Cloud point preconcentration prior to capillary zone electrophoresis: Simultaneous determination of platinum and palladium at trace levels Cerutti, Estela Soledad; Silva, María Fernanda; Gasquez, José Antonio; Olsina, Roberto Antonio; Martinez, Luis Dante The incorporation of a cloud point extraction (CPE) step prior to capillary electrophoresis (CE) for simultaneously determining platinum and palladium at sub-μg/L levels is presented and evaluated. The analytes were extracted as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complexes, at pH 2.0, mediated by micelles of the nonionic surfactant polyethyleneglycolmono-p-nonylphenyl ether (PONPE 7.5). The separation-determination step was developed from 150 μL of the extracted surfactant-rich phase diluted with 50 μL of acetonitrile (ACN). An exhaustive study of the variables affecting the cloud point extraction with PONPE 7.5 and the CZE step was done. The type and composition of the background electrolytes (BGEs) were investigated with respect to separation selectivity, reproducibility, and stability. A BGE of 50 mM monobasic sodium phosphate containing 30% ACN, pH 4.53 was found to be optimal for the separation of metal chelates. Detection was performed at 576 nm. An enrichment factor of 250 was obtained for the preconcentration of 50 mL of sample solution. The detection limits for the preconcentration of 50 mL of sample were 0.04 μg/L for Pt and 0.08 μg/L for Pd. As an analytical demonstration, ultratrace concentrations of platinum and palladium were conveniently quantitated in spiked water and urine samples. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multichannel radiometer calibration: A new approach Diaz, Susana Beatriz; Booth, Charles R.; Armstrong, Roy; Brunat, Claudio; Cabrera, Sergio; Camilion, Carolina; Casiccia, Claudio; Deferrari, Guillermo Alejandro; Fuenzalida, Humberto; Lovengreen, Charlotte; Paladini, Alejandro Alberto; Pedroni, Jorge; Rosales, Alejandro; Zagarese, Horacio Ernesto; Vernet, Maria The error in irradiance measured with Sun-calibrated multichannel radiometers may be large when the solar zenith angle (SZA) increases. This could be particularly detrimental in radiometers installed at mid and high latitudes, where SZAs at noon are larger than 50° during part of the year. When a multi-regressive methodology, including the total ozone column and SZA, was applied in the calculation of the calibration constant, an important improvement was observed. By combining two different equations, an improvement was obtained at almost all the SZAs in the calibration. An independent test that compared the irradiance of a multichannel instrument and a spectroradiometer installed in Ushuaia, Argentina, was used to confirm the results.

NMR Relaxometry analysis of lubricant oils degradation Ballari, Maria de Los Milagros; Bonetto, Fernando Jose; Anoardo, Esteban The present work was undertaken in order to investigate lubricant oil degradation at the molecular level. Ageing effects, as reflected on the proton spin-lattice relaxation rate (T −1 1 ) dispersion, were studied in two different lubricant engine oils. The proton field cycling technique was used to scan relaxation of new and aged samples of monograde and multigrade oils. Relaxation dispersions were interpreted in terms of self-diffusion and molecular rotations. Our study shows that proton T −1 1 could be very sensitive to degradation processes, especially at low Larmor frequencies. The analysis reveals a noticeable sensitivity of the involved correlation times. The pros and cons of the technique are also discussed.

Light-intensity dependence of the steady-state photoconductivity used to estimate the density of states in the gap of intrinsic semiconductors Schmidt, Javier Alejandro; Longeaud, C.; Kleider, J. We present a method to obtain the density of states of photoconductive semiconductors based on the light-intensity dependence of the steadystate photoconductivity. A simple expression—relating the density of states at the electron quasi-Fermi level to measurable quantities—is deduced by performing suitable approximations from the analytical solution of the generalized equations that describe the photoconductivity of semiconductors. The validity of the approximations and the applicability of the final expression are verified from numerical simulations of the process. The usefulness of the method is demonstrated by performing measurements on a standard hydrogenated amorphous silicon sample.

On the a.s. convergence of certain random series to a fractional random field in D'(Rd) Medina, Juan Miguel; Cernuschi Frias, Bruno We prove the almost sure convergence in the sense of Schwartz distributions of certain random series. This result is useful to construct some type of fracional random fields. These series resemble the Karhunen-Loéve expansions.

Dissection of two distinct defense-related responses to agar oligosaccharides in Gracilaria chilensis (Rhodophyta) and Gracilaria conferta (Rhodophyta) Weinberger, Florian; Leonardi, Patricia Ines; Miravalles, Alicia Beatriz; Correa, Juan A.; Lion, Ulrich; Kloareg, Bernard; Potin, Philippe The two agar-producing red algae, Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira and Gracilaria conferta (Schousboe ex Montagne) Montagne, responded with hydrogen peroxide (H2O2) release when agar oligosaccharides were added to the medium. In G. conferta, a transient release was observed, followed by a refractory state of 6 h. This response was sensitive to chemical inhibitors of NADPH oxidase, protein kinases, protein phosphatases, and calcium translocation in the cell, whereas it was insensitive to inhibitors of metalloenzymes. Transmission electron microscopic observations of the H2O2-dependent formation of cerium peroxide from cerium chloride indicated oxygen activation at the plasma membrane of G. conferta. A putative system, consisting of a receptor specific to agar oligosaccharides and a plasma membrane-located NADPH oxidase, appears to be responsible for the release of H2O2 in G. conferta. Subcellular examination of G. chilensis showed that the H2O 2 release was located in the cell wall. It was sensitive to inhibitors of metalloenzymes and flavoenzymes, and no refractory state was observed. The release was correlated with accumulation of an aldehyde in the algal medium, suggesting that an agar oligosaccharide oxidase is present in the apoplast of G. chilensis. The presence of this enzyme could also be demonstrated by polyacrylamide electrophoresis under nondenaturating conditions and proven to be variable. Cultivation of G. chilensis at 16 to 17°C resulted in significantly stronger expression of agar oligosaccharide oxidase than cultivation at 12°C, which indicates that the enzyme is used under conditions that generally favor microbial agar macerating activity.

A novel α-conotoxin, PeIA, cloned from Conus pergrandis, discriminates between Rat α9α10 and α7 nicotinic cholinergic receptors McIntosh, J. Michael; Plazas, Paola Viviana; Watkins, Maren; Gomez Casati, Maria Eugenia; Olivera, Baldomero M.; Elgoyhen, Ana Belen The α9 and α10 nicotinic cholinergic subunits assemble to form the receptor believed to mediate synaptic transmission between efferent olivocochlear fibers and hair cells of the cochlea, one of the few examples of postsynaptic function for a non-muscle nicotinic acetylcholine receptor (nAChR). However, it has been suggested that the expression profile of α9 and α10 overlaps with that of α7 in the cochlea and in sites such as dorsal root ganglion neurons, peripheral blood lymphocytes, developing thymocytes, and skin. We now report the cloning, total synthesis, and characterization of a novel toxin α-conotoxin PeIA that discriminates between α9α10 and α7 nAChRs. This is the first toxin to be identified from Conus pergrandis, a species found in deep waters of the Western Pacific. α-Conotoxin PeIA displayed a 260-fold higher selectivity for α-bungarotoxin-sensitive α9α10 nAChRs compared with α-bungarotoxin-sensitive α7 receptors. The IC50 of the toxin was 6.9 ± 0.5 nM and 4.4 ± 0.5 nM for recombinant α9α10 and wild-type hair cell nAChRs, respectively. α-Conotoxin PeIA bears high resemblance to α-conotoxins MII and GIC isolated from Conus magus and Conus geographus, respectively. However, neither α-conotoxin MII nor α-conotoxin GIC at concentrations of 10 μM blocked acetylcholine responses elicited in Xenopus oocytes injected with the α9 and α10 subunits. Among neuronal non-α-bungarotoxin- sensitive receptors, α-conotoxin PeIA was also active at α3β2 receptors and chimeric α6/α3β2β3 receptors. α-Conotoxin PeIA represents a novel probe to differentiate responses mediated either through α9α10 or α7 nAChRs in those tissues where both receptors are expressed.

Comportamiento de la floración y sistema de apareamiento de los híbridos de algarrobo Cordoba, Ana Andrea; Verga, Aníbal; Mottura, Martín; López Lauenstein, Diego Alejandro; Gailing, Oliver; Finkeldey, Reiner La recuperación de los bosques de algarrobos de Prosopis flexuosa y P. chilensis en la región fitogeográfica del Chaco Árido puede llevarse a cabo, en parte, mediante planes de reforestación y enriquecimiento de bosques. Para ello es necesario conocer la variabilidad existente en las poblaciones locales y sus características particulares en cuanto a fenología, comportamiento reproductivo y descendencia, producción diferencial de frutos y crecimiento, entre otros. Para ello se realizan estudios a campo y desarrollan marcadores moleculares específicos.

Fréchet differentiability of the solutions of a semilinear abstract Cauchy problem Herdman, Terry; Spies, Ruben Daniel Sufficient conditions are found under which the solutions z(t; q) of a semilinear abstract Cauchy problem of the form d/dt z(t) = A(q)z(t) + F(q, t, z(t)) are Fréchet differentiable with respect to the parameter q. An explicit form is provided for the sensitivity equation satisfied by the Fréchet derivative Dqz(t; q).

Changes in the composition of phospholipid fatty acids and sterols of maize root in response to monoterpenes Zunino, María Paula; Zygadlo, Julio Alberto Terpenes are thought to be important in plantYplant interactions because of their phytotoxic action on seed germination and growth. Herein, the effects of five volatile monoterpenes on root sterols and phospholipid fatty acid (PLFA) composition have been studied during maize seedling germination. The investigated monoterpenes (camphor, 1Y8 cineole, geraniol, menthol, and thymol) were applied at their respective IC80 (concentration causing 80% inhibition). They quantitatively affected free sterols and PLFA composition, thus producing an increase in the percentage of unsaturated PLFAs, stigmasterol of the free sterol fraction, and saturated steryl ester fatty acids. Alcoholic and nonalcoholic monoterpenes appeared to have different modes of action. The former affected unsaturated fatty acid and stigmasterol to a greater extent, and accordingly they could interfere in seedling growth by changes in the membrane lipids.

Los límites a la democratización política: Las elecciones de 1919 en Corrientes, ¿triunfo conservador o derrota radical? Solís Carnicer, María del Mar Este trabajo describe el proceso electoral llevado a cabo en Corrientes en el año 1919, luego de una larga intervención federal decretada por el presidente Hipólito Yrigoyen que finalizó con el retorno de los conservadores al gobierno de la provincia. Esta elección constituye un interesante objeto de análisis para revisar ciertas cuestiones relativas a la política de la época. Por un lado, marcó el reinicio de la actividad electoral en la provincia, luego de la intervención federal, por otro, fue la primera vez que el partido radical participó en una elección de gobernador en Corrientes y finalmente, los conservadores lograron recuperar al poder, más allá de las condiciones adversas a las que debieron enfrentarse. En el artículo, se reconstruyen las prácticas políticas que entraron en juego, las diferentes visiones sobre la política que tenían las distintas fuerzas actuantes y se pretende analizar las causas de su resolución a la luz de la cultura política predominante. Asimismo, se buscan las interacciones entre las instituciones, los valores y los actores, para explicar el complejo desarrollo de la puesta en práctica de la política del acuerdo, que permitió a los conservadores correntinos presentarse ante el país como verdaderos custodios del conservadurismo y representantes del antiyrigoyenismo.

Gravity wave drag estimation from global analyses using variational data assimilation principles. I: Theory and implementation Pulido, Manuel Arturo; Thuburn, J. A novel technique to estimate gravity wave drag from global-scale analyses is presented. It is based on the principles of four-dimensional variational data assimilation, using a dynamical model of the middle atmosphere and its adjoint. The global analyses are treated as observations. A cost function that measures the mismatch between the model state and observations is defined. The control variables are the components of the three-dimensional gravity wave drag field, so that minimization of the cost function gives the optimal gravity wave drag field. The minimization is performed using a conjugate gradient method, with the adjoint model used to calculate the gradient of the cost function. In this work, we present the theory behind the new technique and evaluate extensively the ability of the technique to estimate the gravity wave drag using so-called twin experiments, in which the ‘observations’ are given by the evolution of the dynamical model with a prescribed gravity wave drag. The results show that the technique can estimate accurately the prescribed gravity wave drag. When the cost function is suitably defined, there is good convergence of the minimization scheme under realistic atmospheric conditions. We also show that the cost function gradient is well approximated taking into account only adiabatic processes. We note some limitations of the technique for estimating gravity wave drag in tropical regions if satellite temperature measurements are the only observational information available.

A new theoretical approach to multilayer adsorption of polyatomics Romá, Federico José; Ramirez Pastor, Antonio Jose; Riccardo, Jose Luis The multilayer adsorption isotherms of linear particles (k-mers) on homogeneous surfaces were developed on a generalization in the spirit of the well-known Brunauer-Emmet-Teller's approach. The generalized equation is obtained through an analytical approach that provides the isotherm in the multilayer regime from the isotherm in the monolayer regime. The formalism leads to exact results in one dimension and provides an analytical approximation to study multilayer adsorption on two-dimensional surfaces with different geometries (square, honeycomb and triangular). The entropic effects of the nonspherical character of the adparticles on the determination of the monolayer volume and adsorption energy, are shown and discussed for type II and type III isotherms. Comparison with Monte Carlo simulations in the grand canonical ensemble and experimental adsorption isotherms are used to test the accuracy and reliability of the model. Close agreement between simulated, theoretical and experimental results supports the applicability of the proposed model to describe multilayer adsorption in presence of multisite-occupancy.

Cytotoxic T lymphocyte antigen 4 heterozygous codon 49 A/G dimorphism is associated to latent autoimmune diabetes in adults (LADA) Caputo, Mariela; Cerrone, Gloria Edith; Lopez, Ariel Pablo; Villalba, Anabel; Krochik, Andrea Gabriela; Cédola, Federico Norberto; Targovnik, Hector Manuel; Frechtel, Gustavo Daniel Autoimmune diabetes is an organ specific and multifactorial disorder with a classical onset as insulin dependent diabetes mellitus (IDDM) and with another form of onset as latent autoimmune diabetes in adults (LADA), which has a slower onset and a later progress to insulin dependency as a result of the beta cells destruction. The cytotoxic T lymphocyte-antigen 4 (CTLA4) has been identified as a susceptible marker of the disease; it is considered a down regulator of T cell function, playing a key role in autoimmunity. We analyzed CTLA4 codon 49 A/G polymorphism in 123 IDDM patients, 63 LADA patients and 168 healthy non-diabetic control individuals. The frequency of the heterozygous A/G genotype in LADA patients was significantly increased compared to IDDM patients (55.6 vs. 39.8%, p = 0.0415). There was no statistical significant difference in the distribution of the A/G dimorphism between autoimmune diabetes patients (LADA or IDDM) and non-diabetic control individuals. HLA DQ region is responsible for the genetic susceptibility to autoimmune diabetes in IDDM patients in about 50% and it has a lower effect in genetic susceptibility in LADA patients. Several other genetic loci are needed to develop autoimmune diabetes in adult patients. Therefore, LADA may be the result of a combined minor risk loci effect in a major risk haplotype.

Biocontrol of Bacillus subtilis against Fusarium verticillioides in vitro and at maize root level Cavaglieri, Lilia Reneé; Orlando, Julieta Laura; Rodriguez, Maria Ines; Chulze, Sofia Noemi; Etcheverry, Miriam Graciela Bacillus species as a group offer several advantages over other bacteria for protection against root pathogens because of their ability to form endospores, and because of the broad-spectrum activity of their antibiotics. The objectives of this work were to determine the ability of strains of Bacillus to inhibit Fusarium verticillioides growth and fumonisin B1 accumulation in vitro, and to evaluate the ability of the best bacterium for preventing rhizosphere and endorhizosphere colonization by F. verticillioides. Bacterial populations from the maize rhizoplane were obtained, and the capacity of ten Bacillus strains to inhibit fungal growth and fumonisin B1 accumulation in vitro was assayed. According to these results, B. subtilis CE1 was selected as the best antagonist for testing maize root colonization of F. verticillioides. Bacillus subtilis CE1 at 108 and 107 CFUml-1 inocula was able to reduce rhizoplane and endorhizosphere colonization of F. verticillioides in greenhouse trials. The strain B. subtilis CE1 could be a potential biological control agent against F. verticillioides at the root level.

Pricing of Defaultable Bonds with Log-Normal Spread: Development of the Model and an Application to Argentinean and Brazilian Bonds During the Argentine Crisis Cané de Estrada, Mariano; Cortina, Elsa Aurora; Ferro Fontan, Constantino; Fiori, Javier di In this paper we describe a two-factor model for a defaultable discount bond, assuming log-normal dynamics with bounded volatility for the instantaneous short rate spread. Under some simplified hypothesis, we obtain an explicit barrier-type solution for zero recovery and constant recovery. We also present a numerical application for Argentinean and Brazilian Sovereign Bonds during the default crisis of Argentina.

Dynamic Modelling and Optimisation of Large-Scale Cryogenic Separation Processes Rodriguez, Mariela Alejandra; Bandoni, Jose Alberto; Díaz, María Soledad In this work, the open loop dynamic optimisation of a large-scale natural gas processing plant is performed. A rigorous differential-algebraic equation (DAE) model has been formulated to represent main plant units, such as shell and tube heat exchangers, highpressure separator and demethanizing column. In the shell and tube heat exchangers, the hot stream partially condenses and equations to consider the partial condensation of the fluids have been included. A rigorous index one model for the demethanizing column has been developed. The DAE optimisation problem is solved with a simultaneous approach, in which both state and control variables are discretised and the original DAE optimisation model is transformed into a large-scale nonlinear problem (NLP), which is solved using Sequential Quadratic Programming (SQP) methods. Optimal profiles have been obtained for main operating variables to achieve an enhanced product recovery.

Effect of pretreatments and processing conditions on the chemical, physical, microbiological and sensory characteristics of garlic paste Constenla, Diana Teresita; Lozano, Jorge Enrique The influence of storage temperature of garlic bulb and chemical additives (including ascorbic acid, citric acid and potassium sorbate) on the chemical, physical, microbiological and sensory characteristics of garlic paste was evaluated. Formation of undesirable greenish pigment was avoided by storing fresh garlic bulbs at 25 and 40C. Moreover, heating bulbs to 40C a few minutes before processing facilitated skin removal. Garlic paste was processed, packed and thermally treated at 85C for 5 min. The color of garlic paste was affected by chemical treatment, temperature and storage period. The rate of color difference (ΔE) increase was divided into two linear periods with different slopes. Garlic paste exhibited pseudoplasticity with yield stress and flow adequately described by the Herschel-Bulkley model (r2 > 0.990). Both consistency index and apparent viscosity decreased with increase in temperature.

Boundary element method for J-integral and stress intensity factor computations in three-dimensional interface cracks Ortiz, Jhonny E.; Cisilino, Adrian Pablo A general numerical tool for the analysis of three–dimensional bimaterial interface cracks is presented in this paper. The proposed tool is based on a multidomain formulation of the Boundary Element Method (BEM), with the crack located at the interface of the domain. Mixed mode stress intensity factors are computed along the three-dimensional crack fronts using the Energy Domain Integral (EDI) methodology and decoupled via the Interaction Integral. The capability of the procedure is demonstrated by solving a number of examples. The last of these examples consists in a thick centre cracked panel for which the behaviour of the J-integral and the mixed-mode stress intensity factors along the crack front is studied as a function of the material mismatch.

Allylic alcohol synthesis by gas-phase hydrogen transfer reduction of unsaturated ketones Di Cosimo, Juana Isabel; Acosta, A.; Apesteguia, Carlos Rodolfo The gas-phase hydrogen transfer reduction (HTR) of mesityl oxide (MO) with 2-propanol to selectively obtain allylic alcohols was studied on MgO. MO was converted directly to 4-methyl-3-penten-2ol (UOL1) or isomerised to iso-mesityl oxide (i-MO), which consecutively formed 4-methyl-4-penten-2ol (UOL2). Significant amounts of methyl isobutyl carbinol (MIBC) were also formed by the simultaneous reduction of CC and CO groups of MO. The effect of reaction conditions on catalyst activity and selectivity was determined in order to improve total UOL yield that was about 28% under standard reaction conditions (T = 523 K, 2-propanol/MO = 5, W/FMO0 = 15 g h/mol). Total UOL yield increased continuously with contact time up to 42% but when the 2-propanol/MO ratio was varied, UOL yield reached a maximum at a reactant ratio of about 4. UOL2 yield markedly increased with temperature at expenses of MIBC. The increase of temperature also improved the catalyst stability because suppressed formation of coke intermediates. Regarding the effect of the hydrogen donor, higher total UOL yields were obtained by using secondary alcohols, such as 2-propanol and 2-butanol, than primary (1-propanol) or secondary aryl (1-penylethanol) alcohols.