[en] A method of immunoassay of a liquid sample in which a reaction mixture is formed and one or more components of the mixture are selectively removed by contacting the mixture with a particulate reagent comprising a polymeric matrix having a selective absorbent material and magnetic particles incorporated therein. By applying a magnetic field, the particulate reagent can be separated from the mixture. The method may be effected by discrete manual techniques or by automated continuous flow analysis. The particulate reagents and their method of production constitute a further aspect of the invention. (UK)

[en] We performed neutron spin echo measurements, on the geometrically frustrated antiferromagnet Y₂Mo₂O₇ to reveal the magnetic nature of this glass-like system close to the freezing temperature, T_f. Diffuse magnetic scattering S(Q), indicative of spatial correlations, were observed to peak at a wave vector, Q∼0.45 A^-1 below 25 K. The normalized intermediate scattering function, S(Q,t)/S(Q, 0), was measured as a function of temperature and Q. This provides evidence of the dynamics within the system and reveals at least two relaxation processes above and below T_f∼22.5 K

[en] Full text: In my presentation I will present recent results that have determined the spin-spin correlations in geometrically frustrated magnets. This will include polarised neutron diffraction, inelastic neutron scattering and neutron spin echo data. One sample of particular interest is the Gd₂Sn₂O₇ is believed to be a good approximation to a Heisenberg antiferromagnet on a pyrochlore lattice with exchange and dipole-dipole interactions. Theoretically such a system is expected to enter long range ordered ground state known as the Palmer Chalker state[1]. We show conclusively, through neutron scattering data, that the system indeed enters an ordered state with the Palmer-Chalker spin configuration below Tc = 1 K. Within this state we have also observed long range collective spin dynamics, spin waves. I will compare these results to the isostructural Gd₂Ti₂O₇ and Ho₂Ti₂O₇ compounds. Gd₂Ti₂O₇ has two magnetic transitions but never completely freezes. This system appears to be more frustrated than its tin cousin, however 3/4 of the spin system relieve their frustration at the expense of the others [2]. The spin ice compound Ho₂Ti₂O₇, has been studied extensively, but new results from the SNS [3] have shed some light on the low temperature spin dynamics in this material that have troubled experimentalists and theorists alike for over 10 years. (author)

[en] The author places some prior natural hazards research into the context of risk from new technologies to show that some beneficial technologies increase the risk from natural hazards. He examines the role of new technologies in risks from natural hazards in a historical perspective, using examples from research on mountain hazards

[en] We report magnetoresistivity measurements on a La_1.2Sr_1.8Mn₂O₇ single crystal. The charge transport in the ferromagnetic phase is dominated by two-magnon scattering in the high T range and by weak localization effects at lower T, in the non-metallic regime. In the paramagnetic phase, ρ_ab(T) obeys the adiabatic small polaron hopping mechanism, while ρ_c(T) follows an Arrhenius behavior with the same activation energy

[en] We report measurements of the neutron diffuse scattering in a single crystal of the relaxor ferroelectric material 95.5% Pb(Zn_1/3Nb_2/3)O₃-4.5%PbTiO₃. Our results suggest that the nanometer scale structure in this compound exhibits both <100> and <110> polarizations, which contribute to different portions of the total diffuse scattering intensity. These contributions can be distinguished by the differing responses to an electric field applied along (001). While diffuse scattering intensities associated with <110> (T2-type) polarizations show little to no change in a (001) field, those associated with <100> (T1-type) polarizations are partially suppressed by the field at temperatures below the Curie temperature T_C ∼ 475 K. Neutron spin-echo measurements show that the diffuse scattering at (0.05,0,1) is largely dynamic at high temperature and gradually freezes on cooling, becoming mostly static at 200 K.

No abstract available

[en] We report a systematic neutron diffraction study on the coexistence of long-range magnetic order and superconductivity in heavy fermion compounds CeRhl-,M,Ins (M=Ir,Co). In addition to the incommensurate antiferromagnetic component in pure CeRhIn5, new type of antiferromagnetic component is found to concur with appearance of superconductivity in the Ir and Co alloy series. There is no detectable effect of the superconducting transition on magnetic order parameters. We compare those results with similar studies we performed on CeRhIn:, under pressure. We also discuss possible theoretical scenarios.

[en] In order to better understand the distribution pattern of mineral elements in lichen tissues, thin sections (15 μm) of the foliose, vagrant soil lichen Xanthoparmelia chlorochroa were examined using proton microprobe Particle induced X-ray emission (PIXE). This technique was used to make two-dimensional scans, with 5 μm resolution, across tissue cross sections of the test species. Element maps for Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, and As have been prepared. Several elements are strongly localized in the element maps. PIXE data are complimented with STIM, light micrographs, and SEM images. Preliminary data suggest that nuclear microprobe techniques may be useful in elucidating element absorption and transport mechanisms in lichens

[en] Zero-field (ZF) μSR measurements were performed on single crystals of the high temperature superconductor YBa₂Cu₃O_6+x, for x≥0.67. Contrary to early ZF-μSR studies, we find that the muon-spin relaxation function evolves significantly as a function of temperature and oxygen content. The relaxation rate of the ZF-μSR time spectra exhibits a local minimum near 55 K and a subsequent increase with decreasing temperature. These features weaken considerably with decreasing x. A comparison to the results of nuclear quadrupole resonance experiments on highly doped samples suggests that these observations are associated with the build up of long-range charge correlations and not spontaneous orbital moments as suggested by Sonier et al. (Science 292 (2001) 1692)