¿Y dónde quedó el reactivo limitante? Algunas preconcepciones sobre reactivo limitante detectadas en alumnos de licenciatura

El trabajo que se presenta forma parte de un proyecto de investigación educativa cuyo énfasis se centra en conocer algunos factores importantes que interfieren la comprensión de la reacción química. En este caso abordamos las preconcepciones, sobre el reactivo limitante, de un grupo piloto de alumnos de licenciatura de la Facultad de Química (UNAM). Se presenta el análisis de las respuestas después de aplicar un cuestionario de opción múltiple, en el que se solicitaba la justificación de la opción elegida así como de las entrevistas realizadas

Implementation of AMI Systems in CFE-Distribution, Mexico

The Smart Grid concept has been conceived as the integration of the electrical grid (generation, transmission and distribution) and the communications network of an electric utility. Although, traditional communications interfaces, protocols and standards has been used in the electrical grid in an isolated manner, modern communications networks are considered as the fundamental enabling technologies within a Smart Grid environment. Emerging communications technologies, protocol architectures and standards can help to build a common communications network infrastructure for data transport between customer premises, power substations, power distribution systems, utility control centers and utility data centers. The Smart Grid will support traditional applications such as supervisory control and data acquisition (SCADA), distribution automation (DA), energy management systems (EMS), demand site management (DSM) and automated meter reading (AMR), etc., as well as new applications like advanced metering infrastructure (AMI), substation automation (SA), microgrids, distributed generation (DG), grid monitoring and control, data storage and analysis, among others. To make this possible, the Smart Grid requires a two-way wide area communications network between different dispersed areas, from generation to consumer premises. An AMI system uses communication technologies for smart meter reading several times a day to get data consumption of electricity, as well as sending outage alarm information and meter tampering almost in real time, from the meter to the control center. Currently, there are various communication technologies to implement AMI systems. This paper presents an overview of the most relevant communications technologies that can be used to implement AMI communications infrastructure such as neighborhood area networks (NAN), field area networks (FAN) and wide area networks (WAN) using different transmission media such as fiber optics, spread spectrum radio frequency, microwave, WiMax, Wi-Fi, ZigBee, cellular, and power line carrier. In addition, a review of the current state of various AMI projects around the world, including the progress in the implementation of AMI systems in Mexico, besides the evaluation performance of CFE´s AMI networks

BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa

¿Y dónde quedó el reactivo limitante? Algunas preconcepciones sobre reactivo limitante detectadas en alumnos de licenciatura

El trabajo que se presenta forma parte de un proyecto de investigación educativa cuyo énfasis se centra en conocer algunos factores importantes que interfieren la comprensión de la reacción química. En este caso abordamos las preconcepciones, sobre el reactivo limitante, de un grupo piloto de alumnos de licenciatura de la Facultad de Química (UNAM). Se presenta el análisis de las respuestas después de aplicar un cuestionario de opción múltiple, en el que se solicitaba la justificación de la opción elegida así como de las entrevistas realizadas

Surface Modification of nTiO2/Ag Hybrid Nanoparticles Using Microwave-Assisted Polymerization in the Presence of Bis(2-hydroxyethyl) Terephthalate

Titanium dioxide doped silver (nTiO2/Ag) nanoparticles were surface-modified by microwave-assisted polymerization of 2-bis-(hydroxyethyl) terephthalate (BHET). The modified and unmodified nanoparticles were analyzed by FTIR, XRD, TGA, and TEM. A thin layer of grafted PET on the surface of the nanoparticles was observed and quantified by TGA giving a value of 40 wt-%. XRD and electron diffraction analyses showed traces of AgO2 after the modification. The bactericide activity of modified and unmodified nanoparticles was evaluated; the presence of the thin layer of grafted-PET on the nTiO2/Ag did not change significantly the bactericide activity, showing an excellent performance similar to unmodified nanoparticles

The nuclear receptor NR4A1 is regulated by SUMO modification to induce autophagic cell death.

NR4A is a nuclear receptor protein family whose members act as sensors of cellular environment and regulate multiple processes such as metabolism, proliferation, migration, apoptosis, and autophagy. Since the ligand binding domains of these receptors have no cavity for ligand interaction, their function is most likely regulated by protein abundance and post-translational modifications. In particular, NR4A1 is regulated by protein abundance, phosphorylation, and subcellular distribution (nuclear-cytoplasmic translocation), and acts both as a transcription factor and as a regulator of other interacting proteins. SUMOylation is a post-translational modification that can affect protein stability, transcriptional activity, alter protein-protein interactions and modify intracellular localization of target proteins. In the present study we evaluated the role of SUMOylation as a posttranslational modification that can regulate the activity of NR4A1 to induce autophagy-dependent cell death. We focused on a model potentially relevant for neuronal cell death and demonstrated that NR4A1 needs to be SUMOylated to induce autophagic cell death. We observed that a triple mutant in SUMOylation sites has reduced SUMOylation, increased transcriptional activity, altered intracellular distribution, and more importantly, its ability to induce autophagic cell death is impaired

Clavigero. Comunidad de saberes, núm. 29: Movilidad urbana: hacia una ciudad posible

La movilidad urbana se relaciona con otras problemáticas como la pérdida de espacios naturales o verdes, la contaminación del aire, el acceso desigual al espacio público, la discriminación o la violencia en los trayectos de movilidad de las mujeres y disidencias sexo–genéricas, los siniestros viales que ponen en riesgo la vida de las personas, o la mala planeación urbana que afecta el derecho a la vivienda. Los textos de este número plantean un modelo de ciudad justo, a partir de una visión sistemática de la movilidad. Las y los autores incluyen la perspectiva de género, el cuidado de la vida y la sustentabilidad pero, sobre todo, colocan a las personas y al medio ambiente en el centro