Search

Objective: The aim was to investigate whether a bacterial flora exists in the eggs of healthy laying ducks (Ma breed), and if yes, whether the bacterial flora could be associated with those in the genital tract and cecum. Methods: Healthy laying ducks were dissected to collect genital tract and cecum tissues, as well as soft- and hard-shelled duck eggs, and cultivable bacteria were counted by plate count method, and the diversity and correlation of uncultured bacterial flora were analyzed by MiSeq high-throughput sequencing. Results: The decreasing order of the total bacterial counts in the samples was cecum > genital tract > hard-shelled egg > soft-shelled egg. The bacterial gene sequences belonged to 56 phyla and 1 319 genera. The abundance and species evenness of bacteria in the cecum and genital tract were higher. The dominant genera included Bacteroides, Megamonas and Campylobacter. Species abundance and dominant concentration were higher in soft- and hard-shell eggs. Pseudomonas and Acinetobacter accounted for 19.01% and 10.01% of the total abundance, respectively. Gene function prediction showed that all samples had high abundance of metabolic and glycolytic functions. The gram-positive and anaerobic phenotypes in the cecum and genital tract were abundant. The pathogenicity and oxidative stress of bacteria in soft and hard shell eggs were significant. The dominant bacterial genera in the four samples were overlapped, and the overlap rates of egg content with the cecum and genital tract were 13.96% and 24.35%, respectively. In addition, the phylogenetic tree analysis showed that the genera in all samples were closely related to each other and shared homology with the significantly contributing genus Bacteroides in the cecum. Conclusion: Duck eggs are not formed in a sterile environment, the bacteria residing in the cecum and reproductive tract of healthy laying ducks can infect different egg structures during its formation and become a part of the internal flora in duck eggs. These results can provide a reference for further research on the characteristics and control of non-pathogenic bacteria in egg contents.

The effects of Sc, Mg and Si elements in an Al-Cu alloy have been studied by means of hardness tests and transmission electron microscopy analysis. The experimental results show that additions of Sc, Mg and Si can improve the heat resistance of the Al-Cu alloy. The Sc/Mg/Si segregation-sandwiched structure is the most stable, when compared with Sc segregation or Si/Sc co-segregation at the interface of θ′/Al. The additions of Si and Mg promote the aging–hardening response of the Al-Cu alloy. Mg is a micro-alloying element with great potential in stabilizing the size of θ′ phases, which further promotes the number density greatly. Consequently, the Al-Cu alloy achieves a high strength, matched with excellent thermal stability, due to the microalloying of Sc/Mg/Si solutes. [ABSTRACT FROM AUTHOR]

The influence of grain size on the corrosion behavior of pure aluminum and the defect density and diffusion coefficient of surface passive films were investigated using electron backscatter diffraction (EBSD) and electrochemical testing techniques, based on the point defect model (PDM). Samples with three different grain sizes (23 ± 11, 134 ± 52, and 462 ± 203 μm) were obtained by annealing at different temperatures and times. The polarization curves and electrochemical impedance spectroscopy results for the pure aluminum in the 3.5% NaCl solution showed that with decreasing grain size, the corrosion current (icorr) decreased monotonously, giving rise to a noble corrosion potential and a large polarization resistance. The Motte–Schottky results showed that the passive films that formed on pure aluminum with fine grains of 23 ± 11 μm had a low density (3.82 × 1020 cm−3) of point defects, such as oxygen vacancies and/or metal interstitials, and a small diffusion coefficient (1.94 × 10−17 cm2/s). The influence of grain size on corrosion resistance was discussed. This work demonstrated that grain refinement could be an effective approach to achieving high corrosion resistance of passive metals. [ABSTRACT FROM AUTHOR]

The Al–Mn alloy heat exchanger fin production process includes a brazing treatment at s high temperature of 600 °C, in which coarse grains are preferred for their high resistance to deformation at elevated temperatures by decreasing the grain boundary sliding. In this study, Al-1.57Mn-1.57Zn-0.58Si-0.17Fe alloy foils cold rolled by 81.7% (1.1 mm in thickness) and 96.5% (0.21 mm in thickness) were annealed at 100–550 °C for 1 h to investigate their recrystallization behavior, grain sizes, and precipitates by increasing the annealing temperature, using micro-hardness measurement, electron back-scattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The micro-hardness results showed that the recrystallization finishing temperatures for the two samples were almost the same, 323 ± 2 °C. The EBSD results showed that when the annealing temperature decreased from 550 to 400 °C, the recrystallized grain sizes of the two samples were nearly identical—both increased slightly. Further decreasing the annealing temperature from 400 to 330 °C caused the grain sizes to increase more, with the thinner foil sample having a more significant increase. The SEM and TEM observations showed that the micron-sized primary-phase remained unchanged during the annealing process. The nano-sized secondary phase precipitates formed during the hot-rolling process experienced a coarsening and dissolving process upon annealing. The particle size of the secondary phase increased from 32 nm to 44 nm and the area fraction decreased from 4.2% to 3.8%. The nucleation analysis confirmed that the large primary-phase could act as a nucleation site through particle stimulated nucleation (PSN) mode. The relatively dense secondary phase precipitates with small sizes at lower temperatures could provide higher Zener drag to the grain boundaries, leading to fewer nuclei and thereafter coarser grains. The coarsening of the recrystallized grains in the foils could be implemented through thickness reduction and/or precipitation processes to form densely distributed nano-sized precipitates. [ABSTRACT FROM AUTHOR]

This study is aimed to investigate the influence of three pluronics (F127, F87, and P85) on the structure, stability, and cytotoxicity of liposomes (Ls). Pluronics-modified liposomes (pluronic-Ls) were prepared by integrating the film evaporation method and dynamic high pressure microfluidization. The average particle size of liposomes decreased significantly after modification with pluronics. Fourier transform infrared spectroscopy and differential scanning calorimetry analysis revealed that pluronics were successfully incorporated into liposomes. The membrane stability of liposomes was improved by pluronics modification, and increased in the following order: Ls < F87-Ls < F127-Ls < P85-Ls. In vitro cytotoxicity studies indicated that F127-Ls and F87-Ls possess good biocompatibility, and P85-Ls exhibited relatively low inherent toxicity in the phospholipid concentrations ranging from 100 to 400 mg/L. These results demonstrated that pluronics F127 and F87 are the optimal agents for liposomes modification and can potentially be used as a drug delivery platform. [ABSTRACT FROM AUTHOR]