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| 1 | Exogenous plant MIR168a specifically targets mammalian LDLRAPI: evidence of cross-kingdom regulation by microRNA显示文摘 | Lin Zhang Dongxia Hou Xi Chen Donghai Li Lingyun Zhu Yuj ing Zhang Jing Li Zhen Bian Xiangying Liang Xing Cai Yuan Yin Cheng Wang Tianfu Zhang Dihan Zhu Dianmu Zhang Jie Xu Qun Chen Yi Ba Jing Liu Qiang Wang Jianqun Chen Jin Wang Meng Wang Qipeng Zhang Junfeng Zhang Ke Zen Chen-Yu Zhang | 2012 | Cell Research2012，22，1： | 155 |
| 2 | Expression of vascular endothelial growth factor and its receptors KDR and Fit-1 in gastric cancer cells显示文摘AIM: The expression of vascular endothelial growth factor (VEGF) and its receptors KDR and Flt-1 by gastric carcinoma tissues and different gastric carcinoma cell lines was detected to elucidate the molecular mechanism of this growth factor in promoting tumor growth.METHODS: The expression of VEGF, Flt-1 and KDR was determined by reverse transcription-polymerase chain reaction (RT-PCR) in gastric cancer cell lines RF-1, RF-48,AGS-1, NCI-N87, NCI-SNU-1, NCI-SNU-5, NCI-SNU-16 and KATO-Ⅲ. The expression of Flt-1 and KDR in paraffinembedded specimens of gastric cancer was determined by immunohistochemistry. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess the role of VEGF in tumor cell proliferation.RESULTS: All 8 gastric cancer cell lines analyzed expressed VEGF121 and VEGF16s and six of them expressed both Flt-1 and KDR, while cell line NCI-SNU-5 expressed Flt-1 only and cell line KATOⅢ expressed neither Flt-1 nor KDR. The gastric carcinoma tissues expressed Flt-1 and KDR widely,with the positive rate of expression of Flt-1 and KDR being 84.6 % and 70 % respectively. The exogenous VEGF stimulated the growth of KDR-positive cell lines NCI-N87 and AGS-1 in a dose-dependent manner but exhibited no effect on the growth of KDR-negative cell line NCI-N87.CONCLUSION: VEGF and its receptors KDR and Flt-1 were expressed widely in gastric carcinoma cells and the VEGF stimulated KDR-positive tumor cell growth directly. These results suggest that VEGF may play a role in promoting tumor growth and metastasis by participating in both paracrine and autocrine pathways. | Hua Zhang Jian Wu Lin Meng Cheng-Chao Shou,Peking University School ofOncology,Beij ing Institute for Cancer Research,Beijing 100034,China | 2002 | World Journal of Gastroenterology2002，8，6： | 69 |
| 3 | 高速加工发展概况显示文摘本文全面介绍了高速加工的基础理论及发展过程 ,并对高速加工的优点和特性、高速加工的安全性、高速主轴及机床部件的发展从整体上进行了深入的讨论。同时 ,作者对发展高速加工需要的关键技术提出了研究方向 。 | Dr·-Ing·H·舒尔茨 王志刚 武凯 何宁 | 2002 | 机械制造与自动化2002，，1： | 43 |
| 4 | Analysis of the phosphatidylinosit ol 3'-kinase signaling pathway in glioblastoma patients in vivo显示文摘Deregulated signaling through the p hosphatidylinositol 3-kinase(PI3K)pathway is common in many types of can cer,including glioblastoma.Dissecting the molecular events associated with activation of this pathway in glioblastoma p atients in vivo presents an important challenge that has implic ations for the development and clini cal testing of PI3K pathway inhibito rs.Using an immunohistochemical analysis appl ied to a tissue microarray,we performed hierarchical clustering and mul tidimensional scaling,as well as univariate and multivariate analyses,to dissect the PI3K pathway in v ivo.We demonstrate that loss of the t umor suppressor protein PTEN,which antagonizes PI3K pathwa y activation,is highly correlated w ith activation of the main PI3K effec tor Akt in vivo.We also show that Akt activation is signific antly correlated with phosphorylation of mammalian target of rapamycin(mTOR),the family of forkhead transcription factors(FOXO1,FOXO3a,and FOXO4),and S6,which are thought to promote its effects.Expression of the mutan t epidermal growth factor receptor vIII is also tightly correlated with phosphorylation of these effectors,d emonstrating an additional route to PI3K pathway activation in glioblastomas in vivo.These results provide the first dissection of the PI3K path way in glioblastoma in vivo and suggest an approach to stratifying patients for targeted kinase inhi bitor | Choe G Horvath S Cloughesy TF Crosby K Seligson D Palotie A Inge L Smith BL Sawyers CL Mischel PS | 2003 | 癌症2003，22，7： | 41 |
| 5 | 探索MOOC教学方法在mLearning中的运用显示文摘本文把大型开放式网络课程(Massively Open Online Course,以下简称MOOC)作为适应移动学习(mLearning)的一种可能的教学方法,这种教学方法建立在与当前学习或教学形式相适宜的基础上。本文呈现了一个MobiMOOC应用的案例研究,该案例使用MOOC形式创建一门课程,研究展示了MOOC和mLearning之间的协同特性,并将当前数字化的协作学习和知识建构这两个理想领域结合在一起。MobiMOOC是聚焦于mlearning、为期六周的网上课程,于2011年的4月到5月之间进行。MobiMOOC是免费开放的课程,有556位学习者加入了课程谷歌群组。课程结束时的调查结果有力地证明了MOOCs和mLearning之间的协同作用。本篇论文对时间和地点的独立性、情境学习、协作学习、潜在的跨学科信息交流,以及应用于网上学习的技术,如社交媒体,移动设备等方面进行了探讨。 | Inge DE Waard Apostolos Koutropoulos Nilgün zdamar Keskin Sean C.Abajian Rebecca Hogue C.Osvaldo Rodriguez Michael Sean Gallagher 何伏刚 马东明 孙海民 | 2012 | 中国远程教育2012，，5： | 39 |
| 6 | Increasing Incidence and Prevalence of the Inflammatory Bowel Diseases With Time, Based on Systematic Review显示文摘 | Natalie A. Molodecky Ing Shian Soon Doreen M. Rabi William A. Ghali Mollie Ferris Greg Chernoff Eric I. Benchimol Remo Panaccione Subrata Ghosh Herman W. Barkema Gilaad G. Kaplan | 2012 | Gastroenterology2012，，1： | 33 |
| 7 | Proton accumulation accelerated by heavy chemical nitrogen fertilization and its long-term impact on acidifying rate in a typical arable soil in the Huang-Huai-Hai Plain显示文摘Cropland productivity has been significantly impacted by soil acidification resulted from nitrogen(N) fertilization, especially as a result of excess ammoniacal N input. With decades' intensive agricultural cultivation and heavy chemical N input in the Huang-Huai-Hai Plain, the impact extent of induced proton input on soil p H in the long term was not yet clear. In this study, acidification rates of different soil layers in the soil profile(0–120 cm) were calculated by p H buffer capacity(p HBC) and net input of protons due to chemical N incorporation. Topsoil(0–20 cm) p H changes of a long-term fertilization field(from 1989) were determined to validate the predicted values. The results showed that the acid and alkali buffer capacities varied significantly in the soil profile, averaged 692 and 39.8 mmolc kg–1 p H–1, respectively. A significant(P<0.05) correlation was found between p HBC and the content of calcium carbonate. Based on the commonly used application rate of urea(500 kg N ha–1 yr–1), the induced proton input in this region was predicted to be 16.1 kmol ha–1 yr–1, and nitrification and plant uptake of nitrate were the most important mechanisms for proton producing and consuming, respectively. The acidification rate of topsoil(0–20 cm) was estimated to be 0.01 unit p H yr–1 at the assumed N fertilization level. From 1989 to 2009, topsoil p H(0–20 cm) of the long-term fertilization field decreased from 8.65 to 8.50 for the PK(phosphorus, 150 kg P2O5 ha–1 yr–1; potassium, 300 kg K2 O ha–1 yr–1; without N fertilization), and 8.30 for NPK(nitrogen, 300 kg N ha–1 yr–1; phosphorus, 150 kg P2O5 ha–1 yr–1; potassium, 300 kg K2 O ha–1 yr–1), respectively. Therefore, the apparent soil acidification rate induced by N fertilization equaled to 0.01 unit p H yr–1, which can be a reference to the estimated result, considering the effect of atmospheric N deposition, crop biomass, field management and plant uptake of other nutrients and cations. As protons could be consumed by some field practices, such as stubble return and coupled water and nutrient management, soil p H would maintain relatively stable if proper management practices can be adopted in this region. | HUANG P ing ZHANG Jia-bao XIN Xiu-li ZHU An-ning ZHANG Cong-zhi MA Dong-hao ZHU Qiang-gen YANG Shan WU Sheng-jun | 2015 | Journal of Integrative Agriculture2015，14，1： | 18 |
| 8 | Ghrelin在大鼠神经系统中的表达对胃黏膜的保护作用显示文摘目的:研究大鼠脑、小肠肌间神经丛神经元和血浆内Ghrelin的表达,探讨Ghrelin在水浸加束缚应激性胃溃疡中的作用及机制.方法:选择健康♂Wiater大鼠76只,随机分为 6组:水浸加束缚组(10只);侧脑室注射Ghrelin 组(24只);皮下注射L-NAME+侧脑室注射 Ghrelin组(8只)和相应的3个对照组(正常大鼠组18只,侧脑室注射生理盐水组8只,皮下注射 L-NAME+侧脑室注射生理盐水组8只).采用放射免疫分析、荧光免疫组化双染和神经生理学等实验方法,观察脑、小肠肌间神经丛和血浆内Ghrelin的表达,探讨Ghrelin对大鼠束缚加水浸诱导的应激性胃溃疡的影响及机制.结果:在正常大鼠小肠肌间神经丛内和原代培养的肠肌间神经丛神经元均可见有Ghrelin 样免疫反应阳性物(Ghrelin-IR)的表达,且 Ghrelin-IR与胆碱乙酰转移酶(CHAT)共同表达于同一神经元内,但Ghrelin-IR不与一氧化碳合酶(NOS)和消化道感觉性神经元内特有的钙结合蛋白(Calbindin,Calb)共存.在大鼠应激性胃溃疡产生的同时,其血浆内Ghrelin- IR的含量明显减少(198.3±29.6 ng/L vs 141.7 ±26.5 ng/L.P=0.026).而下丘脑、延脑、垂体和肌间神经丛神经元内Ghrelin-IR的含量明显升高(分别为96.2±18.1 pg/mg vs 153.2 ±11.6 pg/mg.P=0.006;89.8±16.5 pg/mg vs 144.4±13.9 pg/mg,P=0.007;108.3± 11.9 pg/mg vs 198.2±23.3 pg/mg,P=0.002; 48.8±12.8 pg/mg vs 86.2±21.5 pg/mg.P= 0.02);侧脑室注射Ghrelin大鼠应激性胃溃疡的产生明显减少,且呈明显的量效依赖关系(溃疡指数:生理盐水,86.7±6.2;50 ng Ghrelin,79.3±10.7 P=2.18;500 ng Ghrelin, 61.3±11.7,P=0.04;5 000 ng Ghrelin,35.6 ±10.8,P=0.005),经sc一氧化氮合酶抑制剂 L-NAME后,Ghrelin的胃黏膜细胞保护作用消失.结论:Ghrelin与ChAT共存表达于肠肌间神经丛胆碱能神经元;应激性胃溃疡发生时,中枢神经系统和血浆内Ghrelin的表达发生变化; 中枢Ghrelin对胃黏膜细胞具有保护作用,且呈明显的量效依赖关系. | 徐珞 孙向荣 韩晓华 钟凤 Inge Depoortere Theo Peeters | 2006 | 世界华人消化杂志2006，14，8： | 14 |
| 9 | “鸟巢一代”奥运志愿服务集体记忆与奥运遗产显示文摘采用定性研究方法将奥运遗产置于志愿者的集体记忆中予以考察,以口述的方式记录了15位2008北京奥运会、残奥会赛会志愿者('鸟巢一代')的奥运志愿服务记忆。运用质性研究软件NVivo 11对访谈资料进行编码分析,挖掘并诠释了'鸟巢一代'集体记忆的关键构成要素,归纳为'我参与、我奉献、我快乐'。研究认为,'鸟巢一代'集体记忆的构建以社会主义核心价值观和志愿服务理念为框架;集体记忆的内容呈现出对参与奥运志愿服务的肯定与怀念,追寻'累并快乐着'的集体意义升华;集体记忆的存在形态以活跃的网络社群和实物为载体,'自媒体晒行为'表现出明显的奥运志愿者身份认同和集体归属感。最后,探讨了奥运志愿服务集体记忆作为潜在奥运遗产的功能及对北京2022冬奥会的启示。 | 王艳 DEROM Inge THEEBOOM Marc | 2018 | 沈阳体育学院学报2018，37，6： | 10 |
| 10 | Ghrelin's second life:From appetite stimulator to glucose regulator显示文摘Ghrelin,a 28 amino acid peptide hormone produced by the stomach,was the first orexigenic hormone to be discovered from the periphery.The octanoyl modification at Ser3,mediated by ghrelin O-acyltransferase(GOAT),is essential for ghrelin's biological activity.Ghrelin stimulates food intake through binding to its receptor(GRLN-R) on neurons in the arcuate nucleus of the hypothalamus.Ghrelin is widely expressed throughout the body;accordingly,it is implicated in several other physiological functions,which include growth hormone release,gastric emptying,and body weight regulation.Ghrelin and GRLN-R expression are also found in the pancreas,suggesting a local physiological role.Accordingly,several recent studies now point towards an important role for ghrelin and its receptor in the regulation of blood glucose homeostasis,which is the main focus of this review.Several mechanisms of this regulation by ghrelin have been proposed,and one possibility is through the regulation of insulin secretion.Despite some controversy,most studies suggest that ghrelin exerts an inhibitory effect on insulin secretion,resulting in increased circulating glucose levels.Ghrelin may thus be a diabetogenic factor.Obesity-related type2 diabetes has become an increasingly important health problem,almost reaching epidemic proportions in the world;therefore,antagonists of the ghrelin-GOAT signaling pathway,which will tackle both energy-and glucose homeostasis,may be considered as promising new therapies for this disease. | Pieter-Jan Verhulst Inge Depoortere | 2012 | World Journal of Gastroenterology2012，18，25： | 10 |
| 11 | SOME DIAGNOSTICS IN NONLINEAR REPRODUCTIVE DISPERSION MODELS显示文摘This article discusses the problem of the detection of influential cases in nonlinear reproductive dispersion models (NRDM). A diagnostic based on case\|deletion approach in estimating equations is proposed. The relationships between the generalized leverage defined by Wei et al. in 1998, statistical curvature, and the local influence of the response vector perturbations are investigated in NRDM. Two numerical examples are given to illustrate the results. | Tang Niansheng 1,2 \ Wei Bocheng 1\ Wang Xueren 21 Dept. ofAppl.Math., SoutheastUniv.,Nanjing 210096.2 Adult Education College,Yunnan Univ.,Kunm ing 650091. | 2000 | Applied Mathematics(A Journal of Chinese Universities)2000，15，1： | 9 |
| 12 | τ蛋白磷酸化位点与其促微管组装及与微管结合活性的体外分析显示文摘目的 探讨 Alzheimer病 (AD) τ蛋白异常磷酸化位点与其促微管组装及与微管结合活性抑制的关系。方法 采用超速离心和离子交换柱层析法分离制备重组 τ蛋白及 τ蛋白的体外磷酸化 ,以 Fe Cl3亲和柱分离纯化 32 Pτ肽 ,手工 Edman降解和氨基酸自动分析仪鉴定 32 Pτ肽磷酸氨基酸位点。结果 (1)酪蛋白激酶 - 1(CK- 1)、c AMP依赖性蛋白激酶 (PKA )和糖元合成酶激酶 - 3(GSK- 3)的磷酸化作用可不同程度地抑制τ蛋白的功能 ,CK - 1或 PKA的预处理可明显增强 GSK - 3对τ促微管组装活性的抑制 ,其中 PKA加 GSK- 3的抑制作用最强。 (2 )单纯GSK- 3磷酸化τ蛋白的位点为 :苏氨酸 (Thr) - 181,丝氨酸 (Ser) - 184,Ser- 2 6 2 ,Ser- 35 6和 Ser- 40 0 ,而 GSK- 3对PKA预处理τ蛋白的磷酸化位点为 :Ser- 195 ,Ser- 198,Ser- 199,Ser- 2 0 2 ,Ser- 2 35 ,Ser- 2 6 2 ,Ser- 35 6 ,Ser- 40 4,Thr-2 0 5和 Thr- 2 31。其中 Ser- 198,Ser- 199,Ser- 2 0 2 ,Thr- 2 0 5 ,Thr- 2 31,Ser- 2 35 ,Ser- 2 6 2 ,Ser- 40 0和 Ser- 40 4为 AD患者τ蛋白异常磷酸化位点。此外 ,Ser- 2 6 2磷酸化仅轻度抑制τ蛋白活性 ,而 Ser- 198,Ser- 199,Ser- 2 0 2 ,Thr- 2 31,Ser- 2 35 ,Ser- 40 0和 Ser- 40 | 王建枝 魏泽兰 王群 Inge Grundke-Iqbal KhalidIqbal | 2000 | 中国医学科学院学报2000，22，2： | 9 |
| 13 | 大学生应对气候变化的伦理取向探讨显示文摘近年来,气候变化作为热点议题不断升温。大量的文献对气候变化形成的原因、气候变化所可能带来的危害作出了多方面的分析(如OECD 1996,编委会2007,Stern 2007.UNDP2007),也出现了大量针对适应气候变化所产生成本和效益的有价值研究(如潘家华等2007,stern 2007)。然而,应对气候变化不仅是一个环境问题和经济问题, | 罗静 潘家华 李恩平 Geir Inge Orderud | 2009 | 科学对社会的影响2009，53，3： | 8 |
| 14 | 地方性环境保护政策的未预后果:以天津水源保护措施为例显示文摘二十世纪九十年代起,为保护天津市饮用水源地,一系列地方性环保政策和措施被制定和实施。这些措施普遍具有'剥离性'特质,并带来一系列后果:居民和水库的联系被割裂;当地居民归属感被削弱;政府介入传统的居民与环境的互动过程等。同时,传统农业的边缘化地位使得农业生产方式向粗放式发展。周边村民在与环境的互动中成为'受害的作恶者'和'沉默的智者'。该区域的环境保护处于一个传统约束机制瓦解而新型约束机制缺席的断裂阶段,这也导致环保措施的实际后果偏离最初的预计。 | 谭宏泽 Geir Inge Orderud | 2017 | 广东社会科学2017，，1： | 8 |
| 15 | Anterograde and Retrograde Regulation of Nuclear Genes Encoding Mitochondrial Proteins during Growth, Development, and Stress显示文摘在植物的 Mitochondrial 生物的续生说和功能要求编码 mitochondrial 蛋白质(NGEMP ) 的超过 1000 原子基因的表示。这些基因的表达式被织物特定、发展、内部、外部的刺激 thatresult 在涉及的一个动态细胞器调整新陈代谢并且许多发信号的进程。尽管线粒体的新陈代谢的 andbiosynthetic 机械很好相对被理解,调整这些过程和 varioussignaling 小径的因素仅仅在分子的水平正在识别包含。anterograde 的分子的部件(对 mitochondrial 原子) 并且后退(mitochondrial 到原子) 与叶绿体调整 NGEMPsinteract 的表示的发信号的小径 -- ,生长 -- ,并且在在许多层次的房间的发信号压力的小径,与在这些信号的传播和执行的普通 componentsinvolved。这作为在 thecell,不是仅仅在 mitochondrial 功能本身的直接发信号,而且在察觉到或集成许多 otherinternal 和外部信号发信号的重要中心放线粒体。这与精力新陈代谢和压力回答集成并且优化生长,哪个在光合、非光合的 cells.Key 词的 isrequired: | Sophia Ng Inge De Clercqc Olivier Van Akena Simon R. Lawd Aneta Ivanovad Patrick Willems Estelle Giraud Frank Van Breusegem James Wheland | 2014 | Molecular Plant2014，7，7： | 8 |
| 16 | Structure and evolution of the continental margin off Norway and the Barents Sea显示文摘 | Jan Inge Faleide Filippos Tsikalas AsbjФrn Breivik Rolf Mjelde Oliver Ritzmann Фyvind Engen Jonas Wilson Olav Eldholm | 2008 | Episodes2008，31，1： | 8 |
| 17 | Developmental Lead Exposure Alters the Distribution of Protein Kinase C Activity in the Rat Hippocampus显示文摘Chronic low-level lead (Pb) exposure in children is known to cause a deficit in learning and memory. In vitro studies have demonstrated that Pb altered protein kinase C (PKC) activityt Especially, hippocampal PKC has been correlated with performance in several learning tasks. The effects of Pb exposure on hippocampal PKC were investigated during development at various postnatal ages: postnatal day (PN) 7, 14, 28, and 56. Two-tenth % Pb acetate was administered to pregnant and lactating dams and then administered to weanling rats in drinking water. PKC activity was measured in both membrane and cytosolic fractions from the hippocampi of the controls and Pb-exposed animals. Pb-induced increase in PKC activity in the cytosolic fraction was obsereved in the PN56 rats. In contrast, PKC activity was decreased by Pb at PN7 in the membrane fraction. Furthermore, a significant decrease in the ratio of membrane to cytosolic PKC activity which is representative of PKC distribution was observed in the PN28 and PN56 Pb-exposed rats relative to the same-age controls. This study indicates that chronic Pb exposure during development influences hippocampal PKC activity and distribution. These changes may be involved in the subclinical neurotoxicity of chronic Pb exposure in young children. | HWEI-HSIEN CHEN TANGENG MA ARTHUR S. HUME AND ING K. HO(Deportment of Pharmacology and Toxicology, University ofMississippi Medical Center, 2500 North State Street,Jackson, MS 39216, USA) | 1998 | Biomedical and Environmental Sciences1998，11，1： | 7 |
| 18 | Effect of S1P5 on proliferation and migration of human esophageal cancer cells显示文摘AIM:To investigate the sphingosine 1phosphate (S1P) receptor expression profile in human esophageal cancer cells and the effects of S1P5 on proliferation and migration of human esophageal cancer cells. METHODS: S1P receptor expression profile in human esophageal squamous cell carcinoma cell line Eca109 was detected by semiquantitative reverse trans cription polymerase chain reaction. Eca109 cells were stably transfected with S1P5EGFP or controlEGFP constructs. The relation between the responses of cell proliferationand migration to S1P and S1P5 expres sion was evaluated by 3(4,5dimethylthiazol2yl)2,5diphenyl tetrazolium bromide and migration assay, respectively. RESULTS: Both normal human esophageal mucosal epithelium and Eca109 cells expressed S1P1, S1P2, S1P3 and S1P5, respectively. Esophageal mucosal epithelium expressed S1P5 at a higher level than Eca109 cell line. S1P5 overexpressing Eca109 cells displayed spindle cell morphology with elongated and extended filopodialike projections. The proliferation response of S1P5transfected Eca109 cells was lower than that of control vectortransfected cells with or without S1P stimulation (P < 0.05 or 0.01). S1P significantly inhibited the migration of S1P5transfected Eca109 cells (P < 0.001). However, without S1P in transwell lower chamber, the number of migrated S1P5transfected Eca109 cells was greater than that of control vectortransfected Eca109 cells (P < 0.001).CONCLUSION: S1P binding to S1P5 inhibits the proliferation and migration of S1P5transfected Eca109 cells. Esophageal cancer cells may downregulate the expression of S1P5 to escape the inhibitory effect. | Hu, Wei-Min Li, Li Ing, Bao-Qian Zhao, Yong-Sheng Wang, Chao-Li Feng, Li Xie, Yong-En | 2010 | World Journal of Gastroenterology2010，16，15： | 7 |
| 19 | Hemodynamic Effects of Inhaled Nitric Oxide in Patients with Pulmonary Hypertension.显示文摘Twelve patients with pulmonary hypertension (primary pulmonary hypertension in 3 cases, secondary to recurrent pulmonary embolism in 4 cases, chronic obstructive pulmonary disease in 2 cases and complicated with congeni- | Zhao Yiju et al. Cardiovascular Institute and Fu Wai Hospital. CAMS Beij- ing 100037. National Medical Journal of China. | 1995 | Chinese Medical Journal1995，，9： | 7 |
| 20 | Influence of grain size on strength of polymineralic crystalline rock: New insights from DEM grain-based modeling显示文摘Grain size effect on rock strength is a topic of great interest in geotechnical engineering.A consensus obtained from earlier laboratory tests is that rock strength generally decreases with the increase of grain size for both silicate and carbonate rocks;however,some recent numerical results conflict with such laboratory test results.To address this intriguing issue,the effect of grain size on strength of polymineralic crystalline rock with low porosity is investigated numerically using the grain-based modeling(GBM)approach in discrete element method(DEM)by interpreting micro-cracking process in response to loading.In agreement with some previous DEM simulation results,the simulated rock strength is found to increase with increasing grain size for both homogeneous and heterogeneous models,even when the number of assembled disks in one mineral grain changes.The mechanism of strength increase with increasing grain size is mainly associated with the number of assembled smooth-joint contacts along grain interfaces and the generation of grain boundary cracks in response to loading.The grain interfaces significantly weaken the integrity of the rock model,which is similar to effects of inherent defects in real rock.As the grain size increases,fewer grain interfaces are built in the model and the rock strength becomes much higher.Hence,by solely changing the mineral grain size in a model,the mechanism of grain size effect as observed in laboratory tests cannot be replicated.To address this issue,a method of degradation of grain boundary strength parameters is used to mimic the possible mechanism of grain size effect.The simulated strength using the method becomes comparable with those obtained from laboratory tests when the heterogeneity in the rock is considered.Degradation of grain boundary parameters with increasing grain size provides a plausible explanation for the grain size effect on rock strength. | Jun Peng Louis Ngai Yuen Wong Cee Ing Teh | 2021 | Journal of Rock Mechanics and Geotechnical Engineering2021，13，4： | 6 |
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