Vol. 60 No. 1 Jan-Jun (2014): Revista Mexicana de Física E
Published:
2014-01-01
Artículos
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Alan Turing's chemical theory of phyllotaxis
Abstract:Alan Turing's seminal 1952 work on morphogenesis \cite{Turing} is widely known and recognised in the field of mathematical biology. Less known is his work on the problem of phyllotaxis, which was never published at his time but is included in Turing's collected works \cite{Saunders}. It consists on three parts: the first is a detailed mathematical description of the arrangements of leaves on the stem of plants; the second is an application of the reaction-diffusion equation to the problem, and the third part is a solution of these equation for the case of spherical symmetry. It is the purpose of this work to present Turing's results contained in the second part in a comprehensive and detailed way. This is motivated by the fact that these researches have remained obscure and ill-understood. In particular, we focus on the morphogen equations for an assembly of cells since this discrete case may be useful in many circumstances where the continuum limit is not adequate or applicable.⬇️ Scroll down to see the full summary -
Bidimensional dynamic maps in optical resonators
Abstract:In this article an introduction to the dynamical behavior of a beam within a ring phase-conjugated optical resonator is presented and modeled using two dimensional iterative maps. Three well known iterative maps are described: Duffing, Tinkerbell and Hénon, and are applied to the description of optical resonators. It is explicitly shown how the difference equations of these maps can be used to describe the dynamic behavior of what we call Tinkerbell, Duffing and Hénon beams i.e. beams that behave according to these maps. The matrix of a map generating device are found in terms of the specific map parameters, the state variables and the resonator parameters for each of the three named maps.⬇️ Scroll down to see the full summary -
Primeras mediciones precisas de la gravedad hechas en México
Abstract:La determinación del valor de la aceleración de la gravedad local ($g_l$), resulta de importancia en problemas como el de la medición del aplanamiento del esferoide terrestre, de ahí que a lo largo del tiempo se hayan hecho esfuerzos serios por determinarlo con precisión en muy diferentes puntos del planeta. En este trabajo se muestra que en el último tercio del siglo XIX, ingenieros mexicanos se interesaron en medir lo más exactactamente posible ese valor en nuestro país, particularmente en el centro de la nación. Se discuten los resultados que obtuvieron.⬇️ Scroll down to see the full summary -
A model of oscillator with variable mass
Abstract:We discuss the general form of Newton's second law for variable mass systems. We then derive the equation of motion of one-dimensional oscillator with time-varying mass. The obtained equation of motion is then analytically solved and the solutions are represented by means of Hypergeometric functions. The work is addressed to physics class at undergraduate level.⬇️ Scroll down to see the full summary -
Ondas solitarias no lineales: una introducción a los solitones ópticos espaciales
Abstract:The basic theory of spatial optical solitons is reviewed, focusing on fundamental bright solitons. The Physics of solitons is illustrated with two programs developed in MATLAB. One of these programs Petvia\_Mex, calculates the profile of fundamental solitons corresponding to the generalized nonlinear Schrödinger equation, while the other program SSF\_Mex, simulates the paraxial propagation of optic beams in non-linear media. Using both codes, various phenomena of spatial optical solitons are discussed to stimulate the interest of the reader into soliton theory and Nonlinear Physics in general.⬇️ Scroll down to see the full summary -
Mec´anica 3d: python y el algoritmo de Verlet
Abstract:In the process of learning there are several important events and activities involved. Some actions such as discussion, exposition of ideas and the development of projects or the possible solution of different shown problems can be complemented with the use of common technologies, experimental facts and visual didactic materials. We consider that the discussion of different propositions or techniques that solve some specific tasks contributes to the interaction between students and, in the case of computer algorithms, enable them to build their own experimental tools. Different situations, questions, results or predictions can be proposed and discussed during and after the construction of a computer program that shows in real time an animated visual 3D view of the numeric solution. We present deduction of Verlet's algorithms and apply them to some particular mechanical systems begining with free particle, and adding in each time some physical considerations that involves more complexity in the problem.⬇️ Scroll down to see the full summary -
La historia en los libros de texto de física y química para secundaria: las diferentes formas de presentar la información histórica y las opiniones relacionadas de los alumnos
Abstract:This article presents the historical information that appears in Spanish Physics and Chemistry textbooks for 14 and 15-year-old students, it focuses on the purpose of the authors when they use this kind of information. Moreover, it has done a 17 questions survey to 69 students of these ages in order to show if the historical aspects that appear in Physics and Chemistry textbooks are useful or not. Some of the students affirm that it is helpful because this information contextualizes Physics, that is useful to understand and remember it better. However, other students declare that history is boring and is not of a great help in Physics learning.⬇️ Scroll down to see the full summary -
Probing students' conceptual knowledge of satellite motion through the use of diagram
Abstract:We investigated students' understanding of satellite motion around the Earth. For that purpose, we surveyed high-school and university students from Croatia. With the objective of gaining insight into teachers' understanding of students' abilities, physics teachers were asked to predict students' answers. The results of the study suggest that most students have difficulties with providing physically based explanations. They tend to approach such problems through the use of phenomenological primitives. Specifically, they tend to use the ``closer is stronger'' p-prim when attempting to identify the satellite orbit which would ensure receiving satellite television signal at a certain location paying no attention to the direction of the gravitational force. We found no statistically significant association between the students' ability to correctly explain the satellite motion and their educational background. The teachers considerably overestimate students' abilities. Generally, the results of this study suggest that diagram-based problem can be useful tool for probing students' understanding of satellite motion.⬇️ Scroll down to see the full summary
