Single-Route Linear Catalytic Mechanism: A New, Kinetico-Thermodynamic Form of the Complex Reaction Rate

For a complex catalytic reaction with a single-route linear mechanism, a new, kinetico-thermodynamic form of the steady-state reaction rate is obtained, and we show how its symmetries in terms of the kinetic and thermodynamic parameters allow better discerning their influence on the result. Its reciprocal is equal to the sum of n terms (n is the number of complex reaction steps), each of which is the product of a kinetic factor multiplied by a thermodynamic factor. The kinetic factor is the reciprocal apparent kinetic coefficient of the i-th step. The thermodynamic factor is a function of the apparent equilibrium constants of the i-th equilibrium subsystem, which includes the (n−1) other steps. This kinetico-thermodynamic form separates the kinetic and thermodynamic factors. The result is extended to the case of a buffer substance. It is promising for distinguishing the influence of kinetic and thermodynamic factors in the complex reaction rate. The developed theory is illustrated by examples taken from heterogeneous catalysis.

The influence of Fe(III) and Mn(IV) on the biotransformation of hydrocarbons in groundwater

According to the thermodynamic ladder, microorganisms in groundwater use electron acceptors consistently – for transformation of pollution from the pollution plume edge to its core. However, some researchers come to the conclusion that only methanogenic biotransformation of pollution or reduction of Fe(III) and Mn(IV) from the solid phase can occur in the plume, and due to the kinetic factor microorganisms use electron acceptors from the aqueous phase (O2, NO3- и SO42-) only on the edge of the pollution plume. The purpose of the research was to determine whether microorganisms use Fe(III) and Mn(IV) as acceptors of electrons for hydrocarbons transformation in groundwater in the northern part of the Middle Heilongjiang-Amur River basin aquifer. In the study area, both lenses of petroleum-hydrocarbons (non-aqueous phase liquids) on the surface of groundwater (up to 2.5 m) and high concentrations of dissolved hydrocarbons (up to 1000 mg/l) are noted. Microbiological processes were assessed in situ by the method of geochemical indicators. The most active biogeochemical processes occurred during the spring-summer rise of groundwater level. The seasonal increasing of level led to the entry of Fe(III) and Mn(IV) into the pollution plume and activation of the microbiological processes of its reduction. Microorganisms mostly use electron acceptors from the solid phase – Fe(III) and Mn(IV), but not NO3, SO42 from the aqueous phase. This is confirmed by the close correlation of HCO3- formation and that of Fe(II) and Mn(II) in groundwater (r2 up to 0.93). This says that for the groundwater self-purification the kinetic factor rather than thermodynamic one is decisive; and microorganisms use electron acceptors that are currently available. As a result of microbiological pollution destruction, the content of Fe(II) in groundwater increased up to 100 mg/l, Mn (II) – up to 16 mg/l, which exceeds the natural background 4 and 8 times, respectively. This was also because the regional geochemical background of the study area (Amur River basin) forms Fe and Mn.

An Old Universe in K-Essence Cosmology

Models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself in k-essence cosmology are considered. In the case of a constant potential, we obtain an exact analytic solution of k-essence, wk=−(3α−2)/3α, under a simple hypothesis, a=a0(t/t0)α, but without any assumption about the form of F(X). In purely kinetic k-essence model, the acceleration can only be induced after the matter-dominated epoch; the Universe is about 33.5−3.4+4.2 Gyr old now and about 3.1 Gyr old at z=3.9 which is consistent with the fact of quasar observation, while this observation contradicts with the prediction of ΛCDM model, and the year where a transition from deceleration to acceleration expansion is about from 18.43 Gyr to 25.2 Gyr after the beginning of the Universe. These results may offer clues to test observationally the k-essence scenario in the future.

Ozonation of Atactic Polypropylene

1. It is determined by study of the accumulation of peroxides in atactic polypropylene that ozone acts as an initiator of oxidation and considerably accelerates the course of the reaction even at room temperature. 2. The surface of the oxidized specimens is an important kinetic factor in the accumulation of the peroxides. 3. In addition to the formation of hydroperoxides in the initial phases of the process there takes place a crosslinking of the surface layer of the oxidized films by polymeric peroxides. These peroxides gradually decompose with the simultaneous formation of hydroperoxides. 4. The degradation of macromolecules under the action of ozone is less than in oxidation by the atmosphere.