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U.S. physicists have unraveled and found out how to avoid the rings the emergence of the typical coffee rings. The analysis of the profitable development of inks and uniform coatings, the researchers write Arjun Yodh of the University of Pennsylvania (USA) in the British journal Nature. If spilled coffee drops dry up, they leave a characteristic dark ring around the edge. This is due to the way the droplet evaporates: On most surfaces the edge of the droplet remains fixed so he can not shrink as it dries. The evaporation of the droplets is therefore always flat, so that the remaining water and everything is pushed to the brink in it by and by. If the drop is finally entirely evaporated, almost all coffee particles have reached the edge in it and sit there from a typical ring. The coffee ring effect is very common in everyday life, explains PhD student Peter Yunker from the research group in a statement of his university. The effect is, among other disturbing in paints and coatings that are to be distributed uniformly over the surface. Scientists have made great efforts to avoid the phenomenon, says Yunker. We have found that the effect can be easily turned off by changing the shape of the particles. Because only round particles migrate in the drying droplet to the edge. They dissolve easily from the water air interface at the top air jordan 11 retro of the drop. Elliptical particle shape, however, wavy ripple on the droplet surface, which they dissolve difficult. The physicists studied the with tiny plastic spheres that could be deformed to different degrees of ellipsoids. As soon as you stretch the spherical particles by about 20 percent, they are deposited evenly, says Yunker. In this way, new coating methods could be developed, the researchers believe. Even with a pinch of elliptical particles under similar large spherical allows the walk to the edge of the ellipsoids prevent blocking while the beads the way and hold it so tightly. There are a lot of occasions when you look uniform coatings wishes, says Yunker. This work will encourage people to think of new ways for it. The first railroad constructed the Welsh mining engineer Richard Trevithick in 1803, 22 years before George Stephenson. His steam engine on rails but was only used for transporting coal underground, which is why the public took no notice of the invention. The first driving license in the world (for trips up to 20 km / h) was established on August 8, 1899 issued by the police in Detroit at the time still working at the Edison Electric Company engineer Henry Ford In the summer of 1925, the jordan 9 shoes for sale biology teacher John Scopes Thomas was sentenced to a fine of $ 100 in Dayton, Tennessee Federal instead. He had dealt with Darwinism in the classroom, even though a state law prohibiting to deny the divine origin of man. The lions that played along in the movie Out of Africa ​​in 1985, were imported for the shooting from California to Kenya. For more information, particularly about whether and how personal data is collected and processed, you will find in our DatenschutzbestimmungenDie Moderation of comments rests solely with THE WORLD. In general: Critical comments and discussions are welcome, abuse / insults, however, be removed. How we moderate, we explain in the statement.