Genetic and pathogenic characteristics of two novel/recombinant avian orthoreovirus.

In recent years, the emerging avian orthoreovirus (ARV) strains that led to viral arthritis have attracted much attention from the chicken industry worldwide, due to the significant economic losses suffered. In mid-2020, with the assistance of next-generation sequencing technology, we achieved success in characterizing two divergent avian orthoreovirus (ARV) variants (0543/SDYT) and isolating them from the broiler tendons characterized by arthritis. As suggested by the genome characterization of the 0543/SDYT strains, they belong separately to clusters Ⅰ and Ⅳ. As revealed by sequence comparison, phylogenetic, and recombination analysis, for µA, µB, and σNS genes, considerable genetic divergences were also observed in the two new isolates. However, in the case of λA, λB, µNS, σA, and σB genes, very clear clustering patterns were observed for SDYT and 0543 field strains, respectively. In terms of the µA, µNS, p10, p17 genes of SDYT isolate and µNS, p17, σC, σA genes of 0543 isolate, the lower similarity was observed with NCBI stored sequences, with nt highest identity values below 90 %. In addition, there is an intra-fragmental recombination event in the M1 gene of the SDYT strain. In regard, the multiple segmental recombination and accumulation of point mutations play a role in the newly-emerging ARV strains. Not only did the isolates strain exhibit strong replication ability in vivo, but they also displayed strong arthritogenicity in broilers with low neutralizing maternal antibodies, indicating that maternal antibody treatment may not effectively reduce the oral infection of avian orthoreovirus. These findings suggest that it is necessary to develop a new strategy for enhanced effectiveness in preventing and controlling ARV infection.

Broadband Quantum Dot Superluminescent Diode with Simultaneous Three-State Emission.

Semiconductor superluminescent light-emitting diodes (SLEDs) have emerged as ideal and vital broadband light sources with extensive applications, such as optical fiber-based sensors, biomedical sensing/imaging, wavelength-division multiplexing system testing and optoelectronic systems, etc. Self-assembled quantum dots (SAQDs) are very promising candidates for the realization of broadband SLED due to their intrinsic large inhomogeneous spectral broadening. Introducing excited states (ESs) emission could further increase the spectral bandwidth. However, almost all QD-based SLEDs are limited to the ground state (GS) or GS and first excited state (ES1) emission. In this work, multiple five-QD-layer structures with large dot size inhomogeneous distribution were grown by optimizing the molecular beam epitaxy (MBE) growth conditions. Based on that, with the assistance of a carefully designed mirror-coating process to accurately control the cavity mirror loss of GS and ESs, respectively, a broadband QD-SLED with three simultaneous states of GS, ES1 and second excited-state (ES2) emission has been realized, exhibiting a large spectral width of 91 nm with a small spectral dip of 1.3 dB and a high continuous wave (CW) output power of 40 mW. These results pave the way for a new fabrication technique for high-performance QD-based low-coherent light sources.

Recent Developments of Quantum Dot Materials for High Speed and Ultrafast Lasers.

Owing to their high integration and functionality, nanometer-scale optoelectronic devices based on III-V semiconductor materials are emerging as an enabling technology for fiber-optic communication applications. Semiconductor quantum dots (QDs) with the three-dimensional carrier confinement offer potential advantages to such optoelectronic devices in terms of high modulation bandwidth, low threshold current density, temperature insensitivity, reduced saturation fluence, and wavelength flexibility. In this paper, we review the development of the molecular beam epitaxial (MBE) growth methods, material properties, and device characteristics of semiconductor QDs. Two kinds of III-V QD-based lasers for optical communication are summarized: one is the active electrical pumped lasers, such as the Fabry-Perot lasers, the distributed feedback lasers, and the vertical cavity surface emitting lasers, and the other is the passive lasers and the instance of the semiconductor saturable absorber mirrors mode-locked lasers. By analyzing the pros and cons of the different QD lasers by their structures, mechanisms, and performance, the challenges that arise when using these devices for the applications of fiber-optic communication have been presented.

Discovery of a novel recombinant avian orthoreovirus in China.

In mid-2020, using next-generation sequencing (NGS) technology, we identified a recombinant cluster 2 avian orthoreovirus (ARV) variant named PHC-2020-0545, isolated from tendons of 33-day-old broilers with leg swelling in China. Complete genomic sequencing and analyses demonstrated that the isolate was genetically significantly distinct from known ARV strains in M1 and M3 genes and its σC coding gene had an extremely high variability, compared with the identified ARV strains grouped into other genotyping cluster. Further analysis showed that many base substitutions were silent and non-silent substitutions are most likely to occur in the first positions of codons. Multiple segmental recombination, intra-segmental recombination and accumulation of point mutations might contribute to the emergence of this isolate. The PHC-2020-0545 strain had a strong replication ability in 1-day-old broilers, and mainly affected the movement, digestion and metabolism of broilers. In addition, the infection route of the isolate is related to its pathogenicity to broilers. Therefore, combined with its unique genetic characteristics and potential origin, we determined that the PHC-2020-0545 field strain is a novel recombinant ARV strain, which has certain reference value for the preparation and evaluation of new vaccines.