Shifts in community structure and function of ammoniaoxidizing archaea in biological soil crusts along a revegetation chronosequence in the Tengger Desert

Metagenomic studies have demonstrated the existence of ammonia-oxidizing archaea(AOA) and revealed they are responsible for ammoxidation in some extreme environments. However, the changes in compositional structure and ammonia-oxidation capacity of AOA communities in biological soil crusts(BSCs) of desert ecosystems remain poorly understood.Here, we utilized Illumina MiSeq sequencing and microbial functional gene array(GeoChip 5.0) to assess the above changes along a 51-year revegetation chronosequence in the Tengger Desert, China. The results showed a significant difference in AOA-community richness between 5-year-old BSCs and older ones. The most dominant phylum during BSC development was Crenarchaeota, and the corresponding species were ammonia-oxidizing_Crenarchaeote and environmental_samples_Crenarchaeota. Network analysis revealed that the positive correlations among dominant taxa increased, and their cooperation was reinforced in AOA communities during BSC succession. Redundancy analysis showed that the dominant factor influencing the change in AOA-community structure was soil texture. GeoChip 5.0 indicated that the amoA gene abundances of AOA and ammonia-oxidizing bacteria(AOB) were basically the same, demonstrating that AOA and AOB played an equally important role during BSCs development. Our study of the long-term succession of BSC demonstrated a persistent response of AOA communities to revegetation development in desert ecosystems.

Effect of inlet volute wrap angle on the flow field and performance of double inlet gas cyclones

In response to the divergent understanding of double inlet cyclone performance in the literature,the effect of inlet volute wrap angle on the performance and flow field of double inlet cyclone separator was studied by Computational Fluid Dynamic(CFD)method.The results showed that the inlet volute wrap angle can affect the comparison results of the single and double inlet gas cyclones with the same total inlet cross-sectional area and velocity.0°and 90°volute double inlet improved the efficiency mainly by separating particles below 10μm,while 180°volute double inlet had no separation advantage for any particles,so the symmetrical double inlet does not always improve the efficiency,and the appropriate inlet volute wrap angle should be selected according to the actual situation,otherwise,the expected performance requirements of the symmetrical double inlet cyclone cannot be achieved.Compared with the flow field,it is found that the inlet volute wrap angle changed the tangential velocity of the sym-metrical double inlet cyclone separator,thus changing the performance.