3 resultados para gap states
em CentAUR: Central Archive University of Reading - UK
Resumo:
We have employed a combination of experimental surface science techniques and density functional calculations to study the reduction of TiO2(110) surfaces through the doping with submonolayer transition metals. We concentrate on the role of Ti adatoms in self doping of rutile and contrast the behaviour to that of Cr. DFT+U calculations enable identification of probable adsorption structures and their spectroscopic characteristics. Adsorption of both metals leads to a broken symmetry and an asymmetric charge transfer localised around the defect site of a mixed localised/delocalised character. Charge transfer creates defect states with Ti 3d character in the band gap at similar to 1-eV binding energy. Cr adsorption, however, leads to a very large shift in the valence-band edge to higher binding energy and the creation of Cr 3d states at 2.8-eV binding energy. Low-temperature oxidation lifts the Ti-derived band-gap states and modifies the intensity of the Cr features, indicative of a change of oxidation state from Cr3+ to Cr4+. Higher temperature processing leads to a loss of Cr from the surface region, indicative of its substitution into the bulk.
Resumo:
At present, there is much anxiety regarding the security of energy supplies; for example, the UK and other European States are set to become increasingly dependant upon imports of natural gas from states with which political relations are often strained. These uncertainties are felt acutely by the electricity generating sector, which is facing major challenges regarding the choice of fuel mix in the years ahead. Nuclear energy may provide an alternative; however, in the UK, progress in replacing the first generation reactors is exceedingly slow. A number of operators are looking to coal as a means of plugging the energy gap. However, in the light of ever more stringent legal controls on emissions, this step cannot be taken without the adoption of sophisticated pollution abatement technology. This article examines the role which legal concepts such as Best Available Techniques (BAT) must play in bringing about these changes.
Resumo:
Marketing research efforts across Eastern European countries continue growing since the introduction of market reforms in this region. Nonetheless, questions remain unanswered as to cross-cultural differences in Eastern Europeans' consumer behavior. The present research addresses this knowledge gap by developing and testing hypotheses about cross-cultural variations in a number of clothing-related consumer behavior phenomena in the Czech Republic and Bulgaria. Our findings indicate significant differences regarding consumer interest in clothing, preference for utilitarian, self-expressive and hedonic meanings of clothing artifacts, preference for well-known clothing brands, brand loyalty, and importance of clothing attributes. The study advances research in marketing by investigating clothing value-expressive symbolism and consumption in the tworecentEUMember States. The study provides valuable insights to marketers for developing effective marketing strategies.