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Preparation of porous semi-IPN temperature-sensitive hydrogel-supported nZVI and its application in the reduction of nitrophenol
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作者 Lixia Li Ruiwei Wang +3 位作者 Xiaodong Xing Wenqiang Qu Shutong Chen Yunlong Zhang 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第8期93-102,共10页
Nanoscale zero-valent iron(n ZVI) particles supported on a porous, semi-interpenetrating(semi-IPN), temperature-sensitive composite hydrogel(PNIPAm-PHEMA). n ZVI@PNIPAmPHEMA, was successfully synthesized and character... Nanoscale zero-valent iron(n ZVI) particles supported on a porous, semi-interpenetrating(semi-IPN), temperature-sensitive composite hydrogel(PNIPAm-PHEMA). n ZVI@PNIPAmPHEMA, was successfully synthesized and characterized by FT-IR, SEM, EDS, XRD and the weighing method. The loading of nZVI was 0.1548 ± 0.0015 g/g and the particle size was30–100 nm. NZVI was uniformly dispersed on the pore walls inside the PNIPAm-PHEMA.Because of the well-dispersed n ZVI, the highly porous structure, and the synergistic effect of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA showed excellent reductive activity and wide p H applicability. 95% of 4-NP in 100 m L of 400 mg/L 4-NP solution with initial p H 3.0–9.0 could be completely reduced into 4-AP by about 0.0548 g of fresh supported n ZVI at 18–25 ℃ under stirring(110 r/min) within 45 min reaction time. A greater than 99% 4-NP degradation ratio was obtained when the initial p H was 5.0–9.0. The reduction of 4-NP by nZVI@PNIPAm-PHEMA was in agreement with the pseudo-first-order kinetics model with Kobsvalues of 0.0885–0.101 min-1.NZVI@PNIPAm-PHEMA was able to be recycled, and about 85% degradation ratio of 4-NP was obtained after its sixth reuse cycle. According to the temperature sensitivity of PNIPAmPHEMA, n ZVI@PNIPAm-PHEMA exhibited very good storage stability, and about 88.9% degradation ratio of 4-NP was obtained after its storage for 30 days. The hybrid reducer was highly efficient for the reduction of 2-NP, 3-NP, 2-chloro-4-nitrophenol and 2-chloro-4-nitrophenol. Our results suggest that PNIPAm-PHEMA could be a good potential carrier, with n ZVI@PNIPAm-PHEMA having potential value in the application of reductive degradation of nitrophenol pollutants. 展开更多
关键词 POROUS SEMI-IPN temperature sensitive HYDROGEL SUPPORTED nanoscale zero-valent iron Reductive degradation NITROPHENOL Storage stability
纳米多维对荷斯坦奶牛产奶性能的影响
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作者 张晓娜 李云波 +2 位作者 韩焕芳 俞圣林 张卢军 《食品工业》 CAS 北大核心 2019年第4期149-151,共3页
为研究纳米多维对荷斯坦奶牛产奶量、乳品质和体细胞数的影响,试验选择94头荷斯坦奶牛,采用随机分组的方法分为对照组和试验组,对照组正常饲喂,试验组在饮水中添加纳米多维,测定其对奶牛产奶性能的影响。结果表明,试验组荷斯坦奶牛产奶... 为研究纳米多维对荷斯坦奶牛产奶量、乳品质和体细胞数的影响,试验选择94头荷斯坦奶牛,采用随机分组的方法分为对照组和试验组,对照组正常饲喂,试验组在饮水中添加纳米多维,测定其对奶牛产奶性能的影响。结果表明,试验组荷斯坦奶牛产奶量、乳脂含量、乳蛋白含量和干物质含量均高于对照组,试验组牛奶中体细胞数低于对照组,说明纳米多维可有效改善牛奶的产奶性能和降低奶牛的体细胞数,显著提高经济效益。 展开更多
关键词 纳米级 液体复合维生素氨基酸 奶牛 产奶量 体细胞数
Stabilization of nanoscale zero-valent iron in water with mesoporous carbon(n ZVI@MC)
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作者 Junming Shi Jing Wang +2 位作者 Wei Wang Wei Teng Wei-xian Zhang 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第7期28-33,共6页
Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxid... Two challenges persist in the applications of nanoscale zero-valent iron(nZVI) for environmental remediation and waste treatment: limited mobility due to rapid aggregation and short lifespan in water due to quick oxidation. Herein, we report the nZVI incorporated into mesoporous carbon(MC) to enhance stability in aqueous solution and mobility in porous media. Meanwhile, the reactivity of nZVI is preserved thanks to high temperature treatment and confinement of carbon framework. Small-sized(~16 nm) nZVI nanoparticles are uniformly dispersed in the whole carbon frameworks. Importantly, the nanoparticles are partially trapped across the carbon walls with a portion exposed to the mesopore channels. This unique structure not only is conductive to hold the nZVI tightly to avoid aggregation during mobility but also provides accessible active sites for reactivity. This new type of nanomaterial contains ~10 wt% of iron. The nZVI@MC possesses a high surface area(~ 500 m~2/g) and uniform mesopores(~ 4.2 nm) for efficient pollutant diffusion and reactions. Also, high porosity of nZVI@MC contributes to the stability and mobility of nZVI. Laboratory column experiments further demonstrate that nZVI@MC suspension(~4 g Fe/L) can pass through sand columns much more efficiently than bare nZVI while the high reactivity of nZVI@MC is confirmed from reactions with Ni(II). It exhibits remarkably better performance in nickel(20 mg/L) extraction than mesoporous carbon, with 88.0% and 33.0%uptake in 5 min, respectively. 展开更多
关键词 MESOPOROUS carbon NANOSCALE zero-valent iron MOBILITY Porous media Heavy metal removal
Local electrical charac terization of t wo-dimensional mat erials with functional atomic force microscopy
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作者 Sabir Hussain Kunqi Xu +5 位作者 Shili Ye Le Lei Xinmeng Liu Rui Xu Liming Xie Zhihai Cheng 《物理学前沿:英文版》 SCIE CSCD 2019年第3期85-105,共21页
Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined... Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined to a plane. The applications of 2D materials are highly affected by the electrical properties of these mat erials, including curren t dist ribution, surface pot ential, dielectric response, conductivity, perm计tivity, and piezoelectric response. Hence, it is very crucial to characterize these properties at the nanoscale. The Atomic Force Microscopy (AFM)-based techniques are powerful tools that can simultaneously characterize morphology and electrical properties of 2D materials with high spatial resolution, thus being more and more extensively used in this research field. Here, the principles of these AFM techniques are reviewed in detail. After that, their representative applications are further demonstrated in the local characterization of various 2D materials? elcctrical properties. 展开更多
关键词 advanced AFM techniques NANOSCALE characteTization ELECTRICAL properties 2D materials
纳米级防紫外无机材料的研究进展
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作者 余红雨 杨荣静 +3 位作者 严波 谢秋慧 王鑫鑫 段冀渊 《上海纺织科技》 北大核心 2019年第2期1-6,共6页
纳米材料在纺织品领域的相关研究逐渐深入,应用也更加广泛,其优异的防紫外性能引起了极大的关注。将应用较广的纳米级防紫外无机材料分为氧化物半导体、无机盐类、金属材料、炭基材料4大类,分别从防紫外机理、材料性质和结构、应用范围... 纳米材料在纺织品领域的相关研究逐渐深入,应用也更加广泛,其优异的防紫外性能引起了极大的关注。将应用较广的纳米级防紫外无机材料分为氧化物半导体、无机盐类、金属材料、炭基材料4大类,分别从防紫外机理、材料性质和结构、应用范围等方面综述了这些材料的研究进展,为织物的功能化改性和规模化生产提供参考。 展开更多
关键词 无机材料 防紫外材料 纳米级 织物
基于分形建模的高煤级煤孔隙结构特征量化表征——以阳泉矿区山西组煤样为例 预览
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作者 赵迪斐 郭英海 +2 位作者 WANG GEOFF 刘静 王琳琳 《东北石油大学学报》 CAS 北大核心 2019年第3期53-66,I0004共15页
以阳泉矿区山西组煤样为例,根据高压压汞及分形建模,获取高煤级煤孔隙结构特征参数,结合氩离子抛光—场发射扫描电镜,识别微—纳米尺度的孔隙发育类型及结构特征,明确储集空间构成及孔隙结构对煤中气体的影响,构建气体行为与孔隙结构的... 以阳泉矿区山西组煤样为例,根据高压压汞及分形建模,获取高煤级煤孔隙结构特征参数,结合氩离子抛光—场发射扫描电镜,识别微—纳米尺度的孔隙发育类型及结构特征,明确储集空间构成及孔隙结构对煤中气体的影响,构建气体行为与孔隙结构的关系。结果表明:阳泉矿区山西组高煤级煤储层孔隙结构复杂,在不同发育尺度具有不同的分形特征;基于孔隙结构特征、分形特征和多孔介质甲烷的分子动力学特征,将孔隙划分为3个大类(超微吸附孔隙、纳米扩散孔隙和微纳米渗流孔隙)和5个小类(超微孔隙、分子扩散孔隙、Knudsen扩散孔隙、层流滑移孔隙和紊流滑移孔隙),将基质孔隙气体的运移方式划分为吸附相—固溶相扩散场、Knudsen扩散场、层流场及紊流场,多数高煤级煤样品层流滑移孔隙的不发育表明层流场的弱势发育。量化高煤级煤储层微观储集空间,建立孔隙结构与煤层气渗流、运移的关系,为高煤级煤层气勘探开发、地质理论研究提供依据。 展开更多
关键词 孔隙结构 分形特征 纳米孔 孔隙分类 高煤级煤 山西组 阳泉矿区
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pH对纳米晶堆积ZSM-5的影响及噻吩烷基化性能 预览
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作者 陈文文 彭伊淇 +1 位作者 刘冬梅 王海彦 《石油化工高等学校学报》 CAS 2019年第3期28-32,共5页
以质量分数为30%硅溶胶为硅源,硫酸铝为铝源,采用水热合成法合成了纳米晶堆积ZSM-5分子筛,并通过XRD、SEM、BET和NH-TPD表征方法对所得样品进行表征,考察不同pH对纳米晶堆积ZSM-5分子筛物化性质的影响。结果表明,当pH为11.50时,催化剂... 以质量分数为30%硅溶胶为硅源,硫酸铝为铝源,采用水热合成法合成了纳米晶堆积ZSM-5分子筛,并通过XRD、SEM、BET和NH-TPD表征方法对所得样品进行表征,考察不同pH对纳米晶堆积ZSM-5分子筛物化性质的影响。结果表明,当pH为11.50时,催化剂的粒径为纳米级结构,表面积较大,介孔数量多,酸性适宜,应用到噻吩烷基化反应后,表现出较好的噻吩烷基化活性。 展开更多
关键词 ZSM-5分子筛 水热合成 纳米级 堆积 噻吩烷基化
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A general aerosol-assisted biosynthesis of functional bulk nanocomposites
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作者 Qing-Fang Guan Zi-Meng Han +5 位作者 Tong-Tong Luo Huai-Bin Yang Hai-Wei Liang Si-Ming Chen Guang-Sheng Wang Shu-Hong Yu 《国家科学评论:英文版》 CSCD 2019年第1期64-73,共10页
Although a variety of nanoparticles with better-than-bulk material performances can be synthesized, it remains a challenge to scale the extraordinary properties of individual nanoscale units to the macroscopic level f... Although a variety of nanoparticles with better-than-bulk material performances can be synthesized, it remains a challenge to scale the extraordinary properties of individual nanoscale units to the macroscopic level for bulk nanostructured materials. Here, we report a general and scalable biosynthesis strategy that involves simultaneous growth of cellulose nanofibrils through microbial fermentation and co-deposition of various kinds of nanoscale building blocks(NBBs) through aerosol feeding on solid culture substrates. We employ this biosynthesis strategy to assemble a wide range of NBBs into cellulose nanofibril-based bulk nanocomposites. In particular, the biosynthesized carbon nanotubes/bacterial cellulose nanocomposites that consist of integrated 3D cellulose nanofibril networks simultaneously achieve an extremely high mechanical strength and electrical conductivity, and thus exhibit outstanding performance as high-strength lightweight electromagnetic interference shielding materials. The biosynthesis approach represents a general and efficient strategy for large-scale production of functional bulk nanocomposites with enhanced performances for practical applications. Industrial-scale production of these bulk nanocomposite materials for practical applications can be expected in the near future. 展开更多
关键词 BACTERIAL CELLULOSE NANOSCALE building blocks BIOSYNTHESIS electromagnetic SHIELDING SCALABLE fabrication
Nanoscale chemical imaging of individual chemotherapeutic cytarabineloaded liposomal nanocarriers
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作者 Karin Wieland Georg Ramer +3 位作者 Victor U. Weiss Guenter Allmaier Bemhard Lendl Andrea Centrone 《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第1期197-203,共7页
Dosage of chemotherapeutic drugs is a tradeoff between efficacy and side-effects.Liposomes are nanocarriers that increase therapy efficacy and minimize side-effects by delivering otherwise difficult to administer ther... Dosage of chemotherapeutic drugs is a tradeoff between efficacy and side-effects.Liposomes are nanocarriers that increase therapy efficacy and minimize side-effects by delivering otherwise difficult to administer therapeutics with improved efficiency and selectivity.Still,variabilities in liposome preparation require assessing drug encapsulation efficiency at the single liposome level,an information that,for non-fluorescent therapeutic cargos,is inaccessible due to the minute drug load per liposome.Photothermal induced resonance (PTIR) provides nanoscale compositional specificity,up to now,by leveraging an atomic force microscope (AFM) tip contacting the sample to transduce the sample's photothermal expansion.However,on soft samples (e.g.,liposomes) PTIR effectiveness is reduced due to the likelihood of tip-induced sample damage and inefficient AFM transduction.Here,individual liposomes loaded with the chemotherapeutic drug cytarabine are deposited intact from suspension via nano-electrospray gas-phase electrophoretic mobility molecular analysis (nES-GEMMA) collection and characterized at the nanoscale with the chemically-sensitive PTIR method.A new tapping-mode PTIR imaging paradigm based on heterodyne detection is shown to be better adapted to measure soft samples,yielding cytarabine distribution in individual liposomes and enabling classification of empty and drug-loaded liposomes.The measurements highlight PTIR capability to detect ~ 103 cytarabine molecules (~ 1.7 zmol) label-free and non-destructively. 展开更多
关键词 tapping PHOTOTHERMAL induced resonance (PTIR) NANOSCALE chemical imaging liposomes CYTARABINE drug delivery NANOCARRIERS
钢中析出相场发射扫描电镜的自动统计分析技术研究 预览
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作者 崔桂彬 鞠新华 +2 位作者 严春莲 郝京丽 杨瑞 《冶金分析》 CAS 北大核心 2019年第2期17-22,共6页
以往对析出相的研究均是通过透射电镜来获取析出相的成分、数量和尺寸等数据,难以实现析出相的自动统计分析。因此,为了实现自动统计分析,借助场发射扫描电镜(FE-SEM)与能谱分析软件Feature功能详细地研究了钢中析出相的自动统计分析技... 以往对析出相的研究均是通过透射电镜来获取析出相的成分、数量和尺寸等数据,难以实现析出相的自动统计分析。因此,为了实现自动统计分析,借助场发射扫描电镜(FE-SEM)与能谱分析软件Feature功能详细地研究了钢中析出相的自动统计分析技术,特别是对该方法中的样品制备、组织类型、析出相以及参数的设置与选择等主要影响因素进行了细致的分析。研究结果表明,实验最佳条件为采用化学侵蚀法、10 000倍的放大倍数、阈值为110~255,总分析面积不超过0.1mm^2。考虑到设备分辨率的影响,该实验方法只能对50nm以上的析出相进行统计分析,结合700L钢的实验结果可知,其析出相的种类有碳氮化钛和碳氮化钛与铌的复合析出,所占比例分别为58%和42%,50~200nm析出相数量较多。 展开更多
关键词 析出相 自动统计分析 纳米尺度 场发射扫描电镜
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A laterally sensitive colloidal probe for accurately measuring nanoscale adhesion of textured surfaces
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作者 Soren Zimmermann Waldemar Klauser +3 位作者 James Mead Shiliang Wang Han Huang Sergej Fatikow 《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第2期389-396,共8页
Adhesiion assessment of nanoscale contacts is a critical capability for the development of future nanoelectromechanical systems and nanobiotechnology devices. However, experimental approaches to investigate interactio... Adhesiion assessment of nanoscale contacts is a critical capability for the development of future nanoelectromechanical systems and nanobiotechnology devices. However, experimental approaches to investigate interactions on micro- and nanostructured surfaces have predominantly been restricted to capturing adhesion force in the normal direction. This provides limited information about the multidimensional nature of surface texture and related interaction mechanisms. Here the design, fabrication, and application of a unique atomic force microscope probe is presented that consists of a focused ion beam-milled cantilever decorated with a colloidal particle. The probe is specifically developed for characterizing textured surfaces with lateral force feedback. Pull-off tests that map the adhesive interaction in microscale cavities are performed to exami ne the capability of the probe. Normal and lateral adhesive forces duri ng nano scale contact are accurately obtai ned and the adhesi on en ergy of the con tact interface is thus determi ned. An in-depth un dersta nding of the effects of surface texture and the correlati on of adhesi on and fricti on is dem on strated. The proposed methodology en ables dedicated in vestigatio ns of in terfacial in teracti on on various norvplanar surfaces. It can be used for un dersta nding the complex in terplay of adhesi on, con tact, and fricti on forces at nano scale, which may facilitate significant advances in challenging research areas such as fibrillar adhesion. 展开更多
关键词 NANOSCALE adhesion FRICTION ATOMIC force MICROSCOPE COLLOIDAL probe LATERAL sensitivity
Unifying quantum heat transfer and superradiant signature in a nonequilibrium collective-qubit system:A polaron-transformed Redfield approach
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作者 陈许敏 王晨 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第5期48-56,共9页
We investigate full counting statistics of quantum heat transfer in a collective-qubit system constructed by multiqubits interacting with two thermal baths.The nonequilibrium polaron-transformed Redfield approach embe... We investigate full counting statistics of quantum heat transfer in a collective-qubit system constructed by multiqubits interacting with two thermal baths.The nonequilibrium polaron-transformed Redfield approach embedded with an auxiliary counting field is applied to obtain the steady state heat current and fluctuations,which enables us to study the impact of the qubit–bath interaction in a wide regime.The heat current,current noise,and skewness are all found to clearly unify the limiting results in the weak and strong couplings.Moreover,the superradiant heat transfer is clarified as a system-size-dependent effect,and large number of qubits dramatically suppress the nonequilibrium superradiant signature. 展开更多
关键词 QUANTUM transport heat conduction PHONONS or vibrational states in LOW-DIMENSIONAL structures and nanoscale materials NONEQUILIBRIUM and IRREVERSIBLE thermodynamics
Two-dimensional metal-organic-framework as a unique theranostic nano-platform for nuclear imaging and chemo-photodynamic cancer therapy
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作者 Wenjun Zhu Yu Yang +5 位作者 Qiutong Jin Yu Chao Longlong Tian Jingjing Liu Ziliang Dong Zhuang Liu 《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第6期1307-1312,共6页
Nanoscale metal organic frameworks (NMOFs) with porous structure and inherent biodegradability are attractive nanomedicine platforms.In addition to conventional particulate NMOFs,two-dimensional (2D) NMOFs are emergin... Nanoscale metal organic frameworks (NMOFs) with porous structure and inherent biodegradability are attractive nanomedicine platforms.In addition to conventional particulate NMOFs,two-dimensional (2D) NMOFs are emerging as a unique type of NMOFs which however have been relatively less explored for nanomedicine applications.Herein,2D NMOFs composed of Zn2+ and tetrakis(4-carboxyphenyl) porphyrin (TCPP) are fabricated and functionalized with polyethylene glycol (PEG).Compared to their particulate counterpart,such 2D NMOFs show greatly increased drug loading capacity and enhanced light-triggered singlet oxygen production,promising for chemotherapy and photodynamic therapy (PDT),respectively.Utilizing the porphyrin structure of TCPP,our 2D NMOFs could be labeled with a diagnostic radioisotope,99mTc,for single photon emission computer tomography (SPECT) imaging,which reveals efficient tumor homing of those 2D NMOFs upon intravenous injection.While offering a remarkable synergistic in vivo antitumor effect for the combined chemo-PDT,such 2D NMOFs show efficient biodegradation and rapid renal clearance.Our work presents the great promise of 2D NMOFs for nanomedicine applications. 展开更多
关键词 nanoscale metal-organic-framework TWO-DIMENSIONAL NANOSHEETS drug delivery photodynamic THERAPY combination THERAPY
Time-resolved,defect-hosted,trace element mobility in deformed Witwatersrand pyrite 预览
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作者 Denis Fougerouse Steven M.Reddy +3 位作者 Christopher L.Kirkland David W.Saxey William D.Rickard Robert M.Hough 《地学前缘:英文版》 CAS CSCD 2019年第1期55-63,共9页
The Pb isotopic composition of rocks is widely used to constrain the sources and mobility of melts and hydrothermal fluids in the Earth’s crust.In many cases,the Pb isotopic composition appears to represent mixing of... The Pb isotopic composition of rocks is widely used to constrain the sources and mobility of melts and hydrothermal fluids in the Earth’s crust.In many cases,the Pb isotopic composition appears to represent mixing of multiple Pb reservoirs.However,the nature,scale and mechanisms responsible for isotopic mixing are not well known.Additionally,the trace element composition of sulphide minerals are routinely used in ore deposit research,mineral exploration and environmental studies,though little is known about element mobility in sulphides during metamorphism and deformation.To investigate the mechanisms of trace element mobility in a deformed Witwatersrand pyrite(FeS2),we have combined electron backscatter diffraction(EBSD)and atom probe microscopy(APM).The results indicate that the pyrite microstructural features record widely different Pb isotopic compositions,covering the entire range of previously published sulphide Pb compositions from the Witwatersrand basin.We show that entangled dislocations record enhanced Pb,Sb,Ni,Tl and Cu composition likely due to entrapment and short-circuit diffusion in dislocation cores.These dislocations preserve the Pb isotopic composition of the pyrite at the time of growth(~3 Ga)and show that dislocation intersections,likely to be common in deforming minerals,limit trace element mobility.In contrast,Pb,As,Ni,Co,Sb and Bi decorate a highangle grain boundary which formed soon after crystallisation by sub-grain rotation recrystallization.Pb isotopic composition within this boundary indicates the addition of externally-derived Pb and trace elements during greenschist metamorphism at~2 Ga.Our results show that discrete Pb reservoirs are nanometric in scale,and illustrate that grain boundaries may remain open systems for trace element mobility over 1 billion years after their formation. 展开更多
关键词 Atom probe microscopy NANOSCALE Nanogeochronology Microstructure Isotope geochemistry Common Pb
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AIMS & SCOPE
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《纳米研究:英文版》 SCIE EI CAS CSCD 2019年第2期471-472,F0003共3页
Nano Research is a peer-reviewed, international and interdisciplinary journal that focuses on all aspects of nanoscience and nanotechnology. Submissions are solicited in all topical areas, ranging from basic aspects o... Nano Research is a peer-reviewed, international and interdisciplinary journal that focuses on all aspects of nanoscience and nanotechnology. Submissions are solicited in all topical areas, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. 展开更多
关键词 NANO Research PEER-REVIEWED NANOSCALE MATERIALS
Nanoscale resetting of the Th/Pb system in an isotopically-closed monazite grain:A combined atom probe and transmission electron microscopy study 预览
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作者 A.-M.Seydoux-Guillaume D.Fougerouse +3 位作者 A.T.Laurent E.Gardés S.M.Reddy D.W.Saxey 《地学前缘:英文版》 CAS CSCD 2019年第1期65-76,共12页
Understanding the mechanisms of parent-daughter isotopic mobility at the nanoscale is key to rigorous interpretation of Ue The Pb data and associated dating. Until now, all nanoscale geochronological studies on geolog... Understanding the mechanisms of parent-daughter isotopic mobility at the nanoscale is key to rigorous interpretation of Ue The Pb data and associated dating. Until now, all nanoscale geochronological studies on geological samples have relied on either Transmission Electron Microscope(TEM) or Atom Probe Microscopy(APM) characterizations alone, thus suffering from the respective weaknesses of each technique. Here we focus on monazite crystals from a ~1 Ga, ultrahigh temperature granulite from Rogaland(Norway). This sample has recorded concordant UeP b dates(measured by LA-ICP-MS) that range over 100 My, with the three domains yielding distinct isotopic Ue Pb ages of 1034 ± 6 Ma(D1; Srich core), 1005 ± 7 Ma(D2), and 935 ± 7 Ma(D3), respectively. Combined APM and TEM characterization of these monazite crystals reveal phase separation that led to the isolation of two different radiogenic Pb(Pb*) reservoirs at the nanoscale. The S-rich core of these monazite crystals contains Cae Srich clusters, 5 -10 nm in size, homogenously distributed within the monazite matrix with a mean interparticle distance of 40 -60 nm. The clusters acted as a sink for radiogenic Pb(Pb*) produced in the monazite matrix, which was reset at the nanoscale via Pb diffusion while the grain remained closed at the micro-scale. Compared to the concordant ages given by conventional micro-scale dating of the grain,the apparent nano-scale age of the monazite matrix in between clusters is about 100 Myr younger, which compares remarkably well to the duration of the metamorphic event. This study highlights the capabilities of combined APM-TEM nano-structural and nano-isotopic characterizations in dating and timing of geological events, allowing the detection of processes untraceable with conventional dating methods. 展开更多
关键词 MONAZITE NANOSCALE RESETTING Nano-clusters APM TEM UHT METAMORPHISM
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纳米级脑靶向递药系统的靶向性提升策略
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作者 黄梦瑶 杨旭 +1 位作者 邢金峰 魏振平 《药学学报》 CAS CSCD 北大核心 2019年第4期629-637,共9页
血脑屏障能选择性阻滞外周血液中的物质进入脑内,这对于维持脑内环境稳定十分重要,但同时会阻碍治疗药物向脑内递送。被动脑靶向递药系统可以通过增强与血脑屏障细胞的亲和力及减弱P-糖基蛋白对药物的外排来提高脑内药物浓度;在被动靶... 血脑屏障能选择性阻滞外周血液中的物质进入脑内,这对于维持脑内环境稳定十分重要,但同时会阻碍治疗药物向脑内递送。被动脑靶向递药系统可以通过增强与血脑屏障细胞的亲和力及减弱P-糖基蛋白对药物的外排来提高脑内药物浓度;在被动靶向递药系统上结合特异性配体或抗体得到的主动脑靶向递药系统,能更精准地实现药物向脑内靶向递送;脑靶向联合肿瘤细胞靶向得到的双级靶向递药系统,对脑部肿瘤的治疗已显示出其独特优势。脑靶向递药系统将为阿尔茨海默病、脑肿瘤及中风等脑部疾病的治疗提供一种独特方式。在介绍被动型、主动型脑靶向及双级脑靶向递药系统的同时,本文重点对降低载体粒径、打开血脑屏障细胞间的紧密连接、于载体表面键合亲水性基团及鼻腔给药等提高药物脑内递送效率的策略进行了展望。 展开更多
关键词 血脑屏障 纳米级 递药系统 双级脑靶向 靶向性提升策略
A Local Region Molecular Dynamics Simulation Method for Nanoscale Sliding Contacts
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作者 Rui-Ting Tong Geng Liu Tian-Xiang Liu 《中国机械工程学报:英文版》 SCIE EI CAS CSCD 2018年第5期119-126,共8页
Computational e ciency and accuracy always conflict with each other in molecular dynamics(MD) simulations. How to enhance the computational e ciency and keep accuracy at the same time is concerned by each correspondin... Computational e ciency and accuracy always conflict with each other in molecular dynamics(MD) simulations. How to enhance the computational e ciency and keep accuracy at the same time is concerned by each corresponding researcher. However, most of the current studies focus on MD algorithms, and if the scale of MD model could be reduced, the algorithms would be more meaningful. A local region molecular dynamics(LRMD) simulation method which can meet these two factors concurrently in nanoscale sliding contacts is developed in this paper. Full MD simulation is used to simulate indentation process before sliding. A criterion called contribution of displacement is presented, which is used to determine the e ective local region in the MD model after indentation. By using the local region, nanoscale sliding contact between a rigid cylindrical tip and an elastic substrate is investigated. Two two?dimensional MD models are presented, and the friction forces from LRMD simulations agree well with that from full MD simulations, which testifies the e ectiveness of the LRMD simulation method for two?dimensional cases. A three?dimensional MD model for sliding contacts is developed then to show the validity of the LRMD simulation method further. Finally, a discussion is carried out by the principles of tribology. In the discussion, two two?dimensional full MD models are used to simulate the nanoscale sliding contact problems. The results indicate that original smaller model will induce higher equivalent scratching depth, and then results in higher friction forces, which will help to explain the mechanism how the LRMD simulation method works. This method can be used to reduce the scale of MD model in large scale simulations, and it will enhance the computational e ciency without losing accuracy during the simula?tion of nanoscale sliding contacts. 展开更多
关键词 LOCAL REGION molecular dynamics simulation NANOSCALE SLIDING contacts CONTRIBUTION of displacement
纳米尺度下气泡核化生长的分子动力学研究 预览
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作者 张龙艳 徐进良 雷俊鹏 《物理学报》 CSCD 北大核心 2018年第23期159-169,共11页
采用分子动力学方法模拟纳米尺度下液体在固体壁面上发生核化沸腾的过程,主要研究壁面浸润性对气泡初始核化过程和气泡生长速率的影响以及固-液界面效应在液体核化沸腾的能量传递过程中所起到的作用.研究结果发现:壁面浸润性越强,气泡... 采用分子动力学方法模拟纳米尺度下液体在固体壁面上发生核化沸腾的过程,主要研究壁面浸润性对气泡初始核化过程和气泡生长速率的影响以及固-液界面效应在液体核化沸腾的能量传递过程中所起到的作用.研究结果发现:壁面浸润性越强,气泡在固壁处越容易核化.该结果与经典核化理论中“疏水壁面易于产生气泡”的现象产生了明显的区别.其根本原因是在纳米尺度下,固-液界面热阻效应不能被忽略.一方面,在相同的壁温下,通过增强固-液相互作用;可以显著降低界面热阻,使得热量传递效率提高,导致靠近壁面处的流体温度升高,气泡核化等待时间缩短,有利于液体沸腾核化.另一方面,气泡的生长速率随着壁面浸润性的增强而明显升高.当气泡体积生长到一定程度时,会在壁面处形成气膜,从而导致壁面传热性能恶化.因此,通过壁面的热流密度呈现出先增大后减小的规律. 展开更多
关键词 纳米尺度 气泡核化 浸润性 界面效应
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The effects of clay minerals and organic matter on nanoscale pores in Lower Paleozoic shale gas reservoirs, Guizhou, China
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作者 Yuantao Gu Quan Wan +2 位作者 Wenbin Yu Xiaoxia Li Zhongbin Yu 《中国地球化学学报:英文版》 EI CAS CSCD 2018年第6期791-804,共14页
In organic-rich gas shales, clay minerals and organic matter(OM) have significant influences on the origin, preservation, and production of shale gas. Because of the substantial role of nanoscale pores in the generati... In organic-rich gas shales, clay minerals and organic matter(OM) have significant influences on the origin, preservation, and production of shale gas. Because of the substantial role of nanoscale pores in the generation,storage, and seepage of shale gas, we examined the effects of clay minerals and OM on nanoscale pore distribution characteristics in Lower Paleozoic shale gas reservoirs.Using the Niutitang and Longmaxi shales as examples, we determined the effects of clay minerals and OM on pores through sedimentation experiments. Field emission–scanning electron microscopy combined with low-pressure N2 adsorption of the samples before and after sedimentation showed significant differences in pore location and pore size distribution between the Niutitang and Longmaxi shales. Nanoscale pores mostly existed in OM in the Longmaxi shale and in clay minerals or OM–clay composites in the Niutitang shale. The distribution differences were attributed largely to variability in thermal evolution and tectonic development and might account for the difference in gas-bearing capacity between the Niutitang and Longmaxi reservoirs. In the nanoscale range, mesopores accounted for 61–76% of total nanoscale pore volume.Considerably developed nanoscale pores in OM were distributed in a broad size range in the Longmaxi shale, which led to good pore connectivity and gas production.Numerous narrow pores(i.e., pores \ 20 nm) in OM–clay composites were found in the Niutitang shale, and might account for this shale’s poor pore connectivity and low gas production efficiency. Enhancing the connectivity of the mesopores(especially pores \ 20 nm and those developed in OM–clay composites) might be the key to improving development of the Niutitang shale. The findings provide new insight into the formation and evolutionary mechanism of nanoscale pores developed in OM and clay minerals. 展开更多
关键词 NANOSCALE PORE CLAY MINERALS Organic matter OM-clay composites PORE distribution characteristics PORE CONNECTIVITY
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