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Inscriptions from the monuments and structures in Copan, Honduras, have allowed scholars of Mayan hieroglyphics to reconstruct the history of the dynasty of rulers that held sway over this city for 350 years. The first king in Copan's dynastic line was Yax K'uk' Mo' whose son Popol K'inich dedicated a tomb to his father around AD 437. Various texts over the next 300-odd years give more information on Copan's dynastic founder. The last of these texts are from Altar Q, which was commissioned by the last bonafide ruler at Copan Yax Pasah.

A systematic study was made on the optical absorption spectra of permethyl oligosilanes, CH3[CH3–Si–CH3]NCH3, as a function of their backbone chain length from N=2 to 16 by using first principles [density functional with local density approximation (LDA)] electronic structure calculations. The general features of the calculated spectra agree with those of experimental measurements. Analysis of the nature of optical transition revealed the existence of two qualitative crossovers at chain lengths of N=2 and around N=10 and 12. The first one is associated with the molecular orbitals giving rise to the first ultraviolet absorption peak, while the second one is associated with the crossover from ‘‘molecular’’ to ‘‘polymeric’’ as the oligomers become larger. The broadening of the first absorption peaks is estimated by the vibration modes and electronic relaxation energies in the oligomers. Comparison with calculated results by a model Hamiltonian based on the Sandorfy C model is made and the relative merit of semiempirical and LDA calculations is discussed. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

With one swift stroke--just 18 minutes of words, delivered with a stern tone and a steel gaze--Barack Hussein Obama sliced through the usual clutter and ambiguities of American politics and [...]