Soil compaction processes in a Vertisol under four handling conditions in Coro Plain, Falcón State, Venezuela [Procesos de compactación en un suelo Vertisol bajo cuatro condiciones de manejo en la llanura de Coro, Estado Falcón, Venezuela]
Reyes R. W.J.,Francisco de Miranda National Experimental University
Bioagro | Year: 2014
The study was conducted on soils classified as Vertisol, belonging to the Academic Support Unit "Ingeniero José Landaeta", Academic Unit of the Francisco de Miranda University, under four management conditions: fallow condition (C1), semi-permanent crop condition (C2), previous pasture conditions (C3), and intensely intervened areas (C4). Under each condition the soil compaction process was evaluated at 0-15 and 15-30 cm using physical, chemical and biological indicators. It was found no differences in the first layer for the management conditions, while in the second layer bulk density significantly increased for conditions of increased mechanical intervention. Likewise, principal component analysis discriminated two groups of soils: one under conditions of increased antropic disturbance (C2 and C4), and the other consisting of resting or less disturbed soils (C1 and C3); the first group was associated to greater variation in bulk density due to higher mechanical manipulation, while the second group was associated to improvements of organic matter content, attributed to the natural vegetation contributions.
Smith D.,Francisco de Miranda National Experimental University |
Graciano C.,National University of Colombia |
Martinez G.,Simon Bolivar University of Venezuela
Thin-Walled Structures | Year: 2014
Previous studies have demonstrated that the failure mechanism and energy absorption capacity of expanded metal tubes strongly depends on the orientation of the cells. This paper presents an experimental investigation on the collapse of concentric expanded metal tubes subjected to quasi-static axial compression. Square tubes with two different cell orientations are tested to failure, and the energy absorption characteristics are calculated. The results show that the combination of cell geometries lead to a complex buckling mode interaction, which enhances the energy absorption capacity of expanded metal tubes. © 2014 Elsevier Ltd.
Corzo O.,University of the East Venezuela |
Bracho N.,University of the East Venezuela |
Rodriguez J.,Francisco de Miranda National Experimental University
LWT - Food Science and Technology | Year: 2012
Application of the Peleg and Azuara etal. models for describing mass transfer during pile salting of goat sheets using different mixtures of NaCl, KCl, CaCl 2 and MgCl 2 was investigated The high coefficient of determination (R 2>0.97 and R 2>0.95 for Peleg and Azuara etal. models, respectively) and the modulus of mean relative errors (MRE<10% for both models) indicated the acceptability of both Peleg and Azuara etal. models for predicting both moisture loss and salt uptake. The equilibrium moisture and salt contents were estimated using Peleg rate constants and Azuara etal. model parameters. Equilibrium moisture (x w) and salt contents (x s) varied from 0.522 to 0.860g water/g db and from 0.311 to 0.352g NaCl/g db respectively. Multiple comparison of means showed that x w and x s predicted by the Peleg model were lower than those estimated by the Azuara etal. model. The values differed by 1.86-13.6% for x w and by 1.13-10.57% for x s. © 2011 Elsevier Ltd.
Corona Lisboa J.L.,Francisco de Miranda National Experimental University
Revista Cubana de Investigaciones Biomedicas | Year: 2015
Determination of genetic sex takes place at the time of fecundation whereas differentiation of gonadal and genital sexes occurs during critical periods of embrionary life. The factors that modify the mechanisms of sex differentiation are varied and their anatomical and pathological, genetic and molecular study have attracted many researchers interested in this topic. The objective of the present article was to describe the genetic anomalies related to the development in sexual morphophysiology of mammals, starting from a deductive approach on the basis of reported research works on this topic. According to the information, it was concluded that anomalies of the chromosomal, gonadal and genital sex respond to a series of genetic alterations that involve a set of enzymatic cascades affecting the normal course of the sexual morphophysiological development of the animal. © 2015, Editorial Ciencias Medicas. All rights reserved.
Vucetich M.G.,Museo de La Plata |
Carlini A.A.,Museo de La Plata |
Aguilera O.,Francisco de Miranda National Experimental University |
Sanchez-Villagra M.R.,University of Zurich
Journal of Mammalian Evolution | Year: 2010
We report a new vertebrate assemblage from the Pliocene Vergel Member of the San Gregorio Formation in northwestern Venezuela, which includes Crocodylia and Testudines indet., toxodonts, at least four species of xenarthrans of the Dasypodidae, Pampatheriidae, Glyptodontidae and Megatheriidae, and rodents. The last are Cardiatherium, cf. Caviodon (Hydrochoeridae), Neoepiblema (Neoepiblemidae), and what is here described as a new genus of a low-crowned octodontoid. cf. Caviodon is the first cardiomyine for northern South America. The rodent assemblage resembles in its ecological composition those of the late Miocene (Huayquerian) from the "Mesopotamian" of Argentina and the Acre region in Brazil, with partially overlapping systematic composition. The stratigraphic position of the San Gregorio Formation and mammals other than caviomorphs suggest a late Pliocene age for these sediments, implying the endurance of rodent taxa beyond their biochron in southern South America. © 2010 Springer Science+Business Media, LLC.