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The impact of bees (Apis mellifera L.) as pollinators in the yield of the zucchini (Cucurbita pepo L.) crop in the Riobamba canton, Chimborazo province, was evaluated using a Randomized Complete Block Design (RCBD). This was done using three treatments and three repetitions. The treatments evaluated were: the zucchini cultivation inside the micro tunnel covered with entomological mesh with the presence of bees, the zucchini cultivation inside the micro tunnel covered with anti aphids mesh without the presence of bees, and the open field zucchini cultivation. The evaluated parameters were number of days to the appearance of the fruits, percentage of fertilized and unfertilized flowers, number of fruits per plant, size of fruits, diameter of fruits, weight of fruit, and yield in kg / ha per treatment. The best results achieved in most parametersthat were evaluated such as the percentage of flowering, number of fruits per plant, size of fruit in cm, diameter of fruit in cm, weight of the fruit in grams, yield in kg/ha by treatment, and economic analysis were obtained with the presence of bees (Apis mellifera L.) as pollinating agents in the tunnel. This is in addition to meshes during the flowering stage of the zucchini crop, with an average yield of 14.9 tn/ha. Se evaluo el impacto de las abejas (Apis mellifera L.) como agentes polinizadores en el rendimiento del cultivo de zucchini (Cucurbita pepo L.) en el canton Riobamba, provincia de Chimborazo. Para llevar a cabo esta evaluacion se utilizo un diseno de bloques completos a azar (DBCA), con tres tratamientos y tres repeticiones. Los tratamientos evaluados fueron: El cultivo de zucchini dentro del micro tunel cubierto con malla entomologica con presencia de abejas, el cultivo de zucchini dentro del micro tunel cubierto con malla antiafidossin presencia de abejas y el cultivo de zucchini a campo abierto. Los parametros evaluados fueron numero de dias transcurridos despues de la aparicion de los frutos, porcentaje de flores fecundadas y no fecundadas, numero de frutos por planta, tamano de frutos, diametro de frutos, peso del fruto y rendimiento en kg/ha por tratamiento. Los mejores resultados alcanzados en la mayoria de los parametros evaluados como el porcentaje de floracion, numero de frutos por planta, tamano de fruto en (cm), diametro de fruto en (cm), peso del fruto en gramos, rendimiento en kg/ha por tratamiento y analisis economico, se obtuvieron con la presencia de las abejas (Apis mellifera L.) como agentes polinizadores en el tunel con mallas durante la etapa de floracion del cultivo de zucchini, con un rendimiento en promedio de 14.9 tn/ha.

Se presentan 319 taxa de hongos del Volcan de Tequila, colectados en los diferentes tipos de vegetacion presentes: bosque de encino, bosque mixto de pino-encino, bosque mesofilo de montana y bosque tropical caducifolio. Del total de especies, 279 son Basidiomycota, 33 Ascomycota del reino fungi y siete de Myxogastrea del reino Protozoa. Los ordenes mejor representados fueron los Agaricales, Polyporales y Boletales.

This paper reports on the pressure dependence of the optical absorption edge of ZnO in the wurtzite and rock-salt phase, up to 14 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films have been investigated. In both types of samples the wurtzite to rock-salt transition is observed at 9.7±0.2 GPa. The absorption tail of the fundamental gap, as measured in monocrystals, exhibits a pressure coefficient of 24.5±2 meV/GPa. The evolution under pressure of the full absorption edge of the wurtzite phase is studied with thin film samples, yielding a slightly lower pressure coefficient (23.0±0.5 meV/GPa for the A–B exciton). Rock-salt ZnO is shown to be an indirect semiconductor with a bandgap of 2.7±0.2 eV. At higher photon energy a direct transition (Egd–4.5 eV) can be also identified in thin films transited to the rock-salt phase. Results on the high-pressure phase are interpreted on the basis of density-functional-theory (DFT) electronic structure calculations.

We use an ab initio total energy pseudopotential technique within the Density Functional Theory in the local-density approximation to determine the vibrational normal modes (phonons) defined within the first Brillouin Zone of BAs. We also study the effects of hydrostatic pressure on these phonons and the mode Gruneisen parameters using the response-function formalism for the computation. There is a very good agreement between the transversal optical phonon frequency at the Γ point calculated on this way and that with the frozen phonon technique. We also study the electronic band structure, the band-gap pressure dependence and the generalized stability criteria.

We used an ab initio total energy pseudopotential technique within the density functional theory in the local-density approximation to determine the full set of first-order elastic constants of BAs, which have not been established experimentally. We also calculated the bulk modulus, the optical phonon frequency at the Γ point, and we present a study of the electronic band structure. Finally we also determined the pressure dependence of the elastic constants Cij. Due to the absence of the experimental data our results can be considered as reliable predictions of the elastic moduli and the pressure derivatives. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003

We present the results of an ab initio theoretical study within the local density approximation to determine the pressure dependence of the second-order elastic constants C ij of BP, AlP, GaP and InP in order to clarify the mechanism of the pressure-induced phase transition in these compounds. Our results do not support the idea of a soft acoustic branch as responsible for the phase transition.

This investigation presents electrochemical analyses of galvanized steel reinforcements in alkaline solutions simulating a concrete-pore environment, in which a commercially available corrosion inhibitor was used. Half-cell potentials and linear polarization resistance were used to determine if the selected inhibitor decreases the corrosion activity of the galvanized coating when the galvanized rebar is in contact with high-pH solutions. Results show a remarkable decrease on passivation times between the solutions with inhibitor υs. without inhibitor.