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.

Additive apoptotic effect of STI571 with the cytoprotective agent amifostine in K-562 cell line Vellón, Luciano; Gonzalez Cid, Marcela Beatriz; de Campos Nebel, Ildefonso Marcelo; Larripa, Irene Beatriz Purpose: To study the apoptotic effect of the 2-phenylaminopyrimidine derivative STI571 in combination with antioxidant agents on K-562 cell line derived from a Philadelphia chromosome-positive chronic myeloid leukemia patient. Materials and methods: K-562 (BCR/ABL+), U-937, and HL60 (BCR/ABL-) leukemic cell lines were incubated with STI571 and the antioxidant agents catalase, glutathione, superoxide dismutase, and amifostine (AMI). Apoptotic effect was analyzed by morphological and flow cytometric criteria. Results: STI571 at concentrations higher than 0.25 μmol L-1 produced apoptosis (P<0.05) in K-562 cells only after treatment for 72 h. At the mentioned concentrations, STI571 also induced an increase in the loss of mitochondrial transmembrane potential from 24.6 to 40%. Combination of STI571 (0.5 μmol L-1) with antioxidant agents showed that the cytoprotective agent AMI (0.75 mg mL-1) produced an additive effect in the proapoptotic activity of STI571 in K-562 cells at nuclear (58.8%±2.0 vs. 28.9%±3.3) and mitochondrial (53.3%±3.6 vs. 29.5%±1.2) levels. Conclusions: Our results show that only AMI in combination with STI571, at submicromolar concentration, has an additive effect in K-562 cell line, and it does not have severe toxic effects on Philadelphia chromosome negative cells. © Springer-Verlag 2005.

Administration of a peptide inhibitor of alpha4-integrin inhibits the development of experimental autoimmune uveitis Martín, Andrea P.; Vieira de Moraes, Luciana; Tadokoro, Carlos E.; Commodaro, Alessandra G.; Urrets Zavalia, Enrique; Rabinovich, Gabriel Adrián; Urrets Zavalía, Julio Alberto; Rizzo, Luiz V.; Serra, Horacio Marcelo Recruitment of lymphocytes into the retina and to the vitreous during the development of experimental autoimmune uveitis (EAU) is governed by factors such as the state of activation of inflammatory cells and the repertoire of adhesion molecules expressed by the local vascular endothelia. alpha4 Integrins and their receptors play an important role during homing of cells to the inflammatory site. In the present study, the effect of alpha4-integrin inhibitor on the development of EAU was investigated.

Acanthagrion hartei sp. nov. from Ecuador (Zygoptera: Coenagrionidae) Muzon, Javier; Lozano, Federico The new sp. is described and illustrated. Holotype: Ecuador, Morona, Santiago prov., Bomboiza, 20-IX-1990, deposited in USNM, Washington. It is assigned to the apicale-group, and differs from the other spp. of that group by characters of the terminalia and genital ligula.

O impacto do rio da Prata no oceano Atlântico Piola, Alberto Ricardo; Möller, Osmar O.; Palma, Elbio Daniel Os habitantes da região costeira que se estende da província de Buenos Aires, na Argentina, a Rio Grande, no sul do Brasil, sabem que a água do mar é quase 10°C mais quente em janeiro que em julho. Um observador mais atento notaria também mudanças de cor na sua superfície em diferentes épocas do ano. Para explicar tais observações, especula-se sobre a existência de freqüentes incursões de água fria oriundas da corrente das Malvinas. Neste artigo são apresentadas evidências que sugerem que as alterações mais importantes ao longo de uma faixa costeira de aproximadamente 1.000 km se devem à influência variável das águas que o rio da Prata derrama no oceano Atlântico.

Antithrombogenic properties of bioconjugate streptokinase-polyglycerol dendrimers Ramos Fernandes, Edson Giuliani; de Queiroz, Alvaro Antonio Alencar; Abraham, Gustavo Abel; San Román, Julio Dendrimers are monodisperse, spherical and hyperbranched synthetic macromolecules with a large number of surface groups that have the potential to act as carriers for drug immobilization by covalent binding or charge transfer complexation. In this work, a bioconjugate of streptokinase and a polyglycerol dendrimer (PGLD) generation 5 was used to obtain fibrinolytic surfaces. The PGLD dendrimer was synthesized by the ring opening polymerization of deprotonated glycidol using polyglycerol as core functionality in a step-growth processes denominated divergent synthesis. The PGLD dendritic structure was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (1H-NMR, 13C-NMR) and matrix assisted laser desorption/ionization (MALDI-TOF) techniques. The synthesized dendrimer presented low dispersion in molecular weights (Mw/Mn = 1.05) and a degree of branching of 0.82 which characterize the polymer dendritic structure. The blood compatibility of the bioconjugate PGLD-Sk was evaluated by in vitro assays such as platelet adhesion and thrombus formation. Uncoated polystyrene –microtitre plates (ELISA) was used as reference. The epifluorescence microscopy results indicate that PGLD-Sk coating showed an improved antithrombogenic character relative to the uncoated ELISA plates.

Galectins as immunoregulators during infectious processes: from microbial invasion to the resolution of the disease Rabinovich, Gabriel Adrián; Gruppi, Adriana Recent evidence has implicated galectins, a family of evolutionarily conserved carbohydrate-binding proteins, as regulators of immune cell homeostasis and host-pathogen interactions. Galectins operate at different levels of innate and adaptive immune responses, by modulating cell survival and cell activation or by influencing the Th1/Th2 cytokine balance. Furthermore, galectins may contribute to host-pathogen recognition and may serve as receptors for specific interactions of pathogens with their insect vectors. Here we will explore the influence of galectins in immunological processes relevant to microbial infection and will summarize exciting recent work related to the specific interactions between galectins and their glycoconjugate ligands as critical determinants of pathogen recognition. Understanding the role of galectin-sugar interactions during the course of microbial infections might contribute to defining novel targets for disease prevention and immune intervention.

Compressional and shear wave velocities in uncemented sediment containing gas hydrate Yun, Tae Sup; Francisca, Franco Matias; Santamarina, J. Carlos; Ruppel, Carola The competing hypotheses for gas hydrate formation at the particle scale in sediments describe processes of pore-filling, frame-building, or cementation. New measurements of compressional (VP) and shear wave (VS) velocities in fine-grained sands subjected to low confinement and monitored during formation of tetrahydrofuran hydrate indicate that hydrate nucleates in the pore space (presumably at grain boundaries) and grows with limited impact on the sediment shear stiffness, VP, and VS until crystals begin to interact with the granular skeleton at ∼40% hydrate concentration. VS increases significantly more than VP at higher hydrate concentrations, reflecting larger changes in the specimen's shear stiffness than its bulk stiffness. The results indicate that seismic velocities and/or their ratio (VP/VS) have limited capability for locating hydrate or constraining hydrate concentrations.

Rendimiento de la técnica de enjambrado artificial como alternativa para el control de Loque Americana Albo, Graciela Noemí; Reynaldi, Francisco José; Casanova, Luciana; Dimenna, S. E. La loque americana (LA) una enfermedad causada por la bacteria esporulada Paenibacillus larvae subsp. larvae  que se encuentra ampliamente distribuida tanto a nivel mundial  como en Argentina. Los objetivos del presente trabajo fueron: 1- Evaluar el rendimiento de la técnica de enjambrado artificial en otoño, con y sin el agregado de antibióticos, a través de la medición porcentual de recurrencia de la enfermedad y la muerte de colonias. 2- Determinar el gasto de alimento artificial (energético y proteico) para obtener un  desarrollo satisfactorio del paquete. La técnica de enjambrado artificial sólo resulta exitosa con el uso de antibiítico lueo del paqueteado en colmenas con una infección sobre la cría no mayor a grado 2 y con una población de abejas adultas no inferior a nivel 2. El porcentaje de recurrencia  es del 1%.

Effects of pH and ionic strength on the adsorption of phosphate and arsenate at the goethite-water interface Antelo, Juan; Avena, Marcelo Javier; Fiol, Sarah; López, Rocío; Arce, Florencio The surface properties of a well-crystallized synthetic goethite have been studied by acid-base potentiometric titrations, electrophoresis, and phosphate and arsenate adsorption isotherms at different pH and electrolyte concentrations. The PZC and IEP of the studied goethite were 9.3±0.1 and 9.3±0.2, respectively. Phosphate and arsenate adsorption decrease as the pH increases in either 0.1 or 0.01 M KNO3 solutions. Phosphate adsorption is more sensitive to changes in pH and ionic strength than that of arsenate. The combined effects of pH and ionic strength result in higher phosphate adsorption in acidic media at most ionic strengths, but result in lower phosphate adsorption in basic media and low ionic strengths. The CD-MUSIC model yields rather good fit of the experimental data. For phosphate it was necessary to postulate the presence of three inner-sphere surface complexes (monodentate nonprotonated, bidentate nonprotonated, and bidentate protonated). In contrast, arsenate could be well described by postulating only the presence of the two bidenate species. A small improvement of the arsenate adsorption data could be achieved by assuming the presence of a monodentate protonated species. Model predictions are in agreement with spectroscopic evidence, which suggest, especially for the case of arsenate, that mainly bidentate inner-sphere complexes are formed at the goethite-water interface.

Increased Monooxygenase Activity Associated with Resistance to Permethrin in Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina Gonzalez Audino, Paola Andrea; Barrios, S.; Vassena, Claudia Viviana; Mougabure Cueto, Gastón Adolfo; Zerba, Eduardo Nicolás; Picollo, Maria Ines We studied the profile of permethrin resistance in head lice populations infesting children 6-12 years old in schools and children´s homes in & around Buenos Aires, Argentina. Five permethrin resistant populations with different levels of resistance -Hogar Loyola (HL), Republica de Turquia (RT), Hogar Mitre (HM), Guardia de Honor (GH), Ricardo Guiraldes (RG)- and one susceptible population, Bandera Argentina (BA) were collected. Their level of resistance was evaluated and results showed resistance ratios (RR) of 13 for HL, 16 for RT, 22 for HM, 61 for GH and 69 for RG. In order to elucidate the possible involvement of the cytochrome P450 monooxygenase system in conferring permethrin resistance, ethoxycoumarin-O-deethylase (ECOD) activity was measured in abdomens of individual third instar nymphs and adults using a fluorometric assay.  The ECOD activity was lower in the susceptible BA population (4.7 ng/insect) than in the resistant ones (13.7 ng/insect for RG, 12.3 ng/insect for GH, 8.6 ng/insect for RT, 8.2 ng/insect for HL). ECOD activity was significantly correlated with the level of resistance in the field populations (r= 0.97, p=0.0009) suggesting a role for cytochrome monooxygenase P450 system in permethrin resistance by P. humanus capitis.

Sorghum kernel weight: Growth patterns from different positions within the panicle Gambin, Brenda Laura; Borras, Lucas The influence of genotype and panicle position on sorghum [Sorghum bicolor (L.) Moench] kernel growth is poorly understood. In the present study, sorghum kernel weight (KW) differences during grain filling were analyzed by kernel water relationships previously described in other crops. Eight commercial genotypes differing in KW were used, and KW, water content, kernel volume, kernel moisture content, and kernel density were measured in two positions within the panicle (apical and basal) throughout the grain-filling period. At physiological maturity (PM), KW ranged from 16.5 to 25.1 mg kernel-1, and a significant (p < 0.05) genotype x position interaction was detected. Independently of final KW, apical kernels always exhibited a higher rate (p < 0.001) and a shorter duration of grain filling (p < 0.001) than basal kernels. Maximum water content was related to kernel growth rate but not to final KW. Basal kernels reached maximum kernel volume after attaining maximum water content, with dry matter accumulation affecting kernel volume determination. Kernel density increased with a similar pattern regardless of genotype or panicle position when related to the kernel moisture decline, but at PM, basal kernels were always more dense than apical ones. Differences in the kernel desiccation pattern and in the critical moisture content for biomass accumulation helped explain differences in the grain-filling duration between positions. A general kernel growth curve based on kernel moisture content was impossible to obtain because of the differences in kernel growth patterns within the panicle.

Acerca de la inevitabilidad de la interpretación jurídica Navarro, Pablo Eugenio El objetivo principal de este trabajo es clarificar y refutar la tesis de la indeterminacion interpetativa (TI). Sin embargo, este trabajo no pretende ofrecer un argumento definitivo contra ninguna escuela o doctrina particular, sino que trata de iluminar rasgos del derecho que han sido indebidamente pasados por alto o que han sido descuidados en el debate contemporáneo. En gran medida, TI parece plausible por la ambigüedad sistemática en que son utilizadas algunas de las principales expresiones en cuestión, i.e., ?caso?, ?norma general?, norma ?individual?, etc. Una vez que se despejan las confusiones que subyacen a TI también es posible advertir por qué razón es frecuente considerar imprescindible a la interpretación de las normas jurídicas, y en qué sentido TI es una exageración de otras ideas valiosas para el análisis de la identificación y aplicación del derecho

New Steiglitz-Mcbride adaptive lattice notch filters Cousseau, Juan Edmundo; Scoppa, Juan P.; Doñate, Pedro Darío Two novel adaptive notch filters are presented. The updating algorithms are based on the Steiglitz-McBride error criterion minimization and the basic realizations of the notch filters are all-pass based lattice filters. The proposed realizations represent an extension of a previous ad-hoc scheme for adaptive notch filtering and avoid finding the roots of a high order polynomial to obtain the unknown frequencies of interest. Since the structure is based on the lattice realization, suitable properties with finite length precision realizations can be expected. Computer simulations are included to verify the adaptive filter performance when compared with alternative realizations.

A mathematical model for zoning of protected natural areas Verdiell, Adriana Beatriz; Sabatini, M.; Maciel, Maria Cristina; Rodríguez Iglesias, Ricardo Manuel When formulated in mathematical terms, the problem of zoning a protected natural area subject to both box and spatial constraints results in a combinatorial optimization problem belonging to the NP-hard class. This fact and the usual dimension of the problem (regularly in the tens of thousands order) suggest the need to apply a heuristic approach. In this contribution we describe a quantitative method for zoning protected natural areas based on a simulated annealing algorithm. Building upon previous work by Bos (1993), we introduce three main innovations (a quadratic function of distance between land units, a non-symmetric matrix of compatibilities among uses, and a spatial connection constraint) that make the approach applicable for ecological purposes. When applied to solving small-size simulated problems, the results were indistinguishable from those obtained via an exact, enumerative method. A coarse-scale zoning of Talampaya National Park (Argentina) rendered maps remarkably similar to those produced by subject area experts using a non-quantitative consensus-seeking approach. Results are encouraging and show particular potential for the periodical update of zoning of protected natural areas. Such a capability is crucial for application in developing countries where both human and financial resources are usually scarce but still critical for updating zoning and management plans.

Interaction of catechol and gallic acid with titanium dioxide in aqueous suspensions. 1. Equilibrium studies Araujo, Paula Zulema; Morando, Pedro Juan; Blesa, Miguel Angel The adsorption isotherms of catechol (1,2-dihydroxybenzene) and gallic acid (3,4,5-trihydroxybenzoic acid) onto titanium dioxide (Degussa P-25) were measured at various pH values and room temperature using attenuated total reflection Fourier transform infrared (FTIR-ATR) data, processed by singular value decomposition. The affinity is largely pH independent, although the deprotonatation of the carboxylic group in gallic acid might produce a slight increase in the affinity. Catechol was shown to form two complexes, with Langmuir stability constants log K of 4.66 (strong mode) and 3.65 (weak mode). Both complexes have the same spectral signature, and mononuclear and binuclear chelate structures are proposed for them. Gallic acid chemisorbs by complexation through two -OH groups and forms one complex only, log K= 4.70. The third -OH and the pendant carboxylate do not influence much the stability of the surface complex. Comparison with literature data demonstrates that the affinity of 4-chlorocatechol is also similar, whereas 2,3-dihidroxynaphthalene and 4-nitrocatechol form more stable complexes, probably because of the solvation contribution to the overall Gibbs adsorption energy. All quoted constants refer to the surface complexation equilibria written as follows: (≡Ti-OH) 2 + H2L = (≡Ti)2-L + 2H2O, i.e., as electroneutral processes. The FTIR-ATR spectra of the surface complexes are also discussed. © 2005 American Chemical Society.

A constitutive equation and generalized Gassmann modulus for multimineral porous media Carcione, Jose M.; Helle, Hans B.; Santos, Juan Enrique; Ravazzoli, Claudia Leonor We derive the time-domain stress-strain relation for a porous medium composed of n - 1 solid frames and a saturating fluid. The relation holds for nonuniform porosity and can be used for numerical simulation of wave propagation. The strain-energy density can be expressed in such a way that the two phases (solid and fluid) can be mathematically equivalent. From this simplified expression of strain energy, we analogize two-, three-, and n-phase porous media and obtain the corresponding coefficients (stiffnesses). Moreover, we obtain an approx imation for the generalized Gassmann modulus. The Gassmann modulus is the bulk modulus of a saturated porous medium whose matrix (frame) is homogeneous. That is, the medium consists of two homogeneous constituents: a mineral composing the frame and a fluid. Gassmann's modulus is obtained at the low-frequency limit of Biot's theory of poroelasticity. Here, we assume that all constituents move in phase, a condition similar to the dynamic compatibility condition used by Biot, by which the P-wave velocity is equal to Gassmann's velocity at all frequencies. Our results are compared with those of the Berryman-Milton (BM) model, which provides an exact generalization of Gassmann's modulus to the three-phase case. The model is then compared to the wet-rock moduli obtained by static finite-element simulations on digitized images of microstructure and is used to fit experimental data for shaly sandstones. Finally, an example of a multimineral rock (n > 3) saturated with different fluids is given.