DESI Begins

A new eye on the sky is about to add to our knowledge of dark energy.



It's interesting that in the list of funding agencies, NASA is absent. This goes to show you that many of these research activities that seem to be "astronomy-related" are not the sole domain of NASA. In fact, the area of particle-astrophysics is more closely related to particle physics than astronomy.

The video didn't clarify explicitly that in looking at the "spectrum" of light from each of these celestial bodies, one gets the radial velocity of these bodies with respect to us (i.e. via the amount of redshift), not its distance from us. That last piece of information can only be "deduced" using the radial velocity and the Hubble equation, i.e. the Hubble constant, a number that is still being refined.

Still, this new telescope is going to be quite exciting in revealing more of the mysteries of dark energy.

Zz.

Scanning Probe Microscopy

The Physical Review is marking the 35th Anniversary of Scanning Tunneling Microscopy (STM) and 30 years of Atomic Force Microscopy (AFM) with free access to notable papers from the Physical Review journals in these two experimental techniques.

So check them out!

Zz.

What Is the Smallest Number Of Water Molecules Needed To Make Ice?

Answer: around 275.

This is a neat work that tries to answer that very question, and actually got the answer.

Zeuch and colleagues obtained infrared spectra for cluster sizes ranging from 85 to 475 molecules. As expected, there was a shift in the spectrum maxima towards lower wavenumbers as cluster size increased. The transition from 3400 to 3200 cm^–1 began at around 275 molecules, with the first crystalline ice occurring in the centre of the cluster, forming a ring of six hydrogen-bonded water molecules in a tetrahedral configuration.

As the cluster size increased further, the crystalline core gradually grew. By 475 molecules, the infrared spectrum was dominated by the ice structure: the formation of the ice crystal was all but complete. This behaviour matched theoretical predictions made by a different group of researchers in 2004.

You may read the rest of the article on the important implication of this work, especially in understanding ice nucleation.

Zz.

How Cooper Pairs Vanish Approaching the Mott Insulator in Bi2Sr2CaCu2O8+d

This paper appeared in Nature this week, but the authors have uploaded it to ArXiv and it appeared today. Using STM/STS technique, they were able to obtained the spectroscopy in both real and momentum space as a function of doping along the nodal direction of the Fermi surface of a high-Tc superconductor. The results show that as the compound approaches the Mott insulating phase, the mobile Bogoliubov quasiparticles from the Cooper pairs are slowly being replaced by the localized electrons.

A first-rate experiment!

Edit: A BNL press release on this work can be found here.

Zz.

The Perfect Summer Combination: Beer and Physics

I posted a while back an article that I found where a university was actually advertising a "postdoctoral fellowship" in .... get this .... beer studies! At that time, I was having quite a bit of fun with it because, frankly, I didn't know if it was a serious article, or an April Fool's joke.

Well, this one appears to be legitimate enough.

And that brings us back to beer. There’s no doubt that bubbles are a large part of the drink’s appeal, and Page’s technique can provide precise information about their evolution.

“A lot of effort has gone into figuring out how to get just the right concentration and size of bubbles, and how to produce the perfect head on a glass of beer,” he says. “There are people who work in that industry who know much, much more about that than I do. Could diffusing acoustic wave spectroscopy be useful to them? Maybe. But for me, beer is just a good example of the kind of thing you can do using this technique.”

I guess the beer bubbles are as good as any. I wonder if you can still drink it after doing all that studies on it?

Zz.