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991.
992.
Mathias Lemke Liming Cai Julius Reiss Heinz Pitsch Jörn Sesterhenn 《Combustion Theory and Modelling》2019,23(1):180-196
An adjoint-based approach for the sensitivity analysis of complex reaction mechanisms is presented. It builds purely on the evaluation of the governing equations. No adjoint equations have to be derived explicitly. Instead, the required adjoint operator is constructed numerically. The approach can be utilised for various kinetic models and in existing codes with minimal implementation effort. All dependencies on the state and on model parameters are fully evaluated without simplifications. Sensitivities are calculated more efficiently and more robustly compared with the often-used brute-force method. The approach is demonstrated for a homogeneous (zero-dimensional) reactor with different complex reaction mechanisms including several reaction types. 相似文献
993.
Stefan Wild Michael Fickert Aleksandra Mitrovic Vicent Lloret Christian Neiss Jos Alejandro Vidal‐Moya Miguel ngel Rivero‐Crespo Antonio Leyva‐Prez Katharina Werbach Herwig Peterlik Mathias Grabau Haiko Wittkmper Christian Papp Hans‐Peter Steinrück Thomas Pichler Andreas Grling Frank Hauke Gonzalo Abelln Andreas Hirsch 《Angewandte Chemie (International ed. in English)》2019,58(17):5763-5768
The chemical bulk reductive covalent functionalization of thin‐layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes. 相似文献
994.
Jiajun Wang Jayesh Arun Bafna Satya Prathyusha Bhamidimarri Mathias Winterhalter 《Angewandte Chemie (International ed. in English)》2019,58(14):4737-4741
Biological channels facilitate the exchange of molecules across membranes, but general tools to quantify transport are missing. Electrophysiology is the method of choice to study the functional properties of channels. However, analyzing the current fluctuation of channels typically does not identify successful transport, that is, distinguishing translocation from binding. To distinguish both processes, we added an additional barrier at the channel exit acting as a molecular counter. To identify permeation, we compare the molecule residence time in the native channel with one that is chemically modified at the exit. We use the well‐studied outer membrane channel from E. coli, OmpF. Position 181, which is below the constriction region, was subsequently mutated into cysteine (E181C) in an otherwise cysteine‐free system, then functionalized by covalent binding with one of the two blockers MTSES or GLT. We measured the passage of model peptides, mono‐, tri‐, hepta‐arginine and of norfloxacin, as an example for antibiotic permeation. 相似文献
995.
Marko kugor Julin Valero Keiji Murayama Mathias Centola Hiroyuki Asanuma Michael Famulok 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7022-7025
There is considerable interest in developing progressively moving devices on the nanoscale, with the aim of using them as parts of programmable therapeutics, smart materials, and nanofactories. Present here is an entirely light‐induced DNA walker based on orthogonal photocontrol. Implementing two azobenzene derivatives, S‐DM‐Azo and DM‐Azo, enabled precise coordination of strand displacement reactions that powered a biped walker and guided it along a defined track in a non‐autonomous way. This unprecedented type of molecular walker design offers high precision control over the movement in back‐and‐forth directions as desired, and is regulated solely by the sequence of the irradiation wavelengths. This concept may open new avenues for advancing non‐autonomous progressive molecular motors, ultimately facilitating their application at the nanoscale. 相似文献
996.
Mathias Steiner Marcus Freitag James C. Tsang Vasili Perebeinos Ageeth A. Bol Antonio V. Failla Phaedon Avouris 《Applied Physics A: Materials Science & Processing》2009,96(2):271-282
We study the optical properties of a single, semiconducting single-walled carbon nanotube (CNT) that is partially suspended
across a trench and partially supported by a SiO2-substrate. By tuning the laser excitation energy across the E
33 excitonic resonance of the suspended CNT segment, the scattering intensities of the principal Raman transitions, the radial
breathing mode (RBM), the D mode and the G mode show strong resonance enhancement of up to three orders of magnitude. In the
supported part of the CNT, despite a loss of Raman scattering intensity of up to two orders of magnitude, we recover the E
33 excitonic resonance suffering a substrate-induced red shift of 50 meV. The peak intensity ratio between G band and D band
is highly sensitive to the presence of the substrate and varies by one order of magnitude, demonstrating the much higher defect
density in the supported CNT segments. By comparing the E
33 resonance spectra measured by Raman excitation spectroscopy and photoluminescence (PL) excitation spectroscopy in the suspended
CNT segment, we observe that the peak energy in the PL excitation spectrum is red-shifted by 40 meV. This shift is associated
with the energy difference between the localized exciton dominating the PL excitation spectrum and the free exciton giving
rise to the Raman excitation spectrum. High-resolution Raman spectra reveal substrate-induced symmetry breaking, as evidenced
by the appearance of additional peaks in the strongly broadened Raman G band. Laser-induced line shifts of RBM and G band
measured on the suspended CNT segment are both linear as a function of the laser excitation power. Stokes/anti-Stokes measurements,
however, reveal an increase of the G phonon population while the RBM phonon population is rather independent of the laser
excitation power. 相似文献
997.
Furkan Bulut Wolfgang Rosellen Mathias Getzlaff 《Applied Physics A: Materials Science & Processing》2009,97(1):185-189
Size-selected iron and iron–cobalt alloy clusters have been studied with high resolution transmission electron microscopy
(HRTEM) and scanning tunneling microscopy (STM). The clusters were produced by a continuously working arc cluster ion source
and subsequently size-selected by an electrostatic quadrupole deflector. The crystalline structure of pure clusters has been
investigated with HRTEM to ensure a reliable determination of the lattice parameter for the alloy clusters. The composition
of the alloy clusters was checked with energy dispersive X-ray spectroscopy (EDX). The height of the deposited FeCo clusters
on the (110) surface of tungsten was determined via STM. These results were compared with the lateral size distribution being
investigated by TEM and allow a conclusion on the shape of the deposited alloy clusters. Furthermore, the behavior of the
alloy clusters on the W(110) surface at elevated temperatures has been examined, at which the clusters show anisotropic spreading. 相似文献
998.
999.
We present experimental results on the reversibility of ultrasound in a multiple scattering medium. An ultrasonic pulsed wave is transmitted from a point source to a 128-element receiving array through 2D samples with various thickness. The samples consist of random collections of parallel steel rods immersed in water. The scattered waves are recorded, time reversed and sent back into the medium. The time-reversed waves are converging back to their source and the quality of spatial and temporal focusing on the source is related to the second-order moments of the scattered wave (correlation) in time and in space. Experimental results show that it is possible to obtain a robust estimation of the correlations on a single realisation of disorder, taking advantage of the wide frequency bandwidth. The spatial resolution of the system is only limited by the correlation length of the scattered field, and no longer by diffraction. Moreover, successful time-reversal focusing using a single element instead of an array is possible, whereas a one-channel monochromatic phase conjugation fails. The efficiency of broad-band time reversal compared to monochromatic phase conjugation lies in the number of 'information grains' in the frequency bandwidth. 相似文献
1000.