George Gershwin, born in 1998, was one of America's greatest composers. He published his first song when he was eighteen years old. During the next twenty years he wrote more than five hundred songs.

Many of Gershwin's songs were first written for musical plays performed in theatres in New York City. These plays were a popular form of entertainment in the 1920s and 1930s. Many of his songs have remained popular as ever. Over the years they have been sung and played in every possible way — from jazz to country.

    In the 1920s there was a debate in the United States about jazz music. Could jazz, some people asked, be considered serious music? In 1924 jazz musician and orchestra leader Paul Whiteman decided to organize a special concert to show that jazz was serious music. Gershwin agreed to compose something for the concert before he realized he had just a few weeks to do it. And in that short time, he composed a piece for piano and orchestra which he called Rhapsody in Blue. Gershwin himself played the piano at the concert. The audience were thrilled when they heard his music. It made him world-famous and showed that jazz music could be both serious and popular.

    In 1928, Gershwin went to Paris. He applied to study composition (作曲)with the well-known musician Nadia Boulanger, but she rejected him. She was afraid that classical study would ruin his jazz-influenced style. While there, Gershwin wrote An American in Paris. When it was first performed, critics (评论家)were divided over the music. Some called it happy and full of life, to others it was silly and boring. But it quickly became popular in Europe and the United States. It still remains one of his most famous works.

    George Gershwin died in 1937, just days after doctors learned he had brain cancer. He was only thirty-nine years old. Newspapers all over the world reported his death on their front pages. People mourned the loss of the man and all the music he might have still written.

The benefits of regular exercise are well documented but there's a new bonus to add to the ever-growing list. New researchers found that middle-aged women who were physically fit could be nearly 90 percent less likely to develop dementia (失智症) in later life and is they did, it came on a decade later than less sporty women.

Lead researcher Dr. Helena Horder, of the University of Gothenburg in Sweden, said: "These findings are exciting because it's possible that improving people's cardiovascular (心血管的) fitness in middle age could delay or even prevent them from developing dementia."

For the study, 191 women with an average age of 50 took a bicycle exercise test until they were exhausted to measure their peak (最大值的) cardiovascular capacity. The average peak workload was measured at 103 watts. A total of 40 women met the criteria for a high fitness level, or 120 watts or higher.

A total of 92 women were in the medium fitness category: and 59 women were in the low fitness category, defined as a peak workload of 80 watts or less, or having their exercise tests stopped because of high blood pressure, chest pain or other cardiovascular problems.

These women were then tested for dementia six times over the following four decades. During that time, 44 of the women developed dementia. Five percent of the highly fit women developed dementia, compared to 25 percent of the women with medium fitness and 32 percent of the women with low fitness

"However, this study does not show cause and effect between cardiovascular fitness and dementia it only shows an association. More research is needed to see if improved fitness could have a positive effect on the risk of dementia and also to look at when during a lifetime a high fitness level is most important" She also admitted that a relatively small number of women were studied, all of whom were form Sweden so the results might not be applicable to other groups.

The United States rose to global power on the strength of its technology, and the lifeblood that technology has long been electricity. By providing long-distance communication and energy electricity created the modern world. Yet properly understood, the age of electricity is merely the second stage in the age of steam which began a century earlier.

It is curious that on one has put together a history of both the steam and electric revolutions." writes Maury Klein in his book The Pore Makers, Seam, Electricity and the Men Invented Modern America. Klein, a noted historian of technology spins a narrative (叙述) so lively that at times it reads like a novel

The story begins in the last years of the 18th century in Scotland, where Watt perfected "the machine that changed the world". Klein writes/'America did not invent the steam engine, but once they grasped its passwords, they put it to more uses than anyone else.

Meanwhile, over the course of 19th century, electricity went from mere curiosity to a basic necessity. Morse invented a code for sending messages over an electromagnetic circuit Bell then gave the telegraph a voice. Edison perfected an incandescent bulb (白炽灯泡) that brought electric light into the American home.

Most importantly, Edison realized that success depended on mass electrification, which he showed in New York City. With help from Tesla, Westinghouse's firm developed a system using alternating current (交流电), which soon became the major forms of power delivery.

To frame his story, Klein creates the character of Ned, a fictional witness to the progress brought about by the steams and electric revolutions in America during one man's lifetime. It's a technique that helps turn a long narrative into an interesting one.