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Autocatalytic chemical networks play a predominant role in a large number of natural systems such as in metabolic pathways and in ecological networks. Despite recent efforts, the precise impact of thermodynamic constraints on these networks remains elusive. In this work, we present a theoretical framework that allows specific bounds on the thermodynamic affinity and on the concentrations of autocatalysts in mass-action autocatalytic networks. These bounds can be obtained solely from the stoichiometry of the underlying chemical reaction network, and are independent from the numerical values of kinetic parameters. This property holds in the specific regime where all the fluxes of the network are tightly coupled and maximal. Our method is applicable to large networks, and can be used to complement constraints-based modeling methods of metabolic networks, which typically do not provide predictions about thermodynamic properties or concentration ranges of metabolites. Autocatalytic chemical networks are crucial in natural systems like metabolic pathways and ecological networks. This study presents a framework to find bounds on thermodynamic affinity and autocatalyst concentrations using stoichiometry, enhancing our understanding of these networks' behavior without relying on kinetic parameters. [ABSTRACT FROM AUTHOR]

A fundamental question associated with chirality is how mixtures containing equal amounts of interconverting enantiomers can spontaneously convert to systems enriched in only one of them. Enantiomers typically have similar chemical properties, but can exhibit distinct reactivity under specific conditions, and these differences can be used to bias the system's composition in favor of one enantiomer. Transport properties are also expected to differ for enantiomers in chiral solvents, but the role of such differences in chiral symmetry breaking has not been clarified yet. In this work, we develop a theoretical framework to show that asymmetry in diffusion properties can trigger a spontaneous and selective symmetry breaking in mixtures of enantiomers. We derive a generic evolution equation for the enantiomeric excess in a chiral solvent. This equation shows that the relative stability of homochiral domains is dictated by the difference of diffusion coefficients of the two enantiomers. Consequently, deracemization toward a specific enantiomeric excess can be achieved when this difference is large enough. These results hold significant implications for our understanding of chiral symmetry breaking. [ABSTRACT FROM AUTHOR]

The construction of hypothetical environments to produce organic molecules such as metabolic intermediates or amino acids is the subject of ongoing research into the emergence of life. Experiments specifically focused on an anabolic approach typically rely on a mineral catalyst to facilitate the supply of organics that may have produced prebiotic building blocks for life. Alternatively to a true catalytic system, a mineral could be sacrificially oxidized in the production of organics, necessitating the emergent 'life' to turn to virgin materials for each iteration of metabolic processes. The aim of this perspective is to view the current 'metabolism‐first' literature through the lens of materials chemistry to evaluate the need for higher catalytic activity and materials analyses. While many elegant studies have detailed the production of chemical building blocks under geologically plausible and biologically relevant conditions, few appear to do so with sub‐stoichiometric amounts of metals or minerals. Moving toward sub‐stoichiometric metals with rigorous materials analyses is necessary to demonstrate the viability of an elusive cornerstone of the 'metabolism‐first' hypotheses: catalysis. We emphasize that future work should aim to demonstrate decreased catalyst loading, increased productivity, and/or rigorous materials analyses for evidence of true catalysis. [ABSTRACT FROM AUTHOR]

The behaviour of a Frank-like chemical network model featuring autocatalytic production of chiral enantiomers from achiral reactants is studied numerically in 1D and 2D systems using fluctuating initial conditions and accounting for diffusion processes. Our results reveal that the achiral substrate concentration can play an ambivalent role. It is shown that when the achiral reactant concentration is maintained constant and homogeneous in 1D systems, global homochirality is not systematically reached when the size of the system or the achiral reactant concentration are increased. However, with a fixed concentration gradient, coexisting homochiral domains of opposite handedness are no longer observed and homogeneous homochirality, i.e. the presence of a single stable homochiral domain, is recovered. In 2D systems, reaching global homochirality is just a matter of time. This time is dramatically increased when insufficient or excessive amount of achiral reactant is used. An optimal amount of achiral material is observed to maximise the enantiomer production rates. [ABSTRACT FROM AUTHOR]

In this paper, we study the emergence of spatiotemporal chaos from mixed-mode oscillations, by using an extended Oregonator model. We show that bursting dynamics consisting of fast/slow mixed mode oscillations along a single attractor can lead to spatiotemporal chaotic dynamics, although the spatially homogeneous solution is itself non-chaotic. This behavior is observed far from the Hopf bifurcation and takes the form of a spatiotemporal intermittency where the system locally alternates between the fast and the slow phases of the mixed mode oscillations. We expect this form of spatiotemporal chaos to be generic for models in which one or several slow variables are coupled to activator-inhibitor type of oscillators. [ABSTRACT FROM AUTHOR]

We study a numerical closure approach for systems of chemical reacting systems on lattices with low-dimensional support, for which a mean-field approximation is insufficiently accurate because of lateral interaction on the lattice. We introduce a hierarchy of macroscopic state variables, taking particle clusters into account, whose time evolution is obtained via microscopic (kinetic Monte Carlo) simulation. The macroscopic state variables are chosen such that can be straightforwardly conserved during reconstruction of a microscopic configuration (the so-called lifting step). We present and compare the effects of different alternatives to initialize the remaining degrees of freedom. We illustrate the strong interplay between the number of macroscopic state variables and the specifics of the lifting and that, for a given lifting operator, accuracy of the macroscopic dynamics does not necessarily improve monotonically when adding macroscopic state variables. [ABSTRACT FROM AUTHOR]

We studied the catalytic NO2(g) + H2(g)/Pt system on model platinum catalysts with nanoscale spatial resolution by means of field emission microscopy (FEM). While the surface of the catalyst is in a non-reactive state at low H2 partial pressure, bursts of activity are observed when increasing this parameter. These kinetic instabilities subsequently evolve towards self-sustained periodic oscillations for a wide range of pressures. Combining time series analyses and numerical simulations of a simple reaction model, we clarify how these observations fit in the traditional classification of dynamical systems. In particular, reconstructions of the probability density around oscillating trajectories show that the experimental system defines a crater-like structure in probability space. The experimental observations thus correspond to a noise-perturbed limit cycle emerging from a nanometric reactive system. This conclusion is further supported by comparison with stochastic simulations of the proposed chemical model. The obtained results and simulations pave the way towards a better understanding of reactive nanosystems. [ABSTRACT FROM AUTHOR]

An extension of classical irreversible thermodynamics pioneered by Ilya Prigogine is developed, in which fluctuations of macroscopic observables accounting for microscopic-scale processes are incorporated. The contribution of the fluctuations to the entropy production is derived from a generalized entropy balance equation and expressed in terms of the fluctuating variables, via an extended local equilibrium Ansatz and in terms of the probability distributions of these variables. The approach is illustrated on reactive systems involving linear and nonlinear steps, and the role of the distance from equilibrium and of the nonlinearities is assessed. [ABSTRACT FROM AUTHOR]

The photosensitive Belousov–Zhabotinsky (pBZ) reaction has been used extensively to study the properties of chemical oscillators. In particular, recent experiments revealed the existence of complex spatiotemporal dynamics for systems consisting of coupled micelles (V ＜ 10−21 L) or droplets (V≈ [10−8–10−11] L) in which the pBZ reaction takes place. These results have been mostly understood in terms of reaction–diffusion models. However, in view of the small size of the droplets and micelles, large fluctuations of concentrations are to be expected. In this work, we investigate the role of fluctuations on the dynamics of a single droplet with stochastic simulations of an extension of the Field–Körös–Noyes (FKN) model taking into account the photosensitivity. The birhythmicity and chaotic behaviors predicted by the FKN model in the absence of fluctuations become transient or intermittent regimes whose lifetime decreases with the size of the droplet. Simple oscillations are more robust and can be observed even in small systems (V ＞ 10−12 L), which justifies the use of deterministic models in microfluidic systems of coupled oscillators. The simulations also reveal that fluctuations strongly affect the efficiency of inhibition by light, which is often used to control the kinetics of these systems: oscillations are found for parameter values for which they are supposed to be quenched according to deterministic predictions. [ABSTRACT FROM AUTHOR]

A stochastic thermodynamics of Brownian motion is set up in which state functions are expressed in terms of state variables through the same relations as in classical irreversible thermodynamics, with the difference that the state variables are now random fields accounting for the effect of fluctuations. Explicit expressions for the stochastic analog of entropy production and related quantities are derived for a dilute solution of Brownian particles in a fluid of light particles. Their statistical properties are analyzed and, in the light of the insights afforded, the thermodynamics of a single Brownian particle is revisited and the status of the second law of thermodynamics is discussed. [ABSTRACT FROM AUTHOR]

In this work, we reconstruct and analyze the micrometeorological dynamics of the transitional forest located south of the Amazon basin. For this, we use time series of micrometeorological variables collected over five years in the transitional forest of Mato Grosso (Brazil). We employ local feature analysis, a recently proposed extension of principal component analysis, to extract the most relevant physical variables from this set. We show in this way that temperature records contain most of the dynamical information in all seasons. Based on this result, the dimensionality of the space spanned by the system's dynamics and the properties of the so defined attractors are obtained. In the dry season, the system presents a robust oscillatory character described by a well-defined limit cycle. In the wet season, the dynamics becomes more irregular but can still be seen as a periodic behavior affected by external noise. These results can help to develop accurate models for the meteorology of the Amazonian transitional forest and can thus lead to a better understanding of this important ecosystem. [ABSTRACT FROM AUTHOR]

In this paper, we show that the Gray-Scott model is able to produce defect-mediated turbulence. This regime emerges from the limit cycle, close or far from the Hopf bifurcation, but always right before the Andronov homoclinic bifurcation of the homogeneous system. After this bifurcation, as the control parameter is further changed, the system starts visiting more and more frequently the stable node of the model. Consequently, the defect-mediated turbulence gradually turns into spatiotemporal intermittency. [ABSTRACT FROM AUTHOR]

This paper studies the spatiotemporal dynamics of a reaction-diffusion-advection system corresponding to an extension of the Oregonator model, which includes two inhibitors instead of one. We show that when the reaction-diffusion, two-dimensional problem displays stationary patterns the addition of a plug flow can induce the emergence of new types of stationary structures. These patterns take the form of spots or arcs, the size and the spacing of which can be controlled by the flow. [ABSTRACT FROM AUTHOR]