Facultad de Ciencias Exactas y Naturales

Publicaciones 2016

A global model of tropospheric chlorine chemistry: Organic versus inorganic sources and impact on methane oxidation

Hossaini, R ;Chipperfield, MP ; Saiz-Lopez, A ; Fernandez, R ; Monks, S ; Feng, WH ; Brauer, P ; von Glasow, R ; JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES ,2016 ,121 ,14271 -14297 .

Chlorine atoms (Cl) are highly reactive toward hydrocarbons in the Earth's troposphere, including the greenhouse gas methane (CH4). However, the regional and global CH4 sink from Cl is poorly quantified as tropospheric Cl concentrations ([Cl]) are uncertain by similar to 2 orders of magnitude. Here we describe the addition of a detailed tropospheric chlorine scheme to the TOMCAT chemical transport model. The model includes several sources of tropospheric inorganic chlorine (Cly), including (i) the oxidation of chlorocarbons of natural (CH3Cl, CHBr2Cl, CH2BrCl, and CHBrCl2) and anthropogenic ( CH2Cl2, CHCl3, C2Cl4, C2HCl3, and CH2ClCH2Cl) origin and ( ii) sea-salt aerosol dechlorination. Simulations were performed to quantify tropospheric [Cl], with a focus on the marine boundary layer, and quantify the global significance of Cl atom CH4 oxidation. In agreement with observations, simulated surface levels of hydrogen chloride (HCl), the most abundant Cl-y reservoir, reach several parts per billion (ppb) over polluted coastal/continental regions, with sub-ppb levels typical in more remote regions. Modeled annual mean surface [Cl] exhibits large spatial variability with the largest levels, typically in the range of 1-5x10(4) atoms cm(-3), in the polluted northern hemisphere. Chlorocarbon oxidation provides a tropospheric Cly source of up to similar to 4320 Gg Cl/yr, sustaining a background surface [Cl] of < 0.1 to 0.5 x 10(3) atoms cm(-3) over large areas. Globally, we estimate a tropospheric methane sink of similar to 12-13 Tg CH4/yr due the CH4 + Cl reaction (similar to 2.5% of total CH4 oxidation). Larger regional effects are predicted, with Cl accounting for similar to 10 to > 20% of total boundary layer CH4 oxidation in some locations.

Morphology and Hydraulic Architecture of Vitis vinifera L. cv. Syrah and Torrontes Riojano Plants Are Unaffected by Variations in Red to Far-Red Ratio

Gonzalez, CV ;Jofre, MF ; Vila, HF ; Stoffel, M ; Bottini, R ; Giordano, CV ; PLOS ONE ,2016 ,11 ,-.

Plants have evolved an array of specific photoreceptors to acclimate to the light environment. By sensing light signals, photoreceptors modulate plant morphology, carbon-and water-physiology, crop yield and quality of harvestable organs, among other responses. Many cultural practices and crop management decisions alter light quantity and quality perceived by plants cultivated in the field. Under full sunlight, phytochromes perceive high red to far red ratios (R:FR; 1.1), whereas overhead or lateral low R:FR (below 1.1) are sensed in the presence of plant shade or neighboring plants, respectively. Grapevine is one of the most important fruit crops in the world. To date, studies on grapevine response to light focused on different Photosynthetic Active Radiation (PAR) levels; however, limited data exist about its response to light quality. In this study we aimed to investigate morphological, biochemical, and hydraulic responses of Vitis vinifera to variations in R:FR. Therefore, we irradiated Syrah and Torronte's Riojano plants, grown in a glasshouse, with lateral FR light (low lateral R:FR treatment), while others, that were kept as controls, were not irradiated (ambient lateral R:FR treatment). In response to the low lateral R:FR treatment, grapevine plants did not display any of the SAS morphological markers (i.e. stem length, petiole length and angle, number of lateral shoots) in any of the cultivars assessed, despite an increase in gibberelins and auxin concentrations in leaf tissues. Low lateral R:FR did not affect dry matter partitioning, water-related traits (stomata density and index, wood anatomy), or water-related physiology (plant conductance, transpiration rate, stem hydraulic conductivity, stomatal conductance). None of the Vitis vinifera varieties assessed displayed the classical morphological and hydraulic responses associated to SAS induced by phytochromes. We discuss these results in the context of natural grapevine environment and agronomical relevance.

Study of the Extraction Kinetics of Lithium by Leaching beta-Spodumene with Hydrofluoric Acid

Rosales, GD ;Ruiz, MC ; Rodriguez, MH ; MINERALS ,2016 ,6 ,-.

Parameters affecting the kinetics of the dissolution of beta-spodumene with hydrofluoric acid have been investigated. The experimental tests were carried out in a closed vessel. The influence of several parameters, such as stirring speed, temperature, and reaction time were studied in order to deduce the kinetics of the dissolution reaction. The other parameters, particle size-45 m; HF concentration 4% v/v, and the solid-liquid ratio 0.95% w/v were kept constant. The results indicate that the stirring speed does not have an important effect on the dissolution of the mineral above 330 rpm. The extent of the leaching of beta-spodumene increases with temperature and reaction time augmentations. Scanning electron microscope (SEM) analyses of some residues in which the conversion was lower than 30% indicated a selective attack on certain zones of the particle. The treatment of the experimental data was carried out using the Modelado software. The model that best represents the dissolution of the mineral is the following: ln(1- X) =-b(1) [ln(1 + b(2)t)- b(2)t/(1 + b(2)t)]. This model is based on nucleation and growth of nuclei theory, and describes the style of attack physically observed by SEM on the residues.

VizRec: Recommending Personalized Visualizations


Visualizations have a distinctive advantage when dealing with the information overload problem: Because they are grounded in basic visual cognition, many people understand them. However, creating proper visualizations requires specific expertise of the domain and underlying data. Our quest in this article is to study methods to suggest appropriate visualizations autonomously. To be appropriate, a visualization has to follow known guidelines to find and distinguish patterns visually and encode data therein. A visualization tells a story of the underlying data; yet, to be appropriate, it has to clearly represent those aspects of the data the viewer is interested in. Which aspects of a visualization are important to the viewer? Can we capture and use those aspects to recommend visualizations? This article investigates strategies to recommend visualizations considering different aspects of user preferences. A multi-dimensional scale is used to estimate aspects of quality for visualizations for collaborative filtering. Alternatively, tag vectors describing visualizations are used to recommend potentially interesting visualizations based on content. Finally, a hybrid approach combines information on what a visualization is about (tags) and how good it is (ratings). We present the design principles behind VizRec, our visual recommender. We describe its architecture, the data acquisition approach with a crowd sourced study, and the analysis of strategies for visualization recommendation.

Streamflow variability in the Chilean Temperate-Mediterranean climate transition (35 degrees S-42 degrees S) during the last 400 years inferred from tree-ring records

Munoz, AA ;Gonzalez-Reyes, A ; Lara, A ; Sauchyn, D ; Christie, D ; Puchi, P ; Urrutia-Jalabert, R ; Toledo-Guerrero, I ; Aguilera-Betti, I ; Mundo, I ; Sheppard, PR ; Stahle, D ; Villalba, R ; Szejner, P ; LeQuesne, C ; Vanstone, J ; CLIMATE DYNAMICS ,2016 ,47 ,4051 -4066 .

As rainfall in South-Central Chile has decreased in recent decades, local communities and industries have developed an understandable concern about their threatened water supply. Reconstructing streamflows from tree-ring data has been recognized as a useful paleoclimatic tool in providing long-term perspectives on the temporal characteristics of hydroclimate systems. Multi-century long streamflow reconstructions can be compared to relatively short instrumental observations in order to analyze the frequency of low and high water availability through time. In this work, we have developed a Biobio River streamflow reconstruction to explore the long-term hydroclimate variability at the confluence of the Mediterranean-subtropical and the Temperate-humid climate zones, two regions represented by previous reconstructions of the Maule and Puelo Rivers, respectively. In a suite of analyses, the Biobio River reconstruction proves to be more similar to the Puelo River than the Maule River, despite its closer geographic proximity to the latter. This finding corroborates other studies with instrumental data that identify 37.5A degrees S as a latitudinal confluence of two climate zones. The analyzed rivers are affected by climate forcings on interannual and interdecadal time-scales, Tropical (El Nio Southern Oscillation) and Antarctic (Southern Annular Mode; SAM). Longer cycles found, around 80-years, are well correlated only with SAM variation, which explains most of the variance in the Biobio and Puelo rivers. This cycle also has been attributed to orbital forcing by other authors. All three rivers showed an increase in the frequency of extreme high and low flow events in the twentieth century. The most extreme dry and wet years in the instrumental record (1943-2000) were not the most extreme of the past 400-years reconstructed for the three rivers (1600-2000), yet both instrumental record years did rank in the five most extreme of the streamflow reconstructions as a whole. These findings suggest a high level of natural variability in the hydro-climatic conditions of the region, where extremes characterized the twentieth century. This information is particularly useful when evaluating and improving a wide variety of water management models that apply to water resources that are sensitive to agricultural and hydropower industries.

Fourth order phase-field model for local max-ent approximants applied to crack propagation

Amiri, F ;Millan, D ; Arroyo, M ; Silani, M ; Rabczuk, T ; COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING ,2016 ,312 ,254 -275 .

We apply a fourth order phase-field model for fracture based on local maximum entropy (LME) approximants. The higher order continuity of the meshfree LME approximants allows to directly solve the fourth order phase-field equations without splitting the fourth order differential equation into two second order differential equations. We will first show that the crack surface can be captured more accurately in the fourth order model. Furthermore, less nodes are needed for the fourth order model to resolve the crack path. Finally, we demonstrate the performance of the proposed meshfree fourth order phase-field formulation for 5 representative numerical examples. Computational results will be compared to analytical solutions within linear elastic fracture mechanics and experimental data for three-dimensional crack propagation. (C) 2016 Elsevier B.V. All rights reserved.

Advances in arid zone archaeology: The 4th Southern Deserts Conference

Williams, AN ;Ditchfield, K ; Cortegoso, V ; Borrazzo, K ; QUATERNARY INTERNATIONAL ,2016 ,422 ,1 -4 .

Hunter-gatherer mobility decisions and synchronous climate change in the Southern Andes: The early and middle Holocene occupations of ARQ-18, San Juan, Argentina (29.5 degrees S)

Marsh, E ;Cortegoso, V ; Castro, S ; QUATERNARY INTERNATIONAL ,2016 ,422 ,66 -80 .

In the southern Andes, Holocene climate records show drastic changes in moisture during the early and middle Holocene. To generate a more refined chronology of climate changes in this region, we present a Bayesian model that combines published cosmogenic dates from the Encierro Valley (29.1 degrees S) and radiocarbon dates on peat and soils from the western slope of the Andes (27-33 degrees S). We compare this to a similar model from the high-altitude archaeological site ARQ-18 in the Las Taguas Valley (29.5 degrees S), San Juan, Argentina. These chronologies indicate synchronous changes in climate and occupational intensity, which shed light on hunter-gatherer mobility decisions. This site was first occupied in the early Holocene, when nearby valleys were deglaciated by around 10,700 cal BP. ARQ-18 was occupied a few centuries later around 10,100 cal BP. The site was first colonized during a regional wet phase, probably by hunters from the highlands to north who moved quickly among humid high-altitude valleys. As regional moisture began dropping around 8700-7800 cal BP, occupational intensity at ARQ-18 reached a maximum as diverse groups gathered in the valley. At this point, an important environmental threshold was crossed as groups reversed their mobility patterns and decisions and did not occupy the site for 1700 years. This "archaeological silence" correlates closely with the middle Holocene's hyperaridity during 7800-5700 cal BP. As soon as humidity returned, groups began visiting the site again. From this point on, strategies increasingly incorporated herding in response to less stable environmental conditions. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.

Geographic vectors of human mobility in the Andes (34-36 degrees S): Comparative analysis of 'minor' obsidian sources

Cortegoso, V ;Barberena, R ; Duran, V ; Lucero, G ; QUATERNARY INTERNATIONAL ,2016 ,422 ,81 -92 .

We have carried out long-term comparative in a wide latitudinal range of the Andes (29 degrees - 37 degrees south), encompassing selected areas that differ in ecology and biogeography. This latitudinal span shows diversity in subsistence modes across time and space, ranging from Andean agro-pastoralists in the north to Patagonian hunter-gatherers in the south. As part of this research, a program of geochemical and archaeological characterization of obsidian sources and distributions is being developed, attempting to assess connections between different biogeographical contexts. This work has allowed recognizing five Andean sources with different geological and topographical properties. Stemming from this macro-regional endeavor, in this paper we present a comparative analysis of the human use of two sources that, based on the intensity of human use on a macro-regional scale, can be interpreted as 'minor' sources.

The disappearing desert and the emergence of agropastoralism: An adaptive cycle of rapid change in the mid-Holocene Lake Titicaca Basin (Peru-Bolivia)

Marsh, EJ ;QUATERNARY INTERNATIONAL ,2016 ,422 ,123 -134 .

The mid-Holocene was an extremely dry period in the Lake Titicaca Basin of South America, when lake levels were at their lowest point in the Holocene. South of the lake, a lack of outflow and very low and irregular precipitation would have created desert-like conditions. This area's 'archaeological silence' seems to reflect an effective lack of population. This situation changed drastically as lake levels rose suddenly in the centuries following 3540 cal BP. As the desert disappeared, a flux of migrants filled the landscape, probably from the population concentration in the basin's western highlands. They imported and developed new technologies and economic practices and reorganized them into an agropastoral lifeway. The emergence of agropastoralism was both rapid and widespread, as people throughout the Lake Titicaca Basin adopted this practice. This major, regional shift can be productively framed as an adaptive cycle or Holling loop. This approach builds on the robust foundation of complexity theory, emphasizes the integrated nature of humans and their environment in a single system, highlights how systems fluctuate between slow and accelerated change, and is useful for developing hypotheses. Cascading feedback loops in climate, ecology, and cultural practices generated the emergence of agropastoralism. This resilient system is still in use today and is currently facing major climate changes, which makes understanding its origins especially relevant. (C) 2016 Elsevier Ltd and INQUA. All rights reserved.

Potters and herders at the southern edge of the Andean world: Risk management and mobility in Northwestern Mendoza, Argentina

Frigole, C ;Gasco, A ; QUATERNARY INTERNATIONAL ,2016 ,422 ,152 -162 .

This study addresses the risk-management activities of Andean pastoralists in northwestern, Mendoza. We compare data from one high-altitude site, Agua de la Cueva, located near a spring and an excellent hunting ground, and a domestic pit house at the site San Ignacio in a nearby mountain valley. We analyze data from roughly contemporaneous contexts dating to 1100-1400 cal BP. Osteometric measurements of camelid post-cranial bones and comparisons to modern camelids with multivariate statistics confirmed the presence of wild guanacos and vicunas as well as castrated and uncastrated domestic llamas. Hence, this is one of the southernmost areas where Andean pastoralism was practiced. Petrographic analysis of pottery and comparisons to local geology suggest strong similarities between the sites. Similar fabrics suggest a closely-connected group that probably made effective and complementary use of these two environments. Previous studies have established the presence of vessels from the other side of the Andes indicating long-distance contacts between populations on both sides of the Andes. These contacts may have been made via caravans that included castrated llamas, which are ethnographically preferred among drovers. The possibility of caravans is a hypothesis to be tested with future research. Our data suggest these groups participated in seasonal and perhaps long-distance movements in addition to other activities such as hunting, herding, and storing food. The combination of these risk-management strategies provided a stable economic base for the potters and herders of northwestern Mendoza. This case can be broadly compared to better-known archaeological and ethnographic examples from other parts of the Andes. (C) 2016 Elsevier Ltd and INQUA. All rights reserved.

Molecular dynamics simulation of polymerlike thin films irradiated by fast ions: A comparison between FENE and Lennard-Jones potentials

Lima, NW ;Gutierres, LI ; Gonzalez, RI ; Muller, S ; Thomaz, RS ; Bringa, EM ; Papaleo, RM ; PHYSICAL REVIEW B ,2016 ,94 ,-.

In this paper, the surface effects of individual heavy ions impacting thin polymerlike films were investigated, using molecular dynamics simulations with the finite extensible nonlinear elastic (FENE) potential to describe the molecular chains. The perturbation introduced by the ions in the lattice was modeled assuming that the initial excitation energy in the ion track is converted into an effective temperature, as in a thermal spike. The track was heated only within the film thickness h, leaving a nonexcited substrate below. The effect of decreasing thickness on cratering and sputtering was evaluated. The results were compared to experimental data of thin polymer films bombarded by MeV-GeV ions and to simulations performed with the Lennard-Jones potential. While several qualitative results observed in the experiments were also seen in the simulations, irrespective of the potential used, there are important differences observed on FENE films. Crater dimensions, rim volume, and sputtering yields are substantially reduced, and a threshold thickness for molecular ejection appears in FENE simulations. This is attributed to the additional restrictions on mass transport out of the excited track region imposed by interchain interactions (entanglements) and by the low mobility of the molten phase induced by the spike.

Monte Carlo model framework to simulate settlement dynamics

Millan, EN ;Goiran, S ; Forconesi, L ; Aranibar, JN ; Garino, CG ; Bringa, EM ; ECOLOGICAL INFORMATICS ,2016 ,36 ,135 -144 .

We developed an open source Monte Carlo based model to simulate Settlement Dynamics in Drylands (SeDD). The model assigns partial probabilities to each pixel within a grid region, based on several factors that can influence the establishment and subsistence of settlements: groundwater depth, vegetation type, proximity to rivers, paved roads, old river beds, and existing settlements. Partial probabilities are considered to be independent from each other, and therefore multiplied to calculate an overall probability for each pixel. Settlements are assigned by maximum probabilities or randomly, according to pre-established threshold probability values. We also modeled the gradual reduction of vegetation caused by a new settlement in neighboring pixels, decreasing the probabilities related to vegetation type. The final distribution of settlements is given by an average over multiple Monte Carlo simulations. The model is computationally efficient and could be used to rapidly explore different scenarios of settlement dynamics and vegetation degradation in arid environments, and other environmental factors that can be added to the framework without performing changes in the source code. (C) 2016 Elsevier B.V. All rights reserved.

Glycosidases Interact Selectively With Mannose-6-Phosphate Receptors of Bull Spermatozoa

Aguilera, AC ;Boschin, V ; Carvelli, L ; Cavicchia, JC ; Sosa, MA ; JOURNAL OF CELLULAR BIOCHEMISTRY ,2016 ,117 ,2464 -2472 .

Glycosidases may play a role in sperm maturation during epididymal transit. In this work, we describe the interaction of these enzymes with bull spermatozoa. We found that -galactosidase associated to spermatozoa can be released under low ionic strength conditions, whereas the interaction of N-acetyl--D-glucosaminidase and -glucuronidase with spermatozoa appeared to be stronger. On the other hand, -mannosidase and -fucosidase cannot be removed from the gametes. In addition, part of N-acetyl--D-glucosaminidase, -galactosidase, and -glucuronidase can also be released by mannose-6-phosphate. Taking into account these data, we explored the presence of cation-independent- and cation-dependent-mannose-6-phosphate receptors in the spermatozoa and found that cation-independent mannose-6-phosphate receptor is highly expressed in bull spermatozoa and cation-dependent-mannose-6-phosphate receptor is expressed at a lesser extent. In addition, by immunofluorescence, we observed that cation-independent-mannose-6-phosphate receptor is mostly located at the acrosomal zone, whereas cation-dependent-mannose-6-phosphate receptor presents a different distribution pattern on spermatozoa during the epididymal transit. N-acetyl--D-glucosaminidase and -glucuronidase isolated from epididymal fluid interacted mostly with cation-independent-mannose-6-phosphate receptor, while -galactosidase was recognized by both receptors. We concluded that glycosidases might play different roles in bull spermatozoa and that mannos-6-phosphate receptors may act as recruiters of some enzymes. J. Cell. Biochem. 117: 2464-2472, 2016. (c) 2016 Wiley Periodicals, Inc.

Hydrogen Storage in Palladium Hollow Nanoparticles

Valencia, FJ ;Gonzalez, RI ; Tramontina, D ; Rogan, J ; Valdivia, JA ; Kiwi, M ; Bringa, EM ; JOURNAL OF PHYSICAL CHEMISTRY C ,2016 ,120 ,23836 -23841 .

The potential and properties of palladium hollow nano particles (hNPs) as a possible H storage material are explored by means of classical molecular dynamics (MD) simulations. First, we study the stability of pure Pd hNPs for different sizes and thicknesses, obtaining good agreement with experimental results for nanometer size Pd hNP. Next we add, every 100 fs, single H atoms into the NP cavity. During the first stages of the simulation, our results show hydride formation on the inner surface, similar to what has been observed in experiments on Pd surfaces and NPs. Formation of the Pd hydride decreases the absorption rate, and H gas is formed inside the cavity. The maximum H gas pressure that is reached is of 7 GPa, before fractures appear in the hNP, and consequently the hNP breaks up. We obtain a maximum H/Pd ratio of 1.21 when H is introduced only inside the cavity. However, when H is deposited both on the inside and outside surfaces, this ratio reaches 1.70, which is 25% larger than previous reports. Beyond this ratio, the hNP breaks up, and the H gas is ejected from the hNP cavity.

Enhanced spectrophotometric detection of Hg in water samples by surface plasmon resonance of Au nanoparticles after preconcentration with vortex-assisted liquid-liquid microextraction


This article presents an efficient, simple, and cost-effective method for the determination of trace amounts of Hg by vortex-assisted liquid-liquid microextraction (VALLME) coupled to microvolume UV-Vis spectrophotometry. This method correlates changes in the intensity of localized surface plasmon resonance (LSPR) of tetraoctylammonium bromide (TOABr) coated Au nanoparticles (NPs) after interaction with Hg2+ ion. Spectroscopic measurements of the TOABr-coated Au NPs phase with particular absorption properties (strong and well-defined absorption bands) after analyte extraction by VALLME, provide an accurate and sensitive determination of Hg in water samples, comparable with measurements obtained by atomic absorption spectrometry (AAS). Different variables including sample volume, extraction time, and TOABr-coated Au NPs dispersion volume were carefully studied; final experimental conditions were 5 mL, 120 mu L and 5 min respectively. The limit of detection (LOD) was 0.8 ng mL(-1). The calibration curve was linear at concentrations between the limit of quantification (LOQ) (4.9 ng mL(-1)) and up to at least 120 ng mL(-1) of Hg. The relative standard deviation for six replicate determinations of 20 ng mL(-1) of Hg was 4.7%. This method exhibited an excellent analytical performance in terms of selectivity and sensitivity and it was finally applied for Hg determination in spiked tap and mineral water samples. (C) 2016 Elsevier B.V. All rights reserved.

Secretory organs: Implications for lipoid taxonomy and kerogen formation (seed ferns, Pennsylvanian, Canada)

Zodrow, EL ;D'Angelo, JA ; Taylor, WA ; Catelani, T ; Heredia-Guerrero, JA ; Mastalerz, M ; INTERNATIONAL JOURNAL OF COAL GEOLOGY ,2016 ,167 ,184 -200 .

Secretory organs likely evolved with land plants in Silurian-Devonian time, but it is questionable if they were passed on to living cycadaleans upon the extinction of seed ferns (Triassic-Jurassic?). They are defined as ducts of schizo-, lysig- or rhexigenous origin that exuded a heterogeneous lipoid mixture that fossilized as secretory products (droplets). In this study we detailed (1) the physical properties and distributions based on the compression-preserved Neuropteris ovata var. simonii and Laveineopteris rarinervis frond sections (Late Pennsylvanian Sydney Coalfield, Canada). Examined were also 1300 cuticular slides representing a number of plant groups, complemented by published data to infer biomass accumulation as potential kerogen in the geological column. In addition, (2) from select pinnules of the two species mentioned, nine secretory products and four surrounding cuticles were analyzed by micro-FTIR to evaluate statistically (PCA) the chemotaxonomic potential, and the kerogen chemistry. Further studies in support of (1), or (2) included methods of NICI, SEM, TEM and AFM, and by EDS.

Rab3A, a possible marker of cortical granules, participates in cortical granule exocytosis in mouse eggs

Bello, OD ;Cappa, AI ; de Paola, M ; Zanetti, MN ; Fukuda, M ; Fissore, RA ; Mayorga, LS ; Michaut, MA ; EXPERIMENTAL CELL RESEARCH ,2016 ,347 ,42 -51 .

Fusion of cortical granules with the oocyte plasma membrane is the most significant event to prevent polyspermy. This particular exocytosis, also known as cortical reaction, is regulated by calcium and its molecular mechanism is still not known. Rab3A, a member of the small GTP-binding protein superfamily, has been implicated in calcium-dependent exocytosis and is not yet clear whether Rab3A participates in cortical granules exocytosis. Here, we examine the involvement of Rab3A in the physiology of cortical granules, particularly, in their distribution during oocyte maturation and activation, and their participation in membrane fusion during cortical granule exocytosis. Immunofluorescence and Western blot analysis showed that Rab3A and cortical granules have a similar migration pattern during oocyte maturation, and that Rab3A is no longer detected after cortical granule exocytosis. These results suggested that Rab3A might be a marker of cortical granules. Overexpression of EGFP-Rab3A colocalized with cortical granules with a Pearson correlation coefficient of +0.967, indicating that Rab3A and cortical granules have almost a perfect colocalization in the egg cortical region. Using a functional assay, we demonstrated that microinjection of recombinant, prenylated and active GST-Rab3A triggered cortical granule exocytosis, indicating that Rab3A has an active role in this secretory pathway. To confirm this active role, we inhibited the function of endogenous Rab3A by microinjecting a polyclonal antibody raised against Rab3A prior to parthenogenetic activation. Our results showed that Rab3A antibody microinjection abolished cortical granule exocytosis in parthenogenetically activated oocytes. Altogether, our findings confirm that Rab3A might function as a marker of cortical granules and participates in cortical granule exocytosis in mouse eggs. (C) 2016 Elsevier Inc. All rights reserved.

A comparative evaluation of different ionic liquids for arsenic species separation and determination in wine varietals by liquid chromatography - hydride generation atomic fluorescence spectrometry

Grijalba, AC ;Fiorentini, EF ; Martinez, LD ; Wuilloud, RG ; JOURNAL OF CHROMATOGRAPHY A ,2016 ,1462 ,44 -54 .

The application of different ionic liquids (ILs) as modifiers for chromatographic separation and determination of arsenite [As(III)], arsenate [As(V)], dimethylarsonic acid (DMA) and monomethylarsonic acid (MMA) species in wine samples, by reversed-phase high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry detection (RP-HPLC-HG-AFS) was studied in this work. Several factors influencing the chromatographic separation of the As species, such as pH of the mobile phase, buffer solution concentration, buffer type, IL concentration and length of alkyl groups in ILs were evaluated. The complete separation of As species was achieved using a C-18 column in isocratic mode with a mobile phase composed of 0.5% (v/v) 1-octyl-3-methylimidazolium chloride ([C-8 mim]Cl) and 5% (v/v) methanol at pH 8.5. A multivariate methodology was used to optimize the variables involved in AFS detection of As species after they were separated by HPLC. The ILs showed remarkable performance for the separation of As species, which was obtained within 18 min with a resolution higher than 0.83. The limits of detection for As(III), As(V), MMA and DMA were 0.81, 0.89, 0.62 and 1.00 mu g As L-1. The proposed method was applied for As speciation analysis in white and red wine samples originated from different grape varieties. (C) 2016 Elsevier B.V. All rights reserved.

Influence of ultrasound speckle tracking strategies for motion and strain estimation

Curiale, AH ;Vegas-Sanchez-Ferrero, G ; Aja-Fernandez, S ; MEDICAL IMAGE ANALYSIS ,2016 ,32 ,184 -200 .

Speckle Tracking is one of the most prominent techniques used to estimate the regional movement of the heart based on ultrasound acquisitions. Many different approaches have been proposed, proving their suitability to obtain quantitative and qualitative information regarding myocardial deformation, motion and function assessment. New proposals to improve the basic algorithm usually focus on one of these three steps: (1) the similarity measure between images and the speckle model; (2) the transformation model, i.e. the type of motion considered between images; (3) the optimization strategies, such as the use of different optimization techniques in the transformation step or the inclusion of structural information. While many contributions have shown their good performance independently, it is not always clear how they perform when integrated in a whole pipeline. Every step will have a degree of influence over the following and hence over the final result. Thus, a Speckle Tracking pipeline must be analyzed as a whole when developing novel methods, since improvements in a particular step might be undermined by the choices taken in further steps. This work presents two main contributions: (1) We provide a complete analysis of the influence of the different steps in a Speckle Tracking pipeline over the motion and strain estimation accuracy. (2) The study proposes a methodology for the analysis of Speckle Tracking systems specifically designed to provide an easy and systematic way to include other strategies. We close the analysis with some conclusions and recommendations that can be used as an orientation of the degree of influence of the models for speckle, the transformation models, interpolation schemes and optimization strategies over the estimation of motion features. They can be further use to evaluate and design new strategy into a Speckle Tracking system. (C) 2016 Elsevier B.V. All rights reserved.

First study of fossil rodent middens as source of paleoparasitological evidences (northwestern Patagonia, Argentina)

Beltrame, MO ;De Porras, ME ; Barberena, R ; Llano, CL ; Sardella, NH ; PARASITOLOGY INTERNATIONAL ,2016 ,65 ,352 -356 .

The present paper reports the first paleoparasitological results obtained from coprolites of fossil rodent middens and demonstrates the potential of rodent middens as a source of paleoparasitological evidences in South America. Ten fossil rodent middens from northwestern Patagonia, Argentina, were studied. Five coprolites of each midden were fully processed, rehydrated, homogenized, subjected to spontaneous sedimentation, and examined through light microscopy. Eight of the 10 examined rodent middens contained parasite eggs. The eggs of parasites were assigned to Heteroxynema (Cavioxyura) viscaciae Sutton & Hugot, 1989 and Helminthoxys sp. (Nematoda: Oxyuridae), Trichuris sp. (Nematoda: Trichuridae) and one unidentified nematode. Fossil rodent middens were assigned to Lagidium viscacia (Caviomorph: Chinchillidae). The excellent preservation of parasite remains in coprolites from fossil rodent middens provided an opportunity to perform paleoparasitological inferences. The results of this papers demonstrates that fossil rodent middens offer an excellent opportunity for the recovery of parasite remains for future paleoparasitological studies in the southwest of South America. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

Flower diversity and bee reproduction in an arid ecosystem

Dorado, J ;Vazquez, DP ; PEERJ ,2016 ,4 ,-.

Background: Diverse flower communities are more stable in floral resource production along the flowering season, but the question about how the diversity and stability of resources affect pollinator reproduction remains open. High plant diversity could favor short foraging trips, which in turn would enhance bee fitness. In addition to plant diversity, greater temporal stability of floral resources in diverse communities could favor pollinator fitness because such communities are likely to occupy the phenological space more broadly, increasing floral availability for pollinators throughout the season. In addition, this potential effect of flower diversity on bee reproduction could be stronger for generalist pollinators because they can use a broader floral spectrum. Based on above arguments we predicted that pollinator reproduction would be positively correlated to flower diversity, and to temporal stability in flower production, and that this relationship would be stronger for the most generalized pollinator species.

Metal-nanotube composites as radiation resistant materials

Gonzalez, RI ;Valencia, F ; Mella, J ; van Duin, ACT ; So, KP ; Li, J ; Kiwi, M ; Bringa, EM ; APPLIED PHYSICS LETTERS ,2016 ,109 ,-.

The improvement of radiation resistance in nanocomposite materials is investigated by means of classical reactive molecular dynamics simulations. In particular, we study the influence of carbon nanotubes (CNTs) in an Ni matrix on the trapping and possible outgassing of He. When CNTs are defect-free, He atoms diffuse alongside CNT walls and, although there is He accumulation at the metal-CNT interface, no He trespassing of the CNT wall is observed, which is consistent with the lack of permeability of a perfect graphene sheet. However, when vacancies are introduced to mimic radiation-induced defects, He atoms penetrate CNTs, which play the role of nano-chimneys, allowing He atoms to escape the damaged zone and reduce bubble formation in the matrix. Consequently, composites made of CNTs inside metals are likely to display improved radiation resistance, particularly when radiation damage is related to swelling and He-induced embrittlement. Published by AIP Publishing.

Mechanical Response of Aluminosilicate Nanotubes under Compression

Gonzalez, RI ;Rogan, J ; Bringa, EM ; Valdivia, JA ; JOURNAL OF PHYSICAL CHEMISTRY C ,2016 ,120 ,14428 -14434 .

The mechanical response of aluminosilicate nano tubes (imogolite) under compression is investigated by means of classical molecular dynamics simulations using the CLAYFF potential. Using the uncompressed length L-0, when there is no strain, to describe each nanotube, we have found that imogolite tends to coil for L-0 > 15 nm to prevent the failure of the nanotube. The simulation also shows that the nanotubes do not break under stress for L-0 >= 100 nm. Hence, the imogolite is a very flexible nanotube, which has been observed with lengths up to 500 nm. Finally, we can report a Young modulus of the order of 200 GPa, which is relatively independent of L-0.

Asymmetric Cancer Hallmarks in Breast Tumors on Different Sides of the Body

Campoy, EM ;Laurito, SR ; Branham, MT ; Urrutia, G ; Mathison, A ; Gago, F ; Orozco, J ; Urrutia, R ; Mayorga, LS ; Roque, M ; PLOS ONE ,2016 ,11 ,-.

During the last decades it has been established that breast cancer arises through the accumulation of genetic and epigenetic alterations in different cancer related genes. These alterations confer the tumor oncogenic abilities, which can be resumed as cancer hallmarks (CH). The purpose of this study was to establish the methylation profile of CpG sites located in cancer genes in breast tumors so as to infer their potential impact on 6 CH: i.e. sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, induction of angiogenesis, genome instability and invasion and metastasis. For 51 breast carcinomas, MS-MLPA derived-methylation profiles of 81 CpG sites were converted into 6 CH profiles. CH profiles distribution was tested by different statistical methods and correlated with clinical-pathological data. Unsupervised Hierarchical Cluster Analysis revealed that CH profiles segregate in two main groups (bootstrapping 90-100%), which correlate with breast laterality (p = 0.05). For validating these observations, gene expression data was obtained by RealTime-PCR in a different cohort of 25 tumors and converted into CH profiles. This analyses confirmed the same clustering and a tendency of association with breast laterality (p = 0.15). In silico analyses on gene expression data from TCGA Breast dataset from left and right breast tumors showed that they differed significantly when data was previously converted into CH profiles (p = 0.033). We show here for the first time, that breast carcinomas arising on different sides of the body present differential cancer traits inferred from methylation and expression profiles. Our results indicate that by converting methylation or expression profiles in terms of Cancer Hallmarks, it would allow to uncover veiled associations with clinical features. These results contribute with a new finding to the better understanding of breast tumor behavior, and can moreover serve as proof of principle for other bilateral cancers like lung, testes or kidney.

Does land use change alter water and nutrient dynamics of phreatophytic trees in the Central Monte desert?

Meglioli, PA ;Villagra, PE ; Aranibar, JN ; ECOHYDROLOGY ,2016 ,9 ,738 -752 .

In the woodlands of the Central Monte desert (Argentina), phreatophyte vegetation is exposed to different levels of disturbance. Livestock and settlement activity produce mainly nutrient inputs and partial vegetation removal, with a consequent reduction on water use by vegetation. We hypothesize that because of the increased soil water and nutrient resources associated with livestock stations, water stress will be relieved for the remaining Prosopis flexuosa trees, favouring water and nutrient status, and plant growth at the plant scale. The goal of this research was to analyse the physiological responses of P. flexuosa trees that grow in interdune valleys under different land uses, and the changes in relative importance of environmental factors controlling these responses. We compared the ecophysiological responses of adult P. flexuosa trees in two contrasting types of disturbance: disturbed (livestock stations) and relatively undisturbed (control woodlands) stands, in the 2011-2013 growing seasons. Pre-dawn and midday leaf water potential and stomatal conductance were higher in livestock stations than in control woodlands, suggesting a better water status of P. flexuosa in livestock stations. Isotopic composition (lower delta C-13, and higher delta N-15) and foliar nitrogen concentration (lower C:N ratios) indicated lower water use efficiency and higher nitrogen absorption from the soil in livestock stations. Both growth of new leaves (foliar area) and the length of young branches were higher in the first season for both land uses, but branch length was higher in livestock stations. This is consistent with the idea that vegetation removal and nutrient contribution of settlement activities improved water and nutrient status of remaining vegetation, and modified the relative importance of factors controlling ecophysiological processes. We concluded that physiological responses and vegetative growth of P. flexuosa were not only affected by meteorological conditions (rainfalls, vapour pressure deficit), but also by the ecohydrological changes caused by changes in land use. Copyright (C) 2015 John Wiley & Sons, Ltd.

Ground-based GNSS network and integrated water vapor mapping during the development of severe storms at the Cuyo region (Argentina)

Calori, A ;Santos, JR ; Blanco, M ; Pessano, H ; Llamedo, P ; Alexander, P ; de la Torre, A ; ATMOSPHERIC RESEARCH ,2016 ,176 ,267 -275 .

Mendoza is a province of Argentina located between 32 degrees S and 34 degrees S at the leeside of the Andes Foothills. Very intense thunderstorms form between October and March (southern hemisphere summer), which produce large hail and damage in crops and properties. Although some hypotheses and conceptual models were proposed in order to identify key possible mechanisms that contribute to trigger convection, they are still waiting for the validation process. As moisture is the main ingredient for storms formation, the identification of its geographical distribution could be used together with other synoptic and mesoscale forcing features to forecast intense convective events. A novel technique in estimating moisture concentration and its geographical distribution has been introduced in order to observe the influx and variability of humidity at this region, during a 45-day period in midsummer. In doing so, we resort to the information provided by the ground-basedGlobal Navigation Satellite System (GNSS) network. More than 300 active stations constitute the continuously operating GNSS network over Southern and Central America (SIRGAS-CON, Sistema de Referencia Geocentric para las Americas de Operation Continua). This network allows to retrieve integrated water vapor (IWV) content, mapping this variable by the use of a digital model of terrain. In the period and region under study, a prevailing influx of humidity from N and NE and a high correlation between the accumulation/depletion of humidity and the hail/no hail precipitation days is observed. We discuss in particular the development of five storms detected by the S-Band radar network belonging to the Province of Mendoza. Although the results strongly suggest that IWV maps are capable to represent the humidity dynamics in the considered region, it is still important to highlight that the calculated values for IWV are unrealistic at some locations as the consequence of deep atmospheric gradients. These biases may be explained by the fact that the GNSS observations are made over the whole horizon of each given site. (C) 2016 Elsevier B.V. All rights reserved.

Nucleation of plasticity in nanoparticle collisions

Millan, EN ;Tramontina, DR ; Urbassek, HM ; Bringa, EM ; PHYSICAL REVIEW E ,2016 ,93 ,-.

While at small collision velocities collisions of nanoparticles (NPs) are elastic, they become plastic at higher velocities. We study the elastic-plastic threshold and the onset of plasticity using molecular dynamics simulation for a Lennard-Jones material. The reasons behind the R-2/3 increase of the threshold velocity for small NP radii R found recently are discussed. At the threshold, NP orientation strongly influences the generation of plasticity, and averaging over many orientations is required to predict the critical velocity for dislocation generation. The onset of plasticity is governed by the generation of isolated stacking faults and nanotwins spanning the entire NP. At higher velocities, the fraction of defects becomes proportional to the total number of atoms in the NP.

Design of artificial genetic regulatory networks with multiple delayed adaptive responses

Kaluza, P ;Inoue, M ; EUROPEAN PHYSICAL JOURNAL B ,2016 ,89 ,-.

Genetic regulatory networks with adaptive responses are widely studied in biology. Usually, models consisting only of a few nodes have been considered. They present one input receptor for activation and one output node where the adaptive response is computed. In this work, we design genetic regulatory networks with many receptors and many output nodes able to produce delayed adaptive responses. This design is performed by using an evolutionary algorithm of mutations and selections that minimizes an error function defined by the adaptive response in signal shapes. We present several examples of network constructions with a predefined required set of adaptive delayed responses. We show that an output node can have different kinds of responses as a function of the activated receptor. Additionally, complex network structures are presented since processing nodes can be involved in several input-output pathways.

Compaction and plasticity in nanofoams induced by shock waves: A molecular dynamics study

Gunkelmann, N ;Rosandi, Y ; Ruestes, CJ ; Bringa, EM ; Urbassek, HM ; COMPUTATIONAL MATERIALS SCIENCE ,2016 ,119 ,27 -32 .

Shock waves are produced in Al nanofoams by a piston moving with velocity U-p. They induce plastic activity in the ligaments before eventually the foam structure is crushed and a compact material results. We demonstrate dislocation formation in the foams and correlate it with the velocity and stress profiles in the shock wave. The profiles exhibit a 3-wave structure indicating 3 wave regimes: elastic precursor, plastic activity in the ligaments, and foam crushing. The shock wave velocity V follows well macroscopic predictions, V proportional to U-p. The length of the non-collapsed part of the foam is well described by an analytical compaction model. (C) 2016 Elsevier B.V. All rights reserved.

Extremal black hole initial data deformations

Acena, A ;Clement, MEG ; CLASSICAL AND QUANTUM GRAVITY ,2016 ,33 ,-.

We study deformations of axially symmetric initial data for Einstein-Maxwell equations satisfying time-rotation (t-phi) symmetry and containing one asymptotically cylindrical end and one asymptotically flat end. We find that the t-phi symmetry implies the existence of a family of deformed data having the same horizon structure. This result allows us to measure how close the solutions are to the Lichnerowicz equation when arising from nearby free data.

Supersonic Dislocation Bursts in Silicon

Hahn, EN ;Zhao, S ; Bringa, M ; Meyers, MA ; SCIENTIFIC REPORTS ,2016 ,6 ,-.

Dislocations are the primary agents of permanent deformation in crystalline solids. Since the theoretical prediction of supersonic dislocations over half a century ago, there is a dearth of experimental evidence supporting their existence. Here we use non-equilibrium molecular dynamics simulations of shocked silicon to reveal transient supersonic partial dislocation motion at approximately 15 km/s, faster than any previous in-silico observation. Homogeneous dislocation nucleation occurs near the shock front and supersonic dislocation motion lasts just fractions of picoseconds before the dislocations catch the shock front and decelerate back to the elastic wave speed. Applying a modified analytical equation for dislocation evolution we successfully predict a dislocation density of 1.5 x 10(12) cm(-2) within the shocked volume, in agreement with the present simulations and realistic in regards to prior and on-going recovery experiments in silicon.


Duran, V ;Winocur, D ; Stern, C ; Garvey, R ; Barberena, R ; Monne, JLP ; Benitez, A ; INTERSECCIONES EN ANTROPOLOGIA ,2016 ,17 ,33 -46 .

A prolonged period of decreased human occupation has been proposed for Mendoza Province, provoked by conditions of increasing aridity during the mid-Holocene. It has also been suggested that the systematic human peopling of the high-altitude Andean environments started ca. 2000-1500 years BP, because of a process of economic intensification in lowland areas with higher availability of resources. In this paper, we present the results of a project designed to assess the role of volcanic activity and glacial advances as the main cause for archaeological discontinuities recorded in the archaeological record of the high Andes. This study covers a latitudinal range between 35 degrees-37 degrees S. We present geochemical and chronological results for tephras recorded in archaeological and geological sites, attempting to define the volcanic sources and their impact on the landscape. The analysis includes a geoarchaeological study of the Valenzuela River, which shows the magnitude of the volcanic activity in the Planchon-Peteroa complex, as well as the extent of Holocene glacial processes. The results presented allow suggesting alternative explanation for the temporal sequences of the archaeological record, inasmuch as highlighting the contribution of geoarchaeology.


Monteoliva, JM ;Villalba, A ; Acena, A ; Pattini, A ; REVISTA HABITAT SUSTENTABLE ,2016 ,6 ,51 -59 .

One of the most efficient ways to reduce the energy consumption of artificial lighting is through the proper use of daylight in indoor spaces. However, current regulations governing the use of daylight in indoor spaces are outdated and in some cases are not easy to apply. Thus, designers are not encouraged to seek energy efficient solutions that enhance the use of daylight to illuminate interior spaces during daytime hours. This paper proposes a simplified model for calculating the useful daylight illuminance (UDI) for individual perimeter rooms under clear skies. This model seeks to combine the precision and validity of dynamic simulations in the study of daylight, in a simple and appropriate prediction tool for professionals in real environments.

Biological substrates: Green alternatives in trace elemental preconcentration and speciation analysis

Escudero, LB ;Maniero, MA ; Agostini, E ; Smichowski, PN ; TRAC-TRENDS IN ANALYTICAL CHEMISTRY ,2016 ,80 ,531 -546 .

Biological substrates have been introduced in Analytical Chemistry to encourage the development of environment-friendly methodologies. This kind of substrates offers advantages such as low cost, very simple production and biodegradability. Moreover, they are considered highly efficient materials for extraction and separation of elemental species.

Alteration of syncytiotrophoblast mitochondria function and endothelial nitric oxide synthase expression in the placenta of rural residents

Osimani, VLR ;Valdez, SR ; Guinazu, N ; Magnarelli, G ; REPRODUCTIVE TOXICOLOGY ,2016 ,61 ,47 -57 .

The impact of environmental organophosphate (OP) pesticide exposure on respiratory complexes, enzymatic antioxidant defense activities, and oxidative damage markers in the syncytiotrophoblast and cytotrophoblast mitochondria was evaluated. Placenta] progesterone (PG) levels and endothelia] nitric oxide synthase (eNOS) expression were studied. Samples from women non-exposed (control group-CG) and women living in a rural area (rural group-RG) were collected during pesticide spraying season (RG-SS) and non-spraying season (RG-NSS).

Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation

Metcalf, JL ;Turney, C ; Barnett, R ; Martin, F ; Bray, SC ; Vilstrup, JT ; Orlando, L ; Salas-Gismondi, R ; Loponte, D ; Medina, M ; De Nigris, M ; Civalero, T ; Fernandez, PM ; Gasco, A ; Duran, V ; Seymour, KL ; Otaola, C ; Gil, A ; Paunero, R ; Prevosti, FJ ; Bradshaw, CJA ; Wheeler, JC ; Borrero, L ; Austin, JJ ; Cooper, A ; SCIENCE ADVANCES ,2016 ,2 ,-.

The causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow time frame (similar to 15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region. We identify a narrow megafaunal extinction phase 12,280 +/- 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonian material reveals that the sequence of climate and extinction events in North and South America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts.

Demography and population growth rate of the tree Prosopis flexuosa with contrasting grazing regimes in the Central Monte Desert

Aschero, V ;Morris, WF ; Vazquez, DP ; Alvarez, JA ; Villagra, PE ; FOREST ECOLOGY AND MANAGEMENT ,2016 ,369 ,184 -190 .

One of the most important current challenges for ecologists is to evaluate how human-induced changes in ecosystems would impact viability of populations. Demographic response to anthropogenic impact could help us to understand how to manage those impacts. Using demographic techniques and population projection models, here we assess if demography and population dynamics of the tree Prosopis flexuosa change in cattle grazed areas compared to ungrazed areas in the Central Monte desert, Mendoza, Argentina. To this end, we quantified vital rates and constructed a population projection matrix model to compare the deterministic population growth rate (lambda) between grazed and ungrazed areas. We also estimated elasticities of vital rates to evaluate their potential importance for future changes in lambda and performed a life table response experiment (LTRE) to identify the life cycle transitions that contribute the most to the observed differences in lambda between the two treatments. Although we found differences in demographic processes, such as lower seed production and higher probability of reversion to smaller size classes in young individuals when cattle were present, our results indicate that cattle grazing had no significant effect on lambda for this species. According to the elasticity analysis, survival of large trees is the main driver of the population growth rate (lambda) of P. flexuosa, and the vital rates related to tree reproduction, such as seed production and germination, have a poor contribution to lambda. Therefore, limitations of activities that can affect survival of large trees should be considered as part of the conservation strategy for this species. Our study provides a compilation of demographic information that can be useful to set policies connecting the conservation objectives for this woodlands with that of ranch managers of the area. (C) 2016 Published by Elsevier B.V.

Controlled rippling of graphene via irradiation and applied strain modify its mechanical properties: a nanoindentation simulation study

Martinez-Asencio, J ;Ruestes, CJ ; Bringa, EM ; Caturla, MJ ; PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2016 ,18 ,13897 -13903 .

Ripples present in free standing graphene have an important influence on the mechanical behavior of this two-dimensional material. In this study, we show through nanoindentation simulations, how out-of-plane displacements can be modified by strain, resulting in softening of the membrane under compression and stiffening under tension. Irradiation also induces changes in the mechanical properties of graphene. Interestingly, compressed samples, irradiated at low doses are stiffened by the irradiation, whereas the samples under tensile strain do not show significant changes in their mechanical properties. These simulations indicate that vacancies produced by the energetic ions cannot be the ones directly responsible for this behavior. However, changes in roughness induced by the momentum transferred from the energetic ions to the membrane, can explain these differences. These results provide an alternative explanation to recent experimental observations of the stiffening of graphene under low dose irradiation, as well as the paths to tailor the mechanical properties of this material via applied strain and irradiation.

Building Household and Community through Active Assemblages: A Late Formative Patio Group at Khonkho Wankane, Bolivia


A community is an active assemblage of human and non-human elements bound together by interactions. Archaeologies of communities shed light on sets of overlapping and geographically emplaced assemblages of individuals, practices, spaces, buildings, objects, animals and landscapes. This article presents an archaeology of communities based a remarkably well preserved Late Formative (ad 1-500) patio group at Khonkho Wankane, Bolivia. Excavation data provide a high-resolution chronology and document two varieties of assemblages: (1) those that played a greater role in biologically and socially reproducing the community, such as daily food and tool production; and (2) those that played a greater role in its transformation, such as gatherings, work parties and construction projects. In the patio group, intimate meetings took place in small, private spaces where incense was burned. Larger gatherings took place in an outdoor space where painted Kalasasaya small jars and bowls were active elements in interactions between residents and visitors. These events most likely involved work parties that contributed to the physical and social construction of the community. Assemblages at multiple scales built a diverse Late Formative community, which played a principal role in regional interaction networks. Within a few generations of residents leaving their homes in Khonkho, local and regional interactions generated the emergence of a state at Tiwanaku.

Hardening under compression in Au foams

Ruestes, CJ ;Farkas, D ; Caro, A ; Bringa, EM ; ACTA MATERIALIA ,2016 ,108 ,1 -7 .

We report the results of compressive tests for a model bi-continuous nanoporous gold structure using atomistic simulations focusing on the densification regime and the plasticity mechanisms taking place. The stress - strain response follows a logarithmic evolution proportional to the inverse of strain and we provide a simple scaling law for this behavior. Hardening is correlated to the dislocation density and an exponential dependence is revealed. The plasticity mechanisms were inspected revealing the presence of Hirth and Frank partials contributing to the hardening of the sample. Lomer-Cottrel locks, perfect dislocations, and twinning were also found. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dispersion of carbon nanotubes in aluminum improves radiation resistance

So, KP ;Chen, D ; Kushima, A ; Li, MD ; Kim, S ; Yang, Y ; Wang, ZG ; Park, JG ; Lee, YH ; Gonzalez, RI ; Kiwi, M ; Bringa, EM ; Shao, L ; Li, J ; NANO ENERGY ,2016 ,22 ,319 -327 .

We can mass-produce metal/carbon nanotube (CNT) composites that show improved radiation tolerance. The 0.5 wt% Al+CNT composite showed improved tensile strength without reduction of tensile ductility before radiation, and reduced void/pore generation and radiation embrittlement at high displacements per atom (DPA). Under helium ion irradiation up to 72 DPA, the 1D carbon nanostructures survive, while sp(2) bonded graphene transforms to spa tetrahedral amorphous carbon. Self-ion (Al) irradiation converts CNTs to a metastable form of Al4C3, but still as slender 1D nanorods with prolific internal interfaces that catalyze recombination of radiation defects, reducing radiation hardening and porosity generation. The 1D fillers may also form percolating paths of "nano-chimneys" that outgas the accumulated helium and other fission gases, providing an essential solution to the gas accumulation problem. (C) 2016 Elsevier Ltd. All rights reserved.

On the formation of tropical rings of atomic halogens: Causes and implications

Saiz-Lopez, A ;Fernandez, RP ; GEOPHYSICAL RESEARCH LETTERS ,2016 ,43 ,2928 -2935 .

Halogens produced by ocean biological and photochemical processes reach the tropical tropopause layer (TTL), where cold temperatures and the prevailing low ozone abundances favor the diurnal photochemical enhancement of halogen atoms. Under these conditions atomic bromine and iodine are modeled to be the dominant inorganic halogen species in the sunlit TTL, surpassing the abundance of the commonly targeted IO and BrO radicals. We suggest that due to the rapid photochemical equilibrium between halogen oxides and halogen atoms a natural atmospheric phenomenon evolves, which we have collectively termed tropical rings of atomic halogens. We describe the main causes controlling the modeled appearance and variability of these superposed rings of bare bromine and iodine atoms that circle the tropics following the Sun. Some potential implications for atmospheric oxidizing capacity are also explored. Our model results suggest that if experimentally confirmed, the extent and intensity of the halogen rings would directly respond to changes in oceanic halocarbon emissions, their atmospheric transport, and photochemistry.

Crater production by energetic nanoparticle impact on Au nanofoams

Anders, C ;Bringa, EM ; Urbassek, HM ; APPLIED PHYSICS LETTERS ,2016 ,108 ,-.

Impact of energetic nanoparticles on solids produces craters on the surface. We use molecular dynamics simulations to compare crater production on a compact Au solid with that in a porous (foam) target. Our results show a complex picture: (i) At low impact velocities, the nanoparticles produce permanent craters in the foam while they cannot penetrate the compact target. (ii) With increasing velocity and/or projectile mass, the crater depth in the foam target increases less strongly than for the compact target. The plasticity-affected zone in the foam target is of similar size as in the compact target. Our results are relevant for the use of porous structures as shields against nanoparticle impact. (C) 2016 AIP Publishing LLC.

Do neophobia and dietary wariness explain ecological flexibility? An analysis with two seed-eating birds of contrasting habits

Camin, SR ;Martin-Albarracin, V ; Jefferies, M ; Marone, L ; JOURNAL OF AVIAN BIOLOGY ,2016 ,47 ,245 -251 .

The neophobia threshold hypothesis (NTH) suggests that the acquisition and maintenance of a high behavioral and ecological flexibility in the evolutionary and adaptive history of a species is the consequence of lower levels of neophobia towards new micro-habitats and of dietary wariness of novel foods. To test this idea we assessed the degree of neophobia and dietary wariness in two seed-eating bird species with contrasting degrees of ecological flexibility that inhabit the central Monte desert (Argentina): a grass-seed specialist, the many-colored chaco-finch, and a generalist feeder, the rufous-collared sparrow. We expected that both species would exhibit neophobia and wariness when faced with new foraging opportunities but that the rufous-collared sparrow would be less neophobic and less wary than the specialized many-colored chaco-finch. Experimental indicators of neophobia and dietary wariness included willingness to eat near novel objects and willingness to eat novel seeds, respectively. Both species showed similar levels of reluctance to novelty, although the sparrow could be slightly more reluctant than the finch. Contrary to our predictions, the sparrow was neither less hesitant nor faster or greedier than the finch. This experimental evidence does not support a negative relationship between neophobia/wariness and ecological flexibility in these two seed-eating birds and it coincides with the growing evidence that challenges the NTH. Some of our results provide support for the dangerous niche hypothesis, especially as the rufous-collared sparrow, that feeds on more diverse and potentially dangerous food, showed higher levels of neophobia in some cases. Although the idea of neophobia and wariness being plausible causes of ecological specialization sounds attractive, the current situation calls for further research so that the causes of ecological flexibility in granivorous birds can be better understood.

Monte Carlo simulations of settlement dynamics in GPUs

Millan, EN ;Goiran, SB ; Piccoli, MF ; Garino, CG ; Aranibar, JN ; Bringa, EM ; CLUSTER COMPUTING-THE JOURNAL OF NETWORKS SOFTWARE TOOLS AND ,2016 ,19 ,557 -566 .

Recently, a Monte Carlo model was proposed in order to simulate settlement dynamics in drylands, including several environmental factors, and it was implemented as a serial CPU code. In this work we present a parallel implementation of that code using graphics processing units (GPU) and NVIDIA CUDA. The code was tested with two experiments, a Baseline case and a Realistic case. We take advantage of the GPU architecture to obtain significant speedups: 8 to 20 with the Baseline case in a NVIDIA Tesla C2050 versus a Phenom 1055T CPU. The Realistic case obtained 80 of speedup in the same hardware. The GPU performance of the code will allow the inclusion of additional factors affecting settlements and large grid sizes for detailed environmental degradation models.

The elastic-plastic transition in nanoparticle collisions

Millan, EN ;Tramontina, DR ; Urbassek, HM ; Bringa, EM ; PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2016 ,18 ,3423 -3429 .

When nanoparticles (NPs) collide with low velocities, they interact elastically in the sense that - besides their fusion caused by their mutual van-der-Waals attraction - no defects are generated. We investigate the minimum velocity, v(c), necessary for generating defects and inducing plasticity in the NP. The determination of this elastic-plastic threshold is of prime importance for modeling the behavior of granular matter. Using the generic Lennard-Jones interaction potential, we find v(c) to increase strongly with decreasing radius. Current models do not agree with our simulations, but we provide a model based on dislocation emission in the contact zone that quantitatively describes the size dependence of the elastic-plastic transition.

Nanoindentation of hcp metals: a comparative simulation study of the evolution of dislocation networks

Alhafez, IA ;Ruestes, CJ ; Gao, Y ; Urbassek, HM ; NANOTECHNOLOGY ,2016 ,27 ,-.

Using molecular dynamics simulation, we study the nanoindentation of three hcp metals: Mg, Ti, and Zr. Both the basal and two prismatic surface planes are considered. We focus on the characterization of the plasticity generated in the crystal. The similarities to, and the differences from, the behavior of the more commonly investigated fcc and bcc metals are highlighted. We find that hcp metals show a larger variety than the fcc and bcc metals studied up until now. The prolific emission of prismatic loops can lead to extended plastic zones. The size of the plastic zone is quantified by the ratio f of the plastic zone radius to the radius of the contact area. We find values of between 1.6 (an almost collapsed zone) and > 5; in the latter case, complex dislocation networks build up which are extended in the direction of easy glide.

State of the art of environmentally friendly sample preparation approaches for determination of PBDEs and metabolites in environmental and biological samples: A critical review

Berton, P ;Lana, NB ; Rios, JM ; Garcia-Reyes, JF ; Altamirano, JC ; ANALYTICA CHIMICA ACTA ,2016 ,905 ,24 -41 .

Green chemistry principles for developing methodologies have gained attention in analytical chemistry in recent decades. A growing number of analytical techniques have been proposed for determination of organic persistent pollutants in environmental and biological samples. In this light, the current review aims to present state-of-the-art sample preparation approaches based on green analytical principles proposed for the determination of polybrominated diphenyl ethers (PBDEs) and metabolites (OH-PBDEs and MeO-PBDEs) in environmental and biological samples. Approaches to lower the solvent consumption and accelerate the extraction, such as pressurized liquid extraction, microwave-assisted extraction, and ultrasound-assisted extraction, are discussed in this review. Special attention is paid to miniaturized sample preparation methodologies and strategies proposed to reduce organic solvent consumption. Additionally, extraction techniques based on alternative solvents (surfactants, supercritical fluids, or ionic liquids) are also commented in this work, even though these are scarcely used for determination of PBDEs. In addition to liquid-based extraction techniques, solid-based analytical techniques are also addressed. The development of greener, faster and simpler sample preparation approaches has increased in recent years (2003e2013). Among green extraction techniques, those based on the liquid phase predominate over those based on the solid phase (71% vs. 29%, respectively). For solid samples, solvent assisted extraction techniques are preferred for leaching of PBDEs, and liquid phase microextraction techniques are mostly used for liquid samples. Likewise, green characteristics of the instrumental analysis used after the extraction and clean-up steps are briefly discussed. (C) 2015 Elsevier B.V. All rights reserved.

A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot

Riga, BJG ;Lamanna, MC ; David, LDO ; Calvo, JO ; Coria, JP ; SCIENTIFIC REPORTS ,2016 ,6 ,-.

Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus-seemingly adapted for bearing extraordinary weight-and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods.

Amorphization and nanocrystallization of silicon under shock compression

Zhao, S ;Hahn, EN ; Kad, B ; Remington, BA ; Wehrenberg, CE ; Bringa, EM ; Meyers, MA ; ACTA MATERIALIA ,2016 ,103 ,519 -533 .

High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with (111) slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shockinduced defects play a very important role in the onset of amorphization. Calculations of the free energy changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. The nucleation of amorphization is analyzed qualitatively by classical nucleation theory.

Hypothyroidism advances mammary involution in lactating rats through inhibition of PRL signaling and induction of LIF/STAT3 mRNAs

Arbocco, FCV ;Sasso, CV ; Actis, EA ; Caron, RW ; Hapon, MB ; Jahn, GA ; MOLECULAR AND CELLULAR ENDOCRINOLOGY ,2016 ,419 ,18 -28 .

Thyroid diseases have deleterious effects on lactation, litter growth and survival, and hinder the suckling induced hormone release, leading in the case of hyperthyroidism, to premature mammary involution. To determine the effects of hypothyroidism (HypoT) on late lactation, we analyzed the effect of chronic 6-propyl-2-thiouracil (PTU)-induced HypoT on mammary histology and the expression of members of the JAK/STAT/SOCS signaling pathway, milk proteins, prolactin (PRLR), estrogen (ER), progesterone (PR) and thyroid hormone (TR) receptors, markers of involution (such as stat3, lif, bcl2, BAX and PARP) on lactation (L) day 21. HypoT mothers showed increased histological markers of involution compared with control rats, such as adipose/epithelial ratio, inactive alveoli, picnotic nuclei and numerous detached apoptotic cells within the alveolar lumina. We also found decreased PRLR, 13-casein and alpha-lactoalbumin mRNAs, but increased SOCS1, SOCS3, STAT3 and LIF mRNAs, suggesting a decrease in PRL signaling and induction of involution markers. Furthermore, Caspase-3 and 8 and PARP labeled cells and the expression of structural proteins such as beta-Actin, alpha-Tubulin and Lamin B were increased, indicating the activation of apoptotic pathways and tissue remodelation. HypoT also increased PRA (mRNA and protein) and er,6 and decreased era mRNAs, and increased strongly TR alpha 1, TR beta 1, PRA and ER alpha protein levels. These results show that lactating HypoT rats have premature mammary involution, most probably induced by the inhibition of prolactin signaling along with the activation of the LIF-STAT3 pathway. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

The Neuropteris ovata frond and its cyclopteroids: micromorphology-spectrochemistry-fractal taxonomy: Propositions for restructuring and taxonomy (Pennsylvanian, Canada)

Zodrow, EL ;D'Angelo, JA ; Cleal, CJ ; BULLETIN OF GEOSCIENCES ,2016 ,91 ,669 -704 .

The primary study material consists of the 65-cm frond Neuropteris ovata (Hoffmann) var. simonii, associate petiole with organically attached cyclopteroid leaflets and trunk. Ancillary N. ovata material is used, all from the Asturian-Cantabrian strata of the Sydney Coalfield, Canada. This material is appropriate for the objective of the study to present an ovata-frond Aufbau in terms of micromorphology coupled with chemistry using an holistic sampling design (co-ordinating epidermal microscopy with chemistry per sample location). Chemical analyses were obtained by the reliable FTIR technique (Fourier transform infrared spectroscopy) and interpreted via chemometrics by methods of principal component analysis. Fractal geometry is introduced as a promising taxonomic parameter. The main conclusions include that the N. ovata plant can be characterized by three distinct epidermal structures: (1) rectangular elongate (trunk and petiole), (2) elongate (rachides of three orders), and (3) undulate (pinnule), which to a certain extent agrees with the chemistry of the frond Aufbau. The frond was also complex - architecturally, histologically, physiologically, chemically and autecologically. It was photosynthetic, had secretory organs (implying a characteristic plant aroma), supporting rodlets, divers epicuticular features, and a distinct chemical composition/structure. The frond was likely 4 m long with complex-pinnate cyclopteroid leaflets, fimbriate or entire-margined, below and above the main bifurcation, which begs the question of cyclopteroid definition and function. The overall results will be beneficial to taxonomy/systematics, and guide pteridospermous reconstruction into a new paradigm.

Detecting DGA Malware Traffic Through Behavioral Models

Erquiaga, MJ ;Catania, C ; Garcia, S ; 2016 IEEE BIENNIAL CONGRESS OF ARGENTINA (ARGENCON) ,2016 ,,-.

Some botnets use special algorithms to generate the domain names they need to connect to their command and control servers. They are refereed as Domain Generation Algorithms. Domain Generation Algorithms generate domain names and tries to resolve their IP addresses. If the domain has an IP address, it is used to connect to that command and control server. Otherwise, the DGA generates a new domain and keeps trying to connect. In both cases it is possible to capture and analyze the special behavior shown by those DNS packets in the network. The behavior of Domain Generation Algorithms is difficult to automatically detect because each domain is usually randomly generated and therefore unpredictable. Hence, it is challenging to separate the DNS traffic generated by malware from the DNS traffic generated by normal computers. In this work we analyze the use of behavioral detection approaches based on Markov Models to differentiate Domain Generation Algorithms traffic from normal DNS traffic. The evaluation methodology of our detection models has focused on a real-time approach based on the use of time windows for reporting the alerts. All the detection models have shown a clear differentiation between normal and malicious DNS traffic and most have also shown a good detection rate. We believe this work is a further step in using behavioral models for network detection and we hope to facilitate the development of more general and better behavioral detection methods of malware traffic.

Broker Scheduler based on ACO for Federated Cloud-based Scientific Experiments

Pacini, E ;Mateos, C ; Garino, CG ; 2016 IEEE BIENNIAL CONGRESS OF ARGENTINA (ARGENCON) ,2016 ,,-.

Federated Clouds are infrastructures arranging physical resources from different datacenters. A Cloud broker intermediates between users and datacenters to support the execution of jobs through Virtual Machines (VM). We exploit federated Clouds to run CPU-intensive jobs, in particular, Parameter Sweep Experiments (PSE). Specifically, we study a broker-level scheduler based on Ant Colony Optimization (ACO), which aims to select the datacenters taking into account both the network latencies and the availability of resources. The less the network latency, the lower the influence on makespan. Moreover, when more VMs can be allocated in datacenters with lower latency, more physical resources can be taken advantage of, and hence job execution time decreases. Then, once our broker-level scheduler has selected a datacenter to execute jobs, VMs are allocated in the physical machines of that datacenter by another intra-datacenter scheduler based on ACO. Experiments performed using CloudSim and job data from a real PSE show that our ACO-based broker-level scheduler succeeds in reducing the makespan compared to similar schedulers based on latency-aware greedy and round robin heuristics.

Changes in lysosomal enzymes and mannose-6-phosphate receptors related to sexual maturation in bull epididymis

Aguilera, AC ;Carvelli, L ; Boschin, V ; Mohamed, F ; Zyla, L ; Sosa, MA ; REPRODUCTION FERTILITY AND DEVELOPMENT ,2016 ,28 ,1608 -1617 .

One of the most striking features of the mammalian epididymis is the secretion of lysosomal enzymes (LE). These LE may play a role in sperm maturation. In the present study we investigated the activity and distribution of four LE (-galactosidase (-Gal), N-acetyl--D-glucosaminidase (-NAG), -mannosidase (-Man) and -glucuronidase (-Glu)) in bull epididymis at two different ages (6 months and 4 years) to determine whether these enzymes vary with sexual maturity. In young, sexually immature (SI) bulls we found high LE activity in the epididymal tissue that accounts for a developed and active lysosomal apparatus. In contrast, low LE activity was measured in sexually mature (SM) bulls, and -NAG and -Gal were mostly secreted into the lumen. We also attempted to correlate LE distribution with the expression and functionality of mannose-6-phosphate receptors (MPRs), which are thought to be involved in proper delivery of LE to lysosomes. The cation-dependent MPR was highly expressed in SI bulls, with expression decreasing during adulthood, whereas the expression of the cation-independent MPR was higher in SM than SI bulls. In addition, the four enzymes recovered from the epididymal lumen interact with both MPRs at each age. We conclude that the activity and distribution of LE in bull epididymis varies with sexual maturity and that the distribution is regulated differently by the two types of MPR. These findings could provide some molecular basis for male infertility.

A bio-inspired scheduler for minimizing makespan and flowtime of computational mechanics applications on federated clouds

Pacini, E ;Mateos, C ; Garino, CG ; Careglio, C ; Mirasso, A ; JOURNAL OF INTELLIGENT & FUZZY SYSTEMS ,2016 ,31 ,1731 -1743 .

Computational Mechanics (CM) concerns the use of computational methods to study phenomena under the principles of mechanics. A representative CM application is parameter sweep experiments (PSEs), which involves the execution of many CPU-intensive jobs and thus computing environments such as Clouds must be used. We focus on federated Clouds, where PSEs are processed via virtual machines (VM) that are lauched in hosts belonging to different datacenters, minimizing both the makespan and flowtime. Scheduling is performed at three levels: a) broker, where datacenters are selected based on their network latencies via three policies, b) infrastructure, where two bio-inspired schedulers based on Ant Colony Optimization (ACO) and Particle Swarm Optimization (PSO) for VM-host mapping in a datacenter are implemented, and c) VM, where jobs are assigned into the preallocated VMs based on job priorities. Simulated experiments performed with job data from two real PSEs show that our scheduling approach allows for a more agile job handling while reducing PSE makespan and flowtime.


Neme, G ;Sugranes, N ; Salgan, L ; Gil, A ; Otaola, C ; Giardina, M ; Morgan, C ; Llano, C ; RELACIONES ,2016 ,41 ,101 -130 .

This paper presents the results of fieldwork at Risco de los Indios, an archaeological site situated at 2.400 m elevation in the upper Diamante River watershed. The site contains twenty nine stacked-rock residential structures and dates to ca. 500 cal BP. Recovered faunal and macrobotanical remains indicate the site focused mainly on hunting camelids, underwritten by exploitation of local plants as well as transport and consumption of domestic beans (Phaseolus vulgaris). Extralocal ceramics and obsidian sourcing indicates substantial mobility and contact with other groups within and across the southern Andes. These results are discussed in the context of the other high-altitude residential sites in the southern Mendoza region.

3D chemical map and a theoretical life model for Neuropteris ovata var. simonii (index fossil, Asturian, Late Pennsylvanian, Canada)

D'Angelo, JA ;Zodrow, EL ; INTERNATIONAL JOURNAL OF COAL GEOLOGY ,2016 ,153 ,12 -27 .

The largest known 65-cm frond segment of Neuropteris ovata var. simonii (Order: Medullosales) from the Late Pennsylvanian of Sydney Coalfield, Canada, is preserved as compression and naturally macerated cuticle and comprises the study sample. The study objectives included (i) analyzing the chemical variability throughout the frond, (ii) interpreting chemical differences in the lower from the upper part of the frond (impossible to do from fragmented specimens), (iii) inferring the likely biopolymeric make-up of the tissues of the once-living plant, (iv) estimating the likely metabolic cost of plant tissue production, and (v) suggesting autecological aspects.

Effect of Na+ ion on the dissolution of ferrocolumbite in autoclave

Rodriguez, MH ;Rosales, GD ; Pinna, EG ; Suarez, DS ; HYDROMETALLURGY ,2016 ,159 ,60 -64 .

The effect of different leaching media on the dissolution of ferrocolumbite from the province of San Luis, Argentina, in an autoclave was investigated. The leaching agents used were aqueous solutions of HF-NaF or HF-Na2C2O4.

Abundance and generalisation in mutualistic networks: solving the chicken-and-egg dilemma

Fort, H ;Vazquez, DP ; Lan, BL ; ECOLOGY LETTERS ,2016 ,19 ,4 -11 .

A frequent observation in plant-animal mutualistic networks is that abundant species tend to be more generalised, interacting with a broader range of interaction partners than rare species. Uncovering the causal relationship between abundance and generalisation has been hindered by a chicken-and-egg dilemma: is generalisation a by-product of being abundant, or does high abundance result from generalisation? Here, we analyse a database of plant-pollinator and plant-seed disperser networks, and provide strong evidence that the causal link between abundance and generalisation is uni-directional. Specifically, species appear to be generalists because they are more abundant, but the converse, that is that species become more abundant because they are generalists, is not supported by our analysis. Furthermore, null model analyses suggest that abundant species interact with many other species simply because they are more likely to encounter potential interaction partners.

An A-based cofibrantly generated model category

Ottina, M ;TOPOLOGY AND ITS APPLICATIONS ,2016 ,197 ,60 -74 .

We develop a cofibrantly generated model category structure in the category of topological spaces in which weak equivalences are A-weak equivalences and such that the generalized CW(A)-complexes are cofibrant objects. With this structure the exponential law turns out to be a Quillen adjunction. (C) 2015 Elsevier B.V. All rights reserved.

A pervasive role for biomass burning in tropical high ozone/low water structures

Anderson, DC ;Nicely, JM ; Salawitch, RJ ; Canty, TP ; Dickerson, RR ; Hanisco, TF ; Wolfe, GM ; Apel, EC ; Atlas, E ; Bannan, T ; Bauguitte, S ; Blake, NJ ; Bresch, JF ; Campos, TL ; Carpenter, LJ ; Cohen, MD ; Evans, M ; Fernandez, RP ; Kahn, BH ; Kinnison, DE ; Hall, SR ; Harris, NRP ; Hornbrook, RS ; Lamarque, JF ; Le Breton, M ; Lee, JD ; Percival, C ; Pfister, L ; Pierce, RB ; Riemer, DD ; Saiz-Lopez, A ; Stunder, BJB ; Thompson, AM ; Ullmann, K ; Vaughan, A ; Weinheimer, AJ ; NATURE COMMUNICATIONS ,2016 ,7 ,-.

Air parcels with mixing ratios of high O-3 and low H2O (HOLW) are common features in the tropical western Pacific (TWP) mid-troposphere (300-700 hPa). Here, using data collected during aircraft sampling of the TWP in winter 2014, we find strong, positive correlations of O-3 with multiple biomass burning tracers in these HOLW structures. Ozone levels in these structures are about a factor of three larger than background. Models, satellite data and aircraft observations are used to show fires in tropical Africa and Southeast Asia are the dominant source of high O-3 and that low H2O results from large-scale descent within the tropical troposphere. Previous explanations that attribute HOLW structures to transport from the stratosphere or mid-latitude troposphere are inconsistent with our observations. This study suggest a larger role for biomass burning in the radiative forcing of climate in the remote TWP than is commonly appreciated.