NIST Tech Beat - March 1, 2007

Researchers at the National Institute of Standards and Technology (NIST) have developed a microelectromechanical system (MEMS) cell-stretcher that can measure the mechanical properties of a living cell, such as its ability to stick to a surface. The new device is expected to enable novel studies of cell mechanics, which influence basic cell functions such as growth and division, and diseases such as sickle cell anemia and asthma.

The prototype device, described in a new paper,* is believed to be the only technique for studying bulk mechanical properties of a single, whole cell while it is spreading out and sticking to a substrate as it would in the body, says the designer, NIST bioengineer David Serrell. Other biomechanical test methods focus on individual cell components or entire tissues.

The heart of the NIST device is a circular cell platform 200 micrometers wide, a tiny fleck just barely visible to the naked eye. The two halves of the circle can be pulled as far as 100 micrometers apart under computer control, while the force needed to separate them is measured by sensors. In a demonstration using a connective tissue cell, the cell is placed on the center of the platform, allowed to spread and adhere for several hours, and then pulled slowly apart until it detaches. In NIST experiments, the cells let go of the substrate at a force of about 1500 nanonewtons. (One nanonewton is the approximate amount of force required to break a single chemical bond between two atoms.)

The devices are made on silicon wafers using a NIST-developed process based on standard chip-making techniques. The geometry of any component can be altered to suit a variety of cell types and experiments. The apparatus could be used for a variety of studies, such as effects of cyclic strain on cells, the elasticity of their response to force, or the effectiveness of different proteins used to encourage attachment of the cells, Serrell says. The newest version of the device, fabricated but not yet tested, is made of silicon nitride, a transparent material that will allow simultaneous real-time imaging of the interior of the cells and perhaps provide new insights into the relationships of force and cell mechanical properties and structure.

Co-authors from the University of Colorado at Boulder contributed to development and testing of the device.

* D.B. Serrell, T. Oreskovic, A.J. Slifka, R.L. Mahajan and D.S. Finch. A uniaxial bioMEMS device for quantitative force-displacement measurements. Biomedical Microdevices. Available online.

Sensor-laden robots capable of vital search and rescue missions at disaster sites are no figment of a science fiction writer’s imagination. Prototypes and commercial models of urban search and rescue (US&R) robots will soon begin to work rubble piles across the country. Too many of these lifesaving robots, however, could be too much of a good thing, according to researchers at the National Institute of Standards and Technology (NIST), who report that the radio transmissions of multiple robots can interfere with each other and degrade search and rescue performance.

A NIST analysis of wireless radio field trials for US&R robots, presented at a conference on February 28,* found that 10 out of the 14 robots tested experienced communication problems due to radio interference from other systems. Engineers carried out tests on the robots last August at a US&R robot standards development gathering in Gaithersburg, Md., sponsored by the Department of Homeland Security. The researchers found that neither use of “industrial, scientific, and medical” (ISM) frequency bands nor adherence to protocols designed to minimize interference between systems in the bands could guarantee flawless communication between a robot and its human operator. Radio interference could happen whenever the ISM frequency bands became crowded or when one user had a much higher output power than the others. An example of the latter problem occurred during the tests when transmitters in the 1760 MHz band knocked out video links in the 2.4 GHz frequency band. In another case, a robot using an 802.11b signal in the 2.4 GHz band overwhelmed and cut off a robot that had been transmitting an analog video link at 2.414 GHz.

The NIST paper lists a number of ways to improve urban search and rescue wireless communications. Options, some of which are currently being investigated by robot manufacturers, include changes in frequency coordination, transmission protocols, power output, access priority, and using relay transformers to increase the range of wireless transmissions (a technique known as multi-hop communications). The paper also suggests establishing new access schemes or software-defined radios that allow interoperable communications.

The August 2006 US&R DHS/NIST robot exercise at the Montgomery County Fire Academy in Gaithersburg offered emergency responders an opportunity to deploy robots in realistic training scenarios as well as helped robot developers and manufacturers refine designs and better understand performance requirements. The work is funded by DHS’s Science and Technology Directorate through NIST’s Office of Law Enforcement Standards.

* K.A. Remley, G. Koepke, E. Messina, A. Jacoff and G. Hough. Standards development for wireless communications for urban search and rescue robots. 9th Annual International Symposium on Advanced Radio Technologies, Feb. 26–28, 2007, Boulder, Colo.
Technical Paper [PDF]
Conference Presentation [PDF]

The chemical bond between carbon and fluorine is one of the strongest in nature, and has been both a blessing and a curse in the complex history of fluorocarbons. Now, in a powerful demonstration of the relatively new field of “computational chemistry,” researchers at the National Institute of Standards and Technology (NIST) and the Interdisciplinary Network of Emerging Science and Technology group (INEST, sponsored by Philip Morris USA) have designed—in a computer—a wholly theoretical molecule to pull the fluorine out of fluorocarbons.*

At sea level, the strong C-F bond makes fluorocarbons thermally and chemically stable. As a result, fluorocarbons have been used in many commercial applications including refrigerants, pesticides and non-stick coatings. In the upper atmosphere, however, high-energy photons and highly reactive ozone molecules can break apart fluorocarbons, with the well-known consequence of a depleted ozone layer and increased ultraviolet radiation at ground level. A determined chemist can break down fluorocarbons at ground level with certain organometallic compounds, but the reactions take a long time at very high temperatures. Other known reagents are both highly toxic and inefficient, so chemists have been searching for an economical and environmentally friendly method to dispose of fluorocarbons.

Reasoning that the problem already may have been solved by nature, the NIST/Philip Morris team looked to an enzyme called fluoroacetate dehalogenase used by a South African bacterium, Burkholderia sp. The enzyme enables the bacterium to pull the fluoride ion out of sodium fluoroacetate (disrupting a poisonous compound) at room temperature and without problematic metal ions. Enzymes are giant molecules, evolved to survive and work in the complex environment of a living organism; they can be difficult and expensive to adapt to an industrial process. Instead, the research team applied basic quantum mechanical theory of electron structures in molecules, together with the example of a known molecule that binds to and extracts chlorine ions, to calculate the make-up and geometry of the critical “active site” in the enzyme that does the work. They then designed in software a large ring-shaped molecule to hold those components in just the right orientation to break the C-F bond in methyl fluoride, a simple fluorocarbon.

Researchers at the University of Texas now are synthesizing the new molecule to test its effectiveness. If it matches theoretical predictions, it will be the first example of a simple organic molecular system able to break C-F bonds without extreme temperature and pressure conditions, and a demonstration of a novel technique for designing man-made molecules that can mimic the extraordinary selectivity and chemical activity of natural enzymes. Notes lead researcher Carlos Gonzalez, “All of these useful things are in nature, you just have to find them and make them more efficient.”

* F. Hæffner, M. Marquez and C. Gonzalez. Theoretical evidence for C-F bond activation by a fluoro-calix[4]pyrrole-tert-amine macrocycle. J. Phys. Chem. A 2007, 111, 268-272.

As if building a computer out of rubidium atoms and laser beams weren’t difficult enough, scientists sometimes have to work as if blindfolded: The quirks of quantum physics can cause correlations between the atoms to fade from view at crucial times.

What to do? Focus on the noise patterns. Building on earlier work by other groups, physicists at the National Institute of Standards and Technology (NIST) have found that images of “noise” in clouds of ultracold atoms trapped by lasers reveal hidden structural patterns, including spacing between atoms and cloud size.

The technique, described in the Feb. 23 issue of Physical Review Letters,* was demonstrated in an experiment to partition about 170,000 atoms in an “optical lattice,” produced by intersecting laser beams that are seen by the atoms as an array of energy wells arranged like an egg carton. By loading just one atom into each well, for example, scientists can create the initial state of a hypothetical quantum computer using neutral atoms to store and process information.

The atoms first are cooled to form a Bose-Einstein condensate (BEC), a unique form of matter in which all the atoms are in the same quantum state and completely indistinguishable. The optical lattice lasers then are slowly turned on and the BEC undergoes a transformation in which the atoms space out evenly in the lattice. More intense light creates deeper wells until each atom settles into its own lattice well. But during this transition, scientists lose their capability to see and measure key quantum correlations among the atoms.

Key structures are visible, however, in composite images of the noise patterns, which reveal not only atom spacing but also cloud size and how much of the BEC has undergone the transition.

In the NIST experiments, the BEC was placed in an optical lattice at various laser intensities. The lattice was turned off, and scientists took pictures of the expanding cloud of atoms after 20 to 30 milliseconds. To identify and enhance the noise signal, scientists looked for identical bumps and wiggles in the images and made composites of about 60 images by identifying and overlaying matching patterns. Lead author Ian Spielman likens the technique to listening to a noisy ballroom: While it may be impossible to hear specific conversations, correlations in noise can show where people (or atoms) are located in relation to each other, and the volume of noise can indicate the size of the ballroom (or atomic cloud), Spielman says.

The authors are affiliated with the Joint Quantum Institute, a new collaborative venture of NIST and the University of Maryland. The work was partially supported by the Disruptive Technology Office, an agency of the U.S. intelligence community that funds unclassified research on information systems, and by the Office of Naval Research.

* I.B. Spielman, W.D. Phillips and J.V. Porto. 2007. The Mott insulator transition in a two dimensional atomic Bose gas. Physical Review Letters. Feb. 23.

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a prototype nanoscale electronic switch that works like lightning—except for the speed. Their proof-of-concept experiments reported last week* demonstrate that nanoscale electrical switches can be built from self-assembled layers of organic molecules on silver wires. Potential applications range from a replacement technology for magnetic data storage to integrated circuit memory devices.

Silver would be a natural choice for nanoscale and microscale electrical contacts because of its high conductivity, but it has one notorious drawback. In an electric field, silver ions readily form silver “whiskers,” tree-like branching growths of crystals that can short-out microelectronic devices.

Two NIST researchers have demonstrated that this can be a feature, not a bug, in an elegant experiment that uses this growth to make a nanoscale binary switch. In the experiment, an extremely fine silver wire is coated with a molecule that forms a self-assembled monolayer on the wire, typically some organic molecule with a sulfur group on one end to bond to the silver. An equally fine gold wire is laid crosswise to the silver wire and a small voltage is applied across the two wires. When the voltage is increased to a critical level, silver ions form and quickly branch through the organic monolayer to the gold wire just like a lightning bolt—except solid. When a silver filament reaches the gold, it forms a short circuit, causing a dramatic change in conductance, which is easily detectable. Reversing the voltage retracts the filament and “opens” the switch.

As a candidate logic switch for nanoscale memory circuits and similar devices, the silver whisker switch has several attractive features:

Problems to be overcome, according to the researchers, include volatility—the voltage has to be kept on to retain the switch state; slow switching speeds—about 10 kilohertz in the prototype; and a tendency of the switch to freeze permanently closed after a large number of cycles.

*J.M. Beebe and J.G. Kushmerick. Nanoscale switch elements from self-assembled monolayers on silver. Applied Physics Letters 90, 083117 (2007). Posted online Feb. 23, 2007.

The NIST Advanced Technology Program (ATP) will conduct a new competition this fiscal year for cost-shared awards to support high-risk industrial R&D.

The ATP provides partial support to single companies or to industry-led joint ventures to accelerate the development of innovative technologies for broad national benefit through partnership with the private sector. ATP projects are selected in a competitive, peer-reviewed process.

Further details will be available when the competition is formally announced in the Federal Register this spring—proposals will not be accepted before that time. Notices also will be posted to www.atp.nist.gov and www.grants.gov. These notices will provide information about the specific ATP competition, including funding availability, selection criteria, guidelines for submitting proposals, proposal deadlines, dates and locations of Proposers Conferences, and other details.

Additionally, all those on the ATP mailing list will receive a competition announcement and the ATP Proposal Preparation Kit. Those interested may register for the ATP mailing list at www.atp.nist.gov/atp/atpform.htm.

Two new publications issued by the National Institute of Standards and Technology (NIST) will help senior executives, auditors and others in federal agencies better understand how to manage, support, and evaluate their information security programs.

Information Security Guide for Government Executives (NISTIR 7359) was developed specifically to help senior managers better understand how to oversee and support information security programs. According to the 14-page document, “senior management’s commitment to information security initiatives is the single most critical element that impacts an information security program’s success.” The guide answers five key questions about information security for senior managers:

Program Review for Information Security Management Assistance (PRISMA) (NISTIR 7358) explains a standardized approach that organizations can use to review and measure the maturity of an information security program in nine areas. Eight of the areas focus on management and operation of the information security program and evaluate the agency’s ability to comply with existing requirements. They include: information security management and culture; information security planning; security awareness training, and education; budget and resources; life cycle management; certification and accreditation; critical infrastructure protection; and incident and emergency response. The ninth area, security controls, reviews the technical aspects of the overall information security program.

Time and frequency information can be transferred between laboratories or to other users in several ways, often using the Global Positioning System (GPS). But today’s best atomic clocks are so accurate—neither gaining nor losing one second in as long as 400 million years—that more stable methods are needed. The best solution may be to use lasers to transfer data over fiber-optic cables, according to scientists at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

The use of fiber-optic channels to transfer time signals allows accurate comparisons of distantly located atomic clocks of different types. This could lead, for example, to enhanced measurement accuracy in experiments to determine whether so-called “constants of nature” are in fact changing. Sharing of clock signals via fiber also will enable synchronization of components for advanced X-ray sources at linear accelerators, which may power studies of ultrafast phenomena in chemistry, biology, physics and materials science; or link arrays of geographically distributed radio telescopes to produce the power of a giant telescope.

Three state-of-the-art techniques for distributing ultra-stable time and frequency signals over fiber are described in a new review article* by NIST Fellow Jun Ye’s group at JILA. Fibers can be far more stable, especially when efforts are made to cancel molecules along the transmission path, than the paths through free-space used by GPS, which requires days of measurement averaging to accurately compare today’s best frequency standards. Moreover, considerable fiber-optic infrastructure already exists. For instance, the new paper is based largely on research performed on a 3.45-km fiber link installed in underground conduits and steam tunnels between JILA and NIST laboratories in Boulder.

Noting that gravitational effects may eventually limit ground-based atomic clocks, the paper suggests someday creating a network of optical atomic clocks in space, which might be used to make flawless distance measurements, transfer clock signals to different locations, and accurately map the Earth’s gravity distribution.

This work was supported by the Office of Naval Research, National Aeronautics and Space Administration, NIST and the National Science Foundation.

* S.M. Foreman, K.W. Holman, D.D. Hudson, D.J. Jones, and J. Ye. Remote transfer of ultrastable frequency references via fiber networks. Invited Review, Review of Scientific Instruments. Vol. 78, No. 228. Published on-line Feb. 28, 2007.

Identifying the most important hazards threatening buildings and other constructions and taking action to eliminate them or reduce their potential impact make sense, but the task can be daunting. What are the risks associated with various natural and man-made hazards? What strategies might mitigate the threats? How do you select the most cost-effective combination of strategies? The National Institute of Standards and Technology (NIST) directs you to some answers in a new Web-enabled Risk Mitigation Toolkit.

The Toolkit is an interactive document version of the printed NIST report, A Guide to Printed and Electronic Resources for Developing a Cost-Effective Risk Mitigation Plan for New and Existing Constructed Facilities (NISTIR 7390). Building managers and owners as well as other key decision makers can turn to the annotated bibliography of printed and electronic resources for useful disaster mitigation data and tools. The guide and toolkit are organized around three main topics: risk assessment, risk management and economic evaluation. References are provided for relevant software programs, data and studies. Appendices outline a step-by-step template for developing a risk-mitigation plan, list relevant clearing houses and web portals for specific types of information and cite key risk mitigation-related research studies on risk-mitigation strategies. Two comprehensive indexes, one organized by subject and one organized by author, make it easy to find key reference documents, databases and software tools. An extensive glossary of economic terms used in evaluating the cost effectiveness of disaster mitigation investments in constructed facilities also is included.

The web-enabled Toolkit includes all features of the printed version plus active Web links to more than 300 cited sources. The indexes and all the Web links within the three main topics are active, enabling users to browse documents and data sources on other sites. Many of the Web links in the guide permit documents and data files to be downloaded for future reference and use. The Toolkit is set up as a PDF file and requires Adobe Acrobat Version 7.0 or higher.

The Toolkit, by providing information on key resources needed to perform a rigorous economic evaluation, makes it easier to use resources such as the “Cost-Effectiveness Tool for Capital Asset Protection,” a NIST economic analysis software product described in “Software Addresses Terrorist Building Threats” (www.nist.gov/public_affairs/techbeat/tb2005_0602.htm).

A new National Institute of Standards and Technology (NIST) Web site showcases the latest advances and applications of the Process Specification Language (PSL) which the International Organization for Standardization formally recognized last August as international standard ISO 18629.

PSL was created to allow computers to use “automated reasoning” to interpret commands. Without such insight, a computerized production system could respond to the command “paint and ship” by doing both at the same time, rather than finishing painting before shipping. To avoid such fiascos, PSL uses mathematical logic to convey “correct” process meaning to computers. PSL is precisely designed to represent unambiguous manufacturing process instructions. It enables the discovery of conflicts in commands, instructions and policies, and also provides a way to exchange process specifications, rather than product data, between different proprietary, PSL-compliant, software programs. (See “Software Advance Helps Computers Act Logically” www.nist.gov/public_affairs/techbeat/tb2005_0616.htm#software.)

The new Web site offers users language updates in downloadable format that can be tested on computerized machines employed in manufacturing and other process-oriented activities. The site references many publications that explore the application of PSL in scheduling, process modeling semantics, process planning, production planning, project management and business process reengineering. It also explains how manufacturers using different software programs can use PSL for exchanging process data. An interactive section enables users to construct PSL-based descriptions of process meanings—such as sequential execution of multiple tasks. A “Frequently Asked Question (FAQ) section offers a comprehensive overview of PSL. Researchers are invited to comment on material on the site as well as contribute news of their PSL projects. The PSL Web site can be found at: www.nist.gov/psl.

The National Institute of Standards and Technology (NIST) recently issued three new publications to help secure electronic mail and wireless local area networks (WLAN) and detect and prevent computer system or network intrusions.

Guidelines on Electronic Mail Security (Special Publication 800-45 Version 2) provides recommendations for securing mail servers that deliver, forward and store e-mail and mail clients that allow users to read, compose, send, receive and store e-mail. It also provides guidance on protecting individual e-mail messages and securing traditional and Web-based access to mailboxes.

Establishing Wireless Robust Security Networks: A Guide to IEEE 802.11i (Special Publication 800-97) provides detailed information on the Institute of Electrical and Electronics Engineers 802.11i standard for WLAN security and recommends ways to ensure the security of the WLAN operating environment. It also provides guidance on protecting the confidentiality and integrity of WLAN communications and authenticating users and devices.

Guide to Intrusion Detection and Prevention Systems (IDPS) (Special Publication 800-94) helps organizations design, implement, configure, secure, monitor and maintain intrusion detection and prevention systems. It provides information on four classes of IDPS products: network- and host-based, wireless, and network behavior analysis software.

Under the National Construction Safety Team (NCST) Act, signed into law in October 2002, the National Institute of Standards and Technology (NIST) is authorized to investigate major building failures in the United States. These investigations establish the likely technical causes of the building failure and evaluate the technical aspects of emergency response and evacuation procedures in the wake of such failures. The goal is to recommend improvements to the way in which buildings are designed, constructed, maintained, and used.

NIST’s NCST Fiscal Year 2006 annual report was recently submitted to Congress and is now available at www.nist.gov/ncst. The 42-page document reviews: (1) the completion of the investigation of the collapses of New York City's World Trade Center (WTC) towers following the terrorist attacks of Sept. 11, 2001; (2) the ongoing investigation of the collapse of the WTC 7 office building on the same day; and (3) efforts to implement the recommendations for improved building and fire safety from both the WTC Towers investigation and an earlier investigation into The Station nightclub fire of Feb. 20, 2003, in W. Warwick, R.I.

Nobel Laureate Bill Phillips, a physicist at the National Institute of Standards and Technology (NIST), will conduct a special, interactive Web seminar for teachers and school children on the physics of ultracold temperatures on Thursday, March 22, from 6:30 to 8:00 p.m. Eastern Time.

“Absolute Zero: The Cold, Hard Facts About the Coolest Stuff in Physics” is sponsored by the National Science Teachers Association (NSTA), in collaboration with NIST. The seminar is tied to “Absolute Zero,” a two-part Public Broadcasting System television special scheduled to air later this year that examines the impact on our lives of our ability to cool things—sometimes to very, very, very low temperatures.

Phillips, a leading researcher in the physics of ultra-low temperature atomic gases, will explain how and why he and his colleagues made the coldest gases ever seen and will provide engaging ideas on how to make the physics of the ultra-cold appealing to middle and high school students. The Web seminar is designed primarily for grades 5-12.

James C. Bergquist, a physicist at the National Institute of Standards and Technology (NIST) in Boulder, Colo., has been awarded the American Physical Society’s 2007 Herbert P. Broida Prize. The award recognizes outstanding experimental advancements in the fields of atomic and molecular spectroscopy or chemical physics. Bergquist was cited for “seminal contributions to ultra-high-resolution laser spectroscopy and the realization of accurate optical frequency standards.” Bergquist developed an atomic clock based on oscillations of a single mercury ion, the first atomic clock operating at optical frequencies to outperform today’s time standards based on microwave frequencies.

The prize was established in 1979 as a memorial to and in recognition of the accomplishments of Herbert P. Broida, late professor of physics at the University of California, Santa Barbara.

National Institute of Standards and Technology (NIST) Director William Jeffrey has named 15 distinguished academic, industry and government experts to serve on the new National Earthquake Hazards Reduction Program (NEHRP) Advisory Committee on Earthquake Hazards Reduction (ACEHR). The NEHRP is the federal government’s program to reduce the risks to life and property from earthquakes, and includes the Federal Emergency Management Agency (FEMA), the National Science Foundation (NSF), the United States Geological Survey (USGS) together with NIST.

The initial roster of the ACEHR includes: Jonathan D. Bray, professor, Department of Civil and Environmental Engineering, University of California, Berkeley, Calif.; David E. Cook, senior manager/fire chief, Enterprise Fire and Disaster Preparedness, Boeing Co., Seattle, Wash.; Lloyd S. Cluff, director, Geosciences Department and Earthquake Risk Management Program, Pacific Gas and Electric Co., San Francisco, Calif.; James R. Harris, president, J.R. Harris and Co., Denver, Colo.; Paul Somerville, principal seismologist and manager, Seismic Hazards Group, URS Corp., Pasadena, Calif.; Ronald O. Hamburger, senior principal, Structural Engineering West, Simpson Gumpertz and Heger Inc., San Francisco, Calif.; Howard Kunreuther, professor, Decision Sciences and Business and Public Policy, and co-director, Wharton Risk Management and Decision Processes Center, University of Pennsylvania, Philadelphia, Pa.; Thomas D. O’Rourke, Thomas R. Briggs Professor of Civil and Environmental Engineering, Cornell University, Ithaca, N.Y.; Anne R. vonWeller, chief building official, Murray (Utah) City Corp.; Yumei Wang, geotechnical engineer and geohazards team leader, Oregon Department of Geology and Mineral Industries, Portland, Ore.; Walter J. Arabasz, research professor, Department of Geology and Geophysics, and director, Seismograph Stations, University of Utah, Salt Lake City, Utah.; Richard K. Eisner, regional administrator and manager (retired), California Integrated Seismic Network, and California Earthquake and Tsunami Programs, California Governor’s Office of Emergency Services, Oakland, Calif.; Chris D. Poland, chairman, president and chief executive officer, Degenkolb Engineers, San Francisco, Calif., who has agreed to serve as the chair of the advisory committee.; Kathleen J. Tierney, professor, Department of Sociology and Institute of Behavioral Science, and director, Natural Hazards Research and Applications Center, Institute of Behavioral Science, University of Colorado, Boulder, Colo.; and Sharon L. Wood, Robert L. Parker Centennial Professor of Engineering, University of Texas, Austin, Texas.

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Editor: Michael Baum

Date created: March 1, 2007
Date updated: March 2, 2007
Contact: inquiries@nist.gov