Before the 1940s, humans had not mastered a drug that could effectively treat bacterial infections with little side effects. At that time, if someone got tuberculosis, it meant that the person was going to die soon. In order to change this situation, researchers have made a long-term exploration, but the breakthrough in this respect stems from an unexpected discovery.
In modern times, British bacteriologist Fleming first discovered the world's first antibiotic-penicillin in 1928, and alexander fleming discovered penicillin by a lucky mistake.
1928, British scientist Fleming discovered penicillin for the first time in experimental research. However, due to the lack of advanced technology and in-depth understanding at that time, Fleming did not isolate penicillin alone. From 65438 to 0929, Fleming published his research results. Unfortunately, this paper has not been paid attention to by the scientific community since it was published.
2.DNA double helix structure
1953 In February, Watson and Crick saw a very beautiful X-ray diffraction photograph of DNA crystal, which was taken by rosalind franklin in June of 195 1+0 1.
This inspired them. They not only confirmed that DNA must have a spiral structure, but also analyzed helix parameter.
They adopted the judgment of Franklin and Wilkins and supplemented it: phosphate formed the skeleton of two polynucleotide chains on the outside of the helix, in opposite directions; The bases are inside the helix and correspond to each other.
For several days, Watson and Crick happily built models with iron wires in their offices. 1953 On February 28th, the first molecular model of DNA double helix structure was finally born.
3, the first generation of electronic computers
The world's first general-purpose computer "ENIAC" was born in February 1946 at the University of Pennsylvania. Inventors are Americans Moakley and J.PresperEckert, and the U.S. Department of Defense uses it for ballistic calculation.
It is a giant, with 18000 electron tubes, an area of 170 square meters, weighing 30 tons, consuming about 150 kilowatts of electricity, and performing 5000 operations per second, which is insignificant now, but unprecedented at that time.
ENIAC uses electron tubes as components, so it is also called electron tube computer, which is the first generation computer. Electron tube computers are bulky, consume high power, are prone to heat, and cannot work for long.
4. TV set
Television (TV, Video) refers to the use of electronic technology and equipment to transmit moving images and audio signals, that is, a television receiver, which is also an important broadcast and video communication tool. Television was first invented by British engineer John Logie Baird in 1925. Television uses electricity to transmit moving visual images instantly.
Similar to movies, TV uses the visual residual effect of human eyes to gradually change the still image frame by frame to form a visually moving image. The transmitter of the TV system converts every tiny part of the scene into electrical signals according to the brightness and chromaticity, and then transmits them in turn. At the receiving end, the brightness and chromaticity of each tiny part are displayed according to the corresponding geometric position to reproduce the whole original image.
The progress of science and technology is an important reason for the rapid popularization of television. The scanning system and channel bandwidth of TV signals in different countries are not exactly the same. According to international radio consultative committee's suggestion, Latin letters are used to distinguish them.
5. radio
Maxwell expounded the theoretical basis of electromagnetic wave propagation for the first time in his paper "Theory of Electromagnetic Field Dynamics" submitted to the Royal Society. His work was completed between 186 1 and 1865.
1864, Maxwell, a British scientist, established a complete electromagnetic wave theory on the basis of summarizing previous studies on electromagnetic phenomena. He concluded that electromagnetic waves exist and concluded that electromagnetic waves and light travel at the same speed.
1887 German physicist Hertz confirmed the existence of electromagnetic waves through experiments. After that, many experiments were carried out, which not only proved that light is electromagnetic wave, but also found more forms of electromagnetic wave. Their essence is exactly the same, but there are great differences in wavelength and frequency.
Heinrich rudolf hertz first verified Maxwell's theory through experiments from 1886 to 1888. He proved that radio radiation has all the characteristics of waves, and found that the electromagnetic field equation can be expressed by partial differential equation, which is usually called wave equation.
Baidu encyclopedia-penicillin
Baidu encyclopedia -DNA double helix structure
Baidu encyclopedia-the first generation of electronic computers
Baidu encyclopedia-TV
Baidu encyclopedia-broadcast