El hidrógeno y la energía

El hidrógeno es el elemento más simple, pero es fundamental para la vida. En el futuro sustituirá a los combustibles fósiles como fuente de energía para las máquinas hechas por el hombre. Hoy en día su uso es muy caro, pero ya existen motores que trabajan quemando este gas. En el sol la fusión de hidrógeno libera cantidades inconmensurables de energía, que en parte es captada por los cloroplastos, que la transforman en la energía química contenida en los carbohidratos resultantes de la fotosíntesis. Esto implica la transferencia del hidrógeno del agua al dióxido de carbono. Los animales liberan la energía de los combustibles biológicos revirtiendo dicha reacción a través del metabolismo oxidativo, la cadena respiratoria y la fosforilación oxidativa. El hidrógeno es vital para producir ATP y por lo tanto para la vida

Funcionamiento e importancia del sistema bicarbonato/CO2 en la regulación del pH sanguíneo

La vida depende de que se mantenga la concentración de hidrogeniones del líquido extracelular y por lo tanto su pH, dentro de un intervalo muy estrecho. El amortiguador compuesto por bicarbonato y CO2 tiene características químicas que sugieren una escasa utilidad para amortiguar los cambios en la [H+] debidos al metabolismo normal o a patologías que alteran el equilibrio ácido-básico. Sin embargo, dicho sistema es el más importante del líquido extracelular y en gran medida es gracias a él que se preserva la homeostasis ácido-básica. La funcionalidad del sistema se debe a la capacidad de los riñones y los pulmones para modular las concentraciones de bicarbonato y dióxido de carbono, respectivamente, de manera que se compensan las alteraciones primarias de tales componentes debidas a patologías de origen respiratorio o metabólic

Automatic generation of robot and manual assembly plans using octrees

This paper aims to investigate automatic assembly planning for robot and manual assembly. The octree decomposition technique is applied to approximate CAD models with an octree representation which are then used to generate robot and manual assembly plans. An assembly planning system able to generate assembly plans was developed to build these prototype models. Octree decomposition is an effective assembly planning tool. Assembly plans can automatically be generated for robot and manual assembly using octree models. Research limitations/implications - One disadvantage of the octree decomposition technique is that it approximates a part model with cubes instead of using the actual model. This limits its use and applications when complex assemblies must be planned, but in the context of prototyping can allow a rough component to be formed which can later be finished by hand. Assembly plans can be generated using octree decomposition, however, new algorithms must be developed to overcome its limitations

Transitions for the Delta Economy

Details threats to the Sacramento-San Joaquin Delta, policy proposals to improve environmental management and water supply reliability, how these changes will affect land and water conditions, and implications for the area's and regional economies

Opportunities for Play-Based Experiences in Post No Child Left Behind Kindergarten Classrooms: The Role of Training, Resources, and Accountability Pressures in Meeting Best Practices

In response to No Child Left Behind (NCLB), opportunities for play-based experiences in classrooms have been challenged over the past decade. Despite research demonstrating the educational benefits of child driven play, teachers and schools have been pressured to focus on improving children\u27s success on standardized assessments which may not relate to the developmental achievements expected from activity based experiences. To explore teachers\u27 response to the tension between assessment driven mandates and best early childhood practices, this study investigated which factors influence teacher practices and values. Specifically, how do teacher training and classroom resources influence teachers\u27 values about the appropriateness of using child driven learning materials as well as creating opportunities in the classroom schedule for play-based experiences? Additionally, how do teachers\u27 perceived accountability pressures to their classroom practice influence their values and opportunities for play-based experiences? Regression analyses were performed to explore 142 NYC kindergarten teachers\u27 responses on the Early Childhood Time Use Scale-Profile. Results suggest that when teachers are trained in developmental theory and adequate resources, play-based experiences in the classroom remain a priority in the classroom. In addition, teachers value of child driven materials remains intact when training and resources are available. By contrast, when accountability pressures influence classroom instructional time teachers\u27 endorsement of child driven materials to promote play-based experiences suffer. These findings speak to implications for professional development of teachers in a post-NCLB context that supports the importance of grounding an early childhood workforce in developmental theory so that play-based experiences can remain a priority

Technology Integration around the Geographic Information: A State of the Art

One of the elements that have popularized and facilitated the use of geographical information on a variety of computational applications has been the use of Web maps; this has opened new research challenges on different subjects, from locating places and people, the study of social behavior or the analyzing of the hidden structures of the terms used in a natural language query used for locating a place. However, the use of geographic information under technological features is not new, instead it has been part of a development and technological integration process. This paper presents a state of the art review about the application of geographic information under different approaches: its use on location based services, the collaborative user participation on it, its contextual-awareness, its use in the Semantic Web and the challenges of its use in natural languge queries. Finally, a prototype that integrates most of these areas is presented

Climate Change, Markets, and Technology

Environmental Economics and Policy, Resource /Energy Economics and Policy, Q15, Q25, Q38,

Virtual assembly rapid prototyping of near net shapes

Virtual reality (VR) provides another dimension to many engineering applications. Its immersive and interactive nature allows an intuitive approach to study both cognitive activities and performance evaluation. Market competitiveness means having products meet form, fit and function quickly. Rapid Prototyping and Manufacturing (RP&M) technologies are increasingly being applied to produce functional prototypes and the direct manufacturing of small components. Despite its flexibility, these systems have common drawbacks such as slow build rates, a limited number of build axes (typically one) and the need for post processing. This paper presents a Virtual Assembly Rapid Prototyping (VARP) project which involves evaluating cognitive activities in assembly tasks based on the adoption of immersive virtual reality along with a novel non-layered rapid prototyping for near net shape (NNS) manufacturing of components. It is envisaged that this integrated project will facilitate a better understanding of design for manufacture and assembly by utilising equivalent scale digital and physical prototyping in one rapid prototyping system. The state of the art of the VARP project is also presented in this paper

Octree-based production of near net shape components

Near net shape (NNS) manufacturing refers to the production of products that require a finishing operation of some kind. NNS manufacturing is important because it enables a significant reduction in: machining work, raw material usage, production time, and energy consumption. This paper presents an integrated system for the production of near net shape components based on the Octree decomposition of 3-D models. The Octree representation is used to automatically decompose and approximate the 3-D models, and to generate the robot instructions required to create assemblies of blocks secured by adhesive. Not only is the system capable of producing shapes of variable precision and complexity (including overhanging or reentrant shapes) from a variety of materials, but it also requires no production tooling (e.g., molds, dies, jigs, or fixtures). This paper details how a number of well-known Octree algorithms for subdivision, neighbor findings, and tree traversal have been modified to support this novel application. This paper ends by reporting the construction of two mechanical components in the prototype cell, and discussing the overall feasibility of the system