In the deep interior of the giant planets Jupiter and Saturn, ordinary hydrogen and helium are transformed into a conducting metallic liquid at extremely high pressure. It is likely that the giant planets' observed magnetic field is constantly generated in the metallic fluid core by magnetohydrodynamic processes, converting mechanic energy in the form of convection into magnetic energy. The maximum strength of their magnetic fields is likely to be limited by magnetic field instabilities which convert the magnetic energy back into convection. The parameter which governs the occurrence of magnetic instabilities is the Elsasser number, A = B2a/2Q, where B is the field strength, 0 is the electrical conductivity, Q is the rotation rate and p is the density. Since magnetic instability will be very active when A exceeds a critical value A, N 10 (the precise value depending on the magnetic field distribution), this imposes an upper bound on the effective electrical conductivity of the metallic fluid which comprises the bulk of Jupiter's interior and much of Saturn's Stability calculations including both toroidal (model) and poloidal (observed) components of the magnetic field in a rapidly rotating spherical shell, have been performed. The most stable configuration of the field is when the poloidal component of field is strong and the toroidal field is weak, in this case we obtain an upper bound for electrical conductivity of 0-3x 106S/m; while the most unstable configuration of the field is when the toroidal and poloidal fields are comparable, giving rise to UM -3 x lo5 S/m. The implications of the results for general dynamo theory are also discussed.

Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening disorder characterized by antibodies to Platelet Factor 4 (PF4)-polyanion complexes which cause thrombocytopenia and thrombosis. Currently used technically-simple frontline assays such as the PF4-polyanion enzyme-linked immunosorbent assays (ELISAs) lack specificity, and more accurate functional assays such as the serotonin release assay (SRA) and PF4-dependent P-selectin expression assay (PEA) have long turnaround times due to technical complexity and availability only in the reference laboratory setting. There is a critical need for accurate near-patient functional testing to guide patient management, but a key barrier to attaining this goal is the short-term viability of platelets. Here, we detail a process of platelet cryopreservation that renders them viable for at least one year and show that PF4-treated cryopreserved platelets, when coupled with ELISA-based measurement of thrombospondin-1 release (a platelet α-granule protein), detects pathogenic HIT antibodies with high accuracy. Furthermore, testing of a cohort of non-pathogenic HIT antibodies that were strongly reactive in PF4/polyanion ELISA but negative in functional assays demonstrated negative results in the thrombospondin-1 release assay, confirming high specificity of this technique. These findings have the potential to transform the diagnostic testing paradigm in HIT by making in-hospital functional testing available for rapid and accurate diagnosis.