6. Oceanapins A-F, unique branched ceramides isolated from the haplosclerid sponge Oceanapia cf. tenuis of the Coral sea

A series of ceramides, called oceanapins A-F (2-7), which are unique for branching at both the sphingosine and fatty-acid chains, have been isolated as pure compounds from the haplosclerid sponge #Oceanapia cf. #tenuis of the Coral Sea. Following acid hydrolysis, both the fatty-acid and the sphingosine portions were obtained separately, which allowed their unequivocal structural definition. The absolute configuration was secured via proctection of C (1')-OH and Mosher's esterification at C (3')-OH of the oceanapins. (Résumé d'auteur

Symmetry breaking in a constrained cheeger type isoperimetric inequality

The study of the optimal constant Kq(Ω) in the Sobolev inequality ∥u∥Lq(Ω) ≤ 1/Kq(Ω)∥Du∥(double-struck Rn), 1 ≤ q < 1∗, for BV functions which are zero outside Ω and with zero mean value inside Ω, leads to the definition of a Cheeger type constant. We are interested in finding the best possible embedding constant in terms of the measure of Ω alone. We set up an optimal shape problem and we completely characterize, on varying the exponent q, the behaviour of optimal domains. Among other things we establish the existence of a threshold value 1 ≤ q < 1∗ above which the symmetry of optimal domains is broken. Several differences between the cases n = 2 and n ≥ 3 are emphasized

Introducing Solar Thermal "Net Metering" in an Actual small-scale District Heating System: A Case-study Analysis☆

Abstract An energy and economic analysis on an hypothesis of introduction of prosumers in an actual small-scale district heating system (DHS) in Northern Italy has been carried out. The study was performed by means of dynamic simulations of the DHS. The investigated configurations include the transformation of one or more customers in prosumers, producing and self-consuming solar thermal heat, and supplying the DHS with the excess heat produced. For the considered case-study the solar heat fed into the DHS is basically antagonist of the CHP production. This leads to a decrease in the non-renewable energy share for the whole DHS, to a decrease in the profit of the DHS utility and to a profitable investment for the prosumers