Search

A new chlorine dioxide–iodine–sodium thiosulfate chemical oscillatory reaction was studied by the UV–Vis spectrophotometric method. The initial concentrations of sodium thiosulfate, chlorine dioxide, iodine, sulfuric acid, and pH have great influences on the oscillations observed at wavelength 238 nm. The oscillations occur as long as the reactants are mixed. The amplitude and the number of oscillations are associated with the initial concentrations of reactants. The equations for the triiodide ion reaction rate changes with reaction time and the initial concentrations in the oscillation stage are an attenuation sine function. Based upon the experimental data in this work and in the literature, a plausible reaction mechanism was proposed for the oscillation reaction.

The effect of electromagnetic radiation with a frequency close to the maximum of absorption of atmospheric oxygen on the Briggs-Rauscher self-oscillating reaction is described. It is shown that the radiation intensifies oxygen production and lengthens the duration of the self-oscillating regime by more than 20%.

When performing oscillating reactions, periodical changes in the concentrations of reactants, intermediaries, and products take place. Due to the mentioned periodical changes of the concentrations, the information about the diffusivity of the components included into oscillating reactions is very important for the control of the oscillating reactions. Non-linear dynamics makes oscillating reactions very interesting for analysis in different reactor systems. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor, with the aim of identifying the limiting component. The geometry of the microreactor microchannel and a well defined flow profile ensure optimal conditions for the diffusion phenomena analysis, because diffusion profiles in a microreactor depend only on the residence time. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor equipped with 2 Y-shape inlets and 2 Y-shape outlets, with active volume of V = 4 μL at different residence times.

In this paper we show that the active interplay of nonlinear kinetics and transport phenomena in a chemical oscillator can be exploited to induce and control chaos. To this aim we use as a model system the ferroin-catalysed Belousov-Zhabotinsky (BZ) oscillating reaction, which is known to evolve to characteristic chaotic transient dynamics when carried out under batch and unstirred conditions. In particular, chemical chaos was found to appear and disappear by following a Ruelle-Takens-Newhouse (RTN) scenario. Here we use medium viscosity as a bifurcation parameter to tune the reaction-diffusion-convection (RDC) interplay and force the reaction in a specific sequence of dynamical regimes: either (i) periodic → quasi-periodic → chaotic or (ii) periodic → quasi-periodic or (iii) only periodic. The medium viscosity can be set by adding different amounts of surfactant (sodium dodecyl sulphate), known to have a little impact on the reaction mechanism, above its critical micelle concentration. Experimental results are supported by means of numerical simulations of a RDC model, which combines self-sustained oscillations to the related chemically-induced buoyancy convection.

In this study, The volume oscillation of the microphase-separated, self-oscillating gel above the volume phase transition temperature is discussed. The self-oscillating gel is composed of N-isopropylacrylamide (NIPAAm) with a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction, which is known as the oscillating reaction. The influence of temperature on the period and the self-oscillating behavior is clarified. The volume change of the gel is explained by a change of the Flory–Huggins interaction parameter, χ, which is induced by the hydration and dehydration of the polymer chain due to a valance change of the metal catalyst (Ru(bpy)32+ Ru(bpy)33+) below the volume phase-transition temperature. In contrast, the volume change of the gel is explained by a change of the Donnan osmotic pressure.

This work investigates experimentally the mechanism by which chemical oscillations emerge in a nanometric system. We monitor the spatiotemporal dynamics of an oscillating reaction on the surface of a nanosized three-dimensional Pt model catalyst. Using high-resolution field emission techniques, we are able to show that the oscillations are generated by nanoscale chemical target patterns of much shorter characteristic time than the period with which the oscillations occur. Our observations are made for a specific reaction system---${\mathrm{NO}}_{2}$ reduction with hydrogen---and represent the first experimental evidence for the presence of target patterns at the nanoscale. They can be seen as an experimental demonstration of reaction-diffusion mechanisms to hold at the nanoscale as they do at the macroscale. These results shed new light on the emergence of complexity through different time and length scales.

When two solutions containing separate reactants A and B of an oscillating reaction are put in contact in a gel, localized spatiotemporal patterns can develop around the contact zone thanks to the interplay of reaction and diffusion processes. Using the Brusselator model, we explore analytically the deployment in space and time of the bifurcation diagram of such an A+B→ oscillator system. We provide a parametric classification of possible instabilities as a function of the ratio of the initial reactant concentrations and of the reaction intermediate species diffusion coefficients. Related one-dimensional reaction-diffusion dynamics are studied numerically. We find that the system can spatially localize waves and Turing patterns as well as induce more complex dynamics such as zigzag spatiotemporal waves when Hopf and Turing modes interact.

Hydroxyapatite-based materials are known to have several applications, most widely are used as implant coatings, but also as support in drug delivery. The impregnation of apatite with antioxidant substances could have a positive effect in both application areas, due to antioxidant-free radical scavenging properties, antimicrobial and antiviral effect, as in the case of red beetroot extract. By the variation of preparation parameters it is possible to control the properties of synthesized materials in function of the application field. In order to obtain hydroxyapatite-based materials with increased adsorption capacity different amounts of silica and copper ions were incorporated in the materials structure. These materials were analyzed by IR spectroscopy and TEM; particle size variation during synthesis was also monitored. Red beetroot is ranked among the ten most potent antioxidant vegetables, and their extract exhibits high antioxidant properties. The extract was examined by UV–Vis spectroscopy, and their degradation in time was monitored. The antioxidant capacity was determined by means of the Briggs–Rauscher oscillating reaction. The antioxidant activity was measured and expressed in Trolox units. The amount of adsorbed substance and adsorption efficiency was determined for the substituted materials. The adsorption mechanism was elucidated by kinetic studies involving different kinetic model evaluation. The kinetic data correlate best with the pseudo-second-order model, and the principal mechanism is the formation of chemical bonds between the active centers on the material surface and the antioxidant molecules.

As a novel biomimetic gels deffering from conventonal stimuli-responsive polymer gels, we have developed a “self-oscillating” gel that swells and deswells periodically under constant condition without on–off switching of external stimuli. The gel is composed of poly(N-isopropylacrylamide) to which the catalyst of the oscillating chemical reaction, called Belousov–Zhabotinsky reaction, is covalently immobilized. The chemical oscillation is converted to the mechanical oscillation of the gel through the change in hydrophilicity of polymer chains with the redox changes of the immobilized catalyst. By utilizing the self-oscillating gel, several kinds of functional material systems such as biomimetic actuators, etc. are expected. Here we review a potential application to functional surface to realize autonomous mass-transport by utilizing the peristaltic motion of the gel. With the propagation of the chemical wave, the loaded cargo is autonomously transported on the surface. In order to fabricate the self-driven gel conveyer for a wider use including biomedical applications, the interactions between the self-oscillating gel and the loaded gel cargo were investigated and their influence on the transport phenomena were evaluated.

A modified recipe for the Briggs–Rauscher oscillating reaction is suggested. The modified recipe, [H2SO4] = 0.10 M, [KIO3] = 0.020 M, [NaIO4] = 0.00062 M, [malonic acid] = 0.050 M, [MnSO4] = 0.0067 M, [H2O2] = 1.0 M with 0.01% starch, turns blue almost immediately, then oscillations start with two “slow” (∼25 s) cycles, then settle into regular approximately 12–15 s cycles. Oscillations end with a clear solution, avoiding cleanup of solid iodine resulting from the “standard” recipe, so that only neutralization of excess acid is needed before disposal. Effects of concentration variations are presented.

We present a novel measurement technique to study an oscillating chemical reaction using a new class of sensor, viz. a pulsating sensor developed in-house. A halogen-free oscillating chemical reaction in the Cu(II)-catalyzed H2O2-KSCN–NaOH system reported by Orban was chosen to examine the performance of this technique. Shift in potential during the oscillating reaction was captured online with high precision and excellent resolution using this simple but high-performance pulsating potentiometric measurement technique. In this work, the influence of bath temperature and flow rate of reagents on the Cu(II)-catalyzed H2O2–KSCN–NaOH oscillating chemical reaction is investigated to optimize the conditions for rapid oscillations. This, in turn, helps to evolve analyte pulse perturbation techniques for rapid assay of hydrazine, uranium(VI), and sodium thiosulfate in aqueous solutions using the above oscillating reaction. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 19–29, 2013

Auto-oxidation of lipids has been recognised as a major deterioration process affecting both the sensory and nutritional quality of foods; the application of antioxidants is one of the technically simplest ways of reducing this process. Previous reports showed that these compounds were found in selected aromatic plants and that thymol, carvacrol, thymoquinone and p -cymene as constituents of different essential oils possess substantial antioxidant activity. In the present study their antioxidant capacities were evaluated using the Briggs–Rauscher oscillating reaction method. Our results indicate that the majority of the antioxidant mixtures demonstrated some level of discrepancy in antioxidant capacity when compared to individual values of their constituents. The strong antagonistic effect was found only when thymoquinone was paired with p -cymene. All other combinations of two antioxidants clearly showed some degree of synergistic effect. The mixtures of three antioxidants showed a decrease in antioxidant capacity when compared to their individual values. The results obtained for more complex mixtures of four antioxidants showed a decrease in antioxidant capacity, indicating and confirming that the antagonistic effect between thymoquinone and p -cymene overrides the synergistic effect of other pairs.

Variations of H+, Mn2+, and \({{\rm BrO}_3^-}\) during chemical oscillating reactions involving amino acids were investigated using H2SO4–\({{\rm BrO}_3^{-}}\) –Mn2+–acetone as an oscillator, and the thermodynamic functions (ΔS, ΔH, and ΔG) were calculated. The results indicated that the oscillating reaction is a process from disorder to order. In the oscillating system, the heat provided by the environment is used to increase the internal energy and entropy. When external positive entropy flow could make the system reach negative entropy flow, the system starts to oscillate and to maintain oscillations by a stable entropy.

So far stimuli-responsive polymer gels and their application to smart materials have been widely studied. On the other hand, as a novel biomimetic gel, we developed gels with an autonomous self-oscillating function like a heart muscle, which was firstly reported in 1996. We designed the self-oscillating polymers and gels by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. In the presence of the reactants, the polymer gel undergoes spontaneous cyclic swelling-deswelling changes without any on-off switching of external stimuli. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as bio-mimetic actuators and mass transport surface. In this review, recent progress on the polymer gels is introduced.

Cerium(III) catalysts can replace manganese(II) in the classic Briggs-Rauscher oscillator also containing acid, iodate, hydrogen peroxide, and malonic acid. H2SO4 was used as an acid; if HClO4 is used, cerium iodate precipitates. Cerium(III) oxalate typically precipitates by the time oscillations end. Ce(III) at low concentrations is roughly three times as effective asMn(II). At higher catalyst concentrations, there is a leveling effect for both. Oscillatory behavior with different concentrations is explored. Response to concentration change and inhibitors is similar with both catalysts. The mechanistic steps involving the catalysts must be similar. Ce(IV) is also an effective catalyst, although some cerium(IV) iodate may precipitate immediately.

A highly sensitive method for the determination of epinephrine was proposed, which was based on the perturbation of epinephrine to Briggs-Rauscher oscillating system involving malonic acid, Mn2+, H+, IO3 - and H2O2 at non-equilibrium stationary state. The concentration of KIO3 was chosen as a control parameter to find the bifurcation point in this paper. Results showed that a well linear relationship between the difference of potential and the negative logarithm concentrations of epinephrine existed in the range of 1.1?10-7?5.2?10-9 mol L-1 with a lower detection limit of 6.8?10-10mol L-1 and a correlation coefficient of 0.9974. Compared to the classical oscillating reaction, this method has a lower detection limit and wider linear range. The effects of some foreign species, which may possibly be existed with epinephrine, on determination were also investigated. The proposed method has been successfully used to determine the epinephrine both in the serum and adrenaline hydrochloride injection.

Life involves many nonlinear phenomena. Non-linear chemical reactions can be a model for biological reactions. In the present research, we examine optical change of BZ reaction, and confirmed discharge of CO2.

Because there are cyclical phenomenons in lives so that the influence of the medicine on oscillating reaction is becoming a hotspot.The author prepares a pharmaceutical intermediate. It is 2,6-dihydroxy-4-methylpyrimidine.In this paper the influence of the pharmaceutical intermediate on BZ oscillation system have been studied at different temperature and different concentration. For instance, dropping the concentration of 0.01mol/Lpharmaceutical intermediate before and after, apparent activation energy E and E’ of the systems are 68094J/mol and 71786J/mol.Higher temperature and higher concentration,oscillating cycles and amplitude are lower.

A closed oscillation system comprised of alanine, KBrO3, H2SO4 and acetone catalyzed by tetraazamacrocyclic nickel(II) complex is introduced, and quantitatively characterized with kinetic parameters, namely the rate constant (kin, kp), the apparent activation energy (Ein, Ep) and pre-exponential constant (Ain, Ap) and thermodynamic functions (ΔHin, ΔGin, ΔSin and ΔHp, ΔGp, ΔSp), where indexes “in” and “p” mean “induction period” and “oscillation period,” respectively. The results indicate that tetraazamacrocyclic nickel(II) complex can catalyze alanine oscillating reaction and the reaction corresponds exactly to the feature of irreversible thermodynamics as the entropy of system is negative.

With the help of the kinetic parameters (the rate constant (kinkp) and the apparent activation energy (EinEp) of the oscillatory induction period and oscillation period) of the oscillating reaction using thirteen amino acids, leucine (Leu), threonine (Thr), arginine (Arg), lysine (Lys), histidine (His), alanine (Ala), glutamine (Glu), glycine (Gly), methionine (Met), cystine (Cys), tryptophan (Trp), serine (Ser) and tyrosine (Tyr), as organic substrates in amino acid-BrO3−-Mn2+-H2SO4-acetone system, then based on the Oregonator model and the thermodynamics theory on irreversible process, the thermodynamic function (ΔHin, ΔGin, ΔSin and ΔHp, ΔGp, ΔSp) of these oscillating system are studied. The results indicate the entropy ΔS of these oscillating reaction are negative, thereby it is proved that the oscillating reaction is a noequilibrium system with dissipation structure in agreement with the character of the oscillating reaction from disorder to order in irreversible thermodynamics. These are satisfactorily to explain the experimental phenomena.

A new BriggsRauscher oscillating reaction with a tetraazamacrocyclic nickel(II) complex [NiL](ClO4)2 as catalyst and pentane-2,4-dione (pe) as the substrate is reported. The ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The experimental results indicate that iodine ion may be an important intermediate, and free radicals can be involved in the reaction. A tentative mechanism based on NoyesFurrow model (NF model) is proposed. Moreover, other factors, such as the variation of concentration of the components and temperature on the oscillator, are discussed.

We have developed self-oscillating polymers and gels as novel biomimetic materials by utilizing an oscillating reaction, known as the Belousov-Zhabotinsky (BZ) reaction. The self-oscillating polymer gel is composed of a poly(N-isopropylacrylamide) (PNIPAAm) network in which the catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the gel undergoes spontaneous cyclic swelling-deswelling changes without any on-off switching of external stimuli. In order to induce self-oscillation while maintaining a larger amplitude at higher temperatures and around body temperature for potential applications to biomaterials, etc., here we prepared a self-oscillating gel composed of a thermosensitive N,N'-ethylmethylacrylamide (EMAAm) polymer exhibiting a higher LCST than that of the NIPAAm polymer. The self-oscillating behavior of the poly(EMAAm-co-Ru(bpy)(3)) gel was investigated by comparing against gels composed of a thermosensitive NIPAAm polymer with a lower LCST or non-thermosensitive N,N'-dimethylacrylamide (DMAAm) polymer. The design concept of self-oscillation at higher temperatures without a decrease in swelling-deswelling amplitude was demonstrated by utilizing a thermosensitive polymer exhibiting a higher LCST.

As a novel biomimetic polymer gel, we have been studying polymer gel with an autonomous self-oscillating function since it was firstly reported in 1996. For developing the polymer gels, we utilized an oscillating chemical reaction, called the Belousov–Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. The self-oscillating polymer gel is composed of a poly(N-isopropylacrylamide) network in which the metal catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the polymer undergoes spontaneous swelling–deswelling changes (in the case of gel) or cyclic soluble–insoluble changes (in the case of uncross-linked polymer) without any on–off switching of external stimuli. Several kinds of functional material systems utilizing the self-oscillating polymer and gel such as biomimetic actuators, mass transport surface, etc. are expected. Here, these recent progress on the self-oscillating polymer and gels and the design of functional material systems are summarized.

This paper demonstrates through a few selected examples including CO oxidation and methane oxidation over metallic catalysts the knowledge that may be obtained from the study of the oscillatory behaviour over supported and massive catalysts under atmospheric pressure conditions. The information about reaction mechanisms that can be obtained from the waveforms of reaction rate oscillations, from the phase shifts between oscillations of different products concentrations, and from visual observations of surface spatiotemporal behaviour is discussed.

A new type of oscillating reaction was found from the systematic design of the chemical oscillator in water in oil (W/O) emulsions. It is an acidity hydrolysis reaction of long chain triglyceride in W/O emulsion at 25.0 ± 0.1°C in a bath stirring reactor. During the process of reaction, there were periodic and semi-periodic changes lasting more than 10 hours both in electrolytic conductivity and electric potential. Microscope also revealed that the emulsion structure changed regularly and quickly. Because of the large difference in the solubility of the hydrolyzed products, it could be thought, that the different redistribution in the two phases of water and oil induces the regular changes. Marangoni effect of interface membrane made oscillation to form. The oscillating reaction can be used to explain the periodic change in the living system produced from coupling between reaction and diffusion.

Analyte pulse perturbation (APP) technique was applied to the study of the perturbation of ascorbic add (AA) on the lactic add-acetone-BrO3−-Mn2+-H2SO4 oscillating reaction, and AA was determined using this new oscillating chemical system. Influence of experimental variables was investigated. The linear range lies between 5.0 × 10−7-5.5 × 10−s mol/L, and the precision and throughput were quite good (2.43% as RSD, and 8–10 samples/h, respectively). This method was applied to the determination of real samples and the results were satisfactory. Some aspects of the potential mechanism of action of AA on the oscillating systems are discussed.

To obtain a novel biomimetic polymer, we have been studying polymers with an autonomous self-oscillating function. We succeeded in developing a novel self-oscillating polymer and gel by using an oscillating reaction, called the Belousov–Zhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the polymer undergoes spontaneous cyclic soluble–insoluble changes or swelling–deswelling changes (in the case of gel) without any on–off switching of external stimuli. Several kinds of functional material systems using the self-oscillating polymer and gel, such as biomimetic actuators, mass transport surface and so on, are expected.

Novel aspects of influence of gas evolution on oscillating chemical reaction are considered on a model of the modified Briggs-Rauscher reaction with acetone. The mechanism proposed by Noyes with Furrow and De Kepper with Epstein, adapted for acetone and expanded with oxygen evolution and first-order escape of iodine by interphase transport, was subjected to further extension, and calculations assuming direct proportionality of the rate of iodine escape on the surface area of the oxygen gas trapped in the solution as well as calculations considering first-order back-flow of iodine from the gas phase into the solution were performed. Furthermore, the concentrations of iodine vapors were considered to be variable within the bubble population, as all the bubbles are not in contact with the reaction mixture for the same length of time. Distribution functions of the surface size over the range of concentrations of iodine in the contacting gas phase were introduced and derived, and whereas they were proved not to play any role in the total intensity of iodine return when it is first-order, the article also demonstrates their explicit consideration in calculations to be essential if the dependence of the rate of iodine return into the solution on its concentration is not linear, for example, in future extensions of the model with bubble radius also considered variable.

This research highlights the use of poly(a- crylic acid) (PAAc) cryogels as a pH oscillator in oscilla- tory bromate-sulfite-ferrocyanide reactions. The cryogels were prepared from frozen aqueous solutions of acrylic acid monomer and N,N 0 -methylenebis(acrylamide) cross- linker at � 18 � C. Fast responsive macroporous PAAc cryo- gels were obtained at or below 4 w/v % initial monomer concentration. SEM images of PAAc cryogel networks exhibited a heterogeneous morphology consisting of pores of sizes 10 1 lm, typical for macroporous networks formed by the cryogelation technique. PAAc cryogels coupled with the bromate oscillator oscillate between swollen and collapsed states, during which a cyclic three-fold change in the gel volume was observed. The results show that, due to the fast response rate of cryogels, macroscopic gel samples can be used as a pH oscillator which would pro- vide generation of significant amount of mechanical energy. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2981-2988, 2010

The malonic acid (MA)-based oscillating Briggs–Rauscher reaction (BR) in batch mode has been shown to be sensitive to various hydrophilic polyphenol antioxidants. Several of these have been shown to cause cessation of oscillations for a period of time before a restart occurs. The length of time before oscillations restart is related to the type of antioxidant and its concentration. Procedures have been devised to use this method as a tool for measuring antioxidant activity from pure compounds and from extracts of natural sources. The antioxidant activity has been related to the reaction of the antioxidants with HOO. radicals present in the oscillating system. Vitamin E (α-tocopherol), a typical highly lipophilic antioxidant containing an phenolic OH group, is soluble in acetone that also is a suitable substrate for the BR reaction. Perturbations of a highly concentrated acetone-based BR oscillator by acetonic solutions of vitamin E were studied. The inhibitory effects were found similar to those provoked by hydrophilic polyphenols in the MA-based oscillator, but to obtain reasonable inhibition times, the concentration of vitamin E must be at the mM level instead μM. However, there is a region of concentrations where there is a nearly linear relation between concentration and inhibition time. A comparison with a hydrophilic diphenol (2,6-dihydroxybenzoic acid) in the acetone-based oscillator showed that the inhibitory reaction is much slower in this system than in the MA one. We were able to model the perturbations by vitamin E assuming its reaction with HOO. radicals by using the FCA mechanism previously reported with some little modifications.

We reported the effects of crosslinked nanoshells covering self-oscillating microgels on their oscillatory behaviors. We carried out seeded precipitation polymerization of N-substituted acrylamide derivatives using preformed, self-oscillating microgels as cores. The core/shell microgels obtained were characterized by dynamic light scattering. Oscillating behaviors were characterized by changes in optical transmittance. In addition, the characteristics (that is, induction period, oscillating period and waveform) of the oscillation of the core/shell microgels were compared with that of the parent core microgel to clarify the effect of the addition of a nanoshell on the autonomous oscillating behaviors of microgels.

Many kinds of stimuli-responsive polymer and gels have been developed and applied to biomimetic actuators or artificial muscles. Electroactive polymers that change shape when stimulated electrically seem to be particularly promising. In all cases, however, the mechanical motion is driven by external stimuli, for example, reversing the direction of electric field. On the other hand, many living organisms can generate an autonomous motion without external driving stimuli like self-beating of heart muscles. Here we show a novel biomimetic gel actuator that can walk spontaneously with a worm-like motion without switching of external stimuli. The self-oscillating motion is produced by dissipating chemical energy of oscillating reaction. Although the gel is completely composed of synthetic polymer, it shows autonomous motion as if it were alive.

It was found that the inhibitory effect of resorcinol is less pronounced if it is added in a later stage of the Briggs-Rauscher reaction, which indicates that an accumulating intermediate--most probably iodomalonic acid--can suppress the inhibition. In fact, when iodomalonic acid was added to the reaction mixture, the inhibitory period was shortened considerably even at micromolar levels of the iodomalonic acid concentration. Moreover, iodomalonic acid can accelerate the rate of the reaction when applied in the same low concentrations, suggesting that it can be an autocatalytic intermediate of the Briggs-Rauscher reaction.

In this paper, the overall antioxidant power of monocultivar extra virgin olive oil (EVOO) from Marche Region (Italy) was determined modifying, for the first time, the Briggs–Rauscher (BR) method to account for the water insolubility of the samples. The modification can pave the way to extend the BR antioxidant capacity assay to other real food systems that are usually heterogeneous mixtures and to easily take into account synergistic effects of antioxidants and food matrix that are essential to determine the antioxidant capacity; the pH of the method is the pH of gastric fluids, and this is noteworthy if we take into account that lipid peroxidation is amplified at this pH. The method is simple, rapid, and inexpensive. The interplay among antioxidant activity and total phenol content is rewarding and witness the feasibility of the method for the fast screening of antioxidant activity of EVOO samples.

A convenient procedure by means of oscillating chemical system as an analytical tool to determine the L-aspartic acid (L-Asp) is proposed. The system involves the Cu(II)-catalyzed reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium. The method relies on the linear relationship between the changes in the oscillation period and the logarithm of concentration of L-aspartic acid. Optimized conditions were further validated to ensure the reliability of the method. Under optimum conditions, the calibration plot is linearly proportional to the concentration of L-aspartic acid over the range from 1.17 × 10-5 mol L-1 to 7.10 × 10-8 mol L-1 with a corresponding regression coefficient of 0.9990 (RSD 2.75%). A lower limit of determination (LOD) was 5.58 × 10-8 mol L-1. The proposed method has been used to determine L-aspartic acid in drug sample. Additionally, the HPLC technique was also used to confirm the determination results.

A rapid and convenient method for the determination of penicillin is presented which is based upon sequential perturbation of the Mn (II)-catalyzed B-Z oscillating system with different quantities of penicillin using a continuous-flow stirred tank reactor (CSTR). The results showed that changes both in oscillating period and amplitude were linearly proportional to the –lg C (where C is the concentration of penicillin) in either the range from 2.97 × 10 −7 to 5.50 × 10 −5 M or the range of 2.97 × 10 −6 – 5.50 × 10 −5 M, with the respective regression coefficients of 0.9981 and 0.9985, respectively. A lower detection limit of 5.94 × 10 −8 M was obtained with excellent throughput (15 samples per hour). The Mn (II)-catalyzed oscillating system where lactic acid is included is more interesting for understanding the oscillator in biological system because lactic acid (LA) is an important intermediate product in the metabolic process of human body. A possible mechanism of penicillin perturbation in the oscillating reaction was also discussed.

生命体は，流入するエネルギーと生体内部で散逸するエネルギーが均衡して，一定の散逸構造を保つ，非平衡開放系の分子システムである．その生体内部には，神経細胞の膜電位，心臓の拍動，サーカディアンリズムなど，細胞レベルから一個体に至るまでの階層においてあらゆる時空間機能を包括している．このような生体が持つ複雑かつ精密に組み立てられた時空間機能を，人工的に組み上げることができれば，生命体に近い分子システムをテイラーメイドで構築することができる．そのようなシステムを構築するため，時空間秩序を生成する Belousov-Zhabotinsky (BZ)反応に着目した．筆者らは，ポリマー鎖に BZ 反応の金属触媒を内包させることで，心臓の拍動のようにゲルの自励的かつ周期的な構造変換を可能にしてきた．しかしながら，これまでの分子デザインでは，膨潤・収縮挙動が非常に小さいため，アクチュエーターとして機能させることが難しかった．本報では，ゲルの分子デザインと合成方法を改良することで，大変形する屈曲型ゲルアクチュエーター，自ら歩行するゲルロボット，ゲル表面の大きな蠕動運動を利用した物質輸送システムへと進化させたことを報告するとともに今後の展開について述べる．

When two gels, each loaded with a different set of reactants A and B of an oscillatory reaction, are brought into contact, reaction-diffusion patterns such as waves or Turing patterns can develop in the reactive contact zone. The initial condition which separates the reactants at the beginning leads to a localization in space of the different dynamical regimes accessible to the chemical oscillator. We study here both numerically and experimentally the composite traveling structures resulting from the interaction between chemical fronts and localized waves in the case in which the reactants of such an A + B → oscillator system are those of the canonical Belousov-Zhabotinsky (BZ) oscillating reaction. A transition between different dynamics is obtained by varying the initial concentration of the organic substrate of the BZ reactants, which is one of the parameters controlling the local excitability. We show that the dynamical regime (excitable or oscillatory) characterizing the BZ oscillator in the initial contact area is the key feature which determines the spatiotemporal evolution of the system. The experimental results are in qualitative agreement with the theoretical predictions.

Effective diffusivity presents an important physical-chemical property of the molecule and it is extremely important for design and optimization of the process in which it is included. Effective diffusivity coefficient presents the diffusivity capacity of the molecule and molecules with higher values of the effective diffusivity coefficient move faster. Due to the small dimensions of the microchannels, microreactors ensure ideal conditions for diffusion phenomena analysis in defined and controlled conditions. Reactor dimensions reduction to micro scale has significant effect on the diffusion time. Diffusion time is defined as the ratio of the square of the path that molecule has to pass in a microchannel and the diffusion coefficient. Due to the small dimension of the microchannels, molecules diffuse very fast in the process space and in the laminar flow rate diffusion profile depends only on the residence time. In this work 2D mathematical model was used to analyse the diffusion profiles of the Briggs-Rauscher (BR) oscillatory reaction components in a microreactor. Mathematical model includes convection in the flow direction and diffusion in two directions. Mathematical model simulations were performed using WR Mathematica 10.0 applying the finite difference method for solving the partial differential equation using the effective diffusivity coefficients data from the literature. The simulations were performed for all six components (hydrogen peroxide, sulfuric acid, potassium iodate, malonic acid, manganese sulphate, starch) of the BR reaction. The obtained diffusivity profiles will be used in the optimization of the BR reaction in the continuous mode at the macro scale.

A computational algorithm based on the lattice Boltzmann method (LBM) is proposed to model reaction–diffusion systems. In this paper, we focus on how nonlinear chemical oscillators like Belousov–Zhabotinsky (BZ) and the chlorite–iodide–malonic acid (CIMA) reactions can be modeled by LBM and provide with new insight into the nature and applications of oscillating reactions. We use Gaussian pulse initial concentrations of sulfuric acid in different places of a bidimensional reactor and nondiffusive boundary walls. We clearly show how these systems evolve to a chaotic attractor and produce specific pattern images that are portrayed in the reactions trajectory to the corresponding chaotic attractor and can be used in robotic control.

The behavior of glycolysis concerning the biochemical reaction was thought to be similar to the oscillatory reaction with glucose being the substrate. The objective of this research is to find a new oscillatory system and study its relevant properties, so new Cu (II)-catalyzed oscillating reaction involved glucose and acetone as the double substrates was investigated systematically. As a function of reaction temperature and concentration of glucose, bromate, and acetone, the features in this novel oscillation system was studied. The results showed that the activation energy reached up to 90.839 KJ/mol and the oxidized product of the double substrates provided the impetus in the course of the new oscillating reaction. A tentative mechanism was considered on the basis of FNK.

The temporal dynamics of the Bray–Liebhafsky reaction (iodate-based catalytic decomposition of hydrogen peroxide in an acidic aqueous solution) was experimentally characterized in a continuous stirred tank reactor by independently varying the temperature and the mixed inflow hydrogen peroxide concentration. When the temperature was the bifurcation parameter, the emergence/disappearance of oscillatory behavior via a supercritical Andronov–Hopf bifurcation was observed for different mixed inflow hydrogen peroxide concentrations. An increase in the mixed inflow hydrogen-peroxide concentration resulted in a shift of the bifurcation point towards higher values of temperature, but did not alter the bifurcation type.

Oscillations in the platinum redox potential during the reaction of bromate ions with acetonedicarboxylic acid catalyzed by Mn(II) ions were observed. The volume of gaseous carbon dioxide produced was measured. A nonoscillatory course was found both at the slow and rapid stirring rates for carbon dioxide evolution. The perturbation experiments suggest supersaturation during the Belousov-Zhabotinsky reaction with acetonedicarboxylic acid. Possible reasons for such observations are discussed.

It has been known for a long time that the decomposition of hydrogen peroxide catalyzed by hydrogen and iodate ions, the Bray-Liebhafsky reaction, can generate oscillations in a batch reactor. Recently, mixed-mode oscillations and chaos have also been observed in a CSTR. The model we had previously proposed to explain the kinetics in a batch reactor can also simulate these new complex behaviors. Time series give only a limited view of the features of the calculated behaviors and more information is obtained studying the properties of the state space. We use projections of the trajectories, calculation of the correlation dimension of the attractor, Poincare sections, and return maps. As the state space of the model is six-dimensional, we try to answer the questions of whether the projections into a 3D subspace give correct pictures of the real trajectories and whether we have reasons to prefer a special subspace.

The effect of putrescine (PUT) on KSCN-H2O2-CuSO4-NaOH oscillating system was investigated by calorimetric method. The oscillating reaction was monitored in a closed reactor with stirring, and the result showed that the oscillating period was linearly related with putrescine concentration and the numbers of oscillation decreased with increase in putrescine concentration. When [PUT]=2.83·10−4 M, no oscillation was observed. A possible mechanism is proposed that putrescine is a scavenger of the active-oxygen species. The result of numerical simulation by a simplified mechanism consisting of 18 kinetic steps and 16 variables is consistent with the experimental findings.

Simulations have been carried out on the bromate - oxalic acid - Ce(IV) - acetone oscillating reaction, under flow conditions, using Field and Boyd's model (J. Phys. Chem. 1985, 89, 3707). Many different complex dynamic behaviors were found, including simple periodic oscillations, complex periodic oscillations, quasiperiodicity and chaos. Some of these complex oscillations can be understood as belonging to a Farey sequence. The many different behaviors were systematized in a phase diagram which shows that some regions of complex patterns were nested with one inside the other. The existence of almost all known dynamic behavior for this system allows the suggestion that it can be used as a model for some very complex phenomena that occur in biological systems.

The oscillating reaction bromate-oxalic acid-acetone-Mn(II)-sulfuric acid was observed for the first time in a CSTR at 20 °C. Depending on the bromate concentrations and flow rate, the system showed large amplitude oscillations, two kinds of mixed mode oscillations, quasiperiodicity and bursts of large amplitude oscillations, all mapped in a phase diagram. More complex behavior was favored at low bromate concentrations. The system without acetone was discovered to oscillate too, but the more complex patterns were not seen, indicating that acetone is implied in their formation.