Discrete-vortex simulation of pulsating flow on a turbulent leading-edge separation bubble

Studies are made of the turbulent separation bubble in a two-dimensional semi-infinite blunt plate aligned to a uniform free stream with a pulsating component. The discrete-vortex method is applied to simulate this flow situation because this approach is effective for representing the unsteady motions of the turbulent shear layer and the effect of viscosity near the solid surface. The numerical simulation provides reasonable predictions when compared with the experimental results. A particular frequency with a minimum reattachment is related to the drag reduction. The most effective frequency is dependent on the amplified shedding frequency. The turbulent flow structure is scrutinized. This includes the time-mean and fluctuations of the velocity and the surface pressure, together with correlations between the fluctuating components. A comparison between the pulsating flow and the non-pulsating flow at the particular frequency of the minimum reattachment length of the separation bubble suggests that the large-scale vortical structure is associated with the shedding frequency and the flow instabilities

Epigenetic toxicity and cytotoxicity of perfluorooctanoic acid and its effects on gene expression in embryonic mouse hypothalamus cells

Premda je perfluorooktanska kiselina (PFOA) dobro znana kao endokrini disruptor, i dalje se malo zna o mehanizmima u pozadini njezina djelovanja na stanice i njezine toksičnosti u kritičnoj fazi razvoja hipotalamusa. Stoga smo istražili njezino djelovanje u staničnoj liniji N46 hipotalamusa mišjeg embrija (mHypoE-N46) da bismo saznali o mehanizmima kroz koje ih PFOA oštećuje. S tom smo svrhom analizirali vijabilnost stanica, globalnu metilaciju DNA i gensku ekspresiju izloženih stanica. Porastom koncentracija PFOA padala je stanična vijabilnost, a globalna DNA metilacija rasla. Usto je PFOA značajno utjecala na ekspresiju gena povezanih s apoptozom i staničnim ciklusom, neurotrofnih gena te Tet, Dnmt i Mecp2 gena. Naše istraživanje ukazuje na to da izloženost PFOA utječe na preživljenje stanica hipotalamusa mišjeg embrija reprogramiranjem obrazaca metilacije DNA te promjenama u genima zaduženim za održavanje homeostaze. Metilacija DNA i promjene u ekspresiji Mecp2 gena izazvane djelovanjem PFOA također imaju široki spektar implikacija, budući da utječu na promjene u genima zaduženim za druge važne mehanizme u embrijskom hipotalamusu. Stoga naše istraživanje može poslužiti kao dobra polazna točka za daljnje istraživanje mehanizama djelovanja PFOA na razvoj hipotalamusa.Even though the endocrine-disrupting potential of perfluorooctanoic acid (PFOA) is well known, the mechanisms underlying its cellular and epigenetic toxicity at the critical stage of hypothalamic development are poorly understood. This is why we studied its effects on the embryonic mouse hypothalamic cell line N46 (mHypoE-N46) with a hope to shed more light on the mechanisms through which PFOA causes embryonic hypothalamic cell damage. To do that, we studied cell viability, global DNA methylation, and gene expression in cells exposed to PFOA. As the PFOA dose increased, cell viability decreased, while global DNA methylation increased. PFOA also significantly altered the expression of genes related to the apoptosis and cell cycle, neurotrophic genes, and the Tet, Dnmt, and Mecp2 genes. Our findings suggest that exposure to PFOA affects cell survival through the reprogramming of embryonic hypothalamic DNA methylation patterns and altering cell homeostasis genes. DNA methylation and changes in the Mecp2 gene expression induced by PFOA also imply wider ramifications, as they alter genes of other major mechanisms of the embryonic hypothalamus. Our study may therefore serve as a good starting point for further research into the mechanisms of PFOA effect of hypothalamic development