PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 696 August 12, 2004
by Phillip F. Schewe, Ben Stein

THE MASSIVE NORTHEAST BLACKOUT of a year ago not only shut off
electricity for 50 million people in the US and Canada, but also shut off
the pollution coming from fossil-fired turbogenerators in the Ohio Valley.
In effect, the power outage was an inadvertent experiment for gauging
atmospheric repose with the grid gone for the better part of the day.  And
the results were impressive.  On 15 August 2003, only 24 hours after the
blackout, air was cleaner by this amount: SO2 was down 90%, O3 down 50%,
and light-scattering particles down 70% over "normal" conditions
in the same area.  The haze reductions were made by University of Maryland
scientists scooping air samples with a light aircraft.  The observed
pollutant reductions exceeded expectations, causing the authors to suggest
that the spectacular overnight improvements in air quality "may result
from underestimation of emission from power plants, inaccurate
representation of power plant effluent in emission models or
unaccounted-for atomospheric chemical reactions."  (Marufu et al.,
Geophysical Research Letters, vol 31, L13106, 2004.)

THE LONG-TERM DYNAMICS OF THE ELECTRICAL GRID are examined in new studies
conducted by Ben Carreras and his colleagues at Oak Ridge National Lab, the
University of Wisconsin, and University of Alaska.  Engineers at the
utilities are of course always looking for ways to make their systems
better, especially in the aftermath of large blackouts, such as the event
on August 14, 2003.  These post-mortem studies typically locate the sources
of the outage and suggest corrective measures to prevent that kind of
collapse again, often by strengthening the reliability of specific
components. Carreras argues that a more effective approach to mitigating
electrical disasters is build more redundancy into the system.  And to do
this, he says, you need to look at how the electrical grid, considered as a
dynamic system subject to many forces, behaves over longer periods of time.
 And to do this one needs to build into any grid model social and business
forces in addition to the physics forces that govern the movement of
electricity. Thus the Oak Ridge model not only solves the equations
(governed by the so-called Kirchoff laws) that determine how much
 power flows through specific lines in a simulated circuit, but also build
in the strain on the system over time caused by an increasing demand for
power, the addition of new generators and transmission lines, and even
elements of chance in the form of weather fluctuations and the occasional
shorting caused by warm, sagging lines contacting untrimmed trees.  The
model proceeds to let the grid evolve, and for each "day" it
computes possible solutions---in the form of successful combinations of
power generation levels and subsequent transmission of that power over
existing lines, some of which come in and out of service---for the
continued running of the grid.  The model derives a probability curve for
blackouts which matches pretty well the observed outage data for North
America.  The Oak Ridge scientists believe that their model could be used
by utility companies to test grid behavior for various
network-configuration scenarios, particularly those where the grid is
operating dangerously close to a cascade threshold.  (Carreras et al.,
Chaos, September 2004; carreras{at}fed.ornl.gov)

PROTEIN-BASED NANOACTUATORS can now be controlled rapidly and reversibly by
thermoelectric signals. In a living creature, contracting or relaxing of
muscle tissue is carried out by motor proteins called actomyosin.
Scientists designing nano-scale devices would naturally like to emulate the
efficiency and compactness of the muscle-moving molecules.  A key issue is
the controlled rapid activation of the protein motors through simple means.
And that's what researchers at Florida State University have done. They
have set up a flow cell in which motor molecules (which can remain viable
for days when refrigerated) can be thermally activated into motion in a
controllable and reversible way using only input wires which provide a
controlled amount of heat. An important goal of this work, according to
Goran Mihajlovic (goran{at}martech.fsu.edu), is to use the protein motors to
power linear motion of nanowires; if the wires are themselves magnetic
(such as nickel), then the motion could be monitored via a field sensor,
such as a micro-Hall probe. The result would a bi-directional
nano-actuator, controlled electrically but powered with biological energy. 
Possible future applications include a role in bioanalysis chips and gene
delivery.  (Mihajlovic et al., Applied Physics Letters, 9 August 2004)

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