The effect of Cu on the hydrogen reduction of molybdenum oxide powders was investigated by measuring the humidity change during a non-isothermal process of hydrogen reduction. The presence of Cu induced a shift in the reduction temperature and strongly affected the reduction processes of MoO3→Mo4O11→MoO2, which comprised the contained chemical vapor transport of MoOx(OH)2. This study suggests that the surface of the Cu grains acts as a nucleation site for the reduction of MoOx(OH)2 to MoO2 particles from MoO3 or Mo4O11 phases. Such an activated reduction process results in the deposition of metallic Mo and MoO2 particles on the surface of the Cu grains.
Three cyclic lipopeptides, including
one known (1)
and two new (2 and 3) compounds, that possess
the rare enamide linkage group were discovered from Streptomyces sp. KCB14A132, an actinobacterium isolated from a soil sample collected
from Jeung Island, Korea. The NMR and MS-based characterization showed
that they differed in the amino acid residues in the peptide backbone.
Application of Marfey’s analysis, GITC derivatization, and
modified Mosher’s method, as well as ECD measurements provided
the absolute configurations of enamidonin (1) and those
of new compounds enamidonins B and C (2 and 3). The two new enamidonin analogues were shown to exhibit antibacterial
activity against Gram-positive bacteria including methicillin-resistant
and quinolone-resistant Staphylococcus aureus. Furthermore,
evaluation of the extraction conditions and a close inspection of
the LC-MS chromatograms revealed that the N,N-acetonide unit of the enamidonin family was formed during
the acetone extraction process. The chemically prepared deacetonide
derivatives of enamidonins were found to lack antibacterial activity,
demonstrating that the dimethylimidazolidinone residue is necessary
for antibacterial activity.
Effect of the W-W contiguity on conductivity of W-Cu composite using the Voronoi diagramW-15wt.% Cu nanocomposite powder samples were fabricated by ball-milling and subsequent hydrogen-reduction. The powder samples were heated to 1200°C at 5 and 20°C min -1 and sintered for 1 h to obtain different sintered microstructures. The homogeneity of the sintered microstructures was evaluated by the standard deviation of the Vickers hardness. The W -W contiguity was calculated by using Voronoi diagrams. The sintered microstructure in case of the 20°C min -1 sample was more homogeneous and had lower W -W contiguity than the 5°C min -1 sample. The microstructural homogeneity was directly related to the W -W contiguity. Thermal conductivity of the 20°C min -1 sample was about 5 % higher than the thermal conductivity of the 5°C min -1 sample. This indicates that the thermal conductivity is affected by the W -W contiguity resulting from the homogeneity of the sintered microstructure.
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