Tenacidad en estudiantes universitarios chilenos: Un estudio inicial de su estructura y red nomológica / Grit in Chilean university students: An initial study of its structure and nomological network

En los últimos años ha surgido un creciente interés por indagar el rol de las habilidades no cognitivas, como la tenacidad, en el desempeño académico. Si bien la investigación sobre tenacidad no ha generado aún conclusiones definitivas, debe considerarse que ella no ha incluido a poblaciones latinoamericanas. Ante este panorama, este estudio inicial se propuso examinar en estudiantes universitarios chilenos de pedagogía en matemáticas: (1) la estructura interna de la tenacidad y (2) su posición en una red nomológica integrada por desempeño académico, sexo, edad y años en el programa educativo. Un total de 153 estudiantes de la Universidad de La Frontera, una institución estatal chilena, respondió la Escala Corta de Tenacidad y un cuestionario sociodemográfico. Análisis factoriales exploratorios revelaron que la tenacidad adquiere una configuración unidimensional que posee una adecuada consistencia interna. Además, adoptando una relación no lineal semejante a una curva hiperbólica, niveles altos de tenacidad se vincularon con desempeño académico alto, en tanto que niveles bajos o moderados se vincularon con desempeño bajo. Finalmente, la tenacidad apareció asociada con sexo (las mujeres mostraron más tenacidad que los hombres) y, en una relación directa, con los años en el programa. Tenacidad no correlacionó significativamente con edad. Este conjunto de hallazgos, que discrepan mayormente de aquellos reportados en la literatura, son discutidos principalmente en términos del dominio disciplinar previo de los participantes y/o de la dificultad del programa educativo. Se proponen explicaciones para estos hallazgos a fin de que sean evaluadas en estudios futuros, empleando un enfoque confirmatorio.

Traditionally, academic performance has been linked to intelligence and some other student´s cognitive abilities. However, in recent 4 years we have witnessed a growing interest in expanding this view by investigating the role that other non-cognitive skills, such as tenacity, may play in academic achievement. Grit can conceptually be conceived as perseverance and passion aimed at achieving long-term goals. A review of the literature shows that grit does not appear to be configured, as some authors claim, as a hierarchical structure with a general second-order construct and two first-order facets (perseverance of effort and consistency of interest). The literature also points out that grit is only a modest predictor of academic performance and that it presents a slightly positive correlation with age and a very weak one with sex and the students' number of years in an academic program. While research on grit has not yet generated any definitive conclusions, it must be considered that it has not included Latin American populations. Given this scenario, this initial study aimed to examine in mathematics teacher Chilean students (1) the internal structure of grit and (2) their position in a nomological network integrated by academic achievement, sex, age and years enrolled in the program. Participants consisted in the total population (n = 153) of students enrolled in a mathematics teacher program at Universidad de La Frontera, a public institution located in the Central-South area from Chile. The program was selected because it presents a high level of difficulty to its students and because it includes highly formalized tasks, as part of its disciplinary courses. Participants responded the Short Grit Scale (Grit-S) and a demographic questionnaire. In this study, Grit-Swas previously translated and adapted into Spanish from the original English version. Grit-Scontains eight items intended to measure the two facets of grit. Exploratory factorial analysis revealed that, after excluding two items due to low factor loadings (items No. 1 and 2), grit presented a one-dimensional configuration, with an adequate internal consistency (ordinal Alpha: .80). A positive linear correlation, although marginally significant, was obtained between grit and academic achievement, r(143)= .12, p =.069, d = .24. However, a planned contrast revealed that a nonlinear relationship, similar to a hyperbolic curve, better explains the link between these two variables. Specifically, this analysis showed that students in the upper grit quintile obtained a significantly higher grade point average than the combined grade point average of the remaining grit quintiles, t(138) =1.87, p = .032, d = .32. This result suggests that academic achievement remains reduced when grit level is low or moderate and only increases when grit level is high. A multiple regression analysis indicated that sex, age and number of years in the program account for 12.6% of grit variance, F(3, 149) = 7.15, p < .001, d = .76. Sex significantly contributed to the prediction (β =.198, p = .011, d = .38) with women, (M = 3.77,dt = .61) reporting higher levels of grit than men (M = 3.53, dt = .69). Whereas age did not significantly contribute to the prediction (β =.102, p = .206), the number of years in the program showed a significant direct association with grit (β = .261, p = .001, d = .60. Due to the originality of these findings, most differing from those reported in the literature, this study offers tentative explanations that future research could use to formulate and empirically test new hypotheses using, hopefully, a confirmatory approach. These possible explanations mainly refer to the participants' previous level of mathematic mastery and/or the level of difficulty demanded by the educational program.

Biomecánica de las fracturas por stress / Biomechanical features of stress fractures

Se define como estrés (stress) tanto la fuerza que una carga externa ejerce sobre un cuerpo sólido como la fuerza reactiva que acompaña a la primera (Ley de Newton), por unidad de área imaginaria transversal a su dirección. Las cargas internas reactivas inducen deformaciones proporcionales del cuerpo. La resistencia del cuerpo a deformarse se llama rigidez. La deformación puede resquebrajar el cuerpo y, eventualmente, producir una fractura por confluencia de trazos. La resistencia del cuerpo a separarse en fragmentos por esa causa se llama tenacidad. La resistencia del cuerpo a la fractura es proporcional al stress que puede soportar sin separarse en fragmentos por deformación (no hay fractura sin deformación y sin stress previo). El stress máximo que un cuerpo puede soportar sin fracturarse resulta de una combinación de ambas propiedades: rigidez y tenacidad, cada una con distintos determinantes biológicos. Una o varias deformaciones del cuerpo pueden provocarle resquebrajaduras sin fracturarlo. La acumulación de resquebrajaduras determina la "fatiga" del material constitutivo del cuerpo, que reduce su rigidez, tenacidad y resistencia a la fractura para la próxima ocasión ("fragilidad por fatiga"). En el caso de los huesos, en general, los términos stress y fatiga tienen las connotaciones amplias referidas, respecto de todas las fracturas posibles. La fatiga predispone a fracturas a cargas bajas, que se denominan (correctamente) "fracturas por fatiga" y también (incorrectamente) "fracturas por stress", para distinguirlas de las que ocurren corrientemente, sin resquebrajaduras previas al trauma, que se denominan (incorrectamente) "fracturas por fragilidad, o por insuficiencia". En realidad, todas las fracturas se producen por stress y por fragilidad o insuficiencia (en conjunto); pero la distinción grosera entre fracturas "por fatiga, o por stress", por un lado, y "por fragilidad" o "por insuficiencia", por otro, aceptando las amplias connotaciones referidas antes, tiene valor en la práctica clínica. Este artículo intenta explicar esas particularidades biomecánicas y describir las distintas condiciones que predisponen a las fracturas "por fatiga o por stress" en la clínica, distinguiéndolas de las fracturas "por fragilidad o por insuficiencia" (manteniendo estas denominaciones) y detallando las características de interés directo para su diagnóstico y tratamiento. (AU)

The term "stress" expresses the force exerted by an external load on a solid body and the accompanying, opposed force (Newton's Law), expressed per unit of an imaginary area perpendicular to the loading direction. The internal loads generated this way deform (strain) proportionally the body's structure. The resistance of the body to strain expresses its stiffness. Critical strain magnitudes may induce micro-fractures (microdamage), the confluence of which may fracture the body. The body's resistance to separation into fragments determines its toughness. Hence, the body's resistance to fracture is proportional to the stress the body can support (or give back) while it is not fractured by the loadinduced strain (no stress, no strain -> no fracture). Therefore, the maximal stress the body can stand prior to fracture is determined by a combination of both, its stiffness and its toughness; and each of those properties is differently determined biologically. One or more deformations of the body may induce some microdamage but not a fracture. Microdamage accumulation determines the fatigue of the material constitutive of the body and reduces body's toughness, leading to a "fatigue-induced fragility". In case of bones, in general, both stress and fatigue have the referred, wide connotations, regarding any kind of fractures. In particular, bone fatigue predisposes to low-stress fractures, which are named (correctly) "fatigue fractures" and also misnamed "stress fractures", to distinguish them from the current fractures that occur without any excess of microdamage, that are named (wrongly) "fragility" or "insufficiency" fractures. In fact, all fractures result from all stress and fragility or insufficiency as a whole; however, the gross distinction between "fatigue or stress fractures", on one side, and "fragility or insufficiency fractures", on the other, accepting the wide connotations of the corresponding terminology, is relevant to clinical practice. This article aims to explain the above biomechanical features and describe the different instances that predispose to "fatigue or stress fractures" in clinical practice, as a different entity from "insufficiency or fragility fractures" (maintaining this nomenclature), and describe their relevant features to their diagnosis and therapy. (AU)

FRAGILIDAD Y COMPORTAMIENTO MECÁNICO DEL ESMALTE DENTAL / BRITLENESS AND MECHANICAL BEHAVIOR OF DENTAL ENAMEL

El esmalte dental es el tejido duro más mineralizado del cuerpo humano. En este trabajo se estudiaron las propiedades mecánicas fundamentales de este tejido para terceros molares de pacientes jóvenes colombianos. Se establecieron la dureza, la tenacidad a la fractura aparente y la fragilidad del esmalte dental en función de la profundidad a partir de la superficie oclusal mediante técnicas de medición de microindentación. Se encontró que las mediciones de dureza son altamente dependientes de la carga utilizada, hallándose que para valores de carga pequeños las huellas alcanzan a representar la dureza de un solo prisma de hidroxiapatita, mientras que para valores altos de carga las huellas abarcan un número de prismas suficientes para estimar la dureza general del esmalte. En términos generales los valores de las propiedades medidas son semejantes a los encontrados en estudios realizados en pacientes jóvenes norteamericanos, evidenciando que estas propiedades del esmalte son independientes de las características raciales o étnicas para pacientes jóvenes, lo cual no es necesariamente extensible al comportamiento de estos tejidos en pacientes mayores.

Dental enamel is one of the hardest and most mineralized tissues of the human body. This work studied the main mechanical properties of this hard tissue for third molars obtained from young Colombian patients. The hardness, apparent fracture toughness and brittleness of enamel were measured as a function of distance from the occlusal surface to the Dental Enamel Junction (DEJ) by means of microndentation techniques. It was found that the hardness measurements are highly dependent on the indentation load, with high values of hardness found when low loads were used. This behavior is explained by the size of the indentations which approached the size of single hydroxyapatite prisms for low load values, while for high load values the size of the indents covered several prisms. Overall, the mechanical properties measured on the enamel from young Colombians are close to the properties reported in the literature for young North American patients. Whether these similarities among young patients persist for older patients deserves further investigation.

Neurología de la resiliencia y desastres / Neurology of resilience and disasters

Con el propósito de explicar las generalidades sobre la neurología de la resiliencia frente a los desastres que pueden afectar a las comunidades, se describen los aspectos psíquicos vinculados a los grandes contratiempos que pueden dañar a cualquier colectividad. Desde una mirada a las necesidades humanas según el grado de perentoriedad, se realiza una aproximación a los desastres naturales y se exponen las bases neurales, estructurales y neurobioquímicas que subyacen en los mecanismos de la imprescindible tenacidad cognitiva, nombrada como resiliencia humana individual y colectiva. Queda revisada la evolución del concepto, las manifestaciones clínicas más importantes y la conducta a seguir muy consustancial al nivel de atención primaria de salud

With the objective of explaining the general aspects of neurology of resilience in disasters that may affect the communities, this paper describes the psychical aspects related to big setbacks that may affect any community. Taking the human needs into account according to their degree of urgency, the paper approached to natural disasters and disclosed the neural, structural and neurochemical underlying bases in the mechanisms of the indispensable cognitive tenacity called individual and collective human resilience. The evolution of this concept, the most important clinical manifestations and the behaviour to be adopted at the primary health care level was reviewed