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Dr. Dongpeng Yan Dr. Dejan‐Krešimir Bučar Dr. Amit Delori Bhavnita Patel Dr. Gareth O. Lloyd Prof. William Jones Prof. Xue Duan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8213-8219
Multi‐component organic nanocrystals that are comprised of two or more supramolecular building blocks can be used to extend the design and assembly scope of solid molecular materials. Herein, we report the use of ultrasonication to prepare halogen‐bonded stilbene‐based nano‐cocrystals that exhibit different photoemission properties, including one‐ and two‐phonon emission and fluorescence lifetimes, relative to those of macrodimensional crystals. The structural transformation from nano‐cocrystals into nanocrystals upon heating results in a luminescence red‐shift from greenish blue to yellow. The temperature‐dependent ratiometric luminescence may allow such nano‐cocrystals to be used as fluorescent sensors and thermosensitive materials. 相似文献
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Zvonimir B. Maksić Krešimir Kovačević Andrea Moguš 《Theoretical chemistry accounts》1980,55(2):127-132
A comparative study of the structural parameters in some strained spirohydrocarbons is presented. The theoretical values provided by the STO-3G, MINDO/3 and IMOA methods are in reasonable agreement with each other and with available experimental data offering thus a posteriori justification of the employed approximate schemes. 相似文献
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A new method for the synthesis of marine alkaloids leucettamines B and C from Leucetta sp. sponges is described. The key step is the base-promoted rearrangement of β-lactam into imidazolone ring. Leucettamines B and C as well as their N-benzoyl derivatives were obtained in high yields. Single-crystal structures of both leucettamines B and C were determined by X-ray diffraction confirming Z-configuration of double bond at 4-position of imidazolone. 相似文献
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Inspired by the results of Ern et al. (Commun Partial Differ Equ 32:317–341, 2007) on the abstract theory for Friedrichs symmetric positive systems, we give the existence and uniqueness result for the initial- (boundary) value problem for the non-stationary abstract Friedrichs system. Despite the absence of the well-posedness result for such systems, there were already attempts for their numerical treatment by Burman et al. (SIAM J Numer Anal 48:2019–2042, 2010) and Bui-Thanh et al. (SIAM J Numer Anal 51:1933–1958, 2013). We use the semigroup theory approach and prove that the operator involved satisfies the conditions of the Hille–Yosida generation theorem. We also address the semilinear problem and apply the new results to a number of examples, such as the symmetric hyperbolic system, the unsteady div–grad problem, and the wave equation. Special attention was paid to the (generalised) unsteady Maxwell system. 相似文献
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On Weakly Formulated Sylvester Equations and Applications 总被引:1,自引:0,他引:1
We use a “weakly formulated” Sylvester equation
to obtain new bounds for the rotation of spectral subspaces of a nonnegative selfadjoint operator in a Hilbert space. Our
bound extends the known results of Davis and Kahan. Another application is a bound for the square root of a positive selfadjoint
operator which extends the known rule: “The relative error in the square root is bounded by the one half of the relative error
in the radicand”. Both bounds are illustrated on differential operators which are defined via quadratic forms. 相似文献
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We study the dynamics of a finite chain of diffusively coupled Lorenz oscillators with periodic boundary conditions. Such rings possess infinitely many fixed states, some of which are observed to be stable. It is shown that there exists a stable fixed state in arbitrarily large rings for a fixed coupling strength. This suggests that coherent behavior in networks of diffusively coupled systems may appear at a coupling strength that is independent of the size of the network. 相似文献
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We have searched for hadronic axions which may be produced in the Sun by a bremsstrahlung-like process, and observed in the HPGe detector by an axioelectric effect. A conservative upper limit on the hadronic axion mass of ma?334 eV at 95% C.L. is obtained. Our experimental approach is based on the axion–electron coupling and it does not include the axion–nucleon coupling, which suffers from the large uncertainties related to the estimation of the flavor-singlet axial-vector matrix element. 相似文献