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The purpose of this study was to evaluate whether bacterial biofilms exist on the sinus mucosa surfaces of human subjects with recalcitrant chronic sinusitis. Scanning electron microscopy was used to evaluate patients with continued symptoms of chronic sinusitis despite prior appropriate medical and surgical management. Morphologic structures that confirm the presence of bacterial biofilms were identified on the sinus mucosa of patients infected with Pseudomonas aeruginosa, a known biofilm former. The presence of bacterial biofilms may explain the recalcitrant nature of some forms of chronic sinusitis.

Back-bonding between an electron-poor, high-oxidationstate metal and poor -acceptor ligand in a uranium(V)-dinitrogen complex . Back-bonding between an electron-poor, high-oxidation-state metal and poor -acceptor ligand in a uranium(V)-dinitrogen complex. Nature Chemistry,11,[806][807][808][809][810][811] Back-bonding between an electron-poor, high-oxidation-state metal and poor π-acceptor ligand in a uranium(V)-dinitrogen complex Abstract A fundamental bonding model in coordination and organometallic chemistry is the synergic, donor-acceptor interaction between a metal and a neutral π-acceptor ligand where the ligand σdonates to the metal, which π-back-bonds to the ligand. This interaction typically involves a metal with an electron-rich, mid-, low-, or even negative, oxidation state and a ligand with a π* orbital.Here, we report that treatment of a uranium-carbene complex with an organo-azide produces a uranium(V)-bis(imido)-dinitrogen complex, stabilised by a lithium counter-ion. This complex, which has been isolated in crystalline form, involves an electron-poor, high-oxidation-state uranium(V) 5f 1 ion that is π-back-bonded to the poor π-acceptor ligand dinitrogen. We propose that this is made possible by a combination of cooperative heterobimetallic uranium-lithium effects and the presence of suitable ancillary ligands rendering the uranium ion unusually electron-rich. This electron-poor back-bonding could have implications for the field of dinitrogen activation.

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