Electron spin resonance study of γ-irradiated poly(acrylic acid)

Electron spin resonance (ESR) spectra of poly(acrylic acid) (PAA) γ-irradiated in air at room temperature and recorded at room temperature and at liquid-nitrogen temperature have been studied to identify the radiation products. The ESR spectra are composed of eight lines with hyperfine splittings of 23 ± 1 G and 11 ± 1 G. The method of least-squares total curve fitting, employing the Lorentzian line shape function, to the observed spectra enabled the assignment of the spectra. Computed spectra obtained by the superposition of a singlet and the spectra due to chain radicals are considered to give the best fits to the observed ESR spectra. The singlet is assigned to the radicals COOH, and the component 10-line spectra are assigned to the chain radicals CH₃? CH? CH₂ ～ and/or ～ CH₂? CH? CH₂ ～. The observed change in line shape with temperature of the ESR spectra is attributed to the hindered oscillations of the methyl groups about the C_α? C_β bond axis of the chain radicals. The existence of the methyl groups is confirmed by the measurement of infrared absorption.     

Strukturelle Aspekte bei Korngrenzensegregationsuntersuchungen

Ohne Zusammenfassung

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Structural aspects for grain boundary segregation studies

     

Extraction of strontium using an irradiated extraction agent of crown structure

The partition coefficient of strontium upon its extraction from the aqueous solutions of picric acid into chloroform containing DC-18-crown-6, B-15-crown-5 after their exposition to gamma radiation has been studied. A significant decrease of the partition coefficient in the studied range of doses 10–70 kGy was observed. This effect can be attributed to the radiolytic products of chloroform. The radiation destruction as well as dehydrogenation of crown ethers were not observed.     

Can Indirect Causation be Real?

Causal realists maintain that the causal relation consists in “something more” than its relata. Specifying this relation in nonreductive terms is however notoriously difficult. Michael Tooley has advanced a plausible account avoiding some of the relation’s most obvious difficulties, particularly where these concern the notion of a cross-temporal “connection.” His account distinguishes discrete from nondiscrete causation, where the latter is suitable to the continuity of cross-temporal causation. I argue, however, that such accounts face conceptual difficulties dating from Zeno’s time. A Bergsonian resolution of these difficulties appears to entail that, for the causal realist, there can be no indirect causal relations of the sort envisioned by Tooley. A consequence of this discussion is that the causal realist must conceive all causal relations as ultimately direct.     

Nickel peroxide: A more probable intermediate in the Ni(II)‐catalyzed decomposition of peroxomonosulfate

The Ni(II) ion catalyzed thermal decomposition of peroxomonosulfate (PMS) was studied in the pH range 3.42–5.89. The rate is first order in [PMS] and Ni(II) ion concentrations. At pH greater than or equal to 5.23, the reaction becomes zero order in [PMS] and this changeover in the order of the reaction occurs at a higher concentration of nickel ions. The first‐order kinetics in PMS can be explained as a rate‐limiting step and is the transformation of nickel peroxomonosulfate into nickel peroxide. This peroxide intermediate reacts rapidly with another PMS to give oxygen and Ni(II). The formation of nickel peroxide is associated with a small negative or nearly zero entropy of activation. The zero‐order kinetics in [PMS] can be explained by the fact that the hydrolysis of aquated nickel(II) ions into hydroxocompounds is the rate‐limiting step. The turnover number is 2 at pH 3.42 and increases with pH. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 320–237, 2007     

The solution of a convection–diffusion–reaction equation arising from cathodic reduction in a pulsating crack

This paper derives the convection–diffusion-reaction equation governing the reaction between the dissolved oxygen in sea-water and the steel walls of a pulsating crack. By the neglect of the diffusion term it is shown that an exact solution of the convection-reaction equation can be obtained. A numerical method for the solution of the complete convection–diffusion-reaction equation is derived by the use of finite differences. The numerical computation of the initial transient and the final periodic steady-state values is also discussed.     

Inner-sphere oxidation of iron(II) by tris(malonato)cobaltate(III)

The kinetics of oxidation of Fe²⁺ by [Co(C₃H₂O₄)₃]^3? in acidic solutions at 605 nm showed a simple first-order dependence in each reactant concentration. The second-order rate constant dependence on [H⁺] is in accordance with eqn (i) k₂ = k′₂ + k₃[H⁺] (i) where k′₂ and k₃ have values of 73.4 ± 14.0 M ^?1 s^?1 and 353 ± 41 M^?2 s^?1, respectively, at 1.0 M ionic strength (NaClO₄) and 25°C. At 310 nm the formation and decomposition of an intermediate, believed to be [FeC₃H₂O₄]⁺, was observed. The increase in the rate of oxidation with increasing [H⁺] was interpreted in terms of a “one-ended” dissociation mechanism which facilitates chelation of Fe₂₊ by the carbonyl oxygens of malonate in the transition state.