Un sistema de apoyo a la decisión en la gestión logística de una PYME Casal, Ricardo Nestor; Frutos, Mariano; Claverie, Agustín En este articulo se presenta un sistema de apoyo a la decisión (SAD) para solucionar los complejos problemas logísticos en empresas can servicio de reparto. Este sistema optimiza un modelo que refleja una situación en la que los clientes se agrupan por clusters, de forma que todas las rutas que sirven a un mismo grupo deban ser finalizarse antes de un instante de tiempo prefijado, sin sobrepasar el ciclo de distribución predeterminado, abasteciendo en cada viaje una cantidad mínima de pedidos y evitando la sobrecarga del vehículo. El objetivo que se plantea es minimizar la distancia total recorrida supeditada alas restricciones indicadas. Este sistema utiliza un enfoque no convencional de procesamiento y aprovecha las utilidades del ordenador para que el algoritmo de búsqueda sea mas eficiente. Par ultimo, se presenta una aplicación practica del sistema anterior que se utilizó en la gestión de la logística de distribución de productos perecederos de una empresa de la zona.; In this paper a decision support system (SAD) to solve complex logistic problems in companies with delivery services is presented. This system optimizes a model that represents a situation in which customers are grouped by Clusters, in a way that all the routes used for a certain group must be completed before a certain predefined moment, without exceeding the predefined distribution cycle, supplying in every trip a certain minimum amount of orders and without overloading the vehicle. The objective is to minimize the total traveled distance under the mentioned restrictions. This system uses a non conventional processing approach and takes advantage of the computer utilities so as to make the search algorithm more efficient. Finally, a practical application of the mentioned system, that was used in the distribution logistic management of perishable products in a regional company, is shown.

Reflexiones en torno a la cultura en América Latina Perilli, Carmen Noemi La descolonización de la cultura latinoamericana supone la revisión de los múltiples relatos tejidos alrededor de la identidad del continente, identidad entendida como esencia. Desde antes de la Conquista La Letra proyectó una imagen virtual del Nuevo Mundo. Las representación estuvo signada por la alteridad del objeto, en relación a un sujeto que lo definía desde fuera.

Stainless Steels Can Be Cathodically Protected Using Energy Stored at the Marine Sediment/Seawater Interface Orfei, Leda Hilen; Simison, Silvia Noemi; Busalmen, Juan Pablo Laboratory-scale experiments were performed in which the corrosion protection of stainless steels in seawater was afforded by cathodic protection. The method was implemented for the first time using the potential difference at the marine sediment/seawater interface as the only source of electric power. Graphite electrodes buried in marine sediment, developing a potential of -0.45 V versus a saturated calomel electrode (SCE), were used as anodes to cathodically polarize UNS S30403 stainless steel coupons that were exposed to seawater. The cathodic protection system was operated with low polarization of stainless steel, typically to -0.2 V (vs SCE) and was found to properly prevent material failure even in the presence of a well-developed biofilm. With voltammetry, the protection current was found to be related to the oxidation of reduced sulfur compounds in the sediments. Results demonstrate that this inexpensive and environmentally friendly method can, so far, extend the service life of stainless steels in seawater.

Thermostatistical description of gas mixtures from space partitions Rohrmann, Rene Daniel; Zorec, J. The new mathematical framework based on the free energy of pure classical fluids presented by Rohrmann is extended to multicomponent systems to determine thermodynamic and structural properties of chemically complex fluids. Presently, the theory focuses on D -dimensional mixtures in the low-density limit (packing factor Ε<0.01). The formalism combines the free-energy minimization technique with space partitions that assign an available volume v to each particle. v is related to the closeness of the nearest neighbor and provides a useful tool to evaluate the perturbations experimented by particles in a fluid. The theory shows a close relationship between statistical geometry and statistical mechanics. New, unconventional thermodynamic variables and mathematical identities are derived as a result of the space division. Thermodynamic potentials Iil, conjugate variable of the populations Nil of particles class i with the nearest neighbors of class l are defined and their relationships with the usual chemical potentials I i are established. Systems of hard spheres are treated as illustrative examples and their thermodynamics functions are derived analytically. The low-density expressions obtained agree nicely with those of scaled-particle theory and Percus-Yevick approximation. Several pair distribution functions are introduced and evaluated. Analytical expressions are also presented for hard spheres with attractive forces due to Kac-tails and square-well potentials. Finally, we derive general chemical equilibrium conditions.

Creaming stability of oil in water (O/W) emulsions: Influence of pH on soybean protein–lecithin interaction Comas, D. I.; Wagner, Jorge Ricardo; Tomás, Mabel Cristina In the present work, the influence of pH on stability of oil in water O/W (25:75 w/w) emulsions prepared with soy isolates and lecithin (Lec) was studied. Emulsions were prepared using native (NSI) and denatured (DSI) soybean isolates, Lec and sunflower oil, with a protein–Lec ratio of 10:1. Dispersions of soybean proteins were adjusted to pH 2.0–6.2. Emulsions were optically characterized by droplet size distribution and using a vertical scan analyzer (Quick Scan) to determine the creaming destabilization and the corresponding kinetics involved. At pH 2, a negative effect was observed on droplet size distribution and stability of Lec emulsion. Changes in droplet size and creaming rate as a function of pH value were observed for NSI–Lec and DSI–Lec emulsions in comparison with their corresponding control systems (Lec, NSI, DSI). NSI–Lec emulsions at pH 2.0 presented an important initial emulsifying activity, but the creaming rate recorded was faster than that corresponding to pH 5.5–6.2. For DSI–Lec systems, the stability increased at pH 2.0 and 6.2, values away from the isoelectric point. The presence of Lec enhanced both the initial characteristics reflected in BS0 and droplet size, and the stability against the creaming process.

Lactobacillus delbrueckii subsp lactis strain CIDCA 133 inhibits nitrate reductase activity of Escherichia coli Hugo, Ayelen Amelia; de Antoni, Graciela Liliana; Perez, Pablo Fernando The aim of the present work was to investigate the effect of strain CIDCA 133 on the nitrate reductase activity of a non-pathogenic Escherichia coli strain. Suspensions containing different ratios of the strains under study were coincubated in MRS or MRS without glucose. In some experiments lactobacilli were killed by UV treatment. The nitrate reductase activity was determined by using a diazotization reaction for nitrite. Presence of live lactobacilli leads to a dose–response diminution in the specific nitrate reductase of E. coli even when no acidification occurred. Killing of lactobacilli by UV treatment completely abolished the anti-nitrate reductase effect. In addition, the effect was only partially observed with filtered spent culture supernatants of lactobacilli. Lactobacillus delbrueckii subsp lactis strain CIDCA 133 is able to antagonize the nitrate reductase activity of E. coli. This effect is neither due to a diminution of the viability of E. coli nor is depending on the acidification of the medium by the lactobacilli. Viability is needed for maximal anti-nitrate reductase activity. Modulation of undesirable enzymatic activities of intestinal microorganisms by means of selected microorganisms constitutes a further insight on the mechanisms by which probiotics lead to beneficial effects. Administration of probiotic strains able to modulate microbial intestinal activities could lead to a protection of the host against harmful effects of some members of the intestinal microflora.

Physicochemical, Water Vapor Barrier and Mechanical Properties of Corn Starch and Chitosan Composite Films Garcia, Maria Alejandra; Pinotti, Adriana Noemi; Zaritzky, Noemi Elisabet Biodegradable flexible films were developed from corn starch (CS) and chitosan (CH); their microstructure, mechanical and barrier properties were evaluated. Chitosan and starch blend filmogenic suspensions showed a pseudoplastic behavior, similar to that of chitosan solutions. Smooth surfaces, homogeneous and compact film structures were observed from microstructure studies using scanning electron microscopy (SEM). The addition of glycerol reduced film opacity and increased film solubility of both CS and composite CS‐CH films. Water vapor permeability values of composite CS‐CH films plasticized with glycerol ranged between 3.76 and 4.54× 10−11 g s−1 m−1 Pa−1, lower than those of the single component films. CS‐CH films were resistant and their flexibility increased with glycerol addition. Tensile strength values of CS‐CH films were comparable to those of low‐density and high‐density polyethylenes but lower than that obtained for cellophane, however, composite biodegradable films showed lower elongation at break values than the synthetic commercial ones. In conclusion, CS‐CH films can be described as biofilms with a homogeneous matrix, stable structure and interesting water barrier and mechanical properties, with great possibilities of utilization, and with the advantage of biodegradability.

Shooting control in Eucalyptus Grandis x E. urophylla hybrid: Comparative effects of 28-homocastasterone and a 5α-monofluoro derivative Pereira Netto, Adaucto B.; Carvalho Oliveira, M.M.C.; Ramirez, Javier Alberto; Galagovsky, Lydia Raquel 28-Homocastasterone (28-HCTS), a brassinosteroid, was used to treat in vitro-grown shoots of a hybrid between Eucalyptus grandis and E. urophylla. Treated shoots showed enhanced elongation and formation of new main shoots (the shoots originating directly from the initial explant) at low doses. Coincidently, there was reduced elongation and formation of primary lateral shoots (shoots originating from the main shoot). However, a 5α-monofluoro derivative of 28-HCTS (5F-HCTS) was unable to either stimulate elongation or formation of new main shoots, although it did stimulate elongation of primary lateral shoots. In conclusion, it is quite apparent that exogenously supplied brassinosteroids are able to change shooting patterns in Eucalyptus. These findings have practical biotechnological applications, for example on the improvement of micropropagation techniques for clonal propagation of woody angiosperms. © Springer Science+Business Media B.V. 2006.

Xylene isomerization in a membrane reactor. Part I: The synthesis of MFI membranes for the p-xylene separation Tarditi, Ana Maria; Irusta, Silvia; Lombardo, Eduardo Agustin The synthesis and characterization of silicalite and ZSM-5 films supported on porous SS tubes are described. Composite membranes were used to separate xylene isomers between 150 and 400 °C. Permeation measurements of the individual isomers and the ternary mixture were performed at each temperature within this interval. N2 permeation measurements together with SEM observations were used to determine whether or not cracks and/or pinholes developed after exposure to the xylene isomers at high temperature. The ZSM-5 membrane was superior to the silicalite one because of its higher permeance flux (1.16 × 10-5 mol s-1 m-2), separation factors (p/o 4.4), and up to 400 °C stability.

Selective migration and engraftment of bone marrow mesenchymal stem cells in rat lumbar dorsal root ganglia after sciatic nerve constriction Coronel, Maria Florencia; Musolino, Patricia Leonor; Villar, Marcelo José Bone marrow mesenchymal stem cells (MSCs) preferentially migrate to the injured hemisphere when administered intravenously to rats with traumatic or ischemic brain injuries. In this study, we have investigated the localization of MSCs injected into the lumbar-4 dorsal root ganglion (L4-DRG) of rats with a sciatic nerve single ligature nerve constriction (SLNC). MSCs were isolated by their adherence to plastic, cultured until confluence and labelled with Hoechst. Animals with a unilateral injection of MSCs were subjected to an ipsilateral, bilateral or contralateral SLNC. After 9 days, they were perfused and the lumbar DRGs were dissected out, cut in a cryostat and observed with a fluorescence microscope. Large numbers of Hoechst-positive cells were observed in the injected L4-DRG, distributed around primary afferent neurons, resembling the anatomical localization of glial cells. In animals with an ipsilateral SLNC, some cells were detected in the ipsilateral L3, L5 or L6-DRGs but not in the contralateral ganglia. In animals with a bilateral lesion, MSCs migrated to both the ipsilateral and contralateral DRGs whereas in animals with a contralateral ligature, MSCs migrated to the contralateral DRGs. These results suggest that MSCs preferentially engraft in DRGs hosting primary sensory neurons affected by a lesion of their peripheral branches. Further studies should be carried out in order to elucidate the molecular mechanisms involved in this migration and homing, in order to evaluate the possible use of MSCs as a new therapeutic strategy for the treatment of peripheral nerve neuropathies.

Photoinduced electron-transfer α-deoxygenation of aldonolactones. Efficient synthesis of 2-deoxy-d-arabino-hexono-1,4-lactone Bordoni, Andrea Veronica; Muchnik, Rosa; Marino, María Carla A photoinduced electron-transfer (PET) reaction was used for the deoxygenation at C-2 of aldonolactones derivatized as 2-O-[3-(trifluoromethyl)benzoyl] or benzoyl esters. By irradiation of different D-galactono- and D-glucono-1,4-derivatives, with a 450 W lamp, using 9-methylcarbazole as photosensitizer, the corresponding 2-deoxy-D-lyxo- and 2-deoxy-D-arabino-hexono-1,4-lactones were efficiently obtained.O-[3-(trifluoromethyl)benzoyl] or benzoyl esters. By irradiation of different D-galactono- and D-glucono-1,4-derivatives, with a 450 W lamp, using 9-methylcarbazole as photosensitizer, the corresponding 2-deoxy-D-lyxo- and 2-deoxy-D-arabino-hexono-1,4-lactones were efficiently obtained.D-lyxo- and 2-deoxy-D-arabino-hexono-1,4-lactones were efficiently obtained.

Sex-related differences in the gastrointestinal disposition of ivermectin in the rat: P-glycoprotein involvement and itraconazole modulation Lifschitz, Adrian Luis; Ballent, Mariana; Virkel, Guillermo Leon; Sallovitz, Juan Manuel; Lanusse, Carlos Edmundo Ivermectin (IVM), a macrocyclic lactone used as antiparasite agent, has been reported as a P‐glycoprotein (P‐gp) substrate. The participation of P‐gp in the IVM excretion process has been previously demonstrated. Sex‐related differences in the kinetic behaviour of some macrocyclic lactone compounds have been observed. The aim of this work was to characterize in‐vivo the comparative gastrointestinal disposition of IVM in male and female rats. The sex‐related influence on the itraconazole (ITZ) modulation of P‐gp‐mediated IVM intestinal transport was also assessed. Sixty Wistar rats (30 male, 30 female) received IVM alone or co‐administered with ITZ. Rats were killed between 6 and 72h after treatment and blood, gastrointestinal tissues and lumen contents were collected. IVM concentrations were determined by high performance liquid chromatography. Substantial sex‐related differences in the IVM disposition kinetics were observed. Higher IVM systemic availability was observed in female rats. The ITZ‐mediated modulation of the IVM disposition kinetics had a differential impact between male and female rats. Co‐administration with ITZ resulted in a marked increase in the IVM concentrations in the wall tissue from different portions of the gastrointestinal tract of male rats. The presence of ITZ induced drastic sex‐related changes on the P‐gp‐mediated IVM gastrointestinal disposition.

Age and growth in Odontocymbiola magellanica (Gastropoda: Volutidae) from Golfo Nuevo, Patagonia, Argentina Bigatti, Gregorio; Penchaszadeh, Pablo Enrique; Cledón, Maximiliano Growth, age and somatic production of the benthic predator Odontocymbiola magellanica were studied in Golfo Nuevo (42S 65W), on the South American Atlantic shelf. Stable oxygen isotope ratios confirmed semiannual formation of internal and external shell growth marks. Mean shell length (SL) of females was 115 and 112 mm for males, while population modal shell-free wet mass (SFWM) was 62.8 g. A Gompertz growth function (SL¥ = 200 mm, K = 0.197, t0 = 5.486) fitted 113 pairs of size-at-age data (12 shells) best. O. magellanica is a long-lived species, reaching up to 20 years of age. The maximum individual somatic production of 29.3 g SFWM per year is attained at 145 mm SL, which corresponds to about 12 years of age. The life span of this volutid seems to be twice compared with other large gastropods. O. magellanica is a valuable and exploitable resource regarding its large size and somatic production, but on the other hand, its slow growth, late maturity and direct development makes it extremely vulnerable to overexploitation.Growth, age and somatic production of the benthic predator Odontocymbiola magellanica were studied in Golfo Nuevo (42S 65W), on the South American Atlantic shelf. Stable oxygen isotope ratios confirmed semiannual formation of internal and external shell growth marks. Mean shell length (SL) of females was 115 and 112 mm for males, while population modal shell-free wet mass (SFWM) was 62.8 g. A Gompertz growth function (SL¥ = 200 mm, K = 0.197, t0 = 5.486) fitted 113 pairs of size-at-age data (12 shells) best. O. magellanica is a long-lived species, reaching up to 20 years of age. The maximum individual somatic production of 29.3 g SFWM per year is attained at 145 mm SL, which corresponds to about 12 years of age. The life span of this volutid seems to be twice compared with other large gastropods. O. magellanica is a valuable and exploitable resource regarding its large size and somatic production, but on the other hand, its slow growth, late maturity and direct development makes it extremely vulnerable to overexploitation.

Kinetics of phosphate adsorption on goethite: Comparing batch adsorption and ATR-IR measurements Luengo, Carina Vanesa; Brigante, Maximiliano Eduardo; Antelo, Juan; Avena, Marcelo Javier The adsorption kinetics of phosphate on goethite has been studied by batch adsorption experiments and by in situ ATR-IR spectroscopy at different pH, initial phosphate concentrations and stirring rates. Batch adsorption results are very similar to those reported by several authors, and show a rather fast initial adsorption taking place in a few minutes followed by a slower process taking place in days or weeks. The adsorption kinetics could be also monitored by integrating the phosphate signals obtained in ATR-IR experiments, and a very good agreement between both techniques was found. At pH 4.5 two surface complexes, the bidentate nonprotonated (FeO)2PO2 and the bidentate protonated (FeO)2(OH)PO complexes, are formed at the surface. There are small changes in the relative concentrations of these species as the reaction proceeds, and they seem to evolve in time rather independently. At pH 7.5 and 9 the dominating surface species is (FeO)2PO2, which is accompanied by an extra unidentified species at low concentration. They also seem to evolve independently as the reaction proceeds. The results are consistent with a mechanism that involve a fast adsorption followed by a slow diffusion into pores, and are not consistent with surface precipitation of iron phosphate.

Non-interacting dimer kinetics in hypercubic lattices Costanza, Gregorio José; Manzi, Sergio Javier; Pereyra, Victor Daniel The exact formulation of the kinetic of dimer in hypercubic lattices is developed in the framework of the kinetic lattice gas model. The so-called local evolution rules are used to obtain the hierarchy of equation of motion for the correlation functions where processes like adsorption and desorption are included. The hierarchy of equations are truncated using a mean field (m, n) closures which allows the analytical treatment of the system. A general expression for non-interacting dimer isotherm and two particle correlation functions are obtained in hypercubic lattices.

Photoisomerization of Azobenzenes and Spirocompounds in Nematic and in Twisted Nematic Liquid Crystals Bossi, Mariano Luis; Murgida, Daniel Horacio; Aramendia, Pedro Francisco Samples of a nematic mixture of ZLI1132 and of a twisted nematic mixture composed of ZLI1132 and chiral inductor S811, including 1%-10% (w/w) 4-N,N-dimethylaminoazobenzene (DAB), (4′-nitro)-4-N,Ndimethylaminoazobenzene (NDAB), spiropyran (SP), or spirooxazine (SO) were irradiated to produce the photochromic transformation of the dopant. The changes in the system were monitored by time-resolved transmission spectroscopy, time-resolved birefringence, or polarized Raman scattering. The medium sensitivity of the kinetics and spectroscopy of some of the probes was used to derive information on polarity of the medium. In the systems studied, apart from the changes in absorption spectrum, great changes in birefringence can be photoinduced and the order of the nematic phase can be changed in either direction, depending on the dopant. The open form of SP can discriminate orientation polarity. Although the polarity parallel to the mesogenic director is similar to that for acetone, the perpendicular orientation has a polarity similar to acetonitrile. In agreement with this observation, the kinetics of the Z f E isomerization of NDAB, oriented parallel to the mesogenic director, also experiences a polarity similar to that for acetone. The decay rate constant of the open form of SP displays a linear relationship between its Arrhenius parameters, which is universal in a great variety of homogeneous solvents, solvent mixtures, and liquid crystals, therefore validating the hypothesis that the same type of transformation is observed in all these cases, namely, the decay of the open form monomer. The dopants used have been proven to be adequate probes of bulklike properties in locally heterogeneous systems as liquid crystals.

Sea quark polarization and semi-inclusive DIS data Jiang, X.; Navarro, Gabriela Alejandra; Sassot, Rodolfo We investigate the potential impact of forthcoming Jefferson Lab semi-inclusive polarized deep inelastic scattering proton measurements in the determination of the sea quark polarization in the nucleons by means of a next to leading order global QCD analysis. Specifically, we estimate the resulting improvement in the constraints on polarized parton densities for different flavors, which is found to be significant for up and strange quarks, and the correlation between remaining uncertainty ranges for each of the parton species.

Spin-charge separation and topological phase transitions in Aharonov-Bohm rings of interacting electrons Normand, B.; Hallberg, Karen Astrid; Aligia, Armando Ángel; Kampf, A. P. We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain flux values, determined by the filling, which are a consequence of spin-charge separation in a nanoscopic system. The conductance through such a molecule or nanodevice is related directly to its spectroscopic properties, opening new experimental possibilities for probing the phenomenology of strongly interacting systems. As a further example, for a ring described by the half-filled ionic Hubbard model we show that the weight of the first conductance peak as a function of gate voltage or external flux allows one to identify the topological charge transition between a correlated insulator and a band insulator.

High level expression of bioactive recombinant human growth hormone in the milk of a cloned transgenic cow Salamone, Daniel Felipe; Barañao, Jose Lino Salvador; Santos, Claudio; Bussmann, Leonardo Edmundo; Artuso, Jorge; Werning, Carlos; Prync, Aida; Carbonetto, Cesar; Dabsys, Susana; Munar, Carlos; Salaberry R; Berra, Guillermo; Berra, Ignacio; Fernández, Nahuel; Papouchado, Mariana; Foti, Marcelo; Judewicz, Norberto; Mujica, Ignacio; Muñoz, Luciana; Fernandez Alvarez, Silvina; González, Eliseo; Zimmermann, Juan; Criscuolo, Marcelo; Melo, Carlos Transgenic farm animals have been proposed as an alternative to current bioreactors for large scale production of biopharmaceuticals. However, the efficiency of both methods in the production of the same protein has not yet been established. Here we report the production of recombinant human growth hormone (hGH) in the milk of a cloned transgenic cow at levels of up to 5 g l(-1). The hormone is identical to that currently produced by expression in E. coli. In addition, the hematological and somatometric parameters of the cloned transgenic cow are within the normal range for the breed and it is fertile and capable of producing normal offspring. These results demonstrate that transgenic cattle can be used as a cost-effective alternative for the production of this hormone.

24-hour rhythms of splenic mitogenic responses, lymphocyte subset populations and interferon γ release after calorie restriction or social isolation of rats Cano, Pilar; Cardinali, Daniel Pedro; Fernández, Pilar; Reyes Toso, Carlos Felipe To assess the effect of calorie restriction equivalent to a 66% food restriction or social isolation on splenic immune responses, calorie-restricted five week-old male Wistar rats, pair fed controls individually caged and pair fed controls caged in groups, were studied for four weeks. Calorie restricted and isolated rats showed increased splenic concanavalin A response with peak activity during the activity span. Mean 24 h values of splenic lipopolysaccharide response decreased in isolated rats compared to grouped rats. The highest values of T cells occurred in calorie restricted rats and those of B cells in isolated rats. Mean values of splenic CD4+ and CD8+ cells augmented in isolated or calorie restricted groups. The highest in vitro interferon-gamma production occurred in the isolated group and the lowest in the grouped rats, the differences among groups being significant. Both experimental procedures generally disrupted 24-h rhythmicity of splenic immune parameters. Mean values of plasma corticosterone were higher in calorie restricted rats than in isolated rats and both differed significantly from grouped rats. The results indicate that either calorie restriction or social isolation augmented cell-mediated immunity in rat spleen.