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131.
Vittorio VinciguerraStefano Spina Marcello LunaGianluca Petrucci Manuela Romagnoli 《Journal of Analytical and Applied Pyrolysis》2011,92(2):273-279
The goal of the study was to determine the percentage of lignin in chestnut wood and to characterize structurally this polymer by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) according to a possible influence on ring shake defect. The sampling was performed in different sites of Lazio Region in Italy. Wood disks from trees with ring shake defect and without ring shake defect were selected and little amount of heartwood (1-2 g) sampled between 6th and 10th and between 11th and 15th annual growth ring were analyzed. The study allowed quantifying lignin content, which is in average 26% and syringyl/guaiacyl (S/G) ratio, which present an average value of 2.43. Belong the pyrolysis products of wood, the trees characterized by ring shake show a higher concentration of the phenol homosyringaldehyde respect to the healthy trees. There is not any evident difference in the products composition of pyrolysis in respect to trees’ age, especially the critical period of 12-14 years in which ring shake generally becomes more evident. The site of wood provenance is the higher factor of variability in the structure of lignin for many phenols. 相似文献
132.
Vincenzo Piazza Vittorio Pellegrini Fabio Beltram Werner Wegscheider M. Bichler Tomas Jungwirth Allan H. MacDonald 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We report experimental evidence of the first-order phase transitions in the two-dimensional electron gas formed in a gated wide GaAs/AlGaAs quantum well at even-integer quantum-Hall states. At the filling factor values of ν=2,4 and low temperatures, crossing of Landau levels through the application of the gate bias yields a suppression of the quantum-Hall-state excitation gap and hysteretical behaviour of the diagonal resistivity in up and down sweeps of the magnetic field. Detailed many-body calculations indicate the occurrence of a first-order phase transition and allow the determination of the exact properties of the electron ground states involved in the transition. 相似文献
133.
Paolo Bortolotti Vittorio Basso Alessandro Magni Giorgio Bertotti 《Journal of magnetism and magnetic materials》2010,322(9-12):1402-1404
Random-field Ising model (RFIM) systems are characterized by a large number of metastable states corresponding to local minima of the system energy with respect to single spin flip. We classified the minima in a hierarchical way based on the possibility of a given state to escape from a basin of mutually reachable states. We investigate the energy properties of the metastable states in relation to the basin they belong to: states of particularly high energy, obtained by fast-quenching randomly initial spin configurations, tend to have access to a complex structure of correlated basins, opposite to what is found for low-energy states. The purpose of this paper is to investigate the connection between the properties of the basin oriented graph and the energy of the corresponding states. 相似文献
134.
F. Pisanello L. Martiradonna P. Spinicelli A. Fiore J.P. Hermier L. Manna R. Cingolani E. Giacobino M. De Vittorio A. Bramati 《Superlattices and Microstructures》2010
We report the evidence of a polarized single photon flux from a colloidal nanoparticle. We analyze, by time and polarization resolved spectroscopy measurements, the polarization behavior of a single CdSe/CdS core/shell dot in rod, achieving a polarization ratio at room temperature of ∼75% and a lifetime of the excited state of ∼11 ns. 相似文献
135.
[Structure: see text] A practical one-pot, regiospecific three-component process for the synthesis of 2,3-disubstituted indoles was developed via consecutive Pd-catalyzed Sonogashira coupling, amidopalladation, and reductive elimination. 相似文献
136.
Liu J Shen M Zhang Y Li G Khodabocus A Rodriguez S Qu B Farina V Senanayake CH Lu BZ 《Organic letters》2006,8(16):3573-3575
[reaction: see text] A one-step method was developed for elaboration of a variety of polycyclic indole skeletons via a novel palladium-catalyzed intramolecular indolization of 2-chloroanilines bearing tethered acetylenes. This novel intramolecular indolization method unveils an unusual syn amidopalladation pathway of a tethered alkyne. 相似文献
137.
Ricerche di Matematica - In this paper we aim to compare a popular numerical method with a new, recently proposed meshless approach for Heston PDE resolution. In finance, most famous models can be... 相似文献
138.
Tamiflu: the supply problem 总被引:1,自引:0,他引:1
139.
Synthesis of 1,6-syn-5,6-anti-2-methyl-5-isopropyl-bicyclo[4.3.0]-non-2-en-8-one in three steps from (rac)-phellandrene; and 1,6-syn-1-methyl-6-methoxy-3-aza-9-oxabicyclo[4.2.1]-non-7-en-4-one in five steps from 2-methoxy-5-methylfuran and tetrabromoacetone, provided these key intermediates for the construction of the skeleton of eleutherobin. 相似文献
140.