Volume 2, Issue 16 November 2005
Driving Hydrogen Car Research
While eco-friendly hybrid automobiles gain popularity, researchers are already developing cars with no emissions at all. Powered by hydrogen fuel cells, future automobiles may travel long distances with only water dribbling out of the exhaust pipe. The path to the hydrogen economy isn't smoothly paved though. One big question is whether a safe and practical hydrogen storage system can be built to store enough fuel for long journeys. To that end, UC Berkeley chemist Jeff Long is developing novel nanomaterials for tomorrow's hydrogen fuel tanks.
In 2002, Jeffrey R. Long was included in Technology Review magazine's TR100, "a list of 100 innovators 35 or younger whose technologies are poised to make a dramatic impact on our world."
"Currently, hydrogen must be stored at low temperature or high pressure, requiring specialized, heavy, and awkward containers that take up a lot of volume," says Long, who is also a researcher with Lawrence Berkeley National Laboratory's Materials Science Division. "That's a problem when you want to have room for passengers and luggage."
Hydrogen storage is a challenge that Long and his collaborators hope to solve through synthetic inorganic chemistry. Indeed, Long's specialty is controlling the chemical structure of compounds to create new materials with specific physical properties. Since May, he's been leading a project with eight UC Berkeley and Berkeley Lab scientists to study, synthesize, and test materials that could store large amounts of hydrogen at ambient temperature and pressure. The effort was funded with $4.5 million from the Department of Energy as part of the agency's broader initiative to make &qot;hydrogen fuel cell vehicles and refueling stations available, practical, and affordable for American consumers by 2020."
While scientists are still exploring how to produce hydrogen cleanly and cheaply, the element has great promise as a renewable source of energy. When combined with oxygen in a fuel cell, hydrogen produces electrical energy. The only waste product is plain water. Eventually, hydrogen fuel cells could become a common power source for laptop computers, cell phones, and even homes.
A graphical visualization of hydrogen molecules flowing into a single cube, one of many in a metallo-organic framework.
"Hydrogen is a very lightweight molecule, so the amount of energy you can get out of hydrogen with a fuel cell is very high," Long says. "But if you have to add a lot of weight to store and transport the hydrogen, you're essentially reducing its energy content."
Gaseous hydrogen must be contained in high pressure cylinders while liquid hydrogen requires extreme cooling, he explains. Long's approach to hydrogen storage leverages the unique material characteristics that emerge at the nanoscale. The hydrogen storage material he's developing consists of a three-dimensional lattice of tiny hollow cubes, each capable of storing eight hydrogen molecules inside. That may not sound like much, but nanomaterials like this lattice have huge surface areas with respect to their volume, sometimes as much as several thousand square meters per gram. A gas tank filled with this material in a powder form could potentially hold enough hydrogen for long range drives between refills, Long says.
Synthesized in a solution reaction, each cube in the lattice consists of metal corners with edges of organic molecules. Hydrogen molecules are then introduced into the framework where they bind to the metal sites inside the cubes. The key though is getting the binding energy just right so that tiny swings in pressure are all that's needed to push the hydrogen in or pull it out.
"If the binding energy is too low, it'll be difficult to keep the hydrogen inside," Long says. "But if it's too high, you won't be able to get it out without heating up the material. You don't want to spend all day filling your tank and you certainly can't be waiting when you push down the accelerator."
Right now, Long and his colleagues are testing various metals to find one with the most desirable binding energy. Long's colleague, chemistry professor Martin Head-Gordon, is helping predict which metals may provide the best results.
"Forming the cubes isn't easy, so the predictions help limit the trial-and-error," Long says.
The researchers stress that the perfect material is still a long way down the road. And even if they demonstrate that the cubes are an effective storage method, they must then determine whether the synthesis process could be commercialized.
"We want these materials to be very cheap so that the cost of using hydrogen can be comparable to that of gasoline," Long says. "There are still many scientific issues that need to be addressed, but I believe that in the long term hydrogen is the ultimate fuel."
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Seeing Cellular Machinery
Eva Nogales is also a staff scientist at the Lawrence Berkeley National Laboratory.
A cell is perhaps the most complex factory in the world. The basic structural and functional unit of all life, cells convert nutrients to energy, perform highly specialized tasks based on instructions stored in their DNA, and reproduce themselves. How are these feats accomplished though? UC Berkeley biologist Eva Nogales is using electron microscopy to watch some of these cellular mechanisms in action.
"Traditional techniques of structural biology break a cell's complex assemblies down into small units," says Nogales, associate professor in the Department of Molecular and Cell Biology and Howard Hughes Medical Institute investigator.. "But we want to look at them closely as they exist in conditions where they're still fully functional."
A ribbon diagram based on the an image of tubulin generated by cryo-electron microscopy.
Several years ago, Nogales was part of a group at Lawrence Berkeley National Laboratory that for the first time unveiled the structure of tubulin, a protein in the cell that's essential to cell division and other cellular processes. In a living cell, tubulins chemically come together, or polymerize, into microtubules, fibers that make up the cytoskeleton to give shape to the cell and organize its contents. The magic of the microtubules is that during cell division, they disassemble and reassemble to organize chromosomal material and shuttle it to the daughter cells. Using cryo-electron microscopy, the researchers generated a high-resolution 3D image of the protein. For Nogales though, that groundbreaking picture was just the beginning.
"Obtaining the structure doesn't tell you much about its dynamics, how it does what it does," she says. "It's like looking at a piece of Lego without having any idea of all the things that can be built when you combine pieces together."
In these stills from a computer animation representing the work of Eva Nogales and Hong-Wei Wang, a sheet of tubulin transitions into a closed cylinder. Full-length video available here.
Nogales is particularly interested in how the mictoubules can shift from growth to shrinkage and back again during cell division. For a cell to divide properly, it must first duplicate its chromosomes. Pairs of connected chromosomes attach to the microtubles through structures called kinetochores. The kinetochores keep the chromosomes lined up along the ends of the microtubule fibers. When the fibers disassemble, the chromosome pairs are literally pulled apart to the opposite ends of the cell.
Since solving the atomic structure of tubulin, Nogales has been investigating how the proteins assemble and disassemble into the microtubules. Unlike the way DNA self-assembles one nucleotide at a time in a helical growth pattern, the microtubules proceed through several distinct states as they form and break down. It's a reaction called polymerization, where many small molecules come together to form macromolecules. By capturing electron microscopy images of the microtubules in various polymerized states, Nogales and postdoctoral researcher Hong-Wei Wang have been able to create a computer animation of the assembly and disassembly process. For example, the tubulins form a sheet that closes itself up into a tube. And during disassembly, the microtubule doesn't simply fall apart. Rather, the chains of tubulins peel back like a banana.
In these animation stills, protein caps fall off the ends of the microtubles spurring it to peel apart. Full-length video available here.
The latest work has already provided insight into an essential mechanism of cell division. In a collaboration with Molecular and Cell Biology professors Georjana Barnes and David Drubin, and their postdoctoral researcher Stefan Westermann, Nogales has helped reveal how a kinetochore "collar" moves down the microtubule. As the fiber peels apart, the kinetochore ring is pushed along to the appropriate daughter cell.
Even as the mechanisms of cell division slowly become clear, Nogales says, more questions arise. The researchers are now beginning a "cell-wide search" to identify the cellular factors that bind to specific tubulin assemblies during the assembly and disassembly of the microtubules. The structures they've already characterized will serve as the bait on this fishing trip, hopefully attracting the molecules they're seeking.
In this electron microscope image generated by the Nogales Lab, kinetochore rings are visibly bound to the microtubules.
In her earlier work, Nogales looked at how the anti-cancer drug Taxol interferes with the flexibility of tubulins. Deepening our understanding of how the microtubules form, she says, could someday lead to a more effective cancer treatment that targets only the tubulins of diseased cells.
"We are very from being able to build structures that have the flexibility and incredible robustness of tubulin," Nogales says. "But nature does it beautifully."
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The Physicist and the SQUID
John Clarke with a photo of a superconducting coil deposited on a SQUID. (courtesy Berkeley Lab)
UC Berkeley scientist John Clarke has spent his career studying SQUIDs. But the SQUIDs that Clarke works with are not the cephalopods of calamari and Jules Verne novels. SQUID is an acronym for Superconducting Quantum Interference Device, a device for detecting incredibly weak magnetic fields. Science's most sensitive energy detecting device, SQUIDs are having a dramatic impact on fields as diverse as medical imaging, cosmology, and computer architecture.
"SQUIDs are the world's most sensitive detector of magnetic flux," says Clarke, a professor of physics and member of Lawrence Berkeley National Laboratory's Materials Sciences Division. "Since flux is generated in so many different ways, SQUIDs have a great number of applications."
Subtle shifts in magnetic fields are difficult to measure, Clarke explains. But SQUIDs convert those fluxes into a voltage that is easily readable. Based on properties of quantum physics, SQUIDs can be billions of times more sensitive to magnetic fluctuations than the needle of a compass.
In lieu of biological tissue, the researchers conduct MRI experiments on bell peppers.
Smaller than the head of a pin, the devices are bulk fabricated in Clarke's own laboratory and in UC Berkeley's Microfabrication Facility with processes similar to those used in the manufacture of silicon computer chips. Each SQUID is a microscopic loop of superconducting metal containing two Josephson junctions, an insulator thin enough for pairs of electrons to tunnel through. When placed near a magnetic field, the voltage across the device changes in response to the strength of that field.
In recent years, Clarke has developed SQUID-based amplifiers to help in the search for axions, hypothetical elementary particles that may be the mysterious "dark matter" that makes up roughly 25 percent of the mass in our universe. Another project focused on using SQUIDs in metallurgy for early detection of failing steel, in bridges or airplane wings, for example.
SQUIDs have also emerged as a possible candidate component for tomorrow's quantum computer, systems that promise to crank out calculations a billion times faster than today's integrated circuits. By exploiting the unusual characteristics of quantum mechanics, the quantum computer might one day quickly determine the physical structure of proteins for drug discovery or generate secure encryption codes for highly sensitive data.
The key ingredient in a quantum computer is the qubit, the equivalent of the binary zero or one of a digital computer. The power of quantum computers lies in a qubit's ability to exist in a zero or one state, or in a superposition somewhere in the middle. This quantum weirdness is what enables quantum computers to process so much data at once. Essentially, each qubit represents an infinite number of values at one time. As more qubits are strung together, the power of the quantum processor grows exponentially.
A variety of physical systems are now being considered as candidates for qubits. Most of these focus on controlling and detecting the state of single photons or electrons. Clarke's approach uses SQUIDS as a key component in a macroscopic system with emergent qubit behavior.
A scanning electron micrograph of two flux qubits.
The flux qubit contains a tiny superconducting loop--in this case containing three Josephson junctions--with current flowing around it. The direction of the current--clockwise, counterclockwise, or a quantum superposition of the two states--can be changed by applying a magnetic field. A SQUID built around the superconducting loop reads out the state of qubit.
"We've had great results making this whole ensemble act like a single atom in terms of its quantum mechanical properties," Clarke says. "Next, we'd like to hook together several so you can have interacting flux qubits. It would take thousands to make a fully-functional quantum computer though."
While quantum computer research is still in its early stages, Clarke has made strides in using the unparalleled sensitivity of SQUIDs to improve medical magnetic resonance imaging (MRI) systems. Conventional MRI systems image soft tissues such as brains and organs by immersing the body within an incredibly strong magnetic field and applying sequences of radio frequency pulses. A computer generates an image based on how the magnetic energy interacts with the protons in the body. Traditional MRI machines require a very large and expensive magnet to produce a good picture.
Clarke's aim is to develop an MRI system based on a single SQUID operating in a magnetic field as much 10,000 times weaker than that of traditional machines. Indeed, the prototype magnets that Clarke's students have constructed are simply copper wire wrapped around wooden forms. Someday, this research could lead to portable and inexpensive MRI machines that generate images as detailed as today's clinical systems but at much lower cost. In addition, low- field MRI may offer a distinct advantage over its high-field counterpart.
"In conventional MRIs, it's very difficult to distinguish between cancer and healthy tissue," Clarke says. "Using SQUIDs, there is a good possibility that we could tell the difference."
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Berkeley's Scientific Legacy
Miller Institute for Basic Research in Science
On February 14, 1955, UC Berkeley established what would become a world-renowned hub for young scientists exploring the frontiers of research. Funded with $4 million in trust, the research would span all realms of scientific inquiry, from biology and chemistry to geophysics and mathematics. The President of the Advisory Board was to be none other than the President of the University him or herself, although that job has since been delegated to the UC Berkeley Chancellor. To date, the Adolph C. and Mary Sprague Miller Institute for Basic Research in Science has supported more than 800 scientists, including seven Nobel Prize winners and six Fields Medalists.
Adolph Miller
Adolph C. Miller was born in San Francisco in 1866 and attended the University of California. Upon graduation, he was awarded the prestigious Harvard Club Prize to support his graduate study there. At age 29, he married Mary Sprague, the daughter of a wealthy Chicago businessman. While the Millers resided in Washington DC, Adolph was not forgotten by Berkeley, and vice versa. In 1937, he was invited to deliver the first Bernard Moses Memorial lecture. Three years later, he received an honorary LL.D. degree. The honor included the following citation from UC Berkeley president Robert Gordon Sproul:
"Native son of California; graduate of this University, and the first head of its Department of Economics; for twenty years a member of the Federal Reserve Board, contributing in a unique and invaluable way to its deliberations through his keen mind, sound thinking, and profound mastery of economic theory."
In 1943, the Millers entered into a trust with the University to establish an institute "dedicated to the encouragement of creative thought and conduct of research and investigation in the field of pure science." In 1953, Adolph Miller passed away and more than $2 million was made available to fund the Institute. On October 14, 1955, the "Statement Establishing the Institute for Basic Research in Science" was approved by the Regents of the University. Two years later, Mary Miller died and an additional $2 million became available. The first appointments to the Miller Institute were announced in January 1957.
The Miller Institute will celebrate its 50th anniversary this year with a celebration at the University on December 9 and 10. An interdisciplinary symposium is planned with esteemed Miller Institute alumni presenting the latest thinking on nanoscience, biology in the twenty-first century, and cosmology and its connection to fundamental physics. While the Millers are gone, their support of basic science continues to keep Berkeley at the forefront of cutting-edge scientific research.