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    POLYPROPYLENE
    November 12, 1999 - Bartlesville, Oklahoma, U.S.A.

    In Bartlesville, Oklahoma, a plaque was placed on the site of the laboratory where the polymer polypropylene was invented, designating it a National Historic Chemical Landmark by the American Chemical Society. The first commercially successful use of the new material was in the Hula Hoop®. In 1951, J. Paul Hogan and Robert L. Banks, research chemists working for Phillips Petroleum Company, discovered the polymer unexpectedly during experiments with catalysts while trying to convert the natural gas components ethylene and propylene into compounds useful for gasoline. Later, they also developed a new catalytic process for making high-density polyethylene. Phillips soon invested in new plastic manufacturing plants.

    PITOT TUBE
    November 12, 1732 - Academy of Sciences, Paris

    Henri Pitot read a paper to the Royal Academy of Sciences in Paris about an instrument he had invented to measure the flow velocity at different depths of water in the River Seine. It had a scale and two open vertical glass tubes on a wood frame. The lower end of one pointed down, the other bent at 90 facing the flow. The belief of the time was that flow velocity at a given depth was proportional to the mass above it, meaning increasing velocity at greater depth. Recording the difference in liquid levels in the two tubes, he showed the opposite was true. Henri Darcy improved the design, with the support of Henri Bazin. Today, the Pitot tube has an important application in aerodynamics for the measurement of the airspeed of aircraft.

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The article concentrates upon digital music downloads, in particular online music download options, including the cost, the listening rights, audio format and quality of downloads.

ARTICLE CONTENT :

There are a great many online services that offer online music. Some sites charge per online music download, whereas other services offer to pay a monthly fee for a limitless number of music downloads. It has been estimated that compact disc sales are in decline (19% in the last few years), and online music download sales are speedily increasing. Revenues from digital music sales are reported to have virtually tripled last year, with Apple's iTunes accounting for more than 85 percent of single song downloads. Nevertheless, the figures do not make Apple the sole source of digital music. Today, legal music download sites account for approximately 6% of record studios' revenues, which is a growth compared to the situation observed a couple of years ago.

Music download sites come in two types: 'rent' and 'buy' websites. 'Rent' sites are music sites involving a monthly fee paid to gain access to the whole music catalogue. 'Buy' services charge per download - iTunes, for example - where a soundtrack can be burned onto a CD once it is paid for. The CD can then be ripped to the pc. Some digital music services offer to pay a monthly fee for limitless listening rights, but also charge to purchase a song. Some digital music download sites charge 9 cents per track. In addition, these sites have tracks that can be downloaded in any format and quality level.

Sometimes music download websites are so cheap and user-friendly that a great many Internet users decide to download songs from these websites instead of ripping CD collections onto the personal computer. For any person downloading songs onto an iPod or iTunes, it is probably the optimum option. For any music not being downloaded onto an iPod, any other music source will work. When seeking the optimum quality music downloads, one should look for music download websites offering the largest choice of music that is updated on a regular basis, and excellent quality downloads. Commonly, the price is directly dependent on quality. In this case, a question arises: Is it worth spending extra money? The answer is typically 'Yes'.

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