Number 400, October 30, 1998 by Phillip F. Schewe and Ben Stein
PROTONS PERSIST for at least 1.6 x 1033 years. With few exceptions (electrons?) everything in the universe falls apart. Even protons, the lightest baryon (particles comprised of three quarks) are, according to grand unified theories of particle physics, supposed to decay, principally into positrons and neutral pi mesons. The versatile Super-Kamiokande underground detector in Japan (where neutrino oscillations were discovered earlier this year) can also look for just this sort of proton decay. Not finding any such evidence, scientists there have now established a new, more stringent, lower limit on the lifetime of the proton. (Shiozawa et al., Physical Review Letters, 19 October 1998.)
THE CONDUCTANCE OF A SINGLE MOLECULE has been measured directly by having the molecule bridge the break in a thin wire. Scientists at Yale use the wire ends as electrodes for sending current through a small polymer molecule poised between them. Previously the electrical properties of single molecules had been studied, but this was through the use of a probe microscope which samples the molecule across a vacuum gap. Mark Reed (203-432- 4300, firstname.lastname@example.org) reports that the current-versus-voltage characteristics of the molecule (important for any potential device application) resemble those of a quantum dot in that certain electron energies are preferred over others, in this case because of the internal energy levels of the molecule itself. See figure at Physics News Graphics. (Paper to be presented at the American Vacuum Society (AVS) meeting in Baltimore, 2-6 November 1998.
STACKED ORGANIC LIGHT EMITTING DEVICES (SOLEDs) produce full color but take up less real estate on a chip than their planar counterparts which require 3 single-color pixels. This higher resolution, as well as tunability and good saturation (vivid primary colors rather than pastels), can now be had with the same voltages and efficiencies that apply to previous organic displays. Paul Burrows of Princeton (email@example.com) believes computer- sized flat panel displays using SOLEDs will be available within a few years. Smaller displays such as for cellphones may be realized even earlier. See figure at Physics News Graphics. (Paper at the AVS meeting.)
NANOCOMPUTERS IN A BOTTLE. UCLA scientist James Heath and his Hewlett Packard collaborators Stan Williams and Phil Kuekes hope to grow computers in chemical solution by building up arrays of atoms or molecules (at first in two-dimensional planes but later in three- dimensional volumes) linked together with tiny wires, perhaps eventually carbon nanotubes. Such a computer could be tiny (smaller than a sand grain), energy efficient (10,000 times more so than current silicon computers), and capable of new tricks, such as being able to sense and respond to its environment through chemically activated switches. Implementing a chemically assembled computer will depend on a high degree of defect tolerance in the wiring, unlike today's microprocessors which require wiring perfection. Presently the UCLA-HP group will be doing rudimentary calculations with a computer including some components at the nano and others at the micro level. An all-nano computer performing simple computations, Heath believes, is a couple of years away. Serious applications would follow years later. Heath (310- 825-2836, firstname.lastname@example.org) will report on nanocomputers at the AVS meeting.
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