Salim Rosales C.B.,CONICET |
Rojas M.I.,National University of Cordoba |
Avalle L.B.,National University of Catamarca
Journal of Electroanalytical Chemistry | Year: 2017
The electrochemical behavior of phosphate species on Ag(111) and Ag(100) single crystal surfaces was studied by experimental techniques and theoretical calculations. Characteristic cathodic/anodic potential peaks (Vp) appear in the current density-potential curves (j–V) for H2PO4 −, H3PO4, and in the case of PO4 3− for concentrations lower than 0.1 M, where the interaction is stronger for the Ag(100) electrode. This demonstrate that the adsorption is sensitive to the surface structure. The adsorption energy (Eads) of the different species on both surfaces was studied by means of DFT-vdW calculations. All phosphate species have tri-dentate binding. The |Eads| increased for the H3PO4; H2PO4 −; HPO4 2− and PO4 3− sequence, and the tetrahedral structures are compressed. Although the same trend was observed on both crystalline surfaces, the films have the symmetry of the substrate, C3v and C4v. The influence of hydroxide co-adsorption was studied for different [HPO4 2−]/[PO4 3−] ratios in solution. The strength of adsorption obtained from experimental and theoretical calculations show an excellent qualitative correlation. © 2017 Elsevier B.V.
Bordcoch M.,National University of Catamarca |
Kozameh C.N.,CONICET |
Rojas T.A.,National University of Catamarca
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016
The dynamical equations for the null surface formulation of general relativity for purely radiative spacetimes are derived. Those asymptotically flat spacetimes describe the nonlinear evolution of gravitational radiation and represent a classical graviton. The evolution equations constitute a set of three partial differential equations in a six-dimensional space and the source term is the free initial data of incoming gravitational radiation. The Huygens part of the wave propagation, backreaction terms, and source terms are identified in the resulting equations. An analysis of the range of validity of these equations based on the development of caustics is also given. © 2016 American Physical Society.
Heredia C.L.,National University of Catamarca |
Heredia C.L.,National University of Salta |
Ferraresi-Curotto V.,National University of Catamarca |
Ferraresi-Curotto V.,National University of La Plata |
Lopez M.B.,National University of Catamarca
Computational Materials Science | Year: 2012
Geometric, magnetic and electronic features, vibrational frequencies and global reactivity descriptors of Pt n (n = 1-12) were studied in the present work within the framework of the density functional theory. Structures for n = 7, 10, 11 and 12 have not been reported before, in other cases agreement exists with results reported by other authors, as are the data obtained through vibrational spectroscopy calculations. Results obtained from global reactivity descriptors such as chemical potential, chemical hardness and electrophilicity index, indicate that platinum clusters up to twelve atoms tend to increase their reactivity with size. © 2011 Elsevier B.V. All rights reserved.
Cappa D.F.,Memorial University of Newfoundland |
Cappa D.F.,National University of Catamarca |
Behm D.G.,Memorial University of Newfoundland
Journal of Strength and Conditioning Research | Year: 2013
The objective of this study was to compare drop (DJ) and hurdle jumps using a preferred, flat foot (FLAT) and forefoot (FORE) landing technique. Countermovement jump height was used to establish the hurdle and the DJ heights. The subjects performed forward hurdles and vertical DJs on a force plate. Measures included vertical ground reaction force (VGRF), contact time, leg stiffness, and rate of force development (RFD). Electromyographic (EMG) activity was measured in the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius during 3 phases: preactivity, eccentric phase, and concentric phase. All the kinetic variables favored hurdles over DJs. Specifically, hurdle-preferred technique and FORE exhibited the shortest contact time and DJ FLAT the longest. The VGRF was higher in hurdle preferred and FORE than in DJ preferred, FLAT, and FORE. For stiffness and RFD, hurdle preferred and FORE were higher than DJ preferred and FLAT. Hurdle jumps showed higher rectus femoris EMG activity than DJ did during preactivity and eccentric phases but lower activity during the concentric phase. Considering the type of landing, FLAT generally demonstrated the greatest EMG activity. During the concentric phase, DJ exhibited higher rectus femoris EMG activity. Biceps femoris activity was higher with hurdles in all the phases. Gastrocnemius showed the highest EMG activity during the concentric phase, and during the eccentric phase, hurdle preferred and FORE showed the highest results. In conclusion, the hurdle FORE technique was the most powerful type of jump. © 2013 National Strength and Conditioning Association.
Marcora P.I.,National University of Cordoba |
Renison D.,National University of Cordoba |
Pais-Bosch A.I.,National University of Catamarca |
Cabido M.R.,National University of Cordoba |
Tecco P.A.,National University of Cordoba
Forest Ecology and Management | Year: 2013
Understanding the factors that determine altitudinal distribution of species is very important to evaluate the influence of global change. Although climate is the major driver of vegetation distribution, other factors, such as herbivory by livestock, can be more important locally and regionally. Despite its importance, the altitudinal range distribution of species and how it is influenced by climate and livestock are generally unknown. In the Sierras Grandes Mountains of central Argentina, woodlands of lower and upper altitudes are interrupted by an intermediate vegetation belt devoid of forest. Traditionally, this pattern was assumed to be determined by climate, although recent studies suggest that forest distribution would be driven by livestock grazing. However, the potential altitudinal range distribution of the principal woody species of these forests and how it is affected by livestock are still poorly known. In this study, we used an experimental approach to evaluate seedling survival and growth - with and without livestock presence - of the three principal woody species of the mountain woodlands along the entire altitudinal gradient of Sierras Grandes. In January 2009, we planted seedlings of Polylepis australis, Maytenus boaria and Escallonia cordobensis inside and outside livestock exclosures at seven altitudinal sites established every 200-400. m. asl, from 940. m. asl to 2700. m. asl (i.e., maximum altitude of Sierras Grandes). During the three following winters, we evaluated seedling survival and height and measured stocking rates. Although the three species were able to sprout after browsing, livestock markedly reduced seedling survival and height. Inside the exclosure, the three species successfully survived and grew along the entire gradient, including the altitudinal belt devoid of forest. Furthermore, after three growing seasons P. australis and E. cordobensis flowered inside the exclosure at the altitudes where seedlings reach greater heights (2200. m. asl and 1200 and 1600. m. asl, respectively). We suggest that under the current high stocking rates, livestock would strongly hinder seedling establishment of the three principal woody species at most altitudes of Sierras Grandes. Our findings are in agreement with the assumption that the present altitudinal belt devoid of forest is not climatically driven; rather, livestock is the major factor of current forest distribution. © 2012 Elsevier B.V.
Lomaglio D.B.,National University of Catamarca
Nutricion Clinica y Dietetica Hospitalaria | Year: 2012
Argentina through the nutrition transition (TN), affecting virtually all populations in the world, with particular characteristics and heterogeneity within provinces and regions. Changes in diet, with lifestyles are traversed by socioeconomic conditions changing of economic crisis experienced by the country in recent decades. The region of northwestern Argentina (NOA) in particular has the lowest human development indicators that articulate with an increasingly growing trend towards obesity, particularly in the poorest strata of society, in addition to food strategies play chords to the family budget other factors, cultural, related to the poorer perceived fatness as a sign of prosperity.
Fernandez L.,National University of Catamarca |
Sanabria E.A.,National University of San Juan |
Quiroga L.B.,National University of San Juan
Ichthyological Exploration of Freshwaters | Year: 2013
Silvinichthys gualcamayo, new species, is described from a stream at 2000 m elevation in the lower slope of the Andean cordillera of San Juan, Argentina. It is distinguished from the three previously described species in the genus by the following combination of characters: the pelvic fin and girdle absent, the caudal peduncle expanded posteriorly toward caudal-fin, the caudal peduncle length 22.0-23.9 % SL, 9-10 dorsal-fin rays, 5-6 branched dorsal-fin rays, 38 vertebrae total, 9 opercular odontodes, 20 interopercular odontodes, 7 pectoral-fin rays, and the wide supraorbital tendon bone. © 2013 by Verlag Dr. Friedrich Pfeil, München, Germany.
Ibezim E.,CONICET |
Duchowicz P.R.,CONICET |
Ortiz E.V.,National University of Catamarca |
Chemometrics and Intelligent Laboratory Systems | Year: 2012
In this work we offer linear regression models on a set of aryl-piperazine derivatives that are obtained by exploring a pool containing 1497 Dragon molecular descriptors, in order to establish the best relationships linking the molecular structure characteristics to their exhibited potencies against chloroquine resistant and chloroquine sensitive strains of Plasmodium falciparum parasite. The adjustment of the training molecular set together with the performance achieved during the internal and external validation processes leads to predictive QSAR models. In addition, we derive alternative linear models based on the Coral methodology, which lead to satisfactory results. We apply the final equations to predict the activity on some unknown compounds having non-observed activities. © 2011 Elsevier B.V.
Duchowicz P.R.,CONICET |
Comelli N.C.,National University of Catamarca |
Ortiz E.V.,National University of Catamarca |
Current Drug Safety | Year: 2012
In our continuing efforts to find out acceptable Absorption, Distribution, Metabolization, Elimination and Toxicity (ADMET) properties of organic compounds, we establish linear QSAR models for the carcinogenic potential prediction of 1464 compounds taken from the "Galvez data set", that include many marketed drugs. More than a thousand of geometry-independent molecular descriptors are simultaneously analyzed, obtained with the softwares E-Dragon and Recon. The variable subset selection method employed is the Replacement Method, and also the improved version Enhanced Replacement Method. The established models are properly validated through an external test set of compounds, and by means of the Leave-Group-Out Cross Validation method. In addition, we apply the Y-Randomization strategy and analyze the Applicability Domain of the developed model. Finally, we compare the results obtained in present study with the previous ones from the literature. The novelty of present work relies on the development of an alternative predictive structure-carcinogenicity relationship in a large heterogeneous set of organic compounds, by only using a reduced number of geometry independent molecular descriptors. © 2012 Bentham Science Publishers.
Sanchez Reinoso C.R.,National University of Litoral |
Sanchez Reinoso C.R.,Institute of Technological Development for the Chemical Industry INTEC |
Sanchez Reinoso C.R.,National University of Catamarca |
Milone D.H.,National University of Litoral |
Buitrago R.H.,Institute of Technological Development for the Chemical Industry INTEC
Applied Energy | Year: 2013
The increase in the power of photovoltaic systems involves a significant grow in the number of modules that make them up. The known problems caused by the shading are not usually taken into account in the design of a photovoltaic central away from urban environments. The aims of this study are to obtain a model for simulation of photovoltaic plants, representing the array under different conditions of dynamic shading, and to investigate its effects on configurations of modules array and converters. Performance measures are also discussed in order to find those most suitable for plants comparison in this context. Analyzing the efficiency of the maximum power point tracker and the inverter under different conditions of dynamic shading, using one or more inverters, a better performance is generally achieved by reducing the number of modules in series and by increasing the number of those in parallel. But the parallel connections are only suitable in certain conditions and the optimal number of parallels cannot be established trivially. The results show that the operating conditions determine the most efficient connection scheme with partial shading by using central inverter. Without using an optimization algorithm, we achieve results with central inverters not far from using microinverters. These results indicate that using the proposed simulator and an optimization algorithm, it can be optimize the complete system energy and take advantage of lower costs of central inverters for large photovoltaic plants. © 2012 Elsevier Ltd.