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排序方式: 共有100条查询结果,搜索用时 40 毫秒
31.
Katia Barbera Leone Frusteri Giuseppe Italiano Lorenzo Spadaro Francesco Frusteri Siglinda Perathoner Gabriele Centi 《催化学报》2014,35(6):869-876
The investigation by SEM/TEM, porosity, and X-ray diffraction measurements of the graphitization process starting from amorphous carbon nanospheres, prepared by glucose carbonization, is reported. Aspects studied are the annealing temperature in the 750–1000 °C range, the type of inert carrier gas, and time of treatment in the 2–6 h range. It is investigated how these parameters influence the structural and morphological characteristics of the carbon materials obtained as well as their nanostructure. It is shown that it is possible to maintain after graphitization the round-shaped macro morphology, a high surface area and porosity, and especially a large structural disorder in the graphitic layers stacking, with the presence of rather small ordered domains. These are characteristics interesting for various catalytic applications. The key in obtaining these characteristics is the thermal treatment in a flow of N2. It was demonstrated that the use of He rather than N2 does not allow obtaining the same results. The effect is attributed to the presence of traces of oxygen, enough to create the presence of oxygen functional groups on the surface temperatures higher than 750 °C, when graphitization occurs. These oxygen functional groups favor the graphitization process. 相似文献
32.
Marco Cicalese Emanuele Nunzio Spadaro Caterina Ida Zeppieri 《Calculus of Variations and Partial Differential Equations》2011,41(1-2):127-150
We study the asymptotic behavior, as ${\varepsilon}$ tends to zero, of the functionals ${F^k_\varepsilon}$ introduced by Coleman and Mizel in the theory of nonlinear second-order materials; i.e., $$F^k_\varepsilon(u):=\int\limits_{I} \left(\frac{W(u)}{\varepsilon}-k\,\varepsilon\,(u')^2+\varepsilon^3(u'')^2\right)\,dx,\quad u\in W^{2,2}(I),$$ where k?>?0 and ${W:\mathbb{R}\to[0,+\infty)}$ is a double-well potential with two potential wells of level zero at ${a,b\in\mathbb{R}}$ . By proving a new nonlinear interpolation inequality, we show that there exists a positive constant k 0 such that, for k?<?k 0, and for a class of potentials W, ${(F^k_\varepsilon)}$ ??(L 1)-converges to $$F^k(u):={\bf m}_k \, \#(S(u)),\quad u\in BV(I;\{a,b\}),$$ where m k is a constant depending on W and k. Moreover, in the special case of the classical potential ${W(s)=\frac{(s^2-1)^2}{2}}$ , we provide an upper bound on the values of k such that the minimizers of ${F_\varepsilon^k}$ cannot develop oscillations on some fine scale and a lower bound on the values for which oscillations occur, the latter improving a previous estimate by Mizel, Peletier and Troy. 相似文献
33.
34.
Artalbic acid, a sesquiterpene with an unusual skeleton from Artemisia alba (Asteraceae) from Sicily
Antonella MaggioSergio Rosselli Celeste Laura BrancazioMuhammad Safder Vivienne SpadaroMaurizio Bruno 《Tetrahedron letters》2011,52(35):4543-4545
From the aerial parts of Artemisia alba (Asteraceae) artalbic acid (1), a sesquiterpene with an unusual skeleton, was isolated. Its structure was elucidated on the basis of extensive proton, 13C and two-dimensional NMR experiments, as well as by transformation in its methyl ester derivative. 相似文献
35.
S. Alessi D. CondurutaG. Pitarresi C. DispenzaG. Spadaro 《Polymer Degradation and Stability》2011,96(4):642-648
A model epoxy resin/anhydride system, modified with a polyethersulfone (PES) engineering thermoplastic toughening agent, has been studied under hydrothermal ageing in order to investigate the modification of the thermal, morphological and mechanical behaviour through dynamical mechanical thermal analysis, SEM microscopy and fracture toughness test respectively. Two different concentrations of the toughening agent were used in the blends and two ageing conditions have been considered, consisting of the immersion of the samples in distilled water at constant temperature of 70 °C for 1 week and for 1 month. Dynamical mechanical thermal analysis results on hydrothermally aged materials indicated the occurrence of progressive segregation effects with the formation of regions with different cross-linking degrees.Fracture toughness tests showed an increase of the KIC value with the increase of the toughening agent concentration, revealing both a dramatic decrease of the same parameter after 1 week ageing for all the materials and the tendency to reach an almost constant value after 1 month ageing for all the formulations, with a slight increase with respect to 1 week ageing. These results have been interpreted on the basis of the SEM analysis, showing the presence of a well defined micrometric PES particles distribution in the epoxy/anhydride matrix, and discussed in the light of different water absorption mechanisms at short and long ageing times. 相似文献
36.
C. Dispenza N. Grimaldi M.-A. Sabatino S. Todaro D. Bulone D. Giacomazza G. Przybytniak S. Alessi G. Spadaro 《Radiation Physics and Chemistry》2012,81(9):1349-1353
In this work the influence of poly(N-vinyl pyrrolidone) (PVP) concentration in water on the organization and dynamics of the corresponding macro-/nanogel networks has been systematically investigated. Irradiation has been performed at the same irradiation dose (within the sterilization dose range) and dose rate. In the selected irradiation conditions, the transition between macroscopic gelation and micro-/nanogels formation is observed just below the critical overlap concentration (~1 wt%), whereas the net prevalence of intra-molecular over inter-molecular crosslinking occurs at a lower polymer concentration (below 0.25 wt%). Dynamic–mechanical spectroscopy has been applied as a classical methodology to estimate the network mesh size for macrogels in their swollen state, while 13C NMR spin–lattice relaxation spectroscopy has been applied on both the macrogel and nanogel freeze dried residues to withdraw interesting information of the network spatial organization in the passage of scale from macro to nano. 相似文献
37.
Sabina Alessi Alberto Spinella Eugenio Caponetti Clelia Dispenza Giuseppe Spadaro 《Radiation Physics and Chemistry》2012,81(9):1328-1331
In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature. 相似文献
38.
A Maggio S Rosselli M Bruno V Spadaro FM Raimondo F Senatore 《Molecules (Basel, Switzerland)》2012,17(9):10232-10241
The use of essential oils as chemotaxonomic markers could be useful for the classification of Artemisia species and to caracterize biodiversity in the different populations. An analysis of the chemical composition of four essential oils from Italian populations of Artemisia alba Turra (collected in Sicily, Marche and Abruzzo) was investigated. In this paper an in depth study of the significant differences observed in the composition of these oils is reported. 相似文献
39.
S Rosselli M Bruno FM Raimondo V Spadaro M Varol AT Koparal A Maggio 《Molecules (Basel, Switzerland)》2012,17(7):8186-8195
A phytochemical analysis of the dichloromethane extract from the flowers of a subspecies of Tanacetum vulgare growing in Sicily was carried out. Five known sesquiterpene lactones with the eudesmane skeleton have been isolated and the cytotoxic activity of these compounds was tested in vitro on A549 (human lung carcinoma epithelial-like) and V79379A (Chinese hamster lung fibroblast-like) cells using the tetrazolium salt reduction (MTT) assay. All of tested compounds induced high time- and concentration-dependent cytotoxic effects. 相似文献
40.
Salvatore Spadaro Marco Santoro Francesco Barreca Angela Scala Simona Grimato Fortunato Neri Enza Fazio 《Frontiers of Physics》2018,13(1):136201
A PEGylated-PLGA random nanofibrous membrane loaded with gold and iron oxide nanoparticles and with silibinin was prepared by electrospinning deposition. The nanofibrous membrane can be remotely controlled and activated by a laser light or magnetic field to release biological agents on demand. The nanosystems were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and thermogravimetric analyses. The drug loading efficiency and drug content percentages were determined by UV-vis optical absorption spectroscopy. The nanofibrous membrane irradiated by a relatively low-intensity laser or stimulated by a magnetic field showed sustained silibinin release for at least 60 h, without the burst effect. The proposed low-cost electrospinning procedure is capable of assembling, via a one-step procedure, a stimuli-responsive drug-loaded nanosystem with metallic nanoparticles to be externally activated for controlled drug delivery. 相似文献