Research on gas-liquid-solid insulation system in stator slot
In evaporative cooling turbogenerator, all structures are immersing in evaporative cooling medium. Evaporative cooling turbogenerator which is transformed from inner water-cooling turbogenerator has been developed successfully. However, it has not taken full advantage of evaporative cooling medium's superiority in insulation. Besides, the amount of cooling medium is relatively large. This paper redesigns and analyzes gas-liquid-solid insulation system in stator slot from the perspective of the evaporative cooling technology. Furthermore, this paper provides the most appropriate materials and optimum thickness for solid insulation layer and fixed insulation layer in new insulation system. At last, this paper discusses wrapping width and interval of fixed insulation layer by three-dimensional model of new-designed insulation system.
Calculation of temperature distribution in the stator of larger evaporative cooling turbo-generator
Evaporative cooling for generator stator is an independent innovative technology developed by China. The development of the technology is in research stage. The mechanism of applying phase transition for evaporative cooling of the generator stator was introduced. according to the 300 MW turbo-generator design specification, and based on the two phase fluxion of cooling medium in the hollow conductor, we proposed the calculation of the medium fluxion resistance and the evaporative point of the cooling medium in the hollow conductor. We also carried out analysis of the temperature distribution along the stator winding and compared our calculation with the experiment results to demonstrate the feasibility of the proposed calculation.
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.