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121.
A Highly Luminescent Tetramer from a Weakly Emitting Monomer: Acid‐ and Redox‐Controlled Multiple Complexation by Cucurbit[7]uril 下载免费PDF全文
Dr. Giacomo Bergamini Andrea Fermi Marianna Marchini Mirko Locritani Prof. Alberto Credi Prof. Margherita Venturi Prof. Fabrizia Negri Prof. Paola Ceroni Dr. Massimo Baroncini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7054-7060
The tetrahedral, shape‐persistent molecule 1 4+, containing four pyridylpyridinium units connected through a central carbon atom, exhibits unexpected photophysical properties including a substantially redshifted absorption (2350 cm?1) and a very strong fluorescence (Φem=40 %), compared with the monomer 2 + (Φem=0.4 %). Density functional theory calculations on the structure and spectroscopic properties of 1 4+ and 2 + show that exciton interactions, homoconjugation, and orbital nature account for the observed differences in their photophysical properties. The protonated tetramer binds four cucurbit[7]uril molecules and the host/guest interactions can be controlled by chemical (acid/base) as well as redox stimuli. 相似文献
122.
Starting from 1-tert-butyloxycarbonyl-3-methyl-4-ethoxycarbonyl-1,2-diaza-1,3-diene and β,β,β and α,β-substituted enamines a careful choice of solvents and temperatures allows the divergent synthesis of 5,6-dihydro-4H-pyridazines, 2-(1-N-boc-hydrazono-ethyl)-4-pyrrolidin-1-yl-but-3-enoic acid ethyl ester, and 1-amino-pyrroles. Moreover, some interesting conclusions about the mechanism(s) of the reaction have been drawn by careful analysis of products' structure and distribution. Thus, the reaction may proceed through a stereospecific [4+2] cycloaddition mechanism giving rise to 5,6-dihydro-4H-pyridazines or by simple addition or domino addition/cyclization pathways affording, respectively, 2-(1-N-boc-hydrazono-ethyl)-4-pyrrolidin-1-yl-but-3-enoic acid ethyl ester and 1-amino-pyrroles (formally the [3+2] cycloaddition product). 相似文献
123.
A. Alessandrello C. Arnaboldi F. T. Avignone III J. Beeman M. Barucci M. Balata C. Brofferio C. Bucci S. Cebrian R. J. Creswick S. Capelli L. Carbone O. Cremonesi A. de Ward E. Fiorini H. A. Farach G. Frossati A. Giuliani D. Giugni E. E. Haller I. G. Irastorza R. J. McDonald A. Morales E. B. Norman P. Negri A. Nucciotti M. Pedretti C. Pobes V. Palmieri M. Pavan G. Pessina S. Pirro E. Previtali C. Rosenfeld A. R. Smith M. Sisti G. Ventura M. Vanzini L. Zanotti 《Physics of Atomic Nuclei》2003,66(3):452-457
CUORE is a proposed tightly packed array of 1000 TeO2 bolometers, each being a cube 5 cm on a side with a mass of 750 g. The array consists of 25 vertical towers, arranged in a square of 5 towers by 5 towers, each containing ten layers of four crystals. The design of the detector is optimized for ultralow-background searches for neutrinoless double beta decay of 130Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals of various sizes (MIBETA) has been completed, and a single CUORE tower is being constructed as a smaller scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported. 相似文献
124.
G. Battistoni E. Bellotti G. Bologna P. Campana C. Castagnoli V. Chiarella A. Ciocio D.C. Cundy B. DEtorre-Piazoli E. Fiorini P. Galeotti E. Iarocci C. Liguori G. Mannocchi G.P. Murtas P. Negri G. Nicoletti P. Picchi L. Zanotti 《Physics letters. [Part B]》1983,130(6):454-458
The inclusive production of η mesons at CM energies around 34 GeV has been studied for e+e− annihilation into hadrons. The average number of η-mesons per event is found to be 0.72 ± 0.10 (stat.) ± 0.18 (syst.). The abundance of η's is studied as a function of event shape parameters and it is compared to the corresponding π0 rates. 相似文献
125.
Daniele Fazzi Eleonora Valeria Canesi Chiara Bertarelli Chiara Castiglioni Fabrizia Negri Giuseppe Zerbi 《Journal of Raman spectroscopy : JRS》2010,41(4):406-413
A combined theoretical and experimental Raman study is presented on a diphenyl bithiophene molecule known as a good candidate for the development of organic nonvolatile memory devices. Spectroscopic markers suitable to distinguish the different stable conformers of the molecule have been predicted and detected. The combined analysis of theoretical and experimental Raman spectra recorded in solution indicates that at room temperature a dynamical equilibrium, characterized by interconversion between the two more stable conformers (namely trans and cis), takes place and that the more populated species is the cis form. Referring to the solid phase instead, Raman spectra of single‐crystal samples show the presence of the only trans conformer, as confirmed by X‐ray measurements. Finally, Raman spectra of thin films, as those used for the memory device, were collected; samples just deposited from solution and after few hours from the deposition were analyzed. Following the evolution of selective spectroscopic Raman markers, an isomerization process from the abundant cis (as‐deposited) to the totally trans (after few hours) conformer in the solid phase was detected. These results open the way to the identification of the molecular isomers present in the thin film of the memory cell and finally of the active molecular species involved in the switching mechanism of the operating device. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
126.
Enantioselective Organocatalytic Reduction of β‐Trifluoromethyl Nitroalkenes: An Efficient Strategy for the Synthesis of Chiral β‐Trifluoromethyl Amines 下载免费PDF全文
Elisabetta Massolo Prof. Maurizio Benaglia Manuel Orlandi Dr. Sergio Rossi Giuseppe Celentano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3589-3595
An efficient organocatalytic stereoselective reduction of β‐trifluoromethyl‐substituted nitroalkenes, mediated by 3,5‐dicarboxylic ester‐dihydropyridines (Hantzsch ester type), has been successfully developed. A multifunctional thiourea‐based (S)‐valine derivative was found to be the catalyst of choice, promoting the reaction in up to 97 % ee. The methodology has been applied to a wide variety of substrates, leading to the formation of differently substituted precursors of enantiomerically enriched β‐trifluoromethyl amines. The mechanism of the reaction and the mode of action of the metal‐free catalytic species were computationally investigated; on the basis of DFT transition‐state (TS) analysis, a model of stereoselection was also proposed. 相似文献
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129.
G. De Negri und G. Fabris 《Fresenius' Journal of Analytical Chemistry》1894,33(1):547-572
Ohne ZusammenfassungRom 1891 und 1893.Publicazione del Laboratorio Chimico Centrale delle Gabelle.Nach dem italienischen Original für die Zeitschrift für analytische Chemie. bearbeitet von Dr. D. Holde.Bei dem Umfang der vorliegenden Monographie war eine Besprechung derselben im Bericht über die Fortschritte der analytischen Chemie nicht möglich. Um daher die wichtige Arbeit unseren Lesern zugänglich zu machen, veröffentlichen wir die vorliegende selbstständige Bearbeitung des Herrn Dr. D. Holde an dieser Stelle der Zeitschrift. 相似文献
130.
Time series data with periodic trends like daily temperatures or sales of seasonal products can be seen in periods fluctuating between highs and lows throughout the year. Generalized least squares estimators are often computed for such time series data as these estimators have minimum variance among all linear unbiased estimators. However, the generalized least squares solution can require extremely demanding computation when the data is large. This paper studies an efficient algorithm for generalized least squares estimation in periodic trended regression with autoregressive errors. We develop an algorithm that can substantially simplify generalized least squares computation by manipulating large sets of data into smaller sets. This is accomplished by coining a structured matrix for dimension reduction. Simulations show that the new computation methods using our algorithm can drastically reduce computing time. Our algorithm can be easily adapted to big data that show periodic trends often pertinent to economics, environmental studies, and engineering practices. 相似文献