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Institution

Technical University of Berlin

EducationBerlin, Germany
About: Technical University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Quantum dot & Laser. The organization has 27292 authors who have published 59342 publications receiving 1414623 citations. The organization is also known as: Technische Universität Berlin & TU Berlin.


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Journal ArticleDOI
20 Jan 2010-ACS Nano
TL;DR: It could be shown that the studied synthesis serves as a model system for growth driven only by coalescence processes after the first demonstration of a continuous-flow SAXS setup for time-resolved studies of nanoparticle formation mechanisms that does not require the use of synchrotron facilities.
Abstract: Gold nanoparticles (AuNP) were prepared by the homogeneous mixing of continuous flows of an aqueous tetrachloroauric acid solution and a sodium borohydride solution applying a microstructured static mixer. The online characterization and screening of this fast process (∼2 s) was enabled by coupling a micromixer operating in continuous-flow mode with a conventional in-house small angle X-ray scattering (SAXS) setup. This online characterization technique enables the time-resolved investigation of the growth process of the nanoparticles from an average radius of ca. 0.8 nm to about 2 nm. To the best of our knowledge, this is the first demonstration of a continuous-flow SAXS setup for time-resolved studies of nanoparticle formation mechanisms that does not require the use of synchrotron facilities. In combination with X-ray absorption near edge structure microscopy, scanning electron microscopy, and UV−vis spectroscopy the obtained data allow the deduction of a two-step mechanism of gold nanoparticle formati...

370 citations

Proceedings ArticleDOI
20 May 2003
TL;DR: These RDF-based P2P networks are able to support sophisticated routing and clustering strategies based on the metadata schemas, attributes and ontologies used, and the use of super-peer based topologies for these networks is described.
Abstract: RDF-based P2P networks have a number of advantages compared with simpler P2P networks such as Napster, Gnutella or with approaches based on distributed indices such as CAN and CHORD. RDF-based P2P networks allow complex and extendable descriptions of resources instead of fixed and limited ones, and they provide complex query facilities against these metadata instead of simple keyword-based searches.In previous papers, we have described the Edutella infrastructure and different kinds of Edutella peers implementing such an RDF-based P2P network. In this paper we will discuss these RDF-based P2P networks as a specific example of a new type of P2P networks, schema-based P2P networks, and describe the use of super-peer based topologies for these networks. Super-peer based networks can provide better scalability than broadcast based networks, and do provide perfect support for inhomogeneous schema-based networks, which support different metadata schemas and ontologies (crucial for the Semantic Web). Furthermore, as we will show in this paper, they are able to support sophisticated routing and clustering strategies based on the metadata schemas, attributes and ontologies used. Especially helpful in this context is the RDF functionality to uniquely identify schemas, attributes and ontologies. The resulting routing indices can be built using dynamic frequency counting algorithms and support local mediation and transformation rules, and we will sketch some first ideas for implementing these advanced functionalities as well.

368 citations

Journal ArticleDOI
TL;DR: The core-shell IrNiO(x)/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.
Abstract: Active and highly stable oxide-supported IrNiOx core-shell catalysts for electrochemical water splitting are presented. IrNix@IrOx nanoparticles supported on high-sur- face-area mesoporous antimony-doped tin oxide (IrNiOx / Meso-ATO) were synthesized from bimetallic IrNix precursor alloys (PA-IrNix /Meso-ATO) using electrochemical Ni leach- ing and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNix /Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core- shell particles. The core-shell IrNiOx /Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.

367 citations

Proceedings ArticleDOI
14 Jun 2009
TL;DR: This work considers a probabilistic model for which the maximum likelihood (ML) trajectory coincides with the optimal trajectory and which reproduces the classical SOC solution and utilizes approximate inference methods that efficiently generalize to non-LQG systems.
Abstract: The general stochastic optimal control (SOC) problem in robotics scenarios is often too complex to be solved exactly and in near real time. A classical approximate solution is to first compute an optimal (deterministic) trajectory and then solve a local linear-quadratic-gaussian (LQG) perturbation model to handle the system stochasticity. We present a new algorithm for this approach which improves upon previous algorithms like iLQG. We consider a probabilistic model for which the maximum likelihood (ML) trajectory coincides with the optimal trajectory and which, in the LQG case, reproduces the classical SOC solution. The algorithm then utilizes approximate inference methods (similar to expectation propagation) that efficiently generalize to non-LQG systems. We demonstrate the algorithm on a simulated 39-DoF humanoid robot.

367 citations

Journal ArticleDOI
Maxime Cailleret1, Steven Jansen2, Elisabeth M. R. Robert3, Elisabeth M. R. Robert4, Lucía DeSoto5, Tuomas Aakala6, Joseph A. Antos7, Barbara Beikircher8, Christof Bigler1, Harald Bugmann1, Marco Caccianiga9, Vojtěch Čada10, J. Julio Camarero11, Paolo Cherubini12, Hervé Cochard13, Marie R. Coyea14, Katarina Čufar15, Adrian J. Das16, Hendrik Davi13, Sylvain Delzon13, Michael Dorman17, Guillermo Gea-Izquierdo18, Sten Gillner19, Sten Gillner20, Laurel J. Haavik21, Laurel J. Haavik22, Henrik Hartmann23, Ana-Maria Hereş24, Kevin R. Hultine25, Pavel Janda10, Jeffrey M. Kane26, Vyacheslav I. Kharuk27, Thomas Kitzberger28, Thomas Kitzberger29, Tamir Klein30, Koen Kramer31, Frederic Lens32, Tom Levanič, Juan Carlos Linares Calderón33, Francisco Lloret34, Raquel Lobo-do-Vale35, Fabio Lombardi36, Rosana López Rodríguez37, Rosana López Rodríguez38, Harri Mäkinen, Stefan Mayr8, Ilona Mészáros39, Juha M. Metsaranta40, Francesco Minunno6, Walter Oberhuber8, Andreas Papadopoulos41, Mikko Peltoniemi, Any Mary Petritan12, Brigitte Rohner1, Brigitte Rohner12, Gabriel Sangüesa-Barreda11, Dimitrios Sarris42, Dimitrios Sarris43, Dimitrios Sarris44, Jeremy M. Smith45, Amanda B. Stan46, Frank J. Sterck31, Dejan Stojanović47, Maria Laura Suarez28, Miroslav Svoboda10, Roberto Tognetti48, José M. Torres-Ruiz13, Volodymyr Trotsiuk10, Ricardo Villalba28, Floor Vodde49, Alana R. Westwood50, Peter H. Wyckoff51, Nikolay Zafirov52, Jordi Martínez-Vilalta34 
ETH Zurich1, University of Ulm2, Vrije Universiteit Brussel3, Royal Museum for Central Africa4, University of Coimbra5, University of Helsinki6, University of Victoria7, University of Innsbruck8, University of Milan9, Czech University of Life Sciences Prague10, Spanish National Research Council11, Swiss Federal Institute for Forest, Snow and Landscape Research12, Institut national de la recherche agronomique13, Laval University14, University of Ljubljana15, United States Geological Survey16, Ben-Gurion University of the Negev17, Center for International Forestry Research18, Dresden University of Technology19, Technical University of Berlin20, University of Arkansas21, University of Kansas22, Max Planck Society23, National Museum of Natural History24, Desert Botanical Garden25, Humboldt State University26, Sukachev Institute of Forest27, National Scientific and Technical Research Council28, National University of Comahue29, Agricultural Research Organization, Volcani Center30, Wageningen University and Research Centre31, Naturalis32, Pablo de Olavide University33, Autonomous University of Barcelona34, University of Lisbon35, Mediterranean University36, Technical University of Madrid37, University of Western Sydney38, University of Debrecen39, Natural Resources Canada40, American Hotel & Lodging Educational Institute41, University of Cyprus42, Open University of Cyprus43, University of Patras44, University of Colorado Boulder45, Northern Arizona University46, University of Novi Sad47, European Forest Institute48, Estonian University of Life Sciences49, University of Alberta50, University of Minnesota51, University of Forestry, Sofia52
TL;DR: The results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.
Abstract: Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-conti- nental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1–100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.

367 citations


Authors

Showing all 27602 results

NameH-indexPapersCitations
Markus Antonietti1761068127235
Jian Li133286387131
Klaus-Robert Müller12976479391
Michael Wagner12435154251
Shi Xue Dou122202874031
Xinchen Wang12034965072
Michael S. Feld11955251968
Jian Liu117209073156
Ary A. Hoffmann11390755354
Stefan Grimme113680105087
David M. Karl11246148702
Lester Packer11275163116
Andreas Heinz108107845002
Horst Weller10545144273
G. Hughes10395746632
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023191
2022650
20213,307
20203,387
20193,105
20182,910