X-ray diffraction patterns reveal the orientation of fat crystals. The distribution and directionality of these crystal nanostructures (parallel to the shear field in C, randomly arranged in D) affects the flavor and texture of foods.

From butter in croissants to cocoa solids in chocolate, edible fats pack a flavor punch that delights like no other macronutrient we consume. Fats are the most energy dense macronutrients, providing more than twice as many kilocalories per gram as proteins or carbohydrates, which may be the reason we’ve developed a taste for them. Fats are an efficient method of fueling a surviving species, but what gives them their oh-so-delicious disposition?

The sensory characteristics of fatty foods come largely from the physical makeup of crystals that form within the nanoscale structure of fat molecules. As explained in a review paper by Alejandro Marangoni published in Soft Matter, fats are made up of fractal-like crystalline structures, which give rise to properties such as flavor, texture, meltability, and mouthfeel.

Fats are composites called triglycerides or triacylglycerides (TAGs) made up of one glycerol molecule and three fatty acid chains. The physical properties of these fatty acids and the positions they take on the glycerol molecule give rise to changes in the foods that contain them. For example, the length of fatty acid chains affects a fat’s melting point. Saturated or longer chain fatty acids, like those in milk fat or cocoa butter, will have higher melting points than triglycerides with mostly shorter or unsaturated fatty acid chains, such as olive oil. That’s why at your dinner table, the salad dressing is liquid, but the butter dish holds a solid stick.

Changes in flavor and texture of fats can also come down to which fatty acids sit where on the glycerol molecule. Milk fat contains short-chained butyric acid, which sits in the 3^rd position, while cocoa butter’s 2^nd position is populated almost exclusively by oleic acid.

Depending on how they are heated and cooled, triglycerides can crystallize into several forms. The resulting fractal-like crystalline structures give rise to flavor, texture, and meltability in foods like chocolate bars. Six different forms of crystal structure have been identified for cocoa butter. But only one form will turn out chocolate that tastes and feels good to eat.

The so-called Form V has a tuning fork structure to its crystals, which produces a melting range close to the temperature of the mouth. Chocolate manufacturers devote much effort to producing bars with this specific form of crystallization through the use of tempering, a process which heats and cools the chocolate to get a desired consistency.

If Form V crystals transform to Form VI, the chocolate will have a higher melting point and the cocoa butter will coat the inside of the mouth, leaving a waxy sensation. Form VI crystals can also bloom into  large, visible crystals, transforming a chocolate bar from a silky melt-in-your-mouth treat into a rough, white, waxy snack.

Marangoni and his collaborators have used x-ray diffraction at the National Synchrotron Light Source to categorize the many facets of fat crystals:

“At the mesoscale level (length scales within the micrometer range), we can witness a very diverse assortment of crystal habits – spherulites, needle-like crystals, microplatelets, disordered crystal aggregates, spherical crystal aggregates, fractal-like aggregates, and even some morphologies that defy proper description.

Despite the wide variety of crystal morphologies, they all share some common attributes: (1) the structures are awe-inspiringly beautiful when viewed under a polarized light microscope and (2) the crystalline mass in a network of these crystals is distributed in a fractal fashion.”

The discovery and characterization of these nanoplatelets adds to the knowledge upon which the food industry bases its design and engineering of food materials. Understanding how the physical chemistry of fats affects the way foods taste and feel could also potentially be useful when trying to curb the excessive consumption of fat-rich foods, writes Marangoni.

With close to 35% of the U.S. adult population and 20% of U.S. children identified as clinically obese, and the incidences of Type II diabetes and cardiovascular disease on the rise, the challenge for food engineers is to produce low-calorie foods containing fewer ‘bad fats’ while retaining many of the quality characteristics historically associated with a particular food.

Where I work, we slam together small things to break them into even smaller things until we have the smallest things possible. This is how we know what matter is made of. We gave names to the smallest things in matter like “up”, “down”, “strange”, “top”, and “bottom”. Each of those things can be either matter or not-matter and can have three types. We use the name of a different color, either red, green, or blue for each type. So we can make a red-up small thing and that red-up-thing can come together with a green-up-thing and a blue-down-thing. But those small things can never be alone. They can’t escape their groups. They are held together by a strong force.

The small things come in groups of two or of three. The groups of three have to have all three colors, like a red-up with a blue-up, and a green-down. The groups of two have to be matter with not-matter like a red-up and a not-red not-up. Sometimes the small things can change groups and new ones can come and go in pairs: a small matter thing and its small not-matter friend thing can pop out of space.

We are made of lots of groups of either up-things, up-things and down-things, or up-things, down-things, and down-things. That’s up, up, and down grouped together, or up, down, and down grouped together. These two little groups are at the heart of almost all the matter we see.

What we really like to do is make big groups of these small things and make them as hot as we can. Really hot. More than ten hundred hundred times hotter than the sun. We do this by slamming four hundred up, up, down, and up, down, down things together all at the same time. When we do this, they all become very hot and new small matter and not-matter things are made out of this thick hot stuff. The new small things are the same number of matter and not-matter. Light comes out of the thick hot stuff too and we can tell how hot the stuff is from the color of the light.

Usually, the little up and down things can’t escape their groups. The field that keeps them together is very strong. But when the thick hot stuff is hot enough, then the little up and down things escape from their groups and become free for a little time. Eventually the thick hot stuff grows and cools until the little things start to stick together again into groups. Those groups fly away until the thick hot stuff is gone. We catch the light and the little groups as they come from the thick hot stuff. By studying how they came out of the thick hot stuff, we learn what the thick hot stuff was like. We also learn about the strong force that holds the groups together.

We found that the thick hot stuff is so thick it makes all the little things move together, dragging on the faster ones, and pulling on the slower ones. It’s a lot like water but not like air. The thick hot stuff we make where I work is the same as what was in all of space one hundred, hundred, hundred, hundred, hundred years ago when time had just begun.

I think I have a cool job! Please tell the people with money to keep letting me do it and I’ll keep telling you about it and using what I know to help everyone as much as I can.

You can also check out Paul talking about his research at RHIC in this video, where he isn’t limited to just those thousand most common words.

Understanding change at the top of the world so we’ll know what is going to happen later

When we drive cars and warm our homes we give out bad stuff that ends up in the air. The bad stuff in the air makes our world warmer, which is not good. Every year there is more bad stuff in the air, and our world gets a little bit warmer. Some people pretend this is not happening, they are wrong.

The green things that live outside suck up the bad stuff in the air that we give out when we drive our cars and use it to grow bigger.  This is good because the green things are slowing down the warming of our world. When the green things die, tiny life forms in the ground eat them and return the bad stuff back to the air, this is normal.

Up near the top of the world it is really cold and lots of old dead green things have been stuck in ice in the ground for a very long time.  When the dead green things are stuck in ice the tiny life forms can’t eat them and the bad stuff is stuck where it can’t make the world hotter. When ice gets warmed up it starts to go away and when it does the tiny life forms in the ground can eat the old dead green things and give out the bad stuff that makes our world warmer. When the world gets warmer more ice goes away, more dead green stuff gets eaten and more bad stuff ends up in the air which makes the world get warmer, and so on. This could make the world get hotter very quickly, and we need to know more about it.

To help work out what might happen at the top of the world years from now we are trying to understand as much as we can about the way the ice goes away, the green things that grow outside and the tiny life forms that eat them.  When we know some more about this stuff we can put what we have learnt in a big thinking box (a bit like the one you are using to read this) and use it to tell us what will happen years from now.

Theoretical physicist Raju Venugopalan

We sat down with Brookhaven theoretical physicist Raju Venugopalan for a conversation about “color glass condensate” and the structure of visible matter in the universe.

Q. We’ve heard a lot recently about a “new form of matter” possibly seen at the Large Hadron Collider (LHC) in Europe — a state of saturated gluons called “color glass condensate.” Brookhaven Lab, and you in particular, have a long history with this idea. Can you tell me a bit about that history?

A. The idea for the color glass condensate arose to help us understand heavy ion collisions at our own collider here at Brookhaven, the Relativistic Heavy Ion Collider (RHIC)—even before RHIC turned on in 2000, and long before the LHC was built. These machines are designed to look at the most fundamental constituents of matter and the forces through which they interact—the same kinds of studies that a century ago led to huge advances in our understanding of electrons and magnetism. Only now instead of studying the behavior of the electrons that surround atomic nuclei, we are probing the subatomic particles that make up the nuclei themselves, and studying how they interact via nature’s strongest force to “give shape” to the universe today.

We do that by colliding nuclei at very high energies to recreate the conditions of the early universe so we can study these particles and their interactions under the most extreme conditions. But when you collide two nuclei and produce matter at RHIC, and also at the LHC, you have to think about the matter that makes up the nuclei you are colliding. What is the structure of nuclei before they collide?

We all know the nuclei are made of protons and neutrons, and those are each made of quarks and gluons. There were hints in data from the HERA collider in Germany and other experiments that the number of gluons increases dramatically as you accelerate particles to high energy. Nuclear physics theorists predicted that the ions accelerated to near the speed of light at RHIC (and later at LHC) would reach an upper limit of gluon concentration—a state of gluon saturation we call color glass condensate.* The collision of these super-dense gluon force fields is what produces the matter at RHIC, so learning more about this state would help us understand how the matter is created in the collisions. The theory we developed to describe the color glass condensate also allowed us to make calculations and predictions we could test with experiments.

Q. Have we seen hints that this color glass condensate exists at RHIC?

A. The very first experimental hints of color glass condensate came from early collisions of gold ions at RHIC in 2000 and more significantly later from collisions of light deuterium ions with the heavier gold ions. The precursor for the LHC phenomenon was seen around 2006 by scientists from RHIC’s STAR collaboration and subsequently PHENIX and PHOBOS. They all saw signs that particles streaming out of the collisions were correlated in an interesting and surprising way that showed up as a little bump on the graph—which we called a “ridge” because it looked like a mountain ridge. RHIC and LHC scientists now use sophisticated analyses to break down this signal into subtle wiggles of varying strengths, which can be further analyzed.

Key aspects of the wiggles in particle correlations could be explained by the “flow” of the hot dense matter produced when the ions collide—which we now know is a liquid-like plasma of quarks and gluons. But the surprising correlations also carried important information about the very earliest stages of matter formation, telling us about how gluons inside the colliding nuclei were creating this matter in the first place. The experimental information was consistent with the structures being generated by very strong gluon force fields at very short distances within the colliding nuclei—distances, predicted by gluon saturation, to be much smaller than the proton size.

The other strong piece of evidence for color glass condensate and gluon saturation we alluded to came from deuteron-gold collisions at RHIC in 2003, which do not create quark-gluon plasma. Certain particles streaming out in the “forward” direction, which the BRAHMS experiment was particularly designed to detect, were suppressed. That is, fewer particles with a given momentum were coming out at this particular angle than had been expected. It appeared that instead of the deuteron colliding and interacting with individual protons or neutrons in the gold nucleus, the smaller particle was hitting a bunch of protons simultaneously—or a dense field of gluons that acts like sticky molasses, making it harder for particles with a given momentum to be produced. PHOBOS, STAR and PHENIX also saw similar suppressions. This was a genuine prediction of the color glass condensate picture. Further experiments at RHIC by STAR and PHENIX during the 2008 deuteron-gold run drew out more details on particle correlation patterns predicted by the CGC theory.

Q. Do the “ridge” correlations have any significance aside from being possible indications of gluon saturation?

A. All the extra wiggles give you much more information about the structure of the flow—similar to the way astronomers have learned how subtle fluctuations in the cosmic microwave background radiation have left their fingerprints on the structure of the universe today. So the discovery of the “ridge effect” at RHIC led us to understand how the details of the initial conditions could lead to detailed variations in the flow of the matter produced at both RHIC and the LHC. To understand the properties of the quark-gluon plasma, we need to understand the initial conditions in detail.

In addition, the ridge may be imaging how strong force field lines behave between color charges, just as the distribution of iron filings around a magnet tells us about the magnetic flux around a magnet. If this analogy is borne out, that would be quite fundamental information about the strong force.

Q. How did these findings affect the development of theory?

A. There were still other possible explanations. That’s how science works. You need to accumulate more and more evidence. With each experimental finding, your model gets tested and refined. The next piece of data can fracture it. Some people try to disprove the model. Other people did a lot of work to refine the theory and make it stronger. So, we made some predictions about what we might see in future experiments, both at RHIC and the LHC. Thus far the heavy ion results from the LHC are consistent with our expectations.

Then, physicists from the CMS collaboration at the LHC, several of whom had worked on RHIC’s PHOBOS detector, used their experience with RHIC collisions to look for the same thing in proton-proton collisions at LHC—at 14 times the energy of the highest-energy proton-proton collisions at RHIC. Because of the higher energy level, they were able to look at extremely rare events where more than 110 charged particles come out in a single collision of two protons. By picking the events with lots of particles, they are essentially choosing the events where gluons are at their highest concentration in the colliding protons. In these rare events, they saw a tiny ridge, just like the one in gold-gold collisions at RHIC.

We spent half a year trying to understand this. We had developed this theory to predict and explain the ridge, but we thought it would only be observed in heavy ion collisions. But one of the theorists had predicted it would be there in proton-proton collisions at the LHC, and there it was. It couldn’t be due to quark-gluon plasma, because you don’t have a big enough system with proton-proton collisions. It had to be caused by gluon saturation, not flow of QGP. When we looked in detail at the LHC data, we were able to explain how these effects would change with various conditions, and we were able to explain things more quantitatively.

Then, when we knew they were going to be doing a very short preliminary run of proton-lead collisions at LHC in late 2012, we made some predictions about what would be seen there.

Q. What did the LHC proton-lead experiments observe? Did these data match your predictions?

A. So the LHC did these proton-lead collisions in a pilot run for just four hours, but they got an immense amount of data—sufficient to see something really dramatic. They observed the same ridge effect we had seen in gold-gold collisions at RHIC. These collisions were at much higher energy—25 times the energy of the deuteron-gold collisions at RHIC. So you get more of a gluon shockwave and a lot more particles coming out. There was enough data to do much more stringent tests of the idea of gluon saturation by looking for these correlations.

In proton-lead collisions they saw a bigger signal than in proton-proton collisions—about six times larger, even in collisions with the same number of particles coming out. The QGP flow explanation would have given you roughly the same signal size for the same number of particles produced, so that seems unlikely to me. Instead, to me, the result is sort of a “smoking gun” that they were seeing gluon saturation, because the bigger signal associated with the same particle number has to be due to more gluons at the initial stage, before the collision.

Q. What kind of further tests can you do?

A. The LHC will get a lot more data to test these ideas from the proton-lead run coming up this winter. Our models are so well detailed that a significant deviation would be able to knock down the model. That’s a good thing. A sign of a good model is that its predictions are sufficiently detailed and clear that it can be tested and even disproved, and one learns something in the process of doing so. If this idea of the color glass condensate is to fail, we would still learn a great deal from the failure of these ideas and we’d have to think deeply about what would replace it.

Even though our model works, there are a number of fundamental things we do not understand and are forced to model imperfectly. That is why we really need an electron ion collider, where we could collide electrons with heavy ions to probe the structure of the gluon fields directly. Though it may not have the tremendous energy reach at the LHC, an electron ion collider would allow us to explore the structure of matter with much greater precision. Subtle details of the properties of these extreme states of matter will give us a much more detailed picture, at the most fundamental level, about the structure of matter.

But in the meantime we can do some very interesting things at RHIC. One thing we’d like to do is collide polarized protons with heavy ions at RHIC. RHIC is the world’s only polarized proton collider, where the spins of the particles (and thus the quarks and gluons within) can be aligned in a chosen direction. When the spin of the polarized quarks and gluons in the proton interact with the gluon shockwave of the nucleus, the spin can be changed in different ways, depending on where the proton travels through the nucleus. Teasing out how the spin directions scatter off the internal gluons will help determine how dense that gluon field is at different parts of the nucleus.

These studies may help us understand how the orbital motion of the quarks and gluons within the proton contributes to proton spin. And they give us a different way of probing gluon saturation.

Q. What will confirmation of gluon saturation mean for physics—and the rest of us?

A. We are studying the structure of matter in its most fundamental form to learn something very deep about the structure of the proton, the most fundamental stable piece of matter we know of in the universe. We are going further than our wildest imagination ever thought possible. What we once thought of as fundamental objects are turning out to be much more complex. What is the origin of visible matter in the universe? It is the quarks and gluons. And we are probing the complexity of those particles as much as possible under the most extreme conditions.

We don’t really know where that will lead. It could open up completely new directions. 100 years ago, people were asking the same kinds of questions about electrons and photons, which we now use in so many ways in our everyday lives. If you had told them then that there would be something like our National Synchrotron Light Source (NSLS) accelerating electrons and using photons to look at atomic-level structures of things like superconductors, proteins, and ribosomes—to make better materials for energy applications or drugs to treat disease—they would never have believed you. But those are the kinds of advances that come out of in-depth studies of subatomic particles and their interactions.

People use diamonds to cut concrete, sharpen knives, and jumpstart wedding plans. As a member of Brookhaven’s Instrumentation Division, I’m on a team that found that diamond also fits the bill for new components in cutting-edge tools we are designing for upgrades for the Relativistic Heavy Ion Collider (RHIC), future linear-accelerator light sources, the National Synchrotron Light Source (NSLS), and NSLS-II– facilities that researchers from around the world are using to understand more about how the natural world works and how we can solve the nation’s energy challenges, too.

Why Diamond and Why Now?

Diamond is a crystalline form of carbon. Among all known natural materials, these crystals of carbon are the hardest and also the best at transferring heat. Diamond is also highly transparent to x-rays. Jewelers who tell you that no two diamonds are alike are right. If you want a diamond for a symbol of undying love, you might prefer a natural, unique diamond. When you need diamonds to produce 50 instrumentation devices, you don’t want the diamonds to be unique, you want them to be uniform. Less expensive synthetic diamonds — which have only become usable for our needs in the past 10 years — provide the uniformity we require and contain far fewer impurities than their natural counterparts.These extreme properties, and the availability of uniform crystals, have made diamond the material of choice for development of tools called electron amplifiers and x-ray beam monitors.

If you direct an electron beam through a diamond electron amplifier, you can increase the electron beam’s current more than 300 times. This kind of amplification would be particularly useful for linear accelerators, or linacs, including the energy recovery linac that is being developed for RHIC and eRHIC, the proposed electron ion collider. Diamond electron amplifiers would also benefit next-generation linac light sources.

In addition to its fantastic electrical and thermal properties, diamond has a low x-ray absorption rate. This combination means that diamond can be used in monitoring devices that can measure the position, flux, and timing of x-ray beams at NSLS and NSLS-II.

More to the Story Than Tools and ‘Bling’

Our work with these diamond-based tools illustrates the benefits of working at a multidisciplinary lab like Brookhaven. We’ve taken measurements to study diamond using 20 different beamlines at Brookhaven’s NSLS. Components for the beam position monitors have been fabricated at the Lab’s Center for Functional Nanomaterials. We were doing research with diamond for the Lab’s Collider-Accelerator Department when we recognized additional potential uses for Photon Sciences.

Realizing the different uses for these new developments occurred because the Instrumentation Division collaborates so well with our partners across the Lab. This reduces overlap and prevents redundant work, increasing our efficiency for discovery.

— John Smedley
Physicist, Instrumentation Division ]]> http://scienceblogs.com/brookhaven/2012/12/20/beyond-the-bling-diamonds-for-cutting-edge-tools/feed/ 0 http://scienceblogs.com/brookhaven/2012/12/03/xbox-x-rays-and-cutting-edge-optics/ http://scienceblogs.com/brookhaven/2012/12/03/xbox-x-rays-and-cutting-edge-optics/#comments Mon, 03 Dec 2012 20:08:40 +0000 Justin Eure http://scienceblogs.com/brookhaven/?p=406

Ever imagined that an Xbox controller could help open a window into the nanoworld of groundbreaking physics? Well, check out the video above.

Brookhaven scientist Ray Conley designed that one-of-a-kind machine to grow (through a technique called sputtering deposition) atomically precise lenses that can focus x-rays to within one billionth of one meter, revealing the internal nanoscale structure of materials such as electric vehicle fuel cells.

When tweaking his recipe for these multilayer Laue lenses (MLL), Conley used to have to manually enter commands into a computer to move a crucial transport car along tracks tightly sealed inside a vacuum chamber. This meant walking back and forth between the machine and computer, eating up time and sacrificing precision. Conley asked his assistant to look into getting an industrial joystick, but that  option proved to be too expensive.  So they went the life–hacking videogame route: a wireless Xbox controller.

The controller arrived one morning, and by that afternoon it was already programmed to interface with all of that custom machinery and complex computing. Conley now uses the Xbox controller to move the transport car at variable speeds based upon which analog joystick he uses, control plasma deposition with different buttons, and even get variable rumble feedback to let him know the speed of the transport car as it travels through the sealed chamber.

The completed MLLs will be deployed at Brookhaven Lab’s forthcoming National Synchrotron Light Source II, one of the world’s most advanced light sources, to address some of the world’s most pressing challenges.

Bonus trivia: The massive lens-building machine is nicknamed Megatron and features a Decepticon sticker on its side. During construction, an engineer mistakenly called a magnetron device “megatron,” and the name stuck.

See the way those smooth, amorphous blobs rapidly transform into textured honeycombs? Something similar is probably happening right now inside your laptop or smartphone’s battery, providing you with portable power.

But the cherished efficiency and portability of those compact lithium-ion batteries comes with a cost: each cycle of discharge/recharge degrades the material’s essential structure and ultimate longevity – you’ve probably noticed that your older electronics just don’t hold a charge like they used to. Preventing this persistent degradation requires insight into a process that plays out on the elusive scale of just billionths of a meter.

Fortunately, Brookhaven scientists just demonstrated a breakthrough transmission electron microscopy technique that captures live action lithium-ion reactions with nanoscale precision.

“We’ve opened a fundamentally new window into this popular technology,” said physicist and lead author Feng Wang. “The live, nanoscale imaging may help pave the way for developing longer-lasting, higher-capacity lithium-ion batteries. That means better consumer electronics, and the potential for large-scale, emission-free energy storage.”

These real-time experimental observations, including the movie above, revealed that the lithium ions swept rapidly across the surface of iron fluoride nanoparticles in a matter of seconds. The transformation then moved slowly through the bulk in a layer-by-layer process that split the compounds into distinct regions (similar to spinodal decomposition).

Imagine watching a fire spread across the surface of a log and then steadily eating its way through the layers of wood—only rather than smoke, the lithium ion reaction forms trails of new molecules. Just as burnt wood reveals fundamental characteristics of fire, the changes in morphology and structure in these individual nanoparticles provided crucial information about the lithium reaction mechanisms.

Get the full story at the official press release.

And way down at the fundamental level, HTS gets weird. Physicists at Brookhaven Lab just probed HTS fluctuations, and they got some unexpected results.

Water, way less exotic and much better understood, can help decode the findings. On its way to a rollicking boil, water develops isolates bubbles of gas – these appear suddenly along the bottom of a pot and then float up through the liquid. This is an in-between zone, the transition space between two very different phases of matter. Water doesn’t transform instantaneously into vapor, instead exhibiting fluctuations across a wide threshold.

As it turns out, as copper-oxide insulators cool down, they exhibit similarly fleeting “bubbles” of superconductivity. Inside that superconductor-insulator transition zone, intermittent islands flit in and out of existence. And that’s not even the strangest part. Cooled down even closer to absolute zero, these superconducting fluctuations vanish entirely – and that’s what really surprised physicists.

This unexpected quenching of superconductivity finds a useful analog, again, in water. Imagine that the flow of electricity between electrodes resembles the motion of a river rushing downhill. Custom-built conductors act as a channel designed to carry electric current as efficiently as possible, just as a smoothly engineered canal carries water.

If the canal is poorly constructed, full of sudden and jagged pits, the water level directly impacts the quality of the flow. A high volume of water will race along continuously, even if occasionally given to the turbulence of crashing whitewater. If, however, the water level falls below some critical value, the current will tumble into those pits, slowing to a trickle or stopping completely.

Physicist Ivan Bozovic with his custom-built Atomic Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) system, which grows atomically precise materials.

In these HTS experiments, the scientists measured the flow of electricity to discern the structure of custom-built copper-oxide “canals.” The water volume corresponds to the density of electrons in the system, which was  fine-tuned with that giant device seen to the right. While atomically smooth, the materials contained deliberately built-in defects – randomly distributed strontium atoms. Once super-cold, these imperfections acted like pits that trapped flowing electrons, rendering them immobile.

“The traps are there all the time, but the electrons only become stuck at extremely low temperature,” said Brookhaven physicist Ivan Bozovic. “This behavior, called electron localization, makes the material insulating. With some heating, however, the electrons gain enough kinetic energy to jump out of the holes and maintain metallic conductivity – and, in the present case, superconductivity.”

There’s (at least) one more layer of weird to add to these frigid traps. The researchers not only discovered that the fluctuations vanish beyond that super-cold threshold, but that the trapping pattern changes with each test. Resistivity depends not just on temperature, but also on the material’s memory – how and where the electrons were previously trapped. This phenomenon, called hysteresis, strongly indicates that the underlying mechanism behind the superconductor-insulator transition is tied to electron localization.

The study unveiled new characteristics of high-temperature superconductivity, and it offers another step in the ongoing quest to understand and harness the phenomenon. Get the full story in the official press release, and get deep into the full electron-doping chemistry in the scientific paper.

Now, a team of scientists has peered into floating water bridges with high-energy x-rays using the Advanced Photon Source (APS) at Argonne National Laboratory. Their work, “Floating water bridges and the structure of water in an electric field,” was published recently in the Proceedings of the National Academy of Sciences. I spoke with Brookhaven National Laboratory chemist John Parise, who worked with the team at APS to explore this unexplained phenomenon. 

Infrared thermal images of the floating water bridge setup at the Advanced Photon Source at Argonne National Laboratory. The color scale goes from 24°C (dark purple) to 50°C (bright yellow). The four quadrants show the water bridges with different thicknesses and temperatures. The bottom left image shows a water bridge immediately before collapse, due to reduced voltage.

Q: For this experiment, you set up a floating water bridge and used the APS to shine a beam of x-rays through the water. What exactly were you looking for? 

A: We were looking specifically for alignments in the water molecules that were different from alignments of the molecules in liquid water. We’ve recently finished a study where we’d gathered some of the best data ever taken on liquid water, so we had those data to compare with directly. That’s one of the things this paper on floating water bridges does—it looks for small differences between liquid water and the water in this water bridge.

Q: What were you expecting to find?

A: We started out thinking, gosh, there’s got to be some structure in this. If it’s not collapsing under the influence of gravity, there must be some alignment of the molecules. When you fire a beam of high energy x-rays through it, you’ll get a diffuse ring of x-rays on the other side, and you can detect these using an x-ray sensitive detector. But you should see modulation of the intensity around the ring that tells you that instead of the water molecules being randomly oriented that there’s a predominant orientation. Theoretical calculations tell us that the alignment, if it exists, should be along the bridge direction.

Q: How did the APS help you test for that alignment?

A: One of the powerful things about high-energy x-ray scattering is that you can take a lot of images vertically across the floating bridge or horizontally along the bridge very rapidly. Synchrotron radiation is so bright that you can take large numbers of images while the bridge is still stable. Plus, you can image the temperature—so you can take images of the part of the bridge that’s hot, the part that’s cold, the skin, and that type of thing.

Q: So, what did you find?

A: As soon as we took our first shot, I said, “That looks awfully even. It just shouldn’t be like that.” The result is that there’s just no quantitative difference between the liquid water and the water in this floating bridge. I was very surprised.

It turns out that you need an awful lot of high voltage to align a significant number of water molecules, and that’s not happening with these water bridges. But we only know that now, after we’ve done the experiment.

The conclusion is that this water bridge must be stabilized by a very thin layer of water, and it’s basically surface tension holding it together—the surface tension across the top and bottom of that bridge.

Q: Did you think your findings were wrong?

A: Well yeah! But we did many, many tests and they all revealed the same thing. Of course, then we started to think that this was a sheath, that in fact the voltage was affecting only the molecules at the surface.

Q: What does this experiment and your research into the nature of water tell us?

A: Well, we wouldn’t be able to exist without water having the properties that it has. Life on Earth wouldn’t exist. And it’s all up to something as simple as the fact that water is a very peculiar sort of liquid, in many ways. These water bridges are a result of the geometry of the molecules and hydrogen bonding. It’s fascinating behavior and understanding the phenomenon at a deep level tells us something fundamental about liquid water.

One aim of our research is to look at things under extreme conditions and see whether extreme conditions can be used to manipulate those materials. Anything that tells you about how you can manipulate matter, especially liquid matter, and how you can direct it to go in this direction rather than that direction is potentially useful fundamental knowledge.

Q: What more do you hope to learn about floating water bridges?

The next thing to do is to look very carefully at the surface and try to use more surface-sensitive techniques. That would be potentially a great thing to look at with the National Synchrotron Light Source II at Brookhaven National Laboratory, which will have much finer beams than the APS. At APS and especially at NSLS-II, we can do some small angle x-ray scattering studies to see if there’s any organization in the skin.

Water is a quantum liquid, the universal solvent, and it is essential to biology. The arrangement of water molecules in electric fields and at charged surfaces has important implications in electrochemistry, mineralogy and biology.

And once we understand this phenomenon in water, the obvious thing is to move on to other solvents. You can form bridges with other materials that are quite different from water and have much lower surface tension–the most likely explanation of the water bridge stability at this stage–but they all seem to have one thing in common: hydrogen bonding.

Water’s many unusual properties depend on its unique molecular interactions, and its structure has long been a matter of debate. Understanding the “how” of the water bridge stability may allow us to manipulate liquids, including water, with electric fields.

Ben Babst has seen things that no one else has ever seen before. A plant biologist in Brookhaven Lab’s Biosciences Department, Babst is among pioneering researchers who are some of the first in the world to study plants using a technique called positron emission tomography or PET imaging, which is more commonly used to diagnose cancer and study brain activity. With this innovative use of PET imaging technologies, Babst has actually watched plants shift nutrients from their leaves down to their roots while under attack by gypsy moth caterpillars — the plants safeguarding energy from their furry, leaf-chomping assailants. This, along with Babst’s other investigations of transport and metabolism in plants, show much promise toward enhancing plants’ abilities to make substances for biofuels that could someday power vehicles, homes, and industry.

Ben Babst with a prototype of a positron emission tomography (PET) device for imaging plants.

What is the focus of your research?

Plants can’t run away from insect attacks and they can’t escape from drought like that suffered in the Midwest this summer. To suit changing environmental conditions, they adjust internal processes such as metabolism and “vascular” transport, which circulates resources throughout the plant. The goal of my research is to provide basic biological information about these adaptations, which are needed to develop crops dedicated for bioenergy — crops that grow large and fast, can be converted to fuel efficiently, and can grow vigorously on less-than-ideal lands to avoid a scenario of competition for real estate to produce both food and fuel.

At Brookhaven, I use radioisotopes and Positron Emission Tomography (PET) to see and quantify how biochemicals are distributed throughout an entire plant. This is “basic” research that supports DOE’s bioenergy mission through its Biomass program.

What’s “cool” or interesting about that?

It’s very cool to be the first person to actually see various phenomena happening in plants. Watching video created in our lab that shows the movement of sugars and plant hormones is an eye opener. It’s also rewarding to contribute toward solutions to the energy crisis that is facing us in the U.S.

What are you working on now?

I am addressing several areas of plant biology, including hormone signaling in grass stem growth and fundamental mechanisms of vascular transport. For example, I am trying to understand the mechanisms that control how nutrients, including sugars, are allocated to different parts of the plant — roots, stems, and leaves. Sugars can be produced in leaves through photosynthesis, and then distributed to stems and roots, where they are metabolized to release energy that the plant needs to grow. We can tap those sugars for our energy needs — for both food and fuel. Converting sugars to biofuel is a very efficient process, because sugars can be fermented directly.

In one of my current projects, I am working to determine how sugars accumulate in stems of certain grasses, such as sugarcane and sweet sorghum. Sorghum is a relative of corn, and compared to sugar cane, it is much better adapted to grow in the temperate climate that is prevalent in much of the United States. Understanding the mechanisms that drive sugar accumulation in sweet sorghum will lead to new ideas for increasing sugar yields, not only for sorghum plants, but for other bioenergy crops as well.

Why do this at Brookhaven Lab?

This plant biology research for bioenergy requires specialized equipment and expertise. PET technology has been used for medical studies for decades, but there are only a few groups in the world, so far, that use it for plant research. Since much technology for PET imaging was developed at Brookhaven Lab, the Lab is unique in the world. Here, we have the specialized equipment as well as people with electronics and chemistry expertise. Applications for plant science are still fairly young, so it is invaluable for me to work with a team of experts who can help find solutions when new challenges arise.

Have your efforts contributed to any discoveries?

Yes. In earlier work, we found evidence that plants may defend themselves from damage, such as a gypsy moth caterpillar attack, by bunkering nutrients below ground to the roots. It has long been known that plants can make toxins to repel herbivorous insects, but our studies suggested a broader whole-plant response to a harmful environmental condition.

More recently, my studies with corn, or maize, mutant plants have raised new questions about the phloem that transports the sugars plants need to grow from the leaves to the roots, stem, and flowers. Right now, plant biologists think that sugar loading into the phloem is what drives nutrient-containing sap to flow. The maize mutant plants I am working with export very little sugar. But surprisingly, we found that the flow of sap in the phloem is only reduced moderately compared to “normal” plants in the wild. That means something else, not sugar loading alone, is helping to drive sap flow in these plants. Identifying that something else is what we need to address now. I think the results of this research will ultimately lead to revisions in plant biology textbooks.