談談正棱柱、正棱錐、正棱台直观图的合理画法

画好正棱柱、正棱锥、正棱台的直观图,关键之一是怎样画好在水平平面的底面。而画好这个底面正多边形,又取决于底面上的轴测轴Ox,Oy的选择。一般地,在底上选取Ox轴,Oy轴的方法有三种: (1) 以底面正多边形的一边或与这边平行的对角线所在的直线为Ox轴,而以这边上的垂线为Oy轴(图1中的<2>,<5>)。 (2) 以一边上的垂线为Ox轴,而以这边或与这边平行的对角线所在的直线为Oy轴(图1中的<1>,<4>,<6>)。 (3) 正方形还可以以两条对角线所在的直线分别为Ox轴和Oy轴(图1中的<3>)。选定了轴测轴后,由正多边形的各顶点向Ox轴,Oy轴引垂线,得到一些横线段和纵线段,然后按照直观图的画法原则,就可以得到这些正多边形在水平平面内的绘象(图2)。对应于上面的底的绘象,所画出的正棱柱、正棱     

Tectonic setting discrimination and ~(40)Ar/~(39)Ar isotope geochronology of the Miba granite

The Miba granite is located in the juncture of Kang County in eastern Gansu Provinceand Lueyang County in Shanxi Province. It is considered to be the post-orogenic granite(POG-type) by major element discrimination method of Maniar. ~40Ar/~39Ar dating indicates that itsemplacement time is about 240-230 Ma and it is the result of the Indo-Sinian magmatism. In theearly Yanshan period (about 193.8 Ma), a thermal event resulted in the partial opening of the ar-gon isotope system of the biotite.     

Magmatism and deformation times of the Xidatan rock series, East Kunlun Mountains

The Xidatan rock series consist of mylonite, gneiss and granite. The U-Pb age showsthat the granite was formed at 206 Ma, and the ~(40)Ar/~(39)Ar ages of the biotite display that the my-lonite was formed at 145 Ma when the Xidatan ductile shear zone occurred. At about 110-100 Mathe Xidatan Fault reactivated again. As a result, the biotite and muscovite of Xidatan rock seriesopened their argon isotope system.     

稳定同位素稀释-超高效液相色谱-串联质谱法快速测定植物油中16种真菌毒素

建立了稳定同位素稀释-超高效液相色谱串联质谱法简单、快速、高效地检测植物油中16种真菌毒素的方法。植物油经乙腈-水-乙酸(84∶15∶1,V/V)提取并离心后,上清液用水1∶1(V/V)稀释,高速低温离心去除油脂,过膜后,加入稳定同位素内标补偿基质效应干扰,以五氟苯色谱柱为分离柱,用甲醇和含有0.1%(V/V)甲酸的1 mmol/L乙酸铵溶液进行梯度洗脱,超高效液相色谱-串联质谱(UPLC-MS/MS)检测,内标标准曲线法定量测定植物油中的16种真菌毒素。16种真菌毒素的线性相关系数均大于0.9994,检出限为0.1~66.7μg/kg,定量限为0.3~200.0μg/kg。4种不同植物油基质中,3个浓度水平的加标回收率为74.2%~105.6%,相对标准偏差为0.3%~13.9%。采用本方法检测了市售38个植物油样品中的真菌毒素。本方法简便、快速、可靠,可用于植物油中16种真菌毒素的快速准确检测。