Reaction-diffusion equations: a chemical application

Obtenemos soluciones exactas para un sistema de reacción-difusión asociado a una reacción cubica autocatalítica entre dos sustancias químicas según la regla con tasa . Para obtener dichas soluciones empleamos una transformación de onda

Effects of cavitation in common-rail diesel nozzles on the mixing process

[EN] A study to experimentally analyze the effect of cavitation on the mixing process in diesel nozzles was carried out. The mixing process was studied through the spray cone angle. It was characterized in two different scenarios: with the liquid length (nearly realistic conditions, that is, evaporative but non-reactive spray) and the heat release fraction (fully realistic conditions, that is, evaporative and reactive spray). In both studied scenarios, the increase in spray cone angle caused by the cavitation phenomenon, which leads to a better mixing process, has been confirmed. Nevertheless, when the variations of the effective injection velocity and the spray cone angle obtained by comparing a cylindrical nozzle (i.e. a nozzle that promotes the cavitation phenomenon) with a conical nozzle (i.e. a nozzle that inhibits this phenomenon) were analyzed together, it was found that, for the cases studied here, the mixing process worsens with the cylindrical nozzle.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors thank the FPU program of the Spanish Ministry of Education for supporting the PhD studies of Oscar A de la Garza (grant: AP2008-01913) and also thank the PSA Peugeot-Citroen, National Council of Science and Technology (CONACYT) of the Mexican Government (project: CB-239943) and the Royal Academy of Engineering, United Kingdom (project: NRCP/1415/238) for supporting this research.López, JJ.; De La Garza De Leon, O.; De La Morena, J.; Martínez Martínez, S. (2017). Effects of cavitation in common-rail diesel nozzles on the mixing process. International Journal of Engine Research. 18(10):1017-1034. https://doi.org/10.1177/1468087417697759S10171034181

Taquicardia de complejos anchos. Un ejercicio académico

ResumenLas taticardias de complejos anchos (TCA) constituyen un problema diagnóstico de importancia, tanto para el médico general como para el especialista en el área, debido a que pueden corresponder a patologías cuyo origen puede ser supraventicular o ventricular .[Rueda OL, Martínez WJ. Taquicardia de complejos anchos. Un ejercicio académico. MedUNAB 2004; 7:185-91].Palabras clave: Taquicardia de complejos anchos, electrocardiografía, Diagnótico diferencial

Single-lead electrocardiogram quality assessment in the context of paroxysmal atrial fibrillation through phase space plots

[EN] Current wearable electrocardiogram (ECG) recording systems have great potential to revolutionize early diagnosis of paroxysmal atrial fibrillation (AF). They are able to continuously acquire an ECG signal for long weeks and then increase the probability of detecting first brief, intermittent signs of the arrhythmia. However, the recorded signal is often broadly corrupted by noise and artifacts, and accurate assessment of its quality to avoid automated misdiagnosis and false alarms of AF is still an unsolved challenge. In this context, the present work is pioneer in exploring the usefulness of transforming the single-lead ECG signal into two common phase space (PS) representations, such as the Poincare plot and the first order difference graph, for evaluation of its quality. Several machine and deep learning models fed with features and images derived from these PS portraits reported a better performance than well-known previous methods, even when they were trained and validated on two separate databases. Indeed, in binary classification of high- and low-quality ECG excerpts, the generated PS-based algorithms reported a discriminant power greater than 85%, misclassifying less than 20% of high-quality AF episodes and non -normal rhythms as noisy excerpts. Moreover, because both PS reconstructions do not require any mathematical transformation, these algorithms also spent much less time in classifying each ECG excerpt in validation and testing stages than previous methods. As a consequence, ECG transformation to both PS portraits enables novel, simple, effective, and computational low-cost techniques, based both on machine and deep learning classifiers, for ECG quality assessment.This research has received financial support from Daiichi Sankyo SLU and from public grants PID2021-00X128525-IV0, PID2021-12380 4OB-I00, and TED2021-130935B-I00 of the Spanish Government 10.13039/501100011033 jointly with the European Regional Development Fund (EU) , SBPLY/21/180501/000186 from Junta de Comunidades de Castilla-La Mancha, Spain, and AICO/2021/286 from Generalitat Valenciana.Huerta, A.; Martínez-Rodrigo, A.; Bertomeu-González, V.; Ayo-Martin, O.; Rieta, JJ.; Alcaraz, R. (2024). Single-lead electrocardiogram quality assessment in the context of paroxysmal atrial fibrillation through phase space plots. Biomedical Signal Processing and Control. 91. https://doi.org/10.1016/j.bspc.2023.1059209

Investigation of laser annealing mechanisms in thin film coatings by photothermal microscopy

We study the evolution of the absorptance of amorphous metal oxide thin films when exposed to intense CW laser radiation measured using a photothermal microscope. The evolution of the absorptance is characterized by a nonexponential decay. Different models that incorporate linear and nonlinear absorption, free carrier absorption, and defect diffusion are used to fit the results, with constraints imposed on the fit parameters to scale with power and intensity. The model that best fits is that two types of interband defects are passivated independently, one by a one-photon process and the other one by a two-photon process.Fil: Zaldivar Escola, Facundo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mingolo, Nélida. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Martínez, Oscar E.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Rocca, Jorge J.. State University of Colorado - Fort Collins; Estados UnidosFil: Menoni, Carmen S.. State University of Colorado - Fort Collins; Estados Unido

Estudio fisicoquímico funcional de los aislados proteicos en semillas de maracuya (Passiflora edulis f).

En este trabajo se presentan las propiedades funcionales de la harina y aislados proteicos de semillas de maracuyá (Passiflora edulis f.). Los aislados proteicos fueron obtenidos de la harina desengrasada por solubilización alcalina a diferentes concentraciones de NaCl seguidas de precipitación isoeléctrica, con un contenido proteico cercano al 90 %. Se evaluaron las distintas propiedades funcionales como; capacidad de retención de agua (CRA), absorción de grasa (CRL), capacidad de hinchamiento (CH), densidad aparente (DA), actividad emulsificantes (IAE) en el rango de pH 2-10 y capacidad espumante (CE). El incremento de la concentración de NaCl contribuye a exponer más grupos hidrófilos en la superficie, lo que explica la alta CRA y baja CRL, las propiedades de emulsión fueron dependientes del pH y concentración de NaCl. Una alta capacidad espumante y estabilidad de la espuma formada fue observada para los aislados obtenidos

Sustainable Orientation of Management Capability and Innovative Performance: The Mediating Effect of Knowledge Management

The literature suggests that innovation allows organizations to reach a desirable level of sustainability. There is evidence to support the role of knowledge management (KM) as well as management capability (MC) in producing a sustainable approach at organizations. Furthermore, organizations commonly achieve sustainable practices through corporate social responsibility (CSR). In particular, the health sector is increasingly implementing CSR strategies, although with a narrow understanding of the factors to success. Hence, trends lead to asymmetric growth between organizations. This study aims to examine the mediating role of KM in the relationship between MC and innovative performance (IP) in 331 Health Provider Institutions (HPIs). The research reflective model was assessed through Partial Least Squares Structural Equation Modeling (PLS-SEM). According to the results, MC has a positive effect on IP, MC has a positive effect on KM, and KM has a positive effect on IP. Likewise, KM significantly mediates the relationship between MC and IP. Our findings support the importance of KM in addressing MCs in HPIs as it enables innovative practices to address CSR goals to achieve a sustainable impact. Moreover, this study contributes by expanding KM to contexts that are not usually studied, such as health in a South American country

Importance of the reach of the social networks of CIGEFI-UCR: A study of the data according to the publications made between 1979-2015

Desde 1979, el Centro de Investigaciones Geofísicas (CIGEFI) de la Universidad de Costa Rica (UCR) ha evolucionado constantemente hasta convertirse en un referente regional de la Geofísica. Esto ha sido facilitado por diversos actores, investigadores, y colaboradores, tanto propios como de otras afiliaciones. El objetivo de este trabajo fue utilizar las publicaciones elaboradas por el CIGEFI para describir y visualizar las redes sociales de este proceso para el período 1979-2015, mostrando los actores involucrados, las ego-redes más influyentes, la evolución de las redes en tres períodos (1979-1990, 1991-2002 y 2003-2015) para mayor facilidad de procesamiento de la información y las afiliaciones. Se calcularon las medidas de centralidad de grado, cercanía, lejanía y mediación, y se realizaron cinco depuraciones de cada red; para ello, se suprimieron de una a cinco relaciones y actores en cada una. Se concluyó que el trabajo en red fue fundamental para el CIGEFI, pues permitió la integración de un equipo y un abordaje entre distintas disciplinas, clave en los procesos de investigación y toma de decisiones.Since 1979, the Center for Geophysical Research (CIGEFI) of the University of Costa Rica (UCR) has constantly evolved to become a regional reference in geophysics. This has been facilitated by different actors, researchers, and collaborators, both their own and those of other affiliations. The objective of this work was to use the publications elaborated by CIGEFI to describe and visualize the social networks of this process between 1979-2015, showing the actors involved, the most influential ego-networks, the evolution of the networks in three periods (1979-1990, 1991-2002 and 2003-2015), for easier processing of information, and affiliations. The centrality measures of degree, proximity, distance and mediation were calculated, and five network debuggings of each network were carried out; in each one, one to five relationships and actors in each were eliminated. It was concluded that networking was fundamental for CIGEFI, since it allowed the integration of a team and an approach between different disciplines, key in the research and decision making processes.Universidad de Costa Rica/[805-A4-906]/UCR/Costa RicaUniversidad de Costa Rica/[805-B7-286]/UCR/Costa RicaUniversidad de Costa Rica/[805-B6-143]/UCR/Costa RicaUniversidad de Costa Rica/[805-B7-507]/UCR/Costa RicaUniversidad de Costa Rica/[805-A1-715]/UCR/Costa RicaUniversidad de Costa Rica/[805-B0-810]/UCR/Costa RicaConsejo Nacional para Investigaciones Científicas y Tecnológicas/[]/CONICIT/Costa RicaMinisterio de Ciencia, Tecnología y Telecomunicaciones/[]/MICITT/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

Extending Graph (Discrete) Derivative Descriptors to N-Tuple Atom-Relations

In the present manuscript, an extension of the previously defined Graph Derivative Indices (GDIs) is discussed. To achieve this objective, the concept of a hypermatrix, conceived from the calculation of the frequencies of triple and quadruple atom relations in a set of connected sub-graphs, is introduced. This set of subgraphs is generated following a predefined criterion, known as the event (S), being in this particular case the connectivity among atoms. The triple and quadruple relations frequency matrices serve as a basis for the computation of triple and quadruple discrete derivative indices, respectively. The GDIs are implemented in a computational program denominated DIVATI (acronym for DIscrete DeriVAtive Type Indices), a module of TOMOCOMD-CARDD program. Shannon‟s entropy-based variability analysis demonstrates that the GDIs show major variability than others indices used in QSAR/QSPR researches. In addition, it can be appreciated when the indices are extended over n-elements from the graph, its quality increases, principally when they are used in a combined way. QSPR modeling of the physicochemical properties Log P and Log K of the 2-furylethylenes derivatives reveals that the GDIs obtained using the tripleand quadruple matrix approaches yield superior performance to the duplex matrix approach. Moreover, the statistical parameters for models obtained with the GDI method are superior to those reported in the literature by using other methods. It can therefore be suggested that the GDI method, seem to be a promissory tool to reckon on in QSAR/QSPR studies, virtual screening of compound datasets and similarity/dissimilarity evaluations

Effect of La3+/Sr2+ ordering on the magnetic properties of La2/3Sr1/3MnO3 by first principles calculations

In this work, using DFT + U formalism, we investigate the effect of order-disorder in the A-site occupation byLa3+and Sr2+on the stability of the ferromagnetic order in La2/3Sr1/3MnO3with−Rc3symmetry. To date, adetailed theoretical discussion of such phenomenon, using a combination of different representations of theelectronic structure, is still missing in the Literature. We employed structural models consisting of 120 atomsupercells constructed according to the precise stoichiometry of the compound. Two configurations, describingrandomized and ordered occupation of the La3+/Sr2+ions, were evaluated. We demonstrate that the ferro-magnetic arrangement of La2/3Sr1/3MnO3with randomly distributed La3+and Sr2+ions is more stable. In suchconfiguration wefind that the Mn3+and Mn4+ions are not distinguished, favoring the double-exchange me-chanism, enhanced by the higher degree of covalence in the MneO bonds near the Fermi level between thespin-upMn-egorbitals and the O-porbitals