Universidad Nacional del Sur
  • Bahía Blanca, Provincia de Buenos Aires, Argentina
Recent publications
Dryland rehabilitation in the central arid region of Argentina is urgently needed to reverse the current high levels of degradation. Neltuma flexuosa var. depressa, adapted to arid environments, gives it the potential to be used in rehabilitation, for extensive livestock grazing and apiculture. When the soil seed bank is exhausted and natural regeneration is impossible, seed-based rehabilitation programmes constitute one of the more promising options. Thornless ecotype selection could improve pods utilization, so studies of the population distribution can be useful as a genetic resource for pre-breeding. Niche occupancy exhibits a large latitudinal extension (32–43°S), mainly in areas of salinity. All populations would have a transient soil seed bank, but seed dormancy release was lower in populations originating in more unpredictable environments, which distributes germination across years and acts as a bet-hedging strategy between seasons. We observed differences between the populations, with greater spinescence being associated with higher isothermality and lower annual precipitation (r > 80***) at the population's place of origin, showing local adaptation. We also found some thornless seedlings (1.67%) in a population with lower spinescence. However, the plastic response of thorns in seedlings, as well as later stages, should be evaluated in stressful environments.
The productivity of approximately 75% of crops worldwide depends to some extent on insect pollination. However, while global agriculture is becoming more dependent on pollinators, wild populations of pollinators are declining. For this reason, hives of Apis mellifera (honeybees), the most widely used pollinator, are commonly placed in the fields; in recent years, alternative managed pollinators (AMPs) such as Bombus spp. or Osmia spp. have also been used. Thus, for evidence-based pollination management, we need to know whether the pollination service provided by AMPs can replace, complement or synergistically interact with that provided by honeybees. We asked: Does crop productivity differ between fields with honeybees and those with AMPs? Does productivity increase by incorporating AMPs in addition to managed honeybees? Do the effects of managed honeybees and AMPs interact? We performed a meta-analysis based on 28 studies on 20 crops. We estimated effect sizes (ln(R)) for crop productivity (fruit/seed set, fruit/seed quality and yield) from 73 comparisons between honeybees and an AMP, and 21 comparisons between honeybees alone and honeybees plus an AMP. Overall, we found no evidence of difference in crop productivity between honeybees and AMPs when managed separately. However, the productivity of crops pollinated by honeybees together with AMPs was 22% ± 6 (SE) higher than that of crops pollinated only by honeybees. Moreover, we found a weak evidence of a positive effect of beehive density on crop productivity when an AMP was added, suggesting a synergistic interaction between honeybees and AMPs. We conclude that, on average, honeybee performance is similar to that of AMPs, and that increasing the number of managed pollinator species can improve crop productivity in the short-term, particularly in systems with impoverished pollinator faunas. More generally, this review confirms the positive effect of pollinator diversity on pollination service, suggesting this can be partly recreated using a suite of managed pollinators.
In this paper, a study on flexural–torsional vibrations of finite beams with a large number of resonators periodically attached along the length is presented. Emphasis is given in determining bandgaps, defined as frequency ranges free of resonances. The structural model is based on a modified Vlasov theory that incorporates the resonators effect by means of sectional inertial properties depending on the excitation frequency. Analyzing these last properties, the mechanism of weak and strong bandgap formation is enlightened. Analytical formulas for the edge frequencies of bandgaps are obtained. Also, an exact analytical solution for the free and forced vibration of simply supported beams is presented. This approach allows exploring, from another point of view, the location of attenuation bands.
When applying the Molecular Dynamics (MD) formalism to the short-time dynamics on a paradigmatic lithium metasilicate glass system, it reveals the major features of the mobility. Experimental evidence of the physical phenomenon known as the Nearly Constant Loss (NCL) can be attributed to the independent motion of a small proportion of uncorrelated lithium ions which can leave their cages. Dynamical and structural results in this work when applying the isoconfigurational ensemble method (IEM) to the lithium metasilicate MD simulation, reveal the existence of two different lithium environment, lithium ions with high and low propensity to move. The dynamics of each kind of lithium shows that those ions hosted in high-propensity sites displace continuously in time and are responsible for contributing to the slow Mean Square Displacement (MSD) increase in time due to a highly interconnected path. On the other side, the low-propensity lithium ions remain confined to their cages for a longer time until they leave them and jump to the next site. Low-propensity lithium ions only contribute to the MSD when they reach the pre-diffusive time, after 40 ps, even after the maximum dynamical heterogeneity time at 700 K. The results reported in this research evidence that the NCL microscopic origin is due to those highly-dynamically- connected system regions which do not confine the lithium ion, i.e. the so called high-propensity lithium ions in this work.
Organochlorine pesticides (OCPs) were assessed for their occurrence, behavior and the associated human health and ecological risks in four fish species (Micropogonias furnieri, Cynoscion guatucupa, Mustelus schmitti, and Ramnogaster arcuata) and sediments from the Bahía Blanca estuary, Argentina, an important coastal environment of South America. Total OCPs values ranged from 0.86 to 6.23 ng/g dry weight in sediments and from <LOD (method detection limits) to 0.74 ng/g wet weight in fish. While lindane and α-endosulfan were the dominant congeners in sediments, β-endosulfan and p,p'-DDE were dominant in fish. OCP levels and residues patterns varied within the fish species and life stage. Finally, after cancer and non-cancer risk analysis, results concluded that the consumption of fish from the estuary would pose no health threats associated with these pollutants.
Yerba mate (Ilex paraguariensis) tea is a well know source of phenolic antioxidants compounds. Caffeoyl derivatives are the primary constituents that account for the antioxidant capacity of this beverage. It was proposed that the interaction of polyphenols with lipid bilayers of various cell types provides the molecular rationale for their hallmark antioxidant and anti-inflammatory activities. In this study, atomistic molecular dynamics (MD) simulations were carried out in order to outline a detailed picture of the molecular interactions between three caffeoyl acids derivatives and two different lipid bilayers. We show that the three phenolic acids are able to interact at the upper regions of lipid bilayers, confining their action to the membrane surface; moreover, the strength of these interactions relay on the probability of metabolite protonation once inserted in the bilayer.
Plodia interpunctella Hübner (Lepidoptera: Pyralidae) is probably the most common moth pest of stored products. Its larvae are considered very effective packaging penetrators, causing serious losses. Therefore, the development of new food packaging technologies to prevent larvae infestation is crucial. In the present work, geranium and peppermint essential oils (EO) were used to elaborate chitosan (Qx) based films (Qx-EO films) at different concentrations (0% (control), 0.1%, 0.25% and 0.5% w/w). The Qx-EO films were tested in repellent and penetration assays for 72 h and 15 days, respectively. In both bioassays, most effective Qx-EO films were those containing geranium and peppermint EO at 0.5% w/w. In repellent assays, Qx-geranium EO films were more effective than Qx-peppermint EO films. In penetration assays, both films reduced penetration percentage to 10% (penetration percentage for control ≈ 50%). Then, possible structural changes, thermal stability and mechanical properties of Qx films containing EOs at 0.5% w/w were analyzed. The loading efficiency of Qx-geranium EO and peppermint EO films were close to 90% and 35%, respectively. It was demonstrated that EO incorporation allows conserving mechanical properties of control films. It is important to emphasize that these films showed repellent activity and could prevent contamination with P. interpunctella larvae.
In this note, we construct a 3×3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3\times 3$$\end{document}-valued Łukasiewicz–Moisil algebras from a monadic 3×3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3\times 3$$\end{document}-valued Łukasiewicz–Moisil algebras, generalizing A. Monteiro’s construction and we construct a monadic 3×3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3\times 3$$\end{document}-valued Łukasiewicz–Moisil algebras from a monadic n×m\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n\times m$$\end{document}-valued Łukasiewicz–Moisil algebras, generalizing V. Boicescu’s construction.
This study presents the preparation of magnetic carbon nanocomposites (MCNCs) through a two-step procedure: (i) in situ co-precipitation of magnetite (Fe 3 O 4) nanoparticles into four different carbonaceous matrixes and (ii) post-pyrolysis treatment to coat the magnetic core. Four post-pyrolysis MCNCs were obtained: MACP (post-pyrolyzed magnetic activated carbon), MCCP (post-pyrolyzed magnetic charcoal), MHCP OR (post-pyrolyzed magnetic hydrochar from orange residue), and MBCP SFH (post-pyrolyzed magnetic biochar from sunflower husk). These four samples were compared with the starting MCNCs prepared without post-pyrolysis treatment: MAC, MCC, MHC OR , and MBC SFH , respectively. After post-pyrolysis treatment, a thin carbon layer surrounding some of the magnetite nanoparticles was identified by transmission electron microscopy. Post-pyrolysis modified the porous structure and chemical composition of MCNCs. Furthermore, a leaching test with acid sulfuric solution at 90 °C was carried out. The results suggested that the MHCP OR and MBCP SFH were more stable in an acidic medium than MACP and MCCP, indicating that the coat generated during post-pyrolysis of hydrochar and biochar could partially protect the magnetic core by reducing Fe leaching into the aqueous solution. Biochar and the hydrochar-based MCNCs before and after post-pyrolysis treatment exhibit superparamagnetic properties; however, their saturation magnetization (M s) decreased considerably. These results open the potential application fields of MCNCs obtained by post-pyrolysis of biochar and hydrochar-based materials in acidic mediums.
Direct laser interference patterning (DLIP) employing sub-picosecond IR irradiation allows for the ultrafast processing of polyaniline surfaces polymerized onto a poly(methyl methacrylate) substrate (PANI@PMMA) achieving excellent quality features. The patterning shows high levels of precision regarding control of width and height in micro/nanoarrays, giving customization to the surfaces. The electroactive property evaluation suggests the conductivity presents anisotropic characteristics following the patterning of the polymeric surfaces (R SL = 54 ± 5 kΩ sq −1 and R ST = 1.7 ± 3 MΩ sq −1 , longitudinal and transversal resistance modes respectively). The evidence is supported by electrostatic force microscopy measurements. These results indicate potential applicability in the biomedical field of nerve and myocardial tissue regeneration.
The introduction of defects is one of the most recurrent pathways to generate modifications to materials’ electronic structure and surface reactivity. In this work, calculations based on the density functional theory (DFT) were applied to study the electronic properties of pristine and reduced TiO2(B)(100) ultrathin sheets to evaluate their potential as a semiconductor material for dye-sensitized solar cells (DSSCs). It was carried out by introducing vacancy defects on these surfaces and then adsorbing a catechol molecule, used as a model of a direct electron injection sensitizer (type-II dye), in different interaction configurations. Geometric, energetic, and electronic analyses were performed, focusing on the electronic structure changes and charge transfer between the dye and surface during molecular adsorption. The obtained results seem to indicate that a thickness of four layers is adequate to obtain a satisfactory slab model approximation of the TiO2(B)(100) surface. The presence of oxygen vacancy states among the majority of the reduced surfaces was observed as well as a reduction of the band gap energy value. Additionally, the adsorption of catechol in the reduced surface induced an increase in light absorption compared to the pristine model. These attributes suggest that reduced ultrathin sheets of TiO2(B) could be a suitable candidate as a photoelectrode for DSSC applications.
Plastic pollution in seafood has become a worldwide safety concern due to its possible harm to humans. This is the first study which has investigated the length-weight relationship, growth patterns and condition factor, together with the concentrations of microplastics (MPs) and mesoplastics (MesoPs) in Pleoticus muelleri from the Bahia Blanca Estuary (BBE), Argentina. Forty-nine individuals were collected from three sampling stations in the BBE, and each abdominal muscle with the gastrointestinal tract was analyzed. P. muelleri showed an isometric growth pattern (b = 3.0054) with values of K similar among the individuals collected (ranged between 0.80 and 0.91), considering them in good condition compared to other crustacean species around the world. 96% of shrimp presented transparent or black synthetic fibers as prevalent types, with an abundance average of (3.0 ± 2.90) MPs/g w. w. And (0.053 ± 0.16) MesoPs/g w. w. as well as a dominant size range of 0.5–1.5 mm, in accordance with recent studies in the same area. The linear regression analysis showed that K was independent of the concentration of MPs ingested by P. muelleri, with R² ranging between 0.024 and 0.194 indicating that MPs contamination does not affect the nutritional condition of shrimp. SEM/EDX detected the presence of elements like C, O, K, and Mg, tissue residues and fractures on the surface of the analyzed fibers. FTIR confirmed different types of polymers in shrimp related to textile fabrics probably from untreated sewage discharges from nearby cities. The results of this research provide useful information for a better understanding of MPs contamination in seafood, suggesting P. muelleri as a suitable species for monitoring MPs in estuarine ecosystems. Likewise, more research is required to know the effects of MPs on food safety in humans.
Micropatterning of metal oxides is of high interest for structuring electrodes in optoelectronic devices. In this work, the impact of infrared (IR) sub-picosecond Direct Laser Interference Patterning (DLIP) on the surface morphology, surface chemistry, optical and electrical properties of Fluorine-doped Tin Oxide (FTO) is studied. The topography characterization reveals periodic microchannels with an average height between 15 and 600 nm, depending on the applied laser fluence, decorated with Laser-Induced Periodic Surface Structures (LIPSS). The doping by aliovalent Sn atoms induced by non-linear IR absorption were revealed by X-ray Photoemission Spectroscopy (XPS) analysis. An increase in the average diffuse optical transmittance up to 730% was obtained in the spectral range 400–1000 nm as a consequence of the interaction of white light with the periodic micro- and nanostructures. The one-dimensionality of the microstructures caused a significant anisotropic electrical behavior, and an enhancement of the conductivity of up to 50% was obtained following the direction of the microchannels of the patterned films as compared to the unstructured material. Our results demonstrate that DLIP is a powerful technique for future application in structuring electrodes for highly efficient optoelectronic devices and sensors.
Peirce's diagrammatic system of Existential Graphs (EG) is a logical proof system corresponding to the Propositional Calculus (PL). Most known proofs of soundness and completeness for EG depend upon a translation of Peirce's diagrammatic syntax into that of a suitable Frege-style system. In this paper, drawing upon standard results but using the native diagrammatic notational framework of the graphs, we present a purely syntactic proof of soundness, and hence consistency, for EG, along with two separate completeness proofs that are constructive in the sense that we provide an algorithm in each case to construct an EG formal proof starting from the empty Sheet of Assertion, given any expression that is in fact a tautology according to the standard semantics of the system.
Vinasse, a by-product of bioethanol production, can be transformed by biotechnological processes into valuable compounds. In this work, the feasibility of incorporate a poly(hydroxyalcanoate)s (PHA)s production process to a bioethanol plant was evaluated. A superstructure whose objective function is maximization of the net present value (NPV) was run employing data reported in the literature about PHAs productivities by using different bacteria strains and vinasse as carbon source. Integration of a PHA production process to a bioethanol plant can produce economic benefits along with a reduction in the environmental impact caused by the disposal of vinasse residue. Positive NPV were reached for some analyzed scenarios, indicating that economic benefits are being obtained or meet the expectations of the investment project. The maximum obtained NPV was 35.09 million dollars using Haloferax mediterranei and a medium with 25% vinasse, pretreated with activated carbon. PHA production cost was calculated and resulted economically competitive compared to PHA production at industrial level. To estimate the economic outcome, the investment viability was evaluated using the project’s internal rate of return (IRR) and calculating the payback period (PBP) and the return on investment (ROI). Finally, a sensitivity analysis was performed to study the influence of different parameters (price, accumulation, and yield of PHA, as well as the cost of thermal and electrical energy) over the NPV and it can be concluded that polymer accumulated by the microorganism and PHA selling price are the most significant factors. Graphical Abstract
In this article we intend to present an experimentally validated complex mathematical framework of electromechanical coupling for a piezoelectric stepped Bernoulli–Euler beam for energy harvesting applications, valid for both the pre- and postbuckled states. The proposed model, takes into account the predeformed buckled configuration due to the out-of-plane displacements caused by an axial compressive load higher than the critical one. Moreover, several sources of nonlinearities are also considered such as: inertia, quadratic damping, geometrical and constitutive relations for the piezoelectric material. In addition, an axial elastic restraint as, a non-ideal boundary condition, is assumed at one end of the beam which allows treating intermediate cases between perfectly restricted and unrestricted axial displacements commonly found in experimental realization of axially loaded beams. The spatial discretization of the problem is carried out according to Galerkin Method. Based on a single-mode assumption, the Method of Multiple Scales (MMS) is used to obtain an approximated analytic solution for the harvester. Several experimental tests, based both in the static and dynamic response of the beam, were carried out for a sample formed by a MFC-8504 piezoelectric sheet and bearing steel beam evidencing not only the usefulness of the model here developed, but also the benefits associated with the bistable regime for energy harvesting applications.
Biological invasions represent one of the most significant threats to the conservation of biological diversity. Understanding the population dynamics of an invasive species is essential to detecting key components that allow the development of an effective management strategy. South American Pampas are particularly vulnerable to the invasion by alien woody plants that threaten the last remnants of native biodiversity. Aleppo pine (Pinus halepensis) invades mountain grasslands in southern Buenos Aires province, Argentina, where it changes the structure and dynamics of the whole ecosystem. We combined information on the biology of the species in its native range with our data in the invaded area to develop a population model aimed at understanding the invasion process and detecting key parameters associated with its success. A 12 × 12 stage-structured matrix model was used to describe the dynamics of the species in the area, through deterministic and stochastic projections. Population growth rates were greater than one for both types of projections, in accordance with its invasive capacity in the area. Elasticity analysis highlights the contribution of survival at the first adult stage (seven to 14 years) to the population growth rate, and in this way, draws attention to this stage when developing a species control strategy. Aleppo pine shares key biological characteristics with other high-impact invasive pine species in Argentina and other countries in the Southern Hemisphere. These similarities include the presence of serotinous cones and an abundant seed bank in the canopy, recruitment conditioned by competition in the regeneration niche, and a relatively short juvenile period. In this way, the model developed in this work could be easily adjusted for similar situations involving invasive congeners in other grassland ecosystems.
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1,295 members
Juan M.C. Larrosa
  • Departamento de Economía
Hugo Acciarri
  • Departamento de Derecho
Sandra Mandolesi
  • Departamento de Química
Ignacio Ponzoni
  • Departamento de Ciencias e Ingeniería de la Computación
Elena Galindez
  • Departamento de Biología, Bioquímica y Farmacia
Alem 1253, 8000, Bahía Blanca, Provincia de Buenos Aires, Argentina