Number 689, June 21, 2004
by Phil Schewe and Ben Stein
Nanotube Water
Nanotube water, a one-dimensional form of water consisting of a string
of water molecules confined in a carbon nanotube, has been studied with
neutron scattering by physicists at Argonne National Lab. Neutron scattering
measurements, along with computer simulations of the molecular interactions
between the water and the surrounding single-walled carbon nanotube,
confirmed that water molecules had successfully been taken up into the
nanotubes in the form of a "wire." But this was not all; surrounding
the water wire was another water structure, a sheath of water, a cylindrical
square-ice- sheet formation (see figure).
The result of this novel architecture was that fluid-like behavior
was observed at temperatures far below the freezing point of normal
water. The hydrogen bonds along the water chain seem to be softened,
allowing, for example, a freer movement of protons along the chain.
The Argonne researchers (contact Alexander Kolesnikov, akolesnikov@anl.gov,
630-252-3555) believe that this anomalous behavior might help to explain
other phenomena featuring nm-scale confined water such as water migration
from soil to plants via xylem vessels and the proton translocation in
transmembrane proteins. (Kolesnikov
et al., Physical Review Letters, 16 July 2004.)
Amorphous Steel
Amorphous steel with large cross-sections, long a goal of metallurgists,
has been fabricated by scientists at Oak Ridge National Lab. The amorphous
steel produced has a hardness and strength more than twice that of the
best ultra-high-strength conventional steel. Some amorphous (glassy)
iron-based alloys have been employed in making transformer cores, the
electrical devices which transform electricity from one voltage to another,
and have reduced energy losses thereby by two-thirds. But not until
now has glassy steel of the kind used in building structures been made.
Steel, an alloy of mostly iron atoms with varying amounts of carbon
and other elements, is ordinarily a crystal, with an internal structure
consisting of neat rows of atoms. If produced quickly from a liquid
phase, however, a disordered solid can result. The trick is to find
conditions---including the chemical content of the alloy, such as the
addition of yttrium in this case---that favor the liquid phase and frustrate
the onset of crystallization even as the solidification temperature
is approached.
The researchers (Zhou Ping Lu, 865-576-7196, luzp@ornl.gov) have produced
centimeter-sized pieces of the amorphous steel, and they feel that structural
steel in bulk metallic glass form can be produced economically with
traditional drop-casting methods, in which metallic glasses are made
by pouring the hot liquid into a cold copper mold. (Lu
et al., Physical Review Letters, 18 June 2004.
See mention of related work reported by a University of Virginia group
(Ponnarnbalam
et al., J. Mat. Res, 5 May 2004) and by a Caltech group (Xu
et al., Physical Review Letters, 18 June 2004).
Nanoimprint Lithography
Nanoimprint lithography featuring line widths of only 16 nm and a line
spacing of 14 nm has been achieved by scientists at Princeton University.
Sustaining this delicate work of fine patterning and fabrication, furthermore,
was sustained across the face of 4-inch wafer.
One way to increase the density of storable data or computing power
of microchips is of course to shrink the circuitry, but new difficulties
arise when the size or spacing of lines gets too small. Getting below
a 35-nm pitch, for example, is difficult when using an electron beam
to do the lithography.
Therefore the Princeton researchers used "photocurable nanoimprint
lithography" (P-NIL), a process in which a mold is pressed into a resist
medium which is then cured with ultraviolet rays. After this the resist
is etched away, leaving behind thin 5-nm-wide polymer walls. Gold contacts
5 nm apart can also be fabricated. (Austin
et al., Applied Physics Letters, 28 June 2004)
Earth's Oceanic Currents and Jupiter's Bands
Earth's oceanic currents and Jupiter's bands bear a certain resemblance
to each other, a new report suggests. The work consists of comparisons
of the stripes visible in Jupiter's upper atmosphere and zones of water
at a depth of 1000 meters stretching across the Pacific Ocean on Earth.
The gas jets on Jupiter and the ocean currents on Earth not only look
alike, but the energy spectra of each are characterized by a downward
sloping "power law" curve; that is, the likelihood of jets of a certain
size is proportional to the size raised to a power. The oceanographers
working on this study themselves stretch halfway across the world, coming
from the University of South Florida (US), the Meteorological Research
Institute (Japan), Columbia University (US), and the Ben-Gurion University
(Israel). (Galperin et al., Geophysical
Research Letters, June 2004)
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