Hydrogen Bond Dynamics Near A Micellar Surface: Origin of the Universal Slow Relaxation at Complex Aqueous Interfaces

The dynamics of hydrogen bonds among water molecules themselves and with the polar head groups (PHG) at a micellar surface have been investigated by long molecular dynamics simulations. The lifetime of the hydrogen bond between a PHG and a water molecule is found to be much longer than that between any two water molecules, and is likely to be a general feature of hydrophilic surfaces of organized assemblies. Analyses of individual water trajectories suggest that water molecules can remain bound to the micellar surface for more than a hundred picosecond. The activation energy for such a transition from the bound to a free state for the water molecules is estimated to be about 3.5kcal/mole.Comment: 12 pages. Phys. Rev. Lett. (Accepted) (2002

Trends in life science grid: from computing grid to knowledge grid

BACKGROUND: Grid computing has great potential to become a standard cyberinfrastructure for life sciences which often require high-performance computing and large data handling which exceeds the computing capacity of a single institution. RESULTS: This survey reviews the latest grid technologies from the viewpoints of computing grid, data grid and knowledge grid. Computing grid technologies have been matured enough to solve high-throughput real-world life scientific problems. Data grid technologies are strong candidates for realizing "resourceome" for bioinformatics. Knowledge grids should be designed not only from sharing explicit knowledge on computers but also from community formulation for sharing tacit knowledge among a community. CONCLUSION: Extending the concept of grid from computing grid to knowledge grid, it is possible to make use of a grid as not only sharable computing resources, but also as time and place in which people work together, create knowledge, and share knowledge and experiences in a community

Fluorescent characteristics of dissolved organic matter produced by bloom-forming coastal phytoplankton

Dynamics and sources of fluorescent dissolved organic matter (FDOM) are important for understanding biogeochemical processes in aquatic ecosystems. This study aimed to analyse direct production of FDOM by marine phytoplankton cultures and reveal fluorescent characteristics of exuded FDOM. Axenic cultures of eight species of bloom-forming marine phytoplankton, including two diatoms; a raphidophyte; two dinoflagellates; a chlorophyte; a cryptophyte and a haptophyte, were incubated in an artificial medium. Excitation emission matrices (EEMs) of FDOM in the culture medium were spectrofluorometrically measured. FDOM production was observed in all species, and fluorescent characteristics of the exudates varied considerably among species. Measured EEMs had peaks at 350/450 nm (excitation/emission) for the diatom Ditylum brightwellii and 370/450–470 nm for the raphidophyte Heterosigma akashiwo and the chlorophyte Oltmansiellopsis viridis, which have previously been regarded as the peaks of terrestrially derived humic-like substances. Direct production of FDOM by marine phytoplankton should be considered in future studies of FDOM dynamics in marine systems. Species-specific features of FDOM might be used for early detection of harmful blooms because this method is simple, rapid and suitable for monitoring

Co-incorporation effects of O and Na with CuInS2 thin films

By using x-ray photoelectron spectroscopy we have examined changes in the electronic structure of CuInS2 thin films with co-incorporation of O and Na that raised up the photovoltaic performance of CdS/CuInS2 solar cells. The electron binding energies of both the core levels and valence band for the film with the co-incorporation were smaller by 0.9 eV than those for the film without the co-incorporation. For the co-incorporated film an increase in the spectral intensity of the valence band was observed below 1-6 eV from the Cu 3d(10) nonbonding states, and it was due to both the Na s, p-S p hybridization and the In s-Op hybridization. The surface of the co-incorporated film can be expressed as (Cu, Na)In(S, O)(2). The (Cu, Na)In(S, O)(2) phase is related to the enlarged open-circuit voltage (0.75 eV) of n-CdS/p-CuInS2 solar cells. (C) 2000 American Institute of Physics