimation of the relative probability of competing transition paths. We showcase this approach on the study of a stochastic partial differential equation describing magnetic field reversal in the presence of advection. [ABSTRACT FROM AUTHOR]

Our goal in this work is to better understand the relationship between replica symmetry breaking, shattering, and metastability. To this end, we study the static and dynamic behaviour of spherical pure p‐spin glasses above the replica symmetry breaking temperature Ts$T_{s}$. In this regime, we find that there are at least two distinct temperatures related to non‐trivial behaviour. First we prove that there is a regime of temperatures in which the spherical p‐spin model exhibits a shattering phase. Our results holds in a regime above but near Ts$T_s$. We then find that metastable states exist up to an even higher temperature TBBM$T_{BBM}$ as predicted by Barrat–Burioni–Mézard which is expected to be higher than the phase boundary for the shattering phase Td