Lipid Solubility and Molecular Weight: Whose Idea Was That

Gene Cooper was a bright theoretician, a skilled product developer, and a motivational leader who applied his talents to the skin science area early in his career. His work led to the development of finite dose skin absorption models, chemical penetration enhancer technologies and quantitative structure-penetration relationships for chemicals contacting human skin. His ideas regarding the impact of molecular weight and lipid solubility on skin transport catalyzed the later development by Potts and Guy of the first successful skin permeability model. But Gene's most important contribution to the field was as a scientific role model and an inspirational leader who launched the careers of several young scientists, including the author of this article.</jats:p

Calorimetric study of phase transitions in the liquid crystal butyloxybenzylidene octylaniline (4O.8)

The heat capacity of butyloxybenzylidene octylaniline has been measured from 0° to 95 °C. Significant pretransitional effects are observed near both the first-order transition from the normal rigid crystal to the B phase plastic crystal and the first-order melting transition from the B phase to the smectic-A liquid crystal phase. Data near the second-order smectic-A to nematic transition require a critical exponent α considerably greater than zero, in agreement with recent results on other materials.La capacité calorifique du butyloxybenzylidène octylaniline a été mesurée entre 0° et 95 °C. Des effets prétransitionnels significatifs sont observés non seulement près de la transition du premier ordre entre le cristal rigide normal et la phase cristalline plastique B mais encore près de la transition de fusion du premier ordre entre la phase B et la phase cristal liquide smectique A. Les données au voisinage de la transition du second ordre smectique A-nématique déterminent un exposant critique α très supérieur à zéro, en accord avec des résultats récents obtenus sur d'autres matériaux

Critical heat capacity of octylcyanobiphenyl (8CB) near the nematic-smectic A transition

An ac technique has been used to measure the heat capacity near the nematic-smectic A (N-SmA) transition in 8CB along isobars at 1, 750 and 1 500 bar. As the pressure is increased, the magnitude of the Cp peak associated with this transition decreases but the shape of the peak remains essentially unchanged. The excess heat capacity at 1 atm. is consistent with a second-order N-SmA transition characterized by an effective critical exponent α = 0.30 ± 0.05.La technique ac a été utilisée pour mesurer la capacité calorifique près de la transition nématiquesmectique A (N-SmA) du composé 8CB le long d'isobars à 1, 750 et 1 500 bar. La grandeur du pic Cp associé à cette transition décroît quand la pression augmente mais la forme du pic reste essentiellement inchangée. La capacité calorifique en excès à 1 atm. est conforme à une transition N-SmA du second ordre, caractérisée par un exposant critique effectif α = 0,30 ± 0,05