Hacia un sistema virtual para la educación en México

El presente estudio está dividido en cuatro partes. En la primera de ellas se vislumbra un panorama de la educación virtual en México, mediante algunos datos que reflejan su importancia en los ámbitos de la educación superior y en los sectores gubernamental y empresarial; también se hará referencia a lo que sucede en Iberoamérica. La segunda parte muestra una realidad en torno a los aspectos tecnológicos y académicos; aspectos que impactan el desarrollo de la educación virtual. La tercera parte expone algunos de los retos que se deben enfrentar para este modelo educativo. Con dichos fundamentos, aparece al final una propuesta acerca de la importancia de crear un sistema virtual para la educación superior, que parte de un trabajo elaborado con anterioridad por la Asociación Nacional de Universidades e Instituciones de Educación Superior (anuies), pero que hoy más que nunca se hace necesario retomar y concretar, puesto que hemos avanzado un trecho importante, pero falta la conjugación de esfuerzos para lograr la consolidación del sistema de educación superior

Editorial

Uno de los temas que en los últimos años ha originado un constante debate en el interior del trabajo científico, se refiere al contenido y orientación humana que requieren las tareas llevadas a cabo en los diferentes campos del conocimiento. En el fondo se trata de recuperar el sentido social del trabajo que realizan los investigadores, colocando en primer plano su compromiso con el desarrollo humano y el mejoramiento del entorn

Antibacterial effect of silver nanoparticles versus chlorhexidine against streptococcus mutans and lactobacillus casei

Abstract The porpoise of the study was to evaluate the antibacterial effect of silver nanoparticles (Ag-NPs) versus chlorhexidine (CHX) against Streptococcus mutans and Lactobacillus casei. Three different reducing agents were used for the synthesis and characterization of Ag-NPs: sodium borohydride (NaBH4), a chemical method, and Heterotheca inuloides (Hi) and Camellia sinensis (Cs), two eco-friendly methods. The synthesized substance was deposited on deciduous teeth. Its behavior in dental tissues was evaluated through an energy dispersive X-ray spectroscopy (EDS) analysis, using a scanning electron microscope (SEM). The characterization of Ag-NPs in terms of shape, size, and polydispersity was performed through spectrophotometry of ultraviolet-visible light analysis (UV-vis), as well as by transmission electron microscopy. Isolation and culture of strains S. mutans and L. casei were done to perform the microbiological analysis. In Petri dishes, paper discs containing different concentrations of Ag-NPs (synthesized by Hi, and by Cs) were deposited and tested along with paper discs containing CHX. Their antibacterial effect against both bacteria was evaluated by the inhibition zones test. By means of UV-Vis and TEM analysis, it was possible to observe that Heterotheca inuloides produced smaller and more stable nanoparticles, also in greater quantities (17.5 nm), when compared to Camellia sinensis. EDS analysis through SEM showed a 6.25 average absorption of silver in dental tissues. The microbiological analysis revealed a greater zone of inhibition when the test bacteria were in contact with 20 μl of Ag-NPs, synthesized by Hi, being statistically significant (p < 0.05), compared to the growth inhibition zones produced by Cs, and CHX against both strains. We can conclude that eco-friendly methods produced Ag-NPs with an important antibacterial effect in both strains

Antimicrobial effect of silk and catgut suture threads coated with biogenic silver nanoparticles

Abstract Two bionanocomposites based on suture threads, silk-silver nanoparticles (Ag NPs) and catgut-Ag NPs, were prepared through a green chemistry methodology using Chenopodium ambrosioides (Mexican Epazote) as reducing agent. UV-Vis spectrophotometry (UV-Vis), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), were used for their characterization. UV-Vis confirmed the synthesis of silver nanoparticles. Micrographs showed polydisperse, mostly spherical, Ag NPs attached to both suture threads. The bionanocomposites antimicrobial properties were evaluated through cultures and inhibition zones tests. The Chenopodium ambrosioides- assisted synthesized bionanocomposites have proved antibacterial effect against S. aureus and E. coli in both sutures (silk and catgut) and could be potentially useful for oral or periodontal surgery. There was no significant difference statistically in inhibition of Staphylococcus aureus versus Escherichia coli

Synthesis and Characterization of Silver Nanoparticles on Orthodontic Brackets: A New Alternative in the Prevention of White Spots

Abstract: Silver nanoparticles (AgNPs) are used for their powerful antibacterial e ect and their ability to adhere to surfaces due to their size; they are used in di erent areas of life, mainly in the area of health as medicine. More recently, in dentistry, the synthesis and characterization of AgNPs attracted significant attention due to their antibacterial properties. In this study, the AgNPs were synthesized using the most e ective method on di erent orthodontic brackets (metallic and esthetic) and characterized by scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and transmission electron microscopy (TEM). Their antimicrobial e ect was tested against the widely used standard human pathogens Staphylococcus aureus (Gram-negative) and Escherichia coli (Gram-positive). Our results showed that, via a simple chemical method, AgNPs can be synthesized on the surface of orthodontic brackets with good antimicrobial activity and the possibility of reducing dental decay, periodontal disease and white spots generated during orthodontic treatment

Ultra‐Small Platinum Nanoparticles with High Catalytic Selectivity Synthesized by an Eco‐friendly Method Supported on Natural Hydroxyapatite

The biosynthesis of Pt-nanoparticles (Pt NPs) supported on bovine bone powder was conducted by an environmentally friendly method that consists on immersing bovine bone powder into a Pt4+ metal ion solution at room temperature, atmospheric pressure and subsequent reduction by Heterotheca inuloides. It is worth pointing out that a calcination process is not required for the synthesis of this catalyst by the method reported herein. The nanocomposite was characterized by transmission electron microscopy (TEM), which revealed uniformly dispersed platinum nanoparticles with quasi-spherical form and average particle size of 7.1 nm. The XPS studies exhibited the presence of 47.62% Pt° and 51.84% PtO. The catalyst activity was tested in the selective hydrogenation of 2-butyne-1,4-diol towards 2-butene-1,4-diol. The nanocomposite exhibits a reasonable catalytic performance with nearly 100% conversion of the alkyne and 96% selectivity towards 2-butene-1,4-diol.CONACY

Microscopy: advances in scientific research and education

Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Sperctroscopy (EDS) are two analysis techniques that are widely used to study all kinds of solid samples, from inorganic to biological. They are used to determine morphological features of interest at a micron and sub-micron level as well as to study the chemical composition of the samples in terms of the amount of each element present. Although these analytical techniques are “routine work” in many research areas, it is not the case of the dental area, mainly because the lack of this equipment in the dental research institutes and in dental schools. Therefore, in this chapter we show the SEM/EDS techniques applied to human dental samples when irradiated with a laser Er:YAG to prevent caries. The intention of this work is to show step by step this analysis showing the key variables to consider when working with this type of biological samples. We explain the SEM conditions to obtain satisfactory images especially when it is important to follow a sequence of steps of a treatment in-vitro that changes the morphological structure of the teeth surface. Also, we discuss the EDS analysis to semiquantitatively determine the elements and their abundance in the dental samples

Editorial

Uno de los temas que en los últimos años ha originado un constante debate en el interior del trabajo científico, se refiere al contenido y orientación humana que requieren las tareas llevadas a cabo en los diferentes campos del conocimiento. En el fondo se trata de recuperar el sentido social del trabajo que realizan los investigadores, colocando en primer plano su compromiso con el desarrollo humano y el mejoramiento del entorn