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Fluorescence regional integration and differential fluorescence spectroscopy for analysis of structural characteristics and proton binding properties of fulvic acid sub-fractions

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Journal of Environmental Sciences 2018年第12期30卷 116-125页

作者： Fanhao Song Fengchang Wu Weiying Feng Zhi Tang John P.Giesy Fei Guo Di Shi xiaofei liu Ning Qin Baoshan Xing Yingchen Bai State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Science Department of Biomedical and Veterinary Biosciences and Toxicology Centre University of Saskatchewan College of Resources Environment and Tourism Capital Normal University Stockbridge School of Agriculture University of Massachusetts

Structural characteristics and proton binding properties of sub-fractions（FA3–FA13） of fulvic acid（FA）, eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration（FRI） and differential fluorescence spectroscopy（DFS）. Humic-like（H-L） and fulvic-like（F-L） materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to *** of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants（p Ka） were calculated by use of results of DFS and the modified Stern-Volmer relationship. The p Kaof H-L, F-L, tryptophan-like and tyrosine-like materials of FA subfractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of p Ka for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like（P-L）materials had greater affinities for protons than did either H-L or F-L materials. The dicarboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH.

关键词： Fluorescence titration Protonation Modified Stern-Volmer equation Dissociation constant Binding

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Senescent bone marrow microenvironment promotes Nras-mutant leukemia

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Journal of Molecular Cell Biology 2021年第1期13卷 72-74页

作者： Peiqing Zhou Chengxiang Xia Tongjie Wang Yong Dong Qitong Weng xiaofei liu Yang Geng Jinyong Wang Juan Du CAS Key Laboratory of Regenerative Biology Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhou 510530China University of Chinese Academy of Sciences Beijing 100049China Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhou 510530China Institute for Stem Cell and Regeneration Chinese Academy of SciencesBeijing 100101China Bioland Laboratory(Guangzhou Regenerative Medicine and Health Guangdong Laboratory) Guangzhou 510005China

Dear Editor,In recent years,there is growing interest regarding the roles of senescent bone marrow(BM)microenvironment in the initiation of *** mice transplanted with AML1-ETO(AML1-ETO fusion protein)-positive hematopoietic stem cells(HSCs)present with a significant increase in the frequency of AMLETO-positive early progenitor cells in BM as well as an in crease of immature myeloid cells compared to young recipients(Vas et aL,2012).BM mesenchymal stem cells(MSCs)from myelodysplastic syndromes(MDS)animal models and MDS patients exhibit impaired proliferation and differentiation potentials,abnormal cytoki ne secretion,and dysregulated gene expression profile(Lopez-Villar et al.,2009;Geyh et al.,2013;Mattiucci et al.,2018).However,the causal relationship between senes・cent BM microenvironment and leukemia development is *** senes・cent BM microenvironment initiates or accelerates leukemia development remains unknown.

关键词： al. microenvironment impaired

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Hierarchical nanostructured composite cathode with carbon nanotubes as conductive scaffold for lithium-sulfur batteries

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Journal of Energy Chemistry 2013年第2期22卷 341-346页

作者： xiaofei liu Qiang Zhang Jiaqi Huang Shumao Zhang Hongjie Peng Fei Wei Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical Engineering Tsinghua University

Carbon nanotubes （CNTs） are excellent scaffolds for advanced electrode materials, resulting from their intrinsic sp2 carbon hybridization, interconnected electron pathway, large aspect ratio, hierarchical porous structures, and low cost at a large-scale production. How to make full utilization of the mass produced CNTs as building blocks for nanocomposite electrodes is not well understood yet. Herein, a composite cathode containing commercial agglomerated multi-walled CNTs and S for Li-S battery was fabricated by a facile melt-diffusion strategy. The hierarchical CNT@S coaxial nanocables exhibited a discharging capacity of 1020 and 740 mAh .g-1 at 0.5 and 2.0 C, respectively. A rapid capacity decay of 0.7% per cycle at the initial 10 cycles and a slow decay rate of 0.14% per cycle for the later 140 cycles were detected. Such hierarchical agglomerated CNT@ S cathodes show advantages in easy fabrication, environmentally benign, low cost, excellent scalability, and good Li ion storage performance, which are extraordinary composites for high performance Li-S battery.

关键词： carbon nanotubes lithium sulfur battery hierarchical nanocomposite cathode energy storage

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Regeneration of immunocompetent B lymphopoiesis from pluripotent stem cells guided by transcription factors

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Cellular & Molecular Immunology 2022年第4期19卷 492-503页

作者： Qi Zhang Bingyan Wu Qitong Weng Fangxiao Hu Yunqing Lin Chengxiang Xia Huan Peng Yao Wang xiaofei liu Lijuan liu Jiapin Xiong Yang Geng Yalan Zhao Mengyun Zhang Juan Du Jinyong Wang CAS Key Laboratory of Regenerative Biology Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhou510530China Bioland Laboratory(Guangzhou Regenerative Medicine and Health Guangdong Laboratory) Guangzhou510005China Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhou510530China University of Chinese Academy of Sciences Beijing100049China Institute for Stem Cell and Regeneration Chinese Academy of SciencesBeijing100101China GMU-GIBH Joint School of Life Sciences Guangzhou Medical UniversityGuangzhou511436China

Regeneration of functional B lymphopoiesis from pluripotent stem cells(PSCs)is challenging,and reliable methods have not been ***,we unveiled the guiding role of three essential factors,Lhx2,Hoxa9,and Runx1,the simultaneous expression of which preferentially drives B lineage fate commitment and in vivo B lymphopoiesis using PSCs as a cell *** the presence of Lhx2,Hoxa9,and Runx1 expression,PSC-derived induced hematopoietic progenitors(iHPCs)immediately gave rise to pro/pre-B cells in recipient bone marrow,which were able to further differentiate into entire B cell lineages,including innate B-1a,B-1b,and marginal zone B cells,as well as adaptive follicular B *** particular,the regenerative B cells produced adaptive humoral immune responses,sustained antigen-specific antibody production,and formed immune memory in response to antigen *** regenerative B cells showed natural B cell development patterns of immunoglobulin chain switching and hypermutation via cross-talk with host T follicular helper cells,which eventually formed T cell-dependent humoral *** study exhibits de novo evidence that B lymphopoiesis can be regenerated from PSCs via an HSC-independent approach,which provides insights into treating B cell-related deficiencies using PSCs as an unlimited cell resource.

关键词： Lhx2 Hoxa9 Runx1 B lymphopoiesis pluripotent stem cells

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Solvent switching and purification of colloidal nano- particles through water/oil Interfaces within a density gradient

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Nano Research 2014年第11期7卷 1670-1679页

作者： Yun Kuang Sha Song xiaofei liu Minglin Li Zhao Cai Liang Luo Xiaoming Sun State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 China

Traditional post-treatment of colloidal nanoparticles （NPs） usually involves repeated centrifugation-wash-sonication processes to separate NPs from the original synthetic environment; however, such separation processes have either high energy cost or low efficiency and tend to cause aggregation. Here we show a general and scalable colloid post-processing technique based on density gradient centrifugation through water/oil interfaces. Such a one-step technique can switch the solvent in a colloid at almost any concentration without aggregation, and meanwhile purify colloidal nanoparticles by separating them from by-products and environmental impurities. Droplet sedimentation was shown to be the mechanism of this one-step concentration/purification process, and mathematical modeling was established to quantify the accumulation and sedimentation velocities of different NPs.

关键词： density gradient water/oil interface solvent switching purification

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C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 pathway as a therapeutic target and regulatory mechanism for spinal cord injury

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Neural Regeneration Research 2025年第8期20卷 2231-2244页

作者： Xiangzi Wang xiaofei Niu Yingkai Wang Yang liu Cheng Yang Xuyi Chen Zhongquan Qi School of Medicine Guangxi UniversityNanningGuangxi Zhuang Autonomous RegionChina Graduate School of Tianjin University of Traditional Chinese Medicine TianjinChina Characteristic Medical Center of People’s Armed Police Forces TianjinChina Fujian Maternity and Child Health Hospital FuzhouFujian ProvinceChina

Spinal cord injury involves non-reversible damage to the central nervous system that is characterized by limited regenerative capacity and secondary inflammatory *** expression of the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis exhibits significant differences before and after *** studies have revealed that the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis is closely associated with secondary inflammatory responses and the recruitment of immune cells following spinal cord injury,suggesting that this axis is a novel target and regulatory control point for *** review comprehensively examines the therapeutic strategies targeting the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis,along with the regenerative and repair mechanisms linking the axis to spinal cord ***,we summarize the upstream and downstream inflammatory signaling pathways associated with spinal cord injury and the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 *** review primarily elaborates on therapeutic strategies that target the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis and the latest progress of research on antagonistic drugs,along with the approaches used to exploit new therapeutic targets within the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 axis and the development of targeted ***,there are presently no clinical studies relating to spinal cord injury that are focusing on the C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 *** review aims to provide new ideas and therapeutic strategies for the future treatment of spinal cord injury.

关键词： apoptosis C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 pathway C-C motif chemokine receptor 2 antagonists chemokine ligand 2 chemokine receptor 2 inflammation macrophage microglia spinal cord injury therapeutic method

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Topological Order Value Iteration Algorithm for Solving Probabilistic Planning

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Communications and Network 2013年第1期5卷 86-89页

作者： xiaofei liu Mingjie Li Qingxin Nie Department of Computer Science DunHua Vocational-technical School Dunhua China Polytechnic School SanYa University Sanya China School of Foundation Courses SanYa University Sanya China

AI researchers typically formulated probabilistic planning under uncertainty problems using Markov Decision Processes (MDPs).Value Iteration is an inef?cient algorithm for MDPs, because it puts the majority of its effort into backing up the entire state space, which turns out to be unnecessary in many cases. In order to overcome this problem, many approaches have been proposed. Among them, LAO*, LRTDP and HDP are state-of-the-art ones. All of these use reach ability analysis and heuristics to avoid some unnecessary backups. However, none of these approaches fully exploit the graphical features of the MDPs or use these features to yield the best backup sequence of the state space. We introduce an improved algorithm named Topological Order Value Iteration (TOVI) that can circumvent the problem of unnecessary backups by detecting the structure of MDPs and backing up states based on topological sequences. The experimental results demonstrate the effectiveness and excellent performance of our algorithm.

关键词： Probabilistic Planning Markov Decision Processes Dynamic Programming Value Iteration

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Isolation and Purification of Bovine Colostrum sIgA and IgG

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Journal of Northeast Agricultural University(English Edition) 2008年第1期15卷 58-61页

作者： YAO Yonghao GAO Xuejun liu xiaofei Key Laboratory of Dairy Science of Ministry of Education Northeast Agricultural University Harbin 150030 China

To further utilize bioactive substance such as bovine colostrum sIgA and IgG, sIgA and IgG were isolated and purified simultaneously by salting out, ultrafiltration and gel chromatography, etc. The analysis of results were showed quantitatively by nonhydrogenized SDS-PAGE, and quanlities of sIgA and IgG were respectively detected by Western Blot. The results showed that the purity and yield of bovine colostrum sIgA were 85.3% and 42.8%, respectively, while the purity and yield of bovine colostrum IgG were respectively 97.2% and 64.4%. This preparative method provides theoretical and experimental foundation for sIgA industrial production.

关键词： bovine colostrum sIgA IgG isolation and purification ultrafiltration Western Blot

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Spatial pattern and decadal change of agro-meteorological disasters in the main wheat production area of China during 1991-2009

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Journal of Geographical Sciences 2014年第3期24卷 387-396页

作者： ZHANG Zhao WANG Pin CHEN Yi ZHANG Shuai TAO Fulu liu xiaofei Academy of Disaster Reduction and Emergency Management/State Key Laboratory of Earth Surface Process and Resource Ecology Beijing Normal University Beijing 100875 China Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China

Agro-meteorological disasters （AMD） have become more frequent with climate warming. In this study, the temporal and spatial changes in the occurrence frequency of major meteorological disasters on wheat production were firstly explored by analyzing the observed records at national agro-meteorological stations （AMS） of China from 1991 to 2009. Fur- thermore, impact of climate change on AMD was discussed by comparing the warmer decade （2000-2009） with another decade （1991-2000）. It was found that drought was the most fre- quent disaster during the last two decades, with a highest proportion of 79%. And the fre- quency of AMD increased significantly with climate change. Specifically, the main disasters occurred more frequently in the reproductive period than in the vegetative period. Besides, the spatial changes in the AMD frequency were characterized by region-specific. For example the wheat cultivation areas located on the Loess Plateau and the middle-lower reaches of the Yellow River suffered mainly from drought. All these results were strongly linked to climate change in China. Therefore, sound adaptation options should be taken based on the latest changes of AMD under global warming to reduce agricultural damages.

关键词： wheat agro-meteorological disasters climate change drought heat stress

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多次爆炸载荷作用下浅埋隧道破坏过程的持续同调特征分析

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应用数学和力学 2020年第11期41卷 1237-1249页

作者：刘小飞游世辉湘潭大学土木工程与力学学院湖南湘潭411105 枣庄学院机电工程学院山东枣庄277160

浅埋隧道在多次爆炸载荷作用下的破坏特征是防护工程设计和评估的重要研究问题,发展适应浅埋特征安全预警方法具有重要意义.采用离散元法建立浅埋隧道力学模型,运用Saint-Venant载荷等效原理将爆炸载荷看作一系列均匀作用在地表的动力,... 详细信息

浅埋隧道在多次爆炸载荷作用下的破坏特征是防护工程设计和评估的重要研究问题,发展适应浅埋特征安全预警方法具有重要意义.采用离散元法建立浅埋隧道力学模型,运用Saint-Venant载荷等效原理将爆炸载荷看作一系列均匀作用在地表的动力,基于离散元法得到各次爆炸载荷作用后的动力响应和隧道围岩损伤演化过程,利用强度折减法得出隧道围岩的安全系数.引入持续同调理论,采用持续同调的数学方法对离散元模型在多次爆炸载荷作用下的破坏特征进行定量与定性分析.结果表明,持续同调的方法能准确反映隧道围岩的拓扑特征,其中1维条形码连通半径最大值能对隧道失稳进行有效预警.这为隧道安全设计与灾害预报研究提供了一种全新的数学方法.

关键词：持续同调浅埋隧道离散元多次爆炸载荷

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