An extension of the characteristic angle method to the easy-plane spin-32 ferromagnet
Abstract The characteristic angle (CA) method [J. Phys. A 27 (1994) 5599], developed previously for the easy-plane spin-1 magnetic systems, has been successfully extended to the spin - 3 2 case. A compact form of the CA spin - 3 2 operator transformation is given. Then the ground state energy, the magnon dispersion relation and the spontaneous magnetization are discussed for an easy-plane spin - 3 2 ferromagnet by using the CA method. A comparison with the old theoretical methods is made.
Induced magnetization of an easy-plane spin-one ferromagnet
Abstract The characteristic angle (CA) method, which was introduced in a previous work, is applied to calculate the induced magnetization of an easy-plane spin-one ferromagnet. The harmonic approximation which is often applied in a spin-Bose expansion is found to be invalid and may even lead to wrong physical results when calculating the induced magnetization of the easy-plane spin-one ferromagnet. Then the complete Bose transformation (CBT) is used to transform the spin operator into a Bose operator, so that high-order terms in the Bose expansion can betaken into account based on an independent Bose representation. Comparison of the result calculated by the CBT and by the harmonic approximation shows that high-order terms in the CBT are helpful in determining a reasonable ground state and getting accurate physical results. Diagrams of the induced magnetization versus the external magnetic field for a simple-cubic lattice are presented for small and large anisotropy, respectively.
Cross talk between redox signalling and metabolic activity of osteoblasts and fibroblasts in the presence of hydroxyapatite-based biomaterials influences bone regeneration
Regeneration of bone tissue defects that result from metabolic disorders, including periodontal diseases, can be supported by biomaterials based on hydroxyapatite. Despite of good biocompatibility of biomaterials they can cause oxidative stress and inflammatory processes as a result of mechanical interaction with surrounding tissues. Because osteoblasts are responsible for bone regeneration process in which gingival fibroblasts may also participate, the aim of the work was to investigate the influence of hydroxyapatite-based biomaterials (allogeneic and xenogeneic) and biomaterials combined with enamel matrix derivative (Emdogain) on osteoblast and fibroblast redox balance in the context of osteoblast proliferation and differentiation.
The results showed that examined substitutes were not cytotoxic in vitro, but affected redox balance of osteoblasts and fibroblasts (ROS level increase and GSH level decrease) which led to oxidative stress (MDA and protein carbonyl groups level increase) resulting in an increase of the Nrf2 and NFκB expression. The consequence of these changes was partial inhibition of proliferation and osteoblast differentiation. Emdogain alone and combined with biomaterials decreased ROS generation and increased GSH level in both osteoblasts and fibroblasts leading to reduction of transcription factors expression especially proinflammatory NFκB, which promoted osteoblast differentiation and mineralization process.