A cool application and more travel

Apologies for the long break between posts.  It's been an incredibly hectic summer, and I'm about to go on a last big trip before the school year starts (and I get to teach honors intro mechanics to ~ 90 frosh - should be exciting, at least).

Before I go, I wanted to point out a very cool application of micromachining and computing power.  There are many consumer electronic devices now that contain within them a little 3-axis accelerometer made by micromachining techniques, like this one.  The basic gadget consists of a micromachined "test mass" (typically a block of Si) suspended on (silicon) springs.  When the whole device is accelerated, the test mass "lags behind" because of its inertia, just as you get pushed back into the seat of your car when the car accelerates forward.  Through (often) capacitive sensing, the displacement of the test mass can be transduced into a voltage that the chip then outputs.  If the displacement can be detected along three axes, voila, you have a 3-axis accelerometer.  This is the widget that tells the Nintendo Wii how you've been swinging the controller, and it tells iPhones and other similar toys how to orient their displays.  With added sophistication, it's also possible to make micromachined gyroscopes.  They aren't true gyros that spin.  Rather, they're micromachined resonators (like tuning forks of particular shapes), and rotation leads to Coriolis forces that twist the resonator in a way that can be detected.  (For Wii aficionados, that is how the "Wii Motion Plus" works.)  Then you can get angular accelerations, too.

What is the point of this discussion?  Well, some people at Microsoft Research had a great insight.  You can put a sensor like this on a digital camera.  If the acceleration data is logged when a picture is snapped, then it is possible to retroactively unblur photos (at least, pictures that were blurry because the camera was moving).  This is the slickest thing I've seen in a while!     

Why there has been no Carl Sagan or Brian Greene of condensed matter physics

It's impossible to be a condensed matter physicist that cares about outreach and scientific literacy, and not think about why condensed matter physics has taken such a back seat, comparatively, in the popularization of science.  It is easy to argue that condensed matter physics has had more direct impact on the daily lives of people living in modern, technological societies than any other branch of physics (we could get into an argument about the relative impacts of the transistor and the laser, but I think the CM folks would win).  So, how come there are specials and miniseries on PBS and Discovery Channel about string theory, the LHC, cosmology, and astrophysics with considerable regularity, people like Stephen Hawking, Brian Greene and Neil DeGrasse Tyson show up on The Daily Show, and the closest condensed matter gets to the public consciousness is a BBC special from several years ago about the Schon scandal?  Is it just that there is no charismatic, telegenic champion of the cause?  I think it's more than that.

First, there is the issue of profundity.  High energy physics makes an obvious play toward people's desire for answers to Big Questions.  What is mass?  What is everything made out of?  How many dimensions are there?  How did the Universe begin, and how will it end?  Likewise, astrophysics talks about the history of the entire Universe, the birth and death of stars, the origin of galaxies, and literally heaven-shaking events like gamma ray bursts.  Condensed matter physics has a much tougher sell.  In some ways, CM is the physics of the everyday - it's the reason water is wet, metals are shiny, diamond is transparent and sparkly, and the stuff in sand can be used to make quasimagical boxes that let me write text read all over the world.  Moreover, CM does look at profound issues (How does quantum mechanics cross over into apparently classical behavior?  How do large numbers of particles interacting via simple rules give rise to incredibly rich and sometimes amazingly precise emergent properties?), just ones that are not easy to state in a five word phrase.

Second, there is the problem of accessibility.  CM physics is in some sense an amalgam of quantum mechanics and statistical mechanics.  People do not have everyday experience with either (at least, the vast majority don't realize that they do).  It's very challenging to explain some of the very nonintuitive concepts that crop up in condensed matter to lay-people without either gross oversimplification or distortion.  There can be a lot of overhead that must be covered before it's clear why some CM questions really are interesting.  An awful lot of CM issues literally cannot be seen by the naked eye, including atoms.  Of course, the same can be said for quarks or colliding neutron stars - this is not an insurmountable problem.

Third, there is perceived relevance.  This is complementary to profundity.  People are naturally interested in Big Questions (the origins of the stars) even if the answers don't affect their daily lives.  People are also naturally interested in Relevant Questions - things that affect them directly.  For example, while I'm not that into meteorology, I do care quite a bit about whether Tropical Storm Bonnie is going to visit Houston next week.  Somehow, people just don't perceive CM physics as important to their daily existence - it's so ubiquitous that it's invisible.  


These issues greatly constrain any attempt to popularize CM physics....

Wow - look what I missed!

I did some travel + have a busy period at work, and what happens?  Scienceblogs implodes, and Chad Orzel laments something I've worried about for a long time:  the difficulty of explaining the importance (and basic coolness) of condensed matter physics to a general audience.  As for the former, serves 'em right for not inviting me to participate -- kidding!  There are enough talented people involved that they'll be fine, and as Dave Bacon points out in his linked post above, mixing up new networks of people interested in communicating science is probably a net good thing.  I do think it's a shame, though, that some interesting blogs have seemed to fade away (Incoherent Ponderer, Angry Physicist, you are missed.).  Regarding the second topic, I do want to point out a previous post I made about topological insulators (the strawman topic of Chad's post), and once I dig out from under work, I'll write more about why condensed matter is particularly difficult to popularize, and thoughts on how to get around those inherent challenges.

Symmetries and level-appropriate teaching

This fall I'm going to be teaching honors introductory mechanics to incoming undergraduates - basically the class that would-be physics majors take.  Typically when we first teach students mechanics, we start from the point of view of forces and Newton's laws, which certainly parallels the historical development of the subject and allows students to build some physical intuition.  Then, in a later class, we point out that the force-based approach to deriving the equations of motion is not really the modern way physicists think about things.  In the more advanced course, students are introduced to Lagrangians and Hamiltonians - basically the Action Principle, in which equations of motion are found via the methods of variational calculus.  The Hamiltonian mechanics approach (with action-angle variables) was the path pursued when developing quantum mechanics; and the Lagrangian approach generalizes very elegantly to field theories.  Indeed, one can make the very pretty argument that the Action Principle method does such a good job giving the classical equations of motion because it's what results when you start from the path integral formulation of quantum mechanics and take the classical limit.

A major insight presented in the upper division course is Noether's Theorem.  In a nutshell, the idea is that symmetries of the action (which is a time integral of the Lagrangian) imply conservation laws.  The most famous examples are:  (1) Time-translation invariance (the idea that the laws of physics governing the Lagrangian do not change if we shift all of our time parameters by some amount) implies energy conservation.  (2) Spatial translation invariance (the laws of physics do not change if we shift our apparatus two feet to the left) implies conservation of momentum.  (3) Rotational invariance (the laws of physics are isotropic in direction) implies conservation of angular momentum.  These classical physics results are deep and profound, and they have elegant connections to operators in quantum mechanics.

So, here's a question for you physics education gurus out there.  Does anyone know a way of showing (2) or (3) above from a Newton's law direction, as opposed to Noether's theorem and Lagrangians?  I plan to point out the connection between symmetry and conservation laws in passing regardless, but I was wondering if anyone out there had come up with a clever argument about this.  I could comb back issues of AJP, but asking my readers may be easier.  

Science and communication

I've tended to stay away lately from the arguments about scientists-as-communicators that seem to flare up periodically.  This recent editorial by Chris Mooney, about how scientists who actively listen to the general public do a better job of communicating and affecting policy, was simultaneously informative and yet blindingly obvious in some ways.   (Here's a shock:  making it clear to an audience that you're listening to their concerns and considering them seriously gets better results than talking down to them or ignoring them dismissively.)  Chad Orzel followed up with a very well-written (as usual) post about scientists and communication skills that is, like Mooney's, really common sense in the end.  (Here's another shock:  not everyone is Carl Sagan or Neil DeGrasse Tyson, and sometimes our scientific and academic institutions do not value public communication as much as they do utter dedication to scientific research.)  

Many people in the general public do have some baseline interest in science and engineering issues, even if they don't label them as such.  Lots of people watch Mythbusters.  Lots of people read about nutritional information or medical research quasiobsessively.  Many people do care about space, and climate, and the environment, and energy, and electronics, and so forth, even if those concerns are not the top of their list all the time.  There is a thirst for information, and this is all good for society.  I do want to point out one additional issue that seems to get neglected to some degree in this discussion, however.  There are people out there who either don't know what they're talking about (the MD who somehow has a column on the Huffington Post who periodically spouts off utter pseudoscientific nonsense), or actively are pushing misleading or inaccurate information (members of the TX Board of Education who grossly mischaracterize the nature of science).  Scientists can do as much as possible to "market" ourselves and communicate our enthusiasm and willingness to have an honest and open dialog about scientific issues.  However, when anti- or pseudo-science can command at least as big a bully pulpit, and when education and time make it difficult for the average person to discriminate between gold and dross, it's an up hill struggle.  Add in to this the mainstream media's love of controversy ("Some say that the earth goes around the sun, but others disagree.  Let's look at both sides of this issue!"), and the situation can get downright depressing.

Edit:  I realize I left out two other confounding factors:  (1) Scientists who end up distorting actual science beyond recognition in a misguided attempt at popularization (Michio Kaku is an example); and (2) Scientists who are so aggressively arrogant and obnoxious that they only hurt their own cause.

Helium

Helium consumption is still a problem.  A real problem.

Lies, damned lies, and lying statistics

This is not physics, but it is interesting.  According to fivethirtyeight.com (a blog run by Nate Silver that specializes in statistical analysis of political polls), a major polling firm is being sued for fraud by liberal blog DailyKos.  The grounds for the suit:  this report, which details a number of statistical anomalies suggesting that the polling firm was either cooking their numbers, or outright making them up.  Bonus:  one of the guys who did this analysis is Mike Weissman, a condensed matter physicist who retired from UIUC.  Weissman is an expert on noise measurements, author of this highly cited review article.  He's a guy who knows statistics.

Excitons

A reader emailed me and asked if I had done a posting about excitons.  Looking back, I see that I haven't, so here is an attempt to rectify the situation.  As I've written previously, condensed matter physicists are fond of giving specific names to excitations of solid state systems when those excitations have well-defined quantum numbers (and are in that sense "particle-like").  An exciton comprises an electron and a "hole" bound together by the attractive Coulomb interaction (since an electron has charge -e and a hole has charge +e).  It is the (negative!) binding energy of the exciton that makes it different than a generic "electron-hole" excitation in which an electron is kicked out of an occupied state (leaving behind a hole) and into a previously empty state.

Excitons can exhibit very rich physics.  In a 3d crystalline system, excitons can be very analogous to hydrogen-like atoms, or more accurately, positronium, the bound state of an electron and a positron.  One can think of the electron and hole as having center-of-mass momentum, and having an exciton wavefunction that describes the relative displacement of the electron and hole, which would look like a hydrogenic orbital (s-like, p-like, etc.).  Like positronium, the electron and hole can annihilate each other and emit a photon.  Several important features crop up, however, due to the fact that the exciton exists within a solid host.  For example, one cannot ignore the screening of the electron-hole Coulomb interaction by the surrounding host.  One approximation commonly shown in textbooks is to treat this screening by using the bulk (relative) dielectric constant of the host material when solving for the exciton wavefunctions.  As a result, the exciton is much larger, spatially, than positronium - say 5 nm in extent rather than 0.5 nm.  (Note that this had better be true!  Otherwise the assumption that the bulk material can screen the interaction would not be internally consistent....)  Large excitons like this are called Wannier excitons.  In contrast, if the screening is relatively weak, the exciton can be small compared to a unit cell of the crystal.  Such a small exciton is called a Frenkel exciton.

Furthermore, the electron and hole parts of the exciton wavefunction are really "built" out of the Bloch wave electronic states of the solid.  In a semiconductor, the hole states "live" in the valence band, while the electron states live in the conduction band.  Hole states often exhibit stronger spin-orbit effects, and as a result, confinement can affect the exciton energy levels quite strongly.

Excitons may be produced by the absorption of light of appropriate energy, and therefore are of intense interest in photovoltaic research.  The comparatively strong screening in traditional semiconductors that gives large exciton spatial sizes also leads to modified binding energies.  Wannier exciton binding energies in materials like silicon can be on the order of 10 meV (as opposed to electron volts for positronium!).  In materials with weaker screening (with Frenkel-like excitons), the exciton binding energy can be higher, more like hundreds of meV.  These binding energies are of critical importance.  In a silicon pn junction, for example, the built-in electric field due to the junction is large enough to rip apart any light-produced excitons - that's how charge separation happens in a silicon solar cell.  In organic semiconductors, in contrast, the binding energies are stronger, and built-in fields are too weak to take apart excitons.  Thus, there are no homojunction organic solar cells, and this is one of a number of reasons why organic photovoltaics is challenging. 

Travel + interesting review article

I'm traveling this week, so blogging is thin. I did want to point out an interesting review article from the arviv: arxiv:1006.3736, Force-detected nuclear magnetic resonance: Recent advances and future challenges, Poggio and Degen. This article take a look at the progress over the years in this micro mechanical approach to incredibly sensitive spin measurements.

Kavli Prizes for Nanoscience

This post is a bit late, but real life has been busy recently. The Kavli Foundation recently announced their 2010 Kavli Prize for Nanoscience, which they awarded to Don Eigler and Nadrian Seeman, for "their development of unprecedented methods to control matter on the nanoscale". As in their previous 2008 award to Louis Brus and Sumio Iijima, this prize is richly deserved by the awardees.

Don Eigler ran the scanning tunneling microscopy (STM) research group at IBM Almaden, where he and co-workers constructed incredibly stable STMs that functioned in ultrahigh vacuum and at low temperatures. With the resulting stability and surface cleanliness, Eigler et al. were able to demonstrate manipulation of matter on the atomic scale, giving us several of the most iconic images in nanoscience. Eigler's intellectual progeny have gone on to many faculty positions and trained generations of practitioners in the art and science of working at the atomic scale.

Nadrian Seeman had the foresight to realize what an incredible toolkit nature has provided for us in the form of DNA. While most people are familiar with double-helix structure of DNA, Seeman and co-workers developed techniques to make nanoscale DNA building blocks that can assemble into complex, three-dimensional structures. This is DNA as a construction tool rather than DNA as a carrier of genetic information. Who knows what the end result will be of this capability - I have been very impressed by some related work.

Nanomechanical mass sensing in fluid

The idea of using mechanical resonators as mass sensors is an old one, and one that may be explained to a first-year physics undergrad. The (angular) frequency of a mass on a simple Hooke's Law spring is (k/m)^0.5, where k is the spring constant. Change the mass, and the resonant frequency changes. With the development of micromachining techniques, there has been a great deal of interest in using tiny, high frequency resonators (e.g., doubly clamped Si beams) as mass sensors. One can have a metal wire along the resonator, and in the presence of a dc magnetic field perpendicular to the wire, an ac current may be used to apply a driving force to the structure. This is the same principle used to move the filament back and forth in those cheesy old flicker light bulbs. By measuring the induced voltage along the wire as it moves through the static magnetic field, the resonator's motion may be detected. Michael Roukes' group at Cal Tech been enthusiastic about the possibility of achieving sensitivities high enough to resolve a single atomic mass unit (1.66 x 10^-27 kg).

There are many situations where one would love to have great mass detection capabilities in a liquid environment (e.g., to detect the binding of some cancer marker). The problem is, if you immerse a mechanical resonator in a liquid, viscous damping completely kills your sensitivity by damping the resonance. An old acquaintance of mine from graduate school, Scott Manalis at MIT, has come up with a solution to this problem. Don't put the resonator inside liquid; rather, put liquid inside the resonator. His group has been making mechanical resonators with micro (and now nano)fluidic flow channels inside them. In their latest work, they report a sensitivity of 30 attograms. I think this is very elegant, and a tour de force fabrication exercise.

Demagnetization cooling

I've been meaning for some time to write a post about demagnetization cooling, a technique that is readily explained in an undergrad stat mech class, but has to be seen to be believed.  I was finally inspired to write this post by seeing this preprint.  Here's the basic idea.  Start with an ensemble of magnetic moments in what we will call a "demag stage".  The sample of interest will be thermally connected to this demag stage.  When I worked on this stuff in grad school, we used the nuclear magnetic moments of copper nuclei, but it's also possible to use electron magnetic moments in a paramagnetic salt of some kind.  Anyway, apply a large magnetic field to these magnetic moments (spins) while attached to a refrigeration source of some kind. It's energetically favorable for the moments to align with the applied field. When they flip to align, the energy that is released is carried away by the refrigerator.  Likewise, in the case of a metal like copper, the ramping up of the magnetic field can generate heat via eddy currents; that heat is also carried away by the refrigerator.  Now, once the spins are basically aligned, unhook the thermal connection between the demag stage and the refrigerator, and gently lower the applied magnetic field.  What happens?

First, the formalistic explanation.  Basic statistical physics tells us that the entropy of an ensemble of magnetic moments like those in our demag stage is only a function of the ratio B/T, where B is the applied magnetic field and T is the temperature of the moments.  If we are gentle in how we lower B, so that the entropy remains constant, that implies that lowering B by a factor of two also lowers T by a factor of two.  When I first did this as a grad student, it seemed like magic.  We thermally isolated the demag stage (plus sample), and I used an ancient HP calculator to tell a power supply to ramp down the current in a superconducting magnet.  Voila - like magic, the temperature (as inferred via the capacitance of a special pressure transducer looking at a mixture of liquid and solid ³He) dropped like a stone, linear in B.  Amazing, and no moving parts!  

So, physically, what's really going on, and what are the limitations?  Well, the right way to think about the ensemble of magnetic moments is as an entropic "sink" of energy.  Equilibrium statistical physics is based on the idea that all microscopic states of a system that have the same total energy are equally likely.  When you create an ensemble of 10²³ magnetic moments all pointed in the same direction (that is, with an aligned population much greater than what one would expect in equilibrium based on the new value of B), the most likely place for thermal energy in your system to go is into flipping those spins, to try and bring the aligned population down and back into the new equilibrium.  That means that heat will flow out of your sample and out of, e.g., the lattice vibrations of the demag stage, and into flipping those spins.  The fortuitous thing is that for reasonable numbers of moments (based on volumes of material) and accessible initial values of B and T, you can get lots of cooling.  This is the way to cool kilogram quantities of copper down to tens of microKelvin, starting from a few milliKelvin.  It's a way to cool a magnetic salt (and attached sample) down from 4.2 K to below 100 mK, with no messy dilution refrigerator, and people sell such gadgets.  

There are practical limitations to this, of course.  For example, there is no point in reducing the external B below the value of the effective internal magnetic field due to spin-spin interactions or impurities.  Also, when demag-ed, the system is a closed box with a finite (though initially large) heat capacity.  Any measurement done on an attached sample will dump some heat into the stage, even if only through stray heat leaks from the rest of the world, limiting the amount of time the stage and sample remain cold before needing another demag cycle.  Finally, and most relevant to the preprint linked above, there are real issues with establishing thermal equilibrium.  For example, it is not hard to get the nuclei of copper to have a much lower effective temperature than the conduction electrons, with an effective equilibration time longer than the demag-ed spin system can be kept cold.  In other words, while the nuclei can get very cold for a while, the electrons are never able to reach similar temperatures.  Still, the whole concept of cooling through demagnetization is very interesting, and really brought home to me that all the abstract concepts I'd learned about entropy and spins had real consequences.   

Workshop: Negotiating the Ideal Faculty Position

For the last few years I have been involved with Rice's ADVANCE program, a NSF-supported initiative designed particularly to increase the number of women faculty members in the sciences and engineering.  This FSP recent post reminded me that now is the right time to advertise ADVANCE's upcoming workshop on negotiating the ideal faculty position, and this blog is one way to reach a wide audience.  Potential participants need to apply, since space is limited.  (Last year there were 1100 applications and 65 slots.)  View this as a way to practice a job talk in a friendly, constructively critical environment, and to discuss issues that come up in the faculty job hunt (e.g., how the process works; picking letter-writers; lab space + startup packages).  This is a way to talk to knowledgeable people in yours and related areas who are not your mentors or direct potential employers.    

Tidbits.

• While modern communications tools are definitely improving, there is still no substitute for actually sitting down with collaborators at a table with pen and paper, and hashing things out face-to-face.   I just returned from a quick trip to talk with some theorist colleagues, and it was a great way to get a lot accomplished in a relatively short period of time.  Much higher bandwidth than repeated emails.
• If you're ever invited to write a review article, and you have any concerns about the quality of the journal or the publisher, don't ignore your instincts.  My postdoc and I just went through a painful experience along these lines - in the end, everything's going to be fine (with another publisher!), but the original publisher (I'll name names some other time) was amazingly incompetent.  You'd think, for example, that a journal editor would have an email system that actually accepts attachments, particularly if their web-based system is utterly fubar.
• A follow-up to my recent post about IR CCDs....  Anyone out there have experience with the MOSIR-950?  It's actually a Si CCD with a special front end that makes it sensitive from 950nm out to around 1700 nm.
• I'm very tempted to buy this.  (If you have never seen the tv show Lost, you won't get this.)

This will be a big new story.

Craig Venter's company appears to have succeeded in creating a synthetic genome and getting it into an emptied-out (prokaryotic bacterial) cell, essentially changing the cell into a new species. This is going to be huge. Of course, we still don't actually understand what everything in that custom genome does, exactly - much of it is copied from another bacterium species. Still, it's an amazing achievement that one can design (on a computer) a DNA sequence, stitch it together via various methods, and get a cell to "run" that software.

IR CCD arrays for spectroscopy?

The charge-coupled device, or CCD, was the gadget behind part of this past year's Nobel prize in physics.  Far and away, the most common CCDs out there are based on silicon, and these devices are highly efficient from the visible out to the near-infrared, with efficiency really taking a major hit at wavelengths longer than about 1100 nm.  One advantage of CCDs is that generally their total efficiency is high:  an incident photon stands a good chance of producing some charge on a pixel, and that charge can be collected well, so that getting a "count" on a particular pixel requires only a couple of photons.  It turns out that one can also get CCDs based on InGaAs, a semiconductor with a smaller band gap than Si, and therefore sensitive to longer wavelengths, typically from around 950 nm out to 1700 nm or so.  I have been thinking about trying to get such a gadget for a few reasons, Raman spectroscopy in particular, and I would welcome reader recommendations.  For our application we really would like something with CCD-like sensitivity (as opposed to a linear array of photodiodes, which is considerably cheaper, but requires on the order of 100 photons to produce a single "count").  Feedback would be greatly appreciated.  I know that Princeton Instruments sells one gadget (though really for imaging rather than spectroscopy), and Newport appears (from press releases)  to offer something with more pixels, though it doesn't show up on their website....

Scale and perspective II

The title of this post harkens back to a previous example of stellar corporate governance.  Today the CEO of BP made the statement that "The Gulf of Mexico is a very big ocean. The amount of volume of oil and dispersant we are putting into it is tiny in relation to the total water volume". While that is literally true, as a physicist I have to ask, is that the right metric? I mean, are we worried about the total fraction of Gulf of Mexico that is oil? No, because everyone knows that the relevant point of comparison is not the total volume of water, but the point at which the oil content is having catastrophic effects on the environment.  We can gain some perspective by comparing with other oil spills. According to experts who have viewed the (long delayed by BP) video of the leak, the flow rate of oil is somewhere around 70000 barrels a day, or about 1 Exxon Valdez disaster (I think everyone sane agrees that it was a real mess) every four days. This has been going on for three weeks. Arguing that "the ocean is really big so this isn't that much of a problem" is just wrong.

update:  It's increasingly clear that BP is far more worried about their liability than about actually fixing the problem.  Check out this quote from the NY Times:  

BP has resisted entreaties from scientists that they be allowed to use sophisticated instruments at the ocean floor that would give a far more accurate picture of how much oil is really gushing from the well.

“The answer is no to that,” a BP spokesman, Tom Mueller, said on Saturday. “We’re not going to take any extra efforts now to calculate flow there at this point. It’s not relevant to the response effort, and it might even detract from the response effort.” 

Right, because good engineering solutions have nothing at all to do with accurately understanding the problem you're trying to solve. Idiots.

What do fancy research tools really cost at a university?

Over the years, I've become convinced that there are lies, damned lies, and cost accounting.  What I mean by this is that "true costs" for various items in a business or at a university (a type of nonprofit business, after all) are sometimes allocated in whatever way is necessary to bolster a particular argument at hand.  If those making an argument want something to look like a bargain, no problem, there's a way to do the accounting for that.  If those making an argument want to make something look so expensive that it's economically unattractive, no problem, there's a way to do that, too.  I remember as a postdoc when the part of Lucent Technologies that dealt with real estate argued (apparently successfully) that they should get rid of the simple general stockroom because somehow having the square footage allocated to that use was losing money.  So they shut down the stockroom, and had a couple of hundred PhD scientists and engineers spending their (expensive) time ordering 4-40 screws from McMaster Carr online or over the phone instead of just walking upstairs and grabbing some.

Let's take an electron microscope as a test case.  Suppose a university or company buys an SEM for $350,000 (for the sake of round numbers).  How much should they charge, fairly, for its use?  Let's assume that this is a shared tool and not just sitting in one person's lab.  This microscope and associated hardware take up something like 100 ft² of floor space.  The microscope also needs electricity (say 1 kW) and cooling water.  Now, a university is unlikely to charge a department or faculty member "rent" on the floorspace, but a large company may decide to "tax" a business unit for space at some rate.  The electricity and cooling water are likely part of a university's or business's "overhead".  Overhead charges are assessed when it's difficult to trace a particular designated responsible source for certain kinds of costs-of-doing-business.  For example, the overhead rate at my institution is 52.5%.  That means that for every $1 of direct research cost (say a grad student's salary), the university charges my research account (and therefore the funding agency) $1.525.  That "extra" $0.525 goes to cover the university's costs in, e.g., keeping the lights on in my lab, the air handlers running for my fume hoods, and the road paved outside my building.

If the university or business wants to maintain the electron microscope, they probably want to buy an annual service contract for, say, $25K.  Now, in the absence of a staff person to run the system, you might think that a reasonable user fee would then be $25K divided by the number of hours the system is used (say 2000 hours per year).  Not so fast - you have to charge overhead.  Moreover, the university or business may decide to depreciate the SEM.  That means that they may have an interest in replacing the SEM eventually, so they are allowed to tack on a depreciation cost, too.  For our example, a typical depreciation schedule would be seven years, so in addition to the actual maintenance cost, they would tack on, in this case, $50K per year.  There are major federal rules about depreciation.  For example, you can't buy something with a federal grant (e.g., a NSF "Instrumentation for Materials Research" grant) and then also depreciate it - that would be like double-billing the government, and that's not allowed.

If the university or business does have some fraction of a staff person responsible for the instrument, it may be fair (depending on the discussion) to consider a fraction of that person's salary (plus fringe benefits [e.g. health insurance] plus overhead) as a cost to be recovered as well.  

So, the next time you are paying $30/hour for access to an electron microscope, and you're wondering where on earth that figure came from, now you have at least some idea.   You can also see how administrations can sometimes argue that they "lose money" on research - they cannot always recover the costs that they put into things (e.g., the actual overhead income may not cover the utility costs), and sometimes they choose not to  (e.g., by not charging rent for space).  This is all stuff about which I was blissfully ignorant back in my student days.

Amateur economics

Perhaps a more economically savvy and inclined reader could comment, but is it fair to say that some fraction of the recent decline of the US stock markets (excepting dramatic short-term spikes like the one this afternoon between 14:30 and 15:00 EDT) is not a "real" decline, but a reflection of the increased value of the dollar relative to the euro?  From what I can see, the euro has fallen about 8.5% against the dollar since mid March, and the US financial markets are actually down about 4% (mostly in the last week or two) over the same time period.  Naively, if dollars are worth more, one should see "deflation" on the dollar-denominated stock markets, I would guess....

Manageable-sized, LaTeX-happy .eps figures

In much of physics, LaTeX is the standard for typesetting scholarly work, including research papers and theses.  Traditionally, when working with figures in LaTeX documents, the preferred format is encapsulated postscript (.eps).  There are any number of ways to produce figures in .eps format, but some people seem to have recurring problems doing this with economical file sizes.  For example, today b/c I am on a committee reviewing doctoral theses for a departmental award, I had to download a thesis that was around 50 MB in size, entirely because the figures were unnecessarily huge.  Over the years I've come up with a few different ways of making small, good (in the sense that they render nicely and LaTeX likes them) .eps files.  Here's a quick how-to.  Mostly this is from the point of view of a windows user, by the way.  (I have both PCs and Macs, fwiw).

On a pc, I cannot recommend gsview and ghostscript strongly enough - they're essential tools.  There are linux versions of these as well, of course.  In general, if a postscript file opens cleanly in gsview, you're going to be fine w/ LaTeX compatibility.  gsview is also perfect for redefining bounding boxes, grabbing individual pages from a multipage postscript file, converting .ps into .eps, and other related tasks.    Another set of tools worth having is ImageMagick.  Very helpful for converting between formats.

Option 1:  Use an application that can natively export nice .eps (that is, vector format rather than automatically using bitmapping) with no attached preview.  For example, Origin can do this, as can Matlab or gnuplot if properly set up.  On the Mac, inkscape is a great vector drawing and editing piece of software.  Adobe (who invented postscript, as far as I know) has programs like Illustrator and Photoshop that can do this.  The former seems better at producing economical output.  The latter, without careful intervention, produces bloated, bitmapped, preview-laden junk.  

Option 2:  Use a generic postscript printer driver that can print to a file in .eps format.  Adobe has one for pc that lives here.  Using this, you can do things like use powerpoint as a cheesy compositing tool to draw something or put together multiple images, and then print a particular slide to an .eps file.  The result will be LaTeX-friendly, but not necessarily economical in file size.

Option 3:  Produce an image in a different, nicely economical format and then use a "wrapper" to produce a .eps file.  Here's one example.  Suppose I have a huge bitmap file.  I can use my favorite software (imagemagick, or even MS Paint or powerpoint) to save the image as .jpg or .png.  Then I can use jpeg2ps (in the former case) or bmeps (in either case) to produce a .eps file that is only slightly larger than the originating image.  

This last option provides a way out of the annoying situation of having a huge (say 10 MB) .eps file produced by some other application (like Matlab).  You can open the offending .eps file in gsview, and try to copy the on-screen image (zoomed as needed) to the buffer (that is, click on the displayed image and hit ctl-c on a windows pc).  Then paste the buffer into either paint or powerpoint, and export it as a .png file (nice format - no compression!).  Once you have the .png file, run bmeps to produce a new .eps, and you're all set.  Your 10 MB old .eps file can end up as a 70 kB new .eps file.  This wrapper strategy is also the one recommended by the arxiv folks.

This is by no means exhaustive, but if it saves anyone the pain of having monster .eps files that warp the final documents, then it was worth posting.  (I suspect that someone will comment about how things like this are one reason that journals are drifting toward MS Word.  Word carries with it many, many other problems for scientific writing, in my opinion, but I'd rather not get into a debate on the subject.)