PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 709 November 17, 2004
by Phillip F. Schewe, Ben Stein
                        
WHAT PROPELS A BOOK TO THE TOP OF ONLINE SALES CHARTS?  Is the latest
bestseller simply the product of clever marketing or has it truly permeated
society?  Will its popularity wane as quickly as it appeared or will the
book be a classic for future generations? Though these questions seem to
lay outside the realm of science, scientists can actually obtain deep
insights into these issues by using the tools of statistical physics, which
can predict the rates at which certain events occur, such as the number of
aftershocks following a major earthquake or the number of large avalanches
in a given sandpile.  Using a unique database of the Amazon.com rankings of
book sales, scientists (Thomas Gilbert, UC-Berkeley, 510-642-5295,
tgilbert{at}haas.berkeley.edu) followed the chart histories of books that
reached the top 50 in sales.  The researchers found that the bestsellers
generally reach their sales peaks in one of two ways, which they classify
as "exogenous shocks" (e.g., a rave review in the New York Times)
and "endogenous shocks" (e.g., word of mouth).  An endogenous
shock appears slowly but results in a long-lived growth and decline of
sales owing to small but very extensive interactions in the network of
buyers.  For example, "The Divine Secrets of the Ya-Ya
Sisterhood," reached the bestseller lists two years after it came out
(and without a major marketing campaign) by making the rounds of
book-discussion clubs and inspiring women to form "Ya-Ya
Sisterhood" groups of their own. In contrast, an exogenous shock (rave
review) appears suddenly and propels a book to bestseller status; however,
these sales typically decline rapidly, much more quickly than those that
made the charts via word-of-mouth.  In either case, single triggering
events (e.g., a mention on "Oprah") appear to have much less
effect on the sales history of a book than the actions of interconnected
groups of people, who may pick up the book after multiple conversations
with acquaintances or by hearing about the book  secondhand or by
remembering a friend's recommendation months or even years after the book
comes out. According to the researchers, marketing agencies could apply
their method of classifying and analyzing bestsellers to measure and to
maximize the impact of their publicity on the network of potential buyers. 
(Sornette, Deschatres, Gilbert, and Ageon, Physical Review Letters, prob 26
November 2004).

ATOM  LITHOGRAPHY, shooting sculpted beams of atoms at a substrate, can
create lines of deposited atoms with widths as narrow as 50 nm. Two groups
in Holland have separately carried out experiments in which atoms, heated
in an oven, released through a baffle, "cooled" by laser rays
striking the beam at right angles, and then focused in optical microlenses
consisting of opposing laser beams.  In the case of physicists at Eindhoven
University of Technology (contact Ton van Leeuwen, 31-40-2474094,
k.a.h.v.leeuwen{at}tue.nl) the best resulting grid of iron atoms had lines
only 50 nm wide and spaced consistently 186 nm apart (see figure at
www.aip.org/png).  The researchers expect to achieve 10-nm lines, but their
chief aim is to move from producing simple grid patterns to making more
elaborate patterns with holographic and other techniques. They are also
pursuing a "single-point writer" option, in which the full atomic
beam will be focused to a single, very intense spot.  What is the advantage
of such slow atom-beam approach to lithography?  Mainly it is the
directness of the method for inscribing microcircuitry (no etching or use
of masks) and exercising great control over line width and spacing.  The
researchers also admit that there are imposing technological hurdles to
using this approach on an industrial scale.  Short-term applications would
most likely be for making MEMS-like structures (teSligte et al., Applied
Physics Letters, 8 November 2004; text at www.aip.org/physnews/select; lab
website at www.phys.tue.nl/aow).  The other Dutch group, at Radboud
University Nijmegen have laid down their own grid of iron atoms with lines
95 nm in width, 186 nm apart, and covering an area of 1.6 x .4 mm^2.
(Myszkiewicz et al., Applied Physics Letters, 25 Oct; contact Theo Rasing,
31-24-3653102) The two groups are now working together on some joint
ventures.

AN AVALANCHE SPIN-VALVE TRANSISTOR switches a current "on" or
"off"depending on whether the magnetizations of two thin films
are parallel (large
current) or anti-parallel (small current).  Such a spintronic transistor is
somewhat like the giant magnetoresistance (GMR) read heads in hard drives,
but is 10 to 100 times more sensitive.  The usual drawback of spin-valve
transistors, a weak output current, is, in the Harvard lab of Venkatesh
Narayanamurti, overcome by using an avalanche process much like the one
used in photodetectors---an incoming electron ionizes several secondary
electrons, each of which ionizes still more electrons, adding up in the end
to a sizable current.  One of the team members, Kasey Russell
(kasey.russell{at}gmail.com, 617-496-5471) says that the extra sensitivity and
strong output could lead to use of the device in magnetic storage
technologies. (Russell et al., Applied Physics Letters, 8 November 2004;
lab website at
http://www.deas.harvard.edu/venky/research.html#overview)

---