Evaluación del sistema de producción de leche "El Corpus" El Menco, Rivas

Para la realización de este estudio se plantearon los siguientes objetivos: contribuir al conocimiento y mejoramiento del sistema de producción de leche "El Corpus" El Menco, Rivas, y de manera específica caracterizar y analizar los componentes del sistema, realizar un anál isis biológico y económico a partir de un estudio de eficiencia y realizar un estudio comparativo de la eficiencia del sistema en dos momentos en el tiempo. Este estudio se realizo en la finca "El Corpus" El Menco, Rivas en el período enero-diciembre del año 2000 y el período julio 2001-junio 2002. La unidad de producción se encuentra localizada a la altura del kilómetro 85 ½ carretera panamericana y 13 kilómetros al este a orilla del lago de Nicaragua, a 70 msnm y una latitud norte de 11°50'16" y una longitud oeste de 85°50'16". Para llevar a cabo la presente investigación se definieron las siguientes etapas generales: Caracterización e identificación del sistema de producción, análisis y comparación del sistema de los dos periodos en estudio, a través de un diagnóstico estático y dinámico. Durante la caracterización se observó que la mayoría de los componentes del sistema presentan óptimas condiciones para lograr una eficiente producción lográndose determinar que existe mal manejo en algunos de ellos. Así mismo en el análisis de eficiencia se logró determinar que las variables productivas del año 2000 en las que se obtuvieron mejores resultados con respecto al período julio 2001-junio 2002 fueron: El porcentaje de parición, porcentaje de mortalidad de terneras y la carga animal, lo cual fue lo contrario para la variable del porcentaje de descarte, la producción de leche/vaca/día y la producción de leche/ha/año. En lo que respecta a las variables reproductivas en las que se obtuvieron mejores resultados fue solamente el numero de servicios por concepción; mientras que para la edad de incorporación, peso de incorporación, edad al primer parto, período de servicio, intervalo entre parto fue lo contrario, no obstante la edad de incorporación y el peso de incorporación, se obtuvieron diferencias significativas a través de la prueba de "t" (a = 0.05); mientras que en la edad al primer parto, período de servicio, intervalo entre parto, no se obtuvieron diferencias. En lo que se refiere a la eficiencia económica del sistema los mejores resultados se obtuvieron en el periodo julio 2001 –junio 2002 el cual fue mas rentable y mas eficiente.

A quantum dot sensitized solar cell based on vertically aligned carbon nanotube templated ZnO arrays

We report on a quantum dot sensitized solar cell (QDSSC) based on ZnO nanorod coated vertically aligned carbon nanotubes (VACNTs). Electrochemical impedance spectroscopy shows that the electron lifetime for the device based on VACNT/ZnO/CdSe is longer than that for a device based on ZnO/CdSe, indicating that the charge recombination at the interface is reduced by the presence of the VACNTs. Due to the increased surface area and longer electron lifetime, a power conversion efficiency of 1.46% is achieved for the VACNT/ZnO/CdSe devices under an illumination of one Sun (AM 1.5G, 100 mW/cm2). © 2010 Elsevier B.V.

Integrating vertically aligned carbon nanotubes on micromechanical structures

The integration of high yield, uniform and preferential growth of vertically aligned carbon nanotubes (VACNT) on low stress micromechanical structures was analyzed. A combination of electron-beam crosslinked surface micromachining and direct current plasma enhanced chemical vapor deposition of electric field aligned carbon nanotubes was used for the analysis. The selective placement of high yield and uniform VACNTs on a partially suspended Ni/SiO2/Ti microstructure was also demonstrated.

Growth of ultrahigh density vertically aligned carbon nanotube forests for interconnects.

We present a general catalyst design to synthesize ultrahigh density, aligned forests of carbon nanotubes by cyclic deposition and annealing of catalyst thin films. This leads to nanotube forests with an area density of at least 10(13) cm(-2), over 1 order of magnitude higher than existing values, and close to the limit of a fully dense forest. The technique consists of cycles of ultrathin metal film deposition, annealing, and immobilization. These ultradense forests are needed to use carbon nanotubes as vias and interconnects in integrated circuits and thermal interface materials. Further density increase to 10(14) cm(-2) by reducing nanotube diameter is possible, and it is also applicable to nanowires.

Innovation processes within the healthcare industry: Determining critical success factors aligned to product strategies

The impact of differing product strategies on product innovation processes pursued by healthcare firms is discussed. The critical success factors aligned to product strategies are presented. A definite split between pioneering product strategies and late entrant product strategies is also recognised.

Polymers with aligned carbon nanotubes: Active composite materials

We review the current state of the polymer-carbon nanotube composites field. The article first covers key points in dispersion and stabilization of nanotubes in a polymer matrix, with particular attention paid to ultrasonic cavitation and shear mixing. We then focus on the emerging trends in nanocomposite actuators, in particular, photo-stimulated mechanical response. The magnitude and even the direction of this actuation critically depend on the degree of tube alignment in the matrix; in this context, we discuss the affine model predicting the upper bound of orientational order of nanotubes, induced by an imposed strain. We review how photo-actuation in nanocomposites depend on nanotube concentration, alignment and entanglement, and examine possible mechanisms that could lead to this effect. Finally, we discuss properties of pure carbon nanotube networks, in form of mats or fibers. These systems have no polymer matrix, yet demonstrate pronounced viscoelasticity and also the same photomechanical actuation as seen in polymer-based composites. © 2008 Elsevier Ltd. All rights reserved.

Suspended multiwalled carbon nanotubes as self-aligned evaporation masks

We describe the nanofabrication study of self-aligned electrodes on suspended multiwalled carbon nanotube structures. When metal is deposited on a suspended multiwalled carbon nanotube structure, the nanotube acts as an evaporation mask, resulting in the formation of discontinuous electrodes. The metal deposits on the nanotubes are removed with lift-off. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gapped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Self-aligned electrodes for suspended carbon nanotube structures

We report on a study into electrode fabrication for the gate control of carbon nanotubes partially suspended above an oxidised silicon substrate. A fabrication technique has been developed that allows self-aligned side-gate electrodes to be placed with respect to an individual nanotube with a spacing of less than 10 nm. The suspended multi-walled carbon nanotube (MWCNT) is used as an evaporation mask during metal deposition. The metal forms an island on the nanotube, with increasing width as the metal is deposited, forming a wedge shape, so that even thick deposited layers yield islands that remain separated from the metal deposited on the substrate due to shadowing of the evaporation. The island can be removed during lift-off to leave a set of self-aligned electrodes on the substrate. Results show that Cr yields self-aligned side gates with around 90% effectiveness. © 2003 Elsevier Science B.V. All rights reserved.

Fabrication of self-aligned side gates to carbon nanotubes

We have fabricated self-aligned, side-gated suspended multi-walled carbon nanotubes (MWCNTs), with nanotube-to-gate spacing of less than 10 nm. Evaporated metal forms an island on a suspended MWCNT, the island and the nanotube act as a mask shielding the substrate, and lift-off then removes the metal island, leaving a set of self-aligned side gates. Al, Cr, Au, and Ti were investigated and the best results were obtained with Cr, at a yield of over 90%.

Self-aligned split gate electrodes fabricated on suspended carbon nanotubes

We describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Self-aligned split gate electrodes fabricated on suspended carbon nanotubes

We describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems. © 2003 Materials Research Society.

Self-aligned, gated arrays of individual nanotube and nanowire emitters

We demonstrate the production of integrated-gate nanocathodes which have a single carbon nanotube or silicon nanowire/whisker per gate aperture. The fabrication is based on a technologically scalable, self-alignment process in which a single lithographic step is used to define the gate, insulator, and emitter. The nanotube-based gated nanocathode array has a low turn-on voltage of 25 V and a peak current of 5 μA at 46 V, with a gate current of 10 nA (i.e., 99% transparency). These low operating voltage cathodes are potentially useful as electron sources for field emission displays or miniaturizing electron-based instrumentation.

Viel, así en el cielo como en el canon : un lugar en el corpus de la poesía argentina

Resumen: Para analizar cuál es el lugar de Héctor Viel Temperley en las letras argentinas tomamos el movimiento editorial en torno de él, sobre todo la edición y reedición de sus obras y, por otro lado, relevamos antologías poéticas. En la labor, sorpresivamente, aparecen rasgos reveladores que desmienten el supuesto acerca de su haber sido ignoto; por otro lado, hemos hallado elementos que iluminan áreas no estudiadas, las que en nuestra investigación —aún en marcha— se van mostrando fundantes. Asimismo, consideramos su papel como ícono motivador en algunas obras recientes, movilizador, afectiva y conceptualmente, de cierto cúmulo de contenidos.