First principles study of local electronic and magnetic properties in pure and electron-doped Nd2_2CuO4_4

The local electronic structure of Nd2CuO4 is determined from ab-initio cluster calculations in the framework of density functional theory. Spin-polarized calculations with different multiplicities enable a detailed study of the charge and spin density distributions, using clusters that comprise up to 13 copper atoms in the CuO2plane. Electron doping is simulated by two different approaches and the resulting changes in the local charge distribution are studied in detail and compared to the corresponding changes in hole doped La2CuO4. The electric field gradient (EFG) at the copper nucleus is investigated in detail and good agreement is found with experimental values. In particular the drastic reduction of the main component of the EFG in the electron-doped material with respect to LaCuO4 is explained by a reduction of the occupancy of the 3d3z^2-r^2 atomic orbital. Furthermore, the chemical shieldings at the copper nucleus are determined and are compared to results obtained from NMR measurements. The magnetic hyperfine coupling constants are determined from the spin density distribution

Pengaruh Latihan Peregangan Terhadap Fleksibilitas Lansia

: Flexibilityis the ability of a joint, muscles, and ligaments around it to move free lyandcomfortably in the space for the expected maximum. Flexibility is influenced by many factors. These factors are the muscles, tendons, ligaments, age, gender, body temperature and joint structure. Less flexibility may lead toa slower movement and injury pronetomuscles, ligaments, andothertissues. With increasing age, the person's flexibility will reduce. The best way to increase the flexibility is stretching exercises. This study aimed to find the effect of stretching exercises for flexibility among the eldery. This was an experimental field study with pre-post test design. Samples were 30 elderly people who were in BPLU Senjah Cerah, Paniki Bawah. Samples were measured by using a goniometer flexibility before doing stretching exercises. After stretching exercises for 3 weeks, they were measured again with the goniometer. The results showed that stretching influenced the flexibility of the elderly (p0.05). Conclusion: Stretching exercises can improve joint flexibility

Density functional electronic spectrum of the CuO−6−10Cu O_{-6}^{-10} cluster and possible local Jahn-Teller distorsions in the La-Ba-Cu-O superconductor

We present a density functional theory (DFT) calculation in the generalized gradient approximation to study the possibility for the existence of Jahn-Teller (JT) or pseudo Jahn-Teller (PJT) type local distortions in the La-Ba-Cu-O superconducting system. We performed the calculation and correspondingly group theory classification of the electronic ground state of the CuO${_{6}}^{-10}$ elongated octahedra cluster, immersed in a background simulating the superconductor. Part of the motivation to do this study is that the origin of the apical deformation of the CuO${_{6}}^{-10}$ cluster is not due to a pure JT effect, having therefore a non {\it a priori} condition to remove the degeneracy of the electronic ground state of the parent regular octahedron. We present a comparative analysis of the symmetry classified electron spectrum with previously reported results using unrestricted Hartree-Fock calculations (UHF). Both the DFT and UHF calculations produced a non degenerate electronic ground state, not having therefore the necessary condition for a pure JT effect. However, the appearance of a degenerate E$_{g}$ state near to the highest occupied molecular orbital in the DFT calculation, suggests the possibility for a PJT effect responsible for a local distortion of the oxidized CuO$_{6}^{-9}$ cluster.Comment: 12 pages, 3 figures, submitted to International Journal of Modern Physics B (IJMPB