液相色谱-串联质谱法同时测定生物组织全基因组DNA甲基化和羟甲基化水平

测定全基因组DNA甲基化和羟甲基化水平对于研究环境污染物暴露的影响及致病机理具有重要的作用。本文建立了液相色谱-串联质谱（LC-MS/MS）同时测定动物组织中全基因组DNA甲基化和羟甲基化水平的方法。从动物组织样品中提取DNA,并将其酶解成单核苷,利用液相色谱-串联质谱法测定5-甲基胞嘧啶核苷、5-羟甲基胞嘧啶核苷和鸟嘌呤核苷的含量,计算全基因组DNA甲基化率和羟甲基化率。利用该方法研究了砷暴露对大鼠肝脏和小脑全基因组DNA甲基化和羟甲基化水平的影响,得到了砷影响DNA甲基化及羟甲基化的初步数据。该方法具有良好的重现性、灵敏度和稳定性,可以同时检测差异较大的DNA甲基化和羟甲基化水平。为同时研究DNA甲基化和羟甲基化水平提供了有力的支持。     

Oxygen ion conductivity of La_(0.8)Sr_(0.2)Ga_(0.83)Mg_(0.17-x)Co_xO_(3-δ) synthesized by laser rapid solidification

Materials La0.8Sr0.2Ga0.83Mg0.17-xCoxO3-δ with x = 0, 0.05, 0.085, 0.10, and 0.15 are synthesized by laser rapid solidification. It is shown that the samples prepared by laser rapid solidification give rise to unique spear-like or leaf-like microstructures which are orderly arranged and densely packed. Their electrical properties each show a general dependence of the Co content and the total conductivities of La 0.8 Sr 0.2 Ga 0.83 Mg 0.085 Co 0.085 O 3-δ prepared by laser rapid solidification are measured to be 0.067, 0.124, and 0.202 S·cm -1 at 600, 700, and 800℃, respectively, which are much higher than by conventional solid state reactions. Moreover, the electrical conductivities each as a function of the oxygen partial pressure are also measured. It is shown that the samples with the Co content values ≤ 8.5 mol% each exhibit basically ionic conduction while those for Co content values ≥ 10 mol % each show ionic mixed electronic conduction under oxygen partial pressures from 10 -16 atm (1 atm = 1.01325×10 5 Pa) to 0.98 atm. The improved ionic conductivity of La 0.8 Sr 0.2 Ga 0.83 Mg 0.085 Co 0.085 O 3-δ prepared by laser rapid solidification compared with by solid state reactions is attributed to the unique microstructure of the sample generated during laser rapid solidification.     

锂离子电池用富锂正极材料的研究进展

富锂材料xLi₂MnO₃·(1-x)LiMO₂（0-1）和低廉的价格已引起人们的广泛兴趣. 但其首次充放电循环的较大不可逆容量损失、较差的倍率性能和循环过程的材料相变等关键问题制约了其发展. 富锂材料结构解析和充放电机理探索一直是研究的热点. 目前,富锂材料是否为固溶体仍有争论,首次充电4.5 V平台的氧流失机理已得到确认. 为了提高富锂材料的电化学性能,可从体相掺杂、表面包覆和结构形貌控制等方面对材料进行改性,其电化学性能有显著提升. 本文综述了富锂材料最新研究进展,归纳了相关制备方法,重点介绍了富锂材料的结构特点、锂嵌脱机理和改性方法,并展望了今后的研究方向.     

Inverse Monte Carlo study on effective interaction potential of Ag--Rh alloy from pair correlation functions

This paper presents an inverse Monte Carlo method to reconstruct pair interaction potential from pair correlation function. This approach adopts an iterative algorithm on interaction potential to fit known pair correlation function by compelling deviations of canonical average to meet with Hamiltonian parameters on a basis of statistical mechanism. The effective interaction potential between particles in liquid Ag--Rh alloys has been calculated with the inverse Monte Carlo method. It demonstrates an effective and simple way to obtain the effective potential of complex melt systems.     

高效液相色谱-串联质谱法分离鉴定绿原酸及其相关杂质

建立了高效液相色谱-串联质谱法（HPLC-MS/MS)分离和鉴定绿原酸及其相关杂质的方法。采用C18色谱柱(5 μm,4.6 mm×150 mm),乙腈-水（含0.1%甲酸）(体积比为8∶92)为流动相,经HPLC-MS/MS和HPLC-二极管阵列检测器在线检测,对工业绿原酸中的奎尼酸、咖啡酸、绿原酸同分异构体等8个相关杂质的结构进行了鉴定。     

一种新型超临界流体萃取-高效液相色谱在线联用系统的构建

天然产物研究一直是植物学、化学和药学的重要研究领域．通过从天然产物中寻找生物活性成分和先导物是创制新药的有效途径之一．有效成分的提取是天然产物研究中最基本和最关键的环节．超临界流体萃取（Supercritical fluid extraction,简称SFE）是近年来发展较快的一种新型样品提取技术．超临界CO2作为最常用的萃取剂已被用于天然药物中非极性和弱极性有效成分的提取,尤其是挥发性和热敏性的物质．此外,通过加入适当的添加剂还可有效地萃取极性化合物,和传统的化学方法相比,     

Route to Stabilize Cubic Gauche Polynitrogen to Ambient Conditions via Surface Saturation by Hydrogen

Cubic gauche polynitrogen(cg-N) is an attractive high-energy density material. However, high-pressure synthesized cg-N will decompose at low pressure and cannot exist under ambient conditions. Here, the stabilities of cg-N surfaces with and without saturations at different pressures and temperatures are systematically investigated based on first-principles calculations and molecular dynamics simulations. Pristine surfaces at 0 GPa are very brittle and will decompose at 300 K, especially(110) sur...     

浅谈如何借助“意外”打造高质数学课堂

<正>在新课改的推动下,数学课堂逐渐向多元化发展,更加关注学生主体作用的发挥,“自主、合作、探究”已成为高效数学课堂不可或缺的三要素,其在数学教学中发挥着不可估量的作用．为了提升数学课堂有效性,使课堂更加高效,教师在数学课堂上需要打破单一的、保守的“讲授式”教学模式,将数学课堂打造成开放的动态课堂^[1]．为了打造高效动态的数学课堂,在教学中就需要引导学生经历自主学习和合作探究,虽然在此过程中可能会出现一些不确定的因素,但这些“不确定”往往可能就是隐藏的意外惊喜．为此,在教学中,教师要鼓励学生进行交流和探究,使不同思维碰撞出耀眼的火花,彰显数学之美．为了激发学生的积极性和探究欲,将课堂引入更深处,笔者结合教学中出现的“意外”,浅谈了探究在数学教学中的重要意义,以期共鉴．     

氮化硅片上光栅耦合器的优化和实验

在785 nm激励的拉曼片上传感器结构中，氮化硅片上光栅耦合器的性能直接关系到激励光的耦合效果。首先建立了光栅耦合器的二维、三维结构模型，采用时域有限差分（FDTD）仿真软件对光栅耦合器进行数值分析。以耦合效率为主要性能指标，分析了光源入射角度、光栅常数、光栅高度、填充因子和光栅刻蚀深度各参数的影响。采用电子束光刻法制备了光栅耦合器。最后，对三维全刻蚀聚焦波导光栅耦合器进行了测试。结果表明，二维波导光栅耦合器的性能最好，其耦合效率可达39.64%，三维全刻蚀聚焦波导光栅耦合器在实际测试中的耦合效率能达19.91%。光栅耦合器能有效将光耦合进波导中，在波导传感中具有潜在的应用。