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Sketch depicts limb bone, which bridges the evolutionary gap between fishes and amphibians.
Credit: Neil Shubin, University of Chicago
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New Fossil Links Four-legged Land Animals to Ancient Fish
How land-living animals evolved from fish has long been a scientific puzzle. A key missing piece has been knowledge of how the fins of fish transformed into the arms and legs of our ancestors. In the April 1, 2004 issue of the journal Science, paleontologists Neil Shubin and Michael Coates from the University of Chicago and Ted Daeschler from the Academy of Natural Sciences in Philadelphia, describe a remarkable fossil that bridges the gap between fish and amphibian and provides a glimpse of the structure and function changes from fin to limb. The fossil, a 365-million-year-old arm bone, or humerus, shares features with primitive fish fins but also has characteristics of a true limb bone. Discovered near a highway roadside in north-central Penn., the bone is the earliest of its kind from any limbed animal.
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(posted April 12, 2004)
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This is a close-up photo of electrodes in the "pumping region" of a new type of cooling technology for computers being developed by mechanical engineers at Purdue. The concept is to use a sort of nano-lightning to create tiny wind currents. Clouds of ions created when electrons react with air are then attracted by these electrodes and "pumped" forward by changing the voltages in the electrodes. The researchers have demonstrated that the pumping concept works with a region of electrodes made of many series, each series containing three electrodes. The first in the series is the most positively charged, followed by an electrode that has a less-positive charge and then a third electrode that is negative. The voltages are rapidly switched from one electrode to the next in such a way that the clouds of ions move forward. The electrode voltages are switched roughly a million times a second, pushing the ion clouds forward and producing a cooling breeze.
Credit: Daniel J. Schlitz, Purdue University School of Mechanical Engineering
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Tiny Wind to Cool the Tiniest Circuits—
Researchers Develop Miniature Cooling System that Generates Nanoscale
Breezes
Researchers have crafted miniature cooling systems similar in concept to the silent fans now available to filter and circulate the air in homes, but the miniscule "fans" are only microns (millionths of a meter) across. Using minute voltages, the devices generate ions that discharge to create small breezes -- perfect for cooling cell phones, laptop computers, and the tiniest devices. As electronics shrink, so must the cooling systems that keep them from overheating. The new technology developed at Purdue University is at the right scale for tiny electronic machines. The system's electrodes are crafted from carbon nanotubes only five nanometers (billionths of a meter) across at the tip, and the device does not use water or other cumbersome cooling fluids.
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(posted April 12, 2004)
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Kathleen Pryer studying ferns.
Credit: Jim Wallace, Duke University Photography
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Ferns Diversified in Shadow of Flowering Plants
Belying the popular notion of ferns as delicate, lacy relics surmounted by the evolution of flowering plants, biologists have presented evidence for a much different scenario. Their studies indicate that when flowering plants, or angiosperms, evolved some 144 million years ago, ferns took advantage of ecological niches in the new angiosperm forests to diversify into a far richer array of species. The study offers a new insight into the critical period in evolution when the rise of flowering plants sparked a dramatic increase in species diversity that eventually fostered the rise of birds, bees and mammals, including humans.
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April 12, 2004)
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Map of PNAS articles from eight biology subfields,
color-coded according to subfield. 2-D views on the 3-D space-this
one selected automatically by the computer.
Credit: Thomas Landauer, University of Colorado, Boulder; Darrell Laham, Marcia Derr, Knowledge Analysis Technologies
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Here There Be Data: Mapping the Landscape of Science
In ancient maps of the world, expanses of unknown territory might hold a warning to would-be explorers: Here there be monsters. For today's explorers seeking to navigate and understand the world of science, the monsters are the untamed collections of data that inhabit a largely uncharted landscape. The April 6, 2004, issue of the Proceedings of the National Academy of Sciences (PNAS) features nearly 20 articles by some of tomorrow's mapmakers. Representing the computer, information and cognitive sciences, mathematics, geography, psychology and other fields, these researchers present attempts to create maps of science from the ever-growing and constantly evolving ocean of digital data.
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April 12, 2004)
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