PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 752  November 2, 2005  by Phillip F. Schewe, Ben Stein

A NANOSCALE GALVANI EXPERIMENT provides a new way to obtain images of
biological tissue.  Applying state-of-the-art technology to a
seldom-exploited electromechanical property in biomolecules, Sergei Kalinin
of Oak Ridge National Laboratory (sv9{at}ornl.gov) and his colleagues have
demonstrated a nanometer-scale version of Galvani's experiment, in which
18th-century Italian physician Luigi Galvani caused a frog's muscle to
contract when he touched it with an electrically charged metal scalpel. 
Described at this week's AVS Science & Technology meeting in Boston,
the new, 21st-century demonstration promises to yield a host of previously
unknown information in a variety of biological structures including
cartilage, teeth, and even butterfly wings.
Employing a technique named Piezoresponse Force Microscopy (PFM), Kalinin
and colleagues sent an electrical voltage through a tiny, nanometer-sized
tip to induce mechanical motion along various points in a biological
sample, such as a single fibril of the protein collagen.  The
electromechanical response at various points of the sample, as measured by
the probe tip, enabled the researchers to build up images of the collagen
fibrils, with details less than 10 nanometers in size.  This resolution
surpasses the level of detail that can be gleaned on those biostructures by
ordinary scanning-probe and electron microscopes (get a lengthier
description at http://www2.avs.org/symposium/boston/pressroom/papers.html
).
The PFM technique exploits the well-known but infrequently used fact that
many biomolecules, especially those that are made of groups of proteins,
are piezoelectric, or undergo mechanical deformations in the presence of an
external electric field.  The researchers have used the PFM technique to
produce images of cartilage as well as enamel and dentin (found inside
teeth).  Besides providing images of biostructures on a nanometer scale,
the new technique yields information about the electromechanical properties
and molecular orientation of biological tissue.  In recent work, the
researchers even found unexpected piezoelectric properties in butterfly
wings which enabled them to yield molecular-level images of wing
structures.  (Kalinin, Rodriguez and Gruverman, meeting paper NS-WeM3)
                                                                
THE FIRST OBSERVATION OF DIGITAL HEAT FLOW in a nanostructure at ambient
conditions has been made using carbon nanotubes suspended between two
electrodes.  A new experiment carried out at Caltech, and reported at the
AVS meeting, furthers the effort to employ nanotubes as a means for
removing unwanted heat from microcircuits.
Carbon nanotubes, nm-wide cylinders made from rolled up graphitic sheets,
as a vital conduit for removing  have a versatile array of mechanical,
electrical, and magnetic properties.  Its thermal properties should be just
as valuable.  Because phonons (the particle manifestations of heat flow)
can move so freely in nanotubes, even ballistically (meaning that they
refrain from scattering and travel in straight lines), the flow of heat in
nanotubes should have quantum properties.  Indeed, Caltech scientist Marc
Bockrath (mwb{at}caltech.edu) and his colleagues have observed that heat
conductivity in nanotubes can readily reach quantum-mechanical limits; heat
conduction occurs in multiples of a quantum unit of heat flow.  Phonons
seem to move nearly as far as a micron (a long distance for nanoscopically
sized objects) even at temperatures of 900 degrees C.  The mean-free path
between scattering for the phonons should be even larger at room
temperature.  This, says Bockrath, underscores the fantastic potential of
nanotubes as thermal conduits.  (Paper NS-ThM4).

COLOR SUPERCONDUCTIVITY, the hypothetical condensation of quark pairs at
the cores of super-dense collapsed stars, might represent a unique example
of superconductivity being made stronger (not weaker) by the presence of
magnetism.  In ordinary electrical superconductivity, in a metallic lattice
of atoms, free electrons can pair up through the agency of a very weak
coupling force mediated by the subtle vibrations in the lattice itself,
establishing a weakly attractive force between pairs of electrons.
An external magnetic field is either repelled from such a superconducting
environment (the Meissner effect) or can serve to undo the fragile
superconducting state.   On the other hand, if quark matter is realized
inside the core of neutron stars--- with densities about 10 times the
density of ordinary atomic nuclei--- or within the still hypothetical quark
stars---objects ranking somewhere between neutron stars and black holes in
terms of matter density --- quarks will be pressed together so firmly that
by the rules of asymptotic freedom (see the description of last year's
physics Nobel prize: "http://www.aip.org/pnu/2004/split/703-1.html)
the force between the quarks will actually be quite weak and attractive.
This weakly interactive highly dense quark matter is expected to behave
similarly to ordinary superconductors in condensed matter and the quarks
will form pairs as do the electrons in metallic superconductivity. Since
quarks possess "color charge"
("colors" like red, green, or yellow are just another way of
referring to a special type of charge, analogous to electric charge,
carried by quarks) the quark-quark pair carries a net color charge; hence
the phenomenon is called color superconductivity (for a detailed
explanation of color superconductivity see the article:
http://www.aip.org/pt/vol-53/iss-8/p22.html).
    One might think that an applied magnetic field will produce in the
color superconductor the same kind of counteracting effect that it does in
ordinary superconductivity. However, a new study by Vivian de la Incera and
Efrain Ferrer of Western Illinois University (Macomb, IL, USA) and Cristina
Manuel of the Instituto de Fisica Corpuscular (Valencia, Spain) shows
theoretically that the powerful magnetic fields inside some
super-compressed stars, can actually enhance color superconductivity.  The
authors say that in the core of compact stars the coming together of very
high nuclear density, an enfeebled color nuclear force, and very strong
magnetic fields (as high as 10^17 gauss in some collapsed stars), enables
the formation of a new phase of low-temperature color superconducting quark
matter, one in which superconductivity and magnetism are on good terms (see
figure at http://www.aip.org/png/2005/237.htm).
    Right now, the authors admit, testing this hypothesis will be
difficult, as more investigations are still needed to identify signatures
that can connect the inner phase of the star to its observable properties,
such as the mass-to-radius ratio. (Ferrer et al., Physical Review Letters,
7 October 2005)

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