1000 resultados para Heus-de, Philipp Wilhelm van, 1778-1839.
Resumo:
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
Resumo:
The curious anecdote in Karel van Mander’s biography of Bruegel, where the artist is said to have swallowed all the mountains and rocks during his crossing of the Alps and spat them out again onto canvas and panels upon returning home, has been quoted by almost every Bruegel scholar. Yet it has never been given a full explanation. In this study, it is proposed that the passage, echoing on one level Bruegel’s frequent depiction of overindulging peasants, disguises a highly cultivated reference to the theory of imitation as a digestive process, or innutrition theory, which was widely used by humanist writers of the time to champion vernacular expression.
Resumo:
The size dependence of the ionization potential I_p(n) of van der Waals (vdW) bound clusters has been calculated by using a model Hamiltonian, which includes electron hopping, vdW interactions, and charge-dipole interactions. The charge-density and dipole-density distributions for both neutral and ionized n-atom clusters are determined self-consistently. The competition between the polarization energy of the neutral atoms surrounding a partially localized hole and the tendency toward hole delocalization in the ionized clusters is found to dominate the size dependence of I_p(n). To test our theory, we culculate I_p(Xe_n) and I_p(Kr_n) for n \le 300. Good quantitative agreement with experiment is obtained. The theory is also applied to calculate I_p(Hg_n). Comparison with experiments suggests that in Hg_n^+ clusters with n \le 20 the positive charge is mainly distributed within a trimer which is situated at the center of the cluster and which polarizes the n - 3 surrounding neutral atoms.
Resumo:
We use a microscopic theory to describe the dynamics of the valence electrons in divalent-metal clusters. The theory is based on a many-body model Harniltonian H which takes into account, on the same electronic level, the van der Waals and the covalent bonding. In order to study the ground-state properties of H we have developed an extended slave-boson method. We have studied the bonding character and the degree of electronic delocalization in Hg_n clusters as a function of cluster size. Results show that, for increasing cluster size, an abrupt change occurs in the bond character from van der Waals to covalent bonding at a critical cluster size n_c ~ 10-20. This change also involves a transition from localized to delocalized valence electrons, as a consequence of the competition between both bonding mechanisms.