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August 30, 2004

  In This Issue:
bullet Chip-Scale Atomic Clock Unveiled by NIST
bullet Software Difficulties Cost Builders Billions
bullet Patented Process Preserves Transplant Tissues/Organs
bullet Scientists Observe 'Atomic Air Force'
bullet Supercool! Model Unscrambles Complex Crystallization Puzzle
bullet New Microfluidic Device Tackles Tough Synthesis Tasks
bullet Lighting the Way to Better Nanoscale Films

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Chip-Scale Atomic Clock Unveiled by NIST

John Kitching close up of chip-scale atomic clock

NIST physicist John Kitching displays the heart of the world’s smallest atomic clock. This “physics package” is about the size of a grain of rice.

© Geoffrey Wheeler
To receive a high-resolution version of this image, contact Gail Porter.

The “physics package” of the chip-scale atomic clock includes (from the bottom) a laser, a lens, an optical attenuator to reduce the laser power, a waveplate that changes the polarization of the light, a cell containing a vapor of cesium atoms, and (on top) a photodiode to detect the laser light transmitted through the cell. The tiny gold wires provide electrical connections to the electronics for the clock.

NIST Photo

The heart of a minuscule atomic clock—believed to be 100 times smaller than any other atomic clock—has been demonstrated by scientists at the National Institute of Standards and Technology (NIST), opening the door to atomically precise timekeeping in portable, battery-powered devices for secure wireless communications, more precise navigation and other applications.

Described in the Aug. 30, 2004, issue of Applied Physics Letters,* the clock’s inner workings are about the size of a grain of rice (1.5 millimeters on a side and 4 millimeters high), consume less than 75 thousandths of a watt (enabling the clock to be operated on batteries) and are stable to one part in 10 billion, equivalent to gaining or losing just one second every 300 years.

In addition, this “physics package” could be fabricated and assembled on semiconductor wafers using existing techniques for making micro-electro-mechanical systems (MEMS), offering the potential for low-cost mass production of an atomic clock about the size of a computer chip and permitting easy integration with other electronics. Eventually, the physics package will be integrated with an external oscillator and control circuitry into a finished clock about 1 cubic centimeter in size.

The mini-clock is comparable in size and long-term stability to temperature-compensated quartz crystal oscillators, currently used in portable devices. NIST scientists expect to improve the clock’s long-term stability and reduce its power consumption to the point where the device could substantially improve the performance of many commercial and military systems that require precision time keeping.

For more information see:

Media Contact:
Laura Ost,, (301) 975-4034

*S. Knappe, V. Shah, P. Schwindt, L. Hollberg, and J. Kitching. 2004. A microfabricated atomic clock. Applied Physics Letters 859(9), Aug. 30.



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Software Difficulties Cost Builders Billions

Inadequate software interoperability in the capital facilities industry cost the commercial, institutional and industrial building sectors $15.8 billion in 2002 in lost efficiency, according to a newly released study commissioned by the National Institute of Standards and Technology (NIST).

Conducted by RTI International (Research Triangle Park, N.C.) and the Logistics Management Institute (McLean, Va.), the report places a price tag on avoidance, mitigation and delay activities due to data-exchange problems. It also takes into account the cost of redundant paper management.

The analysis, expected to benefit key stakeholders throughout the construction industry, breaks down data exchange-related losses for architects and engineers, general contractors, specialty fabricators and suppliers, and owners and operators at three different stages of a building’s life: (1) design and engineering; (2) construction; and (3) operations and maintenance.

The publication, Cost Analysis of Inadequate Interoperability in the U.S. Capital Facilities Industry (NIST GCR 04-867), also identifies barriers and opportunities for improvement. Electronic copies are available at

Media Contact:
John Blair,, (301) 975-4261



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Patented Process Preserves Transplant Tissues/Organs

Body tissues such as blood vessels, cartilage and skin—even whole organs such as kidneys, livers and hearts—could become more widely available for transplants as a result of a patent issued recently to Organ Recovery Systems of Chicago for a method to chill body tissues and organs well below freezing without forming ice crystals. The new process for tissue "vitrification"—chilling tissue and organs to a disordered, glass-like solid without ice formation—was developed with support from the National Institute of Standards and Technology (NIST) Advanced Technology Program and the National Institutes of Health.

There is an urgent need for tissues and organs for transplantation. Doctors conducted over 24,000 organ transplants in the United States in 2002; yet someone is added to the donor waiting list every 12 minutes and 16 people die each day waiting for an organ transplant. A significant roadblock to the broader use of transplantation, regardless of the source (donated human, cross-species or artificial), has been the problem of preserving the transplant tissue. Better preservation techniques would allow transplant materials to be shipped anywhere in the world or, better yet, collected and stored in something akin to blood banks until needed.

Organs and some tissues are presently stored for short periods at refrigerator temperatures (approximately 4 °C) and freezing has not been possible due to ice crystals, which damage delicate cells and greatly reduce the viability or functions of the tissue. Chemicals called cryoprotectants reduce ice formation but have toxic effects that introduce their own problems. The Organ Recovery Systems technique combines a mixture of cryoprotectant compounds that cancel each other’s toxicity and careful control of the cooling and warming processes to minimize damage to the tissue. The technique is discussed in U.S. patent no. 6,740,484. (Patent text available at

Media Contact:
Michael Baum,, (301) 975-2763



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Scientists Observe 'Atomic Air Force'

The first sighting of atoms flying in formation has been reported by physicists at the Department of Commerce’s National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU-Boulder) in the Aug. 13 issue of Physical Review Letters.* While the Air Force and geese prefer a classic “V,” the strontium atoms—choreographed in this experiment with precision laser pulses and ultracold temperatures—were recorded flying in the shape of a cube.

This “really bizarre” behavior is believed to occur with all atoms under similar conditions, says physicist Jun Ye of NIST, who led the research at JILA, a joint institute of NIST and CU-Boulder. Ye is also a faculty member of the CU-Boulder physics department.

Atoms have not previously been seen flying in formation, says Ye. Strontium’s unique physical properties make the observations possible. In particular, the configuration of strontium’s electrons and the resulting atomic properties allow it to efficiently absorb laser energy in two very specific “resonant” wavelengths—a strong resonance at a wavelength of blue light and another, much weaker resonance for longer-wavelength red light. This makes strontium a promising candidate for a next-generation atomic clock based on optical rather than microwave frequencies, and is the reason the JILA team is studying the atom’s quantum behavior.

The experiment was conducted with a dense gaseous cloud of 100 million strontium atoms. The atoms were trapped in the center of a vacuum chamber with both a magnetic field and six intersecting red laser beams, in three sets of facing pairs aligned at right angles to each other. The NIST group coaxed the atoms into the flying cube formation with precise adjustments in the frequency of the laser beams used to trap them. The formation was visualized by illuminating the atoms with a blue laser. The strontium absorbed the energy but then quickly re-emitted it and the clusters of glowing blue atoms were recorded with a video camera.

For further information, see

Media Contact:
Laura Ost,, (301) 975-4034

*T.H. Loftus, T. Ido, A.D. Ludlow, M.M. Boyd, and J. Ye. 2004. Narrow line cooling: finite photon recoil dynamics. Physical Review Letters 93(7), Aug. 13.


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Supercool! Model Unscrambles Complex Crystallization Puzzle

Four sets of simulated images show the striking similarities between crystals "grown" under different conditions.

Four sets of simulation images show the striking similarities between crystals "grown" under different conditions. The first two columns on the left show crystals grown with increasing amounts of impurities. The top row crystal has no "dirt," it has a symmetric crystal pattern (yellow image) and it has no "grains"— all the molecules are aligned in the same direction (blue image.) As greater amounts of impurities are added, the crystal grows more and more randomly.

The two columns on the right show crystals grown with increasing differences between the speed the crystal naturally wants to grow and the speed that liquid molecules can rotate into alignment with the growing crystal or be forced to solidify into a new grain. This type of difference happens in the real world when liquid alloys or polymers are supercooled substantially below the temperature that they would naturally solidify. The low temperature tends to speed up the crystallization process but the increasing viscosity of the liquid makes it harder for molecules to move into aligned grains, so the crystal grows more randomly.

To the wonderment—and the befuddlement—of scientists, the patterns that form as plastics, metals and many other materials crystallize can vary incredibly, ranging from sea-urchin-like spheres to elaborate tree-like branches.

Now, Hungarian and National Institute of Standards and Technology scientists report in the September issue of Nature Materials* that they have developed a way to predict the polycrystalline microstructures that will form as complex liquid mixtures cool and solidify. Ultimately, the team's new simulation tool could help manufacturers of everything from plastic bags to airplane wings to design new products with improved strength, durability and other properties.

Images generated with the team's mathematical model match up almost feature for feature with the seemingly random crystal patterns formed in experiments as temperatures or other processing variables are modified. The model accurately predicts how both impurities (or additives) and process differences affect the sizes, shapes and orientations of crystals that form during the so-called supercooling process.

Whether initiated by "dirt" or by processing conditions, the resulting patterns can be strikingly similar. This "duality in the growth process," notes NIST’s James Warren, may help explain why polycrystalline growth patterns are so prevalent in polymers and other materials derived from complex mixtures.

Findings based on the model indicate that instabilities along the boundary between liquid and solid areas during solidification effectively clash with the otherwise orderly process of crystallization. Tiny crystals-in-the-making move and position themselves along the growth front, assuming an orientation peculiar to the energy conditions at their location. Varying local conditions produce crystals in seemingly disordered arrays, accounting for the rich diversity of microstructural patterns.

Laszlo Granasy, of Hungary’s Research Institute for Solid State Physics and Optics, led the research effort.

*L. Gránásy, T. Pusztai, T. Börzsönyi, J.A. Warren, and J.F. Douglas. A general mechanism of polycrystalline growth. 2004. Nature Materials advance on-line publication, Aug. 8, 2004.

Media Contact:
Mark Bello,, (301) 975-3776


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New Microfluidic Device Tackles Tough Synthesis Tasks

A new type of microfluidic device that can help industry to optimize paints, coatings for microelectronics and specialty polymers has been developed by National Institute of Standards and Technology (NIST) researchers. The device is made of a chemically durable plastic that is resistant to many common organic solvents. It was fabricated with a rapid prototyping method also developed at the agency.

NIST microfluidic device for synthesizing and analyzing polymers and other complex liquids.

NIST microfluidic device for synthesizing and analyzing polymers and other complex liquids.

Described in the Aug. 18 issue of the Journal of the American Chemical Society,* such devices can be used to make specialty polymers in small amounts, or to rapidly change polymer ingredients so that the impact of expensive additives on material behavior can be systematically analyzed. This is becoming important as more specialty polymers use designer elements for applications in nanotechnology and biotechnology.

Devices typically measure about half the size of a credit card and are made with a technique called "frontal photopolymerization." The NIST researchers adapted the technique to fabricating microfluidic devices. Ultraviolet light was shined through patterned "stencils" into a liquid layer of a chemical called thiolene. Areas exposed to the light harden into a solid polymer while unexposed areas remain liquid and can be flushed away, leaving relatively deep channels capable of handling thicker fluids than current lab-on-a-chip devices.

In a separate paper,** the NIST researchers provide detailed data about how varying doses of ultraviolet light affect the height of the polymer structures formed. Such data should be helpful for increasing the complexity of devices that can be fabricated with the technique.

Media Contact:
Scott Nance,, (301) 975-5226

*T. Wu, Y. Mei, J.T. Cabral, C. Xu, and K.L. Beers. 2004. A new synthetic method for controlled polymerization using a microfluidic system. Journal of the American Chemical Society. []

**J.T. Cabral, S.D. Hudson, C. Harrison, and J. Douglas. 2004. Frontal photopolymerization for microfluidic applications. Langmuir. Expected print publication in Nov.


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Lighting the Way to Better Nanoscale Films

Most miniature electronic, optical and micromechanical devices are made from expensive semiconductor or ceramic materials. For some applications like diagnostic lab-on-a-chip devices, thin-film polymers may provide a cheaper alternative, but the structure and properties of these materials—often no more than a few nanometers (nm) thick—are difficult to determine. In addition, defects in the thin polymer masking materials used to "print" integrated circuits can produce malfunctioning components. Consequently, researchers would like to have a non-invasive method for scanning polymer films for defects at high resolution.

Crystal structures of a thin-film polymer.

Left: The crystal structure of a thin-film polymer "seaweed" crystal that is about four micrometers wide. Brighter areas indicate parts of the crystal with the greatest "strain." Center: The same crystal with lines superimposed showing the direction of strain between the crystal's atoms. Right: Closeup of the upper left portion of the center image.

In the Aug. 23 issue of Applied Physics Letters,* researchers at the National Institute of Standards and Technology (NIST) report on an application of a new method for studying ultrathin polymers that makes it possible to visualize defects and structure in these materials and should help improve basic understanding of crystal formation in polymers.

Using a special form of near-field scanning optical microscopy, the NIST researchers were able to determine the structure of, and "strain" (stretching between atoms) in, thin-film crystals of polystyrene. Polystyrene is a ubiquitous plastic found in foam cups, CD cases and many other products.

The films examined formed tiny crystals just 15 nm thick and about 1500 nanometers wide, which makes them difficult to study with other optical microscopes. In the NIST experiments, blue-green light was piped through a glass fiber about 50 nm wide and scanned across the sample about 10 nm above the surface. Changes in the polarization of the light (the direction of the wave's electric field) as it transmits through the sample then were used to investigate the material's crystal structure and to map areas of strain.

The NIST results should help scientists choose and improve polymer materials and processes for fabricating a range of microscale and nanoscale plastic devices.

Media Contact:
Gail Porter,, (301) 975-3392

*L.S. Goldner, S.N. Goldie, M.J. Fasolka, F. Renaldo, J. Hwang, and J.F. Douglas. 2004. Near-field polarimetric characterization of polymer crystallites. Applied Physics Letters 85(8): 1338-1340.


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Fire Tests Provide WTC Floor System Data

During the month of August, the National Institute of Standards and Technology (NIST) conducted a series of four fire resistance tests on composite concrete-steel trussed floor systems typical of those used in the World Trade Center (WTC) towers. The tests showed that the test structures were able to withstand standard fire conditions for between one and two hours. Part of NIST’s building and fire safety investigation of the WTC disaster on Sept. 11, 2001, the four tests provide only a means for evaluating the relative fire resistance rating of the floor systems under standard fire conditions and according to accepted test procedures. The tests alone cannot be used to determine the actual performance of the floor systems in the collapse of the WTC towers. To learn more about what the tests revealed, go to

Checklists for Computer Security

The National Institute of Standards and Technology (NIST), with sponsorship from the Department of Homeland Security (DHS), has issued a new report, Draft NIST Special Publication 800-70: Security Configuration Checklists Program for IT Products. The use of computer security checklists, when combined with well-developed guidance, leveraged with high-quality security expertise, vendor product knowledge, operational experience, and accompanied with tools, can reduce markedly the vulnerability exposure of an organization. The report gives an overview of the NIST Checklist Program, explains how to retrieve checklists from NIST's repository and provides general information about threat models and baseline technical security policies for associated operational environments. The report is available at

Building Brains for Thinking Machines

James S. Albus, a Senior Fellow at the National Institute of Standards and Technology (NIST) described efforts to develop "thinking machines" last month in Portugal at the International Federation of Automatic Control Symposium on Intelligent Autonomous Vehicles. Albus, who predicts that autonomous vehicles could equal human levels of performance in most areas within 20 years, is the co-inventor of the Real-time Control Systems (RCS) architecture and methodology. Albus described how computer modeling, value judgment, sensory processing and knowledge databases and programs may be used to mimic human thought processes. Albus’ address on the artificial intelligence framework and its current and future field applications is at


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Editor: Gail Porter

Date created:08/26/04
Date updated:08//04