Publicaciones académicas

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https://repositorio.uc.cl/handle/11534/7
Esta colección incluye artículos de profesores de la Pontificia Universidad Católica de Chile, publicados en revistas nacionales y extranjeras.

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Browsing Publicaciones académicas by browse.metadata.categoria "Ciencias"

Now showing 1 - 20 of 41
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    Attention is Turing complete
    (2021) Pérez, Jorge; Barceló Baeza, Pablo; Marinkovic, Javier
    Alternatives to recurrent neural networks, in particular, architectures based on self-attention, are gaining momentum for processing input sequences. In spite of their relevance, the computational properties of such networks have not yet been fully explored. We study the computational power of the Transformer, one of the most paradigmatic architectures exemplifying self-attention. We show that the Transformer with hard-attention is Turing complete exclusively based on their capacity to compute and access internal dense representations of the data. Our study also reveals some minimal sets of elements needed to obtain this completeness result.
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    Bayesian variable selection and survival modeling : assessing the most important comorbidities that impact lung and colorectal cancer survival in Spain
    (2022) Rubio, Francisco J.; Silva, Danilo Alvares da; Redondo-Sanchez, Daniel; Marcos-Gragera, Rafael; Sánchez, María-José; Luque-Fernandez, Miguel A.
    Cancer survival represents one of the main indicators of interest in cancer epidemiology. However, the survival of cancer patients can be affected by several factors, such as comorbidities, that may interact with the cancer biology. Moreover, it is interesting to understand how different cancer sites and tumour stages are affected by different comorbidities. Identifying the comorbidities that affect cancer survival is thus of interest as it can be used to identify factors driving the survival of cancer patients. This information can also be used to identify vulnerable groups of patients with comorbidities that may lead to worst prognosis of cancer. We address these questions and propose a principled selection and evaluation of the effect of comorbidities on the overall survival of cancer patients. In the first step, we apply a Bayesian variable selection method that can be used to identify the comorbidities that predict overall survival. In the second step, we build a general Bayesian survival model that accounts for time-varying effects. In the third step, we derive several posterior predictive measures to quantify the effect of individual comorbidities on the population overall survival. We present applications to data on lung and colorectal cancers from two Spanish population-based cancer registries. The proposed methodology is implemented with a combination of the R-packages mombf and rstan. We provide the code for reproducibility at https://github.com/migariane/BayesVarImpComorbiCancer .
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    Building taxonomies. A discourse semantic model of entities and dimensions in biology
    (Routledge, 2021) Hao, Jing
    Science involves nuanced and highly technical distinctions among empirical phenomena. This chapter explores how these deep and multifaceted taxonomies are developed through language in undergraduate biology by examining both pedagogic texts and students written assessments. The chapter presents a major development in modelling ideational meanings within SFL’s discourse semantics. It first builds a system of ‘entity types’ and ‘dimensionality’ from a ‘trinocular’ perspective. It then illustrates how the framework of entities and dimensions can be applied to text analysis by revealing both the diversity and depth of taxonomies demonstrated in a student research report produced at the final year of undergraduate biology. This analysis shows the appliability of the discourse semantic method for examining scientific taxonomies and makes explicit the multitude of ways in which various field-specific resources (presented in Martin and Doran this volume) are realized in language.
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    Campamentos científicos : transformando la visión de científicos en estudiantes chilenos.
    (2017) Cândido Vendrasco, Natália; Maturana, Joyce.; Gallardo Vargas, Felipe.; Guzmán, Eduardo.; Santibáñez, David P.
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    Daily Variation in Plasma Zinc Concentrations in Women Fed Meals at Six-Hour Intervals
    (1994) King, Janet C.; Hambidge, K. Michael; Westcott, Jamie L.; Kern, Deborah L.; Marshall Rivera, Guillermo
    Ten pre-menopausal women participated in two studies to measure the daily variations in plasma zinc when meals were fed at 6-h intervals and to determine if the response was related to shifts in serum insulin, glucose, calcium, or phosphorus concentrations. In Study 1, identical meals were fed at 6-h intervals for 2 d, and blood was sampled 8 times between each meal. In Study 2, the women fasted from 1800 h on d 1 to noon the next day, and blood was sampled hourly from 0700–1200 on d 2. The postprandial plasma zinc response was similar following all four meals and accounted for 50% of the total within subject variation in plasma zinc. A small (2–6%) increase occurred within the first 60 min; then plasma zinc declined to a low point at 4 h after the meal. This characteristic pattern was not observed during the fasting study. Serum phosphorus varied consistently after each meal with a net efflux from circulation that preceded an efflux of zinc by 2 h. The postprandial response of serum glucose and insulin were related to the postprandial plasma zinc response measured 6 h earlier; the variables were not correlated at concurrent time points. The data show that food intake is a determinant of the daily variations in plasma zinc. The net efflux of zinc from circulation following meals may reflect hepatic zinc uptake in association with an increase in postprandial liver metabolism.
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    Developing and implementing an effective public outreach program
    (2009) Harrison, J.; Dassow, Peter von
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    Developing Core/Shell Capsules Based on Hydroxypropyl Methylcellulose and Gelatin through Electrodynamic Atomization for Betalain Encapsulation
    (2023) López de Dicastillo, Carol; Velásquez, Eliezer; Rojas, Adrián; Garrido, Luan; Moreno Constenla, María Carolina; Guarda, Abel; Galotto, María José
    Betalains are bioactive compounds with remarkable functional and nutritional activities for health and food preservation and attractiveness. Nevertheless, they are highly sensitive to external factors, such as oxygen presence, light, and high temperatures. Therefore, the search for new structures, polymeric matrices, and efficient methods of encapsulation of these compounds is of great interest to increase their addition to food products. In this work, betalains were extracted from red beetroot. Betacyanin and betaxanthin contents were quantified. Subsequently, these compounds were successfully encapsulated into the core of coaxial electrosprayed capsules composed of hydroxypropyl methylcellulose (HPMC) and gelatin (G). The effect of incorporating the carbohydrate and the protein both in the core or shell structures was studied to elucidate the best composition for betalain protection. Morphological, optical, and structural properties were analyzed to understand the effect of the incorporation of the bioactive compounds in the morphology, color, and chemical interactions between components of resulting electrosprayed capsules. The results of the thermogravimetric and encapsulation efficiency analysis coincided that the incorporation of beetroot extract in G in the core and HPMC in the shell resulted in the structure with greater betalain protection. The effectiveness of the core/shell structure was confirmed for future food applications.
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    La difusión de la ciencia en Chile.
    (1985) Illanes, Juan Pablo
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    Dual thinking for scientists
    (2015) Scheffer, M.; Marquet, P. A. (Pablo A.)
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    Editorial: Open Access
    (2013) Zacconi, Flavia C. M.; Arias, Hugo R.
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    Experimental and Numerical Analysis of a PCM-Integrated Roof for Higher Thermal Performance of Buildings
    (2024) Pierre Simon, François; Ruíz Valero, Letzai; Girard, Aymeric; Galleguillos, Héctor; CEDEUS (Chile)
    Phase change materials (PCMs) designate materials able to store latent heat. PCMs change state from solid to liquid over a defined temperature range. This process is reversible and can be used for thermo-technical purposes. The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management. The experiment is conducted in two test rooms in Antofagasta (Chile) during summer, fall, and winter. The PCM is integrated into the rooftop of the first test room, while the roof panel of the second room is a sealed air cavity. The work introduces a numerical model, which is built using the finite difference method and used to simulate the rooms’ thermal behavior. Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates. Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1°C±10.6°C, while the one of the air-panel room varies 28.3°C±18.5°C. Under the experiment’s conditions, the PCM room’s indoor temperature observes smoother diurnal fluctuations, with lower maximum and higher minimum indoor temperatures than that of the air-panel room. Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter, as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures. This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs, and improve indoor thermal comfort in different climates of Chile.
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    El informe de arbitraje de rechazo: su microvariación según los tipos de evaluador
    (2019) Astudillo Zepeda, César; Cabezas del Fierro, Paula; Sabaj Meruane, Omar; Varas, Germán
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    Infrastructure Conditions and Service Quality in Rural Drinking Water Systems: A Cluster Analysis of Community-Based Organizations in Chile
    (2024) Bopp, Carlos; Nicolas-Artero, Chloé; Blanco, Elisa; Fuster, Rodrigo
    In many countries, the drinking water provision in rural areas is in the charge of the users themselves, who constitute rural watersupply services (RWS) to operate and maintain the public infrastructure provided by the State. However, in practice, the condition of thecomponents of the implied infrastructure managed by RWS varies considerably, which has important implications for delivering high-qualityservice. This case study explores the nexus among infrastructure conditions, performance outcomes, and organization characteristics usingthe case of Chile. Using representatives’assessments from 406 RWS regarding the need for the replacement of several components oftheir system’s infrastructure, an index of infrastructure conditions was constructed and subjected to a cluster analysis that identified threedissimilar groups of RWS. The top condition cluster represents a reference group (benchmark) that exhibits the highest scores in water quality,quantity, and delivery reliability, which highlights the association between infrastructure conditions and performance outcomes. In addition,a comparison of RWS attributes of these three clusters allowed us to characterize them in terms of structural, organizational, management,and environmental variables. This study sheds light on the role of RWS infrastructure in enabling these organizations to deliver high-qualityservice, and the findings serve to guide policy actions and tailored planning. The methodology presented here can be applied in otherregions beyond that of the case study because it represents a low-cost tool to measure the infrastructure condition of RWS based on rep-resentatives’assessments and is an effective and practical way to distinguish RWS most in need of support. DOI:10.1061/JWRMD5.WRENG-6318 © 2024 American Society of Civil Engineers
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