Text 372, 86 rader
Skriven 2005-03-25 21:17:56 av Herman Trivilino (1:106/2000.7)
Ärende: PNU 724
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PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 724   March 25, 2005
by Phillip F. Schewe, Ben Stein
        
DIRECT DETECTION OF EXTRASOLAR PLANETS has been achieved for the first time.
Previously the existence of planets around other suns has been inferred from
subtle modulation of the light emitted by the star.  Now light from the planet
itself has been recorded directly at infrared wavelengths by the Spitzer Space
Telescope (www.spitzer.caltech.edu).  The planets, one with the prosaic name of
HD 209458b (153 light years away), the other TrES-1 (489 light years away),
orbit their stars more tightly than does Mercury around our sun.  This makes
the Jupiter-sized planets hot enough to be viewed by Spitzer.  (NASA press
conference, 23 March; report to be published in Nature, 7 April.)

SUPERFLUID SOLID HYDROGEN.  Quantum science allows for collective behavior that
runs counter to human intuition.  For example, at very low temperatures
helium-4 atoms, in their wavelike manifestation, can begin to overlap.  When
this happens the atoms are indistinguishable and indeed constitute a single
quantum state.  In this state liquid helium-4 will flow without friction. 
Comparably chilled, quantum-condensed dilute gases (Bose-Einstein condensates,
or BEC) also exhibit superfluid behavior.  What about solids?  Can they "flow"
without friction?  Last year Moses Chan (Penn State) announced the results of
an experiment in which solid helium-4 was revolved like a merry-go-round.  It
appeared that when the bulk was revolved at least part of the solid remained
stationary.  In effect part of the solid was passing through the rest of the
solid without friction.  Chan interpreted this to mean that a fraction of the
sample had become superfluid (see www.aip.org/pnu/2004/split/669-1.html and
www.aip.org/pnu/2004/split/699-2.html).  Now, Chan sees evidence for superfluid
behavior in solid hydrogen as well.  Speaking at this week's meeting of the
American Physical Society (APS) in Los Angeles, Chan said that his hydrogen
results are preliminary and that further checks are needed to be made before
ruling out alternative explanations.  The concept of what it means to be a
solid, Chan said, needs to be re-examined.

HOW EFFECTIVE WILL FLU VACCINE BE?  A new way to study this important issue is
to use the tools of statistical physics.  At the APS meeting, Michael Deem of
Rice University (mwdeem@rice.edu) described a new way of predicting the flu
vaccine's efficacy (a higher efficacy means that fewer vaccinated individuals
get the flu relative to unvaccinated individuals).  To measure efficacy,
researchers examine each strain's hemagglutinin (H) protein, the major protein
on the surface of influenza A virus that is recognized by the immune system. 
In one standard approach, researchers study all the mutations in the entire H
protein from one season to the next.  In another approach, researchers study
the ability of antibodies produced in ferrets to recognize either the vaccine
strain or the mutated flu strain, which had been thought to be a good method
for predicting flu vaccine efficacy in humans.  However, these approaches are
only modestly reliable indications of the vaccine's efficacy.  Deem and his
Rice University colleagues point out that each H protein has 5 "epitopes,"
antibody-triggering regions mutating at different rates.  The Rice team refers
to the one that mutates the most as the "dominant" epitope. Drawing upon
theoretical tools originally developed for nuclear and condensed-matter
physics, the researchers focus on the fraction of amino acids that change in
the dominant epitope from one flu season to the next. Analyzing 35 years of
epidemiological efficacy data, the researchers believe that their focus on
epitope mutations correlates better with vaccine efficacy than do the
traditional approaches. Deem and his colleagues Vishal Gupta and Robert Earl
believe that this new measure may prove useful in designing the annual flu
vaccine and in interpreting vaccine efficacy studies.

SOLVAY: THE MOVIE.  Arguably the most famous photograph of physicists is the
group portrait taken at the 1927 Solvay Conference in Belgium.  It turns out
that a brief motion picture of that event also exists.  In the course of this
three-minute film, a dozen or more present and future Nobel laureates walk in
and out of the frame, including Albert Einstein, Marie Curie, Niels Bohr, and
Max Planck.  Forgotten or neglected for decades, the film was shown in public
for the first time at the APS meeting by Nancy Greenspan, author of "The End of
the Certain World," the first full biography of Max Born
(http://www.maxborn.net).  Born is credited with the insight that the
wavefunction appearing in Erwin Schrodinger's famous equation provided not the
exact location of an electron inside an atom but rather merely a statistical
likelihood of the electron being at various locations.   This view of quantum
reality
would later take on the name of the "Copenhagen interpretation," in honor of
Niels Bohr.  Greenspan argues that Born has been underappreciated in histories
describing the establishment of quantum science.  Speaking at a  press
conference, APS president Marvin Cohen (Univ California, Berkeley) underscored
this point.
Max Born's group at the University of Gottingen, active over the period from
1922 to 1932, was, Cohen suggested, the most illustrious theoretical physics
"school" of all time.  The list of Born students or junior colleagues includes
no less than Werner Heisenberg, Wolfgang Pauli, Enrico Fermi, Maria
Goeppert-Mayer, Linus Pauling, Eugene Wigner, and Robert Oppenheimer.

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 * Origin: Big Bang (1:106/2000.7)