Capture-recapture: Before and after EURING 2000

Capture-recapture studies and analyses have become an important tool for the study of bird populations. One reason for the rapid advancement in this area has been the EURING conferences where population biologists and statisticians meet to review recent progress, identify areas that require further work, and work collaborately to solve real world problems. In this paper, we forecast the needs for future research in this area and review the recent conference to try and identify what questions are yet unsolved. This EURING conference was dedicated to Dr George Seber who was the author of a number of key papers and whose name is synonymous with 'The estimation of animal abundance and related parameter' (Seber, 1982). He has retired from working in this field.

Intermolecular interactions in the molecular ferromagnetic NH4Ni(mnt)(2)center dot H2O

Molecular solids that exhibit ferromagnetism are rare, and thus there is considerable interest in understanding the magnetic coupling mechanisms that operate in the few known examples(1). One such material is the charge-transfer salt NH4Ni(mnt)(2) . H2O, which consists of stacked planar metal ligands separated by ammonium cations. This salt is an insulator with localized spins that exhibit long-range ferromagnetic order at low temperatures (below 4.5 K)(2).3 Here we show that the Curie temperature demarcating the transition to the ferromagnetic state increases markedly with pressure until ferromagnetic order abruptly disappears at 6.8 kbar, indicating that the magnetic coupling is very sensitive to intermolecular separation. Using quantum-chemical calculations(3), we show that this pressure dependence arises from a competition between ferromagnetic coupling (resulting from nickel-sulphur intermolecular spin interactions), and antiferromagnetic coupling (from nickel-nickel interactions). We suggest that a similar interplay of spin-polarization effects might play a key role in determining the nature of the ground states (metallic, superconducting and so forth) observed in other molecular materials of this structural type(4,5)