Preview referat: Louis Pasteur
In 1847 he earned a doctorate at the Ecole Normale in Paris, with a focus on both physics and chemistry. Becoming an assistant to one of his teachers, he began research that led to a significant discovery. He found that a beam of polarized light was rotated to either the right or the left as it passed through a pure solution of naturally produced organic nutrients, whereas when polarized light was passed through a solution of artificially synthesized organic nutrients, no rotation took place. If bacteria or other microorganisms were placed in the latter solution, then after a while it would also rotate light to the right or left.
From this, he concluded that organic molecules exist in one of two forms, "left-handed" or "right-handed" forms. After spending several years researching and teaching at Dijon and Strasbourg, Pasteur moved in 1854 to the University of Lille, where he became the professor of chemistry and dean of the faculty of sciences. There, a main focus of research was on the manufacture of alcoholic beverages. Pasteur immediately began researching the process of fermentation.
He was able to demonstrate that the desired production of alcohol in fermentation is because of yeast, and that the undesired production of substances that make wine sour is because of the presence of additional organisms like bacteria. The souring of wine and beer had caused a major economic problem in France. Pasteur helped to solve the problem by proving that heating the starting sugar solutions to a high temperature would eliminate the bacteria. (www.exsands.com.) « mai multe referate din Fizica