Number 192, August 30, 1994 by Phillip F. Schewe and Ben Stein
A SOURCE OF COHERENT X RAYS , an x-ray laser, is hard to achieve because
of the enormous power needed to bring about a population inversion in which
atoms in the laser medium reside in excited states long enough in time
and high enough in energy to promote a worthwhile laser action. In general
the power requirement is proportional to the inverse fifth power of the
wavelength of the emitted light. Charles Townes of the University of Illinois
at Chicago has partly gotten around this problem by using light from an
ultraviolet laser to excite not atoms but clusters of atoms. The incoming
pump light excites outer electrons in the cluster (xenon) atoms and these
in turn can, by consolidating their energy, ionize a more tightly-bound,
inner electron in one of the atoms, creating thereby a sort of "hollow"
atom. The ejected electron is quickly replaced by an outer electron in
a transition that gives rise to a hard x ray with a wavelength of 2-3 angstroms.
This whole process seems to be aided by a self-focusing of the pump laser
beam along the ionization trail through the laser medium. X-ray lasers
in this wavelength range, when fully realized, will facilitate microscopy
with a much better spatial resolution than is now possible. (A. McPherson
et al., Nature, 25 August 1994.)
COULD QUANTUM MECHANICS PLAY A ROLE in the workings of the conscious
mind? Some physicists, like John Taylor of Kings College London, hold the
negative view: they believe that information born at the quantum level
would be overwhelmed in the warm, wet, and noisy environment of living
cells. By contrast, other scientists, such as Stuart Hameroff of the University
of Arizona, assert that under some circumstances quantum information could
indeed be sustained at the cellular level. Hameroff points to microtubules,
tiny rodlike proteins (only discovered in the 1970s) existing in all bodily
cells, as a possible theater of quantum consciousness. These rods, according
to Hameroff, might possibly serve either as waveguides for photons or as
the host medium for persistent vibrational standing waves. In this model
the action of many rods in neighboring cells, acting in concert, would
constitute a physical matrix for thoughts or memories. All these ideas
were discussed earlier this year at a conference held in Arizona. At the
conference partisans of the quantum approach were a small minority. Even
scientists who gave some credence to the quantum hypotheses had to admit
that experimental searches for coherent effects in microtubule behavior
had found nothing. (New Scientist, 20 August.)
THE EXPERIMENTAL ULTRAVIOLET INDEX , to be issued daily by the National
Weather Service, is a forecast of the noontime ultraviolet level in 58
U.S. cities. So in addition to smog, pollen, and the weather itself, people
can now worry in a quantitative way about the cancer- causing or cataract-causing
effects of UV. An index of 6, for example, is considered "moderate."
At that level a person with skin very susceptible to sunburn, would burn
after 10 minutes of direct exposure, while a much less susceptible person
would burn after 50 minutes. The general advice of the Environmental Protection
Agency is that if you can see your shadow, you may want to use some protection
against UV radiation. (Science News, 23 July.)
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