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991.
Ronald Zirbs Wolfgang Binder Markus Gahleitner Doris Machl 《Macromolecular Symposia》2007,254(1):93-96
Summary: This publication discusses the development of new methods for producing organic-inorganic core-shell-nanoparticles (NP's) via a combination of “grafting-from” techniques and living cationic polymerization reactions. Based on the surface initiated, quasiliving cationic polymerization of isobutylene, polymeric shells of polyisobutylene (PIB) were attached onto nanoparticles (silica NP's of different sizes, r = 12–40 nm) with a high degree of precision. “Grafting-from” polymerization provides an ideal method to control the number of polymer chains per particle by means of the degree of initial derivatization and the length of the polymeric chains. The resulting nanocomposite materials were analyzed using DLS, TEM, GPC, TGA, DSC. 相似文献
992.
Christian Leischner Markus Burkard Anja Michel Susanne Berchtold Heike Niessner Luigi Marongiu Christian Busch Jan Frank Ulrich M. Lauer Sascha Venturelli 《Molecules (Basel, Switzerland)》2021,26(18)
Resveratrol, a natural plant phytoalexin, is produced in response to fungal infection or− UV irradiation. It exists as an isomeric pair with cis- and trans-conformation. Whereas multiple physiological effects of the trans-form, including a pronounced anti-tumoral activity, are nowadays elucidated, much less knowledge exists concerning the cis-isomer. In our work, we analyzed the antiproliferative and cytotoxic properties of cis-resveratrol in four different human tumor entities in direct comparison to trans-resveratrol. We used human cell lines as tumor models for hepatocellular carcinoma (HCC; HepG2, Hep3B), colon carcinoma (HCT-116, HCT-116/p53(−/−)), pancreatic carcinoma (Capan-2, MiaPaCa-2), and renal cell carcinoma (A498, SN12C). Increased cytotoxicity in all investigated tumor cells was observed for the trans-isomer. To verify possible effects of the tumor suppressor p53 on resveratrol-induced cell death, we used wild type and p53-deleted or -mutated cell lines for every tested tumor entity. Applying viability and cytotoxicity assays, we demonstrated a differential, dose-dependent sensitivity towards cis- or trans-resveratrol among the respective tumor types. 相似文献
993.
Markus Enders 《Nachrichten aus der Chemie》2005,53(6):680-681
Unter dem Titel „Dendrimers: Platforms for Chemical Functionality”︁ fand Mitte März in Heidelberg ein zweitägiges Symposium zur Dendrimerforschung statt. 100 Teilnehmer informierten sich in zehn Plenarvorträgen und anhand von 30 Postern über aktuelle Entwicklungen und Ergebnisse. Veranstalter der Tagung waren die Deutsche Akademie der Naturforscher Leopoldina und der Heidelberger Sonderforschungsbereich 623 ‐ „Molekulare Katalyse”︁. 相似文献
994.
995.
Pekka Laukkanen Sami Lehkonen Petteri Uusimaa Markus Pessa Anni Seppl Tommy Ahlgren Eero Rauhala 《Journal of Crystal Growth》2001,230(3-4):503-506
We prepared InGaN layers on GaN/sapphire substrates using rf-MBE. Photoluminescence (PL) from these layers, grown at different temperatures TS, shows that there is a strong tendency of GaN to form a separate phase as TS is increased from 600°C to 650°C. Concomitant with the phase separation, the PL from the InGaN phase broadens, which indicates that indium composition in this phase becomes increasingly non-uniform. Indium compositions measured by Rutherford backscattering (RBS) are consistent with these results. We also observed an increase in PL intensity for InGaN layers grown at higher temperatures. In this paper, we also report on preparing a top-contact InGaN/GaN light emitting diode. The device was operated at 447 nm and had the emission line width of 37 nm with no observable impurity related features. The turn-on voltage was 3.0 V. The output power was 20 μW at 60 mA drive current. 相似文献
996.
Wei Li Jani Turpeinen Petri Melanen Pekka Savolainen Petteri Uusimaa Markus Pessa 《Journal of Crystal Growth》2001,230(3-4):533-536
Strain-compensated GaInNAs/GaAsP quantum well structures and lasers were grown by gas source molecular beam epitaxy using a RF-plasma nitrogen radical beam source. The optimal growth condition for the quantum well structure was determined based on room-temperature photoluminescence measurements. Effects of rapid thermal annealing (RTA) on the optical properties of GaInNAs/GaAsP quantum well structures as well as laser diodes are examined. It was found to significantly increase the photoluminescence from the quantum wells and reduce the threshold current density of the lasers, due to a removal of N induced nonradiative centers from GaInNAs wells. 相似文献
997.
In this contribution the B oundary F inite E lement M ethod (BFEM) is employed for the computation of the orders of stress singularities for several three-dimensional stress concentration problems in linear elastic fracture mechanics. The BFEM combines the advantages of both the FEM and the BEM: while only a discretization on a structural boundary is required, the actual surface mesh consists of standard displacement based finite elements. In contrast to the BEM, no fundamental solution is required. The BFEM is an ef.cient analysis tool which leads to highly accurate results with significantly lesser computational effort when compared to e.g. standard FEM procedures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
998.
999.
In this Letter we study networks that have been optimized to realize a trade-off between communication efficiency and dynamical resilience. While the first is related to the average shortest pathlength, we argue that the second can be measured by the largest eigenvalue of the adjacency matrix of the network. Best efficiency is realized in star-like configurations, while enhanced resilience is related to the avoidance of short loops and degree homogeneity. Thus crucially, very efficient networks are not resilient while very resilient networks lack in efficiency. Networks that realize a trade-off between both limiting cases exhibit core-periphery structures, where the average degree of core nodes decreases but core size increases as the weight is gradually shifted from a strong requirement for efficiency and limited resilience towards a smaller requirement for efficiency and a strong demand for resilience. We argue that both, efficiency and resilience are important requirements for network design and highlight how networks can be constructed that allow for both. 相似文献
1000.
Markus Kirkilionis 《Journal of Mathematical Analysis and Applications》2004,299(1):157-173
We state and prove general comparison principles for ordinary differential equations, discuss the scope of these principles, and present examples. 相似文献