More brief items

Writing writing writing.  In the meantime:

• This is a very solid video about physics careers - especially at around the 10 minute mark.  
• J. Robert Schrieffer has passed away.  Truly a scientific pioneer.
• I came upon this article yesterday in Nat Rev Physics, and it seems like an exceptionally clear review of strong coupling physics between light and matter, beyond the usual Purcell factor cavity QED effects.  
• SpaceX really proceeds in testing at a remarkable pace.
• The scanning Josephson microscope is a very impressive piece of kit!

Ferromagnetic droplets

Ferromagnets are solids, in pretty nearly every instance I can recall (though I suppose it's not impossible to imagine an itinerant Stoner magnet that's a liquid below its Curie temperature, and here is one apparent example). There's a neat paper in Science this week, reporting liquid droplets that act like ferromagnets and can be reshaped. 

The physics at work here is actually a bit more interesting than just a single homogeneous material that happens to be liquid below its magnetic ordering temperature.  The liquid in this case is a suspension of magnetite nanoparticles.  Each nanoparticle is magnetic, as the microscopic ordering temperature for Fe₃O₄ is about 858 K.  However, the individual particles are so small (22 nm in diameter) that they are superparamagnetic at room temperature, meaning that thermal fluctuations are energetic enough to reorient how the little north/south poles of the single-domain particles are pointing.  Now, if the interface at the surface of the suspension droplet confines the nanoparticles sufficiently, they jam together with such small separations that their magnetic interactions are enough to lock their magnetizations, killing the superparamagnetism and leading to a bulk magnetic response from the aggregate.  Pretty cool!  (Extra-long-time readers of this blog will note that this hearkens waaaay back to this post.)

Brief items

I just returned from some travel, and I have quite a bit of writing I need to do, but here are a few items of interest:

• No matter how many times I see them (here I discussed a result from ten years ago), I'm still impressed by images taken of molecular orbitals, as in the work by IBM Zurich that has now appeared in Science.  Here is the relevant video.
• Speaking of good videos, here is a talk by Tadashi Tokieda, presently at Stanford, titled "Science from a Sheet of Paper".  Really nicely done, and it shows a great example of how surprising general behavior can emerge from simple building blocks.
• It's a couple of years old now, but this is a nice overview of the experimental state of the problem of high temperature superconductivity, particularly in the cuprates.
• Along those lines, here is a really nice article from SciAm by Greg Boebinger about achieving the promise of those materials.  
• Arguments back and forth continue about the metallization of hydrogen.
• And Sean Carroll shows how remunerative it can be to be a science adviser for a Hollywood production.

Science and a nation of immigrants

It was very distressing to read this news article in Nature about the treatment of scientists of Chinese background (from the point of view of those at MIT).  Science is an international enterprise, and an enormous amount of the success that the US has had in science and technology is due to the contributions of immigrants and first-generation children of immigrants.  It would be wrong, tragic, and incredibly self-defeating to take on a posture that sends a message to the international community that they are not welcome to come to the US to study, or that tells immigrants in the US that they are suspect and not trusted. 

In any large population, there is always the occasional bad actor - the question is, how does a bureaucracy react to that?  One example:  Clearly some small percentage of medical researchers in the US have behaved unethically, taking money from medical and pharmaceutical companies in ways that set up conflicts of interest which they have hidden.  That's wrong, we should try to prevent it from happening, and those who misbehave should be punished.  The bureaucratic response to this has been that basically nearly every faculty member at a research university in the US now has to fill out annual disclosure and conflict of interest forms.   The number of people affected by the response dwarfs the number of miscreants by probably a factor of 1000, though in this case the response is only at the level of an inconvenience, so the consequences have not been dire.

Reacting to the bad behavior of a tiny number of people by taking wholesale measures that make an entire population feel threatened, unwelcome, and presumed guilty, is wrong and lazy.  The risk of long term negative impacts far beyond the scale of any original bad behavior is very real.