1,720,972 research outputs found
L’effetto sedativo, analgesico e cardiorespiratorio della romifidina, della medetomidina e della xilazina in associazione alla ketamina nella castrazione degli agnelli
No full textInhibited Al diffusion and growth roughening of Ga-coated Al(100)
No full textAb initio calculations indicate that the ground state for Ga adsorption on Al(100) is on surface with local unit coverage. On Ga-coated Al(100), the bridge diffusion barrier for Al is large, but the Al --> Ga exchange barrier is zero: the ensuing incorporation of randomly deposited Al's into the Ga: overlayer realizes a percolation network, efficiently recoated by Ca atoms. Based on calculated energetics, we predict rough surface growth at all temperatures; modeling the growth by a random deposition model with partial relaxation, we find a power-law divergent roughness w similar to t(0.07+/-0.02)
Connection between charge transfer and alloying core-level shifts based on density-functional calculations
No full textThe measurement of alloying core-level binding energy (CLBE) shifts has been used to give a precise meaning to the fundamental concept of charge transfer.:Here, ab initio density-functional calculations for the intermetallic compound MgAu are used to investigate models which try to make a connection between the core levels shifts and charge transfer. The calculated CLBE shifts agree well with experiment, and permit an unambiguous separation into initial-state and screening contributions. Interestingly, the screening contribution is large and cannot be neglected in any reasonable description. Comparison of the calculated results with the predictions of simple models show that these models are not adequate to describe the realistic situation. On the positive side, the accuracy of the density-functional calculations indicates that the combination of experiments with such calculations is a powerful tool to investigate unknown systems
Theory of adsorption and surfactant effect of Sb on Ag(111)
Full text linkWe present first-principles studies of the adsorption of Sb and Ag on clean and Sb-covered Ag(111). For Sb, the substitutional adsorption site is found to be greatly favored with respect to on-surface fcc sites and to subsurface sites, so that a segregating surface alloy layer is formed. Adsorbed silver adatoms are more strongly bound on clean Ag(111) than on Sb-covered Ag. We propose that the experimentally reported surfactant effect of Sb is due to Sb adsorbates reducing the Ag adatom mobility. This gives rise to a high density of Ag islands which coalesce into regular layers
TOWARDS AN UNDERSTANDING OF SURFACTANT ACTION IN THE EPITAXIAL-GROWTH OF METALS - THE CASE OF SB ON AG(111)
No full textWe address the role of ''surfactant'' adsorbates in determining changes in the homoepitaxial growth mode of metals, discussing the case of Sb on Ag (111). From ab initio calculations, we extract evidence that the mechanism operative in this system is that Sb induces an irregular shape and an increase in density of the growing Ag islands, and an ensuing increase of the number of attempts for an adatom to descend to a lower terrace. This results from a combination of peculiar properties of this system: Sb is adsorbed in substitutional surface sites, leading to the formation of a Sb-Ag surface alloy; deposited Ag has reduced mobility on Sb-covered Ag (111), from which follows a higher nucleation probability. The island shape is irregular since the surface alloy is disordered. Surface seggregation of Sb once the growing layer is completed furthers the phenomenon for many deposited Ag layers. Our explanation of the surfactant action of Sb on Ag (111) does not require a reduction of the downstep diffusion barrier, which may, however, be a concurrent factor helpful to interlayer mass transport and layer-by-layer growth
Anestesia prolungata nel suino ottenuta con medetomidina, ketamina, protossido di azoto ed isofluorano e valutazione del risveglio dopo somministrazione di atipamezolo
No full text
- …
