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In the present study, a prediction of hardness deterioration and abrasive wear was performed through a neural network using artificial intelligence on a material printed in SLA. This article aims to predict the mechanical properties, wear resistance and surface hardness of parts manufactured by SLA stereolithography printing. A full factorial DOE was used to associate the peculiar parameters (print orientation, cure time, layer height) to perform experiments. The mechanical properties were evaluated according to ASTM regulations, with the objective of obtaining feeding data and validation of the predictions of the Taber Wear Index and hardness using an artificial neural network. The experimental results are in good agreement with the measured data with satisfactory prediction errors with a mean square error (MSE) of 0.01 corresponding to abrasive wear using the clear resin and a mean absolute error (MSE) of 0.09 with an R2 of 0.756, the prediction with the neural network with a mean square error (MSE) of 2.47 corresponding to abrasive wear using the tough resin and a mean absolute error (MSE) of 14.3 with an R2 of 0.97. It was shown that the accuracy of the prediction is reasonable, and the network has the potential to be improved if the experimental database for training the network could be expanded. Therefore, wear and hardness mechanical properties can be predicted appropriately with an ANN.

Background & aims: To assess the agreement and the association between phase angle (PA) and parameters of nutritional status in surgical patients. Methods: This was a cross-sectional study that involved 98 patients admitted for elective gastrointestinal or hernia repair surgery. The risk and nutritional status were evaluated through Nutritional Risk Screening 2002 (NRS 2002), Subjective Global Assessment (SGA), Body Mass Index (BMI) and Total Lymphocytes Count (TLC). These assessments were compared with the mean standardized PA (SPA), obtained by Bioelectrical Impedance Analysis (BIA). Statistical analysis included kappa coefficient, Student's t-test, Mann-Whitney test, and the construction of a ROC Curve. Results: The highest kappa agreement was obtained between the SPA and the SGA (0.27; CI95% 0.06-0.48). Malnourished patients diagnosed by NRS 2002, SGA and TLC had a significantly lower mean SPA as compared to those who were well-nourished. A cut-off point of 0.8 for SPA showed 82.6% (CI95% 65.0-100.0%) sensitivity and 40.6% (CI95% 23.0-58.2%) specificity. Conclusion: The SPA presented weak agreement with the methods of nutritional assessment, as well as low specificity, and could not be recommended as a marker of nutritional status, despite the fact that the lowest values for SPA were found in malnourished patients.Introducción y objetivos: Evaluar la concordancia y asociación entre el ángulo de fase (AF) y los parámetros del estado nutricional en pacientes quirúrgicos. Métodos: Se desarrolló un estudio de sección transversal con 98 pacientes admitidos para una cirugía gastrointestinal o de hernia. Se evaluó el riesgo y el estado nutricional a través del Rastreo de Riesgo Nutricional 2002 (RRN 2002), la Valoración Global Subjetiva (VGS), el Índice de Masa Corporal (IMC) y el Recuento Total de Linfocitos (RTL). Estos métodos fueron comparados con la media del AF estandarizado (AFE) obtenido por medio del Análisis de Impedancia Bioeléctrica (AIB). Los Análisis estadísticos incluyeron el coeficiente kappa , el test t Student, el test de Mann-Whitney, y la construcción de la Curva ROC. Resultados: La concordancia kappa más alta se obtuvo entre el AFE y el VGS (0,27; CI95% 0,06-0,48). Los pacientes desnutridos diagnosticados por el RRN 2002, VGS y el RTL, tuvieron una media estadística de AFE significativamente menor comparado con aquellos que estaban bien nutridos. Un punto de corte del 0.8 para un AFE mostró 82,6% (CI95% 65,0-100,0%) de sensibilidad y 40,6% (CI95% 23,0-58,2%) de especificidad. Conclusión: El AFE presentó una concordancia débil con los métodos de evaluación nutricional, así como una baja especificidad y no pudo ser recomendado como un indicador del estado nutricional, a pesar de que los valores más bajos del AFE fueron encontrados en pacientes desnutridos.

Twenty nine cetacean species occur in Costa Rican waters but extensive research has been conducted only for three species. The latter shows there is a lack of general and local information about these mammals, even when the country, has shown a remarkable growth in whale watching activities. The increasing use of marine resources in coastal areas has also developed the need to determine the occurrence of cetaceans in areas showing high tourist presence, in order to propose sound conservation measures. In this study, environmental variables were determined and subsequently related to the presence of the species recorded, out of 166 sightings, between 2005 and 2006. The species with highest proportion of sightings were Stenella attenuata (68%), followed by Megaptera novaeangliae (13%) and Tursiops truncatus (10%). The presence of spotted dolphins is related to changes in salinity and water transparency, while that of the humpback whale was related to wave height (Beaufort scale) and water temperature. The presence of seven species of cetaceans was confirmed in two coastal areas of the Pacific coast of Costa Rica, from which three are present throughout the year. Environmental variables were found related to the presence of at least two species.

Dolphins are characterized by a significant behavioral versatility, which allows them to respond to environmental seasonality. Seasonal variation in dolphin behavior in tropical waters is not well known. Stenella attenuata graffmani is a resident dolphin in the clearly defined seasonal Gulf of Papagayo, Costa Rica, and we studied if dolphin group size, occurrence and behavioral patterns were associated with season and time of day in the gulf. Using strip transects we surveyed two locations for three consecutive years. School size ranged from 1 to 50 individuals, mean group size was 10.16 (SD = 9.61) individuals. Overall, foraging activities were the most frequent, followed by social interactions and travel. From 6:00 AM to 9:00 AM we mostly observed social interactions, followed by feeding-socializing (9:00 AM-12:00 PM) and feeding exclusively (12:00 PM-3:00 PM). Social activities intensified afterwards (3:00 PM-6:00 PM). Behavior and gulf seasonality were associated (chi2 = 90.52, gl = 6, p<0.05, n = 99). In the dry season (December-April) feeding predominated over other activities, but socializing was more frequent in the early rainy season (May-July). Larger groups (mean 12 dolphins) forage actively; smaller groups (mean 6 dolphins 6.51 +/- 5.12) foraged more passively. Seasonal variation in dolphin activities are likely to be associated with food availability, as observed in the high number of groups involved in foraging behaviors, and a high investment in foraging activities during the dry season.