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851.
Petr Vinš Martina Vermachová Pavel Drašar Melisa del Barrio Carmen Jarne Vicente L. Cebolla Abel de Cózar Ronen Zangi Fernando P. Cossío 《Tetrahedron》2013
Different generations of dendrimers incorporating one fluorescent core of apigenin and three Fréchet benzylic dendrons have been prepared. The chief geometric features of these dendrimers have been obtained by Molecular Dynamics simulations. These computational data suggest that the asphericities of dendrimers belonging to the third and fourth generations are considerably larger than those associated with lower radii of gyration. Fluorescence spectra of high generation dendrimers evolve along time and quantum yields show an appreciable lowering for the fourth generation dendrimer. All these data suggest aggregation phenomena and lower quantum yields for nonspheric dendrimers in solution. 相似文献
852.
A. D. Averin T. Yu. Baranova A. S. Abel V. V. Kovalev A. K. Buryak G. M. Butov E. N. Savelyev B. S. Orlinson I. A. Novakov I. P. Beletskaya 《Russian Journal of Organic Chemistry》2013,49(1):1-7
Palladium-catalyzed amination of 3-bromopyridine with amines of the adamantane series in the presence of Pd(dba)2/L [L = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl or 2-dimethylamino-2′-dicyclohexylphosphinobiphenyl] gave the desired N-(pyridin-3-yl)-substituted amines in 74–97% yields. Diamines of the adamantane series reacted with 2 equiv of 3-bromopyridine in a complicated fashion to produce mono- and triaryl-substituted derivatives as by-products, while the yields of N,N′-diarylation products were 18–56%. 相似文献
853.
A. Jullien T. Pfeifer M. J. Abel P. M. Nagel M. J. Bell D. M. Neumark S. R. Leone 《Applied physics. B, Lasers and optics》2008,93(2-3):433-442
High-order harmonic emission can be confined to the leading edge of an 800 nm driver laser pulse under moderately intense focusing conditions (7×1014 W/cm2) (Pfeifer et al. in Opt. Express 15:17120, 2007). Here, the experimentally observed curtailment of harmonic production on the leading edge of the driver pulse is shown to be controlled by an ionization-induced phase-matching condition. The transient plasma density inherent to the process of high-harmonic generation terminates the harmonic emission by an ultrafast loss of phase matching on the leading edge of the laser pulse. The analysis is supported by a reconstruction of the in situ intensity envelope of the driver pulse with attosecond temporal resolution, performed by measurements of the carrier-envelope phase dependence of individual half-cycle harmonic cutoffs. The method opens the way to wavelength-tunable isolated attosecond pulse generation. 相似文献
854.
Luis Bustos Carlos Echiburú-Chau Alejandro Castro-Alvarez Ben Bradshaw Mario J. Simirgiotis Marco Mellado Claudio Parra Mauricio Cuellar 《Molecules (Basel, Switzerland)》2022,27(14)
This study aimed to determine the in vitro cytotoxicity and understand possible cytotoxic mechanisms via an in silico study of eleven chalcones synthesized from two acetophenones. Five were synthesized from a prenylacetophenone isolated from a plant that grows in the Andean region of the Atacama Desert. The cytotoxic activity of all the synthesized chalcones was tested against breast cancer cell lines using an MTT cell proliferation assay. The results suggest that the prenyl group in the A-ring of the methoxy and hydroxyl substituents of the B-ring appear to be crucial for the cytotoxicity of these compounds. The chalcones 12 and 13 showed significant inhibitory effects against growth in MCF-7 cells (IC50 4.19 ± 1.04 µM and IC50 3.30 ± 0.92 µM), ZR-75-1 cells (IC50 9.40 ± 1.74 µM and IC50 8.75 ± 2.01µM), and MDA-MB-231 cells (IC50 6.12 ± 0.84 µM and IC50 18.10 ± 1.65 µM). Moreover, these chalcones showed differential activity between MCF-10F (IC50 95.76 ± 1.52 µM and IC50 95.11 ± 1.97 µM, respectively) and the tumor lines. The in vitro results agree with molecular coupling results, whose affinity energies and binding mode agree with the most active compounds. Thus, compounds 12 and 13 can be considered for further studies and are candidates for developing new antitumor agents. In conclusion, these observations give rise to a new hypothesis for designing chalcones with potential cytotoxicity with high potential for the pharmaceutical industry. 相似文献
855.
Alvaro Javier Gmez Rodríguez Dagoberto Oyola Lozano Humberto Bustos Rodríguez Yebrail Rojas Martínez German Antonio Prez Alczar Ligia Edith Zamora Alfonso Juan Sebastian Trujillo Hernandez 《Molecules (Basel, Switzerland)》2022,27(21)
The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of Nd2Fe14B (hard magnetic material) and Fe90Al10 (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the Nd2Fe14B system and 15% of the Fe90Al10 system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the Nd2Fe14B system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the Nd2Fe14B and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the Nd2Fe14B and Fe90Al10 sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for Nd2Fe14B Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the Fe90Al10 system, show a tendency for the nanoparticles to agglomerate. 相似文献
856.
Abel Carreras Andreas Lorbach Guillermo C. Bazan Pere Alemany Guang Wu Miguel A. Garcia-Garibay Emily F. Maverick 《Helvetica chimica acta》2023,106(2):e202200142
A single-crystal X-ray study of a fullerene-imidazole adduct at nine temperatures (80 K≤T≤480 K), accompanied by energy calculations, strongly suggested thermal motion of the C60 moiety with respect to the imidazolium heterocycle. Analysis of the anisotropic displacement parameters, calculations of frequencies, and the refinement of disorder models for the crystal at four temperatures (230 K≤T≤380 K) lead to the conclusion that the rotator is moving at all temperatures. The rotation barrier is low, with one preferred crystallographic site and several other energy minima. 相似文献
857.
It is proven results about existence and nonexistence of unit normal sections of submanifolds of the Euclidean space and sphere, which associated Gauss maps, are harmonic. Some applications to constant mean curvature hypersurfaces of the sphere and to isoparametric submanifolds are obtained too. 相似文献
858.
Maximum likelihood principal component analysis (MLPCA) was originally proposed to incorporate measurement error variance information in principal component analysis (PCA) models. MLPCA can be used to fit PCA models in the presence of missing data, simply by assigning very large variances to the non‐measured values. An assessment of maximum likelihood missing data imputation is performed in this paper, analysing the algorithm of MLPCA and adapting several methods for PCA model building with missing data to its maximum likelihood version. In this way, known data regression (KDR), KDR with principal component regression (PCR), KDR with partial least squares regression (PLS) and trimmed scores regression (TSR) methods are implemented within the MLPCA method to work as different imputation steps. Six data sets are analysed using several percentages of missing data, comparing the performance of the original algorithm, and its adapted regression‐based methods, with other state‐of‐the‐art methods. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献