Artículos de revistas
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Esta colección incluye artículos de revistas de profesores de la Pontificia Universidad Católica de Chile, publicados en revistas nacionales y extranjeras.
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Browsing Artículos de revistas by browse.metadata.categoria "Ciencias"
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- ItemA method for unique phase retrieval of ultrafast optical fields(2009) Seifert, Birger
- ItemAttention is Turing complete(2021) Pérez, Jorge; Barceló Baeza, Pablo; Marinkovic, JavierAlternatives 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.
- ItemBayesian 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 .
- ItemBeyond the GUM: variance-based sensitivity analysis in metrology(2016) Lira, I.
- ItemDaily 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, GuillermoTen 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.
- ItemDeveloping and implementing an effective public outreach program(2009) Harrison, J.; Dassow, Peter von
- ItemLa difusión de la ciencia en Chile.(1985) Illanes, Juan Pablo
- ItemDual thinking for scientists(2015) Scheffer, M.; Marquet, P. A. (Pablo A.)
- ItemEditorial: Open Access(2013) Zacconi Flavia Cristina Milagro; Arias, Hugo R.
- ItemFrom Nature to Representation. Science in the Southern Andes(2017) Sagredo Baeza, Rafael
- ItemHacia una nueva estructura para el desarrollo de la ciencia, la tecnología e innovación(2011) Lavados, H.; Santelices, Bernabé
- ItemHistoria natural: La discusión. Una revisión del concepto, el conflicto y sus ecos a la educación de las Ciencias Biológicas(2015) Elórtegui Francioli, Sergio
- ItemEl 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
- ItemInfrastructure 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, RodrigoIn 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
- ItemInstitucionalidad para ciencia,tecnología y desarrollo en Chile.(2009) Asenjo, J.; Castilla, Juan Carlos; Vicuña, Rafael
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- ItemOn doing relevant and rigorous experiments: Review and recommendations.(2018) Lonati, S.; Quiroga, Bernardo F.; Zehnder, C.; Antonakis, J.Although experiments are the gold standard for establishing causality, several threats can undermine the internal validity of experimental findings. In this article, we first discuss these threats, which include the lack of consequential decisions and outcomes, deception, demand effects and unfair comparisons, as well as issues concerning statistical validity (e.g., minimum sample size per cell, estimating variance correctly). We expose each problem, show potential solutions, and bring to the fore issues of relevance of the findings (i.e., external and ecological validity). Thereafter, we take stock of the state-of-the-science regarding validity threats using a representative sample of 468 recent experiments from 258 articles published in top-tier journals. We compare research practices in three fields of study—management, social psychology, and economics, which regularly use experimental research—to operations management, which has more recently begun to use the experimental paradigm. Our results underscore the importance for journals and authors to follow what we identify to be best-practice methodological suggestions (i.e., the “ten commandments” of experimental research). We show that—on average—markers of methodological rigor and generalizability positively and significantly predict the citations received by published articles. Finally, given that experiments are infeasible in some settings, we conclude with a brief review of often overlooked quasi-experimental designs, which are useful for generating strong counterfactuals and hence allow making causal claims in the field.
- ItemPlagio y ética de la investigación científica(2013) Miranda Montecinos, Alejandro