Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes

Nanostructured materials and exploiting their properties in stereolithography (SL) may open new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small dispersions of MWCNTs resulted in significant effects on the physical properties of the polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™ 11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%, respectively. Electron microscopy was used to examine the morphology of the nanocomposite and results showed affinity between the MWCNTs and SL resin and identified buckled nanotubes that illustrated strong interfacial bonding. These improved physical properties may provide opportunities for using nanocomposite SL resins in end-use applications. Varying types and concentrations of nanomaterials can be used to tailor existing SL resins for particular applications.Mechanical Engineerin

Análisis de la composición mineral en alimentos congelados precocinados de consumo habitual

La realización del presente estudio analítico ha tenido como principal objetivo ampliar y mejorar los datos queactualmente vienen reflejados en las tablas de composición de alimentos españoles, aportando datos que, además depropios, corresponden a alimentos ampliamente distribuidos en el mercado español y son consumidos de formahabitual en nuestro país. El análisis de los diferentes minerales se ha realizado en 28 alimentos precocinados congelados,previamente seleccionados, entre los que se incluyen pastas, pizzas, arroces y fritos de mayor consumo. Estetipo de alimentos son susceptibles de sufrir pérdidas en minerales debido a los procesos de elaboración, congelacióny pretratamiento culinario a que son sometidos antes de su consumo, por lo que es de gran interés el conocimientode su composición mineral, dando respuesta a las exigencias de un amplio grupo de profesionales y consumidoresque requieren de esta información nutricional

Bead, Hoop, and Spring as a Classical Spontaneous Symmetry Breaking Problem

We describe a simple mechanical system that involves Spontaneous Symmetry Breaking. The system consists of two beads constrained to slide along a hoop and attached each other through a spring. When the hoop rotates about a fixed axis, the spring-beads system will change its equilibrium position as a function of the angular velocity. The system shows two different regions of symmetry separated by a critical point analogous to a second order transition. The competitive balance between the rotational diynamics and the interaction of the spring causes an Spontaneous Symmetry Breaking just as the balance between temperature and the spin interaction causes a transition in a ferromagnetic system. In addition, the gravitational potential act as an external force that causes explicit symmetry breaking and a feature of first-order transition. Near the transition point, the system exhibits a universal critical behavior where the changes of the parameter of order is described by the critical exponent beta =1/2 and the susceptibility by gamma =1. We also found a chaotic behavior near the critical point. Through a demostrative device we perform some qualitative observations that describe important features of the system.Comment: 7 pages, 2 tables, 30 figures, LaTeX2

Network distributed generation capacity analysis using OPF with voltage step constraints

The generation capacity connected in distribution networks is increasing, largely because of the necessity of siting renewable generation where resources are available. If distributed generation is connected in inappropriate parts of a network, it can cause a significant decrease in the total potential of the network for new generation. An optimal power flow-based method has previously been proposed for assessing network generation capacities. As, for a realistic assessment, it is necessary to include as many of the relevant physical and technical constraints as possible, limits on the voltage step changes on loss of a generator are added to the model here. Results on the variation of the network capacity with the generator power factors and the allowed voltage step window are presented

Actividad molusquicida de extractos acuosos vegetales sobre el caracol manzana pomacea canaliculata

En el Ecuador, entre el 40 y 48% de la producción de arroz se pierde a causa del ataque de Pomacea canaliculata, una de las cien especies invasivas más dañinas del mundo que actualmente ha infestado alrededor de 170.000 hectáreas del cultivo en todo el territorio nacional