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21.
22.
Romanato Filippo Berti Marina Mazzer Massimo Drigo Antonio Vittorio Lazzarini Laura Franzosi Paolo Salviati Giancarlo Bertone Daniele 《Mikrochimica acta》1994,114(1):431-440
A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBS-channelling respectively, finally TEM has been used for determining the defects densities and distribution. 相似文献
23.
Giancarlo Cravotto Marina Beggiato Giovanni Palmisano Stefano Tollari Werner Bonrath 《Tetrahedron letters》2005,46(13):2267-2271
Pd-catalyzed homo- and cross-couplings of boronic acids and aryl halides were successfully carried out both in aqueous media under high-intensity ultrasound (US) and in DME under microwave (MW). Heterogeneous catalysis with Pd/C was employed, avoiding phosphine ligands and phase-transfer catalysts. In a trial series involving 15 different iodo- and bromoaryls and 7 boronic acids, both energy sources drastically reduced reaction times affording biaryls in acceptable to good yields. With palladium(II) acetate as catalyst, electron-deficient aryl chlorides also reacted, affording a few biaryls in acceptable yields. Ullmann-type zinc-mediated homocoupling of iodo- and bromoaryls in the presence of Pd/C under CO2 atmosphere was achieved in aqueous media under US, though not under MW. Suzuki homo- and cross-couplings were also carried out in a new reactor developed in our laboratory, featuring combined US and MW irradiation, further improving a green synthetic method. 相似文献
24.
Bacchi Alessia Pelizzi Giancarlo Minardi Giovannina Pistuddi Angelo M. Solinas Costantino Chelucci Giorgio 《Transition Metal Chemistry》2002,27(3):274-278
Metal complexes of general formula M(L)X2 and M(L)X3 [L = (4S,5S)-2,2-dimethyl-4,5-bis{6-[(4,5-dihydro-4-(S)-(1-methylethyl)oxazol-2-yl)pyridin-2-yl]}-1,3-dioxolane] were obtained by reacting, respectively, CoII, CuII, NiII, and ZnII nitrate salts and the RhIII chloride salt, with a chiral C2-symmetric bis(oxazolinylpyridinyl)dioxolane (L) ligand, in MeOH/CHCl3 solution. A single crystal X-ray analysis was carried out on [Ni(L)(OH2)2](NO3)2 · 2H2O and the molecular structure of L was also determined. In the free ligand the two symmetric arms are essentially planar and oriented nearly perpendicular to the dioxolane average plane. In the Ni complex one seven-membered and two five-membered chelation rings are formed. The metal atom also lies on the C2 axis, and two symmetry-related water molecules complete the octahedral coordination environment. Both compounds crystallize in chiral space groups; the ligand crystallizes in orthorhombic system, space group C 2 2 21, Z = 4; the nickel complex crystallizes in tetragonal system, space group P 43 21 2, Z = 4. 相似文献
25.
[reaction: see text] 2,3-Disubstituted furo[3,2-b]pyridines, 2,3-disubstituted furo[2,3-b]pyridines, and 2,3-disubstituted furo[2,3-c]pyridines are readily prepared under mild conditions via the palladium-catalyzed cross-coupling of 1-alkynes with o-iodoacetoxy- or o-iodobenzyloxypyridines, followed by electrophilic cyclization by I(2) or by PdCl(2) under a balloon of carbon monoxide. 相似文献
26.
Vesna Radulovi? Alessia Bacchi Giancarlo Pelizzi Du?an Sladi? Ilija Br?eski Katarina Andjelkovi? 《Monatshefte für Chemie / Chemical Monthly》2006,23(3):681-691
Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide
were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized
by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure
was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex
is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation. 相似文献
27.
Summary In this paper we have estimated the sensitivity of a large-mass liquid-scintillation detector to search for supernova neutrinos
of different flavours. Events produced by νμ and ντ interactions can be identified by looking at the distorsion in the neutrino energy spectrum. We have shown here that, overlapped
to the main energy distribution produced by
interactions with protons a peak at 15.11 MeV (due to the de-excitation of12C* nuclei excited by neutral-current neutrino interactions) gives a possible signature of these neutrino flavours.
Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction. 相似文献
28.
Andrea Carati Giancarlo Benettin Luigi Galgani 《Communications in Mathematical Physics》1992,150(2):321-336
For classical Hamiltonian systems containing an harmonic oscillator of high frequency, one has the problem of controlling the energy exchange between the oscillator and the remaining slow degrees of freedom; under very general conditions, such an exchange turns out to be exponentially small with the frequency of the oscillator. In the Jeans-Landau-Teller method, one aims to prove the exponential dependence, and to estimate the coefficient of the exponential, by exploiting the analyticity properties of the solution of the differential equations describing the motion of the system. However, in practice, since the exact solution is not known, such properties are inferred from those of an approximate solution, with no control of the difference; this fact might a priori even invalidate the exponential dependence itself. In the present paper a rigorous treatment is given, for a particular model of interest in the domain of atomic collisions, by keeping control of the difference between the exact and the approximate solution. 相似文献
29.
Di Valentin M Bisol A Agostini G Fuhs M Liddell PA Moore AL Moore TA Gust D Carbonera D 《Journal of the American Chemical Society》2004,126(51):17074-17086
Photoinduced charge separation and recombination in a carotenoid-porphyrin-fullerene triad C-P-C(60)(1) have been followed by multifrequency time-resolved electron paramagnetic resonance (TREPR) at intermediate magnetic field and microwave frequency (X-band) and high field and frequency (W-band). The electron-transfer process has been characterized in the different phases of two uniaxial liquid crystals (E-7 and ZLI-1167). The triad undergoes photoinduced electron transfer, with the generation of a long-lived charge-separated state, and charge recombination to the triplet state, localized in the carotene moiety, mimicking different aspects of the photosynthetic electron-transfer process. Both the photoinduced spin-correlated radical pair and the spin-polarized recombination triplet are observed starting from the crystalline up to the isotropic phase of the liquid crystals. The W-band TREPR radical pair spectrum has allowed unambiguous assignment of the spin-correlated radical pair spectrum to the charge-separated state C(.+)-P-C(60)(.-). The magnetic interaction parameters have been evaluated by simulation of the spin-polarized radical pair spectrum and the spin-selective recombination rates have been derived from the time dependence of the spectrum. The weak exchange interaction parameter (J = +0.5 +/- 0.2 G) provides a direct measure of the dominant electronic coupling matrix element V between the C(.+)-P-C(60)(.-) radical pair state and the recombination triplet state (3)C-P-C(60). The kinetic parameters have been analyzed in terms of the effect of the liquid crystal medium on the electron-transfer process. Effects of orientation of the molecular triad in the liquid crystal are evidenced by simulations of the carotenoid triplet state EPR spectra at different orientations of the external magnetic field with respect to the director of the mesophase. The order parameter (S = 0.5 +/- 0.05) has been evaluated. 相似文献
30.
Giovanni Appendino Giancarlo Cravotto Gian Mario Nano Giovanni Palmisano Rita Annunziata 《Helvetica chimica acta》1993,76(3):1194-1202
The reaction of 4-hydroxycoumarin and certain aliphatic aldehydes affords 1:1 or complex 2:2 adducts besides (or in place) of the expected 2:1 bis(coumarin) adducts. Reaction with heptanal, cyclohexanecarbaldehyde, and pivalaldehyde are reported as representative. The structure of the reaction products was established by spectroscopical techniques, including X-ray analysis, and their formation was mechanistically rationalized. Some of the 1:1 adducts are synthetically useful for the preparation of 3-alkyl-4-hydroxycoumarins. 相似文献