Entity

Time filter

Source Type

Würzburg, Germany

Zeh A.,Am Hubland | Gerdes A.,Institute For Geowissenschaften | Barton Jr. J.,University Of Fort Hare | Klemd R.,Geozentrum
Precambrian Research | Year: 2010

Results of more than 400 in situ U-Th-Pb and Lu-Hf zircon isotope analyses combined with cathodoluminescence images and field relationships reveal that the oldest magmatic rocks of the Limpopo Belt (Musina area) formed during the Palaeoarchaean between 3.40 and 3.27 Ga, experienced a first anatexis at 3.24-3.07 Ga (M1) and were overlain by sediments mainly between 3.24 and 3.0 Ga. Subsequently, the infra- and supracrustal rocks together underwent two high-grade metamorphic overprints, a first during the Neoarchaean at 2.65 Ga (M2), and a second at 2.025 Ga (M3). Hafnium isotope data additionally reveal that the Palaeoarchaean magmatic rocks result from substantial recycling of much older crust. This is well reflected by nearly chondritic εHf int obtained from primary magmatic zircon domains of four Sand River TTG-gneiss samples (εHf 3.27-3.28 Ga = -1.3 to -1.8), from leucosomes within the Sand River Gneisses (εHf 3.40 Ga = -2.0; εHf 3.28 Ga = -1.5), and from two meta-anorthosite samples of the Messina layered intrusion (εHf 3.35 Ga = 0.1-1.4). Crustal recycling is also supported by hafnium isotope data of detrital zircon grains from two quartzite samples. These data reflect a general increase of the εHf int between 3.65 and 3.2 Ga from ca. -4.0 to 0.0, indicating that an Eo- to Palaeoarchaean crust was mixed with juvenile mantel material in the hinterland of the Limpopo Belt. The present study also demonstrates that Hf isotope data provide a powerful tool, which makes it possible to distinguish zircon domains formed during distinct magmatic or metamorphic events, from such affected by a pseudomorphic alteration, even if the investigated zircon grain underwent multiple alteration processes. © 2010 Elsevier B.V. All rights reserved. Source


Kaiser D.,Am Hubland | Sylvain T.-B.C.,Jean Lorougnon Guede University | Yeo K.,Nangui Abrogoua University | Konate S.,Nangui Abrogoua University | Linsenmair K.E.,Am Hubland
Bonn Zoological Bulletin | Year: 2015

From 2004 to 2008, we conducted the first inventory of termites (Blattoidea: Termitoidae) and ants (Hymenoptera: Formicidae) in Burkina Faso (West Africa) where these important ecosystem engineers are the only active, quantitatively remarkable soil macrofauna during a long dry season. We combined two standard assessment protocols for tropical forests and adapted them to semi-arid (agro)ecosystems to representatively characterize termite and ant communities in two agricultural systems, and assess their response to land-use intensification. In total, 65 ant species and 41 termite species were collected along parallel transects replicated during consecutive years. Both taxa were highly sensitive to human impact. Their taxonomic and functional richness strongly decreased with increasing intensification from a near-natural savannah towards cotton fields with recent pesticide application (North Sudan region), and recovered along a succession of the traditional rehabilitation technique Zaï from barren, crusted land towards a long-term fallow with diverse flora and fauna (sub-Sahel region). Fungus-growers dominated the termite communities in all habitats, with the highest variations between habitats noted among soil- and grass-feeders. ©ZFMK. Source


Mischnik M.,Institute of Physics | Boyanova D.,Am Hubland | Hubertus K.,Institute for Clinical Biochemistry and Pathobiochemistry | Geiger J.,Institute for Clinical Biochemistry and Pathobiochemistry | And 7 more authors.
Molecular BioSystems | Year: 2013

Platelets are critical for haemostasis and blood clotting. However, since under normal circumstances blood should flow without clotting, its function is regulated via a complex interplay of activating and inhibiting signal transduction pathways. Understanding this network is crucial for treatment of cardiovascular and bleeding diseases. Detailed protein interaction and phosphorylation data are explored to establish a simplified Boolean model of the central platelet cascades. We implemented the model by means of CellNetAnalyzer and showed how different signalling events coalesce into a fully activated system state. Furthermore, we examined the networks' inherent threshold behaviour using the semi-quantitative modelling software SQUAD. Finally, predictions are verified monitoring phosphorylations which mark different activation phases as modelled. The model can also be applied to simulate different pharmacological conditions as they modify node activity (aspirin, clopidogrel, milrinon, iloprost, combination) and is available for further studies. It agrees well with observations. Activatory pathways are diversified to cope with complex environmental conditions. Platelet activation needs several activation steps to integrate over different network subsets, as they are formed by the interplay of activating kinases, calcium mobilization, and the inhibiting cAMP-PKA system. System stability analysis shows two phases: a sub-threshold behaviour, characterized by integration over different activatory and inhibitory conditions, and a beyond threshold phase, represented by competition and shutting down of counter-regulatory pathways. The integrin network and Akt-protein are critical for stable effector response. Dynamic threshold-analysis reveals a dependency of the relative activating input strength necessary to irreversibly engage the system from the absolute inhibitory signal strength. © 2013 The Royal Society of Chemistry. Source


Reutelshoefer J.,Am Hubland | Striffler A.,Am Hubland | Lemmerich F.,Am Hubland | Puppe F.,Am Hubland
KCAP 2011 - Proceedings of the 2011 Knowledge Capture Conference | Year: 2011

Text-based authoring using knowledge markups is an increasingly popular editing paradigm in manual knowledge acquisition. Closed world authoring environments support the user to form a coherent knowledge base by checking the referenced objects against a set of declared domain objects. In this scenario, the task of efficient translation (compilation) of the text sources is non-trivial. Additionally, in real-world applications frequent small changes are performed on the source documents and instant feedback to the author is crucial. Therefore, a scalable compilation into the target knowledge representations is necessary. In this paper, we introduce a general algorithm for the incremental compilation of knowledge documents, that analyzes the current document modifications and performs minimal updates on the knowledge base. We provide a formal proof of the correctness of the algorithm and show the effectiveness of the approach in several case studies, using various kinds of knowledge representations and markups. © 2011 ACM. Source

Discover hidden collaborations