Interdeffusion in the Co-Ni system-III. Intrinsic diffusion coefficients

The intrinsic diffusion coefficients¯D _Co and¯D _Ni in the Co—Ni system have been calculated with the use of the interdiffusion coefficient values, concentration gradient data (Part I) and from the observed inert markers displacements (Part II). The Darken euqations [1] were used in these calculations and for comparison's sake an attempt was made to apply the Van Loo treatment as well [2, 3].The experimental difficulties related to the determination of the diffusants concentration in the Kirkendall interface are discussed. A simple method had been worked out which enabled us to determine this concentration from the Darken equations, from inert markers velocity and from the penetration curves data.The activation enthalpies¯ H _Co and¯ H _Ni have been calculated from the temperature dependence of the intrinsic diffusion coefficients;¯ H _Co values are slightly higher than¯ H _Co values. The magnitude of the observed Kirkendall effect has been analyzed and compared with the results obtained in some other binary FCC and BCC systems.     

Stress characteristics of creep of alpha-Zr in the temperature interval 300–900 K

The stress experiments of alpha-Zr were performed within the temperature interval 300 to 900 K using the incremental loading method. The temperature interval may be divided into three regions — the low temperature region (300–475 K), the transient region (475–775 K) and the high temperature region (above 775 K). The transient region was characterized by the maximum of the strain-rate sensitivity parameterm and also the creep deformation was — to a certain degree — affected by the athermal mechanism.The authors would like to thank Professor J.adek, DrSc, for many valuable discussions, unfailing support and continual encouragement.     

Ewald's dynamical theory of diffraction for a defect crystal

The paper is based on the Ewald's approach to the problem of interaction of an electromagnetic wave with a coulomb crystal lattice. Born's formalism of the crystal dynamics is used. Defects of the lattice modify the dynamical matrix of the crystal which can be simply inverted in a case of a small defect density. The final formula describes the distribution of the scattered intensity of the incident light wave as a function of the defect configuration. The possibility of the extension of the method to the Laue theory is briefly discussed.     

Birefringence in YA1O3∶Nd between 2–4·7 eV

The paper presents original spectra of the birefringence of the orthorhombic YAlO₃Nd single crystal in the region from 2 to 4·7 eV, describes a reflection method of null ellipsometry which was used for the measurement of the spectra and, in conclusion, makes a comparison between the measured spectra and the values predicted from the values measured over the region of lower energies 1·1 – 2·2 eV.The authors are grateful to J. Kvapil for samples preparation.     

Gnostical analysis of international activities in physics

Conclusion Evidence from several case studies have illustrated interesting possibilities of improving the assessment of scientometric data by non-statistical methods derived from the gnostical theory.     

On the supersymmetric sine-Gordon model

The basic model in a new trend in supersymmetry and soliton theory is presented. Exact soliton-like solutions of the supercovariant coupled equations of motion are obtained. From this a bag model is constructed.Talk given at the ldSymposium on Mathematical Methods in the Theory of Elementary Particles, Liblice castle, Czechoslovakia, June 18–23, 1978.     

Formation of N2 C3Πu and B3Πg by dissociative recombination of Ar 2 + in Ar+N2 early afterglow

The hf pulse excited Ar + N₂ mixtures and early afterglow are investigated at total pressures from 266 to 1995 Pa using nitrogen of 0·05–0·5% concentration. The time-resolved intensity of Ar I atomic lines and N₂ (2nd pos., 1st pos. and 1st neg.) band systems exhibit an intense early afterglow (0·3 ms). Both the decay of electron densityn _e and that of molecular Ar ₂ ⁺ ions and enhancement of coefficient of dissociative recombination due to electron temperature decrease after the pulse lead to the formation of characteristic secondary maximum of Ar I spectral line and N₂ molecular band intensities in the momentt _m after cut-off the pulse. The values oft _m(B³_g)>t _m(C³_u)>t _m(Ar I) decrease with increasing total pressure and increase with growing concentration of N₂ in Ar. In the afterglow period the Ar ₂ ⁺ dissociatively recombine in 5p and 4p Ar states. As a result of radiative transitions the metastable Ar (³P_2,0) atoms are formed which consequently due to collisions with N₂ molecules create electronically excited N₂. With increasing nitrogen concentration this effect becomes less pronounced and at concentration of N₂ greater than 0·5% it is negligible.