Photophysics of anthracene–indole systems in unilamellar vesicles of DMPC and POPC: Exciplex formation and temperature effects Novaira, Ana Ines; Previtali, Carlos Mario The quenching of anthracene fluorescence by indole (IN), 1,2-dimethylindole (DMI), tryptophan (Trp) and indole 3-acetic acid (IAA) in dimiristoylphophatidylcholine (DMPC) and palmitoyloleoylphosphatidylcholine (POPC) lipid bilayers was investigated. The studies were carried out at 25 ºC in POPC vesicles and below (15 C) and above (35 C) the phase transition temperature (24 ºC) of DMPC. A very efficient quenching of the anthracene fluorescence by IN and DMI in the lipid membrane is observed in all cases. It is less efficient in the case of Trp and IAA. Stern–Volmer plots are linear for DMI but present a downward curvature for the other quenchers. This was interpreted as an indication of the presence of an inaccessible fraction of anthracene molecules. By a modified Stern–Volmer analysis the fraction accessible to the quenchers and the quenching constant were determined. Partition constants of the quenchers were obtained from the changes in the fluorescence emission of the indole moiety caused by the presence of the phospholipid. Using the partition constants bimolecular quenching rate constants were determined in terms of the local concentration of quencher in the lipid bilayer. These corrected rate constants are lower than those in homogeneous solvents. In the case of DMPC values the gel phase are higher than in the liquid-crystalline phase. In the quenching by IN and DMI a new, red shifted, emission band appears which could be assigned to an exciplex emission. The exciplex band is absent in the quenching by IAA and Trp.

Impact on growth and aflatoxin B1 accumulation by Kluyveromyces isolates at different water activity conditions La Penna, Mariángeles; Etcheverry, Miriam Graciela This study showed the impact on germination, mycelial growth and aflatoxin B1 accumulation when interacting Aspergillus aflatoxigenic strains with Kluyveromyces isolates and the effect of water activity on this relationship. Isolates Y14 and Y16 reduced the percentage of germination of all Aspergillus strains and decrease germ tube elongation rate at majority of water activity assayed. Similarly they produced an increase of germination lag phase and lag phase of growth beside decreased growth rate of all Aspergillus strains. At water activities 0.994, 0.982, 0.955 and 0.937, no aflatoxins were produced in paired cultures with isolates Y25, Y22, Y16, and Y14, and Kluyveromyces isolates Y14 and Y16 impact both growth and aflatoxin accumulation at wide range of water activity.

Monte Carlo simulation of metal deposition on foreign substrates Giménez, María Cecilia; Ramirez Pastor, Antonio Jose; Leiva, Ezequiel Pedro M. The deposition of a metal on a foreign substrate is studied by means of grand canonical Monte Carlo simulations and a lattice-gas model with pair potential interactions between nearest neighbors. The influence of temperature and surface defects on adsorption isotherms and differential heat of adsorption is considered. The general trends can be explained in terms of the relative interactions between adsorbate atoms and substrate atoms. The systems Ag/Au(1 0 0), Ag/Pt(1 0 0), Au/Ag(1 0 0) and Pt/Ag(1 0 0) are analyzed as examples.

VLSI implementation of an energy-aware wake-up detector for an acoustic surveillance sensor network Goldberg, David H.; Andreou, Andreas; Julian, Pedro Marcelo; Pouliquen, Philippe O.; Riddle, Laurence; Rosasco, Rich We present a low-power VLSI wake-up detector for a sensor network that uses acoustic signals to localize ground-base vehicles. The detection criterion is the degree of low-frequency periodicity in the acoustic signal, and the periodicity is computed from the "bumpiness" of the autocorrelation of a one-bit version of the signal. We then describe a CMOS ASIC that implements the periodicity estimation algorithm. The ASIC is functional and its core consumes 835 nanowatts. It was integrated into an acoustic enclosure and deployed in field tests with synthesized sounds and ground-based vehicles.

Le musée Leleque et le groupe Benetton en Patagonie : Photographies mémoire et parrainage privé; The Leleque museum and the Benetton Group in Patagonia Vezub, Julio Esteban Le groupe Benetton a financé la réalisation d’un musée d’histoire régionale, qui a ouvert ses portes en mai 2000 au milieu d’une grande estancia dont il est propriétaire dans le nord-ouest de la Patagonie argentine. C’est à partir de l’expérience de l’un des membres de l’équipe d’anthropologues et d’historiens qui a élaboré les expositions du Musée Leleque que sont analysées les utilisations et les interprétations de photographies de la fin du XIXe siècle qui représentent des indigènes alors définitivement écartés du contrôle du territoire de la Patagonie. L’article retrace les conflits de mémoire et ceux relatifs à la propriété de la terre qui se sont ouverts à cette occasion entre le groupe Benetton et les familles mapuches. Il s’interroge aussi sur les aspects éthiques de la participation de professionnels des sciences sociales à l’élaboration de récits historiques dans les conditions d’un parrainage privé.; The Benetton Group financed the setting up of a museum of regional history, which opened in May 2000, located on a large estancia owned by the group in northwestern Argentine Patagonia. Based on the experience of a member of the team of anthropologists and historians who planned the exhibitions housed in the Leleque museum, analysis is made of the use and interpretation of late 19th century photographs of natives with no outside territorial monitoring. The article takes a closer look at the conflicts of memory and over land ownership that the event gave rise to between the Benetton Group and Mapuche families, and also considers the ethical aspects of participation by social sciences professionals in the drawing up of historical accounts in a context of private patronage.

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.