Factors Affecting the Occurrence and Transport of Atmospheric Organochlorines in the China Sea and the Northern Indian and South East Atlantic Oceans

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are reported in 97 air samples collected on board the RV <i>Polarstern</i> in November 2007 from the equator to Cape Town, South Africa and the MV <i>Oceanic II</i> (The Scholar Ship) in January-March 2008 from Shanghai, China to Cape Verde in the Central Atlantic Ocean. The atmospheric concentrations were higher close to the coast and lower in remote regions of the Indian and South Atlantic Ocean. Groups of samples were selected in the South China Sea, Indian Ocean and South Atlantic Ocean where the relative wind direction matched the trajectory of the ship, thus all the samples had the same input of sources upwind. In these three regions the concentrations of OCPs and PCBs declined during atmospheric transport following first order kinetics. These sets of measurements provided estimates of field derived residence times (FDRTs) for individual compounds. These values were compared with predicted atmospheric residence times (PARTs) computed using a model of long-range atmospheric transport potential of POPs. The FDRTs are 5–10 times longer for the more volatile PCB congeners and TC, CC, <i>p</i>,<i>p′</i>-DDT and <i>p</i>,<i>p</i>′-DDE than the respective PARTs, while they are similar to PARTs for the less volatile compounds. Possible causes of discrepancies between PARTs and FDRTs are discussed, and revolatilization from the ocean surface seems to be the main cause for the higher values of FDRTs of the more volatile compounds in comparison with the respective PARTs

Consequences of the non-specific binding of a protein to a linear polymer: Reconciliation of Stoichiometric and equilibrium titration data for the Thrombin-heparin interaction

Theoretical aspects of the thermodynamic characterization of cooperative protein interactions with non-specific segments of a linear polymer lattice have been re-examined. This reconsideration has not only provided an alternative derivation of recursive expressions for the stoichiometry of random ligand binding prior to elimination of the parking problem but also extended that treatment to include binding with overlap of additional lattice units. The major obstacle to thermodynamic characterization of non-specific protein-polymer interactions is determination of the lattice capacity for ligand, which in turn defines the length of the polymer segment to which the protein binds. Although these parameters are most readily obtained from studies under conditions that ensure essentially stoichiometric interaction, the endpoint of such a titration is likely to reflect the irreversible rather than the equilibrium binding capacity of the lattice for ligand. Consideration of published results for spectrofluorometric titrations of the thrombin-heparin system under stoichiometric conditions in such terms has permitted their reconciliation with results of a later publication on the interaction under equilibrium conditions. (C) 2000 Academic Press

Results from a gyrotropic two ion fluid model for the comet interaction with the solar-wind

A two-and-a-half-dimensional two ion fluid model (with gyrotropic pressure tensor) for the interaction of cometary pickup plasma with the solar wind has been developed. Whereas previous models have, in general, assumed a single fluid plasma, this generalized model follows the evolution of two fluids - solar wind protons and cometary ions. The two fluids are coupled by the magnetic field and by coupling terms which are the velocity moments of the time relaxation model of Bhatnagar-Gross-Krook. Further more, a gyrotropic pressure tensor replaces the isotropic pressure assumed in other models. Isotropization terms couple the pressures in the directions perpendicular and parallel to the magnetic field. Among the results received, the stand-off distance of the shock increased significantly when the isotropization rate was reduced. The large cometary plasma pressure forces at the shock accelerated the cometary plasma along the shock. As a result, the cometary plasma drifted ahead of the solar wind along the shock flanks parallel to the magnetic field. Close to the nucleus of the comet, in the far tail lobes, and in the far inner tail, the cometary plasma lagged behind the solar wind. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman