Exams

"[Heroin is] not hypnotic, and there is no danger of acquiring a habit." Boston Medical and Surgical Journal (1900) Throughout the nineteenth century, scientists sought a non-addictive substitute for the painkiller morphine. Morphine itself was first derived from the seeds of the white Indian poppy (Papaver somniferum) in 1803 by German pharmacist Friedrich Serturner. Heroin was first processed in 1874 by C. R. Alder Wright, a chemist working at St. Mary's Hospital Medical School, London. He boiled anhydrous morphine alkaloid with acetic anhydride over a stove for several hours and produced a more potent form of morphine, diacetylmorphine. But heroin only became popular after it was independently re-synthesized twenty-three years later by Felix Hoffmann (1868-1946), a German chemist working at the Bayer pharmaceutical company. When the drug was tested on Bayer workers, they said it made them feel "heroic," leading to the name heroin. From 1898to 1910 Bayer marketed heroin more...

"If my films make even one more person feel miserable, I'll feel I've done my job." Woody Alien, movie director In just over 100 years, "moving pictures" have evolved from peep-show parlors into a vast, multibillion dollar industry that spans the globe. Today's movie industry has its roots in numerous nineteenth-century innovations. Thomas Edison sought to develop a device"... which does for the eye what the phonograph does for the ear." Attempts to duplicate the cylinder format of Edison's phonograph proved a dead-end, but Edison's "assistant," W. K. L Dickson, eventually developed the Kinetoscope for viewing pictures in a "peep-show" format, and the Kinetograph camera with which to create footage. The viewing method of this equipment, one person at a time, had obvious limitations, It was the Lu mi ere brothers—Auguste (1862-1954) and Louis (1864-1948)—who created the first practical film camera, projector, the Cinematograph. Despite the fact that it incorporated more...

'Life is not significant details, illuminated by a flash, fixed forever. Photographs are." Susan Sontag, writer and critic Xenon flash lamps were pioneered by Harold Edgerton (1903-1990), a professor of electrical engineering at the Massachusetts Institute of Technology (MIT). He was an expert on the stroboscope as well as a creative photographer whose freeze-frame images are world famous. Xenon flash lamps, which are commonly used in photographic strobe lights, can produce an intense flash of light that lasts for between a millionth and a thousandth of a second depending on the volume and amount of gas in each lamp. The flashes can also be repeated up to a few hundred times per second. At a pressure of between 1 and 10 percent of an atmosphere, the xenon is contained in a sealed tube, usually of fused quartz. The discharge is triggered by switching a radio frequency high-voltage on to a more...

"Our age is... a practical one. It demands of us all clear and tangible results of our work" Theodor Svedberg, chemist The centrifuge has been around since the mid-1800s. It is a device for separating a precipitate from a solution by spinning it at high speeds (the increased gravitational force means that anything suspended in the solution is forced to the bottom of the container much faster than if left to settle naturally). The first centrifuges were hand-driven, reaching speeds of 800 revolutions per minute (rpm). The first ultracentrifuge, developed by Swedish chemist Theodor Svedberg (1884-1971) in 1924, could rotate at speeds of up to 160,000 rpm, meaning it was capable of exaggerating gravity 1,100,000 times. In his first tests, Svedberg separated hemoglobin from blood in about six hours; using normal gravity it would have taken 180 years. The device's speed makes it a powerful analytical tool. It can measure more...

The image of a solar cell glistening in the sun illustrates many a magazine article on modern technology. But the means of converting light energy into electrical energy is nothing new. A "photovoltaic effect," whereby light hitting an electrode immersed in an electrolyte produces a current, was first observed in 1839 by A. E. Becquerel. This phenomenon was harnessed in 1884 when the first solar cell was built by American scientist Charles Fritts. Fritts used the less than economic design of semiconductive selenium coated in a thin layer of gold to achieve the conversion, at an efficiency of just 1 percent. The cell works by absorbing energy in the form of photons of light, which then displace electrons in the semiconductor, generating a current. Despite Fritts's optimism that the technology might replace centralized power plants, no one was ever going to power their home with only this kind of efficiency. more...

Before the arrival of the search engine, computers were linked together simply to let people transfer files between themselves. Those who had files to share set up a server, and those who wanted the files would come and get them. In time these servers clumped together, and having lots of files in one place made them easier to find. But even with clumping, files were spread out over the Internet. If you did not know the location of a file, it was very hard to track it down. This was the problem facing Alan Emtage (b. 1964), studying at McGill University in Montreal. With funding for software limited, it was Emtage's job to find free applications on the Internet for the university to use. At first he searched by hand, building a database of the software he had found, but eventually, being a computer scientist, he made a program to more...

“I put a new engine in my car, but forgot to take the old one out. Now my car goes 500 miles per hour." Stephen Wright, comedian As anyone who has ever tried to start up an old automobile will tell you, a choke is a miserable thing to operate. Pull it out too far and you flood the engine, do not pull it out far enough and the engine will not fire. It is not surprising, therefore, that automotive engineers did everything in their power to eradicate the need for carburetors. How did they do this? They invented fuel injection. Now commonplace on all production cars, fuel injection is an automatic, accurate way of keeping the engine's fuel-to-air ratio at suitable levels. Modern computer systems use precise sensors and gauges that react to very quick changes in operation, such as sudden accelerations to decide how much fuel is needed more...

"We may see and hear a whole Opera as perfectly as If actually present" U.S. Patent Office description for the Kinetoscope Motion pictures and even television may never have become a reality if it were not for the creation of the Kinetoscope by Thomas Alva Edison (1847-1931) and his deputy William Dickson (1860-1935) in 1891. The idea of moving still frames in quick succession to give the illusion of a moving image had already been demonstrated. Edison and Dickson took the principle and built a machine that could show long rolls of film. Edison was apparently inspired by a demonstration of the Zoopraxiscope, which used a fast-spinning disc with images around the outside to give the illusion of movement. Edison took it upon himself to develop a system that brought together moving images and sound; he called it the Kinetoscope. Edison set Dickson and his team to work on the more...

Print editions of journals in the inventory of the library system of the Freie Universität Berlin are completely in the online catalog detected. There, helps the search by magazines on. It demonstrates the most to members of the FU licensed at the FU-line journals. Important: A large number of full text available at the Free University of Anglo-American journals and journal articles located in the database LexisNexis Professional [ Overview of casebooks and journals that are included in full text here ]. The search can be useful in the Bibliography Web of Science (see attachment research). Access to full text only on LexisNexis yourself, as a direct access to the contents of LexisNexis not from the outside through portals and bibliographies is possible. Search for law essay writing journals Search for articles in law journals is possible through online bibliographies, through the portal Primo and within databases. All three paths more...

Home improvement work is risky business. Children's cartoons  serve  as continual  public  service announcements of the hazards of "do-it-yourself"—stepping on garden rakes and putting hammers through thumbs tend to top the charts in terms of accidents. For traveling salesman Peter L. Robertson (1879-1951), however, a real accident in 1906, when he put a sharp screwdriver through his hand, prompted him to find a way of avoiding such accidents. By 1908 Robertson was manufacturing a screw that was to revolutionize the industry. In Henry Petroski's book on the evolution of useful things he talks about the square-headed screw being invented to improve on existing designs—specifically the elimination or reduction of the risk of a slip. However, another improvement that Robertson made on the traditional screw was that his version could be fastened tighter than its rivals and operated with one hand—a very useful advantage for mechanics and other craftsmen alike. The more...