Research on feeding habits and stomach fungi in Eothenomys miletus from Hengduan mountain regions

Eothenomys miletus(E.miletus)is one of the rodent species found in Yunnan,and it has caused significant harm to local agricultural production.In this study,we aimed to investigate the differences in feeding habits and stomach fungi of E.miletus across different areas in the Hengduan mountain regions.By exploring the main factors affecting the feeding habits and fungi of E.miletus,this study provides a theoretical basis for the prevention and control of this species.We collected E.miletus specimens from five regions,namely Deqin,Xianggelila,Lijiang,Jianchuan,and Ailaoshan.We measured their feeding habits and the types of fungi in their stomachs using high-throughput sequencing technology.The results showed that E.miletus primarily fed on Poaceae,Oxalidaceae,Asteraceae,and Fabaceae.Food diversity of E.miletus in Ailaoshan and Jianchuan was significantly lower than in the other three regions.As for stomach fungi,Ascomycota and Basidiomycota were the absolute dominant sectors.Changes in the diversity of fungi in different regions were consistent with changes in food diversity.The diversity of fungi in Ailaoshan and Jianchuan regions was lower than in the other three regions.These findings suggest that the feeding habits of E.miletus in different regions were affected by plant species,which,in turn,affects the diversity of fungi in their stomachs.

Identification of vortex boundaries in two-dimensional incompressible flows based on the Liutex-shear interaction

According to the Liutex-shear decomposition,vorticity can be decomposed into a rotational part,i.e.,the Liutex vector,and a residual shear part.With this decomposition,the vorticity transport equation can be used to formulate a governing equation for Liutex easily for two-dimensional incompressible flows with a source term depending on the residual shear.The dynamics of Liutex-identified structures is then studied in a Taylor-Green vortex flow and a flow past a cylinder at Reynolds number of 200.It is revealed that such boundaries exist outside which the shear has trivial impact on the evolution of Liutex and inside which enhancing and weakening effects of shear on Liutex can be observed.In addition,there is a strong dissipation effect upon Liutex on these boundaries.Based on the interaction mechanism between Liutex and shear,we argue that the vortex boundaries can be identified by these highly dissipative boundaries.In contrast,traditional methods use iso-surfaces of arbitrarily selected thresholds to represent vortex boundaries.The current method of identifying vortex boundaries based on the Liutex-shear interaction has a clearer theoretical base and avoids the arbitrary selection of thresholds.Extensions to three-dimensional incompressible flows can be made in future following the same procedure but with a slightly more complex vorticity transport equation which includes the velocity gradient induced stretching or tilting term.

A Liutex-based subgrid stress model for large-eddy simulation

The concept of vortex is crucial in both understanding and modeling of turbulence.For large eddy simulation(LES),the effect of small-scale eddies onto the large scales or the resolved flow field is modeled by subgrid stress models.Even though the rotating motions of fluids,i.e.,vortices or eddies are central in developing turbulent models,vortex identification methods are seldom used in these models.In this study,we develop a new subgrid model based on the Liutex vector,a new quantity introduced to decompose fluid motions into rigid rotation,pure shear and stretching,and thus identify vortices.The new model is then applied in a decaying homogeneous isotropic turbulence(DHIT)and a turbulent channel flow at Reynolds number Reτ=180.It is shown that the new model can predict accurate energy spectra compared with experiments in DHIT and give a well-matched velocity profile in turbulent channel flow without changing the form of the model.Future directions include improvement of the Liutex based model,for example developing anisotropic subgrid models,and its applications in various turbulent flows.