Effects of Salts on Crystallization Kinetics and Rheological Behavior of Concentrated α,α-Trehalose Solutions Cerdeira, Mariana; Puppo, Maria Cecilia; Martini, Silvana; Herrera, Maria Lidia The effect of addition of CaCl2 · 2H2O and MgCl2 · 6H2O on crystallization kinetics and the rheological behavior of a 70% trehalose solution was studied by polarized light microscopy and dynamic oscillatory rheometry. Salts caused a delay on nucleation with induction times for crystallization longer for Mg2+ than for Ca2+. Divalent cations were incorporated into crystals, changing the growth of certain faces preferentially, which resulted in changes in morphology. Addition of CaCl2 · 2H2O in a high salt/trehalose molar ratio dramatically increased complex modulus (G*), indicating a stronger viscoelastic behavior. A gel-like structure was formed when Ca2+ was added to trehalose solution. The behavior of Mg 2+/trehalose solutions cannot be considered viscoelastic in nature but as a fluid-like system.

Immobilized Artificial Membrane Chromatography: Quantitative Structure-Retention Relationships of Structurally Diverse Drugs Luco, Juan Maria; Salinas, Adriana Paticia; Torriero, Angel Alberto Jesus; Vázquez, Rodolfo Nieto; Raba, Julio; Marchevsky, Eduardo Jorge The Chromatographic capacity factors (log k′) for 32 structurally diverse drugs were determined by high performance liquid chromatography (HPLC) on a stationary phase composed of phospholipids, the socalled immobilized artificial membrane (IAM). In addition, quantitative structure-retention relationships (QSRR) were developed in order to explain the dependence of retention on the chemical structure of the neutral, acidic, and basic drugs considered in this study. The obtained retention data were modeled by means of multiple regression analysis (MLR) and partial least squares (PLS) techniques. The structures of the compounds under study were characterized by means of calculated physicochemical properties and several nonempirical descriptors. For the carboxylic compounds included in the analysis, the obtained results suggest that the IAM-retention is governed by hydrophobicity factors followed by electronic effects due to polarizability in second place. Further, from the analysis of the results obtained of two developed quantitative structure-permeability studies for 20 miscellaneous carboxylic compounds, it may be concluded that the balance between polarizability and hydrophobic effects is not the same toward IAM phases and biological membranes. These results suggest that the IAM phases could not be a suitable model in assessing the acid-membrane interactions. However, it is not possible to generalize this observation, and further work in this area needs to be done to obtain a full understanding of the partitioning of carboxylic compounds in biological membranes. For the non-carboxylic compounds included in the analysis, this work shows that the hydrophobic factors are of prime importance for the IAM-retention of these compounds, while the specific polar interactions, such as electron pair donor-acceptor interactions and electrostatic interactions, are also involved, but they are not dominant.

Use of Back-off Computation in Multilevel MPC Arbiza, María José; Bandoni, José Alberto; Figueroa, Jose Luis The desired operating point in Model Predictive Control is determined by a local steady-state optimization, which may be based on an economic objective.  In this paper we proposes the solution of a linear dynamic back-off problem to obtain a hierarchical scheme that ensures feasible operation in despite of disturbances.  This is performed by computing the critical disturbances and expanding the optimziation problem to ensure the existence of a control action that ensures the rejection of each perturbation.

Aqueous sodium oleate-sodium dehydrocholate mixtures at low concentration Messina, Paula Verónica; Morini, Marcela Ana; Schulz, Pablo Carlos The aqueous mixed system sodium dehydrocholate (NaDHC)-sodium oleate (NaOL) was studied by several methods to determine the influence of the hydrophobic structure of both surfactants in the mixed micellization and the formation of the mixed monolayer adsorbed at the air-water interface. The molecular area at the critical micelle concentration in pure surfactant solutions suggests that the adsorbed oleate chain was folded to allow the double bond in the middle of the molecule to remain in contact with water, and that the NaDHC molecule was situated with its plane laying parallel to the water surface, allowing the three carbonyl groups in the hydrocarbon backbone to form hydrogen bonds with water. The interaction was repulsive at the surface, and in the mixed monolayer some molecules must move away the less hydrophilic groups from water (double bond of NaOL, carbonyl groups of NaDHC). The interaction in mixed micelles was strongly attractive, showing a preferential composition roughly equimolar. The hydrolysis in mixed micelles was augmented in comparison with pure surfactants systems, which could be explained by assuming the existence of a more hydrophobic mixed micelle core. The mixed micelle degree of ionization was below that of the pure micelles, thus indicating a high surface charge density.

Expression of FcRII in chronic lymphocytic leukemia B cells. Gamberale, Romina; Geffner, Jorge Raúl; Sanjurjo, Julieta; Fernandez Calloti, Paula X.; Arrosagaray, Guillermo; Sánchez Ávalos, Julio César Américo; Giordano, Mirta Nilda We have read with interest the paper from Damle et al analyzing the surface membrane phenotype of B lymphocytes in chronic lymphocytic leukemia (B-CLL). The authors stated that the leukemic cells from all B-CLL patients evaluated (irrespective of immunoglobulin heavy chain (IgVH) gene mutational status) bear the phenotype of antigen-experienced B cells based, among other features, on the very low expression of Fcγ receptors type IIb (FcγRIIb, CD32), which is the main isoform of FcγRII in B lymphocytes.

Interaction between process design and process operability of chemical processes: An eigenvalue optimization approach Blanco, Anibal Manuel; Bandoni, Jose Alberto An increasing effort is being devoted to consider controllability issues (or in a wider sense operability issues) at the process design stage. Controllability has mainly to do with dynamics in the face of disturbances. One philosophy for the integration of design and controllability is to explicitly consider dynamic elements within the process design formulation. An outstanding feature of dynamics is stability, which is related with the spectrum (set of eigenvalues) of the dynamic system Jacobian matrix. Dynamic convergence speed may also be analyzed in terms of the eigenvalues of the matrix from a Lyapunov function related to the Jacobian of the system. It is the purpose of this contribution to formulate and solve the chemical process design problem, considering process dynamics from an eigenvalue optimization approach.

Retrofit of multiproduct batch plants through generalized disjunctive programming Montagna, Jorge Marcelo; Vecchietti, Aldo The retrofit problem for multiproduct batch plants deals with the modification of the original structure of the plant to meet new production conditions such as the introduction of new products, a new supply pattern, etc. For this problem, a disjunctive model is presented, which takes into consideration every usual alternative about the configuration of units and storage tanks. A disjunction is generated for that purpose. The selection of one of those alternatives sets up all the corresponding constraints, which are: operation time, unit size and cost, etc. Finally, the performance of this approach is analyzed through the resolution of a set of examples.

Centothecoid grasses and the evolution of panicoid spikelets Rua, Gabriel Hugo An evolutionary pathway leading to acrotonous, 2-flowered spikelets of Panicoideae has been suggested elsewhere, which involves apical reduction of many-flowered mesotonic spikelets. Current phylogenies of the grass family show a sister relationship between Panicoideae and Centothecoideae. A survey of spikelet structures occurring among centothecoid grasses shows that some representatives of this group have intermediate morphologies which are consistent with that hypothesis. Chasmanthium and Bromuniola have many-flowered spikelets with a barren proximal floret, whereas Thysanolaena, Gouldochloa and Gynerium represent a series of apical reductions leading to 2-flowered spikelets. Moreover, many-flowered spikelets with 1-3 proximal male flowers followed by several female-fertile ones occur in Puelioideae, one of the early-diverging clades of the Poaceae. This fact suggests that some "panicoid" characters may have evolved long before the radiation of the Panicoideae took place.

Predictive functional control based on fuzzy model: magnetic suspension system case study Lepetic, Marko; Skrjanc, Igor; Chiacchiarini, Hector Gerardo; Matko, Drago Fuzzy model based predictive functional controller (FPFC) is applied to the magnetic suspension system - a pilot plant for magnetic bearing. High quality control requirements are short settle time with a-periodical step response and zero steady-state error. Open loop unstable process was stabilised with linear lead compensator. The FPFC was used as a cascade controller. Due to some model uncertainties, the Takagi-Sugeno fuzzy model of stabilised system was obtained using fuzzy identification. Comparing to PID, it improved quality and robustness performance. With its computational efficiency, it proved to be ideal solution for high sampling frequency.

Lattice gas study of the kinetics of the NO-CO catalytic reaction on Pd nanoclusters Bustos Giunta, Victor Angel; Uñac, Rodolfo Omar; Zgrablich, Giorgio; Henry, Claude R. The kinetics of the NO-CO reaction on Pd nanoclusters is studied through a lattice-gas model and Monte Carlo simulation. Pd nanoclusters with three typical sizes: 2.8 nm, 6.9 nm and 15.6 nm, are considered. These nanoclusters have been epitaxially grown on MgO(100) and tested for the NO-CO reaction in previous experimental work [ref. 9-11: C. H. F. Peden, D. W. Goodman, D. S. Blair, P. J. Berlowitz, G. B. Fisher and S. H. Oh, J. Phys. Chem., 1988, 92, 1563; C. Duriez, C. R. Henry and C. Chapon, Surf. Sci., 1991, 253, 190; L. Piccolo and C. R. Henry, Appl. Surf. Sci., 2000, 162-163, 670], thus providing the motivation for the present study. According to their size, the nanoclusters present different proportions of Pd(100) and Pd(111) facets. The effects of CO and NO desorption are found to be of fundamental importance for the behavior of the system. In all cases the medium size particles are found to be the most active. At low temperature, where NO desorption can be neglected (since the activation energy for desorption of NO on Pd is about 5 kcal mol-1 greater than that for the desorption of CO), the largest particles are revealed as the less active, while at high temperature, where both NO and CO desorption take place, the smallest particles are found to be the less active. These results are in concordance with the experimentally observed behavior.

Diffusion of particles adsorbed on a triangular lattice: Pairwise and three-particle interactions Tarasenko, Alexander A.; Nieto Quintas, Felix Daniel; Jastrabík, Lubomír; Uebing, Christian In the present paper, the influence of both pairwise and three-particle interactions on the mobility of adsorbed particles diffusing on a lattice with triangular symmetry has been studied. Two different techniques has been used for describing the surface diffusion phenomenon. On one hand, explicit expressions for the chemical and jump diffusion coefficients have been calculated by using real-space renormalization group (RSRG) approach. A number of the RSRG transformations with blocks of different sizes and symmetries have been investigated. In particular, it has been shown that the precision of the method depends strongly not only on the number of sites in the RSRG blocks but also on their composition and structure. On the other hand, numerical simulations by using the Monte Carlo scheme has been used to simulate the process of particle migration. Using both methods, adsorption isotherms for different temperatures and the coverage dependencies for the thermodynamic factor and the chemical diffusion coefficient have been calculated. The behavior of the above mentioned quantities has been compared when the adparticles interact via only either pairwise or three-particle interactions. Despite the fact that both methods constitute very different approaches, the correspondence of numerical data with analytical results is surprisingly good. Therefore, it can be concluded that the RSRG method can be successfully applied for lattice gas systems to characterize the thermodynamic and kinetic properties of strongly interacting adsorbates.

Objective method for classifying air masses: an application to the analysis of the Buenos Aires' (Argentina) urban heat island intensity Bejarán, Rubén Aníbal; Camilloni, Ines Angela During recent years, numerous studies have examined the Buenos Aires urban climate, but the relationship between large-scale weather conditions and the Buenos Aires urban heat island (UHI) intensity has not been studied. The goal of this paper is to apply an objective synoptic climatological method to identify homogeneous air masses or weather types affecting Buenos Aires during winter, and to relate the results to the UHI intensity. A K-means clustering method was used to define six different air masses considering the 03:00, 09:00, 15:00 and 21:00 LT surface observations of dry bulb temperature, dew point, cloud cover, atmospheric pressure and wind direction and velocity at Ezeiza, the most rural meteorological station of the Buenos Aires metropolitan area (Fig. 1). Results show that the mean UHI intensity is at its maximum (2.8 °C) a few hours before sunrise when conditions are dominated by cold air masses associated with cold-core anticyclones, weak winds and low cloud cover. Inverse heat islands are found during the afternoon for all air masses indicating that surface processes are not dominant at that time. The relatively infrequent and warmest air mass is the only one that presents a mean negative urban-rural temperature difference (−0.1 °C) during the afternoon with the smallest diurnal cycle of the UHI intensity probably due to the prevailing high humidity and cloudy sky conditions. The paper provides an insight into the Buenos Aires urban?rural temperature difference under a variety of winter weather types and results could be useful to improve local daily temperature forecasts for the metropolitan area of Buenos Aires on the basis of the routine forecasts of weather types.

Modelling corn starch swelling in batch systems: effect of sucrose and hydrocolloids Krüger, Alejandra; Ferrero, Cristina; Zaritzky, Noemi Elisabet Hydrocolloids are used in starch-based products to improve stability and to obtain specific textural characteristics. In stirred batch systems with constant jacket temperature, xanthan gum, guar gum and sodium alginate (1% w/w) were added to corn starch (10% w/w) and sucrose (15% w/w) in aqueous systems to test their effects on granule swelling, starch gelatinization temperatures and viscoelastic behavior of the hot paste. As heating is not instantaneous, time–temperature relationships cannot be avoided. In this regard, heat penetration was faster in viscoelastic systems with lower complex dynamic modulus ðGÞ values, while pastes containing gums showed lower heat transfer rates during gelatinization. Microscopy and image analysis were applied to describe the granule swelling process in starch gelatinization. Starch granule swelling was considerably reduced by the presence of gums due to the lower heating rates and the decreased mobility of water molecules. The presence of sucrose increased starch gelatinization temperatures, measured by differential scanning calorimetry; gum addition did not show a significant influence on these temperatures. The effect of time and temperature on the starch swelling process was modelled considering, as driving force, the difference between the instantaneous mean curvature of the granule (reciprocal of the diameter) and the asymptotic curvature. Gelatinization rate constants were calculated for the different pastes and the lowest values were observed for starch pastes added with gums. Activation energies ranged from 80 ( 14) to 119 ( 3) kJ mol 1, being comparable to values reported in the literature for starch gelatinization measured by different methods.

Infinite dilution activity coefficients of solvents in fatty oil derivatives Ferreira, O.; Foco, Gloria Margarita Inverse gas-liquid chromatography has been applied to measure infinite dilution activity coefficients (γ ∞) of different solutes in low and high molecular weight triacylglycerides (TAGs) and in mixtures of carboxylic acids with TAGs. The γ ∞ data obtained were used to determine binary interaction and size related parameters for the GCA-EOS group contribution with association equation of sate.

Optimization of the operating conditions of azeotropic distillation columns with pervaporation membranes Hoch, Patricia Monica; Daviou, Maria Carolina; Eliceche, Ana Maria The main objective of this work is the optimization of the operating conditions of azeotropic distillation columns in hybrid distillation/pervaporation systems. In the configuration analyzed, a liquid side stream extracted from the azeotropic distillation column with the distributing non-key component is treated in a pervaporation membrane while the retentate is recycled to the column. The pervaporation membrane separates the pure distributing non-key component from the mixture, thus helping to improve the purity in the top and/or bottom products of the distillation column. The case study shows the hybrid process of a distillation column combined with pervaporation membranes, compared to the classical two-column process for Methyl tert-Butyl Ether production. In both cases, the operating conditions of the distillation columns such as reflux ratio, product and side draw flowrates are selected optimally. The numerical results show a significant reduction in operating cost obtained by using a pervaporation membrane instead of the second column in the original process.

Restricted weak type inequalities for convolution maximal operators in weighted Lp spaces Bernardis, Ana Lucia; Martín Reyes, Francisco Javier Let φ: ℝ → [0, ∞) be an integrable function such that φ(-∞,0) = 0 and φ is decreasing in (0, ∞). Let τh f (x) = f (x - h), with h ∈ ℝ/{0} and φ R(x) = (1/R)φ(x/R), with R > 0. In this paper we study the pair of weights (u, v) such that the operators Mτhφ f (x) = supR>0 |f| * [tau;hφ]R (x) are of restricted weak type (p, p) with respect to (u, v), 1 ≤ p < ∞. As particular cases, these operators include some maximal operators related to Cesàro convergence. We characterize those functions φ for which Mτhφ is of (restricted) weak type (p, p) with respect to the Lebesgue measure. Unlike the case of the Cesàro maximal operators, it follows from the characterization that the interval of those p such that M τhφ is of weak type (p, p) can be left-closed, [p 0, ∞], or left-open, (p0, ∞], without having restricted weak type (p0, p0).

New evolutionary models for massive ZZ Ceti stars, I : first results for their pulsational properties Althaus, Leandro Gabriel; Serenelli, A. M.; Corsico, Alejandro Hugo; Montgomery, M. H. Chaotic orbits suffer significant changes as a result of small perturbations. One can thus wonder whether the dynamical friction suffered by a satellite on a regular orbit, and interacting with the stars of a galaxy, will be different if the bulk of the stars of the galaxy are in regular or chaotic orbits. In order to check that idea, we investigated the orbital decay (caused by dynamical friction) of a rigid satellite moving within a larger stellar system (a galaxy) whose potential is nonintegrable. We performed numerical experiments using two kinds of triaxial galaxy models: (1) the triaxial generalization of Dehnen's spherical mass model (Dehnen; Merritt & Fridman); (2) a modified Satoh model (Satoh; Carpintero, Muzzio, & Wachlin). The percentages of chaotic orbits present in these models were increased by perturbing them. In the first case, a central compact object (black hole) was introduced; in the second case, the perturbation was produced by allowing the galaxy to move on a circular orbit in a logarithmic potential. The equations of motion were integrated with a non-self-consistent code. Our results show that the presence of chaotic orbits does not affect significantly the orbital decay of the satellite.

Up-regulated expression of MICA on activated T lymphocytes involves Lck and Fyn kinases, and signaling through MEK1/ERK, p38 MAP kinase and calcineurin Molinero, Luciana Lorena; Fuertes, Mercedes Beatriz; Fainboim, Leonardo; Rabinovich, Gabriel Adrián; Zwirner, Norberto Walter Major histocompatibility complex class I-related chain (MICA) is a cell stress-regulated molecule recognized by cytotoxic cells expressing the NKG2D molecule. MICA can be induced on T cells after CD3 or CD28 engagement. Here, we investigated the intracellular pathways leading to activation-induced expression of MICA. The Src kinase inhibitor PP1 inhibited up-regulated expression of MICA on anti-CD3-stimulated T cells. Downstream signaling routes involved mitogen-activated protein kinase (MAPK) kinase (MEK)1/extracellular signal-regulated kinase (ERK), p38 MAPK, and calcineurin, as MICA expression was prevented by U0126, SB202190, cyclosporin A, and FK506. Also, Lck and Fyn as well as MEK1/ERK and p38 MAPK were found to regulate MICA expression in anti-CD28/phorbol 12-myristate 13-acetate-stimulated T cells. Expression of MICA on activated T cells involved interleukin-2-dependent signaling routes triggered by Janus tyrosine kinases/signal transducer and activators of transcription and p70S6 kinase, as it could be inhibited by AG490 and rapamycin. This is the first demonstration of the intracellular pathways involved in activation-induced expression of MICA, which may reveal potential targets for immune intervention to modulate MICA expression in pathological disorders.

Role of prolactin in the regulation of cytosolic NADP isocitrate dehydrogenase in the liver of the male rat Zirulnik, Fanny; Anzulovich Miranda, Ana Cecilia; Larregle, Ethel Viviana; Jahn, Graciela Alma; Gimenez, Maria Sofia The activity of cytosolic NADP-linked isocitrate dehydrogenase (ICDH) in rat liver was determined. The administration of 2-bromo-α-ergocryptine (CB-154) to male rats produced a significant increase of the enzyme activity and a decrease of serum prolactin (PRL) levels in relation to control animals. Male rats 21 days after castration had lower levels of serum prolactin and higher activity of the enzyme than controls. Injection of PRL to castrated male rats lowered the enzymatic activity to control values. In intact rats injected with prolactin, the activity of the enzyme also decreased. Female rats were separated into the following groups: (a) virgins; (b) rats on day 15 of lactation; (c) ovariectomized rats. The enzymatic activity was similar in the different groups, but significantly higher than in male rats. However, serum PRL was significantly increased in 15 days lactating rats and decreased in ovariectomized ones in relation to virgins. We conclude that PRL regulates hepatic ICDH activity in male, but not in female rats. Incubation of isolated hepatocytes from intact or castrated male rats maintained the difference in ICDH activity observed in vivo, while there were no differences in ICDH activity in non-parenchymal cells. Addition of PRL, CB-154, androgens or antiandrogens to isolated hepatocytes from intact and castrated rat, had no effect on the ICDH activity, suggesting that the effect of PRL is exerted at the transcriptional level.

Extraction of molybdenum by a supported liquid membrane method Basualto, Carlos; Marchese, Jose; Valenzuela, Fernando R.; Acosta, Adolfo Francisco This is a report on the extraction of molybdenum(VI) ions using a supported liquid membrane, prepared by dissolving in kerosene, the extractant Alamine 336 (a long-chain tertiary amine) employed as mobile carrier. A flat hydrophobic microporous membrane was utilised as solid support. Appropriate conditions for Mo(VI) extraction through the liquid membrane were obtained from the results of liquid-liquid extraction and stripping partition experiments. The influence of feed solution acidity, the carrier extractant concentration in the organic liquid film and the content of strip agent on the metal flux through membrane were investigated. It was established that maximal extraction of metal is achieved at a pH 2.0 if sulphuric acid is used in the feed solution and at a pH value over 11.0 if Na2CO3 is used as strip agent. Moreover, the molybdenum extraction through membrane is enhanced when a 0.02 mol 1-1 content of the amine carrier in the organic phase is used. The present paper deals with an equilibrium investigation of the extraction of Mo(VI) by Alamine 336 and its permeation conditions through the liquid membrane, and examines a possible mechanism of extraction.