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Study on Melting and Recrystallization of Poly(butylene succinate) Lamellar crystals via Step Heating Differential Scanning calorimetry

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chinese Journal of Polymer Science 2017年第12期35卷 1552-1560页

作者： Zhi-yu Lv Michael c.Zhang Yang Zhang Bao-hua Guo 徐军 Key Laboratory of Advanced Materials (Ministry of Education) Department of Chemical Engineering Tsinghua University

Differential scanning calorimetry（DSc） has been widely applied to study crystallization and melting of materials. However, for polymeric lamellar crystals, the melting thermogram during heating process usually exhibits a broad endothermic peak or even multiple endotherms, which may result from changes of metastability via recrystallization process. Sometimes, the recrystallization exotherm cannot be observed due to its overlapping with the melting endotherm. In this work, we employed a step heating procedure consisting of successive heating and temperature holding stages to measure the metastability of isothermally crystallized poly（butylene succinate）（PBS） crystals. With this approach we could gain the fraction of crystals melted at different temperature ranges and quantitatively detect the melting-recrystallization behavior. The melting-recrystallization behavior depends on the polymer chain structure and the crystallization temperature. For instance, PBS block copolymer hardly shows recrystallization behavior while PBS oligomer and high molecular weight PBS homopolymer demonstrate remarkable melting-recrystallization phenomenon. High molecular weight PBS isothermally crystallized in the low temperature range shows multiple melting-recrystallization while those isothermally crystallized at elevated temperatures do not exhibit observable recrystallization behavior. Furthermore, the melting endotherms were fitted via the melting kinetics equations. The original isothermally crystallized lamellae demonstrate quite different melting kinetics from the recrystallized lamellar crystals that melt at the highest temperature range, which is attributed to the different degrees of stabilization. Finally, the mechanism of melting-recrystallization is briefly discussed. We propose that apparent meltrecrystallization phenomenon be observed when melting of preformed lamellar crystals and recrystallization of thicker lamellae have similar free energy barrier.

关键词： DSc Step heating Poly(butylene succinate) Metastability Melting-recrystallization Melting kinetics

The endeavor of total synthesis and its impact on chemistry, biology and medicine

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national Science Review 2014年第2期1卷 233-252页

作者： K.c.nicolaou christopher R.H.Hale Department of chemistry Bio Science Research Collaborative Rice University Department of chemistry The Scripps Research Institute

The synthesis of urea in 1828 set in motion the discipline of organic synthesis in general and of total synthesis in particular, the art and science of synthesizing natural products, the molecules of living *** endeavors in total synthesis had as their main objective the proof of structure of the target *** on, the primary goal became the demonstration of the power of synthesis to construct complex molecules through appropriately devised strategies, making the endeavor an achievement whose value was measured by its elegance and eiciency. While these objectives continue to be important, contemporary endeavors in total synthesis are increasingly focused on practical aspects, including method development,eiciency, and biological and medical relevance. In this article, the emergence and evolution of total synthesis to its present state is traced, selected total syntheses from the author’s laboratories are highlighted,and projections for the future of the ield are discussed.

关键词： organic synthesis natural products chemistry biology medicine

A metal-free composite photocatalyst of graphene quantum dots deposited on red phosphorus

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Journal of Environmental Sciences 2017年第10期29卷 91-97页

作者： Donald K.L.chan Jimmy c.Yu Yecheng Li Zhuofeng Hu Department of chemistry The Chinese University of Hong Kong Shatin New Territories Shenzhen Research Institute The Chinese University of Hong Kong

A simple approach to enhance the photocatalytic activity of red phosphorus（P） was developed.A mechanical ball milling method was applied to reduce the size of red P and to deposit graphene quantum dots onto red P. The product was characterized by scanning electron microscopy, transmission electron microscopy, contact angle measurements, zeta-potential measurements, X-ray diffraction and UV–vis absorption spectroscopy. The product exhibited high visible-light-driven photocatalytic performance in the photodegradation of rhodamine B.

关键词： Metal-free photocatalyst Graphene quantum dots Red phosphorus Mechanical ball milling

AcID cATALYZED REARRAnGEMEnTS OF TRIQUInAnES

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chinese chemical Letters 1995年第3期6卷 177-180页

作者： Zhang, c Guo, Xc Shen, XM Xu, YF Lanzhou Univ Inst Organ Chem Natl Lab Appl Organ Chem Lanzhou 730000 Peoples R China

Acid catalyzed rearrangements of 1 and 3 were examined. The olefinic double bond was the most reactive group in protonation reaction. In the absence of olefinic double bond, tert-hydroxy group reacted faster than cycl... 详细信息

关键词： AcID cATALYZED REARRAnGEMEnTS OF TRIQUInAnES

GO-modified flexible polymer nanocomposites fabricated via 3D stereolithography

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Frontiers of chemical Science and Engineering 2019年第4期13卷 736-743页

作者： chi Him Alpha Tsang Adilet Zhakeyev Dennis Y.c.Leung Jin Xuan School of Environmental Sciences and Engineering Sun Yat-Sen UniversityGuangzhou 510006China Department of Mechanical Engineering The University of Hong KongHong KongChina Department of chemical Engineering Loughborough UniversityLoughboroughLE113TUUK

Graphene oxide(GO)induced enhancement of elastomer properties showed a great deal of potential in recent years,but it is still limited by the barrier of the complicated synthesis ***(SLA),used in fabrication of thermosets and very recently in“flexible”polymers with elastomeric properties,presents itself as simple and user-friendly method for integration of GO into *** this work,it was first time demonstrated that GO loadings can be incorporated into commercial flexible photopolymer resins to successfully fabricate GO/elastomer nanocomposites via readily accessible,consumer-oriented SLA *** material properties of the resulting polymer was characterized and *** mechanical strength,stiffness,and the elongation of the resulting polymer decreased with the addition of *** thermal properties were also adversely affected upon the increase in the GO content based on differential scanning calorimetry and thermogravimetric analysis *** was proposed that the GO agglomerates within the 3D printed composites,can result in significant change in both mechanical and thermal properties of the resulting *** study demonstrated the possibility for the development of the GO/elastomer nanocomposites after the optimization of the GO/“Hexible”photoreactive resin formulation for SLA with suitable annealing process of the composite in future.

关键词： graphene oxide polymer flexible 3D printing stereolithography

Birth,Survival and Death of Languages by Monte carlo Simulation

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communications in computational Physics 2008年第2期3卷 271-294页

作者： c.Schulze D.Stauffer S.Wichmann Institute for Theoretical Physics Cologne UniversityD-50923 KolnEuroland Department of Linguistics Max Planck Institute for Evolutionary AnthropologyDeutscher Platz 6D-04103 LeipzigGermany.

Simulations mostly by physicists of the competition between adult languagessince 2003 are reviewed. The Viviane and Schulze models give good and reasonableagreement, respectively, with the empirical histogram of language sizes. Alsothe numbers of different languages within one language family is modeled reasonablyin an intermediate range. Bilingualism is now incorporated into the Schulze *** the rate at which the majority shifts from one language to another is found tobe nearly independent of the population size, or to depend strongly on it, accordingto details of the Schulze model. Other simulations, like nettle-culicover-nowak, arereviewed more briefly.

关键词： Language competition Schulze model Viviane model agent-based modeling.

Spatial Distribution of Soil Organic Matter Using Geostatistics: A Key Indicator to Assess Soil Degradation Status in central Italy

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Pedosphere 2012年第2期22卷 230-242页

作者： A.MARcHETTI c.PIccInI R.FRAncAVIGLIA L.MABIT Research centre for the Soil-Plant System CRA-RPS Via della Navicella 2-4 00184 Rome (Italy) Soil and Water Management & crop nutrition Laboratory FAO/IAEA Agriculture & Biotechnology Laboratory IAEA Laboratories Seibersdorf PO Box 100 Wagramerstrasse 5 A-1400 Vienna (Austria)

Soil organic matter (SOM) content is one of the main factors to be considered in the evaluation of soil health and fertility. As timing, human and monetary resources often limit the amount of available data, geostatistical techniques provide a valid scientific approach to cope with spatial variability, to interpolate existing data and to predict values at unsampled locations for accurate SOM status survey. Using geostatistical and geographic information system (GIS) approaches, the spatial variability of some physical and chemical soil parameters was investigated under Mediterranean climatic condition in the Abruzzo region of central Italy, where soil erosion processes accelerated by human induced factors are the main causes of soil degradation associated with low SOM content. Experimental semivariograms were established to determine the spatial dependence of the soil variables under investigation. The results of 250 soil sampling point data were interpolated by means of ordinary kriging coupled with a GIS to produce contour maps distribution of soil texture, SOM content related to texture, and c/n ratio. The resulting spatial interpolation of the dataset highlighted a low content of SOM in relation with soil texture in most of the surveyed area (87%) and an optimal c/n ratio for only half of the investigated surface area. Spatial location of degraded area and the assessment of its magnitude can provide decision makers with an accurate support to design appropriate soil conservation strategies and then facilitate a regional planning of agri-environmental measures in the framework of the European common Agricultural Policy.

关键词： c/n ratio ordinary kriging soil organic carbon soil quality spatial variability

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金的选矿

矿产保护与利用 1988年第3期 27-33页

作者： n.c.Wall 吴荣庄

近年来,全世界都在大力开采金矿。理由很明显:金的世界需求量在不断上升,从而造成黄金价格较高而且稳定。这就需要日益增加低品位或难选金矿石的处理量。以及不断寻找提高现有作业的经济效益,使得金的选矿技术有很大的变化和创新。金选... 详细信息

近年来,全世界都在大力开采金矿。理由很明显:金的世界需求量在不断上升,从而造成黄金价格较高而且稳定。这就需要日益增加低品位或难选金矿石的处理量。以及不断寻找提高现有作业的经济效益,使得金的选矿技术有很大的变化和创新。金选矿工艺的最早进展通过增加效益、降低成本,不仅反映出金冶金的经济面貌,而且也反映出主要与金冶炼厂排放的废气和废液有关的环境影响。

关键词：氰化物氰化合物矿石离子交换树脂整理剂洗提液生物氧化法浸出时间含氰废水停留时间树脂纤维堆浸法堆浸矿浆流混和物

comparison of the simulated gamma-ray attenuation coefficients with the real measurements

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nuclear Science and Techniques 2015年第5期26卷 53-57页

作者： E.E.Ermis E.Pilicer c.celiktas Ege University Faculty of Science Physics Department Uludag University Faculty of Arts and Science Physics Department

The gamma-ray linear and the mass attenuation coefficients of Pb, Al, cu, and plexiglass materials were calculated from both experimental and theoretical(simulation) methods. For the experimental results, a spectrometer, which was consisted of a na I(Tl) inorganic scintillation detector, was used. The theoretical attenuation values were calculated by means of the FLUKA Monte carlo(Mc) and XcOM programs. Obtained attenuation coefficients from the experiment and the theoretical methods were compared with each other and literature values.

关键词：质量衰减系数 γ射线实际测量模拟理论计算方法闪烁体探测器蒙特卡罗方法玻璃材料