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George Whitesides has developed a prototype for paper "chip" technology that could be used in the developing world to cheaply diagnose deadly diseases such as HIV, malaria, tuberculosis, hepatitis and gastroenteritis. The first products will be available in about a year, he said. His efforts, which find their inspiration from the simple designs of comic books and computer chips, are surprisingly low-tech and cheap. Patients put a drop of blood on one side of the slip of paper, and on the other appears a colorful pattern in the shape of a tree, which tells medical professionals whether the person is infected with certain diseases. Water-repellent comic-book ink saturates several layers of paper, he said. The ink funnels a patient's blood into tree-like channels, where several layers of treated paper react with the blood to create diagnostic colors. It's not entirely unlike a home pregnancy test, Whitesides said, but the chips are much smaller and cheaper, and they test for multiple diseases at once. They also show how severely a person is infected rather than producing only a positive-negative reading.

Scanning electron micrograph of the nanofossil Chiasmolithus from about 60 million years ago. This genus arose after the Cretacious Paleogene boundary mass extinction. The size about 8 microns.

The darkness caused by the collision would impair photosynthesis and reduce nannoplankton reproduction. While full darkness did not occur, the effects in the north would have lasted for up to six months. However, with ample sunlight and large amounts of nutrients in the oceans, the populations should have bounced back, even in the North, but they did not. The researchers suggest that toxic metals that where part of the asteroid, heavily contaminated the Northern oceans and were the major factor inhibiting recovery. "Metal loading is a great potential mechanism to delay recovery," said Bralower. "Toxic levels in the parts per billions of copper, nickel, cadmium and iron could have inhibited recovery." On the one hand, the researchers considered an impact scenario causing perpetual winter and ocean acidification to explain the slow recovery, but neither explains the lag between Southern and Northern Hemispheres. Trace metal poisoning, on the other hand, would have been severe near the impact in the Northern Hemisphere. When the high temperature debris from the impact hit the water, copper, chromium, aluminum, mercury and lead would have dissolved into the seawater at likely lethal levels for plankton. Iron, zinc and manganese -- normally micronutrients -- would reach harmful levels shortly after the impact. Other metal sources might be acid-rain leached soils or the effects of wildfires. Metals like these can inhibit reproduction or shell formation. The toxic metals probably exceeded the ability of organic compounds to bind them and remove them from the system. Because nannoplankton are the base of the food chain, larger organisms concentrate any metals found in nannoplankton making the metal poisoning more effective. With the toxic metals remaining in the oceans and the lack of sunlight, the length of time for recovery might increase.