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Provasi P.F.,University of Northeastern | Provasi P.F.,CONICET | Sauer S.P.A.,Copenhagen University
Journal of Chemical Physics | Year: 2010

The aug-cc-pVTZ-J series of basis sets for indirect nuclear spin-spin coupling constants has been extended to the atoms B, Al, Si, P, and Cl. The basis sets were obtained according to the scheme previously described by Provasi [J. Chem. Phys. 115, 1324 (2001)]. First, the completely uncontracted correlation consistent aug-cc-pVTZ basis sets were extended with four tight s and three tight d functions. Second, the s and p basis functions were contracted with the molecular orbital coefficients of self-consistent-field calculations performed with the uncontracted basis sets on the simplest hydrides of each atom. As a first illustration, we have calculated the one-bond indirect spin-spin coupling constants in BH4 -, BF, AlH, AlF, SiH4, SiF4, PH3, PF3, H2 S, SF6, HCl, and ClF at the level of density functional theory using the Becke three parameter Lee-Yang-Parr and the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes. © 2010 American Institute of Physics.

Gosain S.,U.S. National Solar Observatory | Demoulin P.,CNRS Laboratory for Space Studies and Astrophysical Instrumentation | Lopez Fuentes M.,CONICET
Astrophysical Journal | Year: 2014

We present a study of two regular sunspots that exhibit nearly uniform twist from the photosphere to the corona. We derive the twist parameter in the corona and in the chromosphere by minimizing the difference between the extrapolated linear force-free field model field lines and the observed intensity structures in the extreme-ultraviolet images of the Sun. The chromospheric structures appear more twisted than the coronal structures by a factor of two. Further, we derive the vertical component of electric current density, jz, using vector magnetograms from the Hinode Solar Optical Telescope (SOT). The spatial distribution of jzhas a zebra pattern of strong positive and negative values owing to the penumbral fibril structure resolved by Hinode/SOT. This zebra pattern is due to the derivative of the horizontal magnetic field across the thin fibrils; therefore, it is strong and masks weaker currents that might be present, for example, as a result of the twist of the sunspot. We decompose jzinto the contribution due to the derivatives along and across the direction of the horizontal field, which follows the fibril orientation closely. The map of the tangential component has more distributed currents that are coherent with the chromospheric and coronal twisted structures. Moreover, it allows us to map and identify the direct and return currents in the sunspots. Finally, this decomposition of jzis general and can be applied to any vector magnetogram in order to better identify the weaker large-scale currents that are associated with coronal twisted/sheared structures. © 2014. The American Astronomical Society. All rights reserved..

Abbas T.,University of Virginia | Mueller A.C.,University of Virginia | Shibata E.,University of Virginia | Keaton M.,University of Virginia | And 3 more authors.
Molecular Cell | Year: 2013

The Cul4-Cdt2 (CRL4Cdt2) E3 ubiquitin ligase is a master regulator of cell-cycle progression and genome stability. Despite its central role in the degradation of many cell-cycle regulators, e.g., Cdt1, p21, and Pr-Set7/Set8, little is known about the regulation of its activity. We report that Cdt2 is autoubiquitylated by the CRL4A E3 ubiquitin ligase. Cdt2 is additionally polyubiquitylated and degraded by Cul1-FBXO11 (CRL1FBXO11). CRL1FBXO11-mediated degradation of Cdt2 stabilizes p21 and Set8, and this is important during the response to TGF-β, with the Set8 induction being important for turning off the activation of Smad2. The migration of epithelial cells is also stimulated by CRL1FBXO11-mediated downregulation of Cdt2 and the consequent stabilization of Set8. This is an interesting example of crossregulation between specific Cullin 4 and Cullin 1 E3 ubiquitin ligases and highlights the role of ubiquitylation in regulating cellular responses to TGF-β and the migration of epithelial cells. © 2013 Elsevier Inc.

Kitazawa H.,Tohoku University | Villena J.,Immunobiotics Research Group | Villena J.,CONICET
Frontiers in Immunology | Year: 2014

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants and young children. Host immune response is implicated in both protective and immunopathological mechanisms during RSV infection. Activation of Toll-like receptor (TLR)-3 in innate immune cells by RSV can induce airway inflammation, protective immune response, and pulmonary immunopathology. A clear understanding of RSV-host interaction is important for the development of novel and effective therapeutic strategies. Several studies have centered on whether probiotic microorganisms with the capacity to stimulate the immune system (immunobiotics) might sufficiently stimulate the common mucosal immune system to improve defenses in the respiratory tract. In this regard, it was demonstrated that some orally administered immunobiotics do have the ability to stimulate respiratory immunity and increase resistance to viral infections. Moreover, during the last decade scientists have significantly advanced in the knowledge of the cellular and molecular mechanisms involved in the protective effect of immunobiotics in the respiratory tract. This review examines the most recent advances dealing with the use of immunobiotic bacteria to improve resistance against viral respiratory infections. More specifically, the article discuss the mechanisms involved in the capacity of the immunobiotic strain Lactobacillus rhamnosus CRL1505 to modulate the TLR3-mediated immune response in the respiratory tract and to increase the resistance to RSV infection. In addition, we review the role of interferon (IFN)-γ and interleukin (IL)-10 in the immunoregulatory effect of the CRL1505 strain that has been successfully used for reducing incidence and morbidity of viral airways infections in children. © 2014 Kitazawa and Villena.

Oliver J.,University of Barcelona | Huespe A.E.,CONICET | Dias I.F.,University of Barcelona
Computer Methods in Applied Mechanics and Engineering | Year: 2012

The work focuses on the connections of strain localization modeling of material failure and discrete fracture mechanics. It is an attempt to give an answer to the old question of whether the finite element solutions of material failure problems based on strain localization techniques, using standard continuum stress-strain constitutive models equipped with strain softening, have physical sense as solutions of de-cohesive fracture mechanics problems. Based on some well-established links of the Continuum Strong Discontinuity Approach (CSDA) to material failure and cohesive fracture mechanics, some objective indicators are proposed to assess the quality of strain localization results. These indicators are simply derived on the basis of the inelastic strain distribution provided by the strain localization solutions and the direction of propagation of the localization band. They can be computed without knowledge of the exact fracture mechanics solution of the problem, and used as error indicators in a large variety of material failure situations. The proposed indicators are assessed, by means of their application to evaluation of a number of strain localization solutions of benchmark problems. Issues as the influence of the mesh structure and alignment, type of constitutive model and considered finite element techniques are examined. On the light of the obtained results, classical flaws in strain localization solutions, as mesh bias dependence and stress-locking are reinterpreted. © 2012 Elsevier B.V.

Bussi I.L.,National University of Quilmes | Levin G.,CONICET | Golombek D.A.,National University of Quilmes | Agostino P.V.,National University of Quilmes
European Journal of Neuroscience | Year: 2014

Duration discrimination within the seconds-to-minutes range, known as interval timing, involves the interaction of cortico-striatal circuits via dopaminergic-glutamatergic pathways. Besides interval timing, most (if not all) organisms exhibit circadian rhythms in physiological, metabolic and behavioral functions with periods close to 24h. We have previously reported that both circadian disruption and desynchronization impaired interval timing in mice. In this work we studied the involvement of dopamine (DA) signaling in the interaction between circadian and interval timing. We report that daily injections of levodopa improved timing performance in the peak-interval procedure in C57BL/6 mice with circadian disruptions, suggesting that a daily increase of DA is necessary for an accurate performance in the timing task. Moreover, striatal DA levels measured by reverse-phase high-pressure liquid chromatography indicated a daily rhythm under light/dark conditions. This daily variation was affected by inducing circadian disruption under constant light (LL). We also demonstrated a daily oscillation in tyrosine hydroxylase levels, DA turnover (3,4-dihydroxyphenylacetic acid/DA levels), and both mRNA and protein levels of the circadian component Period2 (Per2) in the striatum and substantia nigra, two brain areas relevant for interval timing. None of these oscillations persisted under LL conditions. We suggest that the lack of DA rhythmicity in the striatum under LL - probably regulated by Per2 - could be responsible for impaired performance in the timing task. Our findings add further support to the notion that circadian and interval timing share some common processes, interacting at the level of the dopaminergic system. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Disalvo E.A.,CONICET
Sub-Cellular Biochemistry | Year: 2015

The classical view of a biological membrane is based on the Singer- Nicholson mosaic fluid model in which the lipid bilayer is the structural backbone. Under this paradigm, many studies of biological processes such as, permeability, active transport, enzyme activity and adhesion and fusion processes have been rationalized considering the lipid membrane as a low dielectric slab of hydrocarbon chains with polar head groups exposed to water at each side in which oil/water partition prevails. In spite of several analyses and evidence available in relation to membrane hydration, water is not taken into account as a functional component. For this purpose, new insights in the water organization in restricted environments and the thermodynamical and mechanical properties emerging from them are specifically analysed and correlated. This chapter summarizes the progress of the studies of water in membranes along the book in order to give a more realistic structural and dynamical picture accounting for the membrane functional properties. © Springer International Publishing Switzerland 2015.

Depino A.M.,CONICET | Depino A.M.,University of Buenos Aires
Molecular and Cellular Neuroscience | Year: 2013

Recent reports have given a central role to environmental factors in the etiology of autism spectrum disorders (ASD). However, most proposed perinatal factors seem to converge into the activation of the immune system, suggesting that an early inflammatory response could be a unifying factor in the etiology ASD. Here I review the evidence of early immune activation in individuals with ASD, and the chronic peripheral and central alterations observed in the inflammatory response in ASD. This evidence shows that ASD is associated with altered neuroinflammatory processes and abnormal immune responses in adulthood. How these immune alterations can affect developmental programming of adult behavior or directly affect behavior later in life is discussed in the context of both clinical and animal models of research. Recent studies in rodents clearly support a role of elevated cytokines in the behavioral symptoms of ASD, both during development and in adulthood. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'. © 2012 Elsevier Inc.

Kazantzidis S.,Ohio State University | Abadi M.G.,CONICET | Navarro J.F.,University of Victoria
Astrophysical Journal Letters | Year: 2010

Cosmological simulations indicate that cold dark matter (CDM) halos should be triaxial. Validating this theoretical prediction is, however, less than straightforward because the assembly of galaxies is expected to modify halo shapes and to render them more axisymmetric.We use a suite of N-body simulations to quantitatively investigate the effect of the growth of a central disk galaxy on the shape of triaxial dark matter halos. In most circumstances, the halo responds to the presence of the disk by becoming more spherical. The net effect depends weakly on the timescale of the disk assembly but noticeably on the orientation of the disk relative to the halo principal axes, and it is maximal when the disk symmetry axis is aligned with the major axis of the halo. The effect depends most sensitively on the overall gravitational importance of the disk. Our results indicate that exponential disks whose contribution peaks at less than ∼50% of their circular velocity are unable to noticeably modify the shape of the gravitational potential of their surrounding halos. Many dwarf and low surface brightness galaxies are expected to be in this regime, and therefore their detailed kinematics could be used to probe halo triaxiality, one of the basic predictions of the CDM paradigm. We argue that the complex disk kinematics of the dwarf galaxy NGC 2976 might be the reflection of a triaxial halo. Such signatures of halo triaxiality should be common in galaxies where the luminous component is subdominant. © 2010 The American Astronomical Society. All rights reserved.

Individual recognition is expected to enhance fitness by allowing animals to direct appropriate behaviours to specific individuals during interactions with conspecifics. Reduced aggression towards territorial neighbours ('dear enemy phenomenon') is based on the assumption that strangers lacking territories pose a greater threat than territory-holding neighbours. Based on the ability of the subterranean rodent Ctenomys talarum (tuco-tuco) to distinguish between familiar and unfamiliar conspecific odours, I assessed whether males, the more aggressive sex, show dear enemy relationships and whether social experience with odour donors affects the memory of conspecific odours. Maleemale contests in the laboratory were used to compare the aggressive behaviour of pairs of males. Familiar male tuco-tucos responded less aggressively during contests than unfamiliar males, providing evidence of the dear enemy relationship in C. talarum. Memory for familiar odours was affected by social experience since discrimination of known from novel odours lasted longer when males encountered each other in dyadic contests following familiarization with odours. Familiarity by odour cues would represent an important mechanism mediating neighbour recognition and territorial behaviour for tuco-tucos in the wild; intruders may represent a threat of great consequence for territory-holding individuals since they represent the potential loss of their burrow system and their priority of access to neighbouring females. © 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Berli C.L.A.,CONICET | De Vicente J.,University of Granada
Applied Physics Letters | Year: 2012

A structural viscosity model is proposed, which describes the shear viscosity from the balance between build up (magnetic field-induced clustering) and breakdown (shear-induced breakup) of particle aggregates. The model accounts for typical deviations from Bingham model predictions that are extensively reported in the MR literature. More precisely, the model (i) provides a physical ground for the observed Casson-like shear flow behaviour, (ii) predicts the existence of a low shear plateau in weak MR fluids, and (iii) asymptotically recovers the typical Bingham-like behavior that is observed in (strong) conventional MR fluids at experimentally accessible times. © 2012 American Institute of Physics.

A preliminary account of Xylaria in Argentina is presented based primarily on collections from part of "Las Yungas" biosphere reserve in Tucumán province. The following new taxa are proposed: X. culicicephala, X. tucumanensis, X. filiformioidea, X. stilbohypoxyloides and X. microceras var. yungae. The following new combination is made: X. xylarioides. Material morphologically identical to X. ianthino-velutina was found on wood, but a culture difference was noted. It is keyed out as X. aff. ianthinovelutina. A dichotomous key to twenty-nine taxa known so far from the Northern provinces of Argentina is presented. © Kevin D. Hyde 2010.

Tinte S.,CONICET | Stachiotti M.G.,National University of Rosario
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The multiferroic behavior of the hypothetical Aurivillius compound Bi 4Mn 3O 12 has been explored on the basis of density functional calculations. We find that the tetragonal paraelectric phase of this material is ferromagnetic, showing ferroelectric and antiferrodistortive instabilities similar to the ones observed in its ferroelectric parent compound Bi 4Ti 3O 12. Our results indicate, however, that the presence of Mn +4 ions at the B sites shrinks the cell volume and, consequently, the unstable polar mode, associated with the ferroelectric polarization, is overcome by an antiferrodistortive distortion. In this way, Bi 4Mn 3O 12 exhibits incipient ferroelectricity at its equilibrium volume. We show that the ferroelectric state can be favored by strain or partial substitution of Mn with Ti. © 2012 American Physical Society.

Hepatotoxicity is associated with major changes in liver gene expression induced by xenobiotic exposure. Understanding the underlying mechanisms is critical for its clinical diagnosis and treatment. MicroRNAs are key regulators of gene expression that control mRNA stability and translation, during normal development and pathology. The canonical technique to measure gene transcript levels is Real-Time qPCR, which has been successfully modified to determine the levels of microRNAs as well. However, in order to obtain accurate data in a multi-step method like RT-qPCR, the normalization with endogenous, stably expressed reference genes is mandatory. Since the expression stability of candidate reference genes varies greatly depending on experimental factors, the aim of our study was to identify a combination of genes for optimal normalization of microRNA and mRNA qPCR expression data in experimental models of acute hepatotoxicity. Rats were treated with four traditional hepatotoxins: acetaminophen, carbon tetrachloride, D-galactosamine and thioacetamide, and the liver expression levels of two groups of candidate reference genes, one for microRNA and the other for mRNA normalization, were determined by RT-qPCR in compliance with the MIQE guidelines. In the present study, we report that traditional reference genes such as U6 spliceosomal RNA, Beta Actin and Glyceraldehyde-3P-dehydrogenase altered their expression in response to classic hepatotoxins and therefore cannot be used as reference genes in hepatotoxicity studies. Stability rankings of candidate reference genes, considering only those that did not alter their expression, were determined using geNorm, NormFinder and BestKeeper software packages. The potential candidates whose measurements were stable were further tested in different combinations to find the optimal set of reference genes that accurately determine mRNA and miRNA levels. Finally, the combination of MicroRNA-16/5S Ribosomal RNA and Beta 2 Microglobulin/18S Ribosomal RNA were validated as optimal reference genes for microRNA and mRNA quantification, respectively, in rat models of acute hepatotoxicity.

Journal of Physiology Paris | Year: 2012

Neurotransmitter receptors of the Cys-loop superfamily mediate rapid synaptic transmission throughout the nervous system, and include receptors activated by ACh, GABA, glycine and serotonin. They are involved in physiological processes, including learning and memory, and in neurological disorders, and they are targets for clinically relevant drugs. Cys-loop receptors assemble either from five copies of one type of subunit, giving rise to homomeric receptors, or from several types of subunits, giving rise to heteromeric receptors. Homomeric receptors are invaluable models for probing fundamental relationships between structure and function. Receptors contain a large extracellular domain that carries the binding sites and a transmembrane region that forms the ion pore. How the structural changes elicited by agonist binding are propagated through a distance of 50. å to the ion channel gate is central to understanding receptor function. Depending on the receptor subtype, occupancy of either two, as in the prototype muscle nicotinic receptor, or three binding sites, as in homomeric receptors, is required for full activation. The conformational changes initiated at the binding sites are propagated to the gate through the interface between the extracellular and transmembrane domains. This region forms a network that relays structural changes from the binding site towards the pore, and also contributes to open channel lifetime and rate of desensitization. Thus, this coupling region controls the beginning and duration of a synaptic response. Here we review recent advances in the molecular mechanism by which Cys-loop receptors are activated with particular emphasis on homomeric receptors. © 2011.

Occurrence records represent the key to understanding species distribution patterns. I analyzed the historical and geographical occurrence of Dromiciops gliroides, a marsupial endemic to the temperate rain forests of southern Chile and Argentina and the sole living representative of the order Microbiotheria. Eighty-eight localities spanning 7°31′ latitude (∼850 km) and 3°13′ longitude (∼350 km) are known for the species and were taken from previous works and museum specimens and integrated in a geographic information system. Species distribution was analyzed in a historical, geographic, and biogeographic context, with the use of maps at different scales (region, subregion, province, ecoregion, and forest type). The software MaxEnt was used to generate 2 potential distribution models with environmental data. Generated models show a northern contraction and southern expansion in the species' potential distribution, with variation in habitat suitability throughout the current species range. Precipitation and some temperature-related variables influenced both generated models. The species' occurrence lies within the Andean region; Subantarctic and Patagonia subregions; and Maule, Valdivian, and Subandean Patagonia provinces. At a smaller scale, most of the localities occur within the Valdivian Temperate Forests ecoregion, and in the majority of the forest types described for it, implying broader ecological requirements than expected. Identification of critical areas through potential distribution modeling may have implications on species conservation and biogeographic patterns. © 2010 American Society of Mammalogists.

The epilithic algae distribution along a pH gradient and the relationship between the chemical gradient and biomass development were studied in Río Agrio, a naturally acidic river located in Patagonia (Argentina). The epilithic community was monitored during the summer of three consecutive years in sites located above and below the entrance of tributaries. The epilithic community showed differences between sites based on the chemical composition of the water and the precipitates that appear on the streambed of the river. The lowest biomass, diversity, and number of species were found at the most extreme part of the river in terms of pH (ca. 2) and element concentrations. Euglena mutabilis was the dominant species in this section of the river. As pH increased (ca. 3), the community changed to be dominated by filamentous green algae (Ulothrix spp., Mougeotia sp., Klebsormidium sp.) showing luxuriant growths in terms of biomass. With the inflow of a neutral tributary, the pH of Río Agrio increased above 3, and the precipitates of orange-red iron hydroxides appeared. The algal community was not affected by these precipitates or the low P concentrations, along the next 30 km of river downstream from this site. The apparent physical stress that the precipitates impose on algae is in fact a dynamic reservoir of P because diel cycle of Fe could be promoting precipitation and redissolution processes that binds and releases P from these precipitates. Where the pH increased above 6, precipitates of aluminum hydroxides appeared. At this site, the epilithic biomass and density decreased, some algae species changed, but the diversity and the number of species in general remained consistent with the upstream values. The physical stress of the Al precipitates on the algae is added to the chemical stress that represents the sequestering of P in these precipitates that are not redissolved, resulting P a limiting nutrient for algae growth. © 2010 Springer Science+Business Media, LLC.

Olivieri A.C.,CONICET | Faber K.,Chemometry Consultancy
Analytical Chemistry | Year: 2012

Appropriate closed-form expressions are known for estimating analyte sensitivities when calibrating with one-, two-, and three-way data (vectors, matrices, and three-dimensional arrays, respectively, built with data for a group of samples). In this report, sensitivities are estimated for calibration with four-way data using the quadrilinear parallel factor (PARAFAC) model, making it possible to assess important figures of merit for method comparison or optimization. The strategy is based on the computation of the uncertainty in the fitted PARAFAC parameters through the Jacobian matrix. Extensive Monte Carlo noise addition simulations in four-way data systems having widely different overlapping situations are helpful in supporting the present approach, which was also applied to two experimental analytical systems. With this proposal, the estimation of the PARAFAC sensitivity for calibration scenarios involving three- and four-way data may be considered complete. © 2011 American Chemical Society.

Goat production is an important economic activity for rural communities in the Gran Chaco of Argentina. Goat corrals are important for the survival of peridomestic populations of Triatoma infestans. This study evaluated the impact of modifying the traditional structure of goat corrals on T. infestans populations and goat productivity in the region of Los Llanos (La Rioja). Thirty-nine experimental corrals were constructed and 57 traditional corrals were used as controls. We evaluated the infestations of the control and experimental corrals for five years following construction of the structures. The results showed that the new structures did not prevent the colonization, although it enhanced the detection of infestation at low densities of T. infestans. No significant difference was found in T. infestans population abundance between control and experimental corrals, probably because of the different detectability in the two types of structures, especially among the small nymphs. Although goat productivity average was higher in experimental than in control corrals, no significant difference was found because of high variability. The new structures can be used as a complement to promote the development of rural communities. Acceptability and adoption of the new corrals by the owners was high, as the enclosures offered better protection for the goats, increased growth of kids and facilitated herd handling.

Fernandez-Duque E.,Yale University | Fernandez-Duque E.,CONICET
American Journal of Primatology | Year: 2016

Using published and new data from a population of monogamous owl monkeys in the Argentinean Chaco, I examine the hypothesis that social monogamy is a default social system imposed upon males because the spatial and/or temporal distribution of resources and females makes it difficult for a single male to defend access to more than one mate. First, I examine a set of predictions on ranging patterns, use of space, and population density. This first section is followed by a second one considering predictions related to the abundance and distribution of food. Finally, I conclude with a section attempting to link the ranging and ecological data to demographic and life-history parameters as proxies for reproductive success. In support of the hypothesis, owl monkey species do live at densities (7-64ind/km2) that are predicted for monogamous species, but groups occupy home ranges and core areas that vary substantially in size, with pronounced overlap of home ranges, but not of core areas. There are strong indications that the availability of food sources in the core areas during the dry season may be of substantial importance for regulating social monogamy in owl monkeys. Finally, none of the proxies for the success of groups were strongly related to the size of the home range or core area. The results I present do not support conclusively any single explanation for the evolution of social monogamy in owl monkeys, but they help us to better understand how it may function. Moreover, the absence of conclusive answers linking ranging, ecology, and reproductive success with the evolution of social monogamy in primates, offer renewed motivation for continuing to explore the evolution of monogamy in owl monkeys. Am. J. Primatol. 78:355-371, 2016. © 2016 Wiley Periodicals, Inc.

Brunini A.,CONICET
Monthly Notices of the Royal Astronomical Society | Year: 2014

In this paper,we perform a numerical integration of 666 fictitious binary Centaurs coming from the trans Neptunian space. Our population is restricted to tight binaries whose components have sizes between 30 and 100 km. We included the dynamical perturbations from the giant planets, Kozai Cycles induced by the Sun and tidal friction on the orbits of the binaries. We found that most binaries are disrupted during one of the close planetary encounters, making the mean lifetime of binary Centaurs much shorter than the one of single Centaurs. Nearly 10 per cent of the binaries reach a very tight circular orbit, arguing in favour of the existence of a non-negligible population of contact Centaurs. Another 10 per cent survive as a binary during their lifetime as Centaur. Our simulations favour the existence of a small population of very tight binary Centaurs. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

The main aim of the present work is to synthesize the information obtained from our dissections of the pectoral and forelimb muscles of representative members of the major extant taxa of limbed amphibians and reptiles and from our review of the literature, in order to provide an account of the comparative anatomy, homologies and evolution of these muscles in the Tetrapoda. The pectoral and forelimb musculature of all these major taxa conform to a general pattern that seems to have been acquired very early in the evolutionary history of tetrapods. Although some muscles are missing in certain taxa, and a clear departure from this general pattern is obviously present in derived groups such as birds, the same overall configuration is easily distinguishable in these taxa. Among the most notable anatomical differences between the groups, one that seems to have relevant evolutionary and functional implications, concerns the distal insertion points of the forearm musculature. In tetrapods, the muscles of the radial and ulnar complexes of the forearm are pleisomorphically mainly inserted onto the radius/ulna or onto the more proximal carpal bones, but in mammals some of these muscles insert more distally onto bones such as the metacarpals. Interestingly, a similar trend towards a more distal insertion of these muscles is also found in some non-mammalian tetrapod taxa, such as some anurans (e.g. Phyllomedusa). This may be correlated with the acquisition of more subtle digital movement abilities in these latter taxa. © 2010 The Authors. Journal of Anatomy © 2010 Anatomical Society of Great Britain and Ireland.

Volzone C.,CONICET | Zagorodny N.,National University of La Plata
Applied Clay Science | Year: 2014

Mercury intrusion porosimetry (MIP) on archaeological potteries classified as Belen fine and ordinary types from Catamarca, Argentina, was analysed. The MIP technique allowed identifying high percentage of uniform pore size in fine pottery, and inhomogeneous pore size in ordinary pottery. Fragments of neck and body sections of the same ordinary vessel were also studied. The porosity of the body section was smaller than the one of the neck, and the cumulative pore volume curve analysis of the body sectors (of the same vessel) evidenced that some pore sizes were sealed partially with respect to the one of the neck. Such behaviour may provide evidence of physical or chemical transformations from their manufactured process, during their use, and post-depositional effects. © 2014 Elsevier B.V.

Perucca L.P.,CONICET | Ruiz F.,National University of San Juan
Journal of South American Earth Sciences | Year: 2014

The Central and Eastern Precordillera form oppositely verging thrust systems on the western and eastern sides of the Matagusanos-Maradona-Acequión valley, establishing a thick-skinned triangle zone with significant changes in the axis position along strike. Between the del Agua and the de La Fecha rivers, the axis of this triangular zone is located in the eastern portion of the depression. Changes in the position of the triangle zone axis along strike, whether to the east or to the west, took place during Pliocene-Pleistocene times. Geophysical and geodetic data indicate a subsurface structure striking NE, oblique to the general direction of the foreland with dextral displacement. Accordingly, the change in the location of the triangular area could be attributed to stress transfer controlled by heterogeneities in the basement. By analytic signal analysis of magnetic anomalies, it is possible to assess the regional structural coupling between Pie de Palo and Eastern Precordillera. The oblique arrangement of basement blocks could explain transverse lineaments and the sigmoidal geometry of the Eastern Precordillera. Geophysical and geological evidence shows that the depression is crossed by several E-W strike-slip faults. These faults possibly controlled the position of the triangle zone axis until Neogene-Pleistocene times by transferring displacements and provoking its jump along strike.Basement structures might have also played a primary role in the location of Quaternary faults trending N-S. Finally, the east-west cross-section geophysical model shows the triangular zone, responding to the different controls imposed by the pre-existing basement structures. © 2013 Elsevier Ltd.

Jais P.M.,University of Buenos Aires | Murray D.B.,University of British Columbia | Merlin R.,University of Michigan | Bragas A.V.,University of Buenos Aires | Bragas A.V.,CONICET
Nano Letters | Year: 2011

Resonant interaction of laser pulses with plasmons is used to identify vibrations associated with isolated spheres and pairs of contacting spheres in a system of gold nanoparticles. The optical pulses generate coherent mechanical oscillations of both monomers and dimers in the 5-150 GHz range, the amplitudes of which exhibit a strong enhancement when the laser central wavelength is tuned to resonate with the corresponding plasmon. Because of the resonant selection in the excitation process, the widths of the acoustic modes are significantly smaller than broadening caused by the spread in radii in the ensemble. © 2011 American Chemical Society.

Matano R.P.,Oregon State University | Palma E.D.,CONICET
Journal of Physical Oceanography | Year: 2010

This note considers the decay of a bottom-trapped freshwater plume after the causative freshwater inflow has ceased. It is shown that shortly after the low-density inflow stops, the barotropic pressure field that it created radiates away and the ocean circulation becomes controlled by baroclinic pressure gradients generated by the remnants of the inflow. This produces a reversal of the circulation in the region downstream of the inflow, after which the entire plume starts to move in the upstream direction. The decay of the plume is henceforth controlled by upstream oceanic flow and dilution through cross-isopycnal mixing. © 2010 American Meteorological Society.

Immunology, Endocrine and Metabolic Agents in Medicinal Chemistry | Year: 2012

In developed countries, cancer has replaced infectious diseases as a major cause of death. Currently, efforts in the immunoprevention of cancer are beginning to resemble those presented by the prevention of infectious diseases by immunization a century ago. Breast cancer is the most frequent type of tumor in women and is the second leading cause of death by this illness, among them. Moreover, cancer incidence will grow during next years. Some findings in autoimmunity related to breast cancer in animal models have been important to clarify mechanisms that potentiate tumor growth. Clinical and experimental data now clearly indicate that chronic inflammation significantly contributes to cancer development. Emerging out of these studies is an appreciation that persistent humoral immune responses exacerbate recruitment and activation of innate immune cells in the neoplastic microenvironment where they regulate tissue remodeling, pro-angiogenic and pro-survival pathways that together potentiate cancer development. Generally, antigens involved in autoimmune response in breast cancer are modified self-proteins or over-expressed normal proteins that induce autoantibodies (autoAbs) formation, which exhibit tumor promoting actions. Very frequently muscarinic acetylcholine receptors (mAChR) are up-regulated in different types of tumors appearing in different animal species. mAChR have the ability to act as autoantigens for tumor bearers. This article will review recent results concerning to the ability of mAChR expressed in transformed breast cells to trigger autoAbs formation either in experimental models or in breast cancer patients. We will also discuss the action of these antibodies as agonists of mAChR. © 2012 Bentham Science Publishers.

The aim of this opinion article is to point out the basic principles that modify the assembly of biological membranes during lipid peroxidation. With this objective in mind, I describe: the structural and functional properties of membranes, the transport and diffusion of oxygen regulated by cholesterol and fatty acids; the "Lipid Whisker Model" and finally analyzed the changes induced by lipid peroxidation in membrane structure and dynamics, both at the lipid and protein level. Several reviews have appeared in recent years related to the kinetics and biology of lipid peroxidation products (Catala, 2010; Yin et al., 2011; Pinchuk and Lichtenberg, 2014; Vigor et al., 2014; Davies and Guo, 2014). The analysis of lipid peroxidation products has been particularly important in the advancement of research in this field because of the complexity of product mixtures. I also discuss the effect of other membrane modifications, triggered by lipid peroxidation products and reducing sugars. Contrary to what is expected by the LWM, Garrec et al. (2014) have recently investigated the validity of the "floating peroxyl radical" hypothesis by means of molecular modeling and predicted that the peroxyl radical does not "float" at the surface of the membrane. © 2015 Catalá.

Lipina S.J.,CONICET | Posner M.I.,University of Oregon
Frontiers in Human Neuroscience | Year: 2012

Although the study of brain development in non-human animals is an old one, recent imaging methods have allowed non-invasive studies of the gray and white matter of the human brain over the lifespan. Classic animal studies show clearly that impoverished environments reduce cortical gray matter in relation to complex environments and cognitive and imaging studies in humans suggest which networks may be most influenced by poverty. Studies have been clear in showing the plasticity of many brain systems, but whether sensitivity to learning differs over the lifespan and for which networks is still unclear. A major task for current research is a successful integration of these methods to understand how development and learning shape the neural networks underlying achievements in literacy, numeracy, and attention. This paper seeks to foster further integration by reviewing the current state of knowledge relating brain changes to behavior and indicating possible future directions. © 2012 Lipina and Posner.

Olmi M.,Tropical Entomology Research Center | Virla E.G.,CONICET
Zootaxa | Year: 2014

An updated revision of Neotropical Dryinidae is presented. Seven subfamilies, 23 genera and 502 species are treated. Descriptions, geographic distribution, known hosts, natural enemies and type material of each species are presented, together with illustrations of the main morphological characters and keys to the subfamilies, genera and species. Complete lists of references concerning the Neotropical Dryinidae and their hosts are given. A new genus Peckius Olmi & Virla, gen. nov. (type species Peckius insularis Olmi & Virla, sp. nov.) (subfamily Apodryininae) is described. The following eleven new species are described: Anteon xochipalense Olmi & Virla, sp. nov. (Mexico, Guerrero), Deinodryinus levigatus Olmi & Virla, sp. nov. (Peru, Lamabayeque), Deinodryinus xanthonotatus Olmi & Virla, sp. nov. (French Guiana), Dryinus semiruber Olmi & Virla, sp. nov. (Argentina, Corrientes), Dryinus valens Olmi & Virla, sp. nov. (Dominican Republic, Pedernales), Dryinus xanthopus Olmi & Virla, sp. nov. (French Guiana), Megadryinus cacaonis Olmi & Virla, sp. nov. (Brazil, São Paulo), Gonatopus isabelensis Olmi & Virla, sp. nov. (Ecuador, Galapagos Islands), Gonatopus villamilensis Olmi & Virla, sp. nov. (Ecuador, Galapagos Islands), Neodryinus mayanus Olmi & Virla, sp. nov. (Honduras), and Peckius insularis Olmi & Virla, sp. nov. (Ecuador, Galapagos Islands). The following new synonymies are presented: Deinodryinus kawensis Olmi 2011b (April) (=D. caxiuana Coelho, Aguiar & Engel, 2011 (June), syn. nov.); Dryinus gibbosus Olmi, 1984 (=D. multicarinatus Coelho, Aguiar & Engel, 2011, syn. nov.); Dryinus striatus (Fenton, 1927) (=D. sinopensis Olmi, 1984, syn. nov.; =D. cerrensis Olmi, 2004a, syn. nov.); Gonatopus Ljungh, 1810 (=Trichogonatopus Kieffer, 1909, syn. nov.); Eucamptonyx dromedarius (Cameron 1888) (=E. hansoni Olmi, 1991, syn. nov.); Haplogonatopus hernandezae Olmi, 1984 (=H. crucianus Olmi, 1986, syn. nov.). The following new combinations are proposed: Eucamptonyx dromedarius (Cameron, 1888), comb. nov. (from Gonatopus); Gonatopus goiasensis (Olmi 1991), comb. nov. (from Trichogonatopus); G. hispidus (Olmi 1984), comb. nov. (from Trichogonatopus); G. longinoi (Olmi, 1998d), comb. nov. (from Trichogonatopus); G. marinoae (Virla, 1997), comb. nov. (from Trichogonatopus); G. neotropicus (Olmi, 1984), comb. nov. (from Trichogonatopus); G. raptor (Fenton, 1927), comb. nov. (from Chalcogonatopus); G. rubriDRYINIDAE OF THE NEOTROPICAL REGION Zootaxa 3792 (1) © 2014 Magnolia Press . 5 ceps (Kieffer, 1909), comb. nov. (from Trichogonatopus); G. stellaris (Virla, 1997), comb. nov. (from Trichogonatopus). The male of Crovettia brasiliana Olmi 1984, is described for the first time. Copyright © 2014 Magnolia Press.

Aranguren M.I.,University of the Sea | Gonzalez J.F.,CONICET | Mosiewicki M.A.,University of the Sea
Polymer Testing | Year: 2012

The biodegradation of a new tung oil based polyurethane and a derived wood flour (WF) composite was followed during 383 days of exposure to soil or vermiculite media. The hydrolytic degradation was the most important mechanism of deterioration in all cases. A shift of the glass transition towards higher temperatures was observed, which was explained as the result of the preferential attack and removal of free or dangling-pendant chains that plasticize the original material. The contact angle of water was observed to decrease with exposure to soil and vermiculite media, denoting changes in the surface of the material that increased its polarity. Simultaneously, changes in color and fracture surfaces were also evident. © 2011 Elsevier B.V. All rights reserved.

Sellaro R.,University of Buenos Aires | Yanovsky M.J.,University of Buenos Aires | Yanovsky M.J.,CONICET | Casal J.J.,University of Buenos Aires
Plant Journal | Year: 2011

The light environment provides signals that play a critical role in the control of stem growth in plants. The reduced irradiance and altered spectral composition of shade light promote stem growth compared with unfiltered sunlight. However, whereas most studies have used seedlings exposed to contrasting but constant light treatments, the natural light environment may exhibit strong fluctuations. As a result of gaps in the canopy, plants shaded by neighbours may experience sunflecks, i.e. brief periods of exposure to unfiltered sunlight. Here, we show that sunflecks are perceived by phytochromes A and B, and inhibit hypocotyl growth in Arabidopsis thaliana mainly if they occur during the final portion of the photoperiod. By using forward and reverse genetic approaches we found that ELONGATED HYPOCOTYL 5, LATE ELONGATED HYPOCOTYL, PHYTOCHROME KINASE SUBSTRATE 4 and auxin signalling are key players in this response. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Matano R.P.,Oregon State University | Palma E.D.,CONICET
Journal of Physical Oceanography | Year: 2010

It is well known that numerical simulations of freshwater discharges produce plumes that spread in the direction opposite to that of the propagation of coastally trapped waves (the upstream direction). The lack of a theory explaining these motions in unforced environments deemed the numerical results suspect. Thus, it became a common practice in numerical studies to add a downstream mean flow to arrest the development of the upstream perturbation. This approach is generally unjustified, and it remains a matter of interest to determine if the upstream displacement produced by models is a geophysical phenomenon or a consequence of erroneous assumptions in the model setup. In this article, the results of highly idealized numerical experiments are used to investigate these matters. It is shown that this phenomenon is associated with the geostrophic adjustment of the discharge and that upstream motion is endemic to the baroclinic structure of bottom-trapped plumes. It is also shown that downstream displacements are generated by the cross-shelf barotropic pressure gradient generated by the propagation of coastally trapped waves. Sensitivity experiments indicate that the speed of upstream propagation and the density structure of the plume are affected by bottom friction, the slope of the bottom, and the magnitude of the density anomaly. Bottom friction in particular slows down the progression of the plume and changes its density structure, producing a more homogeneous downstream region and a more stratified upstream region. © 2010 American Meteorological Society.

Marazzi B.,University of Arizona | Marazzi B.,CONICET | Bronstein J.L.,University of Arizona | Koptur S.,Florida International University
Annals of Botany | Year: 2013

BackgroundPlants in over one hundred families in habitats worldwide bear extrafloral nectaries (EFNs). EFNs display a remarkable diversity of evolutionary origins, as well as diverse morphology and location on the plant. They secrete extrafloral nectar, a carbohydrate-rich food that attracts ants and other arthropods, many of which protect the plant in return. By fostering ecologically important protective mutualisms, EFNs play a significant role in structuring both plant and animal communities. And yet researchers are only now beginning to appreciate their importance and the range of ecological, evolutionary and morphological diversity that EFNs exhibit.ScopeThis Highlight features a series of papers that illustrate some of the newest directions in the study of EFNs. Here, we introduce this set of papers by providing an overview of current understanding and new insights on EFN diversity, ecology and evolution. We highlight major gaps in our current knowledge, and outline future research directions. Conclusions Our understanding of the roles EFNs play in plant biology is being revolutionized with the use of new tools from developmental biology and genomics, new modes of analysis allowing hypothesis-testing in large-scale phylogenetic frameworks, and new levels of inquiry extending to community-scale interaction networks. But many central questions remain unanswered; indeed, many have not yet been asked. Thus, the EFN puzzle remains an intriguing challenge for the future. © 2013 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

Curatti L.,CONICET | Rubio L.M.,Technical University of Madrid
Plant Science | Year: 2014

Some regions of the developing world suffer low cereal production yields due to low fertilizer inputs, among other factors. Biological N2 fixation, catalyzed by the prokaryotic enzyme nitrogenase, is an alternative to the use of synthetic N fertilizers. The molybdenum nitrogenase is an O2-labile metalloenzyme composed of the NifDK and NifH proteins, which biosyntheses require a number of nif gene products. A challenging strategy to increase cereal crop productivity in a scenario of low N fertilization is the direct transfer of nif genes into cereals. The sensitivity of nitrogenase to O2 and the apparent complexity of nitrogenase biosynthesis are the main barriers identified so far. Expression of active NifH requires the products of nifM, nifH, and possibly nifU and nifS, whereas active NifDK requires the products of nifH, nifD, nifK, nifB, nifE, nifN, and possibly nifU, nifS, nifQ, nifV, nafY, nifW and nifZ. Plastids and mitochondria are potential subcellular locations for nitrogenase. Both could provide the ATP and electrons required for nitrogenase to function but they differ in their internal O2 levels and their ability to incorporate ammonium into amino acids. © 2014 Elsevier Ireland Ltd.

The availability of organic matter and the abundance of soil biota responsible for their decomposition and mineralization often limit vegetation growth. I examine whether leaf-cutting ant nests affect the abundance of soil micro-organisms in a semi-arid steppe of NW Patagonia. External refuse dumps from Acromyrmex lobicornis nests contained between 1-2 orders of magnitude more bacteria and fungi than adjacent, non-nest soils. Since these taxa are responsible for the major fraction of the mineralization occurring in soils, they may be responsible for the high nutrient content in ant refuse dumps documented in earlier works. Ant nest sites should be considered not only as hot spots of plant diversity and abundance, but also as a source of soil improvement biota.

Rabinovich G.A.,CONICET | Rabinovich G.A.,University of Buenos Aires | van Kooyk Y.,VU University Amsterdam | Cobb B.A.,Case Western Reserve University
Annals of the New York Academy of Sciences | Year: 2012

Unlike their protein "roommates" and their nucleic acid "cousins," carbohydrates remain an enigmatic arm of biology. The central reason for the difficulty in fully understanding how carbohydrate structure and biological function are tied is the nontemplate nature of their synthesis and the resulting heterogeneity. The goal of this collection of expert reviews is to highlight what is known about how carbohydrates and their binding partners-the microbial (non-self), tumor (altered-self), and host (self)-cooperate within the immune system, while also identifying areas of opportunity to those willing to take up the challenge of understanding more about how carbohydrates influence immune responses. In the end, these reviews will serve as specific examples of how carbohydrates are as integral to biology as are proteins, nucleic acids, and lipids. Here, we attempt to summarize general concepts on glycans and glycan-binding proteins (mainly C-type lectins, siglecs, and galectins) and their contributions to the biology of immune responses in physiologic and pathologic settings. © 2012 New York Academy of Sciences.

Casal J.J.,University of Buenos Aires | Casal J.J.,CONICET | Candia A.N.,University of Buenos Aires | Sellaro R.,University of Buenos Aires
Journal of Experimental Botany | Year: 2014

In etiolated seedlings, phytochrome A (phyA) mediates very-low-fluence responses (VLFRs), which initiate de-etiolation at the interphase between the soil and above-ground environments, and high-irradiance responses (HIR), which complete de-etiolation under dense canopies and require more sustained activation with far-red light. Lightactivated phyA is transported to the nucleus by FAR-RED ELONGATED HYPOCOTYL1 (FHY1). The nuclear pool of active phyA increases under prolonged far-red light of relatively high fluence rates. This condition maximizes the rate of FHY1-phyA complex assembly and disassembly, allowing FHY1 to return to the cytoplasm to translocate further phyA to the nucleus, to replace phyA degraded in the proteasome. The core signalling pathways downstream of nuclear phyA involve the negative regulation of CONSTITUTIVE PHOTOMORPHOGENIC 1, which targets for degradation transcription factors required for photomorphogenesis, and PHYTOCHROME-INTERACTING FACTORs, which are transcription factors that repress photomorphogenesis. Under sustained far-red light activation, released FHY1 can also be recruited with active phyA to target gene promoters as a transcriptional activator, and nuclear phyA signalling activates a positive regulatory loop involving BELL-LIKE HOMEODOMAIN 1 that reinforces the HIR. © 2014 The Author.

Fernndez F.M.,CONICET
European Journal of Physics | Year: 2010

We study the hydrogen atom confined to a spherical box with impenetrable walls but, unlike earlier pedagogical articles on the subject, we assume that the nucleus also moves. We obtain the ground-state energy approximately by means of first-order perturbation theory and show that it is greater than that for the case in which the nucleus is clamped at the centre of the box. The present approach is valid for strong confinement and resembles the well-known treatment of the helium atom with clamped nucleus. © 2010 IOP Publishing Ltd.

Included within the field of research on changes in drug use patterns and vulnerability are conditions of emergency related to economic crisis, wars, and political conflict. This study addresses the complex connections between the rapid propagation of freebase cocaine (FBC) - locally known as "pasta base" or "Paco" in Argentina and the normalization of the consequences of Argentina's 2001-2002 political-economic crisis. On the basis of the results of an ethnographic study carried out in three neighborhoods of the Greater Buenos Aires area between 2001 and 2005, this article aims to analyze how changes in the material and social living conditions are interrelated with the high toxicity of FBC/Paco and engender the emerging compulsion of its consumption and deterioration to the bodies, subjectivities, and social activities of active drug users from these shantytowns. By analyzing the changes in transactions directly or indirectly involving drugs - specifically those ranging from cocaine to FBC/Paco - we can argue how structural poverty, "new poverty," is not only associated with the expansion of FBC/Paco but is also shaped by its use, modes of consumption, associated health problems, and sufferings. © 2011 Informa Healthcare USA, Inc.

A higher-derivative classical nonrelativistic U(1) × U(1) gauge field model that describes the topologically massive electromagnetic interaction of composite particles in 2+1 dimensions is proposed. This is made by adding a suitable higher-derivative term for the electromagnetic field to the Lagrangian of a model previously proposed. The model contains a Chern-Simons U(1) field and the topologically massive electromagnetic U(1) field, and it uses either a composite boson system or a composite fermion one. The second case is explicitly considered. By following the usual Hamiltonian method for singular higher-derivative systems, the canonical quantization is carried out. By extending the Faddeev-Senjanovic formalism, the path integral quantization is developed. Consequently, the Feynman rules are established and the diagrammatic structure is discussed. The use of the higher-derivative term eliminates in the Landau gauge the ultraviolet divergence of the primitively divergent Feynman diagrams where the electromagnetic field propagator is present. The unitarity problem, related to the possible appearance of states with negative norm, is treated. A generalization of the Becchi-Rouet-Stora-Tyutin algorithm is applied to the model. © 2010 World Scientific Publishing Company.

In conflicts between primate groups, the resource-holding potential (RHP) of competitors is frequently related to group size or male group size, which can remain relatively constant for long periods of time, promoting stable intergroup dominance relationships. Demographic changes in neighboring groups, however, could introduce uncertainty into existing relationships. Among tufted capuchin monkeys (Cebus apella nigritus), dominant male replacement is a relatively infrequent demographic event that can have a profound effect on both the composition and size of the social group. Here, we report such a case and the consequences for home range use and intergroup aggression. Between June 2008 and August 2010, we periodically followed two neighboring groups (Macuco and Rita) in Iguazú National Park, recording daily paths (N = 143) and encounters between the groups (N = 28). We describe the events leading to a change in the male dominance hierarchy in the larger group (Macuco), which resulted in the death or dispersal of all adult males, followed by the succession of a young adult male to the dominant position. This takeover event reduced the numerical advantage in number of males between the two groups, although the ratio of total group sizes remained nearly constant. Following this shift in numerical asymmetry, the degree of escalation of intergroup aggression increased, and we observed reversals in the former intergroup dominance relationship. These changes in behavior during intergroup encounters were associated with changes in the use of overlapping areas. In the 6 months following the takeover, the area of home range overlap doubled, and the formerly dominant group's area of exclusive access was reduced by half. These results suggest that RHPin tufted capuchin monkeys is related to male group size. Furthermore, they highlight the importance of considering rare demographic events in attempts to understand the dynamics of aggression between primate groups. © 2012 Wiley Periodicals, Inc.

Pol D.,CONICET | Rauhut O.W.M.,Ludwig Maximilians University of Munich
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates. © 2012 The Royal Society.

An illustrated key to the 29 genera of Philonthina currently known in the New World is provided, based on adult morphological characters. Updated information on the morphology, taxonomic history, bionomics and distribution of the Phi-lonthina in the study area is also provided. Copyright © 2014 Magnolia Press.

Gangappa S.N.,Gothenburg University | Botto J.F.,CONICET | Botto J.F.,National Institute of Technology Durgapur
Trends in Plant Science | Year: 2014

The B-box (BBX) proteins are a class of zinc-finger transcription factors containing a B-box domain with one or two B-box motifs, and sometimes also feature a CCT (CONSTANS, CO-like, and TOC1) domain. BBX proteins are key factors in regulatory networks controlling growth and developmental processes that include seedling photomorphogenesis, photoperiodic regulation of flowering, shade avoidance, and responses to biotic and abiotic stresses. In this review we discuss the functions of BBX proteins and the role of B-box motif in mediating transcriptional regulation and protein-protein interaction in plant signaling. In addition, we provide novel insights into the molecular mechanisms of their action and the evolutionary significance of their functional divergence. © 2014 Elsevier Ltd.

Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2010

In this paper, we develop a quantum-jump approach for describing the photon emission process of single fluorophore systems coupled to complex classically fluctuating reservoirs. The formalism relies on an open quantum system approach where the dynamics of the system and the reservoir fluctuations are described through a density matrix whose evolution is defined by a Lindblad rate equation. For each realization of the photon-measurement processes it is possible to define a conditional system state (stochastic density matrix) whose evolution depends on both the photon detection events and the fluctuations between the configurational states of the reservoir. In contrast to standard fluorescent systems the photon-to-photon emission process is not a renewal one, being defined by a (stochastic) waiting time distribution that in each recording event parametrically depends on the conditional state. The formalism allows calculating experimental observables such as the full hierarchy of joint probabilities associated with the time intervals between consecutive photon recording events. These results provide a powerful basis for characterizing different situations arising in single-molecule spectroscopy, such as spectral fluctuations, lifetime fluctuations and light-assisted processes. © 2010 IOP Publishing Ltd.

Fernandez F.M.,CONICET
European Journal of Physics | Year: 2010

We solve the Schrödinger equation for a hydrogen atom within a spherical box approximately by means of the variational method. We propose two simple trial functions for the case in which both the nucleus and the electron move within the box. Present results are sufficiently accurate for all values of the box radius and therefore an improvement on an earlier calculation based on perturbation theory. We compare the energies of three alternative approaches for the moving-nucleus model with that of the nucleus clamped at origin. We also outline some physical applications of the model. © 2010 IOP Publishing Ltd.

Mancuso A.C.,CONICET | Caselli A.T.,University of Buenos Aires
Sedimentary Geology | Year: 2012

Extensional basins offer a high preservation potential for sedimentary and fossil records. Nonmarine rift basins contain diverse environments, including fluvial and lacustrine. Lake deposits have long been recognized as significant archives of the paleoenvironmental record. The Ischigualasto-Villa Unión Basin represents the only nearly continuous continental Triassic record with up to 6000 m of alluvial, fluvial, and lacustrine deposits. The deep lacustrine interval is known as the Los Rastros Formation and consists of several lacustrine-deltaic cycles. A detailed facies analysis allowed the characterization of five facies associations and two types of cycles: (1) a shoreline-dominated, progradational Type I cycle containing Facies association A (offshore lacustrine deposits) and Facies association B (marginal palustrine deposits along the shoreline of the lake) or Facies association C (lacustrine siliciclastic coastal deposits) and (2) a delta-dominated, progradational Type II cycle characterized by Facies association A (offshore lacustrine and prodelta deposits), Facies association D (delta front deposits), and Facies association E (delta plain deposits). The sedimentary evolution of the Chañares-Los Rastros sequence is defined within this extensional setting as one depositional sequence with three system tracts (lowstand, transgressive, and highstand system tract). Biotic, abiotic, and sedimentologic data allowed the interpretation of the limnologic dynamics of the Los Rastros paleolake as a deep freshwater lake within a half-graben, exhibiting meromixis, and showing a change from moderate eutrophic conditions with low oxygen content to relatively oxygenated oligotrophic conditions. The successive fluctuations recorded in lake level are considered in the sequence stratigraphic framework of Bohacs et al. to reflect the relative balance of sediment and water input versus accommodation in an overfilled lacustrine basin. © 2012 Elsevier B.V. All rights reserved.

Chantada G.,Hematology Oncology Service | Schaiquevich P.,CONICET
Pediatric Drugs | Year: 2015

In recent years, there have been dramatic changes in the management of intraocular retinoblastoma. Intraocular retinoblastoma is a highly curable malignancy and current treatments are aimed to preserve vision while reducing the late effects such as treatment-induced secondary malignancies. The advent of intra-arterial chemotherapy changed the treatment paradigm from systemic treatment with chemotherapy to local treatment, and new questions emerged. While intra-arterial chemotherapy achieved encouraging results, only experience from major referral centers is reported, so its indications, advantages and risks are still to be elucidated. Many factors should be considered when choosing the appropriate conservative therapy. When the disease has extended outside the eye, the chances of cure are significantly lower and treatment should be tailored by the presence of pathology risk factors such as invasion of the choroid, the optic nerve, and the sclera. Adjuvant therapy is decided upon this information. Children with overt extraocular disease are treated with higher dose neoadjuvant therapy followed by delayed enucleation and adjuvant therapy. © 2015, Springer International Publishing Switzerland.

Goloboff P.A.,CONICET | Simmons M.P.,Colorado State University
Systematic Biology | Year: 2014

When doing a bootstrap analysis with a single tree saved per pseudoreplicate, biased search algorithms may influence support values more than actual properties of the data set. Two methods commonly used for finding phylogenetic trees consist of randomizing the input order of species in multiple addition sequences followed by branch swapping, or using random trees as the starting point for branch swapping. The randomness inherent to such methods is assumed to eliminate any consistent preferences for some trees or unsupported groups of taxa, but both methods can be significantly biased. In the case of trees created by sequentially adding taxa, a bias may occur even if every addition sequence is equiprobable, and if one of the equally optimal positions for each terminal to add to the tree is selected equiprobably. In the case of branch swapping, the bias can happen even when branch swapping equiprobably selects any of the trees of better score in the subtree-pruning-regrafting-neighborhood or tree-bisection-reconnection-neighborhood. Consequently, when the data set is ambiguous, both random-addition sequences and branch swapping from random trees may (i) find some of the optimal trees much more frequently than others and (ii) find some groups with a frequency that differs from their frequency among all optimal trees. When the data set defines a single optimal tree, the groups present in that tree may have a different probability of being found by a search, even if supported by equal amounts of evidence. This may happen in both parsimony and maximum-likelihood analyses, and even in small data sets without incongruence. [Bootstrap group support jackknife phylogenetic analysis resampling tree searches.] © The Author(s) 2014. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved.

Cuadrado-Laborde C.,CONICET
IEEE Photonics Technology Letters | Year: 2010

We numerically demonstrate that an asymmetrical fiber Bragg grating of uniform-period operated in reflection can provide the required spectral response for implementing an all-optical fractional Hubert transformer. The device shows a good accuracy calculating the fractional Hilbert transform of the complex field of some typical input optical waveforms. The sensibility of the proposed device under different conditions was also analyzed. © 2009 IEEE.

Three different types of data sets, for which the uniquely most parsimonious tree can be known exactly but is hard to find with heuristic tree search methods, are studied. Tree searches are complicated more by the shape of the tree landscape (i.e. the distribution of homoplasy on different trees) than by the sheer abundance of homoplasy or character conflict. Data sets of Type 1 are those constructed by Radel et al. (2013). Data sets of Type 2 present a very rugged landscape, with narrow peaks and valleys, but relatively low amounts of homoplasy. For such a tree landscape, subjecting the trees to TBR and saving suboptimal trees produces much better results when the sequence of clipping for the tree branches is randomized instead of fixed. An unexpected finding for data sets of Types 1 and 2 is that starting a search from a random tree instead of a random addition sequence Wagner tree may increase the probability that the search finds the most parsimonious tree; a small artificial example where these probabilities can be calculated exactly is presented. Data sets of Type 3, the most difficult data sets studied here, comprise only congruent characters, and a single island with only one most parsimonious tree. Even if there is a single island, missing entries create a very flat landscape which is difficult to traverse with tree search algorithms because the number of equally parsimonious trees that need to be saved and swapped to effectively move around the plateaus is too large. Minor modifications of the parameters of tree drifting, ratchet, and sectorial searches allow travelling around these plateaus much more efficiently than saving and swapping large numbers of equally parsimonious trees with TBR. For these data sets, two new related criteria for selecting taxon addition sequences in Wagner trees (the "selected" and "informative" addition sequences) produce much better results than the standard random or closest addition sequences. These new methods for Wagner trees and for moving around plateaus can be useful when analyzing phylogenomic data sets formed by concatenation of genes with uneven taxon representation ("sparse" supermatrices), which are likely to present a tree landscape with extensive plateaus. © 2014 Elsevier Inc.

Journal of Steroid Biochemistry and Molecular Biology | Year: 2010

During the last decade a battery of animal models used for the study of polycystic ovary syndrome (PCOS) have allowed a focus on different aspects of the pathology. Since dehydroepiandrosterone (DHEA) was found to be one of the most abundant circulating androgens in women with PCOS, a rodent model showing the salient features found in women with PCOS was developed by the injection of DHEA. Although insulin-sensitizing agents, such as biguanides, are clinically used in the treatment of diabetes and PCOS, the complete understanding of their mechanisms of action remains unknown. The present review discusses the molecular mechanisms involved in the development of PCOS by using the DHEA-PCOS murine model and analyzes the role of the biguanide metformin as treatment. © 2010 Elsevier Ltd.

Uriu K.,RIKEN | Morelli L.G.,CONICET
Biophysical Journal | Year: 2014

Collective cell movement is a crucial component of embryonic development. Intercellular interactions regulate collective cell movement by allowing cells to transfer information. A key question is how collective cell movement itself influences information flow produced in tissues by intercellular interactions. Here, we study the effect of collective cell movement on the synchronization of locally coupled genetic oscillators. This study is motivated by the segmentation clock in zebrafish somitogenesis, where short-range correlated movement of cells has been observed. We describe the segmentation clock tissue by a Voronoi diagram, cell movement by the force balance of self-propelled and repulsive forces between cells, the dynamics of the direction of self-propelled motion, and the synchronization of genetic oscillators by locally coupled phase oscillators. We find that movement with a correlation length of about 2 ∼ 3 cell diameters is optimal for the synchronization of coupled oscillators. Quantification of cell mixing reveals that this short-range correlation of cell movement allows cells to exchange neighbors most efficiently. Moreover, short-range correlated movement strongly destabilizes nonuniform spatial phase patterns, further promoting global synchronization. Our theoretical results suggest that collective cell movement may enhance the synchronization of the segmentation clock in zebrafish somitogenesis. More generally, collective cell movement may promote information flow in tissues by enhancing cell mixing and destabilizing spurious patterns. © 2014 Biophysical Society.

Camicia G.,Laboratorio Of Hemostasia Y Trombosis | Pozner R.,CONICET | De Larranaga G.,Laboratorio Of Hemostasia Y Trombosis
Shock | Year: 2014

Sepsis is the leading cause of death in critically ill patients in intensive care units. Early recognition of sepsis and proper therapy are essential to reduce patient mortality. Moreover, treatment options for this deleterious inflammatory response to infection are limited. Neutrophils play an essential role in the innate immune response, providing the first line of host defense. It has recently been shown that these cells can trap and kill microorganisms by releasing neutrophil extracellular traps (NETs) composed of chromatin and antimicrobial proteins. Although the beneficial role of NETs during infections has been demonstrated, there is increasing evidence that NETs and their components contribute to the pathogenesis of several diseases, including sepsis. The aim of this review was to summarize the current evidence implicating NETs, as well as their components, in the development of sepsis and to discuss their potential use as novel therapeutic targets and as prognostic markers in septic patients. Copyright © 2014 by the Shock Society.

Ocean and Coastal Management | Year: 2013

Coastal villages have grown due the increasing touristic demand of " sun and beach" resorts. This implies more services, more areas for bathing and shadows for tourists. The awkward assessment of touristic beaches and the shortages induced by natural erosion provoked the deterioration of bathing zones. The coastal defence policy and the management of the rain excesses can not reverse this deterioration trend. Storm-water discharges in many places are constructed towards the bathing zones by combined sewer overflows (CSO) systems that increase pollution problems. The decrease of the width of the beach demand interventions. Hard structures (seawalls, groynes) have probed to imply worse impacts; beach nourishment does not solve the problem but permits to rebuilt or modify some beaches under critic stages. The pavements of seaside avenues have been very controversial in some cities subject to storms. Sewage networks were originally oriented to sanitary ponds but odours and pollution of the water table led to reconsider some master plans. At the same time, groundwater is shortening towards the end of the season and new water reserves should be planned. However, federal governments do not envisage the magnitude of future problems, neither the impacts of climatic changes. In this sense, it is necessary to propose alternative coastal-defence policies, to avoid pluvial discharges to bathing areas, to promote aquifer recharges and to reverse the sewage network towards submarine outfalls. © 2012 Elsevier Ltd.

Comparisons between death assemblages and their source living communities are among the most common actualistic methods of evaluating the preservation of compositional and environmental information in fossil assemblages. Although live-dead studies have commonly focused on marine mollusks, the potential of diatoms to preserve ecological information in continental settings has been overlooked. Thus, little is known about the nature and magnitude of the taphonomic biases affecting live-dead agreement of diatom assemblages, despite their extensive application as modern and fossil bioindicators in paleoecological and paleoenvironmental reconstructions. In this study, I analyzed three live-dead data sets in order to evaluate the compositional and environmental fidelity exhibited by diatom death assemblages in shallow lakes. I find that diatom death assemblages (DAs) do differ significantly in their taxonomic composition from living assemblages (LAs), mainly as a consequence of (1) differences in the temporal resolution between time-averaged DAs and non-averaged LAs, and (2) differential preservation of diatom taxa related to the intrinsic properties of their valves. Despite compositional dissimilarities, DAs were able to capture the same environmental gradients as LAs, with high significance. This decoupling between live-dead agreement in community composition and community response to gradients can be related to the existence of at least two mutually exclusive subsets of species that significantly captured compositional dissimilarities based on the full set of the species in the three lakes. This functional redundancy implies that the between-sample relationships of living assemblages can be significantly preserved by DAs even if some taxa are removed by taphonomic processes. The preservation of environmental gradients thus does not require good preservation of all living taxa. Structural redundancy compensates for the loss of compositional fidelity caused by postmortem processes in the diatom data set. © 2015 The Paleontological Society. All rights reserved.

Cochrane K.L.,Food and Agriculture Organization of the United Nations | Andrew N.L.,Worldfish Center | Parma A.M.,CONICET
Fish and Fisheries | Year: 2011

The social and economic importance of small-scale fisheries is frequently under-valued, and they are rarely effectively managed. There is now growing consensus on how these fisheries could be managed for sustainability and to minimize the risks of crossing undesirable thresholds. Using a concept developed in health care, these approaches have been referred to as primary fisheries management. By encouraging the use of best-available information in a precautionary way, the approaches will facilitate sustainable use and should therefore be encouraged, but they accept high scientific and implementation uncertainties as unavoidable because of limited management and enforcement resources and capacity. It is important to recognize that this limitation will result in social costs, because application of a precautionary approach in the face of high uncertainties will require forgoing potential sustainable benefits. Acceptance of primary fisheries management as a final and sufficient goal could therefore add a further constraint on the possibility of fishing communities escaping the poverty trap. Primary fisheries management should be seen as a first and minimum target for fisheries where there is currently no or inadequate management, but the longer-term goal should still be well informed and adaptive management that strives for optimal benefits, referred to here as tertiary management. © 2010 Blackwell Publishing Ltd.

Journal of Physics Condensed Matter | Year: 2010

By combining analytical results and computer simulations, we studied the continuous theory of surface diffusion applied to the decay of periodic high-aspect-ratio patterned substrates. Our results show that, after a transient stage, and for a broad class of initial conditions, patterns adopt a 'universal' mathematically well-specified shape that depends on two coefficients. Moreover, we were able to determine the time-dependence of such coefficients, which enabled us to mathematically reconstruct the pattern's shape at any subsequent time. So, our analysis can be a useful predictive theoretical tool for the design and interpretation of experiments on thermal treatments of high-aspect-ratio patterns. © 2010 IOP Publishing Ltd.

The total lengths (LT) of 193 males (209-556mm) and 130 females (275-515mm) of Amblyraja doellojuradoi, a commercial by-catch species on the Argentinean continental shelf, which are increasingly retained, were analysed. No sexual dimorphism was observed in the LT at which 50% of individuals were sexually mature; males matured at 448mm and females at 411mm, c. 80 and 82% of maximum LT. The hepato-somatic index was similar among sexes, but significantly different between maturity stages, being lower in mature than immature specimens. Males had no seasonal difference in the hepato-somatic index and females had the lowest index in autumn. The gonado-somatic index was lower in males than in females and significantly higher in mature than immature specimens of both sexes. Males had the highest index in autumn and females had no seasonal difference. Collectively, these results would indicate that A. doellojuradoi breeds in autumn. © 2016 The Fisheries Society of the British Isles.

Viale M.,CONICET | Houze R.A.,University of Washington | Rasmussen K.L.,University of Washington
Monthly Weather Review | Year: 2013

Upstream orographic enhancement of the rainfall from an extratropical cyclone approaching the Andes from the Pacific is investigated using the Weather Research and Forecasting (WRF) Model and the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar. The main precipitation from the cyclone over central and coastal Chile fell when a narrow cold-frontal rainband (NCFR) interacted with a midlevel layer cloud deck formed from the orographically induced ascent of the prefrontal "atmospheric river" upstream of the Andes. Model output indicates that low-level convergence enhanced the NCFR where it met low-level blocked flow near the mountains. The NCFR had stronger updrafts with decreasing distance from the mountains, and the NCFR produced larger rain accumulations over the land region upstream of the Andes than over the open ocean. A sensitivity simulation with a 50% reduction in the Andes topography, for comparison to various west coast mountain ranges of North America, demonstrates that the extreme height of the real mountain barrier strengthens frontogenesis and upstream blocking, which produces stronger frontal lifting and a slower progression of the frontal system. The model and the satellite data suggest that the larger precipitation rates upstream of the Andes resulted from a seeder-feeder effect connected with the orographically invigorated NCFR updrafts, when they penetrated the orographically enhanced midlevel stratiform clouds forming as a result of the upstream orographic ascent of the atmospheric river. The supercooled water of the NCFR updrafts formed a feeder zone for the snow particles in the midlevel stratiform cloud just upstream of the Andes. © 2013 American Meteorological Society.

The vegetation on the eastern slope of Cordón del Portillo is studied in order to fill gaps in the floristic and ecological information on the Andean plant communities of Mendoza. Work is developed along an altitudinal gradient between 980 and 4300 m asl using the phytosociological method. After synthesizing of the area characteristics, are describe the major plant communities identified from the analysis of comparative survey tables. The study discriminates 18 plant communities and 26 floristic groups and the occurrence of 3 phytogeographic provinces: Monte, Andean and High Andean, 4 geographic districts and 5 sub-districts. The Monte phytogeographic province and Cuyano Monte district are characterized by the shrubland sub-district of Larrea divaricata (980 to 1600 m asl). The Andean Province and Cuyano Andean district by the shrubland sub-districts of Junellia scoparia-Colliguaja integerrima and Adesmia horrida (1400 to 2600 m asl) and of Adesmia pinifolia (2400 to 3000 m asl). The High Andean province and Cuyano High Andean district are represented by the sub-districts of steppes and cushions of Adesmia subterranea-Azorella monantha (2950 to 3800 m asl) and of the shrub steppe of Nassauvia lagascae-Senecio crithmoides (3700-4200 m asl). Results allow extrapolation of plant communities to the N and S of the area.

Plants have mutualistic relationships with insects in two ways: through domatia provide housing of predators, and extrafloral nectaries secreting nectar and provide food in exchange for control of herbivores or fungal pathogens. The foliar anatomy of 52 species of Bignoniaceae was examined by light and scanning electron microscopy, in order to describe the different types of domatia and extrafloral nectaries. Two types of domatia were observed: small hair-tufts and pockets; the presence and type of domatia represents important taxonomic characters in Bignoniaceae. Extrafloral nectaries are found in all studied species. They are located in different positions: along the midvein, associated with domatia, or grouped in glandular fields, either in leaf or interpetiolar. The Bignoniaceae have simultaneously domatia and extrafloral nectaries on their leaves, these features are described as plant components in a probable mechanism of indirect defense.

Ravindra B.,Indian Institute of Astrophysics | Yoshimura K.,Montana State University | Dasso S.,CONICET
Astrophysical Journal | Year: 2011

The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8°hr-1 on the third day of the observations. On the fourth and fifth days it remained at 4°hr-1 with small undulations in its magnitude. The sunspot rotated about 260° in the last three days. The S-polarity sunspot did not complete more than 20° in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of -7 × 1043Mx2 over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than -6 × 1043Mx2. The observed reversal in the sign of spinning and braiding helicity fluxes could be the signature of the emergence of a twisted flux tube, which acquires the writhe of an opposite sign. The magnetic cloud associated with the ejected mass has carried about -7 × 1041Mx2 of helicity. A time integration of helicity flux of about 1.2hr integrated backward in time of the observation of the coronal mass ejection is sufficient for this event. © 2011. The American Astronomical Society. All rights reserved.

Recalde M.,CONICET
International Journal of Hydrogen Energy | Year: 2010

Despite its great wind endowment, Argentina has not still succeeded in increasing wind power share in its wholesale market. However, the energy supply problem that this country is facing from 2004 on seems to open an opportunity for wind energy projects. A wide range of legislation has recently emerged. In this context, this paper discusses whether policy instruments in the Argentinean regulatory frame contribute to economic feasibility for wind power projects or not. To this purpose, we study wind installed capacity, Argentinean wind potential, the different promotion tools used worldwide and those employed in Argentina. Finally, we realize a feasibility study for a typical project. We found, that in spite of its high wind potential, economic feature, related to policy instruments, have been a boundary to the development of wind energy into the energy mix. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Zumoffen D.,CONICET | Basualdo M.,National University of Costa Rica
Industrial and Engineering Chemistry Research | Year: 2010

In this work a new concept for designing an efficient monitoring system for large scale chemical plants is presented. It is considered that the monitoring problem must be solved integrated with the optimal sensor location together with the plant-wide control structure design. The solution of these problems involves deciding among a great number of possible combinations between the input-output variables. It is done supported by the application of genetic algorithm (GA). The key new idea is to propose an adequate objective function, within the GA, that takes into account a fault detectability index based on combined statistics. Additionally, by using a specific penalty function, it is possible to drive the search to the less expensive structure, that is by using the lowest number of sensors. The well-known benchmark case of the Tennessee Eastman plant (TE) is chosen for testing this methodology and for discussion purposes. Since several authors have studied the TE case, the results obtained here can be rigorously compared with those already published. All of the previous works considered that every TE output variables were available for the abnormal events detection for designing the monitoring system. © 2010 American Chemical Society.

The morphology of the osteocyte lacuno-canalicular system at the bone-biomaterial implant-interface has not been fully investigated. In this study, the resin-cast scanning electron microscopy technique was used, for the first time, to image the lacuno-canalicular network within neoformed bone around bioactive glass (BG) particles implanted in rat tibia bone marrow. The most salient finding was that the osteocyte canaliculi pass through the calcium-phosphorus layer formed at the bone-BG interface and reach the silica-rich layer of the reacted BG. © 2010 Microscopy Society of America.

Ferreiro D.U.,CONICET | Komives E.A.,University of California at San Diego | Wolynes P.G.,Rice University
Quarterly Reviews of Biophysics | Year: 2014

Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their own structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of frustration in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and especially how biomolecular structure connects to function by means of localized frustration. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding mechanisms. We review here how the biological functions of proteins are related to subtle local physical frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. In this review, we also emphasize that frustration, far from being always a bad thing, is an essential feature of biomolecules that allows dynamics to be harnessed for function. In this way, we hope to illustrate how Frustration is a fundamental concept in molecular biology. © Cambridge University Press 2014.

This contribution focuses on the main results and present researches on the Oligocene fauna from Quebrada Fiera (Mendoza, Argentina). This vertebrate assemblage is providing new data on the distribution and evolution of South American Deseadan (late Oligocene) mammals. Descriptions of notoungulate Notohippidae and Archaeohyracidae have been recently published. A new genus of notohippid was identified, while most archaeohyracid material was recognized as the same species present in Salla (Bolivia). Studies in progress on other native ungulates (Hegetotheriidae, Interatheriidae, Leontinidae, Homalodotheriidae, Toxodontidae, ?Proterotheriidae, and Pyrotheriidae), metatheria, xenarthra, and rodents from Quebrada Fiera will increase the knowledge of this fauna. Preliminarily, the faunal association appears as a mix of taxa. On the one hand, with Patagonian affinities, on the other hand, related to species known from lower latitudes (Bolivia), together with exclusive taxa such as Mendozahippus (Notohippidae). The ongoing research will allow a better understanding of the role of Mendoza area in the paleobiogeographic and biostratigraphic context of the South American Oligocene mammals.

Gardiol D.,CONICET
FEBS Journal | Year: 2012

PDZ domains are very abundant protein interaction domains widespread in nature. A large amount of evidence has underscored the importance of the PDZ interactions in the control of intracellular pathways whose abnormal regulation may lead to the development of several pathologies. This series of minireviews covers different aspects of human PDZ-containing proteins, underlining and discussing new concepts and findings. © 2012 The Authors Journal compilation © 2012 FEBS.

Viale M.,CONICET | Nunez M.N.,University of Buenos Aires
Journal of Hydrometeorology | Year: 2011

Winter orographic precipitation over the Andes between 30° and 37°S is examined using precipitation gauges in the mountains and adjacent lowlands. Because of the limited number of precipitation gauges, this paper focuses on the large-scale variation in cross-barrier precipitation and does not take into account the fine ridge-valley scale. The maximum amount of precipitation was observed on the windward slope of the mountain range below the crest, which was twice that observed on the low-windward side between 32.5° and 34°S. Toward the east of the crest, precipitation amounts drop sharply, generating a strong cross-barrier gradient. The rain shadow effect is greater in the north (32°-34.5°S) than in the south (35°-36.5°S) of the low-lee side, which is probably due to more baroclinic activity in southernmost latitudes and a southward decrease in the height of the Andes enabling more spill over precipitation. The effect of the Andes on winter precipitation is so marked that it modifies the precipitation regimes in the adjacent windward and leeward lowlands north of 35°S. Based on the fact that ~75% of the wintertime precipitation accumulated in the fourth quartile, through four or five heavy events on average, the synoptic-scale patterns of the heavy (into fourth quartile) orographic precipitation events were identified. Heavy events are strongly related to strong water vapor transport from the Pacific Ocean in the pre-cold-front environment of extratropical cyclones, which would have the form of atmospheric rivers as depicted in the reanalysis and rawinsonde data. The composite fields revealed a marked difference between two subgroups of heavy precipitation events. The extreme (100th-95th percentiles) events are associated with deeper cyclones than those for intense (95th-75th percentiles) events. These deeper cyclones lead to much stronger plumes of water vapor content and cross-barrier moisture flux against the high Andes, resulting in heavier orographic precipitation for extreme events. In addition, regional airflow characteristics suggest that the low-level flow is typically blocked and diverted poleward in the form of an along-barrier jet. On the lee side, downslope flow dominates during heavy events, producing prominent rain shadow effects as denoted by the domain of downslope winds extending to low-leeward side (i.e., zonda wind). © 2011 American Meteorological Society.

This paper deals with the way in which the environmental dynamics that took place in the lower basin of the Colorado River (Buenos Aires province, Argentina) have affected the degree of archaeological resolution, integrity, and site preservation in different sectors of the study area (e.g., coastal fringe, delta and interior dune fields). Evidence from geomorphologic, stratigraphic, and sedimentary analyses as well as chemical parameters and zooarchaeological assemblages are used in order to propose spatial and temporal variations in the structure of the archaeological record. These lines of evidence were also used for inferring general paleoclimatic trends. The results obtained indicate that the inland landforms that contained Initial Late Holocene archaeological assemblages (3000-1000 14C BP) have suffered important morphodynamic processes that produced site destruction, loss of organic material and lower degrees of integrity and site resolution. Conversely, landforms located near the delta and the coastal fringe underwent more stable geomorphic processes (e.g., pedogenesis) that promoted better preservation, resolution, and integrity during the Initial Late Holocene and, particularly, during the Final Late Holocene (1000-250 14C BP). The recognition of this pattern is crucial in order to evaluate demographic processes linked with the intensity and mode of hunter-gatherer occupation of the area and population dynamics throughout time. © 2011 Elsevier Ltd and INQUA.

Rostagno C.M.,CONICET | Degorgue G.,Institute Cooperacion Economica Internacional ICEI
Geomorphology | Year: 2011

Desert pavements are prominent features of many geomorphic surfaces in arid and semiarid lands. In the semiarid soils of north-eastern Patagonia, gravel cover in the shrub interspace areas of shrub-dominated communities is generally high, and contrast with that of grass-dominated patches where gravel cover is either absent or negligible. In the present study we analyze the relationship between soil erosion and desert pavement formation, in three sites, the upper, middle and lower slope positions of a flank pediment where well-conserved soils served as reference areas. We used the gravel cover and mass, as well as the thickness of the remnant A horizon, as determined by the depth of the Bt horizon of a Xeric Calciargid, as measures of soil erosion. Surface gravel at four cardinal points in respect to mounds associated with shrub-clumps was collected and the depth to the Bt horizon was determined. The mean thickness of the A horizon in the well-conserved soils were 11.3, 10.0 and 13.5cm for the upper, middle and lower slope positions, respectively. For the same positions, the mean coarse fragment contents (>2.0mm) in the 0-10cm depth of the A horizon in the well-conserved soils were 144, 92 and 119gkg-1, and the mean surface gravel mass in the eroded patches were 5.3, 3.1 and 4.7kgm-2. Surface gravel mass and depth of the remnant A horizon gave different estimates of the magnitude of soil erosion in the flank pediment. Thus, the mean/maximum soil loss, as determined by the mean gravel mass on the soil surface for the upper, middle and lower slope positions were, 28.3/68.2, 27.0/63.8 and 31.5/56.4mm, respectively. These figures increased to a mean of 50.0, 52.5 and 82.0mm for the same positions when soil loss was determined as the difference between the thickness of the A horizon of the well-conserved soil and that of the remaining A horizon in eroded patches. The loss of the A horizon by wind and water erosion seems to initiate the change from grass steppe to a stable shrub steppe characterized, in the shrub interspaces, by well-developed desert pavements. The strong correlation between surface gravel mass and the thickness of the remaining A horizon indicates that accelerated soil erosion has played an important role in the formation of desert pavements, and that desert pavements are good indicators of the extent and intensity of the erosion process in the Punta Ninfas area. © 2011 Elsevier B.V.

Molecular BioSystems | Year: 2012

Disordered regions are segments of a protein that do not fold completely and thus remain flexible. These regions have key physiological roles, particularly in phospho-proteins, which are enriched in disorder-promoting residues surrounding their phosphorylation sites. 14-3-3 proteins are ordered hubs that interact with multiple and diverse intrinsically disordered phosphorylated targets. This provides 14-3-3 with the ability to participate in and to regulate multiple signalling networks. Here, I review the effect of structural disorder on the mechanism involved in 14-3-3 protein-protein interactions and how 14-3-3 impacts cell biology through disordered ligands. How 14-3-3 proteins constitute an advantageous system to identify novel classes of biological tools is discussed with a special emphasis on a particular - and innovative - use of small molecules to stabilize 14-3-3 protein complexes, useful to study gene expression, cancer signalling and neurodegenerative diseases.

Ponce J.J.,National University of Rio Negro | Carmona N.,CONICET
Geology | Year: 2011

In this paper we present an outcrop example of coarse-grained sediment waves generated by hyperpycnal discharges at the toe of Miocene clinoform systems exposed in the northeast Atlantic coast of Tierra del Fuego, Argentina. An individual set of these sediment waves is formed during the waxing and waning phases of the hyperpycnal discharge. During the waxing phase, accumulation of coarse-grained sediments with generation and migration of dune bedforms occurs at the base of the clinoforms. These deposits show transitions of tractive sedimentary structures with evidence of bedload transport, and a continuous reworking by the overpassing hyperpycnal flow. The continued erosion and reworking during the waxing phase affect mainly the top and the stoss side of the dunes, resulting in isolated lenses having upcurrent aggradation structures. During the waning phase, these isolated lenses are covered by fine-grained heterolithic strata that are thicker on the stoss side than on the lee side, constituting a differential draping. The pulsating and sustained character of the hyperpycnal flows and the steep depositional slope clinoforms controlled the stacking pattern of the coarse-grained sediment waves during successive hyperpycnal events. In this way, small-scale, coarse-grained sediment waves, with wavelengths of 10-40 m and up to 5 m amplitude, and a stacking pattern showing an up-current growth, are generated by high-density hyperpycnal flows on slopes having steep gradients. © 2011 Geological Society of America.

Perello M.,CONICET | Dickson S.L.,Gothenburg University
Journal of Neuroendocrinology | Year: 2015

'Hunger is the best spice' is an old and wise saying that acknowledges the fact that almost any food tastes better when we are hungry. The neurobiological underpinnings of this lore include activation of the brain's reward system and the stimulation of this system by the hunger-promoting hormone ghrelin. Ghrelin is produced largely from the stomach and levels are higher preprandially. The ghrelin receptor is expressed in many brain areas important for feeding control, including not only the hypothalamic nuclei involved in energy balance regulation, but also reward-linked areas such as the ventral tegmental area. By targeting the mesoaccumbal dopamine neurones of the ventral tegmental area, ghrelin recruits pathways important for food reward-related behaviours that show overlap with but are also distinct from those important for food intake. We review a variety of studies that support the notion that ghrelin signalling at the level of the mesolimbic system is one of the key molecular substrates that provides a physiological signal connecting gut and reward pathways. © 2014 The Authors.

Within the framework of the CLARIS-LPB EU Project, a suite of 7 coordinated Regional Climate Model (RCM) simulations over South America driven by both the ERA-Interim reanalysis and a set of Global Climate Models (GCMs) were evaluated. The systematic biases in simulating monthly mean temperature and precipitation from the 2 sets of RCM simulations were identified. The Climate Research Unit dataset was used as a reference. The systematic model errors were more dependent on the RCMs than on the driving GCMs. Most RCMs showed a systematic temperature overestimation and precipitation underestimation over the La Plata Basin region. Model biases were not invariant, but a temperature-dependent temperature bias and a precipitation-dependent precipitation bias were apparent for the region, with the warm bias amplified for warm months and the dry bias amplified for wet months. In a climate change scenario, the relationship between model bias behaviour and the projected climate change for each individual model revealed that the models with the largest temperature bias amplification projected the largest warming and the models with the largest dry bias amplification projected the smallest precipitation increase, suggesting that models' bias behaviour may affect the future climate projections. After correcting model biases by means of a quantile-based mapping bias correction method, projected temperature changes were systematically reduced, and projected precipitation changes were systematically increased. Though applying bias correction method - ologies to projected climate conditions is controversial, this study demonstrates that bias correction methodologies should be considered in order to better interpret climate change signals. © Inter-Research 2016.

Flores F.G.,National University of Cordoba | Flores F.G.,CONICET
Computer Methods in Applied Mechanics and Engineering | Year: 2013

In this paper a triangular prism solid element for the analysis of thin/thick shells undergoing large elastic-plastic strains is developed. The element is based on a total Lagrangian formulation and uses as strain measure the logarithm of the right stretch tensor (U) obtained from a modified right Cauchy-Green deformation tensor (C̄). Three are the introduced modifications: (a) a classical assumed strain approach for transverse shear strains (b) an assumed strain approach for the in-plane components using information from neighbor elements and (c) an averaging of the volumetric strain over the element. The objective is to use this type of elements for the simulation of shells avoiding transverse shear locking, improving the membrane behavior of the in-plane triangle and to handle quasi-incompressible materials or materials with isochoric plastic flow. Several examples are presented that show the transverse-shear locking free behavior, the importance of the improvement in the membrane approach and the wide possibilities of the introduced element for the analysis of shell structures for both geometric and material non-linear behavior. © 2012 Elsevier B.V.

Hader D.-P.,Neue Str. 9 | Helbling E.W.,CONICET | Williamson C.E.,Miami University Ohio | Worrest R.C.,Columbia University
Photochemical and Photobiological Sciences | Year: 2011

The health of freshwater and marine ecosystems is critical to life on Earth. The impact of solar UV-B radiation is one potential stress factor that can have a negative impact on the health of certain species within these ecosystems. Although there is a paucity of data and information regarding the effect of UV-B radiation on total ecosystem structure and function, several recent studies have addressed the effects on various species within each trophic level. Climate change, acid deposition, and changes in other anthropogenic stressors such as pollutants alter UV exposure levels in inland and coastal marine waters. These factors potentially have important consequences for a variety of aquatic organisms including waterborne human pathogens. Recent results have demonstrated the negative impacts of exposure to UV-B radiation on primary producers, including effects on cyanobacteria, phytoplankton, macroalgae and aquatic plants. UV-B radiation is an environmental stressor for many aquatic consumers, including zooplankton, crustaceans, amphibians, fish, and corals. Many aquatic producers and consumers rely on avoidance strategies, repair mechanisms and the synthesis of UV-absorbing substances for protection. However, there has been relatively little information generated regarding the impact of solar UV-B radiation on species composition within natural ecosystems or on the interaction of organisms between trophic levels within those ecosystems. There remains the question as to whether a decrease in population size of the more sensitive primary producers would be compensated for by an increase in the population size of more tolerant species, and therefore whether there would be a net negative impact on the absorption of atmospheric carbon dioxide by these ecosystems. Another question is whether there would be a significant impact on the quantity and quality of nutrients cycling through the food web, including the generation of food proteins for humans. Interactive effects of UV radiation with changes in other stressors, including climate change and pollutants, are likely to be particularly important. © 2011 The Royal Society of Chemistry and Owner Societies.

During the two-month rearing period, the effect of four water temperatures (15°C, 20°C, 25°C and 30°C) on survival rate, number of molts, and growth rate (molt increment and intermolt period) of juvenile Macrobrachium borellii Nobili, 1896 and Palaemonetes argentinus Nobili, 1901 prawns was evaluated in laboratory conditions. The two species showed some similarities in their both survival and growth pattern at different temperatures. The survival rate was highest at 20°C and 25°C, decreasing at the lowest temperature. The number of molts increased at higher temperatures, ranging the intermolt period from 22.2 days to 9.9 days, for M. borellii, and from 20.8 to 9.5 days for P. argentinus, corresponding those values to 15°C and 30°C, respectively. No difference between species was noted in the intermolt period. The size increment by molting increased significantly from 15°C to 25°C, whereas a reduction in the growth of prawns was observed at 30°C. Significant differences among temperatures were found in the slope of regressions between the size increment by molting and the cephalothorax length. M. borellii showed a significantly higher tolerance to elevated temperature and a faster growth (about twice at 25°C) than P. argentinus. These differences could provide M. borellii a competitive advantage for a better adaptation to the dynamic of freshwater environment, especially in areas with anthropogenic impact.

The objective of this work was to obtain an overview of studies on ecological restoration carried out in Argentina to date. By means of the Scopus database, we performed two literature searches, one in Spanish (restau* and Argentina) and the other in English (restor* and Argentina). Between 1996 and 2013, 105 publications were registered, representing 2% of publications in Biology and Ecology. Most of these appeared in international journals (87%), in English (86%), and 28% were coauthored with researchers from other countries, favoring visibility at an international level. We observed an increase in the number of studies per year over time, with a significant increase beginning in 2008. Of the 18 ecological regions in Argentina, we found studies relating to 12 as well as four studies relating to restoration in urban areas. This review of the literature is intended to increase awareness of restoration in Argentina and help identify current gaps relating either to this subject or to specific ecological regions. © 2015 Society for Ecological Restoration.

Thijssen V.L.,VU University Amsterdam | Rabinovich G.A.,CONICET | Rabinovich G.A.,University of Buenos Aires | Griffioen A.W.,VU University Amsterdam
Cytokine and Growth Factor Reviews | Year: 2013

Galectins are a family of carbohydrate binding proteins with a broad range of cytokine and growth factor-like functions in multiple steps of cancer progression. They contribute to tumor cell transformation, promote tumor angiogenesis, hamper the anti-tumor immune response, and facilitate tumor metastasis. Consequently, galectins are considered as multifunctional targets for cancer therapy. Interestingly, many of the functions related to tumor progression can be linked to galectins expressed by endothelial cells in the tumor vascular bed. Since the tumor vasculature is an easily accessible target for cancer therapy, understanding how galectins in the tumor endothelium influence cancer progression is important for the translational development of galectin-targeting therapies. © 2013 Elsevier Ltd.

Xu X.,CAS Institute of Vertebrate Paleontology and Paleoanthropology | Pol D.,CONICET
Journal of Systematic Palaeontology | Year: 2014

Archaeopteryx, which has often been considered the earliest avialan, is an iconic species, central to our understanding of bird origins. However, a recent parsimony-based phylogenetic study shifted its position from within Avialae, the group that contains modern birds, to Deinonychosauria, the sister-taxon to Avialae. Subsequently, probability-based methods were applied to the same dataset, restoring Archaeopteryx to basal Avialae, suggesting these methods should be used more often in palaeontological studies. Here we review two key issues: arguments recently advocated for the usefulness of probability-based methodologies in the phylogenetic reconstruction of basal birds and their close relatives, and support for different phylogenetic hypotheses. Our analysis demonstrates that Archaeopteryx represents a challenging taxon to place in the phylogenetic tree, but recent discoveries of derived theropods including basal avialans provide increased support for the deinonychosaurian affinities of Archaeopteryx. Most importantly, we underscore that methodological choices should be based on the adequacy of the assumptions for particular kinds of data rather than on the recovery of preferred or generally accepted topologies, and that certain probability methods should be interpreted with caution as they can grossly overestimate character support. © 2013 Natural History Museum.

Microfluidics and Nanofluidics | Year: 2010

Theoretical expressions of the flow rate, output pressure and thermodynamic efficiency of electrokinetic pumping of non-Newtonian fluids through cylindrical and slit microchannels are reported. Calculations are carried out in the framework of continuum fluid mechanics. The constitutive model of Ostwald-de Waele (power law) is used to express the fluid shear stress in terms of the velocity gradient. The resulting equations of flow rate and electric current are nonlinear functions of the electric potential and pressure gradients. The fact that the microstructure of non-Newtonian fluids is altered at solid-liquid interfaces is taken into account. In the case of fluids with wall depletion, both the output pressure and efficiency are found to be several times higher than that obtained with simple electrolytes under the same experimental conditions. Apart from potential applications in electrokinetic pumps, these predictions are of interest for the design of microfluidic devices that manipulate non-Newtonian fluids such as polymer solutions and colloidal suspensions. From a more fundamental point of view, the paper discusses a relevant example of nonlinear electrokinetics. © 2009 Springer-Verlag.

The Malargüe fold-and-thrust belt is a thick-skinned belt developed in Miocene-Pliocene times during the Andean orogeny, which together with the Cordillera Frontal constitutes the Andes of central Argentina in the Diamante River area. Detailed field mapping and construction of three regional balanced cross-sections, supported by seismic and well information, constrains the structural style of this Andean region as two basement uplifts in the western and eastern sectors surrounding a central region of thin-skinned deformation. In the west, large basement wedges related to thrust faults developed during Andean compression propagated along favourable horizons (commonly gypsum) into the sedimentary cover. These wedges transferred shortening to the cover rocks producing the thin-skinned structures. There is therefore a close spatial and temporal relationship between basement and cover deformation. In the thin-skinned region, the abundance of shales and salt horizons in the west facilitated the formation of fault-related folds while the more competent units in the east were deformed into duplex and imbricated thrusts. The basement uplift in the eastern sector represents the southern end of the Cordillera Frontal, where the Carrizalito fault placed pre-Jurassic rocks over tertiary synorogenic sediments in the northern area while in the southern region it remained as a blind thrust. A common feature is the development of backthrust systems related to the major east-vergent basement structures. The backthrusts therefore serve to locate basement uplifts where outcrops are absent. Three-dimensional integration of the cross-sections and a structural map at the top of the pre-Jurassic basement show that although the main structures change considerably along strike, the total shortening of each section shows little variation. © 2009 Elsevier Ltd.

Careaga V.P.,CONICET
Natural product research | Year: 2013

The edible sea cucumber Athyonidium chilensis is a fishery resource of high commercial value in Chile, but no information on its lipid and fatty acid composition has been previously reported. Phospholipids were the major lipid contents of the ethanolic extracts of tubules, internal organs and body wall of A. chilensis. Saturated fatty acids predominated in tubule phospholipids (40.69%), while in internal organs and body wall phospholipids, the monounsaturated fatty acids were in higher amounts (41.99% and 37.94%, respectively). The main polyunsaturated fatty acids in phospholipids were C20 : 2ω-6, arachidonic (C20 : 4ω-6) and eicosapentaenoic (C20 : 5ω-3) acids. These results demonstrate for the first time that A. chilensis is a valuable food for human consumption in terms of fatty acids.

In Northern Patagonia, the long-term vegetation-climate relationships that gave shape to southern South American forests have been the subject of extensive investigations in the Andean regions of Argentina and Chile for about a century. The Río Manso Superior originates in one of the tongues of the Cerro Tronador Glacier, near the international border, discharging into the Pacific Ocean after feeding present Lago Mascardi and flowing east to west on a mountain landscape. Ongoing pollen studies in this watershed provide us with a modern analogue to better understand the vegetation history of the region. A pollen record from a 15 m long sediment core retrieved from Lago Mascardi (41°08°S, 71°34°W) contains continuous evidence of vegetation changes in the Río Manso watershed extending back to the last deglaciation. High Andean steppe vegetation with forest patches, and extended waterlogged areas gave place to a forest, probably deciduous, during the Lateglacial-Holocene transition. A forest diversification took place during the climate amelioration that encompassed the deglaciation whilst the vegetation became more open before the onset of the Huelmo-Mascardi cold reversal. A mixed Nothofagus-Austrocedrus forest expanded during the middle Holocene. This forest became denser under the higher climate variability registered in the region during the late Holocene as shown by independent published data. Statistical analyses of modern pollen samples along an altitudinal transect from low Nothofagus forest and shrubland to high Andean semi-desert support this interpretation. Pollen results are discussed in the context of paleoenvironmental reconstructions at a regional scale. © The Author(s) 2011.

Miraglia J.E.,CONICET
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

In this article we propose an unexplored mechanism to understand the physics underlying the electron emission and exciton formation occurring during grazing impact of neutral hydrogen atoms on LiF(100) surfaces. Instead of adopting the traditional point of view considering the negative ion formation as the precursor of the processes, we investigate the formation of excited hydrogen H(n=2) as a catalyzer to produce excitons and electrons. We base our proposal on ab initio calculations that compare quite well with experiments for impact energies larger than 4 keV. © 2014 American Physical Society.

In recent years, several publications in computer science journals have proposed new heuristic methods for parsimony analysis. This contribution discusses those papers, including methods highly praised by their authors, such as Hydra, Sampars and GA + PR + LS. Trees of comparable or better scores can be obtained using the program TNT, but from one to three orders of magnitude faster. In some cases, the search methods are very similar to others long in use in phylogenetics, but the enormous speed differences seem to correspond more to poor implementations than to actual differences in the methods themselves. © The Willi Hennig Society 2014.

Grinberg H.,University of Buenos Aires | Grinberg H.,CONICET
Annals of Physics | Year: 2011

An intensity dependent nonlinear coupling model of N two-level atoms (generalized Dicke model) interacting dispersively with a bimodal cavity field via two-photon transitions is investigated in a scenario where the rotating wave approximation is assumed. The model becomes homogeneous in the sense that the spin transition frequency is the same for all atoms and the coupling constants emerging from the collective interactions of the atomic system with the cavity field depend only on the particular radiation field mode. This allows us to represent the Dicke Hamiltonian entirely in terms of the total angular momentum J. It is assumed that, initially, the atomic system and the field are in a disentangled state where the field modes are in Glauber coherent states and the atomic system is a superposition of states |JM (Dicke states). The model is numerically tested against simulations of normal squeezing variance of the field, squeezing factors based on the Heisenberg uncertainty principle, along with the statistical properties of the light leading to the possible production of nonclassical effects, such as degree of second-order coherence in the modes, degree of intermode correlation, as well as violation of the Cauchy-Schwartz inequality. Analytical expression of the total density operator matrix elements at t>0 shows the present nonlinear model to be strongly entangled, which is reflected in the time evolution of the linear entropy, where the superposition states are reduced to statistical mixtures. Thus, the present generalized Dicke model does not preserve the modulus of the Bloch vector. The computations, performed in the weak coupling and strong field limits, were conducted via second-order Dyson perturbative expansion of the time evolution operator matrix elements for the totality of the angular momentum states of the atomic system. © 2011 Elsevier Inc.

The genus Agrotis Ochsenheimer, 1816 (Lepidoptera, Noctuidae) contains about 300 described species distributed worldwide, excepting the Poles. For South America 93 species have been described. Different diagnostic characters have been proposed for species from the northern Hemisphere, mostly from male genitalia. Recently, numerous South American species of the genus have been transferred to other genera. In this work, a systematic revision was undertaken of the South American species of Agrotis, restricting to 20 the number of species of this genus for the region and transferring the other species to different genera and/or synonymizing with other species. Based on a detailed study of the external morphology and genitalia of both sexes, several nomenclatural changes are pro-posed. New generic synonymy: Mesembreuxoa Hampson = Feltia Walker. New Agrotis synonymies include: Scotia for-steri Köhler = A. propriens (Dyar); Agrotis peruviana hampsoni Draudt, Rhizagrotis triclava Draudt, and Euxoa andina Köhler = A. peruviana (Hampson); Lycophotia achromatica Hampson, Feltia malefida patagiata Aurivillius, Prout and Meyrick, Agrotis psammophila Köhler, and Scotia (Feltia) canietensis Köhler = A. malefida Guenée; Chorizagrotis ben-efida Draudt = A. experta (Walker); Agrotis livens Köhler and Agrotis capayana Köhler = A. araucaria (Hampson). Spe-cies transferred to Feltia Walker tent. include: Scotia aspersula Köhler, n. comb.; Porosagrotis brachystria Hampson, n. comb.; Agrotis carrascoi Köhler, n. comb.; Mesembreuxoa chilensis Hampson, n. comb.; Euxoa clavisigna Dognin, n. comb.; Euxoa conifrons Draudt, n. comb.; Agrotis consternans Hayes, n. comb.; Euxoa coquimbensis Hampson, n. comb.; Mesembreuxoa fasicola Dyar, n. comb.; Chorizagrotis forasmicans Köhler, n. comb.; Agrotis giselae León, n. comb.; Agrotis gypaetina Guenée, n. comb.; Agrotis hispidula Guenée, n. comb.; Euxoa incarum Cockerell, n. comb.; Agrotis in-dia Köhler, n. comb.; Scotia mansa Köhler, n. comb.; Scotia picata Köhler, n. comb.; Agrotis rondanelli León, n. comb.; Euxoa senta Draudt, n. comb.; and Agrotis submontana Köhler, n. comb. New Feltia tent. synonymies include: Agrotis daguerrei Köhler, Porosagrotis atricentrica Hampson, and Agrotis llanoi Köhler = F. brachystria; Lycophotia baeckstro-emi Aurivillius = F. deprivata (Walker); Agrotis raveni Köhler = F. fasicola; Agrotis gentilii Köhler = F. forasmicans; Sco-tia nyei Köhler, Euxoa australis Köhler, and Scotia liniclinans Köhler = F. hispidula; Euxoa bosqui Köhler and Euxoa griseosparsa Köhler = F. lutescens (Blanchard); Euxoa praeocupata Köhler, Agrotis andinicola Köhler, and Scotia son-goensis Köhler = F. subandina (Köhler); Agrotis maldonadoi Köhler = F. submontana. New combinations of Agrotis spe-cies: Anicla albiorbis (Dyar), n. comb.; Noctubourgognea chimaera (Köhler), n. comb.; Noctubourgognea dissociata (Staudinger), n. comb.; Pseudoleucania nigrocollaris (Köhler), n. comb.; and P. wittmeri (Köhler), n. comb. One lectotype and one paralectotype are designated for A. edmondsi Butler. The 20 species of South American Agrotis are redescribed using characters of color pattern, external morphology of head and thorax, and internal morphology of male (including vesica) and female genitalia. This is the first time complete eversions and description of male genitalia (aedeagus and ves-ica) and female genitalia are done for almost all the South American species. Images of all described characters and di-chotomous keys to identify South American species of Agrotis are included. © 2014 Magnolia Press.

Ecological Entomology | Year: 2015

1. The introduction of livestock in natural areas is a common disturbance that affects both plant and pollinator diversity and might affect their interaction. Understanding whether livestock affect a food resource for pollinators (i.e. flower abundance) and/or a pollinator assemblage (i.e. abundance and richness) has important implications for plant-pollinator interactions and still needs deeper investigation. 2. This study investigated how pollinator communities and flower abundance determined floral visitation frequency along a grazing gradient, using seven large paddocks in Patagonian Monte Desert that varied in livestock densities. Pollinator visitation frequency was measured in five of the most abundant native plant species of the region, present in all the paddocks, but that differed in reproductive strategy ranging from insect-pollinated self-compatible and self-incompatible to wind-pollinated. The influence of livestock density, insect, and flower abundance on visitation frequency was evaluated using D-separation hierarchical path models. 3. Intermediate stocking densities showed the highest insect richness and abundance. Livestock density showed a negative quadratic relationship with insect richness; hymenopterans being the main insect group in the region. Flower density decreased with the increase in livestock density. The five plant species shared several pollinator species although each one supported a distinct assemblage. 4. The path model showed that livestock was not directly associated with pollinator visitation frequency; however, this apparent lack of association was as a result of opposite forces acting together. An increase in livestock density reduced visitation frequency through a decrease in insect abundance, yet, livestock simultaneously increased the pollinator visitation rate through decreased flower abundance. 5. This study describes how changes in the density of exotic mammals can affect pollinator and flower abundance, resulting in contrasting effects on flower visitation rates with, apparently, neutral net consequences. This illustrates the complexity of responses to plant-pollinator interactions to anthropogenic disturbances that alter the ecological context. © 2015 The Royal Entomological Society.

Budzinski M.L.,CONICET
Cell Death and Differentiation | Year: 2016

FK506-binding protein 51 (FKBP51) regulates the activity of the glucocorticoid receptor (GR), and is therefore a key mediator of the biological actions of glucocorticoids. However, the understanding of the molecular mechanisms that govern its activity remains limited. Here, we uncover a novel regulatory switch for GR activity by the post-translational modification of FKBP51 with small ubiquitin-like modifier (SUMO). The major SUMO-attachment site, lysine 422, is required for FKBP51-mediated inhibition of GR activity in hippocampal neuronal cells. Importantly, impairment of SUMO conjugation to FKBP51 impacts on GR-dependent neuronal signaling and differentiation. We demonstrate that SUMO conjugation to FKBP51 is enhanced by the E3 ligase PIAS4 and by environmental stresses such as heat shock, which impact on GR-dependent transcription. SUMO conjugation to FKBP51 regulates GR hormone-binding affinity and nuclear translocation by promoting FKBP51 interaction within the GR complex. SUMOylation-deficient FKBP51 fails to interact with Hsp90 and GR thus facilitating the recruitment of the closely related protein, FKBP52, which enhances GR transcriptional activity. Moreover, we show that the modification of FKBP51 with SUMO modulates its binding to Hsp90. Our data establish SUMO conjugation as a novel regulatory mechanism in the Hsp90 cochaperone activity of FKBP51 with a functional impact on GR signaling in a neuronal context.Cell Death and Differentiation advance online publication, 13 May 2016; doi:10.1038/cdd.2016.44. © 2016 Macmillan Publishers Limited

Statistical models for rainfall downscaling based on multiple linear regression techniques have been developed and tested in the Andean Region of west Argentina, an extended mountainous region where three different rain regimes predominate and rainfall has great spatial and temporal variability. The verification procedure was focused on the model's ability to reproduce observed rainfall trends in recent decades. In the northwest of Argentina, domain of the tropical summer rain regime, the monthly rainfall variance accounted for by downscaling models was 77% on average and models reproduced satisfactorily the negative linear trend observed in the last two decades of the past century. In the arid central-west Argentina, a region of rapid transition between two different rain regimes, model performance was rather poor (an average of 50% of explained variance), even so models were able to capture outstanding differences in the linear trend between the northern and southern sectors of the region. In the southwest of Argentina, domain of the mid-latitude winter rain regime, the monthly variance accounted for by downscaling models was 71% on average and models were capable to reproduce a singular change in the onset of the rainy season that occurred during the 1990s. The results achieved demonstrate that it is feasible to establish significant and useful statistical relationships between atmospheric variables and rainfall at monthly and river basin scales, even for a topographically complex region like western Argentina. © 2009 Springer-Verlag.

Fernandez F.M.,CONICET
European Journal of Physics | Year: 2011

We propose a simple and straightforward method based on Wronskians for the calculation of bound-state energies and wavefunctions of one-dimensional quantum-mechanical problems. We explicitly discuss the asymptotic behaviour of the wavefunction and show that the allowed energies make the divergent part vanish. As illustrative examples we consider an exactly solvable model, the Gaussian potential well, and a two-well potential proposed earlier for the interpretation of the infrared spectrum of ammonia. © 2011 IOP Publishing Ltd.

Rivas A.M.F.,Comision Nacional de la Energia Atomica | Rivas A.M.F.,CONICET
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

In this work, we derived a semiclassical approximation for the matrix elements of a quantum propagator in coherent states (CS) basis that avoids complex trajectories; it only involves real ones. For that purpose, we used the symplectically invariant semiclassical Weyl propagator obtained by performing a stationary phase approximation (SPA) for the path integral in the Weyl representation. After that, for the transformation to CS representation SPA is avoided; instead a quadratic expansion of the complex exponent is used. This procedure also allows us to express the semiclassical CS propagator uniquely in terms of the classical evolution of the initial point without the need of any root search typical of van Vleck-Gutzwiller-based propagators. For the case of chaotic Hamiltonian systems, the explicit time dependence of the CS propagator has been obtained. The comparison with a realistic chaotic system that derives from a quadratic Hamiltonian, the cat map, reveals that the expression here derived is exact up to quadratic Hamiltonian systems. © 2013 American Physical Society.

This paper presents the infrared (IR) emission spectrum of hosts and habitats of Triatoma infestans in the chaco region of NW Argentina, representing the first attempt to correlate the natural infrared stimulus with the known behaviour of these blood-sucking insect, vectors of Trypanosoma cruzi - causative agent of Chagas disease. The study was carried out in two rural villages of La Rioja Province (Argentina). A FLYR i40 camera was used to obtain IR pictures which were analyzed to determine the thermal range for humans, domestic animals, building materials, and general background emissions. From sunset to the first hours of night, the thermal contrast between hosts and their landscape rises, increasing the likelihood that hosts could be differentiated by the vector. However, some building materials, can retain high temperatures during the night, which might add attractiveness to the presence of hosts. The results suggest that the most attractive habitats for dispersing bugs would be those at short distance, with high CO2 emission and strong IR radiation indicative of host presence. Goats corrals may be the most attractive habitat to disperse, within the domestic habitat. Dispersal would be favoured in periods of low atmospheric water saturation when IR perception is highest. In the IR band, the potential host and habitat discrimination available for the insects fits well with their known sensory capacities and observed dispersive behavior. Research in this area could be of considerable interest in relation to vector surveillance, epidemiology of Chagas disease transmission, and to develop new methods to minimise triatomine colonisation of new habitats. © 2011 Elsevier B.V.

Green S.R.,University of Guelph | Carrasco F.,CONICET | Lehner L.,Perimeter Institute for Theoretical Physics
Physical Review X | Year: 2014

We study the dynamics of a 2 + 1-dimensional relativistic viscous conformal fluid in Minkowski spacetime. Such fluid solutions arise as duals, under the ''gravity/fluid correspondence,'' to 3 + 1-dimensional asymptotically anti-de Sitter (AAdS) black-brane solutions to the Einstein equation. We examine stability properties of shear flows, which correspond to hydrodynamic quasinormal modes of the black brane. We find that, for sufficiently high Reynolds number, the solution undergoes an inverse turbulent cascade to long-wavelength modes. We then map this fluid solution, via the gravity/fluid duality, into a bulk metric. This suggests a new and interesting feature of the behavior of perturbed AAdS black holes and black branes, which is not readily captured by a standard quasinormal mode analysis. Namely, for sufficiently large perturbed black objects (with long-lived quasinormal modes), nonlinear effects transfer energy from short- to long-wavelength modes via a turbulent cascade within the metric perturbation. As long-wavelength modes have slower decay, this transfer of energy lengthens the overall lifetime of the perturbation. We also discuss various implications of this behavior, including expectations for higher dimensions and the possibility of predicting turbulence in more general gravitational scenarios.

Neohelice granulata (previously known as Chasmagnathus granulata and C. granulatus) is a burrowing semiterrestrial crab found in the intertidal zone of estuaries, salt marshes and mangroves of the South-western Atlantic Ocean. Beginning in the late 1989s, an explosion of publications appeared in international journals dealing with its ecology, physiology, toxicology and behavior. A bibliometric analysis using the Scopus database allowed detecting 309 papers that deal with this species during the period 1986-2009. The number of papers per year increased continuously, reaching a mean annual value of 22.6 during the last 5 years; a great majority of them were authored by researchers from Argentina and Brazil. Neohelice granulata has become now one of the most studied crab species, after Carcinus maenas, Callinectes sapidus, Scylla serrata and Cancer pagurus and C. magister, and it can be considered as an emergent animal model for biochemical, physiological and ecological research. © 2010 Springer-Verlag and AWI.

Gaggino R.,CONICET
Construction and Building Materials | Year: 2012

The objective of this work was to contribute to decontaminating the environment, and to solving the housing shortage in our country. The technological products developed in this research are sustainable from the ecological, technical and economic points of view. The developed products were panels for housing and equipment. They were manufactured by recycling plastic materials from food, perfumery or cleaning packaging, waste production from factories due to failures in sheet thickness or ink application. It thus contributes to decontaminating the environment, since most of this waste is buried in municipal land without any use, or accumulated and burned in landfills, causing environmental degradation. © 2012 Elsevier Ltd. All rights reserved.

Purlis E.,CONICET | Purlis E.,National University of La Plata
Journal of Food Engineering | Year: 2010

This paper presents a review regarding several aspects of the development of browning during baking of bakery products, mainly from an engineering point of view. During baking, the formation of colour is due to the Maillard reaction, and caramelization of sugars. Besides the major influence of this phenomenon on the initial acceptance of products by consumers, it is the responsible for other relevant changes occurring in food during baking, i.e. production of flavour and aroma compounds, formation of toxic products (e.g. acrylamide), and decrease of nutritional value of proteins. As well as baking, the development of browning in bakery products is a simultaneous heat and mass transfer process that occurs mostly in a non-ideal system under non-ideal conditions. In addition, the mechanisms of chemical reactions involved are still not elucidated completely, so the process is difficult to control and represents a major challenge for food engineers. Effects of browning on properties of products and experimental, modelling and technological aspects of colour formation during baking are reviewed. © 2010 Elsevier Ltd. All rights reserved.

Cockle K.L.,University of British Columbia | Cockle K.L.,Maimonides University | Cockle K.L.,CONICET | Martin K.,University of British Columbia | And 2 more authors.
Frontiers in Ecology and the Environment | Year: 2011

In forests worldwide, tree-cavity supply can limit populations of the 10-40% of bird and mammal species that require cavities for nesting or roosting. Conservation efforts aimed at cavity-using communities have often focused on woodpeckers because, as cavity excavators, they are presumed to control cavity supply. We show that avian excavators are the primary cavity producers in North America (77% of nesting cavities), but not elsewhere (26% in Eurasia and South America; 0% in Australasia). We studied survivorship of 2805 nest cavities and found similar persistence of cavities created by woodpeckers and those created by decay in Canada, but low persistence of woodpecker-excavated cavities in Poland and Argentina. Outside of North America, the ephemeral nature of many woodpecker cavities may render most cavity-using vertebrates critically dependent on the slow formation of cavities by damage and decay. The future of most cavity-using communities will therefore be highly dependent on changing forest policies to stem the current loss of old trees. © The Ecological Society of America.

Megevand A.,CONICET
Journal of Cosmology and Astroparticle Physics | Year: 2013

In cosmological first-order phase transitions, the microscopic interaction of the phase transition fronts with non-equilibrium plasma particles manifests itself macroscopically as friction forces. In general, it is a nontrivial problem to compute these forces, and only two limits have been studied, namely, that of very slow walls and, more recently, ultra-relativistic walls which run away. In this paper we consider ultra-relativistic velocities and show that stationary solutions still exist when the parameters allow the existence of runaway walls. Hence, we discuss the necessary and sufficient conditions for the fronts to actually run away. We also propose a phenomenological model for the friction, which interpolates between the non-relativistic and ultra-relativistic values. Thus, the friction depends on two friction coefficients which can be calculated for specific models. We then study the velocity of phase transition fronts as a function of the friction parameters, the thermodynamic parameters, and the amount of supercooling. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

Zeyher R.,Max Planck Institute for Solid State Research | Greco A.,CONICET
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We present results for magnetic excitations in doped copper oxides using the random phase approximation and itinerant electrons. In the [1,0] direction the observed excitations resemble dispersive quasiparticles both in the normal and in the superconducting state, similarly to recent resonant inelastic x-ray scattering experiments. In the [1,1] direction the excitations form, except for the critical region near the antiferromagnetic wave vector Q=(π,π), only very broad continua. Using the obtained spin propagators we calculate electron self-energies and their effects on electronic Raman spectra. We show that the recently observed additional peak at about twice the pair breaking in B 1g symmetry below Tc in HgBa2CuO 4+δ can be explained as a self-energy effect where a broken Cooper pair and a magnetic excitation appear as final states. The absence of this peak in B2g symmetry, which probes mainly electrons near the nodal direction, is explained by their small self-energies compared to those in the antinodal direction. © 2013 American Physical Society.

Bejas M.,Abdus Salam International Center For Theoretical Physics | Greco A.,CONICET | Yamase H.,Japan National Institute of Materials Science | Yamase H.,Max Planck Institute for Solid State Research
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Motivated by the growing evidence of the importance of charge fluctuations in the pseudogap phase in high-temperature cuprate superconductors, we apply a large-N expansion formulated in a path integral representation of the two-dimensional t-J model on a square lattice. We study all possible charge instabilities of the paramagnetic state in leading order of the 1/N expansion. While the d-wave charge density wave (flux phase) becomes the leading instability for various choices of model parameters, we find that a d-wave Pomeranchuk (electronic nematic phase) instability occurs as a next leading one. In particular, the nematic state has a strong tendency to become inhomogeneous. In the presence of a large second nearest-neighbor hopping integral, the flux phase is suppressed and the electronic nematic instability becomes leading in a high doping region. Besides these two major instabilities, bond-order phases occur as weaker instabilities close to half-filling. Phase separation is also detected in a finite temperature region near half-filling. © 2012 American Physical Society.

Vieytes M.C.,CONICET | Fontenla J.M.,North West Research Associates
Astrophysical Journal | Year: 2013

Neutral nickel (Ni I) is abundant in the solar atmosphere and is one of the important elements that contribute to the emission and absorption of radiation in the spectral range between 1900 and 3900 Å. Previously, the Solar Radiation Physical Modeling (SRPM) models of the solar atmosphere only considered a few levels of this species. Here, we improve the Ni I atomic model by taking into account 61 levels and 490 spectral lines. We compute the populations of these levels in full NLTE using the SRPM code and compare the resulting emerging spectrum with observations. The present atomic model significantly improves the calculation of the solar spectral irradiance at near-UV wavelengths, which is important for Earth atmospheric studies, and particularly for ozone chemistry. © 2013. The American Astronomical Society. All rights reserved.

Madrid J.P.,Swinburne University of Technology | Donzelli C.J.,Institute Investigaciones en Astronomia Teorica y Experimental IATE | Donzelli C.J.,CONICET
Astrophysical Journal | Year: 2013

A spectroscopic follow-up of ultracompact dwarf (UCD) candidates in the fossil group NGC 1132 is undertaken with the Gemini Multi Object Spectrograph. These new Gemini spectra prove the presence of six UCDs in the fossil group NGC 1132 at a distance of D ∼ 100 Mpc and a recessional velocity of vr = 6935 ± 11 km s-1. The brightest and largest member of the UCD population is an M32 analog with a size of 77.1 pc and a magnitude of MV = -14.8 mag with the characteristics in between those of the brightest UCDs and compact elliptical galaxies. The ensemble of UCDs have an average radial velocity of 〈vr 〉 = 6966 ± 208 km s-1 and a velocity dispersion of σ v = 169 ± 18 km s-1 similar to the one of poor galaxy groups. This work shows that UCDs can be used as test particles to determine the dynamical properties of galaxy groups. The presence of UCDs in the fossil group environment is confirmed and thus the fact that UCDs can form across diverse evolutionary conditions. © 2013. The American Astronomical Society. All rights reserved..

Cafaro D.C.,CONICET | Grossmann I.E.,Carnegie Mellon University
Computers and Chemical Engineering | Year: 2014

This short note presents an alternate approximation of concave cost functions used to reflect economies of scale in process design and supply chain optimization problems. To approximate the original concave function, we propose a logarithmic function that is exact and has bounded gradients at zero values in contrast to other approximation schemes. We illustrate the application and advantages of the proposed approximation. © 2013 Elsevier Ltd.

Segovia-Gutierrez J.P.,University of Granada | Berli C.L.A.,CONICET | De Vicente J.,University of Granada
Journal of Rheology | Year: 2012

The yielding behavior of conventional magnetorheological (MR) fluids is revisited for a wide range of magnetic fields and particle concentrations under a colloidal gel perspective. A two-step yielding behavior is found at intermediate magnetic fields (∼10 kA/m) that can be explained as a transition from a strong-link to a weak-link (or transition) regime upon increasing the particle concentration in the MR fluid. This two-step yielding behavior is reminiscent of the classical concepts of static (frictional) and dynamic (Bingham) yield stress. By relating macroscopic elastic properties to a scaling fractal model, we could identify the prevalent gelation regime in MR fluids. © 2012 The Society of Rheology.

Montemurro M.A.,University of Manchester | Zanette D.H.,CONICET
PLoS ONE | Year: 2011

Background: The language faculty is probably the most distinctive feature of our species, and endows us with a unique ability to exchange highly structured information. In written language, information is encoded by the concatenation of basic symbols under grammatical and semantic constraints. As is also the case in other natural information carriers, the resulting symbolic sequences show a delicate balance between order and disorder. That balance is determined by the interplay between the diversity of symbols and by their specific ordering in the sequences. Here we used entropy to quantify the contribution of different organizational levels to the overall statistical structure of language. Methodology/Principal Findings: We computed a relative entropy measure to quantify the degree of ordering in word sequences from languages belonging to several linguistic families. While a direct estimation of the overall entropy of language yielded values that varied for the different families considered, the relative entropy quantifying word ordering presented an almost constant value for all those families. Conclusions/Significance: Our results indicate that despite the differences in the structure and vocabulary of the languages analyzed, the impact of word ordering in the structure of language is a statistical linguistic universal. © 2011 Montemurro, Zanette.

Massaferro J.,CONICET | Larocque-Tobler I.,LimnoPaleoServ
Ecological Indicators | Year: 2013

In the Southern Hemisphere, the lack of quantitative temperature records hampers the understanding of climate change since the Last Glaciation and refrains the comparison with the Northern Hemisphere records. To provide quantitative data, a 63-lake chironomid transfer functions was developed in Patagonia. Mean annual air temperature (MAT) was one of the most important factors explaining the distribution of chironomids while precipitation did not have any significant relationship with chironomid assemblages. The MAT model had a r2 of 0.64, a RMSE of 0.83 and a maximum bias of 1.81 °C, comparable to other transfer functions of this size. This model was applied to the Lake Potrok Aike (PTA) chironomid records which consisted of only four taxa (Phaenopsectra, Cricotopus, Smittia and Polypedilum). The chironomid-inferred air temperatures were colder-than-the-average (10.8°C) during the Lateglacial with the coldest temperatures (9°C in average) during the Antarctic Cold Reversal (ACR). Between ca. 8000 and 3500 cal. years BP, the chironomid-inferred air temperatures were warmer-than-the-average with a decreasing trend. From ca. 3500 cal. years BP to the present, the chironomid-inferred temperatures oscillated around the average. The difference between the chironomid-inferred air temperature in the surface sample and the climate normal (1961-1990) was 0.6°C, suggesting that chironomids are sensitive enough to quantitatively reconstruct MAT at PTA. The general pattern of temperature changes reconstructed by the PTA chironomid record corresponded well to other quantitative records in the Southern Hemisphere. The results presented here show that investing in the development of chironomid transfer functions for quantitative climate research in the Southern Hemisphere is valuable. © 2012 Elsevier Ltd. All rights reserved.

In this paper, results of archaeological studies conducted in the central San Jorge gulf sector (north coast of Santa Cruz Province, Patagonia, Argentina) are presented. A distributional approach was employed, and a systematic surface sampling in several landscape units were performed, registering all lithic artifacts and other variables that could influence the archaeological visibility. The landscape units identified in this sector were: high plateau, plateau flank, cañadón León, temporary lagoons, and coast. The artifactual assemblage recovered is presented, analyzed and discussed in relation to several archaeological expectations derived from the resource availability of the different landscape units. Results are discussed in relation to ways in which these landscape units could have been used by hunter-gatherer populations that inhabited this sector during Late Holocene, considering the differential availability of resources of importance to Patagonian human groups. In this sense, the archaeological expectations were contrasted, with higher densities near the coast and lower densities on inland landscape units. Among the first, the availability of alimentary resources (mainly shellfish, fish and pinniped) would have produced longer residential settlement. Among inland landscape units, some differences were observed, which were related to variation in resources availability, such as fresh water sources and lithic raw materials. In this latter, more variability than anticipated according to the archaeological expectations was detected. © 2014 Elsevier Ltd and INQUA.

Gasaneo G.,CONICET | Ancarani L.U.,University of Lorraine
Journal of Physics A: Mathematical and Theoretical | Year: 2012

A methodology based on generalized Sturmian functions is put forward to solve two- and three-body scattering problems. It uses a spectral method which allows for the inclusion of the correct asymptotic behavior when solving the associated driven Schrödinger equation. For the two-body case, we demonstrate the equivalence between the exterior complex scaling (ECS) and the Sturmian approaches and illustrate the latter by using Hulthén Sturmian functions. Contrary to the ECS approach, no artificial cut-off of the potential is required in the Surmian approach. For the three-body scattering problem, the theoretical framework is presented in hyperspherical coordinates and a set of hyperspherical generalized Sturmian functions possessing outgoing asymptotic behavior is introduced. The Sturmian procedure is a direct generalization of the method discussed for the two-body problem; thus, the comparison with the ECS method is similar. For both the two- and three-body cases, Sturmian bases are efficient as they possess the correct outgoing behavior, diagonalize part of the potentials involved and are essentially localized in the region where the unsolved interaction is not negligible. Moreover, with the Sturmian basis, the operator (H E) is represented by a diagonal matrix whose elements are simply the Sturmian eigenvalues. © 2012 IOP Publishing Ltd.

Leonardi M.S.,CONICET
Parasitology Research | Year: 2014

Among Anoplura, the family Echinophthiriidae includes those species that infest mainly the pinnipeds. Working with large hosts implies methodological considerations as the time spent in the sampling, and the way in that the animal is restrained. Previous works on echinophthiriids combined a diverse array of analyses including field counts of lice and in vitro observations. To collect lice, the authors used forceps, and each louse was collected individually. This implied a long manipulation time, i.e., ≈60 min and the need to physically and/or chemically immobilize the animal. The present work described and discussed for the first a sample technique that minimized the manipulation time and also avoiding the use of anesthesia. This methodology implied combing the host's pelage with a fine-tooth plastic comb, as used in the treatment of human pediculosis, and keeping the comb with the lice retained in a Ziploc® bag with ethanol. This technique was used successfully in studies of population dynamic, habitat selection, and transmission pattern, being a reliable methodology. Lice are collected entirely and are in a good condition to prepare them for mounting for studying under light or scanning electron microscopy. Moreover, the use of the plastic comb protects from damaging taxonomically important structures as spines being also recommended to reach taxonomic or morphological goals. © 2014 Springer-Verlag.

Acosta Hospitaleche C.,CONICET
Polish Polar Research | Year: 2013

Antarctic skulls attributable to fossil penguins are rare. Three new penguin crania from Antarctica are here described providing an insight into their feeding function. One of the specimens studied is largely a natural endocast, slightly damaged, and lacking preserved osteological details. Two other specimens are the best preserved fossil penguin crania from Antarctica, enabling the study of characters not observed so far. All of them come from the uppermost Submeseta Allomember of the La Meseta Formation (Eocene-?Oligocene), Seymour (Marambio) Island, Antarctic Peninsula. The results of the comparative studies suggest that Paleogene penguins were long-skulled birds, with strong nuchal crests and deep temporal fossae. The configuration of the nuchal crests, the temporal fossae, and the parasphenoidal processes, appears to indicate the presence of powerful muscles. The nasal gland sulcus devoid of a supraorbital edge is typical of piscivorous species.

Ibanez A.,University of Buenos Aires | Ibanez A.,Diego Portales University | Manes F.,University of Buenos Aires | Manes F.,CONICET
Neurology | Year: 2012

The significance of social situations is commonly context-embedded. Although the role of context has been extensively studied in basic sensory processing or simple stimulus-response settings, its relevance for social cognition is unknown. We propose the social context network model (SCNM), a fronto-insular-temporal network responsible for processing social contextual effects. The SCNM may 1) update the context and use it to make predictions, 2) coordinate internal and external milieus, and 3) consolidate context-target associative learning. We suggest the behavioral variant of frontotemporal dementia (bvFTD) as a specific disorder in which the reported deficits in social cognition (e.g., facial recognition, empathy, decisionmaking, figurative language, theory of mind) can be described as context impairments due to deficits in the SCNM. Disruption of orbitofrontal-amygdala circuit, as well as the frontal, temporal, and insular atrophy in bVFTD, suggests a relationship between context-sensitive social cognition and SCNM. In considering context as an intrinsic part of social cognition, we highlight the need for a situated cognition approach in social cognition research as opposed to an abstract, universal, and decontextualized approach. The assessment of context-dependent social cognition paradigms, the SCNM, and their possible application to neuropsychiatric disorders may provide new insight into bvFTD and other related frontal disorders. Copyright © 2012 by AAN Enterprises, Inc.

This paper aims to identify technological decisions involved in the production of retouched lithic artifacts recovered from three Late Holocene archaeological sites located in the northeast of the Isla Grande of Tierra del Fuego (Argentina). More specifically, the main goal is to assess whether there is any relationship among raw material selection, retouching intensity, and the morphology of retouched artifacts. Through the analysis of several correlations between the knapping quality of the different raw materials employed and the index of invasiveness and curvature, it is inferred that raw materials were selected according to their homogeneous texture and convex shape in order to produce long retouched edges. As most of the retouched artifacts have been produced on unifacial blanks, using unipolar debitage techniques which does not require specific knapping skills, it is proposed that similarities found in the three archaeological sites can be explained as a result of oral transmission of basic technological knowledge. © 2014 Elsevier Ltd and INQUA.

Borrero L.A.,CONICET
Quaternary International | Year: 2015

The conditions under which the process of human colonization of South America took place are discussed. The modes of acquisition of environmental knowledge, as a way to construct a cultural geography, are also considered. An example concerning the peopling of the forests, particularly in Northwest South America, and the role of plants in the early stages of colonization is also offered. Finally the significance of non-utilitarian items, exchange, and empty lands for our understanding of the process of peopling is discussed. © 2014 Elsevier Ltd and INQUA.

The last several years have witnessed the accumulation of evidence suggesting that the Kraepelinian binary system of classification of the psychoses does not capture their true nature, as Kraepelin himself had cautioned in his late years. The long-awaited new edition of the APA's Diagnostic and Statistical Manual will in all probability incorporate symptom dimensions and suppress schizophrenia subtypes. However, the initial Kraepelinian conceptualization of the psychoses is maintained, along with the diagnostic category that epitomizes its obsolescence: schizoaffective disorder. We hereby make a brief critical appraisal of this fact, pointing out how the current classification system might be an obstacle to much-needed advances in this knowledge field.

Fernandez F.M.,CONICET
Central European Journal of Physics | Year: 2013

We obtain accurate eigenvalues for two recently derived SUSY partner Hamiltonians. We improve the Rayleigh-Ritz variational method proposed by the authors and show how to apply the Riccati-Padé method to those particular partner potentials. © 2013 Versita Warsaw and Springer-Verlag Wien.

Giribet G.,CONICET
Journal of High Energy Physics | Year: 2011

We present an exact asymptotically Lifshitz black hole solution in Brans-Dicke theory of gravity in arbitrary n(≥ 3) dimensions in presence of a power-law potential. In this solution, the dynamical exponent z is determined in terms of the Brans-Dicke parameter ! and n. Asymptotic Lifshitz condition at infinity requires z > 1, which corresponds to ?(n ? 1)/(n ? 2) ≥ w ?n/(n ? 1). On the other hand, the no-ghost condition for the scalar field in the Einstein frame requires 0 < z ≤ 2(n ? 2)/(n ? 3). We compute the Hawking temperature of the black hole solution and discuss the problems encountered and the proposals in defining its thermodynamic properties. A generalized solution charged under the Maxwell field is also presented. © 2011 SISSA.

Caenolestids are a group of poorly known South American marsupials with a restricted distribution in páramo and subpáramo environments of the Andes from Colombia and western Venezuela to Bolivia (represented by the genera Caenolestes and Lestoros), and in Valdivian rain forest in southern Chile and Argentina where a single species (Rhyncholestes raphanurus) lives. The Incan shrew opossum, Lestoros inca, lives in mountains of southern Peru and extreme northwestern Bolivia. Despite being common in trapping surveys, little is known of its cranial and dental intraspecific variability, tooth eruption pattern, and dental anomalies. The objective of this work was to analyze the intraspecific variability of L. inca, which includes an anatomical description of the skull and dentition and analysis of clinal variation, tooth eruption patterns, and dental anomalies. The eruption pattern found in L. inca confirms the sequence P3 → m4 → p3 → M4 as the general pattern for living paucituberculatans. Missing teeth between the procumbent incisor and the 2nd lower premolar are the most common anomaly found (n = 14, 20% of the analyzed specimens). Comparisons with other living caenolestids, lack of clinal variation and significant differences between populations support L. inca as a separate, clearly distinct species. The information presented herein can be used in anatomical and paleontological studies dealing with caenolestids in particular and marsupials in general and also provides a sound basis for anatomical inferences made from fossils. © 2013 American Society of Mammalogists.

Many intracellular bacterial pathogens use type IV secretion systems to deliver effector molecules and subvert the eukaryotic host cell defenses. The genus Brucella comprises facultative intracellular bacteria that cause brucellosis, a disease affecting a wide range of mammals including humans. The virB operon codes for a type IV secretion system that plays a central role in intracellular survival and replication of Brucella within the host. Expression of the virB genes is under the control of various transcription factors that allow this system to respond to different types of environmental signals, and display binding site structures and arrangements that define the intrinsic complexity of the virB promoter. This review focuses on summarizing the current state of research concerning regulation of the Brucella virB operon, with special emphasis on describing the nature and function of the implicated regulatory elements and examining the involved protein-DNA interactions. © 2013 Future Medicine Ltd.

Neuquensaurus, from the Late Cretaceous of Argentina and one of the first dinosaurs described from Patagonia, is one of the most derived sauropod dinosaurs, and its proportions and size place it among the smallest sauropods ever known. In this context, Neuquensaurus is central to understanding late stages of sauropod evolution. This contribution offers a full description of the appendicular skeleton of Neuquensaurus. The anatomical analysis reveals that the appendicular skeleton of Neuquensaurus exhibits unique characteristics only shared with closely related saltasaurine titanosaurs; for example, the laterally directed preacetabular lobe of the ilium, the prominent fibular lateral tuberosity, and the presence of an intermuscular line on the femoral shaft, which is proposed here as a synapomorphy of Saltasaurinae. Neuquensaurus also displays many reversals to primitive character states, such as the presence of a prominent olecranon process of the ulna, a trochanteric shelf, a lesser trochanter and an ischial tuberosity. Additional characters that allow its evaluation in a phylogenetic context are here provided. Among them are the extremely deflected femoral shaft, the elliptical femoral cross-section, and the anterolaterally oriented cnemial crest.

Saurral R.I.,CONICET
Journal of Hydrometeorology | Year: 2010

General circulation models (GCMs) forced under different greenhouse gases emission and socioeconomic scenarios are currently the most extended tool throughout the scientific community that is used to infer the future climate on Earth. However, these models still have problems in capturing several aspects of regional climate variability in many parts of the globe. In this paper, the hydrological cycle of the La Plata Basin is simulated using the variable infiltration capacity (VIC) distributed hydrology model and forced with atmospheric data from different GCMs to determine to what extent errors in temperature and precipitation fields impact the hydrology of the basin. The skill assessment is performed in terms of simulated runoff at different closing points. Simulated hydrographs show that all of the GCMs present deficiencies in simulating the regional climatology of southern South America, and this leads to a very poor representation of the hydrological cycle of the main rivers across the basin. Two unbiasing schemes are then proposed as a means of correcting the GCM outputs before forcing the hydrology model, and comparisons between biased and unbiased simulations are also performed. Results indicate that both schemes, though methodologically different, reduce the water cycle simulation bias. Finally, VIC is forced with bias-corrected data from the GCMs for future decades (2030 and 2070) under different socioeconomic scenarios [e.g., the Intergovernmental Panel on Climate Change's (IPCC) Special Report on Emissions Scenarios (SRES) scenarios A1B, A2, and B1] to determine the potential changes in streamflow due to climate change for the rest of the present century. © 2010 American Meteorological Society.

Physica A: Statistical Mechanics and its Applications | Year: 2013

The properties of some complex many body systems can be modeled by introducing in the dissipative dynamics of each single component a set of kinetic constraints that depend on the state of the neighbor systems. Here, we characterize this kind of dynamics for two quantum systems whose independent dissipative evolutions are defined by a Lindblad equation. The constraints are introduced through a set of projectors that restrict the action of each single dissipative Lindblad channel to the state of the other system. Conditions that guarantee a classical interpretation of the kinetic constraints are found. The generation and evolution of entanglement is studied for two optical qubits systems. Classically constrained dissipation leads to a stationary state whose degree of entanglement depends on the initial state. Nevertheless, independently of the initial conditions, a maximal entangled state is generated when both systems are subjected to the action of local Hamiltonian fields that do not commutate with the constraints. The underlying physical mechanism is analyzed in detail. © 2013 Elsevier B.V. All rights reserved.

Fernandez-Duque E.,University of Pennsylvania | Fernandez-Duque E.,CONICET
American Journal of Physical Anthropology | Year: 2011

Some monogamous primates are characterized by biparental care, territoriality, and a reduced level of physical dimorphism. In others, the relationship between those behavioral patterns and dimorphism is less clear. I tested Bergmann's and Rensch's rules using Aotus spp. body mass data and I characterized the extent of sexual dimorphism in body mass, dental and physical measurements in a socially monogamous owl monkey population (n = 91 adults) from the Argentinean Gran Chaco. A. azarai azarai from the Argentinean Chaco is larger than the more tropical owl monkey species (r = 0.7, N = 6 species), but there is no apparent increase in sexual dimorphism with increased body mass. The body masses of adult male and female A. a. azarai were remarkably similar (Mean = 1.26 kg); there were no marked sex differences in most skeletal measurements, but males had higher and wider upper and lower canines than did females. Body mass and neck circumference were positively and strongly related (r = 0.533, n = 52), and the body mass of adults was not a reliable indicator of their age (r = 0.03, n = 10). The data illustrate the complexities inherent in examining and summarizing within population variation in skeletal and nonskeletal measurements and contribute to a better understanding of the relationships between monogamous behavioral patterns and sexual dimorphism. Am J Phys Anthropol, 2011. © 2011Wiley-Liss, Inc. Copyright © 2011 Wiley-Liss, Inc.

Palombarini J.,GISIQ UTN | Martinez E.,CONICET
Expert Systems with Applications | Year: 2012

With the current trend towards cognitive manufacturing systems to deal with unforeseen events and disturbances that constantly demand real-time repair decisions, learning/reasoning skills and interactive capabilities are important functionalities for rescheduling a shop-floor on the fly taking into account several objectives and goal states. In this work, the automatic generation and update through learning of rescheduling knowledge using simulated transitions of abstract schedule states is proposed. Deictic representations of schedules based on focal points are used to define a repair policy which generates a goal-directed sequence of repair operators to face unplanned events and operational disturbances. An industrial example where rescheduling is needed due to the arrival of a new/rush order, or whenever raw material delay/shortage or machine breakdown events occur are discussed using the SmartGantt prototype for interactive rescheduling in real-time. SmartGantt demonstrates that due date compliance of orders-in-progress, negotiating delivery conditions of new orders and ensuring distributed production control can be dramatically improved by means of relational reinforcement learning and a deictic representation of rescheduling tasks. © 2012 Elsevier Ltd. All rights reserved.

The Voyage of the Beagle that brought Charles Darwin to South America in AD 1832-1835 and particularly, to the present territory of Argentina, was developed under very unfavorable climatic conditions, much colder, drier and windier than today. These circunstances correspond to the dominant conditions during the last phase of the little ice age, which was a global, cold event that characterized the 17th to the 19th centuries. This phase is known as the Dalton Minimum, in reference to the relative small amount of solar spots, which generated a diminution of the solar radiation and in consequence, the lowering of the global mean temperatures in that period. Darwin was perfectly conscious of those climatic conditions, which were clearly shown in Europe at those times and particularly in the Alps, and therefore he is clearly showing that in his writings. Since Darwin's Voyage to Patagonia, the climatic and environmental conditions have changed substantially, particularly after AD 1850 and finally, after the middle portion of the AD 1970's decade. Some of the most important consequences of global climate change are rising mean annual or seasonal temperature, rising or diminishing precipitations at the regional level, rising global sea level, and an increase in the frequency of extreme meteorological events. The impact of these changes has been observed in the glaciers of Patagonia and Tierra del Fuego, at least since AD 1978 and, particularly, in the last decade of the 20th century. The most noticeable impacts are rapid recession of ice margins, thinning of the ice cover, raising elevation of the regional snow line and reduction of Andean areas under permafrost conditions, as recent scientific research has demonstrated. At the present rate of ice recession, most, if not all of the cirque glaciers in Patagonia and Tierra del Fuego will disappear during the next two decades, and both valley glaciers and the Patagonian ice sheets will be severely reduced as well. As a consequence of glaciers vanishing, environmental, hydrological, geomorphological, heritage and tourism damages are expected to occur in these regions and severely affect those communities active in them.

Perez M.E.,Museo Paleontologico Egidio Feruglio | Perez M.E.,CONICET
Journal of Vertebrate Paleontology | Year: 2010

Cavioidea sensu stricto groups three traditionally recognized families that are characterized by hypsodont, double-heart-shaped cheek teeth and moderate hystricognathy: Eocardiidae, Caviidae, and Hydrochoeridae. Eocardiidae was erected to include a diverse assemblage of extinct and plesiomorphic taxa, whereas Caviidae and Hydrochoeridae (the crown group of Cavioidea) include the lineages with extant representatives (cuyes, maras, and capybaras). A new genus and species of Cavioidea sensu stricto, Guiomys unica, is described here from the middle Miocene of west central Patagonia (Argentina). The new taxon is known from mandibular and maxillary fragments with molars, and isolated cheek teeth. A phylogenetic analysis of Cavioidea sensu stricto shows G. unica as the sister taxon of the clade formed by the crown group of Cavioidea sensu stricto ('medialis series'). The new species displays characters states intermediate between eocardiids and the 'medialis series.' The most outstanding character of Guiomys unica is the autapomorphic position of the notch for the insertion of the masseter medialis pars infraorbitalis muscle, isolated from both the masseteric and horizontal crests. This notch is located at the anterior end of the masseteric crest in eocardiids and represents the plesiomorphic state for Cavioidea sensu stricto. In caviids and hydrochoerids, the notch is located at the anterior end of the horizontal crest, the derived state for this character. G. unica allows reinterpretation of the homologies of the mandibular crests in basal cavioids and clarifies the evolutionary origins of crown-group cavioids (Caviidae + Hydrochoeridae). © 2010 by the Society of Vertebrate Paleontology.

Hernandez E.S.,CONICET
Journal of Low Temperature Physics | Year: 2011

The zero temperature adsorption isotherm of 4He in a rigid cylindrical pore with alkali metal walls is computed within finite-range density functional theory, with the radius of the tube as a parameter. It is shown that starting from narrow pores and increasing the radius, the adsorbed helium first becomes bound in a quasi-onedimensional phase, and finally condenses into a quasi-twodimensional configuration by going through an almost filling situation. The results are in agreement with recent calculations for carbon nanotubes based on thermodynamical approaches. © 2010 Springer Science+Business Media, LLC.

Lopez-Bergami P.,CONICET
Pigment Cell and Melanoma Research | Year: 2011

Recent discoveries have increased our comprehension of the molecular signaling events critical for melanoma development and progression. Many oncogenes driving melanoma have been identified, and most of them exert their oncogenic effects through the activation of the RAF/MEK/ERK mitogen-activated protein kinase (MAPK) pathway. The c-Jun N-terminal kinase (JNK) and p38 MAPK pathways are also important in melanoma, but their precise role is not clear yet. This review summarizes our current knowledge on the role of the three main MAPK pathways, extracellular regulated kinase (ERK), JNK, and p38, and their impact on melanoma biology. Although the results obtained with BRAF inhibitors in melanoma patients are impressive, several mechanisms of acquired resistance have emerged. To overcome this obstacle constitutes the new challenge in melanoma therapy. Given the major role that MAPKs play in melanoma, understanding their functions and the interconnection among them and with other signaling pathways represents a step forward toward this goal. © 2011 John Wiley & Sons A/S.

Grellet-Tinner G.,Orcas Island Historical Museums | Grellet-Tinner G.,CONICET | Codrea V.A.,Babes - Bolyai University
Gondwana Research | Year: 2015

We report here the first occurrence of a small pterosaur, Thalassodromeus sebesensis from the Maastrichtian Hateg Island. This new species with its significantly expanded premaxillary crest extends the known distribution of this genus from South America to Europe. Furthermore, this important discovery doubles the thalassadromine fossil record and demonstrates a 42. million years temporal displacement from its older Aptian Gondwanan congener Thalassodromeus sethi. T. sebesensis sp. nov. is diagnosed by an unusual expanded premaxillary crest and synapomorphies shared only with its Brazilian congener, T. sethi. Yet, the new specimen displays enough autapomorphic characters to erect a new thalassodromine species. The discovery of T. sebesensis in an exposure known for its diverse angiosperm assemblage lends more support to the tapejarid and flowering plants co-evolution. It also suggests this new small thalassadromine was a forest dweller, as such possibly not competing with the known giant azhdarchid pterosaurs on this island. Moreover, its presence in this insular ecosystem confirms once more the aberrant nature of the Late Cretaceous Hateg island-dwelling endemic fauna. © 2014 International Association for Gondwana Research.

This study employs statistical modeling techniques and geomorphological mapping to analyze the distribution of active rock glaciers in relation to altitude, aspect, slope, lithology and solar radiation using optical remote sensing techniques with GIS. The study area includes a portion of the Dry Andes of the Cordillera Frontal of San Juan around 30°S latitude, where few geomorphological studies have been conducted. Over 155 rock glaciers have been identified, and 85 are considered active. The relationship between the variables and the rock glaciers distribution was analyzed using the frequency ratio method and logistic regression models. The analytical results show that elevations > 3824 m a.s.l., a south-facing or east-facing aspect, areas with relatively low solar radiation, and slope between 2° and 20° favor the existence of the rock glaciers, and demonstrate that lithology and slope exert major influences. © 2009 Elsevier B.V. All rights reserved.

Ballare C.L.,CONICET
Trends in Plant Science | Year: 2011

Plants have sophisticated defense systems to protect their tissues against the attack of herbivorous organisms. Many of these defenses are orchestrated by the oxylipin jasmonate. A growing body of evidence indicates that the expression of jasmonate-induced responses is tightly regulated by the ecological context of the plant. Ecological information is provided by molecular signals that indicate the nature of the attacker, the value of the attacked organs, phytochrome status and thereby proximity of competing plants, association with beneficial organisms and history of plant interactions with pathogens and herbivores. This review discusses recent advances in this field and highlights the need to map the activities of informational modulators to specific control points within our emerging model of jasmonate signaling. © 2010 Elsevier Ltd.

Uchida A.,University of Texas Southwestern Medical Center | Zigman J.M.,University of Texas Southwestern Medical Center | Perello M.,CONICET
Frontiers in Neuroscience | Year: 2013

Ghrelin is an octanoylated peptide hormone, produced by endocrine cells of the stomach, which acts in the brain to increase food intake and body weight. Our understanding of the mechanisms underlying ghrelin's effects on eating behaviors has been greatly improved by the generation and study of several genetically manipulated mouse models. These models include mice overexpressing ghrelin and also mice with genetic deletion of ghrelin, the ghrelin receptor [the growth hormone secretagogue receptor (GHSR)] or the enzyme that post-translationally modifies ghrelin [ghrelin O-acyltransferase (GOAT)]. In addition, a GHSR-null mouse model in which GHSR transcription is globally blocked but can be cell-specifically reactivated in a Cre recombinase-mediated fashion has been generated. Here, we summarize findings obtained with these genetically manipulated mice, with the aim to highlight the significance of the ghrelin system in the regulation of both homeostatic and hedonic eating, including that occurring in the setting of chronic psychosocial stress. © 2013 Uchida, Zigman and Perelló.

Membrane overexpression of the receptor tyrosine kinase ErbB-2 (MErbB-2) accounts for a clinically aggressive breast cancer (BC) subtype (ErbB-2-positive) with increased incidence of metastases. We and others demonstrated that nuclear ErbB-2 (NErbB-2) also plays a key role in BC and is a poor prognostic factor in ErbB-2-positive tumors. The signal transducer and activator of transcription 3 (Stat3), another player in BC, has been recognized as a downstream mediator of MErbB-2 action in BC metastasis. Here, we revealed an unanticipated novel direction of the ErbB-2 and Stat3 interaction underlying BC metastasis. We found that Stat3 binds to its response elements (GAS) at the ErbB-2 promoter to upregulate ErbB-2 transcription in metastatic, ErbB-2-positive BC. We validated these results in several BC subtypes displaying metastatic and non-metastatic ability, highlighting Stat3 general role as upstream regulator of ErbB-2 expression in BC. Moreover, we showed that Stat3 co-opts NErbB-2 function by recruiting ErbB-2 as its coactivator at the GAS sites in the promoter of microRNA-21 (miR-21), a metastasis-promoting microRNA (miRNA). Using an ErbB-2 nuclear localization domain mutant and a constitutively activated ErbB-2 variant, we found that NErbB-2 role as a Stat3 coactivator and also its direct role as transcription factor upregulate miR-21 in BC. This reveals a novel function of NErbB-2 as a regulator of miRNAs expression. Increased levels of miR-21, in turn, downregulate the expression of the metastasis-suppressor protein programmed cell death 4 (PDCD4), a validated miR-21 target. Using an in vivo model of metastatic ErbB-2-postive BC, in which we silenced Stat3 and reconstituted ErbB-2 or miR-21 expression, we showed that both are downstream mediators of Stat3-driven metastasis. Supporting the clinical relevance of our results, we found an inverse correlation between ErbB-2/Stat3 nuclear co-expression and PDCD4 expression in ErbB-2-positive primary invasive BCs. Our findings identify Stat3 and NErbB-2 as novel therapeutic targets to inhibit ErbB-2-positive BC metastasis.Oncogene advance online publication, 27 July 2015; doi:10.1038/onc.2015.281. © 2015 Macmillan Publishers Limited

Xyophorus Ameghino was described based on mandibular fragments of Xyophorus rostratus Ameghino from the Early Miocene of Patagonia. The specimen herein described was collected in the locality "El Petiso", located in northwestern Chubut Province, in sediments referred to the Middle Miocene and it is represented by a mandibular fragment that is characterized by: (1) posterior margin of the mandibular symphysis anterior to the plane of the caniniform; (2) posterolateral opening of mandibular canal on the lateral side of the coronoid process and nearly to the oclusal plane; (3) oclusal surface of the molariforms with two crests separated by a "V" valley; and (4) molariforms 1-2 presents vertical grooves on the labial and lingual sides, and molariform 3 with a groove on the labial one. The features present in this specimen and in the species herein referred to "Xyophorus" bondesioi Scillato-Yané, and "Xyophorus" villarroeli Saint-André allow distinguishing them from the species of the genus Xyophorus (e.g., X. andinus Ameghino, X. atlanticus Ameghino, X. crassissimus Ameghino) justifying the erection of a new genus and its inclusion in Nothrotheriinae. The record of "Xyophorus" sp. from the Middle Miocene of Chubut Province represents the oldest and australmost for Nothrotheriinae from Argentina, whereas, the record of "Xyophorus" cf. bondesioi from the locality of Cerdas, in Bolivia, would correspond to the oldest one for the subfamily.

de Abelleyra D.,Instituto Nacional de Tecnologia Agropecuaria | Veron S.R.,Instituto Nacional de Tecnologia Agropecuaria | Veron S.R.,CONICET
Remote Sensing of Environment | Year: 2014

Realizing the full benefits of MODIS' temporal resolution requires, among others, the correction of the directional effect (i.e. the combined impact of the variation of the measurement geometry and of the observed land surface upon the registered radiant flux). While different BRDF methods have been proposed to address this effect, its performance has been evaluated at coarse spatial resolutions making it difficult to assess its applicability to, for example, crop monitoring. Here we test 2 approaches based on two different assumptions: the Classic approach that relies on the hypothesis of stable target and a recent Alternative that is based on the idea that despite reflectance magnitude may change rapidly, the BRDF shape varies slowly in time. Additionally, we segmented the growing season into different numbers of periods for the BRDF correction (a single period along the growing season, 3 periods based in phenology and 9-12 periods of fixed 16-days). The resulting 6 methods were compared over annual crops (wheat, maize and soybean) at 250. m spatial resolution from a site located in the Argentine Pampas. We used MOD and MYD 09 GQ and GA as inputs and compared the corrected daily red and infrared reflectances and the NDVI time series against the filtered benchmark (input time series with quality filters applied) by means of the high frequency variability (i.e. noise). We also tested whether corrected time series were better correlated with soybean PAR interception and biomass. Our results showed that methods' performance was more explained by the number of periods than by the approach (Classic or Alternative). Single period methods decreased noise by 52%, 55% and 4% for red, infrared and NDVI time series. The use of 3 periods improved the correction performance to 63, 64 and 24% for red, infrared and NVDI time series respectively, while the highest reductions (65, 68 and 32% for red, infrared and NVDI) were found with 16-day intervals (9-12 periods) considering a magnitude inversion process. Wheat displayed the lowest noise reduction compared to the other crops. BRDF parameters obtained from different methods were associated to crop structure, suggesting that they have biophysical meaning. The decrease in noise obtained with correction methods was translated into a better assessment of the fraction of intercepted PAR and biomass. These promising results suggest the possibility of extensive field crop monitoring at an unprecedented temporal resolution. © 2013 Elsevier Inc.

Scoccola N.N.,Comision Nacional de la Energia Atomica | Scoccola N.N.,CONICET | Scoccola N.N.,Favaloro University | Riska D.O.,Finnish Society of Science and Letters | Rho M.,CEA Saclay Nuclear Research Center
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Using the bound state version of the topological soliton model for the baryons we show that the existence of a bound (or quasibound) D¯-soliton state leads to the possibility of having hidden charm pentaquarks with quantum numbers and masses, which are compatible with those of the candidates recently reported by the LHCb experiment. The implications of heavy quark symmetry are elaborated. © 2015 American Physical Society. © 2015 American Physical Society.

American journal of human biology : the official journal of the Human Biology Council | Year: 2014

The Program for the Control of Intestinal Parasites and Nutrition was designed to intervene in small communities to prevent and control the effects of parasitic infections on children's health. To analyze the association between nutritional status and parasitic infection in suburban and rural children from Buenos Aires, Argentina. Nutritional status was assessed by anthropometric (weight, height, BMI, skinfolds, upper arm circumference, muscle, and fat upper arm areas) and biochemical (Hb, Ca, Mg, Zn, and Cu) indicators. Parasitological analysis were made on both serial stool and perianal swab samples. A total of 708 children aged 3-11 were measured. The biochemical analysis included 217 blood samples and the parasitological study included 284 samples. Anthropometric status was similar in both settings with low rates of underweight and stunting (<6%), and high rates of overweight (~17%) and obesity (~12%). Ca deficiency was significantly higher in suburban children where 80% of them were hypocalcemic. Around 70% of fecal samples contained parasites. Among infected children, the most prevalent species were Blastocystis hominis and Enterobius vermicularis (~43%) followed by Giardia lamblia (~17%). Differences in parasitological status between districts were not significant. In the suburban district parasitized children were lighter, shorter, and had a lower upper arm circumference than their non-infected peers. No differences in anthropometric status were seen among infected and uninfected rural children. The results suggest an association between intestinal parasites and physical growth in suburban children. Rural children seem to be protected against the effects of parasitic infection. Copyright © 2013 Wiley Periodicals, Inc.

Taretto K.,CONICET
Progress in Photovoltaics: Research and Applications | Year: 2014

Analytical modeling of p-i-n solar cells constitutes a practical tool to extract material and device parameters from fits to experimental data, and to establish optimization criteria. This paper proposes a model for p-i-n solar cells based on a new approximation, which estimates the electric field taking into account interface potential drops at the intrinsic-to-doped interfaces. This leads to a closed-form current/voltage equation that shows very good agreement with device simulations, revealing that the inclusion of the interface potential drops constitutes a major correction to the classical uniform-field approach. Furthermore, the model is able to fit experimental current/voltage curves of efficient nanocrystalline Si and microcrystalline Si p-i-n solar cells under illumination and in the dark, obtaining material parameters such as mobility-lifetime product, built-in voltage, or surface recombination velocity. Copyright © 2012 John Wiley & Sons, Ltd.

Aschero V.,CONICET | Garcia D.,University of Oviedo
Applied Vegetation Science | Year: 2012

Question: How does long-term fencing against large domestic herbivores affect regeneration of the dominant tree, Prosopis flexuosa, and hence the structure of semi-arid woodlands? Location: Woodlands in the Central Monte Desert biome of Argentina, Ñacuñán Man and the Biosphere Reserve area (34° 20′ S, 67° 58′ W) and surrounding cattle-grazed ranches. Methods: We compared seedling emergence and survival, the spatial distribution of seedlings and saplings, and the population stage-based structure of P. flexuosa between paired sites inside and outside the Reserve of Ñacuñán (Argentina), which has been fenced to exclude domestic cattle for ca. 40 yr. Results: Reserve sites had lower tree recruitment and seedling emergence, in spite of having greater seed production and seedling survival. Outside the reserve, survival was higher for seedlings in high-density clumps than for isolated seedlings. Seedling clumps occurred mostly near adult individuals, where cattle dung was abundant, suggesting an effect of cattle on seed dispersal. The balance between the effects of cattle exclusion on seedling emergence and on seedling survival was reflected in the stage structure of P. flexuosa woodlands, as populations at fenced sites were dominated by adult individuals, whereas those at cattle-grazed areas presented greater proportions of seedlings and saplings. Conclusion: Fencing is a common practice used worldwide to exclude conservation areas from human disturbance. For example, it is assumed that disturbed woodlands may recover after fencing, thanks to increased tree recruitment after the exclusion of large herbivores. However, the actual effectiveness of fencing as a tool for forest conservation in overgrazed environments could be controversial because sequential effects of herbivores during the tree regeneration cycle may hamper predictions of the overall balance of the recruitment process. Our results suggest that dispersal by cattle influences the regeneration of P. flexuosa woodlands, and that the positive effects of cattle on seedling emergence compensate for the negative effects on seed production and seedling and sapling survival. Future management of P. flexuosa woodlands in the Central Monte Desert should consider that tree recruitment is closely related to land use, and that cattle exclusion does not necessarily guarantee woodland recovery in the long term. © 2012 International Association for Vegetation Science.

Gudesblat G.E.,Vlaams Institute for Biotechnology | Gudesblat G.E.,Ghent University | Gudesblat G.E.,CONICET | Russinova E.,Vlaams Institute for Biotechnology | Russinova E.,Ghent University
Current Opinion in Plant Biology | Year: 2011

Brassinosteroids (BRs) are plant steroid hormones known mainly for promoting organ growth through their combined effect on cell expansion and division. In addition, BRs regulate a broad spectrum of plant developmental and physiological responses, including plant architecture, vascular differentiation, male fertility, flowering, senescence, photomorphogenesis and tolerance to biotic and abiotic stresses. Recently, a complete core BR signaling pathway was defined in which BR signals are conveyed from the cell surface to the nucleus through sequential signaling modules. A major challenge now is to understand precisely how this signaling pathway controls the different BR-regulated actions. The current identification of direct targets of BRASSINAZOLE-RESISTANT1 (BRZ1) and BR-INSENSITIVE-EMS-SUPPRESSOR1 (BES1)/BZR2 transcription factors suggests that BR signaling pathway controls growth and interacts with other signaling pathways mainly at the transcriptional level. © 2011 Elsevier Ltd.

This paper presents a theoretical approach for optimal design of the baking process. Conventional baking of bread was taken as subject of study, and simulation of previously validated models was used to investigate the process. The proposed approach is based on the definition of two different times for the baking process: a critical time, i.e. a minimum baking time assessed by the complete starch gelatinization in the product, and a quality time, i.e. the time necessary to achieve a target value for a given quality attribute. In this work, browning determined the quality time due to its relevance with regard to sensory and nutritional aspects. As a result, feasible solutions are obtained involving a minimum baking (acceptable products) and a minimum thermal input for a given value of browning, which helps to reduce the formation of acrylamide. Optimum solutions can be then obtained by defining specific objectives; weight loss can be minimized by lowering the value of heat transfer coefficient. Furthermore, obtained results can be helpful to build more efficient ovens. © 2012 Elsevier Ltd.

Otranto S.,CONICET | Olson R.E.,Missouri University of Science and Technology
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

X-ray emission originating in charge-exchange collisions between Ar18 + and neutral argon is studied at impact energies of 5-4000 eV/amu by means of the classical trajectory Monte Carlo method (CTMC). Line emission and charge-exchange cross sections obtained from different CTMC versions based on the one-active electron approximation are contrasted among themselves and against the results obtained by means of a three-active electron code that lets us infer the role of multiple electron capture. The present results are compared to the recent experimental data available from the EBIT groups operating at Livermore, NIST, and Berlin. We were not able to reconcile the major difference in x-ray emission cross sections obtained from in situ measurements made in EBIT, versus those made in an exterior, field-free collision chamber using ions extracted from the EBIT. Our calculations support the extracted beam results. © 2011 American Physical Society.

Svagelj W.S.,CONICET | Quintana F.,Wildlife Conservation Society
Emu | Year: 2011

The breeding productivity of seabirds usually declines over the course of a breeding season. Breeding productivity in colonial birds has also been found to be affected by the distance from a nest to the edge of a colony, with peripheral nests usually having lower productivity than centrally located nests. We evaluated the influence of laying date and nest location (distance from the edge of the colony) on clutch-size and breeding success of the Imperial Shag (Phalacrocorax atriceps) during three breeding seasons (2004-06) at Punta Len, Argentina. There was no relationship between year, laying date or nest location and variation in clutch-size. Further, whereas breeding success did not differ between years, breeding success consistently decreased with laying date. We also found an interactive effect between laying date and nest location. Distance from the edge of the colony was not related to breeding success of Shags that laid either early or at the peak of the season, but the breeding success of late breeders increased with distance from the edge of the colony. Our findings of a seasonal decline in breeding success are consistent with the typical pattern exhibited by seabirds. Our results suggest that low-quality (young or less-capable) pairs that breed late in the season may benefit from nesting away from the edge of the colony, reducing levels of disturbance and risk of nest-predation. © 2011 Royal Australasian Ornithologists Union.

Host-parasite interactions between Red-rumped Caciques (Cacicus haemorrhous) and Giant Cowbirds (Molothrus oryzivorus) were studied at 52 nests in the Atlantic Forest, Misiones, Argentina. Cowbird eggs (1-6) occurred in 27 of 38 cacique nests (71%) found during the egg stage. Giant Cowbird eggs were white and unmarked (85%), or marked and spotted over pale buff (15%); the marked eggs somewhat resembled host eggs, but were twice as large. Four host and three parasite eggs were found punctured and broken. Only three cowbird nestlings were observed, and resembled oropendola (Psarocolius spp.) nestlings more than those of Red-rumped Caciques. Botflies (Philornis spp.) infested cowbird and cacique nestlings, but there was no evidence of a cowbird-cacique preening mutualism. © 2011 by the Wilson Ornithological Society.

Cassini M.H.,CONICET | Cassini M.H.,National University of Lujan
Journal of Biogeography | Year: 2011

Most species distribution models (SDMs) assume that habitats are closed, stable and without competition. In that environmental context, it is ecologically correct to assume that members of a species will be distributed in direct relation to the suitability of the habitat, that is, according to the so-called habitat matching rule. This paper examines whether it is possible to maintain the assumption of the habitat matching rule in the following circumstances: (1) when habitats are connected and organisms can move between them, (2) when there are disturbances and seasonal cycles that generate instability, and (3) when there is inter-specific and intra-specific competition. Here I argue that it is possible as long as the following aspects are taken into account. In open habitats at equilibrium, in which habitat selection and competition operate, the habitat matching rule can be applied in some conditions, while competition tends to homogenize the species distribution in other environmental contexts. In the latter case, two methods can be used to incorporate these effects into SDMs: new parameters can be incorporated into the response functions, or the occurrence of proportions of categories of individuals (adult/young, male/female, or dominant/subordinate species in guilds) can be used instead of the occurrence of organisms. The habitat matching rule is not fulfilled in non-equilibrium environments. The solution to this problem lies in the design of SDMs with two strategies that depend on scale. Locally, the disequilibrium can be encapsulated using average environmental conditions, with sufficiently large cells (in the case of metapopulations) and/or long enough sampling periods (in the case of seasonal cycles). At coarse scales, the use of presence-only models can in some cases avoid the destabilizing effect of catastrophic historical processes. The matching law is a strong assumption of SDMs because it is based on population ecology theory and the principle of evolution by natural selection. © 2011 Blackwell Publishing Ltd.

Gonzalez A.D.,CONICET | Frostell B.,KTH Royal Institute of Technology | Carlsson-Kanyama A.,Swedish Defence Research Agency
Food Policy | Year: 2011

The production, transport and processing of food products have significant environmental impacts, some of them related to climate change. This study examined the energy use and greenhouse gas emissions associated with the production and transport to a port in Sweden (wholesale point) of 84 common food items of animal and vegetable origin. Energy use and greenhouse gas (GHG) emissions for food items produced in different countries and using various means of production were compared. The results confirmed that animal-based foods are associated with higher energy use and GHG emissions than plant-based foods, with the exception of vegetables produced in heated greenhouses. Analyses of the nutritional value of the foods to assess the amount of protein delivered to the wholesale point per unit energy used or GHG emitted (protein delivery efficiency) showed that the efficiency was much higher for plant-based foods than for animal-based. Remarkably, the efficiency of delivering plant-based protein increased as the amount of protein in the food increased, while the efficiency of delivering animal-based protein decreased. These results have implications for policies encouraging diets with lower environmental impacts for a growing world population. © 2011 Elsevier Ltd.

Two new species from north-western Argentina are described. The male of a new species of Alisotrichia is described and illustrated as A. benji. This represents the first record of the genus from north-western Argentina. The male and larva of a new species of Leucotrichia are described and illustrated as L. alisensis. The taxonomic positions of A. benji and L. alisensis are discussed. Hydroptila argentinica Flint, H. bidens Flint, Neotrichia gotera Flint and Oxyethyra parce Edwards & Arnold are newly recorded from Bolivia. Oxyethira ulmeri Mosely is recorded for the first time from north-western Argentina. New localities from north-western Argentina are recorded for Hydroptila bidens, Neotrichia elongata Flint and N. gotera. Illustrations of the males of species representing new records are included. © 2011 Taylor & Francis.

Superina M.,CONICET | Loughry W.J.,Valdosta State University
Journal of Mammalian Evolution | Year: 2012

Without doubt, the possession of an armored carapace represents one of the most conspicuous morphological features of all cingulates. Here, we review some of the many ways in which the carapace may have influenced the evolution of other features of extant armadillos (Xenarthra: Cingulata). Effects range from physiological impacts on respiration and thermoregulation, to mechanical and other constraints on reproduction. Additionally, in mammals, armor has been linked with relatively slow plantigrade locomotion, which in turn may have promoted the low metabolic rate and exploitation of a low quality diet typically observed in armadillos. Finally, this network of relationships may help to explain the lack of any obvious kin-selected altruism in the polyembryonic armadillos, such as the nine-banded armadillo (Dasypus novemcinctus), because of time and energy constraints associated with a short active period devoted almost exclusively to feeding. In mammals, there has been growing interest in describing an ecological "lifestyle" as the particular way in which each species makes its living, and how this lifestyle constrains the evolution of other phenotypic traits. Based on our review, it appears the carapace has been a major determinant of the lifestyle of armadillos and has played a central role in shaping the evolution of many other features of these animals. © 2011 Springer Science+Business Media, LLC.

Premise of research. Most studies of Anacardiaceae embryology have focused on seed and fruit development in different genera. None of them, however, included species of Schinopsis. Considering the absence of embryological data and the precedents of chalazogamy in the Anacardiaceae family, the aims of this study were to complete the embryological studies in Schinopsis balansae, providing information about micro-and megasporogen-esis and gametogenesis, fertilization, and embryogenesis, and to investigate the development of the gynoecium and the pathway of the pollen tube. Methodology. Flowers and fruits of S. balansae, a dioecious tree from the family Anacardiaceae, were collected and fixed in the field. The embryology was examined using fluorescence microscopy, LM, and SEM. Microtome section series were used to reconstruct the structure and pollen tube pathway. Pivotal results. Staminate flowers have only rudimentary gynoecia, and the anthers are bithecal and tetrasporangiate. The tapetum is secretory and uninucleate, and the pollen grains are bicellular. The morphologically bisexual flowers are functionally pistillate, and staminodia without sporogenous tissue or pollen grains are present. The pistillate flowers have a superior tricarpellate ovary with three styles, each ending in a capitate stigma. The gynoecium is pseudomonomerous, possessing one fertile carpel (with one locule and a single anatropous, crassinucellar, and unitegmic ovule) and two aborted lateral carpels that neither produce an ovule nor form a locule. Embryo sac development conformed to the Polygonum type. Bicellular pollen grains germinate on the stigma and penetrate the transmitting tract inside the styles. At the apical portion of the ovary, pollen tubes grow through the carpel wall and reach the dorsal portion of the bent funicle, which is in close contact and forms a functional ponticulus. Inside the funicle, the pollen tubes continue through the vascular bundle, where they are branched. One branch continues inside the vascular bundle to the chalaza. Fertilization was aporogamous: the pollen tubes encircled the embryo sac, reaching one synergid. Embryos follow the Onagrad type. The endosperm development is of the coenocytic/multicellular type. Conclusions. The structural floral features described here are shared by other species of Anacardiaceae. The results of the embryological studies in S. balansae provide information about micro-and megasporogenesis and gametogenesis, fertilization, and embryogenesis and describe for the first time the developments of the gynoecium and the unique pollen tube pathway and fertilization; the term funiculogamy was proposed to define this type of pollen tube penetration. © 2016 by The University of Chicago. All rights reserved.

Giribet G.,University of Buenos Aires | Leston M.,CONICET
Journal of High Energy Physics | Year: 2010

Resorting to the notion of a stress-tensor induced on the boundary of a spacetime, we compute the conserved charges associated to exact solutions of New Massive Gravity that obey weakened versions of AdS 3 asymptotic boundary conditions. The computation requires the introduction of additional counterterms, which play the rǒle of regularizing the semiclassical stress-tensor in the boundary theory. We show that, if treated appropriately, different ways of prescribing asymptotically AdS 3 boundary conditions yield finite conserved charges for the solutions. The consistency of the construction manifests itself in that the charges of hairy asymptotically AdS 3 black holes computed by this holographyinspired method exactly match the values required for the Cardy formula to reproduce the black hole entropy. We also consider new solutions to the equations of motion of New Massive Gravity, which happen to fulfill Brown-Henneaux boundary conditions despite not being Einstein manifolds. These solutions are shown to yield vanishing boundary stresstensor. The results obtained in this paper can be regarded as consistency checks for the prescription proposed in [1]. © SISSA 2010.

Genovese D.B.,CONICET
Advances in Colloid and Interface Science | Year: 2012

This paper reviews the shear rheology of suspensions of microscopic particles. The nature of interparticle forces determines the microstructure, and hence the deformation and flow behavior of suspensions. Consequently, suspensions were classified according to the resulting microstructure: hard-spheres, stabilized, or aggregated particles. This study begins with the most simple case: flowing suspensions of inert, rigid, monomodal spherical particles (called hard-spheres), at low shear rates. Even for inert particles, we reviewed the effect of several factors that produce deviations from this ideal case, namely: shear rate, particle shape, particle size distribution, and particle deformability. Then we moved to suspensions of colloidal particles, where interparticle forces play a significant role. First we studied the case of dispersed or stabilized suspensions (colloidal dispersions), where long range repulsive forces keep particles separated, leading to a crystalline order. Second we studied the more common case of aggregated or flocculated suspensions, where net attractive forces lead to the formation of fractal clusters. Above the gelation concentration (which depends on the magnitude of the attractive forces), clusters are interconnected into a network, forming a gel. We differentiate between weak and strong aggregation, which may lead to weak or strong gels, respectively. Finally, we reviewed the case of filler/matrix composite suspensions or gels, where rigid or viscoelastic particles (fillers) are dispersed in a continuous viscoelastic material (matrix), usually a gel. For each type of suspension, predictive curves of fundamental rheological properties (viscosity, yield stress, elastic and complex moduli) vs. particle volume fraction and shear rate were obtained from theoretical or empirical models and sound experimental data, covering ranges of practical interest. © 2012 Elsevier B.V.

Cretaceous sedimentary rocks of the James Ross Basin offer a unique Austral record of the transition from mild mid-Turonian-early Campanian to relatively cold Maastrichtian palaeoclimatic conditions. After deposition of deep-marine Lower to Upper Cretaceous sediments and tectonic inversion of the basin, the Upper Cretaceous-Danian Marambio Group reflects the development of a shelf extended for more than100km into the Weddell Sea. The expansion of the shelf area was punctuated by three major transgressive-regressive cycles: the N (Santonian-early Campanian); NG (late Campanian-early Maastrichtian); and MG (early Maastrichtian-Danian) sequences. Faunal groups sensitive to changing water-mass conditions, such as ammonites and inoceramids, exhibit unusual patterns of diversity changes and/or early extinctions. In the N Sequence ammonite generic richness is minimum in the Santonian, then it increases gradually to an early Campanian maximum and decreases in the latest early Campanian. This pattern is typical for transgressive-regressive cycles, where broadening of the shelf during peak transgression controls maximum diversity. The molluscs Scaphitidae, Nostoceratidae, Inoceramidae, and most Trigoniidae disappeared from Antarctica during the early Campanian. By the early-late Campanian boundary, the last Antarctic inoceramids show a distinctive shell structure that probably reflects thermal stress. In the nearby Tierra del Fuego region, deep-marine inoceramids disappeared by the early Maastrichtian, concomitant with a marked change from anoxic-dysoxic to well-oxygenated bottom conditions. The ammonites of the NG and MG sequences are dominated by kossmaticeratids, both in generic richness (which is much lower than in the N Sequence) and specimen abundance, but their diversity pattern do not reflect the expansion of the shelf during peak transgression. Dominance of the Kossmaticeratidae, concomitant with a known Austral temperature decline in the seawater, supports the idea that kossmaticeratids were stenothermal ammonites that flourished in Antarctica when the water masses had attained their preferred temperature and were displaced towards lower latitudes when a certain minimum threshold temperature was reached in the late Maastrichtian. These diversity changes and local extinctions closely match published temperature-cooling trends in the southern ocean and the oxygenation event at the inoceramid extinction level in Tierra del Fuego probably reflects cooling and enhanced bottom ventilation, promoted by circulation of deep Antarctic waters. © 2011 Elsevier Ltd.

Rodriguez M.A.,CONICET
Corrosion Reviews | Year: 2012

The application of stainless steels and chromium containing nickel-based alloys is limited by their susceptibility to localized corrosion in the forms of pitting and crevice corrosion or environmentally assisted cracking. Inhibitors may be normally found in service environments or added on purpose to mitigate or avoid the effects of aggressive agents such as chloride ions. The present study critically reviews the present knowledge on inhibition of chloride-induced pitting and crevice corrosion. Pioneering studies and recent findings are analyzed in light of the present theories for describing the localized corrosion processes. This review particularly focuses on the inhibition of crevice corrosion of alloy 22, which has been thoroughly studied in the past decade. © 2012 by Walter de Gruyter.

Advances in Meteorology | Year: 2013

This review summarizes the progress achieved on regional climate modeling activities over South America since the early efforts at the beginning of the 2000s until now. During the last 10 years, simulations with regional climate models (RCMs) have been performed for several purposes over the region. Early efforts were mainly focused on sensitivity studies to both physical mechanisms and technical aspects of RCMs. The last developments were focused mainly on providing high-resolution information on regional climate change. This paper describes the most outstanding contributions from the isolated efforts to the ongoing coordinated RCM activities in the framework of the CORDEX initiative, which represents a major endeavor to produce ensemble climate change projections at regional scales and allows exploring the associated range of uncertainties. The remaining challenges in modeling South American climate features are also discussed. © 2013 Silvina A. Solman.

Garcia D.,University of Oviedo | Zamora R.,University of Granada | Amico G.C.,CONICET
Conservation Biology | Year: 2010

Seed dispersal by animals is considered a pivotal ecosystem function that drives plant-community dynamics in natural habitats and vegetation recovery in human-altered landscapes. Nevertheless, there is a lack of suitable ecological knowledge to develop basic conservation and management guidelines for this ecosystem service. Essential questions, such as how well the abundance of frugivorous animals predicts seeding function in different ecosystems and how anthropogenic landscape heterogeneity conditions the role of dispersers, remain poorly answered. In three temperate ecosystems, we studied seed dispersal by frugivorous birds in landscape mosaics shaped by human disturbance. By applying a standardized design across systems, we related the frequency of occurrence of bird-dispersed seeds throughout the landscape to the abundance of birds, the habitat features, and the abundance of fleshy fruits. Abundance of frugivorous birds in itself predicted the occurrence of dispersed seeds throughout the landscape in all ecosystems studied. Even those landscape patches impoverished due to anthropogenic disturbance received some dispersed seeds when visited intensively by birds. Nonetheless, human-caused landscape degradation largely affected seed-deposition patterns by decreasing cover of woody vegetation or availability of fruit resources that attracted birds and promoted seed dispersal. The relative role of woody cover and fruit availability in seed dispersal by birds differed among ecosystems. Our results suggest that to manage seed dispersal for temperate ecosystem preservation or restoration one should consider abundance of frugivorous birds as a surrogate of landscape-scale seed dispersal and an indicator of patch quality for the dispersal function; woody cover and fruit resource availability as key landscape features that drive seedfall patterns; and birds as mobile links that connect landscape patches of different degrees of degradation and habitat quality via seed deposition. ©2010 Society for Conservation Biology.

Padilla N.,University of Santiago de Chile | Lambas D.G.,CONICET | Gonzalez R.,University of Santiago de Chile
Monthly Notices of the Royal Astronomical Society | Year: 2010

We study the properties of Sloan Digital Sky Survey (SDSS) galaxies with and without active galactic nucleus (AGN) detection as a function of the local and global environment measured via the local density, mass of the galaxy host group (parametrized by the group luminosity) and distance to massive clusters. Our results can be divided into two main subjects: the environments of galaxies and their relation to the assembly of their host haloes, and the environments of AGNs. (i) For the full SDSS sample, we find indications that the local galaxy density is the most efficient parameter to separate galaxy populations, but we also find that galaxies at a fixed local density show some remaining variation in their properties as a function of the distance to the nearest cluster of galaxies (in a range of 0-10 cluster virial radii). These differences seem to become less significant, if the galaxy samples are additionally constrained to be hosted by groups of similar total luminosity. If instead of fixing the local density, the mass of the host group is held fixed at a given value, the fraction of red galaxies also increases as the distance to clusters diminishes, indicating that neither the local density nor the host halo mass contains all the information on the environment. (ii) In AGN host galaxies, the morphology-density relation is much less notable when compared to the behaviour of the full SDSS sample, indicating a lack of sensitivity to the host group mass during the AGN phase, probably due to the higher typical luminosities of the AGN hosts. In order to interpret this result, we analyse control samples constructed using galaxies with no detected AGN activity with matching distributions of redshifts, stellar masses, r-band luminosities, g-r colours, concentrations, local densities, host group luminosities and fractions of central and satellite galaxies; the aim in using the control sample is to detect any correlations between the AGN detection and other AGN host properties that are unrelated to the AGN selection. The control samples also show a similar small dependence on the local density, indicating an influence from the AGN selection, but their colours are slightly bluer compared to the AGN hosts, regardless of the local density. Furthermore, even when the local density is held fixed at intermediate or high values, and the distance to the closest cluster of galaxies is allowed to vary, AGN control galaxies away from clusters tend to be bluer than the AGN hosts. However, AGN in bright, low-concentration hosts (i.e. discy morphologies) are bluer than galaxies in the control sample, connecting the presence of discs to AGN activity even under a controlled comparison between active and inactive galaxies. © 2010 The Authors. Journal compilation © 2010 RAS.

Nunez M.A.,CONICET | Dickie I.A.,Landcare Research | Dickie I.A.,Lincoln University at Christchurch
Biological Invasions | Year: 2014

Most plants require mutualistic associations to survive, which can be an important limitation on their ability to become invasive. There are four strategies that permit plants to become invasive without being limited by a lack of mutualists. One is to not be dependent on mutualists. The other three strategies are to form novel mutualisms, form associations with cosmopolitan species, or co-invade with mutualists from their native range. Historically there has been a bias to study mutualisms from a plant perspective, with little consideration of soil biota as invasive species in their own right. Here we address this by reviewing the literature on belowground invasive mutualists of woody plants. We focus on woody invaders as ecosystem-transforming plants that frequently have a high dependence on belowground mutualists. We found that co-invasions are common, with many ectomycorrhizal plant species and N-fixing species co-invading with their mutualists. Other groups, such as arbuscular mycorrhizal plants, tend to associate with cosmopolitan fungal species or to form novel associations in their exotic range. Only limited evidence exists of direct negative effects of co-invading mutualists on native mutualist communities, and effects on native plants appear to be largely driven by altered environmental conditions rather than direct interactions. Mutualists that introduce novel ecosystem functions have effects greater than would be predicted based solely on their biomass. Focusing on the belowground aspects of plant invasions provides novel insights into the impacts, processes and management of invasions of both soil organisms and woody plant species. © 2013 Springer Science+Business Media Dordrecht.

Journal of Systematic Palaeontology | Year: 2015

A phylogenetic analysis of all Eocene taxa assigned to Notopithecinae has been conducted, evaluating relationships amongst notopithecines, basal interatheriids and Interatheriinae. Other groups of native ungulates were also included. New dental and postcranial characters are considered with respect to previously published data; some characters are evaluated in notoungulates for the first time. Two different searches were performed under parsimony and equal weights. The inclusion of postcranial characters strongly influenced tree topology. The most significant result of the phylogenetic analysis was the identification of a novel monophyletic group, including species traditionally grouped as Patagonian Notopithecinae. The ‘notopithecid’ name is linked to the new clade defined as the clade stemming from the most recent common ancestor of the species Notopithecus adapinus, Antepithecus brachystephanus, Transpithecus obtentus and Guilielmoscottia plicifera. This phylogeny supports the main morphological differences of the new clade with respect to Interatheriinae Interatheriidae. In consequence, a diagnosis is proposed based on phylogenetic results, to which some other morphological characters are added. The Chilean basal interatheriids Johnbell and Ignigena as well as Punapithecus (Argentinean Puna) are excluded from the notopithecid clade, implying biostratigraphical and biogeographical changes. Notopithecid distribution now becomes restricted to the middle–late Eocene part of the Sarmiento Formation outcropping in central Chubut and north-east Santa Cruz provinces, Argentina. Other extra-Patagonian records of notopithecids are not confirmed. The resulting phylogeny resolves some relationships within basal interatheriids differently from previous analyses. Interatheriinae is not recovered as a monophyletic group, and Oldfieldthomasiidae and Henricosborniid are paraphyletic. The position of the Archaeopithecidae Acropithecus rigidus is controversial; it appears at the base of the Typotheria lineage or in the notopithecid clade, but systematic taxonomy and phylogenetic relationships amongst members of Archaeopithecidae remain to be established. © The Trustees of the Natural History Museum, London 2015. All rights reserved.

Schmiegelow C.T.,CONICET | Schmidt-Kaler F.,Johannes Gutenberg University Mainz
European Physical Journal D | Year: 2012

We study the interaction of light beams carrying angular momentum with a single, trapped and well localized ion. We provide a detailed calculation of selection rules and excitation probabilities for quadrupole transitions. The results show the dependencies on the angular momentum and polarization of the laser beam as well as the direction of the quantization magnetic field. In order to optimally observe the specific effects, focusing the angular momentum beam close to the diffraction limit is required. We discuss a protocol for examining experimentally the effects on the S 1/2 to D 5/2 transition using a 40Ca + ion. Various applications and advantages are expected when using light carrying angular momentum: in quantum information processing, where qubit states of ion crystals are controlled, parasitic light shifts could be avoided as the ion is excited in the dark zone of the beam at zero electric field amplitude. Such interactions also open the door to high dimensional entanglement between light and matter. In spectroscopy one might access transitions which have escaped excitation so far due to vanishing transition dipole moments. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012.

Hough G.,National University of Central Buenos Aires | Garitta L.,CONICET
Journal of Sensory Studies | Year: 2012

When talking about shelf life of foods, in the vast majority of cases we are talking about sensory shelf life of foods. The review presents an overview of the published research over the past decades classified according to the following topics: (1) cut-off point methodology (arbitrary and regression-based cut-off points); (2) methods based on product failure or consumers' rejection (failure with no censorship, logistic regression and survival analysis); (3) accelerated studies; and (4) other topics and further research. © 2012 Wiley Periodicals, Inc.

Modenutti B.,CONICET
Advances in Limnology | Year: 2014

Mixotrophic organisms appeared in photosynthetic and heterotrophic lineages (i.e., algae and ciliates). In this article we will present examples and discuss diverse aspects of the success of this dual nutrition mode in different lakes from Argentina. Factors as nutrients, light, water mixing intensity, mixing depth, and prey abundance have large effects on the ecological dynamics of these organisms. Traditional studies suggested that the growth rate of mixotrophic protists would depend on light intensity and prey abundance allowing the classification of mixotrophs into different groups. We will discuss this scheme in the scenario of protists currently present in Argentina. Additionally, we will examine the results of field and experimental studies in Argentina lakes regarding the different co-occurring factors that determine the success of different mixotrophic species. In particular, we will focus competitive interactions among mixotrophs in nature, evaluating both, photosynthetic efficiency as a result of the niche partitioning along the water column and the ingestion of picoprokaryotes for food niche overlap. Furthermore, we will present other studies on the relative importance of light (intensity and quality) in the autotrophy and phagotrophy balance. © 2014 E. Schweizerbart'sche Verlagsbuchhandlung, 70176 Stuttgart, Germany.

Lopez-Pamies O.,State University of New York at Stony Brook | Idiart M.I.,National University of La Plata | Idiart M.I.,CONICET | Nakamura T.,State University of New York at Stony Brook
Journal of the Mechanics and Physics of Solids | Year: 2011

It is by now well established that loading conditions with sufficiently large triaxialities can induce the sudden appearance of internal cavities within elastomeric (and other soft) solids. The occurrence of such instabilities, commonly referred to as cavitation, can be attributed to the growth of pre-existing defects into finite sizes. This paper introduces a new theory to study the phenomenon of cavitation in soft solids that: (i) allows to consider general 3D loading conditions with arbitrary triaxiality, (ii) applies to large (including compressible and anisotropic) classes of nonlinear elastic solids, and (iii) incorporates direct information on the initial shape, spatial distribution, and mechanical properties of the underlying defects at which cavitation can initiate. The basic idea is to first cast cavitation in elastomeric solids as a homogenization problem of nonlinear elastic materials containing random distributions of zero-volume cavities, or defects. This problem is then addressed by means of a novel iterated homogenization procedure, which allows to construct solutions for a specific, yet fairly general, class of defects. These include solutions for the change in size of the defects as a function of the applied loading conditions, from which the onset of cavitation - corresponding to the event when the initially infinitesimal defects suddenly grown into finite sizes - can be readily determined. In spite of the generality of the proposed approach, the relevant calculations amount to solving tractable HamiltonJacobi equations, in which the initial size of the defects plays the role of time and the applied load plays the role of space. When specialized to the case of hydrostatic loading conditions, isotropic solids, and defects that are vacuous and isotropically distributed, the proposed theory recovers the classical result of Ball (1982) for radially symmetric cavitation. The nature and implications of this remarkable connection are discussed in detail. © 2011 Elsevier Ltd. All rights reserved.

Galvan D.E.,CONICET | Sweeting C.J.,Northumbria University | Polunin N.V.C.,Northumbria University
Oecologia | Year: 2012

Carbon and nitrogen stable isotope ratios are used to assess diet composition by determining bounds for the relative contributions of different prey to a predator's diet. This approach is predicated on the assumption that the isotope ratios of predator tissues are similar to those of dominant food sources after accounting for trophic discrimination (ΔxX), and is formulated as linear mixing models based on mass balance equations. However, ΔxX is species- and tissue-specific and may be affected by factors such as diet quality and quantity. From the different methods proposed to solve mass balance equations, some assume ΔxX to be exact values whilst others (based on Bayesian statistics) incorporate variability and inherent uncertainty. Using field data from omnivorous reef fishes, our study illustrates how uncertainty may be taken into account in non-Bayesian models. We also illustrate how dietary interpretation is a function of both absolute ΔxX and its associated uncertainty in both Bayesian and non-Bayesian isotope mixing models. Finally, collated literature illustrate that uncertainty surrounding ΔxX is often too restricted. Together, these data suggest the high sensitivity of mixing models to variation in trophic discrimination is a consequence of inappropriately constrained uncertainty against highly variable ΔxX. This study thus provides guidance on the interpretation of existing published mixing model results and in robust analysis of new resource mixing scenarios. © 2012 Springer-Verlag.

Allen P.G.,Comision Nacional de la Energia Atomica | Scoccola N.N.,Comision Nacional de la Energia Atomica | Scoccola N.N.,CONICET | Scoccola N.N.,Favaloro University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The phase structure of magnetized cold quark matter is analyzed in the framework of the two-flavor Nambu-Jona-Lasinio models paying special attention to its dependence on the model parameters as different values within the phenomenological allowed range are considered. We first discuss the simpler chiral limit case, and then the more realistic situation of finite current masses. We show that in spite of the difference in the nature of some transitions, both cases are alike and exhibit a rather rich phase structure for a significant range of acceptable parameters. A simplification of the phase structure is obtained as parameters leading to larger values of the dressed quark mass in the vacuum are considered. Finally, we consider the so-called "inverse catalysis effect" showing that in some phases it implies an actual decrease of the order parameter as the magnetic field increases. © 2013 American Physical Society.

The effect of predators on prey size structure in aquatic communities has been well studied in lentic permanent habits, but less attention has been placed on temporary environments. The biota of seasonal Andean wetlands in Patagonia is basically formed by crustaceans, insects and pond-breeding amphibians. The dominant predators in these wetlands are macroinvertebrates, mostly aquatic insects. The main objectives of this study were to examine the seasonal and interannual variation in the body size of prey and predators in two temporary wetlands located in northwest Patagonia, during two consecutive hydroperiods and to evaluate the effect of different insect predators over different prey sizes and different ontogenetic stages of invertebrate and vertebrate prey. Prey size structure and predator size structure were affected by the wetland type and the sampling months and predator body size was not correlated with prey size structure. The experiments showed that small prey were the most impacted by predaceous insects and all predators showed size-limited predation. Although aquatic insects significantly reduced the number of prey in the predation experiments, they did not significantly affect the body size structure of prey in nature. In this sense, the diversity of aquatic insects with different predatory strategies could maintain the heterogeneity in prey size structure in the wetlands studied. © EDP Sciences, 2016.

Journal of Physical Chemistry C | Year: 2013

In this work, we performed DFT+U periodic calculations to study the geometric and electronic properties of 12.5% Mn-doped CeO2 solid solution. The doping with Mn allowed some Mn2+ cations to substitute Ce4+ ions into the CeO2 lattice and thus drove the formation of a stable O-deficient bulk fluorite-type structure. The Mn-doped CeO2(1 1 1) surface, generated upon the cleavage of the O-deficient bulk, exhibits Mn cations in a (3+) oxidation state. Spin-polarized energy calculations and charge analysis also evidenced the effect of Mn-dopant in facilitating the creation of surface oxygen vacancies; which reflected in extended surface and subsurface ions relaxation and reduction of Mn atoms located on surface and inner cationic layers. Concerning the oxidation state of Ce, it remained unaltered as Ce4+ when an O atom was removed from the topmost anionic layer of the surface system. Reduction of a Ce4+ cation to Ce3+ was evidenced after the creation of a second surface O-vacancy. Our results indicate facilitated surface oxygen release, Mn 3+/Mn2+ redox couples formation, and promoted anionic mobility and can help to better understand the effect of Mn in enhancing Mn-doped CeO2 catalytic performance in oxidation reactions. © 2013 American Chemical Society.

Fuentes M.L.,CONICET | Klimchuk J.A.,NASA
Astrophysical Journal | Year: 2015

We study a two-dimensional cellular automaton (CA) model for the evolution of coronal loop plasmas. The model is based on the idea that coronal loops are made of elementary magnetic strands that are tangled and stressed by the displacement of their footpoints by photospheric motions. The magnetic stress accumulated between neighbor strands is released in sudden reconnection events or nanoflares that heat the plasma. We combine the CA model with the Enthalpy Based Thermal Evolution of Loops model to compute the response of the plasma to the heating events. Using the known response of the X-Ray Telescope on board Hinode, we also obtain synthetic data. The model obeys easy-to-understand scaling laws relating the output (nanoflare energy, temperature, density, intensity) to the input parameters (field strength, strand length, critical misalignment angle). The nanoflares have a powerlaw distribution with a universal slope of -2.5, independent of the input parameters. The repetition frequency of nanoflares, expressed in terms of the plasma cooling time, increases with strand length. We discuss the implications of our results for the problem of heating and evolution of active region coronal plasmas. © 2015. The American Astronomical Society. All rights reserved.

Fernandez F.M.,CONICET
Journal of Mathematical Chemistry | Year: 2014

The non-crossing rule for the energy levels of a parameter-dependent Hamiltonian is revisited and a flaw in a commonly accepted proof is revealed. Some aspects of avoided crossings are illustrated by means of simple models. One of them shows the close relationship between avoided crossings and exceptional points. © Springer International Publishing Switzerland 2014.

The role of heterochronic phenomena in molluscan evolution is insufficiently understood but potentially significant. The aim of this paper is to explore some paedomorphic trends in the evolution of the Myophorellidae (Bivalvia: Trigoniida). Early ontogeny of general shell shape and ornamentation of one species of Steinmanella was analyzed and compared to data obtained for three species of Myophorella: two belonging to the subgenus M. (Promyophorella) (one from the Jurassic and one from the Cretaceous) and one belonging to the Jurassic M. (Myophorella). For general shell shape, a geometric morphometric analysis was performed on lateral views of the shells. Regarding ornamentation, flank costal disposition on the marginal carina, tubercle separation and relative development of the sub-commarginal subset of flank costae were quantified. A qualitative analysis was also performed. A two-trend shell shape development is considered as primitive. The first trend is marked by a relative reduction of the posterior margin together with a relative elongation of the shell. A tangential opisthogyrate growth component characterizes the second trend. There is a transitional stage where both trends interact. Early flank ornamentation is characterized by two or three sub-commarginal costae, continuous through the area, after which oblique costae with fine tubercles start to form. The subgenus M. (Myophorella) evolved by paedomorphic retention of juvenile shell shape and ornamentation, resulting in a large shell with coarse tubercles. Shell morphology in Steinmanella evolved by paedomorphic suppression of the primitive second trend in the development of the shell, resulting in an orthogyrate shell shape, and the retention of juvenile ornamentation (coarse tubercles, more sub-commarginal costae, juvenile rates of costal disposition). The paedomorphic (most likely by deceleration) retention of juvenile shell morphology within the Myophorellidae seems to have been recurrent within the group, resulting in many cases of convergence, and obscuring the phylogenetic relationships among its species. © 2016 Elsevier Masson SAS.

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

The goal of this Letter is to calculate bound, resonant and scattering states in the coupled-channel formalism without relying on the boundary conditions at large distances. The coupled-channel solution is expanded in eigenchannel bases i.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may include discrete and discretized continuum (real or complex energy) single particle states. The coupled-channel solutions are computed through diagonalization in these bases. The method is applied to a few two-channel problems. The exact bound spectrum of the Poeschl-Teller potential is well described by using a basis of real energy continuum states. For deuteron described by Reid potential, the experimental energy and the S and D contents of the wave function are reproduced in the asymptotic limit of the cutoff energy. For the Noro-Taylor potential resonant state energy is well reproduced by using the complex energy Berggren basis. It is found that the expansion of the coupled-channel wave function in these eigenchannel bases requires less computational efforts than the use of any other basis. The solutions are stable and converge as the cutoff energy increases. © 2014 The Author.

Fernandez F.M.,CONICET
Journal of Mathematical Chemistry | Year: 2014

We discuss the application of perturbation theory to a system of particles confined in a spherical box. A simple argument shows that the particles behave almost independently in sufficiently strong confinement. We choose the helium atom with a moving nucleus as a particular example and compare results of first order with those for the nucleus clamped at the center of the box. We provide a suitable explanation for some numerical results obtained recently by other authors. © 2013 Springer Science+Business Media New York.

Moreno M.F.,Bariloche Atomic Center | Gonzalez Oliver C.J.R.,CONICET
Powder Technology | Year: 2011

Pure Al, Alumix 13 (Al-4.5. wt.% Cu 0.5. Mg 0.2 Si) powders and Alumix13 reinforced with 15. wt.% Saffil short fibers were compacted up to 250-386. MPa in an axial die to study their compacting behavior. The final relative densities D were higher than 0.95 for all unreinforced powders and 0.86 for the composite. Different micromechanical and phenomenological models were used to fit density-pressure relations. Arzt model describes the powder compaction with good agreement up to D ~ 0.85. Kawakita equation results as a best linear fit for all tests, but its compressibility parameter b is not in agreement with the hardening behavior of the composite. Panelli and Ambrosio equation could describe the data fairly well qualitatively for all compactions tests, however, over a limited pressure range. Finally, Konopicky relationship turned out to be very useful and fitted the densification data of all three materials quite well. Its slope from linear P vs. ln (1/(1 - D)) plots, is related to the yield stress and characterizes the work hardening developed during plastic deformation while the density was increased. Microhardness values increase with the compacting pressure and such tendency agrees with the rising values of yield stresses, obtained by Konopicky. © 2010 Elsevier B.V.

Gualtieri A.F.,CONICET
Journal of endocrinological investigation | Year: 2011

Controversial effects of bisphenol A (BPA) have been reported on testicular function. These differences might reflect dissimilar exposure conditions. Dose responses to toxicants may be non-linear, e.g. U-shaped, with effects at low and at high levels of exposure and lower or inexistent effects at intermediate levels. Sertoli cells produce high levels of glutathione (GSH) as a cell defense mechanism. In this study, we addressed the question whether the exposure to different doses of BPA could influence Sertoli cell GSH synthesis and recycling. Primary Sertoli cell cultures were exposed to various doses of BPA (0.5 nM-100 μM). Cell viability was measured as an outcome of toxic effect. GSH cell content was determined to evaluate cell response to toxicant exposure. Glutamate-cysteine ligase catalytic (GCLC) and modulatory (GCLM) subunit expression were assessed to estimate GSH synthesis, and GSH reductase (GR) expression to estimate GSH recycling. BPA 100 μM, but not lower doses, decreased cell viability. BPA 10 and 50 μM, but not lower doses, induced an increment in Sertoli cell GSH levels, due to a rapid upregulation of GCLC and GR and a slower upregulation of GCLM. High doses of BPA are deleterious for Sertoli cells. Intermediate doses do not affect Sertoli cell viability and increase cell content of GSH owing to increased GSH synthesis and recycling enzyme expression. Lower doses of BPA are not capable of eliciting a cell defense response. These observations may explain a non-linear dose response of Sertoli cells to BPA.

Gennari F.C.,CONICET | Gennari F.C.,Instituto Balseiro | Gennari F.C.,Bariloche Atomic Center
International Journal of Hydrogen Energy | Year: 2012

In the present study, the synthesis of two different LiBH 4-Y(BH4)3 and LiBH4-YH3 composites was performed by mechanochemical processing of the 4LiBH 4-YCl3 mixture and as-milled 4LiBH4-YCl 3 plus 3LiH. It was found that Y(BH4)3 and YH3 formed in situ during milling are effective to promote LiBH 4 destabilization but differ substantially from each other in terms of the dehydrogenation pathway. During LiBH4-Y(BH4) 3 dehydriding, Y(BH4)3 decomposes first generating in situ freshly YH3 and subsequently, it destabilizes LiBH4 with the formation of minor amounts of YB4. About 20% of the theoretical hydrogen storage was obtained via the rehydriding of YB4-4LiH-3LiCl at 400 °C and 6.5 MPa. As a novel result, a compound containing (B12H12)2- group was identified during dehydriding of Y(BH4)3. In the case of 4LiBH4-YH3 dehydrogenation, the increase of the hydrogen back pressure favors the formation of crystalline YB4, whereas a reduction to ≤0.1 MPa induces the formation of minor amounts of Li 2B12H12. Although for hydrogen pressures ≤0.1 MPa direct LiBH4 decomposition can occur, the main dehydriding pathway of 4LiBH4-YH3 composite yields YB 4 and LiH. The nanostructured composite obtained by mechanochemical processing gives good hydrogen storage reversibility (about 80%) regardless of the hydrogen back pressure. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Bauer E.,National University of La Plata | Bauer E.,CONICET | Garbarino G.,University of Turin
Physical Review C - Nuclear Physics | Year: 2010

The contribution of ground-state correlations (GSCs) to the nonmesonic weak decay of Λ12C and other medium to heavy hypernuclei is studied within a nuclear-matter formalism implemented in a local-density approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons, as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one- and two-nucleon induced decays. Together with fermion antisymmetrization, GSCs turn out to be important for an accurate determination of the decay widths. Besides opening the two-nucleon stimulated decay channels, for Λ12C GSCs are responsible for 14% of the rate Γ1 while increasing the Γn/Γp ratio by 4%. Our final results for Λ12C are ΓNM=0.98, Γn/Γp=0.34, and Γ2/ΓNM=0.26. The saturation property of ΓNM with increasing hypernuclear mass number is clearly observed. The agreement with data of our predictions for ΓNM, Γn/Γp, and Γ2 is rather good. © 2010 The American Physical Society.

Awruch C.A.,University of Tasmania | Awruch C.A.,CONICET
General and Comparative Endocrinology | Year: 2013

The class Chondrichthyes, that includes Elasmobranchii and Holocephali, is a diverse group of fish occupying a key position at the base of vertebrate evolution. Their evolutionary success is greatly attributed to their wide range of reproductive strategies controlled by different endocrine mechanics. As in other vertebrates, hormonal control of reproduction in chondrichthyans is mediated by the neuropeptide gonadotropin-releasing hormone (GnRH) that regulates the brain control of gonadal activity via a hypothalamus-pituitary-gonadal (HPG) axis. Chondrichthyans lack of a direct vascular supply from the hypothalamus to the zone of the pituitary where the gonadotropic activity resides, thus transport between these two zones likely occurs via the general circulation. In the brain of elasmobranchs, two groups of GnRH, GnRH-I and GnRH-II were identified, and the presence of two immunoreactive gonadotropins similar to the luteinising (LH) and follicle stimulating (FSH) hormones was identified in the pituitary. In holocephalans, only GnRH-II has been confirmed, and while gonadotropin activity has been found in the buccal pituitary lobe, the presence of gonadotropin receptors in the gonads remains unknowns. The diversity of reproductive strategies display by chondrichthyans makes it difficult to generalize the control of gametogenesis and steroidogenesis; however, some general patterns emerge. In both sexes, androgens and estrogens are the main steroids during gonadal growth; while progestins have maturational activity. Androgens also form the precursors for estrogen steroid production. Estrogens stimulate the hepatic synthesis of yolk and stimulate the development of different part of the reproductive tract in females. The role of other gonadal steroids may play in chondrichthyan reproduction remains largely unknown. Future work should concentrate in filling the gaps into the current knowledge of the HPG axis regulation, and the use of reproductive endocrinology as a non-lethal technique for management of chondrichthyan populations. © 2013 Elsevier Inc.

Bruls O.,University of Liege | Cardona A.,CONICET | Arnold M.,Martin Luther University of Halle Wittenberg
Mechanism and Machine Theory | Year: 2012

This paper studies a Lie group extension of the generalized-α time integration method for the simulation of flexible multibody systems. The equations of motion are formulated as an index-3 differential-algebraic equation (DAE) on a Lie group, with the advantage that rotation variables can be taken into account without the need of introducing any parameterization. The proposed integrator is designed to solve this equation directly on the Lie group without index reduction. The convergence of the method for DAEs is studied in detail and global second-order accuracy is proven for all solution components, i.e. for nodal translations, rotations and Lagrange multipliers. The convergence properties are confirmed by three benchmarks of rigid and flexible systems with large rotation amplitudes. The Lie group method is compared with a more classical updated Lagrangian method which is also formulated in a Lie group setting. The remarkable simplicity of the new algorithm opens interesting perspectives for real-time applications, model-based control and optimization of multibody systems. © 2011 Elsevier Ltd. All rights reserved.

A mathematical model to describe the amperometric response of a sandwich-type biosensor containing polyphenol oxidase as the recognition catalytic element is proposed. The model was solved numerically and the resulting nonlinear solution was used to simulate chronoamperometric curves as well as to estimate the concentration profiles of reagents and products of the enzymatic reaction within the sensor. Fromm's systematic method was applied to get a kinetic expression for the analysis of polyphenol oxidase enzymes. The simulated data are compared with curves corresponding to a biosensor prepared with an oxidase enzyme that reacts according to a ping-pong mechanism. Although in both cases oxygen is used as mediator of the enzymatic reaction, the electrochemical step can generate it back from the H2O2 released by enzymes such as glucose oxidase but it cannot do the same in the case of working with polyphenol oxidase. Most of the calculated profiles and related data are presented using dimensioned variables so that they can be directly compared with experimental results. Relevant parameters such as limit current, response-time, and sensitivity are analyzed as function of the thickness of membranes, concentration of enzyme and concentration of substrate. © 2014 Elsevier B.V. All rights reserved.

In spite of their central role in orchestrating immunity, dendritic cells (DCs) can also limit harmful reactions and promote immune tolerance by inducing T cell anergy or favoring the differentiation of T regulatory (T(reg)) cells. Several factors may influence the 'decision' of DCs to become immunogenic or tolerogenic including the nature of antigenic challenge, the engagement of selective pathogen recognition receptors (PRRs) and the balance of cytokines and growth factors. In addition, mounting evidence indicates a key role of endogenous lectins including C-type lectins, siglecs and galectins in shaping DC immunogenicity and tailoring adaptive immune responses, through recognition of specific 'glycan signatures' on invading pathogens or host cells. While galectins are in general secreted proteins that act in a paracrine or autocrine manner, all known siglecs and most C-type lectins are membrane-bound receptors that convey glycan-containing information into DC differentiation or maturation programs. Yet, some of the signaling pathways triggered by endogenous lectins converge in similar functional outcomes regardless of divergences in their structure, homology or glycan-binding specificity. To gain a more complete understanding on the role of protein-glycan interactions in DC biology, here we will integrate scattered information on these structurally-divergent but functionally-related lectins and their potential biomedical applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2014

We analyse the effect of the long-range potential of the ionic core on the photoelectron emission in atomic ionization by a linearly polarized subcycle sculpted laser pulse of two-colour components, where one frequency doubles the other. The total ionization yield consists mostly of direct electrons, which can be characterized by both intracycle and intercycle interferences. Using a semiclassical model based on the Simple Man's Model, we can derive an analytical expression for the intracycle interference due to the coherent superposition of different electron trajectories released in the same sculpted optical cycle. In turn, the intercycle interference is the consequence of the superposition of multiple trajectories released at different cycles and is accounted for by the energy conservation in the photon absorption process. We show that a semiclassical description in terms of a diffraction process at a time grating for two-colour laser pulses remains qualitatively unchanged beyond the strong field approximation. In particular, the Coulomb potential shifts the intracycle interference modulations towards the threshold, whereas the intercycle interference pattern remains invariant. The present study completes a recent work by Xie etal (2013 New J. Phys. 15 043050), where the influence of the Coulomb field on atomic ionization by sculpted two-colour laser fields is probed but in which path interferences are not considered. Furthermore, this article gives theoretical support to recent experiments with He and Ar where the sub-cycle interference structures originating from trajectories launched within a time interval of less than one femtosecond were observed (Xie X et al 2012 Phys. Rev. Lett. 108 193004). © 2014 IOP Publishing Ltd.

Agosta E.A.,Pontifical Catholic University of Argentina | Agosta E.A.,CONICET
International Journal of Climatology | Year: 2014

This work shows statistical evidence for lunar nodal cycle influence on the low-frequency summer rainfall variability over the plains to the east of subtropical Andes, in South America, through long-term sea surface temperature (SST) variations induced by the nodal amplitude of diurnal tides over southwestern South Atlantic (SWSA). In years of strong (weak) diurnal tides, tide-induced diapycnal mixing makes SST cooler (warmer) together with low (high) air pressures in the surroundings of the Malvinas/Falklands Islands in the SWSA, possibly through mean tropospheric baroclinicity variations. As the low-level tropospheric circulation anomalies directly affect the interannual summer rainfall variability, such an influence can be extended to the bi-decadal variability present in the summer rainfall owing to the nodal modulation effect observed in the tropospheric circulation. The identification of the nodal periodicity in the summer rainfall variability is statistically robust. © 2013 Royal Meteorological Society.

Megalonychidae are known from the Deseadan of Argentina and Bolivia to the present, represented by the tree sloth Choloepus Illiger. The principal fossil records of this clade are those from the Quaternary of Central America and the Antilles (e.g., Megalocnus Leidy, Acratocnus Anthony) and North America (e.g., Megalonyx Harlan, Pliometanastes Hirschfeld and Webb). From the Quaternary of South America, Megalonychidae are recorded in Peru (Diabolotherium Pujos, De Iuliis, Argot and Werdelin) and Brazil (e.g., Ahytherium Cartelle, De Iuliis and Pujos, Australonyx De Iuliis, Pujos and Cartelle). In Argentina they also have been recorded in the Santa Cruz Formation (early-middle Miocene) on the coast of Santa Cruz Province (Eucholaeops Ameghino), Arroyo Chasicó Formation (Protomegalonyx Kraglievich), Río Negro Formation, in the " conglomerado osífero" (ossiferous conglomerate) or " Mesopotamiense" (late Miocene) at the base of Ituzaingó Formation, Entre Ríos Province, and Pleistocene of Buenos Aires Province. Several authors have studied the Megalonychidae from the " conglomerado osífero", but no systematic revision of the group has been undertaken beyond the original naming of species. Taking into account that a broad range of individual variation has been observed in the Megalonychidae from the Pleistocene of North America and the West Indies, and that a similar range probably existed among the megalonychids from the " conglomerado osífero", then the number of valid species might be lower than previously proposed. Thus, the valid species recovered from the " conglomerado osífero" are Ortotherium laticurvatum Ameghino, Pliomorphus mutilatus Ameghino, Amphiocnus paranense Kraglievich, Protomegalonyx doellojuradoi Kraglievich, Pr. Praecursor Kraglievich, Megalonychops primigenius Kraglievich, and Paranabradys vucetichae Scillato-Yané. However, the establishment of synonymies, as well as the generic and specific assignation of the specimens is not an easy task, due to the peculiar taphonomical context of this stratigraphic unit. © 2010 Elsevier Masson SAS.

Paulina Carabajal A.,CONICET
Journal of Vertebrate Paleontology | Year: 2011

Carnotaurus sastrei is a large abelisaurid dinosaur from the Upper Cretaceous of Patagonia. Its remains include an almost complete skeleton with a well-preserved skull and braincase. Because relatively few abelisaurid braincases are known, the description of the Carnotaurus braincase is important for understanding the variability of this complex structure within the clade. Carnotaurus exhibits traits that characterize the abelisaurid basicranium, such as a well-developed preotic pendant, solid basipterygoid processes, and pneumatic basisphenoid, subsellar, and lateral tympanic recesses. The basipterygoid processes do not project laterally, unlike the divergent processes observed in other abelisaurids. Carnotaurus shares with the Malagasy abelisaurid Majungasaurus crenatissimus caudodorsally oriented paroccipital processes and a maxillomandibular foramen for the trigeminal nerve that in lateral view is aligned with the nuchal crest. The detailed description of the braincase of Carnotaurus presented here provides a better cranial anatomical record of this Patagonian abelisaurid and preliminary insights to the neurocranial morphology within the group. © 2011 by the Society of Vertebrate Paleontology.

Tang Y.,University of California at San Diego | Bringa E.M.,CONICET | Remington B.A.,Lawrence Livermore National Laboratory | Meyers M.A.,University of California at San Diego
Acta Materialia | Year: 2011

The growth and collapse of nanoscale voids are investigated for tantalum (a model body-centered cubic metal) under different stress states and strain rates by molecular dynamics (MD). Three principal mechanisms of deformation are identified and quantitatively evaluated: (i) shear loop emission and subsequent expansion from the surface of the void; (ii) cooperative shear loop emission from slip planes that are parallel to the same 〈1 1 1〉 slip direction and their combination, forming prismatic loops; (iii) twinning starting at the void surface. The generation and evolution of these defects are found to be functions of stress state and strain rate. Dislocations are found to propagate preferably on {1 1 0} and {1 1 2} planes, with Burgers vectors 1/2 〈1 1 1〉. The dislocation shear loops generated expand in a crystallographic manner, and in hydrostatic tension and compression generate prismatic loops that detach from the void. In uniaxial tensile strain along [1 0 0], the extremities of the shear loops remain attached to the void surface, a requisite for void growth. In uniaxial compressive strain, the extremities of the shear loops can also detach from the void surface. The difference in defect evolution is explained by the equal resolved shear stress in the hydrostatic loading case, in contrast with uniaxial strain loading. Nanotwins form preferably upon both uniaxial tensile strain and hydrostatic stress (in tension) and there is a slip-to-twinning transition as the strain rate exceeds 108 s -1. A simplified constitutive description is presented which explains the preponderance of twinning over slip in tension beyond a critical strain rate. The formation of both dislocations and twins is confirmed through laser compression experiments, which provide strain rates (∼108 s -1) comparable to MD. The dislocation velocities are determined by tracking the edge component of the expanding loops and are found to be subsonic even at extremely high stress and strain rates: 680 m s-1 for 10 8 s-1 and 1020 m s-1 for 109 s -1. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Miller Bertolami M.M.,Max Planck Institute for Astrophysics | Miller Bertolami M.M.,CONICET
Astronomy and Astrophysics | Year: 2014

Context. Recent determinations of the white dwarf luminosity function (WDLF) from very large surveys have extended our knowledge of the WDLF to very high luminosities. This, together with the availability of new full evolutionary white dwarf models that are reliable at high luminosities, have opened the possibility of testing particle emission in the core of very hot white dwarfs, where neutrino processes are dominant. Aims. We use the available WDLFs from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey to constrain the value of the neutrino magnetic dipole moment (μν). Methods. We used a state-of-the-art stellar evolution code to compute a grid of white dwarf cooling sequences under the assumptions of different values of μν. Then we constructed theoretical WDLFs for different values of μν and performed a χ2-test to derive constraints on the value of μν. Results. We find that the WDLFs derived from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey do not yield consistent results. The discrepancy between the two WDLFs suggests that the uncertainties are significantly underestimated. Consequently, we constructed a unified WDLF by averaging the SDSS and SSS and estimated the uncertainties by taking into account the differences between the WDLF at each magnitude bin. Then we compared all WDLFs with theoretical WDLFs. Comparison between theoretical WDLFs and both the SDSS and the averaged WDLF indicates that μν should be μν < 5 × 10 -12 eħ/(2mec). In particular, a χ2-test on the averaged WDLF suggests that observations of the disk WDLF exclude values of μν > 5 × 10 -12eħ/(2mec) at more than a 95% confidence level, even when conservative estimates of the uncertainties are adopted. This is close to the best available constraints on μν from the physics of globular clusters. Conclusions. Our study shows that modern WDLFs, which extend to the high-luminosity regime, are an excellent tool for constraining the emission of particles in the core of hot white dwarfs. However, discrepancies between different WDLFs suggest there might be some relevant unaccounted systematic errors. A larger set of completely independent WDLFs, as well as more detailed studies of the theoretical WDLFs and their own uncertainties, is desirable to explore the systematic uncertainties behind this constraint. Once this is done, we believe the Galactic disk WDLF will offer constraints on the magnetic dipole moment of the neutrino similar to the best available constraints obtainable from globular clusters. © 2014 ESO.

Murgida G.E.,CONICET | Ganduglia-Pirovano M.V.,Institute Catalisis Y Petroleoquimica Of The Consejo Superior Of Investigaciones Cientificas
Physical Review Letters | Year: 2013

Oxygen vacancies on ceria (CeO2) surfaces play a crucial role in catalytic applications, yet whether vacancies are at surface or subsurface sites on reduced CeO2(111), and whether vacancies agglomerate or repel each other, is still under discussion, with few and inconsistent experimental results. By combining density-functional theory (DFT) in the DFT+U (U is an effective onsite Coulomb interaction parameter) approach and statistical thermodynamics, we show that the energetically most stable near-surface oxygen vacancy structures for a broad range of vacancy concentrations, Θ (116≤Θ≤1 monolayer) have all vacancies at subsurface oxygen sites and predict that the thermodynamically stable phase for a wide range of reducing conditions is a (2×2) ordered subsurface vacancy structure (Θ=14). Vacancy-induced lattice relaxations effects are crucial for the interpretation of the repulsive interactions, which are at the basis of the vacancy spacing in the (2×2) structure. The findings provide theoretical data to support the interpretation of the most recent experiments, bringing us closer to solving the debate. © 2013 American Physical Society.

Grosse C.,National University of Tucuman | Grosse C.,CONICET
Journal of Physical Chemistry B | Year: 2011

A rigorous extension of the classic Dukhin-Shilov thin double layer polarization theory including the stagnant layer conductivity is presented. Precisely the same assumptions and approximations made in the original theory are maintained, and the same adsorption isotherms are used as in most of the existing numerical calculations. The obtained analytical results improve upon existing approximate extensions, mainly for low surface conductivities and high surface potentials and for high surface conductivities and low surface potentials. Moreover, they avoid the assumption that all the adsorbed ions in the stagnant layer must have a single sign. Finally, they present a very good agreement with numerical calculations specifically made using the same system parameters. © 2011 American Chemical Society.

Reynoso M.M.,National and Kapodistrian University of Athens | Reynoso M.M.,CONICET
Astronomy and Astrophysics | Year: 2014

Context. Gamma-ray bursts (GRB) are the most powerful events in the universe. They are capable of accelerating particles to very high energies, so are strong candidates as sources of detectable astrophysical neutrinos. Aims. We study the effects of particle acceleration and escape by implementing a two-zone model in order to assess the production of high-energy neutrinos in GRBs associated with their prompt emission. Methods. Both primary relativistic electrons and protons are injected in a zone where an acceleration mechanism operates and dominates over the losses. The escaping particles are re-injected in a cooling zone that propagates downstream. The synchrotron photons emitted by the accelerated electrons are taken as targets for pγ interactions, which generate pions along with the pp collisions with cold protons in the flow. The distribution of these secondary pions and the decaying muons are also computed in both zones, from which the neutrino output is obtained. Results. We find that for escape rates lower than the acceleration rate, the synchrotron emission from electrons in the acceleration zone can account for the GRB emission, and the production of neutrinos via pγ interactions in this zone becomes dominant for Eν > 105 GeV. For illustration, we compute the corresponding diffuse neutrino flux under different assumptions and show that it can reach the level of the signal recently detected by IceCube. © 2014 ESO.

Azcoitia I.,Complutense University of Madrid | Arevalo M.-A.,Instituto Cajal | De Nicola A.F.,CONICET | Garcia-Segura L.M.,Complutense University of Madrid
Trends in Endocrinology and Metabolism | Year: 2011

Results from animal experiments showing that estradiol is neuroprotective were challenged 10 years ago by findings indicating an increased risk of dementia and stroke in women over 65 years of age taking conjugated equine estrogens. Our understanding of the complex signaling of estradiol in neural cells has recently clarified the causes of this discrepancy. New data indicate that estradiol may lose its neuroprotective activity or even increase neural damage, a situation that depends on the duration of ovarian hormone deprivation and on age-associated modifications in the levels of other molecules that modulate estradiol action. These studies highlight the complex neuroprotective mechanisms of estradiol and suggest a window of opportunity during which effective hormonal therapy could promote brain function and cognition. © 2011 Elsevier Ltd.

Garbarz A.,National University of La Plata | Leston M.,CONICET
Journal of High Energy Physics | Year: 2014

We revisit the description of the space of asymptotically AdS3 solutions of pure gravity in three dimensions with a negative cosmological constant as a collection of coadjoint orbits of the Virasoro group. Each orbit corresponds to a set of metrics related by diffeomorphisms which do not approach the identity fast enough at the boundary. Orbits contain more than a single element and this fact manifests the global degrees of freedom of AdS3 gravity, being each element of an orbit what we call boundary graviton. We show how this setup allows to learn features about the classical phase space that otherwise would be quite difficult. Most important are the proof of energy bounds and the characterization of boundary gravitons unrelated to BTZs and AdS3. In addition, it makes manifest the underlying mathematical structure of the space of solutions close to infinity. Notably, because of the existence of a symplectic form in each orbit, being this related with the usual Dirac bracket of the asymptotic charges, this approach is a natural starting point for the quantization of different sectors of AdS3 gravity. We finally discuss previous attempts to quantize coadjoint orbits of the Virasoro group and how this is relevant for the formulation of AdS3 quantum gravity. © 2014 The Authors.

Goicoechea H.C.,National University of Santa | Olivieri A.C.,CONICET | Tauler R.,CSIC - Institute of Environmental Assessment And Water Research
Analyst | Year: 2010

Correlation constrained multivariate curve resolution-alternating least-squares is shown to be a feasible method for processing first-order instrumental data and achieve analyte quantitation in the presence of unexpected interferences. Both for simulated and experimental data sets, the proposed method could correctly retrieve the analyte and interference spectral profiles and perform accurate estimations of analyte concentrations in test samples. Since no information concerning the interferences was present in calibration samples, the proposed multivariate calibration approach including the correlation constraint facilitates the achievement of the so-called second-order advantage for the analyte of interest, which is known to be present for more complex higher-order richer instrumental data. The proposed method is tested using a simulated data set and two experimental data systems, one for the determination of ascorbic acid in powder juices using UV-visible absorption spectral data, and another for the determination of tetracycline in serum samples using fluorescence emission spectroscopy. © 2010 The Royal Society of Chemistry.

Martinez E.A.,University of Buenos Aires | Paz J.P.,University of Buenos Aires | Paz J.P.,CONICET
Physical Review Letters | Year: 2013

We analyze the evolution of the quantum state of networks of quantum oscillators coupled with arbitrary external environments. We show that the reduced density matrix of the network always obeys a local master equation with a simple analytical solution. We use this to study the emergence of thermodynamical laws in the long time regime demonstrating two main results: First, we show that it is impossible to build a quantum absorption refrigerator using linear networks (thus, nonlinearity is an essential resource for such refrigerators recently studied by Levy and Kosloff and Levy et al.). Then, we show that the third law imposes constraints on the low frequency behavior of the environmental spectral densities. © 2013 American Physical Society.

Superina M.,CONICET | Pagnutti N.,National University of La Plata | Abba A.M.,National University of La Plata
Mammal Review | Year: 2014

Basic knowledge on the biology and ecology of a species is fundamental for the realistic assessment of its conservation status and for planning effective conservation strategies. The latest assessment of the 21 extant armadillo species (Xenarthra, Dasypodidae) by the International Union for Conservation of Nature (IUCN) for its Red List of Threatened Species shows that considerable gaps exist in our knowledge of these Neotropical mammals. Our goal was to analyse the existing literature on armadillos to define thematic and regional research priorities that will eventually benefit their conservation. We categorized 3117 publications on extant armadillos published between 1660 and 2011 according to their research topic, species studied, country and publication language. The number of publications per research topic and the number per species were very variable. The nine best-studied species are classed as Least Concern by the IUCN, while three of the four least-studied species are classed as Data Deficient. At least one field study was done in each range country, but over 80% of field research took place in the USA, Brazil, Argentina and Bolivia. Most research was done in the USA on leprosy in Dasypus novemcinctus. Most ecological research has been focused on four species, and data on the ecology of Data Deficient and Vulnerable taxa are virtually absent. Field research on armadillos should be intensified to broaden conservation-relevant knowledge. Additional studies in the Guianas, Peru, Ecuador, Colombia, Venezuela and Paraguay are urgently needed to assess the conservation status of armadillos in these regions. Future research should focus on ecology, conservation, population genetics, reproduction and threats. Species priorities should include country endemics, such as Dasypus pilosus (Peru), Tolypeutes tricinctus (Brazil) and Dasypus yepesi and Chlamyphorus truncatus (Argentina), as well as other Data Deficient and Vulnerable species, especially Cabassous centralis and Calyptophractus retusus. © 2013 The Mammal Society and John Wiley & Sons Ltd.

Olivieri A.C.,CONICET
Analytical Methods | Year: 2012

This critical review discusses the advances which have taken place in recent years in the field of multi-way instrumental data, i.e., data that can be arranged into a mathematical object of at least three ways (when they are measured for a group of samples). Particular focus is directed towards research works describing quantitative analytical calibrations. The development of data processing algorithms and the estimation of figures of merit are reviewed, along with the progress in the experimental generation of new three-, four- and five-way data of spectroscopic, chromatographic and electrochemical origin. © 2012 The Royal Society of Chemistry.

Balzarotti F.,Max Planck Institute for Biophysical Chemistry | Stefani F.D.,CONICET
ACS Nano | Year: 2012

Figure Persented: Plasmonics and near-field optical nanoscopy both deal with expanding optics into the subwavelength regime. However, these two fields have so far followed parallel paths of development and only recently have researchers started to explore combinations of their concepts with potential synergy. In this Perspective, we provide an up-to-date summary of the successful combinations reported and give insight into some new possibilities. © 2012 American Chemical Society.

Vila G.S.,CONICET | Romero G.E.,National University of La Plata
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present a general self-consistent lepto/hadronic jet model for the non-thermal electromagnetic emission of microquasars. The model is applied to the low-mass microquasar (LMMQ) GX 339-4 and predicts its high-energy features. We assume that both leptons and hadrons are accelerated up to relativistic energies by diffusive shock acceleration and calculate their contribution to the electromagnetic spectrum through all main radiative processes. The radiative contribution of secondary particles (pions, muons and electron-positron pairs) is included. We use a set of simultaneous observations in radio and X-rays to constrain the model parameters and find the best fit to the data. We obtain different spectral energy distributions that can explain the observations, and make predictions for the high-energy emission. Observations with gamma-ray instruments like Fermi can be used to test the model and determine the proton content of the jets. Finally, we estimate the positron injection in the surrounding medium. Our findings support the suggested association between LMMQs and the observed distribution of the 511 keV line flux observed by INTEGRAL. © 2010 The Authors. Journal compilation © 2010 RAS.

Ancarani L.U.,University of Lorraine | Rodriguez K.V.,CONICET
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

Two-electron atoms embedded in a plasma environment are studied with screened and exponential cosine screened Coulomb model potentials. Within a configuration interaction approach, and using parameter-free explicitly correlated basis functions, we have calculated the ground-state and first excited-state energies (and other mean values) for H-, He, and Li+. We analyze their evolution with the screening parameter and provide simple fits, which allow for practical and rapid evaluations for example in plasma applications. © 2014 American Physical Society.

Eiroa E.F.,Institute Astronomia | Simeone C.,CONICET
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study circular shells in a (2+1)-dimensional background within the framework of Einstein-Born-Infeld theory. For shells around black holes we analyze the mechanical stability under perturbations preserving the symmetry. Shells around vacuum are also discussed. We find a large range in the values of the parameters compatible with stable configurations. © 2013 American Physical Society.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

The large-deviation method can be used to study the measurement trajectories of open quantum systems. For optical arrangements this formalism allows to describe the long time properties of the (nonequilibrium) photon counting statistics in the context of a (equilibrium) thermodynamic approach defined in terms of dynamical phases and transitions between them in the trajectory space. In this paper, we study the thermodynamic approach for fluorescent systems coupled to complex reservoirs that induce stochastic fluctuations in their dynamical parameters. In a fast modulation limit the thermodynamics corresponds to that of a Markovian two-level system. In a slow modulation limit, the thermodynamic properties are equivalent to those of a finite system that in an infinite-size limit is characterized by a first-order transition. The dynamical phases correspond to different intensity regimes, while the size of the system is measured by the transition rate of the bath fluctuations. As a function of a dimensionless intensive variable, the first and second derivatives of the thermodynamic potential develop an abrupt change and a narrow peak, respectively. Their scaling properties are consistent with a double-Gaussian probability distribution of the associated extensive variable. © 2010 The American Physical Society.

Argentine hemorrhagic fever (AHF) is an endemo-epidemic disease caused by Junín virus (JUNV), a member of the arenaviridae family. Although a recently introduced live attenuated vaccine has proven to be effective, AHF remains a potentially lethal infection. Like in other viral hemorrhagic fevers (VHF), AHF patients present with fever and hemorrhagic complications. Although the causes of the bleeding are poorly understood, impaired hemostasis, endothelial cell dysfunction and low platelet counts have been described. Thrombocytopenia is a common feature in VHF syndromes, and it is a major sign for its diagnosis. However, the underlying pathogenic mechanism has not yet been elucidated. We hypothesized that thrombocytopenia results from a viral-triggered alteration of the megakaryo/thrombopoiesis process. Therefore, we evaluated the impact of JUNV on megakaryopoiesis using an in vitro model of human CD34+ cells stimulated with thrombopoietin. Our results showed that CD34+ cells are infected with JUNV in a restricted fashion. Infection was transferrin receptor 1 (TfR1)-dependent and the surface expression of TfR1 was higher in infected cultures, suggesting a novel arenaviral dissemination strategy in hematopoietic progenitor cells. Although proliferation, survival, and commitment in JUNV-infected cultures were normal, viral infection impaired thrombopoiesis by decreasing in vitro proplatelet formation, platelet release, and P-selectin externalization via a bystander effect. The decrease in platelet release was also TfR1-dependent, mimicked by poly(I:C), and type I interferon (IFN alpha/beta) was implicated as a key paracrine mediator. Among the relevant molecules studied, only the transcription factor NF-E2 showed a moderate decrease in expression in megakaryocytes from either infected cultures or after type I IFN treatment. Moreover, type I IFN-treated megakaryocytes presented ultrastructural abnormalities resembling the reported thrombocytopenic NF-E2(-/-) mouse phenotype. Our study introduces a potential mechanism for thrombocytopenia in VHF and other diseases associated with increased bone marrow type I IFN levels.

Journal of Arid Environments | Year: 2016

Grazing by domestic livestock in the Caldenal rangelands has been threatening the ecological balance of this unique biome located in the semiarid zone of central Argentina. The aim of this review was to describe and explain the floristic changes observed in grazed rangelands in the southern Caldenal, discuss management alternatives for the conservation of desirable plant communities, and identify gaps in current knowledge of this distinctive ecosystem. Grazing-induced modification in the species composition entails the replacement of palatable grasses by unpalatable grasses and/or woody plants. Coarse grass and shrub encroachment represents discontinuous stable changes that lead to undesirable regimes in terms of functionality of primary ecological processes, species diversity, carrying capacity, and the economic productivity of livestock operations. Recovery of the desirable regime dominated by palatable grasses requires active restoration technology, which is often constrained by climatic and economic factors. Conservation of the regime dominated by palatable grasses calls for flexible stocking rates and intermittent grazing in replacement of current fixed stocking rates and continuous grazing. However, there is a basic need for more research related to restoration alternatives, grazing management, and for the development of simulation models to encompass the complexity of the system and assess the ecological and economic consequences of different management options of the southern Caldenal rangelands. © 2016 Elsevier Ltd

Samame C.,University of Buenos Aires | Samame C.,CONICET
Psychiatry Research | Year: 2013

Although it is now well documented that bipolar disorder (BD) often presents with cognitive deficits and suboptimal social adjustment, the social cognitive profile of the illness throughout its three phases remains unclear. An extensive search was conducted through the online databases EBSCO, PsychInfo, PubMed, ScienceDirect, and Wiley-Blackwell, covering the period between 1990 and 2012. Fifty-one studies comparing the social cognitive performance of bipolar patients with that of healthy controls were identified. Deficits in emotion recognition and theory of mind were found in manic, depressed, and euthymic bipolar subjects. Furthermore, altered face emotion recognition and brain-related abnormalities were noted both in euthymic patients and subjects at risk for BD. The influence of clinical and neurocognitive variables on the social cognitive performance of bipolar patients remains to be ascertained. Future directions for research are discussed. © 2013 Elsevier Ireland Ltd.

Tissera P.B.,CONICET | Tissera P.B.,Max Planck Institute for Astrophysics | White S.D.M.,Max Planck Institute for Astrophysics | Scannapieco C.,Leibniz Institute for Astrophysics Potsdam
Monthly Notices of the Royal Astronomical Society | Year: 2012

We study the chemical properties of the stellar populations in eight simulations of the formation of Milky Way mass galaxies in a Λ cold dark matter universe. Our simulations include metal-dependent cooling and an explicitly multiphase treatment of the effects on the gas of cooling, enrichment and supernova feedback. We search for correlations between formation history and chemical abundance patterns. Differing contributions to spheroids and discs from in situ star formation and from accreted populations are reflected in differing chemical properties. Discs have younger stellar populations, with most stars forming in situ and with low α-enhancement from gas which never participated in a galactic outflow. Up to 15per cent of disc stars can come from accreted satellites. These tend to be α-enhanced, older and to have larger velocity dispersions than the in situ population. Inner spheroids have old, metal-rich and α-enhanced stars which formed primarily in situ, more than 40per cent from material recycled through earlier galactic winds. Few accreted stars are found in the inner spheroid unless a major merger occurred recently. Such stars are older, more metal-poor and more α-enhanced than the in situ population. Stellar haloes tend to have low metallicity and high α-enhancement. The outer haloes are made primarily of accreted stars. Their mean metallicity and α-enhancement reflect the masses of the disrupted satellites where they formed: more massive satellites typically have higher [Fe/H] and lower [α/Fe]. Surviving satellites have distinctive chemical patterns which reflect their extended, bursty star formation histories. These produce lower α-enhancement at given metallicity than in the main galaxy, in agreement with observed trends in the Milky Way. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

The purpose of this study was to achieve a hypothesis explaining the biogeographical history of the family Fanniidae, especially that of the species from Patagonia, the Neotropics, Australia, and New Zealand. We used "dispersal-vicariance analysis" (DIVA), an event-based parsimony method, to analyze the most parsimonious phylogenetic hypothesis for the family, obtained by Domínguez & Roig-Juñent (2008). The analysis resulted in 32800 alternative equally optimal reconstructions that indicate that the ancestor of the Fanniidae was widely distributed across different regions of the world, which along with the subsequent separation of two clades that correspond to the Laurasic and Gondwanan Landmasses allow the proposal of an older age than in previous hypothesis (Late Jurassic or early Cretaceous times instead of upper Cretaceous) and a Pangeic origin for the Fanniidae. The northern hemisphere species of Fanniidae included in this study highlight the difficulty that arises when analysing with DIVA a tree with a large amount of paralogy or redundant distributions, as illustrated here with several examples. The southern hemisphere species of Fanniidae indicate a clear pattern of vicariance and dispersal consistent with the rupture of Gondwana. © Sociedad de Biología de Chile.

Jakovcevic A.,CONICET | Steg L.,University of Groningen
Transportation Research Part F: Traffic Psychology and Behaviour | Year: 2013

Most Latin American countries face important environmental and societal problems associated with an increase in car traffic, and only recently, transport policies aimed at reducing these harmful consequences of car use have begun to be discussed and put on the public agenda of these countries. Surprisingly, little is known about the factors influencing the acceptability of transport policies and intentions to reduce car use in Latin America, as studies on acceptability of transport policies have typically been conducted in Europe. Previous evidence from European samples - where reducing car used had been widely discussed - showed that the Value-Belief-Norm (VBN) theory of environmentalism was an adequate theoretical framework to predict the acceptability of a transport pricing policy, as well as the intention to reduce car use when this policy would be implemented. But can these results be generalised to non-European samples? In this paper, we report results of a questionnaire study among 160 participants from Buenos Aires, Argentina, aimed to test the VBN theory. We found that the VBN theory was indeed also successful in explaining policy acceptability and intention to reduce car use in Argentina. In addition, we found support for the causal structure of the variables in VBN theory. Interestingly, biospheric and hedonic values were also directly and significantly related to feelings of moral obligation when intermediate variables were controlled for. These results suggest that normative considerations, activated by values, indeed predict policy acceptability and the intention to reduce car use in Argentina and that these considerations should be taken into account to increase the acceptability of policies aimed at reducing car use. © 2013 Elsevier B.V.

Craviotti C. Producer relationships and local development in fresh fruit commodity chains: an analysis of blueberry production in Entre Ríos, Argentina, Regional Studies. In current regional perspectives intangible capitals are considered critical assets of regional economies. The aim of this article is to analyse the role of networks in the development of blueberry production in the province of Entre Ríos, nowadays the most important productive area of Argentina. It argues that although horizontal networks (either private or public-private) were not particularly important for the emergence of blueberry production in the area, they are needed in a situation where a redefinition of the agri-food chain is at stake. Coordination and cooperation networks could help to sustain the continuity of production at the local level and to make local small-scale producers viable in a global context. © 2012 Copyright Regional Studies Association.

Duarte L.,University of the Republic of Uruguay | Gonzalez-Sprinberg G.A.,University of the Republic of Uruguay | Sampayo O.A.,CONICET
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We investigate the possibility of detecting Majorana neutrinos at the Large Hadron-electron Collider, an electron-proton collision mode at CERN. We study the lj++3jets (lj≡e,μ,τ) final states that are, due to leptonic number violation, a clear signature for intermediate Majorana neutrino contributions. Such signals are not possible if the heavy neutrinos have Dirac nature. The interactions between Majorana neutrinos and the Standard Model particles are obtained from an effective Lagrangian approach. We present our results for the total cross section as a function of the neutrino mass, the effective couplings, and the new physics scale. We also show the discovery region as a function of the Majorana neutrino mass and the effective couplings. Our results show that the Large Hadron-electron Collider may be able to discover Majorana neutrinos with masses lower than 700 and 1300 GeV for electron beams settings of Ee=50GeV and Ee=150GeV, respectively. © 2015 American Physical Society.

Ardenghi J.S.,CONICET
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

The aim of this work is to compute the entanglement entropy of real and virtual particles by rewriting the generating functional of φ4 theory as a mean value between states and observables defined through the correlation functions. Then the von Neumann definition of entropy can be applied to these quantum states and in particular, for the partial traces taken over the internal or external degrees of freedom. This procedure can be done for each order in the perturbation expansion showing that the entanglement entropy for real and virtual particles behaves as ln(m0). In particular, entanglement entropy is computed at first order for the correlation function of two external points showing that mutual information is identical to the external entropy and that conditional entropies are negative for all the domain of m0. In turn, from the definition of the quantum states, it is possible to obtain general relations between total traces between different quantum states of a φr theory. Finally, discussion about the possibility of taking partial traces over external degrees of freedom is considered, which implies the introduction of some observables that measure space-time points where an interaction occurs. © 2015 American Physical Society.

Motor execution and planning are tightly regulated by dopamine D1 and D2 receptors present in basal ganglia circuits. Although stimulation of D1 receptors is known to enhance motor function, the global effect of D2 receptor (D2R) stimulation or blockade remains highly controversial, with studies showing increasing, decreasing or no changes in motor activity. Moreover, pharmacological and genetic attempts to block or eliminate D2R have led to controversial results that questioned the importance of D2R in motor function. In this study, we generated an inducible Drd2 null-allele mouse strain that circumvented developmental compensations found in constitutive Drd2-/- mice and allowed us to directly evaluate the participation of D2R in spontaneous locomotor activity and motor learning. We have found that loss of D2R during adulthood causes severe motor impairments, including hypolocomotion, deficits in motor coordination, impaired learning of new motor routines and spontaneous catatonia. Moreover, severe motor impairment, resting tremor and abnormal gait and posture, phenotypes reminiscent of Parkinson’s disease, were evident when the mutation was induced in aged mice. Altogether, the conditional Drd2 knockout model studied here revealed the overall fundamental contribution of D2R in motor functions and explains some of the side effects elicited by D2R blockers when used in neurological and psychiatric conditions, including schizophrenia, bipolar disorder, Tourette’s syndrome, dementia, alcohol-induced delusions and obsessive-compulsive disorder.Molecular Psychiatry advance online publication, 19 July 2016; doi:10.1038/mp.2016.105. © 2016 Macmillan Publishers Limited

Elgoyhen A.B.,CONICET | Elgoyhen A.B.,University of Buenos Aires | Langguth B.,University of Regensburg | De Ridder D.,University of Otago | Vanneste S.,University of Texas at Dallas
Nature Reviews Neuroscience | Year: 2015

Tinnitus is the perception of phantom sound in the absence of a corresponding external source. It is a highly prevalent disorder, and most cases are caused by cochlear injury that leads to peripheral deafferentation, which results in adaptive changes in the CNS. In this article we critically assess the recent neuroimaging studies in individuals with tinnitus that suggest that the disorder is accompanied by functional and structural brain abnormalities in distributed auditory and non-auditory brain regions. Moreover, we consider how the identification of the neuronal mechanisms underlying the different forms of tinnitus would benefit from larger studies, replication and comprehensive clinical assessment of patients. © 2015 Macmillan Publishers Limited.

The vegetation occurring between Bardas Blancas and Pehuenche Pass in the south of Mendoza is studied for the purpose of obtaining floristic-ecological information about plant communities. Work is carried out along an altitudinal gradient from 1420 to 2800 m a.s.l., using phytosociological method. The major plant communities yielded by analyses of comparative survey tables are described. In all, 19 plant communities are revealed, including high- and low-altitude wetlands, and 24 floristic groups characterized by diagnostic, exclusive, preferential and accompanying species. Analysis of dispersal and of hierarchical conglomerates allows confirming the close relationships of plant communities with temperature and altitude. The chorological analysis allowed to identificate two phytogeographic provinces: Patagonia and High Andes. There is a floristic-ecological relationship of phytogeographic environments with life forms. The phytosociological study revealed three vegetation belts: 1- scrubland of Neosparton ephedroides, Larrea nitida, Colliguaja integerrima and Fabiana imbricata, 2- scrubland of Adesmia volckmannii, Chuquiraga oppositifolia, Adesmia pinifolia and Adesmia obovata, and 3- steppe of Azorella monantha, Nassauvia revoluta, Empetrum rubrum and Ochetophila nana. The results may probably allow extrapolation in the north and south of the area.

Aguirre R.,National University of La Plata | Aguirre R.,CONICET
Physical Review C - Nuclear Physics | Year: 2012

The phase diagram of the superfluid phase coupled to spin singlet (S=0) and isospin triplet (T=1) states in infinite nuclear matter is analyzed within the nonrelativistic Skyrme model. We use an approach that allows a unified and consistent treatment of the particle-hole and particle-particle channels. The gap equation is solved for the full range of accessible densities, isospin asymmetries, and temperatures. The characteristic features of each of the components T z=0,±1 are emphasized. The search for signatures of a BCS-BEC crossover yields negative results within the scheme proposed. © 2012 American Physical Society.

Physical Review C - Nuclear Physics | Year: 2012

The pairing Hamiltonian constitutes an important approximation in many-body systems; it is exactly soluble and quantum integrable. On the other hand, the continuum single-particle level density (CSPLD) contains information about the continuum energy spectrum. The question of whether one can use the Hamiltonian with constant pairing strength for correlations in the continuum is still unanswered. In this paper we generalize the Richardson exact solution for the pairing Hamiltonian including correlations in the continuum. The resonant and nonresonant continua are included through the CSPLD. The resonant correlations are made explicit by using the Cauchy theorem. Low-lying states with seniority 0 and 2 are calculated for the even carbon isotopes. We conclude that energy levels can indeed be calculated with constant pairing in the continuum using the CSPLD. It is found that the nucleus 24C is unbound. The real and complex energy representations of the continuum is developed and their differences are shown. The trajectory of the pair energies in the continuum for the nucleus 28C is shown. © 2012 American Physical Society.

This paper focuses on the dynamic mechanisms that create favorable conditions for the occurrence of frosts that affect large areas of Argentina and are denominated generalized frosts (GF). The hemispheric teleconnection patterns linked to extreme cold events affecting central and northeastern Argentina during winter are identified. The objective is to determine whether the conditions found in previous studies for the composite of winters with extreme (maximum and minimum) frequency of GF occurrence respond to typical characteristics of the austral winter or they are inherent to those particular winters. Taking the mean winter as basic state in the 1961ĝ€" 1990 period, a series of numerical experiments are run using a primitive equation model in which waves are excited with a thermal forcing. The positions of the thermal forcing are chosen according to observed convection anomalies in a basic state given by the austral winters with extreme frequency of GF occurrence. The wave trains excited by anomalous convection situated in specific regions may propagate across the Pacific Ocean and reach South America with the appropriate phase, creating the local favorable conditions for the occurrence of GF. However, the anomalous convection is, by itself, not sufficient since the response also depends on the basic state configuration. This is proved by placing the forcing over the region of significant anomalous convection for maximum and minimum frequency of GF occurrence and the response was very different in comparison to the mean winter. It is concluded that the conditions for a greater GF frequency of occurrence are inherent to these particular winters, so that such conditions are not present in the average winter.

Paulina Carabajal A.,CONICET
Palaeontology | Year: 2011

Abstract: The braincases of the abelisaurid theropod dinosaurs Abelisaurus comahuensis and Aucasaurus garridoi are described and compared. These two taxa share the presence of a floccular recess that is '8'-shaped, the absence of a medullar eminence in the floor of the endocranial cavity and the possession of a well-developed, narrow and tall dorsal longitudinal sinus. The basisphenoidal recess is continuous dorsocaudally with two pneumatic cavities, which are separated medially by a thin septum. A connection between the metotic canal and the columellar recess that probably represents the exit of cranial nerve IX is observed in Abelisaurus. Aucasaurus has a skull roof with a wide sagittal crest and a low parietal eminence that differentiates it from other derived abelisaurids such as Abelisaurus, Carnotaurus and Majungasaurus. The abelisaurid braincases described herein show strong consistency in their general morphology and structure. However, there is some variation, and these detailed descriptions are important for understanding the variation and distribution of braincase characters within Abelisauridae. © The Palaeontological Association.

Journal of South American Earth Sciences | Year: 2013

As a result of new studies carried out in the offshore of Perú during the exploration and hydrocarbon evaluation of the forearc basins, new U-Pb SHRIMP and TIMS in zircons and some Ar-Ar data were obtained in the metamorphic and igneous basement. The understanding of this basement was critical to evaluate different hypotheses that have been proposed for the tectonic evolution of pre-Andean crust of Perú. Recent research performed in the basement rocks of the Marañón Massif in northern Perú, claimed that west of this area was a basement-free region in the Paleozoic, where the arc and forearc were developed in a mafic quasi-oceanic crust. However, petrographic studies and new preliminary ages indicate, for the first time, the nature and age of this sialic basement. Reconnaissance studies were performed in several offshore islands, as the Las Hormigas de Afuera Island west of Lima, and Macabí and Lobera islands along the edge of the continental platform. These data were complemented with the studies of some cutting samples obtained in recent exploration wells in northern Perú. The results of the present work show two large crustal domains in the Peruvian offshore forearc. A northern domain contains late Paleozoic igneous rocks that appear to be the southern offshore continuation of the Amotape-Tahuin block, which is interpreted as the southernmost remnant of the Laurentia Alleghenian orogen. The central offshore domain, known as the Paracas High, corresponds to the outer shelf high of previous studies. It contains orthogneisses of Grenville-age, probably recrystallized during an Ordovician magmatic episode. The new results show that the central offshore of Perú is an extension of the Grenville-age basement affected by Famatinian, early Paleozoic magmatism, well exposed in the southern domain in the Arequipa Massif along the coast of southern Perú. © 2012 Elsevier Ltd.

Ardenghi J.S.,CONICET | Castagnino M.,Institutos Of Fisica Of Rosario Y Of Astronomia
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The purpose of this work is to rewrite the generating functional of 4 theory for the n=0 and n=4 correlation functions as the inner product of a state with an observable, as we did in a previous work, for the two-points correlation function. The observables are defined through the external sources and the states are defined through the correlation function itself. In this sense, the divergences of Quantum Field Theory (QFT) appear in the reduced state by taking the partial trace of the state with respect to the internal vertices that appear in the perturbation expansion. From this viewpoint, the renormalization can be substituted by applying a projector on the internal quantum state. The advantage of this new insight is that we can obtain finite contributions to the correlation functions without introducing counterterms in the Lagrangian or by manipulating complex divergent quantities. © 2012 American Physical Society.

Ferrari S.M.,CONICET
Acta Palaeontologica Polonica | Year: 2013

A new gastropod fauna is reported from Chubut province of west-central Patagonia. Members of Trochoidea, Pseudomelanoidea, Campaniloidea, and Nerinoidea are recorded from the Early Jurassic (Late Pliensbachian-Early Toarcian) of Mulanguińeu Formation. The gastropod fauna consists of two new species: the pseudomelaniid Pseudumelania feruglioi sp. nov. and the protorculid Anulifera chubutensis sp. nov. Other members of the association are Pseudumelania sp.; the ampulloispirids Globularia cf. catanlilensis, Globularia sp., and Naricopsina? sp.; the nerineids Nerinea? sp. 1 and Nerinea? sp. 2; the trochids Lithotrochus humblodtii, Lithotruchus cf. rothi, and two indeterminable trochids species. An analysis of diversity was made considering all gastropod fauna recovered so far from five fossiliferous localities sampled in west-central Patagonia. The preliminary results of this study suggests that the Jurassic marine sequences of west central Chubut province are dominated by gastropods of Eucyclidae, Pseudomelaniidae, Procerithiidae, and Ampullinidae groups. However, the rarefaction curves of particular marine gastropod faunas in the Jurassic of Patagonia are still far from saturation requiring further collecting effort. © 2013 S.M. Ferrari. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Membrane overexpression of ErbB-2/HER2 receptor tyrosine kinase (membrane ErbB-2 (MErbB-2)) has a critical role in breast cancer (BC). We and others have also shown the role of nuclear ErbB-2 (NErbB-2) in BC, whose presence we identified as a poor prognostic factor in MErbB-2-positive tumors. Current anti-ErbB-2 therapies, as with the antibody trastuzumab (Ttzm), target only MErbB-2. Here, we found that blockade of NErbB-2 action abrogates growth of BC cells, sensitive and resistant to Ttzm, in a scenario in which ErbB-2, ErbB-3 and Akt are phosphorylated, and ErbB-2/ErbB-3 dimers are formed. Also, inhibition of NErbB-2 presence suppresses growth of a preclinical BC model resistant to Ttzm. We showed that at the cyclin D1 promoter, ErbB-2 assembles a transcriptional complex with Stat3 (signal transducer and activator of transcription 3) and ErbB-3, another member of the ErbB family, which reveals the first nuclear function of ErbB-2/ErbB-3 dimer. We identified NErbB-2 as the major proliferation driver in Ttzm-resistant BC, and demonstrated that Ttzm inability to disrupt the Stat3/ErbB-2/ErbB-3 complex underlies its failure to inhibit growth. Furthermore, our results in the clinic revealed that nuclear interaction between ErbB-2 and Stat3 correlates with poor overall survival in primary breast tumors. Our findings challenge the paradigm of anti-ErbB-2 drug design and highlight NErbB-2 as a novel target to overcome Ttzm resistance.Oncogene advance online publication, 1 September 2014; doi:10.1038/onc.2014.272.