NIST Tech Beat - December 19, 2003

Greeting Another New Year Without a Leap Second

Does it seem like the world is speeding up? That the pace of life is increasing?

If you feel that way, there’s scientific evidence to prove your point. The world has sped up over the last few years. Timekeepers at the National Institute of Standards and Technology (NIST) note that they have not had to insert an extra second (called a leap second) into their time scale for five years. Why? Because the rate of the Earth’s rotation has sped up since 1999.

From 1972 (when the world went to the current system of atomic timekeeping) until 1999, 22 seconds were added to the world’s time in order to keep atomic time synchronized with Earth’s time, as measured by the Earth’s spin. Since then, none, nada. Scientists are not sure why this is so, but they do offer some thoughts.

Tom O’Brian, a physicist and chief of NIST’s Time and Frequency Division in Boulder, Colo., suggests changes in motion of the Earth’s core, the effect of ocean tides and weather, and changes in the shape of the Earth may all be affecting the spin of Mother Earth. In general, he notes, the long-term trend has been for the Earth’s rotation to slow down, but not in the last five years.

O’Brian said most scientists expect the Earth to continue slowing down again in the future. So maybe there is hope for those feeling particularly harried.

“The Earth’s rotation rate has been the primary clock for nearly all of human history,” he says, adding that “only in the last 50 years have we had clocks accurate enough to measure changes in the Earth’s spin.” NIST introduced the world’s first atomic clock in 1949.

For more information about leap seconds, see http://tf.nist.gov/general/leaps.htm.

Media Contact:
Fred McGehan, (303) 497-3246

Experts Stress Importance Of Holiday Fire Safety

NIST fire test demonstrates how quickly a flame can ignite a dry holiday tree.

Every year approximately 400 residential holiday tree blazes kill 10 people, injure 80 and cause more than $15 million in property damage. Typically, shorts in electrical lights or open flames from candles, lighters or matches start tree fires. Fire protection engineers at the National Institute of Standards and Technology (NIST) stress the importance of keeping trees watered.

A video clip on the NIST Web site, www.fire.nist.gov/tree_fire.htm, illustrates how quickly fire can develop when a dry tree is exposed to an open flame. Within three seconds of ignition, the scotch pine is completely ablaze. At five seconds, the fire extends up the tree and black smoke with searing gases streaks across the ceiling. Fresh air near the floor feeds the fire. The sofa, coffee table and the carpet ignite prior to any flame contact. Within 40 seconds “flashover” occurs— that’s when flames completely engulf the room, depleting the oxygen and turning the atmosphere into toxic smoke and other searing gases.

A high-resolution video (broadcast quality) of NIST fire tests with a dry scotch pine is available from madrzy@nist.gov. A report on the test can be found http://fire.nist.gov/bfrlpubs/fire00/PDF/f00147.pdf. (PDF - requires Adobe Acrobat)

Test Method Provides Biocompatibility ‘Barometer’

A new method for quantitatively measuring the compatibility of materials with living tissues has been developed by researchers at the National Institute of Standards and Technology (NIST). Described in a Dec. 11 presentation at the Tissue Engineering Society International’s conference in Orlando, Fla., the technique should provide a more sensitive and reliable means to evaluate the biocompatibility of new materials for a wide range of applications from contact lenses to dental coatings to bone implants.

A paper outlining the new method has been accepted for publication in the Journal of Biomedical Materials Research.

The new method, which represents a novel application of existing bench-top scientific instruments, is a two-step process. The first step involves using a device called a polymerase chain reaction instrument to measure the levels of an organism’s cytokines when exposed to a given material. Cytokines are signaling molecules released by white blood cells to protect the body from foreign materials. Higher levels of cytokine production generally indicate non-biocompatible materials have caused inflammation. The second step involves testing exposed cells for a specific protein in the cell membrane, the presence of which indicates cells are dying. This is a complementary test for more serious responses to materials because dying cells are often not capable of producing cytokines. The NIST tests were conducted on cultured mouse cells, which produce similar responses as whole tissues.

NIST guest researcher LeeAnn Bailey called the new method a “barometer” of biocompatibility.

Whereas current means to test biocompatibility produce a yes/no result that a material is minimally biocompatible or not, the new analysis can tell which materials are more biocompatible than others. Industry and researchers should be able to use this method to produce new materials for dentistry and other medical applications that are even more well matched to the human body.

Low-Cost, Digital Displays Through Ink Jet Printing

A grid of semiconductor polymer transistors jet-printed into a prototype circuit that can be used to control a flat panel display.

Image courtesy Palo Alto Research Center

The ability to print the PARC plastic transistors on flexible substrates may allow manufacturers to produce electronic "paper" and computer displays that roll up like a window shade.

Image courtesy Palo Alto Research Center

Convergent technology is one thing—but using your computer’s printer to make a new TV screen?

Not quite, but close. In a breakthrough for low-cost electronics manufacturing, researchers at Palo Alto Research Center (PARC), a Xerox subsidiary, have successfully created a transistor array of the type used to control a flat-panel display using a modified ink-jet printer and semiconductor “ink.” Still under development, the technique is expected to dramatically lower the cost of the popular displays by replacing more expensive photolithography techniques that dominate display manufacturing. The new technology, co-funded by the National Institute of Standards and Technology (NIST), is expected to work on either rigid or flexible substrates, and could create whole new opportunities for wall-sized TV’s, unbreakable cell phone displays, computer displays that could roll up like a window shade and electronic paper.

PARC researchers used a new polymer-based semiconductor ink from Xerox Research Center Canada (XRCC) to build a prototype flat-panel display circuit. Transistor arrays are complex devices with multiple layers of conductors, insulators and semiconductors. Conventional photolithography uses a multistep process for each layer, first laying down the appropriate material, then creating a pattern for the components, and finally etching or transferring the pattern to the material. By contrast, PARC’s ink-jet process patterns and prints the components of each layer of the transistor array in one step. A key innovation, according to PARC, was a computer-vision system that ensures precise registration of each layer even if the substrate deforms slightly during the process.

The PARC research is part of a joint R&D partnership with Xerox, Motorola Inc. and Dow Chemical Company that is co-funded under NIST’s Advanced Technology Program (ATP). The semiconductor polymer ink also was developed under the ATP award. For more information on the ATP project, go to jazz.nist.gov/atpcf/prjbriefs/prjbrief.cfm?ProjectNumber=00-00-4209.

Inside Hollywood’s historic Pacific Theater, engineers have set up a new tool based on technology developed at the National Institute of Standards and Technology (NIST) to help the motion picture industry move more smoothly into a digital future.

The relatively simple new NIST tool—dubbed a stray-light elimination tube—improves measurements of the contrast and sharpness of images produced with digital projectors. It also may help reduce errors in assessing other projection systems.

Digital cinema should offer movie goers sharper, brighter pictures, but digital projectors currently are expensive and complex. Engineers from the Digital Cinema Lab, a project of the Entertainment Technology Center (ETC), are using the NIST-developed device as one of many tools to evaluate the performance of these new projectors. Part of the University of Southern California, ETC is funded by major studios and other organizations.

The tool, which costs under $100 to construct, is a simple tube made of glossy black plastic with cone-shaped inserts. Light measurements are taken at one end of the tube, while the other end is aimed toward the projector. The cones have a hole in the center (typically 2 inches) so that only those rays arriving directly from the projector reach the light detector, while stray, ambient lighting is filtered out. The device is typically about two feet long and is attached to a tripod or other adjustable, stable mount so that it can be moved to take multiple readings from images projected on a screen. Traditional methods for judging the light output of projectors may introduce error rates of 40 percent or more because ambient light is inadvertently included in the measurement.

Sensor on a Chip—In a Dec. 12 presentation, researchers at the National Institute of Standards and Technology (NIST) reported new results at an Institute of Electronics and Electrical Engineers device research conference showing that a NIST “sensor on a chip” device is 100 times more sensitive in detecting toxic gases than other systems described in the open literature. The device integrates chemical sensor technology with its related electronics on a single semiconductor chip. The technology is based on MEMS, or MicroElectroMechanical Systems, which is the creation of devices and machinery at the microscale. Such integration should gas sensors for homeland security or other applications not only more sensitive and cheap to manufacture, but also much more flexible and customizable. For details, see
http://www.eeel.nist.gov/812/files/afridi-MEMS-Based%20Gas%20Sensor.pdf.

Technology Transfer—On Dec. 18, Gov. Robert L. Ehrlich (R-Md.) announced a memorandum of understanding (MoU) between the Maryland Technology Development Corp. (TEDCO) and the National Institute of Standards and Technology (NIST) to increase technology transfer initiatives between the agency and the state’s small businesses and universities. The agreement calls for NIST and TEDCO to focus on mutually beneficial links by identifying activities that will leverage the capabilities and resources of NIST, Maryland technology-oriented small businesses and leading institutions of higher education. NIST will identify technologies that are available for licensing as well as provide guidance and support on procedures for submitting a license application. For more information, go to www.nist.gov/public_affairs/releases/tedcomou.htm.