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101.
Dirk Ferus 《Archiv der Mathematik》1969,20(3):296-300
Ohne Zusammenfassung 相似文献
102.
103.
We demonstrate the generation of high-energy picosecond pulses directly from a thin-disk laser oscillator by employing a self-imaging active multipass geometry. Stable single-pulse operation has been obtained with an average output power in excess of 50 W, excluding a cw background of 8%, at a repetition rate of 3.8 MHz. Self-starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The maximum pulse energy was 13.4 microJ at a pulse duration of 1.36 ps with a time-bandwidth product of 0.34. Single-pass external frequency doubling with a conversion efficiency of 60% yielded >28 W of average power at 515 nm. 相似文献
104.
105.
Thomas Prenveille Cyrielle Garreau Mathias Matner Dirk Dijkstra Wilhelm Oppermann Diethelm Johannsmann 《Journal of polymer science. Part A, Polymer chemistry》2019,57(5):621-629
The reactivity of urethanes based on 1,6‐hexamethylene diisocyanate (HDI) and 4,4′‐methylene diphenyl diisocyanate (MDI) was investigated at temperatures between 190 °C and 235 °C. Diurethane model compounds end‐capped with either 1‐dodecanol (D‐core‐D) or 1‐hexadecanol (H‐core‐H) were mixed and annealed at high temperature. The core was either MDI or HDI. The transurethanization reaction was followed based on the formation of the compounds (H‐core‐D). The amount of H‐core‐D and of side products, which had formed after variable annealing times, were identified with 1H NMR, FTIR, SEC, and MALDI‐TOF. Transurethanization was considerably faster for MDI‐based urethanes than for HDI‐based urethanes. Only traces of side products were formed during annealing of MDI‐based urethanes, whereas a significant amount of allophanates was formed from HDI‐based urethanes under the same conditions. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 621–629 相似文献
106.
Anna Zieleniewska Prof. Dr. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9602-9607
At the focal point of this work is the photophysical characterization of three meso–meso ethene-bridged diporphyrins featuring a diverse metallation pattern. Detailed investigations by means of cyclic voltammetry, absorption, fluorescence, and femto-/nanosecond transient absorption spectroscopy revealed the impact of open-shell nickel(II) on the electronic communication in ethene-bridged heterobimetallic diporphyrins. 相似文献
107.
Michiel Janssen Prof. Dirk E. De Vos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10724-10734
The practical application of Shilov-type Pt catalysis to the selective hydroxylation of terminal aliphatic C−H bonds remains a formidable challenge, due to difficulties in replacing PtIV with a more economically viable oxidant, particularly O2. We report the potential of employing FeCl2 as a suitable redox mediator to overcome the kinetic hurdles related to the direct use of O2 in the Pt reoxidation. For the selective conversion of butyric acid to γ-hydroxybutyric acid (GHB), a significantly enhanced catalyst activity and stability (turnover numbers (TON)>30) were achieved under 20 bar O2 in comparison to current state-of-the-art systems (TON<10). In this regard, essential reaction parameters affecting the overall activity were identified, along with specific additives to attain catalyst stability at longer reaction times. Notably, deactivation by reduction to Pt0 was prevented by the addition of monodentate pyridine derivatives, such as 2-fluoropyridine, but also by introducing varying partial pressures of N2 in the gaseous atmosphere. Finally, stability tests revealed the involvement of PtII and FeCl2 in catalyzing the non-selective overoxidation of GHB. Accordingly, in situ esterification with boric acid proved to be a suitable strategy to maintain enhanced selectivities at much higher conversions (TON>60). Altogether, a useful catalytic system for the selective hydroxylation of primary aliphatic C−H bonds with O2 is presented. 相似文献
108.
This paper presents a framework for incorporating arbitrary implicit multistep schemes into the lattice Boltzmann method. While the temporal discretization of the lattice Boltzmann equation is usually derived using a second-order trapezoidal rule, it appears natural to augment the time discretization by using multistep methods. The effect of incorporating multistep methods into the lattice Boltzmann method is studied in terms of accuracy and stability. Numerical tests for the third-order accurate Adams-Moulton method and the second-order backward differentiation formula show that the temporal order of the method can be increased when the stability properties of multistep methods are considered in accordance with the second Dahlquist barrier. 相似文献
109.
Tobias Ullrich Piermaria Pinter Julian Messelberger Philipp Haines Ramandeep Kaur Jun.-Prof. Dr. Max M. Hansmann Dr. Dominik Munz Prof. Dr. Dirk M. Guldi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7980-7988
Herein, we present a new class of singlet fission (SF) materials based on diradicaloids of carbene scaffolds, namely cyclic (alkyl)(amino)carbenes (CAACs). Our modular approach allows the tuning of two key SF criteria: the steric factor and the diradical character. In turn, we modified the energy landscapes of excited states in a systematic manner to accommodate the needs for SF. We report the first example of intermolecular SF in solution by dimer self-assembly at cryogenic temperatures. 相似文献
110.
Dr. Bugga Balakrishna Arjun Menon Dr. Kecheng Cao Sebastian Gsänger Dr. Sebastian B. Beil Julia Villalva Oleksandr Shyshov Oliver Martin Prof. Dr. Andreas Hirsch Prof. Dr. Bernd Meyer Prof. Dr. Ute Kaiser Prof. Dr. Dirk M. Guldi Prof. Dr. Max von Delius 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18933-18945