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1
artículo
Publicado 2024
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In this work, the well-possednes of a predator-prey model with reaction-diffusion will be studied where the Allee effect in prey reproduction will be included and predation dynamics will be considered a functional response dependent on the species (prey and predator) with the incorporation of the refuge in the dam. In this way, the existence, uniqueness and positivity of the system's solutions as the main result will be guaranteed.
2
artículo
Publicado 2017
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El artículo tiene como objetivo analizar los factores determinantes de la dinámica de la inversión productiva privada en el Perú, utilizando una serie cronológica para el período 1970-2010. Busca identificar, cuantificar y contrastar las hipótesis de incidencia del nivel de actividad, de las restricciones financieras, de la política tributaria, de la inversión pública y del "clima de inversión", en la acumulación de capital productivo en la economía peruana. El contraste de las sub hipótesis, se efectuó a partir de la técnica econométrica de Vectores Autorregresivos Estructurales (SVAR, Structural Vector Autorregresive, por sus siglas en inglés). Siguiendo la metodología de Sims (1980), se encontró evidencia empírica de que el PBI y la FBKF están relacionadas positivamente, cumpliéndose el principio acelerador; de igual forma, la tasa real de interés incidió nega...
3
artículo
Publicado 2021
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In this research, a mathematical model to determine the concentration of concrete carbonation is investigated using several numerical schemes which provide the distribution of carbonation in a concrete region. This model considers an Arrhenius-type relation which implies a non-uniform diffusion coefficient for a reaction- diffusion problem in the model. To perform the computations of the model investigated, the finitedifferences and finite-volume methods are employed which are implemented in the mathematical software GNU-Octave and the finite-volume software OpenFOAM respectively.
4
artículo
Publicado 2023
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Purpose: The purpose of this paper is to determine the impact of corporate investments in corporate social responsibility (CSR), measured by the environmental, social and government (ESG) rating, on the market valuation of a firm's stocks and to explain the regional differences in the degree of this influence. Design/methodology/approach: The empirical study uses linear and non-linear panel regression models for a panel sample of 951 firms listed in Asia, North America and Europe operating in innovative industries. Findings: The CSR score was found to be significant in terms of stock excess return on the regional level. However, this finding cannot be extrapolated to the global scale. ESG rating is priced by the European and North American markets negatively, while in the Asian market, it is positive. This penalty (negative influence) is greater than the reward for one point increase in ...
5
tesis de grado
Las reacciones químicas autocatalíticas dan lugar a fenómenos complejos como las reacciones oscilatorias y la formación de patrones químicos. Experimentos en las reacciones de Belousov-Zhabotinsky y de iodato-ácido arsenioso (entre otras) exhiben frentes de reacción que separan reactivos de productos de la reacción. La propagación de los frentes es debida al efecto conjunto de la reacción y la difusión molecular. La mayoría de los estudios teóricos en estos sistemas se basan en modelos deterministas. Sin embargo, al realizar experimentos, fluctuaciones aleatorias estarán presentes. El objetivo de este trabajo es realizar un análisis numérico de los efectos del ruido externo en frentes de reacción-difusión. Nos enfocamos en un sistema c ́ubico de reacción-difusión con dos especies químicas que poseen distintos coeficientes de difusión. Al propagarse en dominios bidi...
6
artículo
Publicado 2005
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The technological progress achieved, especially regarding to computerized control systems, are facilitating the chemical engineer a better understanding and control of a larger number of variables, restrictions and specifications that are involved in a determinate process, making them more efficient and allowing to obtainhigher performances, without compromising the product's quality and the production levels that are required. The purpose of the control system suggested is to maintain the desired temperature value for a chemical reaction in order to obtain the best conversion as possible, in presence of disturbances that occur while the process is taking place, and are associated with the flow and concentrations of the reactants and also withthe flow and temperature of the saturated heating steam. From the mathematical model presented in this article and the knowledge of other elements ...
7
artículo
Publicado 2007
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Light absorption spectra were used to estímate gold particles growing kinetics following a gold salt (HAuCl4) reduction by sulfite in aqueous solution. Due this process is extremely fast, e.g. part1cles reach 150nm s1ze in less a second, a special equipment denorninated Stopped Flow Reactor (AFR) was used. Light spectra was modeled using Mie theory for monodisperse particles with1n 30-250nm range size, and tor minor sizes experimental spectra of commercial colloids were used, due to uncertainly in dielectric constant for these sizes.Three different approaches were proposed to estimate the gold particles size distribution evolution, and experimental intensity and shape of spectra were used to validate the computation. The most simply approach considers the assumption that particles are compact spheres and monodisperse, following model of LaMer. A second approach is based on growth model ...
8
artículo
Publicado 2007
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Light absorption spectra were used to estímate gold particles growing kinetics following a gold salt (HAuCl4) reduction by sulfite in aqueous solution. Due this process is extremely fast, e.g. part1cles reach 150nm s1ze in less a second, a special equipment denorninated Stopped Flow Reactor (AFR) was used. Light spectra was modeled using Mie theory for monodisperse particles with1n 30-250nm range size, and tor minor sizes experimental spectra of commercial colloids were used, due to uncertainly in dielectric constant for these sizes.Three different approaches were proposed to estimate the gold particles size distribution evolution, and experimental intensity and shape of spectra were used to validate the computation. The most simply approach considers the assumption that particles are compact spheres and monodisperse, following model of LaMer. A second approach is based on growth model ...
9
tesis doctoral
Publicado 2021
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Descargue en el texto completo en el repositorio institucional de la Universidade Federal de Santa Catarina: https://repositorio.ufsc.br/handle/123456789/231074
10
artículo
Publicado 2023
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Objective: To determine the factors associated with hyperemesis gravidarum and acute stress reaction in pregnant women with hyperemesis gravidarum hospitalized at the National Maternal Perinatal Institute during 2021. Materials and Methods: This research corresponds to an analytical, observational, case-control study, where the medical records of pregnant patients hospitalized for hyperemesis gravidarum attended by the psychology service who presented an acute stress reaction meeting the inclusion and exclusion criteria were collected. An analysis of frequencies and percentages of the different variables and a multivariate analysis were performed to find the significant factors (p<0.05) and the calculation of the Odds Ratio (OR) with a confidence level of 95%; this model was evaluated using multiple logistic regression. Results: A relationship was found between pregnancy planning (p&l...
11
artículo
Publicado 2023
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Objective: To determine the factors associated with hyperemesis gravidarum and acute stress reaction in pregnant women with hyperemesis gravidarum hospitalized at the National Maternal Perinatal Institute during 2021. Materials and Methods: This research corresponds to an analytical, observational, case-control study, where the medical records of pregnant patients hospitalized for hyperemesis gravidarum attended by the psychology service who presented an acute stress reaction meeting the inclusion and exclusion criteria were collected. An analysis of frequencies and percentages of the different variables and a multivariate analysis were performed to find the significant factors (p<0.05) and the calculation of the Odds Ratio (OR) with a confidence level of 95%; this model was evaluated using multiple logistic regression. Results: A relationship was found between pregnancy planning (p&l...
12
artículo
Publicado 2022
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Objetivo: estudio sistemático de incremento de los niveles de transaminasas hepáticas inducidos por tocilizumab (TCZ) en pacientes con infección por SARS-CoV-2. Material y métodos: Se realizaron búsquedas en PubMed, EMBASE y Google Scholar, de estudios publicados entre enero 2020 y agosto 2021. Se incluyeron estudios que reportaban datos con niveles de transaminasas hepáticas (aspartato-aminotransferasa o AST y alanino- aminotransferasa o ALT) en pacientes infección por SARS-CoV-2 en tratamiento con TCZ, ya sea en estudios de casos y controles o cuando se median dichos niveles antes y después de terapia en un mismo paciente. La calidad de los artículos fue evaluada de acuerdo con la escala Newcastle Ottawa (NOS). Se extrajeron datos sobre el diseño del estudio, país, número de pacientes, edad y sexo. Se aplicó un modelo de efectos aleatorios para la construcción del diagram...
13
artículo
Publicado 2021
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The basic characteristics of the MAC (Meaning and Attentional Components) model about boredom according to Westgate (2018) are presented. Its usefulness for the work of the psychologist. The possibility to apply it to any context. What is its theoretical foundation and basic research. Its links with some approaches and interventions in other areas of psychology. What future research can be facilitated with the model as a reference. Finally, it is used to analyze a collective reaction of citizens as a public expression of protest
14
artículo
Publicado 2021
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The basic characteristics of the MAC (Meaning and Attentional Components) model about boredom according to Westgate (2018) are presented. Its usefulness for the work of the psychologist. The possibility to apply it to any context. What is its theoretical foundation and basic research. Its links with some approaches and interventions in other areas of psychology. What future research can be facilitated with the model as a reference. Finally, it is used to analyze a collective reaction of citizens as a public expression of protest
15
artículo
Publicado 2003
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In the present work the revision, deduction and application of mathematical models in the quantification of the reaction kinetics of leaching processes of national sulphided minerals in chemical systems is made. The interaction between the mineral particles and the leaching solution is controlled by three possible mechanisms: by chemical reaction, by diffusion through the porous bed and by mass transfer; Each mechanism has its own mathematical modeling and parametric conditions. Experimental runs of leaching of gold and copper minerals are presented, in which their kinetic control equations of the most relevant variables are shown. Other empirical models are also shown that are used to elucidate the phenomenology of the leaching of mineral species, call chalcopyrite, sphalerite and galena.
16
artículo
Publicado 2003
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In the present work the revision, deduction and application of mathematical models in the quantification of the reaction kinetics of leaching processes of national sulphided minerals in chemical systems is made. The interaction between the mineral particles and the leaching solution is controlled by three possible mechanisms: by chemical reaction, by diffusion through the porous bed and by mass transfer; Each mechanism has its own mathematical modeling and parametric conditions. Experimental runs of leaching of gold and copper minerals are presented, in which their kinetic control equations of the most relevant variables are shown. Other empirical models are also shown that are used to elucidate the phenomenology of the leaching of mineral species, call chalcopyrite, sphalerite and galena.
17
artículo
Publicado 2019
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The aim of this study was to evaluate the alteration of the cellular components of the peritoneal lavage and to characterize the cicatricial remodelling, at the macro and microscopic level, produced by the experimental use of bovine pericardium xenograft (XPB) not treated as a lining of the end to end-jejunal terminal anastomosis in a canine model. Nine canines between 4 and 6 years of age, 15-30 kg of weight, and both sexes were randomly distributed in three experimental groups (A, B and C for a second celiotomy at 5, 10 and 30 days post-surgery) of three animals each, to which an untreated XPB was placed as a lining of the jejunal enterectomy. The results of the analysis of the cellular components of the peritoneal fluid showed a significant increase in lymphocytes, macrophages and eosinophils 30 days after the surgery and to a lesser extent 10 and 5 days after the intervention. In the...
18
artículo
Publicado 2019
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The aim of this study was to evaluate the alteration of the cellular components of the peritoneal lavage and to characterize the cicatricial remodelling, at the macro and microscopic level, produced by the experimental use of bovine pericardium xenograft (XPB) not treated as a lining of the end to end-jejunal terminal anastomosis in a canine model. Nine canines between 4 and 6 years of age, 15-30 kg of weight, and both sexes were randomly distributed in three experimental groups (A, B and C for a second celiotomy at 5, 10 and 30 days post-surgery) of three animals each, to which an untreated XPB was placed as a lining of the jejunal enterectomy. The results of the analysis of the cellular components of the peritoneal fluid showed a significant increase in lymphocytes, macrophages and eosinophils 30 days after the surgery and to a lesser extent 10 and 5 days after the intervention. In the...
19
artículo
Publicado 2019
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In the present article, a mathematical model for the b- immobilized fructofuranosidase was constructed considering the partition equilibrium between the liquid phase and the particle, diffusion and reaction within the particle. The kinetic constants were estimated by fitting the kinetic equations with the experimental data of the fructosyl-stevioside experiments using suspended enzyme. The other constants were estimated by fitting the mathematical model with experimental data of partition equilibrium coefficient, and fructosyl-stevioside synthesis using immobilized enzyme. The model could describe the fructosyl-stevioside formation under several conditions of initial concentration of substrate and total enzyme in the system.
20
artículo
Publicado 2016
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The present study has as aim demonstrate that the high existing levels of environmental noise in the main tenance work shops, can affect the health of the exposed workers in different ways. Nowadays the professional deafnesses admit that they are more for the effects of the labor noise on the persons (effects happened by the reaction of stress, interference with the communication, interference with the mental and psychomotor activities, subjective in convenience). In particular, the exhibition to sonorous high levels can cause a momentary loss of the auditory capacity (temporary displacement of the auditory threshold). We also know that a sound of great intensity can produce a break of the tympanic membrane; this traumatic effect has been observed for sounds by levels superior to 150 decibels (for example, in persons exposed to explosions or shots of fire guns). However, the most habitua...
