Angular dependent NEXAFS study of the molecular orientation of PTCDA multilayers on Au （111） surface

The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The significant angular dependence of important resonant structures (π* and σ*) reveals that PTCDA molecules adopt an ordered geometry on the substrate surface. The average tilt angle of the PTCDA molecular planes is 27°±10° from the Au (111) surface.     

太阳活动峰年和谷年期间黑子群与耀斑的统计分析

基于NOAA/SWPC公布的太阳活动数据,我们选取第24太阳活动峰年附近的12个连续月份(2011年7月至2012年6月)和第23太阳活动周谷年附近的12个连续月份(2005年7月至2006年6月),统计了这两段时间中太阳黑子群和耀斑的活动规律,并根据时间、黑子群分布纬度、寿命和磁场类型等对峰年和谷年进行了详细分析和比较,主要结论如下所述.(1)黑子群数随时间的变化在峰年和谷年均比较随机,峰年期间黑子数比谷年增多1.5倍左右.耀斑爆发与黑子群活动具有良好的相关性,但峰年期间存在某个月份耀斑数很少的现象,而谷年期间存在某个月份耀斑数集中增多的现象.(2)无论峰年还是谷年,δ类型黑子群的耀斑产率(耀斑总数与黑子群总数之比)最大,但β型黑子群产生的耀斑爆发最多.耀斑产率与磁场类型有密切关系,但与其所处太阳活动周中的阶段无关.(3)黑子群和耀斑的纬度分布的南北不对称性,以X级耀斑最为显著.峰年较谷年的耀斑数增加主要集中在C级和M级.(4)耀斑产率同黑子群寿命具有良好的相关性,但黑子群的数目同它们的寿命之间没有明显的规律.     

Regulation of p53 activity through lysine methylation

p53 is a tumour suppressor that regulates the cellular response to genotoxic stresses. p53 is a short-lived protein and its activity is regulated mostly by stabilization via different post-translational modifications. Here we report a novel mechanism of p53 regulation through lysine methylation by Set9 methyltransferase. Set9 specifically methylates p53 at one residue within the carboxyl-terminus regulatory region. Methylated p53 is restricted to the nucleus and the modification positively affects its stability. Set9 regulates the expression of p53 target genes in a manner dependent on the p53-methylation site. The crystal structure of a ternary complex of Set9 with a p53 peptide and the cofactor product S-adenosyl-l-homocysteine (AdoHcy) provides the molecular basis for recognition of p53 by this lysine methyltransferase.     

广义Fibonacci序列的几个性质

本给出了广义Ｆｉｂｏｎａｃｃｉ序列的一些性质,并且引进了相应的广义Ｌｕｃａｓ序列,讨论了这两种序列之间的关系。