Existence of minimal and maximal solutions to first--order differential equations with state--dependent deviated arguments

We prove some new results on existence of solutions to first--order ordinary differential equations with deviating arguments. Delay differential equations are included in our general framework, which even allows deviations to depend on the unknown solutions. Our existence results lean on new definitions of lower and upper solutions introduced in this paper, and we show with an example that similar results with the classical definitions are false. We also introduce an example showing that the problems considered need not have the least (or the greatest) solution between given lower and upper solutions, but we can prove that they do have minimal and maximal solutions in the usual set--theoretic sense. Sufficient conditions for the existence of lower and upper solutions, with some examples of application, are provided too

Kierkegaard y el matrimonio

Indexación: Web of Science; Scielo.Resumen Este artículo considera dos perspectivas de Kierkegaard en relación con el matrimonio, una en favor y otra en contra del mismo. El texto se centra en los principales argumentos del filósofo danés en torno a los motivos para elegir el estado conyugal (entre otros, la procreación de los hijos y la evasión de la soledad) como a las razones que induzcan a alguien a permanecer definitivamente soltero (por ejemplo, si tiene una vocación religiosa o si no quiere perder su libertad). El artículo presenta también otras dos ideas importantes del pensador escandinavo sobre la institución matrimonial: su origen divino y la relación entre el amor y el vínculo nupcial

Validation of a performance model on entrepreneurship based on self-efficacy, personal goal orientation and environment goal orientation using Structural Equation Modeling

Master's thesis in International hotel and tourism managementThree are the main contributions that I pretend to provide through this research. First, I will combine four theoretical constructs that, to my knowledge, have not been worked through this way before. I mean that this research is attempting to validate and estimate the existing relationships between Self-efficacy, Perceived Personal Goal Orientation, Perceived Environment Goal Orientation and Perceived Personal Performance. There is much evidence in the literature that has explored the connections between self-efficacy and the goal theory as I will show later. Those works used to focus on explaining how setting goals improves performance in a varied set of fields. Goals are “what an individual is trying to accomplish; it is the object or aim of an action“ (E. Locke, Saari, L., Shaw, K., and Latham, G., 1981). There is some agreement that setting goals increase performance in two ways: first, there is a direct relation between setting goals and performance, and, second, goals and performance relationship is mediated by self-efficacy: greater performance increase self-perceptions of competence, as a consequence, individuals would set even higher goals (Edwin A. Locke & Latham, 1990). However, for this project, my focus is on the analysis of goal orientation. For the sake of a better understanding of this project, I have to explain -before going deeper- what is the difference between “setting goals” and “goal orientation”. The former refers to the individual’s actions oriented to establish –formally or informally- future goals related to upcoming events. For example, when a university student is getting ready for final exams might set (as a goals) to obtain A or B grades only. The “goal orientation”, which is the central concept involved in this project, refers to something a bit different: if individuals perceive themselves or their environment as performance oriented (PGO): focus on comparisons to others (i.e., I want the best grade of my class) - or as task oriented (TGO): focus on comparisons to one’s self (i.e., I want to improve my last score in this class). [...

Assessment of linear anionic polyacrylamide application to irrigation canals for seepage control

South- central area of Chile area has a Mediterranean climate and high crop water requirements. Irrigation water is distributed through long channels which have low water conveyance efficiency (Ec), difficult to improve by conventional techniques. The objective of this study was to quantify Ec and to evaluate the use of Linear Anionic Polyacrylamide (LA-PAM) to reduce seepage losses. The study was carried out in south-central area of Chile, (UTM Coordinate N 5745000; E 725000 m, datum is WGS-84, zone 18S) in 250 km of channels whose flow varied between 0.12 and 24.6 m3 s–1. Water users indicated channel reaches with potential low Ec, which were selected for LA-PAM application. In 11 reaches between 0.51 and 3 km in length, 1 to 3 LAPAM applications were performed at rates of 10 kg ha–1, considering the wet perimeter area as basis of calculation. Thirty-one LA-PAM applications were performed over a 30.5 km length. Most of the channels were large enough to allow motorboat moving against the current to carry-out LA-PAM application. Water flow was measured (StreamPro ADCP) at both ends of selected reaches before and after granular LAPAM application. Weekly measurements were made to quantify treatment effect duration. Water turbidity and temperature were measured. Channels showed variable Ec from 87% to 94%. Two reaches showed 6% water gains. In more than 80% cases LA-PAM effect was positive, achieving loss reductions of 15 to 760 L s–1. In other cases LA-PAM had a negative effect since it mainly affected water entry into the channel. It was determined that field conditions referred by users as indicators of Ec are not always correct and vary in time according to climatic conditions. Ec was estimated and it was possible to reduce seepage through LA-PAM applications. This allow increasing irrigation security in critical periods, especially under drought conditions

Prevalencia de fracturas maxilofaciales y traumatimos dentoalveolares atendidas en el Servicio de Cirugia Maxilofacial del Hospital Regional de Talca. Julio 2002 - Junio 2007 Chile

93 p.Introducción: Los traumatismos son una constante en la vida del hombre a través de las generaciones, por lo que son un problema grave de la salud pública tanto a nivel mundial, como en la realidad local. Dentro de los traumatismos en general, tenemos las fracturas maxilofaciales y los traumatismos dentoalveolares que son tratados dentro de este estudio, que por la alta prevalencia que presentan, merecen que se aborde la problemática que hay tras ellos. Objetivo: Determinar la prevalencia de fracturas maxilofaciales y traumatismos dentoalveolares (TDA) en pacientes atendidos en el servicio de cirugía maxilofacial del Hospital Regional de Talca (HRT) desde el 1 de Julio de 2002 al 30 de Junio de 2007. Materiales y métodos: Estudio de prevalencia en pacientes atendidos en el servicio de cirugía maxilofacial del Hospital de Talca que presentaban fracturas maxilofaciales y TDA, en el periodo comprendido entre Julio 2002 a Junio 2007. Resultados: Se obtuvo información de un total de 190 pacientes entre 1 y 84 años de edad con una media de 32.62 años, de ellos 159 pacientes presentaron fracturas maxilofaciales, encontrándose un total de 226 fracturas maxilofaciales y 31 pacientes con traumatismos dentoalveolares (TDA) más 6 pacientes que presentaban TDA concomitante a las fracturas maxilofaciales, correspondiendo a un total de 263 patologías individualizadas Las mayores prevalencias corresponden a fractura mandibular 31.6% (n = 83), fractura complejo cigomático-maxilar 25.1% (n = 66) y Traumatismo dentoalveolar 14.1% (n = 37). Discusión: La fractura más prevalente fue la mandibular con 31.6%, en segundo lugar está el complejo cigomático-maxilar con un 25.1%, coincidiendo con otros estudios hechos en otros países. La tendencia de tratamiento es a favor de la tratamiento abierto con un 64.8% versus un tratamiento cerrado 23.3%. Conclusión: La fractura más común es la mandibular. La mayor causa de fracturas maxilofaciales y traumatismos dentoalveolares es la agresión. Los hombres entre 20-39 son los más afectados

Factores neuropsicológicos que predicen la funcionalidad en adultos mayores

133 p.Este estudio tuvo como propósito fundamental investigar las características del envejecimiento cognitivo en distintos grupos de adultos mayores. Se evaluaron 44 sujetos, distribuidos en 3 grupos: 14 sujetos con escolaridad básica, 16 con escolaridad media y 14 con escolaridad alta, con el fin de estudiar las variables cognitivas a través de la aplicación de una batería neuropsicológica. Los resultados de los análisis indicaron una fuerte asociación entre funcionalidad y memoria de trabajo, observándose que a medida que aumenta el rendimiento en memoria de trabajo, disminuye el nivel de deterioro funcional en adultos mayores. En relación a los factores que predicen la funcionalidad e inteligencia en los adultos mayores, se encontró que las funciones ejecutivas actúan como predictor de la funcionalidad en este grupo. Los hallazgos encontrados en esta investigación entregaron evidencia de que las funciones ejecutivas y la memoria episódica son efectivamente los factores que mejor predicen la funcionalidad y la inteligencia en los adultos mayores, denotándose como potenciales y útiles medidas de evaluación en personas de este segmento con deterioro. Palabras claves: envejecimiento, memoria, inteligencia inteligencia fluida,funcionalidad./ABSTRACT:The purpose of this study was to investigate the characteristics of cognitive aging in elderly, equally distributed according to their level of instruction. 44 subjects were evaluated in order to identify their cognitive variables through the application of a neuropsychological battery; they were distributed in three groups:14 subjects with elementary education completed, 16 subjects with high education completed, and 14 subjects with tertiary education completed. The results showed a positive and significant correlation between functionality and working memory,that is, a lower performance in working memory is related with a greater functional deterioration. In relation to the factors that predict functionality in older people, it was possible to conclude that executive functions can be predictors of functionality in this group. Evidence showed that executive functions and episodic memory are predictors of functionality and intelligence in the elderly, becoming potential and useful evaluation measures in the assessment of this group.Key words: aging, memory, fluent intelligence, functionin