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Abstract [Objective] In order to reveal the effects of non-grazing restriction on ecological niches and interspecific associations of the herbaceous species in the dominant plant communities in the temperate grasslands of the Kuizu Mountains in Linzhou County, Tibet, and to provide theoretical basis for the protection of plant diversity in the temperate grasslands in the Tibetan Plateau and for scientific management of the grasslands. [Methods] The “Levins” method, variance ratio method (Vr), Chi-square test, association coefficient (Ac), and Ochiai (Oi) index were used to analyze eight major plant species in the dominant plant communities in the temperate grasslands of the Kuizu Mountains in Tibet. [Results] (1) Non-grazing treatments increased the niche width and niche overlap of grass sedge (Tripogon bromoides), alpine tarragon (Carex parvula), whitegrass (Pennisetum flaccidum ), and silky needle fescue (Stipa capillacea). (2) The enclosure community in the study area showed an overall negative association (Vr =0.43), and the free-grazing community showed an overall positive association (Vr =1.21). According to the Chi square test, 67.9% and 53.6% of the 28 species pairs composed of 8 dominant species displayed negative association under the non-grazing and free grazing treatments, respectively. The association coefficient showed that 50% and 42.9% of species pairs were negatively linked under the non-grazing and free grazing treatments, respectively. The non-grazing treatments increased the Oi values of the main species, including Tripogon bromoides, Carex parvula, Pennisetum flaccidum , and Stipa capillacea. [Conclusion] Based on the interspecific association analysis, non-grazing treatments strengthened inter-species competition within the dominant plant communities in the temperate grasslands in the Kuizu Mountains, and the inter-species relationships become closer with unstable community structures

Abstract This paper presents a design of a gyro‐TWT operating in the large‐orbit electron beam mode, with the aim of reducing the working magnetic field while ensuring operational efficiency. The periodic dielectric‐loaded structure, which has been successfully applied in the development of small‐orbit devices, is adopted as the high‐frequency interaction circuit. This paper conducts a comprehensive study and analysis of this structure and achieves stable operation in the Ka‐band after the optimization of the tube. This tube works at second harmonic of electron frequency in the mode of large‐orbit electron beam. The required magnetic field is only 5100 gauss, which can be generated using electromagnetic coils instead of superconducting magnets. The operational parameters include voltage of 75 kV, current of 9A, and velocity spread of 3.5%. Under these conditions, the device presents stable operation, with −3 dB bandwidth of 4.3 GHz, and maximum output power of 165 kW. This result meets the expected requirements for magnetic field and operational efficiency, thus validating the feasibility of practical fabrication of large‐orbit gyro‐TWT with periodic dielectric‐loaded structure.

Deoxyribozymes capable of catalyzing sequence-specific RNA cleavage have found broad applications in biotechnology, DNA computing and environmental sensing. Among these, deoxyribozyme 8-17 is the most common small DNA motif capable of catalyzing RNA cleavage. However, the extent to which other DNA molecules with similar catalytic motifs exist remains elusive. Here we report a novel RNA-cleaving deoxyribozyme called 10-12opt that functions with an equally small catalytic motif and an unusually short binding arm. This deoxyribozyme contains a 14-nucleotide catalytic core that preferentially catalyzes RNA cleavage at UN dinucleotide junctions (kobs = 0.9 h-1 for UU cleavage). Surprisingly, the left binding arm contains only three nucleotides and forms two canonical base pairs with the RNA substrate. Mutational analysis reveals that a riboguanosine residue 3-nucleotide downstream of cleavage site must not form canonical base pairing for the optimal catalysis, and this nucleobase likely participates in catalysis with its carbonyl O6 atom. Furthermore, we demonstrate that deoxyribozyme 10-12opt can be utilized to cleave certain microRNA sequences which are not preferentially cleaved by 8-17. Together, these results suggest that this novel RNA-cleaving deoxyribozyme forms a distinct catalytic structure than 8-17 and that sequence space may contain additional examples of DNA molecules that can cleave RNA at site-specific locations.

The particle size and processability of the powder are the keys for successful nylon in selective laser sintering (SLS) 3D printing, but the nylon powders on the market have disadvantages such as uncontrollable particle size and large distribution, poor sphericity, and poor processability. In this study, graphene oxidehybridized polyamide 6 (PA6/GO) microspheres perfectly suitable for SLS 3D printing have been fabricated via reaction-induced phase separation. The selective distribution of GO in PA6 microspheres was characterized by thermogravimetric (TG) and transmission electron microscopy (TEM), and the particle size and morphology of PA6/GO microspheres could be effectively controlled by adjusting the ratio of caprolactam and polystyrene. Wherein, when the polystyrene addition amount is 15 wt%, the particle size of the PA6/GO microspheres is between 40 and 50 |im, and the sintering window and thermal stability of the microspheres are significantly improved. These experimental results are surprising for the preparation of new nylon SLS 3D printing materials. KEYWORDS anionic polymerization, GO hybrid materials, polyamide 6 microspheres, reaction induced phase separation, selective laser sintering 3D printing, 1 | INTRODUCTION Selective laser sintering (SLS), as one of the most promising additive manufacturing technologies, has received a lot of attention because it can produce variable and complex geometries [...]