Free University of Berlin

About: Free University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Population & Context (language use). The organization has 35195 authors who have published 66525 publications receiving 2094403 citations. The organization is also known as: FU Berlin.

Effect of friction on oxidative graphite intercalation and high-quality graphene formation

Abstract: Oxidative wet-chemical delamination of graphene from graphite is expected to become a scalable production method. However, the formation process of the intermediate stage-1 graphite sulfate by sulfuric acid intercalation and its subsequent oxidation are poorly understood and lattice defect formation must be avoided. Here, we demonstrate film formation of micrometer-sized graphene flakes with lattice defects down to 0.02% and visualize the carbon lattice by transmission electron microscopy at atomic resolution. Interestingly, we find that only well-ordered, highly crystalline graphite delaminates into oxo-functionalized graphene, whereas other graphite grades do not form a proper stage-1 intercalate and revert back to graphite upon hydrolysis. Ab initio molecular dynamics simulations show that ideal stacking and electronic oxidation of the graphite layers significantly reduce the friction of the moving sulfuric acid molecules, thereby facilitating intercalation. Furthermore, the evaluation of the stability of oxo-species in graphite sulfate supports an oxidation mechanism that obviates intercalation of the oxidant. Scalable graphene production from graphite via an intercalation-oxidation-reduction process is still hampered by low reproducibility and many lattice defects. Here, the authors show that reducing molecular friction by using highly crystalline graphite and mild oxidizing conditions is the key to high quality graphene.

ProTox-II: a webserver for the prediction of toxicity of chemicals.

Abstract: Advancement in the field of computational research has made it possible for the in silico methods to offer significant benefits to both regulatory needs and requirements for risk assessments, and pharmaceutical industry to assess the safety profile of a chemical. Here, we present ProTox-II that incorporates molecular similarity, pharmacophores, fragment propensities and machine-learning models for the prediction of various toxicity endpoints; such as acute toxicity, hepatotoxicity, cytotoxicity, carcinogenicity, mutagenicity, immunotoxicity, adverse outcomes pathways (Tox21) and toxicity targets. The predictive models are built on data from both in vitro assays (e.g. Tox21 assays, Ames bacterial mutation assays, hepG2 cytotoxicity assays, Immunotoxicity assays) and in vivo cases (e.g. carcinogenicity, hepatotoxicity). The models have been validated on independent external sets and have shown strong performance. ProTox-II provides a freely available webserver for in silico toxicity prediction for toxicologists, regulatory agencies, computational and medicinal chemists, and all users without login at http://tox.charite.de/protox_II. The webserver takes a two-dimensional chemical structure as an input and reports the possible toxicity profile of the chemical for 33 models with confidence scores, and an overall toxicity radar chart along with three most similar compounds with known acute toxicity.

How dynamic can organizational capabilities be? Towards a dual-process model of capability dynamization

Abstract: The recent discussion in the field of strategic management broadly favors the idea of dynamic capabilities in order to overcome potential rigidities of organizational capability building. The major question addressed in this paper is whether capabilities can actually be conceived as being in flux—and if so, to what extent and in which way? After briefly recapitulating the distinguishing features of organizational capabilities, path dependency, structural inertia, and commitment are identified as the main capability-rigidity drivers causing a managerial dilemma. In the search for a resolution of this dilemma different approaches of dynamic capabilities are identified and discussed. The analysis shows that the approaches suffer from inherent conceptual contradictions: the dynamization runs the risk of dissolving the original idea and strength of organizational capability building. Ultimately, capabilities would lose the strategic power attributed to them in the resource-based view. The last section of this paper therefore aims to develop an alternative approach, which aims at preserving the original merits of organizational capability and solving the rigidity issue not by integrating a dynamic dimension into the capability construct but rather by establishing a separate function (‘capability monitoring’). The suggestions mount up to a tier solution. Its logic builds on the dynamics of countervailing processes and second-level observation. Copyright © 2007 John Wiley & Sons, Ltd.