[分享]3月听力背景知识-雪花，报纸杂志，家具，化石

sheep-c

和JJ里的不太一样，作为知识背景补充吧

Snowflake

A snowfall consists of myriads of minute ice crystals that fall to the ground in the form of frozen precipitation. The formation of snow begins with these ice crystals in the subfreezing strata of the middle and upper atmosphere when there is an adequate supply of moisture present. At the core of every ice crystal is a minuscule nucleus, a solid particle of matter around which moisture condenses and freezes. Liquid water droplets flouting in the supermodel atmosphere and free ice crystals cannot coexist within the same cloud, since the vapor pressure of ice is less than that of water. This enables the ice crystals to rob the liquid droplets of their moisture and grow continuously.

The process can be very rapid, quickly creating sizable ice crystals, some of which adhere to each other to create a cluster of ice crystals or a snowflake. Simple flakes possess a variety of beautiful forms, usually hexagonal, though the symmetrical shapes reproduced in most microscope photography of snowflakes are not usually found in actual snowfall. Typically, snowflakes in actual snowfalls consist of broken fragments and clusters of adhering ice crystals.

For a snowfall to continue once it starts, there must be a constant inflow of moisture to supply the nuclei. This moisture is supplied by the passage of an airstream over a water surface and its subsequent lifting to higher regions of the atmosphere. The Pacific Ocean is the source of moisture for most snowfalls west of the Rocky Mountains, while the Gulf of Mexico and the Atlantic Ocean feed water vapor into the air currents over the central and eastern sections of the United States. Other geographical features also can be the source of moisture for some snowstorms. For example, areas adjacent to the Great Lakes experience their own unique lake-effect storms, employing a variation of the process on a local scale. In addition, mountainous sections or rising terrain can initiate snowfalls by the geographical lifting of a moist airstream.

Newspaper and magzines

Although social changes in the United States were being wrought throughout most of the nineteenth-century,, public awareness of the changes increased to new levels in the 1890's. The acute, growing public awareness of the social changes that had been taking place for some time was tied to tremendous growth in popular journalism in the late nineteenth century, including growth in quantity and circulation of both magazines and newspapers. These developments, in addition to the continued growth of cities, were significant factors in the transformation of society from one characterized by relatively isolated self-contained communities into an urban, industrial nation. The decade of the 1870's, for example, was a period in which the sheer number of newspapers doubled, and by 1880 the New York Graphic had published the first photographic reproduction in a newspaper, portending a dramatic rise in newspaper readership. Between 1882 and 1886 alone, the price of daily newspapers dropped from four cents a copy to one cent, made possible in part by a great increase in demand. Further more, the introduction in 1890 of the first successful linotype machine promised even further growth. In 1872 only two daily newspapers could claim a circulation of over 100,000,but by 1892 seven more newspapers exceeded that figure. A world beyond the immediate community was rapidly becoming visible.

But it was not newspapers alone that were bringing the new awareness to people In the United States in the late nineteenth century. Magazines as they are known today began publication around 1882, and, in fact, the circulation of weekly magazines exceeded that of newspapers in the period which followed. By 1892, for example, the circulation of the Ladies' Home Journal had reached an astounding 700,000. An increase in book readership also played a significant part in this general trend. For example, Edward Bellamy's utopian novel, Looking Backward, sold over a million copies in 1888, giving rise to the growth of organizations dedicated to the realization of Bellamy's vision of the future. The printed word, unquestionably. was intruding on the insulation that had characterized United Slates society in an earlier period.

Furniture

The conservatism of the early English colonists in North American, their strong attachment to the English way of doing things, would play a major part in the furniture that was made in New England. The very tools that the first New England furniture makers used were, after all, not much different from those used for centuries-even millennia: basic hammers, saws, chisels, planes, augers, compasses, and measures.

These were the tools used more or less by all people who worked with wood: carpenters, barrel makers, and shipwrights. At most the furniture makers might have had planes with special edges or more delicate chisels, but there could not have been much specialization in the early years of the colonies.

               The furniture makers in those early decades of the 1600's were known as "joiners", for the primary method of constructing furniture, at least among the English of this time, was that of mortise-and-tenon joinery. The mortise is the hole chiseled and cut into one piece of wood, while the tenon is the tongue of protruding element shaped from another piece of wood so that it fits into the mortise; and another small hole is then drilled (with the auger) thought the mortised end and the tenon so that a whittled peg can secure the joint-thus the term "joiner". Panels were fitted into slots on the basic frames. This kind of construction was used for making everything from houses to chests.

Relatively little hardware was used during this period. Some nails-forged by hand-were used, but no screws or glue, hinges were often made of leather, but metal hinges were also used. The cruder varieties were made by blacksmiths in the colonies, but the finer metal elements were imported. Locks and escutcheon plates-the latter to shield the wood from the metal key-would often be imported.

Above all, what the early English colonists imported was their knowledge of familiarity with, and dedication to the traditional types and designs of furniture they knew in England.

Fossil

Anyone who has handled a fossilized bone knows that it is usually not exactly like its modern counterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone and other tissues have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is a wrong interpretation; fossils are frequently so dense because the pores and other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up but little from their surrounding. Probably all of the minerals deposited within the bone have been recrystallized from solution by the action of water percolating through tem. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. under optimum conditions the process of mineralization probably takes thousands rather than millions of years perhaps considerably less.

            This amount of change that has occurred in fossil bone, even in bone as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structure of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too-it has the same crystal structure as that of modern bone.

           Although nothing remains of the original collagen, some of its component amino acids are usually still detectable, together with amino acids of the noncollagen proteins of bone.

sheep-c

注：是有位GG或MM发现的，听力和阅读之间的重复，我只是从真题里把他们贴出来而已，希望对大家又帮助

后天考。。。

Veronica_Melody

good`luck~~@@@@@@!!!!!!!thanx`for`sharing!!!!!!

netmeetinglee

so good!

雅惠乖乖

thanks a lot!

good luck~~~~~~~`

beautywawa

thanks for sharing...

springqi

thanks for sharing