Ecology of Amblyomma neumanni (Acari: Ixodidae) Nava, Santiago; Estrada-Peña, Agustín; Mangold, Atilio Jose; Guglielmone, Alberto Alejandro The life cycle of Amblyomma neumanni was described studying the seasonal distribution of free-living stages and parasitic phases during two consecutive years. Development periods of engorged ticks under different photoperiod conditions were recorded. Larvae of A. neumanni have the peak of abundance in autumn. Nymphs reach the peak in winter. Females were collected on cattle from autumn to late spring.The seasonal distribution pattern of females showed a bimodal curve, with a peak in autumn and other during early and middle spring. The engorged females exposed at shortest photoperiod regimen (10 h light–14 h dark) under both laboratory and field conditions undergo morphogenetic diapause, expressed as a delay in the oviposition. It is concluded that females of A. neumanni that feed and copulate in autumn undergo morphogenetic diapause, and they will lay eggs in spring, simultaneously with the females that feed and copulate in this season. Climate niche analysis shows that adequate suitability for A. neumanni depends mainly from temperature (mean, absolute maximum and minimum, and mean temperature in wettest and driest quarters) as well as from rainfall in warmest and coldest quarters. Sequences of 16S rDNA gene belonging to different populations of A. neumanni, showed no intraspecific genetic differentiation.

Is red spotted green frog (Hypsiboas punctatus, Anura: Hylidae) selecting its preys? The importance of prey availability Lopez, Javier Alejandro; Scarabotti, Pablo Augusto; Medrano, María Celeste; Ghirardi, Romina The study of the feeding ecology of amphibians is an old issue in herpetology. Notwithstanding, the lack of food resources data in many studies of amphibians feeding has lead to partial understanding of frog feeding strategies. In this study we evaluate the trophic selectivity of a red spotted green frog (Hypsiboas punctatus) population from a Middle Paraná River floodplain pond in Argentina, and discuss the importance of prey availability data when interpreting results from diet analysis. We analyzed the gut contents of 47 H. punctatus adults and compared frog?s diet with the environmental food resources. Prey availability was estimated by systematically seep-netting the microhabitat where anurans were localized foraging. We identified 33 taxonomic categories from gastrointestinal contents. Numerically, the most important prey categories were dipterans, followed by hemipterans, homopterans and coleopterans. The diet similarity between males and females was high and no statistical differences in diet composition were found. The most abundant food resources in the environment were dipterans, coleopterans, homopterans and collembolans. In order to assess whether frogs were selecting their preys, we calculated Pianka?s niche overlap index and Jacobs? electivity index comparing gut contents to prey availability data. Trophic niche overlap was medium but significantly higher than expected by chance. The electivity index indicated that H. punctatus foraged dipterans slightly above their environmental abundance. Among the secondary preys, hemipterans were foraged selectively, homopterans were consumed in the same proportion to their occurrence in the environment, coleopterans were foraged quite under their availability and collembolans were practically ignored by frogs. Without food resources data, H. punctatus could be classified as a specialist feeder, but dipterans also were quite abundant in the environment. Our results show that H. Punctatus fit better as a generalist feeder, foraging on their main food item and some secondary preys in similar proportion to their environmental availability; even though other secondary preys are being selectively preferred or ignored by frogs. Our data illustrate the importance of including the resource availability data on diet studies to improve the understanding of amphibian feeding ecology.

Canonicity in subvarieties of BL-algebras Busaniche, Manuela; Cabrer, Leonardo Manuel We prove that every subvariety of BL-algebras which is not finitely generated is not σ-canonical. We also prove π-canonicity for an infinite family of subvarieties of BL-algebras that are not finitely generated. To do so we study the behavior of canonical extensions of ordered sums of posets.

NOx adsorption and diesel soot combustion over La2O3 supported catalysts containing K, Rh and Pt Sánchez, B.S.; Querini, Carlos Alberto; Miró, E.E. In this work we report results of NOx adsorption and diesel soot combustion on a noble metal promoted K/La2O3 catalyst. The fresh-unpromoted solid is a complex mixture of hydroxide and carbonate compounds, but the addition of Rh favors the preferential formation of lanthanum oxycarbonate during the calcination step. K/La2O3 adsorbs NOx through the formation of La and K nitrate species when the solid is treated in NO + O2 between 70 and 490 °C. Nitrates are stable in the same temperature range under helium flow. However, they become unstable at ca. 360 °C when either Rh and/or Pt are present, the effect of Rh being more pronounced. Nitrates decompose under different atmospheres: NO + O2, He and H2. The effect of Rh might be to form a thermally unstable complex (Rh-NO+) which takes part both in the formation of the nitrates when the catalyst is exposed to NOx and in the nitrates decomposition at higher temperatures. Regarding soot combustion, nitrates react with soot with a temperature of maximun reaction rate of ca. 370 °C, under tight contact conditions. This temperature is not affected by the presence of Rh, which indicates that the stability of nitrates has little effect on their reaction with soot.

Modeling of Batch Dryers for Shrinkable Biological Materials Ratti, Cristina; Crapiste, Guillermo Hector Design of dryers for biological materials is a complex problem, since in order to solve the model equations, foodstuff physicochemical and equilibrium properties and drying kinetics should be included as a function of water content and operating variables. Shrinkage of biological materials under dehydration must also be taken into account when the macroscopic balances in the bed of drying need to be solved. The main objective of this work was thus to develop a realistic simulation model to predict batch deep bed drying of shrinkable biological materials. Differential macroscopic balances for heat and mass transfer in the air and solid phases were expressed in moving coordinates in order to solve the problem of particle shrinkage during drying. The equation system was solved by the ‘method of lines’ using the Gear package for temporal derivatives and finite differences for spatial ones. All the parameters and physical properties required to solve the model were taken from literature or determined independently in lab-scale experiments. A pilot-scale hot air batch dryer was built in order to carry out experimental determinations during drying of slices or cylinders of potato, apple, and carrot at diverse hot air conditions. The appropriate choice of numerical method and initial conditions gave a reliable and stable solution of the equation system. The simulation results agreed closely to experimental data on deep bed batch drying of food particles under different conditions. The use of variable porosity and volume due to shrinkage during drying improved notably the predictions of the simulation model.

Constituents of Gutierrezia mandonii (Asteraceae) Alarcón, Silvia Rosana; Ocampos, Liliana Soledad Natalia; Pacciaroni, Adriana del Valle; Colloca, Cristina Beatriz; Sosa, Virginia Estela The genus Gutierrezia (Asteraceae) includes approximately 25 species which occur exclusively in the arid areas of América. Eighth species, Gutierrezia baccharoides Sch. Bip., Gutierrezia gilliesii Griseb., Gutierrezia isernii (Phil.) Phil., Gutierrezia mandonii (Sch. Bip.) Solbrig, Gutierrezia pulviniformis Cabrera, Gutierrezia repens Griseb., Gutierrezia solbrigii Cabrera, and Gutierrezia spathulata (Phil.) Kurtz, grow in Argentina (Freire, 1999). G. mandonii is a resinous shrub which grows naturally in the arid areas of northern Argentina and southern Bolivia (Cabrera, 1978). The aerial parts of G. mandonii were collected during the flowering period in Salta, Argentina, on January 2004. The plant was identified by Ing. Julio Tolaba. A voucher specimen (no 3414) was deposited at the Museo de la Facultad de Ciencias Naturales, Universidad Nacional de Salta.

Channeling effect in electronic spectra produced by grazing impact of fast protons on insulator surfaces Archubi, Claudio Darío; Gravielle, Maria Silvia Electron emission due to grazing scattering of fast protons from LiF and KCl surfaces is studied under axial incidence conditions. The differential emission probability is calculated within a distorted-wave formalism, taking into account axial channeled trajectories. For different emission angles, electronic spectra for proton incidence along the two principal crystal axes ([100] and [110]) are compared with those corresponding to an impact velocity in a random direction, finding effects associated with the channeling conditions.

Modeling of Phase and Chemical Equilibrium on the Quaternary System Acetic Acid, n-Butanol, Water and n-ButylAcetate Mandagaran, Beatriz Adriana; Campanella, Enrique Angel The correlation of the data for phase and chemical equilibrium in acetic acid-n-butanol-watern- butylacetate is presented. The azeotropic properties, the topological structure and the existence of a reactive azeotrope are discussed. The data are correlated by Hayden-O’Connell second virial coefficients and NRTL. Chemical equilibrium constant has a strong influence on the reactive azeotrope.

Boundary lipids in the nicotinic acetylcholine receptor microenvironment Barrantes, Francisco Jose; Bermudez, Vicente; Borroni, Maria Virginia; Antollini, Silvia Susana; Pediconi, Maria Filomena; Baier, Carlos Javier; Bonini, Ida Clara; Gallegos, Cristina Eugenia; Roccamo, Ana Maria; Valles, Ana Sofia; Ayala Peña, Victoria Belen; Kamerbeek, Constanza Belén The structural and functional properties of the nicotinic acetylcholine receptor (AChR), the archetype molecule in the superfamily of Cys-looped ligand-gated ion channels, are strongly dependent on the lipids in the vicinal microenvironment. The influence on receptor properties is mainly exerted by the AChR-vicinal (“shell” or “annular”) lipids, which occur in the liquid-ordered phase as opposed to the more disordered and “fluid” bulk membrane lipids. Fluorescence studies from our laboratory have identified discrete sites for fatty acids, phospholipids, and cholesterol on the AChR protein, and electron-spin resonance spectroscopy has enabled the establishment of the stoichiometry and selectivity of the shell lipid for the AChR and the disclosure of lipid sites in the AChR transmembrane region. Experimental evidence supports the notion that the interface between the protein moiety and the adjacent lipid shell is the locus of a variety of pharmacologically relevant processes, including the action of steroids and other lipids. I surmise that the outermost ring of M4 helices constitutes the boundary interface, most suitable to convey the signals from the lipid microenvironment to the rest of the transmembrane region, and to the channel inner ring in particular

Innovations in the development of healthier chicken sausages formulated with different lipid sources Andres, Silvina Cecilia; Zaritzky, Noemi Elisabet; Califano, Alicia Noemi Long chain polyunsaturated n-3 fatty acids (PUFA) are critical nutrients for human health and the fortification of foods with these fatty acids is an important emerging area from the commercial and academic point of view. Development, characterization and changes during refrigerated vacuum storage of low-fat chicken sausages formulated with pre-emulsified squid oil were examined and compared to those formulated with beef tallow. Physico chemical analysis and process yield after heat treatment were determined; the heat treated sausages were evaluated by purge loss, color, texture, microstructure by SEM, microbial counts, fatty acid profile, lipid oxidation and sensory analysis during refrigerated vacuum storage. Process yield of both formulations were higher than 97% and purge losses during storage lower than 7%. Purge losses of oil formulated sausages were lower than those with beef tallow. Sausages with squid oil resulted in higher lightness, lower redness and yellowness, and lower Texture Profile Analysis parameters than the formulation prepared with beef tallow. Microstructure of both formulations were similar, except for the fat droplets that microscopic observations showed in the sausages made with beef tallow. Low lipid oxidation was detected in formulation with squid oil due to the the combination of ingredients and storage conditions. Microbial counts of both products were less than 5 log CFU/g at the end of 90 days of storage. The sausage formulated with squid oil presented more than 30 and 40 g/100 g of monounsaturated and polyunsaturated fatty acids, respectively. Docosahexaenoic acid was the predominant polyunsaturated fatty acid, followed by eicosapentaenoic acid and linoleic acid. Both products showed safe sanitary conditions, good sensory acceptability and presented very good stability and quality attributes but sausages formulated with squid oil showed a better fatty acid profile according to nutritional criteria.

An efficient approach to homochiral indane nucleosides Ugliarolo, Esteban Ariel; Lantaño, Beatriz; Moltrasio, Graciela Yolanda; Moglioni, Albertina Gladys A series of new chiral 6-substituted purinyl and 8-aza-purinyl carbonucleosides based on indanol were synthesized from the commercially available (1R,2S)-1-amino-2-indanol and (1S,2R)-1-amino-2-indanol based on a well-known methodology.

La oposición argentina a la organización panamericana impulsada por Estados Unidos (Segunda Conferencia, México, 1901-1902) Morgenfeld, Leandro Ariel Este artículo analiza el enfrentamiento entre Argentina y Estados Unidos en la Segunda Conferencia Panamericana, realizada en México en 1901-1902. Es parte de una investigación más general, que estudia las tensiones argentino-estadounidenses en el ámbito interamericano durante las distintas conferencias que se realizaron entre 1889 y 1955. Con amplia documentación inédita de las cancillerías argentina y estadounidense, se analiza un capítulo fundamental del proceso panamericano en el que se expresaban las distintas visiones sobre la integración continental. Como en la Primera Conferencia Panamericana, la delegación argentina puso todo su empeño en dificultar en lo posible el avance de la organización impulsada por Estados Unidos.; This article analyzes the confrontation between Argentina and the United States in the Second Pan-American Conference that took place in Mexico between 1901 and 1902. Is part of a more general study about the ArgentineAmerican tensions during the different inter-american conferences between 1889 and 1955. Based on documents from the Argentine and the American Foreign Ministers that were not previously released, this work analyzes a fundamental chapter of the Pan-American process in which the different visions about continental integration were discussed. As they did in the First PanAmerican Conference, the Argentine delegation tried to prevent the progress of the organization driven by the United States.

ICTs in Latin America: An overview Santos, Rodrigo Martin In this paper, the state-of-the-art on the field of Information and Communications Technologies (ICTs) in Latin America is presented. Its main contribution consists in the localization of common objectives for the majority of the countries in the region. Although the countries are very heterogeneous from the cultural and geographical perspectives, there are many common factors that can be exploited in order to develop their economies. At first sight, Brazil or Mexico with their huge populations and big economies are giants compared to other countries like Bolivia or Costa Rica. However there are many common problems in all of them that can be addressed with a common strategy. An important question that this presentation tries to answer is the ICT profile of Latin America: consumer or producer. Data from the World Bank on ICT infrastructure and from the academic sector on the actual situation of the R&D activities in the region are analyzed to answer this question.

Early Cretaceous Radiolarians from southernmost Patagonia, Argentina; Radiolarios del Cretácico Temprano de la Patagonia Austral, Argentina Hollis, Chris; Archangelsky, Sergio; Cardenas, Orlando Se presenta una asociación de radiolarios hallada en el sector inferior de la Formación Río Mayer expuesta en la Estancia La Federica en la provincia Santa Cruz, Argentina. Los elementos dignósticos de valor bioestratigráfico indican una edad Berriasiano tardío-Barremiano temprano (Cretácico Temprano inicial) para este conjunto. Los radiolarios tienen afinidades faunísticas con asociaciones halladas costa afuera del noroeste de Australia y en el Pacífico occidental, al noreste de Nueva Zelanda. Se sugiere que la asociación de radiolarios patagónicos se desarrolló en aguas frías. Diez metros por debajo de los niveles portadores de radiolarios se hallan sedimentos continentales portadores de palinomorfos que fueron referidos a la Formación Springhill de edad BerriasianoValanginiano.; A radiolarian assemblage found in the lowermost strata of the Río Mayer Formation, as exposed at Estancia La Federica in Santa Cruz Province, Argentina, is described. The biostratigraphic markers of this assemblage indicate a late Berriasian-early Barremian age (early Early Cretaceous). The radiolarians have faunal affinities with early Cretaceous assemblages reported from offshore northwestern Australia and the western Pacific, northeast of New Zealand. A cool-water affinity is suggested for the Patagonian assemblage. Ten meters below the levels with radiolarians sediments bearing continental palynomorphs are found. They are referred to the Springhill Formation of Berriasian to Valanginian age.

Proteolytic activity of three probiotic strains in semi-hard cheese as single and mixed cultures: Lactobacillus acidophilus, Lactobacillus paracasei and Bifidobacterium lactis Bergamini, Carina Viviana; Hynes, Erica Rut; Palma, Susana Beatriz; Sabagg, Nora; Zalazar, Carlos Antonio The influence of three probiotic strains (Lactobacillus acidophilus, Lactobacillus paracasei and Bifidobacterium lactis) in semi-hard cheese proteolysis patterns was assessed. Probiotics were inoculated both as single cultures and as a three-strains mix, and added to milk by two different techniques: after a pre-incubation step or directly to vat. B. lactis did not show any effect on proteolysis of cheeses, while L. paracasei showed a little impact at the end of the ripening. On the contrary, L. acidophilus significantly influenced secondary proteolysis from the beginning of ripening, causing an increase in the levels of small nitrogen-containing compounds and free amino acids and changes in the peptide profiles. Lactobacillus acidophilus effect on peptidolysis was more noticeable when it was added to cheese-milk after pre-incubation in an enriched milk-fat substrate. Similar results obtained with the three-strain mixed culture suggest that L. acidophilus played a major role in secondary proteolysis of probiotic cheeses in this trial.

Estudio de la resistencia de fagos temperados de Lactobacillus delbrueckii a factores físicos de conservación e higiene Ebrecht, Ana Cristina; Guglielmotti, Daniela Marta; Reinheimer, Jorge Alberto; Capra, María Luján; Suárez, Viviana Beatriz Se estudió la viabilidad de dos fagos temperados de Lactobacillus delbrueckii subsp. lactis (Cb1/204 y Cb1/342) al pH, a diferentes temperaturas de conservación y a distintos tratamientos térmicos aplicados en la industria. Ambos fagos mantuvieron su nivel de recuento entre pH 4 y 9, hasta 30 min de exposición y el fago Cb1/342 mantuvo igual recuento aún a pH 3. A 4 ºC diminuyeron su recuento en 2 órdenes logarítmicos, mientras que a -80 ºC el fago Cb1/204 resultó levemente menos resistente. En leche, el tratamiento a 63 ºC no fue eficiente. A 72 ºC, el fago Cb1/204 resultó más resistente que el Cb1/342. A 82 ºC, ambos fagos fueron inactivados a los 2 min.

An elasto-visco-plastic model using the finite element method for crustal and lithospheric deformation Quinteros, Javier; Ramos, Victor Alberto; Jacovkis, Pablo Miguel A novel numerical model based on solid deformation is presented in this paper. This thermo-mechanical model can simulate the tectonic evolution of crust and (lithospheric and asthenospheric) mantle under different conditions. Our implementation uses the finite element method (FEM) in order to solve the equations. As a Lagrangian approach is employed, remeshing techniques are implemented to avoid distortion problems when a certain deformation threshold is reached. The translation of the state between the old and new mesh is achieved by means of the information stored on Lagrangian particles, which minimizes the diffusion. The model is able to represent elastic, viscous and plastic behaviour inside the studied domain. Three types of creep mechanism (diffusion, dislocation and Peierls) are included. Two different quadrilateral isoparametric elements were implemented and can be employed to perform the calculations. The first one is an element with 4 nodes, selective reduced integration and a stabilization operator to diminish hourglass modes, which reduces the computational time needed. The second one has 8 nodes located in standard positions, uses full integration scheme and has no hourglass modes as it satisfies the Inf-Sup condition. Several test cases with known solutions were run to validate the different aspects of the implementation.

Melampolides from Argentinean Acanthospermum australe Sánchez, Marianela; Kramer, Fernando Luis; Bargardi, Severino; Palermo, Jorge Alejandro The investigation of the ethanol extract of Acanthospermum australe, collected in the province of Misiones, Argentina, yielded eight melampolides (1-8) of the acanthospermal type. Two of them, 8β-hydroxy-9α-(2-methylbutyryloxy)-14-oxo-acanthospermolide (3) and 9α-hydroxy-8β-(2-methylbutyryloxy)-14-oxo-acanthospermolide (7) are new compounds. Two other compounds (4 and 8) have been previously reported, and the NMR data of 4 are corrected. Compounds 1, 2, 5 and 6 have not been previously reported, but are probably artifacts formed during extraction. Compounds 3, 6 and 7 showed slight antibiotic activity against Gram-positive bacteria.

Cost minimization in a non-catalytic biodiesel production plant Espinosa, Susana; Díaz, María Soledad; Brignole, Esteban Alberto In the present study, we propose an optimization model for the minimization of capital and operating costs in a supercritical methanol biodiesel plant, considering alternative process schemes together with the convenience or not to use a cosolvent in the chemical reaction. A rigorous process simulation model, based on a group contribution equation of state is integrated with a successive quadratic programming algorithm to solve the nonlinear problem. Optimization results show that noncatalytic biodiesel production with supercritical methanol can be economically competitive with conventional catalyzed production. © 2009 Elsevier B.V. All rights reserved.

A new colorimetric method for determination of alkylresorcinols in ground and whole-cereal grains using the diazonium salt Fast Blue RR Sampietro, Diego Alejandro; Vattuone, Marta Amelia; Catalan, Cesar Atilio Nazareno A fast and inexpensive method was developed to determine the content of alkylresorcinols (ARs) in ground and whole-cereal grains. This method is based on the ability of ARs to couple with Fast Blue RR salt in alkaline medium, yielding coloured azo-derivatives that can be quantified colorimetrically. Good linearity was observed for olivetol in the range of 1-10 μg with methanol as solvent (λmax = 480 nm) and 1-7 μg with butanol as solvent (λmax = 530 nm). Sensitivity obtained in butanol was comparable to that obtained in the Fast Blue B based method (methanol as solvent, λmax = 520 nm). In the new colorimetric method described here, incubation time was reduced to 20 min and the stability of the reaction products was as long as 3 h. The method appears promising for the analysis of 1,3-dihydroxybenzene derivatives in samples from plant breeding and food analyses.