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Ítem Geomorphological evolution between 1948 and 2012 of the térraba-sierpe delta, Costa Rica(Cuaternario y Geomorfologia, 2016) Quesada, Adolfo; Acuña Piedra, Jéssica FranciniThe Térraba-Sierpe delta is located at the geographic coordinates 8° 47” North Latitude and 83° 38” West Longitude at the southeast of Costa Rica. It is a delta system formed by the sediments carried from the largest river basin in the country (Térraba), and the Sierpe River. These rivers have modeled a meandriform drainage pattern where it dominates the mangrove vegetation. This fluviomarine complex has had major morphology modifications due to the alteration in sedimentation rates by climate variability and land use changes in the middle and upper basins of the Térraba and Sierpe rivers. For the reconstruction of the geomorphological evolution of the six delta mouths: Coronado, Brava, Chiquita, Zacate, Guarumal and Sierpe; it was used a methodology based on photointerpretation and analysis of four aerial images of the years 1948, 1972, 1992 and 2012. In addition, were analyzed the texture and grain sand distribution from the three types of coastal bars of the delta: submarine, insular, and littoral. The importance of this work lies in the study of morphological changes in a tropical delta threatened by environmental impacts and changes in the climate over 64 years.Ítem Analytical and rheological studies of modified gel dosimeters exposed to X-ray beams(Elsevier Science, 2016-07) Romero, Marcelo Ricardo; Mattea, Facundo; Vedelago, José; Chacón Obando, David M; Valente, Mariana A.; Alvarez, Cecilia; Strumia, Miriam CristinaThe need to know the dose of X-rays to be applied to patients suffering diseases such as cancer requires accurate and stable dosimetric devices. Currently, the use of gelatin-based dosimeters has yielded excellent results but lack adequate thermal stability. In this paper a chemical modification of the gelatin (at concentrations typically used for the preparation of dosimeters) using glutaraldehyde as a cross-linking agent is proposed. Through rheological studies it was found that modified gelatin with glutaraldehyde concentrations between 0.15 and 0.50% w/v shows better thermal stability with an increase in elastic modulus of up to 100 times at 37 °C and convenient reaction times for the preparation of the dosimeters. Subsequently, a mathematical model to easily predict the elastic modulus of materials prepared with different concentrations of gelatin and glutaraldehyde was proposed. The analytical response of modified and unmodified materials was evaluated and no significant alteration of the dosimetric sensitivity was found in the dosimeters (based on itaconic acid and N, N′-methylenebisacrylamide) when an X-ray irradiation dose from 0 to 300 Gy was applied. It was found that the best thermal stability of dosimeters prepared with modified gelatin would decrease the loss of information between the irradiation process and the absorbance reading, thereby improving the stability and linear correlation of data. °C and convenient reaction times for the preparation of the dosimeters. Subsequently, a mathematical model to easily predict the elastic modulus of materials prepared with different concentrations of gelatin and glutaraldehyde was proposed. The analytical response of modified and unmodified materials was evaluated and no significant alteration of the dosimetric sensitivity was found in the dosimeters (based on itaconic acid and N, N′-methylenebisacrylamide) when an X-ray irradiation dose from 0 to 300 Gy was applied. It was found that the best thermal stability of dosimeters prepared with modified gelatin would decrease the loss of information between the irradiation process and the absorbance reading, thereby improving the stability and linear correlation of data. Overall, the results indicated that the dosimeters could be modified as proposed and achieve significant improvements regarding to their thermal stability, without changing significantly the usual preparation process.Ítem Consideration of the seismic hazard on the land use planning of the Poas Canton, Costa Rica(Boletin de Geologia, 2016-07-03) Barrantes, Gustavo; Salcedo, ElkinTo incorporate the seismic hazard assessment in the land use planning can be done using seismic methods and Geographic Information System (GIS), in order to avoid the use of simplifications provided in law. In this paper, we used the deterministic method for assessment of the seismic hazard in Poas County, Province of Alajuela, Costa Rica. Following this method, we identified the seismic sources that represent the main threat to the county, and the possible maximum magnitudes; the seismic attenuation, as well as the maximum acceleration values that were transformed into seismic intensity. The use of a GIS allowed the estimate of values in a 5x5 m mesh, in order to generate the seismic hazard maps at appropriate scale for the land use planning. The results have shown that the northern part of the County has a high seismic hazard (IMM IX) as well as San Pedro town, according to the worst scenario possible.Ítem Propuesta de un Corredor Biológico Interurbano para las comunidades heredianas, una iniciativa de la Universidad Nacional(Diálogo en bioeconomía: la UNA al servicio del desarrollo nacional, 2020) Romero-Vargas, Marilyn; Bermúdez-Rojas, Tania; Durán, Alejandro; Alfaro, MarvinGenera una estrategia de manejo que promueva la recuperación, rehabilitación y conservación de las AVU.