Mostrar la química cotidiana a los estudiantes de secundaria

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Apropar els estudiants de Secundària al món de la Química

Es presenta l'experiència realitzada, durant diverses edicions, a l'Escola Politècnica Supe-rior d'Enginyeria de Manresa (EPSEM) de la Universitat Politècnica de Catalunya (UPC), corresponent a dues activitats: L'exposició "On és la Química?" i el taller "Què és l'en-ginyeria química?" dirigides a estudiants de secundària

"Non-Target-Site" resistance mechanisms of "Papaver rhoeas" L. biotypes with multiple resistance

Hasta el momento en España no se han desarrollado estudios a fin de evaluar los mecanismos de resistencia “Non-Target-Site” en “Papaver rhoeas”. Tras constatar la resistencia múltiple de los biotipos empleados en este ensayo, los resultados de absorción y translocación obtenidos para 2,4-D y tribenuron-metil parecen arrojar conclusiones interesantes. Sobre todo, en el caso de la auxina sintética, donde una destacada menor translocación detectada en biotipos resistentes respecto a los sensibles está en sintonía con las más recientes teorías de mecanismos de resistencia a herbicidas hormonales.So far in Spain studies to evaluate the mechanisms of resistance “Non-Target-Site” on “Papaver rhoeas” have not been done. After finding multiple resistance in the biotypes used in this trial, absorption and translocation results obtained for 2,4-D and tribenuron-methyl seem to throw interesting findings. Mainly in the case of the synthetic auxin, where a lack of translocation was detected in resistant biotypes compared to the sensitive one. This could be related with the latest theories of mechanisms of resistance to synthetic auxin

Absolute magnitudes and kinematics of CP stars from Hipparcos data

The position in the HR diagram and the kinematic characteristics of different kinds of CP stars of the upper main sequence are obtained using the LM method (Luri et al., 1996). Most of the CP stars are main sequence stars occupying the whole width of the sequence. From a kinematic point of view, they belong to the young disk population (ages < 1.5 Gyr). It has also been found that, on kinematic grounds, the behaviour of lambda Bootis stars is similar to the one observed for normal stars of the same spectral range. On the other hand, roAp and noAp stars show the same kinematic characteristics. The peculiar velocity distribution function has been decomposed into a sum of three dimensional gaussians and the presence of Pleiades, Sirius and Hyades moving groups has been clearly established. Finally, a small number of CP stars are found to be high-velocity objects.Comment: 8 pages, 1 figure, to appear in: Proc. of the 26th workshop of the European Working Group on CP stars, eds. P. North, A. Schnell and J. Ziznovsky, Contrib. Astr. Obs. Skalnate Pleso Vol. 27, No

Management options for "Papaver rhoeas" with multiple herbicide resistance

Se han estudiado diferentes sistemas de GIMh en una población de "Papaver rhoeas" con resistencia múltiple a tribenurón-metil y 2,4-D. Se establecieron cuatro sistemas de GIMh, con dos tipos de labores del suelo (siembra directa o mínimo laboreo), que incluyen rotación con girasol, retraso de la fecha de siembra, o aplicaciones herbicidas en diferentes momentos. Las densidades de amapola fueron mayores en siembra directa que en mínimo laboreo. Los sistemas de GIMh más eficaces en el manejo de “P. rhoeas” fueron aquéllos con una rotación con girasol y aplicaciones tempranas de herbicidas (pre-emergencia y/o post-emergencia precoz). La eficacia del retraso de la fecha de siembra difirió entre campañas. En cereales de invierno, es posible el desarrollo de sistemas de GIMh para el control de poblaciones resistentes de “P. rhoeas” integrando herramientas químicas y culturales.Different integrated weed management (IWM) systems have been studied in a multiple herbicide resistant “P. rhoeas” population to tribenuron-methyl and 2,4-D. Four systems were established with two types of soil management (direct drilling and minimum tillage), which included rotation with sunflower, sowing delay or different herbicide application timings. Corn poppy densities were higher during the experiment in direct drilling compared to minimum tillage. Most efficient IWM systems for “P. rhoeas” were those that included rotation with sunflower and early herbicide application timings (pre-emergence and/or early post-emergence). Sowing delay effectiveness depended on the growing season conditions. In winter cereals, the development of IWM systems to manage herbicide resistant P. rhoeas populations is possible integrating chemical and cultural tools

Bromoxynil sensitivity study of a "Papaver rhoeas" L. biotype

“Papaver rhoeas” es la única mala hierba dicotiledónea que presenta resistencia múltiple en España. Se han detectado biotipos resistentes a tribenuron-metil (inhibidor de la acetolactato sintasa) y 2,4-D (auxina sintética). En la zona cerealista del norte de España ha habido problemas en el control de esta mala hierba con mezclas que contenían bromoxinil. En el presente trabajo se ha ensayado, con curvas dosis-respuesta, el efecto de este producto en dos lotes de semillas de un biotipo que no fue controlado en campo por mezclas con bromoxinil en dos años consecutivos. Los lotes B-0313 y B-0314 fueron controlados cuando el bromoxinil se aplicó a la fenología recomendada. Se observó cierto desplazamiento de la curva cuando las plantas de amapola se aplicaron a fenologías más avanzadas.“Papaver rhoeas” is the unique dicot weed that has multiple resistance in Spain. Resistant biotypes have been detected to tribenuron- methyl (acetolactate synthase inhibitor) and 2,4-D (synthetic auxin). In the cereal area of northern Spain there have been problems to control this weed with mixtures containing bromoxynil. In the present work we have tested the effect of this product in one biotype that was not controlled in the field by herbicide mixtures with bromoxynil. The lots B-0313 and B-0314 were controlled with bromoxynil applied at the recommended phenology. A shift in the curve was observed when corn poppy plants were applied in more advanced phenologies

The spatial distribution of O-B5 stars in the solar neighborhood as measured by Hipparcos

We have developed a method to calculate the fundamental parameters of the vertical structure of the Galaxy in the solar neighborhood from trigonometric parallaxes alone. The method takes into account Lutz-Kelker-type biases in a self-consistent way and has been applied to a sample of O-B5 stars obtained from the Hipparcos catalog. We find that the Sun is located 24.2 +/- 1.7 (random) +/- 0.4 (systematic) pc above the galactic plane and that the disk O-B5 stellar population is distributed with a scale height of 34.2 +/- 0.8 (random) +/- 2.5 (systematic) pc and an integrated surface density of (1.62 +/- 0.04 (random) +/- 0.14 (systematic)) 10^{-3} stars pc^{-2}. A halo component is also detected in the distribution and constitutes at least ~5% of the total O-B5 population. The O-B5 stellar population within ~100 pc of the Sun has an anomalous spatial distribution, with a less-than-average number density. This local disturbance is probably associated with the expansion of Gould's belt.Comment: 14 pages, 3 figures, to appear in the May 2001 issue of the Astronomical Journa