Carboxylate-Bridged Copper(II)-Lanthanide(III) Complexes [{Cu3Ln2(oda)6(H2O)6}.12H2O]n (Ln = Dy, Ho, Er, Y; oda = oxydiacetate Rizzi, Alberto Claudio; Calvo, Rafael; Baggio, Ricardo Fortunato; Garland, María Teresa; Peña, Octavio; Perec, Mireille The hydrothermal reaction of Ln2O3 (Ln = Dy and Ho), Cu(OAc)2·2H2O, and oxydiacetic acid in the approximate mole ratio of 1:3:8 resulted in the formation of two new members of the isostructural series of polymers formulated as [{Cu3Ln2(oda)6(H2O)6}·12H2O]n, crystallizing in the hexagonal crystal system, space group P6/mcc (No. 192). Temperature-dependent magnetic susceptibilities and EPR spectra are reported for the heterometallic compounds Cu−Dy 1, Cu−Ho 2, Cu−Er 3, and Cu−Y 4. The results are discussed in terms of the structure of the compounds, the electronic properties of the lanthanide ions, and the exchange interactions between the magnetic ions.

A nonlinear panel method in the time domain for seakeeping flow problems D'elia, Jorge; Storti, Mario Alberto; Oñate, Eugenio; Idelsohn, Sergio Rodolfo A Lagrangian-type panel method, in the time domain, is  proposed for potential flows with a moving free surface. After a spatial semi-discretization, with a low-order scheme, the instantaneous velocity-potential and normal displacement on the moving free surface, are obtained by means of a time-marching scheme. The kinematic and dynamic boundary conditions, at the free surface, are non-lineal restrictions over the related Ordinary Differential Equation system and, for handle them, an alternative Steklov-Poincare operator  technique is proposed. The method is applied to sloshing like flow problems.

Optimal Design of Cams Cardona, Alberto; Lens, Elisabeth; Nigro, Norberto Marcelo We present a methodology to design cams for motor engine valve trains using a constrained optimization algorithm. The imposed constraints are the maximum valve lift and timings while the objective function is to maximize the time integral of the valve area opened to gas flow. A piecewise analytically defined acceleration is imposed, so that the time instants controlling the profile of accelerations are used as variables for optimization. The strategy takes into account some geometrical constraints, e.g. to avoid interference between intake and exhaust valves, and between valves and piston. Also, minimum and maximum levels of acceleration are limited to avoid excessive forces in the mechanisms chain, and to prevent the possibility of separation between cam and follower. Once an optimal lift profile is determined, the cam shape is computed using an inverse kinematics analysis that takes into account all the geometric nonlinearities introduced by the kinematical chain. Finally, the whole mechanism is verified in a dynamics analysis to check satisfaction of the criteria for design. Comparisons with standard profiles of motion were made. Also, the profile was evaluated in an experimental device, where the actual valve displacement was measured.

All-hexahedral element meshing: Automatic elimination of self-intersecting dual lines Calvo, Nestor Alberto; Idelsohn, Sergio Rodolfo There has been some degree of success in all-hexahedral meshing. Standard methods start with the object geometry defined by means of an all-quadrilateral mesh, followed by the use of the combinatorial dual to the mesh in order to define the internal connectivities among elements. For all of the known methods using the dual concept, it is necessary to first prevent or eliminate self-intersecting (SI) dual lines of the given quadrilateral mesh. The relevant features of SI lines are studied, giving a method to remove them, which avoids deforming the original geometry. Some examples of resulting meshes are shown where the current meshing method has been successfully applied.

Energy of interaction in colloids and its implications in rheological modeling Quemada, Daniel; Berli, Claudio Luis Alberto This work deals with the problem of deriving theoretical connections between rheology and interparticle forces in colloidal suspensions. The nature of interparticle forces determines the colloidal structure (crystalline order due to long range repulsive forces, flocculation due to attractive forces, etc.) and hence, the flow behavior of suspensions. The aim of this article is to discuss how these interactions enter the modeling of rheometric functions, in particular, the shear viscosity. In this sense, the main interactions commonly appearing in colloids are reviewed, as well as the role they play in phase transition behavior. Then, a series of approaches relating the interaction potential to viscosity is examined. The results of applying these models to experimental data are also discussed. Finally, examples of viscosity modeling for different interaction potentials are given, by using the structural model proposed previously by the authors. The possibility of relating the flow behavior of colloidal suspensions to the interaction between particles offers new perspectives for the study and technical applications of these systems.

Lista de los escorpiones bolivianos (Chelicerata: Scorpiones), con notas sobre su distribución; Checklist of the Bolivian scorpions (Chelicerata: Scorpiones), with notes on their distribution Acosta, Luis Eduardo; Ochoa, José A. Se presenta una lista actualizada de los escorpiones de Bolivia. Se mencionan 24 especies (tres de elias con dudas) y una subespecie, pertenecientes a las familias Bothriuridae, Buthidae e luridae. Para cadaespecie se proporciona una referencia bibliografica abreviada, así como la nómina completa de las localidades para las que ha sido citada. Brachistosternus ferrugineus (Thorell) y el genero andino Orobothriurus Maury (Bothriuridae) se citan por prirnera vez para Bolivia. Se discuten los motivos para excluir de la escorpiofauna boliviana a siete especies nominales citadas por autores previos. Se adjunta una lista de las localidades bolivianas, con sus coordenadas, donde se han recolectado escorpiones.; An updated checklist of the scorpions of BoIivia is presented. Twenty four species (three of them, with doubts) and one subspecies, belonging to the families Bothriuridae, Buthidae and luridae are listed. For each species, an abbreviated bibliographic reference and the complete list of known localities are given. Brachistosternus ferrugineus (Thorell) and the Andean genus Orobothriurus Maury (Bothriuridae) are mentioned for the first time from Bolivia. Seven nominal species cited by previous authors are excluded from the Bolivian scorpiofauna, and the reasons for these exclusions are discussed. All Bolivian localities where scorpions have been collected are listed in a gazetteer.

The arginine deiminase pathway in the wine lactic acid bacterium Lactobacillus hilgardii X1B: Structural and functional study of the arcABC genes Arena, Mario Eduardo; Manca, Maria Cristina; Muñoz, Rosario The genes implicated in the catabolism of the amino acid arginine by Lactobacillus hilgardii X1B were investigated to assess the potential for formation of ethyl carbamate precursors in wine. L. hilgardii X1B can use arginine via the arginine deiminase pathway. The complete nucleotide sequence of the arc genes involved in this pathway has been determined. They are clustered in an operon-like structure in the order arcABC. No evidence was found for the presence of a homologue of the arcD gene, coding for the arginine/ornithine antiporter. The arc genes have been expressed in Escherichia coli resulting in arginine deiminase (ArcA), ornithine carbamoyltransfera (ArcB) and carbamate kinase (ArcC) activities. The results indicate the need for caution in the selection of lactic acid bacteria for conducting malolactic fermentation in wine since arginine degradation could result in high amounts of ethyl carbamate.

ACTH regulation of mitochondrial acyl-CoA thioesterase activity in Y1 adrenocortical tumour cells Castilla Lozano, Maria del Rocio; Maloberti, Paula Mariana; Mendez, Carlos Fernando; Paz, Cristina del Valle; Podesta, Ernesto Jorge We have previously purified and cloned a phosphoprotein, Arachidonic acid-Related Thioesterase Involved in Steroidogenesis (ARTISt), involved in steroid synthesis through Arachidonic Acid (AA) release. Arachidonic acid-related thioesterase involved in steroidogenesis resulted to be a member of a new family of acyl-CoA thioesterases. The protein was identified by its biocapacity to increase mitochondrial steroidogenesis in a cell free bioassay. In the present study we measure the activity of ARTISt using arachidonoyl-CoA (AA-CoA) as substrate. We demonstrate that ACTH significantly stimulates endogenous mitochondrial thioesterase activity as early as 5 min after ACTH stimulation of Y1 cells. Nordihydroguaiaretic acid (NDGA), an inhibitor of AA release known to affect steroidogenesis, affects the in vitro activity of recombinant ARTISt and also the endogenous mitochondrial acyl-CoA thioesterases. ACTH activation of the enzyme protected ARTISt to the inhibitory effect of NDGA. These results show that an enzyme that release AA from AA-CoA can be regulated in intact cells by steroidogenic hormones.

Telomerase as a cancer target. Development of new molecules Mengual Gómez, Diego Luis; Armando, Romina Gabriela; Cerrudo, Carolina Susana; Ghiringhelli, Pablo Daniel; Gomez, Daniel Eduardo Telomeres are the terminal part of the chromosome containing a long repetitive and non-codifying sequence that has as function protecting the chromosomes. In normal cells, telomeres lost part of such repetitive sequence in each mitosis, until telomeres reach a critical point, triggering at that time senescence and cell death. However, in most of tumor cells in each cell division a part of the telomere is lost, however the appearance of an enzyme called telomerase synthetize the segment that just has been lost, therefore conferring to tumor cells the immortality hallmark. Telomerase is significantly overexpressed in 80?95% of all malignant tumors, being present at low levels in few normal cells, mostly stem cells. Due to these characteristics, telomerase has become an attractive target for new and more effective anticancer agents. The capability of inhibiting telomerase in tumor cells should lead to telomere shortening, senescence and apoptosis. In this work, we analyze the different strategies for telomerase inhibition, either in development, preclinical or clinical stages taking into account their strong points and their caveats. We covered strategies such as nucleosides analogs, oligonucleotides, small molecule inhibitors, G-quadruplex stabilizers, immunotherapy, gene therapy, molecules that affect the telomere/telomerase associated proteins, agents from microbial sources, among others, providing a balanced evaluation of the status of the inhibitors of this powerful target together with an analysis of the challenges ahead.

Antiphospholipid antibodies impact the protein C (PC) pathway behavior Gennari, Laura C.; Blanco, Alicia N.; Alberto, Maria Fabiana; Grosso, Silvia H.; Peirano, Andrea A.; Lazzari, María Ángela Antiphospholipid antibodies may interfere with the PC pathway, displaying a resistance to the activated PC (resistant phenotype). This effect was evaluated by the APCR and the ProCG systems in 36 lupus anticoagulant samples, yielding abnormal results in 47% of APCRoriginal, 17% of APCRmodified, and 22% of ProCG test. ProCG values correlated with APCRoriginal but not with APCRmodified. Most of lupus anticoagulants affecting the PC pathway showed abnormal APCRoriginal results but not abnormal ProCG values. The different behavior between both systems may be due to the heterogeneity of the antibodies or could be attributed to the fact that, in the ProCG, a PC activator is added, while the APCR employs already activated exogenous PC.

Computer aided model analysis and dynamic simulation of a wastewater treatment plant Mussati, Miguel Ceferino; Gernaey, Krist; Gani, Rafiqul; Jørgensen, Sten A nitrogen removal benchmark was analyzed using the Activated Sludge Models No. 1 (ASM1) and No. 3 (ASM3) in order to establish a basis for designing an experimental comparison of the two model types. Differences in steady state effluent concentrations predicted by both models could to a large extent be explained by different model concepts. The steady state system performance was analyzed by evaluating the Monod factor values, and through a sensitivity analysis of the kinetic model parameters. Both methods complement each other. Analysis of the Monod factor values can lead to determination of parameters to be estimated during model calibration. The steady state system response to manipulation of the potential actuators for control was evaluated via a sensitivity analysis. The concept of relative sensitivity was introduced to compare the relative effect of each actuator in both models. The negative relative sensitivities of X S to four of the five control handles analyzed imply an opposite response of both models, which can be important for control structure design. The analysis of the process behavior to different disturbances showed different dynamics of both models. ASM3 simulation results are easier to interpret because the model structure is more transparent, mainly due to the simpler cell decay model principle considered in ASM3. An inverse response was obtained for the return sludge and nitrate recycle flow rate, indicating that multivariable control design is required.

Brain somatostatin receptors are up-regulated in somatostatin-deficient mice Ramírez, José L.; Mouchantaf, Rania; Kumar, Ujendra; Otero Corchon, Veronica; Rubinstein, Marcelo; Low, Malcolm J.; Patel, Yogesh C. The peptide somatostatin (SST) is widely synthesized in the brain and periphery and acts through a family of five receptors (SSTR1-5) to exert numerous effects. A gene product related to SST, cortistatin (CST), also interacts with SSTR1-5. Here we have investigated the regulation of SSTR1-5 and of CST in SST knockout (SSTKO) mice. The five SSTRs were quantitated individually by subtype-selective binding analysis, by immunocytochemistry, and by mRNA measurement and showed, in the brain of SSTKO mice, up-regulation of subtypes 1, 2, 4, and 5, and down-regulation of SSTR3. Peripheral tissues displayed both subtype- and tissue-specific changes in SSTR1-5 mRNA levels of expression. Lack of SST did not up-regulate normal CST expression in brain nor did it induce its expression in the periphery. SST-like immunoreactivity, however, was induced in the proximal midgut in SSTKO animals, suggesting intestinal expression of a novel SST-like gene.

Nicotinic receptor M3 transmembrane domain: Position 8′ contributes to channel gating de Rosa, Maria Jose; Rayes, Diego Hernán; Spitzmaul, Guillermo Federico; Bouzat, Cecilia Beatriz The nicotinic acetylcholine receptor (nAChR) is a pentamer of homologous subunits with composition α2βεδ in adult muscle. Each subunit contains four transmembrane domains (M1-M4). Position 8′ of the M3 domain is phenylalanine in all heteromeric α subunits, whereas it is a hydrophobic nonaromatic residue in non-α subunits. Given this peculiar conservation pattern, we studied its contribution to muscle nAChR activation by combining mutagenesis with single-channel kinetic analysis. Construction of nAChRs carrying different numbers of phenylalanine residues at 8′ reveals that the mean open time decreases as a function of the number of phenylalanine residues. Thus, all subunits contribute through this position independently and additively to the channel closing rate. The impairment of channel opening increases when the number of phenylalanine residues at 8′ increases from two (wild-type nAChR) to five. The gating equilibrium constant of the latter mutant nAChR is 13-fold lower than that of the wild-type nAChR. The replacement of αF8′, βL8′, δV8′ and εV8′ by a series of hydrophobic amino acids reveals that the structural bases of the observed kinetic effects are nonequivalent among subunits. In the α subunit, hydrophobic amino acids at 8′ lead to prolonged channel lifetimes, whereas they lead either to normal kinetics (δ and ε subunits) or impaired channel gating (β subunit) in the non-α subunits. The overall results indicate that 8′ positions of the M3 domains of all subunits contribute to channel gating.

Detailed structure of configuration space and its importance on ergodic separation of ±J Ising lattices Vogel, Eugenio E.; Ramirez Pastor, Antonio Jose; Nieto Quintas, Felix Daniel A complete and exact characterization of the configuration space of 2-D ±J Ising lattices is performed. A new algorithm is introduced here representing advantages for reaching all states for small samples and doing a non-biased sampling of ground states for larger samples. We report efficient procedures to find all ground states grouped in local ensembles of ground states (LEGs) and also a convenient way of storing and comparing states. Properties of such LEGs differ from some approximate descriptions reported in the literature. The onset of lattice size dependence of properties is discussed. Four different ways of performing ergodic separation are used to calculate order parameters. The most significant way of doing ergodic separation requires previous classification of states in LEGs.

Misiones "ad gentes": Manuales misioneros salesianos para la evangelización de la Patagonia (1910-1924) Nicoletti, Maria Andrea Nos proponemos en este trabajo analizar cómo, a través de un escrito inédito del padre Domenico Milanesio (1843-1922) a modo de reglamento misionero, se desprendieron las directivas y manuales de misión a través de los cuales se llevó a cabo la evangelización “ad gentes” de los Salesianos en la Patagonia. Uno de sus protagonistas volcó a través de sus conocimientos teóricos, pero fundamentalmente por su experiencia de misión, las características que debía tener un misionero que decidiera evangelizar en los territorios del sur. Escrito en medio de un vertiginoso período de misiones y del afianzamiento de la obra de la Congregación salesiana (1880-1934)1, analizaremos cómo se desprendieron de este primer manual, los marcos reglamentarios para la Patagonia que siguieron durante las dos inspectorías sucesivas de los padres Giuseppe Maria Vespignani (1909-1911, Inspectoría San Francisco de Sales) y Luigi Pedemonte (1911-1924, Inspectoría San Francisco Javier) respectivamente, en medio de una crisis ocasionada por la falta de personal y de reorganización de los centros de misión. Los documentos centrales que analizaremos a lo largo de este trabajo son: el reglamento misionero escrito por padre Milanesio en 1810, el Reglamento para las misiones escrito por el padre Vespignani en 1914 y, finalmente, la reunión con los misioneros y el padre Pedemonte en 1914. Complementariamente contamos con la documentación original del Archivo histórico de las Misiones salesianas de la Patagonia Norte, Bahía Blanca, que contiene la mayor parte de los escritos de Domenico Milanesio, complementado con los epistolarios de los padres Vespignani y Pedemonte en los Archivos Centrales salesianos de Buenos Aires y Roma.

Bird-like fossil footprints from the Late Triassic Melchor, Ricardo Nestor; de Valais, Silvina; Genise, Jorge Fernando The study of fossilized footprints and tracks of dinosaurs and other vertebrates has provided insight into the origin, evolution and extinction of several major groups and their behaviour; it has also been an important complement to their body fossil record1-4. The known history of birds starts in the Late Jurassic epoch (around 150 Myr ago) with the record of Archaeopteryx5, whereas the coelurosaurian ancestors of the birds date back to the Early Jurassic6. The hind limbs of Late Triassic epoch theropods lack osteological evidence for an avian reversed hallux and also display other functional differences from birds7. Previous references to suggested Late Triassic to Early Jurassic bird-like footprints have been reinterpreted as produced by non-avian dinosaurs having a high angle between digits II and IV8, 9 and in all cases their avian affinities have been challenged10. Here we describe well-preserved and abundant footprints with clearly avian characters from a Late Triassic redbed sequence of Argentina11, 12, at least 55 Myr before the first known skeletal record of birds. These footprints document the activities, in an environment interpreted as small ponds associated with ephemeral rivers, of an unknown group of Late Triassic theropods having some avian characters.

Estimation of Weibull parameters for the flexural strength of PMMA-based bone cements Riccardi, Carmen Cristina; Vallo, Claudia Ines The wide scatter of data observed in the strength of bone cements based on poly(methyl methacrylate) (PMMA) can be described properly by the two-parameter Weibull function. However, the statistical character of the distribution leads to an uncertainty in the parameters evaluated from a limited number of experiments. This study is concerned with the analysis of the methods of estimation as well as sample size on the estimates of the Weibull parameters. The maximum likelihood method, moments method, and linear regression method were studied. Monte Carlo simulations were carried out in order to assess the influence of the number of specimens tested on the Weibull parameters calculated by the different methods. The number of specimens tested displayed a large influence upon the calculated Weibull modulus. By applying weighing factors to the linear regression method, the standard deviation of Weibull parameters decreased significantly. As a compromise between minimizing both the dispersion of the evaluation method and the experimental effort, the use is suggested of the linear regression method with a minimum number of 20 specimens in a nonweighted analysis and 10 in a weighted analysis.

Symptoms of eutrophication in intertidal macroalgal assemblages of Nuevo Gulf (Patagonia, Argentina) Díaz, P.; López Gappa, Juan José; Piriz, Maria Luz The city of Puerto Madryn, located within a section of Nuevo Gulf (Patagonia, Argentina) known as Nueva Bay, can be regarded as an important centre of anthropogenic impact. Intertidal assemblages of macroalgae were studied in order to analyse whether eutrophication symptoms could be detected in the benthos. Three rocky shores showing similar characteristics were selected. One of these was located near the sewage outfall of the city of Puerto Madryn. Two control shores were chosen approximately 30 km northwards and southwards of the latter. Four seasonal surveys were performed between June 1998 and April 1999. Biomass data of 35 macroalgal species were analysed by diversity and evenness indices, non-Metric Multidimensional Scaling, and the ANOSIM permutation test. Species responsible for the differences between shores were identified by the SIMPER routine. The macroalgal assemblage of the impacted site was significantly different from those of the two control shores throughout the year. Ulva rigida, Corallina officinalis and Ralfsia sp. were the species mostly responsible for these differences. Results indicate that the impacted shore showed signs consistent with an intermediate degree of eutrophication, particularly the increased abundance of the opportunist green alga Ulva rigida.

Lithium and KB-R7943 effects on mechanics and energetics of rat heart muscle Bonazzola, Patricia; Egido, P.; Marengo, Fernando Diego; Savio Galimberti, E.; Ponce Hornos, Jorge Emilio The role of calcium influx on energy expenditure during cardiac contraction was studied. For this purpose; the described ability of lithium and KB-R 7943 (KBR) to diminish Ca entry through Na-Ca exchanger (Ponce-Hornos & Langer, J Mol Cell Cardiol 1980, 12, 1367, Satoh et al., Circulation 2000, 101, 1441) were used. In isolated contractions (contractions elicited after at least 5 min of rest) LiCl 45 mmol L -1 decreased pressure developed and pressure-time integral from 42.3 ± 2.7 and 14.5 ± 1.2 to 32.1 ± 3.4 mN mm -2 and 8.3 ± 0.9 mN mm -2 s, respectively. A similar effect was observed in regular contractions (at 0.16 Hz stimulation). The presence of KBR (5 μmol L -1) in the perfusate induced a slight but not significant decrease in pressure developed and pressure-time integral in steady-state contractions. As it was previously described, the heat involved in a heart muscle contraction can be decomposed into several components (H 1, H 2, H 3 and H 4), but only one (H 3) was associated with force generation. While H 3 decreased with lithium in both types of contractions, H 3/PtI ratio remained unaltered, indicating that the economy for pressure maintenance was unaffected. To further investigate the role of Ca entry on force development, a condition in which the contraction is mainly dependent on extracellular calcium was studied. An 'extra' stimulus applied 200 ms after the regular one in a muscle stimulated at 0.16 Hz induces a contraction with this characteristic (Marengo et al., Am J Physiol 1999, 276, H309). Lithium induced a strong decrease in pressure-time integral and H 3 associated with this contraction (43 and 45%, respectively) with no change in H 3/PtI ratio. Lithium also reduced (53%) an energy component (H 2) associated with Ca cycling. The use of KBR showed qualitatively similar results [i.e. a 33% reduction in pressure-time integral associated with the extrasystole (ES) with no changes in H 3/PtI ratio and a 30% reduction in) the H 2 component]. Li and KBR effects appear to be additive and in the presence of 45 mmol L -1 Li and 5 μmol L -1 KBR the extrasystole was abolished in 77%. Lithium and KBR effects particularly for the extrasystole can be explained through the inhibition of Ca entry via Na-Ca exchange giving support to the participation of the Na-Ca exchanger in the Ca influx from the extracellular space. In addition, the results also suggest the possibility of an effect of Li on an additional Ca sensitive locus (different than the Na-Ca exchanger). In this connection, in isolated contractions lithium decreased the energy release fraction related to mitochondrial processes (H 4) increasing the economy of the overall cardiac contraction.

The Magnetic Helicity Injected by Shearing Motions Démoulin, Pascal; Mandrini, Cristina Hemilse; van Driel Gesztelyi, Lidia; Lopez Fuentes, Marcelo Claudio; Aulanier, G. Photospheric shearing motions are one of the possible ways to inject magnetic helicity into the corona. We explore their efficiency as a function of their particular properties and those of the magnetic field configuration. Based on the work of M. A. Berger, we separate the helicity injection into two terms: twist and writhe. For shearing motions concentrated between the centers of two magnetic polarities the helicity injected by twist and writhe add up, while for spatially more extended shearing motions, such as differential rotation, twist and writhe helicity have opposite signs and partially cancel. This implies that the amount of injected helicity can change in sign with time even if the shear velocity is time independent. We confirm the amount of helicity injected by differential rotation in a bipole in the two particular cases studied by DeVore (2000), and further explore the parameter space on which this injection depends. For a given latitude, tilt and magnetic flux, the generation of helicity is slightly more efficient in young active regions than in decayed ones (up to a factor 2). The helicity injection is mostly affected by the tilt of the AR with respect to the solar equator. The total helicity injected by shearing motions, with both spatial and temporal coherence, is at most equivalent to that of a twisted flux tube having the same magnetic flux and a number of turns of 0.3. In the solar case, where the motions have not such global coherence, the injection of helicity is expected to be much smaller, while for differential rotation this maximum value reduces to 0.2 turns. We conclude that shearing motions are a relatively inefficient way to bring magnetic helicity into the corona (compared to the helicity carried by a significantly twisted flux tube).