Angle-resolved photoemission study of MX-chain compound [Ni(chxn)2_2Br]Br2_2

We report on the results of angle-resolved photoemission experiments on a quasi-one-dimensional $MX$-chain compound [Ni(chxn)$_2$Br]Br$_2$ (chxn = 1$R$,2$R$-cyclohexanediamine), a one-dimensional Heisenberg system with $S=1/2$ and $J \sim 3600$ K, which shows a gigantic non-linear optical effect. A "band" having about 500 meV energy dispersion is found in the first half of the Brillouin zone $(0\le kb/\pi <1/2)$, but disappears at $kb / \pi \sim 1/2$. Two dispersive features, expected from the spin-charge separation, as have been observed in other quasi-one-dimensional systems like Sr$_2$CuO$_3$, are not detected. These characteristic features are well reproduced by the $d$-$p$ chain model calculations with a small charge-transfer energy $\Delta$ compared with that of one-dimensional Cu-O based compounds. We propose that this smaller $\Delta$ is the origin of the absence of clear spin- and charge-separation in the photoemission spectra and strong non-linear optical effect in [Ni(chxn)$_2$Br]Br$_2$.Comment: 4 pages, 3 figure

O adsorption and incipient oxidation of the Mg(0001) surface

First principles density functional calculations are used to study the early oxidation stages of the Mg(0001) surface for oxygen coverages 1/16 <= Theta <= 3 monolayers. It is found that at very low coverages O is incorporated below the topmost Mg layer in tetrahedral sites. At higher oxygen-load the binding in on-surface sites is increased but at one monolayer coverage the on-surface binding is still about 60 meV weaker than for subsurface sites. The subsurface octahedral sites are found to be unfavorable compared to subsurface tetrahedral sites and to on-surface sites. At higher coverages oxygen adsorbs both under the surface and up. Our calculations predict island formation and clustering of incorporated and adsorbed oxygen in agreement with previous calculations. The calculated configurations are compared with the angle-scanned x-ray photoelectron diffraction experiment to determine the geometrical structure of the oxidized Mg(0001) surface.Comment: 10 pages, 5 figure

"Cognitive Penetrability" - Ch 3 of Seemings and Epistemic Justification

In this chapter I introduce the thesis that perceptual appearances are cognitively penetrable and analyse cases made against phenomenal conservatism hinging on this thesis. In particular, I focus on objections coming from the externalist reliabilist camp and the internalist inferentialist camp. I conclude that cognitive penetrability doesn’t yield lethal or substantive difficulties for phenomenal conservatism

"Phenomenal Conservatism" - Ch 2 of Seemings and Epistemic Justification

In this chapter I introduce and analyse the tenets of phenomenal conservatism, and discuss the problem of the nature of appearances. After that, I review the asserted epistemic merits phenomenal conservatism and the principal arguments adduced in support of it. Finally, I survey objections to phenomenal conservatism and responses by its advocates. Some of these objections will be scrutinised and appraised in the next chapters

Rail Freight in Europe: Different Perspectives on Achieving Higher Service Levels

Despite European Commission studies and recommendations to improve the share of freight carried by rail in its member countries, the share of goods traveling by rail has declined since the 1990s. Although absolute volume has risen, market share is dropping. Incumbent operators are reluctant to make assets available to newcomers, and country-specific requirements hamper efforts to operate across borders. Manufacturers are experiencing difficulty responding to orders from clients other than the traditional incumbents, which ordered in large volumes and according to set specifications that varied little. Availability of resources, the influence of government policies, and marketing strategies are also analyzed for their role in the situation. Cooperation to ease the transition of freight from road to rail should be combined with competition to increase efficiencies and lower rates. More burdens on road operators could steer freight toward rail, but cooperation between road and rail will lead to greater success. A table shows the stakeholders consulted and their perspectives

Resonant photoemission study of the electronic structure of CuO and Cu₂O

The electronic structures of CuO and Cu2O have been investigated by resonant photoemission at the copper 3p threshold. The experimental data from CuO are compared with the results of a cluster calculation. From this analysis we confirm the dominant d8 character of the states between 8 and 16 eV, and that singlet and triplet final states behave quite differently at the (3p→3d) resonance. It is necessary to specify the multiplet state when calculating the d-d Coulomb interaction in this case since the total energy spread of the d8 multiplets is about 8 eV. The results confirm the charge-transfer nature of the band gap in CuO. The resonance behavior in Cu2O is explained in terms of strong O 2p–Cu 4(sp) hybridization