Sodium polyacrylate-induced pH pattern formation and starch-induced iodine pattern formation were investigated in the iodate-sulfite-thiosulfate (IST) reaction in a one-side fed disc gel reactor (OSFR). As binding agents of the autocatalyst of hydrogen ions or iodide ions, different content of sodium polyacrylate or starch has induced various types of pattern formation. We observed pH pulses, striped patterns, mixed spots and stripes, and hexagonal spots upon increasing the content of sodium polyacrylate and observed iodine pulses, branched patterns, and labyrinthine patterns upon increasing the starch content in the system. Coexistence of a pH front and an iodine front was also studied in a batch IST reaction-diffusion system. Both pH and iodine front instabilities were observed in the presence of sodium polyacrylate, i.e., cellular fronts and transient Turing structures resulting from the decrease in diffusion coefficients of activators. The mechanism of multiple feedback may explain the different patterns in the IST reaction-diffusion system.

Asymmetry in the interaction between an individual and its environment is generally considered essential for the directional properties of active matter, but can directional locomotions and their transitions be generated only from intrinsic chemical dynamics and its modulation? Here, we examine this question by simulating the locomotion of a bioinspired active gel in a homogeneous environment. We find that autonomous directional locomotion emerges in the absence of asymmetric interaction with the environment and that a transition between modes of gel locomotion can be induced by adjusting the spatially uniform intensity of illumination or certain kinetic and mechanical system parameters. The internal wave dynamics and its structural modulation act as the impetus for signal-driven active locomotion in a manner similar to the way in which an animal’s locomotion is generated via driving by nerve pulses. Our results may have implications for the development of soft robots and biomimetic materials.

We study the oxidation dynamics of thiosulfate ions by hydrogen peroxide in the presence of trace amounts of copper(II) using the reaction temperature as a control parameter in a continuous flow stirred tank reactor. The system displays period-doubling, aperodic, and mixed-mode oscillations at different temperatures. We are able to simulate these complex dynamics with a model proposed by Kurin-Csorgei et al. The model suggests that the Cu(2+)-containing term is not essential for the observed oscillations. We find small-amplitude and high-frequency oscillations in the catalyst-free experimental system. The reaction between H(2)O(2) and S(2)O(3)(2-) contains the core mechanism of the H(2)O(2)-S(2)O(3)(2-)-Cu(2+) and H(2)O(2)-S(2)O(3)(2-)-SO(3)(2-) oscillatory systems, while the Cu(2+) and SO(3)(2-) modulate the feedback loops so as to strengthen the oscillatory dynamics.

The Briggs−Rauscher reaction is a popular demonstration to illustrate chemical oscillations in laboratories, classrooms, and public seminars because of its simplicity and visual appeal. Here, we adapt the Briggs−Rauscher reaction to present reaction−diffusion−convection patterns in the undergraduate general or physical chemistry laboratory. By maintaining the ratio between malonic acid and potassium iodate concentrations as 0.2 in an uncovered Petri dish, sequential patterns (transient dendritic patterns and rotating dendritic patterns) can be observed, which are induced by the interaction of reaction, diffusion, and convection. This beautiful demonstration captures students' attention and inspires reflection and discussion about similar phenomena in nature as well as the wealth of behaviors in systems far from equilibrium.

Temperature oscillations and complex pH oscillations in the IO(3)(-)-SO(3)(2-)-S(2)O(3)(2-) system were observed in a continuously flow stirred tank reactor. During one period of oscillation, the temperature increases rapidly while the pH shows an extremely sharp change. High-amplitude pH oscillations undergo 1(1) complex oscillations (L(S), oscillations with L large peaks and S small peaks per period) to another kind of higher-amplitude regular oscillations upon increasing the concentration of sulfite step by step. Importantly, the longstanding experimental phenomena, the extraordinary temperature sensitivity of oscillatory behavior reported 20 years ago by Rabai and Beck, can be eliminated by premixing of sulfite and sulfuric acid before entering into the reactor, avoiding local acidification, which brings out fluctuation and temperature sensitivity. The temperature oscillations can be understood by taking into account the interaction between thermal effect of various reactions and heat transfer. Experimental observations, both temperature oscillations and 1(1)-type pH oscillations, are reproduced with a four-step Horvath model by addition of an energy-balance equation. This new detailed dynamical behavior would have potential applications in designing complex chemical waves and pH responsive gels with rhythmical motion.

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A new mutual coupling compensation method for wideband adaptive arrays is proposed. The new method is developed by combining the element pattern reconstruction method and the system identification method. The element pattern reconstruction method is valid and effective in the mutual coupling compensation for adaptive arrays such as dipole arrays and microstrip arrays. Each entry of the wideband compensation matrix is represented as an analytical expression against frequency. The polynomial coefficients and orders of all entries are obtained via the system identification method. The new wideband compensation method is characterized by the good adaptability of element structures and polarizations owing to the advantages of element pattern reconstruction method. A wideband microstrip array is designed to test the validity and effectiveness of the wideband compensation method.

A new pH oscillator has been constructed by combining the pH clock reaction H2O2-SO3(2-)-H(+) with thiourea (Tu, (NH2)2CS) as a proton-consuming species. The system exhibited oligo-oscillatory behavior in a closed system, and large amplitude oscillations in a continuous-flow stirred tank reactor (CSTR) were observed in a narrow range of input concentrations, flow rate, and temperature. For the purpose of constructing the kinetic model, a reversed-phase ion-pair high-performance liquid chromatography (HPLC) and mass spectrometer (MS) were used to track and determine intermediate species during the oxidation of thiourea by hydrogen peroxide. Experimental results illustrated that the four species: thiourea monoxide (TuO), formamidine disulfide (Tu2(2+)), thiourea dioxide (TuO2), and thiourea trioxide (TuO3) were formed during the oxidation process. A ten-step mechanistic model was proposed, where TuO was another key species participating in two proton feedback loops in addition to bisulfite. Numerical simulations based on this model agreed well with the experimental results.