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81.
Takeshi Isobe Antonella Marini 《Calculus of Variations and Partial Differential Equations》1997,5(4):345-358
We prove that for generic Dirichlet boundary data there exist infinitely many topologically distinct solutions to the Dirichlet
problem for -Yang-Mills equations over . These are absolute Yang-Mills minimizers in topologically distinct connected components of the space of connections considered.
There is a special case for which only finitely many topologically distinct solutions can be found by our method. This corresponds
to the simultaneous existence of self dual and anti-self dual solutions, for the given boundary data. If the boundary data
is non-flat there exists always more than one solution. This paper generalizes to Yang-Mills fields an important result by
Brezis and Coron, who show existence of more than one minimizing harmonic map for non-constant Dirichlet data in two dimensions.
Received February 1, 1996 / Accepted March 15, 1996 相似文献
82.
This work presents the results of the ethene–CO copolymerization with in situ generated catalysts based on atropisomeric 1,4‐diphosphines and nickel(II). The influence of the reaction conditions and the NMR characterization of the copolymers are described. 相似文献
83.
Antonella Casoli Piero Mirti Gerardo Palla 《Fresenius' Journal of Analytical Chemistry》1995,352(3-4):372-379
Proteinaceous organic materials used as ancient painting media were investigated by capillary gas chromatography (GC) and capillary gas chromatography — mass spectrometry (GC/MS). Medieval wall paintings made by the tempera technique were considered and their binding media were studied by the characterization of their main chemical components. The basic methodology is based on the determination of amino acids in samples of paint layers after hydrolysis and derivatization and on the comparison with reference proteinaceous materials. Multivariate chemometric techniques were used to facilitate the recognition of the protein source from chromatographic data. To characterize the binders further, a method was developed for the determination of fatty acids, present as minor components, by GC/MS. The use of fused-silica capillary columns coated with selected stationary phases allowed the separation of amino acid and fatty acid derivatives in a single analytical run. 相似文献
84.
This paper shows the results of underground waters last monitoring in the province of Lecce (Apulia, Southern Italy). We carried out the physical-chemical characterization of the aquifers and their classification in accordance to limit values sanctioned by Italian legislation in force, by European directives and by FAO, in order to define their quality and to establish their possible use for drinkable and irrigation purposes. The attention has been focused on salinity evaluation and underground waters contamination phenomena, due to sea-water intrusion and to the use of fertilizers. Salinity and nitrates concentrations are high in a few wells. Iron and manganese concentrations are very high for almost every sample and this is due to corrosion phenomena of artesian wells metallic structure. For a better interpretation of data, multivariate statistical analysis has been used, in order to obtain the correlation among analytical results, soils hydro-geological properties and anthropic conditions. 相似文献
85.
Maccotta A Fantazzini P Garavaglia C Donato ID Perzia P Brai M Morreale F 《Annali di chimica》2005,95(3-4):117-124
Magnetic Resonance Relaxation (MRR) and Magnetic Resonance Imaging (MRI) are powerful tools to obtain detailed information on the pore space structure that one is unlikely to obtain in other ways. These techniques are particularly suitable for Cultural Heritage materials, because they use water 1H nuclei as a probe. Interaction with water is one of the main causes of deterioration of materials. Porous structure in wood, for example, favours the penetration of water, which can carry polluting substances and promote mould growth. A particular case is waterlogged wood from underwater discoveries and moist sites; in fact, these finds are very fragile because of chemical, physical and biological decay from the long contact with the water. When wood artefacts are brought to the surface and directly dried in air, there is the collapse of the cellular structures, and wood loses its original form and dimensions and cannot be used for study and museum exhibits. In this work we have undertaken the study of some wood finds coming from Ercolano's harbour by MRR and MRI under different conditions, and we have obtained a characterization of pore space in wood and images of the spatial distribution of the confined water in the wood. 相似文献
86.
Dalla Cort A Mandolini L Schiaffino L 《Chemical communications (Cambridge, England)》2005,(30):3867-3869
Whereas the parent uranyl salophen is catalytically inactive, its phenyl derivative effectively catalyses with turnover the reaction of benzoquinone with 1,3-cyclohexadiene, while showing no appreciable affinity towards reactants and product. 相似文献
87.
88.
89.
Crown ether macrocycle 1 including a zinc-salophen unit is obtained via a de novo synthetic design to give a potential pH-driven two-stationed wheel component of [2]-pseudorotaxane systems. 相似文献
90.
Deganello G Giannici F Martorana A Pantaleo G Prestianni A Balerna A Liotta LF Longo A 《The journal of physical chemistry. B》2006,110(17):8731-8739
The catalyst Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L(III) edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formation of a platinum-cerium alloy in redox-aged samples and the stability of the metal particles toward oxidation and sintering during high-temperature treatments. Under CO flux at 773 K, bare ceria-zirconia shows a continuous drift of diffraction peaks toward smaller Bragg angles, due to a progressive increase of Ce(III) content. Under the same treatment, the structural rearrangement of Pt-supported ceria-zirconia starts after an induction time and takes place with an abrupt change of the lattice constant. The experimental evidence points to the role of supported Pt in modifying the redox properties of ceria-zirconia with respect to the bare support. It is proposed that the much faster bulk reduction observed by in situ XRD for redox-aged Pt/ceria-zirconia can be attributed to an easier release of reacted CO(2), producing a more effective turnover of reactants at the catalyst surface. 相似文献