Renormalization group studies of the Ashkin-Teller model

The two-and-three-dimensional Ashkin-Teller model is studied within two renormalization group treatments. The complete flow diagram is obtained for this two-parameter Hamiltonian and the results for the critical couplings and critical exponents are compared to the exact ones when avaible.     

Efficient pairing computation on supersingular Abelian varieties

We present a general technique for the efficient computation of pairings on Jacobians of supersingular curves. This formulation, which we call the eta pairing, generalizes results of Duursma and Lee for computing the Tate pairing on supersingular elliptic curves in characteristic 3. We then show how our general technique leads to a new algorithm which is about twice as fast as the Duursma–Lee method. These ideas are applied to elliptic and hyperelliptic curves in characteristic 2 with very efficient results. In particular, the hyperelliptic case is faster than all previously known pairing algorithms.      

Thermal decomposition of copper(II) glutarate trihydrate. Part I. The mechanism of dehydration of copper(II) glutarate trihydrate

The mechanism of thermal dehydration of copper(II) glutarate trihydrate has been determined from the analysis of the kinetic data for isothermal and non-isothermal dehydration experiments. Microscopic investigations for the dehydration process of a single crystal of copper(II) glutarate trihydrate have been carried out to support the mechanism. The simultaneous DTG—DTA—TG curves of the salt are also described.     

Linear free energy relations in solid state reactions II

Kinetics of the reaction between solid cobalt(II) acetate and solid substituted aniline hydrochlorides have been studied by thermal analysis. All the reactions go to completion. The crystalline products were characterized by physico-chemical methods. The energy of activation is 83.4,44.2,64.2,100.9,79.8,99.9, 135.9 and 168.7 kJ mol^–1for the reactions of aniline, 3- and 4-chloro-, 4-iodo-, 4-bromo-, 4-fluoro-, 4-methyl- and 4-methoxy aniline hydrochlorides with cobalt acetate. A plot of energy of activation against Hammett's constant is linear with a slope of –169.9 kJ mol^–1. A comparison between the reactivity of these reactions by the capillary and the thermal methods has been done.

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Zusammenfassung Mittels Thermoanalyse wurde die Kinetik der Festkörperreaktion zwischen Kobalt(II)azetat und substituierten Anilinhydrochloriden untersucht. Alle Reaktionen laufen vollständig ab. Die kristallinen Produkte wurden mittels physikalisch-chemischer Methoden charakterisiert. Die Aktivierungsenergie der Reaktion von Kobalt(II)azetat mit Anilin, 3- und 4-Chlor-, 4-Jod-,4-Brom-, 4-Fluor-, 4-Methoxy- und 4-Methylanilin beträgt 83.4,44.2,64.2,100.9,79.8,99.9,168.7 bzw. 135.9 kJ/mol. Bei der Darstellung der Aktivierungsenergie in Abhängigkeit von der Hammettkonstante konnte Linearität mit einem Anstieg von – 169.9 kJ/mol festgestellt werden. Die Reaktivität dieser Reaktionen wurde mittels Kapillar- und thermischen Verfahrens verglichen.

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. . - . , 3- 4--, 4--, 4--, 4--, 4- - 4- , , 83,4; 44,2; 64,2; 100,9; 79,8; 99,9; 135,9 168,7 ·^–1. - –169,9 ·^–1. , .

     

Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system

Heterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]⁰, [Ce⁴⁺]^0.63, and [Monomer]^1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H₂SO₄]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.     

Kinetics of isothermal decomposition of Cu(II) succinate

The isothermal decomposition of Cu(CH₂COO)₂ has been studied at 473–523 K using material in the form of powder and pellets. The isothermal decomposition of Cu(II) succinate to cupric oxide takes placevia the intermediate formation of 2 CuCO₃·Cu(OH)₂. The X-ray diffraction technique has been employed to identify the decomposition products. The decomposition curves are best fitted by two kinetic stages: (i) a linear law, and (ii) a unimolecular law. The activation energies for the two stages are 153 ± 10 kJ/mole, and 115 ± 8 kJ/mole, respectively. It has been observed that pelleting has no effect on the kinetics. DTG, DTA and TG curves of the sample have also been recorded. The order of reaction has been calculated from these curves.     

Methyl methacrylate as solvent for the thermal decomposition of the cyclic molecule pinacolone diperoxide: Toward the polymerization process

The decomposition rate constant (k_d) of pinacolone diperoxide (PDP, 3,6‐diterbutyl‐3,6‐dimethyl‐1,2,4,5‐tetraoxacyclohexane) in methyl methacrylate (MMA) is determined by the kinetic study of its thermal decomposition at temperatures from 110 °C to 140 °C. The calculated k_d values for PDP are higher than the corresponding values previously determined and reported for diethyl ketone triperoxide (DEKTP, 3,3,6,6,9,9‐hexaethyl‐1,2,4,5,7,8‐hexaoxacyclononane), for example, at 140 °C the k_d for PDP is 75.4 × 10^?5 s^?1, while for DEKTP, it is 50.6 × 10^?5 s^?1. The difference in the k_d between 130 °C and 140 °C indicates that the decomposition mechanism, sequential and/or concerted, is a function of temperature. The conformations of both initiators justify the higher k_d for PDP in MMA than DEKTP, where one single conformer is found for PDP, whereas 212 conformers are found for DEKTP. Bulk polymerization of MMA using PDP as the initiator reveals also the presence of an induction period, such as in DEKTP case. This work provides mechanistic insights into the interactions among the bifunctional cyclic peroxide PDP and the MMA monomer and their influence on the polymerization kinetics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 997–1007