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Actinobacillus pleuropneumoniae is the causative agent of pleuropneumonia, an economically important lung disease in pigs. In draft genomes of two Cypriot clinical A. pleuropneumoniae isolates (MIDG3457 and MIDG3459), we previously identified single genomic regions with homology to Mu-like bacteriophage and presented preliminary evidence of active phage. Here, updated Phastest genomic analysis identified two loci in both MIDG3457 and MIDG3459 that were predicted to encode proteins with high homology to, and whose organisation was characteristic of, Mu-like phages. Phylogenetically, the closest matches were with Mannheimia Vb and Glaesserella SuMu phages. Phastest scored the loci as "complete", indicating they produced active phage. PCR amplification of the Mu-like phage c and tail genes from DNase-treated polyethylene glycol 8000 (PEG)-precipitated supernatants of MIDG3457 and MIDG3459 (grown in either Brain Heart Infusion-NAD or Grace's Insect Medium-NAD broth) indicated the presence of intact virions. The phages from MIDG3457 and MIDG3459 were named PluMu 3457-1, 3457-2, and PluMu 3459-1 and PluMu 3459-2, respectively. Transmission electron microscopy (TEM) of the PEG-precipitated supernatants of broth-grown MIDG3459 identified virions with icosahedral heads and tails, consistent with other Mu-like phages. We conclude that MIDG3459 produces an active Mu-like phage. [ABSTRACT FROM AUTHOR]

Understanding the role of sintering aids during microstructure evolution is critical to the manufacture of densified SiC fibers. A variety of TEM characterization techniques are combined to investigate grain growth behavior in iron-doped SiC fibers. Ultra-large SiC grains in micron size, as the self-assembly of nano sub-grains into a similar orientation, were consistently discovered at the surface and indicative of abnormal grain growth. The growth front consisted of polycrystalline nanograins wetted by iron-rich particles, where several sub-grains were found to unify their (111) planes with a misorientation angle less than 10°, indicating grain rotation at the growth front. It is proposed that iron-rich particles form a quasi-liquid interfacial phase during sintering, which facilitates coherent attachment of grains and results in fast grain growth using neighboring irregular-shaped nanograins as building blocks. The imperfect ordered coalescence of nanograins introduces structural heterogeneities, including low angle grain boundaries and porosities. [ABSTRACT FROM AUTHOR]

Embrittlement of polycrystalline aluminum by liquid gallium represents a classic example of liquid metal embrittlement, whereas the interfacial atomic structure of Ga penetration front remains elusive despite decades of investigation. We performed aberration-corrected scanning transmission electron microscopy characterization to uncover the atomistic structure of Ga-enriched complexion within Al general grain boundaries. Multiple-layer adsorption of Ga with ordering gradients is revealed, consisting of disordered Ga layers at the GB core that are sandwiched by two more ordered adsorbate layers connecting to both aluminum grains. The ordering gradients within the interfacial complexion are further verified by the hybrid Monte Carlo and molecular dynamic simulations. This study advances our fundamental understandings of complexion structures within general grain boundaries. [Display omitted] [ABSTRACT FROM AUTHOR]

Ultra-high density of parallel planar defects is discovered within WC grains in V-doped cemented carbide. High resolution transmission electron microscopy (HRTEM) shows that such defects are stacking faults on the {10 1 ‾ 0} prismatic planes. The presence of multiple stacking faults within WC grain gives rise to a series of anomalous diffraction patterns, including the streaking of diffraction spots and forbidden fractional diffraction spots. Interestingly, quantitative analysis indicates that the density of stacking faults within the V-doped sample is one order of magnitude higher than that of the Ti-doped counterpart. Because the two doped samples are processed under the same condition, we conclude that the planar defects of WC grains in V-doped samples are largely produced during the sintering of cemented carbide. Aberration-corrected TEM images suggest that the formation of stacking faults can be ascribed to the merging of independently developed WC micro-pillars. The formation of such pillars can be further explained by the segregation of V-rich precipitates at the corners between basal and prismatic planes. The current finding not only unravels a new formation mechanism of stacking faults within WC grains, but also provides a new route to design superhard cemented carbides with interlaced stacking faults by simply doping solute atoms and controlling the sintering process, other than the traditional deformation method. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy is utilized to investigate the microstructure development of iron-containing SiC fibers as a function of their annealing temperatures. Compositional and structural gradients along the radial directions start to form within SiC fibers fabricated at temperatures above 1200 °C. The graded microstructures are associated with the outward diffusion of iron-rich particles along the radial direction. In-situ heating TEM experiments suggest that the iron-rich particles within SiC fibers are highly mobile at elevated temperatures. Therefore, we propose that the graded microstructures along the radial directions are the synergetic effects of iron catalyzation and outgassing, namely, iron-rich particles are progressively driven to the surface of SiC fibers and in the trajectory of iron-rich particles, the decomposition of the amorphous SiC x O y phase is accelerated, promoting the growth of SiC grains. The current study emphasizes the important role of the outgassing process to the microstructure evolution of SiC fibers. Our proposed mechanism can be extended to understand the microstructural evolution of SiC fibers that use metallic additives as sintering aids. Unlabelled Image • Compositional and structural gradients in Fe-SiC fibers are associated with the outward diffusion of Fe-rich particles. • In-situ heating experiments suggest that iron-rich particles start to become mobile at 1200 °C. • The graded microstructure of our SiC fibers is the synergetic effects of iron catalyzation and the outgassing procedure. [ABSTRACT FROM AUTHOR]