PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 753   November 9, 2005  by Phillip F. Schewe, Ben Stein

GUIDED, SLOW LIGHT IN AN ULTRACOLD MEDIUM has been demonstrated by Mukund
Vengalattore and Mara Prentiss at Harvard.  Slowing light pulses in a
sample of atoms had been accomplished before (see for example
http://www.aip.org/pnu/2001/split/521-1.html) by sending light pulses into
a highly dispersive medium, that is, a medium in which the index of
refraction varies greatly with frequency.
    Previously this dispersive quality had come about by tailoring the
internal states of the atoms in the medium.  In the present Harvard
experiment, by contrast, the dispersive qualities come about by tailoring
the external qualities of the atoms, namely their motion inside an
elongated magnetic trap (see figure at www.aip.org/png/2005/238.htm).  In
the lab setup two pump laser beams can be aimed at the atoms in the trap;
depending on the frequency and direction of the pump light, the atomic
cloud (at a temperature of about 10 micro-K) can be made more or less
dispersive in a process called recoil-induced resonance, or RIR.  If now a
separate probe laser beam is sent along the atom trap central axis, it can
be slowed by varying degrees by adjusting the pump laser beam. 
Furthermore, the probe beam can be amplified (the intensity of the light
can be increased by a factor of up to 50) or attenuated depending on the
degree of dispersiveness in the atoms.  This process can be used as a
switch for light or as a waveguide.
    According to Mukund (now working at UC Berkeley,
mukundv{at}calmail.berkeley.edu), slowing light with the recoil induced
resonance approach may be a great thing for nonlinear-optics research. 
Normally nonlinear effects come into play only when the light intensities
are quite high.  But in the RIR approach, nonlinear effects arise more from
the strong interaction of the two laser beams (pump and probe) and the fact
that the slow light spends more time in the nonlinear medium (the trap full
of atoms).  All of these effects are enhanced when the atoms are very cold.
 Moreover, because the slow light remains tightly focused over the length
of the waveguide region, intensity remains high; it might be possible to
study slowed single-photon light pulses, which could enhance the chances of
making an all-optical transistor.  The light in this setup has been slowed
to speeds as low as 1500 m/sec but much slower speeds are expected when the
atoms are chilled further.
(Vengalattore and Prentiss, Physical Review Letters, upcoming article;
MIT-Harvard Center for Ultracold Atoms at atomsun.harvard.edu)

ZEN AND THE ART OF TEMPERATURE MAINTENANCE.  Scientists at the Iwate
University in Japan have shown that the skunk cabbage---a species of arum
lily and whose Japanese name, Zazen-sou, means Zen meditation plant---can
maintain its own internal temperature at about 20 C, even on a freezing day
(picture at www.aip.org/png/2005/239.htm).
    The plant occurs in East Asia and northeastern North America, where its
English name comes from its bad smell and from the fact that its leaves are
like those of cabbage.  Unlike the case of mammals, which maintain their
body temperature by constant metabolism in cells all over the body, heat in
the skunk cabbage is produced chiefly in the spadix, the plant's central
spike-like flowering stalk through chemical reactions in the cells'
mitochondria.  According to one of the authors of the new study, Takanori
Ito (taka1{at}iwate-u.ac.jp), only one other plant species, the Asian sacred
lotus, is homeothermic, that is, able to maintain its own body temperature
at a certain level.  Most other plants do not produce heat in this way
because they seem to lack the thermogenic genes (the technical name for
which, in abbreviated form, is SfUCPb).  Moreover, the researchers,
studying subtle oscillations in the plant's internal temperature, claim
that the thermo-regulation process is chaotic and that this represents the
first evidence for deterministic chaos among the higher plants.  The
resultant trajectory in the abstract phase space (where, typically, one
plots the plant's temperature at one time versus the temperature at another
time) is a strange attractor, which the authors refer to as a Zazen
attractor, a "Zen meditation" attractor.  (Physical Review E,
November 2005)

DROWNING IN QUICKSAND IS IMPOSSIBLE, according to a new study, relegating
this popular plot device in adventure stories to the category of pure
folklore.  Consisting of a mixture of sand, salt water, and clay, quicksand
captured the attention of University of Amsterdam physicist Daniel Bonn
when he went on a family trip to Iran, the birthplace of his wife. 
Collecting a sample of quicksand near a body of water in Iran, and bringing
it to his laboratory for study, Bonn and his colleagues showed that shaking
aluminum beads, designed to have the same density as human beings, would
partially, but never fully, submerge them.  Since quicksand is twice as
dense as water, the beads (and humans) only sink about halfway.  Shaking or
otherwise disturbing the quicksand liquefies it, increasing the downward
flow of the beads by a factor of a million. This is how humans can get
stuck in it.  Since quicksand is often located near bodies of water, Bonn
speculates that high tidal floods passing over individuals stuck in
quicksand may have caused casualties incorrectly ascribed to sinking fully
in it.  Bonn says his conclusions apply to all kinds of quicksand.
Nonetheless, the force required to lift a foot out of quicksand can be
equal to that required to raise a car. His solution: wiggling the stuck
foot will cause water to trickle down, allowing the hapless adventurer to
get out of it. (Khaldoun et al., Nature, September 29, 2005)

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