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El objetivo de este estudio exploratorio es identificar las concepciones que muestran estudiantes universitarios de primer ano al enfrentarse a preguntas que implican resolver sistemas de ecuaciones lineales (SEL) de 3x2 con solucion vacia. El instrumento de recoleccion de datos fue una evaluacion diagnostica aplicada a 60 estudiantes que cursaban algebra lineal e iniciaban el estudio de SEL. Al analizar los datos recopilados sobre la solucion de los estudiantes de un SEL de 3x2 con solucion vacia, se identificaron tres concepciones: 1) el SEL de 3x2 no tiene solucion, 2) el SEL de 3x2 tiene tres soluciones (pues las rectas se interceptan en 3 puntos o hay 3 intercepciones) y 3) el SEL de 3x2 tiene solucion unica. Se concluye que estas concepciones erroneas permiten inferir que los estudiantes no comprenden el significado de la solucion de un SEL y, por esta razon, presentan inconvenientes para resolver correctamente un SEL presentado en forma grafica o analitica.

This study is part of a more extensive research project that addresses the understanding of the derivative concept in university students with prior instruction in differential calculus. In particular, we focus on the analysis of students’ responses to a sequence of tasks that require a high level of understanding of the concept, and complement this information with clinical interviews. APOS (Action-Process-Object-Schema) theory and the configuration of the derivative concept that is characterized by: mathematical elements, logical relations and the representation modes that students use to solve a task were used in the analysis of students’ responses. The results obtained suggest that thematizing the derivative schema is difficult to achieve. In addition, nuances were observed in responses given by those students who succeeded, indicating differences in the construction of relations between the successive derivatives of a function.

The aim of this work was to identify and characterize the levels of development of derivative schema. In order to do so, a questionnaire to 103 university students with previous instruction in Differential Calculus was applied. The questionnaire was composed of three tasks. For the identification of the levels of development of schema and their subsequent characterization, we consider the framework proposed by the APOS theory. In particular, this framework was operationalized through the establishment of 27 variables that allowed for the breakdown of the resolution protocols from the questionnaire into discrete elements. In this way, we obtained a vector associated with each of these variables. The identification of students assigned to each level of development of schema was carried out by a cluster analysis. Subsequently, we performed a statistical analysis of frequencies and implicative, with the 27 variables, which allowed to characterize the levels of development identified.

Resumen Este estudio analiza la importancia del tratamiento de puntos de no-derivabilidad en la tematización del esquema de derivada. Para ello, se consideró el marco propuesto por la teoría APOE, a través del uso y conexiones lógicas que los estudiantes universitarios establecen entre los elementos matemáticos y los modos de representación cuando resuelven tareas sobre derivada. Se utilizaron dos instrumentos: el primero fue un cuestionario conformado por tres tareas propuestas en distintos modos de representación, en cuya resolución era necesaria la utilización de los elementos matemáticos constitutivos del concepto de derivada; este instrumento fue aplicado a los 40 estudiantes participantes del estudio. El segundo instrumento correspondió a una entrevista clínica que se centró en el análisis de las respuestas de los estudiantes en relación con el tratamiento que realizan en los puntos de no-derivabilidad en derivadas sucesivas. Esta entrevista clínica se aplicó a 5 de los 9 estudiantes clasificados en el nivel de desarrollo Trans-derivada. Los resultados del análisis constatan que la coherencia del esquema es fundamental para identificar un esquema tematizado. Además, se observó el importante papel desempeñado por el análisis de los puntos de no-derivabilidad en la conexión y el tránsito entre derivadas de diferentes órdenes, especialmente desde el modo de representación gráfico, lo cual puede ser un factor que favorece la tematización del esquema de derivada. Abstract This study analyzes the importance of the treating non-derivability points in addressing the derivative schema. To do this, we have considered the framework proposed by APOS theory, through the use and logical connections that university students established between mathematical elements and representation modes when solving tasks on derivative concept. To achieve the aim, we devised two instruments: the first was a questionnaire consisting of three tasks proposed in different representation modes, in whose resolution the use of mathematical constituent elements of the concept of derivative was necessary, this instrument was applied to 40 students that participated in the study. The second instrument corresponded to a clinical interview focused on the analysis of student answers regarding the treatment performed in non-derivability points in successive derivatives. This clinical interview was applied to 5 of the 9 students classified in the level of development Trans-derivative. The results of analysis corroborate that the coherence of the schema is fundamental to identify a addressed schema, in addition, they show the important role played by the analysis of the non-derivability points in the connection and transit between derivatives of different orders, especially from the graphic representation mode, which favors addressing the derivative schema.

Background The measurement of psychosocial risk among workers is becoming increasingly important. Aim To adapt, validate and standardize a questionnaire to measure psychosocial risks in the workplace. Material and methods The Spanish version of the Copenhagen Psychosocial Questionnaire was adapted and evaluated. Its contents were first validated with a panel of experts. Afterwards a semantic adaptation of the questionnaires was carried out applying it to a pilot sample. Finally, it was applied to 1,557 workers (65% men). Results A preliminary questionnaire containing 97 questions was constructed. A good item-test correlation was found, the factorial structure was similar to the original questionnaire and it had a good internal consistency, convergent validity with the Goldberg Health Questionnaire and test-retest correlation. Ranges for the different dimensions and sub-dimensions of psychosocial risk were calculated by tertiles. Conclusions The resulting questionnaire is useful for measuring psychosocial risk factors at work, with good psychometric properties.

espanolIntroduccion: El trastorno organico de personalidad (TOP) post traumatismo encefalocraneano (TEC) suele desestimarse por ausencia evidenciable de lesiones cerebrales y alteracion en psicometria habitual (WAIS). Objetivo: Estudio exploratorio de 9 casos de TOP post TEC. Pacientes y metodos: Se analizan 9 casos de TOP post TEC no diagnosticados previamente. Resultados: Los pacientes no presentaron alteraciones de neuroimagenes (TAC), aunque si algunas pruebas psicometricas alteradas, y un cambio consistente y dramatico en sus cogniciones, conductas y afectos, pero no recibieron diagnostico de TOP. Discusion: los equipos medicos parecen considerar mas la indemnidad de las neuroimagenes que la clinica o las pruebas neuropsicologicas, y tienden a desestimar el diagnostico de TOP. Conclusion: El diagnostico de TOP debe considerarse en casos de TEC leve cuando lo sugiera la clinica. EnglishIntroduction: Organic Personality Disorder (OPD) post traumatic brain injury (TBI) is often dismissed due to lack of clear brain damage and alteration in usual psychometrics (WAIS). Objective: An exploratory study of 9 cases of post TBI OPD. Patients and methods: We analyzed 9 previously undiagnosed cases of post TBI OPD. Results: The patients had no neuroimaging abnormalities (TAC), but some altered psychometric tests, and consistent and dramatic changes in their cognitions, behaviors and emotions, but were not diagnosed with OPD. Discussion: medical teams seem to consider more the indemnity of neuroimaging than clinical evidence or neuropsychological testing, and tend to dismiss the diagnosis of TOP. Conclusion: The diagnosis of TOP should be considered in cases of mild TBI when they suggest the clinic.

The measurement of psychosocial risk among workers is becoming increasingly important.To adapt, validate and standardize a questionnaire to measure psychosocial risks in the workplace.The Spanish version of the Copenhagen Psychosocial Questionnaire was adapted and evaluated. Its contents were first validated with a panel of experts. Afterwards a semantic adaptation of the questionnaires was carried out applying it to a pilot sample. Finally, it was applied to 1,557 workers (65% men).A preliminary questionnaire containing 97 questions was constructed. A good item-test correlation was found, the factorial structure was similar to the original questionnaire and it had a good internal consistency, convergent validity with the Goldberg Health Questionnaire and test-retest correlation. Ranges for the different dimensions and sub-dimensions of psychosocial risk were calculated by tertiles.The resulting questionnaire is useful for measuring psychosocial risk factors at work, with good psychometric properties.

The study of the effects of bariatric surgery on quality of life in patients of different socioeconomic levels (SEL) is worthwhile.To study quality of life (QoL), eating behavior, depressive symptoms and sexuality in patients subjected to a gastric bypass (GBP) more than 1 year before.The sample was composed of 33 GPB patients (19 high SEL and 14 low SEL), and 27 non-operated women (18 high SEL and 9 low SEL) of similar weight and age, as controls. Assessment included medical history anthropometry radiological densitometry. Eating behavior was assessed using the three factor eating questionnaire, quality of life using SF-36 and the Bariatric Analysis of Reporting Outcome System (BAROS) depressive symptoms were assessed using the Beck scale version II and sexual behavior using the female sexual function index (FSFI).QoL was lower in operated patients from low SEL, especially when compared to high SEL control women. Operated patients had a predominantly restrictive pattern of eating behavior Eating behavior disorders were detected in 5 of 33 operated patients versus 4 of 27 controls (p =ns). Sexual function was absent or dysfunctional in 22 operated versus 8 controls (p =0,02). No significant differences were observed for depressive symptoms, between operated patients and controls.In the long term, QoL of bariatric patients, especially those from low SEL, is inferior to control women and Chilean general population. Operated patients have restrictive eating patterns and lower sexual satisfaction indexes. Frequency of depressive symptoms was high both in bariatric and control women.

Background: The study of the effects of bariatic surgery on quality of life in patients of different socioeconomic levels (SEL) is worthwhile. Aim: To study quality of life (QoL), eating behaviour, depressive symptoms and sexuality in patients subjected to a gastric bypass (GBP) more than 1 year before. Material and methods: The sample was composed of 33 GPB patients (19 high SEL and 14 low SEL), and 27 non-operated women (18 high SEL and 9 low SEL) of similar weight and age, as controls. Assessment included medical history, anthropometry, radiological densitometry. Eating behaviour was assessed using the three factor eating questionnaire, quality of life using SF-36 and the Bariatric Analysis of Reporting Outcome System (BAROS) depressive symptoms were assessed using the Beck scale version II and sexual behaviour using the female sexual function index (FSFI). Results: QoL was lower in operated patients from low SEL, especially when compared to high SEL control women. Operated patients had a predominantly restrictive pattern of eating behavior. Eating behavior disorders were detected in 5 of 33 operated patients versus 4 of 27 controls (p =ns). Sexual function was absent or dysfunctional in 22 operated versus 8 controls (p =0,02). No significant differences were observed for depressive symptoms, between operated patients and controls. Conclusions: In the long term, QoL of bariatric patients, especially those from low SEL, is inferior to control women and Chilean general population. Operated patients have restrictive eating patterns and lower sexual satisfaction indexes. Frequency of depressive symptoms was high both in bariatric and control women (Rev Med Chile 2009; 137: 625-33). (Key words: Bariatric surgery; Quality of life; Socioeconomic factors)

Este estudio tiene por objetivo determinar si el tamaño de la familia, el orden de nacimiento y el espacio temporal entre hermanos tienen efecto sobre los logros futuros de los individuos. En orden a abordar el problema en cuestión, se analizaron datos obtenidos de la Encuesta deProtección Social 2002, que por primera vez pone a disposición información adecuada para este tipo de estudios en Chile. La metodología usada es la propuesta en Behrman (1986), Kessler (1991) y además se incorpora una nueva variable al análisis: el espacio temporal promedio que separa los nacimientos en cada familia. Primero se indaga en las teorías de distintas áreas de investigación que hacen esperar la existencia de los efectos aquí planteados. No solamente teorías económicas sino también algunas de orden biológico, psicológico y sociológico son en última instancia ordenadas por un modelo microeconómico. Luego en el análisis empírico se utiliza como medida de logro los años de educación. Los resultados sugieren la existencia en Chile de una relación negativa entre el tamaño de la familia y los logros de los individuos, así como un efecto del orden de nacimiento en que se ven favorecidos los hijos que en alguna etapa de sus vidas gozan de la exclusividad del tiempo de los padres, entre otros recursos fijos al interior de la familia. El espacio temporal entre hermanos no influye sobre los logros de manera robusta. A la luz de los resultados se puede sostener que la hipótesis de la dilución de recursos al interior de la familia, que plantea la existencia de un trade off entre calidad y cantidad de hijos, caracteriza la realidad de las familias chilenas actualmente; lo que invita a poner nuevo énfasis en las políticas orientadas a mejorar la planificación familiar, sobre todo en familias de escasos recursos.

Since its rediscovery in 1965 by Cooley and Tukey1, the fast Fourier transform (FFT) has become one of the most widely used computational tools in science and engineering. The term FFT, initially associated to the Cooley-Tukey FFT for sequences of period N = 2 k , has become after the efforts of many researchers over the years, the generic name of a whole family of efficient DFT numerical methods. Each member in the FFT family is specialized in computing the DFT of a particular class of periodic sequences. This period is also referred as the transform’s length and the DFT (FFT) of length N is usually called N-point DFT (FFT). The first member in this family is actually an extension of Cooley and Tukey’s idea to N-point DFTs where N is factorizable. These N-point FFTs compute the N-point DFT through nested sequences of DFTs whose lengths are the factors of N. The Good-Thomas algorithm2 improves over the extended Cooley-Tukey FFT for highly composite transform’s length. Rader’s algorithm3, on its turn, is designed for computing prime length DFTs. These algorithms, all members of the family of traditional FFTs, reduce the N-point DFT arithmetic complexity from O(N 2 ) to O(N log N).