Subjects: Biology >> Botany submitted time 2023-03-28 Cooperative journals: 《干旱区研究》
Abstract： This study aims to provide reference for quantifying the selection model of plant water sources. MixSIAR model and IsoSource model are commonly used to quantify plant water sources by combining hydrogen and oxygen stable isotope technology. However, different models yield varying quantitative results. Hence, choosing the best model is important to reduce the uncertainty of results. In this work, the hydrogen and oxygen stable isotope compositions of stem xylem water and each potential water source of two shrubs were measured from July to September in 2019 and 2021. The dominant tree species Cotoneaster melanocarpus and Berberis heteropoda in the premontane shrub zone of the northern slope of Tianshan Mountain were selected as subjects. MixSIAR and IsoSource models were used to quantify plant water sources, and their results were compared and evaluated according to the root mean square error (RMSE) and parameter R. Results showed (1) differences in the quantification results of the two models for the main potential water sources of plants. These differences were related to the calculation principles of the two models. (2) Under the premise that the two models quantify the same main potential water sources of plants, the IsoSource model quantifies larger values than the MixSIAR model. (3) The results of RMSE and parameter R showed that the error of IsoSource model in quantifying plant water sources was smaller than that of MixSIAR model possibly due to the large difference between C. melanocarpus and B. heteropoda In summary, the MixSIAR model may be more accurate in quantifying the similarity of plant water sources than the IsoSource model.
Subjects: Geosciences >> Geography submitted time 2021-06-13 Cooperative journals: 《干旱区研究》
Abstract：基于1961—2018年柴达木盆地10个气象台站观测资料，分析了柴达木盆地极端强降水量、强降水日数的时空演变特征，定量化分析了柴达木盆地不同量级暴雨灾害的影响程度，结果表明：（1）1961—2018年柴达木盆地夏季（6—8月）降水呈增多趋势，增幅为7.5 mm·(10a)-1，极端强降水次数亦呈增多趋势，增幅为2次·(10a)-1，尤其是近10 a来，夏季极端强降水次数增多尤为明显，年平均强降水次数为17次，与1981—2010年平均值相比偏多6次。（2）柴达木盆地因强降水诱发的暴雨灾害次数总体呈增多趋势，增幅为2.5次·(10a)-1，进入21世纪以来增加尤为明显，都兰、乌兰、天峻及德令哈是暴雨灾害出现次数最多的地区。（3）暴雨灾害风险区划结果：夏季柴达木盆地天峻县（舟群乡、快尔玛乡、木里镇、新源镇、江河镇）为极端强降水诱发的暴雨灾害高风险区；德令哈（蓄集乡、尕海镇）、乌兰县（铜普镇、柯柯镇及茶卡镇）、都兰县（香加乡、热水乡、沟里乡、香日德镇、夏日哈镇、察汗乌苏镇）为暴雨灾害较高风险区，针对暴雨灾害风险级别和影响范围，定量化分析了柴达木盆地暴雨灾害对GDP、人口、土地利用类型的影响程度。
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-11-29 Cooperative journals: 《计算机应用研究》
Abstract： In order to improve the accuracy of truth discovery in multi-truth scene, this paper proposed a multi-ant colonies synchronization optimization based multi-truth discovery (MAC-SO-MTD) algorithm. It modeled the multi-truth discovery problem as the subset problem, which goal was maximizing the weighted sum of similarity between the set of observations provided by each data source and the set of true values of the object. On this basis, then designed ant colony algorithm to solve the problem. It set ant colonies according to the number of objects. Based on the subset problem’s structure graph, this paper used routes’ probability transition equations to search for truths synchronically. After one cycle, the best route of this cycle updating and no updating were two instances of updating pheromone, which improved the convergence speed. Finally, the analysis of algorithm complexity and contrast experiment on the real data set validated the superiority of the algorithm.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-11-29 Cooperative journals: 《计算机应用研究》
Abstract： To further improve the performance of personalized tag recommendation, this paper argued that traditional methods ignore the potential and informative tags hidden in the context of users and items. Aimed at this, this paper proposed a novel personalized tag recommendation method BPR-PITF-P based on potential tag mining and fine-grained preference. Firstly, BPR-PITF-P leverages the context information of both users and items to mine potential and useful tags, and gets three kinds of tags: positive tags, potential tags, and negative tags. Based on the above, it translates the traditional pairwise preference into fine-grained preference relationship among user-item post and tags. This kind of treatment helps alleviate the sparse problem of tagging data. Second, combined with pairwise interaction tensor factorization method to predict preference value, BPR-PITF-P models the preference relationship based on the optimization criteria of Bayesian personalized ranking, and develops a personalized tag recommendation model followed by optimization algorithm. The comparison results show that our proposed method could improve tag recommendation performance in the premise of guarantee convergence speed.
Subjects: Medicine, Pharmacy >> Preclinical Medicine submitted time 2018-01-25 Cooperative journals: 《南方医科大学学报》
Abstract： Objective To modify the structure of psoralidin using in vitro enzymatic glycosylation to improve its water solubilityand stability. Methods A new psoralidin glucoside (1) was obtained by enzymatic glycosylation using a UDP-glycosyltransferase. The chemical structure of compound 1 was elucidated by HR-ESI-MS and nuclear magnetic resonance(NMR) analysis. The high-performance liquid chromatography (HPLC) peaks were integrated and sample solution concentrations were calculated. MTT assay was used to detect the cytotoxicity of the compounds against 3 cancer cell lines in vitro. Results Based on the spectroscopic data, the new psoralidin glucoside was identified as psoralidin-6',7-di-O glucopyranoside (1), whose water solubility was 32.6-fold higher than that of the substrate. Analyses of pH and temperature stability demonstrated that compound 1 was more stable than psoralidin at pH 8.8 and at high temperatures. Only psoralidin exhibited a moderate cytotoxicity against 3 human cancer cell lines. Conclusion In vitro enzymatic glycosylation is a powerful approach for structural modification and improving water solubility and stability of compounds.
Subjects: Medicine, Pharmacy >> Preclinical Medicine submitted time 2017-12-07 Cooperative journals: 《南方医科大学学报》
Abstract： Objective To improve the water solubility and biological activity of neoligans (magnolol and honokiol) and test the antitumor activity of the modified compounds. Methods The glycosylated products of magnolol and honokiol were obtained by enzymatic synthesis using a UDP-glycosyltransferase (YjiC) from Bacillus. The products were characterized by high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and nuclear magnetic resonance (NMR) analysis. MTT assay was used to detect the growth inhibition of 4 human cancer cell lines induced by the compounds. Results We obtained two glucosides of neolignans (magnolol and honokiol) for the first time by enzymatic synthesis using a UDP-glycosyltransferase. Based on the spectroscopic data, the glucosides were identified as magnolol-2- O-β-D-glucopyranoside (1) and honokiol-4'-O-β-D-glucopyranoside (2). Compounds 1-4 exhibited moderate anti-proliferative activities against the 4 human cancer cell lines, with IC 50 values ranging from 9.41 to 111.21 µmol/L. Conclusion The glycoslated products show enhanced water solubility and drug sensitivity against SMMC7721 cells, suggesting their value as potential therapeutic drugs.
Subjects: Library Science，Information Science >> Information Science submitted time 2017-10-11 Cooperative journals: 《数据分析与知识发现》
Abstract：【目的】实时、准确、高效地检测出海量微博中的突发事件, 为舆情应急管理提供重要的决策信息支持。【方法】引入参照时间窗机制, 设计词频、文档频率、话题标签(Hashtag)、词频增长率4 类特征的选择与计算方法, 基于动态阈值实现对突发主题词的抽取。在此基础上, 将微博文本表示为突发主题词的特征向量, 使用凝聚式层次聚类算法实现了突发事件的检测。【结果】将实验结果结合实例进行分析, 突发事件检测达到80%的准确率, 验证该方法的可行性和有效性。【局限】由于语料数据和研究范围的限制, 还未实现对所检测突发事件的自动描述, 对网民情感、事件间语义关系等要素的分析及考量也存在一定欠缺。【结论】本研究突破以往相关研究中文本内容质量、文本形式、突发特征抽取结果的局限, 提升微博突发事件检测的效率。
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