Dichlorolissoclimide, a new cytotoxic labdane derivative from Lissoclinum voeltzkowi Michaelson (Urochordata)

Spectral methods were used to determine the structure of a new cytotoxic compound, dicnlorolissoclimide 1, isolated from the New Caledonian ascidian #Lissoclinum voeltzkowi$ Michaelson. (Résumé d'auteur

Three new potent cytotoxic macrolides closely related to sphinxolide from the New Caledonia sponge Neosiphonia superstes

Three new macrolides 2-4 have been isolated with sphinxolide 1 from the marine sponge #N. superstes$ collected off New Caledonia. The structures of the new compounds were determined by interpretation of NMR spectral data as well as comparison of spectral data with those of 1. These compounds were highly cytotoxic against various human carcinoma cells. (Résumé d'auteur

Transport properties of ybco thin films near the critical state with no applied field

Transport measurements carried out on twinned ybco films are compared to the predictions of a previously proposed model suggesting that the vortices move along the films twin boundaries that behave as rows of Josephson weak links [P.Bernstein and J.F.Hamet, J.Appl.Phys.95 (2004) 2569]. The obtained results suggest that, except if the films are very thin, the twin boundaries consist of superimposed rows of weak links with mean height,ds, whose mean length along the TBs is an universal function of T/Tc, the reduced temperature. This conclusion yields a general expression for the critical surface current density of the films as a function of T/Tc and of the number of superimposed weak links rows, while the critical current density depends on ds. A comparison of the measurements reported by various authors shows that the nature of the substrate and the growth technique have both a strong effect on ds . The existence of superimposed weak links rows is attributed to extended defects generated by y2o3 inclusions.Comment: 33 pages, 13 figures; accepted for publication in Physica