In This Issue...
Nearly Everyone Uses Piezoelectrics. Be Nice to Know How They Work.
Piezoelectrics—materials that can change mechanical stress to electricity and back again—are everywhere in modern life. Computer hard drives. Loud speakers. Medical ultrasound. Sonar. Though piezoelectrics are a widely used technology, there are major gaps in our understanding of how they work. Now researchers at the National Institute of Standards and Technology (NIST) and Canada's Simon Fraser University believe they've learned why one of the main classes of these materials, known as relaxors, behaves in distinctly different ways from the rest and exhibit the largest piezoelectric effect. And the discovery comes in the shape of a butterfly.*
The team examined two of the most commonly used piezoelectric compounds—the ferroelectric PZT and the relaxor PMN—which look very similar on a microscopic scale. Both are crystalline materials composed of cube-shaped unit cells (the basic building blocks of all crystals) that contain one lead atom and three oxygen atoms. The essential difference is found at the centers of the cells: in PZT these are randomly occupied by either one zirconium atom or one titanium atom, both of which have the same electric charge, but in PMN one finds either niobium or manganese, which have very different electric charges. The differently charged atoms produce strong electric fields that vary randomly from one unit cell to another in PMN and other relaxors, a situation absent in PZT.
"PMN-based relaxors and ferroelectric PZT have been known for decades, but it has been difficult to identify conclusively the origin of the behavioral differences between them because it has been impossible to grow sufficiently large single crystals of PZT," says the NIST Center for Neutron Research (NCNR)'s Peter Gehring. "We've wanted a fundamental explanation of why relaxors exhibit the greatest piezoelectric effect for a long time because this would help guide efforts to optimize this technologically valuable property."
A few years ago, scientists from Simon Fraser University found a way to make crystals of PZT large enough that PZT and PMN crystals could be examined with a single tool for the first time, permitting the first apples-to-apples comparison of relaxors and ferroelectrics. That tool was the NCNR's neutron beams, which revealed new details about where the atoms in the unit cells were located. In PZT, the atoms sat more or less right where they were expected, but in the PMN, their locations deviated from their expected positions—a finding Gehring says could explain the essentials of relaxor behavior.
"The neutron beams scatter off the PMN crystals in a shape that resembles a butterfly," Gehring says. "It gives a characteristic blurriness that reveals the nanoscale structure that exists in PMN—and in all other relaxors studied with this method as well—but does not exist in PZT. It's our belief that this butterfly-shaped scattering might be a characteristic signature of relaxors."
Additional tests the team performed showed that PMN-based relaxors are over 100 percent more sensitive to mechanical stimulation compared to PZT, another first-time measurement. Gehring says he hopes the findings will help materials scientists do more to optimize the behavior of piezoelectrics generally.
*D. Phelan, C. Stock, J.A. Rodriguez-Rivera, S. Chi, J.Leão, X. Long,Y. Xie, A.A. Bokov, Z. Ye, P. Ganesh and P.M. Gehring. Role of random electric fields in relaxors. Proceedings of the National Academy of Sciences, Jan. 21, 2014. DOI:10.1073/pnas.1314780111.
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NIST Cell Membrane Model Studied as Future Diagnostic Tool
Researchers at the National Institute of Standards and Technology (NIST) and in Lithuania have used a NIST-developed laboratory model of a simplified cell membrane to accurately detect and measure a protein associated with a serious gynecological disease, bacterial vaginosis (BV), at extraordinarily low concentrations. The work illustrates how the artificial membrane could be used to improve disease diagnosis.
Caused by the bacteria Gardnerella vaginalis, BV is a very common health problem in women and has been linked to infertility, adverse pregnancy outcomes, post-surgery infections and increased risk for acquiring sexually transmitted diseases. Current diagnosis relies on time-consuming, labor-intensive and somewhat inconsistent laboratory cultures or immunological assays.
In a recent paper in the journal PLoS One,* researchers at NIST and Vilnius University (Vilnius, Lithuania) reported that they were able to reveal the presence of G. vaginalis by rapidly detecting and quantifying vaginolysin (VLY), a protein toxin produced exclusively by the bacteria, using the NIST model of cell membranes known as a tethered bilayer lipid membrane (tBLM).
The NIST tBLM is a two-layer sheet of simple lipid molecules analogous to the more complex structures that form the outer shell of animal cells. The membrane is anchored to a substrate with molecular "tethers" that allow it to be surrounded, top and bottom, by typical cellular fluids. Researchers can use the model to study how various factors, such as proteins, affect the integrity of the lipid membrane.
In nature, the protein VLY binds to cholesterol-containing membranes and forms pores in the structure, causing the cell to burst open and die. The researchers prepared a molecular fishing line by baiting their laboratory membrane with cholesterol in concentrations ranging from 0 percent (serving as the control) to 40 percent. VLY proteins hooked by the cholesterol obligingly created pores in the test membranes, which in turn altered the electrochemical behavior of the membranes in a way that could be detected in real time by a sensitive technique called electrochemical impedance spectroscopy (EIS).
The researchers found that they could detect the presence of VLY down to 28 nanograms (billionths of a gram) per milliliter, a four-fold improvement over antibody detection methods now in use. The speed of detection also is faster, with the tBLM-EIS system yielding results in hours rather than days. Additionally, different G. vaginalis strains produce different amounts of VLY, so in many cases, the corresponding EIS readings can help define the specific type of bacteria present in an infection.
Now that they have proven the viability of the tBLM-EIS detection system, the researchers plan to begin tests on clinical samples early this year.
*R. Budvytyte, M. Pleckaityte, A. Zvirbliene, D.J. Vanderah and G. Valincius. Reconstitution of cholesterol-dependent vaginolysin into tethered phospholipid bilayers: implications for bioanalysis. PLos One (December 2013), DOI:10.1371/journal.pone.0082536.
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JILA Strontium Atomic Clock Sets New Records in Both Precision and Stability
Heralding a new age of terrific timekeeping, a research group led by a National Institute of Standards and Technology (NIST) physicist has unveiled an experimental strontium atomic clock that has set new world records for both precision and stability—key metrics for the performance of a clock.
The clock is in a laboratory at JILA, a joint institute of NIST and the University of Colorado Boulder.
Described in a new paper in Nature,* the JILA strontium lattice clock is about 50 percent more precise than the record holder of the past few years, NIST’s quantum logic clock.** Precision refers to how closely the clock approaches the true resonant frequency at which its reference atoms oscillate between two electronic energy levels. The new strontium clock is so precise it would neither gain nor lose one second in about 5 billion years, if it could operate that long. (This time period is longer than the age of the Earth, an estimated 4.5 billion years old.)
The strontium clock’s stability—the extent to which each tick matches the duration of every other tick—is about the same as NIST’s ytterbium atomic clock, another world leader in stability unveiled in August, 2013.*** Stability determines in part how long an atomic clock must run to achieve its best performance through continual averaging. The strontium and ytterbium lattice clocks are so stable that in just a few seconds of averaging they outperform other types of atomic clocks that have been averaged for hours or days.
“We already have plans to push the performance even more,” NIST/JILA Fellow and group leader Jun Ye says. “So in this sense, even this new Nature paper represents only a ‘mid-term’ report. You can expect more new breakthroughs in our clocks in the next 5 to 10 years.”
The current international definition of units of time requires the use of cesium-based atomic clocks, such as the current U.S. civilian time standard clock, the NIST-F1 cesium fountain clock. Hence only cesium clocks are accurate by definition, even though the strontium clock has better precision. The strontium lattice clock and some other experimental clocks operate at optical frequencies, much higher than the microwave frequencies used in cesium clocks. Thanks to the work at NIST, JILA and other research organizations across the world, the strontium lattice clock and other experimental clocks may someday be chosen as new timekeeping standards by the international community.
The strontium clock is the first to hold world records for both precision and stability since the 1990s, when cesium fountain atomic clocks were introduced. In the past decade, the rapid advances in experimental atomic clocks at NIST and other laboratories around the world have surprised even some of the scientists leading the research. NIST, which operates the NIST-F1 time standard, pursues multiple clock technologies because scientific research can take unpredictable turns, and because different types of atomic clocks are better suited for different practical applications.
In JILA’s world-leading clock, a few thousand atoms of strontium are held in a column of about 100 pancake-shaped traps called an optical lattice formed by intense laser light. JILA scientists detect strontium’s “ticks” (430 trillion per second) by bathing the atoms in very stable red laser light at the exact frequency that prompts the switch between energy levels.
To check the performance, the JILA team compared two versions of the strontium clock, one built in 2005 and the other just last year. Both clocks have set previous records of various types. In the latest work, the two clocks fully agreed with each other within their reported precision—demonstrating the ability to make a duplicate copy and maintain the performance level. This is an advantage for clock comparisons to lay the groundwork for the eventual selection of a next-generation time standard.
Recent technical advances enabling the strontium clocks’ record performance include the development of ultrastable lasers and precise measurements of key effects—atom collisions and environmental heating—that cause tiny changes in the clock’s ticking rate.
Next-generation atomic clocks have already contributed to scientific research and are expected to lead to the development of novel technologies such as super-sensors for quantities such as gravity and temperature. For more background on atomic clock research and important definitions, see “A New Era in Atomic Clocks” at www.nist.gov/pml/div688/2013_1_17_newera_atomicclocks.cfm.
The JILA research is supported by NIST, the Defense Advanced Research Projects Agency, and the National Science Foundation.
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*B.J. Bloom, T.L. Nicholson, J.R. Williams, S.L. Campbell, M. Bishof, X. Zhang, W. Zhang, S.L. Bromley and J. Ye. A new generation of atomic clocks: Total uncertainty and instability at the 1018 level. Nature. Posted online Jan. 22, 2014. DOI 10.1038/nature12941.
**See 2010 NIST news story, “NIST's Second 'Quantum Logic Clock' Based on Aluminum Ion is Now World's Most Precise Clock,” at www.nist.gov/pml/div688/logicclock_020410.cfm.
***See Sept. 3, 2013, NIST Tech Beat article, “NIST Ytterbium Atomic Clocks Set Record for Stability,” at www.nist.gov/public_affairs/tech-beat/tb20130903.cfm#clock.
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NIST March Meeting Showcases Advanced Technologies to Help Manage the Nation's Infrastructure
Tiny, self-powered sensors that can be embedded in bridge structures and networked wirelessly to continuously monitor the structure's health. Little fly-by-wire vehicles that can flit around bridges to measure and inspect their condition without the need to shut spans down to accommodate human inspectors. An automated instrument package that transforms city fleet vehicles into rolling inspectors that monitor and map the condition of roadways and bridge decks as they go about their usual routines.
Beginning in 2008, the National Institute of Standards and Technology (NIST) invested $73 million in a portfolio of competitively selected projects led by research universities and industry consortia to leapfrog the state-of-the-art in monitoring and inspection technologies for the nation's aging infrastructure. Most of them will be on display and discussed for interested potential users or investors in a special Civil Infrastructure Showcase held at the NIST laboratories in Gaithersburg, Md., on March 13 and 14, 2014.
Infrastructure maintenance is a critical issue. The United States is estimated to have 1 million miles of water mains, 600,000 bridges and 4,000,000 miles of public roadway. A significant portion of these assets are in less than prime condition. The Environmental Protection Agency has reported that there are roughly 240,000 water main breaks every year in the U.S. And just incidentally, over a decade ago the American Society of Civil Engineers reckoned that Americans spend $54 billion each year in vehicle repairs caused by poor road conditions.
Improved methods for monitoring and assessing the health of the nation's critical infrastructure are essential to planning and prioritizing maintenance and upgrade activities before structures fail. The NIST program, "Advanced Sensing Technologies for the Infrastructure," sponsored research on a cost-shared basis for 17 projects that involved more than 50 U.S. companies, universities and government agencies. The March showcase will highlight 14 of these projects.
There is a $95 fee to attend the showcase. To register, visit www.fbcinc.com/e/nist/cis/. Further details and the showcase agenda are available at www.nist.gov/tip/nist-civil-infrastructure-showcase.cfm.
The NIST civil infrastructure sensing technologies projects were developed under the Technology Innovation Program (TIP). For more on TIP, see: www.nist.gov/tip/index.cfm. For details on the two TIP competitions on infrastructure technologies and the results, see: www.nist.gov/tip/prev_competitions/index.cfm.
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Rita Colwell Joins NIST Advisory Committee
Rita R. Colwell has joined the National Institute of Standards and Technology's Visiting Committee on Advanced Technology (VCAT), the agency's primary private-sector policy advisory group. She is distinguished university professor both at the University of Maryland at College Park and The Johns Hopkins Bloomberg School of Public Health; senior advisor and chairman emeritus, Canon U.S. Life Sciences, Inc.; and president and chairman of CosmosID, Inc. Under Secretary of Commerce for Standards and Technology and NIST Director Patrick Gallagher appointed Colwell to serve a three-year term.
Colwell served as the 11th director of the National Science Foundation (NSF), from 1998-2004, and in that capacity served as co-chair of the Committee on Science of the National Science and Technology Council. She also has held many advisory positions in the U.S. government, nonprofit science policy organizations, private foundations and the international scientific research community. She is a nationally respected scientist and educator, and has authored or co-authored 17 books and more than 800 scientific publications. Colwell produced the award-winning film, Invisible Seas, and has served on editorial boards of numerous scientific journals.
Before joining NSF, Colwell was president of the University of Maryland Biotechnology Institute and professor of microbiology and biotechnology at the University of Maryland. She was also a member of the National Science Board from 1984 to 1990.
Colwell has previously served as chairman of the board of governors of the American Academy of Microbiology and also as president of the American Association for the Advancement of Science, the Washington Academy of Sciences, the American Society for Microbiology, the Sigma Xi National Science Honorary Society, the International Union of Microbiological Societies and the American Institute of Biological Sciences. Colwell is a member of the National Academy of Sciences, the Royal Swedish Academy of Sciences, the Royal Society of Canada, the Royal Irish Academy, the American Academy of Arts and Sciences and the American Philosophical Society.
Colwell has been awarded 57 honorary degrees from institutions of higher education, including her alma mater, Purdue University, and is the recipient of the Order of the Rising Sun, Gold and Silver Star, bestowed by the Emperor of Japan, the 2006 National Medal of Science awarded by the president of the United States and the 2010 Stockholm Water Prize awarded by the king of Sweden. Colwell is an honorary member of the microbiological societies of the United Kingdom, Australia, France, Israel, Bangladesh, Czechoslovakia and the U.S., and has held several honorary professorships, including the University of Queensland, Australia. A geological site in Antarctica, Colwell Massif, has been named in recognition of her work in the polar regions.
Colwell holds a bachelor's degree in bacteriology and a master's degree in genetics from Purdue, and a Ph.D. in oceanography from the University of Washington.
The VCAT was established by Congress in 1988 to review and make recommendations on NIST's policies, organization, budget and programs. The next VCAT meeting will be Feb. 5 and 6, 2014, in Gaithersburg, Md. For more information on VCAT and the meeting, visit www.nist.gov/director/vcat/.
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JILA/NIST Fellow Deborah Jin to Receive 2014 Comstock Prize in Physics
Physicist Deborah Jin of the National Institute of Standards and Technology (NIST) has been named the recipient of the 2014 Comstock Prize in Physics.
The National Academy of Sciences awards the prize every five years to "recognize a North American resident for a recent innovative discovery or investigation in electricity, magnetism, or radiant energy."
Jin works at JILA, a joint institute of NIST and the University of Colorado Boulder. She is cited for "demonstrating quantum degeneracy and the formation of a molecular Bose-Einstein condensate in ultra-cold fermionic atomic gases, and for pioneering work in polar molecular quantum chemistry."*
The Comstock Prize includes a $25,000 award to the recipient plus a $25,000 award to a non-profit research institution of the recipient's choice. The prize will be presented at the Academy's annual meeting in Washington, D.C., on April 27, 2014.
The National Academy of Sciences is one of the world's leading organizations for distinguished scientists. Jin was elected to the Academy in 2005 as one of the youngest women scientists so honored. (All North American scientists are eligible for the Comstock Prize—Academy membership is not a requirement for selection.) Jin has numerous other honors, including the 2008 Benjamin Franklin Medal in Physics, a 2003 John D. and Catherine T. MacArthur Fellowship (commonly called a "genius grant"), and the 2013 L'Oreal-UNESCO For Women in Science Award for North America.
Read the Academy's announcement at www.nasonline.org/news-and-multimedia/news/jan-16-2014-NASawards.html and more about the Comstock Prize at http://www.nasonline.org/about-nas/awards/comstock-prize-in-physics.html.
*For background on Jin's research, see the 2004 NIST press release, "NIST/University of Colorado Scientists Create New Form of Matter: A Fermionic Condensate," at www.nist.gov/public_affairs/releases/fermi_condensate.cfm and the 2010 NIST press release, “Seeing the Quantum in Chemistry: JILA Scientists Control Chemical Reactions of Ultracold Molecules,”at www.nist.gov/pml/div689/ultracold_021110.cfm.
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NIST Director Recognized by the National Safety Council
The National Safety Council has named Under Secretary of Commerce for Standards and Technology and NIST Director Patrick Gallagher one of 2014's "CEOs Who 'Get It.'" The annual recognition honors leaders who demonstrate a personal commitment to world-class safety. Gallagher has made safety a priority at NIST throughout his tenure.
According to Jim Johnson, vice president of workplace safety initiatives at the council, these leaders have instilled within their organizations the four pillars of the Journey to Safety Excellence: leadership and engagement, safety management systems, continuous risk reduction, and performance measurement.
The National Safety Council is a nonprofit organization, founded in 1913, whose mission is to save lives by preventing injuries and deaths at work, in homes and communities and on the road through leadership, research, education and advocacy. The council's educational efforts aim to change behaviors by building awareness, providing training and sharing best practices.
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