Geometrical frustration and incommensurate magnetic order in Na3RuO4 with two triangular motifs

Incommensurate magnetic order in the spin-3/2 antiferromagnet Na3RuO4 is uncovered by neutron diffraction combined with ab initio calculations. The crystal structure of Na3RuO4 contains two triangular motifs on different length scales. The magnetic Ru5+ ions form a lozenge (diamond) configuration, with tetramers composed of two isosceles triangles. These tetramers are further arranged in layers, such that an effective triangular lattice is formed. The tetramers are nearly antiferromagnetic but frustration between them leads to an incommensurately modulated magnetic structure described by the propagation vector →k=(0.242(1),0,0.313(1)). We show that the long-range Ru-O-O-Ru couplings between the tetramers play a major role in Na3RuO4 and suggest an effective description in terms of the spatially anisotropic triangular lattice if the tetramers are treated as single sites

RF Quadrupole Structures for Transverse Landau Damping in Circular Accelerators

The beams required for the high luminosity upgrade of the Large Hadron Collider (HL-LHC) and other potential future circular colliders (FCC) call for efficient mechanisms to suppress transverse collective instabilities. In addition to octupole magnets installed for the purpose of Landau damping in the transverse planes, we propose to use radio frequency (rf) quadrupole structures to considerably enhance the aforementioned stabilising effect. By means of the PyHEADTAIL macroparticle tracking code as well as analytical studies, the stabilising mechanism introduced by an rf quadrupole is studied and explained. It is, furthermore, compared to the influence of the second order chromaticity on transverse beam stability

The effects of male-male contests and female eavesdropping on female mate choice and male mating success in the jumping spider, Thiania bhamoensis (Araneae: Salticidae)

10.1007/s00265-007-0488-xBehavioral Ecology and Sociobiology625639-646BESO