Applying response surface methodology to optimize nimesulide permeation from topical formulation

Nimesulide is a non-steroidal anti-inflammatory drug that acts through selective inhibition of COX-2 enzyme. Poor bioavailability of this drug may leads to local toxicity at the site of aggregation and hinders reaching desired therapeutic effects. This study aimed at formulating and optimizing topically applied lotions of nimesulide using an experimental design approach, namely response surface methodology. The formulated lotions were evaluated for pH, viscosity, spreadability, homogeneity and in vitro permeation studies through rabbit skin using Franz diffusion cells. Data were fitted to linear, quadratic and cubic models and best fit model was selected to investigate the influence of permeation enhancers, namely propylene glycol and polyethylene glycol on percutaneous absorption of nimesulide from lotion formulations. The best fit quadratic model explained that the enhancer combination at equal levels significantly increased the flux and permeability coefficient. The model was validated by comparing the permeation profile of optimized formulations’ predicted and experimental response values, thus, endorsing the prognostic ability of response surface methodology

Oil futures and strategic stocks at sea

A theoretical model explaining the determination of prices in the markets for north sea crude oil is set up. Three markets are analysed in a three-stage game in which market concentration increases by each stage: in the first stage, the international petroleum exchange is modeled as a thick futures market. This market is also used to hedge against the uncertain outcome of the 15-day forward market, modeled in the second stage. There, a small club of traders enter futures contracts knowing that this will affect the storage decision and thereby the spot price profile. The third stage models the spot market as a two-period duopoly with inventories. The strategic effect of, and interaction between, inventories and futures positions is investigated.keywordsfuture marketfuture pricespot pricespot prexstrategic effectthese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves