Search results for "OXIDATION"

Molecular analysis of the nitrate-reducing community from unplanted and maize-planted soils

2002

ABSTRACT Microorganisms that use nitrate as an alternative terminal electron acceptor play an important role in the global nitrogen cycle. The diversity of the nitrate-reducing community in soil and the influence of the maize roots on the structure of this community were studied. The narG gene encoding the membrane bound nitrate reductase was selected as a functional marker for the nitrate-reducing community. The use of narG is of special interest because the phylogeny of the narG gene closely reflects the 16S ribosomal DNA phylogeny. Therefore, targeting the narG gene provided for the first time a unique insight into the taxonomic composition of the nitrate-reducing community in planted an…

Electroorganic synthesis of nitriles via a halogen-free domino oxidation–reduction sequence

2015

A direct electroorganic sequence yielding nitriles from oximes in undivided cells is reported. Despite the fact that intermediate nitrile oxides might be formed, the method is viable to prepare benzonitriles without substituents ortho to the aldoxime moiety. This constant current method is easy to perform for a broad scope of substrates and employs common electrodes, such as graphite and lead.

Possible nitrogen fertilization of the early Earth Ocean by microbial continental ecosystems

2018

While significant efforts have been invested in reconstructing the early evolution of the Earth’s atmosphere–ocean–biosphere biogeochemical nitrogen cycle, the potential role of an early continental contribution by a terrestrial, microbial phototrophic biosphere has been largely overlooked. By transposing to the Archean nitrogen fluxes of modern topsoil communities known as biological soil crusts (terrestrial analogs of microbial mats), whose ancestors might have existed as far back as 3.2 Ga ago, we show that they could have impacted the evolution of the nitrogen cycle early on. We calculate that the net output of inorganic nitrogen reaching the Precambrian hydrogeological system could hav…

Ergosterol biosynthesis: a fungal pathway for life on land?

2012

International audience; Sterols, essential lipids of most eukaryotic cells, ensure important structural and signaling functions. The selection pressure that has led to different dominant sterols in the three eukaryotic kingdoms remains unknown. Here, we investigated the influence of the progression in the different steps of the ergosterol biosynthetic pathway (EBP) on the yeast resistance to transitions from aqueous to aerial media, typical perturbations of the higher fungi habitats. Five mutants of the EBP (ergΔ), accumulating different sterol intermediates in the EBP, and the wild-type (WT) strain were exposed to drying under atmospheric air or nitrogen and wetting. Results show that the …

Nitroxyl Radical‐Mediated Oxidation of Alcohols in Continuous Microreactors

2019

Mössbauer Study of Lanthanum–Strontium Ferromanganite Oxides

2004

The La0.88Sr0.2Mn(1−y)Fey0(3±δ, i (LSMF with y = 0, 0.2, 0.5, 0.8, 1) compounds are prospective cathode materials for advanced solid oxide fuel cells (SOFC) application operating at 700° C. Usual analysis methods like thermogravimetric analysis or redox titration enable to determine the average oxidation state of both manganese and iron cations. The comparative role of iron and manganese in B-site was evaluated by 57Fe Mossbauer spectroscopy. Spectra revealed that the complete substitution of iron for manganese induces the formation of Fe5+ for the compound with y = 1. However, no tetravalent iron cation was observed in air for the LSMF compounds with y = 0.2, 0.5 and 0.8. This means that o…

Niobium implantation effects in BaTiO3 and SrTiO3

1992

Abstract Single crystals of BaTiO3 and SrTiO3 have been implanted at room temperature with 150 keV Nb+ ions to doses ranging from 1014 to 1017 ions cm2. The structure and the oxidation state of the damaged layer have been investigated by Rutherford backscattering-ion channeling and electron spectroscopy, respectively. SrTiO3 is rendered amorphous at relatively low doses of 2 × 1015 ions cm−2, but the damage is efficiently annealed at 450°C for 1 2 h. For both materials, the oxidation state of niobium varies from + 5 to + 2 along the depth. Moreover, a considerable chemical shift (2.3 eV) is observed for barium in BaTiO3.

The passivation of steel in sodium sulphate solution studied by CEMS and aes

1990

The passive layer formed on standard steel by anodic oxidation in 0.5 M sodium sulphate solution was found to contain iron only in the trivalent state. The thickness of the layer increases with the applied potential as well as with the time the passivating potential is applied to the sample. These results, compared with the electrochemical data, lead to the suggestion that the passive behaviour is not due to the whole oxidic layer but due to a thin, low lying interfacial layer with a structural disorder.

A crucial role of adamantanoid Cu(II) complexes in the redox systems: CuCl–diallylsulfoxide–O2 and CuCl2–diallylsulfide–O2

2014

Abstract The hypothetically reversible [Cu(I)(diallylsulfoxide)] ↔ O 2 [Cu(II)(diallylsulfide)] system was examined by FTIR spectroscopy and X-ray diffraction. It is stated that the Cu4OCl6 body centered adamantanoid cages, appearing at both the substrate and product sites, act as a template to promote the oxidation of diallylsulfide to diallylsulfoxide or Cu(I) to Cu(II), thus making the reaction irreversible. Each of these two adamantanoid cores possesses a different point symmetry as well as self assembly mode to form two polymorphs of the [Cu4OCl6(diallylsulfoxide)4] complex. Their polymorphic relationships based on the symmetry homology S4 ← Td → C3, as well as the distortion in the Cu…

Photoelectrochemical and EPR features of polymeric C 3 N 4 and O-modified C 3 N 4 employed for selective photocatalytic oxidation of alcohols to alde…

2019

Four different C 3 N 4 specimens have been prepared, a bulk one (MCN), a thermally etched (MCN-TE), a solid prepared by hydrothermally treating MCN with H 2 O 2 (MCN-H 2 O 2 ) and a polymeric carbon nitride-hydrogen peroxide adduct (MCN-TE-H 2 O 2 ). The principal aim of this work was to correlate the capability of the prepared material to generate reactive oxygen species (ROS), under irradiation, with their photocatalytic activities in terms of conversion and selectivity for partial oxidation reactions. Photoelectrochemical studies revealed that MCN-TE represented the best material in terms of photoconductivity, whereas MCN-H 2 O 2 was defective and evidenced a poor mobility of carriers. E…