Repositorio Académico de la Universidad Católica del Maule
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Bio-desulfurization of different vulcanized rubber blends: an ecofriendly approach for end-of-life tires waste pollution
No full textEnd-of-life tires (ELTs) are among the most complex pollutants to treat due to their cross-linked structure resulting from the vulcanization process. Rubber biodesulfurization is a process used to treat or remove sulfur from rubber materials using microorganisms. This is considered a critical step for altering the cross-linked structure of vulcanized rubber and a subsequent more effective biodegradation or biotransformation treatment. The present study evaluated the desulfurizing capabilities of the strains Gordonia desulfuricans and Rhodococcus erythropolis on different elastomer mixtures of known composition and complex crumb rubber substrates. The results showed significant increases in sulfate concentration in cultures of R. erythropolis, mainly in the presence of butyl rubber and styrene butadiene rubber, achieving concentrations up to 181.9 ± 6.5 mg/L, 8-fold higher compared to controls. Both strains were able to alter the crosslinking density of the different rubber mixtures, reaching a maximum decrease of 26.7 %. An initial pretreatment was performed with Rhodococcus rhodochrous, and the treated crumb rubber samples were subsequently cultivated with the desulfurizing strains. Interestingly, a 2.5-fold higher sulfate concentration was achieved, and the crosslinking density was reduced to 16.3 % after culture with G. desulfuricans, decreasing from 453.4 mmol/L to 379.3 mmol/L. Thermogravimetric analyses confirm this additive effect by achieving a higher decrease in the maximum decomposition temperatures of the rubber samples. Thus, a two-stage bioprocess with greater effectiveness in terms of biodesulfurization is presented
Effects of resistance training on executive functions of cognitively healthy older adults: a systematic review and meta-analysis protocol
No full textBackground/Objectives: Aging involves a series of changes in non-pathological age-related conditions, some of which impact the cognitive functioning of older adults. Executive functions are cognitive skills that are often affected in this process, although they have been shown to improve after physical exercise interventions. This protocol aims to describe the procedures that will be carried out in a systematic literature review, including a meta-analysis of the effects of resistance interventions on the main dimensions of executive function in cognitively healthy older adults compared to active or passive control groups. Methods: The PRISMA-P guidelines will be followed. Eligibility criteria will be organized based on the PICOS strategy (older adults with normal cognition ≥60 years; chronic resistance interventions ≥4 weeks; active or passive control group; direct measures of executive function). The PubMed, EBSCO, Scopus, and Web of Science databases will be used. The risk of bias and quality of evidence will be measured using RoB2 and GRADE, respectively. The DerSimonian–Laird random effects model will be used for the meta-analysis. The effect size will be calculated using Hedges’ g with a 95% confidence interval and p < 0.05 to indicate statistical significance. Discussion: The results of the proposed review may be useful to justify the design and implementation of treatment plans based on resistance training for the prevention and management of cognitive changes typical of aging among older adults. PROSPERO registry: CRD42024571127
Effects of exergaming on morphological variables, biochemical parameters, and blood pressure in children and adolescents with overweight/obesity: a systematic review with meta-analysis of randomized controlled trials
No full textObjectives: This systematic review with meta-analysis aimed to evaluate the available body of published peer-reviewed studies on the effects of exergaming (EXG) compared to the control group (CG) on morphological variables, biochemical parameters, and blood pressure in children and adolescents with overweight/obesity. Methods: A systematic literature search was conducted until September 2024 using five databases: PubMed, Medline, CINAHL Complete, Scopus, and Web of Science. PRISMA, TESTEX, RoB 2, and GRADE tools assessed the methodological quality and certainty of evidence. Hedge’s g effect sizes (ES) for morphological, biochemical, and blood pressure variables were calculated for meta-analyses. Using a random effects model, potential sources of heterogeneity were selected, including subgroup analyses (age) and single training factor analysis (program duration, training frequency). The protocol was registered in PROSPERO (code: CRD42024626992). Results: Out of 72 records, 6 randomized controlled trials with 191 children and adolescents with overweight/obesity were included. Nine meta-analyses were performed, showing significant decreases in body mass index (p = 0.04), waist circumference (p = 0.03), and systolic blood pressure (p = 0.007). However, no significant improvements were observed in diastolic blood pressure, body fat percentage, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, and glucose. Subgroup analyses showed significant decreases in total cholesterol (<15 years, ES = 0.56; p = 0.006), HDL-cholesterol (<15 years, ES = 0.51; p = 0.01), LDL-cholesterol (<15 years, ES = 0.63; p = 0.01), and triglycerides (<15 years, ES = 0.82; p = 0.000). In training duration, only significant decreases in total cholesterol (ES = 0.69; p = 0.02) were presented in favor of <12 weeks vs. ≥12 weeks. While in training frequency only significant decreases in triglycerides (ES = 0.70; p = 0.03) were reported in favor of ≥3 sessions per week vs. <3 sessions per week. Conclusions: EXG significantly decreases body mass index, waist circumference, and systolic blood pressure in children and adolescents with overweight/obesity
Relationships between domain changes and connections: an analysis from the perspective of mathematical work and teacher knowledge
No full textIntroduction: This study addresses the teaching task contextualized in the teaching of different topics of mathematic (functions, sequences, and Thales’ theorem). To do so, the characteristics of the mathematical work and specialized knowledge that the teacher shows during teaching are analyzed, considering as a frame of reference the complementarity between two theoretical perspectives (MWS and MTSK).
Methodology: The study is framed in the qualitative approach, based on an integrated multiple case study design, which allows analysis of the proposed mathematical performance (oral and/or written) of three teachers. Results: The analyses allow a deep examination of the development of mathematical work and demonstration of the relationships between the inter-conceptual connections as well as the domain changes that are expressed in teachers’ work. In general, the results reveal the privileging of algebraic treatments and emphasis on the procedural.
Conclusion: Contributions are identified in the perspective of the connection between theories in the context of the models involved
Síndrome de Joubert y anestesia
No full textEl síndrome de Joubert (SJ) es una rara enfermedad multisistémica caracterizada por malformaciones congénitas del tronco cerebral e hipoplasia del vermis cerebeloso, causando problemas respiratorios, hipotonía y retraso psicomotor. No tiene tratamiento curativo, lo que resalta la importancia del diagnóstico precoz y el seguimiento multidisciplinario para mejorar la calidad de vida del paciente. La anestesia en SJ es compleja debido a la susceptibilidad a la depresión respiratoria y las anomalías anatómicas que dificultan el manejo de la vía aérea. Se recomienda utilizar anestesia regional y monitorización adecuada, evitar opioides y relajantes musculares. Control posoperatorio de la respiración es crucial para evitar complicaciones. Se presenta el caso de un niño de 2 años con SJ, hidrocefalia y retraso psicomotor severo, que sufre traumatismo de labio superior secundario a caída de altura desde la cama y el manejo anestésico entregado
Alienígenas vs. avispas de papel: nuevos registros de avispas de Darwin parasitando avispas sociales en Brasil
No full textThis study reports new associations between Ichneumonidae and social wasps, contributing to the understanding of the ecological relationships between species and expanding current knowledge of their geographic distribution. We identified a total of five Ichneumonidae species associated with colonies of five species of social wasps. Additionally, we established new hosts and occurrence records for these Ichneumonidae species, highlighting the diversity of ecological interactions between parasitoids. These findings provide valuable information for understanding parasitoid-host dynamics and reinforce the importance of further research on the biogeography and ecological roles of Ichneumonidae
Temperature effects on the strength of a nanocrystalline refractory high entropy alloy
No full textRefractory High Entropy Alloys (RHEAs) are advanced materials suitable for high-temperature applications due to their remarkable properties, such as excellent strength, ductility, wear resistance, among others. In this study, the effect of temperature on the mechanical properties of the nanocrystalline bcc HfNbTaZr RHEA is explored under uniaxial loading using molecular dynamics simulations. Temperatures and grain sizes in the range of 100–1200 K and 5–17 nm are considered here. Our results showed that the highest yield strengths and flow stress were achieved in the 10–15 nm range for grain sizes, where the transition from Hall-Petch (HP) to the inverse Hall-Petch (iHP) effect was clearly observed at low temperatures, with a weaker grain size dependence in the HP regime at high temperatures. The MD results align extremely well with a scaling model for the elastic modulus as a function of temperature, and with a strength model which have been extensively employed to understand experimental results up to high temperatures, but the reference strain-rate has to be adjusted to take into account the large values for atomistic simulations. These models are typically based on relatively simple scenarios, like the motion of single straight dislocations, either edge or screw, and lack of dislocation junctions and twinning. Here, deformation includes both edge and screw dislocations, dislocation junctions, grain boundary plasticity, twinning, etc., but the general trend of smooth softening with temperature is observed despite the complex scenario. Some models assume that plasticity in RHEAs would be controlled by edge dislocations but, under the simulated conditions, there are contributions from both edge and screw dislocations. In addition, we quantify twin volume-fraction and find a transition from twin-dominated deformation to dislocation-dominated deformation as temperature increases, with twinning increasing for larger grains. Our results provide quantification of the mechanical properties and plasticity of a nanocrystalline bcc RHEA up to high temperatures, and the proposed adaptation of a strength model allows connection between typical experiments and high strain rate simulations
Analysis of fatty acid-derived lipids in critically ill patients after cardiac surgery yields novel pathophysiologically relevant mediators with possible relevance for systemic inflammatory reactions
No full textIntroduction: Critically ill patients suffer from a wide variety of clinical events, most of them leading to pro-inflammatory states such as sepsis or simply as consequence of major surgery. Many of these patients develop forms of acute kidney injury, heart or acute liver failure during intensive care. Lipid signaling is critically involved in triggering systemic inflammation processes, pain and vascular tone. We therefore hypothesized that fatty-acid-derived lipid mediators might be regulated during inflammatory stages and other clinical events in critically ill patients and might serve as potential biomarker candidates.
Methods and study design: Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we determined the levels of 53 lipid mediators in plasma from nine patients. These patients were hospitalized at Frankfurt University Hospital’s intensive care unit (ICU) after cardiac surgery. Inflammatory stages were illustrated over time using clinically established biomarkers such as interleukin-6 (IL-6) and leukocyte count. Normal range values of the lipids were obtained from healthy volunteers.
Results: Plasma levels clearly outside the normal range were observed for 22 of 53 lipid mediators, of which 13 were increased (including ceramides Cer (d18:0/18:0), Cer (d18:1/16:0), Cer (d18:1/18:1), glucosyl-ceramide GluCer (d18:1/24:1), lactosylceramide LacCer (d18:1/18:0), and LacCer (d18:1/24:1), 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), 11,12- and 14,15-DHET and 1- and 2-arachidonoyl glycerol (1-AG and 2-AG), Sphingosine SPH (d18:1) and 20-HETE. Furthermore, nine lipids were decreased (Cer (d18:1/24:0), LacCer (d18:1/16:0), LacCer (d18:1/24:0), sphingosine-1-phosphate S1P (d18:1), S1P (d18:0), the lysophosphatidic acids LPA (16:0), LPA (18:0), LPA (18:1) and 9-HODE. Among increased lipids, the remarkable changes in 1-AG, 2-AG, and to a lower extent of 6-keto-PGF1-alpha plasma levels showed a certain agreement with inflammatory phases. Furthermore, 6-keto-PGF1alpha had its peak shortly before initiation of continuous veno-venous hemodialysis (at least in 5 of the observed patients), 2-AG was elevated in all our nine patients during (right) heart failure in the context of either re-opening patient’s chest, implementation of veno-arterial ECMO or at least while significantly increasing the amount of catecholamines.
Discussion: In this pilot trial we identified several evaluated lipids in critically ill patients representing either potentially (patho-) physiologically relevant mediators of the pro-inflammatory processes and during heart failure or possible markers preceding veno-venous hemodialysis
Climatic stability and species turnover as potential drivers of latitudinal diversity gradients in Chilean wild bees
No full textThis study explores the latitudinal diversity gradient (LDG) of wild bees (Hymenoptera: Anthophila) in Chile, a region with diverse climates and geographic isolation. By examining species richness patterns, this research seeks to uncover the key factors influencing these patterns in Chilean bees.
We compiled and analysed occurrence records of wild bee species from five families, evaluating species richness across latitudinal gradients. To explain the LDG, we tested hypotheses such as Rapoport's effect, the mid-domain effect (MDE), source-sink dynamics, and the Climatic Variability Hypothesis. Additionally, we conducted cluster analyses and beta diversity assessments to identify distinct ecoregions and understand patterns of species turnover and nestedness along these gradients.
Our analysis revealed a mid-latitudinal peak in wild bee species richness around 34° S, consistent with the global bimodal latitudinal gradient for bees. The data did not support MDE predictions, implying that geometric constraints alone cannot explain these patterns. Instead, the positive correlation between latitudinal extent and latitude supports Rapoport's effect, indicating broader environmental tolerances at higher latitudes.
Beta diversity analyses showed that species turnover, not nestedness, drives diversity variation along latitudinal gradients, reflecting significant species replacement across latitudes due to changing environmental conditions. Cluster analyses identified distinct wild bee groups corresponding to Northern, Central, and Southern Chile ecoregions, reinforcing substantial shifts in species composition across latitudinal bands.
Our findings emphasise the importance of stable climates in supporting high bee species richness and broader environmental tolerances at higher latitudes. Understanding these patterns is vital for predicting biodiversity responses to climate change and guiding conservation strategies, especially in Chile's biodiversity hotspots with high species richness and endemism
University teaching practices and learning-oriented motivation: the mediating effect of basic psychological needs satisfaction
No full textDiversos estudios reconocen la importancia de la relación entre la motivación académica y el aprendizaje en el contexto universitario, lo que contrasta con el menor número de trabajos que abordan la influencia de las variables mediadoras. Esta investigación tuvo como objetivo evaluar el rol mediador de las Necesidades Psicológicas Básicas en la relación entre las prácticas realizadas por profesores universitarios percibidas por los estudiantes como motivadoras y la motivación orientada hacia el aprendizaje. En el estudio participaron 763 estudiantes de programas de salud y educación de diferentes universidades chilenas. Para evaluar el efecto mediador se utilizó la macro PROCESS para SPSS. Los resultados indican que la satisfacción de las necesidades psicológicas básicas media parcialmente el efecto de las prácticas docentes sobre el tipo de motivación orientada hacia el aprendizaje, lo que refuerza la idea de realizar una práctica docente situada, explícita y frecuente con acciones formativas motivadoras que fortalezcan la utilidad, la importancia y la autonomía. Estos hallazgos muestran la relevancia de estas prácticas docentes para generar motivación orientada hacia el aprendizaje, así como el papel de la Satisfacción de las Necesidades Psicológicas Básicas en esta relación