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[en] Variation of second-order Doppler (SOD) shift, recoil-free fraction (f), and hyperfine field (H) are studied for disordered Co₄₉Fe₅₁ and Ni₄₈Fe₅₂ alloys in the temperature range 4.2 to 1000 K. The SOD shift and f-factor data are analysed in terms of the Debye approximation. The average reduced field for Ni₄₈Fe₅₂ is fitted to a modified Brillouin function. The average reduced field for Co₄₉Fe₅₁ alloy shows a kink around 823 K similar to magnetization data. (author)

[en] The easy direction of magnetization in RFe₃ intermetallic compounds with R=Sm, Gd, Tb, Dy, Ho, and Th is determined by means of the Moessbauer effect within a range of temperatures between 3 and 800 K. The magnetization of these compounds is within the basal plane with the exception of SmFe₃, in which the magnetization is parallel to the crystallographic c-axis. In HoFe₃ a magnetic phase transition is observed at T=100 K. At T<100 K the direction of magnetization is along the a-axis, while at T>100 K the magnetization is parallel to the b-axis. For ThFe₃ a very remarkable magnetic behaviour is found. Below T=140 K ThFe₃ is ferromagnetically ordered parallel to the a-axis. Above T=295 K the magnetization is parallel to the b-axis. In the temperature region from T=140 to 295 K ThFe₃ has practically no net magnetization. (author)

[en] Measurements of the nuclear relaxation times T₁, T₂, and Tsub(1rho) are performed on ²⁰³Tl and ²⁰⁵Tl in TlNO₃ from room temperature up to the melting point (210 ⁰C). The indirect nuclear interactions and their effect on the nuclear relaxation times are discussed. From the experimental data, the values of the Tl-Tl indirect coupling constants and the values of the correlation times for Tl⁺ diffusion are deduced. Evidence for spin-lattice relaxation processes driven by lattice vibrations is also shown. (author)

[en] Two basic formulations of the initial-value problem are discussed. In general, the multiplying medium with delayed neutrons, inelastic scattering, the (n, 2n) reaction and other effects are considered. The macroscopic effective cross-sections are considered as functions of space, angular, energetic and time coordinates. Solution of the problem is found by construction and its uniqueness is proved. (author)

[en] The criticality problem of the free slab is dealt with numerically and the thermal utilization is calculated for plane slab lattices based on singular integral equations resulting from the Boltzmann equation by transformation. The advantage of this method consists in the possibility of very precisely determining the corresponding quantities with low need of programming. (author)

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