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A Sustainable Bioleaching of a Low-Grade Chalcopyrite Ore

Lilian Velásquez-Yévenes, Sebastián Malverde, Víctor Quezada
2022 Minerals  
This paper reports on a study of column bioleaching of a low-grade chalcopyrite ore that is currently dump-leached under natural biological conditions without any control over microbial populations. The experimental methodology was focused on the effect of managing the bacterial populations in a raffinate solution sourced from a dump-leach operation. This study presents results from columns of two heights (0.45 and 1.0 m). We demonstrated that intermittent irrigation enhanced the chalcopyrite
more » ... ssolution during column leaching, but excessively long rest periods negatively affected the chemical and bacterial activity due to the shortage of oxidizing agents and/or nutrients for microorganisms. The recovery of low-grade chalcopyrite ore was enhanced by increasing the microbial cell density. The addition of 1.5 × 108 cells/mL to the 0.45 m column and 5.0 × 107 cells/mL to the 1 m column resulted in increased extraction, with the copper dissolution increasing from 32% to 44% in the 0.45 m column and from 30% to 40% in the 1.0 m column over 70 days of leaching. Under these conditions, the pH level remained constant at ~1.8, and the redox potential was around 840 mV vs. the SHE throughout the experiment. These results provided useful insights for evaluating a sustainable controlled dump-based technology for mineral bioprocessing.
doi:10.3390/min12040487 fatcat:tuox7tpgang35hb336x3zhf6de

Artificial Intelligence Methodologies for Data Management

Joel Serey, Luis Quezada, Miguel Alfaro, Guillermo Fuertes, Manuel Vargas, Rodrigo Ternero, Jorge Sabattin, Claudia Duran, Sebastian Gutierrez
2021 Symmetry  
This study analyses the main challenges, trends, technological approaches, and artificial intelligence methods developed by new researchers and professionals in the field of machine learning, with an emphasis on the most outstanding and relevant works to date. This literature review evaluates the main methodological contributions of artificial intelligence through machine learning. The methodology used to study the documents was content analysis; the basic terminology of the study corresponds
more » ... machine learning, artificial intelligence, and big data between the years 2017 and 2021. For this study, we selected 181 references, of which 120 are part of the literature review. The conceptual framework includes 12 categories, four groups, and eight subgroups. The study of data management using AI methodologies presents symmetry in the four machine learning groups: supervised learning, unsupervised learning, semi-supervised learning, and reinforced learning. Furthermore, the artificial intelligence methods with more symmetry in all groups are artificial neural networks, Support Vector Machines, K-means, and Bayesian Methods. Finally, five research avenues are presented to improve the prediction of machine learning.
doi:10.3390/sym13112040 fatcat:dtcfzqmka5byxhupaennbb77xi

Tree carbon stock in evergreen forests of Chiloé, Chile

Jorge F Perez-Quezada, Sebastián Olguín, Juan P Fuentes, Mauricio Galleguillos
2015 Bosque (Valdivia)  
The carbon stock associated with tree biomass was estimated in evergreen forests near the town of Inío in Chiloé Island, Chile (43º21' S, 74º07' W), analyzing its relation with biotic and abiotic properties. A total of 14 sampling plots of 20×50 m were located at variable distances from Inío and different elevations, slopes and aspects. At each plot, tree density, incident solar radiation, and spectral vegetation indices were quantified based on LANDSAT satellite data. Total tree carbon stock
more » ... s estimated for each tree species and in total, using known allometric biomass functions based on the diameter at breast height (DBH), of all the trees in the plot with DBH> 3 cm. Four plots presented post-fire conditions, where tree carbon content had a mean (± SE) 7.7 ± 0.78 Mg ha -1 , while in the unburned plots it was 384.4 ± 120 Mg ha -1 . After removing the value of one plot with high carbon content, the average was 189.7 ± 45.6 Mg ha -1 . Most of the sampled properties had a limited correlation with tree carbon content (R² 0.31-0.69). However, the amount of carbon of Nothofagus nitida was related to the total tree carbon in all the plots (post-fire and unburned) with R² = 0.96. This model substantially simplifies sampling efforts, since only DBH data of N. nitida is needed for the analyses (average of 15 individuals per plot). The tree carbon stock of forests of this area is high when compared to other forest types of the world. Key words: carbon pool, biotic and abiotic variables, Nothofagus nitida, allometric models. RESUMEN El reservorio de carbono asociado a la biomasa arbórea fue estimada en bosques siempreverdes cerca de Inío en la isla de Chiloé, Chile (43º21' S, 74º07' O), analizando su relación con propiedades bióticas y abióticas. Un total de 14 parcelas de 20×50 m fueron ubicadas a distancias variables de Inío y diferentes altitudes y pendientes. Para cada parcela, también se cuantificó la densidad total de árboles, radiación solar incidente e índices espectrales de vegetación basados en datos satelitales LANDSAT. El reservorio de carbono en los árboles por especie y total fue estimado usando funciones alométricas conocidas, basadas en el diámetro a la altura del pecho (DAP), de todos los árboles de cada parcela con DAP > 3 cm. Cuatro parcelas presentaron una condición post-incendio, donde el contenido de carbono arbóreo promedio (± EE) fue de 7,7 ± 0,78 Mg ha -1 , mientras que en las áreas no incendiadas fue de 384,4 ± 120 Mg ha -1 . Después de remover una parcela con contenido de carbono alto, el promedio fue de 189,7 ± 45,6 Mg ha -1 . La mayor parte de las variables muestreadas tuvieron una correlación limitada con el contenido de carbono arbóreo (R² 0,31-0,69). Sin embargo, la cantidad de carbono de Nothofagus nitida se relacionó con el total de carbono arbóreo en todos las parcelas (post-incendio y no incendiadas) con un R² = 0,96. Este modelo simplifica el esfuerzo de muestreo sustancialmente, ya que solo requiere los datos de DAP de N. nitida para el análisis (promedio de 15 individuos por parcela). El reservorio de carbono arbóreo de bosques maduros en esta área es alto en comparación con otros tipos de bosque del mundo. Palabras clave: reservorio de carbono, variables bióticas y abióticas, Nothofagus nitida, modelos alométricos.
doi:10.4067/s0717-92002015000100004 fatcat:45mstdyrqfgnhn6p5x4ygpzdzm

Evaluating How Developers Use General-Purpose Web-Search for Code Retrieval [article]

Md Masudur Rahman, Jed Barson, Sydney Paul, Joshua Kayan, Federico Andres Lois, Sebastian Fernandez Quezada, Christopher Parnin, Kathryn T. Stolee, Baishakhi Ray
2018 arXiv   pre-print
Search is an integral part of a software development process. Developers often use search engines to look for information during development, including reusable code snippets, API understanding, and reference examples. Developers tend to prefer general-purpose search engines like Google, which are often not optimized for code related documents and use search strategies and ranking techniques that are more optimized for generic, non-code related information. In this paper, we explore whether a
more » ... neral purpose search engine like Google is an optimal choice for code-related searches. In particular, we investigate whether the performance of searching with Google varies for code vs. non-code related searches. To analyze this, we collect search logs from 310 developers that contains nearly 150,000 search queries from Google and the associated result clicks. To differentiate between code-related searches and non-code related searches, we build a model which identifies the code intent of queries. Leveraging this model, we build an automatic classifier that detects a code and non-code related query. We confirm the effectiveness of the classifier on manually annotated queries where the classifier achieves a precision of 87%, a recall of 86%, and an F1-score of 87%. We apply this classifier to automatically annotate all the queries in the dataset. Analyzing this dataset, we observe that code related searching often requires more effort (e.g., time, result clicks, and query modifications) than general non-code search, which indicates code search performance with a general search engine is less effective.
arXiv:1803.08612v1 fatcat:f4rshpfx4fflnmgimku62r667a

Expression of the metastasis suppressor BRMS1 in uveal melanoma

Bruna V Ventura, Carlos Quezada, Shawn C Maloney, Bruno F Fernandes, Emilia Antecka, Claudia Martins, Silvin Bakalian, Sebastian di Cesare, Miguel N Burnier
2014 ecancermedicalscience  
To determine the expression of breast metastasis suppressor 1 (BRMS1) in human uveal melanoma (UM) tissues and cell lines. In addition, we intend to establish a possible association between BRMS1 expression and the presence of metastatic disease. Thirty-one formalin-fixed paraffin-embedded tissues from enucleated eyes of patients with UM were immunostained. Clinical-pathological data were obtained, including age, tumour location, largest dimension, cell type, and occurrence of metastasis. The
more » ... pression of BRMS1 mRNA in four human UM cell lines was determined by real-time reverse transcriptase polymerase chain reaction, and protein expression was assessed by immunocytochemistry and western blot. The association between BRMS1 immunostaining and location, largest tumour dimension, and tumour cell type was determined using the correlation coefficient test. The association between BRMS1 immunostaining and the incidence of metastasis was assessed using Kaplan-Meier analysis. Of the 31 cases of UM, 24 (77.42%) stained positive and seven (22.58%) negative for BRMS1. From the positively stained tumours, 21 (87.50%) showed cytoplasmatic staining. Macrophages were usually positive when present in the tumour and staining intensity was generally higher than in UM cells. BRMS1 mRNA was present in all four human UM cell lines, as well as cytoplasmatic immunoexpression of BRMS1. Immunoblotting showed variable BRMS1 protein levels between the different cell lines. No statistically significant correlation was found between BRMS1 protein expression and survival (P = 0.69), tumour cell type (P = 0.68), largest tumour dimension (P = 0.75), and tumour location (P = 0.11). BRMS1 is expressed in UM both at the mRNA and protein level; however, neither was associated with any of the prognosticor outcome parameters that we tested.
doi:10.3332/ecancer.2014.410 pmid:24688598 pmcid:PMC3963706 fatcat:7cgkho7tevhjpctpcbf5kknm2u

Adenosine contribution to normal renal physiology and chronic kidney disease

Carlos Oyarzún, Wallys Garrido, Sebastián Alarcón, Alejandro Yáñez, Luis Sobrevia, Claudia Quezada, Rody San Martín
2017 Molecular Aspects of Medicine  
ENT1 and ENT2 activity was examined to define the mechanisms associated with changes in adenosine levels at the glomerulus Quezada et al. 2013) .  ...  Cárdenas, A., Toledo, C., Oyarzún, C., Sepúlveda, A., Quezada, C., Guillén-Gómez, E., Díaz-Encarnación, M.M., Pastor-Anglada, M., San Martín, R. 2013.  ... 
doi:10.1016/j.mam.2017.01.004 pmid:28109856 fatcat:hsyztzvywzfk5aiptpwtl6vbky

Malakoplakia mimicking a locally advanced colorectal neoplasm

María J Irarrázaval-Mainguyague, Manuel Cabreras, Sebastián Oksenberg, María A Pulgar, Francisco Rojas, Manuel Álvarez, Felipe F Quezada-Diaz
2021 Journal of Surgical Case Reports  
Malakoplakia is a rare disease. Clinical presentation is non-specific, making its diagnosis an incidental finding on histopathological analysis. The aim of this case report is to describe a patient diagnosed with colon, renal and soft tissue malacoplakia mimicking a locally advanced colorectal cancer. A 75-year-old man was admitted due to intense abdominal pain. No relevant findings at the physical examination. Computed tomography showed parietal thickening of the descending colon with left
more » ... ey, iliopsoas muscle and retroperitoneum involvement. An elevated blood serum creatinine, elevated glycated hemoglobin and urinary infection were detected. Surgery was decided for suspicious symptomatic colonic neoplasm. Left segmental colectomy with left partial nephrectomy and retroperitoneal soft tissue resection was performed. Pathology report was compatible with malakoplakia. Malakoplakia is a rare disease and may affect multiple organs. Because there are no clinical-specific findings, diagnosis is usually made with histopathological study of the surgical specimen.
doi:10.1093/jscr/rjab225 pmid:34104407 pmcid:PMC8177963 fatcat:px2vo3zdzfb3ngs4ixnyzsylya

Methodological Proposals for the Development of Services in a Smart City: A Literature Review

Joel Serey, Luis Quezada, Miguel Alfaro, Guillermo Fuertes, Rodrigo Ternero, Gustavo Gatica, Sebastian Gutierrez, Manuel Vargas
2020 Sustainability  
This literature review analyzes and classifies methodological contributions that answer the different challenges faced by smart cities. This study identifies city services that require the use of artificial intelligence (AI); which they refer to as areas of application of A. These areas are classified and evaluated, taking into account the five proposed domains (government, environment, urban settlements, social assistance, and economy). In this review, 168 relevant studies were identified that
more » ... make methodological contributions to the development of smart cities and 66 areas of application of AI, along with the main challenges associated with their implementation. The review methodology was content analysis of scientific literature published between 2013 and 2020. The basic terminology of this study corresponds to AI, the internet of things, and smart cities. In total, 196 references were used. Finally, the methodologies that propose optimization frameworks and analytical frameworks, the type of conceptual research, the literature published in 2018, the urban settlement macro-categories, and the group city monitoring–smart electric grid, make the greater contributions.
doi:10.3390/su122410249 fatcat:yolrbniyarbkfnuooo5spqd76a

Estrategias digitales de difusión museística en tiempos del COVID-19. Estudio comparativo entre Ecuador, España y Perú

Sebastián-Alberto Longhi-Heredia, Laddy Liset Quezada-Tello, Giancarlo Cappello
2021 Contratexto  
Las estrategias de comunicación implementadas por los museos tras la crisis sanitaria del COVID-19 enfrentaron el cierre de las instituciones de cara al público. De allí la necesidad de contrastar cómo Ecuador, España y Perú actuaron para poner en evidencia la cultura y el patrimonio al alcance de la población. El estudio exploratorio fue abordado desde el análisis de contenido mixto. Se clasificaron y categorizaron las acciones implementadas por los museos en el contexto pandémico, tomando en
more » ... uenta el tipo de contenido y los recursos desplegados para llegar al público. Finalmente, se abocó a identificar las áreas estratégicas de acción de la UNESCO. La tendencia supranacional registrada cambia en función de la situación de cada país. En este sentido, se advirtió que las acciones desplegadas desde España entraron en adecuación con los informes internacionales. Desde Ecuador y Perú, las "actividades digitales" y las "actividades en redes sociales" resultaron ser más representativas que la media descrita por los informes. En el plano temático, el contenido difundido fue en su mayoría de orden comunicacional y educativo, quedando relegados los tópicos referidos a la investigación y la preservación.
doi:10.26439/contratexto2021.n036.5243 fatcat:jwnnzrvjazgjxkbdfmcdutljfi

The Action of 2-Aminoethyldiphenyl Borinate on the Pulmonary Arterial Hypertension and Remodeling of High-Altitude Hypoxemic Lambs

Sebastián Castillo-Galán, Daniela Parrau, Ismael Hernández, Sebastián Quezada, Marcela Díaz, Germán Ebensperger, Emilio A. Herrera, Fernando A. Moraga, Rodrigo Iturriaga, Aníbal J. Llanos, Roberto V. Reyes
2022 Frontiers in Physiology  
Nevertheless, in addition to their hypoxemia, highland lambs also differ from lambs with partial gestation at high altitude in their greater pulmonary arterial medial layer thickening (Quezada et al.,  ... 
doi:10.3389/fphys.2021.765281 pmid:35082688 pmcid:PMC8784838 fatcat:r2ujaw5ftfg5fi55iohwb4p55a

Phylogenetic position of "Cochranella" megista (Anura: Centrolenidae) and first records for Ecuador

Scott J. Traseger, Ross J. Maynard, Jaime Culebras, Sebastian Kohn, Amanda Quezada, Juan M. Guayasamin
2021 Phyllomedusa: Journal of Herpetology  
"Cochranella" megista is an Endangered and rarely encountered species of glass frog that, until now, had been only registered in the Colombian Andes. Here we report this species for the first time in Ecuador, expanding its known distribution ca. 530 km south of its original range. Additionally, we include C. megista in a molecular phylogeny for the first time and unambiguously place the species in the genus Nymphargus, resulting in a new combination. Habitat in both countries is fragmented and
more » ... s threatened by mining concessions and agriculture.
doi:10.11606/issn.2316-9079.v20i1p27-35 fatcat:q5mjsquxfnagtaw4m6yjourita

Interleukin-12 bypasses common gamma-chain signalling in emergency natural killer cell lymphopoiesis

Isabel Ohs, Maries van den Broek, Kathrin Nussbaum, Christian Münz, Sebastian J. Arnold, Sergio A. Quezada, Sonia Tugues, Burkhard Becher
2016 Nature Communications  
Differentiation and homeostasis of natural killer (NK) cells relies on common gamma-chain (c)dependent cytokines, in particular IL-15. Consequently, NK cells do not develop in mice with targeted c deletion. Herein we identify an alternative pathway of NK-cell development driven by the proinflammatory cytokine IL-12, which can occur independently of c-signalling. In response to viral infection or upon exogenous administration, IL-12 is sufficient to elicit the emergence of a population of
more » ... D49b+ cells by targeting NK-cell precursors (NKPs) in the bone marrow (BM). We confirm the NK-cell identity of these cells by transcriptome-wide analyses and their ability to eliminate tumour cells. Rather than using the conventional pathway of NK-cell development, IL-12-driven CD122+CD49b+ cells remain confined to a NK1.1lowNKp46low stage, but differentiate into NK1.1+NKp46+ cells in the presence of c-cytokines. Our data reveal an IL-12-driven hard-wired pathway of emergency NK-cell lymphopoiesis bypassing steady-state c-signalling. Differentiation and homeostasis of natural killer (NK) cells relies on common gamma-chain (gc)-dependent cytokines, in particular IL-15. Consequently, NK cells do not develop in mice with targeted gc deletion. Herein we identify an alternative pathway of NK-cell development driven by the proinflammatory cytokine IL-12, which can occur independently of gc-signalling. In response to viral infection or upon exogenous administration, IL-12 is sufficient to elicit the emergence of a population of CD122 þ CD49b þ cells by targeting NK-cell precursors (NKPs) in the bone marrow (BM). We confirm the NK-cell identity of these cells by transcriptomewide analyses and their ability to eliminate tumour cells. Rather than using the conventional pathway of NK-cell development, IL-12-driven CD122 þ CD49b þ cells remain confined to a NK1.1 low NKp46 low stage, but differentiate into NK1.1 þ NKp46 þ cells in the presence of gc-cytokines. Our data reveal an IL-12-driven hard-wired pathway of emergency NK-cell lymphopoiesis bypassing steady-state gc-signalling.
doi:10.1038/ncomms13708 pmid:27982126 pmcid:PMC5172358 fatcat:poqrd32gmndpzkngr5kwy7w66e

Generando buenas prácticas de innovación pública desde las Regiones: "Piensa con I"

Ricardo Gaete Quezada, Sebastián Acevedo Muñoz, Gabriel Carmona Robles, Olga Palta Layana
2019 Innovar: Revista de Ciencias Administrativas y Sociales  
Fuente: diseñada por Ricardo Gaete Quezada para la evaluación de las buenas prácticas de ip en el concurso. bueno y excelente), según la apreciación que tuviera de los antecedentes presentados en cada  ... 
doi:10.15446/innovar.v29n74.82095 fatcat:ktavit2ue5hmdht6kam54ncfsu

Deficient Insulin-mediated Upregulation of the Equilibrative Nucleoside Transporter 2 Contributes to Chronically Increased Adenosine in Diabetic Glomerulopathy

Sebastián Alarcón, Wallys Garrido, Claudio Cappelli, Raibel Suárez, Carlos Oyarzún, Claudia Quezada, Rody San Martín
2017 Scientific Reports  
Sebastián Alarcón holds a doctoral fellowship from CONICYT-Chile. Wallys Garrido holds a Posdoctoral fellowship from FONDECYT-Chile.  ... 
doi:10.1038/s41598-017-09783-0 pmid:28842605 pmcid:PMC5572683 fatcat:7ywlirjw7vfqdlb5lh6gtxvpdq

Telemedicine for postoperative follow-up, virtual surgical clinics during COVID-19 pandemic

María J. Irarrázaval, Martin Inzunza, Rodrigo Muñoz, Nicolás Quezada, Alejandro Brañes, Mauricio Gabrielli, Pedro Soto, Martín Dib, Gonzalo Urrejola, Julian Varas, Sebastián Valderrama, Fernando Crovari (+1 others)
2020 Surgical Endoscopy  
Irarrázaval, Martin Inzunza, Rodrigo Muñoz, Nicolás Quezada, Alejandro Brañes, Mauricio Gabrielli, Pedro Soto, Martin Dib, Gonzalo Urrejola, Julian Varas, Sebastián Valderrama, Fernando Crovari and Pablo  ... 
doi:10.1007/s00464-020-08130-1 pmid:33140151 pmcid:PMC7605475 fatcat:atxewzt6xrb2hia3cpioz6dkv4
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