问题 填空题

点P关于x轴对称的点是(3,-4),则点P关于y轴对称的点的坐标是______.

答案

∵点P关于x轴对称的点是(3,-4),则P点的坐标是(3,4).

∴点P关于y轴对称的点的坐标是(-3,4)

单项选择题

对于自然界中的物质,无论大的还是小的,人类似乎找到了操作它们的合适方法,利用起重机可以移动成吨重的货物,使用光镊可以拨动分子和原子,等等。最近哈佛大学的科学家又有了新的发明,那就是通过模仿生物大分子的融合装配,使微米级的物体能够自己装配自己。

众所周知,DNA和蛋白质等大分子都能依靠形状的互补或分子间的作用力(如氢键和疏水作用力)来进行分子间的牵引。因此,多肽能在被基因表达后自发地折叠成有功能的蛋白质,DNA也能在扭曲成双螺旋后继续缠绕成短棒形状的染色体。然而对于比生物活性分子稍大一些的物体来说,这种作用力方式同样有效吗

为了得到答案,哈佛大学的怀特赛德和他的学生开始模仿蛋白质的融合装配,用被称为二甲基硅氧烷的疏水材料制作了一些六角形的小物体,这些小物体虽然只有几个微米大小,但怀特赛德却设法将它们中的数个黏结在一起,并在个别面上涂上了亲水物质,做成一些具有不同形状的模拟“蛋白分子”。把这些“蛋白分子”放入水和油的混合系统后,亲水部位结合到亲水部位,疏水部位结合到疏水部位,它们果然按照设计的意图完成了自组装。

科学家认为,这项新近发明的技术可以在一些微小物体的精确安装中发挥作用,例如制造电脑芯片和微型机械。但在获得最后的成功之前,还有一个必要的步骤需要完成——把这些自组装好的小东西焊接起来。因为目前里面的黏合力是如此的小,一旦从液体中拿出,它们就会像豆腐一样地散架。

下列对“这种作用力方式”解说符合文意的一项是()。

A.DNA和蛋白蛋等大分子都能依靠形状的互补或分子间的作用力来进行分子间的牵引

B.氢键和疏水的作用力

C.微米级物体组装时物体问的结合

D.多肽能在被基因表达后自发地折叠

单项选择题

There are two types of people in the world. Although they have equal degree of health and wealth and other comforts of life, one becomes happy and the other becomes unhappy. This arises from the different ways in which they consider things, persons, events and the resulting effects upon their minds.
People who are to be happy fix their attention on the convenience of things: the pleasant parts of conversation, the well prepared dishes, the goodness of the wine and the fine weather. They enjoy all the cheerful things. Those who are to be unhappy think and speak only of the opposite things. Therefore, they are continually dissatisfied. By their remarks, they sour the pleasure of society, offend (hurt) many people, and make themselves disagreeable everywhere. If this turn of mind was founded in nature, such unhappy persons would be the more to be pitied. The intention of criticizing and being disliked is perhaps taken up by imitation. It grows into a habit, unknown to its possessors. The habit may be p, but it may be cured when those who have it realize its bad effects on their interests and tastes. I hope this little warning may be of service to them, and help them change this habit.
Although in fact it is chiefly an act of the imagination, it has serious results in life since it brings on deep sorrow and bad luck. Those people offend many others; nobody loves them, and no one treats them with more than the most common politeness and respect. This frequently puts them in bad temper and draws them into arguments. If they aim at getting some advantages in social position or fortune, nobody wishes them success. Nor will anyone start a step or speak a word to favor their hopes. If they bring on themselves public objections, no one will defend or excuse them, and many will join to criticize their wrongdoings. These should change this bad habit and be pleased with what is pleasing, without worrying needlessly about themselves and others. If they do not, it will be good for others to avoid any contact with them. Otherwise, it can be disagreeable and sometimes very inconvenient, especially when one becomes mixed up in their quarrels.

In this passage, the writer mainly ______.

A. describes two types of people
B. laughs at the unhappy people
C. suggests the unhappy people should get rid of the habits of unhappiness
D. tells people how to be happy in life