## Wednesday, April 27, 2011

### Nano and energy

It might be fun to do a few posts on how nanoscale science can be used to the benefit of our energy concerns.  First, let me specify what I mean when I say that there's an "energy problem".  The fact is, average people enjoying first-world standards of living (e.g., US/Canada/Western Europe/Japan) have an enormous per capita energy consumption compared to, e.g., tribesmen in sub-Saharan Africa, or rural farmers in the hinterland of China.  If the goal is to raise the standard of living of the 5-ish billion people not enjoying the high life, and to get everyone up to a high standard of living, then we've got a problem:  there's no nice way to do so without incurring other enormous costs (e.g., burning enormous quantities of fossil fuels; building GW-scale power plants at very high rates, like several per day for the next 30 years).  Either we're not going to raise that standard of living for those billions of people, or the energy costs for the top economic tier are going to have to fall, or we're headed for major upheaval (or possibly some of all of the above).

When I teach my second-semester nano class, I point this out, and if you want interesting quantitative references, check here.  Broadly construed, nanotechnology and nanoscale science (and more broadly, condensed matter physics and materials science) can try to address several aspects of this challenge, though there are certainly no silver bullets.  The areas that come to mind are:  energy generation; energy storage; energy distribution; conservation or improved efficiency; and environmental remediation.  In future posts, I'll try to summarize very briefly a few thoughts on this.

## Saturday, April 23, 2011

On multiple blogs over the last few months, I've read comments from lay-persons (that is, nonscientists) that say, in essence, "As a citizen, I paid for this research, and therefore I should have access to all the data and all the software necessary to analyze that data."  The implications are (1) research funded by the public should be publicly accessible; and (2) the researchers themselves sometimes/often? hold back information or misinterpret the results, perhaps because they are biased and have an agenda to further.

Now, as a pragmatist, there are a number of issues here.  For example, making available raw columns of tab-delimited numerical data and, e.g., matlab code, won't give a nonscientist the technical know-how to do analysis properly, or to know what models to apply, etc.  Things really get tricky if the "data" consists of physical samples (e.g., soil, or ice cores, or zebrafish)....  Yes, scientists that are publicly funded have the responsibility to make their research results available to the public, and to explain those results and their analysis.  As a practical matter, scientists are not obligated to make any interested citizen into an expert on their research.

While this is an interesting topic, I'd rather discuss a related issue:  How much public funding triggers the need to make something publicly available?  For example, suppose I used NSF funding to buy a coaxial cable for $5 as part of project A. Then, later on, I use that coax in project B, which is funded at the$100K level by a non-public source.  I don't think any reasonable person would then argue that all of project B's results should become public domain because of 0.005% public support.  When does the obligation kick in?  Just an idle thought on a Saturday morning.

## Tuesday, April 19, 2011

### Friction, commensurability, and superlubricity

In the limit of clean surfaces, friction has its origins in the microscopic, chemical interactions at the interface between the two objects in question.  One of the more amazing (to me, anyway) consequences of this is the extremely important role played by commensurability between the surfaces.  Let me explain with an example.  Consider a gold crystal terminated at the (111) surface, and another gold crystal also terminated at the (111) surface.  Now, if those two surfaces are brought into contact, with the right orientation so that they match up as if they were two adjacent layers of atoms inside a larger gold crystal, what will happen?  The answer is, in the absence of adsorbed contaminants, the surfaces will stick.  This is called "cold welding".  In contrast, if you bring together two ultraclean surfaces that are incommensurate, they can slide past each other with essentially no friction.  This is called "superlubricity".  Here are two great examples (pdf of first one; pdf of second one) of this.

In this new paper, Liu et al. are able to do some very cute experiments in this regard, looking at the motion of thin graphite flakes (exfoliated from and) sliding on graphite pedestals.  It's clear from the observations that graphite flakes shifted relative to the underlying graphite substrate can slide essentially frictionlessly over micron scales.  Very neat and elegant, and surprising since there is not any rotation at work here to break commensurability.  This is a very firm reminder that our macroscale physical intuition about materials and their interactions can fail badly at the nanoscale.

## Tuesday, April 12, 2011

### Playing chicken with the global economy

I get it - we need to fix the structural problems associated with the US budget.  However, don't these geniuses realize that threatening to default (let alone actually defaulting) on the US sovereign debt will severely undermine the dollar?  It's like they actually want to have hyperinflation, so that they can claim it was all Obama's fault.  Other countries don't have a  "debt ceiling", you know.  Update:  seems I'm not alone in realizing that even talking about default is dangerous.

## Monday, April 11, 2011

### Choosing a postdoctoral position

I had a request a while ago for a post about how to choose a postdoctoral position (from the point of view of a finishing-up grad student, I'm assuming).  This is a tricky topic, precisely because it's somewhere between choosing a grad school (lots of good places to go, with guaranteed open positions every year) and getting a faculty job (many fewer open positions per year in a given field, and therefore a much restricted field of play; plus, a critical need to make some hard decisions that could be postponed or avoided in grad school).  Moreover, different disciplines within the physical sciences have very different approaches on postdocs.  In some fields like astronomy, externally funded fellowships sponsored by observatories/facilities/programs are standard practice, while condensed matter physics is much more principal-investigator-driven.  So, I'll try to stick to general points.
• I strongly suggest going somewhere that is not your graduate institution, unless there are strong extenuating circumstances.  It's just intellectually healthier to get a broad exposure to what is out there, rather than to stay entirely comfortable.
• This is also one of the relatively few points in your career when you can really shift gears, if you are so motivated.  My doctorate was in ultralow temperature physics, but I decided to become a nano researcher, for example.  More dramatically, this is often the point where many people get into interdisciplinary fields like biophysics.  There are trade-offs, of course.  If you do a postdoc in an area very close to your thesis work, you can often make rapid progress.  On the other hand, most people who go on in research (industrial or academic) do not end up working on their thesis topic for the lion's share of their career, and this is a chance to broaden your skill set and knowledge base.
• Word of mouth and self-motivation are essential to getting a good postdoc position, beyond posted ads.  If you're finishing up in grad school, you are enough of a professional that you should be able to email or otherwise contact people whose work you find interesting and exciting, and ask whether they have any postdoctoral openings.  You should make sure that these emails are reasonably detailed and that it's clear they're personalized - not a form letter being spammed to several hundred generic faculty members simultaneously.  Your hit rate won't be high, but it's better than nothing.
• Don't discount industry, though it's a narrowing field.  There are still industrial postdoc positions, and if you've got an interest in industry more so than academia, then you should look at these possibilities.  This includes places like Bell Labs (yes, they still exist), IBM, Intel, HP Labs, etc.  It is a tragedy that there aren't more opportunities like this out there now.
• You need to think about how a particular postdoc position is structured.  Are you going to be acting as middle-management, helping to mentor a team of grad and undergrad students?  Are you going to be leading a research project yourself?  Is there a lot of lab-building or lab-moving?  How long is the position, and how does it match up w/ the seasonal nature of academic hiring, if academia is what you want to do?  Where have previous postdocs in that lab or group ended up?
• How set are you on academia?  If you are set on academia, what kind of academic position would make you happy?  Go into the academic track with your eyes open!  If you're looking beyond academia, what do you need out of a postdoc position (besides a paycheck)?  Are there particular skills you want to learn?
None of this is particularly insightful, but it doesn't hurt to have this written down in one place.  Suggestions for further things to consider are invited in the comments....

## Tuesday, April 05, 2011

### Designing a lab

Designing a lab is not trivial, particularly if you have no experience in doing it before.  My new lab (day 2 of the move....) was perhaps the ideal circumstance: a new building is being constructed, and you have a very free hand in determining the layout, the facilities, and so forth.  In any realistic process you never get everything you want (e.g., this building does not have a building-wide deionized water system; I can't have unlimited space; there are restrictions based on cost and feasibility).  The challenge is to end up with functional space - laid out intelligently, so that work flows well and you don't find yourself fighting with the building or yourselves.  Sometimes this is not simple.  In my original lab space, for example, that floor of the building was never designed with vibration-sensitive work in mind.  The need to position certain pieces of equipment on the vibrationally quiet parts of the floor strongly influenced lab layout, rather than basic experimental logic.

Lab design ranges from the Big Picture (e.g., I have a couple of optics tables, so I should probably have a separate area with independently controlled lighting; I want isolation transformers to keep my sensitive measurement electronics off the power lines used for my big pumps.) to a zillion little details (e.g., where should every single electrical outlet and ethernet port be positioned?  What about emergency power?  Gas lines?  What fittings are going to be on the chilled water lines?).  Nothing is ever perfect, and there are always minor glitches (e.g., mislabeled circuit breakers).  You also want to design for the future.  If you think you're eventually going to need a gizmo that requires chilled water or a certain amount of 480V current, it's better to plan ahead, cost permitting....  The situation is definitely more constrained if you're moving into pre-existing space, particularly in an older building.  Like many aspects of being a professor, this is something that no one ever sits down and teaches you.  Rather, you're left to figure it out, hopefully with the help of a professional.

## Monday, April 04, 2011

### Moving the lab

Today's the beginning of moving my lab into the new Brockman Hall for Physics here at Rice.  As the week goes on, if I have time I'll write a bit about the process of lab design and the joys of moving equipment.  It's exciting, but there's no question that I wish we could skip over the actual transition.