Oscillatory Reaction Research Articles

Influence of the Ligands in Cu(II) Complexes on the Oscillatory Electrodeposition of Cu/Cu2O

Oscillatory electrodeposition reactions have been utilized to create nanostructured materials under the microscale and nanoscale. This alternative method of synthesis, when compared to the traditio...

In-vitro reconfigurability of native chemical automata, the inclusiveness of their hierarchy and their thermodynamics

Living systems process information using chemistry. Computations can be viewed as language recognition problems where both languages and automata recognizing them form an inclusive hierarchy. Chemical realizations, without using biochemistry, of the main classes of computing automata, Finite Automata (FA), 1-stack Push Down Automata (1-PDA) and Turing Machine (TM) have recently been presented. These use chemistry for the representation of input information, its processing and output information. The Turing machine uses the Belousov-Zhabotinsky (BZ) oscillatory reaction to recognize a representative Context-Sensitive Language (CSL), the 1-PDA uses a pH network to recognize a Context Free Language (CFL) and a FA for a Regular Language (RL) uses a precipitation reaction. By chemically reconfiguring them to recognize representative languages in the lower classes of the Chomsky hierarchy we illustrate the inclusiveness of the hierarchy of native chemical automata. These examples open the door for chemical programming without biochemistry. Furthermore, the thermodynamic metric originally introduced to identify the accept/reject state of the chemical output for the CSL, can equally be used for recognizing CFL and RL by the automata. Finally, we point out how the chemical and thermodynamic duality of accept/reject criteria can be used in the optimization of the energetics and efficiency of computations.

Dissipative Self-Assembly of Dynamic Multicompartmentalized Microsystems with Light-Responsive Behaviors

Summary Living cells are compartmentalized systems operating far from thermodynamic equilibrium and consume energy from the environment to carry out their functions. The construction of biomimetic synthetic compartments has both scientific and technological value. Despite many advances, the assembly of synthetic compartments that present nonequilibrium behaviors based on dissipative (or transient) self-assembly remains a grand challenge. Here, we describe the design and synthesis of multicompartmental systems with an active microstructure and complex behaviors. By including an artificial pathway for energy dissipation, we demonstrate the autonomous generation of active polymeric systems using a strategy based on polymerization-induced self-assembly (PISA), driven by chemical fuel. Remarkably, these self-organized synthetic systems exhibit a dynamic change in their multicompartmental structures when exposed to light. This work introduces a strategy toward the design and construction of synthetic compartments with a dynamic structure and also presents pathways to engineer materials with spatially controllable structures and functionalities.

A numerical investigation of the effect of external resistance and applied potential on the distribution of periodicity and chaos in the anodic dissolution of nickel.

The oscillatory electrodissolution of nickel is one among several reactions utilized as a model-system to study the emergence of oscillations and pattern formation in electrochemical interfaces, in addition to frequently providing experimental proofs for theoretical predictions in synchronization engineering. The reaction was modeled in 1992 by Haim and co-workers [J. Phys. Chem. 1992, 96, 2676] and since then the model has been used with great success. Although some numerical studies have been done in this regard, there is apparently no detailed investigation of the effect of control parameters on the complex dynamics of nickel dissolution. Here, we provide a well-detailed and rigorous analysis of the effect of the external resistance and applied potential by simulating high-resolution phase diagrams based on the calculation of Lyapunov exponents and isospike diagrams. Our findings clearly indicate a strong dependence of the self-similar periodic islands, the so-called shrimps (i.e., periodic islands within chaotic domains in the parameter space), with the control parameters. Overall, we have observed a low density of periodic structures in the phase diagrams, being completely suppressed for large values of resistance and potential. The shrimp-like structures become gradually elongated with an increase of the control parameters to the point where only diagonally aligned periodic bands intertwined with chaotic domains are present. Interestingly, period-doubling cascades were observed not only on the shrimps but also on the periodic bands. The detailed distribution of chaos and periodicity of oscillatory electrodissolution reactions in resistance-potential phase diagrams can bring, for instance, important information to experimentalists to set a desired dynamic behavior and, therefore, to create novel nanostructured self-organized materials.

Building Oscillatory Chemical Reaction Networks by Adding Reversible Reactions

We show that if a chemical reaction network (CRN) admits nondegenerate (resp., linearly stable) oscillation, and we add new reversible reactions involving new species to this CRN, then the new CRN so created also admits nondegenerate (resp., linearly stable) oscillation provided certain mild and easily checked conditions are met. This claim that the larger CRN "inherits" oscillation from the smaller one, provided it is built from the smaller CRN in an appropriate way, follows an analogous result involving multistationarity. It also adds to a number of prior results on the inheritance of oscillation; these collectively often allow us to determine the capacity of a given network for oscillation based on an analysis of its subnetworks.

Моделирование колебательных химических реакций с хаотическим поведением

Моделирование колебательных химических реакций с хаотическим поведением

Liquid Marble Photosensor.

A liquid marble is a liquid droplet coated by a hydrophobic powder. The liquid marble does not wet adjacent surfaces and therefore can be manipulated as a dry soft body. A Belousov-Zhabotinsky (BZ) reaction is an oscillatory chemical reaction exhibiting waves of oxidation. We demonstrate how to make a photo-sensor from BZ medium liquid marbles. We insert electrodes into a liquid marble, prepared from BZ solution and coated with polyethylene powder. The electrodes record a potential difference which oscillates due to oxidation wave-fronts crossing the electrodes. When the BZ marble is illuminated by a light source, the oxidation wave-fronts are hindered and, thus, the electrical potential recorded ceases to oscillate. We characterise several types of responses of BZ marble photosensors to various stimuli, and provide explanations of the recorded activity. BZ liquid marble photosensors may find applications in the fields of liquid electronics, soft robotics and unconventional computing.

Aging phenomena in the two-dimensional complex Ginzburg-Landau equation

The complex Ginzburg-Landau equation with additive noise is a stochastic partial differential equation that describes a remarkably wide range of physical systems which include coupled non-linear oscillators subject to external noise near a Hopf bifurcation instability and spontaneous structure formation in non-equilibrium systems, e.g., in cyclically competing populations or oscillatory chemical reactions. We employ a finite-difference method to numerically solve the noisy complex Ginzburg-Landau equation on a two-dimensional domain with the goal to investigate its non-equilibrium dynamics when the system is quenched into the “defocusing spiral quadrant”. We observe slow coarsening dynamics as oppositely charged topological defects annihilate each other, and characterize the ensuing aging scaling behavior. We conclude that the physical aging features in this system are governed by non-universal aging scaling exponents. We also investigate systems with control parameters residing in the “focusing quadrant”, and identify slow aging kinetics in that regime as well. We provide heuristic criteria for the existence of slow coarsening dynamics and physical aging behavior in the complex Ginzburg-Landau equation.

Unusual Chemistry in an Uncatalyzed Bromate–Aniline Oscillator: Ring-Contraction Oxidation of Aniline with Pulsative CO2 Production

The bromate-aniline oscillatory reaction was discovered 4 decades ago, but neither the detailed mechanism nor the key products or intermediates of the reaction were described. We report herein a detailed study of this reaction, which yielded new insights. We found that oscillatory oxidation of aniline by acidic bromate proceeds, to a significant extent, via a novel reaction pathway with the periodic release of carbon dioxide. Several products were isolated, and their structures, not described so far, were justified on the basis of MS and NMR. One of the main products of the reaction associated with the CO2 release route can be assigned to 2,2-dibromo-5-(phenylimino)cyclopent-3-en-1-one. A number of known compounds produced in the studied reaction, including unexpected brominated 1-phenylpyrroles and 1-phenylmaleimides, were identified by comparison with standards. A mechanism is suggested to explain the appearance of the detected compounds, based on coupling of the anilino radical with the produced 1,4-benzoquinone. We assume that the radical adduct reacts with bromine to form a cyclopropanone intermediate that undergoes a Favorskii-type rearrangement. Further oxidation and bromination steps including decarboxylation lead to the found brominated phenyliminocyclopentenones. The detected derivatives of 1-phenylpyrrole could be produced by a one-electron oxidation of a proposed intermediate 2-phenylamino-5-bromocyclopenta-1,3-dien-1-ol followed by β-scission with the abstraction of carbon monoxide. Such a mechanism is known from the combustion chemistry of cyclopentadiene. The proposed mechanism of this reaction provides a framework for understanding the observed oscillatory kinetics.

Interface Fingering Instability Triggered by a Density-Coupled Oscillatory Chemical Reaction via Precipitation.

A density fingering hydrodynamic instability is triggered by a chemical reaction at the interface between two fluids. The density instability is controlled by the density gradient between both solutions, while the excitability of the bubble-free Belousov-Zhabotinsky-1,4-cyclohexanedione (BZ-CHD) oscillatory chemical reaction controls the importance of the chemistry in the system. Both parameters are thoroughly analyzed, and the mechanism underlying the instability is unveiled. The experimental observations lead us to modify the existing and accepted models for the BZ-CHD reaction within this context. The important role played by precipitation is considered in this context and included into the model. The modified kinetic model once coupled with fluid dynamics along with the precipitation mechanism was able to reproduce the experimental observations.

Spiral waves with interfacial oscillatory chemical reactions emerge in a model of reaction-diffusion systems

We propose a model for describing oscillatory chemical reactions involving a variety of immiscible solvents. This model describes the interaction between chemical oscillations on both sides of the interface of different solvents and the effect of the interface on chemical oscillations. Based on this model, we study the spiral chemical wave in a chemical oscillation with interfaces of different solvents, and report a new type of spiral wave. The interface does not hinder the propagation of chemical waves, which can continue to propagate through the interface. The frequency of the chemical wave is increased after the chemical wave passed through the interface. The work of this paper enriched the categories of the dynamics of pattern formation. We believe that the results of this study can provide direction and guidance for chemical experimental research about interfacial oscillatory chemical reactions.

Briggs-Rauscher reaction as a novel electrochemical detector for phosphate tungsten and phosphate molybdenum bronzes

Briggs-Rauscher (BR) oscillatory reaction is a chemical system very sensitive to different analyte addition. Changes in oscillatory dynamics, by analyte addition, could be successfully used for the determination of analyte concentration, as well as for its antioxidative/antiradical activity assessment. In this work, the BR reaction is used as a system detector for distinguishing solid unsolvable materials, such as phosphate tungsten bronze (PWB) and phosphate molybdenum bronze (PMoB), obtained by thermal treatment. The addition of different masses of PWB in BR reaction decreases its oscillation time, while the addition of different masses of PMoB had no effects on the BR oscillation time. Additionally, the BR oscillation time is the linear function of added PWB mass. The mechanism of bronzes action is investigated by using pH and electric conductivity measurements, as well as inductively coupled plasma and the cyclic voltammetry measurements, and it can be ascribed to PWB better catalytic activity then PMoB, under BR reaction condition. This work extends the practical aspect of the BR reaction for testing solid (insoluble) materials, and opening the possibility of using oscillatory reactions in material science and catalysis, in general.

Dynamic Behavior of Superconductor-Permanent Magnet Levitation With Halbach Arrays for Flywheel Design and Control

Our research goal is to construct a general predictive model for the design and control of a flywheel energy storage system (FESS) that utilizes a superconductor-permanent magnetic levitation bearing. The FESS machine design is a hubless field-regulated reluctance machine for which the rotor of the machine is also the rotating mass for the flywheel. Reported are the results of several experiments that show the oscillatory reactions of the levitated systems. For these experiments, the levitation height and the amount of flux penetrating the superconductor is controlled by adding mass to the levitated Halbach array and by the initial cooling conditions. A small impulsive force is delivered to the levitated array, which is then allowed to freely oscillate until it has completely decayed. From this we can find an effective spring constant and damping coefficient for the levitated system as a function of the magnetic field densities and levitation height. The goal of the experiments reported is to understand the dynamic behaviors of a levitation system and incorporate those properties into the control model for the flywheel. Initial experiments have demonstrated near critically damped harmonic behavior when a magnet array levitated by a superconductor is delivered an impulsive force. Using the data from our experiments we aim to gain knowledge of the underlying physics of the forces of interaction and to create a predictive macroscopic model based on magnetic array and YBCO properties. We compare our measured results to those obtained by using the advanced image mirror method and finite element magnetic modeling.

Gravity analog model of non-equilibrium thermodynamics

Abstract The non-equilibrium thermodynamics of Onsager and Machlup and of Hashitsume is reformulated as a gravity analog model, in which thermodynamic variables, kinetic coefficients, and generalized forces form, respectively, coordinates and metric tensor and vector fields in a space of thermodynamic variables. The relevant symmetry of the model is the general coordinate transformation. Then, the entropy production is classified into three categories, when a closed path is depicted as a thermodynamic cycle. One category is time-reversal odd, and is attributed to the number of lines of magnetic flux passing through the closed path, having the monopole as a source. There are two time-reversal-even categories, one of which is attributed to the space curvature around the path, having the gravitational instanton as a source, which dominates for a rapid operation of the cycle. The last category is the usual one, which remains even for the quasi-equilibrium operation. It is possible to extend the model to include non-linear responses. In introducing new terms, dimensional counting is important, using two parameters, the temperature and the relaxation time. The effective action, being induced by the non-equilibrium thermodynamics, is derived. This is a candidate for the action that controls the dynamics of kinetic coefficients and thermodynamic forces. An example is given in a chemical oscillatory reaction in a solvent of van der Waals type. The fluctuation–dissipation theorem is examined à la Onsager, and a derivation of the gravity analog thermodynamic model from quantum mechanics is sketched, based on an analogy to the resonance problem.

Initiation of Vacancy-Mediated, Surface Explosion Reactions: Tartaric and Aspartic Acid on Cu Surfaces

Surface explosion reactions have highly nonlinear reaction kinetics that exhibit autoacceleration under isothermal conditions. These can lead to phenomena such as oscillatory surface reaction rates and to highly enantiospecific reactions of chiral adsorbates on chiral surfaces. Tartaric acid (TA) decomposes on Cu surfaces by an explosion mechanism that is propagated by vacancies, empty adsorption sites that self-replicate autocatalytically during TA decomposition. Surface explosion kinetics result from chain-branching steps in which one vacancy decomposes an adsorbate to yield two vacancies. In the absence of vacancies, surface explosions cannot occur; they require some initiation step that creates vacancies. By comparison with the chain-branching explosion step, little is known about the processes that initiate or nucleate surface explosion reactions. Time-resolved XPS measurements during the early stages of explosion initiation of TA/Cu(hkl) reveal a process that involves direct loss of TA from the surface to create the initial vacancies. In the presence of a gas phase flux to the surface, such vacancy nuclei can be repopulated to suppress the onset of explosion. Measurements on 18 different Cu(hkl) surface orientations demonstrate that the kinetics of the initiation process are structure-insensitive. This implies that the highly enantiospecific TA decomposition kinetics observed on chiral Cu(hkl) surfaces must arise from the structure sensitivity of the chain-branching explosion kinetics.

Is Iodine Oxidation with Hydrogen Peroxide Coupled with Nucleation Processes?

An intriguing step of the Bray–Liebhafsky oscillatory reaction, that is, iodine oxidation with hydrogen peroxide, was examined. This process is characterized by enormous stochasticity of reaction induction times in the presence of mild mixing. In the present investigations, it was found that even in the presence of mixing, stochasticity is seriously reduced with simple glass powder addition. Using transparent glass, standard deviations changed from 184.9 to 10.6 min for 19 °C, and from 128.2 to 1.9 min for 27 °C. Repeating experiments with amber glass further confirmed those results as standard deviations changed from the mentioned ones to 8.7 min for 19 °C and to 2.5 min for 27 °C. Inert glass particles enhanced heterogeneous nucleation of oxygen formed in chemical reactions. Together with the previous analysis of the involved kinetic barrier of the whole reaction, it is an additional strong evidence of a possible energetic coupling between nucleation of glass cavities and chemical reactions. Such proces...

Belousov-Zhabotinsky liquid marbles in robot control

We show how to control the movement of a wheeled robot using on-board liquid marbles made of Belousov-Zhabotinsky solution droplets coated with polyethylene powder. Two stainless steel, iridium coated electrodes were inserted in a marble and the electrical potential recorded was used to control the robot's motor. We stimulated the marble with a laser beam. It responded to the stimulation by pronounced changes in the electrical potential output. The electrical output was detected by the robot. The robot changed its trajectory in response to the stimulation. The results open new horizons for applications using oscillatory chemical reactions in robotics.

Effects of Electroacupuncture on Pain Memory-Related Behaviors and Synchronous Neural Oscillations in the Rostral Anterior Cingulate Cortex in Freely Moving Rats.

Our previous studies have confirmed that electroacupuncture (EA) can effectively intervene in pain memory, but the neural mechanism involved remains unclear. In this study, we observed the effects of EA in regulating pain memory-related behaviors and synchronous neural oscillations in the rostral anterior cingulate cortex (rACC). During nociceptive behavioral testing, pain memory induced a nonpain stimulus that spurred a neural oscillatory reaction similar to that caused by pain stimuli in the rACC. After EA, nonpain stimuli did not induce decreased neural oscillatory activity in the rACC until the presentation of pain stimuli. During aversive behavioral testing, EA, through the downregulation of theta power, inhibited the retrieval of aversive memory and relieved pain memory-induced aversive behaviors. These changes of oscillatory activity may be the hallmarks of EA therapy for pain memory.

Robustness, Entrainment, and Hybridization in Dissipative Molecular Networks, and the Origin of Life.

How simple chemical reactions self-assembled into complex, robust networks at the origin of life is unknown. This general problem-self-assembly of dissipative molecular networks-is also important in understanding the growth of complexity from simplicity in molecular and biomolecular systems. Here, we describe how heterogeneity in the composition of a small network of oscillatory organic reactions can sustain (rather than stop) these oscillations, when homogeneity in their composition does not. Specifically, multiple reactants in an amide-forming network sustain oscillation when the environment (here, the space velocity) changes, while homogeneous networks-those with fewer reactants-do not. Remarkably, a mixture of two reactants of different structure-neither of which produces oscillations individually-oscillates when combined. These results demonstrate that molecular heterogeneity present in mixtures of reactants can promote rather than suppress complex behaviors.

Quenching and revival of oscillations induced by coupling through adaptive variables

An adaptive coupling based on a low-pass filter (LPF) is proposed to manipulate dynamic activity of diffusively coupled dynamical systems. A theoretical analysis shows that tracking either the external or internal signal in the coupling via a LPF gives rise to distinctly different ways of regulating the rhythmicity of the coupled systems. When the external signals of the coupling are attenuated by a LPF, the macroscopic oscillations of the coupled system are quenched due to the emergence of amplitude or oscillation death. If the internal signals of the coupling are further filtered by a LPF, amplitude and oscillation deaths are effectively revoked to restore dynamic behaviors. The applicability of this approach is demonstrated in laboratory experiments of coupled oscillatory electrochemical reactions by inducing coupling through LPFs. Our study provides additional insight into (ar)rhythmogenesis in diffusively coupled systems.