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251.
Carlo Corvaja Giovanni Giacometti Pierluigi Nordio 《Theoretical chemistry accounts》1963,1(5):393-396
A hyperconjugated model is used to calculate the proton h. f. s. constants in H
2CN radical by the m. o. method. Agreement with experiment is excellent. A comparison between various approximations employed gives strong evidence of the importance of configuration interaction in such calculations.
We thank the Italian National Research Council (Chemistry Committee, Research Group IV) for financial support. One of us (P.L.N.) is grateful to Sicedison S.p.A. for a grant. 相似文献
Zusammenfassung Mittels eines hyperkonjugierten Modells werden die Protonenhyperfeinstrukturkonstanten im H 2CN-Radikal nach der MO-Methode berechnet. Die Übereinstimmung mit dem Experiment ist ausgezeichnet. Der Vergleich verschiedener Näherungsmethoden beweist die Notwendigkeit, bei derartigen Rechnungen Konfigurationswechselwirkung einzuschließen.
Résumé A l'aide d'un modèle à hyperconjugaison, les constantes de structure hyperfine protonique du radical H 2CN ont été calculées par la méthode MO. L'accord avec l'expérience est excellent. Une comparaison entre les différentes approximations employées met en évidence l'importance de l'interaction de configuration dans de tels calculs.
We thank the Italian National Research Council (Chemistry Committee, Research Group IV) for financial support. One of us (P.L.N.) is grateful to Sicedison S.p.A. for a grant. 相似文献
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255.
Paolo Quadrelli Bruna Bovio Pierluigi Caramella Fabrizio Machetti 《Tetrahedron》2009,65(51):10679-1852
A new approach to useful precursors for the synthesis of isoxazoline-carbocyclic nucleosides is detailed, starting from the readily available N-benzoyl-2,3-oxazanorborn-5-ene and introducing more polar and hydrophilic functionalities through 1,3-dipolar cycloaddition of carbethoxyformonitrile oxide, generated either from the corresponding hydroximoyl chloride or, more conveniently, by catalyzed condensation with ethyl nitroacetate. 相似文献
256.
E. Angelini S. Grassini D. Mombello A. Neri M. Parvis G. Perrone 《Applied Physics A: Materials Science & Processing》2010,100(3):975-980
A cumulative sensor for in situ monitoring of H2S vapors in museum showcases based on plastic optical fiber (POF) has been developed. H2S is responsible for the tarnishing of silver artifacts, so monitoring their total exposure over time to sulfide rich atmospheres
can help in choosing the correct display procedure and, consequently, lead to improvements in their conservation. 相似文献
257.
Andreina Ricci Simona Piccolella Federico Pepi Alexandros Patsilinakos Rino Ragno Stefania Garzoli Pierluigi Giacomello 《Journal of mass spectrometry : JMS》2012,47(11):1488-1494
2‐Furaldehyde (2‐FA), also known as furfural or 2‐furancarboxaldehyde, is an heterocyclic aldehyde that can be obtained from the thermal dehydration of pentose monosaccharides. This molecule can be considered as an important sustainable intermediate for the preparation of a great variety of chemicals, pharmaceuticals and furan‐based polymers. Despite the great importance of this molecule, its gas‐phase basicity (GB) has never been measured. In this work, the GB of 2‐FA was determined by the extended Cooks's kinetic method from electrospray ionization triple quadrupole tandem mass spectrometric experiments along with theoretical calculations. As expected, computational results identify the aldehydic oxygen atom of 2‐FA as the preferred protonation site. The geometries of O‐O‐cis and O‐O‐trans 2‐FA and of their six different protomers were calculated at the B3LYP/aug‐TZV(d,p) level of theory; proton affinity (PA) values were also calculated at the G3(MP2, CCSD(T)) level of theory. The experimental PA was estimated to be 847.9 ± 3.8 kJ mol?1, the protonation entropy 115.1 ± 5.03 J mol?1 K?1 and the GB 813.6 ± 4.08 kJ mol?1 at 298 K. From the PA value, a ΔH°f of 533.0 ± 12.4 kJ mol?1 for protonated 2‐FA was derived. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
258.
Pierluigi Colli Sergio Frigeri Maurizio Grasselli 《Journal of Mathematical Analysis and Applications》2012,386(1):428-444
A well-known diffuse interface model consists of the Navier–Stokes equations nonlinearly coupled with a convective Cahn–Hilliard type equation. This system describes the evolution of an incompressible isothermal mixture of binary fluids and it has been investigated by many authors. Here we consider a variant of this model where the standard Cahn–Hilliard equation is replaced by its nonlocal version. More precisely, the gradient term in the free energy functional is replaced by a spatial convolution operator acting on the order parameter φ, while the potential F may have any polynomial growth. Therefore the coupling with the Navier–Stokes equations is difficult to handle even in two spatial dimensions because of the lack of regularity of φ. We establish the global existence of a weak solution. In the two-dimensional case we also prove that such a solution satisfies the energy identity and a dissipative estimate, provided that F fulfills a suitable coercivity condition. 相似文献
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260.
Oreste Pezzi Francesco Valentini Pierluigi Veltri 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(5):1-8
In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3Πu → B3 Πg, 0-2) and the first negative bands of N2 + (B2 Σu + → X2 Σg +, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH?(A 2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH(A2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3Πu → B3Πg, 0-0, 337.1 nm) and OH (A2Σ → X2Π, 0-0) are more greater than that on the emission intensity of N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm). 相似文献