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Balance of essential elements in organisms might be changed by environmental stresses. Small fresh water fish, Medaka, was burdened with X-ray irradiation (total dose: 17Gy), keeping in salty water (70% NaCl of sea water) and keeping in metal containing water (10ppm of Cr and Co). These stresses are not lethal doses. Essential elements in liver, gall bladder, kidney, spleen, heart and brain in the stress-loaded fish were measured by PIXE method and compared with a control fish to determine the effect of the stresses. Various changes of the elemental contents were observed. Effect of X-ray irradiation was the smallest among the stresses. Relatively high content elements such as P, S, Cl and K were hardly affected with the stresses examined in this work. The effect of Cr on the metal balance seems to be larger than the other stresses. As PIXE method can analyze many elements in a small sample simultaneously, change of elemental distribution in small organisms induced by environmental stresses can be determined readily.

It is of interest for layered oxides containing copper because they are related to high temperature superconductivity. Among them, LaSrAl_1-xCu_xO₄ solid solution has received much attention due to its elastic and elasto-optic properties and application as promising substrate for high-T_c superconducting thin films. So many theoretical and experimental works have been done to understand the several characteristics of the LaSrAl_1-xCu_xO₄ materials. In this paper, the electron paramagnetic resonance g factors g_//, g_⊥ and hyperfine structure constants A_//, A_⊥ for the tetragonal Cu²⁺ center in LaSrAl_1-xCu_xO₄ solid solution are theoretically explained by the method of diagonalizing the full Hamiltonian matrix. The related crystal field parameters are calculated from the superposition model and the local structural parameters of the impurity Cu²⁺ occupying the host Al³⁺ site. The superposition model parameters used in this work are comparable with those for similar tetragonal (CuO₆)^10- clusters in the previous works. The calculated results are in reasonable agreement with the observed values. The results are discussed.

The EPR g factors g_// and g_⊥ for the six-coordinated Cu²⁺(1) site in YBa₂Cu₃O_6+x are theoretically investigated from the perturbation formulas for a 3d⁹ ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu²⁺(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu²⁺ cluster. Based on the calculations, the effective elongation (≈ 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Δg (=g_// - g_⊥). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.

The spin Hamiltonian (SH) parameters g factors g_‖, g_⊥ and the hyperfine structure constants A_‖ and A_⊥ for the tetragonal Cu²⁺ centers (i.e., [CuX₄(H₂O)₂] clusters) in NH₄X(X = Cl, Br, I) are theoretically investigated by means of the diagonalization procedure of complete (10×10) energy matrix (DPCEM) for a 3d⁹ ion in tetragonal symmetry. The crystal-field parameters in the energy matrix are determined from the superposition model. The calculated SH parameters are in reasonable agreement with the experimental data.

In this paper, based on a two-mechanism model, we derive the complete high-order perturbation formulas of the spin-Hamiltonian (SH) parameters (g factors g_‖, g_⊥ and hyperfine structure constants A_‖, A_⊥) for 3d⁹ ions in tetragonally elongated octahedral clusters. In the model, the contributions to SH parameters due to the crystal-field (CF) mechanism related to CF excited states and the charge-transfer (CT) mechanism related to CT exacted states (the CT mechanism is neglected in CF theory, which is widely used to study the SH parameters) are taken into account. From these formulas, the SH parameters of Cu²⁺ ions in AgCl and NaCl crystals are calculated. It is found that for the exact explanation of SH parameters of (CuCl₆)^4- clusters in crystals, the contribution due to CT mechanism should be considered. The relative importance of CT mechanism (characterized by Q^CT/Q^CF, where Q = Δg_i or , i = ‖ or ⊥) increases with the decreasing metal-ligand distance in ( CuCl₆)^4- clusters. The causes are discussed. The signs of A_i and the defect structures of Cu²⁺ centers in AgCl and NaCl crystals are suggested from the calculations.

The local structure and the EPR parameters (g factors and the hyperfine structure constants) for Cu²⁺ in GaN are theoretically studied from the perturbation formulas of these parameters for a 3d⁹ ion in trigonally distorted tetrahedra. In these formulas, the ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach, in view of the strong covalency effect of the system. Based on the studies, the impurity Cu²⁺ is found not to occupy exactly the host Ga³⁺ site but to suffer a slight displacement (≈ 0.004 Å) towards the ligand triangle along C₃ axis due to charge and size mismatching substitution. The theoretical EPR parameters show good agreement with the experimental data. The validity of the impurity displacement is also discussed.

The spin Hamiltonian parameters (the anisotropic g factors and the hyperfine structure constants) and the local structure for the rhombic Cu²⁺ center in rutile (TiO₂) are theoretically investigated using the formulas of these parameters for a 3d⁹ ion in rhombically elongated octahedra. From the studies, the planar impurity-ligand bond angle is found to be about 5.8° larger than that for the host Ti⁴⁺ site due to the Jahn–Teller effect via bending the planar Cu²⁺–O^2- bonds, which yields much smaller rhombic distortion in the impurity center. The theoretical spin Hamiltonian parameters based on the above local angular distortion show good agreement with the experimental data, and the improvement of the calculation results are also achieved as compared with those of the previous works.