first three chapters established some fundamental principles concerning the structure of organic molecules. In this chapter we begin our discussion of organic chemical reactions by directing attention to alcohols and alkyl halides. These two rank among the most useful classes of organic compounds because they often serve as starting materials for the preparation of numerous other families

24.1 Introduction: the problem of plastic packaging waste Polymers and plastics are typical materials of the last century and have made a tremendous growth of some hundreds of tons/year at the beginning of the 1930s to more than 150 million tons/year at the end of the 20th century with 220 million tons forecast by 2005. Western Europe will account for 19% of that amount. Today

Modified atmosphere packaging (MAPmay be defined as the enclosure of food products in gas-barrier materials in which the gaseous environment has been changed'(Young et al., 1988 Because of its substantial shelf-life extending effect, MAP has been one of the most significant and innovative growth areas in retail food packaging. The potential advantages and disadvantages of MAP have been presented by Farber (1991), Parry(1993) and Davies (1995). Whilst there is considerable information available regarding suitable gas mixtures for different food products, there is still a lack of scientific detail regarding many aspects relating to MAP. These include:

Managing innovation is a necessary skill for senior management of all food companies producing new raw materials, new ingredients or new consumer products. Company growth and even survival depends on the introduction of successful new products into old and new markets. The dividing line between product success and failure depends on many factors, but the most important are new product qualities, skills and resources of the company, market and marketing proficiency, and an organised product development process

材料 材料科学与工程 金属材料 无机非金属材料 高分子材料 复合材料

Ohm's law states that voltage across many types of conducting materials is directly proportional to the current flowing through the material. U= Ri or R= i R--resis tance()( linear resistor) The resistor is a passive element that cannot deliver power or store energy

3.1 Chemistry developed out of interest in materials The ability to control fire allowed ancient people to prepare copper(7000 years ago) and iron (3200 years ago) for tools and weapons

8. 1 Water molecules form an open crystalline structure in ice When water freezes. the water molecules arrange themselves in a six-sided crystalline structure. Increased structural orderliness usually means increased density. Solids and crystals have high structural orderliness and are thus denser than liquid and non-crystalline materials. But water is exception

18.1 Paper is made of cellulose fibers Paper was first made HARDWOOD FIBERS in China as early as AD 100, of mulberry bark, and then introduced to Western world by Arabs in eighth century. The first paper mills were built in spain in 11th century

一、物质波(materials waves) 法国物理学家德布罗意(Louis Victor de Broglie 1892-1987) 思想方法自然界在许多方 面都是明显地对称的,他采用类 比的方法提出物质波的假设