Allosteric collaboration between elongation factor G and the ribosomal L1 stalk directs tRNA movements during translation

Determining the mechanism by which transfer RNAs (tRNAs) rapidly and precisely transit through the ribosomal A, P and E sites during translation remains a major goal in the study of protein synthesis. Here, we report the real-time dynamics of the L1 stalk, a structural element of the large ribosomal subunit that is implicated in directing tRNA movements during translation. Within pre-translocation ribosomal complexes, the L1 stalk exists in a dynamic equilibrium between open and closed conformations. Binding of elongation factor G (EF-G) shifts this equilibrium towards the closed conformation through one of at least two distinct kinetic mechanisms, where the identity of the P-site tRNA dictates the kinetic route that is taken. Within post-translocation complexes, L1 stalk dynamics are dependent on the presence and identity of the E-site tRNA. Collectively, our data demonstrate that EF-G and the L1 stalk allosterically collaborate to direct tRNA translocation from the P to the E sites, and suggest a model for the release of E-site tRNA

Electrochemical Properties of Al2O3-Fe/Si Composites Prepared by High-Energy Mechanical Milling

open accessThe growing demand in the manufacture of advanced materials with desired and unique properties (e.g. high mechanical strength, durability, good corrosion resistance and low cost of maintenance/replacing) is one of reasons to motivate the researchers to pay special attention in Ceramics as high performance materials for industrial applications. This is because conventional materials cannot meet the engineering requirements during their service that is why the need for advanced ceramic materials to achieve these industrial requirements. In the present work a study was made on Al2O3-matrix ceramic composites reinforced with 2%wt. or 5% wt. of Fe/Si particulates that were produced using a mechanical ball milling at high-energy condition. The electrochemical behavior of these ceramics was investigated by anodic polarization and Electrochemical Impedance Spectroscopy (EIS) measurements in a solution containing 0.5N NaCl, whereas the morphology and microstructural features were examined by optical or Scanning Electron Microscopy (SEM)

Freeze-thaw durability of recycled concrete from construction and demolition wastes

Road engineering is one of the most accepted applications for concrete including recycled aggregates from construction and demolition wastes as a partial replacement of the natural coarse aggregates. Amongst the durability concerns of such application, the deterioration due to freeze-thaw cycles is one of the most important causes decreasing the life span of concrete in countries with a continental climate. Moreover, the use of de-icing salts, which is a common practice to prevent ice formation on roadways and walkways, increases the superficial degradation of concrete due to frost-salt scaling. Thus, this paper aims to assess the resistance to frost salt with de-icing salts of two recycled concrete mixtures containing a 50% replacement of the conventional gravel by recycled aggregates both of mixed and ceramic nature, i.e. containing ceramic percentages of 34% and 100%, in comparison to a conventional concrete made with siliceous gravel. Therefore, the surface scaling was evaluated based on EN 1339 (2004) on 28 days cured cylinders, exposed to 7, 14, 21 and 28 freeze-thaw cycles in the presence of sodium chloride solution. Given that no airentraining admixture was used in any of the mixtures, the scaling of both conventional and recycled concretes exceeded the 1 kg/m2 limit established by the European standard. Nonetheless, for the casting surface, the recycled concrete with low ceramic content exhibited a similar behaviour to the conventional concrete, whereas the performance of the recycled concrete with high ceramic content was better. However, as expected, trowelled surfaces showed a worse performance and both recycled concretes had a lower freeze-thaw durability than the conventional mixture. In any case, the results suggested that the composition of the recycled aggregates could be used as a factor to limit the differences in performance between recycled and conventional mixtures

mejora continua del proceso de electrospining por medio del análisis de procesos: caso de estudio CU UAEM Valle de México

Se tiene como misión el innovar e implementar nuevas tecnologías con conocimientos adquiridos de nuestra formación, aplicándolo en el desarrollo de la máquina de electrospínning. Iniciamos por la producción de biotecnología con la preparación y proceso de la solución de Difluoruro de Polivinilideno (PVDF) con el diluyente Dimetilformamida (DMF). Este proceso se emplea a alto voltaje realizando un campo electrostático, este atraerá partículas de la solución o fluido polimérico formando un cono inyector hacia una superficie recolectora la cual formara y solidificara partículas micro y nanofibras, las cuales formaran membranas.Its mission is to improve, create, innovate and implement new technologies with the knowledge acquired from our training, applying it in the development of the electrospinning machine. In this case we started with the production of biotechnology with respect to the preparation and processing of the solution of Polyvinylidene Difluoride (PVDF) with a thinner material such as Dimethylformamide (DMF), as well as the construction of a prototype electrospinning machine.This process employs high voltage for an electrostatic field, which will attract particles from the solution or polymeric fluid thus forming an injector cone towards a collecting surface which will form and solidify micro and nanofibres particles, which in turn will form membrane

Sistema Arquetipo para desarrollo y funcionalidad de ODROID con Android

El microordenador denominado placa ODROID de open source, es utilizado para la difusión de información, entretenimiento, control y automatización a base de aplicaciones Android; diseñado para actuar como plataforma de desarrollo. Se hace uso de la metodología en Cascada (Wikipedia, 2018), que ayuda a ordenar rigurosamente las etapas del proceso de elaboración. Se hace uso e instalación del sistema operativo Android como base del proyecto, incluyendo la conexión de periféricos básicos que una PC particular puede tener. Añadiendo a ello una TV digital básica e integrando diversas aplicaciones (Apps) basada en entretenimiento y redes sociales que dé lugar a una Smart TV. De este modo hacer una configuración y añadiendo un mando (control) que haga que ODROID se convierta en consola de videojuegos. También surge la idea de controlar dispositivos a base de Bluetooth con base en la domótica a través de aplicaciones diseñadas en Android; controlando, así como prototipo un coche de control remoto a través de Bluetooth, armado con Arduino y modulo Bluetooth. Otro punto como uso de sistema de información, desarrollo e implementación de una aplicación que facilita el acceso a la información y dando a conocer los procesos de trámite. Los resultados muestran que es posible transformar cualquier tipo de monitor digital o analógico en un Smart TV, también de acuerdo con ciertas configuraciones transformar la placa ODROID en una consola de videojuegos y controlar dispositivos externos a través de Bluetooth

Evolution of surname distribution under gender-equality measurements

We consider a model for the evolution of the surnames distribution under a gender-equality measurement presently discussed in the Spanish parliament (the children take the surname of the father or the mother according to alphabetical order). We quantify how this would bias the alphabetical distribution of surnames, and analyze its effect on the present distribution of the surnames in Spain

Desarrollo y validación del método para control de calidad de clorhidrato de tiamina en tabletas

Se propone un método espectrofotométrico diferencial para la determinación de Clorhidrato de Tiamina en las tabletas de Vitamina B1 50 mg, el cual es una modificación del método fluorométrico establecido en la Farmacopea USP 32 para este producto. Consiste en la determinación espectrofotométrica a 369 nm del tiocromo producido por oxidación de la tiamina en solución alcalina. La medida de la absorción se realiza tanto en solución alcalina como en las muestras oxidadas. El método resultó válido, ya que los parámetros de linealidad, precisión, exactitud y especificidad cumplieron los criterios de aceptación propuestos en la literatura especializada para éstos fines. Se aplicó el mismo método espectrofotométrico para el ensayode uniformidad de contenido, demostrando su adecuadodesempeño en el rango de 70 a 130% de la cantidad teóricadeclarada en las tabletas

Synthesis and Electrical Characterization of PLZT Piezoelectric-Ceramic

This research describes the synthesis of an outstanding ceramic-composite piezoelectric CCP (lead-lanthanum-zirconate-titanate, PLZT) by means of powders technique procedures. Full dense CCP compacts were obtained with a platinum wire implanted in the center of the piezoelectric, which were used to investigate the microstructural and opto-thermal properties. The microstructural details of this ceramic were investigated by optical microscopy; whereas the opto-thermal characterization was performed by measuring the electrical signal in a bidimensional setup under four different temperatures: 20°C, 35°C, 50°C and 75°C. A 160mW/cm2 LASER beam was used in order to produce the optical energy which is detected by the CCP. A total of one hundred of measurements were registered. Measurements showed that, in the explored thermal range, the CCP signal magnitude increased from 87.2 to 147.2 pA. About the microstructural analysis, the microstructure obtained show different phases as characteristic of the processing method, including porosity. The peculiar optical and thermal properties observed in the piezoelectric ceramic are promising for possible applications in temperature-controlled optical devices that require electrical outputs