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News from the University of Colorado in Boulder.
CU research: Microchips using light instead of wires boosts speed exponentially
Sep 30th
CU, MIT breakthrough in photonics
could allow for faster and faster electronics
could allow for faster and faster electronics
A pair of breakthroughs in the field of silicon photonics by researchers at the University of Colorado Boulder, the Massachusetts Institute of Technology and Micron Technology Inc. could allow for the trajectory of exponential improvement in microprocessors that began nearly half a century ago—known as Moore’s Law—to continue well into the future, allowing for increasingly faster electronics, from supercomputers to laptops to smartphones.
The research team, led by CU-Boulder researcher Milos Popovic, an assistant professor of electrical, computer and energy engineering, developed a new technique that allows microprocessors to use light, instead of electrical wires, to communicate with transistors on a single chip, a system that could lead to extremely energy-efficient computing and a continued skyrocketing of computing speed into the future.
Popovic and his colleagues created two different optical modulators—structures that detect electrical signals and translate them into optical waves—that can be fabricated within the same processes already used in industry to create today’s state-of-the-art electronic microprocessors. The modulators are described in a recent issue of the journal Optics Letters.
First laid out in 1965, Moore’s Law predicted that the size of the transistors used in microprocessors could be shrunk by half about every two years for the same production cost, allowing twice as many transistors to be placed on the same-sized silicon chip. The net effect would be a doubling of computing speed every couple of years.
The projection has held true until relatively recently. While transistors continue to get smaller, halving their size today no longer leads to a doubling of computing speed. That’s because the limiting factor in microelectronics is now the power that’s needed to keep the microprocessors running. The vast amount of electricity required to flip on and off tiny, densely packed transistors causes excessive heat buildup.
“The transistors will keep shrinking and they’ll be able to continue giving you more and more computing performance,” Popovic said. “But in order to be able to actually take advantage of that you need to enable energy-efficient communication links.”
Microelectronics also are limited by the fact that placing electrical wires that carry data too closely together can result in “cross talk” between the wires.
In the last half-dozen years, microprocessor manufacturers, such as Intel, have been able to continue increasing computing speed by packing more than one microprocessor into a single chip to create multiple “cores.” But that technique is limited by the amount of communication that then becomes necessary between the microprocessors, which also requires hefty electricity consumption.
Using light waves instead of electrical wires for microprocessor communication functions could eliminate the limitations now faced by conventional microprocessors and extend Moore’s Law into the future, Popovic said.
Optical communication circuits, known as photonics, have two main advantages over communication that relies on conventional wires: Using light has the potential to be brutally energy efficient, and a single fiber-optic strand can carry a thousand different wavelengths of light at the same time, allowing for multiple communications to be carried simultaneously in a small space and eliminating cross talk.
Optical communication is already the foundation of the Internet and the majority of phone lines. But to make optical communication an economically viable option for microprocessors, the photonics technology has to be fabricated in the same foundries that are being used to create the microprocessors. Photonics have to be integrated side-by-side with the electronics in order to get buy-in from the microprocessor industry, Popovic said.
“In order to convince the semiconductor industry to incorporate photonics into microelectronics you need to make it so that the billions of dollars of existing infrastructure does not need to be wiped out and redone,” Popovic said.
Last year, Popovic collaborated with scientists at MIT to show, for the first time, that such integration is possible. “We are building photonics inside the exact same process that they build microelectronics in,” Popovic said. “We use this fabrication process and instead of making just electrical circuits, we make photonics next to the electrical circuits so they can talk to each other.”
In two papers published last month in Optics Letters with CU-Boulder postdoctoral researcher Jeffrey Shainline as lead author, the research team refined their original photonic-electronic chip further, detailing how the crucial optical modulator, which encodes data on streams of light, could be improved to become more energy efficient. That optical modulator is compatible with a manufacturing process—known as Silicon-on-Insulator Complementary Metal-Oxide-Semiconductor, or SOI CMOS—used to create state-of-the-art multicore microprocessors such as the IBM Power7 and Cell, which is used in the Sony PlayStation 3.
The researchers also detailed a second type of optical modulator that could be used in a different chip-manufacturing process, called bulk CMOS, which is used to make memory chips and the majority of the world’s high-end microprocessors.
Vladimir Stojanovic, who leads one of the MIT teams collaborating on the project and who is the lead principal investigator for the overall research program, said the group’s work on optical modulators is a significant step forward.
“On top of the energy-efficiency and bandwidth-density advantages of silicon-photonics over electrical wires, photonics integrated into CMOS processes with no process changes provides enormous cost-benefits and advantage over traditional photonic systems,” Stojanovic said.
The CU-led effort is a part of a larger project on building a complete photonic processor-memory system, which includes research teams from MIT led by Stojanovic, Rajeev Ram and Michael Watts, a team from Micron Technology led by Roy Meade and a team from the University of California, Berkeley, led by Krste Asanovic. The research was funded by the Defense Advanced Research Projects Agency and the National Science Foundation.
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CU study; Death of microbes could determine time of death
Sep 27th
An intriguing study led by the University of Colorado Boulder may provide a powerful new tool in the quiver of forensic scientists attempting to determine the time of death in cases involving human corpses: a microbial clock.
The clock is essentially the lock-step succession of bacterial changes that occur postmortem as bodies move through the decay process. And while the researchers used mice for the new study, previous studies on the human microbiome – the estimated 100 trillion or so microbes that live on and in each of us – indicate there is good reason to believe similar microbial clocks are ticking away on human corpses, said Jessica Metcalf, a CU-Boulder postdoctoral researcher and first author on the study.
“While establishing time of death is a crucial piece of information for investigators in cases that involve bodies, existing techniques are not always reliable,” said Metcalf of CU-Boulder’s BioFrontiers Institute. “Our results provide a detailed understanding of the bacterial changes that occur as mouse corpses decompose, and we believe this method has the potential to be a complementary forensic tool for estimating time of death.”
Dead and dying microbes could determine time of death for forensics pathologists
Currently, investigators use tools ranging from the timing of last text messages and corpse temperatures to insect infestations on bodies and “grave soil” analyses, with varying results, she said. And the more days that elapse following a person’s demise, the more difficult it becomes to determine the time of death with any significant accuracy.
Using high-technology gene sequencing techniques on both bacteria and microbial eukaryotic organisms like fungi, nematodes and amoeba postmortem, the researchers were able to pinpoint time of mouse death after a 48-day period to within roughly four days. The results were even more accurate following an analysis at 34 days, correctly estimating the time of death within about three days, said Metcalf.
A paper on the subject was published Sept. 23 in the new online science and biomedical journal, eLIFE, a joint initiative of the Howard Hughes Medical Institute, the Max Planck Society and the Wellcome Trust Fund. The study was funded by the National Institutes of Justice.
The researchers tracked microbial changes on the heads, torsos, body cavities and associated grave soil of 40 mice at eight different time points over the 48-day study. The stages after death include the “fresh” stage before decomposition, followed by “active decay” that includes bloating and subsequent body cavity rupture, followed by “advanced decay,” said Chaminade University forensic scientist David Carter, a co-author on the study.
“At each time point that we sampled, we saw similar microbiome patterns on the individual mice and similar biochemical changes in the grave soil,” said Laura Parfrey, a former CU-Boulder postdoctoral fellow and now a faculty member at the University of British Columbia who is a microbial and eukaryotic expert. “And although there were dramatic changes in the abundance and distribution of bacteria over the course of the study, we saw a surprising amount of consistency between individual mice microbes between the time points — something we were hoping for.”
As part of the project, the researchers also charted “blooms” of a common soil-dwelling nematode well known for consuming bacterial biomass that occurred at roughly the same time on individual mice during the decay period. “The nematodes seem to be responding to increases in bacterial biomass during the early decomposition process, an interesting finding from a community ecology standpoint,” said Metcalf.
“This work shows that your microbiome is not just important while you’re alive,” said CU-Boulder Associate Professor Rob Knight, the corresponding study author who runs the lab where the experiments took place. “It might also be important after you’re dead.”
The research team is working closely with assistant professors Sibyl Bucheli and Aaron Linne of Sam Houston State University in Huntsville, Texas, home of the Southeast Texas Applied Forensic Science Facility, an outdoor human decomposition facility known popularly as a “body farm.” The researchers are testing bacterial signatures of human cadavers over time to learn more about the process of human decomposition and how it is influenced by weather, seasons, animal scavenging and insect infestations.
The new study is one of more than a dozen papers authored or co-authored by CU-Boulder researchers published in the past several years on human microbiomes. One of the studies, led by Professor Noah Fierer, a co-author on the new study, brought to light another potential forensic tool — microbial signatures left on computer keys and computer mice, an idea enthralling enough it was featured on a “CSI: Crime Scene Investigation” television episode.
“This study establishes that a body’s collection of microbial genomes provides a store of information about its history,” said Knight, also an associate professor of chemistry and biochemistry and a Howard Hughes Medical Institute Early Career Scientist. “Future studies will let us understand how much of this information, both about events before death — like diet, lifestyle and travel — and after death can be recovered.”
In addition to Metcalf, Fierer, Knight, Carter and Parfrey, other study authors included Antonio Gonzalez, Gail Ackerman, Greg Humphrey, Mathew Gebert, Will Van Treuren, Donna Berg Lyons and Kyle Keepers from CU-Boulder, former BioFrontiers doctoral student Dan Knights from the University of Minnesota, and Yan Go and James Bullard from Pacific Biosciences in Menlo Park, Calif. Keepers participated in the study as an undergraduate while Gonzalez, now a postdoctoral researcher, was a graduate student during the study.
“There is no single forensic tool that is useful in all scenarios, as all have some degree of uncertainty,” said Metcalf. “But given our results and our experience with microbiomes, there is reason to believe we can get past some of this uncertainty and look toward this technique as a complementary method to better estimate time of death in humans.”
Gene sequencing equipment for the study included machines from Illumina of San Diego and Pacific Biosciences of Menlo Park, Calif. The Illumina data were generated at CU-Boulder in the BioFrontiers Next Generation Sequencing Facility.
To access a copy of the paper visit http://dx.doi.org/10.7554/eLife.01104. For more information on the BioFrontiers Institute visit http://biofrontiers.colorado.edu.
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Professor grabs 8th MacArthur award for CU faculty
Sep 25th
Ana Maria Rey, a theoretical physicist and a fellow of JILA, a joint institute of the University of Colorado Boulder and the National Institute of Standards and Technology, today was named a winner of a 2013 MacArthur Fellowship, commonly known as the “genius grant.”
Rey also is an assistant research professor in the CU-Boulder Department of Physics. She teaches undergraduate and graduate classes.
Ana Maria Rey, a CU professor, won the prestigious MacArthur award.
Rey is the eighth CU-Boulder faculty member to win the prestigious award from the John D. and Catherine T. MacArthur Foundation of Chicago as well as the fourth physics faculty member and third JILA fellow. Rey, 36, was one of 24 recipients of the 2013 “no-strings attached” funding. She will receive $625,000 paid out over five years.
“It is a great honor for me to be a MacArthur fellow and to receive such great recognition of my work,” Rey said. “I want to thank JILA, NIST, CU-Boulder and the outstanding group of colleagues, collaborators and students who have allowed and helped me to accomplish the research I have done.”
The MacArthur Foundation selection committee cited Rey as an “atomic physicist advancing our ability to simulate, manipulate, and control novel states of matter through fundamental conceptual research on ultra-cold atoms.”
“We congratulate Professor Rey on this exciting award, and, we also congratulate our faculty, whose ranks now include five Nobel laureates and eight MacArthur Fellowship winners,” said CU-Boulder Chancellor Philip P. DiStefano. “I believe Professor Rey’s work is emblematic of the research, innovation, and discovery at CU-Boulder, a body of work and a collection of great minds that is unmatched anywhere in the Rocky Mountain region and few places around the nation.”
Tom O’Brian, chief of the NIST Quantum Physics Division and Rey’s supervisor, said, “Ana Maria has rapidly established herself as one of the world’s top young theoretical physicists. She has a special ability to make very practical applications of theory to key experiments. Ana Maria has been crucial to the success of such world-leading NIST/JILA programs as ultracold molecules, dramatic improvements in optical lattice clocks, and use of cold atom systems and trapped ion systems for quantum simulations.”
At JILA, Rey works with ultracold atoms and molecules that are trapped in an “optical lattice,” a series of shallow wells constructed of laser light. Atoms that are loaded into an optical lattice behave similarly to electrons in a solid crystal structure. But while it’s difficult to change the properties of a solid crystal, the properties of an optical lattice—which essentially acts as a “light crystal”—are highly controllable, allowing Rey to explore a whole range of phenomena that would be nearly impossible to study in a solid crystal system.
Ultimately, Rey hopes her research will lead to the ability to engineer materials with unique characteristics such as superfluids—liquids that appear to move without regard for gravity or surface tension—and quantum magnets—individual atoms that act like tiny bar magnets.
Rey began studying physics at the Universidad de los Andes in Bogota, Colombia, where she received a Bachelor of Science degree in 1999. She came to the United States to continue her studies, earning a doctorate in physics from the University of Maryland, College Park in 2004.
Before coming to JILA in 2008, Rey was a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and a postdoctoral researcher at NIST in Gaithersburg, Md.
Previous CU-Boulder faculty members who have won a MacArthur Fellowship include David Hawkins of philosophy in 1981, Charles Archambeau of physics in 1988, Patricia Limerick of history in 1995, Margaret Murnane of physics and JILA in 2000, Norman Pace of molecular, cellular and developmental biology in 2001, Daniel Jurafsky of linguistics and the Institute of Cognitive Science in 2002 and Deborah Jin of JILA, NIST and physics in 2003.
“Everyone at JILA is extremely proud of Ana Maria Rey’s accomplishments and wholeheartedly congratulate her for this prestigious MacArthur Fellowship,” said JILA Chair Murray Holland. “She has an incredibly quick mind for physics and is one of the truly creative and ingenious scientists of her time, while also being a wonderful teacher and mentor to both undergraduate and graduate students. This is a great honor for Ana Maria, and a tremendous recognition of the important research programs in JILA and NIST.”
Rey is a highly effective mentor for an unusually large group of graduate students and postdoctoral fellows given the early stage of her career, O’Brian said. One of her recent graduate students, Michael Foss-Feig, won the prestigious 2013 Best Thesis Award of the American Physical Society’s Division of Atomic, Molecular and Optical Physics. Rey herself won the same award in 2005 as a graduate student at the University of Maryland.
On Sept. 24, in another honor, the American Physical Society named Rey the winner of the 2014 Maria Goeppert Mayer Award, which recognizes outstanding achievements by a woman physicist in her early career:
Additional information on Rey is available on the Web at http://www.macfound.org/fellows/901 and http://jila-amo.colorado.edu/science/profiles/ana-maria-rey.
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