Cambrian ensialic rift-related magmatism in the Ossa-Morena Zone

The Late Ediacaran (c. 560–550 Ma) Série Negra sediments of the Évora–Aracena metamorphic belt, Ossa-Morena Zone, SW Iberian Massif, preserve a record of the erosion of an Avalonian–Cadomian magmatic arc and subsequent related turbiditic sedimentation. Detrital zircon from the Série Negra is characterized by predominantly Ediacaran and Cryogenian ages, with few Paleoproterozoic and Archean cores, and a marked lack of Grenvillian ages. These features, when combined with the metasediments' enrichment in LREE (La/Yb=14), negative Eu-anomalies, low 147Sm/144Nd values (0.121) and negative εNd550=−5.5, indicate that the protolith Série Negra sediments were derived from a continental magmatic arc. A period of Late Cadomian (ca. 560–540 Ma) tectonism was followed by an extended episode of widespread bimodal magmatism related to Cambrian (ca. 540–500 Ma) rifting. This tectonic inversion is expressed in the geological record by a regional Early Cambrian unconformity. SHRIMP zircon U–Th–Pb ages from four felsic orthogneisses from the Évora Massif record Cambrian (527±10 Ma, 522±5 Ma, 517±6 Ma and 505±5 Ma) crystallization ages for their igneous protoliths. This confirms the existence of widespread Lower Paleozoic igneous activity in the Ossa-Morena Zone: (i) a Lower Cambrian (ca. 535–515 Ma) igneous–felsic dominated–sedimentary complex (with calc-alkaline signature and associated carbonate and siliciclastic deposition), and (ii) a Middle Cambrian–?Ordovician (ca. 515–490 Ma) igneous–bimodal–sedimentary complex (with calc-alkaline and tholeiitic signatures and associated dominant siliciclastic deposition, but also carbonate sediments). The Cambrian felsic magmatism was characterized by negative Eu-anomalies, (La/Lu)N=0.8–11, 147Sm/144Nd=0.1289–0.1447 and εNd500 ranging from −1.5 to −0.8. A tendency towards peraluminous compositions suggests late fractionation, low degrees of partial melting, or the mixing of crustal and mantle-derived material in the magma source region. Some felsic rocks possibly represent the last residual melts of hightemperature, zircon-undersaturated mafic magmas later affected by crustal contamination, while others indicate partial melting of crustal metasediments variably contaminated by basaltic liquids. The transition from early felsic dominated to later more mafic magmatism suggests the gradual opening of the system to tholeiitic N–E-MORB products (ThN/TaNb1.0). The as yet undated (Cambrian–?Ordovician) E-MORB amphibolites have 147Sm/144Nd=0.1478–0.1797 and εNd500 values ranging from +6.4 to +7.3, while the N-MORB amphibolites have 147Sm/144Nd=0.1818–0.1979 and εNd500 values of +5.8 and +7.0, reaching a maximum of +9.1. In contrast, other amphibolites have a negative Ta-anomaly (1.35bThN/TaNb2.41) reminiscent of lavas from “orogenic” settings or alternatively, typical of crustally-contaminated within-plate magmas. These “VAB-like” amphibolites have 147Sm/144Nd values ranging from 0.1639 to 0.1946 and εNd500 values of +3.5 to +5.2, suggesting derivation by crustal assimilation processes. The subalkaline igneous precursors of the amphibolites were most likely generated in a rift setting by asthenospheric upwelling. These results strengthen the proposed geodynamic scenarios for the SW Iberian Massif by which Cadomian accretion gave rise to an ensialic rift that developed into a proto-oceanic basin and incipient spreading (opening of the Rheic Ocean?). A similar transition from a convergent to a divergent plate boundary during the Ediacaran to Cambrian–?Ordovician has also been reported in other segments of the northern Gondwana margin

Using seabirds to map the distribution of elusive pelagic cephalopod species

The distribution of oceanic cephalopod species is not fully understood but seabirds, which feed on cephalopods and cover vast oceanic areas, might work as samplers and mappers of the occurrence of this elusive group. We tracked 17 wandering albatrosses Diomedea exulans at Bird Island, South Georgia (54° S, 38° W) over the austral winter (breeding period) with GPS-loggers, activity recorders and stomach temperature probes. At logger retrieval, diet composition was accessed via stomach flushings of the tagged individuals. Wandering albatrosses captured circumpolar and rarer oceanic squid in all water masses of the Southern Ocean (i.e. Antarctic, sub-Antarctic and subtropical waters), complementing much of the knowledge about the cephalopod distribution in the Atlantic sector of the Southern Ocean. Some cephalopod species showed a distribution range wider than expected, with oceanic fronts not functioning as ecological barriers as previously thought. This suggests they might be capable of overcoming these frontal regimes and even take advantage of their dynamics as migration pathway

The potential of satellite data to study individual wildfire events

Geophysical Research Abstract of EGU General Assembly 2014, held 27 April - 2 May, 2014 in Vienna, Austria

High-resolution stable isotope stratigraphy of the upper Cambrian and Ordovician in the Argentine Precordillera: Carbon isotope excursions and correlations

We report the occurrence of important carbon isotope excursions in early Paleozoic formations of the Eastern and Central Argentine Precordillera. The Steptoean positive isotope carbon excursion (SPICE) is known from North America, Kazakhstan, South China, Australia and South America, and the negative isotope carbon excursion (SNICE) has been described for the first time in South America. We report here the record of the SPICE and SNICE in a single section in the Eastern Precordillera. In the Central Precordillera, a minor middle Darriwilian positive carbon isotope excursion (MDICE) and a late Sandbian positive isotope carbon excursion, the GICE (~ + 3‰; C. bicornis biozone) are reported from two sections. One pre-GICE positive carbon-isotope excursion (Sandbian Sa1, N. gracilis biozone) in the Central Precordillera with a δ13C peak of ~ + 2‰ is, perhaps, equivalent to the positive Spechts Ferry δ13C excursion of North America. A positive δ13C excursion (~ 6‰; N. persculptus biozone) recorded at the base of the late Hirnantian La Chilca Formation probably corresponds to HICE. These carbon-isotope excursions resulted from more than one factor where paleoceanographic events probably played a major role: (a) sea-level fall and vigorous fluctuations in the Steptoean (SPICE), (b) sea-level rise in the Sunwaptan (SNICE), (c) important transgression in the Sandbian (pre-GICE and GICE), and (d) sea-level fall in the late Hirnantian (HICE). In the Darriwilian and Sandbian stages, organic burial has led to a large 12C sequestration in the deep anoxic ocean with saline bottom water, recorded by the graptoliferous black shales of the Gualcamayo and Los Azules formations in Central Precordillera, helped the building of the MDICE and GICE anomalies. δ18O values for the Upper Cambrian carbonates are likely near-primary isotope signals that point to progressive cooling from the SPICE to the SNICE, whereas for Sandbian carbonates they suggest strong temperature fluctuations. The δ13C peak of the GICE coincides with a cooler period with temperatures warming up towards the late Hirnantian to Rhuddanian. The Upper Cambrian to the Middle Ordovician of the Precordillera recorded a decrease of seawater 87Sr/86Sr ratios in accordance to the global picture. This decrease probably reflects the influence of widespread volcanic activity from arc terranes in low-latitude settings along eastern margins of Laurentia and in the Argentine Precordillera in the Early to Middle Ordovician. Five carbonate samples (from San Juan, Gualcamayo and Los Azules formations) yielded εNd values that along seven already published values seem to plot along the Nd isotopic evolution trend of the Iapetus Ocean. Together, the record of global Upper Cambrian and Ordovician carbon-isotope excursions in the Argentine Precordillera is a valuable proxy in refining Early Paleozoic stratigraphy, establishing of regional/global high-resolution correlations, and sea-level change history in South America.Fil: Sial, A. N.. Universidade Federal de Pernambuco; BrasilFil: Peralta, Silvio Heriberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Gaucher, C.. No especifíca;Fil: Toselli, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaFil: Ferreira, V. P.. Universidade Federal de Pernambuco; BrasilFil: Frei, R.. Universidad de Copenhagen; DinamarcaFil: Parada, M. A.. Universidad de Chile; ChileFil: Pimentel, M. M.. Universidade Federal do Rio Grande do Sul; BrasilFil: Silva Pereira, Natan. Universidade Federal de Pernambuco; Brasi

Prevalence of transmitted HIV-1 antiretroviral resistance among patients initiating antiretroviral therapy in Brazil: a surveillance study using dried blood spots

Introduction: in Brazil, the use of antiretrovirals is widespread: more than 260,000 individuals are currently undergoing treatment. We conducted a survey targeting antiretroviral-naive individuals who were initiating antiretroviral therapy (ART) according to local guidelines. This survey covered five Brazilian regions.Methods: the HIV Threshold Survey methodology (HIV-THS) of the World Health Organization was utilized, and subjects were selected from seven highly populated cities representative of all Brazilian macro-regions. Dried blood spots (DBS) were collected on SS903 collection cards and were transported by regular mail at room temperature to a single central laboratory for genotyping.Results: We analysed samples from 329 individuals initiating highly active antiretroviral therapy (HAART), 39 (11.8%) of whom were harbouring transmitted drug resistance (TDR). the mean CD4+ T cell count was 253 cells/mu L, and the mean viral load was 142,044 copies/mL. the regional prevalence of resistance was 17.0% in the Northeast, 12.8% in the Southeast, 10.6% in the Central region, 8.5% in the North and 8.5% in the South. the inhibitor-specific TDR prevalence was 6.9% for nucleoside reverse transcriptase inhibitors, 4.9% for non-nucleoside reverse transcriptase inhibitors and 3.9% for protease inhibitors; 3.6% of individuals presented resistance to more than one class of inhibitors. Overall, there were trends towards higher prevalences of subtype C towards the South and subtype F towards the North. of the DBS samples collected, 9.3% failed to provide reliable results.Discussion: We identified variable TDR prevalence, ranging from intermediate to high levels, among individuals in whom HIV disease progressed, thus implying that resistance testing before initiating ART could be effective in Brazil. Our results also indicate that the use of DBS might be especially valuable for providing access to testing in resource-limited and remote settings.Abbott BrazilFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal de São Paulo, Infect Dis Unit, São Paulo, BrazilUniv Fed Bahia, Virol Res Lab, Salvador, BA, BrazilFed Dist Hosp Fdn, Brasilia, DF, BrazilLusiada Univ, Mol Biol Lab, Santos, SP, BrazilMunicipal Itajai, Itajai, BrazilMunicipal Porto Alegre, Porto Alegre, RS, BrazilState Univ Amazonas, Div Infect Dis, Manaus, Amazonas, BrazilUniversidade Federal de São Paulo, Infect Dis Unit, São Paulo, BrazilFAPESP: 2007/54923-1CNPq: 479957/2010-0CAPES: 2496/08Web of Scienc

Strain-induced Evolution of Electronic Band Structures in a Twisted Graphene Bilayer

Here we study the evolution of local electronic properties of a twisted graphene bilayer induced by a strain and a high curvature. The strain and curvature strongly affect the local band structures of the twisted graphene bilayer; the energy difference of the two low-energy van Hove singularities decreases with increasing the lattice deformations and the states condensed into well-defined pseudo-Landau levels, which mimic the quantization of massive Dirac fermions in a magnetic field of about 100 T, along a graphene wrinkle. The joint effect of strain and out-of-plane distortion in the graphene wrinkle also results in a valley polarization with a significant gap, i.e., the eight-fold degenerate Landau level at the charge neutrality point is splitted into two four-fold degenerate quartets polarized on each layer. These results suggest that strained graphene bilayer could be an ideal platform to realize the high-temperature zero-field quantum valley Hall effect.Comment: 4 figure

Common questions and misconceptions about protein supplementation: what does the scientific evidence really show?

Protein supplementation often refers to increasing the intake of this particular macronutrient through dietary supplements in the form of powders, ready-to-drink shakes, and bars. The primary purpose of protein supplementation is to augment dietary protein intake, aiding individuals in meeting their protein requirements, especially when it may be challenging to do so through regular food (i.e. chicken, beef, fish, pork, etc.) sources alone. A large body of evidence shows that protein has an important role in exercising and sedentary individuals. A PubMed search of “protein and exercise performance” reveals thousands of publications. Despite the considerable volume of evidence, it is somewhat surprising that several persistent questions and misconceptions about protein exist. The following are addressed: 1) Is protein harmful to your kidneys? 2) Does consuming “excess” protein increase fat mass? 3) Can dietary protein have a harmful effect on bone health? 4) Can vegans and vegetarians consume enough protein to support training adaptations? 5) Is cheese or peanut butter a good protein source? 6) Does consuming meat (i.e., animal protein) cause unfavorable health outcomes? 7) Do you need protein if you are not physically active? 8) Do you need to consume protein ≤ 1 hour following resistance training sessions to create an anabolic environment in skeletal muscle? 9) Do endurance athletes need additional protein? 10) Does one need protein supplements to meet the daily requirements of exercise-trained individuals? 11) Is there a limit to how much protein one can consume in a single meal? To address these questions, we have conducted a thorough scientific assessment of the literature concerning protein supplementation

Searching for network modules

When analyzing complex networks a key target is to uncover their modular structure, which means searching for a family of modules, namely node subsets spanning each a subnetwork more densely connected than the average. This work proposes a novel type of objective function for graph clustering, in the form of a multilinear polynomial whose coefficients are determined by network topology. It may be thought of as a potential function, to be maximized, taking its values on fuzzy clusterings or families of fuzzy subsets of nodes over which every node distributes a unit membership. When suitably parametrized, this potential is shown to attain its maximum when every node concentrates its all unit membership on some module. The output thus is a partition, while the original discrete optimization problem is turned into a continuous version allowing to conceive alternative search strategies. The instance of the problem being a pseudo-Boolean function assigning real-valued cluster scores to node subsets, modularity maximization is employed to exemplify a so-called quadratic form, in that the scores of singletons and pairs also fully determine the scores of larger clusters, while the resulting multilinear polynomial potential function has degree 2. After considering further quadratic instances, different from modularity and obtained by interpreting network topology in alternative manners, a greedy local-search strategy for the continuous framework is analytically compared with an existing greedy agglomerative procedure for the discrete case. Overlapping is finally discussed in terms of multiple runs, i.e. several local searches with different initializations.Comment: 10 page

Spatial Factors Play a Major Role as Determinants of Endemic Ground Beetle Beta Diversity of Madeira Island Laurisilva

The development in recent years of new beta diversity analytical approaches highlighted valuable information on the different processes structuring ecological communities. A crucial development for the understanding of beta diversity patterns was also its differentiation in two components: species turnover and richness differences. In this study, we evaluate beta diversity patterns of ground beetles from 26 sites in Madeira Island distributed throughout Laurisilva – a relict forest restricted to the Macaronesian archipelagos. We assess how the two components of ground beetle beta diversity (βrepl – species turnover and βrich - species richness differences) relate with differences in climate, geography, landscape composition matrix, woody plant species richness and soil characteristics and the relative importance of the effects of these variables at different spatial scales. We sampled 1025 specimens from 31 species, most of which are endemic to Madeira Island. A spatially explicit analysis was used to evaluate the contribution of pure environmental, pure spatial and environmental spatially structured effects on variation in ground beetle species richness and composition. Variation partitioning showed that 31.9% of species turnover (βrepl) and 40.7% of species richness variation (βrich) could be explained by the environmental and spatial variables. However, different environmental variables controlled the two types of beta diversity: βrepl was influenced by climate, disturbance and soil organic matter content whilst βrich was controlled by altitude and slope. Furthermore, spatial variables, represented through Moran’s eigenvector maps, played a significant role in explaining both βrepl and βrich, suggesting that both dispersal ability and Madeira Island complex orography are crucial for the understanding of beta diversity patterns in this group of beetles.Peer reviewe