Fossil biomass preserved as graphitic carbon in a late paleoproterozoic banded iron formation metamorphosed at more than 550°C

Metamorphism is thought to destroy microfossils, partly through devolatilization and graphitization of biogenic organic matter. However, the extent to which there is a loss of molecular, elemental and isotope signatures from biomass during high-temperature metamorphism is not clearly established. We report on graphitic structures inside and coating apatite grains from the c. 1850 Ma Michigamme silicate banded iron formation from Michigan, metamorphosed above 550°C. Traces of N, S, O, H, Ca and Fe are preserved in this graphitic carbon and X-ray spectra show traces of aliphatic groups. Graphitic carbon has an expanded lattice around 3.6 Å, forms microscopic concentrically-layered and radiating polygonal flakes and has homogeneous δ13C values around −22‰, identical to bulk analyses. Graphitic carbon inside apatite is associated with nanometre-size ammoniated phyllosilicate. Precursors of these metamorphic minerals and graphitic carbon originated from ferruginous clayrich sediments with biomass. We conclude that graphite coatings and inclusions in apatite grains indicate fluid remobilization during amphibolite-facies metamorphism of precursor biomass. This new evidence fills in observational gaps of metamorphosed biomass into graphite and supports the existence of biosignatures in the highly metamorphosed iron formation from the Eoarchean Akilia Association, which dates from the beginning of the sedimentary rock record

Ceremony at a Boundary fire: a story of Indigenist Knowledge

National Science Foundation (United States of America

Analyse von Funktionen des prä-B-Zell-Rezeptors anhand induzierbarer Expression von Immunglobulin-Schweren-Ketten

In this paper, we investigate the loss of asymptotic efficiency of semiparametric and quasi-maximum-likelihood estimators relative to maximum-likelihood estimators in models with generalized autoregressive conditional heteroscedasticity (GARCH). For a general time-varying location}scale model, the factors that contribute to differences in efficiency among the estimators can be divided in two categories. One pertains to the parametric speci"cations of the conditional mean and the conditional variance. The other corresponds to the shape characteristics of the conditional density of the standardized errors, summarized in the coefficients of skewness and kurtosis together with the Fisher information for location and scale. The quantification of these factors has practical implications since it can help to decide if the more complex semiparametric estimator provides sufficient efficiency gains with respect to the simplest quasi-maximum-likelihood estimator. We also prove that there is no probability density function, with the exception of the normal, for which the asymptotic efficiency of the three estimators is the same. Particular models are also considered, for which the efficienc

Biomartr: genomic data retrieval with R

$\textbf{MOTIVATION}$: Retrieval and reproducible functional annotation of genomic data are crucial in biology. However, the current poor usability and transparency of retrieval methods hinders reproducibility. Here we present an open source R package, $\textit{biomartr}$, which provides a comprehensive easy-to-use framework for automating data retrieval and functional annotation for meta-genomic approaches. The functions of biomartr achieve a high degree of clarity, transparency and reproducibility of analyses. $\textbf{RESULTS}$: The $\textit{biomartr}$ package implements straightforward functions for bulk retrieval of all genomic data or data for selected genomes, proteomes, coding sequences and annotation files present in databases hosted by the National Center for Biotechnology Information (NCBI) and European Bioinformatics Institute (EMBL-EBI). In addition, $\textit{biomartr}$ communicates with the BioMartr database for functional annotation of retrieved sequences. Comprehensive documentation of $\textit{biomartr}$ functions and five tutorial vignettes provide step-by-step instructions on how to use the package in a reproducible manner. $\textbf{AVAILABILITY AND IMPLEMENTATION}$: The open source $\textit{biomartr}$ package is available at https://github.com/HajkD/biomartr and https://cran.r-project.org/web/packages/biomartr/index.htmlThis work was supported by an European Research Council grant named EVOBREED [grant number 322621] (to JP) and a Gatsby Fellowship [grant number AT3273/GLE] (to JP)

Electrical and ultraviolet characterization of 4H-SiC Schottky photodiodes

Fabrication and electrical and optical characterization of 4H-SiC Schottky UV photodetectors with nickel silicide interdigitated contacts is reported. Dark capacitance and current measurements as a function of applied voltage over the temperature range 20 °C – 120 °C are presented. The results show consistent performance among devices. Their leakage current density, at the highest investigated temperature (120 °C), is in the range of nA/cm2 at high internal electric field. Properties such as barrier height and ideality factor are also computed as a function of temperature. The responsivities of the diodes as functions of applied voltage were measured using a UV spectrophotometer in the wavelength range 200 nm - 380 nm and compared with theoretically calculated values. The devices had a mean peak responsivity of 0.093 A/W at 270 nm and −15 V reverse bias

The missing Rheic Ocean magmatic arcs: Provenance analysis of Late Paleozoic

Early Carboniferous turbiditic sedimentary rocks in synorogenic basins located on both sides of the Rheic suture in SW Iberiawere studied for provenance analysis. An enigmatic feature of this suture, which resulted from closure of the Rheic Ocean with the amalgamation of Pangea in the Late Carboniferous, is that there are no recognizable mid- to Late Devonian subduction-related magmatic rocks,which should have been generated during the process of subduction, on either side of it. U–Pb LA–ICP-MS geochronology of detrital zircons from Early Carboniferous turbidites in the vicinity of the Rheic suture in SW Iberia, where it separates the Ossa–Morena Zone (with Gondwana continental basement) to the north from the South Portuguese Zone (with unknown/Meguma? continental basement) to the south, reveals the abundance of mid- to Late Devonian (51–81%) and Early Carboniferous (13–25%) ages. The Cabrela andMértola turbidites of the Ossa–Morena and South Portuguese zones, respectively, are largely devoid of older zircons, differing from the age spectra of detrital zircons in the oldest (Late Devonian) strata in the underlying South Portuguese Zone, which contain abundant Cambrian and Neoproterozoic ages. Mid- to Late Devonian zircons in the Cabrela Formation (age cluster at c. 391 Ma, Eifelian–Givetian transition) and Mértola Formation (age clusters at c. 369 Ma and at c. 387 Ma, Famennian and Givetian respectively) are attributable to a source terrane made up of magmatic rocks with a simple geological history lacking both multiple tectonic events and older continental basement. The terrane capa- ble of sourcing sediments dispersed on both sides of the suture is interpreted to have been completely re- moved by erosion in SW Iberia. Given that closure of the Rheic Ocean required subduction of its oceanic lithosphere and the absence of significant arc magmatism on either side of the Rheic suture, we suggest: 1) the source of the zircons in the SW Iberia basins was a short-lived Rheic ocean magmatic arc, and 2) given the lack of older zircons in the SW Iberia basins, this short-lived arc was probably developed in an intra-oceanic environment