四

Tetraploid embryos could be produced by electrofusion at the stage of two-cell embryos, which could develop to blastocysts followed by fusion of cyto-plasm and nucleus and cleavage in vitro. During the fusion of cytoplasm, the DNA methylation levels of the fused embryos are as high as these of two-cell diploid embryos in vivo Then the embryos are rapidly demethylated when the nucleus begin to fuse, resulting in the lowest DNA methylation levels when the nucleus are fused completely. After that, the DNA methy-lation levels of the fused embryos are gradually increased until the morula stage. However, whereas an asymmetric distribu-tion of DNA methylation is established in vivo-derived blastocysts with a higher methylation level in the inner cell mass than that in the trophectoderm, we can not detect the asymmetric distribution in most in vitro-derived tetraploid blastocysts.

结果表明：利用电融合方法制备的小鼠四倍体胚胎在体外培养体系中经历细胞质融合、细胞核融合及细胞继续分裂发育直到囊胚期的过程，在细胞质融合的时候胚胎卵裂球同体内体外培养二倍体胚胎一样，呈现高度甲基化状态；在细胞核开始融合的时候，甲基化水平急速下降，在细胞核完全融合的时候甲基化水平达到最低点；随着胚胎继续分裂，胚胎甲基化水平逐渐增加，在桑葚胚期甲基化水平最高；但是囊胚期四倍体胚胎内细胞团同滋养层细胞甲基化荧光信号没有差别，这与体内体外培养二倍体囊胚内细胞团细胞甲基化荧光强度高于滋养层细胞甲基化荧光强度不同。

Tetraploid embryos could be produced by electrofusion at the stage of two-cell embryos, which could develop to blastcysts fellowed by fusion of cytoplasm and nucleus and cleavage in vitro.After fusion of cytoplasm, the DNA methylation levels of the fused embryos was very high as well as two-cell diploid embryos in vivo.Then the embryos was rapiddly demethylated when the nucleus begin to fuse, resulting the lowest DNA methylation levels when the nucleus fused completely.After that, the DNA methylation levels of fused embryos were gradually increased until the blastocysts stage.However, whereas an asymmetric distribution of DNA methylation was established in an vivo-derived blastocysts with a higher methylation level in the inner cell mass than in the trophectoderm, in most vitro-derived tetraploid blastocysts, we can not detect the asymmetric distribution.

结果表明：利用电融合方法制备的小鼠四倍体胚胎在体外培养体系中经历细胞质融合、细胞核融合及细胞继续分裂发育直到囊胚期的过程，在细胞质融合的时候胚胎卵裂球同体内体外培养二倍体胚胎一样，呈现高度甲基化状态；在细胞核开始融合的时候，甲基化水平急速下降，在细胞核完全融合的时候甲基化水平达到最低点；随着胚胎继续分裂，胚胎甲基化水平逐渐增加，在囊胚期甲基化水平最高；但是囊胚期四倍体胚胎内细胞团同滋养层细胞甲基化荧光信号没有差别，这与体内体外培养二倍体囊胚内细胞团细胞甲基化荧光强度高于滋养层细胞甲基化荧光强度不同。

The wind rose, and from a fresh breeze it soon increasedto a regular gale; that is to say, it acquired a speed of from forty toforty-five miles an hour, before which a ship in the open sea would haverun under close-reefed topsails.

风愈刮愈大，很快就由微风一变而为正式的暴风了；它的速度达到每小时四十到四十五英里，船如在海里遇到这种风，即使紧收着中桅的帆，也会象飞似的前进的，乘风破浪号在将近六点钟的时候到了港湾口，可是这时候潮势变了，因此它不能入港。

The wind rose, and from a fresh breeze it soon increasedto a regular gale; that is to say, it acquired a speed of from forty toforty-five miles an hour, before which a ship in the open sea would haverun under close-reefed topsails. Now, as it was nearly six o'clock when the"Bonadventure" reached the gulf, and as at that moment the tide turned, itwas impossible to enter.

风愈刮愈大，很快就由微风一变而为正式的暴风了；它的速度达到每小时四十到四十五英里，船如在海里遇到这种风，即使紧收着中桅的帆，也会象飞似的前进的，乘风破浪号在将近六点钟的时候到了港湾口，可是这时候潮势变了，因此它不能入港。

In this paper,on the basis of the closed loop circuit equation of the equivalent plant mechanism,a design equation of space four-bar mechanism is set up.

本文在当量平面机构回路闭合方程的基础上建立空间四杆机构的设计方程，为叉角90°的空间四杆机构设计的研究提出了又一方法。

The model of an open four-level atomic system is presented on the basis of the closed four-level atomic system.

在封闭的简单四能级原子系统模型的基础上提出了开放的四能级原子系统模型。

This thesis including four chapters: Chapter Ⅰ, Introduction: Chapter Ⅱ, bases and Circuits of Poset Matroids; Chapter Ⅲ, A Class of Functions Associated with Poset Matroids: Chapter Ⅳ, Dependence and Closure Operator of Poset Matroids.

本文包括四章内容，第一章，引言。第二章，偏序集拟阵的基和圈。第三章，一类与偏序集拟阵相关的函数。第四章，偏序集拟阵的相关性和闭包算子。

Add Four Leaf Clover To Your Website, Myspace etc...

增加四个四叶草到您的网站， MySpace的等。。

Of creatures that can fly and are bloodless some are coleopterous or sheath-winged, for they have their wings in a sheath or shard, like the cockchafer and the dung-beetle; others are sheathless, and of these latter some are dipterous and some tetrapterous: tetrapterous, such as are comparatively large or have their stings in the tail, dipterous, such as are comparatively small or have their stings in front.

一些能飞并且无血的动物是鞘翅类动物，因为它们把翅膀藏在鞘中，像是金龟子和蜣螂；一些是无鞘的，后面一类中一些是双翅的，一些是四翅的：四翅的，就像是那些相对较大的，或者刺在尾部的；双翅的，就像是相对较小的，或者刺在前方的。

First, a lot of experiments about changing character on CaCO3 surface has been rearsched,example,fatty acid,pentaerythritol,rosin ester,cocoanut oil,rosin, pentaerythritol + rosin ester,glycerine + rosin ester ,cocoanut oil + oleic acid,titanate + fatty acid,cocoanut oil + fatty acid, and so on surface active agents. Among these surface active agents, cocoanut oil + oleic acid,and titanate+ fatty acid,and cocoanut oil + fatty acid are the best.

本文首先对纳米碳酸钙的活化改性进行了实验研究，在硬脂酸钠、季戊四醇、松香酯、椰子油、松香、季戊四醇+松香酯、甘油+松香酯、椰子油+油酸、钛酸酯+硬脂酸钠、椰子油+硬脂酸钠等表面改性剂中，以硬脂酸钠、椰子油、油酸+椰子油、椰子油+硬脂酸钠等活化剂的活化效果较为理想。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。