Depth profiling by confocal Raman microspectroscopy: Semi-empirical modeling of the Raman response Tomba, Juan Pablo; Arzondo, Luis M.; Pastor, José M. It has been well documented that the use of dry optics in depth profiling by confocal Raman microspectroscopy significantly distorts the laser focal volume, thus negatively affecting the spatial resolution of the measurements. In that case, the resulting in-depth confocal profile is an outcome of several contributions: the broadening of the laser spot due to instrumental factors and diffraction, the spreading of the illuminated region due to refraction of the laser beam at the sample surface, and the influence of the confocal aperture in the collection path of the laser beam. Everall and Batchelder et al. developed simple models that describe the effect of the last two factors, i.e., laser refraction and the diameter of the pinhole aperture, on the confocal profile. In this work, we compare these theoretical predictions with experimental data obtained on a series of well-defined planar interfaces, generated by contact between thin polyethylene (PE) films (35, 53, 75, and 105 μm thickness) and a much thicker polylmethyl methacrylate) (PMMA) piece. We included two refinements in the above-mentioned models: the broadening of the laser spot due to instrumental factors and diffraction and a correction for the overestimation in the decay rate of collection efficiency predicted by Batchelder et al. These refinements were included through a semiempirical approach, consisting of independently measuring the Raman step-response in the absence of refraction by using a silicon wafer and the actual intensity decay of a thick and transparent polymer film. With these improvements, the model reliably reproduces fine features of the confocal profiles for both PE films and PMMA substrates. The results of this work show that these simple models can not only be used to assist data interpretation, but can also be used to quantitatively predict in-depth confocal profiles in experiments carried out with dry optics.

One-step methyl isobutyl ketone (MIBK) synthesis from 2-propanol: Catalyst and reaction condition optimization Torres, Gerardo Carlos; Apesteguia, Carlos Rodolfo; Di Cosimo, Juana Isabel A gas-phase process for methyl isobutyl ketone (MIBK) synthesis from 2-propanol in one-pot is studied as an alternative to the conventional technology for producing MIBK from acetone (DMK). Bifunctional copper/acid-base catalysts able to operate at mild temperatures and atmospheric pressure were prepared and characterized by measuring the acid and base properties as well as the metal dispersion. It was found that a Cu-Mg-Al mixed oxide catalyst gives high MIBK yields. In this catalyst, the metal fraction in loadings of 2-6 wt% promotes the hydro-dehydrogenation steps at high rates whereas the surface acid-base sites of moderate acid and base properties favor the aldol condensation reaction. The effect of different operational conditions such as reaction temperature and reactant partial pressure was also investigated. The MIBK formation rate was enhanced by increasing 2-propanol partial pressure in a wide range, consistently with a positive 2-propanol reaction order in the overall kinetics whereas the presence of hydrogen in the reactant mixture inhibited MIBK synthesis due to a negative order with respect to H2. An increase of the reaction temperature and the use of inert atmosphere improved the MIBK yield. By operation at 533 K in N2 the Cu-Mg-Al catalyst with 6.4 wt% Cu, yields 27% MIBK in comparison to the 30% typically obtained in current commercial liquid-phase high-pressure processes from DMK.

A comparative study of the anti-inflammatory, anticoagulant, antiangiogenic, and antiadhesive activities of nine different fucoidans from brown seaweeds Cumashi, Albana; Ushakova, Natalia A.; Preobrazhenskaya, Marina E.; D'Incecco, Armida; Piccoli, Antonio; Totani, Licia; Tinari, Nicola; Morozevich, Galina E.; Berman, Albert E.; Bilan, María; Usov, Anatolii I.; Ustyuzhanina, Nadezhda E.; Grachev, Alexey A.; Sanderson, Craig J.; Kelly, Maeve; Rabinovich, Gabriel Adrián; Iacobelli, Stefano; Nifantiev, Nikolay E. The anti-inflammatory, antiangiogenic, anticoagulant, and antiadhesive properties of fucoidans obtained from nine species of brown algae were studied in order to examine the influence of fucoidan origin and composition on their biological activities. All fucoidans inhibited leucocyte recruitment in an inflammation model in rats, and neither the content of fucose and sulfate nor other structural features of their polysaccharide backbones significantly affected the efficacy of fucoidans in this model. In vitro evaluation of P-selectin-mediated neutrophil adhesion to platelets under flow conditions revealed that only polysaccharides from Laminaria saccharina, L. digitata, Fucus evanescens, F. serratus, F. distichus, F. spiralis, and Ascophyllum nodosum could serve as P-selectin inhibitors. All fucoidans, except that from Cladosiphon okamuranus carrying substantial levels of 2-O-alpha-D-glucuronopyranosyl branches in the linear (1-->3)-linked poly-alpha-fucopyranoside chain, exhibited anticoagulant activity as measured by activated partial thromboplastin time whereas only fucoidans from L. saccharina, L. digitata, F. serratus, F. distichus, and F. evanescens displayed strong antithrombin activity in a platelet aggregation test. The last fucoidans potently inhibited human umbilical vein endothelial cell (HUVEC) tubulogenesis in vitro and this property correlated with decreased levels of plasminogen-activator inhibitor-1 in HUVEC supernatants, suggesting a possible mechanism of fucoidan-induced inhibition of tubulogenesis. Finally, fucoidans from L. saccharina, L. digitata, F. serratus, F. distichus, and F. vesiculosus strongly blocked MDA-MB-231 breast carcinoma cell adhesion to platelets, an effect which might have critical implications in tumor metastasis. The data presented herein provide a new rationale for the development of potential drugs for thrombosis, inflammation, and tumor progression.

De la revolución de independencia a la consolidación del Estado nacional: la Patagonia en el Siglo XIX. Bandieri, Susana Ofelia El Siglo XIX inauguró cambios importantes respecto del reconocimiento y ocupación del territorio patagónico. Si bien las luchas civiles instaladas por el proceso independentista en el escenario rioplatense demoraron por varios años la preocupación de los sucesivos gobiernos, surgidos en el marco de la revolución de Mayo y de los acontecimientos que la sucedieron, por ocupar un territorio que aparecía como muy lejano y marginal a los sucesos centrados en Buenos Aires y en las viejas provincias del ex-Virreinato, la Patagonia no fue ajena a los enfrentamientos contra la corona española que protagonizaron las nuevas fuerzas republicanas. Particularmente importantes fueron las luchas que se sucedieron en la vertiente oriental de la cordillera, en el noroeste de la actual provincia de Neuquén, donde se refugiaron las fuerzas realistas comandadas por los hermanos Pincheira, de origen chileno, que se refugiaron en las lagunas de Epulafquen para combatir desde allí a los ejércitos del nuevo gobierno. La resistencia realista contó con el apoyo de los grupos pehuenches del lugar, que desconfiaban, no sin cierta lógica, de los cambios que se avecinaban. Las garantías que la corona española había dado a los pueblos originarios del área chilena de la Araucanía ?ubicada al sur del Bío-Bío-, reconociéndoles incluso el status de nación, se veía afectado ahora por el surgimiento de las nuevas estructuras de poder derivadas de la revolución. Hasta el año 1832 se sucedieron estas luchas, donde imperó el uso de la violencia por parte de ambos bandos, cuando el último de los hermanos sobrevivientes, José Antonio Pincheira, se rindió en Mendoza jurando fidelidad al rey español Fernando VII. Fue hasta entonces que el área andina norpatagónica funcionó como escenario de los últimos combates efectuados en el marco de la guerra de independencia en los territorios de la América del Sur.

IgA Production Alter Administration of a Probiotic Gigola, G.; Gandini, Norberto Ariel; Curino, Alejandro Carlos; Fermento, María Eugenia; Ullua, Natalia Paola; Maturi, Horacio Vicente; Perez, Jose Emanuel; Perdigon, Gabriela del Valle Probiotics are live microorganisms that exert health beneficial actions to the host after their oral administration if they are given in suitable amounts. They have a stimulatory effect on humoral immunity by increasing the amount of available local and circulating IgA. However, it is possible that continuos administration might not be the optimal way to administer them. Our objective was to compare two doses of probiotics and study their effect on local immunity in rat intestine. For this purpose we used 27 rats that were divided in three groups: Control group (3 animals), Group A (15 animals ) and group B (9 animals ). Group A was given 1 ml of BIOFLORA (SIDUS Lab) and Group B 0,2 ml. Animals were sacrificed at 3,5,8,10 and 15 weeks of treatment and intestine was resected and processed by freezing technique. Immunofluorescence was performed in order to study the amount of IgA+ cells. Results: BIOFLORA stimulated the production of IgA secretory cells in groupAwith a peak at 3 days whereas in group B it did not exert significant effects with respect to control animals. The amount of IgA+ cells returned to basal values after 8 days of treatment. The results suggest that the increase in IgAsecretory cells is dependent on the dose of probiotic and the period of treatment and that it is possible that a cyclic treatment would be a better way of administering the probiotic

Enzymatic pathways involved in flubendazole biotransformation Maté, María Laura; Virkel, Guillermo Leon; Lifschitz, Adrian Luis; Ballent, Mariana; Sallovitz, Juan Manuel; Lanusse, Carlos Edmundo Flubendazole (FLBZ) is a benzimidazole anthelmintic widely used in poultry and swine, which may be an alternative drug for parasite control in ruminants. The objective of this work was to characterise the main enzymatic pathways involved in the hepatic biotransformation of FLBZ. Liver cytosols and microsomes were obtained from control and phenobarbital (PB)-induced female Wistar rats, and from untreated male Corriedale x Merino cross breed sheep. Subcellular fractions were incubated with 40 µM of either FLBZ or its reduced chiral metabolite (red-FLBZ) in presence of NADPH. Incubation mixtures were analysed by HPLC. Liver microsomes from control rat reduced FLBZ to red-FLBZ and oxidised the later back to the parent molecule. Microsomes obtained from PB-induced rats displayed higher cytochrome (CYP) 3A and 2C-mediated N-demethylase activities, which correlated with an enhanced ability to convert red-FLBZ into FLBZ. CYP-mediated oxidative metabolism of red-FLBZ to FLBZ was absent in sheep liver. Both cytosolic and microsomal fractions obtained from sheep liver were able to reduce FLBZ into red-FLBZ at the same rate; the reduction of FLBZ led to the prevalent (~98%) stereospecific formation of one of the enantiomeric forms of red-FLBZ. A NADPH-dependent ketone-reductase may be involved on FLBZ reduction in sheep liver. The study of drug metabolising enzyme activities may help to predict drug-drug metabolic interactions in Veterinary Therapeutics.

A model for gamma-ray sources in the galactic halo Vila, Gabriela Soledad; Romero, Gustavo Esteban Among the galactic gamma-ray sources detected by the EGRET instrument there exists a group located at high galactic latitudes, distributed as a halo around the galactic centre. These sources are X-ray quiet with soft spectra at gamma-rays. Their variability on short timescales indicates the presence of a compact object. In this work we present a model for gamma-ray halo sources based on hadronic processes in the jet of a low-mass microquasar. Several interaction mechanisms between relativistic protons and local fields are taken into account. We also estimate the contribution to the spectrum of primary leptons. Finally, we compare our results with the general properties of the halo gamma-ray sources and make some predictions for the forthcoming satellite-borne gamma-ray telescopes.

Isolation of Bacillus strain toxic to Spodoptera frugiperda (Lep.: Noctuidae) Alvarez, Analia; Pera, Licia Maria; Virla, Eduardo Gabriel; Baigori, Mario Domingo Introduction. The fall armyworm, Spodoptera frugiperda (Sf), is one of the most important corn pests in tropical and subtropical America. Some microorganisms are important candidates for its control. Bacillus thuringiensis (Bt) is an entomopathogenic sporeforming bacterium, which produces proteinaceous crystalline parasporal inclusions (Cry). Objective. Evaluation of ten “Cry” producer strains against first instar larvae of Sf. Materials and methods. Individuals comes from a laboratory colony maintained under controlled conditions (25°C, 70-75% RH and 12:12 L/D). The artificial diet was immersed in sterile water “Cry” protein suspension. Microorganisms isolated from soil and dead larvae were used. Larval mortality was determined during 7 days. Results and conclusions. One of the native strains tested, called RT3, had a strong toxicity against Sf larvae. Considering two independent assays, a mortality level from 76.6 (F=60.50; gl=1; P=0.0015) to 100% was observed after 3 and 4 days, respectively. Finally, in the first assay no larva was survived. Larval mortality using serial dilution of “Cry” suspension was also determined. According to these results, the isolated RT3 can be considered an active strain. This work were supported by grant CIUNT D308 and CONICET

Determination of LD50 and LT50 of Bacillus native strains toxic to Spodoptera frugiperda (Lep.: Noctuidae) Alvarez, Analia; Pera, Licia Maria; Virla, Eduardo Gabriel; Baigori, Mario Domingo Introducción: Spodoptera frugiperda (Sf) es una de las plagas principales del maíz en las regiones tropicales y subtropicales de América. Algunos microorganismos son importantes candidatos para su control racional. Es el caso de Bacillus thuringiensis (Bt), bacteria gram positiva que durante la esporulación produce proteínas entomopatógenas conocidas como ?cry?. El objetivo de este estudio fue evaluar la dosis letal 50 (DL50) y el tiempo letal 50 (TL50), de tres cepas de Bacillus nativas, cristal positivas, sobre larvas de Sf del primer estadio. Materiales y métodos. Los individuos empleados en los ensayos provienen de una cría de Sf en condiciones reguladas (25 °C ,70% HR, 12:12 L/O). Los microorganismos fueron aislados a partir de larvas muertas colectadas en cultivos de maíz de distintas localidades de Tucumán. Los microorganismos fueron coloreados para visualizar las proteínas cry. La dieta con que se alimentaron las larvas, fue sumergida en distintas diluciones de los cultivos. Se emplearon 600 insectos, incluidos los controles que se alimentaron con dieta sumergida en agua estéril. La DL50 y el TL50 se determinaron mediante un análisis probit. Resultados. La DL50 (UFC) para la cepa RT fue 8,99 X 106; para LSM fue 5,60 x 107; para LQ fue 2,70 X 107 y para la cepa standard Bt kurstaki HD1. 1,04 X 107 Los TL50 (horas) se muestran en la siguiente tabla. RT LSM LQ HD1 Dosis TL50 (h) Dosis TL50 (h) Dosis TL50 (h) Dosis TL50 (h) 6,18 x107 45 6,59 x107 158 6,13 x107 152 6,21 x107 51 2,32 x107 81 2,31 x107 171 2,16 x107 133 3,12 x107 83 7,45 x106 116 7,42 x106 182 1,14 x107 180 1,14 x107 100 2,56 x105 229 5,66 x104 227 2,33 x104 189 5,56 x105 196 Conclusiones. Los resultados de este trabajo muestran que la cepa más efectiva contra Sf fue Bacillus sp RT que requiere una DL50 y un TL50 (en las dos primeras dosis) menor, en comparación a los demás aislamientos. A pesar que los aislamientos LSM y LQ muestran DL50 y TL50 mayores, la mortalidad causada por estos con la primera dosis fue significativamente diferente de la obtenida para el control. Si bien se requieren mayores estudios, los resultados alcanzados con la cepa Bacillus sp RT fundamentalmente, y en general con las otras dos, sugieren un gran potencial como agentes de control biológico para Sf.

Confección y uso de artefactos discoides en contextos de cazadores-recolectores de patagonia meridional: pesas para redes en el sitio HST01AM (prov. Santa Cruz, Argentina) Mansur, Maria Estela El análisis tecnomorfológico y funcional de los conjuntos líticos procedentes de numerosos sitios arqueológicos estratificados y de superficie, ubicados en la margen norte de la ría del Gallegos (provincia de Santa Cruz), permitió poner en evidencia diferentes estrategias tecnológicas en relación con la explotación de materias primas, la confección y el uso de instrumentos. Estas se estructuran según cuatro cadenas operativas. La mejor representada estuvo destinada a la producción de lascas a partir de nódulos de rocas cristalinas heterogéneas (riolita, dacita, etc.) para la confección de filos largos retocados (raederas). La segunda tuvo por objeto producir lascas a partir de guijarros pequeños de rocas silíceas criptocristalinas (madera silicificada, calcedonia, ópalo, sílices) y excepcionalmente de basalto, que fueron retocadas sobre un filo corto para confeccionar raspadores. La tercera estuvo destinada a la confección de instrumentos bifaciales, entre los cuales predominan ligeramente las vulcanitas (basalto/andesita). Finalmente, la última es la de confección de instrumentos por piqueteamiento o pulimentación (esferoides, guijarros con contorno piqueteado, bola con surco, etc.). Sin embargo, un caso excepcional tanto por su singularidad tecnomorfológica como por su proximidad espacial, es el de artefactos discoides descubiertos en el sitio HST01AM. Se trata de piezas confeccionadas mediante percusión directa, sobre placas de rocas de diversa litología (rocas de grano tamaño arena mediano a fino, posiblemente sedimentarias, así como vulcanitas de grano muy fino con escasos fenocristales dispersos). Todos los discos están enteros, son delgados, tienen forma subcircular con perímetro ligeramente irregular, diámetros comprendidos entre los 10 y 13 cm. y frecuentemente presentan un par de escotaduras opuestas. Tanto las superficies como el filo perimetral de los artefactos se encuentran en muy mal estado de conservación. Las características litológicas de las rocas seleccionadas las hacen altamente frágiles frente a procesos de meteorización o de alteración en sedimento, que implican disolución/abrasión de las superficies. En consecuencia, su identificación como artefactos manufacturados por talla puede resultar difícil cuando se encuentran muy erosionados. Por tal motivo, cabe preguntarse si la singularidad del hallazgo de estas piezas para la arqueología patagónica constituye un fenómeno realmente excepcional, o si por el contrario es posible que artefactos de este tipo puedan haber pasado desapercibidos en algún otro yacimiento, especialmente en sitios superficiales, donde piezas meteorizadas y/o fracturadas podrían eventualmente haber sido descartadas como simples litos fragmentados. Su morfología y modo de aparición sugieren que se trata de pesas para redes de pesca, y sólo guardan similitud con las pesas descriptas en contextos arqueológicos del sur de Chile.

Autumn soil water surplus during ENSO events in argentine pampean flatlands Scarpati, Olga Eugenia; Forte Lay, Juan Alberto; Spescha, Liliana Beatriz; Capriolo, Alberto Daniel The main argentine agricultural region (840,000 km2) is located in the pampean flatlands of Buenos Aires, Santa Fe, Córdoba, La Pampa, San Luis and Entre Ríos provinces. Differing phases of ENSO (El Niño and La Niña) have differing impacts on soil moisture conditions across the study area. Daily soil water balances are estimated for the period 1961 - 2003 using records from 76 meteorological stations, and the daily soil water surplus is employed as the major output in the present paper. The sum of autumn soil water surpluses (March, April and May) is analysed, because they are those that have more harmful effects on the crop of the cultivations of the precedent summer and also partially control the risk of floods in the important agriculture and urban areas. Moreover, these months represent the highest soil water surplus values of the year. ENSO events are identified using the multivariate index (MEI). The probabilities of occurrence of predetermined soil water surplus and hence risk are calculated and mapped. The south and south-western areas are generally free of risk during all ENSO events, while the north-eastern area (Santa Fe, Entre Ríos and north-eastern of Buenos Aires) reveal high risks of saturated soils and floods during autumn especially during El Niño years.

A simple technique to detect klebsiella biofilm-forming strains. Inhibitory potential of lactobacillus fermentum CRL 1058 whole cells and products Maldonado, Natalia Cecilia; Silva, Clara del Valle; Cecilia, Marta Elena; Nader, Maria Elena Fatima Klebsiella is one of the pathogens able to form biofilm and then to produce Catheter Associated Infections (CAI). The capability to form biofilm can be considered as a virulence factor. Lactobacilli are included into the potential protective microorganisms to be used for bacteriotherapy to prevent CAI and Urinary tract Infections (UTI). The aim of this work was to isolate Klebsiella strains from CAI and UTI, and to set up a simple technique to detect the biofilm-forming strains in polystyrene microplates by using a spectrophometric assay. Also, to study the kinetics of biofilm formation, supported by standard microbiological assays. Lactobacillus fermentum CRL 1058 whole cells, acid and neutralized supernatants were tested for their inhibitory potential against one biofilm-forming Klebsiella pneumoniae subsp pneumoniae strain selected. The results show that the microplate technique is easy to perform, allows the rapid screening of many strains, and also that lactobacilli whole cells and the acid supernatant inhibit in higher degree that the neutralized supernatant to the biofilm produced by Klebsiella.

Comparative effect of viable, heat- killed or sonicated Lactobacillus fermentum CRL1058 in the protection of uropathogenic E. coli in the urinary tract of a murine experimental model Silva, Clara del Valle; Nader, Maria Elena Fatima Lactobacilli play a protective role against pathogens in the urogenital tract by a combination of multiple mechanisms, not fully understood until now. The purpose of the present paper was to study whether live, heat killed or sonnicated cells of Lactobacillus fermentum are able to protect against the challenge of uropathogenic Escherichia coli in the urinary tract of mice as experimental model. Sonicated, heat treated and live cells of L. fermentum CRL1058 attached to agarose beads were inoculated intra-urethrally to different groups of 2- months-old female BALB/c mice in three doses of 108 CFU/dose. Thereafter, these mice were challenged with an uropathogenic strain, Escherichia coli, also inoculated in the urethra of the animals. A reinoculation of Lactobacilli at the same dose was performed on day 6 and after. Treated cells of L. fermentum exert a protective effect against E. coli colonization at different degree, being lower that that produced by viable cells. Our results suggest that L. fermentum can be used as a probiotic in those infections caused by certain pathogens such as E. coli, based in the results obtained in the in vivo experimental model.

A unified symmetrical formulation for interactions between elastic solids and incompressible fluids Idelsohn, Sergio Rodolfo; Oñate, Eugenio; Marti, Julio Marcelo Variational methods have long been a fundamental tool in the development of mathematical physics. This is a particularly true in the field of mechanics, where they allow physical and geometrical features of the problem in question-such as kinematical and constitutive relations, initial and boundary conditions, including the description of discontinuities-as well as the relationsships among them, to be incorporated in one single expression. Very importantly, such formulations have the additional advantage of leading naturally to methods for the approximate computational solution of the underlyng problems as well as the study of existence and uniqueness of solutions and the estimation of errors incurred by numerical approximations. This book contains seventeen articles authored by internationally renowned specialists who have devoted their research activities to the modelling and implementation of numerical methods for the solution of various problems of relevance in mechanics. Te common element to all papers presented in this book is the use of variational formulations and variational calculus.

Regulación autocrina y paracrina del ovario Tesone, Marta; Abramovich, Dalhia Nurit; Parborell, Maria Fernanda Agustina El reclutamiento cíclico y selección de los folículos representa un proceso continuo, que eventualmente llega a la formación de uno o más folículos preovulatorios, cuyo número varía en cada especie. En los primeros días del ciclo menstrual en la mujer, aumentan los niveles circulantes de FSH, como consecuencia, una cohorte de folículos antrales escapa de la apoptosis que los llevaría a la atresia folicular. Dentro de este grupo, alrededor de 10 folículos antrales crecen más rápido y producen altos niveles de estrógenos e inhibina, seleccionándose entre éstos el folículo dominante. A pesar de que no se conoce exactamente por qué un folículo emerge como dominante, se postula que éste posee una mayor sensibilidad a FSH, debido a una mayor expresión de receptores de FSH y/o LH. Asociado a este proceso, el estradiol y los factores de crecimiento locales ejercen un efecto permisivo, amplificando la acción de la FSH en los folículos que están madurando.

The large scale structure of the Internet Barrat, Alain; Dall'Asta, Luca; Alvarez Hamelin, José Ignacio; Vespigna, Alessandro The Internet is a prototypical example of info-structure that has grown following a self-organized dynamics. Even though governments are waking up to the reality that the Internet is a critical infrastructure that has dramatically changed our way to access information, exploit social relations, and run commerce, nobody has ever run the Internet growth or drawn a blueprint for its development. The dynamics of Internet is indeed defined by the interplay between cooperation (the network has to work efficiently) and competition (providers wish to earn money). These evolutionary prin- ciples have shaped an intrinsically heterogenous system ruled by different administrative policies whose complicate structure cannot be found in any repository or “official” map. For these reasons, in the last years, several research groups have started to deploy technologies and infrastructures in order to obtain a more global picture of the Internet. Several studies aiming at tracking and visualizing the Internet large scale topology and/or performance are now providing Internet maps at different resolution scales.  These projects typically collect data on Internet nodes (routers, domains, etc.) and links in order to create a graph-like representation of large parts of the Internet. The obtained Internet graphs exhibit most of the features characterizing large scale complex networks and in the present chapter we provide a review of the results obtained in the characterization of their structure.  We also present a critical discussion of the eventual experimental biases that might lead to erroneous conclusions on the actual topological properties of the Internet network. Finally we discuss some novel measurements aimed at uncovering the hierarchical and ordering principles underlying the Internet structure.

Aquatic Biodiversity in Latin America: Neotropical Ceratopogonidae (Diptera: Insecta) Borkent, Art; Spinelli, Gustavo Ricardo This book brings together, for the first time, all known information on the 51 genera and 1095 described Neotropical species of biting midges. An overview of the group includes a discussion of bionomics, adaptations of the various life stages, habitats, their ecological roles (including disease transmission), collecting and preparation techniques, zoogeography and classification. A key to adults (including males) provides the first key to all the genera of this region. Limited keys to eggs and larvae are presented. Keys are written in both English and Spanish. A table of all previous descriptions of immatures and a catalog of all Neotropical species is included.

La provincia flotante: Historia de los exiliados argentinos de la última dictadura militar en Cataluña (1976-2006) Jensen, Silvina Inés Este libro es una historia del exilio argentino de la última dictadura militar construida con las voces de aquellos que recalaron en Cataluña a mediados de la década del ´70. Sin embargo, esta pesquisa anclada en la historia social y política catalana, es a vez un "caso" o mejor dicho opera como un laboratorio para entender cómo esa experiencia de destierro fue vivida y pensada y luego recordada desde la contemporaneidad del fenómeno (1976-1983) hasta el presente y tanto por sus protagonistas como por aquellos que de una u otra forma han interactuado con ellos desde la sociedad de origen (Argentina) y desde la de destierro (Cataluña). A lo largo de sus páginas se reconstruye la historia de los protagonistas de la diáspora del ´76, desde su salida abrupta desde Argentina, pasando por sus descubrimientos y aprendizajes en Cataluña, la evaluación o la concreción del retorno tras el final de la dictadura, su reencuentro con la Argentina de adentro y hasta el presente. Este libro intenta por un lado reconocer las marcas que permiten individualizar al exilio dictatorial de Cataluña de otros exilios nacionales contemporáneos. Y, por el otro, pensar desde la experiencia de los argentinos que vivieron su destierro en Cataluña, cómo la sociedad argentina en su conjunto ha recordado/recuerda el exilio dictatorial y cuáles son las razones de lo que a mi juicio es una "memoria silenciosa" o discreta sobre aquel acontecimiento traumático.

Antibacterial and Cytotoxic Activity of Extracts and Secondary Metabolites Obtained from Plants and Lichens of Patagonia Austral Enriz, Ricardo Daniel; Freile, Monica Liliana; Correché, María Susana; Gomez-Lechon, María José In medicinal chemistry, the discovery of a new lead structure substance represents the most uncertain stage in a drug development program. In the past, the discovery of lead compounds depended essentially upon random occurrences such as accidental observations, fortuitous findings, hearsay or laborious screening of a large number of molecules. More recently, more rational approaches have become available, based on the knowledge of structures of the endogenous metabolites and receptors or on the nature of the biochemical disorder implied in the disease at molecular level. Nowadays there are different strategies to obtain lead structure candidates. These methods may consist of more or less intuitive approaches, such as the synthesis of analogues, isomers and bioisosters or they may be based on computer-assisted design, such as identifying pharmacophores by molecular modeling, Structure-Activity Relationship (SAR) or Quantitative SAR (QSAR) studies.

Patrón espacial del paisaje serrano (Córdoba, Argentina) Menghi, Mirta Melva Mercedes; del Sueldo, Ruben Arturo Se analiza el paisaje rural de una área (31°50’S/64°50’W) de las Sierras de Córdoba (Argentina central) objeto de la mayor extensión de plantaciones de Pinus spp. «pino» realizadas en los últimos 30 años. Se describen la estructura y diversidad del patrón espacial actual del paisaje entre 650 y 2.400 m snm., y su relación con factores físicos y con plantaciones de pino. Se realizó la clasificación supervisada de una imagen Landsat TM (30 x) (Envi 3.5, CONAE) de septiembre de 2002, considerando unidades de vegetación y usos del suelo nativas y antrópicas. Se analizó en forma exploratoria toda la cuenca (77.622 Ha) y, con mayor detalle, 21.000 Ha que concentran plantaciones, considerando la estructura del paisaje total, de cada hábitat o unidad de paisaje, y de parche (Fragstats 3.3). La matriz del paisaje actual (77% de la cuenca) es un mosaico de comunidades nativas en distinto estado de conservación con límites irregulares entre ellas, en el cual los bosques nativos representan hoy una superficie menor. El bosque de Lithraea ternifolia («molle») cubre actualmente 3.148 Ha (19% de su área potencial) repartidas en numerosos parches menores a 1 Ha; la mayor parte fue degradado a arbustales compuestos por Acacia spp. y otras especies del sotobosque original, y está invadido por leñosas exóticas. Los bosques y arbustales de Polylepis australis («tabaquillo») representan cerca de 300 Ha, están muy fragmentados en pequeños parches confinados a quebradas; tanto factores antrópicos como físicos explicarían ese patrón. Los bosques nativos mostraron relación espacial escasa (L. ternifolia, «molle») a nula (P. australis, «tabaquillo») con las plantaciones de «pino». La mayor extensión de bosque de «pino» (7.670 Ha) cubre áreas originales del matorral serrano de Hetherotalamus alienus («romerillo») y, en menor grado, de pastizales de altura. La variedad y extensión de hábitat artificiales y exóticos aumentan hacia las zonas media y baja; tienen en común fronteras bruscas y rectas, muy contrastantes con su entorno. Los valores de diversidad (H’ 1,85), de equidad (E’ 0,80) y de dominancia (0,34) de unidades de paisaje indicarían que el patrón espacial es heterogéneo a escala regional, y más diverso hacia los extremos alto (2.43 bits) y bajo (2.20 bits) respecto del sector medio (1.53 bits) de la cuenca. La interacción entre la complejidad y accesibilidad del relieve a lo largo del gradiente altitudinal explicaría esa tendencia por mayor variabilidad espacial de elementos naturales hacia las cumbres, y de origen antrópico hacia zonas bajas. La estructura espacial detectada no es estática y de ella emergen hipótesis para investigación futura. Son de particular interés temas relacionados a la calidad del hábitat, la dirección y dinamismo de las transiciones bióticas en diferentes tipos de fronteras, la percolación de la estructura para organismos y procesos ecosistémicos, entre otros.; Traditional land-uses involving burnt, grazing and/or wood cutting of native plant cover, and more recently its complete replacement by agriculture and urban landuses have all promoted plant cover alteration, retraction and/or fragmentation, with particular impact on native forests. Based on remote sensing (Landsat TM 30 x) (Envi 3.5) the current spatial pattern of a landscape mosaic of 77.622 Ha (31o2’S / 64o30’W) was described taking into account the following cover types: native or exotic forests, agriculture, urban, artificial lake, shrub-land, grassland. The spatial structure was analyzed at mosaic, habitat, and patch levels. The habitat diversity of spatial pattern was also measured. From present analysis emerged a matrix composed by different types of native plant cover still well connected by gradual transitions among them. At the same time, significant degrees of native forests retraction and fragmentation were detected. The Polylepis australis («tabaquillo») (over 1500 m a.s.l) and of Lithraea ternifolia («molle») (from 900 to 1100 m a.s.l.) woods, currently represent from 10 to 19% of their potential areas at the analyzed water-basin. The larger part has been replaced by tall sized and spiny shrub-lands dominated by Acacia («espinillo») in the case of Lithraea, or by grasslands the Polylepis one. The Pinus plantation has replaced 40% of native short sized shrub-lands of Hetherotalamus alienus («romerillo») related to areas with moderated relief, and has involved new boundary types, straight and sharp, related to different cover types all over the basin. Present landscape is dynamic and from its spatial structure hypothesis for future research have emerged. Topics related to forest ecosystem services, to habitat quality, to biotic transitions associated to different boundary types, as well as the spatial structure percolation for organisms and ecosystem processes, among others, are of particular interest.