SOHO CTOF Observations of Interstellar He+ Pickup Ion Enhancements in Solar Wind Compression Regions

We present a recent analysis with 1996 SOHO CELIAS CTOF data, which reveals correlations of He+ pickup ion fluxes and spectra with the magnetic field strength and solar wind density. The motivation is to better understand the ubiquitous large variations in both pickup ion fluxes and their velocity distributions found in interstellar pickup ion datasets. We concentrate on time periods of that can be associated with compression regions in the solar wind. Along with enhancements of the overall pickup ion fluxes, adiabatic heating and acceleration of the pickup ions are also observed in these regions. Transport processes that lead to the observed compressions and related heating or acceleration are discussed. A shift in velocity space associated with traveling interplanetary compression regions is observed, and a simple model presented to explain this phenomenon based on the conserved magnetic adiabatic moment.Comment: 4 pages, 5 figures, Solar Wind 10 Conference Proceedings Pape

Outer Sphere Urea Hydrolysis by Bis-Nickel Complexes: Questioning the Urea Activation by the Urease Enzyme

Urease enzyme has a dinuclear nickel active centre that hydrolyze urea into carbon dioxide and ammonia. In this work, two bis-nickel urease models were synthesized, [Ni2L(OAc)] and [Ni2L(Cl)(Et3N)2], based on the Trost bis-Pro0Phenol ligand (L). Interestingly, both complexes produced ammonia from urea, in which the [Ni2L(OAc)] complex was ten times slower than urease, whereas the more labile complex [Ni2L(Cl)(Et3N)2],was only four times slower. The intermediates were evaluated both experimentally and theoretically, indicating that the [Ni2L(H2O)2]+ intermediate is the most important to activate urea via an outersphere mechanism. Isocyanate was produced in a self-elimination mechanism. The reaction performed with different substrates indicated that the biomimetic complexes were able to hydrolyze isocyanate. The outersphere activation of urea by these complexes reals an alternative activation mechanism to be considered for the urease enzyme, not yet reported in the literature. . <br /