National University of Crdoba

Argentina

National University of Crdoba

Argentina
SEARCH FILTERS
Time filter
Source Type

Gordillo S.,CONICET | Gordillo S.,National University of Crdoba | Martinelli J.,University of Chile | Cardenas J.,University of Chile | Sol Bayer M.,University of Chile
Journal of the Marine Biological Association of the United Kingdom | Year: 2011

This paper evaluates if the bivalve Tawera gayi from southern South America represents an opportunity to test ecological variability and environmental changes during the last 6000 years in southern South America. For this purpose, we analyse both modern and fossil (mid-to-late Holocene) T. gayi shells from Tierra del Fuego using different techniques, including taphonomy, stable isotopes, cathodoluminiscence (CL) and linear morphometrics. Taphonomic analysis shows that differences between modern and fossil shells appear best related to local variations of physical factors such as current speed, wave action and freshwater input along the non-uniform Beagle Channel coast. However, slight changes of hydraulic energy regimes throughout the Holocene cannot be ruled out. The analysis of stable isotopes on T. gayi shells indicates a mixing of oceanic waters with freshwater from precipitation, river runoff and glacier meltwater during the mid-to-late Holocene. The high depletion of 18O at ~4400 years before present would be associated with a period of warmer temperatures, the so-called Hypsithermal. Under CL modern and fossil T. gayi shells show a well defined pattern related to the growth dynamics of the shell, which can lead to a better understanding of its biology, adding details to further palaeoenvironmental analysis. Finally, conventional metrics shows that fossil T. gayi shells are smaller and shorter than modern shells. These differences could be related to Holocene environmental changes, but here are best explained on the basis of a predator-prey relationship. This study shows that T. gayi may be a good candidate for looking at evidences of environmental changes in southern South America, and multi-proxy data are necessary to better understand the driving mechanisms of ecological variability and changes over short geological time intervals of few thousands of years. © 2011 Marine Biological Association of the United Kingdom.


Limandri S.P.,National University of Crdoba | Limandri S.P.,Institute Fsica Enrique Gaviola | Carreras A.C.,National University of Crdoba | Carreras A.C.,Institute Fsica Enrique Gaviola | And 2 more authors.
Microscopy and Microanalysis | Year: 2010

Effects related with the attenuation and deflection suffered by an electron beam when it passes through a carbon conductive coating and an oxide film layer on the surface of bulk samples are studied by Monte Carlo simulations and energy dispersive spectroscopy with electron excitation. Analytical expressions are provided for the primary beam energy and intensity losses and for the deflection of the incident electrons in both layers, in terms of the incidence energy, the film mass thicknesses, and the atomic number of the oxidized element. From these analytical expressions, suitable corrections are proposed for the models used to describe the X-ray spectrum of the substrate, including also the contribution of the X-rays generated in the oxide and conductive films and the characteristic X-ray absorption occurring in those layers. The corrections are implemented in a software program for spectral analysis based on a routine of parameter refinement, and their influence is studied separately in experimental spectra of single-element standards measured at different excitation energies. Estimates for the layer thicknesses are also obtained from the spectral fitting procedure. © Microscopy Society of America 2010.


Nicola J.P.,Yale University | Nicola J.P.,National University of Crdoba | Reyna-Neyra A.,Yale University | Saenger P.,Winthrop University | And 7 more authors.
Journal of Clinical Endocrinology and Metabolism | Year: 2015

Context: Iodide (I-), an essential constituent of the thyroid hormones, is actively accumulated in the thyroid by the Na+/I- symporter (NIS), a key plasma membrane protein encoded by the slc5a5 gene. Mutations in slc5a5 cause I- transport defects (ITDs), autosomal-recessive disorders in which I- accumulation is totally or partially impaired, leading to congenital hypothyroidism. The characterization of NIS mutants has yielded significant insights into the molecular mechanism of NIS. Objective: This study aimed to determine the basis of a patient's ITD clinical phenotype, by sequencing her slc5a5 gene. Design: Genomic DNA was purified and the slc5a5 gene sequence determined. Functional in vitro studies were performed to characterize the V270E NIS mutant. Patient: The index patient was diagnosed with hypothyroidism with minimal radioiodide uptake in a normally located, although enlarged, thyroid gland. Results: We identified a new NIS mutation: V270E. The patient had the compound heterozygous NIS mutation R124H/V270E. R124H NIS has been characterized previously. We show that V270E markedly reduces I- uptake via a pronounced (but not total) impairment of the protein's plasma membrane targeting. Remarkably, V270E is intrinsically active. Therefore, a negative charge at position 270 interferes with NIS cell surface trafficking. The patient's minimal I- uptake enabled sufficient thyroid hormone biosynthesis to prevent cognitive impairment. Conclusions: A nonpolar residue at position 270, which all members of the SLC5A family have, is required for NIS plasma membrane targeting. Copyright © 2015 by the Endocrine Society.


Ochoa J.A.,Scorpion Systematics Research Group | Ochoa J.A.,University of Sao Paulo | Ojanguren Affilastro A.A.,Museo Argentino de Ciencias Naturales Bernardino Rivadavia | Mattoni C.I.,National University of Crdoba | Prendini L.,Scorpion Systematics Research Group
Bulletin of the American Museum of Natural History | Year: 2011

The systematics of the Andean scorpion genus, Orobothriurus Maury, 1976 (Bothriuridae Simon, 1880), is revised. New locality records, obtained during recent field expeditions, distribution maps, and a key to identification of the 15 known species, are provided. Six new species are described: Orobothriurus calchaqui, n. sp., from northwestern Argentina; Orobothriurus compagnuccii, n. sp., from the central Andes of Argentina; Orobothriurus huascaran, n. sp., from central Peru; Orobothriurus quewerukana, n. sp., from southern Peru and northern Chile; Orobothriurus ramirezi, n. sp., from central Chile; and Orobothriurus tamarugal, n. sp., from northern Chile. The known distribution of Orobothriurus and the altitude record for scorpions are discussed. The world's altitude record for a scorpion, previously reported as 5550 m, is demonstrated to be 4910 m. © 2011 American Museum of Natural History.


Dos Santos-Mallet J.R.,Oswaldo Cruz Foundation | Muller G.A.,Federal University of Santa Catarina | Muller G.A.,Federal University of Paran | Gleiser R.M.,National University of Crdoba | And 4 more authors.
Journal of the American Mosquito Control Association | Year: 2010

The eggs of Aedes scapularis analyzed by scanning electron microscopy are black and elliptical in outline, measuring approximately 620.4 ± 16.74 μm long and 163.7 ± 16.90 m (n 10) wide, with an egg index (length/width ratio) of 3.79. The anterior extremity tapered abruptly from a width of 51.6 μm, while such tapering was more gradual at the posterior extremity, from a width of 61.4 m. The ventral surface of the chorionic coating presented cells with a tubular aspect containing tubercles in rows at a density of 5 to 9 per cell with 2 different sizes, the largest measuring 7.23 ± 0.98 m in a longitudinal diameter and the smallest 4.15 ± 0.53 μm (n 30). In the dorsal region, the external chorionic reticulum had a porous appearance, and its thickness ranged from 2.5 to 4.1 μm. Isolated tubercles presented wide variation per cell. In the central region of some chorionic cells were tubercles of greater diameter, characterized as central tubercles of 8.45 ± 0.67 μm, and around them 3 to 5 smaller tubercles measuring 2.57 ± 0.26 μm. The micropylar apparatus presented a collar with a very evident molding and edges with defined margins for the transition area and a thickness of around 11.1 μm. The micropyle disc margins were raised, measuring around 17.8 μm in diameter and 229 m in circumference. The micropyle orifice was very evident, with a diameter of 1.41 μm. © 2010 by The American Mosquito Control Association, Inc.


Goulart L.,Federal University of Rio Grande do Sul | Silva L.K.R.E.,Federal University of Rio Grande do Sul | Chiapello L.,National University of Crdoba | Silveira C.,Federal University of Rio Grande do Sul | And 3 more authors.
Medical Mycology | Year: 2010

Cryptococcus neoformans and Cryptococcus gattii are encapsulated yeast agents of cryptococcosis and facultative intracellular pathogens. The interaction of these yeasts with macrophages is essential for containing the infection. However, Cryptococcus spp. overcome this initial host defense barrier using a unique pathogenic strategy involving intracellular replication and cytoplasmic accumulation of polysaccharide-containing vesicles. Here, we employed representational difference analysis (RDA) to identify C. neoformans and C. gattii genes differentially expressed during intracellular growth in rat peritoneal macrophages. The upregulated transcripts of C. neoformans during macrophage interaction were related to ATP-binding cassette (ABC) transporters, intra-golgi transport, chaperone activity, ribosomal maintenance, NAD metabolism, histone methylation, stress response, and monosaccharide metabolism. In contrast, with C. gattii, upregulated genes were associated with cell growth, aerobic respiration, protein binding, microtubule nucleation, monosaccharides and nitrogen metabolism, inositol or phosphatidylinositol phosphatase activity, cellular signaling, and stress response. Our findings reveal new genes that may be necessary for the intracellular parasitism of C. neoformans and C. gattii. © 2010 ISHAM.


Pighn S.A.,National University of Crdoba | Billoni O.V.,National University of Crdoba | Stariolo D.A.,Federal University of Rio Grande do Sul | Cannas S.A.,National University of Crdoba
Journal of Magnetism and Magnetic Materials | Year: 2010

We present the complete zero temperature phase diagram of a model for ultrathin films with perpendicular anisotropy. The whole parameter space of relevant coupling constants is studied in first order anisotropy approximation. Because the ground state is known to be formed by perpendicular stripes separated by Bloch walls, a standard variational approach is used, complemented with specially designed Monte Carlo simulations. We can distinguish four regimes according to the different nature of striped domains: a high anisotropy Ising regime with sharp domain walls, a saturated stripe regime with thicker walls inside which an in-plane component of the magnetization develops, a narrow canted-like regime, characterized by a sinusoidal variation of both the in-plane and the out of plane magnetization components, which upon further decrease of the anisotropy leads to an in-plane ferromagnetic state via a spin reorientation transition (SRT). The nature of domains and walls are described in some detail together with the variation of domain width with anisotropy, for any value of exchange and dipolar interactions. Our results, although strictly valid at T=0, can be valuable for interpreting data on the evolution of domain width at finite temperature, a still largely open problem. © 2010 Elsevier B.V. All rights reserved.


Visintin A.M.,National University of Crdoba | Visintin A.M.,National University of La Rioja | Laurito M.,National University of Crdoba | Stein M.,Northeast National University | And 4 more authors.
Journal of the American Mosquito Control Association | Year: 2010

The geographical distribution of Aedes pennai, Anopheles galvaoi, Coquillettidia albicosta, Cq. nigricans, Culex usquatissimus, Cx. apicinus, Cx. chidesteri, Cx. coronator s.l., Cx. interfor, Cx. maxi, Cx. pipiens, Cx. saltanensis, Cx. educator, Cx. serratimarge, Cx. theobaldi, Psorophora cyanescens, Ps. cilipes, Ps. cingulata, Ps. pallescens, Uranotaenia lanei, Ur. nataliae, Wyeomyia diabolica, and Wy. melanocephala is extended, including new records for 6 provinces and 2 new records for the country, increasing the number of species in Argentina from 226 to 228. © 2010 by The American Mosquito Control Association, Inc.


Caballero N.B.,National University of Crdoba | Caballero N.B.,CONICET | Zuriaga M.,National University of Crdoba | Zuriaga M.,CONICET | And 3 more authors.
Journal of Chemical Physics | Year: 2012

We present a molecular dynamics study of the liquid and plastic crystalline phases of CCl 3Br. We investigated the short-range orientational order using a recently developed classification method and we found that both phases behave in a very similar way. The only differences occur at very short molecular separations, which are shown to be very rare. The rotational dynamics was explored using time correlation functions of the molecular bonds. We found that the relaxation dynamics corresponds to an isotropic diffusive mode for the liquid phase but departs from this behavior as the temperature is decreased and the system transitions into the plastic phase. © 2012 American Institute of Physics.


Segnorile H.H.,National University of Crdoba | Zamar R.C.,National University of Crdoba
Journal of Chemical Physics | Year: 2011

Explanation of decoherence and quasi-equilibrium in systems with few degrees of freedom demands a deep theoretical analysis that considers the observed system as an open quantum system. In this work, we study the problem of decoherence of an observed system of quantum interacting particles, coupled to a quantum lattice. Our strategy is based on treating the environment and the system-environment Hamiltonians fully quantum mechanically, which yields a representation of the time evolution operator useful for disentangling the different time scales underlying in the observed system dynamics. To describe the possible different stages of the dynamics of the observed system, we introduce quantum mechanical definitions of essentially isolated, essentially adiabatic, and thermal-contact system-environment interactions. This general approach is then applied to the study of decoherence and quasi-equilibrium in proton nuclear magnetic resonance ( 1H NMR) of nematic liquid crystals. A summary of the original results of this work is as follows. We calculate the decoherence function and apply it to describe the evolution of a coherent spin state, induced by the coupling with the molecular environment, in absence of spin-lattice relaxation. By assuming quantum energy conserving or non-demolition interactions, we identify an intermediate time scale, between those controlled by self-interactions and thermalization, where coherence decays irreversibly. This treatment is also adequate for explaining the buildup of quasi-equilibrium of the proton spin system, via the process we called eigen-selectivity. By analyzing a hypothetical time reversal experiment, we identify two sources of coherence loss which are of a very different nature and give rise to distinct time scales of the spin dynamics: (a) reversible or adiabatic quantum decoherence and (b) irreversible or essentially adiabatic quantum decoherence. Local irreversibility arises as a consequence of the uncertainty introduced by the coupling with an infinite quantum environment. The reversible part can be represented by a semiclassical model, similar to standard line-shape adiabatic models. By exploiting the separation existing between the time scales of the spin coherences and the irreversible decoherence, we present a novel technique to obtain the orientational molecular distribution function for a nematic liquid crystal. The procedure is based on the comparison of the observed coherence time evolution and numerical calculation under the adiabatic quantum decoherence approach. As an example, it is used the experimental free induction decay from a nematic PAA d6 sample to extract such an orientational distribution. This is the first theoretical description of the experimental liquid crystal NMR signal in the time domain. On the contrary, the irreversible decoherence is intrinsically full-quantum mechanical, as it is governed by the commutation properties of the environment and the spin-lattice Hamiltonians. Consistently, it depends on the molecular correlation in a decisive way, since it vanishes under a mean-field model for the molecular dynamics. The results of this work can contribute to the understanding of the open question of the applicability of the spin-temperature concept in spin systems with few degrees of freedom. © 2011 American Institute of Physics.

Loading National University of Crdoba collaborators
Loading National University of Crdoba collaborators