Neutron and X-ray diffraction experiments have shown that NaV2O5 consists of zig-zag V chains of average valence 4.5 rather than a charge ordered state at room temperature. Both these experiments revealed superlattice reflections below the phase transition temperature TSP < 34 K. The modulation below TSP is due to displacements predominantly of V atoms for which we propose a model. q 1998 Elsev...

Elucidating the nature of the magnetism of a high-temperature superconductor is crucial for establishing its pairing mechanism. The parent compounds of the cuprate and iron-pnictide superconductors exhibit Néel and stripe magnetic order, respectively. However, FeSe, the structurally simplest iron-based superconductor, shows nematic order (Ts=90 K), but not magnetic order in the parent phase, an...

The H, system has excited much mterest both theoretically [l] and experimentally [2]. In particular It has been used to study elastic, inelastic and reacttve scattermg. The H3 molecule has been observed in an excited Rydberg state [3], a Bndtng confirmed by ab initio calculation [4,5], but as yet we know of no experimental evidence for it in its electronrc ground state. The ground-state potenti...

Pluripotency is defined as the capacity of individual cells to initiate all lineages of the mature organism in response to signals from the embryo or cell culture environment. A pluripotent cell has no predetermined programme; it is a blank slate. This is the foundation of mammalian development and of ES (embryonic stem) cell biology. What are the design principles of this naïve cell state? How...

Structure and bonding for a series of oxo-bridged and sulphur bridged alkali-metal centers (M-X-M: Li, Na and K; X = O, S) are studied for various M-X-M angles. The structures for these charge-transfer systems are compared with H-X-H. These chargetransfer systems show bonding and structures that are distinctively different from the covalent H-X-H molecules. The singlet-triplet gap for all of th...