Artículos Ingeniería

Permanent URI for this collection

Browse

Recent Submissions

Now showing 1 - 20 of 217
  • Publication
    A class of solutions for the graphene hamiltonian operator
    (2022) Conca, C.; San Martín, J.; Solano, Viviana
    The graphene is a substance with carbon atoms arranged in a honeycomb lattice. The dynamics of the electrons in the structure is governed by the Hamilton equations of the system in the form of its associated spectral problem: HΨ = λΨ, with the additional condition that the eigenfunction Ψ must satisfy the so-called Kirchhoff’s conditions. In this paper, we study a class of solutions (λ, Ψ) that, in addition to meeting these conditions, are periodic in one of the two main directions of the lattice, and satisfy a pseudo-periodicity type like condition in the other direction. Our main results lead to an adequate characterization of the dispersion relationships of the honeycomb lattice, providing a precise description of the regions of stability and instability of the eigenfunctions in terms of λ. As a consequence, a tool is thus obtained for a better understanding of the propagation properties and the behavior of the wave function of electrons in a hexagonal lattice, a key issue in graphene-based technologies.
  • Publication
    Electromobility in forest transport. Is it feasible? Perceptions regarding implementation in the chilean industry
    (2022) Valdés-González, Héctor; Larenas-Barra, Sebastián; Méndez-Dedes, Luis; Reyes-Bozo, Lorenzo; Sandoval-Yáñez, Claudia
    Este trabajo examina las distintas impresiones y perspectivas relacionadas con la implementación de electromovilidad en el transporte de rollizos con ca-miones de capacidad de carga de hasta 45 tonela-das en el sector forestal de la octava y decimosexta región de Chile. El objetivo de este trabajo es esta-blecer los aspectos críticos que los actores claves de la industria forestal identifican y perciben para una correcta implementación de camiones eléctricos de alto tonelaje. Para esto se propone un estudio me-todológico de tipo cualitativo con un diseño no ex-perimental basado en entrevistas semiestructuradas dirigidas a actores del sector forestal de la zona es-tudio. Se utiliza una muestra por conveniencia apli-cada a 4 empresarios del rubro, 3 ejecutivos de empresas forestales principales y 2 representantes de distribuidores de camiones. Los datos muestran que actualmente hay poco conocimiento, derivado de la inexistencia de proyectos y plataformas de di-fusión específicos que consideren la tecnología en el rubro, pero, por el contrario, demuestran que existe una buena disposición por parte de los actores para implementar planes piloto con miras a la sustentabi-lidad económica que se le proyecta a la electromo-vilidad. Se evidencia una concentración de aspectos críticos que es necesario abordar para implementar la electromovilidad en el transporte forestal y que, atendi-dos por un trabajo público-privado, permitirían al rubro y al país obtener los beneficios económicos y ambien-tales de esta tecnología.
  • Publication
    Metodologías ágiles: un análisis de los desafíos organizacionales para su implementación
    (2022) Valdés-González, Héctor; Flores-Cerna, Fernando; Sanhueza-Salazar, Víctor-Manuel; Reyes-Bozo, Lorenzo
    Este trabajo analiza las principales brechas que influyen en las PyMEs TI (pequeñas y medianas empresas de tecnología de la información) con metodología tradicional, al iniciar la implementación de metodologías ágiles para la gestión de proyectos. El objetivo de esta investigación es determinar las principales brechas existentes antes de implementar metodologías ágiles en una PyME TI con metodología tradicional para la gestión de proyectos. Para lograrlo se propone una aproximación cualitativa a las opiniones de tres gerentes, dos ingenieros de proyecto y seis analistas programadores de la empresa, basada en entrevistas semiestructuradas, considerando una muestra por conveniencia, para entender las dificultades existentes en la empresa de estudio, contrastando dicha realidad mediante encuestas dirigidas a 29 profesionales de áreas TI de otras organizaciones. Los resultados del análisis revelan que las principales brechas para la implementación de metodologías ágiles en la PyME son la cultura organizacional en desacuerdo con la agilidad, la falta de compromiso de la gerencia y la resistencia al cambio. Se concluye que la propuesta resulta ser efectiva para conocer las principales brechas a resolver antes de comenzar la implementación de una metodología ágil en una PyME TI, permitiendo alinear a la organización con la agilidad.
  • Publication
    Análisis técnico sobre protecciones provisionales de borde para prevenir riesgos de caídas en trabajos en altura en la construcción: el caso de Chile
    (2023) Valderrama-Ulloa, Claudia; Ferrada, Ximena; Serpell, Alfredo; Cabello, María José
    El objetivo principal de este trabajo es presentar un análisis técnico de los distintos sistemas de protección de borde (barandas) y aportar al desarrollo de normativa sobre su uso en Chile. La metodología incluye una amplia revisión bibliográfica nacional e internacional para describir el contexto del uso de barandas. Se realiza un levantamiento de información en terreno para describir los principales problemas de uso de estos sistemas, tales como ritmo de avance del proyecto, singularidad de aspectos geométricos y arquitectónicos, requisitos estructurales y uso de soluciones artesanales. Se realizan 16 entrevistas semi-estructuradas a profesionales de la construcción y de empresas proveedoras nacionales para describir las distintas necesidades respecto a temas técnicos en el uso de barandas, destacándose aspectos como calidad de la información, trazabilidad, homologación y estandarización de productos. En conclusión, este estudio contribuye a especificar los criterios necesarios a aplicar en la industria de la construcción para promover el uso adecuado de protecciones de bordes para evitar caídas.
  • Publication
    Review Breaking Down Barriers: Findings from a Literature Review on Housing for People with Disabilities in Latin America
    (2023) Valderrama-Ulloa, Claudia; Ferrada, Ximena; Herrera, Felipe
    Accessibility to housing is crucial for people with disabilities as it provides them with equal opportunities and allows them to live independently. A systematic literature review has been conducted to understand the current research on accessibility in housing for people with disabilities in Latin America. The study analysed 56 papers and used co-word analysis to identify common themes and topics within the documents. The results of the analysis showed that Brazil (61%) is the country with the most research on the subject, physical disability, at 36%, is the impairment most analysed, and interventions or analysis for the older people (45%) in their homes is the most researched type of population. The co-word analysis revealed that topics such as policy, regulations, the use of technologies, ergonomics interventions, and architectural criteria or barriers to the daily life of disabled people were frequently discussed in the papers. Although this work shows a substantial and growing increase in research on housing for people with disabilities in Latin America, it also demonstrates the importance of increasing research on other types of impairment, such as visual and cognitive-intellectual disabilities, and including children, caregivers, or even young adults.
  • Publication
    A tool for universal accessibility assessment in the interior of dwellings
    (2023) Valderrama-Ulloa, Claudia; Ferrada, Ximena; Rouault, Fabien
    The present study proposes a tool for assessing universal accessibility in the interior of apartments, presenting a novel quantitative model for assessing the accessibility of buildings for buyers or tenants. For this, a multicriteria analysis for aggregating the assessment indicators with different units and scales is employed using a unique grade of accessibility according to four main pillars: Autonomy, Mobility, Comfort, and Safety. The assessment method has been applied in 35 show apartments in the urban area of Santiago in Chile. This work shows the application and results of 4 departments. The evaluation results are presented visually with a circular bar plot and a final grade in letter format from F to A. In general, it is observed that the four apartments proposed have a low degree of accessibility (letters F to D). And, the Autonomy pillar is clearly the lowest pillar in the selected apartments.
  • Publication
    A Robust Statistical Methodology for Measuring Enterprise Agility
    (2023) Moraga-Díaz, Roberto; Leiva-Araos, Andrés; García, José
    In an era characterized by rapid technological advancements, economic fluctuations, andglobal competition, adaptability and resilience have become critical success factors for businessesnavigating uncertainty and complexity. This article explores the role of enterprise agility in today’sbusiness landscape at Latam branch of Tata Consultancy Services, where organizations face complexand diverse operations. We aim to examine how companies can become more agile in the faceof emerging challenges and seize opportunities swiftly to drive growth and deliver value. Since2014, the division has embarked on an agile transformation journey to drive growth, deliver value,foster innovation, and build resilience in an increasingly dynamic environment. We scrutinizean approach to measuring and enhancing enterprise agility, employing statistical analysis andcontinuous improvement methodologies to tackle real-world challenges while offering valuableinsights and recommendations for organizations aiming to implement similar systems. The resultsof an agile transformation in a certain company’s Latam branch serve as a compelling case study,demonstrating how the implementation of targeted measures and continuous improvement cansignificantly bolster enterprise agility. Methodologically, our work applies a novel sequence ofparametric statistical tests which, to the best of our knowledge, have not been used in the industryto validate the results of business agility metrics. In future work, we aim to create a new workflowconsidering non-parametric tests to address data with other statistical distributions. We conclude ourwork by proposing a sequence of steps for organizations to implement business agility metrics
  • Publication
    A data fusion approach with mobile phone data for updating travel survey-based mode split estimates
    (2023) Graells-Garrido, Eduardo; Opitz, Daniela; Rowe, Francisco; Arriagada, Jacqueline
    Up-to-date information on different modes of travel to monitor transport traffic and evaluate rapid urban transport planning interventions is often lacking. Transport systems typically rely on traditional data sources providing outdated mode-of-travel data due to their data latency, infrequent data collection and high cost. To address this issue, we propose a method that leverages mobile phone data as a cost-effective and rich source of geospatial information to capture current human mobility patterns at unprecedented spatiotemporal resolution. Our approach employs mobile phone application usage traces to infer modes of transportation that are challenging to identify (bikes and ride-hailing/taxi services) based on mobile phone location data. Using data fusion and matrix factorisation techniques, we integrate official data sources (household surveys and census data) with mobile phone application usage data. This integration enables us to reconstruct the official data and create an updated dataset that incorporates insights from digital footprint data from application usage. We illustrate our method using a case study focused on Santiago, Chile successfully inferring four modes of transportation: mass-transit (all public transportation), motorised (cars and similar vehicles), active (pedestrian and cycle trips), and taxi (traditional taxi and ride-hailing services). Our analysis revealed significant changes in transportation patterns between 2012 and 2020. We quantify a reduction in mass-transit usage across municipalities in Santiago, except where metro/rail lines have been more recently introduced, highlighting added resilience to the public transport network of these infrastructure enhancements. Additionally, we evidence an overall increase in motorised transport throughout Santiago, revealing persistent challenges in promoting urban sustainable transportation. Findings also point to a rise in the share of taxi usage, and a drop in active mobility, suggesting a modal shift towards less sustainable modes of travel. We validate our findings comparing our updated estimates with official smart card transaction data. The consistency of findings with expert domain knowledge from the literature and historical transport usage trends further support the robustness of our approach.
  • Publication
    Exploring Initialization Strategies for Metaheuristic Optimization: Case Study of the Set-Union Knapsack Problem
    (2023) García, José; Leiva-Araos, Andrés; Crawford, Broderick; Soto, Ricardo; Pinto, Hernán
    In recent years, metaheuristic methods have shown remarkable efficacy in resolving complex combinatorial challenges across a broad spectrum of fields. Nevertheless, the escalating complexity of these problems necessitates the continuous development of innovative techniques to enhance the performance and reliability of these methods. This paper aims to contribute to this endeavor by examining the impact of solution initialization methods on the performance of a hybrid algorithm applied to the set union knapsack problem (SUKP). Three distinct solution initialization methods, random, greedy, and weighted, have been proposed and evaluated. These have been integrated within a sine cosine algorithm employing k-means as a binarization procedure. Through testing on medium- and large-sized SUKP instances, the study reveals that the solution initialization strategy influences the algorithm’s performance, with the weighted method consistently outperforming the other two. Additionally, the obtained results were benchmarked against various metaheuristics that have previously solved SUKP, showing favorable performance in this comparison.
  • Publication
    Forearc tectonics and volcanism during the Devonian–Carboniferous evolution of the North Patagonian segment, southern Chile (41,3°S)
    (2022) Palape, C.; Quezada, P.; Bastías, J.; Hervé, F.; Reyes, T.; Veas, M.; Vildoso, F.; Calderón, M.; Theye, T.; Fuentes, F.; Chiaradia, M.
    Late Paleozoic to early Mesozoic subduction complexes formed during the evolution of southwestern Gondwana and extensively crop out along the Chilean continental margin. Recent findings in northern Patagonia (40°–43°S) revealed that accretionary processes were active since the Devonian when enhanced lithosphere stretching in the forearc led to the formation of Chaitenia island arc. The extension in the crust consecutively developed a backarc basin, which culminated during a compressive episode that re-amalgamated the Chaitenia island arc with the margin. This episode produced intermediate grade metamorphism in the sedimentary rocks that were formed throughout the extension. To constrain the tectonic evolution of these processes, we combined petrology, structural analysis, whole-rock geochemical, and whole-rock isotopic tracing (Sr-Nd-Pb) data along with thermodynamic modelling. Two petro-tectonic domains are here defined. The Western Coastal Range Domain is composed of Carboniferous to Permian metapsammopelitic rocks, which are mainly schists with a metasedimentary Carboniferous protolith exhibiting a penetrative northeast to southwest dipping main foliation associated with basal accretion. The Eastern Coastal Range Domain is comprised by garnet micaschists, metabasalts, metarhyolites, and metasandstones. This unit is folded by three ductile structures: The first is related to rootless isoclinal folds, the second is associated with kilometric scale west-verging tight folds, and the third is associated with west-verging cylindrical folds. The volcanic rocks of this domain are comprised by middle Devonian alkaline metarhyolites and metabasalts with enriched-MORB and normal-MORB affinities. Trace element composition suggests that the metabasalts formed through shallow melting in an extensional setting over a supra-subduction zone. Nd and Pb isotope data point to a mantle source change for the basaltic melts from an EM1-like to a DM-like and are interpreted to reflect the embryonic to mature evolution of the early Devonian to Carboniferous backarc system. The calculated P–T evolution of the garnet micaschists follows: 1) a clockwise IP–IT prograde Barrovian path, 2) an isobaric thermal increase at ∼7 kbar and 540°C, and 3) an adiabatic decompression. Finally, after the metamorphism, these rocks were uplifted by thrusting processes that probably occurred during the late Permian.
  • Publication
    A new method to map groundwater-dependent ecosystem zones in semi-arid environments: A case study in Chile
    (2022) Duran-Llacer, Iongel; Arumi, José Luis; Arriagada, Loretto; Aguayo, Mauricio; Rojas, Octavio; González-Rodríguez, Lisdelys; Rodríguez-López, Lien; Martínez-Retureta, Rebeca; Oyarzún, Ricardo; Kumar Singh, Sudhir
    Groundwater (GW) use has intensified in recent decades, threatening the ecological integrity of groundwater-dependent ecosystems (GDEs). The study of GDEs is limited; therefore, integrated, interdisciplinary environmental approaches that guarantee their monitoring and management amid current climate and anthropogenic changes are needed. A new geospatial method with an integrated and temporal approach was developed through a multicriteria approximation, taking into account expert opinion, remote sensing-GIS, and fieldwork to map groundwater-dependent ecosystem zones (GDEZ). A survey of experts (N = 26) was conducted to assign degrees of importance to the various geospatial parameters, and the mapping was carried out using 14 parameters. The reclassified parameters were normalized on a scale of 1 to 5 according to the degree of probability of the presence of GDE. The validation was carried out through fieldwork and statistical analysis. Then, the spatio-temporal changes amid changing GW levels were assessed using the summer season normalized difference vegetation index (NDVI). Two GDEZ maps were obtained, for 2002 and 2017, between which the high- and very-high-probability zones of GDEs decreased by 31,887 ha (~ 38%). The most sensitive temporal parameters that most influenced the spatio-temporal changes on GDEs were precipitation and land use, with rain exerting a slightly the greatest influence. It was also demonstrated that identified ecosystems decreased in area or were affected
  • Publication
    A physiology-inspired framework for holistic city simulations
    (2022-07) Meta, Irene; Cucchietti, Fernando M.; Navarro Mateu, Diego; Graells Garrido, Eduardo; Guallart, Vicente
    Life, services and activities within cities have commonly been studied by separate disciplines, each one independent from the others. One such approach is the computer simulation, which enables in-depth modelling and cost-effective evaluation of city phenomena. However, the adoption of integrated city simulations faces several barriers, such as managerial, social, and technical, despite its potential to support city planning and policymaking. This paper introduces the City Physiology: a new conceptual framework to facilitate the integration of city layers when designing holistic simulators. The physiology is introduced and applied through a process of three steps. Firstly, a literature review is offered in order to study the terminology and the progress already made towards integrated modelling of different urban systems. Secondly, interactions between urban systems are extracted from the approaches studied before. Finally, the pipeline to carry out the integration strategy is described. In addition to providing a conceptual tool for holistic simulations, the framework enables the discovery of new research lines generated by previously unseen connections between city layers. Being an open framework, available to all researchers to use and broaden, the authors of this paper envisage that it will be a valuable resource in establishing an exact science of cities.
  • Publication
    A Conceptual Model Considering Multiple Agents for Water Management
    (2022-06-30) Rivadeneira Tassara, Benjamín; Valdés González, Héctor; Fúnez Guerra, Carlos; Reyes-Bozo, Lorenzo
    In Chile, as in many other areas of the world, water supplies have been poorly managed and water availability is decreasing. In order to manage water resources more sustainably and equitably, it is necessary to understand and predict their supply and use considering the characteristics of a particular zone. This study aimed to develop a conceptual model for water management in the Libertador Bernardo O’Higgins Region in Chile. The model considers the water needs of industries with production activities, human consumption, and the ecological flow of each sub-basin in the area. The results show that the proposed model contributes to the understanding of the critical variables, their agents, and the interaction between the hydric demands, which enables the prioritization of human consumption and the ecological flow. Furthermore, the cross-analysis between the offer and demand indicates that current and predicted consumption levels will only be sustainable up to the year 2031. The findings may be of use to decision-makers seeking to improve water management plans in this area and elsewhere, and to others interested in modeling water management in different areas.
  • Publication
    Long-term airborne particle pollution assessment in the city of Coyhaique, Patagonia, Chile
    (2022) Solís, Rafael; Toro A., Richard; Gómez, Luis; Vélez-Pereira, Andrés M.; López, Manuela; Fleming, Zöe; Fierro, Nicolás; Leiva G., Manuel
    An air pollution assessment in a small city located in the heart of Chilean Patagonia is presented. Seven years (2014–2020) of PM concentration levels retrieved from two monitoring stations permits an evaluation of the city’s pollution variability, the effect of meteorological variables and long-term trends of air pollution. The highest PM concentration levels observed during the coldest months are mainly related to an increasing emission associated with the intensive use of firewood for residential heating and cooking. The most polluted days are associated with low temperatures, low wind speed and high PM2.5/PM10 ratios, which is consistent with the predominance of local firewood sources over background emissions. A decrease in both PM fractions over time has been estimated (PM10: -4.1, CI99%: − 5.7 to − 2.9 and PM2.5: -2.2, CI99%: − 3.5 to − 1.3 μg m− 3 year− 1 ). However, the annual average PM mass concentrations in Coyhaique exceeded both national and international air quality thresholds. The city reported a percent of annual exceedances of the daily WHO guidelines of 57% for PM10 and 77% for PM2.5. These numbers highlight the serious air pollution problem of the city of Coyhaique, which exhibits air pollution levels comparable to those of many polluted megacities in the world.
  • Publication
    Photochemical sensitivity to emissions and local meteorology in Bogotá, Santiago, and São Paulo: An analysis of the initial COVID-19 lockdowns
    (2022) Seguel, Rodrigo J.; Gallardo, Laura; Osses, Mauricio; Rojas, Néstor Y.; Nogueira, Thiago; Menares, Cmilo; Andrade, María Fátima; Belalcázar, Luis C.; Carrasco, Paula; Eskes, Henk; Fleming, Zöe; Huneeus, Nicolás; Ibarra-Espinosa, Sergio; Landulfo, Eduardo; Leiva, Manuel; Mangones, Sonia C.; ernando G. Morais8 , Gregori A. Moreira11, Nicola´ s Pantoja3 , Santiago Parraguez1,12, Jhojan P. Rojas13, Roberto Rondanelli1,2, Izabel da Silva Andrade8 , Richard Toro9 ,; Moreira, Gregori A.; Pantoja, Nicolás; Parraguez, Santiago; Rojas, Jhojan P.; Rondanelli, Roberto; Silva Andrade, Izabel da; Toro, Richard; Yoshida, Alexandre C.
    This study delves into the photochemical atmospheric changes reported globally during the pandemic by analyzing the change in emissions from mobile sources and the contribution of local meteorology to ozone (O3) and particle formation in Bogotá (Colombia), Santiago (Chile), and São Paulo (Brazil). The impact of mobility reductions (50%–80%) produced by the early coronavirus-imposed lockdown was assessed through high-resolution vehicular emission inventories, surface measurements, aerosol optical depth and size, and satellite observations of tropospheric nitrogen dioxide (NO2) columns. A generalized additive model (GAM) technique was also used to separate the local meteorology and urban patterns from other drivers relevant for O3 and NO2 formation. Volatile organic compounds, nitrogen oxides (NOx), and fine particulate matter (PM2.5) decreased significantly due to motorized trip reductions. In situ nitrogen oxide median surface mixing ratios declined by 70%, 67%, and 67% in Bogotá, Santiago, and São Paulo, respectively. NO2 column medians from satellite observations decreased by 40%, 35%, and 47%, respectively, which was consistent with the changes in mobility and surface mixing ratio reductions of 34%, 25%, and 34%. However, the ambient NO2 to NOx ratio increased, denoting a shift of the O3 formation regime that led to a 51%, 36%, and 30% increase in the median O3 surface mixing ratios in the 3 respective cities. O3 showed high sensitivity to slight temperature changes during the pandemic lockdown period analyzed. However, the GAM results indicate that O3 increases were mainly caused by emission changes. The lockdown led to an increase in the median of the maximum daily 8-h average O3 of between 56% and 90% in these cities.
  • Publication
    Impact of mining on the metal content of dust in indigenous villages of northern Chile
    (2022) Zanetta-Colombo, Nicolás; Fleming, Zöe; Gayo, Eugenia M.; Manzano, Carlos A.; Panagi, Marios; Valdés, Jorge; Siegmund, Alexander
    Indigenous communities from northern Chile have historically been exposed to the impacts of massive copper industrial activities conducted in the region. Some of the communities belonging to the Alto El Loa Indigenous Development Area are located less than 10 km from the “Talabre'' tailings dam, which contains residues from copper production and other metals that can be toxic to human health (e.g., As, Sb, Cd, Mo, Pb). Given the increasing demand of copper production to achieve net-zero emission scenarios and concomitant expansions of the tailings, the exposure to toxic metals is a latent risk to local communities. Despite the impact that copper production could generate on ancestral communities from northern Chile, studies and monitoring are limited and the results are often not made accessible for local communities. Here, we evaluate such risks by characterizing metal concentrations in dust collected from roofs and windows of houses from the Alto El Loa area. Our results showed that As, Sb, Cd, Cu, Mo, Ag, S, and Pb concentrations in these matrices can be connected to local copper mining activities. Additionally, air transport models indicate that high concentrations of toxic elements (As, Sb, and Cd) can be explained by the atmospheric transport of particles from the tailings in a NE direction up to 50 km away. Pollution indices and Health Risk Assessment suggested a highly contaminated region with a health risk for its inhabitants. Our analysis on a local scale seeks to make visible the case of northern Chile as a critical territory where actions should be taken to mitigate the effects of mining in the face of this new scenario of international demand for the raw materials necessary for the transition to a net-zero carbon global society.
  • Publication
    Effects of Using High-Strength Reinforcement in the Seismic Performance of a Tall RC Shear Wall Building
    (2023) Puentes, Juan; Parra, Pablo F.; Magna-Verdugo, Carolina; Cendoya, Patricio; Avudaiappan, Siva
    Chile’s reinforced concrete (RC) design is based on ACI 318-08, where high-strength reinforcement is not allowed in seismic force-resistant members. In 2019, new requirements adopted by ACI 318 permitted the incorporation of high-strength reinforcement in walls. This study compared the seismic performance of two Chilean 20-story residential buildings on soft soil, one designed with traditional Grade 60 and the other with high-strength Grade 80 reinforcement. The performance was assessed in terms of the probability of exceeding the ASCE 41 limit states during a 50-year lifecycle. Analyses showed that both buildings had similar seismic performance. However, the reduction in reinforcement in the Grade 80 building was close to 18%. It is concluded that using high-strength reinforcement in a typical wall building implies a significant reduction in the reinforcement used without affecting the seismic performance.
  • Publication
    Reciprocity heightens academic performance
    (2022) Candia, Cristián; Oyarzún, Melanie; Landaeta, Víctor; Yaikin, T.; Monge, Cecilia; Hidalgo, Cesar; Rodríguez-Sickert, Carlos
    Social relationships are pivotal for human beings. Yet, we still lack a complete understanding of the types and conditions of social relationships that facilitate learning among children. Here, we present the results of a study involving 855 elementary school children from 14 different public schools in Chile designed to understand their social learning strategies in classrooms. We mapped students' social relationships using a behavioral experiment–a non-anonymous social dilemma–that allows us to measure cooperation and infer reciprocal and asymmetrical relationships between peers. We implemented the experiment synchronously in each classroom using networked tablets and a friendly user interface to mitigate cognitive barriers and boost students' engagement. Using regression models, we found a positive and significant association between reciprocity and academic performance. This result holds after controlling for class attendance, sex, parents’ education, social status, individual cooperative dispositions, and fixed effects per class group. Finally, using a difference-in-difference framework, we found robust evidence that reciprocity heightens academic performance by comparing two consecutive academic semesters. This effect is heterogeneous and is considerably more prominent for the top 20% students experiencing higher levels of reciprocity in their social relationships. We expect these results to inform cooperative learning interventions in elementary education.
  • Item
    Thermochronological Evidence for Eocene Deformation in the Southern Patagonian Andes: Linking Orogenesis Along the Patagonian Orocline
    (2023) Goddard, A.L.Stevens; Fosdick, J.C.; Calderón, Mauricio; Ghiglione, M.C.; VanderLeest, R.A.; Romans, B.W.
    Thermochronologic results from zircon fission track and (U-Th)/He data collected across the Patagonian batholith, basement and thrust belt of the southern Patagonian Andes between 51°S and 53°S resolves new spatiotemporal patterns of Paleogene rock cooling that allows us to reconstruct deformational and erosional events along- and across-strike. Our study applies a novel modeling strategy, the Path Family Approach, to filter geologically plausible thermal solutions from inverse modeling results for rocks in this study according to a sample's structural and tectonic context. Our results identify minimal cooling and interpreted exhumation of batholith rocks throughout the Paleogene. However, in the western domain we identify synchronous cooling of Jurassic volcaniclastic rocks in the thrust belt both along- and across-strike between 50 and 35 Ma, which we interpret as a period of out-of-sequence deformation that coincides with the start of a distinct period of orogenesis in the Fuegian Andes (54°S). This finding may suggest that the southern Patagonian Andes and Fuegian Andes evolved as a connected orogenic system along the bend of the Patagonian orocline. In the central domain, modeled cooling of thermally reset Cretaceous basinal strata from 60 to 50 Ma corresponds to a well-recognized erosional unconformity in the adjacent Cenozoic foreland depocenter, indicating that contemporaneous exhumation occurred beyond the margins of the basin. Although not diagnostic, exhumation within the orogenic belt, beyond the Cenozoic foreland basin, provides a new regional context to interpret the cause of this regional erosion event. Collectively these results inform the Paleogene tectonic evolution of the orogen.
  • Item
    The role of physicochemical and biochemical processes on carbonate precipitation within the Laguna Timone maar in the Pali Aike Volcanic Field, southernmost extra-Andean Patagonia
    (2022) Henríquez, Carolina; Calderón, Mauricio; Fadel Cury, Leonardo; Athayde, Gustavo; Carvajal, Sergio; Oyarzún, Poldie; Bahniuk, Anelize
    in the regional environmental register. The Laguna Timone is situated within a maar of the Pali Aike Volcanic Field, a Quaternary volcano-tectonic complex in southernmost South America and represents one of hundreds of “pools” of brines developed after explosive volcanic eruptions in a periglacial environment. The lake constitutes an endorheic hydrological system where processes leading to carbonate precipitation took place under extreme physicochemical conditions and biological influences that can be explored. Laguna Timone is recharged by groundwater and sporadic episodes of precipitation (ca. 200 mm/year) and high evaporation rates are controlled by regimes of strong wind (westerlies) and seasonal solar radiation. Carbonate precipitation was studied in microbialite fragments of tufa deposits and carbonate crust located in the edge of the lake, and the mineralogy of all samples is calcite. The clay fraction of the sediment underlying the carbonates was characterized and HRTEM analysis shows that authigenic smectites have influence on calcite crystal precipitation. The positive δ18O values (2.28 ‰) in thin crust layers are associated with evaporation processes. In contrast, the negative δ18O values (−6.52 ‰) in the microbialites show meteoric and/or groundwater influences. The δ13C (−0.43 ‰ to 2.50 ‰) values indicate physico-chemical and biochemical processes controlling the precipitation. The carbonate precipitation involves the interrelations of hydrogeological properties, climate and biological influences. Laguna Timone provides a natural laboratory for understanding mineral precipitation processes that register continuous climatic and environmental archives.