Evolution of roughness parameters along polishing tests of previously ground surfaces
In polishing tests, precise determination of polishing time needed is difficult, since representation of 
surface roughness against polishing time leads to an asymptotic curve. In the present work, results of 
the polishing tests of previously ground surfaces are presented. Different roughness parameters were 
considered. Grinding wheels of 100 and 150 Norton grain size respectively were used. Cutting speed 
was 25 m s-1 and depth of cut was 0.02 mm. Two different feeds were considered: 9 m min-1 and 15 m 
min-1. A polishing test was performed by means of corundum polishing pads of grain size 2500. 
Results show that, the higher the initial grain size of the grinding wheel, the higher initial roughness is 
as expected. Amplitude roughness parameters such as Ra and Rq decrease with polishing time. 
Regarding material percentage parameters, Rk and Rpk decrease more sharply than amplitude 
roughness parameters in the first 20 s of the polishing test, and afterwards decrease slightly. Rvk 
decreases more slowly than amplitude roughness parameters along the polishing test. 
Keywords: grinding, polishing, roughness parameters
A neuro-fuzzy approach to generating mold/die polishing sequences
A neuro-fuzzy approach to generating polishing sequences is presented. The measured initial surface roughness of the EDMed mold or die and the desired final polished surface roughness are the major inputs fed to the system. After receiving this input, the system consults its database for the polishing efficiency curves of the abrasive stone grain sizes available to it. With the outputs of this system being optimized for minimum polishing time, there is a selected sequence of grain sizes from among an available set, with each grain size used for each polishing step. There was a series of initial polishing experiments which were conducted for the different available grain sizes and workpiece roughness at different pressures and RPM's, with a change in roughness measured for polishing duration. From this, the database is constructed for designing the fuzzy logic rules. For constructing the exact membership function of the fuzzy interface, the neuro-fuzzy technique is combined with learning ability of neural network and the inferring ability of fuzzy logic system. Finally, while considering the stone-changing time, the actual experimental results from suggested polishing sequences are compared with the predicted value in order to establish the proposed approach.
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.