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61.
Angelo Liguori Loredana Maiuolo Antonio De Nino Antonio Procopio Giovanni Sindona 《Journal of the American Society for Mass Spectrometry》1999,10(10):975-982
Rules for the gas-phase fragmentation mechanism of the negative ions of lipophilic phosphotriester molecules of biological interest have been established by fast-atom bombardment mass spectrometry/mass spectrometry. The mass-analyzed ion kinetic energy spectra of the [M ? H]? of dinucleoside (1–4) and nucleoside glucopyranoside (5–9) phosphotriesters show that in the absence of charges on the phosphate bridge, the availability of acidic protons on the 5′-end nucleobase drives a preferred reaction path which leads to 5′-O-nucleotide or 6-O-glucopyranoside monophosphate anions. 相似文献
62.
Liborio I. Costa Giuseppe Storti Massimo Morbidelli Loredana Ferro Alessandro Galia Onofrio Scialdone Giuseppe Filardo 《大分子反应工程》2012,6(1):24-44
A kinetic model is developed for the heterogeneous free‐radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO2. The model accounts for polymerization in both the dispersed (polymer‐rich) phase and in the continuous (polymer‐free) supercritical phase, for radical interphase transport, diffusion limitations, and chain‐length‐dependent termination in the polymer‐rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer feed composition, monomer concentration, interphase area, and pressure of the system.
63.
María A. Ramírez Gisela M. Ortiz Alejandra Salerno Isabel A. Perillo María M. Blanco 《Tetrahedron letters》2012,53(11):1367-1369
In this work, we describe the synthesis of a series of 1,2,3-trisubstituted-1,4,5,6,7,8-hexahydro-1,3-diazocinium salts (1) by alkylation of the corresponding 1,2-diaryl-1,4,5,6,7,8-hexahydro-1,3-diazocines (2). Compounds 2 were obtained by ethyl polyphosphate-promoted cyclocondensation of N-aroyl-N′-arylpentamethylenediamines (3). Reaction of compounds 2 with alkyl iodides led to 1,2,3-trisubstituted 1,4,5,6,7,8-hexahydro-1,3-diazocinium iodides (1), a new family of cyclic amidinium salts. The best yields for the alkylation were achieved using a mixture of DCM–DMSO (10:1) as solvent. The reaction times of both, the cyclocondensation of compounds 3 and the reaction of 2 with alkyl halides, are dramatically decreased when using microwave irradiation. 相似文献
64.
Valeria Ambrogi Luana Perioli Morena Nocchetti Loredana Latterini Cinzia Pagano Elena Massetti Carlo Rossi 《Journal of Physics and Chemistry of Solids》2012,73(1):94-98
Kojic acid (KOJ) is a melanin synthesis inhibitor widely used as skin lightening agent in topical preparations. Unfortunately it is easily susceptible to photo-oxidation, phenomenon responsible for chemical and organoleptic modifications. The aim of this work was the intercalation of KOJ in hydrotalcite-like compounds (HTlc) in order to stabilize KOJ and to reduce its photolability. Hydrotalcite containing Zn and Al (ZnAl-HTlc) was used as host to obtain the final compound ZnAl-HTlc-KOJ. The intercalation was carried out, after many attempts, by ionic exchange mechanism by means of the strong base EtO? in anhydrous ethanol/dimethylsulfoxide (DMSO) mixture as solvent in order to generate KOJ? anions. The final product was characterized by the X-ray powder diffraction (XRPD), FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis. The intercalated compound was formulated in a siliconic water free self-emulsifying ointment and the in vitro release profile was evaluated. All samples (intercalation compound and its formulation) were submitted also to spectrophotometric assays in order to evaluate the matrix protective effect towards ultraviolet rays. 相似文献
65.
Anicuta Stoica-Guzun Marta Stroescu Iuliana Jipa Loredana Dobre Sorin Jinga Traian Zaharescu 《Macromolecular Symposia》2012,315(1):198-204
The development of biodegradable packaging materials, especially from renewable resources is a constant preoccupation of nowadays, because of the environmental problems caused by synthetic polymers. The combination of cellulose with other polymeric materials could be an ecologic alternative and a way to use renewable resources for food packaging. Bacterial cellulose which is produced by microbial fermentation is also a promising material which can be used not only in biomedical application, but also as food packaging material. In this research different composite films between poly(vinyl alcohol)-bacterial cellulose (PVA-BC) were obtained by casting method. The obtained films were UV irradiated for different periods of times from 1 to 10 hours, using a mercury lamp, Philips TUV-30, emitting light mainly at 254 nm. Changes in FT-IR spectra before and after UV irradiation and the modification of transparency and of the swelling characteristics of the films were observed. As it was expected the composites materials are sensitive at UV exposure. 相似文献
66.
Ginevra Salerno Gianmarco de Felice 《International Journal of Solids and Structures》2009,46(5):1251-1267
Continuum models of periodic masonry brickwork, viewed at a micro-level as a discrete system, are identified within the frame of linearized elasticity. The accuracy of various identification schemes is investigated for standard and micropolar continua, which are directly compared with the help of some numerical benchmarks, for different loading conditions that induce periodic and non-periodic deformation states. It is shown that periodic deformation states of brickwork are exactly reproduced by both continua, provided that a suitable identification scheme is adopted. For non-periodic states micropolar continuum is shown to better reproduce the discrete solutions, due to its capability to take scale effects into account. Both continua are asymptotically equivalent as the characteristic length of the discrete system tends to zero, while providing an upper and a lower bound of the discrete solution. 相似文献
67.
Giuseppe Bruno Francesco Nicol Manuela Panzalorto Mario Gattuso G. Loredana La Torre 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):254-255
The title compound, C23H16N4O4, can be considered as consisting of two connected fragments: a nitrophenylhydrazone moiety, which assumes an E configuration, and an isoxazole moiety. In this latter fragment, the weak π‐electron delocalization shortens the carbonyl–isoxazole O?O distance [2.643 (2) Å] to less than the van der Waals radii sum. 相似文献
68.
69.
Dependence of the exciton-polariton photoluminescence lineshape in GaAs on epitaxial layer thickness
W.L. Bloss E.S. Koteles E.M. Brody B.J. Sowell J.P. Salerno J.V. Gormley 《Solid State Communications》1985,54(1):103-105
The lineshape of the exciton-polariton photoluminescence spectra in thin undoped GaAs layers is observed to be a function of the layer thickness. A doublet peak (or alternatively a single peak with a “reabsorption” dip at the maximum) in thick samples is transformed into a “single” peak as the layer thickness is reduced by etching. This behavior is in agreement with a model based on enhanced scattering near the exciton energy. This scattering is a function of the concentration of scattering centers which is fixed in these samples and of the average scattering length; (i.e., the sample thickness). 相似文献
70.
Vincenzo Busico Cosimo Carfagna Vincenzo Salerno Michele Vacatello 《Thermochimica Acta》1980,39(1):1-5
The thermal behaviour and some relationships between the physical properties and structure of complexes of general formula (n-CnH2n+1NH2)2CuCl2, with n = 10, 12, ? 18, have been investigated by DSC and X-ray powder diffraction techniques. The high enthalpy solid—solid phase transitions observed for the complexes in the temperature range 350–390 K could be associated with the disordering of the hydrocarbon regions of the structure, as already observed for other similar layer compounds. 相似文献