Preparation and Characterization of In Situ (TiC-TiB2)/Al-Cu-Mg-Si Composites with High Strength and Wear Resistance.

This study involved the preparation and characterization of in situ (TiC-TiB2)/Al-4.7Cu-0.32Mg-0.44Si composites with excellent mechanical and abrasive wear properties. The composites were synthesized in an Al-Ti-B4C system by combining combustion reaction synthesis with hot-pressed sintering and hot extrusion. The in situ TiB2 and TiC particles were of multi-scaled sizes ranging from 20 nm to 1.3 µm. The TiB2 and TiC particles effectively increased the yield strength (σ0.2), ultimate tensile strength (σUTS), hardness (HV), and abrasive wear resistance of the composites. The 40 wt.% (TiC-TiB2)/Al-4.7Cu-0.32Mg-0.44Si composite exhibited the highest σ0.2 (569 MPa), σUTS (704 MPa) and hardness (286 HV), which were 74%, 51% and 110% higher than those of the matrix alloy, respectively. Compared with the matrix alloy, the abrasive wear resistance of the 40 wt.% (TiC-TiB2)/Al-4.7Cu-0.32Mg-0.44Si composite was increased by 4.17 times under an applied load of 5 N and Al2O3 abrasive particle size of 13 µm. Micro-ploughing and micro-cutting were the main abrasive wear mechanisms for the Al-Cu-Mg-Si alloy and the composites.

Identification of a novel avian coronavirus infectious bronchitis virus variant with three-nucleotide-deletion in nucleocapsid gene in China.

A novel avian infectious bronchitis virus (IBV) variant, designated as GX-NN160421, was isolated from vaccinated chicken in Guangxi, China, in 2016. Based on analysis of the S1 gene sequence, GX-NN160421 belonged to the New-type 1 (GVI-1) strain. More importantly, three consecutive nucleotides (AAC) deletions were found in the highly conserved structure gene N. The serotype of GX-NN160421 was different from those of the commonly used vaccine strains. The mortality of the GX-NN160421 strain was 3.33%, which contrasted with 50% mortality in the clinical case, but high levels of virus shedding lasted at least 21 days. In conclusion, the first novel IBV variant with three-nucleotide-deletion in the N gene was identified, and this unique variant is low virulent but with a long time of virus shedding, indicating the continuing evolution of IBV and emphasizing the importance of limiting exposure to novel IBV strains as well as extensive monitoring of new IBVs.

Protection against Virulent Infectious Bronchitis Virus Challenge Conferred by a Recombinant Baculovirus Co-Expressing S1 and N Proteins.

Avian infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis, which results in considerable economic losses. It is imperative to develop safe and efficient candidate vaccines to control IBV infection. In the current study, recombinant baculoviruses co-expressing the S1 and N proteins and mono-expressing S1 or N proteins of the GX-YL5 strain of IBV were constructed and prepared into subunit vaccines rHBM-S1-N, rHBM-S1 and rHBM-N. The levels of immune protection of these subunit vaccines were evaluated by inoculating specific pathogen-free (SPF) chickens at 14 days of age, giving them a booster with the same dose 14 days later and challenging them with a virulent GX-YL5 strain of IBV 14 days post-booster (dpb). The commercial vaccine strain H120 was used as a control. The IBV-specific antibody levels, as well as the percentages of CD4+ and CD8+ T lymphocytes, were detected within 28 days post-vaccination (dpv). The morbidity, mortality and re-isolation of the virus from the tracheas and kidneys of challenged birds were evaluated at five days post-challenge (dpc). The results showed that the IBV-specific antibody levels and the percentages of CD4+ and CD8+ T lymphocytes were higher in the rHBM-S1-N vaccinated birds compared to birds vaccinated with the rHBM-S1 and rHBM-N vaccines. At 5 dpc, the mortality, morbidity and virus re-isolation rate of the birds vaccinated with the rHBM-S1-N vaccine were slightly higher than those vaccinated with the H120 control vaccine but were lower than those vaccinated with the rHBM-S1 and rHBM-N vaccines. The present study demonstrated that the protection of the recombinant baculovirus co-expressing S1 and N proteins was better than that of recombinant baculoviruses mono-expressing the S1 or N protein. Thus, the recombinant baculovirus co-expressing S1 and N proteins could serve as a potential IBV vaccine and this demonstrates that the bivalent subunit vaccine including the S1 and N proteins might be a strategy for the development of an IBV subunit vaccine.