PHYSICS NEWS UPDATE                        
The American Institute of Physics Bulletin of Physics News
Number 362 March 12, 1998   by Phillip F. Schewe and Ben Stein

TUNABLE CHEMISTRY IN BOSE-EINSTEIN CONDENSATES
(BECs) has been demonstrated by an MIT group (Wolfgang
Ketterle, 617-253-6815), allowing researchers to choose whether
atoms in this new state of matter attract each other, repel each
other, or hardly interact at all.  A BEC is a gas of atoms so cold
and so dense that they overlap and act as a single, unified entity
(Update 233).  To control the chemistry of a sodium BEC, the
researchers turned on a magnetic field which slightly altered the
shape of the electron clouds surrounding each atom.  This in turn
could modify the force that the atoms applied on each other
(Nature, 12 March 1998). Controlling whether BEC atoms attract
or repel will help researchers to test theoretical ideas about BECs
and understand chemical reactions and collisions in ultracold gases.
In addition, the researchers developed an all-optical trap for BECs
rather than the magnetic fields previously used (Physical Review
Letters, 9 March 1998).  This in itself is an advantage because (1)
researchers now have the chance to create BECs of atoms that don’t
respond to magnetic fields, and (2) a laser beam can control atoms
to a high degree, for example by guiding them down a hollow
optical fiber (Update 245). Once produced in just 3 laboratories in
the US, BECs have now been created in Germany (2 labs), and 4
additional labs in the US.   (See Georgia Southern University’s BEC
Page at amo.phy.gasou.edu/bec.html/)

COMPLEMENTARITY PRINCIPLE DEMONSTRATED FOR
ELECTRONS.  When light waves pass through a pair of slits in a
screen, an interference pattern will form at a detector further along.
If one of the slits is closed, or if one tries to take a peek at which
way the light went then the interference pattern starts to go away.
Quantum reality is shy; if you look at it, it disappears. Now a group
at the Weizmann Institute in Israel have done a sort of double slit
experiment with electrons and observed (for the first time with
fermions, spin-one-half particles)  how the resultant interference
pattern dissipates the more you watch the electrons as they go
through the slits, thus demonstrating Niels Bohr’s complementarity
principle which states that objects can have wave and particle
properties, but not both at the same time.  In the Weizmann
experiment, led by Mordehai Heiblum, the electrons (or electron
waves, depending on whether you look or not) slalom through a
two-dimensional obstacle course, where they must negotiate a pair
of channels, one of which (via a separate circuit called a "quantum
point contact," or QPC) gives a hint as to whether an electron
passed that way.  Essentially, as a wave the electron passes through
both channels; but if it senses that it is being watched, the electron
(as a particle) goes through only the one path, diminishing the
interference thereby.  (E. Buks et al., Nature, 26 Feb. 1998.)

WATER ON MOON, ASTEROID NEAR EARTH.  The Lunar
Prospector spacecraft has detected the presence of water ice, at a
level of about 1%, in the soil at the Moon’s two poles.  Perhaps
brought to the Moon by passing comets, the water ice lies in valleys
away from the Sun’s rays. Its density was inferred from the number
of neutrons flung up when cosmic rays strike the lunar surface
(NASA press conference, 5 March).  Meanwhile, several observers
have spotted an asteroid, named 1997 XF11, whose orbit might
bring it to within 30,000 miles of our planet in the year 2028. Its
diameter may be as big as one mile, making it one of the largest
asteroids expected to have passed within a distance equal to the
moon’s orbit. (IAU press release, 11 March.)

How much will the precision of the trajectory prediction
improve with time? Now we have a 1% of probability of it
hitting Earth. Could further observation dismiss this
possibility entirely, or, instead, guarantee a virtual
certainity of a hit?

[looks like less than 24 hours was needed to revise the prediction - mod.]

—–== Posted via Deja News, The Leader in Internet Discussion ==—–
http://www.dejanews.com/   Now offering spam-free web-based newsreading

I know the pitch of the solar oscillations changes slightly over the solar
cycle, but I forget how.  When the solar activity is greatest, is the
pitch lowest, or highest (ie frequency of the various oscillations
monitored)?

Ross Tessien

Help!  I need some info on the orbit of Alpha Centauri B about Alpha
Centauri A for a story. =20

Specifically, I’m looking for the plane of the orbit in celestial
coordinates.  I particularly need to know the position in the sky of the
"North Pole" of the system.

I have some orbital elements [1], but I’m finding them hard to
interpret.  The inclination is 79.24 degrees and the longitude of the
ascending node is 204.87 degrees.

I take it the inclination is with respect to the plane of the sky, a
plane defined by Alpha Centauri A’s position:

RA  =3D 14h 39m 36.2s
Dec =3D -60=B0 50′ 07"

But the rest just throws me.  Could some kind soul guide me through the
procedure and help me get a reasonable figure?

Thanks in advance

–=20
                   Del Cotter    d…@branta.demon.co.uk
C E Worley and W D Heintz,=20
"Fourth catalog of orbits of visual binaries",=20
Publications of the US Naval Observatory, vol. XXIV, part VII (1983)

Hi,
I’m interested in false colouring algorithms, if there are such a thing.  I have data
in a 2d raster that ranges from 0.0 to 1.0, plus I know how to generate computer images
(jpg) with 24-bit colour (RGB-alpha, with R=0..255, G=0.255, etc).

Unfortunately, when I form the jpg, I scale my data from 0 to 255, and set the R,G,B
values to that, resulting in a boring greyscale image.  

I’d like to jazz it up a bit, but when I tried making bins for the colours (let’s say n
bins), the resulting image uses only n colours.  

I’d like to have some kind of formula that takes a number from 0.0 to 1.0 and smoothly
transforms it into a pleasing colour pattern in terms of the RGB values.  For example,
does anyone know how to transform the wavelength spectrum (red -> violet) into RGB?  

Thanks
Bill

PHYSICS NEWS UPDATE                        
The American Institute of Physics Bulletin of Physics News
Number 363 March 23, 1998   by Phillip F. Schewe and Ben Stein

NANO-ELECTROMECHANICAL SYSTEMS (NEMS) will be
faster, smaller, and more energy efficient than the present day
micro-electromechanical systems (MEMS), an example of which is
the accelerometer that triggers airbags in cars.  At last week’s
American Physical Society meeting in Los Angeles, Michael
Roukes of Caltech (626-395-2916) described the leading edge of
NEMS research.  Using lithography and etching techniques, he has
fabricated a 10x10x100-nm suspended beam of silicon which
oscillates at an estimated frequency of 7 GHz (although no detector
can yet "hear" the vibrations). Such a resonator will eventually be
used in microwave signal processing (for modulating or filtering
signals).  The speed and stability of nanoscopic silicon arms might
even facilitate the advent of some new kind of Babbage-type
computer in which mechanical levers once again serve as processing
or memory elements.(In other words, a machine with "moving
parts" may not be so bad.)  Silicon structures in this size regime will
also be used as cantilever probes in magnetic resonance force
microscopy (the goal being atomic-resolution NMR imaging; see
Update 313) and as calorimeters for the study of quantized heat
pulses (Update 320).  Roukes’ colleague, Andrew Cleland of UC
Santa Barbara, described a paddle-shaped silicon structure (whose
smallest lateral feature was 200 nm) for detecting very small
amounts of electrical charge, with a potential application in high-
sensitivity photodetection (see also Nature, 12 March 1998).  At the
same APS session, Rex Beck of Harvard reported a NEMS force
sensor which integrates a field effect transistor into a scanned probe
microscope. The present sensitivities are about 10 angstroms for
displacement and 5 pico-Newtons for force (per square root of the
frequency), but Beck expects improvements as the size of the device
shrinks. The smallest transistor-probe structure Beck reported had
dimensions of 3×2 microns x 140 nm.

NEW METHODS OF STUDYING TURBULENCE, reported at
the APS meeting, have enabled physicists to track in detail for the
first time the accelerations of a particle moving through flows with
atmospheric-level turbulence (Eberhard Bodenschatz, Cornell, 607-
255-0794), and to cause magnetically trapped electrons to act like
fluid particles on a flat surface (Fred Driscoll, UC-San Diego, 619-
534-2498).  Bodenschatz described how a light-sensitive diode
measured the movements of a particle jiggling through a fluid at up
to 200 times the acceleration of gravity.  For upcoming
experiments, the group has installed a "silicon-strip detector" used
in high-energy physics to make up to 100,000 measurements per
second of multiple particles in the fluid, the better to study how
particles that are initially close together move apart in a very
turbulent flow such as a volcanic eruption.  Meanwhile, Driscoll
investigated turbulence by using a strong magnetic field to trap a
cigar-shaped column of a billion electrons.  Viewed from the end
of the column, the electrons moved like fluid particles on a 2D
surface.  Intriguingly, turbulent flows of these electrons
spontaneously settled into "vortex crystals," geometric patterns of
whirlpool-like eddies that stayed frozen in place.

DNA WIRES, only 12 microns long and 100 nm wide, have been
strung between gold electrodes.  DNA is attractive as a potential
component in nano-design applications because of its molecular-
recognition, self-assembly, and mechanical properties.  DNA does
not, however, conduct electricity. In an experiment at the Technion-
Israel Institute of Technology, researchers first spanned the gap
between two electrodes with a tiny DNA causeway and then
exposed the structure to silver ions, which made a conducting path.
(Nature, 19 Feb. 1998.)

The discovery of a unique, twice-an-orbit bursting, pulsating star
yields insight on strange energetic objects in the galaxy. The full
story is at

http://science.msfc.nasa.gov/newhome/headlines/ast25mar98_1.htm

D2

==============================================================
Dave Dooling / D2 Associates
555 Sparkman Drive, Suite 820C / Huntsville, AL 35816
205-890-0972
dees…@advicom.net        http://advicom.net/~deesqrd/d2.html
==============================================================

When discussing the early Universe or the latest data
concerning it or for that matter any aspect of it
before the Solar system had formed, the units of time
are all derived from our YEAR.

What meaning can be attached to the conjecture that
the surface of last scattering occurred at a time
expressed in our units? Or that the galaxy 0140+326RD1,
with a redshift of 5.34, is seen as it was 820 million
years after the Big Bang?

Is there not a more appropriate way of expressing the
time parameter in cosmology?

****
D A A Fagandini
danny
d…@cerium.demon.co.uk

———————————————————-
FORSALE — TINSLEY LABS CLASSICAL CASSEGRAIN TELESCOPE !!!
———————————————————-

I have for sale a Tinsley Labs 8-inch Classical Cassegrain
telescope, complete with the original German equitorial
mount and clock drive.  Tinsley produced these fine scopes
in the mid 1960s and are known for their fine optical and
mechanical properties.  They were (are) research quality
instruments which are quite rare and retain their value.

In mint shape, they go for around $3000.  The one that
I have is in very good condition, but needs a few minor
items to bring it to "mint", as follows:

  – mirrors are excellent, no scratches or chips, and
   bright.  Although very good and workable, a
   recoating would make them mint.

  – clock drive needs an external 12V battery pack and
   rheostat to make it operational (this is as it was
   intended).  A nicad pack or motorcycle battery would
   be appropriate.

  – A low tripod or pedestal base (about 20" high) and
   "rocker box" is needed for the equitorial mount to
   sit on.

  – the optical tube has some scratches in the paint and
   a small dent, which absolutely does NOT interfere with
   the optical path.  Paint scheme is the original Tinsley
   gray.

Thats about it.  I just don’t have the time to use this
scope and it’s too valuable to just let it lay idle.

I’m asking $2150. for scope and mount (and absolutely will
NOT sell them separately).

The equipment is located in Monmouth County, NJ.  For
further information, please contact me.

Thanks,

Joe Levantino
Lucent Technologies – Bell Laboratories
732-949-0664 (days)
jlevant…@lucent.com

PS — I will consider a trade for equally valued Amateur
Radio Equipment, in particular a high quality, heavy
duty, HF linear amplifier (Ten-tec, etc).

Number 358 February 11, 1998   by Phillip F. Schewe and Ben
Stein

SUPERCONDUCTIVITY-DEPENDENT FRICTION.  A common
parlor trick consists of yanking a tablecloth out from beneath an
assortment of tableware.  If you yank fast enough, the wineglasses
remain where they are.  At Northeastern University, this feat is
acted out on a nanometer scale, with a thin (only one or two
molecules thick) sliver of frozen nitrogen acting as the tableware,
and a lead substrate as the tablecloth.  Jacqueline Krim (617-373-
2902) and her colleagues perform this kind of experiment in order
to study friction at the atomic level.  Despite the billion-dollar
industrial importance of friction, it is still relatively little
understood.  In Krim’s work a delicate quartz microbalance (with
the lead substrate) is moved back and forth about 10 nm at rates of
a million times per second, with the overlying nitrogen going along
for the ride. With this approach the Northeastern researchers have
measured what are probably the smallest frictional shear stresses yet
seen (excepting only superfluids, which experience no friction).
But a phenomenon even more interesting has emerged: when the
lead substrate is chilled below its superconducting transition, the
friction between the lead and the frozen nitrogen dramatically
drops.  This seems to represent a new and unexpected behavior of
superconductors, and this has fascinated and puzzled theorists.  (A.
Dayo et al., upcoming article in Physical Review Letters.)

INK-JET PRINTING OF LIGHT-EMITTING POLYMERS onto
a thin film has been demonstrated by a Princeton group (James
Sturm, 609-258-5610), bringing about a new way to fabricate a
light-emitting diode (LED) made of polymers.  An LED is typically
built by surrounding a semiconducting material with two electrodes.
When an electron from one electrode and a hole from the other
meet in the semiconductor, they can annihilate each other and
release the energy as light.  LEDs in which the semiconductor
materials are polymers instead of inorganic materials such as
gallium phosphide would be cheaper and easier to manufacture. To
make polymer LEDs, the Princeton researchers replaced the ink
cartridges of  a conventional ink-jet printer with a polymer solution
containing the semiconducting polymer polyvinylcarbazol (PVK)
and a light-emitting dye dissolved in a chloroform solvent.  The
researchers printed this solution onto a thin polyester film coated
with indium tin oxide (ITO), which served as one of the electrodes.
 Over the polymer layer they deposited a metal film, which served
as the other electrode.  With this technique, they produced LEDs
emitting green light.  In separate experiments, they used the ink-jet
printer to make dot patterns of PVK mixed with either red, green,
or blue dyes on the ITO-coated polyester film, although they have
not yet used these patterned films to make LEDs. (T.R. Hebner et
al., Applied Physics Letters, 2 February 1998.)

LIQUID CARBON is difficult to produce because a sample of solid
carbon, melted quickly by a laser, will want to repose back into the
form of graphite. Physicists at the Russian Academy of Sciences
(Moscow) have sought to melt carbon with picosecond laser pulses,
and report the observation of a liquid phase, the evidence being the
fleeting presence of periodic stripes in microscopic pictures of the
tiny (200 micron) spots on a graphite surface under bombardment.
The researchers argue that the stripes could not be present in a fully
solid phase. The liquid is scarcely glimpsed, however, before it
quickly solidifies, partly into an amorphous carbon structure.
(M.B. Agranat et al., Journal of Experimental and Theoretical
Physics (JETP) Letters, a Russian journal translated into English by
AIP.)