“一切景语皆情语”。“____，____。____，在水一方（〈诗经·蒹葭〉）”于浓浓的秋凉中折射出人物淡淡的凄婉之情。

     When I was a child, my parents always told ~ne that I should never talk to strangers. This was part of a whole list of things I should never do: Never accept food or candy from strangers, never get in a car with strangers, and so on.

      But if we didn't start a conversation with strangers, we'd never make new friends. We'd never get a job. ①We may miss the joy that comes from talking with strangers. And the more people you know, the more chances you can find.

     The following passage offers you some advice on how to ②break the ice.

     Don't just stare at your shoes. Go and say "Hi" to that new guy. It will be easier to break the ice if you know more about different cultures.

     British : Beautiful day, isn't it?

     The weather in Britain is changeable. So, it's one of the topics the British care most about. And there's a simple rule: Say "Yes" whether you agree with the person's idea on the weather or not. ③That's because the British start a conversation using the weather so that they era, continue their talk.

     French: Where did you. go on holiday?

     To talk with a French person, the safest way is to ask about his or her last holiday. French students enjoy a 10-to-15-day holiday every two months. French employees(雇员) get more than six weeks of holidays per year.

     American: So, where are you from?

     The US is so big and people move so often that location is always a source (来源) of talk. You can try to find a connection with the place they're from. For example, if someone's from Los Angeles, you could say, "Oh, I have a friend who studied there."

Don't talk here. My mother     .

在研究凸透镜成像实验中，小柯不断改变蜡烛到透镜的距离，移动光屏寻找蜡烛的像，并将实验结果记录在表格中。

纳米材料的小尺寸效应

     物质的尺度加工到1 ~10nm，它的物理性质或者化学性能与较大尺度时相比，会发生变化，这些物质组成的材料称为“纳 米材料”． 纳米材料在声、光、电、磁、热、力学等性能呈现出“新奇”的现象．随着颗粒尺寸变小，在一定条件下会引起颗粒性质改 变．由此引起的宏观物理性质的变化称为“小尺寸效应”．纳米材料小尺寸效应主要表现在如下方面：

⑴．特殊光学性质：所有金属在纳米状态时都呈现黑色．尺寸越小颜色愈黑，银白色的铂变成铂黑，金属铬变成铬黑．金属超微颗粒对光的反射率很低，通常低于1%，约几微米厚度就能完全消光．利用此特性可制造高效率光热、光电转换材料，以很高效率将太阳能转变为热能、电能．还可用于红外敏感元件、红外隐身技术等．

⑵．特殊热学性质：通常晶体具有固定的熔点，但当晶体达到纳米尺寸时却截然不同．例如：金的熔点为1064℃，而直径为10nm的金粉熔点降低到940℃，直径为5nm的金粉熔点降低到830℃．此特性可应用于粉末冶金工业．

⑶．特殊电学、磁学性质：纳米材料的导电性有所改变．例如：铜颗粒达到纳米尺寸就变得不能导电；通常绝緣的二氧化硅颗粒在 时却开始导电．此外，纳米材料呈现出超顺磁性，科学家发现鸽子、海膝、蝴蝶、蜜蜂以及生活在水中的趋磁 细菌等生物体中都存在超微磁性颗粒，使这类生物在地磁场导航下能辨别方向，具有回归的本领．

⑷．特殊力学性质：氟化鈣纳米材料在室温下可大幅度弯曲而不断裂．研究表明，人的牙齿具有高强度，是因为它由磷酸鈣 等纳米材料构成．纳米金属要比传统金属硬3 ~5倍．金属陶瓷复合纳米材料不但强度高且韧性好，制成的刀具比金钢石制品 还要坚硬．

      纳米技术目前已成功应用于许多领域，在工业、农业、能源、环保、医疗、国家安全等都有广泛应用．

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