[Cerebral circulation disorders in COVID-19].

Present two clinical cases of cerebral circulation disorders in COVID-19. Cerebrovascular disorders in patients have been associated with COVID-19. Despite the similarity of symptoms, the pathogenesis of neurological damage in these patients was different due to damage to the arterial system in the first case and the venous system in the second case.

Structural and Optical Properties of Silicon Nanowire Arrays Fabricated by Metal Assisted Chemical Etching With Ammonium Fluoride.

Here we report on the metal assisted chemical etching method of silicon nanowires (SiNWs) manufacturing, where the commonly used hydrofluoric acid (HF) has been successfully replaced with ammonium fluoride (NHF). The mechanism of the etching process and the effect of the pH values of HO: NHF solutions on the structural and optical properties of nanowires were studied in detail. By an impedance and Mott-Schottky measurements it was shown that silver-assisted chemical etching of silicon can be attributed to a facilitated charge carriers transport through Si/SiO/Ag interface.

[Ultramicroscopic evaluation of teeth enamel de- and remineralization].

The paper presents the results of scanning electronic microscopy evaluation of teeth enamel surface. The method allows studying objects at huge magnification and without preliminary preparation. Research was conducted in vitro on extracted teeth.