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The enzyme kinetics reaction scheme of single enzyme-sub-strate dynamics, originally proposed by V. Henri, is considered. The system of ODEs induced by the reaction scheme is compared to two approximate models, namely the Michaelis-Menten model and the model of exponential decay. Validity conditions for the Michaelis-Menten model are briefly reviewed. A case specific for ``superefficient enzymes'' is used as a setting for a comparison between the three models via computational experiments. The case study proves the importance of validating the applicability of the approximate model.A novel cell growth model is proposed and analyzed. The approach of model development is to make use of the original Henri enzyme kinetics law in the context of metabolic processes in living cells, namely cell growth. Two approximations corresponding to different cell growth phases are introduced in order to study the model analytically.

The original version of this article unfortunately contains the error in reaction Scheme 1 Index Abstract and inside text.

Column chromatography-free stereoselective synthesis of Corey's intermediate for Tamiflu (oseltamivir phosphate) was achieved, starting from l-glutamic acid γ-ethyl ester. The reagents and solvents used in the reaction scheme are industrially tractable, rendering the synthesis a potential starting point for process research.

Reaction of 1-butene was studied over silicalite-1 and H-ZSM-5 zeolites with different Al contents (SiO2/Al2O3 molar ratio (Si/Al2) = 23, 80, and 280) to explore an efficient catalyst for the formation of propene as well as to elucidate the reaction scheme and the relevant acid sites involved in the reaction. The formation of alkenes, including propene, increased and those of alkanes and aromatics decreased with decreasing Al content. The percentage of alkenes other than n-butene isomers was 60 C-wt % over silicalite-1 at 550 °C with 34.1 C-wt % propene. Over H-ZSM-5 with Si/Al2 = 23, the formation of alkenes was negligible, and the main products were alkanes and aromatics, the sum of alkanes and aromatics being 65.4 C-wt % at 550 °C. These product distributions are consistently interpreted by the successive reactions of oligomerization, cracking, and hydrogen transfer. For oligomerization and cracking, in addition to strong acid sites on H-ZSM-5 zeolites, weak acid sites present on silicalite-1 act as ac...

The reaction between hydrogen and chlorine shows resemblance to that between hydrogen and bromine but is considerably more complicated, owing to the larger number of elementary processes that play a significant part in it. The reaction scheme proposed for the hydrogen-chlorine reaction differs in several important respects from that for the hydrogen-bromine reaction. The main differences are seen to be (1) the inclusion of the reaction H + HBr → H 2 + Br and the exclusion of H + HCl → H 2 + Cl, and (2) the different chain-terminating steps, Br + Br → Br 2 being assumed for bromine and the three processes H + O 2 , Cl + O 2 , and Cl + X in the chlorine reaction. The rather marked difference between the reactions of chlorine, bromine, and iodine with hydrogen is that the hydrogen-iodine reaction is elementary while the others are not.

The kinetic characteristics of the formation of liquid products by the hydrogenation of coal from the Karazhir deposit (Republic of Kazakhstan) were studied. Two kinetic models were considered to describe nonlinear (parallel-consecutive reactions) and linear (consecutive reactions) schemes. Within the frame-work of each particular reaction scheme, analytical equations were obtained to describe the yields of fractions with boiling points to 200, 200–350, and above 350°C; gas; and solid residue depending on time and corresponding calculations were performed. A comparative analysis of the experimental results was carried out according to the two kinetic schemes.

The thermodynamic optimization of the Sn-Y and Mg-Sn-Y systems was critically carried out by means of the CALPHAD (CALculation of PHAse Diagram) technique. In the Sn-Y system, the solution phases (liquid, bcc, bct and hcp) were described by the substitutional solution model. The compound Sn 3 Y 5 , which has a homogeneity range, was treated as the formula (Sn, Y) 3 (Sn, Y) 2 Y 3 by a three-sublattice model in accordance with the site occupancies. In the Mg-Sn-Y system, the liquid phase was treated as the formula (Mg, Sn, Y, Mg 2 Sn) using an associated solution model, and bcc, bct and hcp were treated as the formula (Mg, Sn, Y). The compound Sn 3 Y 5 was treated as the formula (Sn, Y, Mg) 3 (Sn, Y, Mg) 2 Y 3 . The ternary compound MgSnY was treated as stoichiometric compound. A set of self-consistent thermodynamic parameters of the Mg-Sn-Y system was obtained. The projection of the liquidus surfaces and the reaction scheme of the Mg-Sn-Y system were predicted.

Software application is implemented in this work to take full advantage of the characteristics of current operating systems and to provide the optimized symbolic kinetic equations for both enzyme and ligand species involved in enzyme reactions. This software, called SKEE-w2013, is implemented using C# language and runs under all operating systems from Windows XP up to Windows 8. It is applicable to any enzyme reaction mechanism that fits the general reaction scheme proposed previously by our group. It can be downloaded, free of charge, from http://oretano.iele-ab.uclm.es/~BioChem-mg/software.php . Besides the optimized equations, the software can provide non-optimized equations, so that the user can compare the advantage of using optimized equations rather than the non-optimized ones, whenever they do not coincide. Moreover, the software circumvents the limitations of other existing previous software tools implemented with what are nowadays obsolete programming languages and that, moreover, are limited to non-optimized kinetic equations.

This paper discusses a method for determining the kinetics of biomass pyrolysis based on comparing isoconversional methods, such as the Kissinger and KAS methods, and least squares fitting in a parallel reaction scheme with three pseudo-components roughly representing cellulose, hemicellulose and lignin. The activation energies of the different pseudo-components reported in the literature vary widely. This variation could be reduced if care were taken to determine the kinetics of biomass pyrolysis: First, the reference experiments with pure cellulose are reproduced to validate the thermogravimetric analysis. Then, experiments are performed and analyzed with different heating rates and isoconversional methods are employed to verify the reliability of the experiments and to avoid selecting inappropriate reaction models in a fitting routine.

A thermodynamic assessment of the ternary Cr–Ni–Ti system together with a refinement for the thermodynamic description of the binary Ni–Ti sub-system is performed following the CALPHAD method and using the compound energy formalism (CEF). The ordered/disordered transition between disordered Bcc_A2 and ordered Bcc_B2 phases is described using a four-sublattice (4SL) model. An optimal set of thermodynamic parameters for the Cr–Ni–Ti system is obtained by considering the experimental data from the literature. Comparisons between the calculated and measured phase diagrams indicate that almost all of the reliable experimental information is satisfactorily accounted for by the present modeling. The complete liquidus projection and reaction scheme of the Cr–Ni–Ti system are also presented.

A convenient and modular synthesis involving diastereoselective Michael addition followed by regioselective Huisgen 1,3-dipolar cycloaddition reaction was carried out to furnish 1,4-disubstituted-1,2,3-triazoles of Ludartin. This reaction scheme involving Michael addition followed by regioselective Huisgen 1,3-dipolar cycloaddition reaction leading to the formation of triazolyl analogs is being reported for the first time. All the triazolyl products were characterised using spectral data analysis. Sulphorhodamine B cytotoxicity screening of the resulting products against a panel of five human cancerous cell-lines revealed that few of the analogs display promising broad spectrum cytotoxic effect. Among all the synthesized compounds, only 3q displayed the best cytotoxic effect with IC50 values of 12, 11, 38, 39 and 8.5 μM but less than the standard Ludartin (1) with IC50 values of 6.3, 7.4, 7.5, 6.9 and 0.5 μM against human neuroblastoma (T98G), lung (A-549), prostate (PC-3), colon (HCT-116) and breast (MCF-7) cancer cell lines, respectively. The present synthesis was designed based on the previous literature reports of Ludartin as an aromatase inhibitor. Our work provides an initial study on structure-activity relationship of triazolyl analogs of sesquiterpene lactones in general and Ludartin (1) in particular.

C-Phosphorylation of diacetone alcohol with phosphorus pentachloride was studied. The products, pentadienyltrichlorophosphonium hexachlorophosphates and (4-chloro-2-methylpenta-1, 3-dien-1-yl)phosphonyl and (2-chloro-4-methylpenta-1, 3-dien-1-yl)phosphonyl dichlorides were isolated and characterized by NMR and IR spectroscopy. A reaction scheme was suggested.

Liquid-phase oxidation of 2,4-dinitrotoluene with ozone in the presence of acetic anhydride as stop reagent and manganese(II) acetate as catalyst was studied. The major products of oxidation with ozone in acetic anhydride are 2,4-dinitrobenzyl alcohol (65.8%) and 2,4-dinitrobenzaldehyde (18.8%) in the form of the corresponding acetates. A reaction scheme accounting for the results obtained is considered.

International audience; The present work proposes a new experimental strategy based on a general model which describes and includes different reactor technologies. The strategy is based on a sequential iterative approach where, in a predictive step, the model is used to propose optimal experimental conditions, and, in a validation step, experimental data are used to improve the parameter estimation. A specific work bench with three types of reactors (batch, semi-batch stirred tank and continuous plug flow reactor) has been developed. The demonstration of the strategy is performed by using a classical parallel-consecutive reaction scheme, for which it has been demonstrated experimentally that the use of several reactors enlarges the experimental window, which enables to improve the accuracy on kinetic constants by comparison to using a restricted experimental window, with only one kind of reactor.

4-[2-(Arylmethylidene)hydrazinylidene]cyclohexa-2,5-dienones react with aromatic amines according to the 1,8-addition pattern with formation of N-aryl-N′-(4-oxocyclohexa-2,5-dien-1-ylidene)arenecarbohydrazonamides. The reaction is favored by increase of electron-donating power of the substituent in aromatic amine and electron-withdrawing power of the benzylidene fragment of quinone imine. A probable reaction scheme has been proposed.

Previous research on brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) has largely focussed on their concentrations in the environment and their adverse effects on human health. This paper explores their transfer from waste streams to water and soil. A comprehensive mass balance model is developed to track polybrominated diphenyl ethers (PBDEs), originating from e-waste and non-e-waste solids leaching from a landfill. Stepwise debromination is assumed to occur in three sub-systems (e-waste, aqueous leachate phase, and non-e-waste solids). Analysis of landfill samples and laboratory results from a solid-liquid contacting chamber are used to estimate model parameters to simulate an urban landfill system, for past and future scenarios. Sensitivity tests to key model parameters were conducted. Lower BDEs require more time to disappear than high-molecular weight PBDEs, since debromination takes place in a stepwise manner, according to the simplified reaction scheme. Interphase mass transfer causes the decay pattern to be similar in all three sub-systems. The aqueous phase is predicted to be the first sub-system to eliminate PBDEs if their input to the landfill were to be stopped. The non-e-waste solids would be next, followed by the e-waste sub-system. The model shows that mass transfer is not rate-limiting, but the evolution over time depends on the kinetic degradation parameters. Experimental scatter makes model testing difficult. Nevertheless, the model provides qualitative understanding of the influence of key variables.

We employ a Monte Carlo simulation scheme based on the bond fluctuation model to simulate template polymerization via controlled polymerization scheme involving copolymerization of free monomers (A...

Spatial and temporal patterns generated in ecological and chemical systems have become a central object of research in recent decades. In this work, we are concerned with a reaction–diffusion model with the Degn–Harrison reaction scheme, which accounts for the qualitative feature of the respiratory process in a Klebsiella aerogenes bacterial culture. We study the global stability of the constant steady state, existence and nonexistence of nonconstant steady states as well as the Hopf and steady state bifurcations. In particular, our results show the existence of Turing patterns and inhomogeneous periodic oscillatory patterns while the system parameters are all spatially homogeneous. These results also exhibit the critical role of the system parameters in leading to the formation of spatiotemporal patterns.

In homopolymers with additives, blends, and copolymers, synergism can be accomplished in the structure/property/cost relationships if a proper gradient in components compositions is reached. Here, a description of gradients that can be formed in those materials is shown, briefly describing the methods used to obtain gradients in homopolymers. The core of this chapter is devoted to the formation of gradients in multicomponent polymer systems (MPSs) (polymer blends and copolymers), presenting the methods of preparation, the properties that can be obtained, and the advantages of such types of polymeric materials with respect to those containing uniform composition in the polymer bulk. The evolution of blends to make gradient interpenetrating polymer networks, and the synthesis of gradient copolymers represent nowadays the way to prepare tailormade MPSs when searching for specific properties. To design the properties of gradient copolymers, the change in chains composition as the conversion proceeds can be used in the controlled radical polymerization reaction scheme. Alternatively, the weight distribution of copolymer chains composition of the polymer bulk can be used (presented here for gradient copolymers formed by traditional radical polymerization) to design and interpret the mechanical and thermal behavior of the gradient copolymers.

International audience; Some of hazardous liquid organic wastes, radioactive or not, are waiting from outlet to be destroyed. The ELIPSE process is a new technology of organic liquid destruction, involving a thermal plasma working under a water column, which ensures the cooling, the filtration and the scrubbing of the gases coming from the degradation. This study deals with the ability of the ELIPSE process to destroy the pure organic liquids and then to reduce the amount of organic matter remaining in the aqueous solution by means of the thermal or radiative properties of plasma. Preliminary test have shown how efficient the process is for the destruction of the organic liquids when they are directly fed in the plasma hearth. Extensive researches have been performed to assess the ability of the submerged plasma to destroy the remaining organic matters either by reinjecting them with the aqueous solution into the plasma or by using the UV ray coming from the plasma itself. A comparison of the experimental results obtained with various mechanisms proposed by the work carried out highlighted that this UV radiation could, by excitation of water molecules, produce radicals OH which may either dimerise to produce hydrogen peroxide H$_2$O$_2$, or react with organic substances present. The calculation of an activation energy of 8.5 $\pm$ 0.9 kJ mol$^{−1}$ during the experiments shows that these radicals OH$^\circ$ act directly after having been formed which explains a low H$_2$O$_2$ content stability when the solution contains organic compounds. Thus, this photo-oxidation taking place in the water column could be used to improve the destruction of residual organic matter in the solution by maintaining the plasma after processing a given amount of organic liquids.

Soluble CNTs and especially water-soluble ones, functionalized with biomolecules, could get many applications in medicinal chemistry; that is why a host of efforts has been dedicated to CNT treatment with biologically active species, sugars, and their derivatives. Thus, as a first step before incorporation into poly(amide–imide) matrix, MWCNTs were modified with glucose and fructose (reaction scheme 4.1) carbohydrates as biomolecules to obtain Gl-MWCNTs and Fr-MWCNTs, leading to water-soluble and biocompatible products [1].

Understanding the reaction-diffusion processes of metal species is essential for an adequate description and control of metal availability. Electroanalytical techniques are well suited to probe dynamic speciation in aqueous systems, because transport and reaction influence the current. This short review hinges on the quantification of the contribution of complexes to the resulting flux via the lability degree, while highlighting extensions and other approaches. The reaction scheme is the Chemical Electrochemical (CE) mechanism, but special emphasis is focussed in mixtures of ligands given their relevance in natural waters. Despite the intensive theoretical work devoted to dynamic speciation, there is still a need of further progress, especially regarding heterogeneous ligands, nanoparticles, etc. Rigorous numerical solutions are progressively more accessible. Analytical contributions are usually restricted to limiting cases, but greatly facilitate the physicochemical interpretation of complex systems. The authors gratefully acknowledge support for this research from the Spanish Ministry MINECO (Projects CTM2013-48967 and CTM2016-78798) and by the “Comissionat d'Universitats i Recerca de la Generalitat de Catalunya” (2014SGR1132).

A reaction scheme has been proposed for the oxidative steam reforming (OSR) of raw bio-oil on a Rh/CeO 2-ZrO 2 catalyst, based on the study of the effect reaction conditions (temperature, space time, oxygen/carbon ratio and steam/carbon ratio) have on product yields (H 2, CO, CO 2, CH 4, hydrocarbons). The runs were performed in a two-step system, with separation of pyrolytic lignin (first step) followed by catalytic reforming in a fluidized bed reactor (second step), under a wide range of reaction conditions (600–750 °C; space time, 0.15–0.6 g catalysth/g bio-oil; oxygen to carbon molar ratio (O/C), 0–0.67; steam to carbon molar ratio (S/C), 3–9). The catalyst is very active for bio-oil reforming, and produces high H 2 yield (between 0.57 and 0.92), with low CO yield (0.035–0.175) and CH 4 yield (below 0.045) and insignificant light hydrocarbons formation. The proposed reaction scheme considers the catalyzed reactions (reforming, water gas shift (WGS) and combustion) and the thermal routes (decomposition/cracking and combustion). The deactivation of the catalyst affects progressively the reactions in the following order: CH 4 reforming, hydrocarbons reforming, oxygenates reforming, combustion and WGS.

A model reaction scheme in which two species $$A$$ and $$B$$ react to form an inert product is considered, with the possible linear decay of $$A$$ to a further inert prduct also included. The reaction between $$A$$ and $$B$$ is maintained by the input of $$A$$ from the boundary which keeps $$A$$ at a constant concentration. The cases when $$B$$ is immobile or free to diffuse are treated. In the former case reaction fronts in $$B$$ are seen to develop. Large time asymptotic solutions are derived which show that these fronts propagate across the reactor at rates proportional to $$t^{1/2}$$ or $$\log t$$ ( $$t$$ is a dimensionless time) depending on whether the extra decay step is included. A similar situation is seen when $$B$$ can diffuse when the linear decay step is not present. However, when this extra step is included in the reaction scheme the reaction zone reaches only a finite distance fronm the boundary at large times.

We characterize the influence that external noise, with both spatial and temporal correlations, has on the scale dependence of the reaction parameters of a cubic autocatalytic reaction diffusion (CARD) system. Interpreting the CARD model as a primitive reaction scheme for a living system, the results indicate that power-law correlations in environmental fluctuations can either decrease or increase the rates of nutrient decay and the rate of autocatalysis (replication) on small spatial and temporal scales., Comment: 10 pages, 6 figures

Hybridoma cells are commonly grown for the production of monoclonal antibodies (MAb). For monitoring and control purposes of the bioreactors, dynamic models of the cultures are required. However these models are difficult to infer from the usually available experimental data. This paper explores a practical situation where hybridoma are cultured in a sequential batch reactor. The simplest macroscopic reaction scheme translating the data is first derived using a maximum likelihood principal component analysis. Subsequently, nonlinear least-squares estimation is used to determine the kinetic laws.

International audience; The adaptation of prevertebra size to embryo size is investigated in the framework of a reaction-diffusion model involving a Turing pattern. The reaction scheme and Fick's first law of diffusion are modified in order to take into account the departure from dilute conditions induced by confinement in smaller embryos. In agreement with the experimental observations of scaling in somitogenesis, our model predicts the formation of smaller prevertebrae or somites in smaller embryos. These results suggest that models based on Turing patterns cannot be automatically disregarded by invoking the question of maintaining proportions in embryonic development. Our approach highlights the nontrivial role that the solvent can play in biology.

In the article are described the microbioassay system based on infusorians thermotaxis test reaction: generate test reaction scheme, a model of the temperature distribution along the narrow cell, and investigated the effects of chemicals to the test reaction thermotaxis Paramecium caudatum.

Transient absorption measurement of urea-anthracene species n PUA ( n = 1, 2, 9; PUA = 1-anthracen- n -yl-3-phenylurea) in the presence of acetate anions (tetrabutylammonium acetate, TBAAc) gave relatively long-lived transient species with lifetimes of ∼100 μs, which were unaffected by O 2 . The lifetimes showed significant temperature dependence, which allowed us to determine Δ H ‡ and Δ S ‡ . Δ S ‡ had a large negative value, in contrast to Δ H ‡ , indicating that the dissipation process of the transient species was entropy-controlled. A linear relationship between T Δ S ‡ and Δ H ‡ suggested entropy–enthalpy compensation, which is generally found in host–guest systems with hydrogen bonding. These findings allowed us to assign the transient species as X , which is the ground state responsible for longer wavelength emissions, and conclude that the dissipation of the transient species corresponded to recovery of the complex in the ground state. We propose a reaction scheme for the photochemical process applying to urea derivatives in the presence of anions.

Dynamic modeling of bioprocesses is of fundamental importance for optimization and control. The underlying macroscopic models, i.e., reaction scheme stoichiometry and kinetics, have to be derived and identified from experimental data. This study addresses the problem of determining the kinetics, and proposes a systematic procedure based on the use of decision graphs collecting well-established kinetic laws, and organizing them according to their complexity (i.e., number of unknown parameters). An algorithm for selecting the most likely kinetic structures, starting from the simplest models in the decision graphs, is developed based on the concepts of nested models and likelihood ratio tests. The potential of the procedure is illustrated with the determination of the synthesis rate of a biopolymer from the mutant strain Azotobacter vinelandii utilizing glucose.

This paper discusses the concepts of rate-determining step and potential-determining step in the context of electrocatalytic reaction schemes, illustrates how the simpler concept of potential-determining step often captures the essence of a bottleneck in a reaction scheme, and thereby provides straightforward hints for developing better catalysts.

Pyrolysis of bitumen is a key contributor to gas production in in situ combustion and in situ gasification recovery processes, yet a detailed reaction scheme, that includes a breakdown of products into the most abundant gas components, that is simple enough to be used in detailed thermal-reactive simulation models, does not exist. Here, we present a novel reaction scheme for pyrolysis of Athabasca bitumen that was developed and calibrated against four experimental data sets (65 data points) over a temperature range from 130 to 422°C. The new model was then verified by comparing its thermogravimetric behaviour against published literature. © 2012 Canadian Society for Chemical Engineering

Two types of rearrangements have been investigated computationally at the B3LYP/6-311+G(d,p) level. The activation barriers for rearrangement of acyl thiocyanates RCO-SCN to the corresponding isothiocyanates RCO-NCS are 30-31 kcal/mol in agreement with the observation that the thiocyanates are in some cases isolable albeit very sensitive compounds. Alkoxycarbonyl-, (alkylthio)carbonyl- and carbamoyl thiocyanates are isolable and have higher calculated barriers (ca. 40 kcal/mol) toward rearrangement to isothiocyanates, whereas all thioacyl thiocyanate derivatives are rather unstable compounds with barriers in the range 20-30 kcal/mol for rearrangement to the isothiocyanates. Acyl-, alkoxycarbonyl-, and carbamoyl cyanates R-CO-OCN are predicted to be in some cases isolable compounds with barriers up to ca. 40 kcal/mol for rearrangement to the isocyanates RCO-NCO. All of the rearrangements of this type involve the HOMO of a nearly linear (thio)cyanate anion and the LUMO of the acyl cation, in particular the acyl C═X π* orbital. The second type of rearrangement involves 1,3-shifts of the groups R attached to the (thio)acyl groups, that is, acyl isothiocyanate-thioacyl isocyanate and imidoyl isothiocyanate-thioacyl carbodiimide rearrangements. These reactions involve four-membered cyclic, zwitterionic transition states facilitated by lone pair-LUMO interactions between the migrating R group and the neighboring iso(thio)cyanate function. Combination of the two rearrangements leads to the general reaction scheme RCX-YCN ⇌ RCX-NCY ⇌ RCY-NCX ⇌ RCY-XCN (X and Y = O, S, NR').

Norrish-type-II reaction on a semiquinone radical: Stable semiquinone radicals serve as novel molecular platforms on which a Norrish-type-II photoreaction can be initiated. A detailed reaction scheme involving a 1,5-hydrogen transfer followed by a cyclization step that finally leads to a new CC bond formation could be verified. Transient absorption spectroscopy and DFT calculations trace convincingly the intermediates and transition states along the reaction path (see scheme). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

First, the kinetics of the reaction of a polyoxypropylene (POP) diamine and the diglycidyl ether of Bisphenol A (DGEBA), taking account of the induced unequal reactivity (substitution effect) of th...

The thermodynamic optimization of the Ag–Bi–Sb system was critically carried out by means of the CALPHAD (CALculation of PHAse Diagram) technique. The solution phases, liquid, fcc, rhomb and hcp_A3(ζ) were described by the substitutional solution model. The compound ɛ(Ag 3 Sb) was treated as the formula (Ag, Sb) 3/4 (Ag, Sb) 1/4 using two sublattice model in the Ag–Bi–Sb ternary system, which is directly from the Ag–Sb binary system. A self-consistent thermodynamic description of the Ag–Bi–Sb system was developed. The vertical sections at 10 at.% Bi, 10 at.% Ag and 70 at.% Ag, the isothermal section at 300 K, the projection of the liquidus surfaces, and the complete reaction scheme for the Ag–Bi–Sb system in the literature were reproduced in the present work.