Enzyme Kinetic Equations of Irreversible and Reversible Reactions in Metabolism

This paper compares the irreversible and reversible rate equations from several uni-uni kinetic mechanisms (Michaelis-Menten, Hill and Adair equations) and bi-bi mechanisms (single- and double- displacement equations). In reversible reactions, Haldane relationship is considered to be identical for all mechanisms considered and reversible equations can be also obtained from this rela- tionship. Some reversible reactions of the metabolism are also presented, with their equilibrium constant.

Statistical deduction and experimental verification on kinetic equations for the curing reactions of epoxy resins/amines

Based on three typical mechanisms (second-order, third-order and competitive mechanisms) for the curing reactions of the epoxy resins with amines, a pair of the kinetic equations (for primary and secondary aminations) was presented to explain the uniformity and relationship among the three different kinetic mechanisms of the reactions. The presented macro-equations were deduced from the kinetic micro-equations by the statistics method. And the constitutive equations were verified by experimental data at different reaction times and temperatures (95°C, 60°C and 39°C), taking diglycidyl ether of bisphenol A (DGEBA) /ethyleneamine (EA) as a model.

KINETIC EQUATIONS WITH VARIATION OF LIQUID REACTANT CONCENTRATION

For two common types of liquid-solid heterogeneous reactions,the kinetic equations have been established which involved both the variation of liquid reactant concentration and the va- riation of solid reactant geornetry with the reaction time.The experimental results show that the kinetic equations are more accurate and reasonable than those appeared in previous litera- tures.Moreover,they are also suitable for gas-solid heterogeneous reactions in principle.

Exchange Reaction Between Selenite and Hydroxyl Ion of Variable Charge Soil Surfaces: Ⅱ. Kinetics of Hydroxyl Release

A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.

Mechanism and Kinetics Analysis of NO/SO_2/N_2/O_2 Dissociation Reactions in Non-Thermal Plasma

The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.

Quantitative kinetic analysis on oxygen reduction reaction:A perspective

Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.

Kinetics of catalytically activated duplication in aggregation growth

We propose a catalytically activated duplication model to mimic the coagulation and duplication of the DNA polymer system under the catalysis of the primer RNA. In the model, two aggregates of the same species can coagulate themselves and a DNA aggregate of any size can yield a new monomer or double itself with the help of RNA aggregates. By employing the mean-field rate equation approach we analytically investigate the evolution behaviour of the system. For the system with catalysis-driven monomer duplications, the aggregate size distribution of DNA polymers αk（t） always follows a power law in size in the long-time limit, and it decreases with time or approaches a time-independent steady-state form in the case of the duplication rate independent of the size of the mother aggregates, while it increases with time increasing in the case of the duplication rate proportional to the size of the mother aggregates. For the system with complete catalysis-driven duplications, the aggregate size distribution αk（t） approaches a generalized or modified scaling form.

Kinetics of celestite conversion to acidic strontium oxalate hydrate in aqueous solution of oxalic acid

Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.

Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

This investigation was carried out to establish a new domestic landfill gas(LFG)generation rate model that takes into account the impact of leachate recirculation.The first-order kinetics and two-stage reaction(FKTSR)model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages.In this study,the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate.Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model.The model calibration was then calculated by using the experimental data.The results suggested that the new model was in line with the experimental data.The main parameters of the modified FKTSR model,including the LFG production potential(L0),the reaction rate constant in the first stage(K1),and the reaction rate constant in the second stage(K2)of 64.746 L,0.202 d^(–1),and 0.338 d^(–1),respectively,were comparable to the old ones of 42.069 L,0.231 d^(–1),and 0.231 d^(–1).The new model is better able to explain the mechanisms involved in LFG generation.

The Chemical Channel of Earthquake Reactions and Decrease in the Magnitude of Earthquakes

The first necessary condition for the onset of an earthquake is the penetration of explosive gas into an explosive zone as a result of physical or chemical reaction. The second necessary condition is to ensure the subsequent propagation of the flame after ignition. The latter condition has made it possible to explain the impact of a cyclone on the emergence of 42 strongest earthquakes in the 21st century. If violation of this condition can be achieved with the help of vibrators or explosions, this will result in a decrease in the magnitude of an earthquake or even a complete prevention of earthquakes. Thus, the second condition is essentially a “pressure lock” that opens (with a decrease in the pressure caused by a cyclone), which leads to an earthquake or closes (with an increase in the pressure caused by an anticyclone or human interference using vibrators or explosions), which leads to earthquake prevention. Kinetic equations of the 2nd type were used to describe chemical reactions and obtain formulas for the precursor time, which made it possible to describe earthquakes of the chemical channel. The set of experimental time values of the earthquake precursor described by the physical model includes about 20% of all earthquakes;80% of earthquakes can be attributed to the chemical channel for earthquakes that occurred in Dushanbe in 1983. All earthquakes in Tiberias in June 2018 passed through the chemical channel, which can be concluded from the small magnitude of these earthquakes. Several proposals have been made, including: 1) creating a new sensor for the geochemical method, which allows determining the epicenter of a future earthquake;2) creating a network of stations with a new sensor for determining the epicenter and an atmospheric pressure meter installed at each station (this will determine if the “pressure lock” is closed by an anticyclone, which can lead to a decrease in the magnitude of an earthquake or even prevent an earthquake);3) installing vibrators in epicenters (or making daily explosions with explosives delivered by trucks, drones, airplanes or helicopters, which should lower the magnitudes of future dangerous earthquakes);4) alerting the public to the expected future earthquake;5) developing specialized vibrators for reducing the magnitude of an impending catastrophic earthquake. Thus, this article is a breakthrough, describing a new mechanism in earthquakes for understanding and theory of earthquakes, which are used for the vast majority of earthquakes, including for program to reduce the magnitude of dangerous earthquakes.

基于数学模型的城市河道补水需求研究——以六盘水市水城河为例

水源补给对缺水的城市河道至关重要。论文以六盘水市水城河为例,基于S-P模型、一级反应动力学方程等数学模型展开研究,结果表明:BOD5及氨氮浓度与补水量拟合度极高,拟合曲线判定系数R2均大于0.99;基于拟合关系推算河道污染物达标所需补水量,并以水体氧平衡进行核算,最终计算得出适宜的补水量。城市河道形态平直、地形简单,河道内水体流态接近一维恒定流,与数学模型原理接近,因而数学模型在城市河道补水研究具有较好的应用性,可大幅减少使用商业软件的工作量。本研究可为城市河道补水研究提供思路借鉴和手段参考。

基于热分析-炮制动力学的焦栀子火力/火候的量化研究

目的:采用热分析技术明确栀子及其主要成分的热解温度范围,以化学动力学原理研究焦栀子炮制过程中京尼平苷及西红花苷I变化规律,建立京尼平苷、西红花苷I动力学方程,为焦栀子生产工艺参数优化提供参考。方法:采用热重-微商热重(TG-DTG)技术,对生栀子、京尼平苷和西红花苷I进行程序升温及恒温的热解特性研究及热分析动力学研究,确立生栀子热解主要温度范围;以该温度范围为参考,确立焦栀子不同炮制温度,利用HPLC测定不同炮制温度-时间焦栀子过程饮片京尼平苷及西红花苷I含量。结果:生栀子主要热解温度范围为229.7~329.4℃,所得京尼平苷动力学方程为ln K=9.5938-6968.3•T^(-1),西红花苷I动力学方程为ln K=5.4161-472.7•T^(-1)。符合一级动力学特征。结论:焦栀子最佳温度为260℃,京尼平苷、西红花苷I动力学方程的建立可为建立焦栀子火候量化标准提供参考。

考虑转化率的亚硝酸钠与氯化铵体系反应动力学

针对现有未考虑反应物转化率的NaNO_(2)/NH_(4)Cl反应动力学方程难以有效预测生热/生氮气情况的问题,运用实验测试分析方法探究氮气生成反应的H^(+)浓度界限、反应转化率及其变化规律;采用灰色关联分析法研究各因素的影响程度;利用牛顿-拉斐逊迭代方法计算引入反应转化率的反应动力学参数,探讨生热/生氮气反应的预测方法。结果表明:NaNO_(2)/NH_(4)Cl体系氮气生成反应的H^(+)浓度界限为c_(H^(+))≤0.0225 mol/L(或pH≥1.65),且氮气生成反应转化率随着反应物和H^(+)浓度的增大,温度的升高而增大,其关联性最高的反应物浓度的关联度为0.8;考虑反应转化率的NaNO_(2)/NH_(4)Cl体系反应动力学方程为dηd t=4.74×10^(4)e^(-3389/T)c^(1.545)_(H^(+))c^(1.346)c_(0)(1-η)2.346或(1-η)^(-1.346)-1/1.346=4.74×10^(4)e^(-3389/T)c^(1.545)_(H^(+))c^(1.346)0_t,η<1,可有效、便捷地进行生热/生氮气反应预测。

KINETICS STUDIES OF MINERAL-WATER REACTIONS IN HYDROTHERMAL FLOW SYSTEMS AT ELEVATED TEMPERATURES AND PRESSURES

This paper describes new experimental results on mlneral-water reaction kinetics obtained in plug-flow systems at high temperatures and pressures. As an example, the rates of reaction between calcite, fluorite, albite and water in the continuous flowing system have been measured in three separate studies. All experiments are carried out by suspending a sample bag in the plug-flow vessel, by pumping water at carefully controlled rates through the vessel, and by collecting and analyzing the reacted solution. In addition, the reaction mechanisms of fluorite and albite in a packed bed reactor have been studied with the aid of an axial dispersion model. The main factors controlling the effective dissolution rate with respect to temperature, solvent flow rate, and chemistry of the input solutions have been evaluated. It is also found that a non-steady state process is, in some cases, still observed, even under conditions where steady state conditions should have been attained. These results provide information useful in developing models for mineral-water reaction kinetics in the open flow system at high temperatures and pressures.

胶凝酸反应动力学试验研究

胶凝酸是目前酸化压裂技术中广泛应用的一种酸液体系,具有良好的缓速、降滤失、造缝、携砂与减阻性能,并能减轻二次伤害,在低渗透油气藏改造中,可有效提高酸的穿透距离和酸蚀裂缝的导流能力.介绍了胶凝酸反应动力学的试验方法及基本原理,开展了普通酸和胶凝酸与灰岩的反应动力学试验,得出不同条件下的酸岩反应动力学参数及反应动力学方程.从试验结果可以看出,在相同温度和酸液浓度条件下,普通酸的反应速度大于胶凝酸反应速度,普通酸的反应速度为胶凝酸的2～3倍;温度对酸岩反应速度的影响较大,在相同酸液浓度下,温度升高,酸岩反应速度增加,其中普通酸反应速度增加明显,胶凝酸增加缓慢.

水泥生料分解动力学的研究

应用高精度热重仪对水泥生料及其石灰石在氮气气氛、不同升温速率下的分解动力学进行了研究,采用普适积分法、微分方程法以及多重速率扫描Kissinger法相结合的方式确定分解机理,求解动力学参数。研究结果表明:水泥生料及其石灰石分解符合相边界反应的收缩圆柱体反应机理,并且还发现活化能E和指前因子A随试验条件的改变呈规律性的变化。

液相法苯选择加氢制环己烯催化反应动力学方程

测定了Ru M B/ZrO2 催化剂上选择加氢制环己烯反应过程中苯、环己烯及环己烷浓度随时间变化的c～t曲线 ,获得了苯选择加氢制环己烯反应中各步反应的级数和速率常数等动力学参数 .结果给出 ,苯转化的反应级数对苯为 1,对氢低压下为 2 ,高压下为 0 ;环己烯继续加氢生成环己烷的反应级数对环己烯为 0 ,对氢低压下为 2 ,高压下为 0 .在此基础上建立了苯选择加氢制环己烯各步反应的动力学方程 。

不饱和聚酯树脂/CaCO_3体系固化动力学非等温DSC研究

采用示差扫描量热(DSC)法对不饱和聚酯树脂(UP树脂)/CaCO3复合体系的固化过程进行研究,得出不同升温速率下UP树脂/CaCO3复合体系固化过程中的DSC曲线,并由动态DSC曲线求出固化反应的活化能、固化反应级数及动力学方程中的指前因子等参数,建立了复合体系固化反应动力学的数学模型。

Fenton试剂氧化降解甲烷的动力学规律

为研究Fenton试剂产生的羟基自由基·OH对甲烷的降解与动力学规律,利用自制的鼓泡反应装置,系统研究反应时间、H2O2浓度(c(H2O2))、Fe2+浓度(c(Fe2+))、初始pH值、反应温度等因素对煤矿瓦斯(甲烷)降解率的影响。实验结果表明,Fenton试剂对甲烷有较好的降解效果,对于浓度为4.9%的甲烷气体,当c(H2O2)=100 mmol/L、c(Fe2+)=2.0 mmol/L、初始pH=2.5、T=25℃时,反应30 min后,甲烷的最高降解率达0.25。通过对甲烷降解率与时间的变化关系进行非线性拟合,结果表明其反应动力学规律符合Boltzmann方程,而且方程中的参数d x即为影响Fenton试剂氧化降解甲烷效果的浓度经验校正系数,并最终得出甲烷降解率的定量计算公式。

Photocatalytic activity of Fe-doped diopside

UV-visible light induced photocatalytic degradation of methylene blue (MB) over Fe-doped diopside was investigated. The structure, composition, morphology and absorption property of UV-visible light of as-prepared samples were characterized using XRD, SEM, FTIR and UV-vis DRS. The experimental results show that doping Fe3+ induced the formation of some new species in diopside, and promoted light adsorption property of diopside in UV-visible region. Photochemical reactivity of Fe-doped diopside obviously depended on the content of doping Fe3+. The diopside with 1.848% Fe3+ exhibited the superior photocatalytic activity with 95% degradation of MB under UV-visible light for 3 h. The photocatalytic degradation kinetics of MB over all samples showed the first-order reaction nature.