Molecular dynamics study of nanoconfined TIP4P/2005 water: how confinement and temperature affect diffusion and viscosity.

In the past few decades great effort has been devoted to the study of water confined in hydrophobic geometries at the nanoscale (tubes and slit pores) due to the multiple technological applications of such systems, ranging from drug delivery to water desalination devices. To our knowledge, neither numerical/theoretical nor experimental approaches have so far reached a consensual understanding of structural and transport properties of water under these conditions. In this work, we present molecular dynamics simulations of TIP4P/2005 water under different nanoconfinements (slit pores or nanotubes, with two degrees of hydrophobicity) within a wide temperature range. It has been found that water is more structured near the less hydrophobic walls, independently of the confining geometries. Meanwhile, we observe an enhanced diffusion coefficient of water in both hydrophobic nanotubes. Finally, we propose a confined Stokes-Einstein relation to obtain the viscosity from diffusivity, whose result strongly differs from the Green-Kubo expression that has been used in previous works. While viscosity computed with the Green-Kubo formula (applied for anisotropic and confined systems) strongly differs from that of the bulk, viscosity computed with the confined Stokes-Einstein relation is not so much affected by the confinement, independently of its geometry. We discuss the shortcomings of both approaches, which could explain this discrepancy.

Ethnobotanical inventory of medicinal plants used by the Guaymi Indians in western Panama. Part II.

A list of newly identified plants is presented to supplement Part I (Joly et al. (1987) Journal of Ethnopharmacology 20, 145-171). A comparative analysis is made between our work and two other recent inventories of plants used by the Guaymi Indians of Panama and Costa Rica. As in Part I, the results of a literature survey are also provided, including medicinal uses, known constituents and pharmacological effects.

Ethnobotanical inventory of medicinal plants used by the Guaymi Indians in western Panama. Part I.

Plants used by Guaymi "Curanderos" in Western Panama (Bocas del Toro and Chiriquí) are listed. Results of a literature survey are also reported, including medical use, known constituents and pharmacological effects.