Repositorio Institucional UCSC (Univ. Católica de la Santísima Concepción)
Not a member yet
3697 research outputs found
Sort by
Periodic orbits in a Hamiltonian system of stellar type
No full textWe investigate the existence of periodic orbits in a perturbed Hamiltonian system of stellar type in 1:1 resonance. The perturbation consists of a potential of degree four with two real parameters. We determine six families of periodic orbits using reduction and averaging theories. Also, we characterize the stability of these orbits and their bifurcation curves in terms of the parameters. Finally, we show a complete picture of the choreographies of critical points originating the periodic orbits
Optimization of a photocatalytic process for removal of phenolic compounds from wastewater generated in the production of cellulose from Pinus Radiata and Eucalyptus Grandis wood
No full textThis study aimed to improve the sustainability of the kraft pulp production process by recovering Pinus radiata and Eucalyptus grandis wastewater generated during the bleaching process. The effluents were obtained from the first alkaline extraction stage (E0) of the ECF bleaching sequence used to produce white Kraft cellulose, considering that this stage is where the highest contamination by phenolic compounds occurs and the effluent exhibits an intense color. A photochemical oxidation system, utilizing TiO2/S2O82-/UV, was implemented to generate in situ two highly oxidizing radical species, with high redox potential, a hydroxyl radical (HO• 2.8 eV ) and a sulfate radical (SO4•- 2.5-3.1 eV), which promote rapid degradation of contaminants. To obtain the optimal response, we employed the 2n model to construct a matrix of 15 experiments, utilizing the Box-Behnken design. According to the experimental variables studied, phenolic compounds were completely removed from the Eucalyptus effluent (0.0312 min-1) and 80% of them were removed from the pine effluent (0.0102 min-1), at pH 5.0 with 0.6 gL-1 of persulfate and 1.0 gL-1 of titanium dioxide. Under these conditions, the bioavailability of effluents from Pinus radiata and Eucalyptus grandis increases from 0.16 and 0.26 to 0.90, after the treatment. The excellent bioavailability of the effluents obtained after the treatment demonstrates that the process used is efficient in recovering wastewater from the pulp industry and that the treated water could be reused in the same process or returned to the ecosystem, without harming the environment
Effectuation and strategic evolution for sustainable longevity: The case of a 19th-generation family firm
No full textPurpose: This article explains the causal mechanism supporting sustainable longevity by analysing the last three generations of one of the oldest family firms in Latin America.
Design/methodology/approach: An explanatory single-case qualitative research based on critical realism explores why and how this family firm has been able to maintain its multigenerational longevity.
Findings: Los Lingues's evolutionary strategy, driven by transgenerational entrepreneurship under effectuation, has supported this family firm's sustainable longevity. Its effectual logic emerged mainly from the richness of the firm's historical resources embedded in its identity, knowledge and social capital and priority to preserve socioemotional wealth.
Originality/value: This study integrates socioemotional wealth and effectuation theory to explain a family firm's ability to survive through generations and sustain longevity. The study demonstrates the relevance of effectual logic in the entrepreneurial dynamics of a multigenerational family firm. Effectual logic drives the firm evolution and adaptation for sustainable longevity
Mechanistic perspective on the actions of vitamin a in autism spectrum disorder etiology
No full textVitamin A (VA) has many functions in the body, some of which are key for the development and functioning of the nervous system, while some others might indirectly influence neural function. Both hypovitaminosis and hypervitaminosis A can lead to clinical manifestations of concern for individuals and for general global health. Scientific evidence on the link between VA and autism spectrum disorder (ASD) is growing, with some clinical studies and accumulating results obtained from basic research using cellular and animal models. Remarkably, it has been shown that VA deficiency can exacerbate autistic symptomatology. In turn, VA supplementation has been shown to be able to improve autistic symptomatology in selected groups of individuals with ASD. However, it is important to recognize that ASD is a highly heterogeneous condition. Therefore, it is important to clarify how and when VA supplementation can be of benefit for affected individuals. Here we delve into the relationship between VA and ASD, discussing clinical observations and mechanistic insights obtained from research on selected autistic syndromes and laboratory models to advance in defining how the VA signaling pathway can be exploited for treatment of ASD
Programas de Treinamento para Promover a Autorregulação da Aprendizagem em Estudantes Universitários: Uma Revisão Sistemática
Get PDFEn este artículo se realizó una revisión sistemática de investigaciones publicadas entre 2019 y 2023 en tres bases de datos indexadas. El objetivo fue caracterizar las investigaciones empíricas sobre programas de entrenamiento para promover la autorregulación del aprendizaje en estudiantes universitarios. Se utilizó el método PRISMA, que resultó en 41 artículos seleccionados de 445 textos examinados. Se evidencia escasa implementación de programas de intervención a nivel sudamericano, una gran diversidad de instrumentos de medición y un bajo reporte del tamaño del efecto de la intervención
Simple and fast prediction of gestational diabetes mellitus based on machine learning and near-infrared spectra of serum: A proof of concept study at different stages of pregnancy
Get PDFGestational diabetes mellitus (GDM) is a hyperglycemic state that is typically diagnosed by an oral glucose tolerance test (OGTT), which is unpleasant, time-consuming, has low reproducibility, and results are tardy. The machine learning (ML) predictive models that have been proposed to improve GDM diagnosis are usually based on instrumental methods that take hours to produce a result. Near-infrared (NIR) spectroscopy is a simple, fast, and low-cost analytical technique that has never been assessed for the prediction of GDM. This study aims to develop ML predictive models for GDM based on NIR spectroscopy, and to evaluate their potential as early detection or alternative screening tools according to their predictive power and duration of analysis. Serum samples from the first trimester (before GDM diagnosis) and the second trimester (at the time of GDM diagnosis) of pregnancy were analyzed by NIR spectroscopy. Four spectral ranges were considered, and 80 mathematical pretreatments were tested for each. NIR data-based models were built with single- and multi-block ML techniques. Every model was subjected to double cross-validation. The best models for first and second trimester achieved areas under the receiver operating characteristic curve of 0.5768 ± 0.0635 and 0.8836 ± 0.0259, respectively. This is the first study reporting NIR-spectroscopy-based methods for the prediction of GDM. The developed methods allow for prediction of GDM from 10 µL of serum in only 32 min. They are simple, fast, and have a great potential for application in clinical practice, especially as alternative screening tools to the OGTT for GDM diagnosis
Sociodemographic factors related to perceived physical activity on Chilean adults after COVID-19 pandemic
Get PDFThe current study aimed to examine the relationship between sociodemographic variables (i.e., sex, age, marital status, educational level, socioeconomic status, and working mode) and physical activity levels declared by Chilean adults. The sample comprised 483 Chilean adults, 159 men (32.9%) and 324 women (67.1%) aged from 18 to 69 years old (36.5 ± 12.0). The participants completed an ad hoc sociodemographic online survey between December 2022 and March 2023 that included questions about characteristics of participants such as sex, age, educational level, household income, marital status, and working mode. Vigorous, moderate, and walking activities were measured using the International Physical Activity Questionnaire-Short Form (IPAQ-SF), a self-administered questionnaire. Men declared significantly higher vigorous and moderated physical activity than women. People aged 18 to 25, single or unmarried, and with the lowest household income, showed significantly higher scores in vigorous physical activity than those aged 26 to 45, cohabiting with a partner or married, and middle household income, respectively. Regarding working mode, people working at their job site said walking more than people not working, working in a hybrid mode, and working online. Our findings suggest that promoting strategies that increase physical activity during the pandemic is necessary to avoid health problems
ESG performance on the value of family firms: International evidence during Covid-19
Get PDFThe link between the financial success of family companies during COVID-19 and their environmental, social, and governance (ESG) performance is examined for the first time in this research. We have a natural setting in the COVID-19 era to see if the market rewards family-run firms that integrate social and environmental concerns into their goals during uncertain times. Since they can enhance their image and reputation, which the market values, these companies are likely to pursue broader social objectives, such as environmental improvement (socioemotional wealth perspective); alternatively, managers can act as stewards of the family’s interests by using these initiatives to increase the company’s value (stewardship perspective). However, it is also possible that in this type of companies economic interests prevail over social wellness (“amoral familism”). Therefore, family-owned firms could be reluctant to implement ESG practices unless they yield certain socioemotional benefits, including enhancing or maintaining their reputation in the public eye. In light of the above, we use an international display of the 500 biggest family firms in the world from 2015 to 2021. Taking into account an endogenous relationship between ESG performance and family business value, the study uses generalized moments to construct a dynamic panel (GMM). The primary conclusion is that there is a positive correlation between corporate valuation and ESG performance. Nonetheless, it has been noted that the performance of the companies is negatively impacted during the COVID-19 period. However, for firms with superior ESG performance, this negative impact did not exist over this period, supporting the idea that investors view better ESG performance as a prediction of future good stock performance. The results have a variety of implications. To begin with, this study adds to the body of knowledge on the environmentally friendly and sustainable expansion of family companies by providing recommendations for investors and businesses to better understand the influence of ESG on the profitability of family businesses. Furthermore, managers have to concentrate on enhancing the ESG performance of their organizations as it has the potential to increase value, draw in investments, encourage sustainability, control risks, affect earnings, and interact with the ownership structure. Additionally, managers need to consider how important it is to have a strong ESG performance in order to mitigate the negative effects of external crises like the COVID-19 epidemic. It’s crucial to remember that the precise impact might change based on the sector and other aspects unique to each company
Methodological challenges in indigenous language acquisition research: A methodological experience from Mapuzundun
Get PDFEl propósito del siguiente artículo es presentar una propuesta metodológica para investigar el desarrollo fonológico en niños y niñas de 18 a 42 meses de edad que están aprendiendo mapuzungun en dos áreas geográficas con una fuerte vitalidad lingüística, ubicadas en las regiones del Biobío (VIII) y La Araucanía (IX). Esto se lleva a cabo a través de la implementación de un estudio a lo largo del tiempo, convirtiéndose en la primera investigación sobre la adquisición fonológica del mapuzungun. La ejecución de esta metodología participativa y contextualizada en el proceso de investigación ha llevado a una reflexión constante por parte de las familias sobre su lengua y la importancia de transmitirla y enseñarla a sus hijos. Esta conciencia sociolingüística se hizo evidente en las conversaciones, reuniones y apoyos, y se observó cómo las familias se involucraron cada vez más en este proceso, especialmente aquellas que provienen de La Araucanía, donde la transmisión representa un desafío significativo.
Development of an asymmetric cellulose acetate-ionic liquid P6,6,6,14[PHOS] gel membrane for the perstraction of succinic acid from a model fermentation solution of yarrovia lipolytica
No full textThis study introduces a novel approach to separate succinic acid (SA) from fermentation mixtures using an asymmetric membrane based on the gelation of the ionic liquid [P6,6,6,14][PHOS] coated with two layers of cellulose acetate. The membrane was designed to explore the synergistic effect of polymer-ionic liquid interfaces according to the solution-diffusion theory. The gelation of the ionic liquid was achieved using 12-hydroxystearic acid at a concentration of 1.5%, allowing the use of ionic liquid gels as new materials for the generation of membranes. The perstraction performance of the membrane was evaluated over 5 h at two different temperatures (25◦C and 37◦C), with an initial feed solution concentration of 50 kg m− 3 for SA and glycerol and pure water as a receiving phase., Several flow rates and phase-volume ratios were studied anda mass transfer model based on the resistance-in-series theory was assessed to understand the behavior of each mass transfer stage considering the distribution in each interphase. Interestingly, optimal perstraction results were obtained at 37◦C, with an average transmembrane flux of 0.22 kg m-2h− 1 for SA, an extraction percentage of 43.1% for SA and 0.7% for glycerol, and a SA/glycerol selectivity of 54.98. Besides presenting a novel composite membrane, this study reports pioneering perstraction outcomes, highlighting its potential as an innovative SA separation strategy and structured new materials for selective extractions