Word: nucleus
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Dates: during 1980-1989
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Ordinary conductivity, the measure of a material's ability to transmit electrical current, is determined by events that take place at the atomic level. Atoms consist of a tiny dense nucleus that contains positively charged protons and chargeless neutrons. Around the nucleus whirl the negatively charged electrons, residing in shells with shapes determined by the electrons' energy levels...
...outer shell has a number of empty slots, and the electrons that it does contain are not bound as tightly to it as those in the inner shells. Just as the sun's gravitational pull is weaker on distant Pluto than on nearby Mercury, the hold of an atomic nucleus is also weaker on electrons in the outermost layers...
...tried similar surgery on four Parkinson's victims. They achieved only slight improvements that soon faded. Madrazo credits his team's success to modifications in surgical technique. The Swedes had transferred the adrenal tissue directly into a C-shaped structure in the middle of the brain called the caudate nucleus, where dopamine exerts its primary effects. The Mexicans, by contrast, used surgical staples to anchor the cells onto the exterior of the caudate, which is continually bathed in cerebrospinal fluid. This nourishing bath may have helped the graft survive. In addition, Madrazo says, he transplanted "much more" tissue than...
...sustain it, the now all-iron core, hidden under the star's outer layers, begins its final, catastrophic collapse. In the incredibly short time of just 1 second, according to University of Arizona Astrophysicist Adam Burrows, the core is compressed to more than the density of an atomic nucleus. "It's as if the earth had suddenly collapsed to the size of New York City," says Burrows. "At this point the rest of the star is oblivious. It doesn't know the core has collapsed and that it's doomed...
...began to suspect the cause. He had just returned from a medical seminar on a newly recognized disorder called Fragile X syndrome, which results from a weakness in the structure of the X sex chromosome (one of the 46 chromosomes -- complex molecules containing long segments of DNA -- in the nucleus of the human cell). The behavior of the Lancaster children seemed to fit the patterns described at the meeting, and tests at Denver's Children's Hospital soon confirmed that they both had the defective chromosome...