In This Issue...
Slippery When Stacked: NIST Theorists Quantify the Friction of Graphene
Similar to the way pavement, softened by a hot sun, will slow down a car, graphene—a one-atom-thick sheet of carbon with wondrous properties—slows down an object sliding across its surface. But stack the sheets and graphene gets more slippery, say theorists at the National Institute of Standards and Technology (NIST), who developed new software to quantify the material's friction.
"I don't think anyone expects graphene to behave like a surface of a three-dimensional material, but our simulation for the first time explains the differences at an atomic scale," says NIST postdoctoral researcher Alex Smolyanitsky, who wrote the modeling program and co-authored a new paper* about the study. "If people want to use graphene as a solid-state lubricant or even as a part of flexible electrodes, this is important work."
With the capacity to be folded, rolled or stacked, graphene is super-strong and has unusual electronic and optical properties. The material might be used in applications ranging from electronic circuits to solar cells to "greasing" moving parts in nanoscale devices.
Friction is the force that resists the sliding of two surfaces against each other. Studying friction at the atomic scale is a challenge, surmountable in only the past few years. The NIST software simulates atomic force microscopy (AFM) using a molecular dynamics technique. The program was used to measure what happens when a simulated AFM tip moves across a stack of one to four graphene sheets (see image) at different scanning rates.
The researchers found that graphene deflects under and around the AFM tip. The localized, temporary warping creates rolling friction or resistance, the force that exerts drag on a circular object rolling along a surface. Smolyanitsky compares the effect to the sun melting and softening pavement in the state where he got his doctoral degree, Arizona, causing car tires to sink in slightly and slow down. The NIST results are consistent with those of recent graphene experiments by other research groups but provide new quantitative data.
Most significantly, the NIST study shows why friction falls with each sheet of graphene added to the stack (fast scanning also has an effect on the friction). With fewer layers, the top layer deflects more, and the friction per unit of AFM contact force rises. The top surface of the stack becomes less yielding and more slippery as graphene layers are added. By contrast, the friction of three-dimensional graphite-like material is virtually unaffected by deformation and rolling friction, and is due instead to heat created by the moving tip.
* A. Smolyanitsky, J.P. Killgore and V.K. Tewary. Effect of elastic deformation on frictional properties of few-layer graphene. Physical Review B. Posted online Jan. 9.
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NIST Standard Available for Better Diagnosis, Treatment of Cytomegalovirus
A new clinical Standard Reference Material (SRM) from the National Institute of Standards and Technology (NIST) will help health care professionals more accurately diagnose and treat cytomegalovirus (CMV), a common pathogen that is particularly dangerous for infants and persons with weakened immune systems.
CMV is found in 50 to 80 percent of the population. It is a member of the herpes family of viruses that includes two herpes simplex viruses (the causes of cold sores and genital herpes), the varicella-zoster virus (the cause of chicken pox and shingles) and the Epstein-Barr virus (the cause of mononucleosis). Like its cousin herpes viruses, CMV generally remains latent in an infected person unless certain conditions trigger its activation. CMV poses a significant health risk to people who are immunocompromised (such as organ transplant patients or cancer patients undergoing chemotherapy) and babies who receive the virus from their mothers before birth. Congenital CMV infections cause more long-term problems and childhood deaths than many other prenatal disorders including fetal alcohol syndrome, Down syndrome and neural tube defects such as spinal bifida.
If a CMV infection becomes dangerous, antiviral agents can be used to moderate the impact. Unfortunately, many of these compounds are toxic, so a physician must know the severity of the infection—a measure known as viral load (number of virus copies per microliter of blood)—to prescribe the optimal dosage and duration of treatment. The current means of measuring viral load is to use polymerase chain reaction (PCR)—the standard technique for "amplifying" or making multiple copies of a DNA segment or molecule—to amplify a region of the CMV gene and then use a calibration curve to estimate the number of virus particles in the original sample. Accuracy of these measurements can vary greatly from one test facility to another as there are many different PCR protocols used to determine viral load, including commercial and "in-house" (privately developed) laboratory assays.
The new NIST reference, SRM 2366, addresses the variability problem by providing a standardized CMV DNA. Consistency of the viral DNA in the standard was ensured by manufacturing it in Escherichia coli bacteria. These E. coli cells each contain a copy of the CMV genome in a "DNA construct"—an artificially constructed segment of nucleic acid that codes for a specific product, in this case, CMV DNA. The DNA copies made by this E. coli cell culture "factory" can then be purified and quantified using digital PCR
SRM 2366 consists of three solutions, each with a specific concentration of CMV DNA copies per microliter: 420, 1,702 and 19,641. These are designed to qualify prepared calibration samples (known as calibrants). They also can be used as quality control samples for diagnostic equipment. For added traceability, the SRM certificate of analysis includes the genetic sequences of the nine CMV genome regions copied for the standard.
SRM 2366 joins more than 50 reference materials produced by NIST for quality control in clinical testing. Standard Reference Materials are among the most widely distributed and used products from NIST. The agency prepares, analyzes and distributes about 1,300 different materials that are used throughout the world to check the accuracy of instruments, validate test procedures and serve as the basis for quality control standards worldwide.
To get information on purchasing SRM 2366 and download the certificate of analysis, go to https://www-s.nist.gov/srmors/view_detail.cfm?srm=2366.
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Stretching Exercises: Using Digital Images to Understand Bridge Failures
With a random-looking spatter of paint specks, a pair of cameras and a whole lot of computer processing, engineer Mark Iadicola of the National Institute of Standards and Technology (NIST) has been helping the Federal Highway Administration (FHWA), in cooperation with the American Association of State Highway and Transportation Officials (AASHTO), to assure the safety of hundreds of truss bridges across the United States. Iadicola has been testing the use of a thoroughly modern version of an old technique—photographic measurement or “photogrammetry”—to watch the failure of a key bridge component in exquisite detail.
The impetus for the FHWA project was the disastrous collapse of the Interstate 35-W bridge in Minneapolis, Minnesota. On Aug. 1, 2007, in the middle of the evening rush hour, a thousand feet of the bridge’s main deck truss collapsed, part of it falling 108 feet into the Mississippi River. Thirteen people died. One hundred and forty five were injured.
According to FHWA engineer Justin Ocel, an investigation by the National Transportation Safety Board (NTSB), assisted by FHWA, determined that the immediate culprit was a failed gusset plate, a flat heavy piece of steel bolted in pairs to join the ends of the steel members that make up the bridge truss. As a result of a design error decades before, the gusset plates in the bridge were about half as thick as they should have been.
Although that design flaw was clearly a major factor in the disaster, Ocel says, the collapse highlighted the fact that gusset plates were not generally considered by engineers during periodic reviews of bridge capacity, a process called load rating. It was assumed that gusset plates were properly sized to be stronger than the members they connect. “One of the recommendations from the NTSB was that we include gusset plates in load ratings, and until that point it hadn't been done,” Ocel explains. “To assist the states with this process we developed a guidance document on how to load rate gusset plates.”
In developing the guidance, Ocel says, FHWA used the best available data on the failure modes of gusset plates in major bridges—but there wasn’t much. So at the FHWA's Turner-Fairbank Highway Research Center in Virginia they began building full-scale models of bridge gusset plate joints and pulling them apart with a huge hydraulic test machine.
NIST’s Iadicola is there to watch what happens as the plate stretches and fails. He covers the plate with an irregular pattern of paint speckles and then trains a pair of carefully calibrated, high-definition digital cameras on it. The cameras repeatedly image the plate, send the pictures to a computer that uses custom software to compare each image to the previous one, and calculate which of the paint spots have moved, in what direction and by how much. Using two cameras allows the computer to “see” the plate in three dimensions, so it can tell if points on the surface move in or out as well as up, down or sideways.
“The NIST digital image correlation method is a good complement to the FHWA measurement methods,” Iadicola explains. “Their techniques—strain gages and photoelasticity—are very good for the normal range of stress in which the plate will stretch and spring right back to its original shape. Our method can tell you a little about that, but it really shines in showing you what happens past that point, when the plate starts permanently deforming and finally rips apart. The failure modes.”
After more than a year of experiments, Ocel says, the FHWA has learned a lot about how to predict what loads will cause a gusset plate to fail. Currently, FHWA is working with AASHTO to translate those findings into language that can be adopted into the AASHTO Bridge Design Specification and Manual for Bridge Evaluation, two documents used throughout the country for designing and load rating bridges.
The FHWA project is just one of a range of applications for digital image correlation being studied at NIST, Iadicola says. “We’ve been using it in looking at sheet metal forming—you have very high strains during the forming process—and we’ve used it at very small scales, looking at targets with an optical microscope.”
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NIST Releases Two New SRMs for Monitoring Human Exposure to Environmental Toxins
The National Institute of Standards and Technology (NIST), in collaboration with the Centers for Disease Control and Prevention (CDC), has developed two new Standard Reference Materials (SRMs) for measurements of human exposure to environmental toxins. Used as a sort of chemical ruler to check the accuracy of tests and analytic procedures, the new reference materials replace and improve older versions, adding measures for emerging environmental contaminants such as perchlorate, a chemical that the Environmental Protection Agency has targeted for regulation as a contaminant under the Safe Drinking Water Act.
The CDC will use the new SRMs—3668, “Mercury, Perchlorate, and Iodide in Frozen Human Urine” and 2668, “Toxic Elements in Frozen Human Urine”—as quality controls for urine tests during their biennial National Health and Nutrition Examination Survey (see www.cdc.gov/nchs/nhanes.htm.)
Because sample collection is non-invasive and the test results reflect exposures as recent as two days, urine is preferred for clinical diagnostics and monitoring of toxic environmental chemicals. Once collected, samples are frozen while they await testing.
In order to generate comparable results among tests, best practices in clinical chemistry state that a reference material should closely mimic how a specimen would respond to these tests. The best way to achieve such close resemblance is to make the physical, chemical and biological properties of the reference material as close as possible to the specimen. NIST researchers developed these new SRMs to replace the freeze-dried SRMs 2670a, 2671a and 2672a because when the frozen urine SRM is thawed it matches the properties of clinical urine specimens much more closely than reconstituted freeze-dried urine SRM.
In addition to NIST, the CDC, Mayo Clinic and the New York State Department of Health made certification measurements of the two SRMs to ensure their relevance for the intended applications. The development of SRMs 2668 and 3668 reflects NIST’s commitment to continually improve chemical metrology to improve the health of the nation.
For more on SRM 3668, see https://www-s.nist.gov/srmors/view_detail.cfm?srm=3668. For more on SRM 2668, see https://www-s.nist.gov/srmors/view_detail.cfm?srm=2668.
Standard Reference Materials are among the most widely distributed and used products from NIST. The agency prepares, analyzes and distributes about 1,300 different materials that are used throughout the world to check the accuracy of instruments, validate test procedures and serve as the basis for quality control standards worldwide.
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NIST SBIR Program Soliciting Proposals to Solve Manufacturing and IT Challenges
The National Institute of Standards and Technology (NIST) needs American innovators and entrepreneurs to help solve technological problems and develop NIST technologies into marketable products. The NIST Small Business Innovation Research (SBIR) program is seeking to fund proposals that address specific challenges in the fields of advanced manufacturing and information technology and cybersecurity (including communications-related technologies).
The NIST SBIR program seeks to fuel technological innovation in the private sector by strengthening the role small business plays in meeting federal R&D needs and bringing to market innovations derived from federal research and development. The program also works to increase participation by socially and economically disadvantaged persons and women-owned small business concerns in technological innovation.
Intended to determine if the proposed research is feasible and to gauge how well the awardee performs that research, SBIR phase 1 awards provide up to $90,000 over a performance period of seven months. Awardees that successfully complete their phase 1 research projects will be eligible to apply for phase 2 funding to further develop the technology.
The NIST 2012 SBIR solicitation names 12 specific technologies for development. In the category of Manufacturing, they include:
In the interest of competitive fairness, communication with NIST concerning a specific technical topic or subtopic during the open solicitation period is not allowed, with the exception of the public discussion group at www.nist.gov/sbir. All questions and responses will be publicly, though anonymously, posted on the discussion group website.
Read the 2012 SBIR proposal solicitation, available at http://go.usa.gov/NhU for a full explanation of the SBIR process, rules and the specific challenges the proposals should address. Unsolicited proposals, i.e. proposals that do not address the challenges outlined in the SBIR proposal solicitation, will not be accepted. The solicitation closes March 12.
For general information about the NIST SBIR program, call (301) 975-4188 or send an e-mail to email@example.com.
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New DOC Report Examines the Federal Role in U.S. Innovation and Competitiveness
On Jan. 6, 2012, the U.S. Department of Commerce (DOC) issued a new report highlighting key policy priorities to sustain and promote American innovation and economic competitiveness. The report, The Competitiveness and Innovative Capacity of the United States, examines the historic role of federal investments in research, education and infrastructure in driving the nation's economic competitiveness, business expansion and job creation, and argues for continued strong support for those three areas as well as manufacturing.
The report was mandated as part of the America COMPETES Reauthorization Act of 2010. It addresses a diverse range of topics and policy options, including tax policy; the general business climate in the U.S.; barriers to setting up new firms; trade policy, including export promotion; the effectiveness of Federal Research and Development policy; intellectual property regimes in the U.S. and abroad; the health of the manufacturing sector; and science and technology education.
The policy recommendations and observations in the COMPETES report include:
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Text Retrieval Conference 2012 Seeks Information Retrieval Experts for Data Digging
The National Institute of Standards and Technology (NIST) is conducting the 21st annual Text Retrieval Conference (TREC), the premier experimental effort in the field, to encourage research in information retrieval and related applications. TREC is a rather unusual conference in that it starts months ahead of the actual meeting (Nov. 6-9, 2012) with the distribution of test data sets and challenges that TREC participants will use to develop and test advanced text retrieval techniques.
Finding valuable information rapidly is much more than a game for people with a high-tech phone. Text retrieval is a field of research that can save lives by helping medical researchers locate key patient information or aid lawyers seeking important data in large digital data collections—both modern-day examples of needles in haystacks.
TREC brings together scientists from academia and public and private-sector organizations to focus on improving information retrieval in specific areas. The groups develop algorithms to find information from large, challenging datasets often provided by NIST. They work throughout the year and come to NIST's headquarters in Gaithersburg, Md., to discuss their findings at the November meeting.
A recent economic impact study* prepared for NIST found that the NIST-led TREC project has significantly improved the ability to retrieve digital data. The report notes that TREC-related improvements are responsible for about one-third of the web-search advances between 1999 and 2009 and that the improvements may have saved up to 3 billion hours of web-search time.
TREC challenges are grouped into tracks that target difficult text-retrieval challenges. Retrieving text within Medical Records, for example, addresses a common problem in designing clinical trials: finding important information from patient records that is generally in unstructured "comment" fields. Of a vast patient data set, for example, which patients take herbal products for osteoarthritis?
The 2012 TREC adds two new tracks, "Contextual Suggestion" and "Knowledge Base Acceleration." In Contextual Suggestion, researchers will study methods for answering vague queries specifically based on personal demographics and information from calendar and contacts apps. For example, according to TREC Conference Organizer Ellen Voorhees, "A person arrives in a city for a business trip and has a free evening, so asks the search system in their smart phone 'What should I do tonight?' To answer this well, the system will need to integrate information about the user's likes/dislikes with external information such as schedules of events in the city, availability of tickets, whether friends of the user are also in the area and other data."
The Knowledge Base Acceleration track looks to automate the process of keeping a knowledge base up-to-date. One example is having a system monitor a news feed to keep a Wikipedia page current about an event, such as the Occupy Wall Street Movement, for example.
Six tracks will continue from TREC 2011: Crowdsourcing, Legal, Medical Records, Microblog, Session and Web.
Applications to participate in TREC 2012 are being accepted through February 22. For more information on TREC and participating, see http://trec.nist.gov.
* B.R. Rowe, D.W.Wood, A.N. Link and D.A. Simoni. Economic Impact Assessment of NIST's Text REtrieval Conference (TREC) Program. RTI Project Number 0211875, July 2010. Available on-line at: http://trec.nist.gov/pubs/2010.economic.impact.pdf.
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Four at NIST Elected AAAS Fellows
The American Association for the Advancement of Science (AAAS), the world's largest general scientific society, has elected four researchers at the National Institute of Standards and Technology (NIST) to this year's class of AAAS Fellows.
AAAS Fellows are nominated and selected by their peers to recognize meritorious efforts to advance science or its applications. The four new fellows from NIST are:
Jeffrey Voas, of the NIST Information Technology Laboratory, for distinguished contributions in the development of trustworthy software systems and advanced software fault injection-based testing techniques;
Jeffrey Nico, from the NIST Physical Measurement Laboratory, for distinguished contributions to precision measurements and fundamental symmetry tests using cold neutrons and to radiochemical determinations of the proton-proton fusion solar neutrino flux;
Vijay Srinivasan, from the NIST Engineering Laboratory, for distinguished contributions to scientific theory, algorithms, and standards for computer-aided design and manufacturing; and
Cedric Powell, from the NIST Material Measurement Laboratory, for outstanding contributions to electron spectroscopies of solids, especially in application to quantitative analysis of surfaces and establishment of surface measurement standards.
The AAAS elected 539 new fellows in 2011 from the association's 24 technical sections. The new fellows will be formally recognized on Feb. 18, 2012, during the 2012 AAAS Annual Meeting in Vancouver, B.C., Canada. A complete list of the new AAAS Fellows is available at www.aaas.org/aboutaaas/fellows/2011.shtml.
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NIST Technologies Contribute to Top Science Stories of 2011
The top science stories of 2011, as selected by several science magazines, include two experiments and a famous computer, that relied on technology from the National Institute of Standards and Technology (NIST).
Physics World's top breakthrough of the year was an experiment that "shifted the morals of quantum measurement" by doing something previously thought to be impossible—tracking the paths of single particles of light (photons) passing through two closely spaced openings. Led by a University of Toronto physicist, the experiment used a NIST-made quantum dot as the source of single photons. The Physics World story can be found at http://physicsworld.com/cws/article/news/48126 and the NIST contribution is described at http://www.nist.gov/pml/newsletter/quantum_dot.cfm.
Science News and Physics Today highlighted experiments at the Atacama Cosmology Telescope in Chile that measured "gravitational lensing" of the cosmic microwave background and verified the existence of dark energy, believed to make up most of the universe and to drive its expansion. More than a dozen institutions collaborate on the research. The telescope camera relies on superconducting sensors based on a NIST design and superconducting amplifiers and electronics made at NIST. Gravitational lensing refers to distortions in the afterglow of the Big Bang caused by the gravitational force of matter distributed across the universe.
Physics Today editors selected the research as one of seven highlights of the most important and interesting news in physics and related sciences: http://www.aip.org/pt/e-alerts/ptpicks/2011_12.html (see "The demonstration of gravitational lensing of the cosmic microwave background"). Science News included the work in its roundup of 2011 Science News of the Year, as one of 18 items in the Atom & Cosmos category: http://www.sciencenews.org/view/feature/id/336994/title/2011_Science_News_of_the_Year_Atom_%2B_Cosmos (see "Dark Check" entry).
Several groups, including New Scientist, Discover magazine and National Public Radio, also cited one of the most-watched technology events of the year: the February 2011 victory of the IBM supercomputer Watson on the TV game show Jeopardy. IBM researchers have noted that Watson's roots are in the question answering (QA) systems developed by IBM for their participation in the NIST Text REtrieval Conference (TREC) QA track starting in 1999. See our story above for news on the 21st Annual Text Retrieval Conference.
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