Preprints

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/20508

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Feasibility of dose enhancement assessment: preliminary results by means of Gd-infused polymer gel dosimeter and Monte Carlo study
(Elsevier, 2018) Santibáñez, M.; Guillen, Y.; Chacón Obando, David M; Figueroa, R.G.; Valente, M.
Abstract. This work reports the experimental development of an integral Gd-infused dosimeter suitable for Gd dose enhancement assessment along with Monte Carlo simulations applied to determine the dose enhancement by radioactive and X-ray sources of interest in conventional and electronic brachytherapy. In this context, capability to elaborate a stable and reliable Gd-infused dosimeter was the first goal aimed at direct and accurate measurements of dose enhancement due to Gd presence. Dose-response was characterized for standard and Gd-infused PAGAT polymer gel dosimeters by means of optical transmission/absorbance. The developed Gd-infused PAGAT dosimeters demonstrated to be stable presenting similar dose-response as standard PAGAT within a linear trend up to 13 Gy along with good post-irradiation readout stability verified at 24 and 48 hours. Additionally, dose enhancement was evaluated for Gd-infused PAGAT dosimeters by means of Monte Carlo (PENELOPE) simulations considering scenarios for isotopic and X-ray generator sources. The obtained results demonstrated the feasibility of obtaining a maximum enhancement around of (14±1)% for 192Ir source and an average enhancement of (70±13)% for 241Am. However, dose enhancement up to (267±18)% may be achieved if suitable filtering is added to the 241Am source. On the other hand, optimized X-ray spectra may attain dose enhancements up to (253±22) %, which constitutes a promising future alternative for replacing radioactive sources by implementing electronic brachytherapy achieving high dose levels.
Persistent chlorophyll maxima in the Eastern Tropical North Pacific
(Cornell Tech (Estados Unidos), 2021) Márquez-Artavia, Amaru; Márquez-Artavia, Xiomara M.; Salazar-Ceciliano, Juan P.; Paulmier, Aurélien; Sánchez-Velasco, Laura; Beier, Emilio
Abstract. This study aims to describe the response of two persistent chlorophyll-a maxima to physical processes affecting the thermocline/nitracline position in the Eastern Tropical North Pacific (ETNP). We focused on Long Rossby Waves given their relevance to the ETNP circulation and its potential as a mechanism introducing nutrients into the euphotic zone. We found the shallower chlorophyll-a maximum in oxygenated waters became more intense when denser waters (more nutrients) moved toward the surface. It suggests that isopycnals and nitracline displacements modify the nutrient supply in the euphotic zone, which produces changes in phytoplankton growth. The suboxic and deeper chlorophyll-a maximum showed a strong association with the 26 kg m-3 isopycnal being only mechanically displaced, and its chlorophyll-a content does not seem to covary with irradiance or nutrients. The different responses of the chlorophyll-a maxima could be explained if different phytoplankton groups are associated with them. Long Rossby Waves can affect the position of the thermocline/nitracline and isopycnals in an annual cycle, but it seems to be a “background” signal modulated by higher frequency processes such as mesoscale eddies and other Rossby waves. The co-occurrence of processes can control the nitracline depth, and hence the input of nutrients into the euphotic zone that can cause sporadic enhancements of the chlorophyll-a concentration of one maximum.
Numerical Modeling for Costa Rica of Tsunamis Originated at Tonga‐ Kermadec and Colombia‐Ecuador Subduction Zones
(Multidisciplinary Digital Publishing Institute (MDPI) (Suiza), 2025) Chacón-Barrantes, Silvia; Rivera-Cerdas, Fabio; Espinoza-Hernández, Kristel; Murillo-Gutiérrez, Anthony
Abstract. Costa Rica has experienced 37 tsunamis at both its Pacific and Caribbean coasts, with none to moderated impact. However, the coastal population has increased exponentially in the past decades, which might lead to higher impact from future tsunamis. In 2018 and 2019, IOC/UNESCO organized Experts Meetings of Tsunami Sources, Hazards, Risks and Uncertainties associated with the Tonga-Kermadec and Colombia-Ecuador subduction zones, where experts defined worst-case scenarios. Here we modeled the propagation of those tsunami scenarios to Costa Rica and their inundation for selected sites. We found that the Tonga-Kermadec scenarios provoked larger inundation than previous modeled sources from that region. However, the large travel time for those scenarios, about 14 hours, would allow for a timely evacuation. In the case of the Colombia-Ecuador scenarios, they provoked smaller inundation than previously modeled sources from that region, a good outcome as their arrival time is between 75 and 150 minutes. These new results required the update of tsunami evacuation maps and/or plans for many communities but provided more favorable conditions for tsunami preparedness. Yet, the short arrival times of the Colombia-Ecuador scenarios still require a prompt response from the population and authorities. For this, additional to updated tsunami evacuation maps and plans, it is recommended to have tsunami exercises in a regular basis.

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