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Activity-dependent mechanisms of neuroprotection:promising avenues against dementia
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作者 Davide Tampellini 《Neural Regeneration Research》 SCIE CAS CSCD 2024年第7期1409-1410,共2页
The study of the brain and its complex functions is highly fascinating and,at the same time,extremely important.Indeed,furthering our understanding of the biology of neurons and synapses is a prerequisite to uncover t... The study of the brain and its complex functions is highly fascinating and,at the same time,extremely important.Indeed,furthering our understanding of the biology of neurons and synapses is a prerequisite to uncover the mechanisms involved in memory formation and the coordination of movement as well as their alterations occurring in several neurological disorders. 展开更多
关键词 alterations mechanismS NEUROLOGICAL
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Characteristics of Element Migration in the Process of Wall-Rock Alteration in the Shibangou Gold Deposit,Western Henan 被引量:2
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作者 WEI Junhao LI Jianwei YUAN Yanbin 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 1999年第2期201-207,共7页
Abstract The Shibangou gold deposit in western Henan is associated with irregular quartz veinlets occurring in altered shear zones dissecting a dioritic intrusion. The altered shear zones are characterized by silicifi... Abstract The Shibangou gold deposit in western Henan is associated with irregular quartz veinlets occurring in altered shear zones dissecting a dioritic intrusion. The altered shear zones are characterized by silicification, pyritization, sericilization, chloritization and K-feldspar alteration. Zoning of altered rocks adjacent to the Au-bearing quartz veins is obviously exhibited. Fine-grained sulphides and quartz veinlets of different ages and small-scale fissures are widely distributed in the central part of the altered zones. Major mineralization types in this gold deposit are Au-bearing quartz veinlets and altered rocks in the shear zones. Samples were collected from drilling cores according to the alteration zoning and mineralization type and all samples were analyzed for major and trace elements. Mass balance, volume change (fv=97.3–71.9%) and major element variation sequences are studied in terms of major elements. The changes of mobile components (SiO2, K2O, Fe2O3) and CaO) and immobile component (Al2O3) in the wall-rock alteration are discussed. The gold mineralization is associated with the enrichment of As, Ag, Hg and Pb and depletion of Cu and Zn. The study of compositional variation of altered rocks proves to be a very efficient method for defining the extent of wall-rock alteration, fluid activity and mineralization and enrichment. 展开更多
关键词 wall-rock alteration element migration mass balance Shibangou gold deposit
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Combined OVX and Concurrent Mechanical Disuse Induced Osteocytes Morphological Alteration, and Mitigation by Mechanobiology and Sclerostin Antibody
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作者 Tony Zhang Yixian Qin 《医用生物力学》 EI CAS CSCD 北大核心 2019年第A01期29-29,共1页
Osteoporosis and osteopenia are major health issues that mainly affect elderly people,women after menopause and immobilized patients.Our previous studies have proved that sclerostin antibody(Scl-Ab)can dramatically en... Osteoporosis and osteopenia are major health issues that mainly affect elderly people,women after menopause and immobilized patients.Our previous studies have proved that sclerostin antibody(Scl-Ab)can dramatically enhance bone formation and reduce bone resorption in a severe osteoporosis rat model with the combination of ovariectomy(OVX)and hindlimb immobilization(HLS).However,the mechanism in the cellular level is unclear.The objective of this study is to assess the effect of Scl-Ab on osteocytic morphology change in a combined OVX and HLS rat model via quantification of long-and short-axis and the ratio and osteocyte volume in midshaft cortical bone.Four-month-old virgin female SD rats were divided into 7 groups(n=11 per group):Sham+Veh,Sham+HLS+Veh,Sham+HLS+Scl-Ab,OVX+Veh,OVX+Scl-Ab,OVX+HLS+Veh,OVX+HLS+Scl-Ab.HLS was performed 2 weeks after sham or OVX surgery;and treatment was initiated at the time of HLS.Scl-Ab(25 mg/kg)or vehicle was subcutaneously injected twice per week for 5 weeks.Femurs were harvested at the end of study and embedded in PMMA and polished for SEM imaging.Cortical bone mid shaft osteocyte number per bone area was quantified under 1K magnification;the ratios between long axis and short axis of osteocytes were quantified under 2K magnification;osteocyte dendrite number and surface area were quantified under 5K magnification.Osteocyte dendrites width was quantified using 10K magnification.All the quantification was done by ImageJ.We have reported that multiple morphological and structural changes in osteocytes,including a decreased osteocyte density and reduced osteocyte dendrite number in HLS,OVX or the combination group and Scl-Ab’s ability to abolish these unfavorable alterations.We continued our SEM analysis on osteocytes and discovered that the oval shape of osteocyte under HLS,OVX or HLS+OVX has been distorted toward a spindle-like shape,with relatively longer long axis and shorter short axis,assuming osteocyte has a perfect spheroid shape.The ratio between long-and short-axis showed an increased trend in OVX and HLS condition,but Scl-Ab inhibited these increases(P<0.001,P<0.01,respectively).The volume decreased in HLS,OVX group,but Scl-Ab maintained osteocytes’volume in HLS condition(P<0.001).It indicates that cortical bone responds to HLS and/or OVX and Scl-Ab treatment via multiple cellular mechanisms,including density of osteocyte,dendrite number and osteocyte shape.The change of osteocyte shape may imply an altered cytoskeleton system within osteocyte and a subsequent disruption of mechanosensing ability for osteocyte,which lead to bone loss macroscopically.These data suggest Scl-Ab’s therapeutic potential could be related with its ability to maintain osteocyte’s morphologic and structural changes induced by OVX,HLS or both. 展开更多
关键词 OVX HLS Mitigation by mechanOBIOLOGY SCLEROSTIN Antibody SCLEROSTIN Combined OVX and Concurrent mechanical DISUSE Induced OSTEOCYTES Morphological alteration
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Accumulation Mechanisms and Evolution History of the Giant Puguang Gas Field,Sichuan Basin,China 被引量:4
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作者 HAO Fang GUO Tonglou +6 位作者 DU Chunguo ZOU Huayao CAI Xunyu ZHU Yangming LI Pingping WANG Chunwu ZHANG Yuanchun 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2009年第1期136-145,共10页
Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field, the largest gas field so far found in marine carbonates in China, confirming that the Puguang gas field evolved from a paleo-oil ... Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field, the largest gas field so far found in marine carbonates in China, confirming that the Puguang gas field evolved from a paleo-oil reservoir. The fluid conduit system at the time of intensive oil accumulation in the field was reconstructed, and petroleum migration pathways were modeled using a 3-D model and traced by geochemical parameters. The forward modeling and inversion tracing coincided with each other and both indicated that oils accumulated in the Puguang-Dongyuezhai structure originated from a generative kitchen to the northwest of the Puguang gas field. The deposition of organic-rich Upper Permian source rocks dominated by sapropelic organic matter in the Northeast Sichuan Basin, the development of fluid conduit system that was vertically near-source rock and laterally near-generative kitchen, and the focusing of oils originated from a large area of the generative kitchen, were the three requirements for the formation of the giant paleo-oil reservoir from which the giant Puguang gas field evolved. The Puguang gas field had experienced a three-stage evolution. The post-accumulation processes, especially the organic-inorganic interaction in the hydrocarbon-water-rock system, had not only profoundly altered the composition and characteristics of the petroleum fluids, but also obviously changed the physicochemical conditions in the reservoir and resulted in complicated precipitation and solution of carbonate minerals. 展开更多
关键词 migration pathway accumulation mechanism chemical alteration evolution history Puguang gas field
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Potential mechanisms of non-suicidal self-injury(NSSI)in major depressive disorder:a systematic review 被引量:1
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作者 Baichuan Wu Huifeng Zhang +5 位作者 Jinghong Chen Jiaye Chen Zhifen Liu Yuqi Cheng Tifei Yuan Daihui Peng 《General Psychiatry》 CSCD 2023年第4期220-230,共11页
Background Non-suicidal self-injury(NSSI)is a frequent and prominent phenomenon in major depressive disorder(MDD).Even though its prevalence and risk factors are relatively well understood,the potential mechanisms of ... Background Non-suicidal self-injury(NSSI)is a frequent and prominent phenomenon in major depressive disorder(MDD).Even though its prevalence and risk factors are relatively well understood,the potential mechanisms of NSSI in MDD remain elusive.Aims To review present evidence related to the potential mechanisms of NSSI in MDD.Methods According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines,articles for this systematic review were searched on Medline(through PubMed),Embase(through Elsevier),PsycINFO(through OVID)and Web of Science databases for English articles,as well as China National Knowledge Infrastructure(CNKI),SinoMed,Wanfang Data,and the Chongqing VIP Chinese Science and Technology Periodical(VIP)Databases for Chinese articles published from the date of inception to 2 August 2022.Two researchers(BW,HZ)independently screened studies based on inclusion and exclusion criteria and assessed their quality.Results A total of 25157 studies were searched.Only 25 of them were ultimately included,containing 3336 subjects(1535 patients with MDD and NSSI,1403 patients with MDD without NSSI and 398 HCs).Included studies were divided into 6 categories:psychosocial factors(11 studies),neuroimaging(8 studies),stress and hypothalamic-pituitary-adrenal(HPA)axis(2 studies),pain perception(1 study),electroencephalogram(EEG)(2 studies)and epigenetics(1 study).Conclusions This systematic review indicates that patients with MDD and NSSI might have specific psychosocial factors,aberrant brain functions and neurochemical metabolisms,HPA axis dysfunctions,abnormal pain perceptions and epigenetic alterations. 展开更多
关键词 METABOLISM alterations mechanismS
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Cyclic mechanical stretch regulates MMPs and TIMPs expression in corneal fibroblasts
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作者 Chengxing Liu Pengfei Feng +2 位作者 Xiaona Li Xiaojun Wang Weiyi Chen 《医用生物力学》 EI CAS CSCD 北大核心 2013年第S1期7-8,共2页
Laser in situ keratomileusis(LASIK)is a relatively new ophthalmic procedure in refractive surgery.It involves the use of a microkeratome to create a thin corneal flap followed by excimer laser ablation of the corneal ... Laser in situ keratomileusis(LASIK)is a relatively new ophthalmic procedure in refractive surgery.It involves the use of a microkeratome to create a thin corneal flap followed by excimer laser ablation of the corneal stroma and repositioning of the flap.However,complications are bound to occur when a surgical procedure is performed with increasing frequency.In some cases,serious complications such as keratectasia occurred.Risk factors for corneal keratectasia include a thin cornea at baseline,thick corneal flap,excessive ablation,irregular corneal thickness,diverse ablation rates,preexisting keratoconus or form fruste keratoconus,and high intraocular pressure(IOP)~[1].It is evident from incisional refractive surgery that the cornea is not mechanically inert.The mechanical environment of the central corneal tissue is also altered un- 展开更多
关键词 CORNEAL KERATOMILEUSIS ablation INTRAOCULAR STRETCH alterED refractive diverse TIMPS mechanically
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Surface Analysis Correlated with Structural and Mechanical Properties of Laser Irradiated Brass
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作者 Shahbaz Ahmad Shazia Bashir +2 位作者 Daniel Yousaf Nisar Ali Tousif Hussain 《Materials Sciences and Applications》 2015年第1期23-32,共10页
Brass targets were irradiated with various laser pulses of Excimer laser ranging from 1200 to 3000 for constant fluence of 3.4 J/cm2 in oxygen atmosphere (100 Torr). The surface morphology and crystallographic analyse... Brass targets were irradiated with various laser pulses of Excimer laser ranging from 1200 to 3000 for constant fluence of 3.4 J/cm2 in oxygen atmosphere (100 Torr). The surface morphology and crystallographic analyses were performed by using Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD). SEM analysis reveals the formation of laser-induced micro-sized cavities, bumps, cones and wave-like ridges with non-uniform shape and density distribution. These features are formed for all number of pulses;however with increasing number of pulses from 1200 to 2400, the density of cavities decreases whereas, the wave-like ridges become more pronounced and bump-formation is vanished. For maximum number of 3000 shots, the appearance of cones and wave-like ridges becomes diffusive, whereas the density and size of cavities increase again. XRD analysis demonstrates that no new phases are formed in irradiated brass. However, the change in peak intensity along with lower and higher angle shifting is observed which is attributed to generation of laser induced stresses. The Yield Stress (YS), Ultimate Tensile Strength (UTS) as well as Microhardness increase monotonically with increasing number of laser pulses. 展开更多
关键词 LASER PULSES Surface Morphology mechanICAL Properties Crystallographic alteration
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Petrographic Studies on Hydrothermally Altered Conglomerates at Naer Creek, Sichuan Province, China
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作者 Liu Li and Yu Junmin (Changchun University of Science and Technology, Changchun 130026,China) 《Global Geology》 1999年第1期1-6,共6页
Based on analysing the wall rock alterations and related rocks which were used as a hint for mineral deposits and as a basis of mechanism research of fluid rock interaction, according to the results of petrographic an... Based on analysing the wall rock alterations and related rocks which were used as a hint for mineral deposits and as a basis of mechanism research of fluid rock interaction, according to the results of petrographic analysis, the authors of this paper consider that the hydrothermally altered conglomerates have the following features. First, the conglomerates studied can be divided into two groups: Group A consists mainly of the gravels of granite and basalt; Group B is mainly composed of the gravels of basalt, limestone, mudstone and granite. Second, three distinct hydrothermal alterations or diagenesis were distinguished in Group A, that is, pre depositional hydrothermal alteration of the volcanic gravels (saussuritzation chloritization, epidotization chloritization, albitization and sericitization), mechanical diagenesis and post diagenetic hydrothermal alteration (epidote chlorite and prehnite calcite association). Third, the Group B is subjected mainly to pre depositional hydrothermal alteration; the alteration types are the same as of Type A. Last, the origin of the post diagenetic hydrothermal alteration of Group A is presumed to be related to the ascending of thermal water along the Naer Creek fault. 展开更多
关键词 hydrothermally alterED CONGLOMERATES Naer CREEK wall-rock interation FLUID ROCK interation
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矿田构造岩相学填图理论及应用 被引量:1
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作者 方维萱 郭玉乾 +2 位作者 李天成 贾润幸 马振飞 《地质力学学报》 CSCD 北大核心 2024年第1期88-106,共19页
开展成矿蚀变−构造岩相解析建相和建模预测研究已成为矿田构造与找矿预测的创新方向之一。文章对国内外8类重要的成矿蚀变−构造岩相模型和形成机制进行论述总结,南美洲智利科皮亚波地区IOCG型矿田受到主岛弧带−弧相关盆地及岩浆叠加−盆... 开展成矿蚀变−构造岩相解析建相和建模预测研究已成为矿田构造与找矿预测的创新方向之一。文章对国内外8类重要的成矿蚀变−构造岩相模型和形成机制进行论述总结,南美洲智利科皮亚波地区IOCG型矿田受到主岛弧带−弧相关盆地及岩浆叠加−盆地变形样式的复合控制,而中国云南东川沉积岩型铜矿床(SSC型)+IOCG型铁铜矿田受陆缘裂谷盆地、盆地变形构造样式和岩浆叠加侵入构造系统的复合控制。中国内蒙古甲−查浅成低温热液型银铅锌矿田受火山洼地、火山穹隆构造、火山岩岩相类型和火山热液隐爆角砾岩的复合控制,而深成岩浆弧控制了蒙古国南戈壁斑岩型金铜钼−浅成低温热液金银矿田;中国秦岭热水沉积型(SEDEX)银铜铅锌−菱铁矿−重晶石矿田受到陆缘拉分盆地内三级热水沉积盆地、同生断裂带和热水沉积岩相的控制。大陆造山带内不同层次的脆韧性剪切带,控制了金矿田和金钼多金属矿田定位。在新疆塔西盆−山−原镶嵌区盆地系统内,侏罗系煤系烃矿源岩是金属矿田和天然气气田的成矿成藏物质供给源区;乌拉根砂砾岩型天青石−铅锌矿田受到山前挤压—伸展转换盆地、气成热流柱构造和山前冲断褶皱带的复合控制;萨热克铜多金属矿田赋存于旱地扇杂砾岩,受到对冲式厚皮型逆冲推覆断裂带和幔源热流柱带的复合控制。其中在矿集区−矿田尺度上,电气石热流柱构造、岩浆气囊构造、复合岩溶构造岩相等是成矿蚀变−构造岩相的3种新类型;在归纳前期对矿田构造岩相、矿田构造古地理单元和典型矿田构造岩相形成机制研究基础上,文章提出了矿田成矿蚀变−构造岩相类型的新划分方法和划分原则方案,并划分确定了12种变形构造岩相类型。研究成果为矿田构造研究和找矿预测提供了新理论和新方法支撑。 展开更多
关键词 矿田构造 矿田岩相学 成矿蚀变−构造岩相 成矿系统 构造岩相模型 形成机制
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Tumor initiation and early tumorigenesis:molecular mechanisms and interventional targets 被引量:2
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作者 Shaosen Zhang Xinyi Xiao +5 位作者 Yonglin Yi Xinyu Wang Lingxuan Zhu Yanrong Shen Dongxin Lin Chen Wu 《Signal Transduction and Targeted Therapy》 SCIE CSCD 2024年第7期2900-2935,共36页
Tumorigenesis is a multistep process,with oncogenic mutations in a normal cell conferring clonal advantage as the initial event.However,despite pervasive somatic mutations and clonal expansion in normal tissues,their ... Tumorigenesis is a multistep process,with oncogenic mutations in a normal cell conferring clonal advantage as the initial event.However,despite pervasive somatic mutations and clonal expansion in normal tissues,their transformation into cancer remains a rare event,indicating the presence of additional driver events for progression to an irreversible,highly heterogeneous,and invasive lesion.Recently,researchers are emphasizing the mechanisms of environmental tumor risk factors and epigenetic alterations that are profoundly influencing early clonal expansion and malignant evolution,independently of inducing mutations.Additionally,clonal evolution in tumorigenesis reflects a multifaceted interplay between cell-intrinsic identities and various cell-extrinsic factors that exert selective pressures to either restrain uncontrolled proliferation or allow specific clones to progress into tumors.However,the mechanisms by which driver events induce both intrinsic cellular competency and remodel environmental stress to facilitate malignant transformation are not fully understood.In this review,we summarize the genetic,epigenetic,and external driver events,and their effects on the co-evolution of the transformed cells and their ecosystem during tumor initiation and early malignant evolution.A deeper understanding of the earliest molecular events holds promise for translational applications,predicting individuals at high-risk of tumor and developing strategies to intercept malignant transformation. 展开更多
关键词 alterations mechanismS restrain
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磺胺甲噁唑对绿藻的生长抑制作用及其潜在毒理学机制
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作者 熊倩 田斐 +3 位作者 刘芳 张林宝 张喆 陈海刚 《生态毒理学报》 CAS CSCD 北大核心 2024年第3期342-352,共11页
磺胺甲噁唑(sulfamethoxazole,SMX)常用于动物和人类疾病治疗,导致其在多种环境介质中广泛检出。绿藻作为水生生态系统中的初级生产者,因其灵敏度较高而常用作毒性评估的模式生物。然而,目前关于SMX对绿藻的毒性研究普遍以传统毒性测试... 磺胺甲噁唑(sulfamethoxazole,SMX)常用于动物和人类疾病治疗,导致其在多种环境介质中广泛检出。绿藻作为水生生态系统中的初级生产者,因其灵敏度较高而常用作毒性评估的模式生物。然而,目前关于SMX对绿藻的毒性研究普遍以传统毒性测试为主,缺乏对其生物大分子水平毒性效应的深入认识。本研究结合藻类生长抑制实验和傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)分析深入探究SMX对绿藻生物大分子水平的毒性作用机制。藻类生长抑制实验结果表明,SMX对3株绿藻的EC 50(置信度95%)依次为斜生栅藻(8.53 mg·L^(-1))<四尾栅藻(14.30 mg·L^(-1))<尖细栅藻(90.45 mg·L^(-1))。基于FTIR分析发现,SMX暴露引起绿藻生物大分子发生变化且存在明显的剂量效应关系。脂质水平上,脂质发生过氧化、改变脂肪酸烷基链长度,进而影响细胞膜的流动性和通透性。蛋白质水平上,酰胺Ⅰ和酰胺Ⅱ的变化揭示蛋白质二级结构发生变化。DNA水平上,DNA构型发生变化,由常见的B-DNA型转换为能抵御外界干扰A-DNA型。3株绿藻在生物大分子水平对SMX暴露的响应差异可能与其细胞壁结构组成差异有关。 展开更多
关键词 磺胺甲噁唑 微藻 毒理学机制 傅里叶变换红外光谱 生物大分子变化
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嫦娥五号月壤纳米级单质金属铁的形成及生长规律的原位电镜研究
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作者 李瑞 李阳 姚伟 《空间科学与试验学报》 CSCD 2024年第1期72-77,共6页
纳米级单质金属铁(纳米铁)是无大气保护的地外星体表层长期受太空风化改造的特征产物,是记录月壤形成与演化信息的关键载体,同时也是影响月表反射光谱遥感探测的主要因素。纳米铁的形成机制除了汽化沉积作用之外,近年来在嫦娥五号月壤... 纳米级单质金属铁(纳米铁)是无大气保护的地外星体表层长期受太空风化改造的特征产物,是记录月壤形成与演化信息的关键载体,同时也是影响月表反射光谱遥感探测的主要因素。纳米铁的形成机制除了汽化沉积作用之外,近年来在嫦娥五号月壤中还发现了分解反应和歧化反应成因的纳米铁,但其生长规律和形成条件约束目前尚不清楚。因此,本文采用先进的电镜原位加热技术,选取嫦娥五号月壤中的橄榄石、辉石和陨硫铁等含铁矿物作为研究对象,系统性地模拟月壤中含铁成分的物质在亚固相线条件下(湿度不高于800℃)的热改造过程,记录纳米铁在各矿物中的形成方式及生长规律。通过统计纳米铁的粒径尺寸,探讨不同矿物相中纳米铁的粒径分布,为遥感探测光谱数据的解译提供有价值的参考。 展开更多
关键词 纳米级单质金属铁 热改造过程 形成机制 生长规律
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某抽水蓄能电站蚀变花岗岩的物理力学性质及分级研究 被引量:1
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作者 李正顺 马加顺 +1 位作者 刘卫今 邓黎水 《红水河》 2024年第1期106-111,共6页
笔者以某抽水蓄能电站蚀变花岗岩为例,研究不同蚀变程度对花岗岩物理力学性质的影响。通过统计分析蚀变花岗岩物理力学性质试验结果,参考岩石坚硬程度分级,并结合工程需要,提出蚀变花岗岩的分级标准,并建立蚀变等级与蚀变花岗岩物理力... 笔者以某抽水蓄能电站蚀变花岗岩为例,研究不同蚀变程度对花岗岩物理力学性质的影响。通过统计分析蚀变花岗岩物理力学性质试验结果,参考岩石坚硬程度分级,并结合工程需要,提出蚀变花岗岩的分级标准,并建立蚀变等级与蚀变花岗岩物理力学性质之间的联系。结果表明:蚀变越严重,物理力学性质越劣化;轻微蚀变花岗岩可以有条件地使用,中等蚀变花岗岩可以限制使用,而强蚀变花岗岩使用则需要专门研究。研究结果为其他类似工程蚀变花岗岩分级和应用提供参考。 展开更多
关键词 蚀变花岗岩 蚀变花岗岩分级 物理力学性质 抽水蓄能电站
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Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit(>100 t Au)in Northern Hebei Province,China:A review
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作者 Shi-min Zhen Da-zhao Wang +2 位作者 Zhong-jian Zha Hai-jun Bai Jiang Wang 《China Geology》 CAS CSCD 2024年第3期533-550,共18页
The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization origi... The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization originally occurred at 400-380 Ma,simultaneous with emplacement of the Shuiquangou alkaline complex,and was overprinted by the hydrothermal activity in the Yanshanian.Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex.Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity,while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3.These systematic changes are closely related to the processes of mineral precipitation and fluid evolution.Sulfide precipitation from Stage Ⅰ to Stage Ⅱ was triggered by fluid boiling,which leads to the precipitation of Pb-Bi-Te,due to decrement of sulfur fugacity.Condensation of gas phase containing high concentration of H_2Te leads to precipitation of Te-Au-Ag minerals and native tellurium.Based on these hypotheses,this paper present a polyphase metallogenic model as follow.During the Devonian,fluids were released from alkaline magmas,which carried ore-forming materials form the surrounding rocks and precipitate the early ores.During the Jurassic-Cretaceous,fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite,which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks,and finally formed the Dongping gold deposit. 展开更多
关键词 Mineralization and alteration Alkaline intrusion Au deposit Physicochemical conditions Metallogenic model Oxygen fugacity Sulfur fugacity mechanisms of mineral precipitation Fluid boiling Fluorine-enriched fluid Dongping gold deposit North China Craton Mineral exploration engineering
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Ecological view of carcinogenesis:Niche-altering(NC3)mechanisms
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作者 Mesut Tez 《Cancer Innovation》 2023年第2期96-98,共3页
Over the last 30 years,a new actor in the area of ecology and evolution has emerged:niche construction theory(NCT).The fundamental premise of NCT is that organisms may actively influence evolutionary processes by modi... Over the last 30 years,a new actor in the area of ecology and evolution has emerged:niche construction theory(NCT).The fundamental premise of NCT is that organisms may actively influence evolutionary processes by modifying their circumstances[1].According to Trappes et al.,[2]the concept of niche construction should only be applied to species that alter their environment,which they believe to be its intuitive scope.They add two more terms to describe the ways that organisms engage with their surroundings and so influence their niches:when organisms choose their environment,this is known as niche choice,and when they adapt their phenotype to fit their environment,this is known as niche conformance.These three concepts are often referred to as niche-altering mechanisms,or NC3 mechanisms:niche conformance,niche construction,and niche choice.This is in line with definitions of mechanisms developed in scientific philosophy[2]. 展开更多
关键词 CANCER NICHE niche altering mechanisms
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大岗山坝区辉绿岩脉蚀变泥化特征及机理研究 被引量:17
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作者 苗朝 沈军辉 +3 位作者 李文纲 李金标 陈卫东 朱柯俊 《工程地质学报》 CSCD 北大核心 2014年第1期130-136,共7页
针对大岗山水电站坝区辉绿岩脉蚀变泥化问题,在系统调研和室内试验基础上探讨了蚀变泥化带的空间分布特征、结构构造、矿物学特征及物理力学性质,并结合区域地质环境分析了蚀变泥化岩形成的主要原因。研究表明,坝区SN向辉绿岩脉劈理化强... 针对大岗山水电站坝区辉绿岩脉蚀变泥化问题,在系统调研和室内试验基础上探讨了蚀变泥化带的空间分布特征、结构构造、矿物学特征及物理力学性质,并结合区域地质环境分析了蚀变泥化岩形成的主要原因。研究表明,坝区SN向辉绿岩脉劈理化强烈,蚀变泥化带发育,且主要集中发育于岩脉与花岗岩接触面及内部强烈劈理化部位。蚀变泥化岩松散易碎,具有塑性高、含水量高、重度低及中等压缩性等物性特征。X衍射和扫描电镜显示蚀变生成了大量的黏土矿物,且具有多孔隙空洞的微观结构特征。富含辉石等暗色矿物和热液交代、多期次的构造挤压错动及浅表生风化作用构成岩脉蚀变泥化的主要原因。 展开更多
关键词 辉绿岩脉 蚀变泥化 蚀变空间特征 蚀变矿物学特征 蚀变机理
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风化、蚀变对花岗斑岩物理力学特性影响分析 被引量:21
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作者 魏伟 沈军辉 +3 位作者 苗朝 刘海 李刚 聂德新 《工程地质学报》 CSCD 北大核心 2012年第4期599-606,共8页
地壳浅表层岩体因受到风化和蚀变作用的影响而导致岩体的孔隙性增加,干密度、抗压强度等物理力学特性降低;孔隙度作为岩体遭受风化和蚀变作用的重要特征,可以反映出风化和蚀变作用对岩体物理力学特性的影响。因此,可以通过对风化和蚀变... 地壳浅表层岩体因受到风化和蚀变作用的影响而导致岩体的孔隙性增加,干密度、抗压强度等物理力学特性降低;孔隙度作为岩体遭受风化和蚀变作用的重要特征,可以反映出风化和蚀变作用对岩体物理力学特性的影响。因此,可以通过对风化和蚀变花岗斑岩物理力学特性的室内试验,建立孔隙度与其他各项物理力学参数的函数关系,以此分析风化和蚀变对花岗斑岩物理力学特性的影响。研究表明:风化和蚀变花岗斑岩的干密度和抗压强度均随孔隙度的增加而减小,且呈乘幂函数关系,相关系数皆大于0.83;吸水率与孔隙度则呈二项式函数关系,且随着孔隙度的增加而增加,其相关系数大于0.90;风化和蚀变都削弱了花岗斑岩的物理力学特性,且随着风化、蚀变程度的增加,花岗斑岩的物理力学特性也呈相应的函数关系降低;陡倾结构面受风化和蚀变的影响较缓倾结构面强。 展开更多
关键词 风化 蚀变 花岗斑岩 物理力学特性
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小秦岭镰子沟金矿床成矿物质来源与成矿过程 被引量:9
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作者 王雷 刘家军 +2 位作者 翟德高 朱文兵 孟旭阳 《地质学报》 EI CAS CSCD 北大核心 2018年第2期341-358,共18页
镰子沟金矿是小秦岭驾鹿金矿田内的一个十分重要的金矿床,主要赋存于太古宇太华群秦仓沟组深变质片麻岩系中。金矿体受构造破碎蚀变带控制,主要呈脉状产出,走向与矿区主要断裂方向(北东向)基本一致。在金矿体两侧由内向外可见以钾长石化... 镰子沟金矿是小秦岭驾鹿金矿田内的一个十分重要的金矿床,主要赋存于太古宇太华群秦仓沟组深变质片麻岩系中。金矿体受构造破碎蚀变带控制,主要呈脉状产出,走向与矿区主要断裂方向(北东向)基本一致。在金矿体两侧由内向外可见以钾长石化+硅化、绢云母化+硅化+黄铁矿化、绿泥石化+绿帘石化为特征的蚀变分带现象。氢氧同位素组成显示成矿流体具有岩浆水和大气降水混合的特征。氦氩同位素结果说明成矿流体具有壳幔混合来源的特点。硫同位素组成表明,矿石硫明显富集轻硫的特征,可能和成矿过程中硫同位素分馏作用有关。矿石铅同位素组成较为稳定,可能来源于太华群围岩。氢、氧、硫、铅同位素均指示了成矿过程中的水-岩反应:成矿流体在早期为富含K+的碱性热液,在上涌过程中与浅部流体逐渐混合,同时与围岩发生充分接触,通过水-岩反应进行物质和能量的交换,在矿体和围岩接触带形成了以钾长石化为特征的蚀变分带。随着成矿作用的进行,含矿热液的物理化学条件不断发生变化,同时金可能以Au(HS)2-和Au(HTe)2-形式在流体中迁移,最终在适宜的条件下沉淀、富集成矿。 展开更多
关键词 小秦岭 镰子沟 蚀变分带 同位素示踪 沉淀机理
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与碳酸岩碱性杂岩体相关的内生稀土矿床成矿作用研究进展 被引量:38
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作者 宋文磊 许成 +4 位作者 王林均 吴敏 曾亮 王丽泽 冯梦 《北京大学学报(自然科学版)》 EI CAS CSCD 北大核心 2013年第4期725-740,共16页
综述与碳酸岩碱性杂岩体相关的内生稀土矿床的基本特征和成矿作用研究进展。根据矿化特征,该类矿床大体可以分为原生岩浆型和热液型,前者稀土矿物是从碳酸岩岩浆中直接结晶出来,矿化主要产于碳酸岩岩体中;后者稀土矿物通常与方解石、萤... 综述与碳酸岩碱性杂岩体相关的内生稀土矿床的基本特征和成矿作用研究进展。根据矿化特征,该类矿床大体可以分为原生岩浆型和热液型,前者稀土矿物是从碳酸岩岩浆中直接结晶出来,矿化主要产于碳酸岩岩体中;后者稀土矿物通常与方解石、萤石、重晶石、石英等矿物共生形成脉体,穿插于碳酸岩杂岩体及围岩中,或作为裂隙或空洞充填物,或呈细粒多晶集合体叠加在碳酸岩中早期形成的矿物之上。以往的研究对于稀土富集成矿的主要机制是碳酸岩和硅酸岩岩浆的液态不混溶作用或碳酸岩岩浆中碳酸盐矿物的分离结晶作用,还是岩浆期后热液蚀变或不混溶的碳酸岩质流体的萃取作用,存在很大的争议;同时,与稀土成矿相关的碳酸盐体系选择性地富集轻稀土,该类矿床中很少见到重稀土矿物,亦是有待解决的问题。因此,加强稀土元素在富挥发份的碳酸岩熔体和碱性硅酸岩熔体或流体之间,以及碳酸盐矿物及共沉淀相与碳酸岩熔体之间分配行为的高温高压实验研究,将是揭示该类稀土矿床成因的关键。 展开更多
关键词 碳酸岩碱性杂岩体 内生稀土矿床 稀土富集机制 不混溶 分离结晶 热液蚀变
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沙子江铀矿外围地化特征、元素迁移及铀成矿机理 被引量:13
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作者 王正庆 范洪海 +5 位作者 陈东欢 郑可志 罗桥花 刘军港 王凤岗 王勇剑 《高校地质学报》 CAS CSCD 北大核心 2018年第2期185-199,共15页
沙子江矿床外围某钻孔不同矿化蚀变位置具有U含量与SiO_2、CaO、Fe_2O_3、LOI、HREE含量正相关、Na均消失殆尽、稀土和微量元素配分型式相似、LREE呈较富集的右倾特征。与新鲜围岩相比,蚀变围岩Sb、U明显增高,Ni、W略有增加;与新鲜围岩... 沙子江矿床外围某钻孔不同矿化蚀变位置具有U含量与SiO_2、CaO、Fe_2O_3、LOI、HREE含量正相关、Na均消失殆尽、稀土和微量元素配分型式相似、LREE呈较富集的右倾特征。与新鲜围岩相比,蚀变围岩Sb、U明显增高,Ni、W略有增加;与新鲜围岩和蚀变围岩二者相比,碎裂花岗岩(矿石)中Cd、Sb明显增高,W、Ni、Pb略有增加,Be、Bi明显减少;相对于新鲜围岩,碎裂花岗岩(矿石)和蚀变围岩分别表现出Sb、U和Sb、Cd、U明显增高,共同表现出W、Ni略有增加的特征。矿化蚀变带元素迁移研究表明,矿化蚀变带样品Sb、LOI、CaO、Ni、Cu、In、Sr均迁入,Na2O、FeO、Be、Cs、Th、Nb均迁出,迁入率最大的组分均为Sb,迁出率最大的组分均为Na_2O。地球化学特征及元素迁移规律指示花岗质围岩是重要的U源及组分来源,成矿流体呈碱性,氧逸度较高。 展开更多
关键词 沙子江铀矿床 矿化蚀变 地球化学 成矿机理
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