An acetone extract of the fruits of the Taiwanese medicinal plant Schisandra arisanensis has yielded 11 new oxygenated lignans. Four of these, named arisantetralones A-D (1-4), possess the aryltetralone skeleton, while the other seven, named arisanschinins F-L (5-11), are polyoxygenated C(18)-dibenzocyclooctadiene lignans. Structures were determined on the basis of spectroscopic analyses, especially 2D-NMR techniques. The structure of compound 1 was confirmed by X-ray crystallographic analysis. Immunomodulatory activity of the isolated lignans was tested and evaluated.
Rhombohedral graphite behaves as a topological semimetal, possessing flat surface subbands while being semimetallic in the bulk. The bulk-surface correspondence arises from the ABCstacking configuration of graphene layers. The bulk subbands in rhombohedral graphite can be interpreted as a three-dimensional Dirac cone structure, whose Dirac points form continuous lines spiraling in momentum space. In this paper, we studied the evolution of the gapped bulk subbands in ABC-stacked N -layer graphene in the increase of N and their dimensional crossover to the 3D Dirac cone structure in the bulk limit, where the bulk gap closes up at the Dirac-point spirals. In order to clarify the effect of coupling to the surface subbands, we use a non-perturbative effective Hamiltonian closed in the bulk subspace. As a consequence, the wave length of the standing wave function across the stack of layers depends on the in-plane Bloch momentum. In the bulk limit, the coupling vanishes and hence the wave length is irrelevant to the surface. 73.21.Ac, 73.22.Pr
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