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21.
The reactivity of free radical cations, produced by anodic oxidation of 9, 10-diphenylanthracene (and perylene), with polymerizable organic monomers has been investigated by amperometry.It results that the radical cations, which are relatively stable in acetonitrile and nitrobenzene, decay with the monomer substrate by either an addition reaction or an electron transfer process. The cationic species of the monomer thus produced by catalyze the cationic polymerization of the substrate.The cationic polymerization initiated in this way has been investigated in the case of styrene: this reaction shows some similarity with the process initiated by perchloric acid, but carbonium ion carriers seem to give the main contribution to the propagation stage. 相似文献
22.
Giuseppina Castronuovo Vittorio Elia Marcella Niccoli Filomena Velleca 《Thermochimica Acta》1998,320(1-2):13-22
The thermodynamics of dissolution in water of a set of substances has been studied calorimetrically. The examined substances were: potassium chloride, (glycyl-glycyl)diketopiperazine, (alanyl-alanyl)diketopiperazine, (leucyl-glycyl)diketopiperazine. They were chosen on the basis of their solubilities, going from a highly soluble electrolyte to the sparingly soluble diketopiperazines. It is shown that, using a commercially available calorimeter, it is possible to perform in a single calorimetric experiment the simultaneous determination of all thermodynamic parameters characterizing dissolution of a substance in a given solvent, i.e. solubility, dissolution enthalpy and dilution enthalpy. The solubility values in water obtained through the proposed method are in good agreement with those reported in the literature and obtained by other techniques. 相似文献
23.
Vincenzo G. Albano Carlo Castellari Cristina Femoni M. Carmela Iapalucci Giuliano Longoni Magda Monari Stefano Zacchini 《Journal of Cluster Science》2001,12(1):75-87
The new Au8{Fe(CO)4}4(P^P)2 and Au6Cu2{Fe(CO)4}4(P^P)2 (P^P=dppm, dppe) neutral cluster compounds were isolated in good yields by condensation of the [Au3{Fe(CO)4}2(P^P)]- anions with Au(SEt2)Cl and CuCl, respectively, and have been characterized by IR, NMR and microanalyses. The molecular structures of Au8{Fe(CO)4}4(dppe)2 and Au6Cu2{Fe(CO)4}4(dppe)2 have been determined by X-ray diffraction studies. Both molecules adopt a stereogeometry of the heavy atoms consisting of a triangulated and corrugated ribbon twisted around the elongation direction. Contrary to the expectations the latter displays the two copper atoms in the sites of highest connectivity. This implies that site exchange between copper and gold occurs during the synthesis. 相似文献
24.
Licia Guzzella Fiorenzo Pozzoni Giuseppe Giuliano 《International journal of environmental analytical chemistry》2013,93(1):87-106
Abstract A field site equipped with suction cup lysimeters was installed at Treviglio (BG) to assess the migration capacity of the herbicides linuron and monolinuron from topsoil to groundwater and to verify the appearance of their relevant transformation products in soil and water samples. A constant hydraulic head was applied in order to develop water saturation conditions in the upper layers. KCl was used as a tracer to evaluate water infiltration velocity through the vertical soil profile. The constant hydraulic head accelerated infiltration rates, while herbicide concentrations reached maximum contamination because soil adsorption capacity was underdeveloped. The results indicated two main processes of pesticide transport: firstly transport due mainly to water infiltration through macropores; secondly the transport driven by matrix flow. Linuron was found to be the most mobile herbicide, while chloroanilines were found to be the major transformation products of the herbicides considered. 相似文献
25.
New families of unit memory as well as multi-memory nonbinary convolutional codes are constructed algebraically in this paper. These convolutional codes are derived from the class of group character codes. The proposed codes have basic generator matrices, consequently, they are noncatastrophic. Additionally, the new code parameters are better than the ones available in the literature. 相似文献
26.
Ken Wilson developed the Numerical Renormalization Group technique which greatly enhanced our understanding of the Kondo effect and other quantum impurity problems. Wilson’s NRG also inspired Philippe Nozières to propose the idea of a large “Kondo screening cloud”. While much theoretical evidence has accumulated for this idea it has remained somewhat controversial and has not yet been confirmed experimentally. Recently a new possibility for observing an analogous crossover length scale has emerged, involving a Majorana fermion localized at the interface between a topological superconductor quantum wire and a normal wire. We give an overview of this topic both with and without interactions included in the normal wire. 相似文献
27.
28.
Giuliano Benenti Stefano Siccardi Giuliano Strini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(6):1-7
Inhibited decoherence has been recently observed in a dissipative two-level system by increasing the strength of the coupling with the reservoir. The system is described by the spin-boson model under a perturbation approach in the delocalized phase regime occurring in weak-coupling limit at zero temperature. Within this scenario, persistence of coherence is found over long times for various low frequency structures of the bosonic environment near a band gap. Special resonances provoke transitions in the long time dynamics if the transition amplitude of the two-level system is greater than the band gap frequency or in absence of any band gap. These transitions may hinder the the loss of coherence in the spin-boson model. Limitations of the approximations are also discussed. 相似文献
29.
Giuliano Bandoli Sandro Calogero Domenico Idá Giuseppe C. Pappalardo Giuseppe Scarlata 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):265-270
Abstract Crystals of 2-pyridyl-phenyl sulphone are monoclinic, space group P21/c, with eight molecules in the unit cell of dimensions a = 11.781, b = 5.903, c = 29.748 Å and B = 94.13°. The dihedral angles between the best planes of the two aromatic rings are significantly different in two crystallographically independent molecules (88.4° and 71.9° for molecule A and molecule B, respectively), as well as those between the CSC plane and the pyridine ring (59.4° and 67.4°) and between the CSC plane and the phenyl ring (51.7° and 81.8°). The average bond distances of interest include C?S 1.77(1) and S?O 1.44(1) Å; among the bond angles there are CSO = 108.1(7), CSC = 105.0(6) and OSO = 118.7(6)°. The packing of the molecule in the crystal is determined by the van der Waals interactions and by two intermolecular H?O contacts of 2.43 and 2.49 Å. The observed conformation in the solid state agrees well with results of previous investigations, in the solution state, by means of dipole moment method and theoretical M.O. calculations, for the analogous di-2-pyridyl sulphone. 相似文献
30.
Vittorio Elia Nadia Marchettini Elena Napoli Marcella Niccoli 《Journal of Thermal Analysis and Calorimetry》2013,114(2):927-936
This study presents some experimental results on the variation of the physico-chemical properties of pure MilliQ water, when subjected to a procedure of iterated filtration through Millipore filters with porosity ranging from 450 to 25 nm. The parameters measured were: calorimetry, electrical conductivity, density, and pH. Release of chemical impurities can be ruled out due to the nature of the materials used. As in the case of iteratively filtered water prepared using Pyrex glass filters, the specific electrical conductivity and the pH were found to increase with increasing number of iterations. There was also a dependence on the average pore size of the filters. The idea of water as a system capable of self-organization triggered by various perturbations (mechanical and/or electromagnetic) is gaining momentum. It responds to such perturbations by forming dissipative structures, i.e., far-from-equilibrium systems. 相似文献