X-ray research of polycrystals. X-ray diffraction methods for precision determinations of polycrystal lattice parameters over unsolved double lines

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Magnetic carbon

The discovery of nanostructured forms of molecular carbon has led to renewed interest in the varied properties of this element. Both graphite and C60 can be electron-doped by alkali metals to become superconducting; transition temperatures of up to 52 K have been attained by field-induced hole-doping of C60 (ref. 2). Recent experiments and theoretical studies have suggested that electronic instabilities in pure graphite may give rise to superconducting and ferromagnetic properties, even at room temperature. Here we report the serendipitous discovery of strong magnetic signals in rhombohedral C60. Our intention was to search for superconductivity in polymerized C60; however, it appears that our high-pressure, high-temperature polymerization process results in a magnetically ordered state. The material exhibits features typical of ferromagnets: saturation magnetization, large hysteresis and attachment to a magnet at room temperature. The temperature dependences of the saturation and remanent magnetization indicate a Curie temperature near 500 K.     

Contribution to the method for approximation of X-ray diffraction line profile

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Species-specific responses of Late Quaternary megafauna to climate and humans

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.     

低聚肽分子结构与其薄层色谱Rm的关系

利用23种与吗啡衍生物有关的低聚肽薄层分析的实验结果计算证明,lnR_M值可看作是构成这些化合物的各基团贡献的总和。实验值lnR_M与计算值lnR′_M很好相符。lnR′_M=sum from n_i lnR′_(Mi),式中lnR′_(Mi)是i基团的lnR′_M值,n_i是分子中i基团的数目,lnR′_(Mi)是由R_M的实验值用最小二乘法计算出的。文中还初步讨论了流动相组成对lnR_M的影响。     

Contribution to the X-ray diffraction methods for precision determinations of polycrystal lattice parameters

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柳杉树轮δ~(13)C与气候要素的分析与应用

<正>对采自气候为非限制性因子地区的柳杉树轮稳定碳同位素比 δ１３ Ｃ进行气候响应分析。用排除法消除大气二氧化碳中δ１３Ｃ的变化对柳杉树轮δ１３Ｃ变化的影响后,建立残差年序列ＲＥ,并结合西天目山气象站的气象记录,分析了树轮δ１３Ｃ年序列对气候要素的响应。结果表明：西天目山地区树轮 δ１３Ｃ的高频振荡与 １１、１２月最高气温的平均值,１、２、３月降水总和以及６、７月降水总和显著相关,在一定程度上反映了东亚季风对该区的影响大小。可见气候非限制性因子地区树轮稳定碳同位素组成年序列同样可以作为气候变化指针。     

X-ray research of polycrystals. The methods for approximation at determination of the real width of X-ray interferentional lines with the application of a standard-sample

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X-ray research for polycrystals. The formation geometry of instrumental width of the diffractional line at the investigation of the polycrystals in the translucent X-rays

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