Novel binderless zeolite-coated monolith reactor for environmental applications Zamaro, Juan Manuel; Miro, Eduardo Ernesto A novel structured catalyst based on a binderless zeolite film was developed onto a cordierite monolith. The zeolitic film was obtained performing a binderless washcoating which was followed by a hydrothermal treatment, which resulted in a coating with hybrid physicochemical properties, having a porous washcoat-like microstructure with an intergrowth between the aggregates. This combination confers to the zeolite coating an open structure which is an advantage of washcoats and a high mechanical stability characteristic of the zeolite growths. It should be emphasized that these desired properties are obtained without the use of binders. The physico-chemical properties were investigated through MIP (mercury intrusion porosimetry), SEM (scanning electron microscopy), ultrasonic adherence tests, NO-TPD (temperature-programmed desorption of NO) and EPMA (electron probe microanalysis). The catalytic properties of the monolith were evaluated in the selective catalytic reduction of NOx at high spatial velocities, showing promising results.

Insecticidal, Mutagenic and Genotoxic Evaluation of Annonaceous Acetogenins Álvarez Colom, Olga; Salvatore, Silvana Analia; Willink, Eduardo; Ordóñez, Roxana Mabel; Isla, Maria Ines; Neske, Adriana Neske; Bardon, Alicia del Valle Annonaceous acetogenins represent a class of bioactive compounds whose primary mode of action is the inhibition of NADHubiquinone oxidoreductase (Mitochondrial Complex I). Given the potential pesticidal use of these compounds, we evaluated the effects of seven acetogenins: squamocin (1), molvizarin (2), itrabin (3), almuñequin (4), cherimolin-1 (5), cherimolin-2 (6), and tucumanin (7) isolated from Annona cherimolia Mill. against Ceratitis capitata Wiedemann (Tephritidae). These acetogenins did not display insecticidal action at 250 µg of treatment per g of adult diet. However, the oviposition capacity of C. capitata females was significantly altered by some of the acetogenins at this concentration. The most potent compounds were itrabin, molvizarin and squamocin. Moreover, significant differences were detected in the preference of oviposition sites when itrabin and squamocin were spread on the surface of artificial fruits at doses of 30 µg/cm2 . Additionally, we investigated the mutagenic effects displayed by itrabin, as well as the phytotoxic and genotoxic action of squamocin and itrabin. Both compounds displayed slight phytotoxic and genotoxic effects on roots of Allium cepa at 2.5 µg/mL though no mutagenic effects were detected at 0.25, 0.5 and 2.5 µg/mL on Salmonella typhimurium strains TA98 and TA100.

Stenomicra (Diptera: Opomyzoidea) in Argentina, with information on the biology of the genus; Stenomicra (Diptera: Opomyzoidea) en Argentina, con información sobre la biología del género Campos, Raul Ernesto; Gramajo, Maria Cecilia; Lizarralde, Mercedes Sara This is the first literature record of the genus Stenomicra Coquillett (Diptera: Periscelididae) from South America (Neotropical Region). New information on the biological cycle of Stenomicra species in the wild is provided, and four species of the genus Eryngium L. (Apiaceae) are recorded as host plants for immature stages of this taxon. The specimens of Stenomicra sp. were collected in Sierra de la Ventana, Buenos Aires province, Argentina.; En este estudio, se publica por primera vez para Sudamérica (Región Neotropical) el género Stenomicra Coquillett (Diptera: Periscelididae). Se aporta información sobre su ciclo biológico en condiciones naturales y se mencionan cuatro especies del género Eryngium L. (Apiaceae), como plantas hospedadoras de los estados inmaduros. Los ejemplares de Stenomicra sp. fueron colectados en Sierra de la Ventana, Provincia de Buenos Aires, Argentina.

On the estimation of the cost of equity in Latin America Grandes, Martin; Panigo, Demian Tupac; Pasquini, Ricardo Aníbal This paper researches the sources of stock market risk influencing the pricing of 921 Latin American stocks and computes their corresponding opportunity cost (COE) over the period 1997–2004 by firm and sector. Running an adjusted version of the Capital Asset Pricing Model (CAPM) it finds that systematic risk accounts on average for more than 32% of COE total variance. This implies that potential CAPM mispricing related to undiversified idiosyncratic risk in Latin America has been relatively lower (but absolutely higher) than in United States and other European and Asian stock markets (such as the United Kingdom, Canada or Japan). A first robustness test for the omission of international sources of un-diversifiable risk suggests that both global market and real currencies portfolios do not add significant information to domestic market portfolios. Moreover, a second robustness check offers further evidence that well-diversified portfolios constructed by sorting stocks according to their size and book-to-market ratios a la Fama and French do not improve the goodness of fit in the regressions based on the adjusted version of CAPM.

Anisotropy of the Taylor scale and the correlation scale in plasma sheet magnetic field fluctuations as a function of auroral electrojet activity Weygand, James M.; Matthaeus, W. H.; El Alaoui, M.; Dasso, Sergio Ricardo; Kivelson, M. G. Magnetic field data from the Cluster spacecraft in the magnetospheric plasma sheet are employed to determine the correlation scale and the magnetic Taylor microscale from simultaneous multiple‐point measurements for multiple intervals over a range of mean magnetic field directions for three different levels of geomagnetic activity. We have determined that in the plasma sheet the correlation scale along the mean magnetic field direction decreases from 19,500 ± 2200 to 13,100 ± 700 km as the auroral electrojet activity increases from quiet (<80 nT) to active conditions (>200 nT). The reverse occurs for the correlation scale perpendicular to the magnetic field, which increases from 8200 ± 600 km to 13,000 ± 2100 km as the auroral electrojet activity increases from quiet to active conditions. This variation of the correlation scale with geomagnetic activity may mean either a change in the scale size of the turbulence driver or may mean a change in the predominance of one over another type of turbulence driving mechanism. Unlike the correlation scale, the Taylor scale does not show any clear variation with geomagnetic activity. We find that the Taylor scale is longer parallel to the magnetic field than perpendicular to it for all levels of geomagnetic activity. The correlation and Taylor scales may be used to estimate the effective magnetic Reynolds numbers separately for each angular channel. Reynolds numbers were found to be approximately independent of the angle relative to the mean magnetic field. These results may be useful in magnetohydrodynamic modeling of the magnetosphere and can contribute to our understanding of energetic particle diffusion in the magnetosphere.

Increased nitration and diminished activity of copper/zinc superoxide dismutase in placentas from diabetic rats White, Verónica; Capobianco, Evangelina Lorena; Higa, Romina Daniela; Martinez, Nora Alicia; Sosa, María; Jawerbaum, Alicia Sandra Nitration-induced protein damage in the placenta leads to impaired blood flow and deficient feto–placental exchange in diabetic pregnancies. This work studied the effect of nitric oxide and peroxynitrite on Cu/Zn SOD activity in rat placentas and evaluated whether Cu/Zn SOD is nitrated in the placenta from diabetic rats at mid-gestation. Protein nitration was evaluated by EIA, Cu/Zn SOD activity by inhibition of the epinephrine auto-oxidation, Cu/Zn SOD expression by western blot and specific nitration by immunoprecipitation. This study found higher levels of protein nitration (p < 0.001), diminished Cu/Zn SOD activity and enhanced protein expression (p < 0.01) in placentas from diabetic rats. Placental Cu/Zn SOD activity was inhibited by peroxynitrite (p < 0.01). Besides, nitration of Cu/Zn SOD was elevated in placentas from diabetic rats (p < 0.01). These results show that rat Cu/Zn SOD can be nitrated, a modification that could lead to the depressed activity of this enzyme found in placentas from diabetic rats.

Ambientación y aplicación variable de insumos en áreas con influencia freática Nosetto, Marcelo Daniel; Jobbagy Gampel, Esteban Gabriel; Mercau, Jorge L. El manejo por ambientes es muy útil para aumentar la eficiencia de producción en campos con influencia freática. El aporte de napas a los cultivos puede determinar altos rendimientos y reducir el riesgo hídrico en ambientes semiáridos o subhúmedos.

Experiencia didáctica en el aula de ciencia: el suelo como integrador de conceptos químicos; Teaching experience in the classroom of science: the soil as chemical thread concept Moro, Lucrecia E.; Tintori Ferreira, María Alejandra; Lorenzo, Maria Gabriela En este trabajo presentamos una propuesta didáctica innovadora para alumnos de la Educación Secundaria, sobre le tema suelo en la cual se tiene en cuenta el impacto de la actividad humana. Esta propuesta se implementó durante el desarrollo del tema disoluciones y ofreció una nueva alternativa para la interpretación de los conceptos de disolución y de pH. Se relacionaron los compuestos químicos con los agentes formadores del suelo y sus contaminantes. La experiencia didáctica se desarrolló simultáneamente en cinco escuelas de la Provincia de Buenos Aires empleando una metodología “en red” en el marco del Programa “Ciencia entre Todos” (CET). Presentamos la propuesta didáctica por su carácter innovador para el tratamiento de los diseños curriculares de química, por su enfoque integrador con las problemáticas sociales de la región y la promoción del cuidado del ambiente desde el punto de vista del desarrollo sustentable.; We present a new didactic approach for secondary students about “the soil”. The impact of the human activity was especially considered. This design was carried out for solutions and provided new strategies for understanding pH concept. Chemical compounds were related with the training agents of the ground and its pollutant. This didactic experience was simultaneously put into practice in five schools of Provincia de Buenos Aires employing net methodology. This belongs to the Program “Science by and for Everyone” (CET). We present this proposal because of its innovation characteristics for chemical contents, its focus on social and regional problems and the promotion of environment care from sustainable development perspective.

Recombinant horseradish peroxidase production in species of lepidoptera frequently found in Argentina Romero, Lucía Virginia; Targovnik, Alexandra Marisa; Wolman, Federico Javier; Fogar, M.; Simonella, M.; Cascone, Osvaldo; Miranda, Maria Victoria Horseradish peroxidase isozyme C (HRPC) is an important commercial biocatalyst. In this study, a screening of different lepidopteran species frequently found in Argentina to produce this protein was carried out. Two recombinant viruses were constructed: AcMNPV HRPC polyhedrin-minus (occ−), an intrahemocelical infective virus; and AcMNPV HRPC polyhedrin-plus (occ+), to achieve an oral infective baculovirus. Each lepidopteran species was infected either with AcMNPV HRPC occ− or AcMNPV HRPC occ+ and the harvesting days post-infection (dpi) were optimized. All species were susceptible to AcMNPV HRPC occ− infection, giving Spodoptera frugiperda the best yield: 41 μg per larva. Rachiplusia nu was highly susceptible to oral infection, reaching 22 μg per larva at 4 dpi. HRPC was purified by IMAC from S. frugiperda extracts with a yield of 86% and a purification factor of 29.

Factores que afectan el éxito reproductivo y la calidad de la nidada del pingüino patagónico (Spheniscus Magellanicus) en el Canal Beagle, Tierra del Fuego, Argentina; Factors affecting reproductive success and clutch quality of Magellanic Penguin (Spheniscus Magellanicus) in the Beagle Channel, Tierra del Fuego, Argentina Scioscia, Gabriela; Raya Rey, Andrea Nélida; Favero, Marco; Schiavini, Adrian Carlos Miguel En este estudio se estimó la duración de los viajes de alimentación y el tamaño corporal de machos y hembras del pingüino patagónico durante el período reproductivo en una colonia del Canal Beagle, Tierra del Fuego, y se determinaron las implicancias de estos parámetros sobre el éxito reproductivo y la calidad de la nidada. La duración de los viajes difirió significativamente entre sexos y entre las distintas etapas reproductivas. Las hembras realizaron viajes más extensos que los machos durante la etapa de incubación. Esto podría deberse a diferencias en las reservas corporales y en capacidades de alimentación relacionadas con su condición corporal. En ambos sexos, los viajes realizados durante la etapa de incubación fueron más prolongados, mientras que los realizados durante el cuidado temprano de pichones fueron más cortos. Los viajes de alimentación tuvieron menor duración cuando los pichones eran más pequeños y necesitaban de un mayor cuidado parental. Se registró un alto valor de éxito reproductivo (1.51 pichones por nido) comparado con el de colonias de las Islas Malvinas y Punta Tombo. Estos resultados podrían explicarse por diferencias en la disponibilidad de alimento en aguas cercanas a la colonia. El tamaño corporal de los padres no se relacionó con el éxito reproductivo. No obstante, las hembras con mayor tamaño corporal produjeron pichones de mayor tamaño al comienzo de la muda y nidadas de mayor calidad. La correlación positiva entre el tamaño de la hembra y el tamaño de los pichones al comienzo de la muda sugiere un aporte importante de las hembras en el desarrollo del pichón.; The aim of this work was to study foraging trip duration and body size of male and female Magellanic Penguins during the breeding season and to determine the association of these parameters with both reproductive success and clutch quality in a colony located in the Beagle Channel, Tierra del Fuego. Trip duration differed significantly between sexes and between breeding stages. Females performed longer trips than males during incubation. We suggest that this could be due to differences in body reserves and foraging capabilities related with their body condition. In both sexes, foraging trips during incubation were longer than in the other stages, while the shortest trips were observed during early chick rearing. Trips were shorter when chicks were smaller and required greater parental care. A high value of reproductive success (1.51 chicks per nest) was recorded in comparison to that observed in colonies from the Malvinas Islands and Punta Tombo. These results could be related to differences in food availability in nearby waters. Body size of parents was not associated with reproductive success. Notwithstanding, larger females produced larger chicks at early moult and clutches of higher quality. The correlation between female body size and chick size at early moult suggests an important contribution of females on chick's development.

Synthesis and Characterization of superparamagnetic Iron Oxide Nanoparticles for bio-medical applications Cano, Leonardo Andres; Cagnoli, Maria Virginia; Stewart, Silvana Jacqueline; Cabanillas, Edgardo Domingo; Romero, E. L.; Marchetti, Sergio Gustavo Monodisperse iron oxide nanoparticles (NPs) of 4 nm were obtained through high-temperature solution phase reaction of iron (III) acetylacetonate with 1, 2-hexadecanediol in the presence of oleic acid and oleylamine. The as-synthesized iron oxide nanoparticles have been characterized by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and magnetic measurements. The species obtained were Fe3O4 and/or γγ -Fe2O3. These NPs are superparamagnetic at room temperature and even though the reduced particle size they show a high saturation magnetization (MS ≈ 90 emu/g).

As estatísticas como objeto de estudo González Bollo, Hernán Gustavo De 12 a 15 de novembro de 2010, a “Sociedade Brasileira de História da Ciência” (SBHC), estará promovendo seu 12º Seminário Nacional de História da Ciência e da Tecnologia, na cidade de Salvador, nas dependências da Universidade Federal da Bahia. Junto, tendo por objetivo precípuo a reativação da “Sociedade Latino-Americana de História da Ciência e da Tecnologia”, estará sendo realizado seu 7º Congresso. Pois este ano, pela primeira vez, haverá um simpósio focalizando as estatísticas como objeto de estudo, e não como meio de análise: “As instituições estatísticas oficiais: conceitos, medições, comunidades profissionais e a criação de políticas públicas”. Foi uma idéia de Nelson de Castro Senra, que logo recebeu aceitação entusiástica de Hernán González Bollo, quando, então, ambos passaram a trabalhar em colaboração, elaborando a proposta enviada à SBHC.

Bordes dinámicos sobre el método de Lattice Boltzmann para simulación de superficies de fluidos en tiempo real Garcia Bauza, Cristian Dario; Lazo, Marcos Gonzalo; Boroni, Gustavo Adolfo; Dalponte, Diego David; Clausse, Alejandro Un problema típico en flujos en geometrías complejas son los bordes móviles, como por ejemplo en la simulación de flujo de sangre en arterias o el movimiento de un barco. En este trabajo se presenta una implementación especial en un autómata de Lattice Boltzmann 2D de aguas superficiales con bordes y obstáculos internos móviles. El esquema permite simular en forma flexible escenarios de ondas superficiales producidas por embarcaciones, reflejos en puentes, y otras situaciones de interés en animación.

Environmental risks, demographic dynamic and Life Quality: Argentina at beginning of XXI century Velázquez, Guillermo Ángel In this work we analyze the relationship among: 1) Certain environmental risks: Flood problems, Earthquakes, Tornadoes and Soil degradation, 2) Demographic dynamics (inter census growth and migratory balances) and 3) Grade of Life Level Quality of Argentinian people. We use a Geographical Information System (GIS) in which we have done the digitalization of the respective layers of environmental risks. Following, we examine the information on demographic dynamics. At last, we present a synthetic index of the population’s Life Quality, which was elaborated starting from a combination of weighted indicators of environmental and socioeconomic dimensions (education, health and housing). The next step is to study the demographic behaviour and the grade of well-being of Argentina’s people different segments for each one of the environmental risks. We start from an operation of overlapping of different layers (for example: flood risk, growth rate, migration balance, etc). All previous stepladder let us size and compare the obtained Life Quality Index with Demographic Dynamics according to the degree of affectation of each one of the considered physical-environmental events. Finally we can establish the future scenario by projecting these phenomena impacts into the process of global environmental change.

O resultado do conhecimento no segundo comentário de Boécio à Isagogé de Porfírio Bertelloni, Carlos Francisco Uma pequena parte do corpus textual conhecido como Aristoteles latinus foi chamado pelos medievais de Logica vetus. Esta era constituída pelas Categorias e o Perí hermeneias, de Aristóteles, pela Isagogé de Porfírio e pelos comentários de Boécio às obras de Aristóteles e de Porfírio. Hoje é indiscutível a importância dos comentários neoplatônicos da Antiguidade tardia para a compreensão dos textos de Aristóteles. Dentro desse programa neoplatônico, os comentários deste também contribuíram para essa compreensão. No caso de Boécio produz-se, contudo, um fenômeno paradoxal, porque, apesar de seu neoplatonismo, em seu segundo comentário à Isagogé de Porfírio, Boécio conseguiu formular uma das interpretações mais profundas do pensamento aristotélico concernente ao resultado de nossa atividade cognitiva. No segundo comentário, Boécio procede por três passos: 1) analisa as três perguntas sobre os universais, formuladas por Porfírio; 2) realiza uma aporia do modo pelo qual Porfírio resolve o problema dos universais; e 3) apresenta sua própria posição acerca dos universais, que é diversa da posição de Porfírio.

Producción ovina extensiva en la Patagonia Austral: el caso de la zona centro de Santa Cruz Andrade, Larry Dennys; Bedacarratx, Valeria de Los Ángeles; Alvarez, Roberto El propósito del artículo consiste en analizar la meseta central de Santa Cruz en sus aspectos socioproductivos. El objetivo de la investigación, de la cual este trabajo es una elaboración parcial, se orienta a establecer la viabilidad del modelo vigente en la región -ovino extensivo-, así como las posibilidades de que las prácticas asociativas se constituyan en el eje articulador de un relanzamiento productivo. Aquí presentamos un primer análisis socioeconómico y productivo con la finalidad de definir el escenario en el que actualmente se lleva adelante la producción ovina extensiva. Incluimos una descripción de los nuevos actores que actualmente operan en el centro-norte de la provincia y, especialmente en nuestra área de estudio, destacándose entre ellos las empresas mineras transnacionales.; The intention of the article is to analyze the central plateau of Santa Cruz in its socio-productive aspects. The main aim of the investigation, from which this work is a partial elaboration, is to establish: on the one hand, the viability of the traditional extensive ovine model in the region; on the other hand, the possibilities that the associative practices have to become the articulador axis of a productive relaunching. Here, we present a first socioeconomic and productive analysis in order to define the scene in which, at the moment, the extensive ovine production takes ahead. We include a description of the new actors who, nowadays, operate in the area of study, standing out among them, the transnational mining companies.

La conformación de nuevas teorías sobre el arte latinoamericano en el proceso de crisis epistemológica de la modernidad Serviddio, Luisa Fabiana El Mayo francés y la entrada de los tanques soviéticos a Praga señalaron simbólicamente el año de 1968 como el momento de apogeo de una crisis –política, socioeconómica, culturalque relativizó los principales proyectos occidentales del siglo XX. En el campo del arte latinoamericano en se trató de un momento de transición, en el que se reformularon algunas respuestas en nuevos términos, y se anticiparon desarrollos teóricos posteriores. Los críticos, transformados en teóricos, ubicaron sus reflexiones dentro de una temporalidad predictiva –la futurología de Romero Brest- y prescriptiva –el pensamiento visual independiente de Acha, o la resistencia de Marta Traba-, buscando figurarse hacia adonde iban las prácticas artísticas de la región.

Música y memoria: La representación del detenido-desaparecido en la industria cultural de la Argentina reciente Quiña, Guillermo Martín En el presente trabajo abordamos la problemática de la representación de los detenidos-desaparecidos por la última dictadura militar argentina en un producto mercantil cultural concreto: la música. Se trata de una indagación acerca de las características que dicha representación asume, preguntándonos por diversas especificidades que hacen a la industria cultural en tanto tal, a la música como producción simbólica y a los modos de su inscripción en la historia reciente de una lucha política concreta. ¿Qué relevancia analítica asumen las condiciones materiales de existencia de la obra musical en la representación del detenido-desaparecido? ¿Qué vínculo establece la obra musical con su propia condición de producto social? ¿Cómo indagar la relación inherente a la obra musical en tanto producto artístico y objeto mercantil? Intentamos reflexionar críticamente acerca de diversos aspectos que constituyen la relación entablada entre las mercancías culturales en sentido amplio y musicales en particular, y los sujetos colectivos históricos involucrados, atendiendo al carácter industrial que asumen hoy aquellas. Se trata de una reflexión que pretende abonar a la construcción de un interés analítico sobre las transformaciones del campo musical local en los últimos años por parte de las ciencias sociales.; In this paper we approach the issue of the representation of disappeared and detained people during the last military dictatorship in Argentina in a concrete cultural and merchant product: music. We look for the characteristics that representation assumes, focusing the different specifications of cultural industry, of music as symbolic production and of the modalities of its presence into the recent history of a particular politic struggle. What is the relevance of material conditions of the existence of musical work on disappeared and detained people representation? Which relation does music establish with its own social product condition? How we should ask about the double condition of music, as an art object and a commodity? We try to think critically about diverse aspects which constitute the relation between cultural and musical commodities, on one side, and collective actors involved, on the other. With this reflection we try to contribute to build an analytic interest on recent changes of the local music field by social sciences.

The surface organization of diacylglycerol pyrophosphate and its interaction with phosphatidic acid at the air-water interface Villasuso, Ana Laura; Wilke, Natalia; Maggio, Bruno; Machado, Estela Edelmira Diacylglycerol pyrophosphate (DGPP), a phosphorylated form of phosphatidic acid (PA), gained attention recently due to its role as signaling lipid. However, little is known about its surface organization and potential impact on membrane-mediated function. In this work we investigated the interfacial behavior of Langmuir monolayers formed with pure DGPP and of its mixtures with PA. We found that changes of the subphase pH affect the surface behavior of DGPP. At pH 8, DGPP forms liquid expanded monolayers with a compressibility modulus of about 60 mN m−1 at collapse. On acidic solutions, the compressibility modulus increases to 90 mN m−1 and the average molecular area is smaller. At pH 8, DGPP and its precursor PA form thermodynamically favored topographically homogeneous non-ideal mixtures. The interaction among these lipids leads to a non-ideal diminution of the mean molecular area and consequently, to an increase of the compressibility modulus, with variations of the surface electrostatics. The favorable interaction of PA and DGPP, leading to changes of the film packing suggest that DGPP may act as a structural signal transducer in membrane-mediated cellular processes.

Role of the quorum sensing mechanism in the response of pseudomonas aeruginosa to lethal and sublethal UVA irradiation Costa, Cristina Susana; Pezzoni, Magdalena; Fernández, Rubén O.; Pizarro, Ramón Augusto The role of quorum sensing (QS) in the response of Pseudomonas aeruginosa to UVA radiation was investigated in the PAO1 strain and derivatives defective in the synthesis of the QS signals 3OC12-HSL (lasI strain), C4-HSL (rhlI strain) or both (lasI rhlI strain). Cell viability measurements demonstrated that the double mutant was significantly more sensitive to UVA than single mutants, which in turn showed reduced cell survival with regard to the PAO1 strain. Irradiation under nitrogen atmosphere and chemiluminescence measurements indicated the oxidative nature of the UVA-induced damage. The activity of the antioxidant enzymes catalase and superoxide dismutase was assayed in these strains before and after irradiation, and a strong correlation between catalase levels and UVA sensitivity was observed. When a sublethal UVA dose was applied to PAO1, a growth delay was observed and this mechanism depended on the rhl system. Moreover, low doses of UVA irradiation triplicated the level of C4-HSL in log PAO1 cells. It is concluded that QS is fundamental in the defense against the toxic effects of UVA in P. aeruginosa. The induction of the QS system by UVA independently of cell density could function as an adaptative strategy to withstand this hostile environmental condition.