When illuminated by near-UV light, titanium dioxide (TiO2) exhibits excellent bactericidal activity.
However, there exist some different mechanisms for cell killing via photocatalysis. In the present study,
the photocatalytically bactericidal mechanism of TiO2 thin films was investigated by atomic force microscopy
(AFM) in conjugation with some other techniques. The decomposition process of the cell wall and the cell
membrane was directly observed by AFM for the first time. The resultant change in cell permeability was
confirmed by potassium ion (K+) leakage. Quantum dots (QDs) were designed originally as a probe to
examine the cell permeability for macromolecules. The corresponding bactericidal activity of TiO2 thin
films was examined by cell viability assay. These results suggested that the cell death was caused by the
decomposition of the cell wall and the cell membrane and the resultant leakage of intracellular molecules.
In this paper, a novel approach for designing tapered periodic meta-surfaces (TPMS) is proposed for suppressing electromagnetic scattering from a trailing edge of a square metallic plate with a given thickness. The TPMS is realized by periodic square metallic patches with tapered dimensions at the direction perpendicular to the considered edge but keeping its period unchanged. Based on the geometric phase interaction, the mechanism of suppressing electromagnetic scattering is analyzed. The lossy material is not required in this design, so it doesn’t generate thermal energy and benefits infrared stealth of military objects. The backscattering properties from the trailing edge with the proposed TPMS loading are analyzed and compared with that of original trailing edge. It is observed that wide angular trailing edge scattering suppressing can be obtained and the average value of mono-static radar cross section (RCS) reduction is 10 dB for L-band, S-band and C-band. Finally, the bi-static RCS properties and energy distribution of the proposed structure are also proposed to explain the mechanism of the electromagnetic scattering suppression of the trailing edge employed with the TPMS.
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