RESUMEN
Many commercially important catalysts consist of small metal particles dispersed on inorganic oxide surfaces. Although in most cases there is no significant interaction between the metal and the support, strong bonding can be demonstrated in a recently discovered class of supported-metal catalysts. These cases typically involve group VIII metals dispersed on transition metal oxides whose surfaces can be reduced to form cations with lower valences. Spectroscopic measurements indicate that an electron is transferred from the cation (such as Ti(3+) or Nb(4+)) to the metal particle. This, in turn, leads to profound changes in the catalytic and chemisorption properties and the morphology of the metal particles.
RESUMEN
Isotope-selective photodissociation of the volatile complex uranyl hexafluoroacetylacetonate . tetrahydrofuran [UO(2)(hfacac)(2) . THF] has been achieved with both a continuous-wave and a pulsed carbon dioxide laser. The photodissociation was carried out in a low-density molecular beam under collisionless conditions. Transitions of the laser are in resonance with the asymmetric O-U-O stretch of the uranyl moiety, a vibrational mode whose frequency is sensitive to the masses of the uranium and oxygen isotopes. Unimolecular dissociation is observed mass spectrometrically at an extremely low energy fluence, with no evidence of an energy fluence or intensity threshold. The dissociation yield increases nearly linearly with increasing energy fluence. At constant fluence the dissociation yield is independent of contact time between the radiation field and the molecule, indicating that the decomposition is driven by laser energy fluence and not laser intensity. The oxygen and uranium isotope selectivities measured in these experiments are nearly those predicted by the ratio of the linear absorption cross sections for the respective isotopes. Thus, essentially complete selectivity is observed for oxygen isotopes, while a selectivity of only about 1.25 is measured for the uranium isotopes. A model presented to describe these results is based on rapid intramolecular vibrational energy flow from the pumped mode into a limited number of closely coupled modes.
RESUMEN
As the practice of research increasingly becomes a part of the nursing profession, nurses must develop their ability to evaluate and incorporate the findings gained through the research process. This article reports the results of a survey aimed at determining problem areas existing among nursing staffs in understanding, accepting, and incorporating research findings. The report will help nursing administrators identify specific factors that inhibit the use of research findings and improve the conditions for incorporating research in their facilities.