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En Colombia, las áreas de siembra en pera (<em>Pyrus communis</em> L.) han incrementado en los últimos años, debido a las ventajas nutricionales y medicinales que presenta el consumo de esta fruta.  En el estudio se evaluó el efecto de la reducción de riego durante la etapa de crecimiento rápido del fruto en la producción y calidad del cultivar Triunfo de Viena de pera, con el fin de implementar estrategias para una mayor efi-ciencia de la utilización de agua durante los periodos fenológicos del cultivo.  La investigación se realizó en 2012 y 2013 en árboles de pera de 16 años de edad en el municipio de Sesquilé, Cundinamarca (Colom-bia) aplicando tres tratamientos de riego:  (1) control (T1) = aplicación de riego equivalente al 100% de la (evaporación del cultivo) (ETc) durante todo el ciclo de producción, (T2) = aplicación de riego equivalente a 73% de la ETc durante el periodo de crecimiento rápido del fruto, y (T3) = aplicación de riego equivalente a 53% de la ETc durante el mismo periodo T2.  El diseño experimental fue bloques completos al azar con cuatro repeticiones por tratamiento y los resultados fueron sometidos a análisis de varianza (Anova) y prueba de comparación de medias de Duncan (P &lt; 0.05).  La reducción de riego equivalente a 53% de la ETc en época de sequía no afecto la producción ni la calidad del fruto, lo que permitió un ahorro de 47% de agua en esta etapa de crecimiento del fruto cuando se requiere aplicación de riego.

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We investigate the Casimir force F between two parallel semiconductor slabs taking into account magnetoplasmon effects. For our calculations we consider an external magnetic field applied in the Voigt geometry. Studies are carried out using the formula of F, which is written in terms of the reflectivities of the incident electromagnetic (EM) waves onto the surfaces of the semiconductor slabs, in the vacuum gap between slabs. Results show that the Casimir force depends strongly on the slab thickness as well as on the magnetic‐field strength (or equivalently on the cyclotron frequency). At a constant cyclotron frequency and for small slab thickness F/F0 (F0 is the ideal force) displays a dip at small separation distances L between slabs. F/F0 increases with L up to saturation as the slab thickness increases. The curve with the strongest value of F/F0 corresponds to the semi‐infinite medium geometry. For a constant slab thickness and small cyclotron frequency, F/F0 as a function of L shows a monotonic increase as L increases, and eventually reaches saturation. At high cyclotron frequency F/F0 displays a dip. The curve of F/F0 with no applied external field corresponds to the one with the strongest Casimir force. Therefore, magnetoplasmon effects, with an applied magnetic field in the Voigt geometry may inhibit the Casimir force. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The first phase of the EU collaborative project on sub-kelvin thermometry, 'ULT Dissemination', is nearing completion, leading to the development of several thermometers and devices, and the instrumentation needed to disseminate the new Provisional Low Temperature Scale, PLTS-2000, to users. Principal among these are a current-sensing noise thermometer (CSNT), a CMN thermometer adapted for industrial use, a Coulomb blockade thermometer, a second-sound acoustic thermometer and a superconductive reference device SRD-1000. Several partners have set up 3 He melting-pressure thermometers to realise the PLTS-2000, and will check it using Pt-NMR, CMN and other thermometers. The scale, which was formally adopted by the Comité International des Poids et Mesures in October 2000, covers the range of temperature from 1 K down to 0.9 mK, and is defined by an equation for the melting pressure of 3 He. The SRD employs novel fabrication and detection techniques with up to 10 samples, and is expected to meet the requirement for fixed points below 1 K, formerly filled by the NIST SRM 767 and 768. Other devices included in the project are ruthenium oxide sensors and a self-contained 3 He melting pressure thermometer. This paper reviews the project progress to date and indicates the potential for research, metrological and industrial application of the devices developed.

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