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A series of D-erythro ceramide analogues, N-(2S, 3R, 4E)-1, 3-dihydroxy-5-phenyl pent-4-en-2-yl alkyl sulfonamides, were synthesized and evaluated for their in vitro cytotoxic activities against five human tumor cell lines. The aromatic sulfon amido ceramide analogue (10f) showed more potent cytotoxic activity than that of the B13, indicating that a sulfonamide group appears to serve as a bioisostere of an amide in drug design. Variations in the alkyl sulfonyl chain length significantly influenced the cytotoxic activity of the sulfonamido ceramide analogues, but the introduction of a para halogen on the phenyl ring of aromatic ceramide analogues had no affect on the activity.

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We investigated the selective etching of Si versus Si1−xGex with various Ge concentrations (x = 0.13, 0.21, 0.30, 0.44) in tetramethyl ammonium hydroxide (TMAH) solution. Our results show that the Si1−xGex with a higher Ge concentration was etched slower due to the reduction in the Si(Ge)–OH bond. Owing to the difference in the etching rate, Si was selectively etched in the Si0.7Ge0.3/Si/Si0.7Ge0.3 multi-layer. The etching rate of Si depends on the Si surface orientation, as TMAH is an anisotropic etchant. The (111) and (010) facets were formed in TMAH, when Si was laterally etched in the <110> and <100> directions in the multi-layer, respectively. We also investigated the effect of the addition of Triton X-100 in TMAH on the wet etching process. Our results confirmed that the presence of 0.1 vol% Triton reduced the roughness of the etched Si and Si1−xGex surfaces. Moreover, the addition of Triton to TMAH could change the facet formation from (010) to (011) during Si etching in the <100>-direction. The facet change could reduce the lateral etching rate of Si and consequently reduce selectivity. The decrease in the layer thickness also reduced the lateral Si etching rate in the multi-layer.