... well, for the physics world anyways.

Last week our latest paper was published in Physical Review Letter (PRL) and I promised to write more, though I wasn’t quite expecting to say this. Our letter was used as the cover article for that issue. So if you go look at Vol 103, Issue 16, then you’ll see two little hexagons at the top of the page. That’s from our article and is part of Figure 1.

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Surface X-Ray Speckles: Coherent Surface Diffraction from Au(001)
M. S. Pierce, K. C. Chang, D. Hennessy, V. Komanicky, M. Sprung, A. Sandy, and H. You

Published 15 October 2009
165501  Full Text: PDF (526 kB)  | Buy Article

We present coherent speckled x-ray diffraction patterns obtained from a monolayer of surface atoms. We measured both the specular anti-Bragg reflection and the off-specular hexagonal reconstruction peak for the Au(001) surface reconstruction. We observed fluctuations of the speckle patterns even when the integrated intensity appears static. By autocorrelating the speckle patterns, we were able to identify two qualitatively different surface dynamic behaviors of the hex reconstruction depending on the sample temperature.

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First, I am ecstatic about this news. In fact, I’m ecstatic just to have another paper published in PRL. Making on the cover is something else! This is my third PRL, but it’s significant for another reason as well. This is solely from my work at Argonne and, while a “coherent x-ray scattering experiment,” it is significantly different from my first two which came from my thesis work. It’s an important step to show that my publication record and potential is not totally tied to just one thing (be it thesis or post-doc). My choice to switch fields so drastically from my thesis work has been a hard decision to bear (both for me as well as those that I work with). It was a gamble, but I believe it has paid off.

Now about that figure. I’ve posted similar versions of it before on this website to help explain some of the features of the surfaces we study.

The figure is a representation of the two possible orientations of the surface atoms on a gold crystal cut along one of the cubic directions. Instead of maintaining the underlying face-centered-cubic structure, the surface atoms rearrange (reconstruct is the term we use) into a hexagonal pattern. Now, if you think about it, you there’s not a single preferred way to lay down a hexagon over a square. Cut out a square and hexagon and see for yourself. If you try to align two of the hexagon sides with two of the square sides, you’ll be left with points of the hexagon protruding over the other two sides of the square. Now, rotate the hexagon by 90 degrees (1 quarter of a turn). The hexagon sides that used to overlap will now have points over the square edges and the sides which used to be points will now be aligned with the square. So you can see, there are two equivalent ways to lay down hexagons over squares. Nature is no fool and so naturally our crystals contain surface regions with each of the different orientations. In a nutshell, that’s what the figure is meant to show (or remind the scientists reading the article).

Perhaps it’s easier to see if I rotate the entire figure by 45 degrees.

The only detracting thing here is that all of the above is not new. In fact, it’s 30 years old more or less. What we did was to observe changes in those hexagons in a clever way. But we were not establishing the existence of the hexagons.

In truth I did lobby a bit for a different figure. We were informed earlier in the week that our paper was being considered for the cover art. “Considered” is still a long shot and I was gratified to have the article be up for consideration, but wasn’t hoping for too much. They requested high resolution copies of our Figure 1 (which I sent). But I also included higher quality versions of some of our other figures which I thought were quite aesthetically pleasing, but also show cased some of the newer results. Figure 1 was just too pedagogical for my tastes. But in the end I was only willing to push so much for fear that it would remove our slim chance.



This is the basic figure I was lobbying to be modified for use. Right now it still has too many labels and numbers to be cover art, but ignore those for a second. The vertical “component” of each is collection of speckles. Where a speckle is bright, the plot is red. Where it is dim (or absent), the figure is blue. The horizontal direction in each of the 3 plots is time. So, if a speckle is bright (red) and unchanging with time, then there will be a red streak in the horizontal direction. If the speckle is changing, then the red will change to some other color and other places, not previously bright will begin to show red. If it’s rapidly changing then there will be only short periods of persistence of the speckles. That’s what you see in the 3 figures. What could be labeled, hot, hotter, and really hot. On the left the speckle is not changing very rapidly. On the right you see very rapid fluctuation. The middle is well, somewhere in the middle.

Anyhow, get rid of the numbers, massage them a bit, and you’d have an aesthetically pleasing image that contains the core of the new science that we did.

That aside, figure 1 is a nice graphic and I’m of course very happy they decided to use it. The “atoms” are raytraced using the open-source POVRAY package. In fact, coupling the graphical rendering power of POVRAY with the mathematical ability of Matlab can make for some very beautiful (and complicated) images. By ray-tracing standards my little pictures are not anything special. In fact, compared to some of the computer rendered artwork out there, these images are plain bland. However, they’re still pretty in their own right, and have some content to them. They’re also much nicer than any of the normal simple chemical rendering programs out there. So thank you to the people that wrote POVRAY.

Wow! I am simply giddy at the moment.

Our new paper has just been published in Physical Review Letters : Surface X-Ray Speckles: Coherent Surface Diffraction from Au(001).

This is just wonderful news. I’ll write more later about it, but for now I’m just giddy.

We’ve had wonderful news this evening! We have new bouncing baby fishes! In fact we have two different broods, one of Rusty Cichlids (Iodotropheus sprengerae, Lavender mBuna) and a Red-Empress Hap (Protomelas taeniolatus) brood.

A few weeks ago we noticed one our rusty cichlids was holding eggs. They are mouth brooders, so after a pair spawns, the female collects the fertilized eggs and holds them in her mouth for several weeks. For this entire time, the female will not eat. The rusty cichlids are particularly important for a couple of reasons. They are a threatened species in the wild and we got them intentionally with the idea of breeding them. We started with 1 male (let him get old enough to really be a male) and then slowly added other rusty cichlids from different sources. He’s the biggest by far and as such is the only one that gets to breed. While we’ve been told he is F1 (first generation captive breed, meaning his parents are wild), there’s no real way to verify that statement and I don’t trust everyone anyways. Such as it is, we got him and subsequently several more in a way to make certain we had fish that while all the same species are not related.

And so we found one of the little females holding a few weeks ago. We waited a few days to do anything just to see if she would swallow the eggs (hey sometimes it takes practice. You try not eating for a month). During that time we noticed that a female red empress hap in the tank was also holding (and her male was being very ornery). We decided to move both females to a small breeding tank. For the past 3 weeks they’ve been holding the eggs, coming out to see us, but refusing any food. However, this evening Kerri found the Rusty had released her fry! We removed her, feed her in isolation for a bit and then returned her to her normal tank. At the same time we decided to got ahead and nab the other female to see if we could strip the eggs from her. To my surprise she then also released free swimming fry.

At this point both females are recovering and we’ve got around 35 fry in the breeding tank.




These are surprisingly difficult to photograph. The picture above shows mostly red-empress fry. Since they are younger, the yolk sac is still visible and large on some of them. They look as thought they’ve got giant bellies. There’s maybe one rusty in that picture too.




Here there is more variety (more Rusties), but it’s not quite as focused. Anyhow, the little Rusty cichlids look just like miniature adults. They’re already fully orange brown and are quite active. Kerri even saw a couple of them facing off and locking jaws. We’ll be starting them on a diet of tiny brine shrimp and crushed flakes soon. Hopefully the two sets of fry can be raised together (similar conditions, diet, etc).

For some reason the little fish seem to like one corner in particular of the tank despite there being several rocks and some fake plants in the tank.

We’ll try our best to raise both broods and then bring them to a couple of the local fish shops. Again, while it’s nice that the Red-Empress spawned, we’re most excited about the Rusty cichlids. Aside from being just a beautiful fish (and relatively mild tempered for an African cichlid), they are threatened in the wild. They are only found in very limited areas in Lake Malawi. As such, we’ve very happy to have a diverse breeding colony of them.

Welcome to another installment of “Michael likes to make graphs, plots, and figures.” Here’s one of my latest:

It’s latest in an unusual sense. It’s not the research work that I’ve been doing recently and is not even data taken in the last couple of years. But it is data left over from my thesis work. We’ve had a paper that’s been, well... languishing, for some time now. However, there’s been a nice little lull over the past weekend and I’m very excited to finish off this paper.

So what are you looking at above? Basically our friends Olav and Eric grew a series of 6 magnetic samples with increasing roughness (disorder), but otherwise identical. The higher the pressure during sample growth, the more disorder in the samples. On the left you can see reflectivity curves (literally measuring x-rays reflected specularly from the sample) for a few of the samples. The two low pressure (3 and 7) show nice fringe structure, well defined peaks, and slower decay. The two shown high pressure samples show no (or little) fringes, weak peaks, and quick decay in the scattering. All of that tells us some of properties as the disorder increases. On the top right is a plot of the magnetic domain structure imaged using a magnetic force microscope for all 6 samples. For the lowest disorder samples there is a well defined domain structure and for the high pressure samples the domains get more disordered. The bottom right is a plot of the surface roughness of the samples. Those data points are actually determined from the plot on the right hand side.

Actually the above figure is one of the “background” figures that we use to explain the basics of what went into the experiment. So there’s not anything new in it. Nonetheless the figure came out nicely and I thought it deserved to be immortalized here.

Both the physics and chemistry Nobel prizes awarded this year are quite “close to home.”

The Physics Nobel was awarded Charles Kao, Willard Boyle, and George Smith for the developments in two different, though related, fields. Their work led to modern telecommunications and charge coupled device (CCD) cameras. Essentially they developed the necessary science to create fiber optics and the “electronic eye.” There work is fundamental to our ability to do any sort of electronic imagining, regardless of the field of science or medicine. It’s also made your cell-phone cameras, USB cameras, digital cameras, and pretty much anything else like it possible. So, the next time you take a picture with your cellphone, thank Kao, Boyle, and Smith (among many others). The development of fiberoptics revolutionized our ability to communicate. There work has directly influenced your life.

Kao’s most important contributions are in developing fiber-optics. Until that point communication either had to be done through radio waves(or other electro-magnetic radiation) or with direct copper wires and electrons. Both radio communication and metal conductors have disadvantages as a communication medium. Communicating by electromagnetic radiation waves requires either “line of sight” between the two points or some pretty clever bouncing of signals (either low-tech by literally bouncing them off objects or the atmosphere, or high-tech via satellites). The old “copper wire” suffers from a different ailment, namely that it takes significant power, is slower than light, and it’s more difficult to “squeeze” information into the same “space” (bandwidth). Fiber-optics circumvents all of these disadvantages. Light can travel through the medium more quickly, with less signal loss, with greater information content, and go between any two points that you can run a cable across (not only that, but the material itself is relatively cheap).

Boyle and Smith made significant contributions to the development of electronic cameras. Ask yourself how your digital camera actually records an image. The fundamental components to a CCD camera are tiny pieces of semi-conductor that become charged when they adsorb light. The amount of charge on a piece of semi-conductor is the “brightness,” and can be measured directly by the circuitry in the camera. Each piece of semiconductor is a “pixel,” and when you’ve got enough pixels in a small area and the appropriate optics to focus an image, then you can create a digital picture.

It’s also worth noting that Bell Labs where Boyle and Smith (now very, very sadly essentially defunct) were employed has added another Nobel prize, bringing its total to 7 different physics prizes.

Needless to say that my research would not be possible without the CCD camera (though ours detect x-rays and not visible light) and I benefit enormously from the ability to transfer huge amounts of data (generated by the CCD cameras!).

The Chemistry Nobel prize was awarded to Thomas Steitz, Ada Yonath, and Venkatraman Ramakrishnan for their work in understanding the structure and function of ribosomes. While being very “wet” by my standards, the work is in practice quite similar to what I do, just on very different materials and systems. The ribosome is a “protein factory” that takes RNA and aminoacids and turns them into proteins. It is a very large, complicated molecule compared to most of what has been studied previously (in fact, I’m even sure it’s a molecule but more an assembly of molecules. anyhow, I’ll be honest about my ignorance here). What makes it “close to home” is that the tools they used to explore the ribosome were modern x-ray light sources, and in large part, the Advanced Photon Source here at Argonne Lab. They’ve published around 60 papers of work done at the lab.

They use the x-rays to explore ribosomes. We use different beamlines at the same light source to study the surfaces of metals and metal oxides. It’s not the first Nobel prize awarded for work done at Argonne, but it’s always very exciting to see recognition of the great work that can be done here.

... as measured by human contact.

The world seems a bit smaller today. Which, while not quite as much the world traveler as Kerri is, I have lived in some pretty different places. Something very odd happened when I was looking at Stephen Hawking’s webpage a few days ago. Something I really didn’t expect.

I noticed a name that struck me as... unusual, Chamblin. When I was very young (5-8ish) I had a friend whose last name was Chamblin. I’ve not seen him in let’s say at least 25 years. However, it’s not a name I’ve seen spelled that way anywhere else and I suppose for some reason when I saw it written it struck me as kind of odd. So there it is on the Cambridge University website along with Stephen Hawking.

Now, the little neurons in my head (overworked and deficient to be sure) probably would not have made any connection were it not for something I’d heard uttered while I believe I was an undergraduate. I remember my mother saying that, “do you remember your friend? His older brother has gone on to study mathematics in England.”

Mathematics, England, and Chamblin... that statement hit enough things in my head while looking at Hawking’s publications to wonder, could it possibly be that this Chamblin and my friend could be related(or even his brother)? I shelved the thought last week as I got busy with some other work, but it’s come back into my consciousness a few more times since then. Today I had the thought while sitting at a computer and looking for something else to do while one of my programs finished running.

The story, at least the start of it, is that in fact the Andrew Chamblin, theoretical physicist and Andrew Chamblin, older brother to my friend, were one in the same. I say “were” because tragically he passed away 3 years ago.

It is a very odd feeling... Amarillo TX is a pretty small town, especially when one considers the mentality of many of the people there. I’d more or less assumed that I’d been about the only person to leave Amarillo for a career as an academic/research physicist, at least during my own years. What’s more is as soon as I’d made the connection that indeed there was someone else that had come from the same place, going out into the wide-wide-world doing physics, that the connection was broken. For the shortest moment I knew that there was someone that would be really fun to contact. Someone perhaps to meet if we overlapped on a holiday visit some winter. Someone that had traveled the same road out of Amarillo and into the world of physics.

It’s actually not the same road and I’m being a little too liberal with my nostalgia. Andrew Chamblin excelled early in school and showed a bright future very early on. I on the other-hand experienced a terrible education by the same school district, gaining the distinction of “mentally retarded” during the 2nd grade and having it follow me through high-school. Andrew Chamblin went to Rice, then Oxford, and then Cambridge directly from Amarillo after high school. My high-school guidance councilor recommended that I “find a good trade school,” and there was some mention that I could make a decent plumber. My path to physics was a bit circuitous. Hmmm.... I’ll be nice and say I took the scenic route. It was only after attending community college that I found people that inspired me to do well (and even since, throughout the years, my academic path has been somewhat unusual).

What is more is that I may well have seen Andrew Chamblin during my adult life, perhaps passing him in a hallway though without realizing our common geographical origin. In fact, had I not decided to switch from theoretical physics to experimental condensed matter physics I almost certainly would’ve met him (again). He collaborated with several of the theorists at the University of Washington while I was a graduate student there.

This has been a rather unusual half an hour.

I only have only a couple sets of memories of Andrew Chamblin. Even then they’re not of him as “Andrew Chamblin”, but only the older brother of my friend. There’s nothing insightful to my memories, just typical things of kids growing up, one from a birthday party and one of running down an alley.

I’ve not spoken to my friend nor anyone from his family in years. I’m not even sure if he’d remember me. However, I think it’s worth tracking him down just to see where this goes.

A short article Héctor G. Riveros and Julián Betancourt was published in The Physics Teacher this month that is quite fun. The paper centers on what happens when compasses interact.

Basically, if the magnetic fields are strong enough and you bring them close enough together, then compasses will influence each other. Ok fine, that’s not so interesting in and of itself until you make use of it. They arrayed lots of compasses together in a hexagonal packing arrangement, all as close as possible to each other.


On the top, the compasses are responding to an external magnetic field.





What’s really cool is when they take the external magnetic field away as you see on the right hand side (or bottom). The compasses form magnetic domains!

This is a really beautiful demonstration of how magnetic materials behave and I bet would make a great tool for teaching. I would not have thought that the magnetic fields produced by individual compasses would be sufficient to cause this kind of interaction.

Now, the next step is to see if you could add temperature to the mix. Given that we’re approximating spins as compasses, then it might be possible to approximate temperature as some sort of small random motion. Take each compass, put it on a small spring (or place small springs between each), and then shake the how ensemble. Eventually the shaking should be enough to cause the compasses to lose their orientation and the magnetic domains will disappear. Voila, you’ve got a Curie temperature.

Yesterday was the end of an era. Professor Stephen Hawking has resigned the Lucasian Chair of Mathematics.

Thankfully he is not resigning the post due to complications from his illness. Rather it is apparently academic tradition to step down from that post at the age of 67. However, I think it worth taking a few moments to pause and contemplate his story.

Hawking is one of the most recognized faces in physics, if not all of science. Many times I’ve asked students to name a few physicists and Hawking is always among those listed (though disappointingly sometimes as ``that guy in the wheelchair” ).

Hawking suffers from amyotrophic lateral sclerosis, or commonly called just ALS*. He was diagnosed while very young, still in school and unmarried at the time. The disease is usually a death sentence with a 10 year mortality rate of over 80%. Despite this illness, he has been very productive in science and one of its most inspirational personalities.

Hawking’s work usually deals with cosmology and astrophysics, the universe on a very, large scale. He has made fundamental contributions to our understanding of black-holes, the evolution of the universe, and the properties of the universe today. He has authored nearly 200 articles, books and letters on various subjects in theoretical physics. All of this, while having to overcome more difficulty than many of us can understand.

I first came across Hawking’s name and work as a kid when I found a copy of “A Brief History of Time.” For many years that book (and a later one by Weinberg) formed most of my understanding of modern theoretical physics and cosmology. I remember reading it again while in high-school, perhaps understanding a little more from it, and greatly thinking how cool it would be to be a physicist. At the time it wasn’t quite enough to push me to the realization that perhaps I actually could study physics. It was however a step in that direction from my early life.

So let us wish Prof. Hawking well, let us be inspired by his story and work, and let us try to meet adversity with dignity in our own lives when it arises.

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*it’s unfortunate that the acronym is also shared by the Advanced Light Source where I did my thesis work. I have a baseball cap from the ALS with the letters, a logo depicting the synchrotron, and the full name spelled out in smaller type. I’ve been asked several times why I’m wearing a hat with the name of a disease by people that don’t bother to read the smaller words below the letters ALS. sigh...