Physics News

[Astronuc]

Hydrophobic Water - Huh?

Hydrophobic water sounds like an impossibility. Nevertheless, scientists at Pacific Northwest National Lab have produced and studied monolayers of water molecules (resting on a platinum substrate) which prove to be poor templates for subsequent ice growth. Picture the following sequence: at temperatures below 60 K, isolated water molecules will stay put when you place them on a metallic substrate. At higher temperatures, the molecules become mobile enough to begin forming into tiny islands of two-dimensional ice. New molecules landing on the crystallites will fall off the edges into the spaces between the islands. In this way the metal surface becomes iced over completely with a monolayer. But because the water molecules' four bonds are now spoken for (1 to the Pt substrate and 3 to their neighboring water molecules), the addition of more water does not result in layer-by-layer 3D ice growth. Only when there is an amount of overlying water equivalent to about 40 or 50 layers does 3D crystalline ice completely cover the hydrophobic monolayer.

http://www.aip.org/pnu/2005/split/747-2.html

[Astronuc]

Somewhat related to the topic in the first post - Superhydrophobic surface -

A superhydrophobic surface, devised by scientists at UCLA, greatly reduces the friction felt by a fluid as it moves across the surface. It does this by inducing a blanket of air to lodge between nano-posts built onto the surface; the air keeps the fluid from coming into contact with the solid surface.

- http://www.aip.org/pnu/2006/split/764-1.html

[Astronuc]

The best study of the rare "atom" consisting of two electrons and one positron is being reported.

Positronium (abbreviated Ps) is a very "clean" two-body object: it consists of an electron and a positron which after about 150 nanoseconds annihilate each other. For studying the theory of quantum electrodynamics (QED), Ps is in some ways better even than the hydrogen atom: with pointlike constituents and with no complicating nuclear forces (the size of the proton and its own internal structure interject uncertainties into QED estimates of hydrogen behavior), Ps is a simpler, albeit fragile, quantum system.

- http://www.aip.org/pnu/2006/split/763-1.html

 

[Astronuc]

Fission Fragments Weighed

The fissioning of uranium results in a variety of unstable neutron-rich nuclei. A team of scientists from the University of Jyväskylä in Finland has for the first time made high-precision mass measurements of a number of isotopes produced in proton-induced fission reactions of uranium, including strontium, zirconium, and molybdenum.

These so-called refractory elements are hard to study as ionized beams because of their high boiling points. Instead, the researchers reach a high level of precision by coaxing the nuclei into a Penning trap, which employs a combination of a strong magnetic field and a static quadrupole field to trap ions. In this kind of device, the particle's mass can be deduced from the observed cyclotron motion -- that is, from the particle's looping orbit in a strong magnetic field.

The reason for wanting better isotope masses is that they provide information about nuclear binding energies. The mass of the simplest compound nucleus, the deuteron, for instance, is several million electron volts less than the sum of the masses of its constituent proton and neutron. The difference is the net binding energy.

In the case of the new studies, the isotope masses are determined with a precision of thousands of electron volts. By measuring the mass of several zirconium isotopes of increasing neutron numbers, one can see subtle effects in the complex structures of these nuclei.

Astrophysicists, who consider how larger nuclei are built inside stars or novas also will be interested in knowing how nuclear mass increases with neutron number.

- http://www.aip.org/pnu/2006/split/762-1.html

 

[Astronuc]

Best Direct Test of E=mc²

Albert Einstein's formulation of how matter and energy are equivalent is an important enunciation of the principle of conserved energy. As far as we know, it is at work at the moment an atom bomb explodes, when the fissioning of uranium is exploited for making commercial electricity, or when an electron and positron annihilate inside a PET scanner. A new experiment -- conducted by scientists from MIT, Université Laval in Quebec City, Canada, Florida State University, Oxford University, the National Institute of Standards and Technology, and the Institut Laue-Langevin in Grenoble, France -- keeps careful account of both matter mass and electromagnetic energy for a process in which ions of sulphur and silicon absorb neutrons, transforming them into new isotopes as they emit gamma rays. In this transaction Einstein's equation is shown experimentally to be true at a level of 0.00004 percent, a factor of 55 better than the previous best test.

http://www.aip.org/pnu/2006/split/761-1.html

 

[Astronuc]

8th Asia-Pacific Conference on Plasma Science and Technology
and 19th Symposium on Plasma Science for Materials
2-5th July 2006

http://wwwrsphysse.anu.edu.au/~mdl112/apcpst/

Well this just happened last month - nice place.

Links to the previous APCPST are on this site.

[Astronuc]

http://physicsweb.org/articles/news/10/8/13/1

The most creative physicist in 2006 - Philip Anderson.  So how did someone determine that?

Well, a study has been carried out by José Soler, a statistical physicist at the University of Madrid, who has developed a "creativity index"!

Soler's method involves calculating the number of references, n, that a particular paper makes to previous papers as well as the number of citations, m, that it receives from papers written at a later date. According to his definition of creativity, a paper that has lots of references but only a few citations will have a low level of "creativity", while a paper with just a few references and lots of citations, in contrast, will have a very high creativity. The creativity index (C_a) of a particular scientist can then be calculated by summing the total creativity for every paper that author has written, normalized for the number of co-authors in each case.

Well, sorry, but I am a bit skeptical.  Hopefully all papers are substantive and not repetitive.

This was brought to my attention by ZapperZ who has a small yahoo group devoted to physics - http://groups.yahoo.com/group/undernetphysics/