二氧化锗同类异构体在标化及高量锗测定中的影响

研究了用X-射线衍射分析纯二氧化锗分子结构与组成，以及结构中存在同类异构体时，不同分解方法对标定和锗测定结果的影响。提出了在锗滴定法中使用的基准二氧化锗，用Na2O2高温熔融分解，以消除因低温碱溶不完全，在标定时产生的误差导致锗结果偏高。拟定方法经实际运用，结果准确、满意。     

锗的分析概况

本文是关于锗分析方法的综述，共分锗的分析和分离方法，锗的定量法和有机锗Ｇｅ－１３２产量质量控制法研究现状三大部分。锗的分析和分离方法中，介绍了锗的分析方法及分类，锗样品前处理、分离与预浓集的原理和方法，并便 出了有参考价值的图表，锗的定量法中介绍了重量法、容量法、分光光度法、荧光法和发光分析法原子吸收分光光度法、原子发射光法、电化学分析法。每一分析法中又介绍了测定法研究及应用实例。在测定法研究及应     

土壤全锗的催化极谱测定

１引言锗是地球上含量极少的元素之一，在地壳中的丰度仅为１．５ｕｇ／ｇ。它虽未被正式确定为人体中必需的微量元素，但在人体中的重要生理作用已逐渐为人们所了解。锗能刺激人体血液中红血球的生成，增强人体血液吸收氧的能力，促进新陈代谢，防止衰老。由于人体所摄入的锗主要是来自食品，归根究底来源于土壤，所以测定土壤锗显得十分必要。近年来关于矿石中锗、水中锗、生物样品如人发、人参中锗的极谱测定方法已有很多报道，但土壤中锗的测定方法尚未见报道。本试验利用锗与前素红在硫酸介质中并有钒（Ⅳ）存在时产生灵敏度较高的二阶…     

龙头山饮用天然锗泉水概况

报告了龙头山饮用天然锗泉水的锗浓度，水质和保健作用等概况。     

锗的应用与市场分析

分析了锗产量增长速度不快的原因和当前应用领域现状。并根据锗的性质，对锗市场作了分析，提出了扩大锗应用的看法。     

高含量锗物料中锗的滴定法测定

从碘酸钾容量法测定高含量锗物料中锗量的关键步骤蒸馏分离入手,分析了方法误差的原因,推出了一套设计合理、无泄漏、易于操作的蒸馏装置,使用该蒸馏装置蒸馏分离效果好,标准回收率高,测定结果精密高,具有推广价值。     

电感耦合等离子体发射光谱法测定锗精矿中锗量

建立了用硝酸、氢氟酸、磷酸溶解样品,电感耦合等离子体发射光谱法测定锗精矿中锗量的方法。试验选择209.426nm作为最优分析谱线,锗的检出限为0.006μg/mL,测定下限为0.020 μg/mL,在磷酸基体匹配的条件下测定,测定范围为1%-15%,与经典碘酸钾滴定法对比,数据一致,相对标准偏差<3%(n=11),加标回收率98%~101%,能够满足快速测定及批量处理锗精矿中1%-15%的锗含量的需求。     

锗的环境生态研究

锗是分散性元素，在动、植物中属于微量，超微量元素。在动物中，锗多存在于肝脏、肌肉，亦见于骨骼及鱼鳃中，在植物中，锗主要分布于叶子及糖类淀粉贮藏的器官中。通过动植物肿瘤的分析，说明锗不是致病元素。锗用于保健，主要在于促进糖类代谢，提高免疫力，而不是直接杀死癌细胞或其它病原体。     

硼-锗骨架无机微孔材料研究进展

作为潜在的新型功能材料，硼-锗骨架微孔化合物近年来得到科学家的普遍关注。本文从结构化学的角度，分别讨论了硼酸盐、锗酸盐及硼锗酸盐研究体系，并对其中的典型结构进行了描述、归类与总结；针对硼、锗易成簇聚集的特点，探讨了硼-锗骨架无机微孔化合物研究的发展趋势。     

锗的市场结构变化与光纤通信

介绍了锗在光纤通信中的作用，分析了世界光纤市场的变化及其对锗的市场结构的影响，预测近期国内锗的市场结构不会有大的变化。     

Residue‐centric modeling and design of saccharide and glycoconjugate structures

The RosettaCarbohydrate framework is a new tool for modeling a wide variety of saccharide and glycoconjugate structures. This report describes the development of the framework and highlights its applications. The framework integrates with established protocols within the Rosetta modeling and design suite, and it handles the vast complexity and variety of carbohydrate molecules, including branching and sugar modifications. To address challenges of sampling and scoring, RosettaCarbohydrate can sample glycosidic bonds, side‐chain conformations, and ring forms, and it utilizes a glycan‐specific term within its scoring function. Rosetta can work with standard PDB, GLYCAM, and GlycoWorkbench (.gws ) file formats. Saccharide residue‐specific chemical information is stored internally, permitting glycoengineering and design. Carbohydrate‐specific applications described herein include virtual glycosylation, loop‐modeling of carbohydrates, and docking of glyco‐ligands to antibodies. Benchmarking data are presented and compared to other studies, demonstrating Rosetta's ability to predict glyco‐ligand binding. The framework expands the tools available to glycoscientists and engineers. © 2016 Wiley Periodicals, Inc.     

THE EFFECT OF CLAY DISPERSION ON THE CRYSTALLIZATION AND MORPHOLOGY OF POLYPROPYLENE／CLAY COMPOSITES

PP/clay composites with different dispersions, namely, exfoliated dispersion, intercalated dispersion and agglomerates and particle-like dispersion, were prepared by direct melt intercalation or compounding. The effect of clay dispersion on the crystallization and morphology of PP was investigated via PLM, SAXS and DSC. Experimental results show that exfoliated clay layers are much more efficient than intercalated clay and agglomerates of clay in serving as nucleation agent due to the nano-scale dispersion of clay, resulting in a dramatic decrease in crystal size (lamellar thickness and spherulites) and an increase of crystallization temperature and crystallization rate. On the other hand, a decrease of melting temperature and crystallinity was also observed in PP/clay composites with exfoliated dispersion, due to the strong interaction between PP and clay. Compared with exfoliated clay layers, the intercalated clay layers have a less important effect on the crystallization and crystal morphology. No effect is seen for samples with agglomerates and particle-like dispersion, in regard to melting temperature, crystallization temperature, crystal thickness and crystallinity.     

Contributions to the Chemistry of the Binary Compounds of the Transition Elements

Phase and structural relationships of the sulfur, selenium, and tellurium compounds of the 4d and 5d transition elements of groups IV to VII of the periodic system are discussed. Homologous elements behave very similarly with respect to the chalcogens, and this is particularly the case for niobium and tantalum, and for molybdenum and tungsten. However, zirconium, niobium, and molybdenum have a greater tendency towards formation of chalcogen-poor phases than their homologues hafnium, tantalum, and tungsten. Subchalcogenides are known only for zirconium and niobium. The number of phases and the tendency towards formation of solid solutions are considerably smaller among the tellurides than among the sulfides and selenides. The crystal structures of the telluride phases also differ from those of the sulfide and selenide phases of analogous composition. In addition, a review of the phase and structural relationships of the arsenic and antimony compounds of the 4d and 5d transition elements of groups V to VII is given.     

Tautomeric and conformational isomerism of natural hydroxyanthraquinones

Natural 1,5-di-, 1,4,5-tri-, and 1,4,5,8-tetrahydroxyanthraquinones and their anions and metal complexes were shown to be equilibrium mixtures of tautomers and conformers using quantum-chemical and correlation analysis of elecronic absorption spectra. Solvent effects, ionization, complexation, and the introduction and substitution of substituents were accompanied by shifts of tautomeric and conformational equilibria that determine the color of the compounds. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 224–229, May–June, 2006.     

线状铜电极在磷酸溶液中电流混沌振荡的同步行为

研究了恒电位下两个铜线电极在磷酸溶液中的电流混沌振荡行为,通过恒定不同的电位数值,改变单个电极的电流振荡混沌行为,研究了不同混沌间的相互作用.调整线电极间的距离,研究了电极间距对电流振荡行为的影响.实验中两电极的振荡间呈现了复杂的耦合作用,耦合后的频率与耦合前电极原有的频率不同.两电极的混沌电流振荡中呈现出同步、准周期同步和反相同步等现象.电极距离一定时,振荡波形差别很大的两电极的电流容易呈现反相同步和准周期同步,波形差别不大时容易产生同步.强的耦合导致电极间电流振荡的同步,电极距离的加大,电极间电流振荡难以产生同步.对耦合作用机制也进行了探讨.     

Carbenes and Nitrenes: Recent Developments in Fundamental Chemistry

Carbenes and nitrenes can exist in both singlet and triplet states, sometimes equally stable and interconverting either thermally or photochemically. Many carbene and nitrene reactions proceed via tunneling at low temperatures. Numerous singlet and triplet states have been characterized spectroscopically, and a detailed understanding of the chemical and physical properties of carbenes and nitrenes is emerging. There has been significant progress in the direct observation of carbenes, nitrenes, and many other reactive intermediates in recent years through the application of matrix photolysis and flash vacuum pyrolysis linked with matrix isolation at cryogenic temperatures. Our understanding of singlet and triplet states has improved through the interplay of spectroscopy and computations. Bistable carbenes and nitrenes as well as many examples of tunneling have been discovered and numerous rearrangements and fragmentations have been documented. The correlation of the zero‐field splitting parameter D with calculated spin densities on nitrenes and carbenes is discussed. This Minireview gives an overview of some of these developments.     

Two-dimensional Metal-Organic Frameworks and Derivatives for Electrocatalysis

The most important topics in the world today are environmental and resource issues. The development of green and clean energy is still one of the great challenges of social sustainable development. Two-dimensional(2D) metal-organic frameworks(MOFs) and derivatives have exceptional potential as high-efficiency electrocatalysts for clean energy technologies. This review summarizes various synthesis strategies and applications of 2D MOFs and derivatives in electrocatalysis. Firstly, we will outline the advantages and uniqueness of 2D MOFs and derivatives, as well as their applicable areas. Secondly, the synthetic strategies of 2D MOFs and derivatives are briefly classified. Each category is summarized and we list classic representative fabrication methods, including specific fabrication methods and mechanisms, corresponding structural characteristics, and insights into the advantages and limitations of the synthesis method. Thirdly, we separately classify and summarize the application of 2D MOFs and derivatives in electrocatalysis, including electrocatalytic water splitting, oxygen reduction reaction(ORR), CO₂ reduction reaction(CO₂RR), and other electrocatalytic applications. Finally, the development prospects and existing challenges to 2D MOFs and derivatives are discussed.     

Selecting polymers for medical devices based on thermal analytical methods

This biomaterials overview for selecting polymers for medical devices focuses on polymer materials, properties and performance. An improved understanding of thermoplastics and thermoset properties is accomplished by thermal analysis for device applications. The medical applications and requirements as well as the oxidative and mechanical stability of currently used polymers in devices are discussed. The tools used to aid the ranking of the thermoplastics and thermosets are differential scanning calorimetry (DSC), thermogravimetry (TG), thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA) as well as a number of key ASTM polymer tests. This paper will spotlight the thermal and mechanical characterization of the bio-compatible polymers e.g., olefins, nylon, polyacetals, polyvinyl chloride and polyesters.     

Nature spermidine and spermine alkaloids: Occurrence and pharmacological effects

Spermidine and spermine are special polyamines in organisms, and produced in vivo by putrescine and S-adenosylmethionine catalyzed by a variety of enzymes. Spermidine and spermine possess multiple amino groups, and are closely related to cell division, growth and survival. Spermidine and spermine alkaloids are widely distributed in plants, bacteria and marine organisms, and can be divided into macrocyclic and open chain according to the skeletons. Spermidine and spermine alkaloids exhibited numerous pharmacological effects such as anti-inflammatory, antibiotics, anti-tumor, anti-Alzheimer and anti-virus. However, up to now, there are few systematic reviews on spermidine and spermine alkaloids. In this review, based on the number of atoms in the ring, we summarized the distributions and pharmacological effects of spermidine and spermine alkaloids. Spermidine and spermine alkaloids have special chemophenetic significances in the plant kingdom, especially the macrocyclic spermidine and spermine alkaloids. Spermidine alkaloids are much more abundant in nature than spermine alkaloids. The pharmacological activities of the open chain spermidine and spermine alkaloids are studied in depth. Polycyclic guanidine spermidine alkaloids, isolated from marine sponge, exhibit great potential in various cancer cells. However, pharmacological studies of macrocyclic spermidine and spermine alkaloids are scarce. Synthesis is an effective way to get more spermidine and spermine alkaloids and their analogues for further study.     

聚硅氧烷侧链甲基化β-环糊精键合交联手性毛细管柱分离对映体

合成了聚硅氧烷侧链的甲基化β-环糊精衍生物手性固定相,成功地进行了固载化,固载化程度高于90%。经测试,柱性能稳定,可在200℃下长期使用。暴露于空气中存放两年,柱效及选择性未见明显改变。对卤代烃及一些醇对映体的直接分离表现出良好的立体选择性,并应用于毛细管电色谱拆分手性化合物。