Kinetik und Mechanismus der Photolyse von Aryldiazoniumsalzen in Methanol. Ermittlung absoluter Geschwindigkeitskonstanten einiger Teilreaktionen

Kinetics and Mechanism of Aryldiazonium Salt Photolysis in Methanol. Determination of Absolute Rate Constants of Some Reaction Steps For benzene diazonium tetrafluoroborate and some p-substituted derivatives, the following values are determined:

• velocity constants for the photochemical electron transfer from pyrene and benzanthracene to aryl diazonium salts in acetonitrile solution (determination by quenching the donor fluorescence).
• velocity constants for electron transfer under the condition of pulse radiolysis in tert.-butanol-water solution;
• quantum yields and product composition (ArOMe, ArF and ArH, respectively) for the photolyses in methanol in the presence of varying concentrations of 2-methyl-2-nitroso-propane as a quencher of the thermal chain reaction.

The electron transfer reaction comes out be a diffusion controlled reaction, k_E = 2 …︁ 3 × 10¹⁰ M⁻¹ s⁻¹. For the total reaction a kinetic model is set up which affords absolute velocity constants from the experimental results for the following steps: Hydrogen transfer within the case radical pair \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {{\rm Ar} - {\rm N} = {\rm N}{\rm . CH}_{\rm 3} {\rm OH}{\rm .}} {\rm }^ \oplus $\end{document} (formation of ArH) k_H ≈ 10¹¹ s⁻¹; Maximal values for the photo-solvolyses (formation of Ar^⊕ → ArOMe and ArF, respectively), k_s ≲ 10⁻¹; Trapping of aryl radicals outside of the solvent cage by t-BuNO, k_q ≈ 2 × 10⁷ M⁻¹ s⁻¹. The results are discussed in the light of the kinetic model and some other facts.     

Managing uncertainty and discontinuous condition numbers in geometric computation

We consider operations on subdivision surfaces under the strict robustness requirement that these floating-point computations return an object with the same topological form as the true solution. The problems involved may however be ill-conditioned, and defined in terms of uncertain data, and even supplementary interval arithmetic may not ensure robustness. Trapping mechanisms are therefore proposed to resolve this difficulty.     

RELATIONAL STABILITY

ABSTRACT

International stability is interpreted in terms of the number and quality of relationships among nations and cultures. Stability based on relationships is further characterized by an overlaid formal international structure of the type described by Chestnut as a cooperative security system. Cultural diversity is interpreted as further enhancing stability in two ways—through cultural diversity within individual nations and through cultural characteristics that transcend national boundaries.     

A mini cogeneration station constructed on the basis of a inverted gasifier

The basic process circuit of a mini cogeneration station constructed on the basis of an internal combustion engine and a inverted gasifier operating on coal fuel is developed. The optimal mode of gasifier operation for obtaining gasification products with the maximal heating value is selected. An experimental check of gasifier operation is carried out.     

Selecting the thermal circuit and profile of a Russian large new-generation power-generating gas turbine unit and a combined-cycle plant built around it

Proposals on the most advisable lines in which the Russian industry can develop advanced new-generation gas-turbine units and combined-cycle plants competitive in the first half of the 21st century are formulated.     

A new type of potentiometric sensors based on perfluorinated,sulfonated cation-exchange membranes for quantitative analysis of multicomponent aqueous solutions

The organization principles of a new type of sensors were developed whose analytical signal is the Donnan potential at the ion-exchange polymer/test solution interface (PD-sensors) for the determination of organic and inorganic electrolytes in multicomponent aqueous solutions. It was found that the cross sensitivity of PD-sensors based on perfluorinated, sulfonated cation-exchange polymers (PSPs) in the initial inorganic forms depends on the potential-determining reactions of protolysis and ion exchange at the PSP/multicomponent test solution interface. The effects of the hydrophilicity, moisture capacity, and ionic form of the ion-exchange polymer on PD-sensor sensitivity were investigated. It was found that treatment of PSP with ethylene glycol at the glass-transition temperature of the polymer makes it possible to obtain modified PSPs in organic forms, which differ from the initial materials by a larger concentration of dissociated counterions, and thus lead to enhanced PD-sensor response and sensitivity to an appropriate organic component. Potentiometric multisensor systems including cross-sensitive PD-sensors, ion-selective electrodes (ISEs), and algorithms for the processing of multidimensional data for the quantitative determination of lysine, novocaine, lidocaine, thiamine, pyridoxine, nicotinic acid, and alkali and alkaline earth metal cations in multicomponent solutions were developed.