1、人人网雅思公共主页 http:/ Climate and Country Wealth Why are some countries stupendously rich and others horrendously poor? Social theorists have been captivated by this question since the late 18th century, when Scottish economist Adam Smith argued in his magisterial work The Wealth of Nations that the best
2、 prescription for prosperity is a free-market economy in which the government allows businesses substantial freedom to pursue profits. Smith, however, made a second notable hypothesis: that the physical geography of a region can influence its economic performance. He contended that the economies of
3、coastal regions, with their easy access to sea trade, usually outperform the economies of inland areas. Coastal regions and those near navigable waterways are indeed far richer and more densely settled than interior regions, just as Smith predicted. Moreover, an areas climate can also affect its eco
4、nomic development. Nations in tropical climate zones generally face higher rates of infectious disease and lower agricultural productivity (especially for staple foods) than do nations in temperate zones. Similar burdens apply to the desert zones. The very poorest regions in the world are those sadd
5、led with both handicaps: distance from sea trade and a tropical or desert ecology. The basic lessons of geography are worth repeating, because most economists have ignored them. In the past decade the vast majority of papers on economic development have neglected even the most obvious geographical r
6、ealities. The best single indicator of prosperity is gross national product (GNP) per capita the total value of a countrys economic output, divided by its population. A map showing the world distribution of GNP per capita immediately reveals the vast gap between rich and poor nations. The great majo
7、rity of the poorest countries lie in the geographical tropics. In contrast, most of the richest countries lie in the temperate zones. Among the 28 economies categorized as high income by the World Bank, only Hong Kong, Singapore and part of Taiwan are in the tropical zone, representing a mere 2 perc
8、ent of the combined population of the high-income regions. Almost all the temperate-zone countries have either high-income economies (as in the cases of North America, western Europe, Korea and Japan) or middle-income economies (as in the cases of eastern Europe, the former Soviet Union and China).
9、In addition, there is a strong temperate-tropical divide within countries that straddle both types of climates. Most of Brazil, for example, lies within the tropical zone, but the richest part of the nation the southernmost states is in the temperate zone. There are two major ways in which a region
10、s climate affects economic development. First, it affects the prevalence of disease. Many kinds of infectious diseases are endemic to the tropical and subtropical zones. This tends to be true of diseases in which the pathogen spends part of its life cycle outside the human host: for instance, malari
11、a (carried by mosquitoes) and helminthic infections (caused by parasitic worms). Although epidemics of malaria have occurred sporadically as far north as Boston in the past century, the disease has never gained a lasting foothold in the temperate zones, because the cold winters naturally control the
12、 mosquito-based 人人网雅思公共主页 http:/ transmission of the disease. Winter could thus be considered the worlds most effective public health intervention. It is much more difficult to control malaria in tropical regions, where transmission takes place year-round and affects a large part of the population.
13、According to the World Health Organization, 300 million to 500 million new cases of malaria occur every year, almost entirely concentrated in the tropics. Widespread illness and early deaths obviously hold back a nations economic performance by significantly reducing worker productivity. But there a
14、re also long-term effects that may be amplified over time through various social feedbacks. A high incidence of disease can alter the age structure of a countrys population. Societies with high levels of child mortality tend to have high levels of fertility: mothers bear many children to guarantee t
15、hat at least some will survive to adulthood. Young children will therefore constitute a large proportion of that countrys population. With so many children, poor families cannot invest much in each childs education. High fertility also constrains the role of women in society, because child rearing t
16、akes up so much of their adult lives. Moreover, temperature affects agricultural productivity. Of the major food grains wheat, maize and rice wheat grows only in temperate climates, and maize and rice crops are generally more productive in temperate and subtropical climates than in tropical zones. O
17、n average, a hectare of land in the tropics yields 2.3 metric tons of maize, whereas a hectare in the temperate zone yields 6.4 tons. Farming in tropical rain-forest environments is hampered by the fragility of the soil: high temperatures mineralize the organic materials, and the intense rainfall le
18、aches them out of the soil. In tropical environments that have wet and dry seasons such as the African savanna farmers must contend with the rapid loss of soil moisture resulting from high temperatures, the great variability of precipitation, and the ever present risk of drought. Moreover, tropical
19、environments are plagued with diverse infestations of pests and parasites that can devastate both crops and livestock. Moderate advantages or disadvantages in geography can lead to big differences in long-term economic performance. Favorable agricultural or health conditions may boost per capita inc
20、ome in temperate-zone nations and hence increase the size of their economies. The resulting inventions further raise economic output, spurring yet more inventive activity. The moderate geographical advantage is thus amplified through innovation. In contrast, the low food output per farm worker in tr
21、opical regions tends to diminish the size of cities. With a smaller proportion of the population in urban areas, the rate of technological advance is usually slower. The tropical regions therefore remain more rural than the temperate regions, with most of their economic activity 人人网雅思公共主页 http:/ con
22、centrated in low-technology agriculture rather than in high-technology manufacturing and services. Geographical factors, however , are only part of the story. Social and economic institutions are critical to long-term economic performance. It is particularly instructive to compare the post-World War
23、 II performance of socialist and free-market economies in neighboring countries that share the same geographical characteristics: North and South Korea, East and West Germany, the Czech Republic and Austria, and Estonia and Finland. In each case we find that free-market institutions vastly outperfor
24、med their counterparts. If these findings are true, the policy implications are significant. Aid programs for developing countries will have to be revamped to specifically address the problems imposed by climate and geography. In particular, new strategies have to be formulated that would help natio
25、ns in tropical zones raise their agricultural productivity and reduce the prevalence of diseases such as malaria. 人人网雅思公共主页 http:/ Yawn While fatigue, drowsiness or boredom easily bring on yawns, scientists are discovering theres more to yawning than most people think. Not much is known about why we
26、 yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn. Here are the four most common: The physiological theory: Our bodies induce yawning to draw in more oxygen or remove a buildup of carbon dioxide. Th
27、is theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to draw in needed oxygen, wouldnt we yawn during exercise? Robert Provine, a
28、 developmental neuroscientist at the University of Maryland, Baltimore County and a leading expert on yawning, has tested this theory: Giving people additional oxygen didnt decrease yawning, and decreasing the amount of carbon dioxide in a subjects environment also didnt prevent yawning. The evoluti
29、on theory: Some think that yawning began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities. Another speculated reason for yawning is the desire to stretc
30、h ones muscles. Yawns are often accompanied by the urge to stretch. Prey animals must be ready to physically exert themselves at any given moment. There have been studies that suggest yawning, especially psychological “contagious“ yawning, may have developed as a way of keeping a group of animals al
31、ert. If an animal is drowsy or bored, it may not be as alert as it should to be prepared to spring into action. Therefore, the “contagious“ yawn could be an instinctual reaction to a signal from one member of the “herd“ reminding the others to stay alert. Nervousness has also been suggested as a pos
32、sible reason. Nervousness often indicates the perception of an impending need for action. Anecdotal evidence suggests that yawning helps increase the state of alertness of a person. Paratroopers have been noted to yawn in the moments before they exit the aircraft. The brain-cooling theory: A more re
33、cent theory proposed by researchers is that since people yawn more in situations where their brains are likely to be warmer - tested by having some subjects breathe through their noses or press hot or cold packs to their foreheads - its a way to cool down their brains. In 2007, researchers, includin
34、g a professor of psychology, from the University of Albany proposed that yawning may be a means to keep the brain cool. Mammalian brains operate best within a narrow temperature range. In two experiments, they demonstrated that both subjects with cold packs attached to their foreheads and subjects a
35、sked to breathe strictly nasally exhibited reduced contagious yawning when watching videos of people yawning. A similar recent hypothesis is that yawning is used for regulation of body temperature. Similarly, a study by Jared Guttmann at Worcester Polytechnic Institute found that when a subject wear
36、ing earplugs yawned, a breeze is heard caused by the flux of the air moving between the subjects ear and the environment. Researcher Guttmann determined that a 人人网雅思公共主页 http:/ yawn causes one of three possible situations to occur: the brain cools down due to an influx or outflux of oxygen, the pres
37、sure in the brain is reduced by an outflux of oxygen, or the pressure of the brain is increased by an influx of air caused by increased cranial space. What does it matter if our brains are cold or hot? Cool brains can think more clearly; hence, yawning might have developed to keep us alert. Interest
38、ingly, while all vertebrates (including fish) yawn, only humans, chimps and possibly dogs find yawns contagious. And people dont find them contagious until theyre about 4 years old. Recent studies show contagious yawning may be linked to ones capacity for empathy. In one study, autistic and non-auti
39、stic children were shown videos of people yawning and people simply moving their mouths. Both groups of kids yawned the same amount when viewing the video of people moving their mouths. But the non-autistic kids yawned much more frequently than those with autism when watching people really yawning.
40、Since autism is a disorder that affects a persons social interaction skills, including the ability to empathize with others, the autistic kids lack of yawning when watching others do so could indicate theyre less empathetic. The study also found the more severe a childs autism, the less likely he or
41、 she was to yawn. On a positive note, someday doctors may be able to diagnose cognitive disabilities in young children more easily by seeing whether or not they can catch a yawn from other. So even though we still dont know for sure why we yawn, we do know lots of interesting things about yawning: y
42、ou start yawning in utero; you yawn when youre aroused; more than half of you will yawn if you see someone else yawn; and reading about yawning makes you yawn. 人人网雅思公共主页 http:/ The soviet calendar There are no fortresses that Bolsheviks cannot storm. With these words, Stalin expressed the dynamic se
43、lf-confidence of the Soviet Unions Five Year Plan: weak and backward Russia was to turn overnight into a powerful modern industrial country. Unlimited enthusiasm was the mood of the day, with the Communists believing that iron will and hard-working manpower alone would bring about a new world. Enthu
44、siasm spread to Time itself, in the desire to make the state a huge efficient machine, where not a moment would be wasted, especially in the workplace. Lenin had already been intrigued by the ideas of the American Frederick Winslow Taylor (1856-1915), whose time-motion studies had discovered ways of
45、 stream-lining effort so that every worker could produce the maximum. The Bolsheviks were also great admirers of Henry Fords assembly line mass production and of his Fordson tractors that were imported by the thousands. The engineers who came with them to train their users helped spread what became
46、a real cult of Ford. Emulating and surpassing such capitalist models formed part of the training of the new Soviet Man, a heroic figure whose unlimited capacity for work would benefit everyone in the dynamic new society. All this culminated in the Plan, which has been characterized as the triumph of
47、 the machine, where workers would become supremely efficient robot-like creatures. Yet this was Communism whose goals had always included improving the lives of the proletariat. One major step in that direction was the sudden announcement in 1927 that reduced the working day from eight to seven hour
48、s. In January 1929, all industries were ordered adopt the shorter day by the end of the Plan. Workers were also to have an extra hour off on the eve of Sundays and holidays. Typically though, the state took away more than it gave, for this was part of a scheme to increase production by establishing
49、a three-shift system. That meant that the factories were open day and night and that many had to work at highly undesirable hours. Hardly had that policy been announced, though, than Yuri Larin, who had been a close associate of Lenin and architect of his radical economic policy, came up with an idea for even greater efficiency. Workers wer
