Determinación de la influencia de la altitud en el índice de protección natural (IPN) de la piel y el factor de protección solar requerido (SPF) / Determination of the influence of altitude on the contents of natural protection (IPN) skin and sun protection factor required (SPF)

Se evalúa la influencia de la altitud sobre el Índice de Protección Natural (IPN) y el Factor de Protección Solar requerido (SPF) comparando niños de Mucuchies, Mérida, Venezuela (3100 m.s.n.m.) y Palmarito, Mérida, Venezuela (5 m.s.n.m.), utilizando el equipo Sun Protection Diagnostic SP 37®. Según el análisis de los resultados a través de estadísticas descriptivas, se evidencia que el IPN y el SPF son variables dependientes de la altitud de la localidad en que se encuentran los niños, ya que en las localidades más altas los rayos solares inciden de forma más directa que en las más bajas.

It is evaluated the effect of altitude on Natural Protection Index (IPN) and the required Sun Protection Factor (SPF) comparing children Mucuchies, Merida, Venezuela (3100 m) and Palmarito, Merida, Venezuela (5 m) using Sun Protection Diagnostic SP37® equipment. According to the analysis of results through descriptive statistics, it appears that the IPN and the SPF are variable dependent on the altitude of the locality in which children are, as in the most high solar rays more directly than in the lowest.

Giant regular polyhedra from calixarene carboxylates and uranyl.

Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO(2)2+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components.

Chemical composition and antibacterial activity of the essential oil of Lantana camara var. moritziana.

The essential oil obtained from the leaves of Lantana camara var. moritziana (Otto & Dietr.) López-Palacios collected at Rubio, Táchira State, Venezuela, was obtained by hydrodistillation in a Clevenger trap (0.1% yield). The oil was analyzed by gas chromatography-mass spectrometry (GC/MS) on HP GC-MS System, model 5973, identifying 33 compounds (97.1%) of which the major components were germacrene D (31.0%), followed by beta-caryophyllene (14.8%), a-phellandrene (6.7%), limonene (5.7%) and 1,8-cineole (5.2%). Evaluation of the antibacterial activity by agar diffusion method with discs against international reference bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Salmonella Typhi, Pseudomonas aeruginosa) showed growing inhibition of E. faecalis and S. aureus at MIC of 350 mg/mL and 400 mg/mL, respectively.

Supramolecular control of a fast and reversible Diels-Alder reaction.

A new cyclophane featuring two opposite anthracene units linked in 9,10-positions has been synthesized thanks to the template effect of the Me4N(+) ion. It forms pseudorotaxane complexes with alkylviologen ions and undergoes a fast and reversible reaction with tetracyanoethylene. A quantitative analysis has been carried out of the formation of Diels-Alder adducts, whose distribution can be controlled by host-guest complexation. These findings open interesting perspectives in the field of Dynamic Covalent Chemistry.