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121.
122.
Renato Dogliotti Angelo Luvison Giancarlo Pirani 《Optical and Quantum Electronics》1979,11(6):541-550
The problem of pulse shaping and sensitivity to timing errors in optical fibre data communication is considered. The performance of the overall transmission system is the average probability of error, which is computed for intersymbol interference, thermal noise, and shot noise in avalanche photodiodes. An analysis of the immunity to small sampling errors of various Nyquist pulses indicates useful design criteria. 相似文献
123.
Giulio Ceccarelli Giancarlo Berti Giorgio Lippi Bruno Macchia 《Magnetic resonance in chemistry : MRC》1970,2(4):379-388
NMR spectra of several styrene, stilbene and stilbazole oxides have been determined, and chemical shifts and coupling constants have been correlated with cis-and trans-configurations. Assignments have been made for all protons, and double resonance technique and 13C? H coupling constants have been used in some particular cases. An explanation is proposed for the observation that chemical shifts of oxirane protons are higher for cis than for trans isomers. 相似文献
124.
The bis- and tris-pyrylium and thiopyrylium cations 1-4 were prepared in gram scale by heterocyclization of the corresponding bis- and tris-1,5-pentanediones 6 and 8. Their reaction with CD3ONa in CD3OD was studied by 1H NMR at -40 degrees C and at +25 degrees C. At low temperature, kinetically controlled mixtures of 2H and/or 4H adducts were detected, whereas at room temperature the mixtures equilibrated to yield, in all of the cases, the more stable 2H adducts exclusively. A spectrophotometric study of the reactions with sodium methoxide in methanol was carried out at 25.0 degrees C with the aim of determining the stepwise equilibrium constants for the addition of MeO- at the alpha position of the heteroaromatic rings. The obtained equilibrium constants allowed the evaluation of the electronic effects of chalcogenopyrylium and 2H-chalcogenopyran subunits as substituents. Despite the different sensitivity to electronic effects, pyrylium and thiopyrylium rings have a similar electron-withdrawing effect with a sigma(+)p approximately 0.8 and a sigma(+)m approximately 0.5. Apart from the expected importance of the inductive effect due to the positive charge, the difference between these two values remarks the importance of the resonance contribution. In contrast both the neutral 2H-pyranyl and thiopyranyl rings have a negligible effect as substituents, independently of the position, para or meta, they occupy. 相似文献
125.
Cationic nickel catalysts with monodentate phosphoramidites and Wilke's azaphospholene as ligands are highly regio- and enantioselective catalysts for the cycloisomerisation of diethyl diallylmalonate. 相似文献
126.
127.
Ugo Abbondanno Ferruccio Demanins Maria Rosa Malisan Giancarlo Nardelli 《Nuclear Physics A》1978,305(1):117-143
The de-excitation gammas following the inelastic scattering of neutrons from 75As have been studied for incident neutron energies from 1300 to 2800 keV in steps of 100 keV. The energy levels and the branching ratios of their decays have been deduced from excitation function measurements: 58 energy levels have been found in the excitation energy region below 2.8 MeV, twelve of which are reported for the first time in this work. The experimental excitation functions and angular distributions have been compared with the theoretical predictions based on the statistical theory of the compound nucleus. Spin and parity assignments for the levels and multipolarities for the decays are proposed for excitation energies of levels up to 2300 keV. 相似文献
128.
Giancarlo Bettoni Carlo Cellucci Vincenzo Tortorella 《Journal of heterocyclic chemistry》1976,13(5):1053-1055
(+)-3-Phenylpyrrolidine and (+)-phenylsuccinic acid have been chemically correlated through (-)-N-benzyl-3-phenylpyrrolidine. All these compounds have an S absolute configuration. 相似文献
129.
Giancarlo Jug 《Annals of Physics》1982,142(1):140-184
The origin and importance of swelling corrections in the field-theoretic model describing an isolated, unscreened polyelectrolyte chain below six dimensions are examined in detail using the renormalization theory of higher composite operators. It is shown that these corrections become relevant below an unspecified dimension , when the unphysical exact result for the size exponent breaks down and the system should be described by a new model. 相似文献
130.