Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Protocol for the in vitro rearing of honey bee (Apis mellifera L.) workers

Abstract: The in vitro rearing of worker honey bees (Apis mellifera L.) has become an increasingly important method in honey bee research in general, and in pesticide risk assessment specifically. Authorities from the European Organization for Economic Co-operation and Development and the United States Environmental Protection Agency are requesting data on pesticide impacts on immature bee survivorship prior to registering new crop protection products. Those using the current in vitro rearing protocols have had variable success with immature bee survival and protocol repeatability. Here, we present an improved method for the in vitro rearing of worker honey bees from larvae to adult emergence. We have achieved consistently high survival (>95%) in our control and solvent-control rearing trials. Changes in the proportion of diet components, royal jelly source, maintenance of the developing bee, and rearing environment are the main contributors for our high rearing success and are discussed herein. Our in vitro rearin...

Propagação vegetativa de cedro-rosa por miniestaquia

Abstract: This work had the objective to evaluate the minicutting technique as a method for vegetative propagation of cedro-rosa (Cedrela fissilis), in terms of the production and survival of the ministumps after successive harvesting, as well as rooting and growth (height and root collar diameter) of the minicuttings. The minicuttings were obtained from seedlings of Cedrela fissilis, successively collected and submitted to different dosages of the growth regulator IBA. The results showed the efficiency of this technique in the vegetative propagation of this species. Up to 79% survival was obtained at 120 days of age, but when IBA was not applied, survival was higher. Overall, minicutting of Cedrela fissilis from material of seminal origin is technically viable. Its is an alternative method for producing seedlings of this species throughout the year, mainly when seeds are unavailable.

Investigation on the Esterification of Fatty Acids Catalyzed by the H3PW12O40 heteropolyacid

Abstract: In this work, the H3PW12O40 heteropolyacid (HPW) was employed as a homogeneous catalyst to promote the efficient esterification (ethanolysis) of a number of saturated and unsaturated fatty acids (myristic, palmitic, stearic, oleic, and linoleic) under mild reaction conditions. HPW showed a similar activity to those observed for p-toluene sulfonic acid (PTSA) and sulfuric acid (H2SO4), the other acidic catalysts we compared them with in this study. In the HPW-catalyzed esterification of stearic acid, the addition of water caused a remarkable decrease in the ethyl stearate yields. On the other hand, the increase in the HPW concentration (up to a maximum value) promoted a proportional improvement in the oleic acid to ethyl oleate conversion. Kinetic measurements using oleic acid as a prototype substrate revealed that the esterification reactions catalyzed by HPW, H2SO4, and PTSA are of first-order in relation to the fatty acid concentration. Finally, the catalytic activity of HPW remained unaltered even after several recovery/reutilization cycles whereas the tungsten content in the final product (biodiesel produced by the HPW-catalyzed esterification of oleic acid) was found to be at an acceptably low level (0.0095 mg of W per g of biodiesel).

Estimation of inside-bark diameter and heartwood diameter for Tectona grandis Linn. trees using artificial neural networks

Abstract: The objective of this study was to obtain neural networks that would precisely estimate inside-bark diameter (dib) and heartwood diameter (dh) and compare to the results obtained by the Taper models. The databank was formed so as to eliminate inconsistent and biased data, and stratified: minimum dib of 4, 6 and 8 cm and minimum dh of 10, 15 and 20 cm. The adjusted Taper model used was the Kozak model. For the fitting of artificial neural networks (ANN), tests were performed to identify the independent variables and the database scope level, i.e., the following input variables were tested: diameter at breast height (dbh), total height (H), height at diameter dib or dh (h) and outside-bark diameter at h (dob), bark thickness at 1.3 m and project, and the scope at database level or project level. The estimates obtained by the neural networks and Kozak model were evaluated by residual graphs in function of the respective diameter observed and graph of the observed versus estimated values. ANN were found to be more efficient in estimating inside-bark and heartwood diameters for Tectona grandis trees than the Kozak model. The variables that must be used to fit the networks are dbh, H, h and dob. Stratification by project results in precision gain, with precision being higher for wider commercial diameters. Thus, linear-type artificial neural networks can be efficient in describing the taper of Tectona grandis trees.

Bioactivity of compounds from Acmella oleracea against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) and selectivity to two non-target species.

Abstract: BACKGROUND: Tropical plants are recognised sources of bioactive compounds that can be used for pest control. The objective of this study was to evaluate the biological activity of compounds present inAcmellaoleracea (Asteracea) againstTutaabsoluta (Meyrick) (Lepidoptera: Gelechiidae), which is the main pest of tomato crops in Latin America. The selectivity of these compounds to the predator Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) and to the pollinator Tetragonisca angustula (Latr.) (Hymenoptera: Apidae: Meliponinae) was also of interest. RESULTS: A bioassay screening with hexane and ethanol extracts from 23 plants was performed. The hexane extract of A. oleraceae was the most active of the extracts and was selected for further study. The following three alkamides were isolated from a hexane extract of the aerial parts of A. oleracea: spilanthol, (E)-N-isobutylundeca-2-en-8,10-diynamide and (R,E)-N-(2methylbutyl)undeca-2-en-8,10-diynamide. All of the isolated compounds showed insecticidal activity, with spilanthol being the most active (LD50 = 0.13 µ gm g −1 )a gainstT.absoluta. The alkamides were selective to both beneficial species studied. CONCLUSION: The crude hexane extract ofA.oleraceae showed high insecticidal activity and can be used to controlT.absoluta in organic or conventional crops. Quantification of LD50 values of isolated compounds against T.absoluta showed that alkamides could serve as potent insecticides for T. absoluta control programmes. Spilanthol was the main alkamide active isolated. This alkamide is the most promising as it has the highest insecticidal activity and is selective to non-target organisms. c � 2011 Society of Chemical Industry