Biogeochemical behavior of Ampelozizyphus amazonicus Ducke in the Pitinga mining district, Amazon, Brazil

The vegetal species Ampelozizyphus amazonicus Ducke (Rhamnaceae Family) was chosen as a sampling medium for the lateritic surfaces of the Pitinga Mine in the Amazon region, in order to study the biogeochemical behavior of this species and compare it with the chemical composition of a reference plant. The Pitinga mining district is one of the largest producers of tin in the world. This district contains unique deposits of cryolite and rare metals such as Zr, Nb, Ta, Y and REEs related to granitic bodies that intrude into the volcanic and acid pyroclastic rocks. The results showed that the species A. amazonicus predominantly concentrates significant levels of Zr, Nb, Ta, Th, Be, Sc over U, Hf, Ga and In. These elements are characteristic of the mineral paragenesis for the region, suggesting that this plant can provide a representative sampling medium future geochemical exploration programs in the region.     

Settlement Analysis of Açu Dam,Brazil

Geotechnical and Geological Engineering - The Armando Ribeiro Gonçalves Dam, popularly known as The Açu Dam, is an important geotechnical construction in Rio Grande do Norte state,...     

The optical/X-ray connection: intra-cluster medium iron content and galaxy optical luminosity in 20 galaxy clusters

X-ray observations of galaxy clusters have shown that the intra-cluster gas has iron abundances of about one-third of the solar value. These observations also show that part (if not all) of the intra-cluster gas metals was produced within the member galaxies. We present a systematic analysis of 20 galaxy clusters to explore the connection between the iron mass and the total luminosity of early- and late-type galaxies, and of the brightest cluster galaxies (BCGs). From our results, the intra-cluster medium (ICM) iron mass seems to correlate better with the luminosity of the BCGs than with that of the red and blue galaxy populations. As the BCGs cannot produce alone the observed amount of iron, we suggest that ram-pressure plus tidal stripping acts together to enhance, at the same time, the BCG luminosities and the iron mass in the ICM. Through the analysis of the iron yield, we have also estimated that SN Ia are responsible for more than 50 per cent of the total iron in the ICM. This result corroborates the fact that ram-pressure contributes to the gas removal from galaxies to the ICM, being very efficient for clusters in the temperature range  2 < kT (keV) < 10  .     

On the stability of the satellites of asteroid 87 Sylvia

The triple asteroidal system (87) Sylvia is composed of a 280-km primary and two small moonlets named Romulus and Remus ( Marchis et al. 2005b ). Sylvia is located in the main asteroid belt, with semi-major axis of about 3.49 au, eccentricity of 0.08 and 11° of orbital inclination. The satellites are in nearly equatorial circular orbits around the primary, with orbital radius of about 1360 km (Romulus) and 710 km (Remus). In this work, we study the stability of the satellites Romulus and Remus. In order to identify the effects and the contribution of each perturber, we performed numerical simulations considering a set of different systems. The results from the three-body problem, Sylvia–Romulus–Remus, show no significant variation of their orbital elements. However, the inclinations of the satellites present a long-period evolution with amplitude of about 20° when the Sun is included in the system. Such amplitude is amplified to more than 50° when Jupiter is included. These evolutions are very similar for both satellites. An analysis of these results shows that Romulus and Remus are librating in a secular resonance and their longitude of the nodes are locked to each other. Further simulations show that the amplitude of oscillation of the satellites' inclination can reach higher values depending on the initial values of their longitude of pericentre. In those cases, the satellites get caught in an evection resonance with Jupiter, their eccentricities grow and they eventually collide with Sylvia. However, the orbital evolutions of the satellites became completely stable when the oblateness of Sylvia is included in the simulations. The value of Sylvia's J ₂ is about 0.17, which is very high. However, even just 0.1 per cent of this value is enough to keep the satellite's orbital elements with no significant variation.     

Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: Relationships to Gondwana breakup and passive margin development

The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins.     

Waterfall notch-filtering for restoration of acoustic backscatter records from Admiralty Bay,Antarctica

A series of multibeam sonar surveys were conducted from 2009 to 2013 around Admiralty Bay, Shetland Islands, Antarctica. These surveys provided a detailed bathymetric model that helped understand and characterize the bottom geology of this remote area. Unfortunately, the acoustic backscatter records registered during these bathymetric surveys were heavily contaminated with noise and motion artifacts. These artifacts persisted in the backscatter records despite the fact that the proper acquisition geometry and the necessary offsets and delays were applied during the survey and in post-processing. These noisy backscatter records were very difficult to interpret and to correlate with gravity-core samples acquired in the same area. In order to address this issue, a directional notch-filter was applied to the backscatter waterfall in the along-track direction. The proposed filter provided better estimates for the backscatter strength of each sample by considerably reducing residual motion artifacts. The restoration of individual samples was possible since the waterfall frame of reference preserves the acquisition geometry. Then, a remote seafloor characterization procedure based on an acoustic model inversion was applied to the restored backscatter samples, generating remote estimates of acoustic impedance. These remote estimates were compared to Multi Sensor Core Logger measurements of acoustic impedance obtained from gravity core samples. The remote estimates and the Core Logger measurements of acoustic impedance were comparable when the shallow seafloor was homogeneous. The proposed waterfall notch-filtering approach can be applied to any sonar record, provided that we know the system ping-rate and sampling frequency.     

Geostatistical seismic Amplitude‐versus‐angle inversion

Seismic inversion plays an important role in reservoir modelling and characterisation due to its potential for assessing the spatial distribution of the sub‐surface petro‐elastic properties. Seismic amplitude‐versus‐angle inversion methodologies allow to retrieve P‐wave and S‐wave velocities and density individually allowing a better characterisation of existing litho‐fluid facies. We present an iterative geostatistical seismic amplitude‐versus‐angle inversion algorithm that inverts pre‐stack seismic data, sorted by angle gather, directly for: density; P‐wave; and S‐wave velocity models. The proposed iterative geostatistical inverse procedure is based on the use of stochastic sequential simulation and co‐simulation algorithms as the perturbation technique of the model parametre space; and the use of a genetic algorithm as a global optimiser to make the simulated elastic models converge from iteration to iteration. All the elastic models simulated during the iterative procedure honour the marginal prior distributions of P‐wave velocity, S‐wave velocity and density estimated from the available well‐log data, and the corresponding joint distributions between density versus P‐wave velocity and P‐wave versus S‐wave velocity. We successfully tested and implemented the proposed inversion procedure on a pre‐stack synthetic dataset, built from a real reservoir, and on a real pre‐stack seismic dataset acquired over a deep‐water gas reservoir. In both cases the results show a good convergence between real and synthetic seismic and reliable high‐resolution elastic sub‐surface Earth models.     

Simulation of debris flow on an instrumented test slope using an updated Lagrangian continuum particle method

We present an updated Lagrangian continuum particle method based on smoothed particle hydrodynamics (SPH) for simulating debris flow on an instrumented test slope. The site is a deforested area near the village of Ruedlingen, a community in the canton of Schaffhausen in Switzerland. Artificial rainfall experiments were conducted on the slope that led to failure of the sediment in the form of a debris flow. We develop a 3D mechanistic model for this test slope and conduct numerical simulations of the flow kinematics using an SPH formulation that captures large deformation, material nonlinearity, and the complex post-failure movement of the sediment. Two main simulations explore the impact of changes in the mechanical properties of the sediment on the ensuing kinematics of the flow. The first simulation models the sediment as a granular homogeneous material, while the second simulation models the sediment as a heterogeneous material with spatially varying cohesion. The variable cohesion is meant to represent the effects of root reinforcement from vegetation. By comparing the numerical solutions with the observed failure surfaces and final free-surface geometries of the debris deposit, as well as with the observed flow velocity, flow duration, and hot spots of strain concentration, we provide insights into the accuracy and robustness of the SPH framework for modeling debris flows.

     

Influence of a breakwater on nearby rocky intertidal community structure

It is widely recognised that coastal-defence structures generally affect the structure of the assemblages they support, yet their impact on adjacent systems has been largely ignored. Breakwaters modify the nearby physical environment (e.g. wave action) suggesting a local impact on biological parameters. In the present study, an ACI (After-Control-Impact) design was used to test the general hypothesis that the artificial sheltering of an exposed coast has a strong effect on the structure and functioning of adjacent systems. The effects of a reduction in hydrodynamics were clear for a number of taxa and included the replacement of barnacles, limpets and frondose algae by an increasing cover of ephemeral algae. These effects were evident both at early and late successional stages. Results suggest that the artificial sheltering of naturally exposed coasts can have a strong impact promoting a shift from consumer- to producer-dominated communities, which has important ecological and energetic consequences for the ecosystem.