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Additively manufactured 316L steel reinforced by multi-layer Ti3C2Tx for enhanced mechanical and bio-tribological performance
No full textImplant materials often suffer from wear, surface degradation, and poor biocompatibility, leading to reduced durability and compromised patient outcomes. Addressing these challenges requires the development of advanced biomaterials with enhanced mechanical strength and bio-tribological performance. In this context, we explore the incorporation of multi-layer Ti3C2Tx into a 316L metal matrix to enhance mechanical and biotribological properties for biomedical applications. Metal matrix composites (MMCs) with 1, 2, and 3 wt.-% Ti3C2Tx were fabricated using laser powder bed fusion (LPBF). Mechanical properties, including surface roughness and hardness, and the bio-tribological behavior were evaluated under dry and synovial body fluid (SBF)-lubricated conditions at 37 ◦C. Lower Ti3C2Tx concentrations yielded smoother surfaces, while higher concentrations increased roughness due to particle agglomeration and clustering. However, the resulting hardness improved especially for an addition of 3 wt.-% Ti3C2Tx. The 1 wt.-% Ti3C2Tx MMCs reduced wear by 31 and 19 % under dry and SBF conditions, respectively, while balls wear (counter-bodies) were reduced by 51 and 13%, respectively. These results highlight the potential of multi-layer Ti3C2Tx to improve the durability and performance of medical devices, demonstrating their promise as advanced biomaterials.FONDECYT; Folio: 122033
The CEO as an Influencer: The Case of Mauricio Russo and Casaideas (Chile)
No full textEsta investigación describe la manera en que Mauricio Russo, fallecido CEO del retailer chileno Casaideas, se convirtió en influenciador en medios sociales y logró crear vínculos emocionales entre su marca y las audiencias, que le permitieron sortear amenazas operacionales y comunicacionales de distinto tipo (p.e. los relativos a la pandemiadel Covid-19). Desde un enfoque cualitativo se analizaron posts de Russo en LinkedIn, y de otras personas en distintos medios sociales, para entender cómo se construyó el vínculo emocional entre Casaideas y el público. Se concluye que la marca personal del CEO se vinculó con la marca de la compañía, en particular gracias a su estrategia de relación con las redes sociales online, algo que hasta entonces no se había visto en Chile.This researchdescribes how Mauricio Russo, the late CEO of the Chilean retailer Casaideas, became an influencer on social media and managed to create emotional bonds between his brand and audiences. These connections allowed him to navigate various operational and communication threats (e.g., those related to the Covid-19 pandemic).The case is justified by the significance that Russo had in the Chilean businessand communicationlandscape. First, due to Casaideas’ positioning in the home improvement retail market, where it competes with major regional brands (Easy and Homecenter) as well as a global brand (Ikea). Second, because Russo played a key role in the company's corporate communication, serving not only as its face and primary voice but also exercising symbolic leadership at a national level in the fields of entrepreneurship and customer service excellence. Third, because after his passing—due to cancer—his legacy became evident among various stakeholders, highlighting the importance of his figure for both the company and the retail sector.In this regard, although the comparison may seem exaggerated, Russo was to Casaideas and Chile something akin to what Steve Jobs was to Apple or what Elon Musk has been to Tesla.The literature review focuses on two key areas. First, the increasing importance of the Chief Executive Officer in corporate communication management in recent years. Second, the branding management perspective known as ‘lovemarks,’ which characterizes brands that establish such a strong emotional bond with their stakeholders—e.g., consumers, employees, shareholders—that they are willing to support them even in adverse scenarios.This branding term coined by Roberts becomes relevant in this context, where brand communication strengthens and complements the CEO's role.Both perspectives support the research design.Using a case study methodology, the research first narrates the history of Casaideas to provide contextand highlight Russo’s significance. It then analyzes his trajectory as a CEO influencer by drawing on four documentary sources: his original LinkedIn posts from March 2020 to September 2023 (when he passed away); his comments on Casaideas’ posts; posts and comments from other users on X (formerly Twitter) related to Russo and his management during the Covid-19 pandemic; and four interviews that Russo gave to various media outlets.The analysis shows that Russo became a CEO influencer through a combination of a strategic discourse, which reflected his vision as an entrepreneur and business leader, and a community-oriented discourse, demonstrating awareness of the challenges faced by both his company and society. Two phenomena illustrate this duality well: the communication management of Casaideas and Russo during the Covid-19 pandemic and the potential crisis triggered by Ikea’s arrival in Chile.Additionally, the study examines the reactions of users and customers following the CEO’s death, which further highlight his legacy.The research concludes that the CEO’s personal brand became closely linked to the company’s brand, particularly through his social media engagement strategy—something unprecedented in Chile until then.The authors have no current or pastaffiliation with Casaideas or Mauricio Russo, and this research did not receive any funding of any kin
“Somos islas”: currículum oculto y deslegitimación escolar desde los discurso docentes en un colegio paricular pagado: análisis crítico sobre la violencia antiescuela
No full textTesis (Magíster en Educación mención Estudios Curriculares)--Pontificia Universidad Católica de Chile, 2025La violencia hacia profesores, profesoras e instituciones escolares se ha intensificado en el contexto chileno durante los últimos años. A partir de esto, este estudio de caso cualitativo examina la relación entre la violencia antiescuela y el currículum oculto a través de los discursos de docentes en un colegio particular pagado de Santiago de Chile. Se aplica Análisis Crítico del Discurso (ACD) a cinco entrevistas semiestructuradas. La investigación revela que los docentes suelen reproducir ideologías hegemónicas que contribuyen a la deslegitimación de la escuela como institución. Estos discursos construyen con frecuencia la figura de un “otro docente” como responsable de las deficiencias educativas, lo que oculta factores estructurales e ideológicos más profundos. Los hallazgos sugieren que estas narrativas internas no solo reflejan, sino que también refuerzan sentimientos antiescuela. Como respuesta, el estudio propone un plan de mejora colaborativo orientado a fomentar el apoyo entre colegas, restituir la legitimidad de la profesión docente y reestablecer la autoridad de la escuela mediante una cultura profesional más solidaria y colaborativa
Química para estudiantes de primer año de agronomía: Impacto de los apoyos remediales en el rendimiento académico
No full textTesis (Magíster en Educación mención Educación Superior)--Pontificia Universidad Católica de Chile, 2025Este Trabajo Final de Egreso problematiza las altas tasas de reprobación (40-50%) en el curso de Química, de primer año en la carrera de Agronomía de una universidad privada altamente selectiva. Los estudiantes que rinden un examen diagnóstico de nivelación para química obtienen un promedio de logro del 25%, lo que implica que quienes ingresan no cuentan con los conocimientos base requeridos por el curso. La hipótesis de este trabajo es que los apoyos académicos existentes no han sido eficaces porque la dificultad radica en la alta carga académica del curso, que no responde al perfil del estudiantado. Para esto, se utilizó una metodología mixta, y se dividió el análisis en 3 objetivos. El primero, con enfoque cuantitativo, analizó la correlación entre la asistencia a los apoyos y el promedio final del curso. El segundo, consistió en la realización de entrevistas a docentes del curso. Y, para el tercero, se realizaron 2 grupos focales para estudiantes de las cohortes 2023 y 2024, con el fin de conocer sus perspectivas del curso y de la eficacia de los apoyos. Estos dos últimos fueron diseñados y analizados en base a los principios orientadores del CDDoc UC (PUC, s.f.).Los resultados muestran que solo las tutorías de nivelación del 2024 tuvieron un efecto positivo, pero marginal, lo que concuerda con las apreciaciones del estudiantado al respecto. Docentes y estudiantes coinciden en que la relación docente-estudiante es positiva, pero la carga académica es elevada
A penalized estimation of the variogram and effective sample size
No full textThe variogram function plays a key role in modeling intrinsically stationary random fields, especially in spatial prediction using kriging equations. However, determining whether a computed variogram accurately fits the underlying dependence structure can be challenging. Current nonparametric estimators often fail to guarantee a conditionally negative definite function. In this paper, we propose a new valid variogram estimator, constructed as a linear combination of functions from a predefined class, ensuring it meets essential mathematical properties. A penalty coefficient is introduced to prevent overfitting, reducing spurious fluctuations in the estimated variogram. We also extend the concept of effective sample size (ESS), an important metric in spatial regression, to a nonparametric framework. Our ESS estimator is based on the reciprocal of the average correlation and is calculated using a plug-in approach, with the consistency of the estimator being demonstrated. The performance of these estimates is investigated through Monte Carlo simulations across various scenarios. Finally, we apply the methodology to rasterized forest images, illustrating both the strengths and limitations of the proposed approach
Contributions to the singular perturbation theory of infinite-dimensional coupled systems
No full textTesis (Doctor en Matemáticas)--Pontificia Universidad Católica de Chile, 2025Singular perturbation and separation of time scales methods have been used to study the stability and control design for coupled ODE systems with different time scales for many years. This important literature was motivated by the fact that systems with significantly different time scales appear in several applications, in which the constituents of a coupled system may model different physical phenomena taking place in different time scales. The singular perturbation method (SPM), roughly speaking, aims to decouple a full system into two approximated subsystems based on a suitable time-scale separation. This thesis addresses problems concerning the stability, Tikhonov's approximation, stabilization, and control of singularly perturbed coupled infinite-dimensional systems.ANI
New steatotic liver disease criteria diagnostic performance in an agricultural population in Chile
No full textIntroduction and Objectives: This study aims to assess the performance of Steatotic Liver Disease (SLD) criteria in identifying liver steatosis compared to the NAFLD and MAFLD definitions in an agricultural population in Chile. Patients and Methods: We performed a cross-sectional analysis on the MAUCO cohort, composed of 9,013 individuals aged 38 to 74. Health conditions, socio-demographics, anthropometrics, hepatic ultrasonography, blood pressure, and biological samples were obtained. Participants were classified as NAFLD, MAFLD, or any of the five SLD categories: Metabolic dysfunction-associated steatosis liver disease (MASLD), Metabolic and Alcohol-Associated Liver Disease (MetALD), Alcohol-Associated Liver Disease (ALD), Specific aetiologies, and Cryptogenic. The Framingham cardiovascular risk score and BARD liver fibrosis score were used to assess clinical relevance. Results: Liver steatosis was present in 4,082 participants (45%); SLD criteria captured an additional 176 individuals not classified under NAFLD and 103 not included under MAFLD definition. The main SLD subgroups were MASLD (95%), MetALD (1.9%) and ALD (1.3%). Individuals classified in the MetALD and ALD subgroups exhibited more severe liver steatosis and a higher cardiovascular risk. Notably, participants categorized under specific etiologies and cryptogenic subgroups were younger and had a higher risk for liver fibrosis. Conclusions: The study reveals that SLD offers a more inclusive classification to identify high-risk individuals in the Chilean population, capturing cases that could be missed by NAFLD or MAFLD definitions by using the same resources
Reformas en salud: análisis y propuestas para el diálogo
No full textA veinte años de la gran reforma que creó las Garantías Explícitas en Salud (GES), el sistema sanitario chileno vuelve a encarar un ciclo decisivo: mientras persiste el consenso sobre la necesidad de fortalecerlo, distintas visiones han trabado los cambios estructurales. Hoy las iniciativas en marcha —desde la eliminación del copago en la red pública y el reforzamiento de la Atención Primaria, hasta la Ley Corta de Isapres, la nueva Modalidad de Cobertura Complementaria de Fonasa, el Sistema de Acceso Priorizado y los proyectos encaminados a modernizar Fonasa, la red pública, el ISP, Cenabast y la Superintendencia de Salud— apuntan a responder a los desafíos de acceso, protección financiera y eficiencia que exhibe el modelo. Este documento ofrece una lectura técnica y pragmática de ese conjunto de propuestas, analiza su coherencia con el marco conceptual de cobertura universal en salud de la OMS y formula recomendaciones para lograr un sistema más integrado, equitativo y sostenible de cara a las próximas décadas
Advanced Simulation System for Orbitozygomatic Fracture Reconstruction: Multicenter Validation of a Novel Training and Objective Assessment Platform
No full textOrbitozygomatic fractures represent a complex surgical challenge. Given the urgent need for validated educational tools that surpass traditional learning models, this multicenter study developed and validated a novel synthetic advanced simulation model for the reconstruction of these fractures. The model integrates platinum-cured silicones and 3D-printed bony structures with prefabricated fractures, accurately replicating the anatomy and tactile properties of soft and hard tissues, including simulated herniation of orbital contents. To our knowledge, it is the only available synthetic model combining both tissue types for this training. Ten participants (faculty and residents) completed simulated procedures. Technical performance was assessed using a hand motion tracking system, the global OSATS (Objective Structured Assessment of Technical Skills) scale, and a task-specific error measurement (Specific Fault Measurement, SFM) scale. Statistically significant differences (p = 0.021) were observed in operative time and error count between novices and experts, confirming the model’s construct validity. Faculty completed the surgery in significantly less time (mean 18.16 min vs. 37.01 min for residents) and made fewer errors (mean 12.25 vs. 53.25). Face and content validity were strongly supported by participant surveys, with 100% stating they would use the simulator to practice before real surgery. A strong inverse correlation (r = –0.786, p = 0.021) between OSATS and SFM scores demonstrated concurrent validity. This model enables ethical, repeatable, and cost-effective training, supporting its implementation into surgical curricula to enhance competence and provide objective skill assessment in orbitozygomatic trauma surgery
Search and competition in the market for sick leaves
No full textTesis (Master Thesis in Economics)--Pontificia Universidad Católica de Chile, 2024This paper develops a market framework for sick leaves between physicians and patients, where patients imperfectly search for physicians based on their heterogenous quality and endogenous issuance leniency. This framework ratio- nalizes the effects of competition on sick leave issuance as well as the assortative matching between “dishonest” physicians and patients. Using data on sick leaves from Chile’s national insurer, a specification of this framework is estimated and counterfactual scenarios are run. We find that a 64% rise in the fine associated to sick leave issuance would reduce aggregate sick leaves in the market by 32%