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Eloy Alfaro, Ecuador

Olivito R.S.,University of Calabria | Codispoti R.,University of Calabria | Cevallos O.A.,National University of Chimborazo
Composite Structures | Year: 2016

In this paper an experimental investigation on bond adhesion between sustainable composite material and masonry support was carried out in the Civil Engineering Laboratory of the University of Calabria. This topic was addressed performing experimental tests and considering a theoretical approach. For this purpose, double-lap shear bond tests were carried out on typical masonry clay bricks, externally strengthened with composite materials (NFRCM - Natural Fibers Reinforced Cementitious Matrix). In particular, two different composite materials were studied: flax fabric-reinforced cementitious matrix (Flax-FRCM) and PBO fabric-reinforced cementitious matrix (PBO-FRCM) composites. In the end, a comparison between the experimental results achieved and those proposed by the Italian design code CNR 200 R1/2012 was performed, picking out some relevant aspects of the design procedures. © 2016 Elsevier Ltd. Source

This review describes synthetic methods for the preparation of such modern and versatile building-blocks as 2-CF3-4-pyrones (2-(trifluoromethyl)-4H-pyran-4-ones), and their use in regioselective syntheses of various CF3-containing compounds. Synthesis of 2-CF3-4-pyrones bearing a substituent (substituents) at position(s) 3, 5 and 6, as well as regioselective preparation of trifluoromethylated 4(1H)-pyridin-4-one, benzo[c][1,6]naphthyridine, 4-thiopyrone, 2-quinaxolinone, diazepine, benzo[b][1,4]oxazin-2-one, pyrazole, 3-(pyrazolyl)indlole, pyrazolo[1,5-c]pyrimidine derivatives on the basis of these building-blocks has been described. The closest analogs of 2-CF3-4-pyrones, 2-RF-4-pyrones (RF = CF2H, C2F4H, C3F7, C4F9, C6F13, CF2CFCl2, CF2CHFCF3) has also been presented in the review. Due to unique regioselectivity, a strong regio-sensitivity to solvents and availability, 2-CF3-4-pyrones can be attributed to excellent starting or intermediate substrates for the preparation of various trifluoromethylated compounds. In contrast to other 2-RF-4-pyrones, 2-CF3-4-pyrones are more synthetically available and interact with nucleophiles usually more selectively. ©2015 Elsevier B.V.All rights reserved. Source

Usachev B.I.,National University of Chimborazo
Journal of Fluorine Chemistry | Year: 2015

This review describes synthetic methods for the preparation of such advanced conjugated cyclic dienes and electrophiles as 6-CF3-2-pyrones (6-(trifluoromethyl)-2H-pyran-2-ones), their versatile chemical properties and use in the syntheses of various CF3-containing cycloadducts, highly functionalized trifluoromethylated aromatic and heteroaromatic compounds. Synthesis of 6-CF3-2-pyrones bearing a substituent (substituents) at position(s) 3, 4 and 5, regio- and stereoselective preparation of trifluoromethylated cycloadducts (and their derivatives) via Diels-Alder reactions (and retro hetero-Diels-Alder reaction) from these pyrones and compounds containing in their molecules a reactive double (triple) bond, as well as reactions with nucleophiles has been presented in the review. Due to the presence of the electron-withdrawing trifluoromethyl group and the diene moiety, 6-CF3-2-pyrones are highly reactive substrates towards both dienophiles and nucleophiles. High regio- and stereoselectivity of the reactions allows the use of these excellent CF3-containing building-blocks for the preparation of various bicyclic, aromatic and heteroaromatic compounds, important starting substrates in biological or medicinal chemistry and related areas. © 2015 Elsevier B.V. All rights reserved. Source

Gonzalez-Castro A.,CSIC - Institute of Natural Products and Agrobiology | Gonzalez-Castro A.,National University of Chimborazo | Calvino-Cancela M.,University of Vigo | Nogales M.,CSIC - Institute of Natural Products and Agrobiology
Ecology | Year: 2015

Seed dispersal effectiveness (SDE) is the contribution of dispersers to plant recruitment and is estimated as the product of the number of seeds dispersed (quantity) and the probability of recruitment of each dispersed seed (quality). Although SDE is a key concept in seed dispersal ecology, few studies estimate SDE and none has a community approach. Oceanic islands, with simple communities, are ideal for this purpose. In this study, we compared the SDE of the main types of dispersers (lizards and passerine birds) at the community level in a given habitat. We estimated SDE using a stochastic simulation model parameterized with empirical data on quantity and quality components measured throughout the recruitment process. Although lizards are highly frugivorous and their density was ~20 times higher than that of birds, lizards and birds dispersed a similar quantity of seeds. This may be due to lower intake of seeds by lizards due to their slower metabolism (~20 times lower than birds). This low metabolic rate limits the importance of lizards as seed dispersers, but it is compensated by extraordinarily high lizard densities in the study area (~9600 individuals/km2). High densities of lizards are typical of islands, and this helps to explain why dispersal by lizards seems mainly an island phenomenon. Birds and lizards showed functional complementarity, especially regarding seed dispersal distribution patterns. In fact, lizards dispersed more seeds in shrublands and open sites, and birds in woodlands and beneath canopies, with their joint contribution helping to maximize recruitment. Lizards provided higher SDE than birds for 7 out of 11 plant species. The disperser with a higher quantity for a given plant generally had the higher quality, and plants could be classified as bird- or lizarddependent for dispersal. This dependence increased when considering SDE instead of dispersal quantity only. Moreover, quality was a better predictor of SDE than quantity, which should be considered when parameterizing interaction networks, as this might affect inferences about their architecture. © 2015 by the Ecological Society of America. Source

Synthesis, significance and potential applications of such medicinally and biologically beneficial compounds as fluoroalkylated at the pyrrole moiety indoles (1-/2-/3-fluoroalkyl-substituted indoles) are described. Having various bioactive properties, RF-indoles are promising medicinally and biologically beneficial compounds. At present, known synthetic routes for the preparation of RF-indoles affect a fairly wide variety of advanced methods. These important substances can be synthesized either via direct fluoroalkylation or via procedures involving transformations of fluoroalkylated building-blocks. In direct fluoroalkylation (trifluoromethylation), indole and its derivatives were used in the reactions with such fluoroalkylating agents as fluoroalkyl halides, CF3CO2Na (in the presence of CuI), Ruppert-Prakash reagent (a Pd-catalyzed trifluoromethylation), CuI/FO2SCF2CO2Me. 2-CF3-4-pyrones can be used as trifluoromethylated building blocks for regioselective syntheses of CF3-indoles. Cyclizations of some RF-bearing ortho-disubstituted benzene derivatives allow preparation of various RF-indoles. Reactivity of the trifluoromethyl group and indole moiety of CF3-indoles is considered. © 2016 Elsevier B.V. All rights reserved. Source

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