Electronic structure of a Mn12 molecular magnet: Theory and experiment

金沢大学大学院自然科学研究科物質情報解析We used site-selective and element-specific resonant inelastic x-ray scattering (RIXS) to study the electronic structure and the electron interaction effects in the molecular magnet [Mn12 O12 (C H3 COO)16 (H2 O)4] 2C H3 COOH 4 H2 O, and compared the experimental data with the results of local spin density approximation +U electron structure calculations which include the on-site Coulomb interactions. We found a good agreement between theory and experiment for the Coulomb repulsion parameter U=4 eV. In particular, the p-d band separation of 1.8 eV has been found from the RIXS spectra, which is in accordance with the calculations. Similarly, the positions of the peaks in the XPS spectra agree with the calculated densities of p and d states. Using the results of the electronic structure calculations, we determined the intramolecular exchange parameters, and used them for diagonalization of the Mn12 spin Hamiltonian. The calculated exchanges gave the correct ground state with the total spin S=10. © 2007 The American Physical Society

ANGPTL4 is produced by entero-endocrine cells in the human intestinal tract

Gut hormones produced by entero-endocrine cells (EEC) located throughout the gastrointestinal tract play a major role in the regulation of glucose and energy homeostasis. Angiopoietin-like 4 (ANGPTL4, also referred to as fasting induced adipose factor) is a secreted factor involved in regulation of lipid homeostasis and has been proposed as circulating mediator between the gut microbiota and fat storage in adipose tissue, although discordant data exist. Currently, little is known about the site and regulation of ANGPTL4 production in the intestine. Here, we show using immunohistochemistry and immunofluorescence that cells positive for ANGPTL4 are scattered along the epithelial layer in the human small and large intestine. ANGPTL4-positive cells exhibit typical features of EEC characterized by large ANGPTL4-positive secretory granules directed towards the basolateral side. In support, extensive overlap was observed between ANGPTL4-positive cells and cells positive for the entero-endocrine marker chromogranin A. Higher resolution images revealed that ANGPTL4 and chromogranin A are partially present in distinct intracellular vesicles. Using entero-endocrine HuTu-80 cells, ANGPTL4 secretion was shown to be induced by short chain fatty acids and reduced by bile acids. Finally, levels of ANGPTL4 in human plasma were significantly decreased following meal consumption. In conclusion, ANGPTL4 is produced by EEC in human intestine and expression may be regulated by short chain fatty acids and bile acids

Understanding the gap in polyoxovanadate molecule-based magnets

Contains fulltext : 34814.pdf (publisher's version ) (Open Access)We report a joint experimental and theoretical investigation of the transport gap, optical properties, and electronic structure of two chemically similar, inhomogeneously mixed-valent polyoxovanadate molecule-based magnets. We attribute the substantial gap in [NHEt3](4)[(V8V4As8O40)-V-IV-As-V(H2O)]center dot H2O to weak p-d hybridization and a large on-site Coulomb repulsion (U=6 eV). The reduced gap in [NHEt3](3)[(V6V6As8O40)-V-IV-As-V(HCO2)]center dot 2H(2)O is associated with a smaller value of U (4 eV), at least from a molecular point of view, although the transport properties also reflect subtle organization of the molecular structure and differences between direct and indirect intermolecular charge transfer. A detailed analysis of the vibrational response supports the important role of local molecular distortions and hydrogen bonding in the intramolecular and intermolecular charge transport of [NHEt3](4)[(V8V4As8O40)-V-IV-As-V(H2O)]center dot H2O

Electronic structure of a Mn-12 molecular magnet: Theory and experiment

Contains fulltext : 34826.pdf (publisher's version ) (Open Access