Mitragynine (1) is a major alkaloidal component in the Thai traditional medicinal herb, Mitragyna speciosa, and has been proven to exhibit analgesic activity mediated by opioid receptors. By utilizing this natural product as a lead compound, synthesis of some derivatives, evaluations of the structure-activity relationship, and surveys of the intrinsic activities and potencies on opioid receptors were performed with guinea pig ileum. The affinities of some compounds for mu-, delta-, and kappa-receptors were determined in a receptor binding assay. The essential structural moieties in the Corynanthe type indole alkaloids for inducing the opioid agonistic activity were also clarified. The oxidative derivatives of mitragynine, i.e., mitragynine pseudoindoxyl (2) and 7-hydroxymitragynine (12), were found as opioid agonists with higher potency than morphine in the experiment with guinea pig ileum. In addition, 2 induced an analgesic activity in the tail flick test in mice.

No abstract

Nanocarbon-doped Fe-sheathed MgB 2 tapes with different doping levels were prepared by the in situ powder-in-tube method. Compared to the undoped tapes, J c for all the C-doped samples was enhanced by more than an order of magnitude in magnetic fields above 9 T. At 4.2 K, the transport J c for the 5 at% doped tapes reached 1.85×10 4 A/cm 2 at 10 T and 2.8×10 3 A/cm 2 at 14 T, respectively. Moreover, the critical temperature for the doped tapes decreased slightly. Transmission electron microscopy showed a number of intra-granular dislocations and the dispersed nanoparticles embedded within MgB 2 grains induced by the C doping. The mechanism for the enhancement of flux pinning is also discussed. These results indicate that powder-in-tube-processed MgB 2 tape is very promising for high-field applications.

122 type pnictide superconductors are of particular interest for high-field applications because of their large upper critical fields H c2 (> 100 T) and low anisotropy γ (<2). Successful magnet applications require fabrication of polycrystalline superconducting wires that exhibit large critical current density J c , which is limited by poor grain coupling and weak-link behavior at grain boundaries.Here we report our recent achievement in the developing Sr 0.6 K 0.4 Fe 2 As 2 tapes with transport J c up to 0.1 MA/cm 2 at 10 T and 4.2 K. This value is by far the highest ever recorded for iron based superconducting wires and has surpassed the threshold for practical application. The synergy effects of enhanced grain connectivity, alleviation of the weak-link behavior at grain boundaries, and the strong intrinsic pinning characteristics led to the superior J c performance exhibited in our samples. This advanced J c result opens up the possibility for iron-pnictide superconducting wires to win the race in high-field magnet applications.