Browsing by Author "Troncoso, Andres"

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    Bioavailable Strontium, Human Paleogeography, and Migrations in the Southern Andes: A Machine Learning and GIS Approach
    (2021) Barberena, Ramiro; Cardillo, Marcelo; Lucero, Gustavo; le Roux, Petrus J.; Tessone, Augusto; Llano, Carina; Gasco, Alejandra; Marsh, Erik J.; Nuevo-Delaunay, Amalia; Novellino, Paula; Frigole, Cecilia; Winocur, Diego; Benitez, Anahi; Cornejo, Luis; Falabella, Fernanda; Sanhueza, Lorena; Santana Sagredo, Francisca; Troncoso, Andres; Cortegoso, Valeria; Duran, Victor A.; Mendez, Cesar
    The Andes are a unique geological and biogeographic feature of South America. From the perspective of human geography, this mountain range provides ready access to highly diverse altitudinally arranged ecosystems. The combination of a geologically and ecologically diverse landscape provides an exceptional context to explore the potential of strontium isotopes to track the movements of people and the conveyance of material culture. Here we develop an isotopic landscape of bioavailable strontium (87Sr/86Sr) that is applied to reconstruct human paleogeography across time in the southern Andes of Argentina and Chile (31 degrees-34 degrees S). These results come from a macro-regional sampling of rodents (N = 65) and plants (N = 26) from modern and archeological contexts. This "Southern Andean Strontium Transect" extends over 350 km across the Andes, encompassing the main geological provinces between the Pacific coast (Chile) and the eastern lowlands (Argentina). We follow a recently developed approach to isoscape construction based on Random Forest regression and GIS analysis. Our results suggest that bioavailable strontium is tightly linked with bedrock geology and offers a highly resolved proxy to track human paleogeography involving the levels of territories or daily mobility and anomalous events that disrupt home ranges, such as migration. The southern Andes provide an ideal geological setting to develop this approach, since the geological variation in rock age and composition produces distinctive isotopic signatures for each main biogeographical region. Finally, we apply this framework to a set of results from human remains from the Uspallata Valley in Mendoza (Argentina), to assess the incidence of migration in the key period of the consolidation of agropastoral economies between AD 800 and 1400. The application of the isoscape to the values from human remains confirms the persistence of human groups with relatively restricted territories encompassing Uspallata and the adjacent Precordillera between AD 800 and 1500. We also identify a pulse of human migration between AD 1280 and 1420, shortly preceding the Inka conquest. Looking forward, we expect to converge with ongoing efforts in South America to build a continental research framework to track the movement of people, animals, and artifacts across space and time.
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    Terminal Pleistocene-Early Holocene human occupation in north-central Chile
    (2024) Troncoso, Andres; Pascual, Daniel; Escudero, Antonia; Pino, Mariela; Hernandez, Daniel; Lopez-Mendoza, Patricio; Moya, Francisca; Armstrong, Felipe; Vera, Francisca; Delgado, Manuela; Artigas, Diego; Larach, Pablo; Chavez, Maria Alejandra
    While a clear human presence may be recognised in the Andes by 12 000-11 000 cal BP, most archaeological research has focused on occupation of the Andean highlands. To understand the initial occupation of inland areas of South America, the authors consider regional connections and spatial exploitation strategies of hunter-gatherers highlighted in a recent survey of Andean sites. Focusing on north-central Chile, artefacts and radiocarbon dates from three rock shelters suggest sporadic and brief occupation during the Terminal Pleistocene-Early Holocene. Co-occurrence of marine and montane resources, the authors argue, demonstrates a strategy of high mobility and local adaptation in early Andean occupation, using rock shelters as landmarks to navigate and learn new landscapes.
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    Trasplante hepático: Evolución, curva de aprendizaje y resultados después de los primeros 300 casos
    (2019) Francisco Guerra, Juan; Luis Quezada, Jose; Cancino, Alejandra; Arrese, Marco; Wolff, Rodrigo; Benitez, Carlos; Carlos Pattillo, Juan; Cristobal Gana, Juan; Concha, Mario; Cortinez, Luis; Vera, Magdalena; Miranda, Paula; Rubilar, Francisco; Troncoso, Andres; Briceno, Eduardo; Dib, Martin; Jarufe, Nicolas; Martinez, Jorge
    Background: Liver transplantation (LT) is an option for people with liver failure who cannot be cured with other therapies and for some people with liver cancer. Aim: To describe, and analyze the first 300 LT clinical results, and to establish our learning curve. Material and Methods: Retrospective cohort study with data obtained from a prospectively collected LT Program database. We included all LT performed at a single center from March 1994 to September 2017. The database gathered demographics, diagnosis, indications for LT, surgical aspects and postoperative courses. We constructed a cumulative summation test for learning curve (LC-CUSUM) using 30-day post-LT mortality. Mortality at 30 days, and actuarial 1-, and 5-year survival rate were analyzed. Results: A total of 281 patients aged 54 (0-71) years (129 women) underwent 300 LT. Ten percent of patients were younger than 18 years old. The first, second and third indications for LT were non-alcoholic steatohepatitis, chronic autoimmune hepatitis and alcoholic liver cirrhosis, respectively. Acute liver failure was the LT indication in 51 cases (17%). The overall complication rate was 71%. Infectious and biliary complications were the most common of them (47 and 31% respectively). The LC-CUSUM curve shows that the first 30 patients corresponded to the learning curve. The peri-operative mortality was 8%. Actuarial 1 and 5-year survival rates were 82 and 71.4%, respectively. Conclusions: Outcome improvement of a LT program depends on the accumulation of experience after the first 30 transplants and the peri-operative mortality directly impacted long-term survival.