Browsing by Author "Diaz, Pablo"

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    Chronological sequence (early and late Holocene) and cultural trajectories in Quebrada Pedernales, southern Puna, Chile (26°S-3,456-3,730 masl)
    (2023) Mendoza, Patricio Lopez; Carrasco, Carlos; Loyola, Rodrigo; Mendez, Victor; Varas, Daniel; Diaz, Pablo; Santana-Sagredo, Francisca; Quiroz, Luciana; Soto, Angelica; Flores-Aqueveque, Valentina; Maldonado, Antonio; Vera, Francisca; Bravo, Alvaro; Hernandez, Daniel; Alamos, Ignacio; Orrego, Vanessa
    This article presents the results of the interdisciplinary investigation in Quebrada Pedernales (26 degrees S-69 degrees W, Chile 3456 masl), in the highlands of northern Chile. The excavations and surveys carried out revealed a great diversity of pre-Hispanic evidence in an area of the Andes that has been little investigated. This evidence allowed us to reconstruct a sequence of continuous occupation between 11,201-11,612 and 539-634 cal. BP. Zooarchaeological, radiocarbon, technological, geochemical, and carpological analyses suggest wide mobility circuits between the coast and the puna on both slopes of the Andes at the start of the Holocene, coinciding with improved environmental conditions in this area and greater aridity on the coast. A severe lack of human occupation is observed during the mid-Holocene, a phenomenon associated with extreme arid environmental conditions. These trends indicate that the southern limit of influence of this environmental event, which has been recorded in a large part of the south-central Andes, extended into the study area, with a direct impact on the settlement and mobility of human groups. Towards ca. 3000 cal. BP, environmental conditions similar to those of today are associated with the reappearance of archaeological evidence and greater complexity in the formation of settlements, especially in terms of hunting activities.
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    Emerging platforms to monitor the occurrence and threats to critically endangered seabirds: The waved albatross in Chile and the Southeast Pacific
    (UNIV VALPARAISO, 2017) Suazo, Cristian G.; Yates, Oliver; Azocar, Jorge; Diaz, Pablo; Gonzalez But, Juan C.; Cabezas, Luis A.
    Long-lived seabird species such as albatrosses and petrels, which are widely distributed at sea and have small populations are threatened globally by bycatch in fisheries. Among these, the waved albatross Phoebastria irrorata is scarcely detected in the Exclusive Economic Zones (EEZs) of countries beyond its traditional distribution throughout the Southeast Pacific. In this article, in situ distributional records on the waved albatross obtained from non-systematic (pelagic birdwatching) and systematic (fishery monitoring) records were compiled. Occurrence of sightings was carried out in relation to recording traits as presence/absence of breeding period and El Nino proxies such as the Southern Oscillation Index (SOI), among others. A total of 13 sightings of waved albatrosses was described which 76.9% of sightings were related to non-breeding period (December to April). Records indicated waved albatrosses reached 4,391 km south of the Galapagos Islands (38 degrees S) and 920 km west of the South American coast (79 degrees W). The waved albatross was associated with industrial pelagic longline and demersal trawl fisheries, and although there were no records of bycatch, the observation of individuals feeding on discards and offal suggests a potential risk of mortality for this species. 53.8% of sightings were during positive readings of the Southern Oscillation Index (SOI), representing colder conditions than neutral El Nino Southern Oscillation (ENSO).
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    Impact of COVID-19 Pandemic on Stroke Severity and Mortality in the South-East of Santiago, Chile
    (2021) Silva-Pozo, Andres; Vallejos, Jose; Almeida, Juan; Martoni, Mariano; Uribe-San Martin, Reinaldo; Miranda, Maria; Diaz, Pablo; Garcia, Dominga; Navia, Victor
    Background and purpose; Chile has been one of the most affected countries by the COVID-19 pandemic, with one of the highest case rates per population. This has affected the epidemiological behaviour of various pathologies. We analyze the impact of the pandemic on the number of admissions due to stroke, its severity and mortality in Santiago, Chile. Methods: a multicenter observational study based on the records of the 3 hospitals of the South East health service in Santiago, Chile. We recorded the number of patients admitted for ischemic stroke between 01 January 2020 and 30 June 2020. We grouped the cases into two periods, pre-pandemic and pandemic, according to the setting of the state of emergency in Chile. Results: 431 patients were admitted with ischemic stroke during the study period. There was a non -significant decrease in weekly admissions (17 vs 15 patients per week). No differences were observed in the proportion of patients with medical treatment (p = 0.810), IVT (p = 0.638), EVT (p = 0.503) or IVT + EVT (p = 0.501). There was a statistically significant increase in the NIHSS on admission (7.23 vs 8.78, p = 0.009) and mortality (5.2% vs 12.4%, p = 0.012). In a multivariate analysis the NIHSS on admission was associated with the increased mortality (RR 1.11, CI 1.04-1.19, p = 0.003). Conclusion: We found an increase in the severity of ischemic stroke on admission and in-hospital mortality during the pandemic period. The main factor to increase in-hospital mortality was the NIHSS on admission. (c) 2021 Elsevier Inc. All rights reserved.
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    Physical Violence and Social Tension in the Atacama Desert: Osteobiography of a Woman from the Tarapaca 40 Formative Period Cemetery
    (2024) Herrera-Soto, Maria Jose; Gonzalez-Ramirez, Andrea; Diaz, Pablo; Pacheco, Aryel; Retamal, Rodrigo; Saez, Arturo; Santana-Sagredo, Francisca; Uribe, Mauricio
    Physical violence and social conflict have been widely studied in the ancient societies of the Andes. However, studies about violence are scarce for the Formative period of northern Chile (1000 BC-AD 900). Evidence from these investigations is generally interpreted as interpersonal violence, whose protagonists are mostly men. Here, we present the case of an adult female recovered from the Tarapaca 40 cemetery (Tarapaca region, Chile) displaying lesions suggestive of trauma. We reconstruct her life and death in the context of this era's social and political conditions. Results of our bioanthropological characterization, cranial trauma analysis, carbon and nitrogen isotope analysis, and recording of the funerary offerings suggest she was a local member of the Formative community buried in the Tarapaca 40 cemetery and that she suffered intentional lethal lesions. Her death is unusual because there are no previous bioarchaeological records of lethal violence against women in the Tarapaca region. The osteobiography of this woman reflects a context characterized by an increase in inequality and social complexity, whereby physical violence could be used as a mechanism of internal regulation and exercise of power during the Formative period.
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    Random forest model predictive control for paste thickening
    (2021) Diaz, Pablo; Salas, Juan C.; Cipriano, Aldo; Nunez, Felipe
    As processes involved in mineral processing operations increase their complexity, automation and control become critical to ensure an economically viable and environmentally sustainable operation. In the context of modern mineral processing, paste thickening stands out as a relatively new method for producing high density slurries that has proven challenging for standard control algorithms. In this setting, the use of machine-learning-based models within a predictive control strategy arises as an appealing alternative. This work presents a Random Forest Model Predictive Control scheme for paste thickening based on a purely data-driven approach for modeling and evolutionary strategies for solving the associated optimization problem. Results show that the proposed strategy outperforms conventional predictive control both qualitatively and quantitatively.