Browsing by Author "Vera, Francisca"

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    An electrochemical deposition route for obtaining alpha-Fe2O3 thin films - II. EQCM study and semiconductor properties
    (ELECTROCHEMICAL SOC INC, 2007) Schrebler, Ricardo; Llewelyn, Cynthia; Vera, Francisca; Cury, Paula; Munoz, Eduardo; del Rio, Rodrigo; Meier, Humberto Gomez; Cordova, Ricardo; Dalchiele, Enrique A.
    The electrochemical formation of hematite (alpha-Fe2O3) precursor thin films (oxyhydroxide iron compounds), onto gold substrates in an aqueous solution of Fe (III) + KF + H2O2 was investigated in situ using an electrochemical quartz crystal microbalance (EQCM) and voltammetric techniques. Nanostructured alpha-Fe2O3 obtained after annealing of oxyhydroxide iron compounds thin films have been prepared onto SnO2/F covered glass substrates through a potential cycling procedure in this electrolytic bath. Photoelectrochemical measurements, carried out in 0.1 M NaOH + 0.05 M KI electrolyte at pH 13, show an n-type behavior, a flatband potential of -1.08 V vs saturated mercury/mercury sulfate reference electrode, and an apparent donor density of 1.26 X 10(19) cm(-3) at 1 kHz. (C) 2007 The Electrochemical Society.
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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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    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.