Staggered local density of states around the vortex in underdoped cuprates.

We have studied a single vortex with the staggered flux (SF) core based on the SU(2) slave-boson theory of high T(c) superconductors. We find that, whereas the center in the vortex core is a SF state, as one moves away from the core center a correlated staggered modulation of the hopping amplitude chi and pairing amplitude Delta becomes predominant. We predict that in this region the local density of states exhibits staggered modulation when measured on the bonds, which may be directly detected by STM experiments.

Electron spectral function and algebraic spin liquid for the normal state of underdoped high T(c) superconductors.

We propose to describe the spin fluctuations in the normal state (spin-pseudogap phase) of underdoped high T(c) cuprates as a manifestation of an algebraic spin liquid. Within the slave boson implementation of spin-charge separation, the normal state is described by massless Dirac fermions, charged bosons, and a gauge field. The gauge interaction, as an exact marginal perturbation, drives the mean-field free-spinon fixed point to a new spin-quantum fixed point-the algebraic spin liquid. Luttinger-liquid-like line shapes for the electron spectral function are obtained in the normal state, and we show how a coherent quasiparticle peak appears as spin and charge recombine.

Characterisation of an anti-ulcer pectic polysaccharide from leaves of Panax ginseng C.A. Meyer.

Structural characterisation of an anti-ulcer polysaccharide (GL-BIII), purified from leaves of Panax ginseng C.A. Meyer, was studied. Methylation analysis indicated that GL-BIII consisted mainly of terminal Arap, 4- or 5-substituted Ara, 2,4-disubstituted Rha, 4- and 6-substituted Gal, and 3,6-disubstituted Gal. Single radial gel diffusion using beta-glucosyl-Yariv antigen indicated that GL-BIII contained a small proportion of a beta-(1-->3,6)-galactan moiety. GL-BIII also contained terminal, 4-substituted, and 3,4-disubstituted GalA, and terminal and 4-substituted GlcA. Base-catalysed beta-elimination suggested that some 2-substituted Rha in GL-BIII was attached to position 4 of a 4-substituted uronic acid. Both mild acid hydrolysis and endo-alpha-(1-->4)-polygalacturonase digestion of GL-BIII did not give fragments consisting mainly of GalA. Methylation analysis and GC-MS analysis of acidic oligosaccharides liberated by partial acid hydrolysis indicated that GL-BIII contained a GalA-(1-->4)-Rha unit in addition to longer acidic units consisting of 2-substituted Rha and 4-substituted GalA. Lithium-mediated degradation of GL-BIII followed by borohydride reduction gave small amounts of fractions containing long and intermediate neutral oligosaccharide-alditols and a large amount of a fraction containing short oligosaccharide-alditols. The long neutral oligosaccharide-alditol fraction mainly comprised 4- or 5-substituted Ara, terminal Galf, 6-substituted Glc, and 2-substituted Man, whereas the intermediate oligosaccharide-alditol fraction consisted mainly of terminal and 6-substituted Galp, 6-substituted Glc, and 2-substituted Man. Methylation analysis and GC-MS analysis of the short oligosaccharide-alditol fraction suggested that it contained at least 14 kinds of di- to tetra-saccharide-alditols such as Gal-(1-->2)-Rha-ol, Gal-(1-->4)-Rha-ol, Ara-->Ara-ol, and Ara-->Ara-->Ara-ol.

[Structure of pingbeimine C].

A new C-nor-D-homosteroid alkaloid, C27H43O6N, mp 171.5-173 degrees C, named pingbeimine C, was isolated from the bulb of Fritillaria ussuriensis Maxim. On the basis of IR, MS, 1HNMR and 13CNMR spectroscopic data, particularly X-ray crystallographic analysis, structure IV has been assigned to this alkaloid.

[Structure of pingbeidinoside, an alkaloid isolated from the stems and leaves of Fritillaria ussuriensis Maxim].

A new steroid alkaloid glucoside, pingbeidinoside, was isolated from the stem and leaf of Fritillaria ussuriensis Maxim by column chromatographic techniques. On the basis of the IR, MS, 1HNMR and 13CNMR spectra of pingpeidinoside and products of its transformation, the structure of pingbeidinoside has been established as 3 beta,16 alpha,20-trihydroxy-delta 5-22,26-epiminocholestane-25-O-beta-D- glucoside.