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San Miguel de Tucuman, Argentina

The National University of Tucumán is an Argentine national university located in Tucumán Province and the largest in Argentina's northwest region. Founded on 25 May 1914 in San Miguel de Tucumán, access to the university is unrestricted and free of charge. Wikipedia.

Luccioni B.,National University of Tucuman | Rougier V.C.,University of Concepcion del Uruguay
Construction and Building Materials | Year: 2011

Research activities carried out during the past years concerning the use of fibre reinforced polymers (FRP) as external reinforcement of masonry walls have shown that this system considerably improves structural stability and ductility with minimum increase in the load transmitted to foundations. However, different aspects of this retrofitting system should still be analyzed. The mechanical behaviour under in-plane compression and diagonal compression of clay masonry panels reinforced or repaired with carbon fibre reinforced polymer laminates is experimentally assessed in this paper. The results show that if correct retrofitting schemes are chosen, reinforcement and repairing with fibre reinforced polymers improves masonry behaviour, increasing ductility and, in some cases, ultimate strength and even stiffness. In this way, brittle behaviour and sudden failure of unreinforced masonry can be avoided. © 2010 Elsevier Ltd. All rights reserved. Source

Escapa I.H.,CONICET | Catalano S.A.,National University of Tucuman
International Journal of Plant Sciences | Year: 2013

Premise of research. Phylogenetic relationships of Araucariaceae (Coniferophyta, Araucariales) are revised on the basis of the first combined data matrix for the family. Methodology. Taxon sampling includes 39 ingroup species (31 extant, 8 fossils) and outgroup species of all the remaining conifer families. Five fossil Araucaria species, one species of the genus Araucarites, and two species of the extinct genera Wairarapaia and Emwadea were included in the analyses. Character sampling includes 23 genomic regions (19 plastid, 2 nuclear, and 2 mitochondrial) and 62 morphological characters (52 discrete and 10 continuous). The phylogenetic analyses were conducted with equally weighted parsimony. Additionally, several analyses under different taxon- and gene-sampling regimes were analyzed for identifying the causes of the long-lasting controversies in the interrelationships of the three extant genera of Araucariaceeae. Pivotal results. Monophyletic Araucariaceae is the sister group of Podocarpaceae, forming the order Araucariales. Monophyly of Araucaria and Agathis is also strongly supported by the data. The results of both molecular and combined analyses indicate that Wollemia and Agathis form a clade (pagathioid clade) sister to Araucaria. Within Araucaria, the analyses support the monophyly of the four currently recognized sections: Araucaria, Bunya, Intermedia, and Eutacta. Results support the monophyly of living and fossil Araucaria (including Araucarites), whereas the remaining extinct genera are placed as the stem of the agathioid clade. In terms of the sensitivity analyses performed, results suggest that inconsistencies among previous results would be related to ingroup sampling. Conclusions. By means of a combined phylogenetic analysis, we have been able to obtain a strongly supported and well-resolved phylogeny of Araucariaceae that includes both living species and fossil species for the group. This study shows the feasibility and usefulness of phylogenetic analyses that incorporate multiple sources of evidence (molecules/morphology, living/fossil species, discrete/continuous characters). © 2013 by The University of Chicago. All rights reserved. Source

Grosse C.,National University of Tucuman | Delgado A.V.,University of Granada
Current Opinion in Colloid and Interface Science | Year: 2010

In this work we describe the fundamentals of the phenomenon of dielectric dispersion in aqueous colloidal suspensions, as well as the most recent advances on the subject. We begin by establishing the admitted definitions of the permittivity of a heterogeneous system consisting of a certain volume of a material dispersed in the form of identical spheres (the particles) in a liquid medium (an electrolyte solution). Attention is also paid to the relationship between the electric permittivity of the suspension and the strength and frequency dependence of the dipole moment induced by the external field. A thorough historical revision is provided, describing the key contributions, both experimental and theoretical, to the development of this field of electrokinetics and interface physics. In fact, elucidation of the mechanisms responsible for the values of the permittivity of disperse systems over a wide enough frequency range is a rich exercise in electromagnetism, fluid mechanics and electrochemistry of interfaces. Three mechanisms are typically responsible for the dielectric dispersion of the suspension. The gamma dispersion is a manifestation of the frequency dependence of the permittivity of the aqueous electrolyte solution where the particles are suspended. It is mainly determined by the polar nature of the water molecules and its characteristic frequency is in the GHz range. The delta dispersion (typically in the MHz range) is determined by the Maxwell-Wagner-O'Konski relaxation mechanism: it occurs because of the different permittivities and conductivities of the particle and the surrounding medium. Finally, the alpha- or Low Frequency Dielectric Dispersion (LFDD) is a phenomenon characterized by a huge increase of the permittivity at very low frequencies (kHz range). Its relationship with the phenomenon of concentration polarization is carefully discussed, as it is an essential feature of the electric permittivity of suspensions. The mathematical treatment of the problem is rather complex, and analytical solutions are only available in a limited number of cases. Attention is hence also devoted to describing and comparing the numerical approaches that can be used. Experimental determination of the (particularly low frequency) dielectric dispersion is complicated mainly because of the phenomenon of the polarization of the electrode-solution interface. In this contribution we describe the solutions reported to this problem, both in the frequency and in the time domains. An interesting aspect of dielectric dispersion determinations, not shared by other techniques, is their applicability to concentrated suspensions. The modifications of the theory of the permittivity of suspensions, required to account for the hydrodynamic and electrical interactions are also described, stressing the fact that suspensions often considered as dilute are actually far from being so. The review is finished with a description of the most recent advances, namely the consideration of suspensions of soft particles and extensions of the standard electrokinetic model in order to reach a better agreement between theory and experiments. The conclusion of the work refers to the expected developments, particularly in the field of experimental determinations (mainly in the high frequency side of the dispersion), and of descriptions of the solid/liquid interface with corresponding extensions of the standard electrokinetic model. © 2009 Elsevier Ltd. All rights reserved. Source

Mroginski J.L.,Northeast National University | Etse G.,National University of Tucuman
Computers and Geotechnics | Year: 2013

In this paper a new finite element formulation for numerical analysis of diffused and localized failure behavior of saturated and partially saturated gradient poroplastic materials is proposed. The new finite element includes interpolation functions of first order (C1) for the internal variables field while classical C0 interpolation functions for the kinematic fields and pore pressure. This finite element formulation is compatible with a thermodynamically consistent gradient poroplastic theory previously proposed by the authors. In this material theory the internal variables are the only ones of non-local character. To verify the numerical efficiency of the proposed finite element formulation, the non-local gradient poroplastic constitutive theory is combined with the modified Cam Clay model for partially saturated continua. Thereby, the volumetric strain of the solid skeleton and the plastic porosity are the internal variables of the constitutive theory. The numerical results in this paper demonstrate the capabilities of the proposed finite element formulation to capture diffuse and localized failure modes of boundary value problems of porous media, depending on the acting confining pressure and on the material saturation degree. © 2012 Elsevier Ltd. Source

Dos Santos D.A.,National University of Tucuman
Fundamental and Applied Limnology | Year: 2013

The structure of the EPT group (Ephemeroptera, Plecoptera and Trichoptera) reflects changes operating on the underlying freshwater system. We study the structure of the EPT assemblages inhabiting a Neotropical basin with mountain rain forests. Taxonomic richness and functional diversity are two relevant indicators of that structure. We measured real biological traits rather than using trait classifications arising from the Northern hemisphere, allowing us to more accurately calculate functional diversity metrics in these Neotropical streams. We also formalized a new approach to measuring functional dissimilarity. Our main scope is to know the effects of space (altitudinal zonation) and time (seasonality) on the behavior of both diversity indexes. We find complementarities between them, suggesting that the replacement in taxonomic composition is a process decoupled from the replacement in trait composition. While the taxonomic richness of sites in the dry season differs from the richness in upland sites sampled during spates, the functional diversity allows us to differentiate lowland sites sampled during spates from other sites. We hypothesize that functional diversity goes down in lowland sites because of the anthropogenic pressure on the riparian area. We additionally stress that the knowledge of functional diversity contributes to the better design of conservation strategies. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung. Source

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