On the number of amorphous phases in n-butanol: Kinetics of free radicals oxidation by oxygen in frozen n-butanol

We report on the discovery of a new solid, presumably amorphous n-butanol at ambient pressure. According to the literature data the melting point T_m of n-butanol is 183 K and the glass transition temperature T_g is 118 K. If kept isothermally at a fixed temperature between 130 and 160 K, the supercooled liquid n-butanol undergoes remarkable phase transformations to a solid phase. The new phase converts to liquid at a temperature of about 170 K. It is presumably amorphous because foreign substances dissolved in liquid n-butanol keep the same state in this new phase of butanol. The kinetics of free radical oxidation by dissolved oxygen in both solid amorphous phases is investigated in detail.     

OJ287: Post-Newtonian Calculation in Harmonic Coordinate and Pulsar Timing Residual Confirmation

We calculate and discuss the motion of the binary black hole OJ287 based on Post-Newtonian approximation in a harmonic coordinate. With gravitational waveform obtained, theoretical timing residual of PSR B1855+09 induced by gravitational radiation of OJ287 is presented and compared with observed data, further shows that hypothesis referring to OJ287 as a binary BH system might be proper. The energy flux of gravitational radiation from binary is also provided, from which we find that the flux changes sign successively: ?_N >0, ?_1PN <0, ?_2PN >0, in agreement with the relative signs of forces of each PN order, revealed in the previous work.     

蝎虎天体OJ287中等时标光变的周期特性研究

收集了蝎虎天体OJ287光学B, V, R, I波段37年的观测数据, 获得了从1972年至2009年的光变曲线. 运用Lomb-Scargle傅里叶变换方法分析中等时标光变的周期性特性, 发现存在52.0±1.1 d与255±23 d的主要周期成分,并模拟了存在倍周期分岔的准周期信号, 与不同时段观测数据的相图和关联维数进行对比. 结果表明, OJ287具有多周期尺度特征, 不同时段准周期光变中谐波成分不同, 谐波成分的变化与次黑洞对主黑洞吸积流的扰动有关, 光变中的谐波成分可能是主黑洞吸积流受强扰动时分岔形成的.     

MK-287的对映选择性合成

MK-287,即(2S,5S)-2-{3′-甲氧基-2′丙氧基-5′-[5″(3′″,4′″,5″′三甲氧苯基)四氢呋喃-2′-基]苯基砜基}乙醇,具有反式-2,5-二取代四氢呋喃的结构,是血小板活化因子(PAF)的良好拮抗剂,对许多由PAF引发的疾病有很好的治疗作用。立体选择性合成反式-2,5-二取代四氢呋喃的方法已有报道,MK-287的合成有γ-二酮法环合法和γ-芳基丁内酯法。前者立体选择性低(反式和顺式异构体之摩尔比为4：1),并需高效液相色谱分离两种异构体,后者反应步骤多,虽然反式和顺式异构体之比提高到50：1,但仍存在异构体不易分离问题,本文报道利用内酯醇(—)-1的结构特点,立体选择性和对映选择性地合成MK-287的新方法。     

基于聚合经验模态分解方法的OJ 287 射电流量变化周期分析

BL Lac 天体OJ 287 是一个重要的Blazar天体, 光变具有准周期特点. 本文从密歇根大学射电天文台数据库收集了OJ 287射电波段4.8, 8.0和 14.5 GHz超过30年时间的观测数据. 由于天文观测资料的复杂性, 一些传统寻找周期的方法不是太理想. 近几年迅速发展起来的聚合经验模态分解(EEMD) 特别适合于具有非线性和非平稳动态变化特性的Blazar天体光变规律的研究. 运用EEMD方法对OJ 287 的3个射电波段流量分别进行多时间尺度分解, 各获得6个代表不同时间尺度局部特征信息的本征模态函数分量和一个趋势项. 研究结果表明: 4.8 GHz射电流量变化的主要周期是18.9, 11.9, 5.7 和2.4年; 8.0 GHz 的主要周期是12.2, 5.2和2.4 年; 14.5 GHz的主要周期是21.8, 12.0, 4.3和 2.4 年. 尽管3个波段流量变化主要周期大小有一定的差别, 但是存在着近似相同的变化周期12.0 和2.4年, 说明这3个波段可能来源于相同的辐射机制, 也证实了OJ 287 射电波段和光学波段具有相同的长光变周期12.0 年. 这些结论表明: EEMD 作为一种全新的非线性、非平稳信号处理方法, 可以更精确地提取Blazar天体中不同光变周期的分量. 关键词： OJ 287 光变周期 聚合经验模态分解     

The magnetoresistance effect in a nanostructure with the periodic magnetic barriers

The magnetoresistance (MR) effect is theoretically investigated in a periodic magnetically modulated nanostructure, which can be realized experimentally by depositing periodic parallel ferromagnetic strips on the top of a heterostructure. We find that there exists a significant conductance difference for electrons through the parallel (P) and antiparallel (AP) magnetization configurations, which results in a considerable magnetoresistance effect. We also find that the magnetoresistance effect depends not only on the temperature but also on the number of the periodic magnetic barriers.