The Australasian muricid gastropod Lepsiella as Pleistocene visitor to southernmost South America

Six shells belonging to a muricid gastropod species were recovered from a Pleistocene marine raised beach located on Navarino Island, in southern South America. None of the living species in the Beagle Channel or in the area is close, and none of the fossil species in the vicinity regions shows the diagnostic characters of the Navarino Pleistocene fossils. Our material resembles Lepsiella baileyana from southern Australia, although some differences in the suture and in the spire outline are recognized. Haustrinae was previously confined geographically to New Zealand and to the temperate coast of Australia, now extending its range of distribution to southern South America. This finding of Lepsiella ukika sp. nov. is best explained on the basis of transoceanic migration from Australasia by means of the Antarctic Circumpolar Current perhaps during a Quaternary glacial period. The presence of this Pleistocene visitor in southern South America is important because it clearly demonstrates that transcontinental traverse of taxa with direct (non-planktonic) development might have happened by rafting on kelp that served as transport platforms.Fil: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Centro de Investigaciones Paleobiologicas; ArgentinaFil: Nielsen, Sven N.. Universität Zu Kiel; Alemania. Universidad Austral de Chile; Chil

The Site-Diluted Ising Model in Four Dimension

In the literature, there are five distinct, fragmented sets of analytic predictions for the scaling behaviour at the phase transition in the random-site Ising model in four dimensions. Here, the scaling relations for logarithmic corrections are used to complete the scaling pictures for each set. A numerical approach is then used to confirm the leading scaling picture coming from these predictions and to discriminate between them at the level of logarithmic corrections.Comment: 15 pages, 5 ps figures. Accepted for publication in Phys. Rev.

Muestreo de fitoplancton para extracción de PUA (Aldehídos Volatiles Poliinsaturados)

Metodología para obtener muestras de fitoplancton para posterior extracción, caracterización y cuantificación de Aldehídos volátiles insaturados

Microcanonical finite-size scaling in specific heat diverging 2nd order phase transitions

A Microcanonical Finite Site Ansatz in terms of quantities measurable in a Finite Lattice allows to extend phenomenological renormalization (the so called quotients method) to the microcanonical ensemble. The Ansatz is tested numerically in two models where the canonical specific-heat diverges at criticality, thus implying Fisher-renormalization of the critical exponents: the 3D ferromagnetic Ising model and the 2D four-states Potts model (where large logarithmic corrections are known to occur in the canonical ensemble). A recently proposed microcanonical cluster method allows to simulate systems as large as L=1024 (Potts) or L=128 (Ising). The quotients method provides extremely accurate determinations of the anomalous dimension and of the (Fisher-renormalized) thermal $\nu$ exponent. While in the Ising model the numerical agreement with our theoretical expectations is impressive, in the Potts case we need to carefully incorporate logarithmic corrections to the microcanonical Ansatz in order to rationalize our data.Comment: 13 pages, 8 figure

Efecto del agregado de alúmina en la calidad del material de aleación de Zinc Níquel. Adsorción de la alúmina en las partículas que ermiten una mayor transferencia de materia al cátodo

En las aleaciones de Zn-Ni es importante un alto contenido de Ni porque aumenta la resistencia del material contra la corrosión. En este sentido, se encontró que la adición de concentraciones mayores de partículas de alúmina a la solución de electrólisis, hace que las mismas se incorporen al recubrimiento y aumente la composición de Ni y la microdureza. La adsorción se estudió por Voltametría mediante electrodo gotero de mercurio para explicar por la adsorción, porque mayores concentraciones de partículas aumentan la concentración de Níquel en la aleación. Se estudiaron las texturas en muestras preparadas a espesores crecientes, y su relación con la resistencia a la corrosión. El principal aporte de éste trabajo es que el material del recubrimiento con alúmina, modifica las texturas con espesores crecientes. El espesor óptimo en el que aumenta la textura disminuye la corriente de corrosión, a la vez que a 8Adm-2 el contenido de Ni es de 15 % y la dureza es alta para ZnNi de 350 Vickers, que está ligada al desgaste.Fil:Mahmud, Z. Instituto Nacional de Tecnología Industrial (INTI). Procesos SuperficialesFil:Pina, J. Instituto Nacional de Tecnología Industrial (INTI). Procesos SuperficialesFil:Gagliardi, J. Instituto Nacional de Tecnología Industrial (INTI). Procesos SuperficialesFil:Míngolo, N. Comisión Nacional de Energía Atómica (CNEA)Fil:Túlio, P. Universidade Tecnológica Federal do Paraná (UTFPR)Fil:Gordillo, G. Universidad de Buenos Aires (UBA). Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Físic

Voltage dip generator for testing wind turbines connected to electrical networks

This paper describes a new voltage dip generator that allows the shape of the time profile of the voltage generated to be configured. The use of this device as a tool to test the fault ride-through capability of wind turbines connected to the electricity grid can provide some remarkable benefits: First, this system offers the possibility of adapting the main features of the time–voltage profile generated (dip depth, dip duration, the ramp slope during the recovery process after clearing fault, etc.) to the specific requirements set forth by the grid operation codes, in accordance with different network electrical systems standards. Second, another remarkable ability of this system is to provide sinusoidal voltage and current wave forms during the overall testing process without the presence of harmonic components. This is made possible by the absence of electronic converters. Finally, the paper includes results and a discussion on the experimental data obtained with the use of a reduced size laboratory prototype that was constructed to validate the operating features of this new device

Mesozooplankton community structure during summer months in the bay of Cádiz.

Mesozooplankton organisms (>250 μm) were sampled at two stations (inner and outer Bay) in the Bay of Cádiz between May and July 2008. Samples were analysed by means of a semi-automated technique in order to give a preliminary view of the mesoozooplankton community structure in the Bay, based on taxonomic diversity and biomass distribution among size classes. The abundance of organisms increased from May to July in accordance with the increase in temperature and Chlorophyll a (Chla) concentrations. Abundances were higher in the outer Bay station, where Chla concentrations are greater and the water column is more stable. The community changed from being meroplankton- to holoplankton-based due to an increase of Calanoida and especially Cladocera individuals (mainly Penilia avirostris), which are known to peak acutely in the summer. The analysis of Normalised Biomass-Size spectra revealed fairly steep slopes (average -1.3) and relatively high departures from steady state (r2 = 0.8 – 0.94), expectable in a coastal system such as the Bay of Cádiz were disturbance factors are introduced from benthic and tidal processes, together with anthropogenic pressure

Scaling behavior of the Heisenberg model in three dimensions

We report on extensive numerical simulations of the three-dimensional Heisenberg model and its analysis through finite-size scaling of Lee-Yang zeros. Besides the critical regime, we also investigate scaling in the ferromagnetic phase. We show that, in this case of broken symmetry, the corrections to scaling contain information on the Goldstone modes. We present a comprehensive Lee-Yang analysis, including the density of zeros and confirm recent numerical estimates for critical exponents.Comment: 19 pages, 9 figure