Structural relationships in high temperature superconductors

The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 90/sup 0/K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La/sub 2-x/Sr/sub x/CuO/sub 4-y/ and YBa/sub 2/Cu/sub 3/O/sub 7-delta/ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometry. In this paper we discuss the relationship of these features to the superconducting properties. 30 refs., 6 figs

Release of satiety hormones in response to specific dietary proteins is different between human and murine small intestinal mucosa

BACKGROUND/AIM: High protein diets are the most effective to stimulate cholecystokinin (CCK) and glucagon-like peptide 1 (GLP-1) release; however, which proteins are the most potent is not known. Here, the effects of specific dietary proteins on intestinal CCK and GLP-1 release were examined. METHODS: Duodenal biopsies of 10 healthy male subjects and 10 male rats were taken and placed in an Ussing chamber system. The biopsies were exposed on the luminal side to buffer, egg protein, codfish protein, ovomucoid, pea protein, and wheat protein. After an exposure time of 2 h, samples were taken from the serosal side. RESULTS: Pea protein and wheat protein increased CCK and GLP-1 release in human duodenal tissue, while codfish protein only increased CCK release. No elevated levels of CCK and GLP-1 were found after exposure of rat tissue to different proteins. CONCLUSION: Pea and wheat protein are the most potent stimulators of CCK and GLP-1 release in human duodenal tissue, and may therefore be good dietary additives in weight management

The possible occurrence of multi-phase behavior in the high T sub c superconductor YBa sub 2 Cu sub 3 O sub x

We report here the results obtained for powder diffraction studies on four YBa{sub 2}Cu{sub 3}O{sub x} samples in which a model with two orthorhombic phases was used to obtain an improved agreement. The implications of this structural model on the systematic variation of {Tc} with oxygen content will be discussed. 28 refs., 3 figs., 2 tabs