Technical University of Berlin

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

Jüngste Entwicklungen bei der gekreuzten Olefinmetathese

Abstract: Unter den vielen ubergangsmetallvermittelten C-C-verknupfenden Reaktionen ist die Olefinmetathese in den letzten Jahren durch die grose Bandbreite an moglichen Umsetzungen mit kauflichen und leicht handhabbaren Katalysatoren hervorgetreten und gilt heutzutage als eine der machtigsten Synthesemethoden in der Organischen Chemie. Die intermolekulare Variante dieser Reaktion, die Kreuzmetathese, fuhrte trotz ihres hohen synthetischen Nutzens bis vor kurzem eher ein Schattendasein. Durch die Entwicklung neuer, besserer Katalysatoren konnte die Selektivitat, die Toleranz gegen funktionelle Gruppen und die Effizienz der Katalyse jedoch auf ein Niveau gesteigert werden, das noch bis vor wenigen Jahren als unvorstellbar galt. Dank dieser Fortschritte und dem verbesserten Verstandnis des Reaktionsmechanismus und der Katalysator-Substrat-Wechselwirkungen werden Kreuzmetathesen heute in zunehmendem Mase in mehrstufigen Reaktionssequenzen und Naturstoffsynthesen verwendet. Die kurzlich vorgestellte Einbeziehung von Alkinen und sterisch gehinderten bicyclischen Olefinen als Substrate fur bimolekulare Kupplungen, die Entwicklung von enantioselektiven und in Wasser ausfuhrbaren Kreuzmetathesen und die erfolgreiche Kombination der Olefinmetathese und der Festphasensynthese in der Organischen Chemie haben die Anwendungsbreite der Kreuzmetathese noch zusatzlich vergrosert.

Service Function Chaining in Next Generation Networks: State of the Art and Research Challenges

Abstract: Service function chaining is a network capability that provides support for application-driven-networking through the ordered interconnection of service functions. The lifecycle management of service function chains is enabled by two recently emerged technologies, software defined networking and network function virtualization, that promise a number of efficiency, effectiveness, and flexibility gains. This article introduces a service function chaining taxonomy that considers architecture and performance dimensions as the basis for the subsequent stateof- the-art analysis. The article concludes with a gap analysis of existing solutions and the identification of future research challenges.

Ab initio calculations of the optical properties of 4-Å-diameter single-walled nanotubes

Abstract: We performed density-functional theory calculations in the local-density approximation of the structural, electronic, and optical properties of 4-$\mathrm{\AA{}}$-diameter single-walled carbon nanotubes. The calculated relaxed geometries show significant deviations from the ideal rolled graphene sheet configuration. We study the effect of the geometry on the electronic band structure finding the metallic character of the (5,0) nanotube to be a consequence of the high curvature of the nanotube wall. Calculations of the dielectric function and optical absorption of the isolated nanotubes were performed under light polarized parallel and perpendicular to the tube axis. We compare our results to measurements of the optical absorption of zeolite-grown nanotubes and are able to assign the observed maxima to the nanotube chiralities.

Mesoporous carbon nitride–silica composites by a combined sol–gel/thermal condensation approach and their application as photocatalysts

Abstract: Mesoporous carbon nitrides, silicas and their composites have been prepared by a combined sol–gel and thermal condensation approach. Precursors for the carbon nitride (cyanamide) and silica (TEOS) are mixed and condensed simultaneously. After condensation and heat treatment it is observed that the carbon nitride and silica formed highly interpenetrating mesophases which leads either to the formation of mesoporous carbon nitride or silica after selective removal of one of the phases. Importantly, the carbon nitride preserves its graphitic stacking even in the spatial confinement introduced by the surrounding silica phase. As both precursors are liquids this approach allows convenient shaping into thin and thick films or monoliths of mesoporous carbon nitrides. Enhanced photocatalytic activity is observed for the production of hydrogen from water when these mesoporous carbon nitrides are applied as photocatalyst in comparison to the bulk, but also to other mesoporous carbon nitrides, prepared by the reported two-step, hard templating approach.