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41.
When certain trivalent rare-earth ions (Ln's) are co-doped in CaGa2S4:Mn2+ as sensitizers, the Mn red emission of the compound is strikingly enhanced. In this work, efficiency of each lanthanide is studied. The best efficiencies are achieved with La3+-, Pr3+-, and Tb3+- co-doped compounds, for each of which the effects of concentrations of the co-doped ions on the Mn2+ emission are investigated. The energy-transfer mechanisms and the location of electronic energy levels of both the trivalent and the divalent lanthanides in the energy band gap of the host material are discussed. Depending on Ln's, charge transfer or cross-relaxation should be taken into account. 相似文献
42.
[reaction: see text] The readily available N-(O-ethyl thiocarbonylsulfanyl)amides are powerful amidyl radical precursors that undergo 5-exo cyclization to give pyrrolidinone derivatives via a radical-chain reaction initiated by a small amount of lauroyl peroxide. 相似文献
43.
Impurity profiles of 3,4-methylenedioxymethylamphetamine (MDMA) tablets seized in France have been examined. The samples were extracted with methylene chloride under basic conditions and then analyzed by capillary gas chromatography. Almost 30 compounds were identified as precursors, intermediates and by-products. Palmitic and stearic acid were also found as tableting materials. The comparison of the different profiles obtained by the reported procedure provided very useful information about the synthetic processes used by clandestine laboratories and enabled a classification into several groups of profiles. According to these results, the reductive amination route appears to be the most common synthetic pathway in Western Europe. Furthermore, 3,4-methylenedioxyphenyl-2-propanone seems to be the most used precursor in clandestine laboratories. 相似文献
44.
We study the nature of the ground state of the two-dimensional extended boson Hubbard model on a square lattice by quantum Monte Carlo methods. We demonstrate that strong but finite on-site interaction U along with a comparable nearest-neighbor repulsion V result in a thermodynamically stable supersolid ground state for densities larger than 1/2, in contrast to fillings less than 1/2 or for very large U, where the checkerboard supersolid is unstable towards phase separation. We discuss the relevance of our results to realizations of supersolids using cold bosonic atoms in optical lattices. 相似文献
45.
The second-order partial derivative of the Stokes signal with respect to frequency and position shows a maximum or minimum at the boundary between two different strained sections. This idea is used to locate the boundary of different stress regions. Knowing the boundaries, we then fit the Brillouin spectrum at the middle between them to get the strain value. This allows a location accuracy of between 5 and 10 cm, which is shorter than the pulse length of 20 cm used in the experiment. The lowest detectable Brillouin frequency difference between two strain sections is 1.2 MHz. 相似文献
46.
We reformulate a recent result of Arason and
Elman by giving a very simple presentation of the
powers of the fundamental ideal of the Witt ring of a field
of characteristic 2.
Sur les puissances de lidéal fondamental de lanneau de Witt
Nous reformulons un résultat récent de Arason et Elman en donnant une présentation très simple des puissances de lidéal fondamental de lanneau de Witt dun corps de caractéristique 2.相似文献
47.
We investigate correlations of the intensity fluctuations of two-dimensional arrays of nonidentical, locally coupled lasers, numerically and experimentally. We find evidence of a power-law dependence of spatial correlations as a function of laser pair distance (or coupling strength) near the phase-locking threshold. 相似文献
48.
49.
50.
Floraine Collette Régis Delatouche Christophe Blanquart Fabien Gueugnon Marc Grégoire Philippe Bertrand Valérie Héroguez 《Journal of polymer science. Part A, Polymer chemistry》2013,51(1):176-189
In this contribution, a versatile approach for the synthesis of functionalized particles for drug delivery is presented, using two nonaggressive standardized procedures. The first procedure considered is the functionalization of an azido‐terminated α‐norbornenyl poly(ethylene oxide) (PEO) macromonomer with an alkyne‐containing active molecule via the copper catalyzed azide alkyne cycloaddition, click type reaction. The functionalized macromonomer is then polymerized by Ring‐Opening Metathesis Polymerization (ROMP) in dispersion to form functionalized particles. The second procedure consists in synthesizing particles by ROMP in dispersed media of norbornene with azido‐terminated α‐norbornenyl PEO macromonomer. The ROMP was initiated by the first generation Grubbs catalyst. Such functionalized core‐shell particles have stealthy properties due to their PEO shell and can be viewed as universal nanocarriers on which any alkyne‐modified active molecule can be grafted by click chemistry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献