Catalytic Combustion of Diesel Soot: Experimental Design for Laboratory Testing Peralta, María Ariela; Gross, Martin Sebastian; Sanchez, Barbara Sabrina; Querini, Carlos Alberto In order to abate diesel soot particles many catalysts have been studied at several industrial and academic laboratories. However, the comparison of kinetic data obtained with such catalysts is not straightforward, due to the different experimental conditions used in the activity measurement carried out by each research group. Temperature-programmed analysis is the most common technique used to determine catalytic activity for soot oxidation. For a given catalyst, the temperature-programmed oxidation profile depends on variables such as heating rate, oxygen partial pressure, gas flow rate, catalyst:soot weight ratio, type of contact between the catalyst and the soot, and existence of energy and/or mass transfer limitations during the analysis. This work presents a systematic study of the influence of all these testing variables on the TPO profile, and the optimum testing conditions to obtain good reproducibility during the kinetic study. Both experimental and computer simulation results are included to assist researchers in the comparison of results obtained under different experimental conditions.

AFLP characterization in pathogenic and coprophilous fungi Cinto, Isabel Esther; Gottlieb, Alexandra Marina; Gally, Marcela Edith; Ranalli, Maria Esther; Ramos, Araceli Marcela The objective of this study was to ascertain the usefulness of the AFLP technique in assessing genetic diversity among 47 strains belonging to three Ascomycota genera and as a tool for solving taxonomic problems in related morphological species. Four MseI +1 primers were assayed in combination with two EcoRI +2 and four EcoRI +3 primers. In the present study both +2 and +3 EcoRI primers were informative, but EcoRI +2 produced profiles with high complexity. The addition of the extra selective nucleotide reduced the complexity of the banding patterns generating easily readable patterns to evaluate genetic diversity within and among species. Of the three ascomycetous genera assessed in this study, Colletotrichum (Glomerellaceae) presented the highest proportion of polymorphic AFLP loci, followed in order by Iodophanus (Pezizaceae) and Saccobolus (Ascobolaceae).

Taxonomic and nomenclatural aspects of Hypoxylon taxa from southern South America proposed by Spegazzini Hladki, Adriana Ines; Romero, Andrea Irene The holotypes and isotypes of 20 Hypoxylon taxa described by Spegazzini have been examined and their taxonomic positions and nomenclatural problems are discussed. Two new combinations, Annulohypoxylon apiahynum comb. nov. and A. subeffusum comb. nov., are proposed. H. goliath is considered a synonym of Rosellinia bunodes. H. albostigmatosum and H. guarapiense are synonyms of H. anthochroum, H. anthracoderma of H. monticulosum, H. mbaiense of H. notatum, H. paulistanum of H. diatrypeoides, H. plumbeum and H. rubiginosum var. microcarpum of H. perforatum. H. porteri and H. intermedium belong in Biscogniauxia capnodes, H. puiggarii in Annulophypoxylon subeffusum, H. subvinosum. in H. lenormandii, H. turbinatum var. guaraniticum in Phylacia turbinata and H. valsarioides in Creosphaeria sassafras. H. leptascum is transferred to A. leptascum, H. circostomum to Nemania circostoma and H. latissimum to N. latissima. The holotype of H. albostigmatosum has been recovered, thus the lectotypification by Shear no longer is needed. H. subnigricans and H. umbilicatum are confirmed as good taxa. H. anthochroum and H. lenormandii are reported as first records from Argentina (Tucumán).

Gene flow between cultivated sunflower and Helianthus petiolaris (Asteraceae) Gutierrez, Agustina; Carrera, Alicia Delia; Basualdo, Jessica; Rodríguez, R.; Cantamutto, Miguel Ángel; Poverene, María Mónica Helianthus petiolaris (Asteraceae) native to North America has naturalized in Argentina. The extensive overlapping with sunflower crop regions, the coincidence of life cycles and the common pollinators facilitate interspecific crosses with sun- flower, H. annuus var. macrocarpus. To estimate the occurrence of crop-to-wild and wild-to-crop gene flow, off-type plants in progenies of pure stands of both species flowering in coincidence and the presence of crop alleles in H. petiolaris populations were investigated in 26 wild populations and nine crop fields. Morphological traits and RAPD markers were used to attempt hybrid characterization. Off-type individuals were found in frequencies of 0.5 and 0.3% among crop progenies and wild populations, respectively. Off-type plants showed intermediate values for metric morphological traits and low fertility traits. Some off-type plants proved to carry crop alleles based on molecular analysis. The average frequency of cultivar-marker introgression across the wild populations was very low (0.02). Although observed hybridization rates seem to be low, the extension of crop-wild overlapping in Argentina make hybrid formation a noticeable process. Therefore, the new sunflower varieties and eventually GM varieties would transfer their traits through pollen flow and they would persist in H. petiolaris populations.

Global environmental effects versus galaxy interactions Perez, Maria Josefa; Tissera, Patricia Beatriz; Padilla, Nelson David; Alonso Giraldes, Maria Sol; Garcia Lambas, Diego Rodolfo We explore properties of close galaxy pairs and merging systems selected from the Sloan Digital Sky Survey Data Release 4 in different environments with the aim to assess the relative importance of the role of interactions over global environmental processes. For this purpose, we perform a comparative study of galaxies with and without close companions as a function of local density and host halo mass, carefully removing sources of possible biases. We find that at low- and high-local-density environments, colours and concentration indices of close galaxy pairs are very similar to those of isolated galaxies. At intermediate densities, we detect significant differences, indicating that close pairs could have experienced a more rapid transition on to the red sequence than isolated galaxies. The presence of a correlation between concentration index and colours indicates that the physical mechanism responsible for the colour transformation also operates in the transformation of the luminous matter distribution. At fixed local densities, we find a dependence of the red galaxy fraction on dark matter halo mass for galaxies with or without a close companion. This suggests the action of host halo mass related effects. Regardless of dark matter halo mass, we show that the percentage of red galaxies in close pairs and in the control sample are comparable at low- and high-local-density environments. However, at intermediate local densities, the gap in the red fraction between close pairs and the control galaxies increases from ∼10 per cent in low-mass haloes up to ∼50 per cent in the most massive ones. Interestingly, we also detect that 50 per cent of merging systems populate the intermediate local environments, with a large fraction of them being extremely red and bulge dominated. Our findings suggest that in intermediate-density environments galaxies are efficiently pre-processed by close encounters and mergers before entering higher local density regions.

Chemical composition of four essential oils from Eupatorium spp. Biological activities toward Tribolium castaneum (Coleoptera: Tenebrionidae) Lancelle, Hugo Guillermo Ramon; Giordano, Oscar Santiago; Sosa, Marta Edit; Tonn, Carlos Eugenio Toxic and repellent properties of whole essential oils from four Eupatorium (Asteraceae) species (E. buniifolium Hook. et Arn, E. inulaefolium Kunth, E. arnottii Baker, and E. viscidum Hook. & Arn) were investigated in different concentrations toward Tribolium castaneum Herbst adults. The essential oils were isolated by hydrodistillation techniques from the aerial parts. The analysis was performed by GC-FID and GC-MS methods. Contact toxicity assays showed that all the evaluated essential oils were toxic. Furthermore, in all the cases mortality was dose dependent. The main repellency was observed for the essential oil recovered from E. buniifolium.

IRI 2001/90 TEC predictions over a low latitude station Scida, Luis Alberto; Ezquer, Rodolfo Gerardo; Cabrera, Miguel Angel; Mosert, Marta Estela Total electron content (TEC) over Tucumán (26.9°S, 294.6°W) measured with Faraday technique during the high solar activity year 1982, is used to check IRI 2001 TEC predictions at the southern crest of the equatorial anomaly region. Comparisons with IRI 90 are also made. The results show that in general IRI overestimates TEC values around the daily minimum and underestimates it the remaining hours. Better predictions are obtained using ground ionosonde measurements as input coefficients in the IRI model. The results suggest that for hours of maximum TEC values the electron density profile is broader than that assumed by the model. The main reason for the disagreement would be the IRI shape of the electron density profile. In a previous work using TEC measurements over Tucumán, obtained from GPS satellite signals during the high solar activity year 1999, a better agreement between IRI predictions and measurements has been observed. That better agreement was produced by the fact that 1999 GPS TEC measurements are 50% lower than those obtained by Faraday rotation technique during 1982. An equator ward movement of the southern peak of the EA plus the minor ionization level in 1999 could produce this reduction in TEC values. Moreover, it can be seen that in most of cases IRI TEC values around daily minimum show an hour displacement with respect to the experimental data.

A parametric representation of totally mixed Nash equilibria Jeronimo, Gabriela Tali; Perrucci, Daniel Roberto; Sabia, Juan Vicente Rafael We present an algorithm to compute a parametric description of the totally mixed Nash equilibria of a generic game in normal form with a fixed structure. Using this representation, we also show an algorithm to compute polynomial inequality conditions under which a game has the maximum possible number of this kind of equilibria. Then, we present symbolic procedures to describe the set of isolated totally mixed Nash equilibria of an arbitrary game and to compute, under certain general assumptions, the exact number of these equilibria. The complexity of all these algorithms is polynomial in the number of players, the number of each player´s strategies and the generic number of totally mixed Nash equilibria of a game with the considered structure.

Quantum-mechanics-derived 13Cα chemical shift server ( CheShift) for protein structure validation Vila Jorge A.; Arnautova, Yelena A.; Martín, Osvaldo Antonio; Scheraga, Harold A. A server (CheShift) has been developed to predict 13Cα chemical shifts of protein structures. It is based on the generation of 696,916 conformations as a function of the φ, ψ, ω, χ1 and χ2 torsional angles for all 20 naturally occurring amino acids. Their 13Cα chemical shifts were computed at the DFT level of theory with a small basis set and extrapolated, with an empirically-determined linear regression formula, to reproduce the values obtained with a larger basis set. Analysis of the accuracy and sensitivity of the CheShift predictions, in terms of both the correlation coefficient R and the conformational-averaged rmsd between the observed and predicted 13Cα chemical shifts, was carried out for 3 sets of conformations: (i) 36 x-ray-derived protein structures solved at 2.3 Å or better resolution, for which sets of 13Cα chemical shifts were available; (ii) 15 pairs of x-ray and NMR-derived sets of protein conformations; and (iii) a set of decoys for 3 proteins showing an rmsd with respect to the x-ray structure from which they were derived of up to 3 Å. Comparative analysis carried out with 4 popular servers, namely SHIFTS, SHIFTX, SPARTA, and PROSHIFT, for these 3 sets of conformations demonstrated that CheShift is the most sensitive server with which to detect subtle differences between protein models and, hence, to validate protein structures determined by either x-ray or NMR methods, if the observed 13Cα chemical shifts are available. CheShift is available as a web server.

Two New Supramolecular Assemblies Obtained by Reaction Between Saccharin and Long-chain Diamines Castellano, Eduardo Ernesto; Piro, Oscar Enrique; Parajón Costa, Beatriz Susana; Baran, Enrique José The crystal structures of heptamethylenediammonium bis(saccharuinate) monohydrate,[H3N-(CH2)7-NH3](sac)2.H2O (I) and octamethylenediammonium bis(saccharinate) hemihydrate, [NH3-(CH2)8-NH3].1/2H2O (II) were determined by single-crystal X-ray diffraction methods. Compound I crystallizes in the triclinic space group P(-1) with 2 molecules per unit cell, and II in the monoclinic space group P21/a with Z = 4. The saccharinate moiety is planar in both compounds. The ionic crystals are further stabilized by an extensive H-bonding network, which links the anions and cations into an infinite three dimensional supramolecular assembly. The FTIR spectra of the adducts are briefly discussed in comparison with those of the constituent molecules.

D2 receptor stimulation, but not D1, restores striatal equilibrium in a rat model of Parkinsonism Ballion, Bérangère; Frenois, Francois; Zold, Camila Lidia; Chetrit, Jonathan; Murer, Mario Gustavo; Gonon, Francois In Parkinson´s disease dopamine depletion imbalances the two major output pathways of the striatum. L-DOPA replacement therapy is believed to correct this imbalance by providing effective D1 and D2 receptor stimulation to striatonigral and striatopallidal neurons, respectively. Here we tested this assumption in the rat model of Parkinsonism by monitoring the spike response of identified striatal neurons to cortical stimulation. As predicted, in 6-hydroxydopamine lesioned rats we observed that L-DOPA (6 mg/kg+benserazide), apomorphine and the D2 agonist quinpirole (0.5 mg/kg i.p.) counteract the enhanced responsiveness of striatopallidal neurons. Unexpectedly, the depressed responsiveness of striatonigral neurons was corrected by quinpirole whereas D1 stimulation exerted no (apomorphine, cPB) or worsening effects (L-DOPA, SKF38393 10 mg/kg). Therefore, quinpirole, but not D1 stimulation, restores functional equilibrium between the two striatal output pathways. Our results might explain the therapeutic effect of D2-based medications in Parkinson´s disease.

Diversity of hepatitis B and C viruses in Chile Di Lello, Federico Alejandro; Piñeiro y Leone, Flavia Guadalupe; Muñoz, Gabriela; Campos, Rodolfo Hector Although there is a low prevalence rate (around 1% of the population) of infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) in Chile, little is known about the diversity and molecular characteristics of the circulating viruses. In the present study, 40 HBV and 57 HCV samples from Santiago City, Chile, were examined. The phylogenetic analysis of HBV samples showed the autochthonous genotype F as the most represented genotype in the study (67.5%), while genotypes A, B, C, and D were less frequent (7.5%, 5%, 7.5%, and 12.5%, respectively). The frequency of circulation of HBV genotypes observed is in accordance with the genetic background of the Chilean population. Most of the HCV samples tested belonged to subtype 1b (82%). The coalescent analysis conducted for both the NS5A and NS5B regions of the HCV strains showed similar population growth rates, with a most recent common ancestor estimated to date between 1893 and 1901. This result may indicate that genotype 1b strains circulating in Chile have epidemiological features similar to those described for HCV genotype 1b in Brazil and the United States. However, the most recent common ancestor for Chile is older than that reported recently for genotype 1b in Argentina.

Phylogeographic analysis reveals association of tick-borne pathogen, Anaplasma marginale, MSP1a sequences with ecological traits affecting tick vector performance Estrada-Peña, Agustín; Naranjo, Victoria; Acevedo-Whitehouse, Karina; Mangold, Atilio Jose; Kocan, Katherine M; de la Fuente, José Background: The tick-borne pathogen Anaplasma marginale, which is endemic worldwide, is the type species of the genus Anaplasma (Rickettsiales: Anaplasmataceae). Rhipicephalus (Boophilus) microplus is the most important tick vector of A. marginale in tropical and subtropical regions of the world. Despite extensive characterization of the genetic diversityin A. marginale geographic strains using major surface protein sequences, little is known about the biogeography and evolution of A. marginale and other Anaplasma species. For A. marginale, MSP1a was shown to be involved in vectorpathogen and host-pathogen interactions and to have evolved under positive selection pressure. The MSP1a of A. marginale strains differs in molecular weight because of a variable number of tandem 23-31 amino acid repeats and hasproven to be a stable marker of strain identity. While phylogenetic studies of MSP1a repeat sequences have shownevidence of A. marginale-tick co-evolution, these studies have not provided phylogeographic information on a global scale because of the high level of MSP1a genetic diversity among geographic strains.Results: In this study we showed that the phylogeography of A. marginale MSP1a sequences is associated with world ecological regions (ecoregions) resulting in different evolutionary pressures and thence MSP1a sequences. The results demonstrated that the MSP1a first (R1) and last (RL) repeats and microsatellite sequences were associated with world ecoregion clusters with specific and different environmental envelopes. The evolution of R1 repeat sequences was foundto be under positive selection. It is hypothesized that the driving environmental factors regulating tick populations could act on the selection of different A. marginale MSP1a sequence lineages, associated to each ecoregion.Conclusion: The results reported herein provided the first evidence that the evolution of A. marginale was linked to ecological traits affecting tick vector performance. These results suggested that some A. marginale strains have evolved under conditions that support pathogen biological transmission by R. microplus, under different ecological traits whichaffect performance of R. microplus populations. The evolution of other A. marginale strains may be linked to transmission by other tick species or to mechanical transmission in regions where R. microplus is currently eradicated. The information derived from this study is fundamental toward understanding the evolution of other vector-borne pathogens.

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.