Nueva información palinológica sobre la Formación Poti (Viseano superior) en el arroyo Roncador, Cuenca Parnaíba, noreste de Brasil

Se presenta el resultado del análisis palinológico de seis muestras de superficie de la Formación Poti expuesta en el arroyo Roncador (Jerumenha, Piauí), noreste de Brasil. Esta unidad sobreyace en discordancia a la Formación Longá (Famenniano superior-Tournaisiano) y sobre ella se dispone en discordancia la Formación Piaui (Pennsylvaniano inferior). Lutitas carbonosas y limolitas brindaron una diversa asociación de palinomorfos bien preservados, compuesta por 95 especies: 58 especies autóctonas de esporas y 5 de algas, y 9 especies de esporas y 23 especies de microplancton retrabajados principalmente de depósitos del Devónico. Se describen tres nuevas especies (Verrucosisporites iannuzzii, V. roncadorense, V. souzai). Se documenta el primer registro de 24 especies para el Mississippiano de Brasil y 7 especies para América del Sur. Entre las especies con valor estratigráfico registradas en la sección aquí estudiada Anapiculatisporites amplus, A. concinnus, Foveosporites pellucidus, Grandispora maculosa, Reticulatisporites magnidictyus, Verrucosisporites morulatus, Waltzispora polita, junto con otras no registradas previamente en la Formación Poti (Apiculiretusispora microseta, Densosporites spinosus, Knoxisporites ruhlandi, Punctatisporites subvaricosus, Retusotriletes mirabilis, Tricidarisporites phippsae), confirman una edad Viseano tardío y su correlación con la Zona R. magnidictyus (Mag) Melo y Loboziak. La comparación mundial del presente conjunto palinológico indica una gran afinidad con palinofloras coetáneas distribuidas en paleolatitudes similares en América del Sur, Norte de África y Australia (Reino Paracas). Las características sedimentológicas (e.g., areniscas con estratificación cruzada sigmoidal y ondulitas) y paleontológicas (e.g., restos de plantas y abundante materia orgánica terrestre) de la sección indican que la depositación ocurrió en un ambiente de estuario de baja profundidad.This contribution presents the results of the palynological analysis of six surface samples of the Poti Formation cropping out at the Roncador creek (Jerumenha, Piauí), northeastern Brazil. This unit unconformable overlies the upper Famennian-Tournaisian Longá Formation and it is unconformable overlain by the lower Pennsylvanian Piaui Formation. Carbonaceous shales and siltstones yielded a diverse assemblage of well-preserved palynomorphs, composed of 95 species: 58 indigenous spore, and 5 algal species, and 9 reworked spore and 23 reworked microplankton species mostly from Devonian strata. Three new species are described (Verrucosisporites iannuzzii, V. roncadorense, V. souzai). First records for the Mississippian of Brazil (24 species) and South America (7 species) are also documented. Several age diagnostic species recorded in the Poti Formation (Anapiculatisporites amplus, A. concinnus, Foveosporites pellucidus, Grandispora maculosa, Reticulatisporites magnidictyus, Verrucosisporites morulatus and Waltzispora polita), completed with others not previously documented in subsurface deposits of this unit (Apiculiretusispora microseta, Densosporites spinosus, Knoxisporites ruhlandi, Punctatisporites subvaricosus, Retusotriletes mirabilis and Tricidarisporites phippsae), confirms a late Visean age and its correlation to the R. magnidictyus Melo and Loboziak Zone. Worldwide comparison of the Roncador association indicates greater affinity with coeval palynofloras with similar paleolatitudinal position in South America, North Africa and Australia (Paracas Realm). Sedimentologic (e.g., sandstones with sigmoidal cross and wave ripples beddings) and paleontological features (e.g., plant remains and abundant terrestrial organic matter) along this section document a shallow estuarine depositional environment.Fil: Di Pasquo Lartigue, Maria. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Iannuzzi, R.. Universidade Federal do Rio Grande do Sul; Brasi

Investigation of the concept of beauty via a lock-in feedback experiment

Lock-in feedback circuits are routinely used in physics laboratories all around the world to extract small signals out of a noisy environment. In a recent paper (M. Kaptein, R. van Emden, and D. Iannuzzi, paper under review), we have shown that one can adapt the algorithm exploited in those circuits to gain insight in behavioral economics. In this paper, we extend this concept to a very subjective socio-philosophical concept: the concept of beauty. We run an experiment on 7414 volunteers, asking them to express their opinion on the physical features of an avatar. Each participant was prompted with an image whose features were adjusted sequentially via a lock-in feedback algorithm driven by the opinion expressed by the previous participants. Our results show that the method allows one to identify the most attractive features of the avatar

Halving the Casimir force with conductive oxides

The possibility to modify the strength of the Casimir effect by tailoring the dielectric functions of the interacting surfaces is regarded as a unique opportunity in the development of Micro- and NanoElectroMechanical Systems. In air, however, one expects that, unless noble metals are used, the electrostatic force arising from trapped charges overcomes the Casimir attraction, leaving no room for exploitation of Casimir force engineering at ambient conditions. Here we show that, in the presence of a conductive oxide, the Casimir force can be the dominant interaction even in air, and that the use of conductive oxides allows one to reduce the Casimir force up to a factor of 2 when compared to noble metals.Comment: modified version, accepted for publication in Phys Rev Let

Progress towards Bell-type polarization experiment with thermal neutrons

Experimental tests of Bell-type inequalities distinguishing between quantum mechanics and local realistic theories remain of considerable interest if performed on massive particles, for which no conclusive result has yet been obtained. Only two-particle experiments may specifically test the concept of spatial nonlocality in quantum theory, whereas single-particle experiments may generally test the concept of quantum noncontextuality. Here we have performed the first Bell-type experiment with a beam of thermal-neutron pairs in the singlet state of spin, as originally suggested by J. S. Bell. These measurements confirm the quantum-theoretical predictions, in agreement with the results of the well-known polarization experiments carried out on optical photons years ago

No anomalous scaling in electrostatic calibrations for Casimir force measurements

In a recent paper (Phys.Rev.A78, 020101(R) (2008)), Kim at al. have reported a large anomaly in the scaling law of the electrostatic interaction between a sphere and a plate, which was observed during the calibration of their Casimir force set-up. Here we experimentally demonstrate that in proper electrostatic calibrations the scaling law follows the behavior expected from elementary electrostatic arguments, even when the electrostatic voltage that one must apply to minimize the force (typically ascribed to contact potentials) depends on the separation between the surfaces.Comment: Final versio

Further evidence of antibunching of two coherent beams of fermions

We describe an experiment confirming the evidence of the antibunching effect on a beam of non interacting thermal neutrons. The comparison between the results recorded with a high energy-resolution source of neutrons and those recorded with a broad energy-resolution source enables us to clarify the role played by the beam coherence in the occurrence of the antibunching effect.Comment: 4 pages, 3 figure

Direct experimental evidence of free fermion antibunching

Fermion antibunching was observed on a beam of free noninteracting neutrons. A monochromatic beam of thermal neutrons was first split by a graphite single crystal, then fed to two detectors, displaying a reduced coincidence rate. The result is a fermionic complement to the Hanbury Brown and Twiss effect for photons.Comment: 4 pages, 2 figure

Effect of nickel in solid solution on hydrogen transport kinetics in low alloy steels

The use of low alloy steels (LAS) in H2S-containing environments in the oil and gas industry is governed by the ISO standard 15156-2 (NACE MR0175-2). One requirement, which has been disputed over the years, is that the nickel (Ni) content shall not exceed 1 wt%. This work investigated the effect of Ni in solid solution on hydrogen diffusion, solubility, and trapping in ferritic/pearlitic research-grade LAS with nominal Ni contents from 0 to 3 wt%. Hydrogen permeability experiments were carried out in a Devanathan-Stachurski setup at 15, 45 and 70 °C. The effective diffusion coefficients, calculated by the tlag method, decreased with increasing Ni content. The sub-surface hydrogen concentration in lattice and trap sites increased with increasing Ni content. There was no difference between the first and subsequent hydrogen permeation transients, suggesting that Ni in solid solution forms reversible traps. The effect of Ni in refining the microstructure may be superimposed on the effect of Ni in solid solution, and should be investigated in future work