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This work designed a mesoscale method of multi-step reduction of Fe 2 O 3 with H 2 based on Lattice Gas Cellular Automata (LGCA). Particles in the LGCA were marked to distinguish all the reactants, intermediates, products, and inert. A self-organized evolutionary mechanism is designed. The hydrogen reduction of Fe 2 O 3 in the temperature range of 460–550 °C and 650–800 °C was simulated. Results show that the intermediate product Fe 3 O 4 was found in both conditions, and its mass fraction quickly reach a peak at ∼0.8 and gradually decrease thereafter. An "induction period" can be identified in the initial stage of the reaction at 650–800 °C, where the reduction rate is slow due to the hindered formation of FeO. The porosity inside the Fe 2 O 3 particles increases continuously through the reduction process, resulting in significant changes in the flow field around the particles. Consequently, the wake vortex gradually decreases and disappears eventually. • The multiple step reduction of Fe 2 O 3 by hydrogen is investigated in mesoscale. • A mesoscale method with self-organized evolutionary mechanism is developed. • Three obvious reaction rate transitions can be identified at 650–800 °C by the method. • The flow field is altered from internal structural of Fe 2 O 3 changes during reduction. [ABSTRACT FROM AUTHOR]

The transformation reactions of indole derivatives are fundamental knowledge in organic chemistry. Using electrons as clean reagents, electrochemistry serves as a sustainable alternative to traditional redox organic transformations and received considerable attention in recent years. In this study, 3-aryl indole was used as raw materials to realize dehydrogenation coupling and coupling-cyclization only by prolonging the electrolysis reaction time. The reaction runs under mild conditions and the reaction operation is simple and safe. The reaction is efficient to gain product in good yield and can be monitored by using thin-layer chromatography. There are various reaction phenomena for students to observe. Moreover, the final product of the reaction is controllable via simply tuning the reaction time. The experiment can be reproduced with similar efficiency after many times. All products are solid and can be purified via silica gel column chromatography. Nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HRMS) were recorded to analyze the structure of products which also show different fluorescence properties. Based on the basic knowledge of indole transformation chemistry, this experiment uses green electrolysis strategies to develop practical synthesis methods for nitrogen-containing heterocyclic compounds, and guides students to learn interdisciplinary knowledge of organic synthesis chemistry and physical chemistry, establishes interdisciplinary knowledge awareness and pays attention to the frontiers of organic chemistry. [ABSTRACT FROM AUTHOR]

Fiber-reinforced phenolic composite has become an ideal material for solid rocket motor's (SRM) nozzle, because of its excellent high temperature resistance and ablation resistance. The physical and chemical properties of reinforcing fiber would significantly affect the cure reaction of phenolic (PF) resin, which results in the obvious difference between the cure characteristics of the fiber-reinforced phenolic system and neat resin. To clarify the difference in cure reaction between fiber-reinforced phenolic system and PF resin, meanwhile, to obtain the kinetics of high silica glass fiber/phenolic (GF-HSi/PF) prepreg and carbon fiber/phenolic (CF/PF) prepreg, the dynamic experiments of PF resin, GF-HSi/PF prepreg and CF/PF prepreg are carried out by differential scanning calorimetry (DSC). Iso-conversional kinetics is proposed, and the activation energy is determined as a function of cure degree. The reaction model f(α) is obtained by introducing the kinetics compensation effect, founding that the f(α) of PF resin is influenced significantly by reinforcing fiber. The kinetics of three materials are determined by the model-fitting method, founding that the kinetic models of PF resin, GF-HSi/PF prepreg and CF/PF prepreg are a one-step autocatalytic model, two-step model from autocatalytic reaction to N-order reaction and three-step model from autocatalytic reaction to N-order reaction respectively. [ABSTRACT FROM AUTHOR]

Multi-enzyme cascade reactions for the synthesis of complex products have gained importance in recent decades. Their advantages compared to single biotransformations include the possibility to synthesize complex molecules without purification of reaction intermediates, easier handling of unstable intermediates, and dealing with unfavorable thermodynamics by coupled equilibria. In this study, a four-enzyme cascade consisting of ScADK, AjPPK2, and SmPPK2 for ATP synthesis from adenosine coupled to the cyclic GMP-AMP synthase (cGAS) catalyzing cyclic GMP-AMP (2′3′-cGAMP) formation was successfully developed. The 2′3′-cGAMP synthesis rates were comparable to the maximal reaction rate achieved in single-step reactions. An iterative optimization of substrate, cofactor, and enzyme concentrations led to an overall yield of 0.08 mole 2′3′-cGAMP per mole adenosine, which is comparable to chemical synthesis. The established enzyme cascade enabled the synthesis of 2′3′-cGAMP from GTP and inexpensive adenosine as well as polyphosphate in a biocatalytic one-pot reaction, demonstrating the performance capabilities of multi-enzyme cascades for the synthesis of pharmaceutically relevant products.

Artificial cascade reactions involving biocatalysts have demonstrated a tremendous potential during the recent years. This review just focuses on selected examples of the last year and putting them into context to a previously published suggestion for classification. Subdividing the cascades according to the number of catalysts in the linear sequence, and classifying whether the steps are performed simultaneous or in a sequential fashion as well as whether the reaction sequence is performed in vitro or in vivo allows to organise the concepts. The last year showed, that combinations of in vivo as well as in vitro are possible. Incompatible reaction steps may be run in a sequential fashion or by compartmentalisation of the incompatible steps either by using special reactors (membrane), polymersomes or flow techniques. Chasing waterfalls! Artificial cascades involving biocatalysts are selected from the last year and are classified. The recent examples showed, that even combinations of in vivo as well as in vitro cascades are possible. Incompatible reaction steps may be run in a sequential fashion or by compartmentalisation of the incompatible steps. [ABSTRACT FROM AUTHOR]

In the present paper, combustion phenomenon and heat transfer simulation in a 3-D porous radiant burner (PRB) are numerically studied. Multi-step reaction of methane/air with detailed chemical kinetics is considered to model the combustion process inside the porous matrix. Assuming the nonlocal thermal equilibrium between solid and gas phases, separate energy equations are considered for these two phases. Porous medium is assumed as a gray medium that can absorb, scatter, and emit thermal radiation, whereas the gas phase is considered to be transparent to thermal radiation. The governing equations are gas and porous energy equations, the chemical species transport equation and the radiative transfer equation that should be simultaneously and numerically solved. Discrete ordinates method is used to solve the radiative transfer equation in order to calculate the radiative term in the solid energy equation. The simulation results include temperature fields for the gas and solid phase, species mass fraction distributions, and radiative heat flux distributions along the burner. Finally, the effect of different parameters such as optical thickness, scattering albedo, and excess air ratio (EAR) on the performance of the burner are explored. [ABSTRACT FROM AUTHOR]

Cytochrome P450 (P450, CYP) family 51 enzymes catalyze the 14α-demethylation of sterols, leading to critical products used for membranes and the production of steroids, as well as signaling molecules. In mammals, P450 51 catalyzes the 3-step, 6-electron oxidation of lanosterol to form (4β,5α)-4,4-dimethyl-cholestra-8,14,24-trien-3-ol (FF-MAS). P450 51A1 can also use 24,25-dihydrolanosterol (a natural substrate in the Kandutsch-Russell cholesterol pathway). 24,25-Dihydrolanosterol and the corresponding P450 51A1 reaction intermediates, the 14α-alcohol and -aldehyde derivatives of dihydrolanosterol, were synthesized to study the kinetic processivity of the overall 14α-demethylation reaction of human P450 51A1. A combination of steady-state kinetic parameters, steady-state binding constants, dissociation rates of P450-sterol complexes, and kinetic modeling of the time course of oxidation of a P450-dihydrolanosterol complex showed that the overall reaction is highly processive, with k off  rates of P450 51A1-dihydrolanosterol and the 14α-alcohol and 14α-aldehyde complexes being 1 to 2 orders of magnitude less than the forward rates of competing oxidations. epi-Dihydrolanosterol (the 3α-hydroxy analog) was as efficient as the common 3β-hydroxy isomer in the binding and formation of dihydro FF-MAS. The common lanosterol contaminant dihydroagnosterol was found to be a substrate of human P450 51A1, with roughly one-half the activity of dihydrolanosterol. Steady-state experiments with 14α-methyl deuterated dihydrolanosterol showed no kinetic isotope effect, indicating that C-14α C-H bond breaking is not rate-limiting in any of the individual steps. The high processivity of this reaction generates higher efficiency and also renders the reaction less sensitive to inhibitors., Competing Interests: Conflict of interest All of the authors declare that they have no conflict of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

• Isothermal kinetic predictions were performed by using the advanced isoconversional method. • The effects of reaction type, set temperature and range of heating rates on predicted accuracy were evaluated. • The predictions of the single-step and multi-step reactions are conducted. • The reason of failure on isothermal prediction is given. Isothermal prediction based on kinetic parameters from advanced isoconversional method (NLN) has been successfully used in various materials. However, the validity of the method is sometimes suspected because of some depressing predictions. In this paper, we set a single-step solid state reaction and a multi-step solid state reaction to simulate and predict. The effects of set temperature and composition of heating rate group on the isothermal prediction are evaluated. For the single-step reaction, all the relative errors of single-step reaction are less than 10%. Therefore, the method provides accurate enough isothermal predictions at different set temperatures and heating rate groups. As for the multi-step reaction, the accuracy of prediction varies with the set temperature and the composition of heating rate group. The reason for the failure of multi-step reaction prediction is the inconsistency in the concept of isothermal and nonisothermal isoconversional activation energy. [ABSTRACT FROM AUTHOR]

In the advent of the miniaturized mobile devices, the packaging technology is required utmost high performance of the thin composite laminates in such materials properties as the coefficient of thermal expansion (CTE) and stiffness. Accordingly, the composition of a thermosetting resin becomes extremely complicated often including multiple fillers, monomers and/or catalysts in thermoset-based glass fiber prepregs. The prepreg systems is so complicated that it is usually difficult to obtain a reliable kinetic description and methodology that could be used for the complex thermal cycles including both isothermal and dynamic-heating segments in a facile manner. In this investigation, we propose an isoconversional kinetic using an ultra-thin glass fiber epoxy prepreg with highly loaded silica filler (the ultra-thin glass fiber/silica bead epoxy prepreg) as a model system. The activation energy was determined as a function of the conversion of curing reactions, which was fitted to linear models. The kinetic prediction using the linear models showed an excellent agreement to isothermal experiments. The master curve of a conversion-dependent function which derived from activation energy dependency used to investigate the complex reactions of the ultra-thin glass fiber/silica bead epoxy prepreg. [ABSTRACT FROM AUTHOR]

Abstract: A practical route to 6-bromo-5,7-dihydroxyphthalide 5-methyl ether, a versatile intermediate in the synthesis of hericenones and related bioactive polyphenols, was developed. The synthesis features a combination of tandem Michael addition-Claisen condensation and CuBr2-mediated multi-step reactions. With this product in hand, total syntheses of hericenone J and 5′-deoxohericenone C (hericene A) were achieved. [Copyright &y& Elsevier]

The crystallization kinetic of the basalt glass ceramic of the oxide composition, (%): SiO2 − 50.82; Al2O3 − 12.05; Fe2O3 − 9.28; CaO − 15.48; MgO − 11.08; Na2O+K2O − 1.14; TiO2 − 0.15, with addition of 10% TiO2 as nucleating agent has been studied using thermal analysis under non-isothermal conditions. In this order, the non-isothermal DTA curves were obtained at different heating rates between 4 and 20°C min−1 in the temperature range of 25–1000°C using a Derivatograph-C (MOM, Hungary). The kinetic parameters of the crystallization process were calculated on the basis of Ozawa-Flynn-Wall, Friedman, Budrugeac-Segal and non-parametric kinetic methods. [ABSTRACT FROM AUTHOR]

Multi-enzyme cascade reactions for the synthesis of complex products have gained importance in recent decades. Their advantages compared to single biotransformations include the possibility to synthesize complex molecules without purification of reaction intermediates, easier handling of unstable intermediates, and dealing with unfavorable thermodynamics by coupled equilibria. In this study, a four-enzyme cascade consisting of ScADK, AjPPK2, and SmPPK2 for ATP synthesis from adenosine coupled to the cyclic GMP-AMP synthase (cGAS) catalyzing cyclic GMP-AMP (2′3′-cGAMP) formation was successfully developed. The 2′3′-cGAMP synthesis rates were comparable to the maximal reaction rate achieved in single-step reactions. An iterative optimization of substrate, cofactor, and enzyme concentrations led to an overall yield of 0.08 mole 2′3′-cGAMP per mole adenosine, which is comparable to chemical synthesis. The established enzyme cascade enabled the synthesis of 2′3′-cGAMP from GTP and inexpensive adenosine as well as polyphosphate in a biocatalytic one-pot reaction, demonstrating the performance capabilities of multi-enzyme cascades for the synthesis of pharmaceutically relevant products. [ABSTRACT FROM AUTHOR]