News Scan Briefs; May 2004; Scientific American Magazine; by Alexander Hellemans, Charles Choi, JR Minkel; Ian Steer; 2 Page(s)

An electron completes an orbit around a hydrogen atom in a mere 150 attoseconds - what the tick of a secondhand is to 200 million years. (One attosecond is 1018 second.) Hoping to investigate such brief phenomena, physicists have made attosecond-scale laser flashes, typically by exciting electrons into ultimately releasing the flash. But precisely measuring the pulses has proved difficult; techniques have relied on indirect means or calculations based on how the pulse was made. A team led by Ferenc Krausz at the Vienna University of Technology has come up with a more accurate way. The group directed attosecond-scale x-ray flashes at neon atoms to strip the electrons off. Then a second light pulse sweeps the electrons sideways. Knocked clear, the electrons could have their energies measured. That enables researchers to determine the duration of the original pulse, which, in the data reported in the February 26 Nature, was 250 attoseconds long.

That women are born with all the eggs they will ever have may be a myth. Researchers have found that mice retain the ability to make egg-generating oocyte cells into adulthood. In juvenile female mice, follicles (oocytes encased in support cells) died rapidly enough that egg supplies should have been depleted in days or weeks. Still, mice can remain fertile past one year of age; moreover, follicle numbers overall remained virtually unchanged. This evidence suggests female mice have a previously undiscovered type of stem cell that continuously generates reproductive cells, just as males do. About 60 cells near each mouse ovary possessed chemicals typical of these stem cells. If these findings prove true in humans, theories about how a woman's reproductive system ages and how smoking, chemotherapy and radiation affect fertility will have to be reexamined. The report appears in the March 11 Nature.