[EAS] Two about Temperature

Peter J. Kindlmann pjk at design.eng.yale.edu
Sat Mar 10 16:59:00 EST 2007

This issue of Physics News Update has a more general tone, 
recounting the 20th anniversary of the 1987 meeting of the American 
Physical Society when physics briefly reached rock-star status, and 
new findings about the fascinating ability of some organisms to 
withstand freezing.  --PJK

The American Institute of Physics Bulletin of Physics News
Number 814   March 9, 2007 by Phillip F. Schewe, Ben Stein

"THE WOODSTOCK OF PHYSICS," the famous session at the March 1987
meeting of the American Physical Society, earned its nickname
because of the rock-concert fervor inspired by the convergence of
dozens of reports all bearing on copper-oxide superconductors.  The
20th anniversary of this singular event was celebrated this week at
the APS meeting in Denver.
Why such an uproar over the electrical properties of an unlikely
ceramic material?  Because prior to 1987 the highest temperature at
which superconductivity had been observed was around 23 K.  And
suddenly a whole new set of compounds-not metallic alloys but
crystals whose structure put them within a class of minerals known
as perovskites---with superconducting transition temperatures above
35 K and eventually 100 K generated an explosion of interest among
physicists.  Because of the technological benefits possibly provided
by high-temperature superconductivity (HTSC)---things like bulk
power storage and magnetically levitated trains---the public was
intrigued too.
This week's commemoration of the Woodstock moment (the months of
feverish work leading up to the 1987 meeting) provided an excellent
history lesson on how adventurous science is conducted.  Georg
Bednorz (IBM-Zurich), who with Alex Mueller made the initial HTSC
discovery, recounted a story of frustration and exhilaration,
including working for years without seeing clear evidence for
superconductivity; having to use borrowed equipment after hours;
overcoming skepticism from IBM colleagues and others who greatly
doubted that the cuprates could support supercurrents, much less at
unprecedented temperatures; and finally arriving at the definitive
result-superconductivity at 35 K in a La-Ba-Cu-O compound.
In October 1986 Bednorz and Mueller prepared a journal article
confirming their initial finding in the form of observing the
telltale expulsion of magnetism (the Meissner effect) from the
material during the transition to superconductivity.  Submitting
this paper, however, required the approval of the IBM physics
department chairman, Heinrich Rohrer who, that very week, had been
declared a co-winner of the Nobel prize for his invention of the
scanning tunneling microscope (STM).  Afraid that he would not be
able to obtain the preoccupied Rohrer's attention, Bednorz obtained
the needed signature by thrusting the approval form at Rohrer as if
he (Bednorz) desired only a celebratory autograph.  A scant year
later Bednorz and Mueller pocketed their own Nobel Prize.
The IBM finding was soon seconded by work in Japan and at the
University of Houston, where Paul Chu, testing a YBaCuO compound,
was the first to push superconductivity above the temperature of
liquid nitrogen, 77 K.  Very quickly a gold rush began, with dozens
of condensed matter labs around the world dropping what they were
doing in order to irradiate, heat, chill, squeeze, and magnetize the
new material.  They tweaked the ingredients list, hoping to devise a
sample superconducted at still higher temperatures or with a greater
capacity for carrying currents.  At this week's APS meeting Chu said
that he and his colleagues went for months on three hours sleep per
night.  Several other speakers at the 2007 session spoke of the
excitement of those few months in 1987 when-according to such
researchers as Marvin Cohen (UC Berkeley) and Douglas Scalapino (UC
Santa Barbara)-the achievement of room-temperature superconductivity
did not seem inconceivable.
The Woodstock event, featuring 50 speakers delivering their fresh
results at a very crowded room at the New York Hilton Hotel until
3:15 am, was a culmination.  In following years, HTSC progress
continued on a number of fronts, but expectations gradually became
more pragmatic.  Paul Chu's YBaCuO compound, under high-pressure
conditions, still holds the transition temperature record at 164 K.
Making lab samples had been easy compared to making usable
power-bearing wires in long spools, partly because of the brittle
nature of the ceramic compounds and partly because of the tendency
for potentially superconductivity-quenching magnetic vortices to
form in the material.  Paul Grant, in 1987 a scientist at
IBM-Almaden, pointed out that HTSC applications have largely not
materialized.  No companies are making a profit from selling HTSC
products. Operating under the principle of "You get what you
need," Grant said, superconducting devices operating at liquid-nitrogen
temperatures weren't better enough so as to displace devices
operating at liquid-helium temperatures.
Nevertheless, the mood of the 2007 session (Woodstock20) was
upbeat.  Bednorz said the 1986/87 work showed that a huge leap
forward could still take place in a mature research field whose
origins dated back some 70 years.  Bednorz felt that another wave of
innovation could occur.  Paul Chu ventured to predict that within
ten years, HTSC products would have an impact in the power
industry.  Paul Grant referred to the study of superconductivity as
the "cosmology of condensed matter physics," meaning that even
after decades of scrutiny there was still much more to learn about these
materials in which quantum effects, manifested over macroscopic
distances, conspire to make electrical resistance vanish, a
phenomenon which at some basic level might also be related to the
behavior of protons inside an atomic nucleus and the cores of
distant neutron stars.  (Photographs and an original summary press
release from the 1987 meeting is available at our Physics News
Graphics website, www.aip.org/png)

HYPERACTIVE ANTIFREEZE PROTEINS, naturally secreted by an insect
known as the spruce budworm, prevent it from freezing to death
during winters in North American forests. Ohio University's Ido
Braslavsky (braslavs at helios.phy.ohiou.edu) and his colleagues
presented studies of these potent yet nontoxic proteins at this
week's APS Meeting. Found in several other species such as snow
fleas, the hyperactive proteins bind to ice, modify its crystalline
shape, and prevent ice from growing further, effectively reducing
the freezing point of ice for an organism that excretes them. These
nontoxic substances have more recently been renamed "ice structuring
proteins" (ISPs) to distinguish them from the toxic antifreeze
products for automobiles.  Extracting ISPs from biological sources
has many potential applications, such as preserving organs and blood
products, protecting against agricultural frost damage, and even
preventing frostbite.  These natural proteins are currently used in
some "light" ice cream products to improve their texture, but those
ISPs, derived from fish, are much less potent.
How the hyperactive versions inhibit ice from growing is a topic of
interest to Braslavsky's group and their collaborators, such as
Peter Davies from Queen's University (daviesp at post.queensu.ca). The
researchers attached fluorescent molecules, derived from jellyfish,
to the protein.  Through a microscope, they watched how the
fluorescing ISPs inhibited ice crystals from growing.  They observed
that the ISPs prevent ice crystals from expanding in their normal
disk-shaped form.  Instead, they inhibit ice growth in certain
directions and cause the crystals to grow in altered shapes. While a
fish ISP promotes the growth of a "bipyramidal" ice-crystal form
that looks like two pyramids whose bases are attached to each other,
the spruce budworm ISP blocks growth in the preferred direction of
the pyramid's apexes. Using the fluorescence microscopy they watched
the proteins attached to the ice blocking growth in this direction.
(Meeting Paper J35.8,
http://meetings.aps.org/Meeting/MAR07/Event/58982; for more
information, see http://www.phy.ohiou.edu/~braslavs/APS2007/)

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