In This Issue...
NIST’s Fiscal Year Budget to Increase 8.3 Percent to $819 M
For fiscal year 2009, which ends on Sept. 30, the National Institute of Standards and Technology (NIST) has received $819 million in appropriations, an increase of 8.3 percent over the previous fiscal year. Funding for NIST was included in the FY 2009 Omnibus Appropriations Act (Public Law 111-8) passed by Congress and signed by President Obama on March 11. These fiscal-year appropriations come in addition to the $610 million in funds that NIST is receiving as a result of the American Recovery and Reinvestment Act (see “NIST to Receive $610 Million Through Recovery Act”).
The total fiscal-year budget for NIST is broken down into three appropriations:
Further information on the NIST budget can be found at www.nist.gov/public_affairs/releases/approps-summary2009.htm.
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Making a Point: Picoscale Stability in a Room-Temperature AFM
Forget dancing angels, a research team from the National Institute of Standards and Technology (NIST) and the University of Colorado (CU) has shown how to detect and monitor the tiny amount of light reflected directly off the needle point of an atomic force microscope probe, and in so doing has demonstrated a 100-fold improvement in the stability of the instrument’s measurements under ambient conditions. Their recently reported work* potentially affects a broad range of research from nanomanufacturing to biology, where sensitive, atomic-scale measurements must be made at room temperature in liquids.
Atomic force microscopes (AFMs) are one of the workhorse tools of nanotechnology. AFMs have a sharp, pointed probe fixed to one end of a diving-board-like cantilever. As the probe is scanned across a sample, atomic-scale forces tug at the probe tip, deflecting the cantilever. By reflecting a laser beam from the top of the cantilever, researchers can sense changes in the force and build up a nanoscale topographic image of the sample. The instruments are terrifically versatile—in various configurations they can image electrostatic forces, chemical bonds, magnetic forces and other atomic-scale interactions.
While extremely sensitive to atomic-scale features, AFMs also are extremely sensitive to interference from acoustic noise, temperature shifts and vibration, among other factors. This makes it difficult or impossible either to hold the probe in one place to observe the specimen under it over time (useful for studying the dynamics of proteins) or to move the probe away and return to exactly the same spot (potentially useful for nanoscale manufacturing). “At this scale, it’s like trying to hold a pen and draw on a sheet of paper while riding in a jeep,” observes NIST physicist Thomas Perkins. A few instruments in specialized labs, including some at NIST, solve this problem by operating at extremely cold temperatures in ultra-high vacuums and in heavily isolated environments, but those options aren’t available for the vast majority of AFMs, particularly those used in bioscience laboratories where the specimen often must be immersed in a fluid.
The JILA solution uses two additional laser beams to sense the three-dimensional motion of both the test specimen and the AFM probe. The beams are held stable relative to each other to provide a common reference. To hold the specimen, the team uses a transparent substrate with tiny silicon disks—“fiducial marks”—embedded in it at regular intervals. One laser beam is focused on one of these disks. A small portion of the light scatters backwards to a detector. Any lateral vibration or drift of the sample shows up at the detector as a motion of the spot while any vertical movement shows up as a change in light intensity.** A similar trick with the second beam is used to detect vibration or drift in the probe tip, with the added complication that the system has to work with the scant amount of light reflected off the apex of the AFM probe. Unwanted motion of the tip relative to the sample is corrected on the fly by moving the substrate in the opposite direction. “This is the same idea as active noise cancellation headphones, but applied to atomic force microscopy,” says Perkins.
In its most recent work, the JILA team has controlled the probe’s position in three dimensions to better than 40 picometers (1 nanometer = 1000 picometers) over 100 seconds. In imaging applications, they showed the long-term drift at room temperature was a mere 5 picometers per minute, a 100-fold improvement over the best previous results under ambient conditions. Just like photographers use the stability of a tripod and longer exposures to improve picture quality, the JILA team used their improved stability to scan the AFM probe more slowly, leading to a 5-fold improvement in AFM image quality. A bonus, says Perkins, is the technique works with standard commercial probes.
* G.M. King, A.R. Carter, A.B. Churnside, L.S. Eberle and T.T. Perkins. Ultrastable atomic force microscopy: Atomic-scale stability and registration in ambient conditions. Nano Letters, Article ASAP, March 12, 2009 (DOI: 10.1021/nl803298q).
** The sample control technique was first reported in: A.R. Carter, G.M. King and T.T. Perkins. Back-scattered detection provides atomic-scale localization precision, stability, and registration in 3D. Optics Express V. 15, No. 20. Oct. 1, 2007.
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NIST Research Collaboration Spies Galfenol’s Inner Beauty Mark
The sonar on submarines may get far more sensitive ears in the near future thanks to a mysterious compound developed by the military. Developed over a decade ago, it took a collaboration of scientists from the Virginia Polytechnic Institute and State University and the National Institute of Standards and Technology (NIST) to determine why the material works. Surprisingly, the critical factor is a sprinkling of useful imperfections within an otherwise regular crystal.
The scientific team solved the internal structure of Galfenol, a compound of iron and gallium that changes shape when exposed to a magnetic field. Because the effect also works in reverse—a tiny bit of pressure that distorts its shape slightly and induces detectable magnetism—such "magnetostrictors" are the key ingredients in sound detection equipment.
Iron alone has some talent as a magnetostrictor, but U.S. Navy researchers discovered in 1998 that doping iron with gallium amplifies iron’s magnetostrictive capability tenfold. They dubbed their creation Galfenol, but the basis for the material’s behavior went unexplained.
"It’s important to know why a material works the way it does," says Peter Gehring of the NIST Center for Neutron Research (NCNR). "If you can relate its atomic structure to its behavior, you might be able to improve the recipe."
The scientists used neutron beams to determine Galfenol’s structure, settling a running debate over which model of its innards was correct. The investigation showed that the added gallium changes the structure of the iron, which on the atomic level forms a lattice of regular cubic cells. When the gallium combines with the iron, the faces of some cells become rectangular rather than square. These elongated gallium-iron cells then congregate into tiny clumps within the lattice, resembling "something like raisins within a cake," as Gehring describes it.
The study also showed that these clusters of distorted cells respond to a magnetic field by rotating their magnetic moments, like tiny compass needles, to align with the field; it is this rotation that changes the exterior dimensions of the crystal. The clusters are thus responsible for Galfenol's performance—it changes in size by 400 parts per million compared to iron's 30—even though it seems surprising that imperfections in iron's otherwise orderly lattice should improve its magnetostrictive talents.
"These irregularities give the iron more complex and richer properties," Gehring says. "We see this theme repeated frequently in nature, where similar kinds of disorder lead to improved performance in high-temperature superconductors, giant magnetoresistive oxides, and other exotic new materials. It's like the supermodel with a beauty mark on her cheek—we don’t know why it’s so appealing, but it is."
The study was funded in part by the Office of Naval Research.
* H. Cao, P.M. Gehring, C.P. Devreugd, J.A. Rodriguez-Rivera, J. Li and D. Viehland. The role of nano-scale precipitates on the enhanced magnetostriction of heat-treated Galfenol (Fe1-xGax) alloys. Physical Review Letters, forthcoming.
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Flatland Physics Probes Mysteries of Superfluidity
If physicists lived in Flatland—the fictional two-dimensional world invented by Edwin Abbott in his 1884 novel—some of their quantum physics experiments would turn out differently (not just thinner) than those in our world. The distinction has taken another step from speculative fiction to real-world puzzle with a paper* from the Joint Quantum Institute (JQI) reporting on a Flatland arrangement of ultracold gas atoms. The new results, which don’t quite jibe with earlier Flatland experiments in Paris, might help clarify a strange property: “superfluidity.”
In three dimensions, cooling a gas of certain atoms to sufficiently low temperatures turns them into a Bose-Einstein condensate (BEC). As predicted in the 1920s (and first demonstrated in 1995) the once individualistic gas atoms begin to move as a single, coordinated entity. But back in 1970, theorists predicted that something different would happen in two dimensions: an ultracold gas of interacting atoms would undergo the analogous “Berezinskii, Kosterlitz and Thouless” (BKT) transition, in which atoms don’t quite move in lockstep as they do in a BEC, but mysteriously share some of a BEC’s properties, such as superfluidity, or frictionless flow.
In new experiments at the Joint Quantum Institute (JQI), a partnership of the National Institute of Standards and Technology (NIST) and the University of Maryland, a team of physicists led by JQI Fellow Kristian Helmerson has achieved the latest experimental observation of the BKT transition. The JQI researchers trap and cool a micron-thick layer of sodium atoms, confined to move in only two dimensions. At higher temperatures, the atoms have normal “thermal” behavior in which they act as individual entities, but then as the temperature lowers, the gas transforms into a “quasi-condensate,” consisting of little islands each behaving like a tiny BEC.
By further lowering the temperature, the gas makes the transition to a BKT superfluid where the islands begin to merge into a sort of “United States” of superfluidity. In this situation, an atom can flow unimpeded between neighboring “states” since the borders of the former islands are not well defined, but one can tell that the atom is “not in Kansas anymore,” in contrast to a BEC where one cannot pinpoint the location of a particular atom anywhere in the gas.
When a Paris group lowered the temperature of their 2-D gas in earlier experiments, they only saw a sharp transition from thermal behavior to a BKT superfluid, rather than the additional step of the non-superfluid quasi-condensate. But the Paris group used rubidium atoms, which are heavier and more strongly interacting, possibly exhibiting a qualitatively different behavior. These new results may cast light on superfluidity, which decades after its discovery still seems to hold new mysteries.
* P. Cladé, C. Ryu, A. Ramanathan, K. Helmerson and W.D. Phillips. Observation of a 2D Bose-gas: From thermal to quasi-condensate to superfluid. Physical Review Letters, Vol.102, No.17. (May 1, 2009) DOI: 10.1103/PhysRevLett.102.170401.
Edited on April 27, 2009, to update publication data.
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NIST Stairwell Evacuation Study Finds ‘What We Know We Don’t Know’
Most of the time, we use the stairs in buildings—especially in high-rise structures—only as a back-up for faster elevators and escalators, but during a fire or other emergency, stairs become our primary passage to survival. In a new study, researchers at the National Institute of Standards and Technology (NIST) examined what we know about how stairs work as an emergency evacuation route and found that the answer is—not nearly enough.
NIST researchers studied people movement speeds during three full-building fire drill evacuations and compared the data to already published results—including those from NIST’s investigation of the World Trade Center disaster on Sept. 11, 2001— to try to identify the factors that could hamper rapid evacuation using stairways. Their conclusions: research to date provides limited insight into how people react and behave during evacuations, and that for the most part, variances in speed cannot be explained by the evacuation models currently used in building design and emergency planning. Or as the title of the new NIST report acknowledges, “What we know we don’t know.”
Building engineers typically use five factors to describe occupant descent down stairwells during building evacuations: pre-evacuation delay, distance traveled during evacuation (movement from higher floors versus lower), counterflow situations (such as firefighters moving up a stairwell while occupants are moving down), stairwell geometry and density of persons in the stairwell. Models make use of such variables to predict the performance of egress systems and the expected speed for a complete evacuation.
However, the NIST researchers found that these engineering parameters could only explain about 13 percent of the differences they observed in evacuation speeds for the three fire drills. Since these speeds were similar to ones reported by previous studies, the researchers suggest that psychological and behavioral factors may be more important in determining how fast occupants can actually exit a building. They also note that inaccurate evacuation data based on simplifications about behavior could lead to unsafe building designs and procedures.
“Clearly,” the researchers state in the report, “there is a need to better understand all the factors that impact the ability of building occupants to take appropriate protective action in the event of a building emergency.”
As a start toward improving understanding, the NIST Building and Fire Research Laboratory has posted a Web page, www.fire.nist.gov/CDPUBS/bldg_occupant, with links to all four building occupant research studies completed in 2008, including the stairwell evacuation report Stairwell Evacuation from Buildings: What We Know We Don’t Know (NIST Technical Note 1624).
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New Program Evaluates Labs for Emergency Communications Tests
To help ensure that first responders, public safety officers and military personnel can always talk with each other no matter what communications equipment they are using (a characteristic known as interoperability), the National Institute of Standards and Technology (NIST) and the Department of Homeland Security (DHS) have teamed up to create the Project 25 Conformity Assessment Program (P25 CAP).
The latest milestone of the recently launched program is the publication of the 2009 edition of NIST Handbook 153, Laboratory Recognition Process for Project 25 Compliance Assessment. The guide details the procedures by which independent testing laboratories can be evaluated for their ability to determine how well public safety and emergency communications devices meet the performance standard for interoperability known as Project 25 (P25).
NIST Handbook 153 – Laboratory Recognition Process for Project 25 – Compliance Assessment, January 2009 may be downloaded from the OLES documents Web site at www.eeel.nist.gov/oles/Publications/NIST%20Handbook%20153%20edition%202009.pdf.
Initially, P25 CAP focuses on the most mature of the nine interoperability standards that will eventually make up the P25 suite—the Common Air Interface (CAI). The CAI is the standard that describes the physical and logistical characteristics of a link between the two stations that make up a radio communication system—the base and mobile handsets. A radio using P25 CAI should be able to communicate with any other P25 CAI radio, regardless of what manufacturers produced the two units.
As other interfaces become better defined, they will be added to the testing lab assessment criteria.
NIST’s Office of Law Enforcement Standards (OLES) designed the P25 CAP protocols that are being used by DHS’s Office of Interoperability and Compatability (OIC) to recognize independent laboratories across the country capable of offering interoperability testing of equipment to manufacturers and users.
The P25 suite of interoperability standards is being developed by representatives from local, state and federal public safety associations and agencies. It is administered by the Telecommunications Industry Association.
Laboratories wishing to be reviewed for their P25 testing ability should contact Dereck Orr, firstname.lastname@example.org, (303) 497-5400. For more information on the P25 CAP, contact Orr or Luke Berndt, DHS, at email@example.com, (202) 254-5332.
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Magnetism Governs Properties of Iron-Based Superconductors
Though a year has passed since the discovery of a new family of high-temperature superconductors, a viable explanation for the iron-based materials’ unusual properties remains elusive. But a team of scientists working at the National Institute of Standards and Technology (NIST) may be close to the answer.
The team has found strong evidence that magnetism is a pivotal factor governing the physical properties of iron pnictides, a group of materials that conduct electricity without resistance at temperatures of up to 56 kelvin (-217 degrees celsius). Iron pnictides are composed of regularly spaced layers of iron sandwiched between other substances. And although -217 might sound pretty cold, they are the first class of materials found to superconduct at that high a temperature since the discovery of copper-based superconductors more than two decades ago.
The team’s evidence shows that, without taking magnetism into account, theoretical calculations of iron pnictides’ inner structure do not line up with actual lab measurements. Factor in magnetism, though, and these discrepancies vanish—a decisive difference that, according to theorist Taner Yildirim, could imply that magnetism is also key to iron pnictide superconductivity.
“Without considering magnetism, for example, the calculated distance between iron layers—a distance that has been thoroughly measured—comes out to be wrong,” says Yildirim, of NIST’s Center for Neutron Research. “However, provided that we consider magnetic spin in our calculations, we can explain almost all of the iron pnictides’ structural and dynamic properties.”
Yildirim gave an invited talk* at the March meeting of the American Physical Society, where he presented theoretical evidence demonstrating how magnetism controls basic aspects of iron pnictides as the position of the atoms, the materials’ phase transition, i.e. the sudden changes in the structure with temperature, and—probably, Yildirim says—their superconducting properties.
“Determining the mechanism of superconductivity in iron pnictide systems is very important in solving the long-standing mystery of the high temperature superconductor phenomena in general,” Yildirim says. “Once we have such an understanding of this strange phenomenon, we can then make predictions and design new materials with even higher superconductivity temperatures.”
For more on Dr. Yildirim’s work, see www.ncnr.nist.gov/staff/taner/highlights.htm. For more on iron-based superconductors at NIST, see “Iron-based Materials May Unlock Superconductivity’s Secrets,” NIST Tech Beat, Nov. 12, 2008.
* T. Yildrim. Competing magnetic interactions, structural phase transition, and the unprecedented giant coupling of Fe-spin state and the As-As interactions in iron-pnictide. Presented at the March Meeting of the American Physical Society, March 17, 2009. An abstract is available at http://meetings.aps.org/Meeting/MAR09/Event/96315.
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Conference on Safeguarding Health Information, May 18-19Most people’s experience with the Health Insurance Portability and Accountability Act (HIPAA) consists of a quick glance at a photocopied document at the doctor’s office followed by signing a form stating that we have reviewed the information. But there is much more to the law that was enacted by Congress to promote health care industry proficiency by using electronic health information while protecting the confidentiality, integrity and availability of the information.
To assist the understanding and expansion of these standards and practices, the National Institute of Standards and Technology (NIST) is co-hosting “Safeguarding Health Information: Building Assurance through HIPAA Security” May 18-19 at its Gaithersburg, Md., facility. The co-host is the Centers for Medicare and Medicaid Services (CMS), the federal agency mandated in the 1996 act to be responsible for creating a more efficient and effective health care system that increasingly uses electronic healthcare transactions.
NIST provides ongoing expertise in risk management, security and standards to CMS and has been involved in health information technology (IT) research since 1994. NIST is receiving $20 million through the American Recovery and Reinvestment Act of 2009 to accelerate the development and harmonization of standards and to develop conformance test tools for health IT.
Organizations required to follow the HIPAA Security Rule include government agencies involved in health records, health care providers, health plans such as health insurance issuers and Medicaid and Medicare programs, health care clearinghouses and Medicare prescription drug card sponsors.
The meeting is expecting to draw hundreds of HIPAA security rule implementers; security, privacy and compliance officers; assessment teams and audit staff. During the meeting attendees will learn techniques for implementing the HIPAA Security Rule requirements with focus on strategies for assessing the effectiveness of implemented security controls to support compliance, auditing, and an organization’s overarching risk management program. Sessions will be dedicated to security assessment frameworks and methodologies, new technologies and security safeguards, e-prescribing, security automation, the Federal Information Security Management Act and the American Recovery and Reinvestment Act of 2009 and its impact on security and privacy of health information.
For more information about the meeting, see the registration site www.nist.gov/public_affairs/confpage/090518.htm.
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