Search for flavor changing neutral currents in top quark decays in pp collisions at 7 TeV

The results of a search for flavor changing neutral currents in top quark decays t→Zq in events with a topology compatible with the decay chain tt̄→Wb+Zq→ℓνb+ℓℓq are presented. The search is performed with a data sample corresponding to an integrated luminosity of 5.0 fb-1 of proton-proton collisions at a center-of-mass energy of 7 TeV, collected with the CMS detector at the LHC. The observed number of events agrees with the standard model prediction and no evidence for flavor changing neutral currents in top quark decays is found. A t→Zq branching fraction greater than 0.21% is excluded at the 95% confidence level. © 2012 CERN.

Identification of steel bars immersed in reinforced concrete based on experimental results of eddy current testing and artificial neural network analysis

This paper presents an experimental research on the use of eddy current testing (ECT) and artificial neural networks (ANNs) in order to identify the gauge and position of steel bars immersed in concrete structures. The paper presents details of the ECT probe and concrete specimens constructed for the tests, and a study about the influence of the concrete on the values of measured voltages. After this, new measurements were done with a greater number of specimens, simulating a field condition and the results were used to generate training and validation vectors for multilayer perceptron ANNs. The results show a high percentage of correct identification with respect to both, the gauge of the bar and of the thickness of the concrete cover. © 2013 Copyright Taylor and Francis Group, LLC.

The effects of pinning on critical currents of superconducting films

Using molecular dynamics simulations, we analyze the effects of artificial periodic arrays of pinning sites on the critical current of superconducting thin films as a function of vortex density. We analyze two types of periodic pinning array: hexagonal and Kagomé. For the Kagome pinning network we make calculations using two directions of transport current: along and perpendicular to the main axis of the lattice. Our results show that the hexagonal pinning array presents higher critical currents than the Kagomé and random pinning configuration for all vortex densities. In addition, the Kagomé networks show anisotropy in their transport properties. © 2012 Springer Science+Business Media, LLC.

Critical currents and melting temperature of a two-dimensional vortex lattice with periodic pinning

The critical current and melting temperature of a vortex system are analyzed. Calculations are made for a two-dimensional film at finite temperature with two kinds of periodic pinning: hexagonal and Kagomé. A transport current parallel and perpendicular to the main axis of the pinning arrays is applied and molecular dynamics simulations are used to calculate the vortex velocities to obtain the critical currents. The structure factor and displacements of vortices at zero transport current are used to obtain the melting temperature for both pinning arrays. The critical currents are higher for the hexagonal pinning lattice and anisotropic for both pinning arrays. This anisotropy is stronger with temperature for the hexagonal array. For the Kagomé pinning lattice, our analysis shows a multi stage phase melting; that is, as we increase the temperature, each different dynamic phase melts before reaching the melting temperature. Both the melting temperature and critical currents are larger for the hexagonal lattice, indicating the role for the interstitial vortices in decreasing the pinning strength. © 2012 Springer Science+Business Media New York.

Search for Flavor-Changing Neutral Currents in Top-Quark Decays t -> Zq in pp Collisions at root s=8 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Erythrina mulungu Alkaloids Are Potent Inhibitors of Neuronal Nicotinic Receptor Currents in Mammalian Cells

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Flavor-changing neutral currents in the minimal 3-3-1 model revisited

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Profile and crowding of currents in mesoscopic superconductors with an array of antidots

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Eddy-induced upwelling off Cape Sao Tome (22 degrees S, Brazil)

The regional ocean off southeast Brazil (20 degrees S-28 degrees S) is known as a current-eddy-upwelling region. The proximity of the Brazil Current to the coast in the Cape Sao Tome vicinities, as well as of its quasi-stationary unstable meanders, suggests the possibility of background eddy-induced upwelling. Such phenomenon can intensify the prevalent coastal upwelling due to wind and topographic effects. In this paper, with the help of a numerical simulation, we provide evidence that eddy-induced upwelling in the absence of wind is possible in this region. The simulation was conducted with a regional configuration of the 3-D Princeton Ocean Model initialized by a feature-based implementation of the Brazil Current and Cape Frio eddy, blended with climatology. (C) 2010 Elsevier Ltd. All rights reserved.

Is the Brazil Current eddy-dominated to the north of 20 degrees S?

The Brazil Current (BC) originates with the arrival and bifurcation of the southernmost branch of the South Equatorial Current (sSEC) between 10-20 degrees S. Previous climatological studies showed a stratified sSEC bifurcation and that the resulting southern branch formed a shallow BC - a weak western boundary current. The analysis of three recent synoptic surveys and global model outputs challenge the description of a continuous BC. The sSEC bifurcation signal near the continental margin was unclear in the analyses, and the velocity fields were dominated by mesoscale eddies. Recurrent anticyclones that seemed to be related to the meandering BC led us to construct a picture of a flow strongly influenced by topography and probably very unstable. Given this new emerging scenario, we hypothesize that the Brazil Current is eddy-dominated to the north of 20 degrees S. Citation: Soutelino, R. G., I. C. A. da Silveira, A. Gangopadhyay, and J. A. Miranda (2011), Is the Brazil Current eddy-dominated to the north of 20 S?, Geophys. Res. Lett., 38, L03607, doi:10.1029/2010GL046276.

Cognitive, Mood, and Electroencephalographic Effects of Noninvasive Cortical Stimulation With Weak Electrical Currents

Objectives: The use of noninvasive cortical electrical stimulation with weak currents has significantly increased in basic and clinical human studies. Initial, preliminary studies with this technique have shown encouraging results; however, the safety and tolerability of this method of brain stimulation have not been sufficiently explored yet. The purpose of our study was to assess the effects of direct current (DC) and alternating current (AC) stimulation at different intensities in order to measure their effects on cognition, mood, and electroencephalogram. Methods: Eighty-two healthy, right-handed subjects received active and sham stimulation in a randomized order. We conducted 164 ninety-minute sessions of electrical stimulation in 4 different protocols to assess safety of (1) anodal DC of the dorsolateral prefrontal cortex (DLPFC); (2) cathodal DC of the DLPFC; (3) intermittent anodal DC of the DLPFC and; (4) AC on the zygomatic process. We used weak currents of 1 to 2 mA (for DC experiments) or 0.1 to 0.2 mA (for AC experiment). Results: We found no significant changes in electroencephalogram, cognition, mood, and pain between groups and a low prevalence of mild adverse effects (0.11% and 0.08% in the active and sham stimulation groups, respectively), mainly, sleepiness and mild headache that were equally distributed between groups. Conclusions: Here, we show no neurophysiological or behavioral signs that transcranial DC stimulation or AC stimulation with weak currents induce deleterious changes when comparing active and sham groups. This study provides therefore additional information for researchers and ethics committees, adding important results to the safety pool of studies assessing the effects of cortical stimulation using weak electrical currents. Further studies in patients with neuropsychiatric disorders are warranted.

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Currents controlling sedimentation, deposits recording palaeo-hydrodynamics – lessons from the continental shelf-slope system off SE South America

The continental margin off SE South America hosts one of the world’s most energetic hydrodynamic regimes but also the second largest drainage system of the continent. Both, the ocean current system as well as the fluvial runoff are strongly controlled by the atmospheric circulation modes over the region. The distribution pattern of particular types of sediments on shelf and slope and the long-term built-up of depositional elements within the overall margin architecture are, thus, the product of both, seasonal to millennial variability as well as long-term environmental trends. This talk presents how the combination of different methodological approaches can be used to obtain a comprehensive picture of the variability of a shelf and upper-slope hydrodynamic system during Holocene times. The particular methods applied are: (a) Margin-wide stratigraphic information to elucidate the role of sea level for the oceanographic and sedimentary systems since the last glacial maximum; (b) Palaeoceanographic sediment proxies combined with palaeo-temperature indicating isotopes of bivalve shells to trace lateral shifts in the coastal oceanography (particularly of the shelf front) during the Holocene; (c) Neodymium isotopes to identify the shelf sediment transport routes resulting from the current regime; (d) Sedimentological/geochemical data to show the efficient mechanism of sand export from the shelf to the open ocean; (e) Diatom assemblages and sediment element distributions indicating palaeo-salinity and the changing marine influence to illustrate the Plata runoff history. Sea level has not only controlled the overall configuration of the shelf but also the position of the main sediment routes from the continent towards the ocean. The shelf front has shifted frequently since the last glacial times probably resulting from both, changes in the Westerly Winds intensity and in the shelf width itself. Remarkable is a southward shift of this front during the past two centuries possibly related to anthropogenic influences on the atmosphere. The oceanographic regime with its prominent hydrographic boundaries led to a clear separation of sedimentary provinces since shelf drowning. It is especially the shelf front which enhances shelf sediment export through a continuous high sand supply to the uppermost slope. Finally, the Plata River does not continuously provide sediment to the shelf but shows significant climate-related changes in discharge during the past centuries. Starting from these findings, three major fields of research should, in general, be further developed in future: (i) The immediate interaction of the hydrodynamic and sedimentary systems to close the gaps between deposit information and modern oceanographic dynamics; (ii) Material budget calculations for the marginal ocean system in terms of material fluxes, storage/retention capacities, and critical thresholds; (iii) The role of human activity on the atmospheric, oceanographic and solid material systems to unravel natural vs. anthropogenic effects and feedback mechanisms

What drives the seasonality of photosynthesis across the Amazon basin? A cross-site analysis of eddy flux tower measurements from the Brasil flux network

We investigated the seasonal patterns of Amazonian forest photosynthetic activity, and the effects thereon of variations in climate and land-use, by integrating data from a network of ground-based eddy flux towers in Brazil established as part of the ‘Large-Scale Biosphere Atmosphere Experiment in Amazonia’ project. We found that degree of water limitation, as indicated by the seasonality of the ratio of sensible to latent heat flux (Bowen ratio) predicts seasonal patterns of photosynthesis. In equatorial Amazonian forests (5◦ N–5◦ S), water limitation is absent, and photosynthetic fluxes (or gross ecosystem productivity, GEP) exhibit high or increasing levels of photosynthetic activity as the dry season progresses, likely a consequence of allocation to growth of new leaves. In contrast, forests along the southern flank of the Amazon, pastures converted from forest, and mixed forest-grass savanna, exhibit dry-season declines in GEP, consistent with increasing degrees of water limitation. Although previous work showed tropical ecosystem evapotranspiration (ET) is driven by incoming radiation, GEP observations reported here surprisingly show no or negative relationships with photosynthetically active radiation (PAR). Instead, GEP fluxes largely followed the phenology of canopy photosynthetic capacity (Pc), with only deviations from this primary pattern driven by variations in PAR. Estimates of leaf flush at three