Monge, DA ;Holec, M ; Zelezny, F ; Garino, CG ; CLUSTER COMPUTING-THE JOURNAL OF NETWORKS SOFTWARE TOOLS AND ,2015 ,18 ,1317 -1329 .
The adequate management of scientific workflow applications strongly depends on the availability of accurate performance models of sub-tasks. Numerous approaches use machine learning to generate such models autonomously, thus alleviating the human effort associated to this process. However, these standalone models may lack robustness, leading to a decay on the quality of information provided to workflow systems on top. This paper presents a novel approach for learning ensemble prediction models of tasks runtime. The ensemble-learning method entitled bootstrap aggregating (bagging) is used to produce robust ensembles of M5P regression trees of better predictive performance than could be achieved by standalone models. Our approach has been tested on gene expression analysis workflows. The results show that the ensemble method leads to significant prediction-error reductions when compared with learned standalone models. This is the first initiative using ensemble learning for generating performance prediction models. These promising results encourage further research in this direction.
Saen-Oon, S ;de Vaca, IC ; Masone, D ; Medina, M ; Guallar, V ; BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS ,2015 ,1847 ,1530 -1538 .
In the photosynthetic electron transfer (ET) chain, two electrons transfer from photosystem I to the flavin-dependent ferredoxin-NADP reductase (FNR) via two sequential independent ferredoxin (Fd) electron carriers. In some algae and cyanobacteria (as Anabaena), under low iron conditions, flavodoxin (Fld) replaces Fd as single electron carrier. Extensive mutational studies have characterized the protein-protein interaction in FNR/Fd and FNR/Fld complexes. Interestingly, even though Fd and Fld share the interaction site on FNR, individual residues on FNR do not participate to the same extent in the interaction with each of the protein partners, pointing to different electron transfer mechanisms. Despite of extensive mutational studies, only FNR/Fd X-ray structures from Anabaena and maize have been solved; structural data for FNR/Fld remains elusive. Here, we present a multiscale modelling approach including coarse-grained and all-atom protein-protein docking, the QM/MM e-Pathway analysis and electronic coupling calculations, allowing for a molecular and electronic comprehensive analysis of the ET process in both complexes. Our results, consistent with experimental mutational data, reveal the ET in FNR/Fd proceeding through a bridge-mediated mechanism in a dominant protein-protein complex, where transfer of the electron is facilitated by Fd loop-residues 40-49. In FNR/Fld, however, we observe a direct transfer between redox cofactors and less complex specificity than in Fd; more than one orientation in the encounter complex can be efficient in ET. (C) 2015 Elsevier B.V. All rights reserved.
Zhao, S ;Kad, B ; Hahn, EN ; Remington, BA ; Wehrenberg, CE ; Huntington, CM ; Park, HS ; Bringa, EM ; More, KL ; Meyers, MA ; EXTREME MECHANICS LETTERS ,2015 ,5 ,74 -80 .
Here we report that high-power, pulsed, laser-driven shock compression of monocrystalline silicon produces directional amorphization, revealed by high-resolution transmission electron microscopy and confirmed by molecular dynamics simulations. At the lowest energy level experiment, generating a pressure of similar to 4 GPa, silicon reacts elastically. At intermediate energy levels (P similar to 11 and 22 GPa), amorphization is observed both at the surface and directionally, along planes making angles close to the maximum shear. At the highest laser energy level explored here, (P-peak similar to 28 GPa), the recovered sample shows a nanocrystalline microstructure near the surface. This nanocrystalline structure forms by crystallization from the amorphous phase and is thought to be a post-shock phenomenon. Shearinduced lattice defects (stacking faults and twins) on crystallographic slip planes play a crucial role in the onset of amorphization. Molecular dynamics show that silicon behaves elastically until similar to 10 GPa and, at slightly higher pressures, partial dislocations and stacking faults are emitted from the surface. Driven by the high-amplitude stress pulse, these defects travel inwards along specific crystallographic orientations and intersect, leading to further defect creation, additional plastic work, and, at higher pressures, amorphous bands in intersecting patterns. The typical high-pressure solid-solid phase transitions of silicon are not observed whereas the high shear stresses are relaxed by localized dislocation motion/interactions and eventually by directional amorphization, which occurs below the critical hydrostatic pressure for melting of silicon in shock compression. It is therefore proposed that the combined effects of hydrostatic and shear stresses lead to directional amorphization. (C) 2015 Elsevier Ltd. All rights reserved.
Marsh, EJ ;Schreiber, K ; JOURNAL OF ARCHAEOLOGICAL SCIENCE-REPORTS ,2015 ,4 ,54 -64 .
The Wari empire (AD 600-1000) deployed a variety of strategies to consolidate its provinces in Middle Horizon Peru. One strategy may have been building imperial sites in places with large visual magnitudes, which are attractive to empires because they are more defensible, they are suitably located for direct and implied surveillance, and they project a visually-dominant presence on the landscape. In the Sondondo Valley, Peru, the Wari empire made a significant investment of labor and resources in the construction of terraces, roads, and five imperial sites. The viewsheds of these sites are compared to those of 20 non-imperial sites, 495 randomly-placed individual sites, and 99 randomly-placed groups of five sites each. Parametric and non-parametric comparisons reject the null hypothesis that there is no difference between viewsheds. Imperial sites had significantly larger and better-coordinated viewsheds, as estimated from overlap and coverage indices. These results support-the argument that imperial agents' site-placement decisions considered the benefits of locations with large viewsheds. From these sites, the empire's representatives effectively advanced imperial goals for two and half centuries. Similar factors may have been salient in other imperial settings, so this approach may help explore site-placement decisions in other regions. (C) 2015 Elsevier Ltd. All rights reserved.
Figueroa, E ;Tramontina, D ; Gutierrez, G ; Bringa, E ; JOURNAL OF NUCLEAR MATERIALS ,2015 ,467 ,677 -682 .
In this work we study, by means of molecular dynamics simulation, the change in the mechanical properties of a gold nanowire with pre-existing radiation damage. The gold nanowire is used as a simple model for a nanofoam, made of connected nanowires. Radiation damage by keV ions leads to the formation of a stacking fault tetrahedron (SFT), and this defect leads to a reduced plastic threshold, as expected, when the nanowire is subjected to tension. We quantify dislocation and twin density during the deformation, and find that the early activation of the SFT as a dislocation source leads to reduced dislocation densities compared to the case without radiation damage. In addition, we observed a total destruction of the SFT, as opposed to a recent simulation study where it was postulated that SFTs might act as self-generating dislocation sources. The flow stress at large deformation is also found to be slightly larger for the irradiated case, in agreement with recent experiments. (C) 2015 Elsevier B.V. All rights reserved.
Ruestes, CJ ;Bringa, EM ; Rudd, RE ; Remington, BA ; Remington, TP ; Meyers, MA ; SCIENTIFIC REPORTS ,2015 ,5 ,-.
Plasticity is often controlled by dislocation motion, which was first measured for low pressure, low strain rate conditions decades ago. However, many applications require knowledge of dislocation motion at high stress conditions where the data are sparse, and come from indirect measurements dominated by the effect of dislocation density rather than velocity. Here we make predictions based on atomistic simulations that form the basis for a new approach to measure dislocation velocities directly at extreme conditions using three steps: create prismatic dislocation loops in a near-surface region using nanoindentation, drive the dislocations with a shockwave, and use electron microscopy to determine how far the dislocations moved and thus their velocity at extreme stress and strain rate conditions. We report on atomistic simulations of tantalum that make detailed predictions of dislocation flow, and find that the approach is feasible and can uncover an exciting range of phenomena, such as transonic dislocations and a novel form of loop stretching. The simulated configuration enables a new class of experiments to probe average dislocation velocity at very high applied shear stress.
Gunkelmann, N ;Bringa, EM ; Urbassek, HM ; JOURNAL OF APPLIED PHYSICS ,2015 ,118 ,-.
Intense shock waves may lead to spallation of the sample. Recent experiments show differences of shock spallation in iron depending on whether the samples underwent the pressure-induced bcchcp phase transformation or not. In this study, we perform molecular dynamics simulations of shock-induced spallation in polycrystalline iron. Our results show that the phase transformation decreases the probability of multiple spallation and crack formation. In agreement with experiments, the phase transformation changes the surface morphology showing smoother spallation surfaces. (C) 2015 AIP Publishing LLC.
Giri, N ;Del Popolo, MG ; Melaugh, G ; Greenaway, RL ; Ratzke, K ; Koschine, T ; Pison, L ; Gomes, MFC ; Cooper, AI ; James, SL ; NATURE ,2015 ,527 ,216 -+ .
Porous solids such as zeolites(1) and metal-organic frameworks(2,3) are useful in molecular separation and in catalysis, but their solid nature can impose limitations. For example, liquid solvents, rather than porous solids, are the most mature technology for post-combustion capture of carbon dioxide because liquid circulation systems are more easily retrofitted to existing plants. Solid porous adsorbents offer major benefits, such as lower energy penalties in adsorption-desorption cycles(4), but they are difficult to implement in conventional flow processes. Materials that combine the properties of fluidity and permanent porosity could therefore offer technological advantages, but permanent porosity is not associated with conventional liquids(5). Here we report free-flowing liquids whose bulk properties are determined by their permanent porosity. To achieve this, we designed cage molecules(6,7) that provide a well-defined pore space and that are highly soluble in solvents whose molecules are too large to enter the pores. The concentration of unoccupied cages can thus be around 500 times greater than in other molecular solutions that contain cavities(8-10), resulting in a marked change in bulk properties, such as an eightfold increase in the solubility of methane gas. Our results provide the basis for development of a new class of functional porous materials for chemical processes, and we present a one-step, multigram scale-up route for highly soluble 'scrambled' porous cages prepared from a mixture of commercially available reagents. The unifying design principle for these materials is the avoidance of functional groups that can penetrate into the molecular cage cavities.
Millan, EN ;Bederian, CS ; Piccoli, MF ; Garino, CG ; Bringa, EM ; COMPUTERS & ELECTRICAL ENGINEERING ,2015 ,48 ,12 -24 .
Cellular Automata (CA) are of interest in several research areas and there are many available serial implementations of CA. However, there are relatively few studies analyzing in detail High Performance Computing (HPC) implementations of CA which allow research on large systems. Here, we present a parallel implementation of a CA with distributed memory based on MPI. As a first step to insure fast performance, we study several possible serial implementations of the CA. The simulations are performed in three infrastructures, comparing two different microarchitectures. The parallel code is tested with both Strong and Weak scaling, and we obtain parallel efficiencies of similar to 75%-85%, for 64 cores, comparable to efficiencies for other mature parallel codes in similar architectures. We report communication time and multiple hardware counters, which reveal that performance losses are related to cache references with misses, branches and memory access. (C) 2015 Elsevier Ltd. All rights reserved.
Garcia, V ;Aranibar, J ; Pietrasiak, N ; ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY ,2015 ,69 ,35 -45 .
Biological soil crusts (BSC) play diverse roles in arid and semi-arid ecosystems such as increasing soil fertility and reducing soil loss due to aeolian and hydric erosion, but they are very sensitive to disturbances. These attributes point to the relevance of BSC for soil conservation and restoration. In order to use BSC for restoration of degraded soils, we need to understand the ecological drivers of BSC. In this study, we analyzed the effect of environmental factors on BSC cover at different spatial scales in the central Monte Desert (Argentina), including landform, slope, aspect, vascular plants, and disturbance intensity. We evaluated the effects of different factors with linear mixed effect models, comparing the adjustment of models of different complexity, which included different number of factors. First, at the landscape scale, we analyzed BSC cover in two geomorphological units with different soils, topography, and vegetation. BSC cover was higher in the old riverbed, which has a higher proportion of fine clay soil particles, than in the aeolian plain. Disturbance effects were apparent in the old riverbed, showing increasing BSC cover at higher distances from settlements, and BSC located both, under and outside plant canopies. At the mesoscale, we found no differences of BSC cover in dune flanks and inter-dune valleys of the aeolian plain. Finally, at the microscale, BSC patches of higher surface cover were found in association with vascular plants (Larrea divaricata, Bulnesia retama, Lycium sp.), on mounds, and in microsites of southern exposure and high slopes. Our findings suggest that BSC develop preferentially associated with vascular plants, which generate mounds and sloped microsites with southern exposure, where lower irradiances reduce desiccation in these extremely dry environments. (C) 2015 Elsevier Masson SAS. All rights reserved.
Gonzalez, C ;Panizo-Laiz, M ; Gordillo, N ; Guerrero, CL ; Tejado, E ; Munnik, F ; Piaggi, P ; Bringa, E ; Iglesias, R ; Perlado, JM ; Gonzalez-Arrabal, R ; NUCLEAR FUSION ,2015 ,55 ,-.
The trapping and mobility of hydrogen in nanostructured tungsten grain boundaries (GBs) have been studied by combining experimental and density functional theory (DFT) data. Experimental results show that nanostructured W coatings with a columnar grain structure and a large number of (1 1 0)/(2 1 1) interfaces retain more H than coarsed grained W samples. To investigate the possible influence of GBs on H retention, a complete energetic analysis of a non-coherent W(1 1 0)/ W(1 1 2) interface has been performed employing DFT. Our results show that this kind of non-coherent interface largely attracts point defects (both a H atom and a metallic monovacancy separately) and that the presence of these interfaces contributes to a decrease in the migration energy of the H atoms with respect to the bulk value. When both the W monovacancy and H atom are introduced together into the system, the HV complex becomes the most stable configuration and one of the mechanisms explaining the H retention in the radiation damaged GB observed experimentally.
Valencia, F ;Mella, JD ; Gonzalez, RI ; Kiwi, M ; Bringa, EM ; CARBON ,2015 ,93 ,458 -464 .
Swift heavy ion irradiation does not generate amorphous tracks in diamond, contrary to what happens in graphite or in diamond-like carbon. Since nanocrystalline diamond is of interest for several technological applications we investigate the reason for this difference, by means of large scale atomistic simulations of ion tracks in nanocrystalline diamond, using a thermal spike model, with up to 2.5 million atoms, and grain sizes in the range 5-10 nm. We conclude that tracking can be achieved under these conditions, when it is absent in single crystal diamond: for 5 nm samples the tracking threshold is below 15 keV/nm. Point defects are observed below this threshold. As the energy loss increases the track region becomes amorphous, and graphitic-like, with predominant sp(2) hybridization. This higher sensitivity to irradiation can be related to a very large decrease in thermal conductivity of nanocrystalline diamond, due to grain boundary confinement of the heat spike which enhances localized heating of the lattice. (C) 2015 Elsevier Ltd. All rights reserved.
Lu, CH ;Hahn, EN ; Remington, BA ; Maddox, BR ; Bringa, EM ; Meyers, MA ; SCIENTIFIC REPORTS ,2015 ,5 ,-.
The structural and mechanical response of metals is intimately connected to phase transformations. For instance, the product of a phase transformation (martensite) is responsible for the extraordinary range of strength and toughness of steel, making it a versatile and important structural material. Although abundant in metals and alloys, the discovery of new phase transformations is not currently a common event and often requires a mix of experimentation, predictive computations, and luck. High-energy pulsed lasers enable the exploration of extreme pressures and temperatures, where such discoveries may lie. The formation of a hexagonal (omega) phase was observed in recovered monocrystalline body-centered cubic tantalum of four crystallographic orientations subjected to an extreme regime of pressure, temperature, and strain-rate. This was accomplished using high-energy pulsed lasers. The omega phase and twinning were identified by transmission electron microscopy at 70 GPa (determined by a corresponding VISAR experiment). It is proposed that the shear stresses generated by the uniaxial strain state of shock compression play an essential role in the transformation. Molecular dynamics simulations show the transformation of small nodules from body-centered cubic to a hexagonal close-packed structure under the same stress state (pressure and shear).
Pacini, E ;Mateos, C ; Garino, CG ; IEEE LATIN AMERICA TRANSACTIONS ,2015 ,13 ,3359 -3369 .
For executing current simulated scientific experiments it is necessary to have huge amounts of computing power. A solution path to this problem is the federated Cloud model, where custom virtual machines (VM) are scheduled in appropriate hosts belonging to different providers to execute such experiments, minimizing response time. In this paper, we study schedulers for federated Clouds. Scheduling is performed at three levels. First, at the broker level, datacenters are selected by their network latencies via three policies - Lowest-Latency-Time-First, First-Latency-Time-First, and Latency-Time-In-Round-. Second, at the infrastructure level, two Cloud VM schedulers based on Ant Colony Optimization (ACO) and Particle Swarm Optimization (PSO) are implemented. At this level the scheduler is responsible for mapping VMs to datacenter hosts. Finally, at the VM level, jobs are assigned for execution into the pre-allocated VMs. We evaluate, through simulated experiments, how the proposed three-level scheduler performs w.r.t. the response time delivered to the user as the number of Cloud machines increases, a property known as horizontal scalability.
Arbocco, FCV ;Sasso, CV ; Nasif, DL ; Hapon, MB ; Jahn, GA ; MOLECULAR AND CELLULAR ENDOCRINOLOGY ,2015 ,412 ,26 -35 .
Thyroid hormones (TH) regulate mammary function. Hypothyroidism (HypoT) has deleterious effects on lactation, litter growth and survival. We analyzed the effect of chronic 6-propyl-2-thiouracil (PTU)-induced HypoT in the expression of nuclear receptors, co-regulators and oxytocin receptor (OTR) on lactation (L) days 2, 7 and 14. TH receptors (TRs) were increased on L7 at mRNA and protein levels, except TR alpha protein, that fell on L14. HypoT decreased TR alpha 2 mRNA on L7 and TR alpha 1 protein on L2, while TR beta 1 protein increased on L14. HypoT increased estrogen receptor beta (ER beta) mRNA on L7 but decreased its protein levels on L14. Progesterone receptor A (PRA) mRNA decreased from L2 to L14 while PRB increased, and at protein levels PRA levels showed a nadir on L7, while PRB peaked. HypoT decreased PRA mRNA and protein and increased PRB mRNA at L14. Nuclear receptor co-activator (NCOA) 1 and RXR alpha mRNA showed an opposite pattern to the TRs, while NCOA2 increased at L14; HypoT blocked the variations in NCOA1 and NCOA2. HypoT increased NCOR1 on L2 and decreased OTR at L2 and circulating estradiol and NCOR2 at L14. In controls the most notable changes occurred on L7, suggesting it is a key inflection point in mammary metabolism. The low levels of TR alpha 1, NCOA1 and OTR, and increased NCOR1 produced by HypoT on L2 may hinder the mammary ability to achieve normal milk synthesis and ejection, leading to defective lactation. Later on, altered ER and PR expression may impair further mammary function. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
Monge, DA ;Holec, M ; Zelezny, F ; Garino, CG ; IEEE LATIN AMERICA TRANSACTIONS ,2015 ,13 ,3088 -3095 .
One of the central issues for the efficient management of Scientific workflow applications is the prediction of tasks performance. This paper proposes a novel approach for constructing performance models for tasks in data-intensive scientific workflows in an autonomous way. Ensemble Machine Learning techniques are used to produce robust combined models with high predictive accuracy. Information derived from workflow systems and the characteristics and provenance of the data are exploited to guarantee the accuracy of the models. A gene-expression analysis workflow application was used as case study over homogeneous and heterogeneous computing environments. Experimental results evidence noticeable improvements while using ensemble models in comparison with single/standalone prediction models. Ensemble learning techniques made it possible to reduce the prediction error with respect to the strategies of a single-model with values ranging from 14.47% to 28.36% for the homogeneous case, and from 8.34% to 17.18% for the heterogeneous case.
Ochoa, P ;COMMUNICATIONS ON PURE AND APPLIED ANALYSIS ,2015 ,14 ,1841 -1863 .
In this work, we propose and analyse approximation schemes for fully non-linear second order partial differential equations defined on the Heisenberg group. We prove that a consistent, stable and monotone scheme converges to a viscosity solution of a second order PDE on the Heisenberg group provided that comparison principles exists for the limiting equation. We also provide examples where this technique is applied.
Pol, RG ;Lopez de Casenave, J ; Milesi, FA ; MYRMECOLOGICAL NEWS ,2015 ,21 ,1 -12 .
Foraging strategy determines the way harvester ants use space and therefore their access and impact on seed resources. In this study, we described the foraging strategy of three sympatric South American species of Pogonomyrmex ants to confirm that they are solitary foragers as is suggested anecdotally in the literature. Then we tested whether those foraging strategies are fixed or flexible in response to seed density and distribution. Based on individual and group movements of foraging ants, we determined that P. rastratus MAYR, 1868 is exclusively a solitary foraging species, P. inermis FOREL, 1914 use a group-foraging strategy with limited recruitment, and P. mendozanus CUEZZO & CLAVER, 2009 displays an intermediate foraging system in which workers are typically solitary foragers but also recruit nestmates to high-density seed patches. The addition of seeds near the nest modified the foraging behavior of the three species by different amounts. Individual foragers of each species reduced their search time and search area, and colonies increased their foraging activity rate, probably as a result of a higher returning rate of successful foragers after seed addition. Such behavioral responses were much more conspicuous in P. mendozanus than in the other two species. Flexibility in foraging and diet breadth reported for some of these harvester ants may constitute important adaptive features in the central Monte desert where seed abundance is highly heterogeneous, irregular, and severely affected by anthropic disturbances.
Baldo, MN ;Hunzicker, GA ; Altamirano, JC ; Murguia, MC ; Hein, GJ ; INTERNATIONAL JOURNAL OF PHARMACEUTICAL SCIENCES AND RESEARCH ,2015 ,6 ,3752 -3760 .
The use of noninvasive biological samples such as saliva, it is of great interest for therapeutic drug monitoring (TDM), including the anticonvulsants Phenytoin (PHT). A simple analytical methodology by liquid chromatography-tandem mass spectrometry was developed and validated to carry out a relative comparative bioavailability (RBA) study of two PHT formulations in human plasma and saliva and the subsequent correlation between both matrixes. A single-dose, randomized-sequence, open-label, two-way crossover study, was conducted in 24 healthy Latin American male volunteers. The bioequivalence of 200 mg PHT tablet was evaluated using plasma and saliva to determine C-max, T-max, AUC(0-t) and AUC(0-infinity). Figures of merit of the proposed methodology were as follows: linear ranges of 40-5055 ng/mL and 5-1340 ng/mL for plasma and saliva, respectively, with a correlation coefficient of (r)>0.999. The LOD and LOQ were 15 ng/mL -40ng/mL for plasma and 1.5 ng/mL -5.0 ng/mL for saliva. Accuracy, precision (as % CV) and recovery were accepted according the bioequivalence criteria. Stability showed % bias<15%. The PHT saliva/PHT plasma ratios for all parameters were: 5.4, 2.2, 1.4 for C-max, and 1.7, 1.2, 1.1 for AUC. Plasma and saliva results were correlated (R=0.9889 and R=0.9947 for Reference and Test, respectively). Saliva not only is a suitable matrix for RBA studies and TDM, but also a more convenient tool since it provides analogous information with mayor analytical, ethical, and biosafety advantages. However, an additional pre-study of product dissolution in oral cavity is suggested before carrying out complete RBA studies for prompt-release drugs.
Barberena, R ;LATIN AMERICAN ANTIQUITY ,2015 ,26 ,304 -318 .
In this paper I present an intensively dated chrono-stratigraphic sequence for the Cueva Huenul 1 archaeological site, Neuquen Province, Argentina. Located in the inland deserts of northwestern Patagonia, Cueva Huenul 1 offers a remarkable temporal record of events for a largely unstudied desert region. I connect this local record with available data on a macro-regional scale to reassess (1) the timing of the first human colonization of the area and its implications for explaining the extinction of megafauna (ca. 14,000-10,000 cal B.P.) and (2) the decrease in human occupation recorded in several South American deserts during parts of the mid-Holocene (ca. 8000-6000 cal B.P.). The data presented here show a gap of about 1,500 calendar years between the extinction of megafauna and the appearance of humans. A review of evidence from the northern Patagonia and southern Cuyo regions is consistent with this record, favoring ecological causes for regional extinction of megafaunal taxa. Integration of this record with those indicating the earliest human presence in South America (e.g., Monte Verde, Chile) is consistent with a process of human radiation to the inland Patagonian deserts from nodes of initial occupation. The chrono-stratigraphic sequence from Cueva Huenul 1 also contributes to an assessment of a trough in human occupation along the South American Arid Diagonal around 8000-6000 cal B.P. Evidence for a decrease in occupational intensity during this period is found in the highland and lowland deserts in Mendoza and San Juan, the Puna region in northwestern Argentina, the Atacama Desert in Chile, and possibly the Pampean region. Previous researchers have suggested that persistent arid conditions would have produced increasing landscape fragmentation, particularly affecting desert areas. A more specific understanding of the demographic processes underlying this archaeological signal is needed. In this paper I suggest that this trough reflects not only spatial and social rearrangements, but also a macro-regional demographic retraction. This could have caused a population bottleneck with lasting biological and cultural implications.
Cuervo, PF ;Di Cataldo, S ; Fantozzi, MC ; Deis, E ; Isenrath, GD ; Viberti, G ; Artigas, P ; Peixoto, R ; Valero, MA ; Sierra, RMY ; Mas-Coma, S ; ACTA PARASITOLOGICA ,2015 ,60 ,536 -543 .
Fascioliasis has recently been included in the WHO list of Neglected Zoonotic Diseases. Besides being a major veterinary health problem, fascioliasis has large underdeveloping effects on the human communities affected. Though scarcely considered in fascioliasis epidemiology, it is well recognized that both native and introduced wildlife species may play a significant role as reservoirs of the disease. The objectives are to study the morphological characteristics of Fasciola hepatica adults and eggs in a population of Lepus europaeus, to assess liver fluke prevalence, and to analyze the potential reservoir role of the European brown hare in northern Patagonia, Argentina, where fascioliasis is endemic. Measures of F. hepatica found in L. europaeus from northern Patagonia demonstrate that the liver fluke is able to fully develop in wild hares and to shed normal eggs through their faeces. Egg shedding to the environment is close to the lower limit obtained for pigs, a domestic animal whose epidemiological importance in endemic areas has already been highlighted. The former, combined with the high prevalence found (14.28%), suggest an even more important role in the transmission cycle than previously considered. The results obtained do not only remark the extraordinary plasticity and adaptability of this trematode species to different host species, but also highlight the role of the European brown hare, and other NIS, as reservoirs capable for parasite spillback to domestic and native cycle, representing a potentially important, but hitherto neglected, cause of disease emergence.
de Paola, M ;Bello, OD ; Michaut, MA ; PLOS ONE ,2015 ,10 ,-.
Cortical granule exocytosis (CGE), also known as cortical reaction, is a calcium- regulated secretion that represents a membrane fusion process during meiotic cell division of oocytes. The molecular mechanism of membrane fusion during CGE is still poorly understood and is thought to be mediated by the SNARE pathway; nevertheless, it is unkown if SNAP (acronym for soluble NSF attachment protein) and NSF (acronym for N-ethilmaleimide sensitive factor), two key proteins in the SNARE pathway, mediate CGE in any oocyte model. In this paper, we documented the gene expression of alpha-SNAP, gamma-SNAP and NSF in mouse oocytes. Western blot analysis showed that the expression of these proteins maintains a similar level during oocyte maturation and early activation. Their localization was mainly observed at the cortical region of metaphase II oocytes, which is enriched in cortical granules. To evaluate the function of these proteins in CGE we set up a functional assay based on the quantification of cortical granules metaphase II oocytes activated parthenogenetically with strontium. Endogenous alpha-SNAP and NSF proteins were perturbed by microinjection of recombinant proteins or antibodies prior to CGE activation. The microinjection of wild type alpha-SNAP and the negative mutant of alpha-SNAP L294A in metaphase II oocytes inhibited CGE stimulated by strontium. NEM, an irreversibly inhibitor of NSF, and the microinjection of the negative mutant NSF D1EQ inhibited cortical reaction. The microinjection of anti-alpha-SNAP and anti-NSF antibodies was able to abolish CGE in activated metaphase II oocytes. The microinjection of anti-gamma SNAP antibody had no effect on CGE. Our findings indicate, for the first time in any oocyte model, that alpha-SNAP, gamma-SNAP, and NSF are expressed in mouse oocytes. We demonstrate that alpha-SNAP and NSF have an active role in CGE and propose a working model.
Sanabria, EA ;Rodriguez, CY ; Vergara, C ; Ontivero, E ; Banchig, M ; Navas, AL ; Herrera-Morata, MA ; Quiroga, LB ; JOURNAL OF THERMAL BIOLOGY ,2015 ,52 ,52 -57 .
Rhinella spinulosa is an anuran toad species distributed latitudinal and altitudinal (1200-5000 m) from Peru to Argentina, inhabiting mountain valleys in the Andes. Considering the broad range of habitats where they live, it is important to understand the thermal physiological mechanisms, thermal tolerances and physiological adaptations for surviving in rigorous environments. We investigated the thermal parameters (field body temperature, selected body temperature, locomotor performance in field and laboratory conditions, and thermal extremes) during diurnal activity for a population of juvenile, post-meta-morphosed toads (Rhinella spinulosa) from the Monte Desert of San Juan, Argentina. Post-metamorphic toads are active from approximately 1100-1900 (in contrast to nocturnal adult toads). Our findings show that these toads have a wide thermal tolerance range, ranging from a critical thermal maximum of 36.9 degrees C to crystallization temperatures below 0 degrees C. During their active period, toads always showed suboptimal thermal conditions for locomotion. Despite the suboptimal condition for the locomotion, diurnal activity is likely to confer thermal advantages, allowing them to search for food and increase digestion and growth rates. We also found that the toads are capable of super-cooling, which prevents mortality from freezing when the environmental temperatures drop below 0 degrees C. The environmental temperatures are below zero at night, when toads are inactive and take refuge under rocks. In summary, this toad population demonstrates high thermal plasticity, as shown by a relatively high level of activity sustained over a wide range of ambient temperature (similar to 35 degrees C). These thermal adaptations allow this species of juvenile toads to inhabit a wide range of altitudes and latitudes. (C) 2015 Published by Elsevier Ltd.
Grijalba, AC ;Escudero, LB ; Wuilloud, RG ; SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY ,2015 ,110 ,118 -123 .
A highly sensitive dispersive micro-solid phase extraction (D-mu-SPE) method combining an ionic liquid (IL) and multi-walled carbon nanotubes (MWCNTs) for inorganic As species (As(III) and As(V)) species separation and determination in garlic samples by electrothermal atomic absorption spectrometry (ETAAS) was developed. Trihexyl(tetradecil)phosphonium chloride IL was used to form an ion pair with the arsenomolybdate complex obtained by reaction of As(V) with molybdate ion. Afterwards, 1.0 mg of MWCNTs was dispersed for As(V) extraction and the supernatant was separated by centrifugation. MWCNTs were re-dispersed with tetradecyltrimethylammonium bromide surfactant and ultrasound followed by direct injection into the graphite furnace of ETAAS for As determination. Pyrolysis and atomization conditions were carefully studied for complete decomposition of MWCNTs and IL matrices. Under optimum conditions, an extraction efficiency of 100% and a preconcentration factor of 70 were obtained with 5 mL of garlic extract. The detection limit was 7.1 ng L-1 and the relative standard deviations (RSDs) for six replicate measurements at 5 mu g L-1 of As were 5.4% and 4.8% for As(III) and As (V), respectively. The proposed D-mu-SPE method allowed the efficient separation and determination of inorganic As species in a complex matrix such as garlic extract (C) 2015 Elsevier B.V. All rights reserved.
Suarez, ML ;Villalba, R ; Mundo, IA ; Schroeder, N ; TREES-STRUCTURE AND FUNCTION ,2015 ,29 ,1053 -1067 .
Recent variations in climate appear to induce similarities in the responses of N. dombeyi growth along its entire distribution, supporting global convergence in tree growth responses to climate changes.
Riga, BJG ;David, LDO ; Tomaselli, MB ; Candeiro, CRD ; Coria, JP ; Pramparo, M ; JOURNAL OF SOUTH AMERICAN EARTH SCIENCES ,2015 ,61 ,134 -141 .
New findings of dinosaur ichnites from Agua del Choique section (Mendoza Province, Argentina) provides ichnological and anatomical information about the Cretaceous sauropods and theropods. Around 330 tracks distributed in six footprint levels were identified in this area, one of most important of South America. Two ichnocenoses are located in different paleoenvironmental contexts. In the Anacleto Formation (early Campanian) around 20 titanosaurian tracks were found in floodplain and ephemeral channel deposits. Herein, one pes track shows three claw impressions and this is congruent to two new titanosaur specimens recently discovered in Mendoza Province that have articulated and complete pedes. In this context, for the first time to titanosaurs, ichnological evidences are supported by skeletal elements. In the Loncoche Formation (late Campanian-early Maastrichtian) titanosaurian tracks of Titanopodus mendozensis are abundant (around 310 tracks) and were produced by titanosaurs that walked in a very wet substrate of tidally dominated deltas related with the first Atlantic transgression for northern Patagonia. In this facies association, three different trydactl tracks indicate the presence of small theropods (1-2 m long), expanding the knowledge about the faunistic components that lived in these marine marginal environments. (C) 2014 Elsevier Ltd. All rights reserved.
Faria, CCD ;Riga, BG ; Candeiro, CRD ; Marinho, TD ; David, LO ; Simbras, FM ; Castanho, RB ; Muniz, FP ; Pereira, PVLGD ; JOURNAL OF SOUTH AMERICAN EARTH SCIENCES ,2015 ,61 ,154 -163 .
The South American sauropod dinosaurs fossil record is one of the world's most relevant for their abundance (51 taxa) and biogeographical implications. Their historical biogeography was influenced by the continental fragmentation of Gondwana. The scenery of biogeographic and stratigraphic distributions can provide new insight into the causes of the evolution of the sauropods in South America. One of the most important events of the sauropods evolution is the progressive replacement of Diplodocimorpha by the Titanosauriformes during the early Late Cretaceous. The fluctuation of the sea levels is frequently related to the diversity of sauropods, but it is necessary to take into account the geological context in each continent. During the Maastrichthian, a global sea level drop has been described; in contrast, in South America there was a significant rise in sea level (named 'Atlantic transgression') which is confirmed by sedimentary sequences and the fossil record of marine vertebrates. This process occurred during the Maastrichtian, when the hadrosaurs arrived from North America. The titanosaurs were amazingly diverse during the Late Cretaceous, both in size and morphology, but they declined prior to their final extinction in the Cretaceous/Paleocene boundary (65.5Yrs). (C) 2014 Elsevier Ltd. All rights reserved.
Rodriguez, MH ;Rosales, GD ; Pinna, EG ; Suarez, DS ; HYDROMETALLURGY ,2015 ,156 ,17 -20 .
Pressure acid leaching was used to extract niobium and tantalum from a ferrocolumbite ore. The leaching was carried out in a pressure reactor using hydrofluoric acid as leachant Various parameters, such as temperature, reaction time, HF concentration, stirring speed, particle size and solid-to-liquid ratio in the leaching process, were optimized. The reactants and products were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and specific surface area (BET). Experimental results showed that the maximum extraction of Nb and Ta, 90 and 80% respectively, it was achieved at an HF concentration of 9% v/v, reaction temperature of 220 degrees C, particle size of 45 pm, solid-to-liquid ratio of 1.82% w/v and reaction time of 80 min. Crystalline structures, different from those originally present in the ore, were not detected by XRD analysis of the leaching residues. (C) 2015 Elsevier B.V. All rights reserved.
Gimenez, MC ;Aguirre, JFR ; Colombo, MI ; Delgui, LR ; CELLULAR MICROBIOLOGY ,2015 ,17 ,988 -1007 .
Infectious bursal disease virus (IBDV) internalization is sparsely known in terms of molecular components of the pathway involved. To describe the cell biological features of IBDV endocytosis, we employed perturbants of endocytic pathways such as pharmacological inhibitors and overexpression of dominant-negative mutants. Internalization analysis was performed quantifying infected cells by immunofluorescence and Western blot detection of the viral protein VP3 at 12h post-infection reinforced by the analysis of the capsid protein VP2 localization after virus uptake at 1h post-infection. We compared IBDV infection to the internalization of well-established ligands with defined endocytic pathways: transferrin, cholera-toxin subunit B and dextran. To describe virus endocytosis at the morphological level, we performed ultrastructural studies of viral internalization kinetics in control and actin dynamics-blocked cells. Our results indicate that IBDV endocytic internalization was clathrin- and dynamin-independent, and that IBDV uses macropinocytosis as the primary entry mechanism. After uptake, virus traffics to early endosomes and requires exposure to the low endocytic pH as well as a functional endocytic pathway to complete its replication cycle. Moreover, our results indicate that the GTPase Rab5 is crucial for IBDV entry supporting the participation of the early endosomal pathway in IBDV internalization and infection of susceptible cells.
Cremades, H ;Mandrini, CH ; Schmieder, B ; Crescitelli, AM ; SOLAR PHYSICS ,2015 ,290 ,1671 -1686 .
The cluster formed by active regions (ARs) NOAA 11121 and 11123, approximately located on the solar central meridian on 11 November 2010, is of great scientific interest. This complex was the site of violent flux emergence and the source of a series of Earth-directed events on the same day. The onset of the events was nearly simultaneously observed by the Atmospheric Imaging Assembly (AIA) telescope onboard the Solar Dynamics Observatory (SDO) and the Extreme-Ultraviolet Imagers (EUVI) on the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite of telescopes onboard the Solar-Terrestrial Relations Observatory (STEREO) twin spacecraft. The progression of these events in the low corona was tracked by the Large Angle Spectroscopic Coronagraphs (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the SECCHI/COR coronagraphs on STEREO. SDO and SOHO imagers provided data from the Earth's perspective, whilst the STEREO twin instruments procured images from the orthogonal directions. This spatial configuration of spacecraft allowed optimum simultaneous observations of the AR cluster and the coronal mass ejections that originated in it. Quadrature coronal observations provided by STEREO revealed many more ejective events than were detected from Earth. Furthermore, joint observations by SDO/AIA and STEREO/SECCHI EUVI of the source region indicate that all events classified by GOES as X-ray flares had an ejective coronal counterpart in quadrature observations. These results directly affect current space weather forecasting because alarms might be missed when there is a lack of solar observations in a view direction perpendicular to the Sun-Earth line.
Masone, D ;Chanforan, C ; COMPUTATIONAL BIOLOGY AND CHEMISTRY ,2015 ,56 ,152 -158 .
Due to the high amount of artificial food colorants present in infants' diets, their adverse effects have been of major concern among the literature. Artificial food colorants have been suggested to affect children's behavior, being hyperactivity the most common disorder. In this study we compare binding affinities of a group of artificial colorants (sunset yellow, quinoline yellow, carmoisine, allura red and tartrazine) and their natural industrial equivalents (carminic acid, curcumin, peonidin-3-glucoside, cyanidin-3-glucoside) to human serum albumin (HSA) by a docking approach and further refinement through atomistic molecular dynamics simulations. Due to the protein-ligand conformational interface complexity, we used collective variable driven molecular dynamics to refine docking predictions and to score them according to a hydrogen-bond criterion. With this protocol, we were able to rank ligand affinities to HSA and to compare between the studied natural and artificial food additives. Our results show that the five artificial colorants studied bind better to HSA than their equivalent natural options, in terms of their H-bonding network, supporting the hypothesis of their potential risk to human health. (C) 2015 Elsevier Ltd. All rights reserved.
Locatelli, DA ;Altamirano, JC ; Gonzalez, RE ; Camargo, AB ; JOURNAL OF FUNCTIONAL FOODS ,2015 ,16 ,1 -8 .
Numerous studies have demonstrated that garlic has many biological properties due to its phytochemicals. These components include organosulphur compounds (OSCs) such as allicin, which is a chemically unstable metabolite. The aim of this study was to evaluate whether garlic could still be considered a healthy food after home cooking procedures. For that purpose, an experimental design with two factors and three levels was used. Pre-cooking and cooking procedures were the selected factors. Allicin, ajoenes, 2-vinyl-4H-1,3-dithiin (2-VD), diallyl sulphide (DAS), diallyl disulphide (DADS) and diallyl trisulphide (DATS) were the target analytes. Samples were analyzed by high performance liquid chromatography coupled to ultraviolet detector (HPLC-UV). The results showed that it was possible to find OSCs with important biological activities after all pre-cooking and cooking treatments. This is the first study to our knowledge to investigate cooked garlic using an analytical methodology, which avoid artifacts formation. (C) 2015 Elsevier Ltd. All rights reserved.
Milesi, FA ;Marone, L ; JOURNAL OF AVIAN BIOLOGY ,2015 ,46 ,225 -235 .
Conventional evolutionary and behavioral reasoning expects foragers to show strong spatial preferences in environments with heterogeneous resource distribution. Moreover, consumers should benefit from exploiting the information embedded in environmental features that indicate resource abundance. In desert soils seed abundance associates strong and reliably with vegetation and litter cover at small spatial scales. However, other spatially correlated factors (substrate complexity, temperature, predation risk) may affect foraging costs, benefits and decisions by ground-feeding granivores. We used a sequence of three semi-controlled field experiments of binary spatial choice within a portable aviary to identify the main cause of foraging microhabitat selection by the most abundant postdispersal granivorous bird in the central Monte desert (Argentina). In the first experiment we placed the aviary at field to offer pairs of adjacent microhabitats of unmodified, naturally-contrasting substrates and environmental conditions to single, untrained rufous-collared sparrows Zonotrichia capensis. Birds selected covered microhabitats in winter and summer, ruling out substrate complexity or thermoregulation as main single causes of patch selection. The other two experiments dissociated seed abundance, tree cover and litter to reveal their effects on patch selection. The results indicate that 1) sparrows do not restrict microhabitat exploration relying on environmental indicators, 2) distance to tree cover influences the order of patch exploration, probably in association with apprehension or risk-assessment behavior, and 3) patch exploitation is determined by short-term local estimation of seed abundance. The integration of these with previous results obtained under variable degrees of realism and experimental control allows for a better explanation of the spatial component of postdispersal granivory and its consequences on plants. The unconstrained selective foraging strategy of these sparrows would allow them to detect sporadic or ephemeral rich patches with structural characteristics indicating low-quality', should promote the spatial homogenization of the palatable seed bank, and would favor indirect interactions between plants.
Alma, AM ;Pol, RG ; Pacheco, LF ; Vazquez, DP ; BIOTROPICA ,2015 ,47 ,347 -354 .
Defensive mutualisms mediated by extrafloral nectaries are particularly variable; their net results may change with seasons, communities and environmental contexts. Particularly, an environmental factor that can promote changes in outcomes of ant-plant interactions is elevation in mountainous regions. We tested whether (1) the interaction between the cactus Opuntia sulphurea and ant visitors of extrafloral nectaries is a defensive mutualism; and (2) ant-plant interaction outcomes vary with elevation as a result of changes in herbivory rate and ant activity. To evaluate if the outcome of interactions was consistent at two extremes of the range distribution of O.sulphurea, we performed an ant-exclusion experiment with plants at two growth conditions (natural or potted) in two sites with contrasting elevation (1235-1787m asl) in a temperate region (Villavicencio Nature Reserve, Mendoza, Argentina), and in a tropical region (Huajchilla, La Paz, Bolivia). Although herbivory rate and ant visitation frequency increased with elevation, herbivore damage, plant reproductive success, and cladode growth rate were similar between plants excluded and non-excluded from ants among sites, geographic regions and growth conditions. These results do not support the hypotheses that the interaction between O.sulphurea and ants is a defensive mutualism, and that elevation affects the net outcome of this ant-plant interaction.
Marone, L ;Camin, SR ; Cueto, VR ; CANADIAN JOURNAL OF ZOOLOGY ,2015 ,93 ,353 -359 .
Flexibility of foraging behaviour affects our capacity to predict ecological outputs such as population responses to habitat change. Some birds forage following rules of absolute value of the food item (i.e., absolute valuation). Their realized diet is strongly correlated with the profitability of the food item and it is predictable. Consumers, however, do not always follow absolute rules. Opportunistic foragers adjust food consumption based on the availability of the food item. Their diet is still predictable but more elusive. Relativistic or context-dependent foragers change the ranks of food preferences depending on the presence of alternative food options in the choice set. Predicting their contingent diet is particularly difficult. We tested if the context of seed availability affects foraging decisions of three seed-eating bird species (the Rufous-collared Sparrow (Zonotrichia capensis (Statius Muller, 1776)), the Many-colored Chaco Finch (Saltatricula multicolor (Burmeister, 1860)), and the Common Diuca Finch (Diuca diuca (Molina, 1782))) using choice experiments aimed at detecting if seed preferences for two types of target seeds changed according to context. Birds showed very similar rankings of preferences for target seeds; however, preferences for attractive food items were not fixed but often increased in less valuable contexts. Although results imply some degree of context-dependent behaviour, predictability of bird diet was preserved because the ranking of preferences remained mostly unchanged between contexts (and among bird species), and the higher consumption of target grass seeds in a less attractive context was widely expected from the intrinsic properties of the seeds.
Ochoa, P ;ELECTRONIC JOURNAL OF DIFFERENTIAL EQUATIONS ,2015 ,,-.
In this work, we prove a comparison principle for singular parabolic equations with boundary conditions in the context of the Heisenberg group. In particular, this result applies to interesting equations, such as the parabolic infinite Laplacian, the mean curvature flow equation and more general homogeneous diffusions.
Ringl, C ;Gunkelmann, N ; Bringa, EM ; Urbassek, HM ; PHYSICAL REVIEW E ,2015 ,91 ,-.
Using a granular-mechanics code, we study the impact of a highly porous granular body on a hard wall. The projectile consists of monodisperse adhesive micrometer-sized silica grains. For the impact velocities studied, v < 0.5 m/s, the sample does not fragment, but is compacted. We find that the compaction is proportional to the impact speed. The proportionality constant increases with decreasing porosity. However, the compaction is inhomogeneous and decreases with distance from the target. A compaction wave runs through the aggregate; it slows down while the compaction becomes less efficient.
Cueto, JA ;Rodriguez, C ; Vega, IA ; Castro-Vazquez, A ; PLOS ONE ,2015 ,10 ,-.
Hemocytes in the circulation and kidney islets, as well as their phagocytic responses to microorganisms and fluorescent beads, have been studied in Pomacea canaliculata, using flow cytometry, light microscopy (including confocal laser scanning microscopy) and transmission electron microscopy (TEM). Three circulating hemocyte types (hyalinocytes, agranulocytes and granulocytes) were distinguished by phase contrast microscopy of living cells and after light and electron microscopy of fixed material. Also, three different populations of circulating hemocytes were separated by flow cytometry, which corresponded to the three hemocyte types. Hyalinocytes showed a low nucleus/cytoplasm ratio, and no apparent granules in stained material, but showed granules of moderate electron density under TEM (L granules) and at least some L granules appear acidic when labeled with LysoTracker Red. Both phagocytic and non-phagocytic hyalinocytes lose most (if not all) L granules when exposed to microorganisms in vitro. The phagosomes formed differed whether hyalinocytes were exposed to yeasts or to Gram positive or Gram negative bacteria. Agranulocytes showed a large nucleus/cytoplasm ratio and few or no granules. Granulocytes showed a low nucleus/cytoplasm ratio and numerous eosinophilic granules after staining. These granules are electron dense and rod-shaped under TEM (R granules). Granulocytes may show merging of R granules into gigantic ones, particularly when exposed to microorganisms. Fluorescent bead exposure of sorted hemocytes showed phagocytic activity in hyalinocytes, agranulocytes and granulocytes, but the phagocytic index was significantly higher in hyalinocytes.
Barbosa, LI ;Gonzalez, JA ; Ruiz, MD ; THERMOCHIMICA ACTA ,2015 ,605 ,63 -67 .
Chlorination roasting was used to extract lithium as lithium chloride from beta-spodumene. The roasting was carried out in a fixed bed reactor using calcium chloride as chlorinating agent. The mineral was mixed with CaCl2 on a molar ratio of 1:2. Reaction temperature and time were investigated. The reactants and roasted materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and atomic absorption spectrophotometry (AAS). The mineral starts to react with CaCl2 at around 700 degrees C. The optimal conditions of lithium extraction were found to be 900 degrees C and 120 min of chlorination roasting, under which it is attained a conversion degree of 90.2%. The characterization results indicate that the major phases present in the chlorinating roasting residue are CaAl2Si2O8, SiO2, and CaSiO3. (C) 2015 Elsevier B.V. All rights reserved.
de la Torre, A ;Pessano, H ; Hierro, R ; Santos, JR ; Llamedo, P ; Alexander, P ; ATMOSPHERIC RESEARCH ,2015 ,156 ,91 -101 .
On the basis of 180 storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range at southern mid-latitudes, we consider those registered in the northern and central crop areas (oases). The regions affected by these storms are currently protected by an operational hail mitigation project. Differences with previously reported storms detected in the southern oasis are highlighted. Mendoza is a semiarid region situated roughly between 32S and 37S at the east of the highest Andes top. It forms a natural laboratory where different sources of gravity waves, mainly mountain waves, occur. In this work, we analyze the effects of flow over topography generating mountain waves and favoring deep convection. The joint occurrence of storms with hail production and mountain waves is determined from mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properly represent diverse structures observed in the region are considered in detail. A continuous wavelet transform is applied to each variable and profile to detect the main oscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radar echo, time and location are determined. The necessary energy to lift a parcel to its level of free convection is tested from the Convective Available Potential Energy and Convection Inhibition. This last parameter is compared against the mountain waves' vertical kinetic energy. The time evolution and vertical structure of vertical velocity and equivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able to provide the necessary energy to lift the air parcel and trigger convection. A simple conceptual scheme linking the dynamical factors taking place before and during storm development is proposed. (C) 2015 Elsevier B.V. All rights reserved.
Luques, CG ;Arbocco, FCV ; Pietrobon, EO ; Scanlan, T ; Jahn, GA ; Hapon, MB ; PLACENTA ,2015 ,36 ,518 -518 .
Pereyra, M ;Pol, RG ; Galetto, L ; ARTHROPOD-PLANT INTERACTIONS ,2015 ,9 ,175 -186 .
Little is known about the role of ants visiting extrafloral nectaries (EFNs) of plants in fragmented forests of South America. The aim of this work was to determine whether patch size and edge effect affect the composition and frequency of ants that visit the EFNs of Croton lachnostachyus, and how these changes may alter the reproductive success of plants in a fragmented landscape of the Chaco forest, Argentina. Data were analyzed considering patch size and edge effects-as indicators of fragmentation-on ant assemblages visiting plants and on plant reproductive success through a field experiment. Ant species composition differed between the edge and interior of fragments, but not among fragments of different sizes. Dolichoderinae species and some bigger ants as Camponotus mus (Formicinae) were more abundant at the edges, whereas Myrmicinae ants dominated the interior of fragments. Foliar damage was higher in plants located at interior than at edges of fragments. The ant-exclusion experiment showed that seed mass, germinability, and foliar damage did not differ between control and ant-excluded plants. In contrast, fruit (year 2011) and seed production (years 2010 and 2011) was higher in control plants. We highlight the importance of studying ant-plant interactions combining different attributes of biodiversity (composition, structure, and function) to better understand ecological processes in fragmented landscapes.
Vazquez, DP ;Ramos-Jiliberto, R ; Urbani, P ; Valdovinos, FS ; ECOLOGY LETTERS ,2015 ,18 ,385 -400 .
The strength of species interactions influences strongly the structure and dynamics of ecological systems. Thus, quantifying such strength is crucial to understand how species interactions shape communities and ecosystems. Although the concepts and measurement of interaction strength in food webs have received much attention, there has been comparatively little progress in the context of mutualism. We propose a conceptual scheme for studying the strength of plant-animal mutualistic interactions. We first review the interaction strength concepts developed for food webs, and explore how these concepts have been applied to mutualistic interactions. We then outline and explain a conceptual framework for defining ecological effects in plant-animal mutualisms. We give recommendations for measuring interaction strength from data collected in field studies based on a proposed approach for the assessment of interaction strength in plant-animal mutualisms. This approach is conceptually integrative and methodologically feasible, as it focuses on two key variables usually measured in field studies: the frequency of interactions and the fitness components influenced by the interactions.
Sanchez-Puerta, MV ;Zubko, MK ; Palmer, JD ; NEW PHYTOLOGIST ,2015 ,206 ,381 -396 .
The structure and evolution of angiosperm mitochondrial genomes are driven by extremely high rates of recombination and rearrangement. An excellent experimental system for studying these events is offered by cybrid plants, in which parental mitochondria usually fuse and their genomes recombine. Little is known about the extent, nature and consequences of mitochondrial recombination in these plants. We conducted the first study in which the organellar genomes of a cybrid - between Nicotiana tabacum and Hyoscyamus niger - were sequenced and compared to those of its parents. This cybrid mitochondrial genome is highly recombinant, reflecting at least 30 crossovers and five gene conversions between its parental genomes. It is also surprisingly large (41% and 64% larger than the parental genomes), yet contains single alleles for 90% of mitochondrial genes. Recombination produced a remarkably chimeric cybrid mitochondrial genome and occurred entirely via homologous mechanisms involving the double-strand break repair and/or break-induced replication pathways. Retention of a single form of most genes could be advantageous to minimize intracellular incompatibilities and/or reflect neutral forces that preferentially eliminate duplicated regions. We discuss the relevance of these findings to the surprisingly frequent occurrence of horizontal gene - and genome - transfer in angiosperm mitochondrial DNAs.
Hayes, KA ;Burks, RL ; Castro-Vazquez, A ; Darby, PC ; Heras, H ; Martin, PR ; Qiu, JW ; Thiengo, SC ; Vega, IA ; Wada, T ; Yusa, Y ; Burela, S ; Cadierno, MP ; Cueto, JA ; Dellagnola, FA ; Dreon, MS ; Frassa, MV ; Giraud-Billoud, M ; Godoy, MS ; Ituarte, S ; Koch, E ; Matsukura, K ; Pasquevich, MY ; Rodriguez, C ; Saveanu, L ; Seuffert, ME ; Strong, EE ; Sun, J ; Tamburi, NE ; Tiecher, MJ ; Turner, RL ; Valentine-Darby, PL ; Cowie, RH ; MALACOLOGIA ,2015 ,58 ,245 -302 .
Apple snails (Ampullariidae) are among the largest and most ecologically important freshwater snails. The introduction of multiple species has reinvigorated the field and spurred a burgeoning body of research since the early 1990s, particularly regarding two species introduced to Asian wetlands and elsewhere, where they have become serious agricultural pests. This review places these recent advances in the context of previous work, across diverse fields ranging from phylogenetics and biogeography through ecology and developmental biology, and the more applied areas of environmental health and human disease. The review does not deal with the role of ampullariids as pests, nor their control and management, as this has been substantially reviewed elsewhere. Despite this large and diverse body of research, significant gaps in knowledge of these important snails remain, particularly in a comparative framework. The great majority of the work to date concerns a single species, Pomacea canaliculata, which we see as having the potential to become a model organism in a wide range of fields. However, additional comparative data are essential for understanding this diverse and potentially informative group. With the rapid advances in genomic technologies, many questions, seemingly intractable two decades ago, can be addressed, and ampullariids will provide valuable insights to our understanding across diverse fields in integrative biology.
Koch, E ;Martin, SM ; Ciocco, NF ; IHERINGIA SERIE ZOOLOGIA ,2015 ,105 ,69 -75 .
For over 40 years malacologists have been discussing the taxonomical status of Heleobia species, an enigmatic genus from Cochliopidae family (Caenogastropoda: Rissooidea). As with other rissooidean families, the considerable character convergence and the paucity of anatomical synapomorphies has proved to be a problem in resolving cochliopid phylogenetic relations and establishing the validity of several nominal cochliopid species. Here we present a molecular contribution to solve the taxonomical status of one of the most abundant Southern South America cochliopid genera which has many endemic species. We report molecular evidence that supports three of the four Heleobia groups described for this region, the "australis","parchappa" and "piscium" groups. The fourth, the "hatcheri" group, belongs not to Heleobia but to a different genus which itself should not be considered as part of the family Cochliopidae but closely related to genus Potamolithus Pilsbry & Rush, 1896.
Bellera, CL ;Balcazar, DE ; Vanrell, MC ; Casassa, AF ; Palestro, PH ; Gavernet, L ; Labriola, CA ; Galvez, J ; Bruno-Blanch, LE ; Romano, PS ; Carrillo, C ; Talevi, A ; EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY ,2015 ,93 ,338 -348 .
In spite of remarkable advances in the knowledge on Trypanosoma cruzi biology, no medications to treat Chagas disease have been approved in the last 40 years and almost 8 million people remain infected. Since the public sector and non-profit organizations play a significant role in the research efforts on Chagas disease, it is important to implement research strategies that promote translation of basic research into the clinical practice. Recent international public-private initiatives address the potential of drug repositioning (i.e. finding second or further medical uses for known-medications) which can substantially improve the success at clinical trials and the innovation in the pharmaceutical field.
Garcia, LE ;Sanchez-Puerta, MV ; PLOS ONE ,2015 ,10 ,-.
Molecular taxonomy and evolution of nematodes have been recently the focus of several studies. Mitochondrial sequences were proposed as an alternative for precise identification of Meloidogyne species, to study intraspecific variability and to follow maternal lineages. We characterized the mitochondrial genomes (mtDNAs) of the root knot nematodesM. floridensis, M. hapla and M. incognita. These were AT rich (81-83%) and highly compact, encoding 12 proteins, 2 rRNAs, and 22 tRNAs. Comparisons with published mtDNAs of M. chitwoodi, M. incognita (another strain) andM. graminicola revealed that they share protein and rRNA gene order but differ in the order of tRNAs. The mtDNAs of M. floridensis andM. incognita were strikingly similar (97-100% identity for all coding regions). In contrast, M. floridensis, M. chitwoodi, M. hapla andM. graminicola showed 65-84% nucleotide identity for coding regions. Variable mitochondrial sequences are potentially useful for evolutionary and taxonomic studies. We developed a molecular taxonomic marker by sequencing a highly-variable similar to 2 kb mitochondrial region, nad5-cox1, from 36 populations of root-knot nematodes to elucidate relationships within the genus Meloidogyne. Isolates of five species formed monophyletic groups and showed little intraspecific variability. We also present a thorough analysis of the mitochondrial region cox2-rrnS. Phylogenies based on either mitochondrial region had good discrimination power but could not discriminate between M. arenaria, M. incognita and M. floridensis.
Papaleo, RM ;Thomaz, R ; Gutierres, LI ; de Menezes, VM ; Severin, D ; Trautmann, C ; Tramontina, D ; Bringa, EM ; Grande, PL ; PHYSICAL REVIEW LETTERS ,2015 ,114 ,-.
We show direct experimental evidence that radiation effects produced by single MeV heavy ions on a polymer surface are weakened when the length of the ion track in the material is confined into layers of a few tens of nanometers. Deviation from the bulk (thick film) behavior of ion-induced craters starts at a critical thickness as large as similar to 40 nm, due to suppression of long-range additive effects of excited atoms along the track. Good agreement was found between the experimental results, molecular dynamic simulations, and an analytical model.
Schuster, JK ;Harner, T ; Fillmann, G ; Ahrens, L ; Altamirano, JC ; Aristizabal, B ; Bastos, W ; Castillo, LE ; Cortes, J ; Fentanes, O ; Gusev, A ; Hernandez, M ; Ibarra, MV ; Lana, NB ; Lee, SC ; Martinez, AP ; Miglioranza, KSB ; Puerta, AP ; Segovia, F ; Siu, M ; Tominaga, MY ; ENVIRONMENTAL SCIENCE & TECHNOLOGY ,2015 ,49 ,3680 -3686 .
A passive air sampling network has been established to investigate polychlorinated dibenzo-p-clioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at Global Atmospheric Passive Sampling (GAPS) sites and six additional sites in the Group of Latin American and Caribbean Countries (GRULAC) region. The air sampling network covers background, agricultural, rural, and urban sites. Samples have been collected over four consecutive periods of 6 months, which started in January 2011 [period 1 (January to June 2011), period 2 (July to December 2011), period 3 (January to June 2012), and period 4 (July 2012 to January 2013)]. Results show that (i) the GAPS passive samplers (PUF disk type) and analytical methodology are adequate for measuring PCDD/F burdens in air and (ii) PCDD/F concentrations in air across the GRULAC region are widely variable by almost 2 orders of magnitude. The highest concentrations in air of Z(4-8)PCDD/Fs were found at the urban site Sao Luis (Brazil, UR) (i.e., 2560 fg/m(3)) followed by the sites in sao Paulo (Brazil, UR), Mendoza (Argentina, RU), and Sonora (Mexico, AG) with values of 1690, 1660, and 1610 fg/m3, respectively. Very low concentrations of PCDD/Fs in air were observed at the background site Tapanti (Costa Rica, BA), 10.8 fg/m(3). This variability is attributed to differences in site characteristics and potential local/regional sources as well as meteorological influences. The measurements of PCDD/Fs in air agree well with model-predicted concentrations performed using the Global EMEP Multimedia Modeling System (GLEMOS) and emission scenario constructed on the basis of the UNEP Stockholm Convention inventory of dioxin and furan emissions.
Piaggi, PM ;Bringa, EM ; Pasianot, RC ; Gordillo, N ; Panizo-Laiz, M ; del Rio, J ; de Castro, CG ; Gonzalez-Arrabal, R ; JOURNAL OF NUCLEAR MATERIALS ,2015 ,458 ,233 -239 .
The hydrogen behavior in nanocrystalline W (ncW) samples with grain size of 5 and 10 nm is studied using Molecular Dynamics (MD) with a bond order potential (BOP) for the W-H system. The dependence of the hydrogen diffusion coefficient on grain size (5 and 10 nm) and hydrogen concentration (0.1 at.% < [H] < 10.0 at.%) is calculated. These data show that in all cases the hydrogen diffusion coefficient is lower for ncW than for coarse-grained samples. Trapping energies of grain boundaries are estimated and a broad distribution roughly centered at the vacancy trapping energy is found. Hydrogen diffusion results are interpreted within the trapping model by Kirchheim for nanocrystalline materials. The H-H interaction is evaluated and the possible formation of H-2 is disregarded for the conditions in these simulations. Hydrogen segregation and trapping in grain boundaries for ncW is discussed, including extrapolations for micron-sized polycrystals. (C) 2014 Elsevier B.V. All rights reserved.
Marsh, EJ ;ENVIRONMENTAL ARCHAEOLOGY ,2015 ,20 ,13 -29 .
In the fourth millennium BP, there were major environmental and cultural changes on the Andean altiplano of South America, but the chronology remains vague. A recent synthesis describes a slow, gradual transition from hunting and gathering to agropastoralism. This proposal is tested by refining the date of the onset of more humid and stable conditions, around 3550 cal BP, based on a Bayesian model of 26 dates from Lake Winaymarka and an updated calculation of the lacustrine offset. This is compared to Bayesian models of 191 dates from 20 archaeological sites, which incorporate a number of recently processed radiocarbon dates. A synthesis is presented of 15 full coverage surveys, a summed probability distribution, and a Bayesian model of the transition to ceramics, which together support a scenario of a very rapid demographic increase. Fourteen models from archaeological sites are cross-referenced in a composite model, which identifies a brief, altiplano-wide emergence of agropastoralism with starting and ending boundaries of 3540 and 3120 cal BP, respectively. This starting boundary correlates strongly with the onset of improving environmental conditions, indicating synchronous cultural and environmental change. The suite of accelerating cultural changes included a marked reduction in mobility, a demographic surge, increased subsistence diversity, the adoption of ceramics, farming and the integration of camelid herding into a remarkably resilient economic strategy still in use today. This is a highly relevant but yet to be used comparative case study for the variable tempos of 'big histories', and ecocultural interactions that generate rapid, emergent episodes of wide-spread and enduring cultural change.
Llano, C ;JOURNAL OF ARCHAEOLOGICAL SCIENCE ,2015 ,54 ,182 -192 .
In this paper, optimal foraging theory is used to interpret wild plant collecting behaviors using experimental data and remains recovered from eleven archaeological sites in the Argentine Andes. Using simple techniques believed to approximate those of traditional hunting and gathering societies, I collected and processed twelve plant species endemic to southern Mendoza Province to assess their utility as human food resources. Experimental collection and processing events were timed and total caloric yield weighed against post-encounter handling time to determine each resource's relative rank. In addition, I calculated maximum transport distances to better understand which resources are likely to be recovered in the archaeological record. The results suggest that the distance that must be traveled to reach each plant gathering site determines the whether particular plants will be collected since people should maximize caloric yield relative to both handling costs and transport distance. I conclude by cautioning that optimal foraging theory does not explain all of the variation in hunter-gatherer plant collection, but suggest that the value of the approach lies in its capacity to provide testable hypotheses of foraging behavior and behavioral changes likely to occur under different circumstances. (C) 2014 Elsevier Ltd. All rights reserved.
Cuello-Carrion, FD ;Shortrede, JE ; Alvarez-Olmedo, D ; Cayado-Gutierrez, N ; Castro, GN ; Zoppino, FCM ; Guerrero, M ; Martinis, E ; Wuilloud, R ; Gomez, NN ; Biaggio, V ; Orozco, J ; Gago, FE ; Ciocca, LA ; Fanelli, MA ; Ciocca, DR ; CLINICAL & EXPERIMENTAL METASTASIS ,2015 ,32 ,151 -168 .
In human breast cancer, beta-catenin localization has been related with disease prognosis. Since HER2-positive patients are an important subgroup, and that in breast cancer cells a direct interaction of beta-catenin/HER2 has been reported, in the present study we have explored whether beta-catenin location is related with the disease survival. The study was performed in a tumor bank from patients (n = 140) that did not receive specific anti-HER2 therapy. The proteins were detected by immunohistochemistry in serial sections, 47 (33.5 %) patients were HER2-positive with a long follow-up. HER2-positive patients that displayed beta-catenin at the plasma membrane (completely surrounding the tumour cells) showed a significant better disease-free survival and overall survival than the patients showing the protein on other locations. Then we explored the dynamics of the co-expression of beta-catenin and HER2 in human MCF-7 and SKBR3 cells exposed to different stressful situations. In untreated conditions MCF-7 and SKBR3 cells showed very different beta-catenin localization. In MCF-7 cells, cadmium administration caused a striking change in beta-catenin localization driving it from plasma membrane to cytoplasmic and perinuclear areas and HER2 showed a similar localization patterns. The changes induced by cadmium were compared with heat shock, H2O2 and tamoxifen treatments. In conclusion, this study shows the dynamical associations of HER2 and beta-catenin and their changes in subcellular localizations driven by stressful situations. In addition, we report for the first time the correlation between plasma membrane associated beta-catenin in HER2-positive breast cancer and survival outcome, and the importance of the protein localization in breast cancer samples.
Gao, Y ;Ruestes, CJ ; Tramontina, DR ; Urbassek, HM ; JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS ,2015 ,75 ,58 -75 .
Using molecular-dynamics simulation, we study nanoindentation in fcc (Cu and Al) and bcc (Fe and Ta) metals by a spherical indenter and investigate the size of the plastic zone generated. We find that while it does not strongly depend on crystal structure, surface orientation, and indentation parameters, the extent of the plastic zone is substantially larger before the retraction of the indenter. After retraction, the results are in good agreement with available published data. Plasticity develops by the generation, propagation and reaction of dislocations; they fall into two groups, those that adhere to the indentation pit, and those that have been emitted either into the substrate interior or glide along the surface. The total length of the dislocation network generated roughly follows available geometrical estimates; results for individual surface orientations may, however, differ quite strongly. The radial distribution of the dislocations attached to the indentation pit is computed; as a rule it shows a maximum at some depth below the indentation pit. (C) 2014 Elsevier Ltd. All rights reserved.
Gonzalez, CV ;Fanzone, ML ; Cortes, LE ; Bottini, R ; Lijavetzky, DC ; Ballare, CL ; Boccalandro, HE ; PHYTOCHEMISTRY ,2015 ,110 ,46 -57 .
Sunlight exposure has multiple effect on fruits, as it affects the light climate perceived by fruit photore-ceptors and fruit tissue temperature. In grapes (Vitis vinifera L), light exposure can have a strong effect on fruit quality and commercial value; however, the mechanisms of light action are not well understood. The role of fruit-localized photoreceptors in the control of berry quality traits was evaluated under field conditions in a commercial vineyard in Mendoza (Argentina). Characterization of the diurnal dynamics of the fruit light environment in a vertical trellis system indicated that clusters were shaded by leaves during most of the photoperiod. Supplementation of the fruit light environment from 20 days before veraison until technological harvest showed that red (R, 660 nm) and blue (B, 470 nm) light strongly increased total phenolic compound levels at harvest in the berry skins without affecting sugar content, acidity or berry size. Far-red (FR, 730 nm) and green (G, 560 nm) light supplementation had relatively small effects. The stimulation of berry phytochromes and cryptochromes favored accumulation of flavonoid and non-flavonoid compounds, including anthocyanins, flavonols, flavanols, phenolic acids and stilbenes. These results demonstrate that the chemical composition of grape berries is modulated by the light quality received by the clusters under field conditions, and that fruit photoreceptors are not saturated even in areas of high insolation and under management systems that are considered to result in a relatively high exposure of fruits to solar radiation. Therefore, manipulation of the light environment or the light sensitivity of fruits could have significant effects on critical grape quality traits. Published by Elsevier Ltd.
Barberena, R ;Prates, L ; de Porras, ME ; QUATERNARY INTERNATIONAL ,2015 ,356 ,111 -126 .
Archaeological radiocarbon databases are being increasingly used as a proxy of past demographic trends. In this paper we compile and analyze an extensive database of paleoecological information and C-14 dates from archaeological sites in northwestern Patagonia (Argentina, South America). On this basis, we assess the regional distribution of human populations since the late Pleistocene, and their relation with the evolution of Patagonian climate and landscapes. We explore the spatial and temporal distribution of evidence and discuss sampling biases affecting the record in different ecological contexts. The analysis is set in the frame of three main ecological regions that have implications for human subsistence: Andean forest, grass steppe, and shrub steppe. The intensity of the archaeological signal differs among these regions through time, being stronger and more homogeneous in the grass steppe. In the Andean forest and the shrub steppe the signal is weaker and even absent during short periods of the middle Holocene. We suggest likely sampling biases contributing to these tendencies, since these three regions present variable research cover and intensity. On the other hand, we also suggest that these differences may reflect variations in the intensity of human occupation, in favor of more attractive environments for hunting (i.e., areas where guanaco are generally more abundant). This macro-regional synthesis of the paleoecology and archaeology of northwestern Patagonia provides a platform for developing future oriented research. (C) 2014 Elsevier Ltd and INQUA. All rights reserved.
D'Angelo, JA ;Zodrow, EL ; INTERNATIONAL JOURNAL OF COAL GEOLOGY ,2015 ,138 ,42 -54 .
A larger chemometric study (data derived from Fourier transform infrared spectroscopy-FTIR interpreted by principal component analysis) is undertaken involving species (numbers bracketed) from the four medullosalean families Neurodontopteridaceae (7), Potonieaceae (1), Cyclopteridaceae (1), and Alethopteridaceae (1). Samples originated from the fossil Lagerstatte ("medullosalean forest") in the Late Pennsylvanian of Sydney Coalfield, Nova Scotia, Canada, where they are preserved as compressions or fossilized-cuticles. The study aims at demonstrating how the level of objectivity for medullosalean fossil-plant determinations can be raised through inquiring (i) if the chemistry of isolated foliage supports the specific classification based on morphologies alone, (ii) if chemistry of different preservation states hampers the application of chemometrics, and (iii) if taxonomic assignation of poorly preserved specimens can be assisted by chemometrics. Given the similar thermal history, direct chemical comparisons amongst taxa having the same preservation state were possible. The chemometric approach resulted into a two principal-component model (80% cumulative-explained variance) that provided information on the relative contributions of aromatic structures, oxygen-containing, and aliphatic groups. These functional groups enabled statistical distinction amongst most of the morphology-defined species, and families, irrespective of the two preservation states. We concluded that results, overall, support the aims of the study, with implications to solve some palaeobotanical difficulties related to biostratigraphy and palaeobiogeography. (C) 2014 Elsevier B.V. All rights reserved.
Ardiani, F ;Manelli, AA ; Ruestes, CJ ; Careglio, CA ; Bringa, EM ; PROCEEDINGS OF THE 1ST PAN-AMERICAN CONGRESS ON COMPUTATIONAL MECHANICS ,2015 ,,156 -165 .
Metallic glasses with porosity have been in the spotlight in recent years and much research has been done on them, in an effort to improve the understanding of the mechanics of deformation. The behavior of the material in the elastoplastic regime may be controlled by the introduction of pores, thus the interest on simulating them. Large deformation is normally a consequence of shear transformations zones (STZ) collapsing into shear bands (SB) which may lead to catastrophic failure. It is widely known that in crystalline metals the addition of nanopores slows down dislocation motion and changes the resulting plastic deformation. Similarly, pores in metallic glasses limit the propagation of shear bands and allow a more homogeneous deformation. In previous work we determined constitutive parameters of the Cu46 Zr54 metallic glass as a function of temperature. We now present results for a metallic glass with the same composition, but fabricated by sintering of BMG nanoparticles, which results in samples with porosity, similar to nanoglass samples in some experiments and simulations. Atomistic simulations arc carried out using Molecular Dynamics (MD), and analysis includes atomic Voronoi polyhedra, and atomic stress and strain. We analyse the dependence of deformation on solid volume fraction, and the way deformation is distributed throughout the sample, as a function of initial porosity.
Manelli, AA ;Ardiani, F ; Careglio, CA ; Bringa, EM ; PROCEEDINGS OF THE 1ST PAN-AMERICAN CONGRESS ON COMPUTATIONAL MECHANICS ,2015 ,,166 -176 .
Plasticity in bulk metallic glasses (BMGs), is normally dominated initially by shear transformations zones (STZ), which expand to form shear bands (SB) through the material. In order to control and thus improve the dynamics of plasticity, composition of metallic glasses has been modified in different ways.
Barberena, R ;Borrazzo, K ; Rughini, AA ; Romero, G ; Pompei, MP ; Llano, C ; de Porras, ME ; Duran, V ; Stern, CR ; Re, A ; Estrella, D ; Forasiepi, A ; Fernandez, FJ ; Chidiak, M ; Acuna, L ; Gasco, A ; Quiroga, MN ; MAGALLANIA ,2015 ,43 ,137 -163 .
Northern Neuquen Province (Pehuenches Dept., Argentina) is barely known from an archaeological perspective, though it is centrally placed in terms of several large-scale key issues in the peopling of South America: the extinction of the megafauna and its causes, early human presence, and the existence of archaeological discontinuities during the Mid-Holocene. In this paper we present the first body of paleoecological and archaeological data for Cueva Huenul 1 site, recently excavated, which offers a sedimentary sequence extending during the last of 16.000 calendar years. Initially, we present a chronostratigraphic frame for the site, including new tephro-chronological information. On this basis, four temporal components are defined, providing the historical scheme for the analysis of the recovered evidences that include: archaeofaunas (paleontological and archaeological), archaeobotany, lithic and ceramic technology, and rockart. These results at a site scale provide a first approach to a discussion of macro-regional processes, as well as the basis for the continuation of our research.
Fusari, CM ;Locatelli, DA ; Altamirano, JC ; Camargo, AB ; JOURNAL OF CHEMISTRY ,2015 ,,-.
Total isothiocyanates content (ITC) is considered a good indicator of bioactive compounds responsible for beneficial effects related to Brassicaceae vegetables. Analytical performance is a critical factor for routine analysis in plant tissues. The extraction technique for isolating phytochemicals from Brassicaceae vegetables is currently the bottleneck of the methodology. The aim of this work was to optimize this step in the analytical process. Fast and less expensive alternative, based on ultrasound-assisted extraction technique (UAE) for direct extraction of GLS into an aqueous phase and further analysis of the hydrolysis product, was optimized. Full factorial (2(k)) design followed by Central Composite Design (CCD) was used to obtain the optimum extraction conditions. Selected conditions were homogenization time (9 min); ultrasound bath time (5 min); and sample-to-solvent ratio (1 : 5 w/v mg mL(-1)). The proposed analytical methodology exhibits satisfactory analytical performance in terms of linearity, precision (RSD < 2.4%), and limits of detection (26 nmol g(-1) w.w.). The new analytical methodology was applied to cauliflower, cabbage, watercress, and broccoli samples with recoveries higher than 86%. The UAE extraction technique was showed to be efficient for real samples analysis leading to sensible, selective, and reproducible methodology for ITC analysis.
Duplancic, MA ;Carretero, EM ; Cavagnaro, B ; Moratta, MH ; Romero, ALN ; REVISTA DE LA FACULTAD DE CIENCIAS AGRARIAS ,2015 ,47 ,71 -82 .
A. araucana is a dioecious conifer endemic of Argentina and Chile. Female trees produce large seeds that are dispersed between February and May. Some aspects on the self-ecology of this species, particularly in the xeric forest and in its eastern border of distribution, remain yet under study. The objectives of this study were to evaluate the effect of temperature and pre-germinative treatments on germination of A. araucana seeds from the xeric forest. Temperature effect was assessed in growth chambers considering six temperatures levels from 10 degrees C to 35 degrees C, with intervals of 5 degrees C. Cardinal minimum, maximum and optimal germination temperatures were 15 degrees C, 30 degrees C and 25 degrees C, respectively. Pre-germinative treatment effect was assessed considering five treatments: imbibition, complete mechanical scarification, partial mechanical scarification, chemical scarification and control. The use of pre-germinative treatments doubled the percentage of germination as regards the reference control. To maximize the germination of seeds of A. araucana is recommended the use of a pre-germinative treatment of imbibition in distilled water and incubate the seeds at 25 degrees C.
Escudero, LB ;Garcia, CB ; da Silva, SM ; Baron, JH ; ANALYTICAL METHODS ,2015 ,7 ,7480 -7487 .
A simple and environmentally friendly technique named cellular phase microextraction (Cell-PME) was developed for thallium (Tl) species determination. Basically, Tl(III) species were mixed with a solution containing Chlorella vulgaris microalgal cells (480 mg L-1) at pH 7 and the resulting system was stirred with a vortex for 8 min. After a centrifugation process, the sediment phase was directly injected into the graphite furnace of an electrothermal atomic absorption spectrometer. In contrast to Tl(III), Tl(I) species were not retained by the biomass. Optimization of variables influencing the biosorption process, including sample pH, microalgal mass and sample volume, was performed. A biosorption efficiency of 65% and an enrichment factor of 50 were obtained with only 5.00 mL of sample. The limit of detection (LOD) was 8.3 ng L-1 Tl, while the relative standard deviation (RSD) was 5.1% (at 1 mu g L-1 Tl and n = 10), calculated from the peak height of absorbance signals (Gaussian-shape and reproducible peaks). The proposed method was successfully applied to determine Tl species in environmental samples, including drinking and natural water. To the best of our knowledge, a biosorption process is applied for the first time for Tl species separation and determination in the analytical field.
Grijalba, AC ;Martinis, EM ; Lascalea, GE ; Wuilloud, RG ; SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY ,2015 ,103 ,49 -56 .
A flow injection system based on a modified polytetrafluoroethylene (PTFE) knotted reactor (KR) was developed for arsenite [As(III)] and arsenate [As(V)] species preconcentration and determination by electrothermal atomic absorption spectrometry (ETAAS). Activated carbon (AC) was immobilized on the inner walls of a PTFE KR by a thermal treatment. A significant increase in analyte retention was obtained with the AC-modified KR (100%) as compared to the regular PTFE KR (25%). The preconcentration method involved the on-line formation of As(III)-ammonium pyrrolidinedithiocarbamate (As-APDC) complex, followed by its adsorption onto the inner walls of the AC-modified KR. After analyte retention, the complex was eluted with acetone directly into the graphite furnace of ETAAS. The parameters affecting the flow injection system were evaluated with a full central composite face centered design with three center points. Under optimum conditions, a preconcentration factor of 200 was obtained with 10 ml of sample. The detection limit was 4 ng L-1 and the relative standard deviation (RSD) for six replicate measurements at 0.2 mu gL(-1) of As were 4.3% and 4.7% for As(III) and As(V), respectively. The developed methodology was highly selective towards As(III), while As(V), monomethylarsonic acid [MMA(V)] and dimethylarsinic [DMA(V)] were not retained in the AC-modified KR. The proposed method was successfully applied for As speciation analysis in infusions originated from medicinal herbs and tea. (C) 2014 Elsevier B.V. All rights reserved.
Grijalba, AC ;Escudero, LB ; Wuilloud, RG ; ANALYTICAL METHODS ,2015 ,7 ,490 -499 .
The capabilities of several phosphonium-ionic liquids (PILs) to form ion-pairs with a complex obtained by reaction of arsenate species with molybdate were evaluated. Phosphonium-ILs containing the tetradecyl(trihexyl)phosphonium cation but different anions (dicyanamide and decanoate) and tributyl(methyl)phosphonium methylsulphate IL were studied. The size, polarity and localization of charges in PIL cations were shown to influence their capability to form ion-pairs with the arsenomolybdate (AsMo12O403-) complex and to extract As(V). The performance of PILs was compared with that of a widely used ion-pairing reagent, cetyltrimethylammonium bromide (CTAB). Finally, the IL tetradecyl(trihexyl)phosphonium dicyanamide was chosen to develop a liquid-liquid microextraction (LLME) procedure using only 80 mL of tetrachloroethylene as the extractant. The organic phase was directly injected into the graphite furnace of an electrothermal atomic absorption spectrometer (ETAAS) for As determination. An extraction efficiency of 100% and a sensitivity enhancement factor of 130 were obtained with 5 mL of sample. The detection limit was 1.9 ng L-1 and the relative standard deviation for six replicate measurements of 1.0 mg L-1 for As was 4.9%, 5.0% and 5.1% for As(V), As(III) and organic As species, respectively.
Camin, SR ;Cueto, VR ; de Casenave, JL ; Marone, L ; EMU ,2015 ,115 ,261 -269 .
Habitat degradation caused by cattle grazing may be a serious threat for seed-eating birds because the availability of beneficial seeds usually diminishes in grazed areas. Ecologically plastic species might, however, circumvent food deprivation via changes in foraging behaviour. We studied the limits of feeding flexibility and factors affecting seed preferences in Zonotrichia capensis, Diuca diuca, and Saltatricula multicolor. We experimentally assessed preferences for seeds of eight grass and eight forb species by using a protocol that combines choice and non-choice trials, and employed a different batch of experiments to evaluate some plausible causes of different feeding flexibility. On average, birds consumed 45-140% more grass than forb seeds, confirming previous results. Z. capensis preferred several grass and forb seeds, and showed maximum feeding flexibility. S. multicolor and, to a lesser extent, D. diuca, were grass specialists that preferred large and medium-sized grass seeds. The size of forb seeds did not affect preferences. Coat thickness of grass seeds did not seriously reduce consumption levels. Birds showed low ability to feed on resources characteristic of degraded environments (i.e. annual grass seeds). Species-specific differences in behavioural flexibility could be used to predict dietary and numerical responses of seed-eating birds to habitat degradation.
Porasso, RD ;Ale, NM ; Aloia, FC ; Masone, D ; Del Popolo, MG ; Ben Altabef, A ; Gomez-Zavaglia, A ; Diaz, SB ; Vila, JA ; RSC ADVANCES ,2015 ,5 ,43537 -43546 .
The interaction of unblocked glycine, lysine, proline, and histidine (in their three forms, namely two tautomers and the protonated form) with a dipalmitoylphosphatidylcholine (DPPC) bilayer was assessed using extensive atomistic molecular dynamics simulations. Free energy profiles for the insertion of each amino acid into the lipid bilayer were computed along an appropriated reaction coordinate. The simulation results for glycine in the presence of DPPC were compared with experimental data obtained by Fourier transform infrared spectroscopy. Experimental results predict, in good agreement with simulations, the existence of intermolecular interactions between the DPPC head groups and glycine. Atomistic simulations were further extended to investigate the free energy profiles for lysine, proline and histidine, leading to the following conclusions: (i) lysine free energy profiles computed using a united atom force-field and an analog molecule, where the side-chain is truncated at the beta-carbon atom, differ significantly from each other; (ii) the free energy profiles for the three forms of histidine are all very similar, although the charged form interacts mostly with the carbonyl groups of DPPC, while the tautomers interact with the phosphate groups; and (iii) proline does not show a minimum in the free energy profile, pointing to the absence of binding to the membrane lipids. Overall, this work contributes to our general understanding of the various factors affecting the interactions between amino acids and a model cell membrane, and may spur progress in the effort to develop new molecular models to study larger biological systems.