Cation self-diffusion and impurity diffusion in Fe2O3+

Cation self-diffusion D¹_Fe, parallel to the c axis has been measured as a function of temperature (1100–1300°C) and oxygen partial pressure p_o2 (2 × 10^?3-1 atm) in the same single crystals of Fe₂O₃ as those used by Chang and Wagner. Whereas the p_o2 dependence of D1_Fe, observed by Chang and Wagner has been confirmed, the absolute value of D¹_Fe and the activation enthalpy for self-diffusion are much higher than those reported by them. The various diffusion studies indicate that cation self-diffusion occurs by an interstitial-type mechanism. However, the sample-to-sample variations in D¹_Fe, suggest that all diffusion measurements may have been performed on samples where the defect concentrations are impurity controlled. Impurity diffusion of ⁶⁰Co, ⁵¹Cr, and ⁸⁸Y has also been measured as a function of p_o2 at 1200°C. The results indicate that these impurities diffuse by an interstitialcy mechanism in Fe₂O₃.     

Palladium charcoal-catalyzed deprotection of O-allylphenols

Allyl aryl ethers can be easily cleaved by the use of 10% Pd/C under mild and basic conditions. The present reaction would involve a SET process rather than a π-allyl-palladium complex. The scope and limitation of this new deprotective methodology is also described.     

Photographic measurements of propagation speeds of the conducting zone in polyaniline films during electrochemical switching

In order to observe the propagation of a conducting zone of a polyaniline film in response to anodic switching, propagation perpendicular to the film surface was simulated by propagation along the film by mounting the film on an insulated plate. A polyaniline film electrochemically deposited on an indium tin oxide (ITO) electrode was reinforced by casting polymethylmethacrylate solution on the film. It was peeled off the ITO, chemically reduced and then potentiostatically oxidized at one end in 1 mol dm⁻³ H₂SO₄ solution. Dynamic growth of the conducting zone was observed through an optical microscope. A well-defined boundary between the conducting zone and the insulating zone was seen. The contrast of the boundary did not vary with the electrolysis time, the growth length or the applied potential. The growth rate decreased slightly with the electrolysis time as a result of IR drop across the film. A differential equation for growth rate involving the effect of the IR drop was presented and solved to give more accurate values of the rate. The logarithmic growth ratio exhibited a linear relation with the applied potential, indicating a charge-transfer rate of the Tafel type. The anodic transfer coefficient was 0.2 and the rate constant was 5 × 10⁻⁵ m s⁻¹. The propagation on a molecular scale was discussed on the basis of the experimental results.     

13C-NMR study of cellulose derivatives in the solid state

The application of NMR for natural organic compounds has been carried out from the early history of NMR. But they reported on the liquid state NMR and the samples were limited to the materials which dissolved in proper solvents. It has been possible to measure the samples in the solid state in 1970s and is widely used as a familiar analytical method in 1980s. Whereas some of the data is inadequate, concerning cellulose derivatives, in particular, only nitrate and acetate were reported by Patterson¹ and Doyle,² respectively. In this paper, the ¹³C CP/MAS solid state NMR spectra of several cellulose derivatives are shown and the relationship between the structure and spectrum is discussed.     

Stability of fermion and momentum cut-off in quantum gravity in flat background spacetime

The momentum cut-off Λ_G for quantum gravity is determined quantitatively in connection with the stability of the fermion and is found to be Λ_G ? 1.00 M_P (M_P is Planck's mass) in Feynman gauge and Λ_G #x2A7D; 0.87 M_P in Landau gauge.     

Configurational stabilization of mixed-valence states in the star-burst tetranuclear ruthenium complex bridged with acetylene links

A new tetranuclear ruthenium complex in which a metal was bridged radially to three identical metals with acetylene links showed a mixed-valence state in cyclic voltammograms. The peak potential difference for the mixed-valence state was twice the potential difference for a mixed-valence state of the corresponding binuclear complex. This fact suggests stabilization of the mixed-valence state twice by configurational modification of redox centers. However, this is inconsistent with the prediction from the additive pair model of the redox interaction. A quantum chemical model of the redox interaction was presented, in which the potential difference was expressed by the overlap integral S and the nearest neighbor interaction energy between the reduced center and the oxidized one. Application of the theory gave a negative value of S, which demonstrated reasonably the stabilization of the mixed-valence state from a quantum chemical viewpoint.     

LP-based heuristics for the distinguishing string and substring selection problems

Annals of Operations Research - This work aims to evaluate and propose matheuristics for the Distinguishing String Selection Problem (DSSP) and the Distinguishing Substring Selection Problems...