Efecto de Diferentes Técnicas de Acabado y Pulido Sobre la Rugosidad de un Composite de Nanoparticulas / Effect of Different Finishing and Polishing Techniques on the Roughness of a Nanoparticle Composite

El objetivo fue comparar la rugosidad de un composite nanoparticulado con diferentes técnicas de acabado y pulido. Se obtuvieron 20 discos en conformadores ad-hoc en los que se insertó un composite nanoparticulado en capas de 2mm. Se activó cada incremento durante 30s con una intensidad de 1450 mw/cm2. Todas las probetas se pulieron con la secuencia completa de discos Sof-lex a velocidad media y luego se asignaron a uno de 4 grupos (n=5) tratados de la siguiente manera: G1: sin tratamiento extra; G2: con cepillos Astrobrush y JC-SICRA-G; G3: con pasta de diamantes Diamond Gloss aplicada con fieltro; y pasta de óxido de aluminio Poligloss y fieltro; G4: igual que G3 + cepillos (igual que G2). Las superficies se evaluaron con un perfilómetro óptico tridimensional. Se registró la rugosidad promedio (Ra) en tres puntos de cada espécimen, se consideró la Ra a la media de los tres registros obtenidos. Los datos se analizaron mediante ANOVA de una vía y prueba de Tukey para comparaciones múltiples. Los resultados obtenidos fueron: G1: 132,20nm (26,16); G2: 77,20 nm (20,64); G3: 78,74 nm (10,04); G4: 66,47nm (31,08). Se encontró diferencia estadísticamente significativa entre los grupos (P=0.0017); de las comparaciones múltiples surge que G1 presentó una rugosidad media significativamente mayor que los restantes. G1>G2 (P<0.01), G1>G3 (P<0,05), G1>G4 (P<0,01). En conclusión, el uso de sistemas anexos de pulido permite lograr mayor lisura superficial. El uso de más de un sistema complementario no mejora el resultado (AU)

Fungal survival in ensiled swine faeces.

The survival of several genera of fungi was determined in the ensiled solid fraction of swine faeces after 0, 7, 14, 28 and 56 days of ensiling. The experiment had two treatments, un-ensiled and ensiled manure, in a split-plot design. The manure was distributed into 50 containers; samples, taken at the specified times, were cultured in agar potato dextrose medium, incubated, and colony forming units (CFU/g) were counted and log-transformed. The ensiling process decreased the number of CFU after 56 days. Five fungal genera were identified (Absidia spp., Aspergillus spp., Penicillium spp., Rhizopus spp. and non-fructiferous fungi), and their vulnerability to the ensiling conditions varied, although most of them slowed their growth or disappeared after 14 days of ensiling.

Study on external exposure doses received by the Cuban population from environmental radiation sources.

The results are described of the study carried out with the aim of assessing doses received by the Cuban population due to the external exposure to environmental radiation sources. Contributions of cosmic radiation's ionising and indirectly ionising components to these doses, as well as the fraction resulting from terrestrial radiation, were also assessed as part of this study. Measurements made enabled us to estimate representative effective average doses received by the Cuban population from external exposure to cosmic and terrestrial radiation. Both outdoor and indoor permanency were taken into account for this estimate as well as the distribution of the Cuban population by altitude. The average representative dose due to cosmic radiation was estimated to be 298 +/- 17 microSv per year, while the dose received by terrestrial radiation represented 180 +/- 14 microSv per year, for a total annual dose of 78 +/- 20 microSv. These values are within the range of those reported throughout the world by other authors.

[Seroprevalence of antibodies against Plasmodium falciparum in volunteer donors from various cities in Venezuela]. / Seroprevalencia de anticuerpos a Plasmodium falciparum en donantes voluntarios de varias ciudades de Venezuela.

The prevalence of antibodies to Plasmodium falciparum was studied in 890 blood donors from different geographical areas of Venezuela. The overall prevalence, as established by ELISA, was (1.7%). Seropositivity was higher in those samples obtained in Sucre (2.5%) and Apure (1.7%) states both with foci of malaria transmission. It is proposed that medical history should be reinforced by screening antimalarial antibodies in donors at risk.