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111.
Xin Gai Yi Yu Bart Kuyken Pan Ma Steve J. Madden Joris Van Campenhout Peter Verheyen Gunther Roelkens Roel Baets Barry Luther‐Davies 《Laser \u0026amp; Photonics Reviews》2013,7(6):1054-1064
The wavelength dependence of the nonlinear absorption and the third order nonlinear refraction of crystalline silicon between m and m as well as at m have been measured. It was found that at all wavelengths multi‐photon and free carrier absorption can be significant. In particular nonlinear absorption can affect silicon devices designed for the mid‐infrared that require strong nonlinear response, such as for the generation of a supercontinuum. 相似文献
112.
Mikesell TD van Wijk K Blum TE Snieder R Sato H 《The Journal of the Acoustical Society of America》2012,131(3):EL275-EL281
The accuracy of scattered Rayleigh waves estimated using an interferometric method is investigated. Summing the cross correlations of the wave fields measured all around the scatterers yields the Green's function between two excitation points. This accounts for the direct wave and the scattered field (coda). The correlations themselves provide insights into the location of the scatterers, as well as which scatterer is responsible for particular parts of the coda. Furthermore, these measurements confirm a constant-time arrival in the correlations, not part of the Green's function, but which has previously been derived as a result of the generalized optical theorem. 相似文献
113.
Formal Synthesis of Solanoeclepin A: Enantioselective Allene Diboration and Intramolecular [2+2] Photocycloaddition for the Construction of the Tricyclic Core
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Roel A. Kleinnijenhuis Brian J. J. Timmer Dr. Ginger Lutteke Dr. René de Gelder Prof. Dr. Jan H. van Maarseveen Prof. Dr. Henk Hiemstra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1266-1269
An enantioselective synthesis of an intermediate in the Tanino total synthesis of solanoeclepin A has been developed. The key step was an intramolecular [2+2] photocycloaddition, which led to the tricyclo[5.2.1.01, 6]decane core in six steps. The first photosubstrate, prepared through an indium‐mediated Barbier‐type reaction, gave an excellent [2+2] cycloaddition, but it could not be obtained in sufficient enantiopurity. The second photosubstrate, prepared through an asymmetric allene diborylation in high enantiomeric excess, gave the [2+2] cycloaddition product in high yield on irradiation at 365 nm on 20 g scale in a flow system. Other important steps were the replacement of a boronate group at the quaternary carbon by a vinyl group and diastereoselective cyclopropanation of an allylic alcohol. 相似文献
114.
We study project scheduling so as to maximize the expected net present value when task durations are exponentially distributed. Based on the structural properties of an optimal solution we show that, even if preemption is allowed, it is not necessary to do so. Next to its managerial importance, this result also allows for a new algorithm which improves on the current state of the art with several orders of magnitude, both in CPU time and in memory usage. 相似文献
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Phenomena such as shear thinning and thickening, occurring when complex materials are exposed to external forces, are generally believed to be closely connected to changes in the microstructure. Here, we establish a direct and quantitative relation between shear thinning in a colloidal crystal and the surface area of the locally melted region by dragging a probe particle through the crystal using optical tweezing. We show that shear thinning originates from the nonlinear dependence of the locally melted surface area on the drag velocity. Our observations provide unprecedented quantitative evidence for the intimate relation between mechanical properties and underlying changes in microscopic structure. 相似文献
119.
A pulsed mid-infrared pump at λ=2173 nm is used to demonstrate wideband optical parametric gain in a low-loss 2 cm long silicon photonic wire. Using dispersion engineering to obtain negative second-order (β2) and positive fourth-order (β4) dispersion, we generate broadband modulation instability and parametric fluorescence extending from 1911 nm-2486 nm. Using a cw probe signal to interrogate the modulation instability spectrum, we demonstrate parametric amplification >40 dB with an on-chip gain bandwidth wider than 580 nm, as well as narrowband Raman-assisted peak gain >50 dB. 相似文献
120.
We present detailed investigations of a femtosecond green-pumped optical parametric oscillator (OPO) based on lithium triborate.
As pump source, a frequency-doubled Yb-fiber laser-amplifier system is used. The OPO generates signal pulses tunable over
a spectral range from 780 to 940 nm and idler pulses tunable from 1630 to 1190 nm. More than 250 mW are generated in the signal
beam and more than 300 mW in the idler beam. Without dispersion compensation chirped signal pulses with a pulse duration between
100 and 250 fs are measured. Using this system for coherent anti-Stokes Raman scattering spectroscopy, vibrational resonances
between 1110 and 6760 cm−1 can be excited. Due to the chirped pulses, a spectral resolution of 100 cm−1 is achieved, which is 2.5 times higher compared to an excitation with time-bandwidth limited pulses. 相似文献