Experimental infection of rabbits (Oryctolagus cuniculus) with Brucella suis biovar 1 isolated from wild hares (Lepus europaeus) Fort, Marcelo; Baldone, Valeria; Fuchs, Lumila Ivana; Giménez, Hugo; Rojas, María; Breccia, Javier Dario; Oyhenart, Jorge Brucella suis biovar 1 is the causative agent of brucellosis in several domestic and wild animals and it is a common agent of human brucellosis. European hares (Lepus europaeus) have been shown to be infected by B. suis biovar 1 and the transmission to other animals has been suggested. In this work, experimental rabbits (Cuniculus orictolagus) were infected with B. suis biovar 1 isolated from wild hares. Infected rabbits showed high serological response in 2 weeks after discharge and typical granulomatous lesions (2. mm diameter) were found in liver, spleen and kidneys after 50 days. B. suis biovar 1 was cultured from the lesion of the organs mentioned above as well as from urine, placenta and fetuses. These data suggest that hares are a potential source for horizontal transmission of B. suis biovar 1 to other mammalians.

Efficient energy transfer via the cyanide bridge in dinuclear complexes containing Ru(ii) polypyridine moieties Cadranel, Alejandro; Alborés, Pablo; Yamazaki, Shiori; Kleiman, Valeria D.; Baraldo Victorica, Luis Mario We report the synthesis, structure and properties of the cyanide-bridged dinuclear complex ions [Ru(L)-(bpy)(μ-NC)M(CN)5]2−/− (L = tpy, 2,2′;6′,2′′-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2′- bipyridine, M = Fe(II), Fe(III), Cr(III)) and the related monomers [Ru(L)(bpy)X]2+ (X = CN− and NCS−).All the monomeric compounds are weak MLCT emitters (λ = 650?715 nm, ϕ ≈ 10−4). In the Fe(II) and Cr(III) dinuclear systems, the cyanide bridge promotes efficient energy transfer between the Ru-centered MLCT state and a Fe(II)- or Cr(III)-centered d?d state, which results either in a complete quenching of luminescence or in a narrow red emission (λ ≈ 820 nm, ϕ ≈ 10−3) respectively. In the case of Fe(III) dinuclear systems, an electron transfer quenching process is also likely to occur.

Global W 2,p estimates for nondivergence elliptic operators with potentials satisfying a reverse Hölder condition Bramanti, M.; Brandolini, L.; Harboure, Eleonor Ofelia; Viviani, Beatriz Eleonora In this article, we give some a priori L p(ℝ n) estimates for elliptic operators in nondivergence form with VMO coefficients and a potential V satisfying an appropriate reverse Hölder condition, generalizing previous results due to Chiarenza-Frasca-Longo to the scope of Schrödinger-type operators. In particular, our class of potentials includes unbounded functions such as nonnegative polynomials. We apply such a priori estimates to derive some global existence and uniqueness results under some additional assumptions on V.

Difficulties of undergraduate students in the organic chemistry laboratory Lorenzo, Maria Gabriela; Reverdito, Ana Maria; Blanco, Mercedes; Salerno, Alejandra In order to study the learning difficulties of university students in the organic chemistry laboratory, a new Model for the Analysis of Experimental Work (MAEW) was developed. This article is organized into three parts: first, a historical look at the role of experimental work in science education, including the purpose of the laboratory class; next, a description of the MAEW; finally, we show how the MAEW can be applied to an actual laboratory class of organic chemistry. An original proposal for the classification of the materials used in an organic chemistry laboratory is also offered.

Nucleophile- or light-induced synthesis of 3-substituted phthalides from 2-formylarylketones Gerbino, Darío César; Augner, Daniel; Slavov, Nikolay; Schmalz, Hans Günther The surprisingly facile conversion (isomerization) of 2-formyl-arylketones into 3-substituted phthalides, as observed for the marine natural product pestalone and its per-O-methylated derivative, was investigated using a series of simple 2-acylbenzaldehydes as substrates. The transformation generally proceeds smoothly in DMSO, either in a Cannizarro-Tishchenko-type reaction under nucleophile catalysis (NaCN) or under photochemical conditions (DMSO, 350 nm). © 2012 American Chemical Society.

Assessment of water quality in temperate-plain streams (Argentina, South America) using a multiple approach; Evaluación de la calidad del agua mediante un enfoque múltiple en arroyos de la llanura templada (Argentina, América del Sur) Ocon, Carolina Silvia; Rodrigues Capitulo, Alberto We assessed the water quality in two pampean lotic systems (Argentina), the Juan Blanco and Buñirigo streams, subjected to different land uses (i. e., the UNESCO Biosphere Nature Reserve versus industry and agriculture, respectively) through measurements of physicochemical data and the structural parameters of the macroinvertebrate assemblages in addition to ecotoxicological analyses. The objective was to identify the degree of ecological impairment in adversely affected areas and the consequent effects on the biota. The results obtained allowed the establishment of different water-quality classes within the study area. According to the indices applied, the downstream zone of the Buñirigo stream was categorized as moderately polluted on the basis of losses of sensitive benthic species or changes in their abundance. Likewise, acute ecotoxicological bioassays demonstrated that the water from this site had lethal effects on Caenis nemoralis (Ephemeroptera: Caenidae) larvae. This sampling point also exhibited relevant physicochemical features, such as high water conductivity and nutrient levels as well as low contents of dissolved oxygen.; Se realizó un estudio de la calidad del agua en dos sistemas lóticos, los arroyos Juan Blanco y Buñirigo (Argentina), sujetos a diferente uso del suelo (el primero se ubica dentro de una reserva de Biosfera de la UNESCO, mientras que el segundo en una zona agrícolo-ganadera e industrial). Se analizaron datos físico-químicos, parámetros estructurales del ensamble de macroinvertebrados y ensayos ecotoxicológicos. El objetivo fue identifi car el grado de deterioro en las áreas afectadas por efl uentes y los consiguientes efectos sobre la biota. Los resultados obtenidos permitieron establecer diferentes clases de calidad del agua dentro de la zona de estudio. De acuerdo a los índices aplicados la cuenca baja del arroyo Buñirigo fue caracterizada como moderadamente contaminada sobre la base de la pérdida de especies bentónicas sensibles o cambios en su abundancia. Del mismo modo, los ensayos ecotoxicológicos agudos demostraron que el agua de este sitio tuvo efectos letales sobre larvas de Caenis nemoralis (Ephemeroptera: Caenidae). Este punto de muestreo también evidenció características físico-químicas desfavorables para la biota, como alta conductividad y niveles de nutrientes, así como bajo contenido de oxígeno.

Ethanol-induced locomotor activity in adolescent rats and the relationship with ethanol-induced conditioned place preference and conditioned taste aversion Acevedo, María Belén; Nizhnikov, Michael; Spear, Norman E.; Molina, Juan Carlos; Pautassi, Ricardo Marcos Adolescent rats exhibit ethanol-induced locomotor activity (LMA), which is considered an index of ethanol's motivational properties likely to predict ethanol self-administration, but few studies have reported or correlated ethanol-induced LMA with conditioned place preference (CPP) by ethanol at this age. The present study assessed age-related differences in ethanol's motor stimulating effects and analyzed the association between ethanol-induced LMA and conventional measures of ethanol-induced reinforcement. Experiment 1 compared ethanol-induced LMA in adolescent and adult rats. Subsequent experiments analyzed ethanol-induced CPP and conditioned taste aversion (CTA) in adolescent rats evaluated for ethanol-induced LMA. Adolescent rats exhibit a robust LMA after high-dose ethanol. Ethanol-induced LMA was fairly similar across adolescents and adults. As expected, adolescents were sensitive to ethanol's aversive reinforcement, but they also exhibited CPP. These measures of ethanol reinforcement, however, were not related to ethanol-induced LMA. Spontaneous LMA in an open field was, however, negatively associated with ethanol-induced CTA.

Thin‐film β‐MoO3 Supported on α‐Fe2O3 as a Shell–Core Catalyst for the Selective Oxidation of Methanol to Formaldehyde Shir, Guojun; Franzke, Thomas; Sanchez, Miguel Dario; Xia, Wei; Weis, Frederik; Seipenbusch, Martin; Kasper, Gerhard; Muhler, Martin β‐MoO3/α‐Fe2O3 catalysts synthesized by chemical vapor deposition exhibit a uniform shell–core structure. The structure of the metastable β‐MoO3 film is retained even after calcination in air at 873 K, owing to strong Mo_O_Fe links at the interface. The shell–core β‐MoO3/α‐Fe2O3 catalysts are much more active than, and comparably selective to, the reference α‐MoO3 catalyst in the selective oxidation of methanol to formaldehyde.

Pollen morphology of the three subgenera of Alnus Leopold, Estella B.; Birkebak, Joshua; Reinink-Smith, Linda; Jayachandar, Anitha P.; Narvaez, Paula Liliana; Zaborac-Reed, Stephanie The three subgenera of alder (Alnusroman Clethropsis and Alnobetula) are taxonomically distinctive, but how does their pollen match up with their gross morphology? This study links pollen characters with the taxonomic divisions of the genus alder based on nrDNA ITS sequence data. The value of the study is in the breadth of the taxonomic coverage of the three subgenera, as the samples per species only range from 1 to 6. From 29 Alnus species, the authors studied pollen from 59 modern reference collections (prepared by acetolysis) and recorded the number and type of apertures (pores), thickness of the arci, pollen size and polar arci. Tallies of the number of pores on the pollen grains in a reference collection typically have a range of ± 1 or 2. Exceptions are presumed hybrid collections in Alnus rugosa with a range of ± 5, which have malformed pollen cells suggesting infertility. The presumed hybrids show a greater range of both pore number and size of pollen grains. The dominant pore number is a key feature that separates the subgenus Alnobetula (= Alnaster) from the other two subgenera by consistently having predominantly 5-, 6- or 7-pored pollen grains, while all other Alnus taxa sampled have pollen with predominantly 4- or 5-pored pollen. The dominant pore number is a consistent feature within the subgenus Alnobetula (10 species), but is inconsistent in 3 out of 16 species of the subgenus Alnus and within the subgenus Clethropsis (3 species). Thickenings of the pore lip, aspidate (protruding) and vestibulate pores are important features of Alnus pollen on a species level. Alnus-like pollen morphology occurs occasionally in certain other betulaceous genera (Betula and Carpinus). Differences in character or thickness of arci (band-like thickenings on the pollen wall between pores) tend to be somewhat consistent within a species and vary within subgenera. Two Alnobetula species in the Alnus viridis complex (Alnus crispa and Alnus sinuata) have arci that are weakly developed or appear as simple folds; walls are fragile and pores are typically less aspidate. Pollen sizes in different species overlap greatly, may be partly influenced by processing methods and do not seem to be generally helpful in characterizing species. Circular doughnut-shaped arci thickenings on the polar area of pollen grains are a common feature (16–40%) in two closely related East Asian taxa of subgenus Alnobetula with large pollen (‘Clade A’: Alnus firma and Alnus sieboldii). These ‘Clade A’ features have been reported from Miocene collections of Alnus pollen from Alaska, and support megafossil evidence in determining the biogeography of this group along the Pacific Rim in the Neogene. The Miocene appearance of subgenus Alnobetula megafossils in both Alaska and Japan can only have occurred via a Bering Land Bridge. This relation is now confirmed by Reinink-Smith's Miocene ‘Clade-A-type’ pollen data of Alaska. These taxa had Pacific Rim distributions, similar fruiting carposamaras and now correspond to a DNA ITS subgroup within Alnobetula. Depending on the geographic location with limited number of local alder species, certain Holocene identifications are possible based on pore structure and arci thickness, e.g. the Alnus crispa-type in eastern Canada and the Alnus sinuata-type in the Pacific northwest.

Environmental pesticide distribution in horticultural and floricultural periurban production units Querejeta, Giselle Andrea; Ramos, Laura Mabel; Flores, Andrea Pamela; Hughes, Enrique Alejandro; Zalts, Anita; Montserrat, Javier Marcelo The environmental pesticide distribution on non-target systems (soil, drift and agricultural plastics) during the application stage in small periurban production units (open field and greenhouses), was studied for various crops (tomato, lettuce, broccoli, strawberry and flowers) using different pesticides (endosulfan, procymidone, chlorothalonil, chlorpyrifos and deltamethrin). In all cases, soil was the most exposed non-target system. For greenhouses, a general pesticide distribution was found of approximately 2/3 for crop, 1/4 for soil and 1/20 for plastic, of the total amount applied. In horticultural open fields, although the distribution was very dependent on the crop size and type, soil was also the most exposed non-target subsystem. Pesticide drift seems not to be significant in these production units, whilst pesticide accumulation on agricultural plastics reached up to 45% of the total applied, for polyethylene mulching in strawberry fields.

Social inequality, environmental justice and water policy In Buenos Aires Merlinsky, Maria Gabriela; Fernandez Bouzo, Maria Soledad; Montera, Carolina; Tobias, Melina Privatisation of potable water and sanitation services in the Metropolitan Area of Buenos Aires during the 1990s led to important consequences in terms of investment and equality in the provision of the services. A new period was started in 2006 with the creation of the State-run company Agua y Saneamientos Argentinos SA, which became responsible for managing the provision of water and sewerage services in the region. Today, the company has to deal with the historical backwardness in terms of investment, the growing pressure from the population demanding access to the services, and the significant inequality of the covered area. On the other hand, due to the public impact of the court case regarding the sanitation of Matanza-Riachuelo basin, different territorial collectives have reformulated their demands for infrastructure works by including environmental terms. Besides, the Supreme Court of Justice has required the joint coordination of the works by Agua y Saneamientos Argentinos SA and the Authority of the basin. This means that water and sanitation management must answer to a great variety of actors and be able to operate in highly conflictive areas while meeting, at the same time, the environmental goals. This article describes the main actors involved in water and sanitation management in the Metropolitan Area of Buenos Aires and their approaches to the new plans of expansion of the services. The focus is to identify the opposing interests in terms of the distribution (which territories are the priority for the expansion of the water and sanitation networks); the implementation timetable (how to define the order of the works); and the emergence of different criteria of social and environmental justice. To this effect, we present an in-depth analysis of interviews to public officers, technicians and representatives of social organisations.

Characterization of novel Trichoderma spp. isolates as a search for effective biocontrollers of fungal diseases of economically important crops in Argentina Consolo, Verónica Fabiana; Monaco, Cecilia Ines; Cordo, Cristina Alicia; Salerno, Graciela Lidia Monoconidial cultures of 33 isolates of Trichoderma from Buenos Aires Province, Argentina were characterized on the basis of twenty eight morphological, physiological and biochemical features. All of them were screened for proteinase, endochitinase and â-1,3 glucanase activity. Universally primed PCR (UP-PCR) and inter-simple sequence repeat (ISSR) techniques were used to examine the genetic variability among isolates, which resulted in 127 bands for the total number of isolates. These results were subjected to numerical analysis revealing 20 haplotypes grouped in five clusters. The ability of Trichoderma isolates to antogonize soil-borne fungal plant pathogens using a dual culture assay was done against five fungal species: Alternaria sp., Bipolaris sorokiniana, Fusarium graminearum, F. solani, and Pyricularia oryzae. The highest inhibition values (85% RI) were obtained against B. sorokiniana and P. oryzae. Three isolates of T. harzianum named as FCCT2, FCCT3 and FCCT9 were capable of causing a high growth inhibition on four of the fungal species assayed, which was in agreement with their higher extracellular hydrolytic activity. Our results suggest that these isolates have the potential to be effective agents for biocontrol of cereal and tomato fungal pathogens.

Bioactive proteins from edible plants of Solanum genus. Ordóñez, Roxana Mabel; Sayago, Jorge Esteban; Zampini, Iris Catiana; Rodriguez, Ivana Fabiola; Cattaneo, Florencia; Isla, Maria Ines Bioactive proteins have been detected in manydifferent food sources. Beyond their nutritionalvalue many of them exhibit functional effects bothon the producing and on the consuming organisms.In recent years it has been recognized that proteinsprovide a rich source of biologically activepeptides. The genus Solanum has a great varietyof edible species that are an important source ofprotein. In this sense, some proteins might beinvolved in the response to wounding in plantdefense mechanisms like patatine and solamarineand snakin 1 and 2 isolated from S. tuberosumtubers and cyphomine isolated from S. betaceumfruits. They have shown in vitro inhibitory actionon hydrolases released by microorganisms involvedin cell wall degradation during the invasion process.They also have in vitro inhibitory effect onphytopathogenic microorganism growth for bothbacteria and fungi. It is thought that these proteinscould be part of the so-called pathogenesis-relatedproteins. As they are also present in edible tissue,these proteins have been studied from a functionalpoint of view. The purified proteins showedantioxidant or antiradical activities by a series ofin vitro tests, including DPPH, ABTS, hydroxyland superoxide radicals scavenging activityassays, anti-human low-density lipoproteinperoxidation tests, protections against hydroxylradical-mediated DNA damages, peroxynitritemediateddihydrorhodamine 123 oxidations andâ-carotene bleaching assay. A non mutagenic effectBioactive proteins from edible plants of Solanum genuswas observed in solamarine and cyphomine;solamarine also showed an antimutagenic effectagainst a direct mutagen. At present, an enzymatichydrolysis process on proteins is being carried outin order to obtain smaller molecules (peptides andfree amino acids) with improved nutritional qualityand safety. Three bioactive peptides (5A, 5C and6C) from potato protein hydrolysate fractions haverecently been isolated and showed antioxidantactivity. Hence, it would be possible to generatenew products and carry out alternative applicationsfor several agricultural and nutritional products.

Chemical Wear of Commercial Magnesia-Carbon Refractory Bricks in Air Camerucci, Maria Andrea; Galliano, Pablo German; Cavalieri, Ana Lia; Tomba Martinez, Analia Gladys In this work, the chemical degradation in air of different commercial MgO-C refractories used in the steelmaking industry was studied. Materials were characterized by mineralogical, microstructural, differential thermal and thermo-gravimetric analyses and measurements of density and porosity. Cylindrical samples were subjected to isothermal treatments at different temperatures and times in air and then, the weight loss and percentage of decarburized area were determined. Moreover, different surface conditionings (protective antioxidant paint and graphite powder muffle) were evaluated in regard to gas attack, and compared with non-conditioned specimens. The obtained results showed differences between the studied refractory materials according to the experimental conditions (temperature and time). At the low temperature regimen, pitch-based refractories exhibited the smallest chemical degradation whereas at high temperature, the material bonded with resin was the most resistant to oxygen chemical attack. The analysis of other phenomena related to microstructural changes helps to achieve a description of thermo-chemical processes occurring in the refractory samples during thermal treatments.

Siper-Virtual Reality Simulator of Periscope Boroni, Gustavo Adolfo; Garcia Bauza, Cristian Dario; D'amato, Juan Pablo; Lazo, Marcos Gonzalo In this paper an application designed to simulate the environment seen in a periscope by means of a virtual reality environment is presented. The application allows full viewing of all objects visible from the periscope, sea, ships, airplanes, etc. With the appropriate hardware (3D mouse and tracking systems) it is possible to navigate into the virtual world and interact with the elements. Each of the objects that appear in the navigation environment has been reproduced in the simulation model, including the behavior laws associated with it, so the complete functionality of the all objects can be simulated. This module is built into a larger and more complex computer system composed of the actual submarine simulator, with all its characteristic components (except the periscope) and the functional system, which simulates all the external signals that are captured by the submarine. The application automatically updates in the virtual environment any changes to the environment navigation and allows access, from this environment, to information on every component the same way as is done from a real periscope. The virtual reality application has been implemented in a hardware configuration and has the same interface as that used in the real periscope. In this way, the system developed can be integrated into a replica of the submarine emulating a real periscope, it being able to fully interact with the global system and allow totally real situations to be simulated.

La pedagogía de la investigación en la escuela secundaria y la implementación de Recorridos de Estudio e Investigación en matemática Otero, Maria Rita; Llanos, Viviana Carolina; Gazzola Bascougnet, María Paz En este trabajo se presentan resultados de una enseñanza por REI en la escuela secundaria, basada en la pedagogía de la investigación y del cuestionamiento del mundo, propuesta por Chevallard en la Teoría Antropológica de lo Didáctico (TAD). Se analizan protocolos para mostrar la actividad matemática del grupo de estudio. Se discuten algunos logros y se señalan ciertos obstáculos relativos a la implementación del REI y a la magnitud del cambio que es necesario realizar en la institución escuela secundaria.; In this paper some results related to teaching based on pedagogy of research and world questioning using Paths of Study and Research (PSR) at secondary school are presented. e framework of the Anthropological eory of Didactic (ATD) is used. Some protocols showing the mathematical activity of the study group are analyzed. Some achievements and obstacles related to the implementation of Paths of Study and Research (PSR) at secondary school are discussed, also, the challenges of the necessary changes in the secondary school are considered.

El diario Clarín y la "campaña antiargentina": la construcción de un consenso en torno a las violaciones a los derechos humanos Iturralde, Micaela Este artigo propõe uma indagação acerca do tratamento informativo e da linha editorial realizada pelo jornal diário argentino Clarín, sobre violações de direitos humanos cometidas na Argentina durante o regime militar 1976-1983. O texto está centrado na análise da conjuntura que começa em 1977 e continua em 1978, quando os militares iniciam uma campanha pública dizendo que há uma “campanha anti-argentina” e que as queixas de organismos internacionais pelo quadro dentro da Argentina eram, na realidade, interpretadas como parte da “ameaça subversiva” que se operava desde o interior do país, assim como do próprio exterior. Considerando que a omissão informativa que caracteriza a denúncia de uma “campanha anti-argentina” se refere diretamente à questão da repressão militar, consideramos também que as construções discursivas e representações criadas e difundidas por Clarín neste contexto - caracterizadas por uma adesão total à chamada “luta anti-subversiva” e pela exaltação nacionalista e patriótica (e êxito) em torno da Copa do Mundo de Futebol de 1978 -, constituíram o modo com que o jornal abordou o tema das violações dos direitos humanos.; En este artículo nos proponemos indagar el tratamiento informativo y editorial otorgado por el diario Clarín a las violaciones a los derechos humanos cometidas en la Argentina por el régimen militar que gobernó entre 1976 y 1983. Nos abocaremos al análisis de la coyuntura que se abre en 1977 y se extiende durante todo 1978, cuando se vuelve recurrente en las intervenciones públicas de los militares la denuncia de una supuesta “campaña antiargentina”, en la que los reclamos internacionales por la situación nacional fueron interpretados como parte de la “amenaza subversiva” que operaba desde el interior y el exterior. Dado que la omisión informativa que caracteriza la denuncia de una “campaña antiargentina” refiere directamente a la cuestión de la represión estatal, consideramos que las construcciones discursivas y representaciones creadas y difundidas por Clarín en este contexto, caracterizadas por una adhesión total a la llamada “lucha antisubversiva” y por la exaltación nacionalista y patriótica y el exitismo en torno al Mundial de Fútbol, constituyeron el modo en que el diario abordó el tema de las violaciones a los derechos humanos.

The relationship of clinical, cognitive and social measures in schizophrenia: A preliminary finding combining measures in probands and relatives Huepe, David; Riveros, Rodrigo; Manes, Facundo Francisco; Couto, Juan Blas Marcos; Hurtado, Esteban; Cetkovich Bakmas, Marcelo Gustavo; Escobar, Maria; Vergara, Viviana; Parrao, Teresa; Ibanez Barassi, Agustin Mariano This study examines performance of schizophrenia patients, unaffected relatives and controls in social cognition, cognitive and psychiatric scales looking for possible markers of vulnerability in schizophrenia. Performance of schizophrenia patients from multiplex families, first-degree relatives, and matched controls was compared and, subsequently, discriminant analysis method was used for identifying the best predictors for group membership. By using Multigroup Discriminant Analyses on the three groups, the best predictors were PANSS, Premorbid Adjustment Scale, Faux Pas test, and a face/emotion categorizing task. This model obtained 82% correct global classification, suggesting that the combination of psychiatric scales and neuropsychological/ social cognition tesks are the best approach for characterizing this disease. Although preliminary, our results suggest that social cognition tasks are robust markers of schizophrenia family impairments, and that combining clinical, social and neuropsychological measures is the best approach to asses patients and relatives vulnerability.

The role of vision in auditory distance perception Calcagno, Esteban; Abregú, Ezequiel Lucas; Eguia, Manuel Camilo; Vergara, Ramiro Oscar In humans, multisensory interaction is an important strategy for improving the detection of stimuli of different nature and reducing the variability of response. It is known that the presence of visual information affects the auditory perception in the horizontal plane (azimuth), but there are few researches that study the influence of vision in the auditory distance perception. In general, the data obtained from these studies are contradictory and do not completely define the way in which visual cues affect the apparent distance of a sound source. Here psychophysical experiments on auditory distance perception in humans are performed, including and excluding visual cues. The results show that the apparent distance from the source is affected by the presence of visual information and that subjects can store in their memory a representation of the environ- ment that later improves the perception of distance.

Abundance and diversity of tintinnids (planktonic ciliates) under contrasting levels of productivity in the Argentine Shelf and Drake Passage Santoferrara, Luciana Fernanda; Alder, Viviana Andrea The relationship between the abundance and diversity of tintinnids and the concentration of chlorophyll a (Chla) was contrasted between neritic and oceanic waters of the SW Atlantic during autumn and summer. Chla and tintinnid abundance and biomass reached maximum values (17.53μgL -1, 2.76×10 3ind.L -1, and 6.29μgCL -1, respectively) in shelf waters during summer, and their mean values generally differed by one order of magnitude between environments. Peaks in species richness (13) and Shannon diversity index (2.12) were found in the shelf-ocean boundary, but both variables showed nonsignificant differences between areas. Species richness correlated significantly with both Chla and abundance. Such relationships, which followed a negative linear or quadratic function in the shelf and a positive linear function in oceanic waters, are thought to reflect either the competitive dominance of one species or a relatively wide spectrum of tintinnid size-classes, respectively.