Two nanoscience tidbits

Since nearly everyone else in the science blogging world has touched on this (see here, here, here, here, and here, to name a few), I might as well do so, also.  Leo Gross and coworkers at IBM Zurich have used an atomic force microscope to do something incredibly impressive:  They have been able to image the bonding orbitals in individual pentacene molecules with better than atomic resolution, using the very short-range forces that contribute to the "hard core repulsion" between atoms.  Atoms tend to be attracted to each other on nanometer scales, even in the absence of strong chemical interactions, due to the van der Waals interaction, which comes from the fluctuating motion of their electron clouds.  At very short distances, though, atoms effectively repel each other extremely strongly, both from the Coulomb interaction (electrons don't like each other overly much) and the effects of the Pauli Exclusion Principle.  Gross and colleagues accomplished this feat by working in ultrahigh vacuum (around 10^-15 of atmospheric pressure) and at 5 K, and by deliberately attaching a single CO molecule to their conducting atomic force microscope (AFM) tip.  It's a heck of a technical achievement for AFM.  Atomic resolution has been demonstrated before, but this kind of sensitivity is remarkable.  (FWIW, I once heard one of the major coauthors, Gerhard Meyer, speak at a meeting about the same group's ultrahigh resolution STM work.  He seemed very low key about their obviously impressive achievements - amazingly so.  I hope he got excited about this!)

Also, a group at Berkeley has made a laser based on a CdS nanowire, and like the result mentioned last week, this gadget uses plasmons (this time in a Ag film) to act as an effective cavity.  Clearly using the extreme confinement of some plasmon modes to do photonics is going to be a growth industry.

Industrial R&D

I've felt for a long time that the current business climate, which punishes rather than rewards long-term research investments by companies, is misguided. When most stock is owned and traded by institutional investors and large funds who don't have any interest in holding particular companies for the long term, and when executive compensation massively overvalues year-over-year growth (because we all know that 40% annual growth in cell phone sales is sustainable forever, right? There's no such thing as market saturation, is there?), you end up where long-term investment is viewed by company boards as a misuse of resources. This article in Business Week makes some interesting arguments on ways to try and fix this. Unfortunately I think most of these ideas are not very compelling or likely. Norm Augustine had an interesting suggestion: scale the capital gains tax rate inversely with the amount of time one owns a stock. If someone holds a stock less than a year, tax the capital gains at 90%. If they own the stock 10 years or more, tax the capital gains at nearly 0%. Interpolate appropriately. The idea here is to set up a system that incentivizes long-term investment, which in turn is more likely to support industrial research. Hard to see how such an overhaul would ever get passed in Congress, though. I imagine the financial industry would crush it like a bug, since anything that slows down trading is viewed as interference in the free market, or, more cynically, interference in their enormous transaction fee profits.

How we fund grad students

As new grad students flood onto campuses across the US, I just got around to reading this piece in Science from a few of weeks ago about Roald Hoffman's idea for changing the way we support grad students in the sciences and engineering. Most S&E grad students in the US are supported by a mix of teaching assistantships (TAs), research assistanceships (RAs), and fellowships. A typical S&E grad student at an American university shows up and is supported during their their first year by a mix of university funds and pay for teaching. They then often make the transition to being supported as an RA by research funds obtained by their advisor through research grants. (Some remain as TAs - this is more common at large, public institutions with large undergraduate teaching needs.) Some relatively small fraction of S&E grad students are supported instead by fellowships, awarded competitively by agencies like NSF, DOE, DOD, NIH, etc. or by private foundations such as the Hertz Foundation.

Prof. Hoffman suggests that we should move to a system where all grad student support is fellowship-based. The idea is that this will (a) fund only the best students; (b) allow students much greater independence since an advisor will no longer be able to say "You have to do boring experiment #23 because that's what the grant that's paying your salary says we're going to do"; (c) result in better mentoring b/c faculty will no longer view students as "hands". Now, there's basically no way to see how such a drastic change in the system would ever happen, but it's worth looking at the idea.

As someone lucky enough to have a fellowship in grad school, I understand the appeal from the student side. Independence is great - it means that you and your advisor are freed from the stress of worrying that your grant won't get renewed when you're in year 3 of your program. It means that you are a free agent.

However, I think Hoffman's idea would be a disaster, for two main research-related reasons (not to mention the challenge of how you'd handle TA duties at large places that suddenly had many fewer grad students). First, there is little doubt that this would skew an already tilted system even further in favor of the top, say, 20 institutions in the country. Right now it's possible for good researchers at second tier universities to write grants, hire students, and do research. Imagine instead if the only source of student support were competitive external fellowships. It's all well and good to talk about overproduction of PhDs, and say that drastically reducing the number of grad students would be good for employment and salaries. There is a point to that. However, you would effectively end research as an enterprise at many second and third-tier schools, and there are a fair number of really good programs that would go away. Second, since federally funded fellowships would presumably only go to US citizens, this idea would drastically reduce international PhD students in S&E. That, too, would be a mess. Some of our best students are international students, and whether or not they stay in the US after their degrees, training these people is a valuable service that the current US system provides.

It is worth considering other funding schemes, though. I know that in the UK students are supported through their PhD, rather than on a schedule set by external grant deadlines. Perhaps some of my UK readers could comment on the pluses and minuses of this approach.

plasmons instead of cavities

Sorry for the delay in posts. The beginning of the new academic year is a hectic time.

This paper is a very exciting new result. Unfortunately there does not appear to be a publicly accessible version available. Ordinarily, lasing (that is, light amplification by the stimulated emission of radiation) requires a few things. One needs a "gain medium", some kind of optically active system that has (at least one) radiative transition. In this paper, the medium is a dielectric oxide containing dye molecules known to fluoresce at a wavelength of 520 nm. This medium needs to be pumped somehow, so that there are more optically active systems in the excited state than in the ground state. This is called "population inversion". (It is possible to get lasing without inversion, but that's a very special case....) Finally, one generally needs a cavity - an optical resonator of high enough quality that an emitted photon stays around long enough to stimulate the emission of many more photons. The cavity has to be somewhat leaky, so that the laser light can get out. However, if the cavity is too leaky, the optical gain from stimulated emission in the pumped medium can't outpace the cavity losses. The usual approach is to have a rather high quality cavity, made using either dielectric mirrors, total internal reflection, or some other conventional reflectors.

In this paper, however, the authors take a different tactic. They use the near-field from the plasmon resonance of the gold core (not coincidentally, at around 520 nm wavelength) of Au-core-dielectric-shell nanoparticles. Plasmon resonances are often quite lossy, and this is no exception - the Q of the plasmon resonance is around 14. However, the enhanced near field is so large, and the effective mode volume (confinement) is so small, that gain still outpaces loss. When the dye is optically pumped, it is possible to make these nanoparticles lase. This paper is likely to spawn a great deal of further work! It's cool, and there are many clear directions to pursue now that this has been demonstrated.

This week in cond-mat

Where did summer go? Several interesting things on the arxiv recently. Here are two from this past week that caught my eye.

arxiv:0806.3547 - Katz et al., Uncollapsing of a quantum state in a superconducting phase qubit
This paper first appeared on the arxiv last year, and it made it onto this week's mailings because the authors uploaded the final, published version (PRL 101, 200401 (2008)). This experiment is important as a technical development in the quantum computing community, since the ability to restore some measure of purity to a quantum state after that state gets entangled with some environmental degrees of freedom could be very useful. It is also a great example of why simplistic thought experiments about wavefunction collapse are misleading. A better way to think about this experiment is in (an imperfect) analogy to spin echo in nuclear magnetic or electron spin resonance. In a spin echo experiment, an ensemble of spins is set precessing, and the evidence of their coherent precession gets smeared out as a function of time as the spins "dephase" (get out of sync because of perturbing interactions with other degrees of freedom). However, in these echo experiments, a properly defined external perturbation (a pulse of microwaves) can flip all of these spins around, so that the ones originally going ahead of the pack are put in the back, and the slow ones are put in the front. The spins rephase, or become coherent in their motion again. The authors do something rather analogous here using superconducting devices. Nice!

arxiv:0908.1126 - N. P. Armitage, Electrodynamics of correlated electron systems
I'm not promoting this just because Peter sometimes comments on this blog. This is a great set of lecture notes from a 2008 summer school at Boulder. These notes provide a very good, pedagogical overview of how electromagnetic radiation interacts with the electronic systems of real materials, and how one can use measurements ranging from the THz (mm-wave) to the ultraviolet to infer details of the electronic properties. These sorts of reviews are a wonderful feature of the arxiv.

LHC and the hazards of Big Science

This article in the NY Times about the LHC's current problems was interesting. To be fair, the LHC is an incredibly complex undertaking. Making high quality superconducting joints between magnets is a complex business, involving spot-welding annoying materials like niobium-titanium alloys. Testing is a real pain, since room temperature measurements can't always identify bad joints. Still, they clearly didn't design an optimal testing and commissioning regimen. I'm sure they'll get these problems licked, and great science will eventually come out of the machine - it's just a question of how long that'll take. I do wonder, though, if stories like this are, in part, a consequence of their own publicity machine, which has been hammering the general public relentlessly for years about how the LHC is going to unlock the secrets of the universe.

This situation is a prime hazard of Big Science. One thing I definitely like about condensed matter and AMO physics, for example, is that you are often (though not always) in control of your own destiny. Progress is generally not dependent on 1000 other people and 500 vendors and suppliers, nor do you have to hope that some launch schedule isn't screwed up by a hailstorm. The general public needs to know that really good science can be done on a much smaller scale. While the LHC outreach effort is meant to inspire young people into pursuing physics, situations like these delays and the accompanying reporting probably frighten away more people from the field than they attract. If a layperson ends up with the impression that all physics is hugely expensive, and even then doesn't work right, that's not a good thing.

Chemistry vs. Physics blogging

Interesting. The pseudonymous Kyle Finchsigmate at The Chem Blog just gave some stats about his blogging. He gets something like 6000 unique visitors a day, while I get about 150. Admittedly, we have rather different styles (pseudonymity makes it easy to write with more, umm, gusto, and to slam lousy papers openly, both of which probably make his blog have more broad appeal), and there are a lot more chemists out there than condensed matter physicists. Still, the factor of 40 is a bit intimidating.

More musing about phase transitions

Everyone has seen phase transitions - water freezing and water boiling, for example. These are both examples of "first-order" phase transitions, meaning that there is some kind of "latent heat" associated with the transition. That is, it takes a certain amount of energy to convert 1 g of solid ice into 1 g of liquid water while the temperature remains constant. The heat energy is "latent" because as it goes into the material, it's not raising the temperature - instead it's changing the entropy, by making many more microscopic states available to the atoms than were available before. In our ice-water example, at 0 C there are a certain number of microscopic states available to the water molecules in solid ice, including states where the molecules are slightly displaced from their equilibrium positions in the ice crystal and rattling around. In liquid water at the same temperature, there are many more possible microscopic states available, since the water molecules can, e.g., rotate all over the place, which they could not do in the solid state. (This kind of transition is "first order" because the entropy, which can be thought of as the first derivative of some thermodynamic potential, is discontinuous at the transition.) Because this kind of phase transition requires an input or output of energy to convert material between phases, there really aren't big fluctuations near the transition - you don't see pieces of ice bopping in and out of existence spontaneously inside a glass of icewater.

There are other kinds of phase transitions. A major class of much interest to physicists is that of "second-order" transitions. If one goes to high enough pressure and temperature, the liquid-gas transition becomes second order, right at the critical point where the distinction between liquid and gas vanishes. A second order transition is continuous - that is, while there is a change in the collective properties of the system (e.g., in the ferro- to paramagnetic transition, you can think of the electron spins as many little compass needles; in the ferromagnetic phase the needles all point the same direction, while in the paramagnetic phase they don't), the number of microscopic states available doesn't change across the transition. However, the rate at which microstates become available with changes in energy is different on the two sides of the transition. In second order transitions, you can get big fluctuations in the order of the system near the transition. Understanding these fluctuations ("critical phenomena") was a major achievement of late 20th century theoretical physics.

Here's an analogy to help with the distinction: as you ride a bicycle along a road, the horizontal distance you travel is analogous to increasing the energy available to one of our systems, and the height of the road corresponds to the number of microscopic states available to the system. If you pedal along and come to a vertical cliff, and the road continues on above your head somewhere, that's a bit like the 1st order transition. With a little bit of energy available, you can't easily go back and forth up and down the cliff face. On the other hand, if you are pedaling along and come to a change in the slope of the road, that's a bit like the 2nd order case. Now with a little bit of energy available, you can imagine rolling back and forth over that kink in the road. This analogy is far from perfect, but maybe it'll provide a little help in thinking about these distinctions. One challenge in trying to discuss this stuff with the lay public is that most people only have everyday experience with first-order transitions, and it's hard to explain the subtle distinction between 1st and 2nd order.

The Anacapa Society

Hat tip to Arjendu for pointing this out. The Anacapa Society is a national society that promotes and encourages research in computational and theoretical physics at primarily undergrad institutions. They've had a good relationship with the KITP at UCSB, and have just signed an agreement that gives them a real home at Amherst College. (I've had a soft spot for Amherst since back in the day when I was struggling to decide whether to do the tier-1 research route vs. the undergrad education trajectory.) The nice thing about promoting this kind of research is that, particularly on the computational side of things, well-prepared undergrads at smaller institutions can make real contributions to science without necessarily the expensive infrastructure required for some hardcore experimental areas.

Cute optics demo

This youtube video is something that I'll have to remember for a future demo. It shows that cellophane tape makes (1-side) frosted glass appear to be transparent. Quite striking! The reason this works is pretty straightforward from the physics perspective. Frosted glass looks whitish because its surface has been covered (by sandblasting or something analogous) with little irregularities that have a typical size scale comparable to the wavelengths of visible light. Because of the different in index of refraction between glass and air, these little irregularities diffusely scatter light, and they do a pretty equitable job across the visible spectrum. (This is why clouds are white, too, by the way.) By coating the glass intimately with a polymer layer (with an index of refraction closer to the glass than that of the air), one is effectively smoothing out the irregularities to a large degree. As far as I know, this is essentially the same physics behind why wet fabrics often appear darker than dry fabrics. Some of the apparent lightness of the dry material is due to diffuse scattering by ~ wavelength-sized stray threads and fibers. A wetting liquid acts as an index-matching medium, effectively smoothing out those inhomogeneities and reducing that diffuse scattering.

Phase transitions and "mean field theory"

One truly remarkable feature of statistical physics (and condensed matter physics in particular) is the emergence of phase transitions. When dealing with large numbers of particles one often finds that, as a function of some parameter like temperature or pressure, the whole collection of particles can undergo a change of state. For example, as liquid water is warmed through 100 C at atmospheric pressure, it boils into a vapor phase of much lower density, even though it is still made up of the same water molecules as before. Understanding how and why phase transitions take place has kept many physicists occupied for a long time.

Of particular interest is understanding how microscopic interactions (e.g., polar attraction between individual water molecules) connect to the phase behavior. A classic toy model of this is used to examine magnetism. It's a comparatively simple statistical physics problem to understand how a single magnetic spin (in real life, something like one of the d electrons in iron) interacts with an external magnetic field. The energy of a magnetic moment is lowered if the magnetic moment aligns with a magnetic field - this is why it's energetically favorable for a compass needle to point north. So, one does the statistical physics problem of a single spin in a magnetic field, and there's a competition between this alignment energy on the one hand, and thermal fluctuations on the other. At large enough fields and low enough temperatures, the spin is highly likely to align with the field. Now, in a ferromagnet (think for now about a magnetic insulator, where the electrons aren't free to move around), there is some temperature, the Curie temperature, below which the spins spontaneously decide to align with each other, even without an external field. Going from the nonmagnetic to the aligned (ferromagnetic) state is a phase transition. A toy model for this is to go back to the single spin treatment, and instead of thinking about the spin interacting with an externally applied magnetic field, say that the spin is interacting with an average (or "mean") magnetic field that is generated by its neighbors. This is an example of a "mean field theory", and may be solved self-consistently to find out, in this model, the Curie temperature and how the magnetization behaves near there.

Mean field theories are nice, but it is comparatively rare that real systems are well described in detail by mean field treatments. For example, in the magnetism example the magnetization (spontaneous alignment of the spins, in appropriate units) goes like (1-T/T_C)^1/2 at temperatures just below T_C. This is not the case for real ferromagnets - the exponent is different. Because of the nature of the approximations made in mean field theory, it is expected to be best in higher dimensionality (that is, when there are lots of neighbors!). Here's a question for experts: what real phase transitions are well described by mean field theory? I can only think of two examples: superconductivity (where the superconducting gap scales like (1-T/T_C)^1/2 near the transition, just as mean field theory predicts) and a transition between liquid crystal phases. Any others?

The elevator message

I had a conversation today that made me think about the following. These days we're told countless times that it's essential for a scientist to have an "elevator message". That is, we need to be able to describe what we're doing in a pitch accessible to a lay person ideally in something like a single sentence. Some people have a comparatively easy time of this. They can say "I'm trying to cure cancer", or "I'm trying to solve the energy crisis", and have that be a reasonable description of their overarching research goals. Condensed matter physicists in general often have trouble with this, and tend to fall back on things like "My work will eventually enable faster computers" or "...better sensors". I'm all in favor of brief, accessible descriptions of what scientists do, but there are times when I think the elevator message idea is misguided. Not every good research program can be summed up in one sentence.

In the case of my group, we are trying to understand the (electronic, magnetic, and optical) properties of matter on the smallest scales, with an eye toward eventually engineering these properties to do useful things. It's basic research. Sometimes we can test existing theoretical ideas or address long-standing questions; sometimes, because we're working in previously unexplored regimes, we find surprises, and that can be really fun. I know that this italicized section is more sophisticated and therefore less pithy than "it'll give us faster computers". Still, I feel like this longer description does a much better job of capturing what we're actually doing. Our work is much more like puzzle-solving and exploring than it is a focused one-goal pursuit. I don't think that this means I lack vision, but I'm sure others would disagree.

On a separate note: Thanks, Arjendu, for pointing me to this, Microsoft Research's hosting of a series of Feynman lectures at Cornell in 1964. Very cool, even if I had to install MS's plug-in for the video.

We need more papers like this.

Somehow I had missed this paper when it came out on the arxiv last November, but I came across it the other day while looking for something else in the literature. It's all about the challenges and hazards of trying to measure magnetization of either tiny samples or those with extremely small magnetic responses. Some of the cautions are rather obvious (e.g., don't handle samples with steel tools, since even tiny amounts of steel contamination will give detectable magnetic signals), and others are much more subtle (e.g., magnetic signatures from Kapton tape (due to dust! I learned about this one first hand a few years ago.) and deformed plastic straws (commonly used as sample holders in a popular brand of magnetometer)). Papers like this are incredibly valuable, and usually hard to publish. Still, I much prefer this style, writing a substantive, cautionary paper that is informative and helpful, to the obvious alternative of writing aggressive comments in response to papers that look suspect to you. The paper is so good that I'm even willing to forgive them their choice of font.

Figures and permissions - Why, AAAS?

Perhaps someone out there can enlighten me. For review articles, if you want to reproduce a figure from someone's published work, you are required to get permission from the copyright holder (e.g., APS for Physical Review, ACS for Nano Letters, etc.). As far as I can tell, the professional societies (APS, ACS) are cool about this, and won't charge you for permission. Even Nature, a for-profit magazine, does not charge for this if all you're doing is using a figure here and there. However, Science, run by the non-profit AAAS, wants to charge $31.25 per figure for permission to reproduce that figure in a review article. Why is Science doing this? Is this some attempt to recoup publication costs? Anyone got an explanation?

arxiv failure

It would appear that the arxiv is having some issues. Bizarrely, this seems to affect cond-mat, but not (for example) astr-ph. In cond-mat, asking for "recent" papers points you to October, 2008. Asking for "new" papers gets you things like:

New submissions for Wed, 8 Jul 09

Error with 0907.1092

Error with 0907.1096

Error with 0907.1111

Very odd. Hopefully this will be fixed soon. Come to think of it, this is the first problem I've seen like this in a decade of reading cond-mat.

This week in cond-mat

There have been a number of exciting (to me, anyway) papers on the arxiv this past week. One in particular, though, seems like a neat illustration of a physical principal that crops up a lot in condensed matter physics.

arxiv:0906.5206 - Tanda et al., Aharonov-Bohm Effect at liquid-nitrogen temperature: Frohlich superconducting quantum device

There are several examples in condensed matter physics of "special" (I'll explain what I mean in a second) electronic ground states that are "gapped", meaning that the lowest energy excited states for the many-electron system are separated from the ground state by an energy range where there are no allowed states. When I say that a ground state is special, I mean that it has some particular order parameter (or broken symmetry) that is distinct from that of the excited states. In this sense, a band insulator or semiconductor is not special - the many-body filled valence band states really don't have any different symmetries than the empty conduction band states. However, the superconducting ground state is special, with broken gauge symmetry (when compared to the normal metallic state) and a minimum energy (the gap energy) required to make any excitations (in this case, by breaking apart a Cooper pair). Fractional quantum Hall states are similarly gapped. The consequence of that energy gap is that the ground state can be very robust. In particular, the gap means that low energy (compared to the gap) inelastic processes cannot perturb the system, since there are no allowed final states around. This is one reason why it is possible to see macroscopic quantum effects in superconductors, as long as T is small compared to the gap.

The authors of this paper have decided to see whether such macroscopic quantum effects (detectable via quantum interference measurements analogous to the two-slit experiment) can survive in another gapped system. The distinction here is that the special state is something called a charge density wave (CDW), where the electronic density in a material (in this case tantalum trisulfide) spontaneously takes on a spatially periodic modulation. This gapped state kicks in at much higher temperatures than typical superconducting transitions. The authors have been able to measure quantum interference robustly in their device at liquid nitrogen temperatures, which is pretty impressive, and there is reason to believe that this could be extended to room temperature. The sample fabrication is very impressive, by the way. You can't just take a sheet of this stuff and punch a hole in it to make your ring-shaped interferometer. Instead, you have to actually curl a sheet up into a tube. Neat stuff, and quite surprising to me. I need to read up more about CDWs....

A cool result

There's a new asap paper in Nano Letters that is very slick. There has been a lot of interest in the last few years in plasmonics - the controlled manipulation of plasmons, collective oscillations of the electronic fluid in metals. Plasmons are pretty remarkable excitations. Because they involve displacement of the electron density, they necessarily result in local electric fields near metal surfaces (useful for optical antenna sorts of effects), and they can (under the right circumstances) couple efficiently to electromagnetic radiation. Plasmon response to light can be very pronounced, ranging from resonant scattering or absorption (for example, why certain types of glass are colored) to more complex dispersive effects, including negative (effective) indices of refraction. Plasmons are also responsible for helping light to transmit through sub-wavelength apertures. However, as far as I know, until now none of these effects have depended in any significant way on the angular momentum of light. In this new result, researchers from the Technion in Israel have designed aperture structures that can couple selectively to left- or right-circularly polarized light. The trick is in finding a situation such that the angular momentum of the light (essentially the spin of the photons) couples selectively to plasmon modes in the apertures that have matching orbital angular momentum. I don't fully understand how the two experiments described in the paper work, but it's a neat, clever result.

Four items

Four items, and a physics post later in the week.

• Is "just-in-time" supply chain management truly the work of the devil, or merely incredibly annoying? We've had a problem with a gate valve on a piece of cleanroom equipment at my institution, and the vendor (a) has no spare valves; (b) has no spare parts for the valves; and (c) says it'll take around 4 weeks to fab a replacement valve. Now, I understand why a business wouldn't want a huge inventory sitting on shelves, and that there are real fixed costs associated with inventories. Still, how hard would it be to have some spare parts, particularly when these things don't go bad when stored? I can tell you that it doesn't make me predisposed to ever buy anything from this supplier again. So, while it may be penny-wise, it sure feels pound-foolish for companies to alienate customers by having no backup supplies at all.
• Ahh, scientific publishing. Two folks from Cornell used an amusing computer program to generate a grammatically correct but completely nonsensical fake paper (pdf). They then got that paper accepted to an open-access journal, without the knowledge of the editor (!), with the strong implication being that this publisher was willing to publish literally anything as long as the authors are willing to pay the fees. Wonderful. I've suspected for a while (basically when a couple of publishers spammed me about being a contributing editor on journals I'd never heard of, back when I was a brand new assistant prof) that there are some shady practices out there.
• Also regarding scientific publishing, I was shocked and appalled (ok, not really, but certainly surprised) when I got the proofs of an article that we have coming out in Phys Rev B. Why? Because it was clear from the marked-up "author query" version of the manuscript that the AIP production office had converted our beautiful LaTeX manuscript into Microsoft Word format for editing. What is the world coming to?!
• Lastly, I was fortunate enough to receive a new iPod Touch as a gift. Anyone out there have suggestions for must-have apps?
  

The revolution will be twittered.

Not a physics post, but an observation. There is a major event going on in Iran right now - protests involving many thousands of people; rioting; the most political upheaval since the 1979 revolution. I hope that everything works out for the best - any country with a Supreme Leader needs a new governance structure, IMO. Anyway, twitter is being used as a major tool by the Iranian protesters. So much for my general perception that twitter was only for people more self-indulgent than bloggers (ahem.). It's fascinating and alarming to watch events unfold from halfway around the world, while CNN reports on things like Sarah Palin/David Letterman feuds. It's as though the "news" network has forgotten what real news is....

Nanoscale, the book

No, I have not compiled my blog postings into dead-tree format. Nor have I finished my textbook based on my graduate nanoscale physics course sequence. Instead, I wanted to point out this book, which is a cute volume with lots of computer-rendered pictures of crystal structures and the like. It's an admirable attempt to give the reader a sense of the atomic-scale composition of materials, along with brief, informative, often fun descriptions. While there are a few minor typos that seem to be caused by autocorrection run amok, the book remains entertaining and educational, with very well crafted illustrations. The book has its own website, too.