排序方式: 共有105条查询结果,搜索用时 250 毫秒
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Pierre Thureau Simone Sturniolo Miri Zilka Fabio Ziarelli Stéphane Viel Jonathan R. Yates Giulia Mollica 《Magnetic resonance in chemistry : MRC》2019,57(5):256-264
Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. Nuclear magnetic resonance crystallography approaches based on the comparison of experimental and Density Functional Theory (DFT)-computed 1H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study, we discuss the possibility of using 13C-13C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarization, to realize a DFT-free, rapid screening of a pool of structures predicted by ab initio random structure search. We show that although 13C-13C dipolar couplings can identify structures possessing long range structural motifs and unit cell parameters close to those of the true structure, it must be complemented with other data to recover information about the presence and the chemical nature of the supramolecular interactions. 相似文献
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The aim of this work is to establish the existence of multi-peak solutions for the following class of quasilinear problems where \(\epsilon\) is a positive parameter, \(N\geq2\), \(V\), \(f\) are continuous functions satisfying some technical conditions and \(\phi\) is a \(C^{1}\)-function.
相似文献
$$ - \mbox{div} \bigl(\epsilon^{2}\phi\bigl(\epsilon|\nabla u|\bigr)\nabla u \bigr) + V(x)\phi\bigl(\vert u\vert\bigr)u = f(u)\quad\mbox{in } \mathbb{R}^{N}, $$
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Cellulose - The electrical conductivity of cotton fabrics was enhanced using an in situ synthesis of graphene or polymerization of conductive polymer. The impact of conductive materials... 相似文献
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In this study, the Bonner sphere spectrometer (BSS) used for measurement of neutron spectra based a BF3 long counter. The most important problem for this system was a high count of scattered neutrons. This spectrometer was established
by designed a new shadow cone with a smaller length and improved attenuation coefficient. Because of shortening the length
of the shadow cone, distance of source and center of the sphere was decreased. Furthermore, external part of the thermal detector
was covered with a suitable layer to reduce the contribution count of scattering neutrons. Experimental results show that
BSS system with BF3 long cylindrical counter, applying the proper developments, can be used in neutron fluence spectrometry. 相似文献
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Ranjbar Sara Edraki Najmeh Firuzi Omidreza Khoshneviszadeh Mehdi Miri Ramin 《Molecular diversity》2019,23(2):471-508
Molecular Diversity - 5-Oxo-hexahydroquinoline (5-oxo-HHQ) represents a biologically attractive fused heterocyclic core. Various synthetic analogs of 5-oxo-HHQ have been synthesized and assessed... 相似文献
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Vahid Khakyzadeh Mohammad Ali Zolfigol Fatemeh Derakhshan-Panah Majid Jafarian Mir Vahid Miri Maryam Gilandoust 《Molecular diversity》2018,22(2):335-342
The aim of this work is to introduce, model, and optimize a new non-acid-catalyzed system for a direct N\(=\)N–C bond formation. By reacting naphthols or phenol with anilines in the presence of the sodium nitrite as nitrosonium (\(\hbox {NO}^{+})\) source and triethylammonium acetate (TEAA), a N\(=\)N–C group can be formed in non-acid media. Modeling and optimization of the reaction conditions were investigated by response surface method. Sodium nitrite, TEAA, and water were chosen as variables, and reaction yield was also monitored. Analysis of variance indicates that a second-order polynomial model with F value of 35.7, a P value of 0.0001, and regression coefficient of 0.93 is able to predict the response. Based on the model, the optimum process conditions were introduced as 2.2 mmol sodium nitrite, 2.2 mL of TEAA, and 0.5 mL \(\hbox {H}_{2}\hbox {O}\) at room temperature. A quadratic (second-order) polynomial model, by analysis of variance, was able to predict the response for a direct N=N–C group formation. Predicted response values were in good agreement with the experimental values. Electrochemistry studies were done to introduce new Michael acceptor moieties. Broad scope, high yields, short reaction time, and mild conditions are some advantages of the presented method. 相似文献
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