The goal of synthetic biology is to create artificial organisms. To achieve this it is essential to understand what life is. Metabolism-replacement systems, or (M, R)-systems, constitute a theory of life developed by Robert Rosen, characterized in the statement that organisms are closed to efficient causation, which means that they must themselves produce all the catalysts they need. This theory overlaps in part with other current theories, including autopoiesis, the chemoton, and autocatalytic sets, all of them invoking some idea of (...) closure. A simple model of an (M, R)-system has been implemented in the computer, and behaves in ways that may shed light on the requirements for a prebiotic self-organizing system. In addition to a trivial steady state in which nothing happens, it can establish a non-trivial steady state in which all intermediates have finite concentrations, with their rates of degradation balanced by their rates of synthesis. The system can be regenerated from the set of food components plus a single intermediate, and maintain itself in that state indefinitely, despite continuous degradation. At the very low compartment volumes that may have existed in prebiotic conditions, for example in cavities in minerals, or in micelles formed by simple amphiphiles, statistical fluctuations in the numbers of molecules need to be taken into account. With the stochastic approach there is no non-trivial steady state in strict mathematical terms, because the system will always collapse to the trivial state after sufficient time. However, the average time before collapse is so long for volumes greater than $10^{-19}\;{\textsc{l}}$ (much smaller than the volume of the order of $10^{-15}\;{\textsc{l}}$ for a typical bacterial cell) that for practical purposes the self-maintaining state of non-null concentrations becomes significant, recalling the situation of bistability that is observed in deterministic analysis. In turn, there exists a minimum size below which the self-organizing system cannot maintain itself on chemically relevant time scales. The value of the critical volume depends on the particular concentrations and rate constants assumed, but the principle could apply generally. (shrink)

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we provide brief summaries of debates with respect to (1) definitions (or theories) of life, what life is and how research should be conducted in the absence of an accepted theory (...) of life, (2) the distinctions between synthetic, historical, and universal projects in origins-of-life studies, issues with strategies for inferring the origins of life, such as (3) the nature of the first living entities (the “bottom up” approach) and (4) how to infer the nature of the last universal common ancestor (the “top down” approach), and (5) the status of origins of life as a science. Each of these debates influences the others. Although there are clusters of researchers that agree on some answers to these issues, each of these debates is still open. With respect to history, we outline several independent paths that have led to some of the approaches now prevalent in origins-of-life studies. These include one path from early views of life through the scientific revolutions brought about by Linnaeus (von Linn.), Wöhler, Miller, and others. In this approach, new theories, tools, and evidence guide new thoughts about the nature of life and its origin.We also describe another family of paths motivated by a” circularity” approach to life, which is guided by such thinkers as Maturana & Varela, Gánti, Rosen, and others. These views echo ideas developed by Kant and Aristotle, though they do so using modern science in ways that produce exciting avenues of investigation. By exploring the history of these ideas, we can see how many of the issues that currently interest us have been guided by the contexts in which the ideas were developed. The disciplinary backgrounds of each of these scholars has influenced the questions they sought to answer, the experiments they envisioned, and the kinds of data they collected. We conclude by encouraging scientists and scholars in the humanities and social sciences to explore ways in which they can interact to provide a deeper understanding of the conceptual assumptions, structure, and history of origins-of-life research. This may be useful to help frame future research agendas and bring awareness to the multifaceted issues facing this challenging scientific question. (shrink)

Se ha realizado una revisión sistemática siguiendo el protocolo PRISMA para caracterizar la producción científica de la didáctica de la higiene alimentaria en Educación Primaria. Se analizan indicadores bibliométricos y metodologías de investigación utilizadas. La búsqueda se realizó en la base de datos Web of Science. Solo 12 artículos cumplían con todos los criterios de inclusión. Hay escasas publicaciones sobre higiene alimentaria en la etapa, tratándose de estudios cualitativos, autoría conjunta y en su mayoría pertenecen al sector sanitario. Es necesario (...) aumentar las investigaciones especialmente en el ámbito educativo e introducir la higiene alimentaria en la formación del profesorado. (shrink)

Esta obra se concentra en cuatro temas cruciales de la formación de docentes, tanto antes como durante el servicio y en la enseñanza en diferentes áreas y niveles educativos. En primer lugar, se aborda el asunto de las creencias que los docentes tienen sobre el proceso educativo, las cuales parecen influir en la práctica profesional que estos desarrollan y, por lo tanto, deberían recibir la atención explícita de los procesos de formación de docentes que deseen promover prácticas específicas. El segundo (...) tema de la obra es la relación entre la formación de docentes y la política pública que la rige. En particular, se analizan las reformas curriculares implementadas por varias licenciaturas en universidades privadas colombianas, en respuesta a reformas a la normatividad sobre las condiciones de calidad que a las que deben ajustarse todas las licenciaturas del país. El tercer tema analizado es en qué medida los docentes en educación superior van más allá del dominio de su saber disciplinar atribuyendo importancia a la pedagogía, la didáctica y la práctica reflexiva en su propia práctica docente. Finalmente, se discuten aspectos de la formación de docentes relacionados con los procesos vividos y los retos encontrados por los docentes al entrar en la profesión, su socialización en la comunidad docente, sus identidades como maestros y su motivación para ser docentes. Vale la pena señalar que las contribuciones a este libro comparten el uso de metodologías cualitativas y presentan los resultados de historias de vida, entrevistas, observaciones, y análisis documentales, entre otros. (shrink)