[en] The model spin Hamiltonian is used to explain the magnetic ordering of rare-earth compounds HoP and GdMg. These compounds have two ordered phases, namely, the intermediate ferromagnetic phase and the flopside phase where the two sublattice magnetizations are nearly perpendicular each other. The basic mechanism for such magnetic phase transitions is attributed to the competing bilinear interactions and the presence of the biquadratic interactions. (author)

[en] X-ray absorption near-edge structure spectra (XANES) of the Ba_1-xK_xBiO₃ (BKBO) (0.37≤x≤1.0) superconductor have been measured at the Bi L_III edge. To estimate changes of the Bi valence state, and reveal its influence on the superconducting properties of this solid solution, quantitative spectral characteristics of the 2p^3/2→6s transition in the series comprising different Ba/K ratios were determined. The superconducting transition T_c of the BKBO samples, determined from dc magnetic susceptibility measurements, monotonously decreases from Ba_0.63K_0.37 BiO₃ (T_c=30.4 K) to Ba_0.26K_0.74BiO₃ (a very low diamagnetic signal was detected at T∼3 K). This corresponds to the increase of Bi valence determined from XANES data in the range +4.36≤ν≤+4.74. Further increase of the K content to x>0.8 results in reappearance of superconductivity with T_c=9 K. The maximum value of formal Bi valence versus K content corresponds with the minimum in T_c

[en] Thermoelectric power (TEP) of MgB₂ and its changes with the superconducting transition temperature (T_c) have been investigated. MgB₂ samples synthesized with different techniques--sample 1 by the encapsulation method and sample 2 by the high pressure and high temperature technique--showed different T_c (T_c of sample 1= 38.7 K, and T_c of sample 2 = 40.4 K). The characteristic features of the TEP of these samples--low temperature linear behavior, deviation from the low temperature linear behavior at a certain temperature, and an almost saturating value at ∼300 K--were found to vary systematically with T_c, consistent with the previously reported TEP changes in Mg_1-xAl_xB₂. These changes of the TEP behaviors with T_c in the superconducting diborides system are discussed in comparison with those of high T_c cuprates and bismuthates. The common feature of the saturating TEP at high temperatures suggests the importance of an anharmonic electron-phonon interaction

[en] We have performed first-principles electronic structures calculations for a Ni overlayer on Cu₃Au(0 0 1) substrate with Cu termination by using the all-electron full-potential linearized augmented plane wave method, with the generalized gradient approximation. Ni/Cu(0 0 1) system with the same lattice constant of Cu₃Au(0 0 1) has also been calculated for comparison. It is interesting that calculated magnetic moments of Ni on Cu₃Au(0 0 1) substrate depend on their sites. The magnetic moment of Ni on Cu site is calculated to be 0.62 μ_B, which is the same value as that of the Ni on Cu(0 0 1) substrate, while that of the Ni on Au site is reduced to 0.57 μ_B. The calculated layer-projected densities of states reveal that the difference in magnetic moments depends delicately on subsurface atoms and the subsurface atoms affect the detailed electronic structures near the Fermi level of Ni overlayers

[en] The large q expansion formalism of the q state Potts model is used to obtain the susceptibility and the spontaneous magnetization series at the first order phase transition temperature for and three dimensional lattices. The series analysis in three dimensions dose not reveal any definite information as to singularity structure at the critical value of q where the transition becomes continuous. Accurate estimates of the transition temperatures of three dimensional lattices for q>=3 are obtained. (Author)

[en] Exact critical exponents, ν and γ describing the self-avoiding walks statistics are calculated for several finitely ramified fractals. (Author)

[en] Kinetic analysis of the tissue distribution of human epidermal growth factor (hEGF) in rats was performed in vivo. The plasma disappearance half-life of [125I]hEGF was prolonged by coadministration of unlabeled hEGF, indicating saturation of the mechanism for hEGF removal from the systemic circulation. To analyze the contribution of each tissue to the uptake of hEGF, the amount of [125I]hEGF taken up by each tissue was determined after coadministration of various amounts of unlabeled hEGF. Kinetic analysis of the data yielded the following results. (1) Among the tissues examined, the distribution of [125I]hEGF to the liver, kidney, small intestine, stomach, and spleen was much greater than that accounted for by the distribution to the extracellular space of each tissue. (2) The binding (or uptake) of hEGF by these tissues showed remarkable saturation, which may represent the receptor-dependent binding (or uptake) mechanism. (3) The apparent binding (or uptake) clearance per gram of tissue at the low dose (in the range of first-order kinetics), defined with regard to the arterial plasma concentration, was greatest in the kidney, followed by the liver and small intestine. The larger binding (or uptake) clearance of the kidney compared with that of the liver can be attributed to the higher plasma flow rate (per gram of tissue) in the kidney. However, the intrinsic ability to take up hEGF was much greater in the liver than that in the kidney. The hepatic binding (or uptake) of hEGF at the low dose was almost limited by the hepatic plasma flow rate

[en] The whole region of superconductivity in the Ba_1-xK_xBiO₃ (BKBO) system (0.35< x<1) has been investigated by synthesizing the samples with the high pressure and high temperature technique. As the K doping ratio (x) increases, the superconducting transition temperature (T_c) of the BKBO system decreases from 30.4 K for x=0.37 to very low diamagnetic signal below 3 K for x=0.74. The synthesis of the samples without including any bariums in the starting composition (x=1) resulted in different T_c and lattice parameters from sample to sample with partial substitutions of Bi at the K site in final products. With detailed synthesis information of the BKBO samples which varies with x, the evolution of T_c by doping in the cubic BKBO system is compared with other superconducting bismuthates and discussed on a basis of its electronic band structure

No abstract available

[en] The superconducting Sr_1-xK_xBiO₃ samples with x = 0.45 minus 0.6 were synthesized by the high-pressure-high-temperature technique in a belt type apparatus (2 GPa, 700 C, 1 h, Pt capsules) with stoichiometric mixtures of Sr₂Bi₂O₅, Bi₂O₃ and KO₂ as described earlier. The X-ray diffraction results appear as a single perovskite-like phase. The superconductivity occurs at Tc approximately 12 K in the A.C. susceptibility measurement. The onset (zero resistivity) temperature of superconductivity in resistivity measurement of the investigated sample was T_conset = 12.5 K (T_c0 = 10.2 K). The transition temperature region was a little bit broad and a shoulder was present about 11.3 K indicating probably the existence of crystallites of different K content. The particularly interesting point is that the resistance begins to reappear at T < 6 K at zero magnetic field. As the external magnetic field is applied, the reentrant resistance disappears and superconductivity is recovered until the applied magnetic field becomes higher than 0.65 Tesla. The superconductivity for T < 6 K is destroyed for the higher magnetic field. The T_conset decreases as the magnetic field increases like in the BCS type superconductors. The transition region becomes broader under the magnetic field, which indicate a kind of vortex transition as in the case of high Tc cuprates