aThe presence of water in lubricating oil affects the performance of lubricated rolling contacts. This work particularly focuses on the role of water in altering the evolution of zinc dialkyldithiophosphate (ZDDP)-derived reaction layers. A series of tribological tests were carried out using a rolling four-ball machine. Different initial water amounts were added to 2 wt% ZDDP in poly-alpha-olefin (PAO). The reaction layer evolution and its chemical properties were studied using XPS and SEM. SEM analyses show that water seems to inhibit the growth of the ZDDP-derived reaction layer. XPS analyses reveal that the reaction layer undergoes a depolymerisation of the polyphosphate chain when water is present in lubricated contacts. Surface distress was observed in 2 wt% ZDDP in poly-alpha-olefin, whereas when water was mixed with pure base oil, the surface distress increased. Different mechanisms of the influence of water on the ZDDP-derived reaction layer evolution are discussed.

BackgroundHuman Herpesvirus 8 (HHV8), the causative agent of Kaposi’s sarcoma, induces an intense modification of lipid metabolism and enhances the angiogenic process in endothelial cells. In the present study, neutral lipid (NL) metabolism and angiogenesis were investigated in HHV8-infected HUVEC cells. The viral replication phases were verified by rtPCR and also by K8.1 and LANA immunostaining.ResultsLipid droplets (Nile Red) were higher in all phases and NL staining (LipidTOX) combined with viral-antigen detection (immunofluorescence) demonstrated a NL content increase in infected cells. In particular, triglyceride synthesis increases in the lytic phase, whereas cholesteryl ester synthesis rises in the latent one. Moreover, the inhibition of cholesterol esterification reduces neo-tubule formation mainly in latently infected cells.ConclusionsWe suggest that a reprogramming of cholesteryl ester metabolism is involved in regulating neo-angiogenesis in HHV8-infected cells and plays a likely role in the high metastatic potential of derived-tumours.

Modelling of surface roughness evolution in time, as a function of the lubrication condition and other operating parameters (i.e. load, sliding/rolling ratio, and initial roughness of both contacting surfaces), is important for the understanding and prediction of various surface damage modes, such as surface distress, wear, and scuffing. Moreover, it is one of the key aspects in understanding friction and running-in phenomena. In the present study, a previously developed model for partial micro-elastohydrodynamic lubrication conditions is combined with a local Archard-type wear model to describe the surface topography evolution during the operation of a rolling/sliding lubricated contact. The model has been compared with a series of experimental results showing similar trends.

11A modelling framework has recently been developed which considers tribochemistry in 12 deterministic contact mechanics simulations in boundary lubrication. One of the capabilities of 13 the model is predicting the evolution of surface roughness with respect to the effect of