Non-equilibrium Reactions Research Articles

Inverse Power Law Scaling of Energy Dissipation Rate in Nonequilibrium Reaction Networks.

The energy dissipation rate in a nonequilibrium reaction system can be determined by the reaction rates in the underlying reaction network. By developing a coarse-graining process in state space and a corresponding renormalization procedure for reaction rates, we find that energy dissipation rate has an inverse power-law dependence on the number of microscopic states in a coarse-grained state. The dissipation scaling law requires self-similarity of the underlying network, and the scaling exponent depends on the network structure and the probability flux correlation. Existence of the inverse dissipation scaling law is shown in realistic biochemical systems such as biochemical oscillators and microtubule-kinesin active flow systems.

Pattern Recognition of Chemical Waves: Finding the Activation Energy of the Autocatalytic Step in the Belousov-Zhabotinsky Reaction.

The Belousov–Zhabotinsky (BZ) reaction is an example of a homogeneous, nonequilibrium reaction used commonly as a model for the study of biological structure and morphogenesis. We report the experimental effects of temperature on spontaneously nucleated trigger waves in a quasi-two-dimensional BZ reaction–diffusion system, conducted isothermally at temperatures between 9.9 and 43.3 °C. Novel application of filter-coupled circle finding and localized pattern analysis is shown to allow the highly accurate extraction of average radial wave velocity and nucleation period. Using this, it is possible to verify a strong Arrhenius dependence of average wave velocity with temperature, which is used to find the effective activation energy of the reaction in accordance with predictions elaborated from the widely used Oregonator model of the BZ reaction. On the basis of our experimental results and existing theoretical models, the value for activation energy of the important self-catalyzed step in the Oregonator model is determined to be 86.58 ± 4.86 kJ mol–1, within range of previous theoretical prediction.

Nonthermal and selective crystal bridging of ZnO grains by irradiation with electron beam as nonequilibrium reaction field.

Ceramic particles, such as titanium oxide and indium tin oxide, are expected to be used as electric or catalytic materials for various applications. In this work, we progressed to employ the irradiation with an electron beam as the nonequilibrium reaction field for ceramic composition, and we successfully obtained the basic technology for a ceramic thin-film fabrication using a field emission (FE) electron beam with low energy resolution having a half width under 100 meV that had a homogeneous planar electron emission as the nonequilibrium reaction field. In particular, ZnO particles synthesized by electron beam irradiation show selective crystal bridging along the c-axis during FE electron beam irradiation, which is important for synthesizing poly-ZnO crystals without a heating process, because the energy fluctuations of FE electron beams are small and affect the directionality of ZnO crystal growth along the c-axis. This accomplishment may make a significant contribution to the analysis of the formation mechanism of ZnO particles with a uniform morphology and crystal structure by the FE electron beam during the crystallization. Moreover, we will be able to provide basic elements for next-generation nanodevices with highly functional properties by controlling each terminal crystal interface of metals, ceramics, and semiconductors with this technique.

Turbulent flow with nonequilibrium chemical reaction in single snorkel RH

PurposeThe reported mathematical models of gas–liquid flow in single snorkel Rheinstahl–Heraeus (SSRH) are based on the assumption of steady Ar-molten steel flow. The purpose of this paper is to develop a mathematical model to describe the unsteady turbulent flow (CO-Ar-molten steel) with nonequilibrium decarburization reaction.Design/methodology/approachOn the base of the finite volume method, the computational fluid dynamics software CFX is used to predict the unsteady fluid flow, the spatial distributions of CO/argon gas and carbon element. The water model experiment and the industrial experiment are carried out to verify the mathematical models.FindingsA two-way coupling model (T-WCM) based on algebraic slip model is developed to investigate the coupling phenomena. The related results show that T-WCM is more rigorous and accurate than one-way coupling model in predicting carbon content of molten steel. The amount of CO gas, which can enhance turbulent flow and mass transfer, is about three times the argon gas blown into SSRH.Originality/valueCO gas is the key factor in investigating the transport phenomena. This study fully reveals the truth about the unsteady gas-liquid flow in SSRH. It is necessary to adopt T-WCM based on algebraic slip model to describe the CO-Ar-molten steel flow phenomenon.

Emergence of homochirality in large molecular systems

The selection of a single molecular handedness, or homochirality across all living matter, is a mystery in the origin of life. Frank's seminal model showed in the '50s how chiral symmetry breaking can occur in nonequilibrium chemical networks. However, an important shortcoming in this classic model is that it considers a small number of species, while there is no reason for the prebiotic system, in which homochirality first appeared, to have had such a simple composition. Furthermore, this model does not provide information on what could have been the size of the molecules involved in this homochiral prebiotic system. Here, we show that large molecular systems are likely to undergo a phase transition toward a homochiral state, as a consequence of the fact that they contain a large number of chiral species. Using chemoinformatics tools, we quantify how abundant chiral species are in the chemical universe of all possible molecules of a given length. Then, we propose that Frank's model should be extended to include a large number of species, in order to possess the transition toward homochirality, as confirmed by numerical simulations. Finally, using random matrix theory, we prove that large nonequilibrium reaction networks possess a generic and robust phase transition toward a homochiral state.

Energy transfer along Müller cell intermediate filaments isolated from porcine retina: I. Excitons produced by ADH1A dimers upon simultaneous hydrolysis of two ATP molecules

IR exciton propagation was explored in Müller cell (MC) intermediate filaments (IFs) filling a capillary matrix. These IFs have been isolated from porcine retina using different methods, while their properties were almost identical. Therefore, IFs isolated from the whole retinas were used presently. IR excitons were generated by IR radiation at 2 μm wavelength, or by enzymatic ATP hydrolysis, with the energy transferred to IFs. Excitons produced by ATP hydrolysis required simultaneous energy contribution of two ATP molecules, indicating simultaneous hydrolysis of two ATP molecules in the naturally dimeric human alcohol dehydrogenase enzyme (ADH1A). ATP hydrolysis was thus catalyzed by ADH1A…NAD+ enzymatic complexes absorbed at the IF extremities protruding out of the capillary matrix. The IR emission spectra of excitons were dependent on the exciton generation method. We believe this resulted from the exciton energy distribution varying in function of the generation method used. The latter seems reasonable, given the very long excited-state lifetimes, implying low nonradiative relaxation rates. The energy liberated by ATP hydrolysis has been measured directly in these experiments, for the first time. The results demonstrate that contrary to the predictions of equilibrium thermodynamics, the liberated energy is independent on the ATP/ADP concentration ratio, indicating that non-equilibrium reactions take place. Time-resolved experiments with excitons produced by pulsed IR radiation evaluated characteristic exciton propagation and emission times. For the first time, biexcitonic processes were observed in biological objects, whereby simultaneous hydrolysis of two ATP molecules bound to the same dimeric ADH1A molecule generated excitons carrying twice the energy liberated by hydrolysis of a single ATP molecule. The results reported indicate that ATP-liberated energy may be transmitted along natural polypeptide nanofibers in vivo, within and between live cells. These ideas could promote new understanding of the biophysics of life.

Microfluidic enhancement of self-assembly systems.

Dynamic, kinetically-controlled, self-assembly processes are commonly observed in nature and are capable of creating intricate, functional architectures from simple precursors. However, notably, much of the research into molecular self-assembly has been performed using conventional bulk techniques where the resultant species are dictated by thermodynamic stability to yield relatively simple assemblies. Whereas, the environmental control offered by microfluidic systems offers methods to achieve non-equilibrium reaction conditions capable of increasingly sophisticated self-assembled structures. Alterations to the immediate microenvironment during the assembly of the molecules is possible, providing the basis for kinetically-controlled assembly. This review examines the key mechanism offered by microfluidic systems and the architectures required to access them. The mechanisms include diffusion-led mixing, shear gradient alignment, spatial and temporal confinement, and structural templates in multiphase systems. The works are selected and categorised in terms of the microfluidic approaches taken rather than the chemical constructs which are formed.

Nanometer-Thick Crystalline Carbon Films Having a Spinel Structure Grown on ZnO Substrates: Implications for New Ceramic–Carbon Composition

I developed a bottom-up process of crystal growth using a field emission (FE) electron beam without transfer of heat energy. In this study, highly crystalline single-walled carbon nanotubes were used as the FE electron source. Acetylene was irradiated with an electron beam of high-resolution energy emitted from the electron source. Then, zinc oxide (ZnO) was irradiated with the carbon-based ions dissociated from the acetylene and electron beam, which formed a nonequilibrium excitation reaction field. As a result, a crystalline carbon thin film with a spinel-like structure different from the structures of graphite and diamond was grown on the ZnO surface. It is considered that the carbon film can be formed on substrates with a periodic crystal structure, not only ZnO. I confirmed that a carbon film with a periodic crystal structure independent of the crystal structure of the underlying substrate was grown, which bridged with the substrate. Thus, I have established a technique of crystal bridging between a ceramic and carbon for the first time to the best of our knowledge.

Insights into the Reversible Redox Pathways in Lithium-Sulfur Batteries By in Situ AFM-SECM Coupled Raman Spectroscopy

Among many emerging energy storage systems, lithium-sulfur (Li-S) is the most sought-after technology due to its high energy density (2600 Wh/kg) and low cost.(1) However, its performance is guided by highly complex and non-equilibrium conversion reactions of several sulfur intermediates, known as lithium polysulfides (LiPS), along with solid-liquid-solid phase transformations at the cathode surface. Such Li-S batteries often face formidable challenges like rapid capacity fade, sluggish reaction kinetics, short cycle life, and poor coulombic efficiency(2). In spite of some success in mitigating these issues by employing a variety of cathode surface modifications(3, 4), the fundamental understanding of LiPS reaction pathways towards discharge end-products and their relation to the cathode surface are still not well established. It is commonly believed that the morphology, composition and physio-chemical characteristics of the discharge products can be closely correlated to the deteriorating performance issues like internal resistance buildup and capacity fade in Li-S cell(5-7). Herein, we provide mechanistic perspectives of the substrate guided reaction pathways of LiPS and their correlation to redox activity of discharge end products using in situ atomic force microscopy-based scanning electrochemical microscopy (AFM-SECM) coupled Raman spectroscopy at a high spatiotemporal resolution. With a detailed spectro-electrochemical and morphological mapping, we decipher the substrate-dependent charge/discharge end product’s formation and their effect on redox processes in the subsequent cycles.

Interstellar Formation of Biorelevant Pyruvic Acid (CH3COCOOH)

<h2>Summary</h2> Pyruvic acid represents a key molecule in prebiotic chemistry to form metabolites and amino acids. Without liquid water on the early Earth, endogenous formation of pyruvic acid is unlikely, and an exogenous delivery constitutes an appealing alternative. However, despite the detection of more than 200 molecules in space, pyruvic acid is elusive. Here, we describe its formation by barrierless recombination of hydroxycarbonyl (HOCO⋅) and acetyl (CH₃CO⋅) radicals in ices of acetaldehyde (CH₃CHO) and carbon dioxide (CO₂) modeling interstellar conditions driven by cosmic rays. Exploiting isotopically labeled ices and photoionization reflectron time-of-flight mass spectrometry, the reaction products were selectively photoionized in the temperature-programmed desorption phase and isomers discriminated based on their ionization energies. This reveals a key reaction pathway for pyruvic acid synthesis through non-equilibrium reactions in interstellar cold molecular clouds and star-forming regions, thus offering a unique entry point to abiotic organic synthesis in deep space.

Radiative feedback for supermassive star formation in a massive cloud with H2 molecules in an atomic-cooling halo

ABSTRACT Recent three-dimensional cosmological simulations of protogalaxy formation have suggested that supermassive stars (SMSs) can form in gas clouds in which H2 cooling is suppressed by dynamical heating prior to the activation of atomic cooling, but they stopped short of the following growth of a central protostar. Here, we examine whether accretion on the protostellar core in this cloud is sufficiently rapid, in the face of the radiation feedback, to produce an SMS. We perform one-dimensional radiation-hydrodynamical simulations of the hot collapsing cloud with non-equilibrium chemical reactions directly adopting the cloud properties from Wise et al. as an initial condition. We find that the stellar Lyman–Werner (LW) radiation from the SMS dissociates H2 in the inner regions of the gas flow, increasing gas temperature and thermal pressure, and temporarily stopping the accretion. However, this negative feedback ceases when the self-gravity and inward ram pressure force on larger scales push the gas inwards. The central protostar is unable to expand an H ii region due to the high density, and grows to a mass of ${\gtrsim}10^5\, {\rm M}_{\odot }$. Our results suggests the successful formation of SMSs, and resulting massive (${\sim}10^5\, {\rm M}_{\odot }$) remnant black holes in the clouds, but need to be confirmed in two- or three-dimensional simulations.

La2Ga3O7.5: A Metastable Ternary Melilite with a Super-Excess of Interstitial Oxide Ions Synthesized by Direct Crystallization of the Melt

The La1+xAE1-xGa3O7+x/2 melilite family (AE = Ca, Sr, Ba, and 0 0.65 with very high Oint concentrations (referred to here as compositions) have the potential to support correspondingly high ionic conductivities, but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here we report that fully-substituted La2Ga3O7.5 (x = 1) melilite ceramics can be synthesized by direct crys-tallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S.cm-1 at 800 °C, three orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7, and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S.cm-1). It crystallizes in an orthorhombic √2a x √2a x 2c expansion of the parent melilite cell, in space group Ima2, with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D melilite framework, which appears to be an incipient feature of previously reported partially-ordered melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended com-positional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.

Process Intensification through Directly Coupled Autothermal Operation of Chemical Reactors

Summary Autothermal operation of a chemical reactor involves coupling exothermic and endothermic chemical reactions for the purpose of thermal management without resorting to external energy sinks or sources. Often this is accomplished through regenerative or recuperative heat exchange between spatially or temporally separated exothermic and endothermic reactions. However, it is also possible to directly couple these reactions simultaneously within the same reactor volume, eliminating the heat-transfer bottleneck that characterizes much of chemical manufacture. It is not widely recognized that directly coupled autothermal operation allows dramatic process intensification. This perspective defines autothermal operation and contrasts it with conventional heat transfer for thermal management of chemical processes. The intensification and cost savings that can be achieved are quantified, and the implications to modular chemical process intensification are presented. Guidelines are proposed for designing directly coupled autothermal processes. Diverse examples are presented. Several challenges to expanding the field are critically discussed.

Enzyme activities predicted by metabolite concentrations and solvent capacity in the cell.

Experimental measurements or computational model predictions of the post-translational regulation of enzymes needed in a metabolic pathway is a difficult problem. Consequently, regulation is mostly known only for well-studied reactions of central metabolism in various model organisms. In this study, we use two approaches to predict enzyme regulation policies and investigate the hypothesis that regulation is driven by the need to maintain the solvent capacity in the cell. The first predictive method uses a statistical thermodynamics and metabolic control theory framework while the second method is performed using a hybrid optimization–reinforcement learning approach. Efficient regulation schemes were learned from experimental data that either agree with theoretical calculations or result in a higher cell fitness using maximum useful work as a metric. As previously hypothesized, regulation is herein shown to control the concentrations of both immediate and downstream product concentrations at physiological levels. Model predictions provide the following two novel general principles: (1) the regulation itself causes the reactions to be much further from equilibrium instead of the common assumption that highly non-equilibrium reactions are the targets for regulation; and (2) the minimal regulation needed to maintain metabolite levels at physiological concentrations maximizes the free energy dissipation rate instead of preserving a specific energy charge. The resulting energy dissipation rate is an emergent property of regulation which may be represented by a high value of the adenylate energy charge. In addition, the predictions demonstrate that the amount of regulation needed can be minimized if it is applied at the beginning or branch point of a pathway, in agreement with common notions. The approach is demonstrated for three pathways in the central metabolism of E. coli (gluconeogenesis, glycolysis-tricarboxylic acid (TCA) and pentose phosphate-TCA) that each require different regulation schemes. It is shown quantitatively that hexokinase, glucose 6-phosphate dehydrogenase and glyceraldehyde phosphate dehydrogenase, all branch points of pathways, play the largest roles in regulating central metabolism.

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Ro-vibrationally excited molecules of deuterium are involved in non-equilibrium chemical reactions in divertor region of tokamak (see molecular assisted recombination) or in neutral beam injector to produce negative ion (see dissociative electron attachment) for fusion plasmas. These molecules produced both in a plasma volume and on surfaces are no longer in their electronic ground state X1∑g+(v”⩾0,J”) and populate non-uniformly different vibrational (v″) and rotational levels (J″). The high resolution VUV Fourier Transform spectrometer of the DESIRS beam line (SOLEIL synchrotron) is applied to directly scrutinize the ro-vibrationally excited levels of the D2 ground state from v″ = 0 to 10 and J″ up to 8 in an electron cyclotron resonance (ECR) cold plasma. This is performed for different plasma-facing materials, i.e. quartz, tantalum, tungsten, and stainless steel, in order to compare their relative impact in molecular excitation through recombinative desorption from surfaces. A significant effect of these materials on the absolute distribution of the vibrationally states has been found above v″ > 3. The experimental detection limit for Quartz is v″ = 7 whereas tungsten and stainlees steel excite the molecules up to v″ = 9 and tantalum up to v″ = 10. The use of a bare, temperature-controlled surface of Quartz as a reference, compared to metallic surfaces, allows us to determine the relative production of these excited levels. The recombinative desorption rate on tungsten and stainless steel compared to quartz is ~ 2.6 higher and reaches ~ 5 for tantalum.

The Nonequilibrium Back Reaction of Hawking Radiation to a Schwarzschild Black Hole

We investigate the nonequilibrium back reaction on the Schwarzschild black hole from the radiation field. The back reactions are characterized by the membrane close to the black hole. When the membrane is thin, we found that larger temperature difference can lead to more significant negative surface tension, larger thermodynamic dissipation cost, and back reaction in energy and entropy as well as larger black hole area. This may be relevant to the primordial black holes in early universe. Moreover, our nonequilibrium model can resolve the inconsistency issue of the black hole back reaction under zero mass limit in the equilibrium case. In the thick membrane case, the nonequilibrium back reaction is found to be more significant than that in the thin membrane case. The nonequilibrium temperature difference can increase the energy and entropy loss as well as the thermodynamic dissipation of the black hole and the membrane back reactions. The nonequilibrium dissipation cost characterized by the entropy production rate appears to be significant compared to the entropy rate radiated by the black hole under finite temperature difference. This may shed light on the black hole information paradox due to the information loss from the entropy production rate in the nonequilibrium cases. The nonequilibrium thermodynamic fluctuations can also reflect the effects of the back reactions of the Hawking radiation on the evolution of a black hole.

Controlling control-A primer in open-source experimental control systems.

Biological systems are composed of countless interlocking feedback loops. Reactor control systems—such as Chi-Bio (https://chi.bio/), recently published in PLOS Biology—enable biologists to drive multiple processes within living biological samples, using a single experimental framework. Consequently, the dynamic relationships between many biological variables can be explored simultaneously in situ. Similar multivariable experimental reactors are employed beyond biology in the study of active matter and non-equilibrium chemical reactions, in which physical systems are maintained far from equilibrium through the continuous introduction of energy or matter. Inexpensive state-of-the-art components enable open-source implementation of such multiparameter architectures, which represent a move away from expensive systems optimised for single measurements, towards affordable and reconfigurable multi-measurement systems. The transfer of well-understood engineering knowledge into the hands of biological and chemical specialists via open-source channels allows rapid cycles of experimental development and heralds a change in experimental capability that is driving increased theoretical and practical understanding of out-of-equilibrium systems across a wide range of scientific fields.

Organocatalytic Control over a Fuel-Driven Transient-Esterification Network*.

Signal transduction in living systems is the conversion of information into a chemical change, and is the principal process by which cells communicate. In nature, these functions are encoded in non‐equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. However, man‐made catalytically controlled networks are rare. We incorporated catalysis into an artificial fuel‐driven out‐of‐equilibrium CRN, where the forward (ester formation) and backward (ester hydrolysis) reactions are controlled by varying the ratio of two organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. This fuel‐driven strategy was expanded to a responsive polymer system, where transient polymer conformation and aggregation are controlled through fuel and catalyst levels. Altogether, we show that organocatalysis can be used to control a man‐made fuel‐driven system and induce a change in a macromolecular superstructure, as in natural non‐equilibrium systems.

Two-dimensional droplet ripening in a concentration gradient

The discovery of various membraneless subcellular structures (biological condensates) in the cytoplasm and nucleus of cells has generated considerable interest in the effects of non-equilibrium chemical reactions on liquid–liquid phase separation and droplet ripening. Examples include the suppression of droplet ripening due to ATP-driven protein phosphorylation and the spatial segregation of droplets due to regulation by protein concentration gradients. Most studies of biological phase separation have focused on 3D droplet formation, for which mean field methods can be applied. However, mean field theory breaks down in the case of 2D systems, since the concentration around a droplet varies as ln R rather than R−1, where R is the distance from the center of a droplet. In this paper we use the asymptotic theory of diffusion in domains with small holes or exclusions (strongly localized perturbations) to study the segregation of circular droplets in gradient systems. We proceed by partitioning the region outside the droplets into a set of inner regions around each droplet together with an outer region where mean-field interactions occur. Asymptotically matching the inner and outer solutions, we derive dynamical equations for the position-dependent growth and drift of droplets. We thus show how a gradient of regulatory proteins leads to the segregation of droplets to one end of the domain, as previously found for 3D droplets.

Active motion of synthetic nanomotors in filament networks

This paper describes how collections of small synthetic chemically-powered motors function in complex filament networks. Like biological molecular machines, these synthetic motors derive their chemical fuel from nonequilibrium reactions in their environment, attach to filaments and move along them but, unlike biological machines, they use self-generated chemical gradients to effect propulsion. The structure of the filament network strongly influences the character of the collective motions of these motors.