The local structure of OH species on the V2O3(0 0 0 1) surface: a scanned-energy mode photoelectron diffraction study

Scanned-energy mode photoelectron diffraction (PhD), using O 1s photoemission, together with multiple-scattering simulations, have been used to investigate the structure of the hydroxyl species, OH, adsorbed on a V2O3(0 0 0 1) surface. Surface OH species were obtained by two alternative methods; reaction with molecular water and exposure to atomic H resulted in closely similar PhD spectra. Both qualitative assessment and the results of multiple-scattering calculations are consistent with a model in which only the O atoms of outermost layer of the oxide surface are hydroxylated. These results specifically exclude significant coverage of OH species atop the outermost V atoms, i.e. in vanadyl O atom sites. Ab initio density-functional theory cluster calculations provide partial rationalisation of this result, which is discussed the context of the general understanding of this system

Adiponutrin Functions as a Nutritionally Regulated Lysophosphatidic Acid Acyltransferase

SummaryNumerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism are unclear. Here we show that ADPN promotes cellular lipid synthesis by converting lysophosphatidic acid (LPA) into phosphatidic acid. The ADPN-catalyzed LPA acyltransferase (LPAAT) reaction is specific for LPA and long-chain acyl-CoAs. Wild-type mice receiving a high-sucrose diet exhibit substantial upregulation of Adpn in the liver and a concomitant increase in LPAAT activity. In Adpn-deficient mice, this diet-induced increase in hepatic LPAAT activity is reduced. Notably, the I148M variant of human ADPN exhibits increased LPAAT activity leading to increased cellular lipid accumulation. This gain of function provides a plausible biochemical mechanism for the development of liver steatosis in subjects carrying the I148M variant

Lipidomics Analysis Reveals Efficient Storage of Hepatic Triacylglycerides Enriched in Unsaturated Fatty Acids after One Bout of Exercise in Mice

Background: Endurance exercise induces lipolysis, increases circulating concentrations of free fatty acids (FFA) and the uptake and oxidation of fatty acids in the working muscle. Less is known about the regulation of lipid metabolism in the liver during and post-exercise

The self-assembly of metallic nanowires

We have demonstrated that nickel adatoms self-assemble into quasi one-dimensional nanowires on vicinal Rh(111) surfaces by decorating their regular monoatomic step arrays, while V adatoms do not. The step decoration process has been followed experimentally by variable-temperature scanning tunnelling microscopy and high-resolution X-ray photoelectron spectroscopy. The physical origin of the different step-assisted self-assembly behaviour of Ni and V adatoms has been elucidated theoretically and is ascribed to different diffusion barriers and trapping capability of Ni and V at Rh steps. (c) 2006 Elsevier B.V. All rights reserved

V2O3(0001) surface terminations: from oxygen- to vanadium-rich

Well-ordered epitaxial V2O3(0 0 0 1) films (thickness > 80 Angstrom) have been prepared on the clean Rh(1 1 1) surface and investigated with scanning tunnelling microscopy, low-energy electron diffraction, high-resolution electron energy loss spectroscopy and high-resolution X-ray photoelectron spectroscopy with synchrotron radiation. Atomically flat V2O3(0 0 0 1) surfaces, terminated by vanadyl (V=O) groups, have been obtained after the reactive oxide deposition and subsequent annealing in vacuum to 600 degreesC. Annealing the V=O termination in oxygen atmosphere (500 degreesC, 5 x 10(-6) mbar) results in the partial removal of the vanadyl groups and in the formation of an oxygen-richer surface termination, exhibiting a (root3 x root3)R30degrees structure. Structure models for this oxygen-rich termination are proposed, which are characterised by (O=V)(0.66)-O-3-V-V-. . . and (O=V)(0.33)-O-3-V-V (. . .) stacking sequences. Conversely, deposition of sub-monolayer V coverages onto the V=O surface leads to the formation of a metal-rich V2O3(0 0 0 1) surface, terminated by a close-packed V-3 layer on top of the bulk-type O-3 plane. Such a VO(1 1 1)-layer is only metastable and oxidises back readily upon annealing in vacuum to the vanadyl-terminated V2O3(0 0 0 1) surface. (C) 2004 Elsevier B.V. All rights reserved

Chemical Reactivity of Ni-Rh Nanowires

The properties of bimetallic Ni-Rh nanowires, fabricated by decorating the steps of vicinal Rh(111) surfaces by stripes of self-assembled Ni adatoms, have been probed by STM, photoemission, and ab initio density functional theory calculations. These Ni-Rh nanowires have specific electronic properties that lead to a significantly enhanced chemical reactivity towards oxygen. As a result, the Ni-Rh nanowires can be oxidized exclusively, generating novel quasi-one-dimensional oxide structures

Metal supported oxide nanostructures: model systems for advanced catalysis

Metal supported oxide nanostructures are discussed within the framework of the "inverse model catalyst" concept. We show that oxide nanostructures on metal surfaces may be regarded as artificial oxide materials, which display novel properties as compared to bulk oxide compounds and are stabilised by interfacial interactions and two-dimensional confinement effects. This is illustrated for prototypical examples of vanadium oxide overlayers on Rh(111) and Pd(111) surfaces. Structure and morphological changes of the oxide phase on V-oxide/Rh and V-oxide/Pd inverse catalyst surfaces are discussed, and the mass transport problem in catalyst systems during oxidation-reduction cycles is addressed. We demonstrate that the diffusion of oxide cluster over the metal surface provides a effective means of mass transport. The role of metal-oxide interface in determining the oxide nanolayer structure on particular substrate surfaces is investigated, and interfacial chemistry and interfacial strain effects are identified as important parameters

Experimental and Theoretical Study of a Surface Stabilized Monolayer Phase of Nickel Oxide on Pd(100)

A surface stabilized monolayer phase of nickel oxide, c(4 x 2)-Ni3O4, has been found to grow epitaxially under reactive deposition conditions on Pd(100), in the presence of other adsorbed phases and in competition with them. High-quality scanning tunneling microscopy data are reported and discussed, including a detailed analysis of the defects and of the border morphology of this new phase. The data are discussed in the light of ab initio simulations of the electronic, energetic, and geometric properties of such a phase. A hybridexchange density functional theory approach has been used, and a slab model is adopted where palladium is simulated by a thin film covered on both sides by regular epilayers. A growth model has been developed that explains both the unusual stoichiometry of the phase and the observed defects

Growth and thermal behaviour of NiO nanolayers on Pd(100)

The growth of ultrathin nickel oxide overlayers (nanolayers) on Pd(100) from submonolayer coverages up to 20 monolayer thick films has been investigated by scanning tunneling microscopy (STM), in conjunction with LEED and high-resolution electron energy loss spectroscopy (HREELS). The first nickel oxide monolayer on Pd(100) forms a wetting layer with a c(4 x 2) structure, which has been interpreted in terms of an interface stabilised Ni3O4-type structure. Stoichiometric NiO grows on top of the c(4x 2) monolayer in a strained lattice with the (100) surface orientation parallel to the substrate. The lattice relaxation of the NiO phase occurs gradually and is completed after 10 monolayers, where a bulk-type NiO phase is obtained. The phonon spectra of the c(4 x 2) monolayer and the subsequent NiO layers, as measured by HREELS, are characteristic and of diagnostic value to identify the different oxide phases. The morphology of the nickel oxide nanolayers has been analysed by quantitative evaluation of the STM images in terms of their roughness parameters. The roughness of nickel oxide nanolayers prepared by different kinetic routes has been compared and the optimal preparation conditions for obtaining smooth morphologies are proposed