PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 742   August 19, 2005
by Phillip F. Schewe, Ben Stein, and Davide Castelvecchi        

ROOM TEMPERATURE ICE is possible if the water molecules you're freezing are
submitted to a high enough electric field.  Some physicists had predicted
that water could be coaxed into freezing at fields around 10^9 V/m.  The
fields are thought to trigger the formation of ordered hydrogen bonding
needed for crystallization.
Now, for the first time, such freezing has been observed, in the lab of
Heon Kang at Seoul National University in Korea, at room temperature and at
a much lower field than was expected, only 10^6 V/m. Exploring a new
freezing mechanism should lead to additional insights about ice formation
in various natural settings, Kang believes (surfion{at}snu.ac.kr).  The
field-assisted  room-temperature freezing took place in cramped quarters:
the water molecules were constrained to the essentially 2-dimensional
enclosure between two surfaces: a gold substrate and the gold tip of a
scanning tunneling microscope (STM).  Nevertheless, the experimental
conditions in this case, modest electric field and narrow spatial gap,
might occur in nature.  Fields of the size of 10^6 V/m are, for example,
are thought to exist in thunderclouds, in some tiny rock crevices, and in
certain nanometer electrical devices.   (Choi et al., Physical
Review Letters, 19 August 2005; for another example of seemingly
room-temperature ice, see http://www.aip.org/pnu/1995/split/pnu225-1.htm )
        
NETWORKING CAN BE CRITICAL, LITERALLY.  The theory of "small-world"
networks yields insight into innumerable real-world situations, from the
Internet to the power grid, from epidemics to opinion making. A small-world
network is one where certain nodes, called hubs, have an unusually large
number of connections, so that going through hubs one can reach any other
node in just a few steps.  In real-life small-world networks, researchers
have observed "critical" thresholds -- for example, epidemics
that spread uncontrollably or spontaneously die out, depending on
thresholds in the disease's degree of infectivity or in the number of
social contacts individuals have. But network theory has so far been poor
at modeling critical thresholds.  Now, Joseph Indekeu of Katholieke
Universiteit Leuven in Belgium (joseph.indekeu{at}fys.kuleuven.be) and his
colleagues have shown that small-world networks can model critical
thresholds if one tunes the hubs to be less influential on their neighbors
than the ordinary nodes. For example, a friend's opinion could be more
influential in shaping your voting preferences than the opinion of a
prominent TV commentator, whose wide audience makes him a hub in the
network.  The tuning idea, the paper shows, is mathematically equivalent to
cutting off most of a hub's
connections.   The authors also say their results could shed light on, and
perhaps help prevent, phenomena such as electrical blackouts and epidemics.
 The new model even suggests a  parallel between networks and general
relativity since trading in the interactions between nodes for changes in
the network's structure is reminiscent of the gravitational interactions
between bodies---gravitational attraction---which can be mimicked by
changes in the structure of spacetime---that is, the curvature created by
the presence of mass.  (Giuraniuc et al., Physical Review Letters, upcoming
article)

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