Open Reaction System Research Articles

Multifunctional and anti-migration plasticizers based on bio-based phenol-functionalized liquid 1,2-polybutadiene

With the increasing demands for environmental friendliness, bio-based additives in rubber materials have attracted extensive research attention from the academy and industry. However, the low molecular weight and high polarity are detrimental to mixing compatibility with rubber materials. In this work, we prepare a phenol-functionalized 1,2-PB (1,2-PB-g-CA) by grafting bio-based cardanol onto 1,2-polybutadiene rubber (1,2-PB) based on the olefin metathesis. The 1,2-PB-g-CA demonstrate a controlled number average molecular weight from 7 × 103 to 4 × 104 and tuned functionality from 0% to 20%. The open reaction system exhibited a higher functionality due to the removal of small molecules. The 1,2-PB-g-CA was used as a plasticizer for silica filled styrene-butadiene rubber (SBR). The enhanced interfacial interaction between phenolic hydroxyl groups of cardanol and the silanol groups of silica significantly increased the compatibility of silica and rubber matrix. Compared with the common paraffinic oil, the obtained SBR/silica compounds were afforded low rolling resistance, high wet grip, and low heat build-up. Moreover, the 1,2-PB-g-CA showed better anti-migration properties. Therefore, our preparation method of bio-based modified liquid rubber has broad application prospects in high-performance “green tire.”

Chaos Synchronization of Two Györgyi–Field Systems for the Belousov–Zhabotinsky Chemical Reaction

Chemical reactions with oscillating behavior can present a chaos state in specific conditions. In this study, we analyzed the dynamic of the chaotic Belousov–Zhabotinsky (BZ) reaction using the Györgyi–Field model in order to identify the conditions of the chaos behavior. We studied the behavior of the reaction under different parameters that included both a low and high flux of chemical species. We performed our analysis of the flow regime in the conditions of an open reaction system, as this provides information about the behavior of the reaction over time. The proposed method for determining the favorable conditions for obtaining the state of chaos is based on the time evolution of the intermediate species and phase portraits. The synchronization of two Györgyi–Field systems based on the adaptive feedback method of control is presented in this work. The transient time until synchronization depends on the initial conditions of the two systems and on the strength of the controllers. Among the areas of interest for possible applications of the control method described in this paper, we can include identification of the reaction parameters and the extension to the other chaotic systems.

Glycothermally Synthesized Carbon Dots with Narrow-Bandwidth and Color-Tunable Solvatochromic Fluorescence for Wide-Color-Gamut Displays.

Fluorescent carbon dots (CDs) represent a promising eco-friendly next-generation phosphor. However, most CDs exhibit broad photoluminescence (PL) spectra [full width at half-maximum (fwhm) over 60 nm]; few works on CDs with sharp PL spectra (fwhm less than 40 nm) have been reported. In addition, their syntheses and color tuning require harsh conditions of high temperatures, long reaction times, and high pressures with catalysts. Here, we successfully prepared narrow-bandwidth emissive CDs (fwhm of 27–40 nm) from phloroglucinol in a glycol solvent of 1,2-pentanediol at temperatures as low as 180 °C for a reaction duration of as short as 6 h under ambient conditions without any catalysts via an open reaction system in which dehydration and condensation reactions among phloroglucinol molecules were enhanced. We shifted the emission peak from 463 to 511 nm by selecting seven kinds of solvents with different polarities, that is, emission colors could be tuned from blue to green by taking advantage of fluorescence solvatochromism. The CD-dispersed polymer films showed a similar solvatochromic behavior and sharp PL spectra, verifying the feasibility of applying the CDs to displays with a wide color gamut.

Mechanism and Origin of Chemoselectivity of Ru-Catalyzed Cross-Coupling of Secondary Alcohols to β-Disubstituted Ketones.

Ru-catalyzed cross-coupling of secondary alcohols with only byproducts H2 and H2O provides a green synthetic strategy to prepare β-disubstituted ketones. Density functional theory (DFT) calculations were performed with the coupling of 1-phenylethanol and cyclohexanol as a model reaction to gain deeper mechanistic insights herein. The mechanistic details of the main reaction and the key steps of possible side reactions were clarified, and the obtained results are consistent with reported selectivity. Hydrogenation of α,β-unsaturated ketones and dehydrogenation of ruthenium hydride intermediate are direct chemoselectivity-determining stages. The hydrogenation via 1,4-addition generates more stable intermediates, being favored over that via 1,2-addition, and thus avoids the formation of alkene products. The conjugation and π-π stacking effects of phenyl and the weak electronic effect of alkyls explain the dominance of specific ketone products in the hydrogenation stage. Hydrogenation of ketone products is kinetically operative but not exergonic enough to stop the irreversible dihydrogen release in an open reaction system, and thus alcohol products are absent. Furthermore, water evaporation in aldol condensation is found to be a double-edged sword, as it can accelerate the hydrogenation stage to prevent α,β-unsaturated ketones from being the main products but decrease the selectivity therein from thermodynamics overall.

Synthesis of Zeolite LTN-(SOD) Self-Supporting Membranes from SiO2-Rich Industrial Waste

Synthesis of zeolite LTN (“Linde Type N”) was investigated under insertion of a SiO2-rich filtration residue (FR) from waste water cleaning of the silane production. A new synthesis procedure was therefore developed applying a flotation mechanism with the aim to grow LTN in form of thin membrane like sheets. Preparation starts with preactivation of FR by slurrying first in alkaline solution, followed by an addition of aluminate solution and citric acid. The latter was added as suitable chelating agent for the initiation of the flotation process. In the course of these experiments, we succeeded in synthesizing zeo-lite LTN with more or less zeolite SOD as byproduct in the form of a stable compact membrane-like layer at low temperature of 60℃. The crystallization was performed under isotherm static conditions in an open reaction system without addition of organic templates as structure directing agents (OSDA’s). FR was utilized as a total substitute of sodium silicate in all experiments and an expansive pre-treatment procedure like calcinations was not needed. Furthermore, membrane formation with LTN of usual synthesis needs chemically functionalized supports. In contrast self-supporting membranous LTN layers were grown for the first time in the present study.

Enzyme efficiency: An open reaction system perspective.

A measure of enzyme efficiency is proposed for an open reaction network that, in suitable form, applies to closed systems as well. The idea originates from the description of classical enzyme kinetics in terms of cycles. We derive analytical expressions for the efficiency measure by treating the network not only deterministically but also stochastically. The latter accounts for any significant amount of noise that can be present in biological systems and hence reveals its impact on efficiency. Numerical verification of the results is also performed. It is found that the deterministic equation overestimates the efficiency, the more so for very small system sizes. Roles of various kinetics parameters and system sizes on the efficiency are thoroughly explored and compared with the standard definition k2/KM. Study of substrate fluctuation also indicates an interesting efficiency-accuracy balance.

A composite CdS thin film/TiO2 nanotube structure by ultrafast successive electrochemical deposition toward photovoltaic application.

Fabricating functional compounds on substrates with complicated morphology has been an important topic in material science and technology, which remains a challenging issue to simultaneously achieve a high growth rate for a complex nanostructure with simple controlling factors. Here, we present a novel simple and successive method based on chemical reactions in an open reaction system manipulated by an electric field. A uniform CdS/TiO2 composite tubular structure has been fabricated in highly ordered TiO2 nanotube arrays in a very short time period (~90 s) under room temperature (RT). The content of CdS in the resultant and its crystalline structure was tuned by the form and magnitude of external voltage. The as-formed structure has shown a quite broad and bulk-like light absorption spectrum with the absorption of photon energy even below that of the bulk CdS. The as-fabricated-sensitized solar cell based on this composite structure has achieved an efficiency of 1.43% without any chemical doping or co-sensitizing, 210% higher than quantum dot-sensitized solar cell (QDSSC) under a similar condition. Hopefully, this method can also easily grow nanostructures based on a wide range of compound materials for energy science and electronic technologies, especially for fast-deploying devices.

Preparation of small silicon carbide quantum dots by wet chemical etching

Abstract

Real time observation of proteolysis with Fourier transform infrared (FT-IR) and UV-circular dichroism spectroscopy: Watching a protease eat a protein

Fourier transform infrared (FT-IR)- and UV-circular dichroism (UV-CD) spectroscopy have been used to study real-time proteolytic digestion of β-lactoglobulin (β-LG) and β-casein (β-CN) by trypsin at various substrate/enzyme ratios in D 2O-buffer at 37 °C. Both techniques confirm that protein substrate looses its secondary structure upon conversion to the peptide fragments. This perturbation alters the backbone of the protein chain resulting in conformational changes and degrading of the intact protein. Precisely, the most significant spectral changes which arise from digestion take place in the amide I and amide II regions. The FT-IR spectra for the degraded β-LG show a decrease around 1634 cm −1, suggesting a decrease of β-sheet structure in the course of hydrolysis. Similarly, the intensity around the 1654 cm −1 band decreases for β-CN digested by trypsin, indicating a reduction in the α-helical part. On the other hand, the intensity around ∼1594 cm −1 and ∼1406 cm −1 increases upon enzymatic breakdown of both substrates, suggesting an increase in the antisymmetric and symmetric stretching modes of free carboxylates, respectively, as released digestion products. Observation of further H/D exchange in the course of digestion manifests the structural opening of the buried groups and accessibility to the core of the substrate. On the basis of the UV-CD spectra recorded for β-LG and β-CN digested by trypsin, the unordered structure increases concomitant with a decrease in the remaining structure, thus, revealing breakdown of the intact protein into smaller fragments. This model study in a closed reaction system may serve as a basis for the much more complex digestion processes in an open reaction system such as the stomach.

Thermodynamically consistent model calibration in chemical kinetics

BackgroundThe dynamics of biochemical reaction systems are constrained by the fundamental laws of thermodynamics, which impose well-defined relationships among the reaction rate constants characterizing these systems. Constructing biochemical reaction systems from experimental observations often leads to parameter values that do not satisfy the necessary thermodynamic constraints. This can result in models that are not physically realizable and may lead to inaccurate, or even erroneous, descriptions of cellular function.ResultsWe introduce a thermodynamically consistent model calibration (TCMC) method that can be effectively used to provide thermodynamically feasible values for the parameters of an open biochemical reaction system. The proposed method formulates the model calibration problem as a constrained optimization problem that takes thermodynamic constraints (and, if desired, additional non-thermodynamic constraints) into account. By calculating thermodynamically feasible values for the kinetic parameters of a well-known model of the EGF/ERK signaling cascade, we demonstrate the qualitative and quantitative significance of imposing thermodynamic constraints on these parameters and the effectiveness of our method for accomplishing this important task. MATLAB software, using the Systems Biology Toolbox 2.1, can be accessed from http://www.cis.jhu.edu/~goutsias/CSS lab/software.html. An SBML file containing the thermodynamically feasible EGF/ERK signaling cascade model can be found in the BioModels database.ConclusionsTCMC is a simple and flexible method for obtaining physically plausible values for the kinetic parameters of open biochemical reaction systems. It can be effectively used to recalculate a thermodynamically consistent set of parameter values for existing thermodynamically infeasible biochemical reaction models of cellular function as well as to estimate thermodynamically feasible values for the parameters of new models. Furthermore, TCMC can provide dimensionality reduction, better estimation performance, and lower computational complexity, and can help to alleviate the problem of data overfitting.

Cellular Biology in Terms of Stochastic Nonlinear Biochemical Dynamics: Emergent Properties, Isogenetic Variations and Chemical System Inheritability

Based on a stochastic, nonlinear, open biochemical reaction system perspective, we present an analytical theory for cellular biochemical processes. The chemical master equation (CME) approach provides a unifying mathematical framework for cellular modeling. We apply this theory to both self-regulating gene networks and phosphorylation-dephosphorylation signaling modules with feedbacks. Two types of bistability are illustrated in mesoscopic biochemical systems: one that has a macroscopic, deterministic counterpart and another that does not. In certain cases, the latter stochastic bistability is shown to be a “ghost” of the extinction phenomenon. We argue the thermal fluctuations inherent in molecular processes do not disappear in mesoscopic cell-sized nonlinear systems; rather they manifest themselves as isogenetic variations on a different time scale. Isogenetic biochemical variations in terms of the stochastic attractors can have extremely long lifetime. Transitions among discrete stochastic attractors spend most of the time in “waiting”, exhibit punctuated equilibria. It can be naturally passed to “daughter cells” via a simple growth and division process. The CME system follows a set of nonequilibrium thermodynamic laws that include non-increasing free energy F(t) with external energy drive Q hk ≥0, and total entropy production rate e p =−dF/dt+Q hk ≥0. In the thermodynamic limit, with a system’s size being infinitely large, the nonlinear bistability in the CME exhibits many of the characteristics of macroscopic equilibrium phase transition.

Preparation and characterization of sodium-free nanocrystalline sodalite

Zeolitic membranes based on the sodalite structure are of special interest for the separation of very small atoms and molecules (He, H 2, H 2O, NH 3). The two-step technique for the preparation of zeolitic membranes requires first the synthesis of suitable nanocrystals which act as seed crystals in the second step, the preparation of membrane. This work deals with the possibilities of synthesizing crystalline nanoparticles of pure silica sodalites and of aluminosilicate sodalites with a high Si:Al ratio. In the case of silica sodalites prepared with different neutral organic molecules as structure-directing agents, preparation of nanocrystals proved difficult and was possible only with low yields in a tedious process. With the tetramethylammonium cation (TMA) as structure-directing agent, aluminosilicate sodalite with idealized framework Si:Al ratio of 5:1 can be obtained as colloidal suspensions of nanocrystalline sodalite from a clear solution. By changing the reaction conditions from hydrothermal to an open reaction system, it is possible to generate sodalite nanocrystals in high yield. The characterization of these nanoparticles was done via dynamic light scattering, X-ray powder diffraction and high resolution scanning electron microscopy. The aluminosilicate sodalite nanocrystals thus produced can be used as seed crystals in the preparation of silica sodalite crystals with varying Si:Al ratios.

Fe0-based system as innovative technology for degrading trichloromethane: redox removal characteristics.

The spent waste of aliphatic chlorinated solvents has caused severe deterioration of groundwater quality. Trichloromethane (TCM), which shows health and toxicological effects on human beings, was selected as a model compound to be dechlorinated through a redox system. The Fe0-based system including Fe0/H2O, Fe0/UV, Fe0/H2O2, and Fe0/UV/H2O2 was explored to evaluate its performance in dechlorinating TCM. H2O2 was dosed at later reaction time points to initiate Fenton or photo-Fenton reactions. The first two systems demonstrate the reductive dechlorination of TCM by Fe0-released electrons, while the latter two show dechlorination of TCM by both electron reduction and hydroxyl radical oxidation. The system parameters of TCM remaining, Cl- buildup, Fe2+ accumulation, H2O2 residue, and ORP were measured to describe different redox characteristics of TCM dechlorination. The Cl- buildup was used as a way to describe the degree of TCM dechlorination in an open reaction system. Reductive dechlorination efficiencies of TCM were 5% and 6% for the systems of Fe0/H2O and Fe0/UV, respectively. In contrast, the Fe/H2O2 and Fe0/UV/H2O2 systems were capable of dechlorinating TCM reductively and oxidatively by 14% and 15%, respectively. The presence of UV light was found to retard the dissolution of Fe2+, but it enhanced the rate of chloride buildup, based on the comparison of Fe0/H2O and Fe0/UV systems. In addition, WV irradiation plays only a minor role in the Fe0/UV/H2O2 system, in view of TCM dechlorination. Application of small amount of H2O2 results in the increase of Fe2+ accumulation rate in the Fe0/H2O2 system. TCM was dechlorinated mostly through post Fenton oxidation; reductive reaction represents a less efficient way to dechlorinate TCM. The efficiencies of overall TCM dechlorination for the two systems of Fe0/H2O2 and Fe0/UV/ H2O2 are comparable to each other, and this implies that the presence of UV irradiation imposes no significant enhancement. RECOMMENDATIONS AND OUTLOOKS: It is highly recommended to initiate effective redox dechlorination of TCM with the system of Fe0/H2O2, where the H2O2 in excess is applied at a later reaction time point.

Advantages of external periodic events to the evolution of biochemical oscillatory reactions.

We compare, by calculations on a simple model of glycolysis, the evolutionary development of oscillatory reaction mechanisms in the presence and absence of external periodic events, such as an oscillatory or constant influx of glucose in an open reaction system. The chosen model has autonomous oscillations for given choices of the parameters of the feedback loops responsible for the oscillations, and for a given range of the total adenylate pool concentration. We change first one, then two of the parameters, so that there are no autonomous oscillations, and then vary these parameters with a genetic algorithm method in which the parameters are represented by binary strings that evolve by selection, crossover, and mutations; the optimization goal is the attainment of a high ATP/ADP concentration ratio in the system. This goal is taken to provide evolutionary advantages and is shown to be achieved more quickly in the presence of external periodic events, rather than constant influx of glucose. The results suggest the possibility of the enhanced evolutionary development of oscillatory biological reactions at shores where waves impinge on rocks and bring nutrients periodically. Measurements have shown that animals and plants grow more rapidly in the presence of such wave action than in its absence.

Hydrothermal Alteration Zoning and Kinetic Process of Mineral‐Water Interactions

AbstractThis study reports the kinetic experimental results of albite in water and in KCl solution at 22 MPa in the temperature range of 25 to 400°C. Kinetic experiments have been carried out in an open flow‐through reaction system (packed bed reactor). Albite dissolution is always incongruent in water at most temperatures, but becomes congruent at 300°C (close to the critical point 374°C). At temperatures from 25 to 300°C, the incongruent dissolution of albite is reflected by the fact that sodium and aluminum are easily dissolved into water, from 300 to 400°C it is reflected by silicon being more easily dissolved in water than Al and Na. Maximum albite dissolution rates in the flow hydrothermal systems have been repeatedly observed at 300°C, independent of flow rates.The kinetic experiments of albite dissolution in a KCl aqueous solution (0.1 mol KCl) indicate that the dissolution rate of albite increases with increasing temperature. Maximum silicon release rates of albite have been observed at 400°C, while maximum aluminum release rates of albite at 374°C. The reaction rates of albite also depend on the potassium concentration in the aqueous solution.These results can be used to interpret the mechanism for forming hydrothermal alteration. The kinetic experiments of mineral‐aqueous solutions interactions in the hydrothermal system from 25 to 400°C and at 22 MPa indicate that the formation of the feldspar‐mica‐kaolinite zoning occurring in some ore deposits may depend not only on the mineral stability but also on the kinetics of feldspar hydration, which is affected by the water property variation when crossing the critical point.

Lipase-catalyzed synthesis of lysophosphatidic acid in a solvent free system

The direct, lipase-catalyzed esterifications of glycerol-3-phosphate in an organic solvent system and in a solvent free system were carried out. In a solvent free system only, LPA synthesis could be achieved within the acceptable reaction time. Open reaction system was preferable to closed reaction system for LPA synthesis. Yield of LPA isolated by silica gel column chromatography was 32.3%.

Bistability and the ordered bimolecular mechanism

An equation describing the instantaneous velocity of an ordered bimolecular enzymatic reaction that exhibits inhibition by substrate and product was derived. Using kinetic constant values for horse liver alcohol dehydrogenase, the velocity expression was applied to an open-reaction system. The calculated steady-state surfaces displayed regions of bistability, which further substantiates the link between substrate inhibition and multiple steady states. This general computational approach may be applied to any system that can be described by an instantaneous velocity equation.

Catalytically reactive (η 4-tetracyclone)(CO) 2(H) 2Ru and related complexes in dehydrogenation of alcohols to esters

(η 4-Tetracyclone)(CO) 3Ru and [(η 4-tetracyclone)(CO) 2Ru] 2 are catalyst precursors in the direct oxidation of primary alcohols to esters. Their use without a H-acceptor in an open reaction system leads to bimolecular dehydrogenation of primary alcohols to esters and also of secondary alcohols to ketones with evolution of H 2. The structure of (η 4-tetracyclone)(CO) 2(H) 2Ru was assigned to a reaction intermediate observed during the catalysis. A catalytic cycle is proposed.

Multiple steady‐state phenomena within enzyme reactors: The enzyme reaction with two substrates

AbstractThe theoretical dynamic characteristics of an isothermal continuous flow stirred tank enzyme reactor (CFSTER) operating on two substrates are investigated. Under certain conditions multiple steady states are possible; namely, with an enzyme which binds with the two substrates sequentially. The occurrence of multiple steady states is found to be primarily dictated by three dimensionless parameters which incorporate rate law constants. The global stability of certain steady states is examined by numerically solving the transient material balance on the CFSTER. The effect of recycle on the dynamics of an isothermal plug flow enzyme reactor (PFER) is also studied. A general conclusion indicated by this work is that any open isothermal reaction system wherein the reaction rate law passes through a maximum with increasing substrate concentration and where back mixing occurs with exhibit multiple steady‐state behavior in some operating range.

Three steady state situation in an open chemical reaction system I.

In an isothermal continuously stirred tank reactor (open chemical reaction system) fed by sulphuric acid solutions of bromate, bromide and cerium (III) bistability (three steady state situation) is experimentally observed. This remarkable behavior, based on the instability of one steady state, has important consequences for the understanding of excitability and biochemical control mechanisms. The mass-balance equations for the reactor and the chemical mechanism of the reaction are combined into a simple mathematical model. The behavior of the resulting nonlinear differential equations is examined analytically and by a graphical integration procedure (method of isoclines). Using realistic kinetic data, the model shows the same behavior as observed in the experiment.