Tuesday, June 26, 2012

At least they're being explicit about it.

The Texas Republican Party platform for 2012 is out (pdf).  I've complained about previous incarnations before.  This time they include this gem: 
We oppose the teaching of Higher Order Thinking Skills (HOTS) (values clarification), critical thinking skills and similar programs that are simply a relabeling of Outcome-Based Education (OBE) (mastery learning) which focus on behavior modification and have the purpose of challenging the student’s fixed beliefs and undermining parental authority.  [Emphasis mine - DN]
Wow.   They explicitly oppose teaching students to think critically, because that might be a threat to their fixed beliefs.  Wow.  And somehow these people keep winning statewide office.  Boggles the mind.  As a bonus, they also say:
We support objective teaching and equal treatment of all sides of scientific theories. We believe theories such as life origins and environmental change should be taught as challengeable scientific theories subject to change as new data is produced. Teachers and students should be able to discuss the strengths and weaknesses of these theories openly and without fear of retribution or discrimination of any kind.
So, they like the idea of challenging scientific theories with new data, but they don't like critical thinking.  Right.

Precision engineering.

Here's an experimentalist complaint for which I do not think there is an analogous theorist problem.  In my lab we have a piece of equipment of European manufacture that is very good and beautifully engineered.  The one problem is, it's so precisely made that it's impossible to service.  For example, after years of repeated thermal cycling, an electrical connector has failed and needs to be replaced.  The problem is, the way the system was put together, there is essentially no slack in the relevant cabling.  They strung the cable through during the original assembly, cut it precisely to length, and then attached connectors that make it topologically impossible to take apart without their removal.  One can't replace the connector without either cutting cabling and inserting more connections, or other approaches with similar levels of inconvenience.  This is the lab equivalent of having to remove half of the guts of a car in order to get to the oil pan.  Ahh well.  Let this be a lesson to mechanical designers:  It's never a bad idea to design a complex system with the possibility that it may need to be taken apart nondestructively someday.

Sunday, June 24, 2012

Grants and ethics

I recently came across this story.  I'd heard about it at a NSF panel but hadn't gotten all the details.  This person (who plead guilty and has not yet been sentenced that I can see) did at least two bad things.  First, and obviously illegal, he had a NIH award in which there was supposed to be a significant subcontract to another institution, and instead he spent that money on something else (possibly even on personal stuff).  It's actually amazing to me that he didn't get caught earlier on that by his institution's research office.  As chronically understaffed and overworked as ours is, they are zealous about making sure that subcontracts and reporting are properly handled, so I don't see how something like not passing along $500K could happen.

Second, and potentially trickier, after getting an award from the NSF, he applied for a grant from the DOE's ARPA-E for basically the same work, without telling either the DOE or NSF about the overlap.  That's also illegal, though I suspect it's more common simply because there are shades of grey possible here.  Research projects can have overlap - particularly if a PI has a particular technique or tool that they've developed and want to push in many directions - the question is, how much commonality is too much?  This particular case was egregious.  Still, after reviewing some grants recently for a few places, I want to encourage my junior colleagues to take these issues seriously.  When you review a proposal and realize that you've actually already reviewed something with lots of overlap before from the same PI, and it was funded, yet the PI claims there is no overlap in the programs, it's not a good situation for anyone.

Friday, June 22, 2012

Classical elasticity is surprisingly robust.

This paper was just published in Nano Letters.  The authors use suspended, single-layer graphene as a template for the growth (via atomic layer deposition) of aluminum oxide, Al2O.  Then they use an oxygen plasma to etch away the graphene, leaving a suspended alumina membrane 1 nm thick.  This is very cute, but what I find truly remarkable is how well the elastic properties of that membrane are modeled by simple, continuum elasticity.  The authors can apply a pressure gradient across the membrane and measure the deformed shape of the membrane as the pressure difference causes it to bulge.  That shape agrees extremely well with a formula from continuum mechanics that just assumes some average density and elastic modulus for the material.  That's the point of continuum mechanics and elasticity:  You don't have to worry about the fact that the material is really made out of atoms; instead you assume it's smooth and continuous on arbitrary scales.  Still, it's impressive to me that this works so well even when the total thickness of the material is only a few atoms!

Thursday, June 21, 2012

The Higgs and the media

There are a variety of blog discussions going on right now concerning rumors of the Higgs boson.  Peter Woit's post about Higgs rumors sparked a back-and-forth about whether blog discussions of rumors are actually harmful to science, to the scientific process, and to the public perception of the science.  I agree completely with Chad Orzel's take on this:  Given that CERN's press office and many high energy physicists have continuously hyped this experiment for years, no one should be surprised that there is interest in its status.  Complaining about this is absurd. 

Assuming that the CERN collaborations do announce the discovery of a particle with Higgs-like properties at around 125 GeV, I would be willing to wager the following things:
1) Some fraction of high energy physics theorists will become completely insufferable.
2) Some fraction of high energy physics theorists will be quoted in poorly written popular media articles that imply the result favors (a) string theory; (b) the multiverse; (c) supersymmetry.  These articles will also imply that high energy physics is pretty much all of physics.
3) The phrase "so-called 'God Particle'" will shoot up in google's rankings.
4) There will be articles talking about the need for the next big accelerator.

Wednesday, June 13, 2012

Handy numbers to know

My thesis advisor has a mastery of an impressive library of handy physics tidbits, the kinds of things that have proven very useful to him and his group over the years.  These are facts that it's better to know from memory so you can hash problems out at a whiteboard without having to run to reference books.  Here are a few of his:
  • One liquid liter of helium becomes about 700 gas liters at STP.
  • One liquid liter of nitrogen becomes about 500 gas liters at STP.
  • The latent heat of liquid helium is such that one Watt of heatung will boil off one liquid liter per hour.
  • For thermal conduction through metals, when the temperature difference between \( T_{\mathrm{hot}} \) and \( T_{\mathrm{cold}} \) is not small, the rate of heat flow is given by \( (T_{\mathrm{hot}}^{2} - T_{\mathrm{cold}}^{2})/(2 R_{\mathrm{th}}T) \), where \( R_{th} \) is the thermal resistance.
  • The Wiedemann-Franz rule for heat conduction through metals means that an electrical resistance of 150 n\(\Omega\) corresponds to \(R_{\mathrm{th}} T = 6 \) K\(^{2}\)/W.
  • 20 GHz is equivalent to 1 K in terms of energy.
  • 1 meV is about 12 K in terms of energy.
Here are a few that I've adopted over the years in working with nanoscale physics:
  • The conductance quantum, \( G_{0} \equiv 2 e^{2}/h\), is about 12.9 k\(\Omega\).
  • A typical elastic mean free path for electrons in a polycrystalline good metal is 10-20 nm.
  • Tunneling of electrons from a metal through vacuum drops off by about a factor of 7.2 for every additional Angstrom of distance.
  • The density of states for gold at the Fermi energy is about \(\nu = 10^{47}\)/Jm\(^{3}\).
  • The Fermi velocity for gold is \(v_{\mathrm{F}} = 1.4 \times 10^{6}\) m/s.
  • You can go back and forth between the resistivity and the mean free path in a metal using the Einstein relation:  \( (1/\rho) = e^{2} \nu D \), where \(e\) is the electronic charge, \(\nu\) is the density of states at the Fermi energy, and \(D\) is the diffusion constant.  In 3d, \(D = (1/3)v_{\mathrm{F}}\ell\).
  • In goofy energy units, 8000 cm-1 is 1 eV.
  • \(\hbar c\) = 200 eV-nm.
 There are others of varying degrees of obscurity.  Please feel free to add others in the comments.  To use math in the comments, you need to preface your LaTeX math with a \ and a (, and end your math expression with a \ and a ). 

MathJax = outstanding.

I've just found MathJax, which is a javascript-based rendering plug-in for either LaTeX or MathML formatted equations. It took me a few minutes to get the syntax working right in blogger, but it seems pretty excellent. If you have scripts turned off, then LaTeX code should show up as LaTeX source. However, if you have scripts turned on, then equations can be rendered very nicely, and can either be in-line, like this: \( -\frac{\hbar^2}{2 m}\nabla^{2} \Psi = E \Psi \), or as display equations, like this: \[ \nabla \cdot \mathbf{B} = 0. \] I'm going to have to donate money to these people - they've done a really nice job.

Tuesday, June 05, 2012


Just pointing out that real life has been very busy of late.  Hopefully I'll have more blogging time shortly.  In the meantime, definitely check out this post by Ash Jogalekar.  It's a topic I've written about more than once, and I've been thinking hard about what to do to address this.  Things like TedEd are intriguing.  It should be possible to do some about the remarkable aspects of condensed matter.  Heck, you could do a great one about Pauli Exclusion....