Abstract: This work presents the design and fabrication of two different vacuum chuck systems for a spin-coater apparatus. One of the vacuum chuck designs considered was sealed with toric joints and the other was sealed with bearings. These vacuum chucks were adapted to a DC brushless motor which has a non-perforated shaft. The vacuum chuck with toric joints presented a superior performance when compared to the design with bearings. The best chuck design showed variations in temperature below 1 °C for spin-coating speeds in the range of 100 to 4000 rpm. In all cases, the vibrations of the spin-coating apparatus were measured to be below 1 μm RMS. To test the performance of the spin-coater, photoresist (PR) films were spin-coated at different rotational speeds. At 3000 rpm the measured PR thickness was 0.42 ± 0.02 μm, giving a good match to the data reported by the PR manufacturer.

In this study we evaluated the initial plant growth and some biochemical changes produced in rizhosphere soil of blueberry (Vaccinium corymbosum L.) cv. 'Elliot' plantlets obtained from in vitro culture and inoculated with six arbuscular mycorrhizal (AM) fungi strains (Gigaspora rosea; Glomus claroideum; G. deserticola; G. viscosum; G. intraradices and G. constrictum) and five saprobe fungi (Coriolopsis rigida; Phanerochaete chrysosporium; Trametes versicolor; Trichoderma harzianum and Penicillium chrysogenum). Our results showed a significant "like" AM root colonization (25-46%), highlighting the treatment co-inoculated with G. rosea + P chrysosporium or C. rigida; G. intraradices + C. rigida; G. viscosum + P chrysosporium, but this root colonization was morphologically atypical, and dominated by interstitial hyphae, without develop of other typical AM structures. Furthermore, significant increase in the shoot and root growth of the plantlets inoculated with G. viscosum + P chrysosporium, and G. intraradices + C. rigida were observed. On the other hand, G. claroideum + T. versicolor showed the high increase in the dehydrogenase enzyme activity, while inoculation with G. claroideum alone showed the greatest β-glucosidase activity. These results suggest that the interaction of AM symbionts together with saprobe fungi could be a biological alternative to promote the growth of micro-propagated blueberry plantlets in their early growth stages.

The beams deflection is an important subject in physics and engineering courses to study the elastic properties of a great variety of industrial materials . In this work the experimental deflection of thin glass sheets in cantilever is presented. The deflection test is realized putting weights on the free extreme of glass sheets, in order to determine the dependence of elastic properties and breaking point with length and width of the beams. The material is also examined to verified if presents mechanical hysteresis. Finally a comparison between the experimental elastic curve and the calculated whit the small slopes model is performed. This is a very cheap experiment which could be implemented easily in physics or engineering labs to illustrate materials elastic properties.

La flexión de vigas es una importante área en los cursos de física e ingeniería para el estudio de las propiedades elásticas de una gran variedad de materiales que se emplean en la industria. En el presente trabajo se realiza un experimento de la flexión de láminas delgadas de vidrio en voladizo, sometiéndolas a un ensayo de flexión por medio de masas que se colocan en el extremo libre. Lo anterior con el fin de determinar hasta que grado el material es elástico y observar la dependencia del punto de fractura con la longitud y el ancho de la lámina de vidrio. Se examina si el material presenta histéresis mecánica. Finalmente se compara la curva experimental de la elástica con la calculada a partir del modelo de pequeñas pendientes. Este es un experimento de muy bajo costo, que puede ser implementado fácilmente en los laboratorios de física o de ingeniería para ilustrar las propiedades elásticas de materiales.