Correction to: Accelerating Reactive Transport Modeling: On-Demand Machine Learning Algorithm for Chemical Equilibrium Calculations

Transport in Porous Media - In the original publication of the article, Table 2 was published incorrectly.     

Triacetic acid lactone as a bioprivileged molecule in organic synthesis

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On a bifurcation governed by hysteresis nonlinearity

We consider autonomous systems with a nonlinear part depending on a parameter and study Hopf bifurcations at infinity. The nonlinear part consists of the nonlinear functional term and the Prandtl--Ishlinskii hysteresis term. The linear part of the system has a special form such that the close-loop system can be considered as a hysteresis perturbation of a quasilinear Hamiltonian system. The Hamiltonian system has a continuum of arbitrarily large cycles for each value of the parameter. We present sufficient conditions for the existence of bifurcation points for the non-Hamiltonian system with hysteresis. These bifurcation points are determined by simple characteristics of the hysteresis nonlinearity.     

Coupling for Markov renewal processes and the rate of convergence in ergodic theorems for processes with semi-Markov switchings

Coupling procedures for Markov renewal processes are described. Applications to ergodic theorems for processes with semi-Markov switchings are considered.This paper was partly prepared with the support of NFR Grant F-UP 10257-300.     

Phenol biosensor based on electrochemically controlled integration of tyrosinase in a redox polymer

An amperometric biosensor for the detection of phenolic compounds was developed based on the immobilization of tyrosinase within an Os-complex functionalized electrodeposition polymer. Integration of tyrosinase within the redox polymer assures efficient catechol recycling between the enzyme and the polymer bound redox sites. The non-manual immobilization procedure improves the reproducibility of fabrication process, greatly reduces the desorption of the enzyme from the immobilization layer, and, most importantly prevents fast inactivation of the enzyme by its substrate due to fast redox cycling. A two-layer sensor architecture was developed involving ascorbic acid oxidase entrapped within an electrodeposition polymer in a second layer on top of the redox polymer/tyrosinase layer. Using this sensor architecture it was possible to eliminate the current interference arising from direct ascorbate oxidation up to a concentration of 630 μM ascorbic acid. The effects of the polymer thickness, the enzyme/polymer ratio, and the applied potential were evaluated with respect to optimal sensor properties. The sensitivity of the optimized sensors for catechol was 6.1 nA μM⁻¹ with a detection limit of 10 nM, and for phenol 0.15 nA μM⁻¹ with a detection limit of 100 nM.     

Extended generalized octagons and the groupHe

Let be an extended generalized octagon such that the points of a triple {u, v, w} not on a block are pairwise adjacent if and only if the distance betweenv andw in the local generalized octagon _u equals 3 and there is a thick line through any point of _u . Then is one of the two examples related to the groups 2·L ₃(4).2² andHe. It is also shown that does not admit further extensions.     

Activation of dimethyl zirconocene by methylaluminoxane (MAO)-size estimate for Me-MAO(-) anions by pulsed field-gradient NMR

In a study of the reaction system MAO/(C5H5)2ZrMe2, the size of the ion pair [(C5H5)2Zr(mu-Me)2AlMe2]+ [Me-MAO]- was determined by pulsed field-gradient NMR of its cationic moiety. A mean effective hydrodynamic radius of 12.2-12.5 A, determined from diffusion rates in benzene solution at different zirconocene and MAO concentrations, indicates that the ion pair remains associated even at the lowest concentrations studied. At elevated concentrations, aggregation to ion quadruples or higher aggregates is indicated by an apparent size increase and by shifts of the C5H5 and Me 1H NMR signals. The equilibrium constant for the reaction [(C5H5)2ZrMe+...Me-MAO-] + 1/2Al2Me6 right harpoon over left harpoon [(C5H5)2Zr(mu-Me)2AlMe2]+ [Me-MAO]- changes at different Al/Zr ratios; this indicates that MAO contains various species that produce Me-MAO- anions with different Lewis basicities. The volume of the Me-MAO- anion suggests that it contains 150-200 Al atoms.     

Solid-state synthesis of a conducting polythiophene via an unprecedented heterocyclic coupling reaction

Prolonged storage ( approximately 2 years) or gentle heating (50-80 degrees C) of crystalline 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) affords a highly conducting, bromine-doped poly(3,4-ethylenedioxythiophene) (PEDOT), as confirmed by solid-state NMR, FTIR, CV, and vis-NIR spectroscopies. The novel solid-state polymerization (SSP) does not occur for 2,5-dichloro-3,4-ethylenedioxythiophene (DCEDOT), and requires a much higher temperature (>130 degrees C) for 2,5-diiodo-3,4-ethylenedioxythiophene (DIEDOT). X-ray structural analysis of the above dihalothiophenes reveals short Hal.Hal distances between adjacent molecules in DBEDOT and DIEDOT, but not in DCEDOT. The polymerization may also occur in the melt but is significantly slower and leads to poorly conductive material. Detailed studies of the reaction were performed using ESR, DSC, microscopy, and gravimetric analyses. SSP starts on crystal defect sites; it is exothermic by 14 kcal/mol and requires activation energy of approximately 26 kcal/mol (for DBEDOT). The temperature dependence of the conductivity of SSP-PEDOT (sigma(rt) = 20-80 S/cm) reveals a slight thermal activation. It can be further increased by a factor of 2 by doping with iodine. Using this approach, thin films of PEDOT with conductivity as high as 20 S/cm were fabricated on insulating flexible plastic surfaces.     

Modified Ceria-Zirconia Fluorite-Like Catalysts for the Combustion of Methane

For dispersed ceria-zirconia-based solid solutions prepared via the polymerized complex method and annealed at 700℃, effects of bulk doping by Ca, Mn, Co, Bi or Nb cations and surface modification by Mn and Pt on their structural features, surface/bulk oxygen reactivity and catalytic activity in methane combustion are considered. With up to 20 mol% doping, a structural type of homogeneous solid solutions of anion-deficient fluorite with disordered anion vacancies is formed. Doping by transition metal cations or Pt increases the mobility and reactivity of the surface/bulk oxygen. A broad variation in specific rates of methane combustion for the studied systems was observed, suggesting structural sensitivity of this reaction. In general, there is no universal relationship between the oxygen mobility, the reactivity and the catalytic activity in methane combustion, which is explained by the factor of specific methane activation on surface active sites. For the Pt-promoted samples, Pt efficiency in methane activation depends on the Pt-support interaction, and the most favorable ones being mixed Pt/MnOx and Pt/NbOx clusters on the surface of the supports that exhibit high lattice oxygen mobilities.     

Modified synthesis of Ru–Rh heterobimetallic metallacarboranes based on ruthenium exo-nido complexes and not accompanied by exo-nido → closo rearrangement

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