TAILIEUCHUNG - The Self-Made Tapestry Phần 2

Và bọt bong bóng xà phòng không bao giờ hết, và tôi cho rằng đó là một phần kháng cáo của họ: vẻ đẹp mong manh, đi trong một thời điểm. | Soap bubbles and foams do not last for ever and I suppose that is part of their appeal fragile beauty gone in a moment. The collapse of foams is brought about partly by the drainage of the films under the influence of gravity and capillary forces until they become too thin to resist the slightest disturbancea vibration or a breath of air. But in their passing soap films can treat us to a wonderful display. Held vertically on a wire frame a thinning soap film becomes striated with bands of rainbow colours that pass from top to bottom Plate 2 . Finally the top becomes silvery and then black and the blackness like a premonition of the film s demise Page 2 moves over the entire surface. Once it is black the film is doomed to burst at the merest perturbation. Fig. Cell membranes are made from double layers of surfactants called phospholipids. These bilayers are studded with other membrane components such as protein molecules and are sometimes strengthened with a protein web called the cytoskeleton. These colours are the result of interference between light reflected from the front and the back of the film. Interference takes place when the distance between the front and back becomes comparable to the wavelength of light a few hundred millionths of a millimetre and as this distance changes so too does the wavelength that is the colour of the light affected by interference. When the film is black all reflected visible light cancels itself out by interference. The film is by that stage only about four-and-a-half millionths of a millimetre thickabout the same thickness as a double layer of soap molecules. The two films at the surfaces have almost met back to back. This back-to-back arrangement of surfactant molecules has some similarities to the wall of a living cell. Cell membranes Fig. are composed of amphiphilic moleculesbiological surfactants if you likecalled phospholipids or just lipids. A double layer of lipids called a bilayer is one of the fundamental .

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