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181.
182.
We consider a system consisting of two immiscible fluids and their interface. The equilibrium interface is assumed to be planar. The velocity fields in the fluids are described by the linearized Navier-Stokes equations with appropriate boundary conditions at the interface. Explicit expressions for the response of the system to arbitrary bulk and/or surface forces are derived. In particular, we consider the transmission and reflection of sound modes and conclude that ultrasonic techniques can be used to measure the coefficient of sliding friction between fluids. In addition, we obtain dispersion relations for the free surface modes. 相似文献
183.
184.
Aromatic hydroxylation catalyzed by toluene 4-monooxygenase in organic solvent/aqueous buffer mixtures 总被引:3,自引:0,他引:3
Toluene 4-monooxygenase is a four-protein component diiron enzyme complex. The enzyme catalyzes the hydroxylation of toluene
to give p-cresol with ∼96% regioselectivity. The performance of the enzyme in two-phase reaction systems consisting of toluene, hexane,
or perfluorohexane and an aqueous buffer was tested. In each of the cosolvent systems, containing up to 93% (v/v) of solvent,
the enzyme was active and exhibited regioselectivity indistinguishable from the aqueous reaction. Using the perfluorohexane/buffer
system, a number of polycyclic aromatic hydrocarbons were oxidized that were not readily oxidized in aqueous buffer. An instability
of the hydroxylase component and a substantial uncoupling of NADH utilization and product formation were observed in reactions
that were continued for longer than ∼3 min. More stable enzyme complexes will be needed for broad applicability of this hydroxylating
system in nonaqueous media. 相似文献
185.
Shekhar KC Roshan K. Dhungana Namrata Khanal Prof. Ramesh Giri 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8124-8128
We report a Ni-catalyzed regioselective α-carbonylalkylarylation of vinylarenes with α-halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α-halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ-diarylcarbonyl derivatives with α-secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug. 相似文献
186.
The black hole information problem provides important clues for trying to piece together a quantum theory of gravity. Discussions on this topic have generally assumed that in a consistent theory of gravity and quantum mechanics, quantum theory is unmodified. In this review, we discuss the black hole information problem in the context of generalisations of quantum theory. In this preliminary exploration, we examine black holes in the setting of generalised probabilistic theories, in which quantum theory and classical probability theory are special cases. We are able to calculate the time it takes information to escape a black hole, assuming that information is preserved. In quantum mechanics, information should escape pure state black holes after half the Hawking photons have been emitted, but we find that this get’s modified in generalisations of quantum mechanics. Likewise the black-hole mirror result of Hayden and Preskill, that information from entangled black holes can escape quickly, also get’s modified. We find that although information exits the black hole as predicted by quantum theory, it is fairly generic that it fails to appear outside the black hole at this point—something impossible in quantum theory due to the no-hiding theorem. The information is neither inside the black hole, nor outside it, but is delocalised. 相似文献