Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The development of microfluidic devices presents itself as an innovative approach to improving current assisted reproduction techniques, which are far from being highly efficient. The design of these microdevices is generally very flat, is characterized by many channels and all the walls play a fundamental role, located at micrometric distances from each other. To study this high-confinement effect, human sperm motion was modeled in two dimensions using Langevin dynamics. The cellular density was calculated within channels (with asymmetric entry and exit) of micrometric width and an aspect ratio (width/length, w/L) less than one. To achieve an accurate representation of the oscillatory dynamics, a phenomenological model with experimentally obtained sperm motility parameters was used. As the channel width decreases, the proximity of the walls significantly influences the density distribution, primarily when the distance between them is a few cells, making the effects of the device's high confinement evident. It was observed that the transverse profile varies at different positions along the channel, especially near the entrances and exits, and remains constant around the middle of the length (L/2). For example, for a length of 300 μm, the profile remains constant along 125 μm, instead, in very short channels as L=50 μm the profiles vary along the length of the channel, that is, the asymmetry dominates.

one of the most intense of this century, reaching levels G4 to G5 on the NOAA classification scale. Since the ejectahave supersonic speeds, they cause a shock wave. Upon reaching the terrestrial environment, it produces significantvariations in the geomagnetic field. In the present paper it is analyzed the perturbation of the system of equivalentionospheric currents due to the arrival of the first shock wave, using the records of ten permanent geomagnetic stations.In order to provide a possible interpretation of the relationships that could be established during the first hour afterthe arrival of the shock wave, the linking model among the different systems of equivalent currents and the differentgeomagnetic indices that represent them, is postulated.

The potential development of hybrid proton beam radiotherapy equipment guided by magnetic resonance imaging, will allow the optimization of the visualization and accuracy of the imaging system in conjunction with a highly conformal dose distribution. However, careful studies on the influence of the external magnetic field on the radiation beam particles are necessary. Therefore, a methodology is proposed and described to quantitatively characterize, by means of analytical and numerical techniques, the effect of intense magnetic fields on the proton trajectory, propagating in vacuum and in material media typically present in radiotherapy situations. In both cases it has been observed that the influence of the magnetic field on the proton trajectories increases with its intensity. In the presence of air as a scattering medium, thegeneration of secondary particles starts to become relevant in high energy regimes. The results constitute a startingpoint for future studies on the dosimetric influence of changes in proton fluence due to the presence of magnetic field, in future proton beam therapies guided by MRI systems.

A portable radiometer was developed with two sensors measuring total Ultraviolet Radiation (UVA + UVB) and UVIndex. To obtain basic meteorological data, the radiometer has another device that simultaneously measures Atmospheric Pressure, Temperature, and Relative Humidity. The control, acquisition, data storage, and communication device with external devices is an open Firmware development module based on ESP32 (NODEMCU32 ESP-WROOM-32s). This Microcontroller not only operates and controls the sensors but also performs simultaneous tasks of acquisition, calculation, and conversion of units. A real-time clock and an SD unit were associated with it for data recording and saving. The acquired and preprocessed signals are transmitted to an external device via Bluetooth for reading the acquired signals in real-time. The instant results can be read with any external computer system that has a Bluetooth interface; said values can be viewed by a Tablet, Notebook, or Smartphone. Keywords: Sensors, ESP32, UV Radiation, UV Index, Smartphone.

This work aimed to develop and test a graphical user interface in Matlab language (gui) for the quantification of parathyroid SPECT studies. The gui allowed the correct reading of the image files without loss of information, their transformation into activity concentration values ​​and the obtaining of semiquantitative indices such as the standard uptake value (suv). It was tested with phantoms that simulated thyroid and parathyroid compartments and on images of a cohort of patients with a clinical diagnosis of hyperparathyroidism. Their analysis verified the correct and fluid operation of the application and allowed parathyroid and thyroid tissues to be differentiated in the patients' images through quantitative analysis.

Incompressible Alfvén waves have been detected in a variety of space and astrophysical plasmas. Some of these plasmascan be studied within the framework of magnetohydrodynamics with extended conditions. In this work, the propagationof large amplitude Alfvén waves in uniform plasmas is studied, when the electronic pressure gradient, Hall’s term andthe inertial terms of Ohm’s law are taken into account. Instead of linearizing the system of equations and developingthe perturbation into plane waves, Alfvén waves conditions are imposed. In this way, a solution is found that, in thelimit when the inertial terms are neglected, coincides with the result found by Sallago and Platzeck (2004), for Alfvénwaves in magnetohydrodynamics with Hall term.

This work presents a study on the characteristics of the textbooks used in the upper courses of Physics careers. The study consists of an analysis of the hamiltonian in Analytic Mechanics which is carried out in two stages: in the first one an example was characterized; in the second one, several interviews with professors were performed. The importanceof this study lies in the fact that textbooks are one of the main instructional materials used by senior undergraduatestudents so that if those texts are not easy to understand, students will make an enormous effort to learn from them and this cognitive effort might not contribute to a good performance. On the basis of this analysis, it is concluded that the example does not result in an easy reading for students. Moreover, the interviews show that the characteristics of the example make the reading difficult for those who try to learn from it.

Les mythes d'établissement des Quichés des Hautes Terres du Guatemala font appel, dans toutes leurs variantes historiques préhispanique, coloniale et moderne, au modéle de la migration. On peut se demander si, sous ce paradigme commun, ne joue pas une facon de dire l'histoire par le déploiement du temps dans l'espace, comme si la figure de la migration donnait lieu à une “mise en scéne” dans l'espace des événements du passé que la mémoire collective sauvegarde. Il y a en fait deux catégories de récits de migration: Pune, la plus connue, situe origine des Quichés à Tulán Zuyua très loin des Hautes Terres; et l'autre, qui lui succède, décrit une geste d'origine dans des montagnes tout à fait locales. La premiére met sans doute en jeu dans le discours plusieurs figures complexes relevant de l'histoire qu'il faut faire d'un passé trés “lointain” et renvoyant à des conceptions politiques en référence à létranger (Arnauld 1994). La seconde renvoie clairement à l'histoire locale dans un cadre territorial défini; c'est celle qui nous intéresse ici.

Dans la tentative de définir les concepts essentiels de la cosmologie maya préhispanique, c’est l’organisation de l'espace terrestre, horizontal, qui a surtout retenu l'attention. Il a été défini initialement, d'après les documents du XVI° siècle, comme un espace quadrangulaire, divisé en quatre secteurs correspondant aux directions cardinales, dotés chacun d'une couleur différente et d’autres attributs spécifiques (divinités, arbres, oiseaux, jours du calendrier). Les enquêtes menées chez les Mayas contemporains ont permis de préciser que l'orientation principale qui régissait l’ensemble était celle du parcours diurne du soleil, ét que les côtés est et ouest étaient délimités par les points extrêmes atteints par le soleil sur l'horizon aux solstices d'hiver et d'été. Il a été récemment proposé d’ôter toute valeur aux orientations nord et sud, en les remplaçant par le zénith et le nadir. Nous avons présenté une réfutation de ce point de vue, et il nous semble que le modèle des quatre directions de l’espace maya sur le plan horizontal, ainsi que ses corrélations avec le calendrier cérémoniel de 260 jours et avec le calendrier solaire, peut être considéré comme bien établi (Becquelin 1991).

La lecture des textes en tzeltal fait apparaitre un phénomène remarquable, qui est l'absence presque totale de formes spécifiques de futur. Cette particularité ne provient pas seulement du fait que nombre de textes résultent d'enquêtes sur la tradition et que bien des narrations sont des récits concernant le passé, car l'échange quotidien présente le même trait. Elle tient également à la structure des langues mayas qui, dans la caractérisation du procès, accordent à l'expression de l'aspect et du mode la prééminence sur celle du temps. Corrélativement à l'absence d'un morphéme clairement spécifique de futur, Pexpression du futur se fait au moyen d'un grand nombre de formes, le plus souvent périphrastiques. C'est à cet aspect grammatical, á sa signification et à sa relation avec les représentations que s'attachent ces notes, qui sont plus expression d'un programme de recherche collective en cours que la présentation de résultats.