Fwd: tech: Physics News Update 442

Gina Miller (echoz@hotmail.com)
Wed, 11 Aug 1999 17:21:27 PDT

>From: Larry Klaes <lklaes@bbn.com>
>Reply-To: transhumantech-l@excelsior.org
>To: "META@onelist.com" <META@onelist.com>, "Also
>transhumantech-l@excelsior.org" <transhumantech@planetx.com>,
>CC: Andrew LePage <lepage@visidyne.com>, "Dr. Stuart A. Kingsley"
><skingsley@coseti.org>, "AllenTough@aol.com" <AllenTough@aol.com>,
> "Fractenna@aol.com" <Fractenna@aol.com>
>Subject: tech: Physics News Update 442
>Date: Tue, 10 Aug 1999 09:17:15 -0400
> >Date: Mon, 9 Aug 1999 14:39:18 -0400 (EDT)
> >From: AIP listserver <physnews@aip.org>
> >To: physnews-mailing@aip.org
> >Subject: update.442
> >
> >The American Institute of Physics Bulletin of Physics News
> >Number 442 August 9, 1999 by Phillip F. Schewe and Ben Stein
> >
> >Laser Interferometer Gravitational-wave Observatory (LIGO),
> >when fully deployed, will consist of two facilities (Hanford, WA
> >and Livingston, LA). At each site laser beams pass up and down
> >two perpendicular 4-km-long vacuum pipes, reflecting repeatedly
> >from mirrors hung from wires. The presence of a passing
> >gravitational wave would announce itself by a flexing of space-
> >time which would very slightly lengthen the path of light in one
> >arm and shorten the path in the other arm, causing a subtle change
> >in the interference pattern made by the converging light beams
> >from the two arms. The full LIGO, by about November 2001,
> >should be able to detect a strain, defined as the fractional change in
> >the position of the mirrors divided by the length of the arm (4 km),
> >of 10^-21. This is the expected disturbance one expects from the
> >gravity waves emitted by the coalescence of two solar-sized stars at
> >a distance from Earth of 30-50 million light years. But before
> >LIGO scientists possess their full instrument, they do have a 40-m
> >prototype at Caltech, built for doing engineering studies but also
> >capable of sensing gravity waves, albeit with the lesser strain
> >sensitivity of a few times 10^-19. Thus the LIGO team, while
> >testing methods for searching (directly via gravity waves) for
> >binary coalescences, have thereby rendered an upper limit for such
> >events of less than one every two hours in our galaxy. This result
> >is useful for the test of the procedures, but is not significant for
> >astronomers, who have previously established more stringent upper
> >bounds with electromagnetic waves (visible and radio). (Contact
> >Barry Barish at Caltech, 626-395-3853 or 818-601-2643; Stan
> >Whitcomb 626-395-2131; or Bruce Allen, University of
> >Wisconsin-Milwaukee, 626-893-2003 or 414-229-6439; Allen et
> >al., Physical Review Letters, 16 August 1999.)
> >
> >July, the US team had its second-best showing since it started
> >competing in 1986, with 3 gold medals and 2 silver medals brought
> >home by the 5 high school students who participated. In informal
> >rankings, the US placed 3rd out of the 62 countries that competed,
> >after Russia and Iran. Taking place this year in Padua, Italy, where
> >Galileo discovered the 4 Jupiter moons named after him, the
> >Olympiad contains two days of grueling theoretical and
> >experimental problems amounting to what is the world's most
> >difficult high-school physics test. For example, the students had
> >to compute the precise trajectory of a space probe that uses
> >Jupiter's gravity as a slingshot--a technique used in real-life
> >spacecraft such as Cassini. Gold medalists included Peter Onyisi
> >(Arlington, VA), who had the tenth highest overall score out of the
> >approximately 300 competitors at the Olympiad, Benjamin
> >Mathews (Dallas, TX), and Andrew Lin (Wallingford, CT). Silver
> >medalists include Jason Oh (Baltimore, MD) and Natalia Toro
> >(Boulder, CO), who earlier this year also became the youngest
> >person (at 14 years of age) ever to win the top prize of the Intel
> >(formerly Westinghouse) Science Talent Search. (More
> >information at http://www.aip.org/releases/1999/release05.html)
> >
> >IN-PLANE-GATE (IPG) TRANSISTORS can be excavated using
> >nanomachining techniques. IPG transistors, in which the source,
> >drain, and gate all lie in a plane rather than in a sandwich, might be
> >especially useful for high-frequency applications. Scientists at the
> >University of Hannover (Hans Werner Schumacher, 011-49-511-
> >762-2523, schumach@nano.uni-hannover.de) have carved out an
> >IPG structure in a semiconductor surface using the probe from an
> >atomic force microscope (see figure at
> >www.aip.org/physnews/graphics). The probe makes an incision
> >into the material extending down about halfway toward a buried
> >interface where, lodged between GaAs and AlGaAs layers, a
> >reservoir of electrons is confined to a plane. The incisions from
> >above do not penetrate into this two-dimensional electron gas
> >(2DEG) but they do shape (and can even pinch off) the conduction
> >of the electrons. The Hannover researchers have also used their
> >inscribing approach to make single-electron transistors (SETs),
> >devices that register the coming and going of single electrons.
> >(Schumacher et al., Applied Physics Letters, 23 August 1999.)
> >
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