RESUMEN
BACKGROUND: Skin dullness has long been a major concern of Japanese women. It is usually evaluated and judged visually by experts. Although several factors are recognized to play a role, it is unclear to what extent such physiological characteristics contribute to skin dullness. The purpose of this study is to establish an objective method for evaluation, which will assist in developing cosmetics products targeting skin dullness. METHODS: We conducted a skin measurement study on 50 Japanese women in their 30-50s, where skin dullness was visually assessed by a group of experts to obtain an average dullness score, and several skin parameters were obtained. We then developed a regression model that explains the visual assessment score using these physiological parameters. RESULTS: The results of partial least squares analysis of the dullness perception and physiological characteristics showed that skin dullness can be defined by colorimetric, optical, and skin surface microtopography parameters. Additionally, the contribution of each parameter to the model was determined. Our results suggest that dullness perception is highly affected by the melanin content and yellowness of the skin, followed by skin reddishness, roughness, and translucency score, whereas glossiness has less effect. Strikingly, the contribution ratio of each parameter varied among age groups. Furthermore, we confirmed that the predicted value of skin dullness increases with age. CONCLUSION: Our results will help the design of cosmetics targeting factors specific to age groups in developing effective solutions for skin dullness.
Asunto(s)
Cosméticos , Piel , Humanos , Femenino , Piel/diagnóstico por imagen , Colorimetría , Modelos Teóricos , Propiedades de SuperficieRESUMEN
Nickel complexes with hydrotris(pyrazolyl)borate ( = Tp(R)) ligands catalyze alkane oxidation with organic peroxide meta-Cl-C(6)H(4)C([double bond, length as m-dash]O)OOH ( = mCPBA). The electronic and steric hindrance properties of Tp(R) affect the catalyses. The complex with an electron-withdrawing group containing a less-hindered ligand, that is, Tp(Me2,Br), exhibits higher alcohol selectivity. Higher selectivity for secondary over tertiary alcohols upon oxidation of methylcyclohexane indicates that the oxygen atom transfer reaction proceeds within the coordination sphere of the nickel centers. A reaction of the catalyst precursor, dinuclear nickel(ii)-bis(µ-hydroxo) complexes, with mCPBA yields the corresponding nickel(ii)-acylperoxo species, as have been characterized by spectroscopy. Thermal decomposition of the nickel(ii)-acylperoxo species in CH(2)Cl(2) yields the corresponding nickel(ii)-chlorido complexes through Cl atom abstraction. Employment of the brominated ligand increases the thermal stability of the acylperoxo species. Kinetic isotope effects observed on decay of the nickel(ii)-acylperoxo species indicate concerted O-O breaking of the nickel-bound acylperoxide and H-abstraction from the solvent molecule.