From: LARRY KLAES (ljk4_at_msn.com)
Date: Sun Apr 10 2005 - 09:45:51 PDT
----- Original Message -----
From: physnews_at_aip.org<mailto:physnews_at_aip.org>
To: ljk4_at_MSN.COM<mailto:ljk4_at_MSN.COM>
Sent: Thursday, April 07, 2005 1:37 PM
Subject: Physics News Update 726
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 726 April 7, 2005 by Phillip F. Schewe, Ben Stein
THE SMALLEST ELECTRIC MOTOR in the world, devised by physicists at
UC Berkeley, is based on the shuttling of atoms between two metal
droplets---one large and one small---residing on the back of a
carbon nanotube. An electric current transmitted through the
nanotube causes atoms to move from the big to the small droplet. In
effect, potential energy is being stored in the smaller droplet in
the form of surface tension. Eventually the smaller drop grows so
much that the two droplets touch. Then the accumulated energy is
suddenly discharged as the larger droplet reabsorbs its atoms
through the newly created hydrodynamic channel. This device
constitutes a "relaxation oscillator" with an adjustable operating
frequency. If the oscillator is attached to a mechanical linkage, it
acts as a motor and can be used to move a MEMS device in inchworm
fashion (movie:
physics.berkeley.edu/research/zettl/projects/Relax_pics.html). The
peak pulsed power is 20 microwatts. Considering that the device is
less than 200 nm on a side, the power density works out to about 100
million times that of the 225 hp V6 engine in a Toyota Camry. Chris
Regan (bcregan_at_berkeley.edu<mailto:bcregan_at_berkeley.edu>), a member of Alex Zettl's group at
Berkeley, reported these and related results at the recent APS
meeting in Los Angeles and in the 21 March 2005 issue of Applied
Physics Letters.
A SINGLE-PROTEIN WET BIOTRANSISTOR has been devised by physicists at
the INFM-S3 Center in Modena, Italy. Metalloproteins help to
shuttle electrons among molecules, a necessary task for powering
such life-critical functions as respiration, photosynthesis, and
enzyme reactions. To do this the protein bristles with side chains
where binding can be achieved. Why not harness all this
functionality normally used for keeping an organism alive for
performing digital information processing? Paolo Facci
(p.facci_at_unimo.it<mailto:p.facci_at_unimo.it>, 39-059-205-5654) and his colleagues use a
particular bacterial protein called azurin in a strategic position
between two gold electrodes, which act as the source and drain of a
transistor. A third electrode, acting as the gate, enables the
centrally located azurin to allow the passage of an electrical
current (see figure at www.aip.org/png<http://www.aip.org/png>). The whole process takes
place in a wet environment, the first time a single-protein
bio-transistor has been operated in this way. Facci believes that
with the addition of bio-inorganic electrodes, his bio-transistor
could be implemented in various wet situations, such as serving in
brain-machine interfaces or for sensing cellular events.
(Alessandrini et al., Applied Physics Letters, 4 April, 2005 )
USING THE LHC TO STUDY HIGH ENERGY DENSITY PHYSICS? The Large Hadron
Collider (LHC) will be the most powerful particle accelerator around
when, according to the plans, it will start operating in the year
2007. Each of its two 7-TeV proton beams will consist of 2808
bunches and each bunch will contain about 100 billion protons, for a
total energy of 362 megajoules, enough to melt 500 kg of copper.
What if one of these full-power beams were to accidentally strike a
solid surface, such
as a beam pipe or a magnet? To study this possibility, scientists
have now simulated the material damage the beam would cause. (In
the case of an actual emergency, the beam is extracted and led to a
special beam dump.) The computer study showed, first of all, that
the proton beam could penetrate as much as 30 m of solid copper, the
equivalent of two of LHC's giant superconducting magnets. It is also
indicated that the beam
penetrating through a solid material would not merely bore a hole
but would create a potent plasma with a high density (10 percent of
solid density) and low temperature (about 10 eV). Such plasmas are
known as strongly coupled plasmas. One way of studying such plasmas
would therefore be to deliberately send the LHC beam into a solid
target to directly induce states of high-energy-density (HED) in
matter, without using shock compression. This is a novel technique
and could be potentially a very efficient method to study this
venerable subject. (Tahir et al., Physical Review Letters, upcoming
article; contact Naeem Tahir of the GSI Laboratory
in Darmstadt, n.tahir_at_gsi.de<mailto:n.tahir_at_gsi.de>)
***********
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