Principal research areas on mechanical face-seals
Abstract A critical review of world literature on radial face-seals is presented in order to further understanding of seal operation and to obtain some elements of a design method for optimization of their performance. The principal areas examined are hydrostatic, hydrodynamic and boundary lubrication of the faces, and in particular cavitation and the influence of different constructive parameters on the dynamic behaviour of these seals.
Thermoelastic and Dynamic Phenomena in Seals.
Abstract : An analysis of a seal model is made where the rotating element has both fixed tilt and two-lobe waviness. The stator is assumed to be gimbal mounted and to have inertial mass. Hydrodynamic lubrication is assumed, following the short bearing or narrow seal model. Conditions are examined where the stator precesses in synchronism with the rotor rotation. Particular interest is given to operating conditions where such behavior appears to degenerate. (Author)
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.