FT-Raman spectra of human enamel surfaces from sound, affected (with 1 cavity) and highly affected (with at least 3 cavities) tooth samples were analyzed by principal component analysis (PCA). Major differences between the unaffected and affected tooth samples seem to arise from the structural changes along the c-axis of hydroxyapatite, the chief crystalline component of human dental enamel. Based on Fisher index calculations, the most discriminative value was obtained for the intensity of the only Raman active ν 2 PO 4 3− (E 1 ) symmetric deformation mode at 428 cm −1 . Moreover, these changes can be observed through the whole tooth enamel surface, establishing a predisposition to caries correlated to chemical and structural composition of tooth enamel. No spectral changes regarding the CO 3 2− substitution were detected by both nondestructive FT-Raman and FTIR (Fourier transform infrared) spectroscopy of the powdered teeth samples.

We consider the polarization of unstable type-IIB D0-branes in the presence of a background five-form field strength. This phenomenon is studied from the point of view of the leading terms in the non-abelian Born Infeld action of the unstable D0-branes. The equations have SO(4) invariant solutions describing a non-commutative 3-sphere, which becomes a classical 3-sphere in the large-N limit. We discuss the interpretation of these solutions as spherical D3-branes. The tachyon plays a tantalizingly geometrical role in relating the fuzzy S 3 geometry to that of a fuzzy S 4 .

Zinc oxide (ZnO) thin-film transistors (TFTs) were fabricated by thermal chemical vapor deposition (CVD) using aqueous solutions of zinc acetate (ZnAc 2 ) dihydrate as a source. The precursor was supplied to the substrate by the nitrogen bubbling method through a plate with numerous orifices in the ZnAc 2 solution. The ZnO thin films were grown on silicon substrates in the growth temperature (T G ) range from 280 to 700 C. The growth rate of ZnO thin films were linearly proportional to the growth temperature, which suggested that the growth rate is limited by the decomposition of ZnAc 2 . Depletion-mode TFTs with the ZnO film grown at T G ¼ 350 C was found to exhibit a relatively low saturation mobility ( sat ). However, sat increased from 1 to 14 cm 2 ÁV À1 Ás À1 and the operational mode was changed from the depletion mode to the enhancement mode by annealing treatment at 200 C for 2 h under N 2 ambient. #

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