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In this paper, a new macroscopic traffic model is presented which characterizes driver response during transitions. The commonly employed Payne–Whitham (PW) model characterizes this response using a constant regardless of the reaction time and interaction and distance between vehicles. As a consequence, the resulting traffic behavior can be unrealistic. In this paper, a model is proposed which considers the reaction time, transition distance, and velocity profile based on the traffic density. This produces smooth changes in density and velocity during transitions compared to the PW model. Results are presented for a bottleneck along a circular road which show that the proposed model provides more realistic behavior than the PW model.

β-Agarase produced by Paenibacillus sp. WL (agarase WL) was purified using a combination of ammonium sulfate precipitation, DEAE-ion exchange, and gel-filtration chromatography. The purity of the agarase was increased by 11.9× with a recovery of 5.1% and a specific activity of 4,670.1 U/mg of protein. The molecular mass of the purified agarase was approximately 30 kDa (SDS-PAGE). The agarase was stable at temperature below 50°C and the favorable agar-hydrolysis activity was at 40°C. The agarase was active in the range of pH 5.0 to 8.0, and the optimal agar-hydrolysis pH value was approximately 6.0. Metal ions normally found in seawater (Na+, K+, Ca2+, Mg2+, and Al3+) could activate agarase WL. The Michaelis-Menten constant Km and maximal reaction velocity Vmax of purified agarase WL were 3.22 mg/mL and 41.5 μg/mL·min, respectively. The agarase WL was highly agar specific.

Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J g−1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.

Methylene diphenyl dicarbamate (MDC) was synthesized from methyl phenyl carbamate (MPC) and trioxane using sulfuric acid (H2SO4) as catalyst. The effects of reaction temperature, reaction time, molar ratio of reactants and the content of catalyst have been studied in details. The results showed that H2SO4 exhibited high catalytic activity with the merits of moderate reaction velocity. Under the conditions of n(MPC)/n(trioxane) = 3:1, reaction temperature of 95°C, reaction time of 3.5 h and 30% H2SO4, the conversion of MPC reached 99.0% with the selectivity of MDC 81.6%. Moreover, the H2SO4 catalyst was reused five times without obviously activity decrease. Based on the identification of byproducts, a possible reaction mechanism was proposed.

Dealt with in this paper is the relationship between Cu contents of soil and activity parameters for soil invertase and urease from the Changtai loquat orchards in Fujian Province. The soil invertase activity and maximum reaction velocity (enzyme kinetic parameters: Vmax and Vmax/Km) have no remarkable negative correlation with Cu concentrations, but Cu concentrations have an obvious positive effect on invertase Km, indicating a reversible competitive restraint on the reaction between Cu and invertase. The soil urease activity and maximum reaction velocity (Vmax,Vmax/Km) have a remarkable negative correlation with Cu concentrations, and in this aspect, they can be used as ecological indices of the soil polluted by Cu. A slightly variable Km indicates the non-reversible competitive restraint between Cu and soil urease. Cu concentration= 2.00 mg·L−1 in soil is an indicative of the moderate Cu pollution level.

Four Ti-C-Fe powder mixtures, with a same molar ratio but a different particle size, were used for a combustion synthesis of TiC-Fe cermet to investigate effects of the particle size on the characteristics of the combustion synthesis. The results showed that the mixture with the finer Ti powder gave out a higher combustion temperature, a higher reaction velocity, a higher product density, a layer-shaped pore, and a greater size of TiC particles whether the Fe powder was finer or coarser. While in the case of the coarser Ti powder used, a small amount of residual phase remained in the product, and what is more interesting that the mixture with the finer Fe powder gave out a lower reaction velocity than that by the mixture with the coarser Fe powder. These effects were successfully explained with the previously proposed mechanisms of the combustion synthesis of TiC-Fe, and the mechanisms were proved to be valid thereby.

Propane and butane have very low reaction velocity and are abundant in the atmosphere of the Mexico City Metropolitan Zone (MCMZ). An important contribution of those alkane to ozone formation is observed. The present work studies to what extent the atmospheric concentrations and emissions of propane and butane contribute to the ozone formation. This evaluation was realized with the trajectory photochemical model, emissions and meteorological data of the MCMZ. Propane contributes to the maximum of ozone concentration with 0.013 ppm (7.78% of the total) and butane with 0.027 ppm (15.34% of the total). The total contribution of propane and butane to ozone formation can be split, respectively, in 0.001 ppm and 0.013 ppm of ozone produced by emission, and 0.012 ppm, and 0.014 ppm of ozone produced by atmospheric concentrations from the initial conditions. Propane and butane have a total contribution to a maximum of ozone concentration of 23.12%. The maximum concentration of propane has a decrement of 68.62% in the photochemical modeling.

Sevoflurane, a new inhalational anesthetic, is metabolically broken down into several decomposition products in the presence of CO2 absorbents. One of the products, CF2=C (CF3) OCH2F (compound A), which appears to be the most toxic, was quantitated in 20 surgical patients subjected to more than 3 h of anesthesia using a low-flow anesthesia circuit. To minimize the variables in the reaction velocity between sevoflurane and the CO2 absorbents, we maintained the sevoflurane concentration at 2%. Wakolime-A, one type of soda lime, resulted in the highest increase in compound A concentration. The peak concentration was 27.1±3.1 ppm, less than one-tenth of the LC50 (50% lethal concentration) of compound A, which was previously reported as 420 or 400 ppm in rats. We also measured the temperature in CO2 absorbents, which had been reported to influence compound A production. The elevation in the temperature was 27.9±1.3°C in Wakolime-A, 29.4±8.4°C in Baralyme, and 31.0±5.0°C in Sodasorb II. Further studies are needed to assess the safety and efficacy of sevoflurane.

The chitin synthetase of Phycomyces blakesleeanus mycelium is a particulate enzyme sedimenting mostly at 1000xg. The activity in crude extracts or cellular fractions can be increased more than tenfold by mild trypsin treatment. Plotting the reaction velocity versus UDP-N-acetylglucosamine concentration yields a sigmoidal curve. N-acetylglucosamine, which greatly stimulates the enzyme, changes the kinetics to an almost normal hyperbolic relationship.

A numerical study is made of the interaction of a detonation wave having finite reaction velocity with a rarefaction wave of different intensity which approaches it from the rear, for the Zeldovich-Neumann-Doring (ZND) model with a single irreversible reaction A → B. It is found that, for a fixed value of the parameter characterizing the initial supercompression (depending on the activation energy and the heating value of the mixture), the considered interaction leads either to a gradual relaxation of the detonation wave and its transition to the Chapman-Jouguet (CJ) regime, or to the development of undamped oscillations.

The rate of oxidative inactivation may be approximately described by {ie411-01}, which for constantE andT gives {ie411-02}. It was found that the effect of a certain amount of residual chlorine varied with the amount of non-viral organic or inorganic matter, but that these variations could be explained through the dependence of the reaction velocity on the oxidation potential.

1. The homogeneous destructive hydrogenation of toluene was investigated at high hydrogen pressures, 2. A chain mechanisms is advanced for the investigated process on the basis of which an equation for the reaction velocity is derived which is consistent with the experimental results.

1. We have synthesized and characterized epoxyethylphenyldi(trimethylsiloxy)silane, epoxyethyltri(trimethylsiloxy)silane, and methylepoxyethyldi(trimethylsiloxy)silane. 2. Epoxidation of vinylorganosiloxanes by perbenzoic acid is a second-order reaction; the reaction velocity depends on the polarities and volumes of the substituent radicals at the silicon atom.

New theoretical considerations and a new approximation strategy were applied to the kinetic analysis of the experimental relationship between the reaction velocity in the steady state and the concentrations of ethanol and NAD. It could be shown that horse-liver ADH consists of two kinetically heterogeneous components.

CERTAIN considerations introduced by Franck and Haber1, Haber and Willstatter2 and Haber and Weiss3 can be developed to give a simple mechanism for oxidation-reduction processes in solution, which reproduces in all cases investigated the experimental observations, both qualitatively and quantitatively. The relation sometimes observed4 between reaction velocity and electrochemical potential can also be obtained, so that for the first time a comprehensive theoretical treatment becomes possible.

STAVELEY and Hinshelwood have recently shown that the thermal homogeneous decompositions of certain substances such as ethers and aldehydes are to a greater or less extent inhibited by small amounts of nitric oxide, and they have used this as a means of establishing the extent to which these reactions proceed via a mechanism of reaction chains1. With dimethyl ether the effect is most marked, and in this case, when the decomposition is about half completed, the reaction velocity rises fairly abruptly to its normal value.

IT has been generally assumed that the hydrogen chloride produced when a mixture of hydrogen and chlorine is illuminated has no effect on the velocity of reaction. If, however, the magnitudes of the Draper effects are considered for two reaction mixtures which do not differ in hydrogen, chlorine, and oxygen concentrations, but only in the circumstance that one (a) contains no hydrogen chloride, and the other (b) an amount of hydrogen chloride equal, say, to that of the concentration of chlorine, then the magnitude of the Draper effect in (a) can be observed to fall off very rapidly on illumination, while that of (b) shows no such rapid initial fall but is always smaller than the initial value in the case of (a). Indications of a rapid initial fall in reaction velocity in mixtures containing initially no hydrogen chloride can indeed be recognised in the ‘velocity coefficients’ given by several workers; for example, by Bodenstein and Dux.1

FOR a long time two viewpoints regarding the mechanism of enzymatic activity have profoundly influenced our conceptions in this field. To Oscar Loew is due the credit for the original suggestion that the enzymes possessing atomic groups with kinetic lability are able, even at a comparatively low temperature, to perform chemical action. This suggestion was later abandoned more and more, and we now generally assume that, as in the case of heterogeneous reactions, the reactants arc adsorbed by the enzyme in order that reaction may ensue. In accordance with this we believe with Bayliss that the reaction velocity is determined by the concentration of adsorption complex, that is, reactant—enzyme, present in the system. The possibility of carrying out such reactions depends doubtlessly on certain conditions of the surface, which are also profoundly influenced by the hydrogen ion concentration.

THE well-known “sequence” theories of blood coagulation1,2 attempt to rationalize the participation of a dozen or so clotting factors in the formation, and consolidation of a fibrin clot. It has been proposed3 that “normal prothrombin activation involves a number of functionally and perhaps physically distinct entities (clotting factors) present in the plasma, that these react one upon the other in a preferential sequence during normal clotting and that most, if not all, are proenzymes each yielding an enzyme capable of activating the next component of the sequence”. Several investigations have been concerned with the last of these propositions4–11. Each of these has involved the assumption that a linear response in reaction velocity with changing concentration is indicative of an enzyme while a saturation response is indicative of a substrate. The validity of these assumptions and their consequences will now be considered.

THE autopoisoning of catalytically active copper in dehydrogenating ethyl alcohol above 280° C., previously reported1, has been further studied. Assuming a linear law of variation of the velocity constant ks of the poisoning with the heat of activation ɛ on the distribution2 of centres of activity on the surface over the narrow range of values of ɛ which determine the reaction velocity in the form

EARLIER experiments of ours have shown that the organism regulates the coagulability of the blood by the inactivation of thrombin1,2. Many factors take part in the system causing the thrombin to disappear. We distinguish an adsorption effect and a fermentative inactivation process, and indicate the inactivating process by its reaction velocity factor.

IN recent years a good deal of attention has been given to the relation between the catalytic effect of a surface and its structure, and in this connexion it is perhaps of interest to point out that the general idea underlying many theories was published by me in 1911 (J. Chem. Soc., 475 ff., 1911) in a qualitative form. The hypothesis in relation to the specific problem studied, the dehydration of a salt crystal, was based on the view that the lattice structure of such a system was disturbed, and that the rearrangement of the surface (described as ‘amorphous’, in harmony with the prevailing views before the application of the X-rays to crystal analysis had been discovered) underwent a recrystallisation, a process which required time. It was further pointed out that “a treatment of somewhat simpler systems than the present, such as occur, for example, in the ‘ageing’ of deposited catalytic surfaces, would probably present points of interest”; and such has, in fact, proved to be so. This view of a catalytic surface is incompatible with a smooth ‘chess-board’ surface. The latter has now been recognised as inadequate. The application of the idea to heterogeneous reactions has been considered by Slonim (Z. Elektrochem., p. 439, 1930). The examination of all such surfaces by X-ray analysis would, clearly, throw much light on the general problem, as Slonim shows in a particular case. The method contemplated had, however, the use of reaction velocity in mind.

IN the Philosophical Magazine for November, 1920, Prof. Lindemann has shown that if Prof. W. C. McC. Lewis's hypothesis is true, i.e. that the velocity of a chemical reaction is proportional to the intensity in the system of the radiation of a wave-length which is characteristic of the reaction, then in the case of the inversion of cane-sugar by dilute acid, exposure to the radiation of the sun should increase the reaction velocity 5 × 1013 times.

IN studying reactions between two solid phases, it is found that the reaction velocity in systems such as MgO/Ag2SO41, MgO/Ag3PO41, MgO/Mg2P2O72 and MgO/MgSiO33 is not determined by the diffusion process through the reaction products, but by reactions at one of the phase limits. The reaction velocity is independent of the thickness of the layer of reaction product and changes with temperature according to the exponential equation