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1,643 results on '"LU XueFeng"'

301. Quasi-periodic Oscillations of the X-Ray Burst from the Magnetar SGR J1935–2154 and Associated with the Fast Radio Burst FRB 200428

Author

Li, Xiaobo, primary, Ge, Mingyu, additional, Lin, Lin, additional, Zhang, Shuang-Nan, additional, Song, Liming, additional, Cao, Xuelei, additional, Zhang, Bing, additional, Lu, Fangjun, additional, Xu, Yupeng, additional, Xiong, Shaolin, additional, Tuo, Youli, additional, Tan, Ying, additional, Jiang, Weichun, additional, Qu, Jinlu, additional, Zhang, Shu, additional, Wang, Lingjun, additional, Wang, Jieshuang, additional, Zhang, Binbin, additional, Zhang, Peng, additional, Li, Chengkui, additional, Liu, Congzhan, additional, Li, Tipei, additional, Bu, Qingcui, additional, Cai, Ce, additional, Chen, Yong, additional, Chen, Yupeng, additional, Chang, Zhi, additional, Chen, Li, additional, Chen, Tianxiang, additional, Chen, Yibao, additional, Cui, Weiwei, additional, Du, Yuanyuan, additional, Gao, Guanhua, additional, Gao, He, additional, Gu, Yudong, additional, Guan, Ju, additional, Guo, Chengcheng, additional, Han, Dawei, additional, Huang, Yue, additional, Huo, Jia, additional, Jia, Shumei, additional, Jin, Jing, additional, Kong, Lingda, additional, Li, Bing, additional, Li, Gang, additional, Li, Wei, additional, Li, Xian, additional, Li, Xufang, additional, Li, Zhengwei, additional, Liang, Xiaohua, additional, Liao, Jinyuan, additional, Liu, Hexin, additional, Liu, Hongwei, additional, Liu, Xiaojing, additional, Lu, Xuefeng, additional, Luo, Qi, additional, Luo, Tao, additional, Ma, Binyuan, additional, Ma, Ruican, additional, Ma, Xiang, additional, Meng, Bin, additional, Nang, Yi, additional, Nie, Jianyin, additional, Ou, Ge, additional, Ren, Xiaoqin, additional, Sai, Na, additional, Song, Xinying, additional, Sun, Liang, additional, Tao, Lian, additional, Wang, Chen, additional, Wang, Pengju, additional, Wang, Wenshuai, additional, Wang, Yusa, additional, Wen, Xiangyang, additional, Wu, Bobing, additional, Wu, Baiyang, additional, Wu, Mei, additional, Xiao, Shuo, additional, Yang, Sheng, additional, Yang, Yanji, additional, Yi, Qibin, additional, Yin, Qianqing, additional, You, Yuan, additional, Yu, Wei, additional, Zhang, Fan, additional, Zhang, Hongmei, additional, Zhang, Juan, additional, Zhang, Wanchang, additional, Zhang, Wei, additional, Zhang, Yifei, additional, Zhang, Yuanhang, additional, Zhao, Haisheng, additional, Zhao, Xiaofan, additional, Zheng, Shijie, additional, and Zhou, Dengke, additional

Published
2022
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313. Hydrocracking diversity in n-dodecane isomerization on Pt/ZSM-22 and Pt/ZSM-23 catalysts and their catalytic performance for hydrodewaxing of lube base oil

Author

Aijun Duan, Lu Xuefeng, Xiang-Bin Meng, Zhen Zhao, Li Mengchen, Yu Hongyue, Gao Shanbin, Ming-Wei Tan, Liu Yanfeng, Kebin Chi, and Shen Yuge

Subjects
Materials science, Dodecane, Base oil, Energy Engineering and Power Technology, Geology, 02 engineering and technology, Fuel oil, Raw material, 010402 general chemistry, 021001 nanoscience & nanotechnology, Geotechnical Engineering and Engineering Geology, 01 natural sciences, 0104 chemical sciences, Catalysis, chemistry.chemical_compound, Cracking, Geophysics, Fuel Technology, chemistry, Chemical engineering, Geochemistry and Petrology, Economic Geology, 0210 nano-technology, Isomerization, Naphtha
Abstract

Nobel metallic Pt/ZSM-22 and Pt/ZSM-23 catalysts were prepared for hydroisomerization of normal dodecane and hydrodewaxing of heavy waxy lube base oil. The hydroisomerization performance of n-dodecane indicated that the Pt/ZSM-23 catalyst preferred to crack the C–C bond near the middle of n-dodecane chain, while the Pt/ZSM-22 catalyst was favorable for breaking the carbon chain near the end of n-dodecane. As a result, more than 2% of light products (gas plus naphtha) and 3% more of heavy lube base oil with low-pour point and high viscosity index were produced on Pt/ZSM-22 than those on Pt/ZSM-23 while using the heavy waxy vacuum distillate oil as feedstock.

Published
2020

314. Influence of stacking sequence of basalt-fiber grilles on mechanical properties for textile-reinforced concrete and theoretical prediction

Author

Kun Qian, Jia Minghao, Guyu Feng, Xueliang Xiao, and Lu Xuefeng

Subjects
Mechanical property, Materials science, Polymers and Plastics, 0211 other engineering and technologies, Stacking, 02 engineering and technology, 021001 nanoscience & nanotechnology, Laying, Basalt fiber, 021105 building & construction, Chemical Engineering (miscellaneous), Concrete composites, Composite material, 0210 nano-technology, Textile-reinforced concrete, Sequence (medicine)
Abstract

The purpose of this study is to investigate the effective way of laying up basalt-fiber grilles in concrete to improve mechanical properties, involving how the evolution of cracks is hindered and how the strength of concrete is increased by basalt filaments. In this research, three layers of basalt fiber grilles were placed in different positions of concrete composites. The compressive, splitting tensile, and beam flexural properties of the concrete composites were studied after 28 days of as-made sample curing. The reason for reduced cracks growing from basalt fiber grilles was analyzed to reveal the mechanism of increased strength and toughening of concrete composites. The results showed that a reasonable lay-up method has the highest value of utilization rate and can improve the compressive and split tensile strength of concrete specimens, especially for the flexural specimens. The reason was found to be the energy absorption, stress transfer, and bridging load-bearing effect of the basalt-fiber grilles on the hindering of the expansion of loading-induced cracks effectively. A theoretical model was thereafter developed to predict the flexural strength of concrete beam composites based on grille lay-up architecture. According to the analytical model, the corresponding predicted values compared with experimental results indicate a good coincidence and a reasonable accuracy, which is less than 12% of their discrepancy.

Published
2020

317. Measurement report: Source apportionment of carbonaceous aerosol using dual-carbon isotopes (13C and 14C) and levoglucosan in three northern Chinese cities during 2018–2019

Author

Zhao, Huiyizhe, Niu, Zhenchuan, Zhou, Weijian, Wang, Sen, Feng, Xue, Wu, Shugang, Lu, Xuefeng, and Du, Hua

Abstract

In this study, we investigated the characteristics of and changes in the sources of carbonaceous aerosols in northern Chinese cities after the implementation of the Action Plan for Air Pollution Prevention and Control in 2013. We collected PM2.5 samples from three representative inland cities, viz. Beijing (BJ), Xi’an (XA), and Linfen (LF) from January 2018 to April 2019. Elemental carbon (EC), organic carbon (OC), levoglucosan, stable carbon, and radiocarbon were measured in PM2.5 to quantify the sources of carbonaceous aerosol employing Latin hypercube sampling. The best estimate of source apportionment showed that the emissions from liquid fossil fuels contributed 33.6 ± 12.9 %, 26.6 ± 16.4 %, and 24.6 ± 13.4 % of the total carbon (TC) in BJ, XA, and LF, whereas coal combustion contributed 11.2 ± 9.1 %, 19.2 ± 12.3 %, and 39.2 ± 20.5 %, respectively. Non-fossil sources accounted for 55 ± 11 %, 54 ± 10 %, and 36 ± 14 % of the TC in BJ, XA, and LF, respectively. In XA, 48.34 ± 32.01 % of non-fossil sources was attributed to biomass burning. The highest contributors to OC in LF and XA were fossil sources (65.4 ± 14.9 % and 44.9 ± 9.5 %, respectively), whereas that in BJ was non-fossil sources in BJ (56.1 ± 16.7 %). The main contributors to EC were fossil sources, accounting for 92.9 ± 6.13 %, 69.9 ± 20.9 %, and 90.8 ± 9.9 % of the total EC in BJ, XA, and LF, respectively. The decline (6–17 %) in fossil source contributions in BJ and XA since the implementation of the Action Plan indicates the effectiveness of air quality management. We suggest that measures targeted to each city should be strengthened in the future.

Published
2021

318. Nonmetallic trace elements induced rhenium co-segregation in nickel Σ5 [001](210) symmetrical tilt grain boundary

Author

Xue, Hongtao, Dang, Ruidong, Tang, Fuling, Lu, Xuefeng, Ren, Junqiang, and Li, Junchen

Abstract

The thermally/mechanically-driven structural instability of nano- and coarse-grained polycrystalline metals originates from the unstable grain boundaries (GBs). GB segregation of solute elements could not only stabilize but also embrittle GBs. To improve GB stability and cohesion in parallel via solute segregations, in this work the segregation behavior of six non-metallic impurities Xat the Σ5 [001](210) GB of nickel-based alloys, their co-segregations with Re element that has no GB segregation tendency, and segregation-induced changes in GB properties were investigated comprehensively from first-principles calculations. We discovered that these nonmetallic elements can segregate to the Ni GB and thus stabilize it, but they are GB embrittlers except B. Annealing temperature and bulk concentration have no effect on the S segregation. With the Xpre-segregations, induced GB segregations of Re were observed, which lowers the excess energy and enhances the cohesive strength of all X-segregated GBs. The attractive interactions between C/N/B and Re atoms promote the Re segregation. The stabilizing and strengthening mechanisms of Re segregation were mainly attributed to the changes in Fermi level location and the increased interplanar bonding, respectively. Our findings may gain more insights into the atomic-scale GB co-segregations and stabilization of polycrystalline Ni-based alloys.

Published
2023
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331. Supplementary material to "Measurement report: Source apportionment of carbonaceous aerosol using dual-carbon isotopes (<sup>13</sup>C and <sup>14</sup>C) and levoglucosan in three northern Chinese cities during 2018–2019"

Author

Zhao, Huiyizhe, primary, Niu, Zhenchuan, additional, Zhou, Weijian, additional, Wang, Sen, additional, Feng, Xue, additional, Wu, Shugang, additional, Lu, Xuefeng, additional, and Du, Hua, additional

Published
2021
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337. CvkR is a MerR-type transcriptional repressor of class 2 type V-K CRISPR-associated transposase systems.

Author

Ziemann, Marcus, Reimann, Viktoria, Liang, Yajing, Shi, Yue, Ma, Honglei, Xie, Yuman, Li, Hui, Zhu, Tao, Lu, Xuefeng, and Hess, Wolfgang R.

Subjects
CRISPRS, GENOME editing, TRANSPOSONS, CRYSTAL structure, RNA, SYNECHOCOCCUS, ANABAENA
Abstract

Certain CRISPR-Cas elements integrate into Tn7-like transposons, forming CRISPR-associated transposon (CAST) systems. How the activity of these systems is controlled in situ has remained largely unknown. Here we characterize the MerR-type transcriptional regulator Alr3614 that is encoded by one of the CAST (AnCAST) system genes in the genome of cyanobacterium Anabaena sp. PCC 7120. We identify a number of Alr3614 homologs across cyanobacteria and suggest naming these regulators CvkR for Cas V-K repressors. Alr3614/CvkR is translated from leaderless mRNA and represses the AnCAST core modules cas12k and tnsB directly, and indirectly the abundance of the tracr-CRISPR RNA. We identify a widely conserved CvkR binding motif 5'-AnnACATnATGTnnT-3'. Crystal structure of CvkR at 1.6 Å resolution reveals that it comprises distinct dimerization and potential effector-binding domains and that it assembles into a homodimer, representing a discrete structural subfamily of MerR regulators. CvkR repressors are at the core of a widely conserved regulatory mechanism that controls type V-K CAST systems. RNA-guided, CRISPR-associated transposons hold great promise for precision genome editing. Here, the authors provide genetic, biochemical and structural data how their activity is regulated in situ by CvkR, an unusual MerR family regulator. [ABSTRACT FROM AUTHOR]

Published
2023
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339. Effect of solute atoms on grain boundary stability of nanocrystalline Ni–Co alloy.

Author

Chen, Xiaotong, Lu, Xuefeng, Ren, Junqiang, Xue, Hongtao, Tang, Fuling, and Ding, Yutian

Subjects
*CRYSTAL grain boundaries, *SOLUTION strengthening, *MOLECULAR dynamics, *DISLOCATION structure, *ATOMS
Abstract

In this contribution, molecular dynamics method is used to accurately add quantitative Co atoms in the grain boundary (GB) region of nano-polycrystalline Ni to study the effect of solute atoms on the GB and the deformation mechanism of the material. It was found that adding an appropriate amount of Co atoms at the GBs can improve the tensile strength of the material to a certain extent through solid solution strengthening. However, excessive introduction of solute atom will increase the activity of GB atoms, destroy the stability of GBs, and accelerate the appearance of material yielding. At the same time, the Co atoms at the GB gradually detached from the GB region and diffused into the grains. In addition, the dislocations are distributed in a grid at the GBs, and with the increase in strain, the number and length of dislocations gradually increase, forming a large number of entanglements. Moreover, the Shockley dislocation interacts with other dislocations to form a more stable dislocation structure by hindering the generation and movement of other dislocations, which greatly enhances the strength of the system. [ABSTRACT FROM AUTHOR]

Published
2022
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340. Genetic engineering tools for the filamentous microalga Tribonema minus.

Author

Wang, Jianing, Zhou, Wenjun, Chen, Lin, Liu, Tianzhong, and Lu, Xuefeng

Abstract

Tribonema minus , a eukaryotic filamentous yellow-green alga, is widely regarded as an optimal candidate for the production of biofuels and high-value chemicals such as palmitoleic acid and eicosapentaenoic acid. To achieve artificial regulation of the biosynthetic pathways for target compounds in T. minus , it is crucial to establish a stable multi-gene genetic expression system. Genetic engineering provides an effective approach for regulating the expression of multiple genes. A crucial breakthrough in this context involves expanding the effective genetic tools, which enables the integrated use of promoters, terminators, resistance markers and reporter genes to express the endogenous or heterologous gene-of-interest. To this end, we have devised tools suitable for multi-gene expression in T. minus. These tools include promoters (Ptubulin, Phsp70A and Phsp90A), F2A peptide, resistance marker genes (nptII , aadA and ble) and an enhanced green fluorescent protein reporter gene (eGFP). The genetic elements incorporated into the tools have demonstrated efficacy in T. minus. The experimental findings indicate that the endogenous promoters identified in T. minus exhibit transcriptional activity, and are capable of driving enhanced green fluorescent protein gene (eGFP) expression and could result in the production of corresponding proteins that can be easily detected through fluorescence microscopy. The F2A peptide functions properly in T. minus , with its activity remaining unaffected by the location when the gene sequences preceding and following the F2A peptide are relatively short (<1 kbp). The precise cleavage of enhanced green fluorescent protein (eGFP) has been confirmed through immunoblotting experiments, which can be readily detected using fluorescence microscopy. The utilization of the F2A peptide not only decreases the number of promoters required but also mitigates gene silencing. • Tools for multi-gene expression of Tribonema minus were developed. • The promoter Phsp70A showed the highest level of transcriptional activity. • The F2A peptide demonstrated the capacity of yielding two independent proteins. • The efficiency of the promoter is influenced by the length of the linked gene. [ABSTRACT FROM AUTHOR]

Published
2024
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342. Highly Stretchable, Crack-Insensitive and Compressible Ceramic Aerogel

Author

Su, Lei, primary, Wang, Hongjie, additional, Jia, Shuhai, additional, Dai, Sheng, additional, Niu, Min, additional, Ren, Junqiang, additional, Lu, Xuefeng, additional, Cai, Zhixin, additional, Lu, De, additional, Li, Mingzhu, additional, Xu, Liang, additional, Guo, Sheng-Wu, additional, Zhuang, Lei, additional, and Peng, Kang, additional

Published
2021
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349. Densification rate and mechanical properties of carbon/carbon composites with layer-designed preform

Author

Zhang Jie, Lu Xuefeng, and Qian Kun

Subjects
010302 applied physics, Work (thermodynamics), Materials science, Process Chemistry and Technology, Delamination, Reinforced carbon–carbon, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Matrix (geology), Shear (sheet metal), Compressive strength, Chemical vapor infiltration, 0103 physical sciences, Materials Chemistry, Ceramics and Composites, Composite material, 0210 nano-technology, Layer (electronics)
Abstract

In this work, carbon fiber needle-punching preforms were designed into two structure according to the density change along the thickness direction. One structure is designed to two layers with low-density layer and high-density layer, and the other is to three layers with low-density exterior layer and high-density interior layer. Then the effect of the preform with different structure on the densification rate and compressive properties of C/C composites was investigated. The results show that both two designed preforms can effectively avoid surface blocking, and lead to the faster densification rate of C/C composites during the chemical vapor infiltration processes. These results are attributable to the change of pore size distribution and pyrocarbon thickness, which was caused by fiber architecture designs. Meanwhile, these structural changes can improve the compressive strength of C/C composites, especially for the three-layer preforms. When the density of preforms is 0.45 g/cm3, C/C composites with three-layer preform has the highest compressive strength. The damage of most C/C composites with two and three-layer preforms is caused by shear or delamination failure, while that of C/C composites with common preforms usually caused by matrix collapse. Cracks in C/C composites with two and three-layer preforms always happened on the low-density layer, and consequently ceased or changed propagation direction in the interface between two layers.

Published
2019

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