Absolute measurements are presented for the positron-impact cross sections for positronium formation, direct ionization, and total ionization of the diatomic molecules N2, CO, and O2, in the range of energies from threshold to 90 eV. Cross sections for the electronic excitation of the a 1 and a 1 state in N2 and the A 1 state in CO near threshold are also presented. The experiment uses a cold, ...

Multiple strains per plant and root-to-root (not seed-borne) transmission should favor rhizobia that invest in their own reproduction, rather than symbiotic N2 fixation, as analogous factors may favor pathogen virulence. But legumes can select for greater mutualism, controlling nodule O2 supply and reducing reproduction of rhizobia that fix less N2.

A highly gas permeable polymer with exceptional size selectivity is prepared by fusing triptycene units together via a poly-merization reaction involving Tröger's base formation. The extreme rigidity of this polymer of intrinsic microporosity (PIM-Trip-TB) facilitates gas permeability data that lie well above the benchmark 2008 Robeson upper bounds for the important O2 /N2 and H2 /N2 gas pairs.

Soluble methane monooxygenase (sMMO) expression and activity were monitored under conditions that either promoted or suppressed the expression of nitrogenase in Methylosinus trichosporium OB3b wild-type (WT) and in its sMMO-constitutive mutant, PP319. Both WT and mutant cultures had reduced sMMO activity and protein levels under elevated O2 conditions (188 WM) compared with low O2 conditions (2...

In the modern ocean, a significant amount of nitrogen fixation is attributed to filamentous, nonheterocystous cyanobacteria of the genus Trichodesmium. In these organisms, nitrogen fixation is confined to the photoperiod and occurs simultaneously with oxygenic photosynthesis. Nitrogenase, the enzyme responsible for biological N2 fixation, is irreversibly inhibited by oxygen in vitro. How nitrog...

A three dimensional, time-evolving field of atmospheric potential oxygen (APO ∼O2/N2+CO2) was estimated using surface O2, N2 and CO2 fluxes from the WHOI ocean ecosystem model to force the MATCH atmospheric transport model. Land and fossil carbon fluxes were also run in MATCH and translated into O2 tracers using assumed O2:CO2 stoichiometries. The modeled seasonal cycles in APO agree well with ...

Abstract Since the growth morphology along and perpendicular to interface is important for supermirror applications, dependence of this on reactive gas has been investigated in Ni/Ti multilayers prepared by magnetron sputtering with variable O2/N2 ratios. The properties are characterized GIXRR, XDS, TEM measurements. Compared case without O2, presence 20% O2 deposition Ni layers contributes smo...

The Trichodesmium genus comprises some of the most abundant N2-fixing organisms in oligotrophic marine ecosystems. Since nitrogenase, key enzyme for N2 fixation, is irreversibly inhibited upon O2 exposure, these have to coordinate their ability with simultaneous photosynthetic production. Although being principal object many laboratory and field studies, overall process how reconciles two mutua...

Fe0.5Mn1.84Ni0.66O4 NTC ceramic thermistors were annealed in nitrogen or oxygen atmosphere at 600°C. The change of the electrical properties of the thermistors with time was reduced sharply by annealing in N2, whereas it was enhanced upon annealing in O2. N2-annealed samples exhibited a less degree of redistribution of cations in the lattice as compared with O2-annealed samples. The aging of th...

The adsorption of common gas molecules (N2, CO, CO2, H2O, NH3, NO, NO2, and O2) on germanene is studied with density functional theory. The results show that N2, CO, CO2, and H2O are physisorbed on germanene via van der Waals interactions, while NH3, NO, NO2, and O2 are chemisorbed on germanene via strong covalent (Ge-N or Ge-O) bonds. The chemisorption of gas molecules on germanene opens a ban...