In silico study of the wettabilitty effects on gas cluster growth by solute diffusion in correlated porous media Rodríguez, C.M.; Felipe, Carlos; Vidales, Ana Maria; Domínguez, Armando; Kornhauser, Isaac; Rojas, Fernando Simulations of bubble growth in porous media are carried out with a 2D numerical automaton built on a set of hypotheses derived from experimental observations at pore scale. Various types of 2D numerical networks are used as models of porous media with the aim to study the outcome of the combined effects of the wettabilitty (homogeneous and mixed) and the spatial correlation among the porous network entities on the evolution of a gas cluster growing by solute diffusion into it. The porous networks are constructed by using a variation of the dual site bond model (DSBM) framework. For the same pore-size distribution, the DSBM can provide simulated porous media of different topological structures. Under these scenarios, numerical simulations concerning the growth pattern and the growth rate of a single gas cluster are performed.

Use of vegetation chemical signals for digging orientation in the subterranean rodent Ctenomys talarum (Rodentia: Ctenomyidae) Schleich, Cristian; Zenuto, Roxana Rita Sensory modalities involved in the localization and selection of food represent critical information for understanding the foraging behavior of subterranean rodents. The objective of this study was to determine if a subterranean rodent that forages on aboveground plant parts, Ctenomys talarum, is able to detect the presence of odorous chemicals released by the plants into the soil to guide its excavation, as has been shown for subterranean species that forage on roots and bulbs. Individuals were introduced into an artificial Y‐maze, whose arms were filled with sandy soil in which plants either had or had not been growing (control). Digging activity exhibited in each soil type was recorded. The following plant species, present in the natural habitat of C. talarum, were used: Panicum racemosum (three different concentrations), Cortadeira sp., Margiricarpus pignatus, Ambrosia sp. and Raphanus sativus. The individuals allocated more time to excavation in the soil in which vegetation had been growing in comparison with the control for the five analysed plant species, except in the case of P. racemosum at its lowest concentration. The number of individuals that completed excavation in the tube‐containing soil in which plants had been growing was significantly higher than in the tube‐containing soil in which no plants had been growing, with the exception of P. racemosum at its lowest concentration and R. sativus. The results of the present study suggest that C. talarum have the ability to use olfaction to orient their digging while foraging even though members of this species consume mainly aboveground plant parts.

Magneto-optic imaging: Normal and parallel field components of in-plane magnetized samples Ferrari, Hernan Javier; Bekeris, Victoria Isabel; Thibeault, M.; Johansen, T. H. Magneto-optical (MO) imaging has become a powerful tool for determining magnetic properties of materials by detecting the stray magnetic fields. The technique consists in measuring the Faraday rotation, θF, in the light polarization plane when light travels through a transparent sensitive garnet (ferrite garnet film, FGF) placed in close contact to the sample. For in-plane magnetized samples, the MO image is not trivially related to the sample magnetization, and to contribute to this understanding we have imaged commercial audio tapes in which computer-generated functions were recorded. We present MO images of periodically in-plane magnetized tapes with square, sawtooth, triangular and sinusoidal waveforms, for which we analytically calculate the perpendicular and parallel stray magnetic field components generated by the tape. As a first approach we correlate the measured light intensity with the perpendicular magnetic field component at the FGF, and we show that it can be approximated to the gradient of the sample magnetization. A more detailed calculation, taking into account the effect of both field components in the Faraday rotation, is presented and satisfactorily compared with the obtained MO images. The presence of magnetic domains in the garnet is shown to be related to the change in sign of the parallel component of the stray magnetic field, which can be approximated to the second derivative of the sample magnetization. © 2007 Elsevier B.V. All rights reserved.

Sur quelques nouveaux Phytocoris Fallén, 1814 provenant de l'Argentine et du Chili. I. (Heteroptera: Miridae) Carpintero, Diego Leonardo; Cherot, Fréderic 12 espèces nouvelles du genre Phytocoris FALLÉN, 1814 sont décrites d'Argentine et du Chili, à savoir: P. albiventris n. sp., P. chaquensis n. sp., P. comechingon n. sp., P. eylesi n. sp., P. neuquinus n. sp., P. patagoniensis n. sp., P. pehuenche n. sp., P. picunche n. sp., P. puelche n. sp., P. quichua n. sp., P. quilmes n. sp., P. rionegrensis n. sp. Autant que faire ce peut, l'habitus, ainsi que les structures génitales des deux sexes sont figurés.

Use of 13Ca chemical-shifts in protein structure determination Vila, Jorge Alberto; Ripoll, Daniel R.; Scheraga, Harold A. A physics-based method aimed at determining protein structures by using NOE-derived distances together with observed and computed 13C chemical shifts is proposed. The approach makes use of 13Cα chemical shifts, computed at the density functional level of theory, to obtain torsional constraints for all backbone and side-chain torsional angles without making a priori use of the occupancy of any region of the Ramachandran map by the amino acid residues. The torsional constraints are not fixed but are changed dynamically in each step of the procedure, following an iterative self-consistent approach intended to identify a set of conformations for which the computed 13Cα chemical shifts match the experimental ones. A test is carried out on a 76-amino acid, all-α-helical protein; namely, the Bacillus subtilis acyl carrier protein. It is shown that, starting from randomly generated conformations, the final protein models are more accurate than an existing NMR-derived structure model of this protein, in terms of both the agreement between predicted and observed 13Cα chemical shifts and some stereochemical quality indicators, and of similar accuracy as one of the protein models solved at a high level of resolution. The results provide evidence that this methodology can be used not only for structure determination but also for additional protein structure refinement of NMR-derived models deposited in the Protein Data Bank.

Ghost resonance in a pool of heterogeneous neurons Balenzuela, Pablo; Garcia Ojalvo, Jordi; Manjarrez, Elías; Martínez, Lourdes; Mirasso, Claudio R. We numerically study the subharmonic response of a heterogeneous pool of neurons to a pair of independent inputs. The neurons are stimulated with periodic pulse trains of frequencies f1 = 2 Hz and f2 = 3 Hz, and with inharmonic pulses whose frequencies f1 and f2 are equally shifted an amount Δ f. When both inputs are subthreshold, we find that the neurons respond at a frequency equal to f2 - f1 in the harmonic situation (Δ f = 0), that increases linearly with Δ f in the inharmonic case. Thus the neurons detect a frequency not present in the input; this effect is termed "ghost resonance". When one of the inputs is slightly suprathreshold the ghost resonance persists, but responses related with the frequency of the suprathreshold input also emerge. This behavior must be taken into account in experimental studies of signal integration and coincidence detection by neuronal pools.

Diets of three species of andean carnivores in high-altitude deserts of Argentina Walker, Rebecca Susana; Novaro, Andres Jose; Perovic, Pablo Gastón; Palacios, Rocio; Donadio, Emiliano; Lucherini, Mauro; Pia, Monica Valeria; López, María Soledad We present the 1st data on the diet of the Andean mountain cat (Leopardus jacobitus), and the 1st on the colocolo (Leopardus colocolo) and the culpeo (Lycalopex culpaeus) in high-altitude deserts of northern Argentina, based on fecal analysis. Feces of Andean mountain cats and colocolos were distinguished by DNA analysis. The Andean mountain cat (n= 57) was the most specialized, relying heavily on southern mountain vizcachas (Lagidium viscacia). The colocolo (n = 504) also was specialized, consuming mostly cricetine rodents and tuco-tucos (Ctenomys). The culpeo (n= 399) was a generalist, consuming all prey items that the cats used, and a greater variety of invertebrates. Short-tailed chinchillas (Chinchilla chinchilla) were found in 3 culpeo feces, indicating that this rodent, considered extinct in Argentina, is still present in the wild. Both southern mountain vizcachas and tuco-tucos have a patchy distribution, indicating that very large areas may be required to support populations of the cats that depend on these prey species.

Groundwater chemical pollution risk: Assessment through a soil attenuation index Heredia, Olga Susana; Fernandez Cirelli, Alicia Aquifer vulnerability is frequently estimated through methodologies that don't consider most physical and chemical soil parameters. A soil attenuation index is proposed to estimate groundwater chemical pollution risk, that takes into account organic carbon content, pH, cation exchange capacity, clay content, phreatic depth and landscape position. The attenuation index is constructed by a methodology similar to that developed for water quality index. P, Mn and Zn concentrations in groundwater from selected places were used to validate the proposed index. © 2007 Springer-Verlag.

A quantitative method for zoning of protected areas and its spatial ecological implications Sabatini, Maria del Carmen; Verdiell, Adriana Beatriz; Rodríguez Iglesias, Ricardo Manuel; Vidal, Marta Cecilia Zoning is a key prescriptive tool for administration and management of protected areas. However, the lack of zoning is common for most protected areas in developing countries and, as a consequence, many protected areas are not effective in achieving the goals for which they were created. In this work, we introduce a quantitative method to expeditiously zone protected areas and we evaluate its ecological implications on hypothetical zoning cases. A real-world application is reported for the Talampaya National Park, a UNESCO World Heritage Site located in Argentina. Our method is a modification of the zoning forest model developed by Bos [Bos, J., 1993. Zoning in forest management: a quadratic assignment problem solved by simulated annealing. Journal of Environmental Management 37, 127-145.]. Main innovations involve a quadratic function of distance between land units, non-reciprocal weights for adjacent land uses (mathematically represented by a non-symmetric matrix), and the possibility of imposing a connectivity constraint. Due to its intrinsic spatial dimension, the zoning problem belongs to the NP-hard class, i.e. a solution can only be obtained in non-polynomial time [Nemhausser, G., Wolsey, L., 1988. Integer and Combinatorial Optimization. John Wiley, New York.]. For that purpose, we applied a simulated annealing heuristic implemented as a FORTRAN language routine. Our innovations were effective in achieving zoning designs more compatible with biological diversity protection. The quadratic distance term facilitated the delineation of core zones for elements of significance; the connectivity constraint minimized fragmentation; non-reciprocal land use weightings contributed to better representing management decisions, and influenced mainly the edge and shape of zones. This quantitative method can assist the zoning process within protected areas by offering many zonation scheme alternatives with minimum cost, time and effort. This ability provides a new tool to improve zoning within protected areas in developing countries.

Anti-beta1-adrenergic receptor autoantibodies in patients with chronic Chagas heart disease Labovsky, Vivian; Smulski, Cristian Roberto; Gomez, Karina Andrea; Levy, Gabriela Vanesa; Levin, Mariano Jorge Chronic Chagas heart disease (cChHD), a chronic manifestation of the Trypanosoma cruzi infection, is characterized by high antibody levels against the C-terminal region of the ribosomal P proteins (i.e. peptide R13, EEEDDDMGFGLFD) which bears similarity with the second extracellular loop of beta1-adrenergic receptor (beta1-AR, peptide H26R HWWRAESDEARRCYNDPKCCDFVTNR). Because it has not been demonstrated clearly that IgGs from cChHD patients bind to native human beta1-AR, the aim of this study was to investigate further the physical interaction between cChHD IgGs and the human beta1-AR. Immunofluorescence assays demonstrated the binding of these antibodies to the receptor expressed on stably transfected cells, together with a beta1-AR agonist-like effect. In addition, immunoadsorption of the serum samples from cChHD patients with a commercially available matrix, containing peptides representing the first and the second extracellular loop of the beta1-AR, completely abolished reactivity against the H26R peptide and the physiological response to the receptor. The follow-up of this specificity after in vitro immunoadsorption procedures suggests that this treatment might be used to diminish significantly the serum levels of anti-beta1-AR antibodies in patients with Chagas heart disease.

Solvent and substituent effects on the conformational equilibria and intramolecular hydrogen bonding of 4-substituted-2-hydroxybenzaldehydes Blanco, Sonia Encarnacion; Ferretti, Ferdinando Hector By applying the B3LYP/6-31G(d) method with the SCIPCM model on seven 4X substituted 2-hydroxybenzaldehydes, some structural characteristics related with their conformational equilibria and intramolecular hydrogen bonds have been clarified. The compounds are almost completely under the planar conformation characterized by a strong intramolecular hydrogen bond, which decreases in those solvents that possess a higher hydrogen bond donating capability and polarity. The substituents exert a marked influence on the conformational equilibrium constants and the strength of the IHB. Moreover, the excellent Hammett-type equations obtained support the proposed conformational reactions to quantify the IHB in the o-hydroxybenzaldehydes studied.

Peptide synthesis: Chemical or enzymatic Guzmán, Fanny; Barberis, Sonia Esther; Illanes, Andrés Peptides are molecules of paramount importance in the fields of health care and nutrition. Several technologies for their production are now available, among which chemical and enzymatic synthesis are especially relevant. The present review pretends to establish a non-biased appreciation of  the advantages, potentials, drawbacks and limitations of both technologies. Chemical synthesis is thoroughly reviewed and their potentials and limitations assessed, focusing on the different strategies and challenges for large-scale synthesis. Then, the enzymatic synthesis of peptides with   proteolytic   enzymes    is   reviewed    considering  medium, biocatalyst and substrate engineering, and recent advances and challenges in the field are analyzed. Even though chemical synthesis is the most mature technology for peptide synthesis, lack of specificity and environmental burden are severe drawbacks that can in principle be successfully overcame by enzyme biocatalysis. However, productivity of enzymatic synthesis is lower, costs of biocatalysts are usually high and no protocols exist for its validation and scale-up, representing challenges that are being actively confronted by intense research and development in this area. The combination of chemical and enzymatic  synthesis is probably the way to go, since the good properties of each technology can be synergistically used in the context of one process objective.

Further evidence for the absence of persistent polyproline II conformation in the XAO peptide Makowska, Joanna; Rodziewicz-Motowidlo, Sylwia; Baginska, Katarzyna; Makowski, Mariusz; Vila, Jorge Alberto; Liwo, Adam; Chmurzynski, Lech; Scheraga, Harold A. It has been suggested that the alanine-based peptide with sequence Ac-XX-[A]7-OO-NH2, termed XAO where X denotes diaminobutyric acid and O denotes ornithine, exists in a predominantly polyproline-helix (PII) conformation in aqueous solution. In our recent work, we demonstrated that this “polyproline conformation” should be regarded as a set of local conformational states rather than as the overall conformation of the molecule. In this work, we present further evidence to support this statement. Differential scanning calorimetry measurements showed only a very small peak in the heat capacity of an aqueous solution of XAO at 57°C, whereas the suggested transition to the PII structure should occur at ∼30°C. We also demonstrate that the temperature dependence of the 3JHNHα coupling constants of the alanine residues can be explained qualitatively in terms of Boltzmann averaging over all local conformational states; therefore, this temperature dependence proves that a conformational transition does not occur. Canonical MD simulations with the solvent represented by the generalized Born model, and with time-averaged NMR-derived restraints, demonstrate the presence of an ensemble of structures with a substantial amount of local PII conformational states but not with an overall PII conformation.

Resonance light scattering and derived techniques in analytical chemistry: past, present, and future Lu, Wei; Fernández Band, Beatriz Susana; Yu, Yu; Geng Li, Qin; Chuan Shang, Jing; Wang, Chi; Fang, Yan; Tian, Rui; Ping Zhou, Li; Li Sun, Li; Tang, Yu; Hua Jing, Shu; Huang, Wei; Ping Zhang, Ji From 1993 to 1995, with a conventional fluorescence spectrophotometer (CFS) (convenient) and working in a synchronous scan model (easy-to-use), Pasternack et al. proposed the resonance light-scattering (RLS) technique, to efficiently characterize self-assemblies or self-aggregations of chromophores with good electronic coupling. Incident wavelengths were specially considered within their absorption envelopes (rather unorthodox), and their amplified signals were observed (good sensitivity and selectivity). Due to these absorbing benefits, RLS technique, as a novel readout method, commenced on its exciting analytical tours soon after Liu et al. and especially Li et al., separately, set out their corresponding pioneering investigations from 1995 to 1997. From then on, it has received an increasing attention by analysts, as a consequence exhibiting more and more fascinating analytical applications. Moreover, various attractive RLS-derived techniques have been developed successively to improve it or to enlarge its possibilities. Later on, Liu et al. and Li et al., Tabak et al., Yguerabide et al., Huang et al., Lakowicz et al. and Fernández Band et al. have made their outstanding contributions. In this review, we concentrate on major achievements of RLS in analytical chemistry for over a decade, involving the developments and analytical applications of RLS derived techniques treated as an impacting progress of RLS technique in analytical chemistry. Finally, an indication of future directions of RLS technique in analytical chemistry is provided.

Successive projections algorithm improving the multivariate simultaneous direct spectrophotometric determination of five phenolic compounds in sea water Di Nezio, Maria Susana; Pistonesi, Marcelo Fabian; Fragoso, Wallace D.; Pontes, Márcio J.C.; Goicoechea, Hector Casimiro; Araujo, Mário C.U.; Fernández Band, Beatriz Susana This paper proposes an analytical method to determine directly and simultaneously five phenolic compounds (4-nitrophenol, 2-nitrophenol, phenol, 2,4,6-trichlorophenol and 4-chlorophenol) in sea water (Ria de Bahía Blanca, Argentine). The advantages of this method is that only requires spectrophotometric measurements (separation steps and derivatization reagents are avoided) and chemometric modelling (PLS and MLR-SPA). The statistical comparison between PLS - a well established multivariate method - and MLR-SPA - a recently presented chemometric modelling - demonstrated better analytical performance for the later one. This fact is indicative of the potentiality of MLR-SPA for solving complex analytical problems.

Design of catalyst systems for the one-pot synthesis of menthols from citral Trasarti, Andres Fernando; Marchi, Alberto Julio; Apesteguia, Carlos Rodolfo Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liquid-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids containing exclusively Lewis (ZnO/SiO2) or strong Brönsted (CsHPA) acid sites, and also on catalysts containing both Lewis and Brönsted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Brönsted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts containing Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepared and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.

The origin of the enhanced activity of Pt/zeolites for combustion of C2-C4 alkanes Garetto, Teresita Francisca; Rincon, Eduardo Ricardo; Apesteguia, Carlos Rodolfo The deep oxidations of ethane, propane and butane were studied on Pt supported on MgO, alumina, and zeolites KL, HY, ZSM5, and Beta. The catalyst activities were evaluated through both conversion versus temperature (light-off curves) and conversion versus time catalytic tests. The Pt oxidation activity for the three lower alkanes was drastically increased when supported on zeolites as compared to Pt/Al2O3 or Pt/MgO. C2-C4 alkane oxidation turnover rates were about two (ethane, propane) and one (butane) orders of magnitude higher on Pt/acid zeolites than on Pt/Al2O3, but also weakly acid Pt/KL zeolite was significantly more active as compared to Pt/Al2O3 (more than one order of magnitude for ethane and propane). This latter result showed that the support acidity is not a major contributing factor for lower alkane combustion. Promotion of the alkane oxidation activity on Pt/zeolites was explained by considering the drastic increase observed for the density of alkane adsorbed species on zeolite supports; it was found, in fact, that the alkane uptake per m2 was about one order of magnitude higher on Pt/zeolites than on Pt/Al2O3. This alkane confinement in zeolite pores would enhance the Pt oxidation rate because the reaction is positive order with respect to the hydrocarbon and probably also because would promote an additional oxidation pathway in the metal-oxide interfacial region.

The SCR of NO with CH4 over Co-, Co,Pt-, and H-mordenite catalysts Lónyi, F.; Valyon, J.; Gutierrez, Laura Beatriz; Ulla, Maria Alicia del H.; Lombardo, Eduardo Agustin The catalytic reduction of NO with methane was studied operando in the presence and absence of oxygen in the reaction mixture over Co-, Co,Pt-, and H-mordenite (CoM, CoPtM, HM) catalysts using the coupled methods of diffuse reflectance infrared Fourier-transform spectroscopy and mass spectroscopy (Operando-DRIFTS-MS). The reaction temperature was in the 573-773 K range, and the GHSV for nitric oxide was varied between 6000 and 60,000 h-1. In general, the Co-containing mordenite catalysts were more active than the HM. Over each catalyst two major surface intermediates were identified such as nitrosonium ion (NO+) and ammonia. The NO+ cations were shown to balance the negative charge on the zeolite framework. The NH3 molecules were bound either coordinately to Lewis-acid site Co2+ ions or were protonated on Brønsted acid sites and retained by the zeolite as NH4 + cations. The prevailing route of N2 formation was found to involve the reaction of NO+ and NH3 or NH4 + surface species. It was shown that the surface concentration of the intermediate ammonia governed the rate of NO conversion. If O2 was present in the feed gas it competed with the NO in the oxidation of methane and the surface intermediate ammonia. As a result, the steady-state concentration of the ammonia intermediate and the overall NO conversion to N2 decreased. Additional routes of N2 formation were revealed over the CoM and CoPtM catalysts. The cobalt facilitated the formation of NO+ and surface nitrate (NO3 -). Also nitrile (CN) and isocyanate (NCO) surface species were detected. The NO3 - could be rapidly reduced by methane to intermediate NH3 and, thereby, it increased the rate of NO conversion significantly. Nitrogen forming reactions can pass also through CN and NCO intermediates; however, the share of these reaction routes in the overall N2 generation process was minor.

Aprostocetus (Ootetrastichus) infulatus (Hymenoptera: Eulophidae): description of the male, new distribution and first host records Luft Albarracin, Erica Beatriz; Triapitsyn, Serguei V. The eulophid Aprostocetus (Ootetrastichus) infulatus (De Santis) has been previously known only from a single female holotype from Buenos Aires Province in Argentina. We obtained a series of specimens of this species using sentinel eggs of different species of Cicadellidae and Delphacidae, exposed in cornfields near El Manantial and San Miguel de Tucumán, in Tucumán Province, Argentina. The previously unknown male of A. (O.) infulatus is described and illustrated. For the first time, information on the host associations of this species is provided while its known distribution range is expanded to northern Argentina. This eulophid is an economically significant species in Argentina, where its hosts include two well-known vectors of corn diseases, the leafhopper Dalbulus maidis (DeLong & Wolcott) and the planthopper Peregrinus maidis (Ashmead).

The activated glucocorticoid receptor inhibits the transcription factor T-bet by direct protein-protein interaction Liberman, Ana Clara; Refojo, Damian; Druker, Jimena; Toscano, Marta Alicia; Rein, Theo; Holsboer, Florian; Arzt, Eduardo Simon Glucocorticoids (GCs) immunosuppression acts via regulation of several transcription factors (TF), including AP-1, NFkB and NFAT. GCs inhibit Th1 cytokines and promote a shift towards Th2 differentiation. Th1 phenotype depends on TF T-bet. In this study we examined GC regulation of T-bet. We found that GCs inhibit T-bet transcriptional activity. We show that glucocorticoid receptor (GR) physically interacts with T-bet both in transfected cell lines and in primary splenocyte cultures with endogenous GR and T-bet. This interaction also blocks GR-dependent transcription. We show both in vitro and in vivo at endogenous binding sites that the mechanism underlying T-bet inhibition further involves reduction of T-bet binding to DNA. Using specific mutations of GR, we demonstrate that the first zinc finger region of GR is required for T-bet inhibition. GCs additionally inhibit T-bet both at mRNA and protein expression levels, revealing another layer of GR action on T-bet. Finally, we examined the functional consequences of GR/T-bet interaction on interferon-gamma, showing that GCs inhibit transcriptional activity of T-bet on its promoter. In view of the crucial role of T-bet in T cell differentiation and inflammation, we propose that GR inhibitory interaction with T-bet may be an important mechanism underlying the immunosuppressive properties of GCs.