Clinical Course of acute-on-chronic liver failure syndrome and effects on prognosis

Cellular mechanisms in basic and clinical gastroenterology and hepatolog

Climate change and freshwater zooplankton: what does it boil down to?

Recently, major advances in the climate–zooplankton interface have been made some of which appeared to receive much attention in a broader audience of ecologists as well. In contrast to the marine realm, however, we still lack a more holistic summary of recent knowledge in freshwater. We discuss climate change-related variation in physical and biological attributes of lakes and running waters, high-order ecological functions, and subsequent alteration in zooplankton abundance, phenology, distribution, body size, community structure, life history parameters, and behavior by focusing on community level responses. The adequacy of large-scale climatic indices in ecology has received considerable support and provided a framework for the interpretation of community and species level responses in freshwater zooplankton. Modeling perspectives deserve particular consideration, since this promising stream of ecology is of particular applicability in climate change research owing to the inherently predictive nature of this field. In the future, ecologists should expand their research on species beyond daphnids, should address questions as to how different intrinsic and extrinsic drivers interact, should move beyond correlative approaches toward more mechanistic explanations, and last but not least, should facilitate transfer of biological data both across space and time

New Insights into the Investigation of Smoke Production Using a Cone Calorimeter

International audienc

Reconstruction of a 3700 Ma transgressive marine environment from Isua (Greenland): Sedimentology, stratigraphy and geochemical signatures

The rare preservation of a stratigraphy in the northwest of the Eoarchean Isua supracrustal belt (Greenland) demonstrates the world\u27s earliest-recognised marine transgression. Stratigraphically lowest is the ~3710 Ma Solvang Volcanic Formation of picrites, basalts and basaltic-andesites with arc-like geochemical signatures. Close to its erosional top, this formation\u27s volcanic rocks show increase in K2O with depletion of Na2O, depletion in Sr with no alteration in Eu abundance and δ18OVSMOW increase to +16‰, interpreted as subaerial weathering at ~3700 Ma. The sedimentary Snowpatch Formation was deposited unconformably on the Solvang Volcanic Formation. Locally, the unconformity is marked by the laterally discontinuous Conglomerate Member dominated by rounded quartz clasts, but also with clasts of basalt and andesite up to \u3e10 cm across, layered chert and ultramafic rocks. The Conglomerate Member carries sparse detrital zircons, the youngest of which are ~3710 Ma. The conglomerates are succeeded by the Sandstone and Dolostone Member of layered quartz and dolomite clastic sandstones that locally preserve relict shallow marine cross-bedding with scoured layers, tempestite breccia beds and very rare stromatolite horizons. The Sandstone and Dolostone Member is succeeded by the ~3695 Ma BIF Member. The Snowpatch Formation quartz-dolomite sandstones and interlayered stromatolites have seawater-like REE + Y trace element patterns variably modified by a negligible to significant influx of a terrigenous component. Trace element signatures such as Ti/V ratios and normalising REE + Y data to a 3710 Ma weathered volcanic rock (rather than Post Archean Average Shale) suggest this component was derived from a juvenile arc source, resembling the basement Solvang Volcanic Formation. The detailed field and geochemical evidence such as positive correlation between Fe/Mg and Pr/Yb* in the Snowpatch Formation dolostones and BIF (banded iron formation) indicates that the dolomitic lithologies developed in a shallow water setting with clastic sedimentation, during a marine transgression over a weathered ~3710 Ma volcanic arc basement, followed by BIF deposition in deeper water. Thus by 3700 Ma, shallow-water, exposed, settings had already been established, which were the site of stromatolite development

3806 Ma Isua rhyolites and dacites affected by low temperature Eoarchaean surficial alteration: Earth\u27s earliest weathering

This paper reports evidence for Earth\u27s oldest-recognised low temperature alteration, at ∼3800 Ma. Potassic felsic schists with a protolith age of 3806 ± 2 Ma form a ∼30 km long unit in the amphibolite facies, deformed, Isua supracrustal belt (West Greenland). At a single locality, boudinaged layers (nodules) within the schists are low strain zones: they are fine-grained, weakly feldspar-phyric, contain quartz amygdules and have fiamme-like structures, all supporting a volcanic protolith. The nodules and surrounding schistose matrix contain abundant, 100-50 μm, euhedral, oscillatory zoned 3806 Ma zircons. The rare earth patterns of the zircons indicate crystallisation was magmatic. Some zircons contain axial lobate voids indicating that they grew at low pressure as the magma exsolved a fluid. Ti-in-zircon thermometry indicates crystallisation temperatures of 750-650 °C. Taken together, these zircon features indicates growth at eutectic temperatures in a hypabyssal chamber as the magma was exsolving a fluid phase. The magmatic zircons have ɛHf initial values of ∼0 and δ18OVSMOW of +5.0‰ ( Hiess et al., 2009), showing that the source of the volcanic rocks was devoid of assimilated markedly older or weathered crustal material, and probably essentially juvenile. In contrast, the whole rock δ18OVSMOW values are elevated at +14.7 to +16.2‰, indicative of superimposed low-temperature alteration processes. The nodules and matrix schists have non-igneous bulk compositions, exemplified by strong enrichment in K2O and depletion in Na2O. They are depleted in Sr, have no negative Eu anomalies, but have high Rb/Sr, with an Rb-Sr age of 3760 ± 140 Ma (Jacobsen and Dymek, 1988). This indicates that the alteration involving strong degradation of plagioclase occurred in the Eoarchaean. Trace element compositions and establishment of alteration vectors suggest the protoliths were likely rhyolitic and dacitic in composition. The strongest-modified matrix schist compositions contain biotite ± calcite ± dolomite with increase in MgO relative to the nodules, which indicates early magnesian carbonate growth. The whole-rock chemistry, decoupling of the igneous zircon and whole-rock oxygen isotope signatures and the Rb-Sr dating indicate that after eruption, the 3806 Ma felsic volcanic rocks underwent Eoarchaean low-temperature potassic alteration with weathering and groundwater circulation the most likely process. The geochemistry of the Isua felsic schists is compared with that of better-preserved volcanic rocks where the alteration conditions are known. This suggests a subaerial environment. The carbonatisation of the Isua felsic schists demonstrates drawdown of atmospheric CO2 into rocks made porous by the weathering

Evaluation of Cowpea [Vigna unguiculata (L.) Walp.] varieties for intercropping with maize (

No Abstract.URJAST Vol. 9 (2) 2006: pp. 117-15

Cross-examining Earth\u27s oldest stromatolites: Seeing through the effects of heterogeneous deformation, metamorphism and metasomatism affecting Isua (Greenland) ∼3700 Ma sedimentary rocks

The ∼3700 Ma and 3800 Ma meta-volcanic and -sedimentary rocks in the Isua supracrustal belt (Greenland) were affected by heterogeneous ductile deformation under amphibolite facies conditions (∼500-650 °C), and variably modified by secondary silica and carbonate mineralisation deposited from diagenetic and metasomatic fluids. Rare low-deformation areas preserve original volcanic features - submarine basaltic pillows and sedimentary features - including bedding. These are best-preserved in two dimensions on flat- to moderately-inclined outcrop surfaces, but invariably are tectonically-stretched along a steeply-plunging third dimension, through stretching in the direction of fold axes; a style of deformation found throughout Earth\u27s history. There is a debate about whether rare relicts of ∼3700 Ma stromatolites preserved in metadolomites that formed in a shallow marine setting (Nutman et al., 2016) represent bona fide biogenic primary structures fortuitously preserved in low deformation, or whether these structures are manifestations of deformation combined with non-biogenic deposition of secondary carbonate (Allwood et al., 2018). Here, we critically test the primary nature of the sedimentary rocks hosting the proposed stromatolites and also the veracity of the proposed stromatolites, by addressing the following questions: (i) Are the rocks an in situ outcrop of known age, or displaced blocks of unknown age or origin?; (ii) How much of the carbonate is of an originally sedimentary versus a secondary (i.e., metasomatic - introduced) origin?; (iii) Is the seawater-like REE + Y (rare earth element and yttrium) trace element signature carried definitely by carbonate minerals and therefore diagnostic of a cool, surficial sedimentary system?; (iv) Are the proposed stromatolites consistent with biogenicity in terms of their geometry and fine-scale layering, or could they be the product of soft sediment or structural deformation (compression in folding)? The answers to these questions, which combine diverse observations from geologic context, geochemistry and stromatolite morphology show that the weight of evidence is consistent with a biogenic origin for the stromatolites formed in a shallow water setting and are inconsistent with formation entirely through inorganic processes