Water activity in lamellar stacks of lipid bilayers: "Hydration forces" revisited

Water activity and its relationship with interactions stabilising lamellar stacks of mixed lipid bilayers in their fluid state are investigated by means of osmotic pressure measurements coupled with small-angle x-ray scattering. The (electrically-neutral) bilayers are composed of a mixture in various proportions of lecithin, a zwitterionic phospholipid, and Simulsol, a non-ionic cosurfactant with an ethoxylated polar head. For highly dehydrated samples the osmotic pressure profile always exhibits the "classical" exponential decay as hydration increases but, depending on Simulsol to lecithin ratio, it becomes either of the "bound" or "unbound" types for more water-swollen systems. A simple thermodynamic model is used for interpreting the results without resorting to the celebrated but elusive "hydration forces"Comment: 24 pages, 12 figures. Accepted for publication in The European Physical Journal

La posición taxonómica de Scilla beirana Samp. (Hyacinthaceae)

Populations of Scilla beirana Samp. were sampled in NW Portugal and compared with its relatives S. ramburei Boiss, and S. peruviana L. Leaf and scape anatomy, morphology, chromosome number and idiogram were identical in S. beirana and S. ramburei, but differed from S. peruviana. Diagnostic characters previously used to discriminate S. beirana (width of leaves and flower number) showed continuous, but not clinal, variation, and failed to provide a clear-cut basis for identification and no other morphological attributes were found to separate the taxa. All available evidence suggests that S. beirana should be put into synonymy with S. ramburei, as was earlier suggested by COUTINHO (1935).Se muestreó Scilla beirana Samp. en diversas poblaciones del noroeste de Portugal y se comparó con dos táxones con los que se había relacionado previamente, S. ramburei Boiss, y S. peruviana L. La macromorfología, la anatomía de la hoja y escapo, el número cromosomático y el idiograma de S. beirana y S. ramburei fueron indistinguibles, pero diferentes de los de S. peruviana. Los caracteres diagnósticos que se habían utilizado previamente para discriminar a S. beirana -anchura foliar y número de flores- revelaron una variación continua y no permitieron diferenciarla de S. ramburei, en la cual debería ser incluida como sinónimo, tal como había sugerido COUTINHO (1935)

Optical Nanoantennas for Multiband Surface-Enhanced Infrared and Raman Spectroscopy

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