volume 106, number 4, july–august 2001 journal of research ... · volume 106, number 4,...

Volume 106, Number 4, July–August 2001Journal of Research of the National Institute of Standards and Technology

General DevelopmentsInquiries about News Briefs, where no contact personis identified, should be referred to the Managing Editor,Journal of Research, National Institute of Standardsand Technology, Building 101, Room E215, Gaithers-burg, MD 20899-2500; telephone: (301) 975-3577.

WANTED: MEASUREMENTS WITH GOODREFERENCESIn nearly all types of activities-be they related to manu-facturing, finance, health, regulatory affairs or evensports-people and organizations are becoming sticklersfor measurement uncertainty.

NIST, the nation’s measurement authority, has re-sponded to this growing customer need for demonstra-ble uncertainty. It has created an on-line resource—www.nist.gov/traceability—devoted to matters pertain-ing to the integrally related topic of measurementtraceability—whether the result of a specific measure-ment can be related to accepted international or nationalstandards through an unbroken chain of comparisons.

Factors driving the growth of traceability require-ments include increasing world trade, growing relianceon laboratory accreditation as a means of assuringconfidence in calibration and test reports, the continu-ing spread of quality standards and, in some technologyareas, a proliferation of regulations.

At the new web site, visitors can read the NIST policyon traceability. They also can review, among otherresources, a glossary of terms, answers to an extensiveset of frequently asked questions on traceability,examples of relevant NIST measurement programs, anda traceability checklist for users of calibration services.

To learn more, visit the NIST traceability web site atwww.nist.gov/traceability. For technical information,contact Mary Saunders, NIST Global StandardsProgram, (301) 975-2396, [email protected] Contact: Mark Bello, (301) 975-3776; [email protected].

News Briefs

NEW NIST PRACTICE GUIDE ON ROCKWELLHARDNESS TESTING AVAILABLEThe NIST Recommended Practice Guide: RockwellHardness Measurement of Metallic Materials (NISTSpecial Publication 960-5)—the latest in the newpractice guide publication series—is now available.Rockwell is a method-based test primarily used bymetals and metal products producers to measure thehardness of metal parts, such as those found in aircraftand automobiles. The new guide is aimed at promotingaccuracy and consistency in test results in the labora-tory and on the production floor.

Offering good practice recommendations, the guidehighlights the causes of variability in test results. Tohelp machine operators avoid errors, the guide coverscommon problems, such as using the correct Rockwellscale, surface preparation, speed of testing, machineverification and environmental factors.

As part of its Rockwell hardness standardizationprogram, NIST has developed standard referencematerial (SRM) test blocks for the Rockwell C scale,which is used for hard metals, primarily steel. TheSRMs are used to calibrate commercial hardnessmachines. Researchers are working on SRMs for theB scale softer metals, such as aluminum, bronze, copperand brass. NIST also is involved with the AmericanSociety for Testing and Materials, the InternationalStandards Organization and the International Commit-tee of Weights and Measures in developing an inter-national reference standard.

Responding to a related industry problem, NIST hasestablished a microform calibration system for measur-ing the geometry of diamond indenters with highaccuracy.

To obtain a copy of NIST SP 960-5, contact PublicInquiries, (301) 975-NIST (6478), [email protected] more information on NIST’s Rockwell hardnessresearch, contact Sam Low, (301) 975-5089,[email protected]. The contact for NIST’s diamondindenter calibration effort is John Song, (301) 975-3799, [email protected] Contact: Pamela A. Houghtaling, (301) 975-5745; [email protected].

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WANT SKILLS IN NEUTRON SPECTROSCOPY?GO TO SUMMER SCHOOL!In June 2001, the NIST Center for Neutron Research(NCNR) conducted its seventh annual summer schoolgeared for students at the graduate level. Partiallyfunded by the National Science Foundation, this year’scourse focused on the methods and applications of low-energy neutron spectroscopy, an experimental techniquewidely used to study the motion of atoms, molecules andmagnetic moments in a variety of condensed mattersystems (mostly solids). The emphasis was on scatteringmethods that employ long-wavelength neutrons toachieve high-energy resolution.

Students performed a variety of hands-on experi-ments using five of NCNR’s state-of-the-art neutronscattering instruments: the disk-chopper time-of-flightspectrometer, the filter-analyzer spectrometer, the high-flux backscattering spectrometer, the neutron spin-echospectrometer, and the spin-polarized inelastic neutronscattering spectrometer. Each device is unique in theUnited States. For each instrument, students learned thescientific motivation for the measurements, how theinstrument works, how to mount samples, how to set upthe instrument to collect data, and how to visualize andanalyze the data.

NCNR’s neutron source is operated as a national userfacility open to guest researchers from universities,private industry and other government laboratories inthe United States and abroad.

For more information on NCNR’s summer school,contact John Copley, (301) 975-5133; [email protected], or Peter Gehring, (301) 975-3946; [email protected]. The summer school’s web site iswww.ncnr.nist.gov/staff/john/ss01.html.Information on the NCNR can be found at www.ncnr.nist.gov.Media Contact: Pamela Houghtaling, (301) 975-5745;[email protected].

SEMICONDUCTOR LABS PUT NEW NISTSOFTWARE THROUGH ITS PACESForty semiconductor industry laboratories that requireaccurate measurements of the concentration anddistribution of dopant atoms within nanometer-scaledevices are field testing a beta version of NIST’s newFASTC2D (“fast capacitance to dopant” level) software.The software provides an essential link between qualita-tive images captured by a scanning capacitance micro-scope (known as an SCM) and quantitative data requiredto design transistors for future integrated circuits.

Dopants are like a seasoning within semiconductordevices. The distribution of dopants controls how atransistor works. To control the flow of electrons to thelevels required in modern circuits, engineers must knowthe precise distribution of dopants, with a spatialresolution better than 10 nanometers.

SCMs are strong candidates for achieving targetlevels of precision and resolution. Therefore, the Inter-national Technology Road Map for Semiconductors hasidentified them as a critical measurement tool forcontinued miniaturization of semiconductors.

Capacitance—a measure of electrical charge-storingcapacity—also could benefit from the use of SCMs. TheSCM senses capacitance between the doped region anda sharp tip positioned close to the surface of a crosssection cut through the transistor structure. However,details of the resulting image have resisted accurateinterpretation.

The FASTC2D computer software transforms pixeldata from an SCM image into a map that accuratelyshows the distribution of dopant atoms. NISTresearchers developed the underlying theory and laterpackaged it into software suitable for manufacturingengineers. Designed to run on a desktop computer, thesoftware features a user-friendly graphical interface. Italso produces highly accurate results achieved withmodels based on principles of physics that translatecapacitance into two- or three-dimensional quantitativedata on dopant concentrations.

NIST is improving the software based on responsesfrom the 40 laboratories and plans to publish a newversion and a user’s guide to the software. Both thesoftware and the guide will be available via NIST’sWorld Wide Web site.Media Contact: Philip Bulman, (301) 975-5661;[email protected].

NEW PUBLICATION SHOWCASES KEY NISTRESEARCH ACHIEVEMENTSAs part of NIST’s 100th birthday celebration,the agency has published a retrospective of the pivotalscientific and technical papers that marked its mostsignificant contributions to science, technology, theeconomic growth of the nation and a better qualityof life for all Americans. A Century of Excellence inMeasurements, Standards and Technology: A Chronicleof Selected NBS/NIST Publications 1901-2000(NIST Special Publication 958) is now available on theWorld Wide Web via the NIST Centennial site,www.100.nist.gov.

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This book, which consists of vignettes describingsome of the classic publications from NIST’s firstcentury, features titles such as “Development of theVisual-Type Airway Radio-Beacon System” (tellingabout the NIST system which made possible the first“blind” landing of an aircraft using radio signals in1931); “Reversal of the Parity Conservation Law inNuclear Physics” (recounting the 1956 experiment thatshattered a fundamental concept of nuclear physicsuniversally accepted for 30 years previously); “TheTopografiner: An Instrument for Measuring SurfaceMicrotopography” (recognizing the 1972 developmentof the world’s first scanning probe microscope);“HAZARD I: Software for Fire Hazard Assessment”(describing one of the first fire simulation models forpersonal computers in 1989); “Observation of AtomsLaser-Cooled Below the Doppler Limit” (chroniclingthe research that led to NIST’s William Phillips sharingthe 1997 Nobel Prize in Physics); and “Bose-EinsteinCondensation in a Dilute Atomic Vapor” (detailing theresearch that led to the first observation of a new state ofmatter in 1995).

NIST SP 958 will be available in hard copy at a futuredate from the National Technical Information Service,5285 Port Royal Road, Springfield, VA 22161,(800) 553-6847. Ask for order No. PB 2000-107702.Media Contact: Michael E. Newman, (301) 975-3025;[email protected].

PAPER DESCRIBES NEW SYSTEM FORDETECTING CONCEALED WEAPONSNIST scientists are developing a system for detectingconcealed weapons that could be mounted on a vehicle.Driven into a crowd, the system would scan membersand identify guns, knives and other dangerous objectshidden under clothing.

The approach combines the chief advantages of bothactive and passive detection systems into one unit. Theactive part involves the illumination of a subject with amillimeter-wave source and then detecting the radiationreflected from it. Because the NIST system usesbolometers (devices that detect and measure smallamounts of radiation), it is a significantly more powerfuldetection tool than conventional passive imagingsystems.

On the other hand, the NIST system is relativelybroadband so it eliminates the problem of glint oftenassociated with active detection systems. Glint isproduced by uncontrolled standing waves generatedbetween the target and its environment. To obtain a largebandwidth, the developers use high power oscillators

that operate at 95 GHz in a pulsed mode. These arecommercially available at a low-enough price that doesnot impact the overall system cost.

The detection portion of the system is centered on afocal plane array of uncooled, millimeter-wave bolo-meters. The array consists of a 75 mm diameter siliconwafer populated by a 117-element array of thin-filmniobium bolometers, each of which is coupled tothe incident radiation by a planar, lithographicallyfabricated, millimeter-wave antenna.

For a copy of paper no. 12-01 describing this system,contact Sarabeth Harris, NIST, MC104, Boulder,CO 80305-3328; (303) 497-3237; [email protected] Contact: Fred McGehan, (303) 497-3246;[email protected].

NEW INTERNATIONAL STANDARDS ACTIVITYIN POLYMER MASS SPECTROMETRYA new technical working area—TWA 28—in quantita-tive mass spectroscopy of synthetic polymers has beenformed within the Versailles Project on AdvancedMaterials and Standards (known as VAMAS) to explorethe development of a standard method for determiningthe molecular mass distribution of synthetic polymers(plastics).

With recent advances in mass spectrometry, it is nowpossible to measure the molecular mass of some bio-logical and synthetic polymers. The distribution of themolecular chain lengths—the number of small and longones—affects the processing of materials and theproperties of the final product. The first step is to iden-tify the mixture of chains. A variation of time-of-flight(refererred to as ToF) mass spectrometry called matrixassisted laser desorption ionization (MALDI) has thepotential to be an absolute method for measuring themolecular mass of polymers. MALDI ToF massspectrometry uses laser ablation to produce chargedpolymers in the vapor state, which allows the directmeasurement of the mass distribution.

The VAMAS activity brings together leading labora-tories in Japan, Germany, Italy, Canada and the UnitedStates in a collaborative research project that willdevelop the test protocols and establish the systematicmeasurement uncertainties of the MALDI method.NIST is chairing the new working area.

For more information on the new VAMAS activity,contact NIST’s Charles Guttman, chair of TWA 28, at(301) 975-6729; [email protected] Contact: Pamela Houghtaling, (301) 975-5745;[email protected].

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NIST SAYS “MORE ATTENTION MUST BE PAIDTO REPAIR WELDS”A new paper from NIST suggests that more attentionmust be paid to weld repairs in order to avoid failuresdue to problems such as stress-corrosion cracking. Evenat the outset, a welded joint has a higher risk of failurefrom degradation of base material near the weld becauseof the welding process itself. This risk of failure isincreased if repair welding is performed.

“Therefore, the welding, quality control and qualityassurance technologies need to be developed to morestringent requirements if we want to avoid the conditionsfor failure, and so achieve higher reliability for weldedconstruction,” reads the report. The paper discussespossible difficulties that could occur during repairwelding of high-strength steel used to manufacturepressure vessels for the storage and transport of lique-fied gases. The crux of these problems is the complextemperature variations that occur during the weldingrepair which “can cause significant degradation of thewelded-joint zone.”

Repair welds are usually short, so their temperaturefields are more complex than long welds. The degra-dation is most severe at weld starts and stops, but alsocan occur at other locations along the weld and fordifferent stress conditions. Much of the report concernsdegradation in properties at the weld starts and stops.

For a copy of paper No. 18-01, contact SarabethHarris, NIST, MC104, Boulder, CO 80305-3328;(303) 497-3237; [email protected] Contact: Fred McGehan, (303) 497-3246;[email protected].

NIST CONTRIBUTES TO NEW ANSI STANDARDFOR FINANCIAL SERVICES INDUSTRYThe American National Standards Institute (ANSI)recently approved ANSI X9.42-2001, Public KeyCryptography For the Financial Services Industry:Agreement of Symmetric Keys Using DiscreteLogarithm Cryptography, as an ANSI standard. NIST’srole in producing the standard involved coordinating thedevelopment of the standard and serving as primaryeditor. The X9.42-2001 standard defines the secureestablishment of cryptographic data for the keying ofsymmetrically keyed algorithms (e.g., Triple DataEncryption Algorithm [TDEA]). Schemes are providedfor the agreement of symmetric keys using Diffie-Hellman and MQV algorithms.

The Diffie-Hellman key agreement mechanism is awell-understood and widely implemented public keytechnique that facilitates cost-effective cryptographic

key agreement across modern distributed electronicnetworks such as the Internet. The MQV algorithm is avariation of the Diffie-Hellman algorithm that has moresecurity attributes and may provide better performanceover analogous Diffie-Hellman methods. Because theDiffie-Hellman and the MQV techniques are based onthe same fundamental mathematics as the DigitalSignature Algorithm (DSA), additional efficiencies andfunctionality may be obtained by combining these andother cryptographic techniques.

The standard divides the key agreement process intothe following major components: domain parametergeneration, domain parameter validation, key pairgeneration, public key validation, shared secret valuecalculation, key derivation, and test message authentica-tion code computation for discrete logarithm problem-based key agreement schemes. Using these components,different parties may establish a piece of commonshared secret information such as cryptographic keys.The shared secret information may be used with sym-metrically keyed algorithms to provide confidentiality,authentication, and data integrity services for financialinformation or used as a key-encrypting key with otherANSI X9 key management protocols.

Currently, NIST is developing guidelines for validat-ing implementations of ANSI X9.42. These validationtests are designed to address the individual componentsof ANSI X9.42. ITL will write both a document andthe software to perform these validation tests for thedifferent components of ANSI X9.42.CONTACT: Sharon S. Keller, (301) 975-2910; [email protected].

NIST RESEARCHERS LEAD DEVELOPMENTOF STANDARDS FOR WIRELESS PERSONALAREA NETWORKSA growing number of industry groups are developingspecifications for Wireless Personal Area Networks(WPAN), such as the specifications developed by theBluetooth Special Interest Group (SIG), HomeRF, andIEEE 802.15. WPANs, essentially cable replacementtechnologies, allow closely located digital devices toexchange information. Most technologies considered forWPANs employ an unlicensed radio frequency band inthe range of 2.4 GHz (the so-called industrial, scientific,and medical, or ISM, band). This same frequency rangealso is used by existing standards for wireless local areanetworks (WLAN), for example IEEE 802.11. As thenumber of technologies using the ISM band increases,concern arises about the possibly deleterious effects ofmutual electromagnetic interference.

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Designing wireless protocols that can share thisscarce spectrum presents a key challenge in the designof WPANs.

A team of NIST researchers made significantcontributions to industry’s ongoing efforts to standard-ize WPAN technology in the IEEE 802.15. Specificcontributions include: (1) modeling and validation ofthe Bluetooth protocol specifications, (2) assessment ofinterference among wireless devices operating in the2.4 GHz band, and (3) development and evaluation ofcoexistence mechanisms for wireless devices sharingthe same spectrum.

NIST researchers led efforts within the IEEE 802.15Task Group on Coexistence to study, characterize, andquantify the radio-frequency interference betweenBluetooth and the now widely deployed IEEE 802.11bWLAN devices. Further, NIST researchers haveproposed mechanisms and technical solutions to allowthese devices, emitting radio frequency energy in thesame 2.4 GHz frequency band, to coexist and operateeffectively when in close proximity. Proposed solutionsfrom the NIST researchers, for both the Medium AccessControl (MAC) and Physical (PHY) layers, werecombined with contributions by private companies andthen adopted by the IEEE 802.15 as the basis for adocument on recommended practices for devicedesigners.

In another contribution, NIST researchers used aformal specification technique, known as the Specifica-tion and Description Language (SDL), to model andvalidate the Bluetooth protocols for link control andMAC. Using these models, numerous flaws in theoriginal protocol specifications were identified, result-ing in hundreds of suggestions for improvement to theBluetooth specifications. These SDL models, createdby NIST, will be published as part of the official 802.15specifications, significantly clarifying the intent of thestandard and thereby improving its testability.

Due to the growing importance of the scarceunlicensed wireless spectrum, NIST’s work continueswithin the IEEE 802.15 Task Group on Coexistence.The NIST team continues to lead industry work in thisarea, concentrating on modeling the MAC and the PHYlayers. The studies published by NIST on the inter-ference between various technologies under differentdata traffic conditions and deployment scenarios havecontributed to the task group’s bimonthly meetings andpresented in several professional conferences. NISTresearchers also serve as editors of the RecommendedPractices document on the coexistence of various wire-less devices in the 2.4 GHz band. IEEE 802.15 isexpected to release this document later this year.

Beyond the IEEE 802.15, NIST is working withother industry partners to further disseminate relevanttechnical results.CONTACT: Nada Golmie, (301) 975-4190; [email protected].

NIST RECOMMENDED PRACTICE GUIDE“SURGES HAPPEN!” EXPLAINS PROTECTIONOF CONSUMER APPLIANCESAs part of the new series of “NIST RecommendedPractices Guides,” a 20-page booklet has been devel-oped for the general public on how to protect residentialappliances and consumer electronics against powersurges. The booklet, NIST Special Publication 960-6,is entitled “Surges Happen!”

Surges are momentary events in which the electricalpower exceeds the normal levels, often with devastatingresults. They occur in electric power distribution net-works during normal operation and during electricalstorms. These menacing surges can end up in residentialwiring systems where they can damage expensiveelectronics like computers, television sets, and VCRs,but even worse, they may cause house fires.

Written in easy-to-understand language, “SurgesHappen!” explains what surges are, how they affectappliances, and how to obtain the most effectiveprotection with readily available surge protectors. Thislayman’s booklet also discusses sensitive equipment,provides answers to common questions, and gives someinstallation hints for both the home owners and electri-cians. “Surges Happen!” does not rate products in termsof their susceptibility to power surges but insteadexplains the whys and hows of surges. There hasbeen considerable interest in this guide, which isco-sponsored by an insurance company and the electricpower industry. After incorporating comments frommany industry experts, “Surges Happen!” is now beingdistributed to relevant professional groups, such as theIEEE Surge Protective Devices Committee, and tothe general public. It is available at www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf.CONTACT: Gerald FitzPatrick, (301) 975- 8922;[email protected].

A WEB-BASED FACILITY FOR EVALUATINGPEAK-FITTING METHODS IN X-RAYPHOTOELECTRON SPECTROSCOPYX-ray photoelectron spectroscopy (XPS) is the mostcommonly used technique for determining the chemicalcomposition of surfaces. It is customary to fit analyticalfunctions to overlapping peaks in a measured spectrum

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to determine peak positions, which identify thechemical state, and peak intensities, which quantify thesurface composition. Thus, the reliability of variouspeak-fitting methods for XPS quantification, such asfitting different non-linear functions, is of interest to theXPS community. In addition, analysts should know howreliably they are employing a particular peak analysismethod from the uncertainties associated with operatorchoices such as the type of background function used intheir fits.

NIST researchers recently developed a web-basedfacility to help analysts determine the veracity of peak-fitting approaches in XPS. The NIST researchers hadearlier prepared simulated spectra, based on a factorialdesign that consisted mainly of overlapping doublets forcarbon 1s photoelectrons from polymers. An inter-national group of 20 surface analysts fitted variationsof Gaussian or Gaussian-Lorentzian functions to thedoublets. Their results were analyzed at NIST to yieldmeasures of bias and random error in the peak positionsand intensities for each doublet spectrum in the factorialdesign. These error measures were analyzed furtherwith respect to seven peak-fitting methods used by theanalysts. A statistical analysis of the errors showedthat some peak-fitting methods are more accurate andprecise than others depending on the extent of overlapbetween peaks in the spectrum and the relative heightsof the peaks.

Users of the NIST web site (www.acg.nist.gov/std)can analyze the simulated spectra and then assess theirresults for their chosen peak-fitting approach as itmatches one of the seven peak-fitting methods usedpreviously. Analysts enter the peak parameters fromtheir own fits at the web site, and then receive an on-lineanalysis of their results in terms of bias and randomerror. They then can compare their errors with statisticsfor the subgroup of the 20 analysts who employed thesame peak-fitting method.CONTACT: Joseph M. Conny, (301) 975-3932; [email protected] or Cedric J. Powell, (301) 975-2534;[email protected].

SYSTEMATIC UNCERTAINTY IDENTIFIED INMEASUREMENTS OF SILICON DIOXIDE FILMTHICKNESSES BY X-RAY PHOTOELECTRONSPECTROSCOPYSilicon dioxide is currently used as a gate dielectricmaterial in the semiconductor industry, and it is con-sidered necessary to measure oxide film thicknessesbetween 1.0 nm and 2.5 nm with a relative uncertainty(3�) of �4 %. Many techniques have been used forsuch thickness measurements but the results can dis-agree by more than a factor of two in this thickness

range. These disagreements are due to different assump-tions in the models for the various techniques and to thelack of adequate data.

X-ray photoelectron spectroscopy (XPS) is one ofthe techniques that have been used to measure silicondioxide film thicknesses. The measured thicknessesdepend on knowledge of the effective attenuation length(EAL) of the detected photoelectrons in SiO2 for theparticular film thickness and measurement configura-tion. Unfortunately, experimental measurements of theEAL typically have varied by up to 50 % and it has beennecessary instead to use the electron inelastic mean freepath (IMFP). The EAL differs from the IMFP due to theeffects of elastic-electron scattering on photoelectrontrajectories. The extent of this difference, a systematicuncertainty in the measurement of SiO2 film thick-nesses by XPS, has not been previously investigated.

NIST has collaborated with the Institute of PhysicalChemistry in Warsaw, Poland, in a calculation of EALvalues for SiO2 films of varying thicknesses and fortypical XPS measurement configurations. For commonmeasurement conditions, the ratio of the EAL to theIMFP is approximately constant (within 3 %) forphotoelectron emission angles up to 60�. The averagevalue of this ratio is between 0.906 and 0.935 dependingon the x-ray source, the film-thickness range, and theparticular XPS configuration. The difference betweenthe value of this ratio and unity, here about 8 %, is ameasure of the systematic uncertainty in the XPS thick-ness measurement. For larger emission angles (oftenused to increase surface sensitivity), the EAL/IMFPratio can appreciably exceed unity. These results can beused to make corrections for the systematic uncertaintydue to elastic-electron scattering that are appropriate forthe specific conditions. Similar calculations can bemade for other thin-film materials where the systematicuncertainty in the XPS thickness measurement can be asmuch as 40 % for common conditions.Contact: Cedric J. Powell, (301) 975-2534; [email protected].

INTERACTIVE WEBSITE FOR ANALYZINGMITOCHONDRIAL DNAA new interactive web site called MitoAnalyzer hasbeen developed by NIST researchers that allows usersto determine the effects of single nucleotide poly-morphisms, mutations, insertions, or deletions in humanmitochondrial DNA. The user enters the nucleotidenumber and the new nucleotide (A,G,C,T) that has beenfound, and the program provides information on theeffect of changing that nucleotide including if thechange has occurred in one of the 22 tRNAs, 2 rRNAs,

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or one of the 13 proteins coded by human mitochondrialDNA. If in a protein, the program will provide information on whether an amino acid has been changed andwhat the new amino acid is. The program also willcalculate the position of the new amino acid in theprotein (e.g., � 456 in a protein containing 904 aminoacids). It will print out the new amino acid sequenceand compare it to the original Cambridge Referencesequence. If the change has been associated with amitochondrial disease, information on the diseaseis also provided. The web site is at http://www.cstl.nist.gov/biotech/strbase/mitoanalyzer.html. Thisweb site has been accessed over 568 times since itopened on March 16, 2001.CONTACT: Barbara Levin, (301) 975-6682;[email protected].

NON-DESTRUCTIVE MEASUREMENT OFMAGNETOSTRICTION IN THIN FILMSThin films of magnetic materials deposited on varioussubstrates are of fundamental importance to themagnetic recording industry as well to the operation ofmicroscale actuators. Their magnetostrictive propertiesmust be tailored to the application and are usuallymeasured by depositing the film on one side of aslender, non- magnetic reed. When an external mag-netic field is applied, the bending of the reed yieldsvalues for the magnetic field dependence of the mag-netostriction coefficient of the film. Drawbacks of thiscommon procedure are that (1) it is destructive in thatthe reed must be fabricated with specific dimensions,(2) the results are characteristic of the entire film, and(3) the material of the substrate may not be the same asthat used in the final application. NIST is developingan ultrasonic technique that can be applied to a localregion of the film on any substrate for application toCombinatorial Libraries of magnetostrictive films. Thismethod employs an ultrasonic wave in the substrate toapply an elastic strain of known wave length and fre-quency to the film. Since the film is magnetostrictive, itgenerated a magnetic field above the surface that can bedetected by a non-contacting coil held above the film.The magnitude of this field and hence the amplitude ofthe electrical signal from the coil measures the magne-tostrictive coefficient of the film under the coil. Anexternal source of a DC biasing magnetic field allowsthe magnetic field dependence of the magnetostrictivecoefficient to be measured. At present, the ultrasonicwave is introduced by a piezoelectric transducer at-tached to an edge of the substrate some distance fromthe sensor coil. In the future, this transducer will bereplaced by a coil that uses the film’s magnetostrictionto generate the ultrasonic wave. Thus, a probe that canbe scanned over the surface of a magnetic film on any

substrate can be constructed and used to measure localmagnetostrictive properties of films on devices.CONTACT: George Alers, (303) 497-7899; [email protected].

SMALL-ANGLE NEUTRON SCATTERINGUNIQUELY PROBES GENE REGULATORYPROTEIN/DNA COMPLEXESScientists at the NIST Center for Neutron Research(NCNR) are using small-angle neutron scattering toobtain unique information about the structure of generegulatory protein/DNA complexes in solution. Generegulatory proteins control gene expression in develop-mental and cellular processes of many organisms. Someare activators, turning genes on and some are repressors,turning genes off. All gene regulatory proteins recog-nize and bind specific DNA sequences. The binding ofgene regulatory proteins to DNA often results in adeformation of the DNA. There also has been recentindirect evidence that the proteins undergo a structuralchange as well upon DNA binding. Small-angle neutronscattering (SANS) is currently being used at the NCNRto study the structural changes in both the DNA andprotein components of DNA/gene regulatory proteincomplexes. The goal is to better understand the interac-tions between DNA and proteins in these importantbiological systems.

SANS is ideal for studying protein/DNA complexessince the neutron scattering strengths of DNA andprotein differ with respect to each other. By measuringthe complex in solutions containing different amounts ofD2O, with respect to H2O, different structural compo-nents can be highlighted, while others are suppressed.By measuring the protein/DNA complex under a suffi-cient number of solvent conditions, the structure of thetwo components can be separately determined, eventhough both components are bound together as one com-plex! Thus, SANS allows a unique determination of thestructure of the individual components in the complex.

Recent SANS experiments have confirmed that thegene activator protein, cyclic AMP receptor protein(CRP), undergoes a significant structural, or conforma-tional, change in solution upon DNA binding. Further-more, the regions of the protein that undergo the confor-mational change contain the binding site for RNApolymerase, which plays a crucial role in the early stagesof protein synthesis. This structural change may benecessary in order for CRP to interact with RNApolymerase during this process. Further SANS studiesare under way on other protein/DNA complexes thatplay a role in gene regulation.CONTACT: Susan Krueger, (301) 975-6734; [email protected] or Fred Schwarz, (301) 738-6219;[email protected].

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ANALYSIS OF DENTAL COMPOSITES BY NEARINFRARED SPECTROSCOPYCollaborative research among the American DentalAssociation, the University of Colorado, and NIST ledto an improved method to analyze dental composites.Vinyl resin based composites are increasingly beingused as alternatives to amalgam fillings. The durabilityand biocompatibility of dental restoratives materials,however, may be affected by the thoroughness to whichthey polymerize and how much water they will absorbin the oral environment. The collaborative workexploited near infrared (NIR) spectroscopy, which usesclinically relevant sized specimens, to provide informa-tion on both vinyl group conversion and water uptakeon the same composite specimen. Owing to the non-destructive nature of this analytical technique, theseproperties can be monitored versus time and aqueousexposure. With NIR spectroscopy, it now becomespossible to assess the influence of the type and amountof filler phase of the composite on conversion and waterabsorption. In contrast to conventional gravimetricwater absorption studies, NIR spectroscopy allowsdifferentiation between free or unbound water andhydrogen-bonded water, thereby aiding in elucidatinghow water interacted with the polymer network. Recentstudies have extended the use of NIR spectroscopy tomonitor the conversion of the oxirane group in newtypes composites utilizing epoxy resin binders.CONTACT: Joseph Antonucci, (301) 975-6794;[email protected] or Sabine Dickens,(301) 975-6802; [email protected].

NIST PUBLISHES OPEN SOURCE SOFTWARETOOLKIT FOR XML APPLICATIONINTEGRATIONThe XSLToolbox, a freely available open sourcetoolkit, helps developers avoid the drudgery of writingcomplicated transformations often needed to integrateXML (Extensible Markup Language) applications.The XSLToolbox includes a tool for transforming XMLdocuments as specified by ISO/IEC 10744:1997architectural forms as well as a tool for adding defaultattribute values to XML data.C O N T A C T : J o s h L u b e l l , ( 3 0 1 ) 9 7 5 - 3 5 6 3 ;[email protected].

COOPERATIVE RESEARCH DETERMINESPOWER QUALITY EFFECTS ON MACHINETOOLSNIST scientists have been working with the ElectricPower Research Institute (EPRI) to investigate the needfor power quality ride-through standards on machine

tools. Such standards define the level of power qualityevents a piece of equipment must be able to tolerate(ride-through) before it automatically shuts down.EPRI standards have been developed and adopted in anumber of areas, particularly within the semiconductorequipment industry. Last summer, EPRI engineers andNIST staff measured the performance of a machine tooland several machine tool performance measurementdevices (e.g., lasers and encoders) in the NIST SoundBuilding during synthesized power quality events. Thisresearch resulted in close collaboration between NISTand EPRI for conference presentations, participation inpower quality workshops, and standards developmentfor the performance assessment of machine tools. Theresulting power quality analysis technique and solutionsare being considered for a number of machine toolsacross the United States, with the potential for great costsavings in time and materials.

Since purchasing a particular machining center,NIST has experienced unacceptable machine behaviorduring local power events that have damaged in-processparts. Malfunctions occur when typical local powerevents unexpectedly shut down the machine’s controller,resulting in the machine spindle falling into the part dueto gravity. So far, two frames and one base for the jointU.S. Charters of Freedom Project with the NationalArchives and Records Administration have beendamaged with much loss of time and materials.This machine behavior is not reproducible usingthe emergency stop function, during a controlled shut-down, or when halting the power using the mainbreaker. In correspondence with the machine toolmanufacturer and controller provider, the local machinedistributor was not able to resolve this problem. Anoption to install special power monitoring and supply toeliminate power fluctuations was not affordable.

In response to this need, the NIST-EPRI collaborationconducted extensive testing of the machining center.The machine performance was measured while subject-ing it to varying levels of voltage sag across electricalphases for varying durations. At 60 % of line voltage (a40 % drop in line voltage on two phases, A and B) andfor as little as 5 cycles in duration, the machinecontroller shuts down in an error mode and the spindleconsistently drops up to 18 mm due to gravity. Voltagesags of this level are common in raw, utility-suppliedpower. The testing also established that the machineelectrical systems, with the exception of the controllerpower supply, stay functional until the 50 % threshold isexceeded.

The testing was able to replicate the machine behaviorsuch that the problem could be quantified. By wiringa constant voltage transformer (CVT) in series withthe controller power supply, the problems of machine

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malfunctions and damaged in-process parts were over-come. This solution allows the controller to sense anunder-voltage condition and shut down the equipmentin a controlled fashion. The CVT has been installedpermanently on the machine in question, and NISTstaff will be monitoring the resulting installation forlong-term performance under actual conditions. Furthercollaboration between NIST and EPRI will add to theexisting knowledge through evaluation of additionalmachine tools and power quality effects.CONTACT: Brad Damazo, (301) 975-6611; [email protected].

NEW WEB RESOURCES FOR DIMENSIONALMETROLOGYNIST has launched two new web pages (http://patapsco.nist.gov/mel/div821/) that perform calculations com-monly required by engineers and metrologists who areinvolved in ultrahigh accuracy length measurement. Oneweb page calculates the index of refraction of air, whichis needed to determine the wavelength of laser light inair. (This wavelength serves as the basic unit of lengthwhen performing high-precision distance measurementsbased on interferometry.) The second web page calcu-lates the magnitude of elastic deformation of surfaces incontact under force. This deformation must be taken intoaccount in all high-accuracy length measurements whensurfaces are probed mechanically.

The refractive index of air is computed from atmo-spheric conditions (air temperature, pressure, andhumidity) using either the Edlen or Ciddor equations(the two equations most commonly used to determineair refractive index). The usual version of the Edlenequation was modified to make it more accurate fornon-laboratory conditions, such as high air temperatureand humidity as might be encountered on the shop floor.

The deformation calculation web page will allow auser to correct for elastic deformation at the point ofcontact between a mechanical probe and part. Thiscorrection is essential when submicrometer accuracy isdesired. Currently the web page performs the computa-tion for the seven most common types of contact geo-metry (for example, a sphere in contact with a plane ortwo crossed cylinders). Additional geometric cases willbe added in the future.CONTACT: Jack Stone, (301) 975-5638; [email protected] or Jay Zimmerman, (301) 975-3480; [email protected].

NEW FITTING ALGORITHM FORSHAPE-SENSITIVE LINEWIDTH METROLOGYIs a scanning electron microscope (SEM) image of asemiconductor line produced by a rectangular line of

width w , or by a non-rectangular line of different widthw'? When the lines are less than 100 nm wide andnanometer-scale accuracies are the goal, distinguishingbetween the different possibilities is crucial to linewidthmetrology. NIST scientists are implementing a schemeto make distinctions that are based upon matchingmeasured images to a library of images corresponding,as determined by Monte Carlo model calculations, for avariety of line shapes and widths.

Matching images to the library will be done in threeparts:

• a model function that computes the expected imagefor a given set of parameters that describe the stateof the instrument and the width and shape of the line,

• a residuals function that determines the differencebetween this model image and the one actuallyobserved, and

• a nonlinear least squares fitting algorithm thatadjusts model parameters to determine the bestmatch, as judged by minimizing the sum of squaresof residuals. The new system has several improvedcapabilities compared to the system in place latelast year:

• It can fit entire images (not merely single line scans)in a single fitting operation. This allows one torealistically require instrument parameters to befixed for the whole image, instead of varying fromline to line.

• It can fit any number of line features per line scan.This means it can handle the industrially importantcase of dense lines, instead of only isolated lines.

• Parameters can be “pinned.” A pinned parameter isgiven a fixed value that is not varied for fittingpurposes. This provides a convenient way to usecalibration data determined from an independentmeasurement. For example, if the instrument’s beamdiameter, brightness, and contrast are knownindependently, these can be pinned to their knownvalues, leaving sample geometry as the only thingthat can be adjusted to produce a fit.

CONTACT: John Villarrubia, (301) 975-3958; [email protected].

DIELECTRIC BEHAVIOR OF MATERIALS FORWIRELESS COMMUNICATIONS PREDICTEDFROM FIRST PRINCIPLESDielectric materials for wireless communicationsapplications must have high dielectric constant, low loss,and temperature stability. For high-power base station

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resonators, the only ceramic known with the requireddielectric properties is Ba3ZnTa2O9 (BZT). The driveto find low-cost alternatives to BZT motivates ourinterest in determining the microscopic origin ofuseful electronic properties. As part of this effort,NIST researchers have performed first-principlescalculations of the dielectric properties of CaTiO3 (CT)and CaAl1/2Nb1/2O3 (CAN). These systems are bothcomponents of solid solutions that contain phases withfavorable dielectric properties. CT and CAN havesimilar perovskite-related crystal structures but verydifferent room temperature dielectric constants:� = 170 for CT; � = 27 for CAN. With lattice para-meters and space groups as the only experimentalinputs, the researchers used density-functional theorymethods to compute � for CT and CAN as a function oftemperature, and obtained room temperature values of140 and 25, respectively, in good agreement with exper-iment. Low-frequency phonons dominate the dielectricproperties, and their calculations predict importantdifferences between the properties of the low-frequencyphonons in CT and CAN. In CT, frequencies are lowerand all cations move in opposition to the oxide ions;in CAN however, frequencies are higher and Al and Nbmove with the oxide ions. Their calculations of phononproperties have been verified experimentally by infraredreflectivity measurements. Ultimately, determinationof the microscopic origin of dielectric behavior willpermit the rational, efficient discovery and developmentof advanced ceramics needed for next-generationapplications.CONTACT: Eric Cockayne, (301) 975-4347; [email protected].

NEW HIGH-SPEED MEASUREMENTCOLLABORATIONNIST is creating a “High-Speed Measurement Labora-tory.” This laboratory will develop calibratable high-speed electrical and optoelectronic measurements fornext-generation optical telecommunications, electricalphase standards for nonlinear and other microwavemeasurements, and high-speed digital integratedcircuits.

The laboratory already boasts one success, the devel-opment of an electro-optic sampling system for charac-terizing the magnitude and phase response of fastphotoreceivers to 30 GHz. This is significant not onlybecause this unique measurement system is fullycalibratable but because it can be extended to the muchhigher frequencies critical to the optical telecommuni-cations market. The next target is photoreceiver charac-terization over a 100 GHz bandwidth, which NISTscientists hope to achieve later this year to aid the devel-opment of the new 40 GB/s optical links.

But high-speed photodetector characterization isn’tthe only objective. A photoreceiver with one or twohundred GHz of calibrated bandwidth has many appli-cations. These very fast photoreceivers can be used astransfer standards to establish absolute electrical phase,a critical quantity required for nonlinear device charac-terization at microwave frequencies, and to pushcalibrated temporal measurements to microwavefrequencies, creating a new microwave-measurementparadigm.CONTACT: Thomas R. Scott, (303) 497-3651; [email protected] or Robert Judish, (303) 497-3380;[email protected].

NEW LAW ENFORCEMENT STANDARD FORINTERCEPTS ON DIGITAL NETWORKSNIST’s Office of Law Enforcement Standards (OLES)has completed work on NIJ Standard 0227.00, DigitalIntercept System (DIS) For Integrated Services DigitalNetworks (ISDN). The digital intercept system providesthe capability to intercept any voice or digital datatraffic between a subscriber and an associate andforward it to a central collector station for decoding andprocessing. The central collector allows a monitoringagent to monitor the progress of the call and to recordand play back information captured from the sub-scriber’s line.

The standard was developed under the sponsorship ofthe National Institute of Justice (NIJ). The projectstarted when NIST/OLES entered into an interagencyagreement with the Federal Bureau of Investigation toprovide technical guidance in developing ISDN inter-cept methodologies. After the technology was success-fully demonstrated, the preparation of the performancestandard was undertaken. Since the standard is quitelengthy (over 800 pages), it has been published as aCD-ROM. The CD is available without charge to thoseindividuals or organizations who submit a request to thecontact listed below. The standard bears a “For OfficialUse Only” classification, thus the request must indicatean official need to know this information.CONTACT: George Lieberman, (301) 975-4258;[email protected].

SUPERCONDUCTOR WITH HIGH NIOBIUMARCHITECTURE HAS UNEXPECTEDLY GOODELECTROMECHANICAL PROPERTIESThe fabrication of the next generation of particleaccelerators for high energy physics will require thedevelopment of new niobium-tin/copper superconduc-tors able to carry extremely high current densities athigh magnetic fields. One technique for accomplishingthis is to push the density of superconductor in the

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composite wire to new limits. Such an experimental,high-niobium composite was fabricated recently by aprivate company. A concern in the high-energy-physicscommunity was that the conductor would have very lowtolerance to mechanical strain. To test the conductor,NIST scientists modified their axial electromechanicaltest apparatus and used a new 16.5 T, high field magnet.Surprisingly, the conductor had electromechanicaltolerance similar to standard Nb3Sn composites. Theirreversible strain, beyond which the conductor showspermanent degradation, had a relatively high value of0.85 %. The peak critical current was measured at astrain of 0.34 %. This result clears the way for wiremanufacturers to push the niobium density to evenhigher values, which would provide a significantextension of the magnetic field limit of present acceler-ator magnets.CONTACT: Jack Ekin, (303) 497-5448; [email protected].

MAGNETIC SUBSTRATES REDUCEPERFORMANCE OF Y-Ba-Cu-O COATEDSUPERCONDUCTORSMeasurements by NIST scientists on Y-Ba-Cu-O coatedsuperconductor tapes revealed that the use of magneticsubstrates may reduce the current carrying capacity ofthe tapes when they are arranged in stacks of two ormore layers. This finding has a significant bearing onthe potential use of coated superconductors with mag-netic substrates, particularly in low-field applicationssuch as transmission lines. The disclosure of NIST’sfindings resulted in an accelerated effort at the Depart-ment of Energy’s national labs and their industrialpartners to develop non-magnetic substrates for coated-conductor fabrication.

High temperature superconducting tapes based uponcoatings of Y-Ba-Cu-O on textured, buffered, magneticnickel substrates showed a 15 % degradation in critical-current density when the Y-Ba-Cu-O layer wassandwiched between two magnetic nickel substrates.This configuration commonly occurs in many applica-tions where the conductor needs to be cabled or wound,such as in transmission lines and magnets. The interac-tion of the top and bottom nickel layers increases theperpendicular component of magnetic flux at the super-conductor tape edges. This reduces the current carryingcapacity of the superconductor due to the presence ofthe magnetic field. Removing the top nickel substraterestores the critical current density to its original value.CONTACT: Jack Ekin, (303) 497-5448; [email protected].

NIST CO-SPONSORS PERVASIVE COMPUTING2001 CONFERENCEIn May 2001, NIST, with NSA’s Advanced DevelopmentResearch Activity, cosponsored its second annualpervasive computing conference. As an open forum forthe IT industry, the conference offered key perspectiveson pervasive computing, including the latest in technolo-gies, real applications, and business views.

Presentations centered about the need to understandthe nature of change and opportunity associated withthis new computing environment. A noteworthy confer-ence benefit to industry will be reflected in its ongoingcollaboration with NIST in such critical areas as multi-modal industry standards, interfaces, privacy, andsecurity. Pervasive computing topics discussed includedhealth care industry applications, business-wideapplications, intelligent environments, applications inmobile commerce, software and services, networkingtechnology infrastructure, concluding with a technologyupdate on emerging standards for pico-cellular wirelesscommunications and dynamic service discovery.

Pervasive computing refers to the emerging trendtoward numerous, easily accessible computing devicesconnected to an increasingly ubiquitous networkinfrastructure composed of a wired core and wirelessedges. This trend likely will create new opportunitiesand challenges for the IT marketplace, placing high-performance computers and sensors in virtually everydevice, appliance and piece of equipment, in buildings,homes, workplaces, and factories, and even in clothing.Pervasive computing will require innovative approachesto human-computer interaction and information accesstechnologies, as there will be a shift toward interactingwith small, distributed, and often invisible devices.More information about the conference is available atwww.nist.gov/pc2001.CONTACT: Bill Young, (301) 975-8701; [email protected].

NIST AND PARTNERS HELP BLAZE THEPATH TO METATOPIAHaving an enormous amount of information at yourdisposal to help you make decisions is a wonderfulexperience. Yet, people often complain of the overloadproblem that comes from having too much data.

Some researchers believe a partial solution may befound in metadata—essentially data about data thatdescribe how, when and by whom a particular set ofdata was collected, and how the data are formatted. If itworks well, say IT experts, you have a state of informa-tion heaven, or “metatopia.” To help data managers

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reach this “IT Nirvana,” NIST is sponsoring Metatopia2001, a symposium on metadata and data manage-ment, on Sept. 20-21, 2001, at NIST headquarters inGaithersburg, MD.

The conference is of interest to executives in fieldssuch as data mining, knowledge management, and datawarehousing. The primary focus is on metadata and howit can be standardized.

The Data Management Association-National CapitalRegion is co-sponsoring the conference along with theANSI NCITS Metadata Committee (L8).

More information about the Metatopia 2001 sympo-sium is available at www.dama-ncr.org/Metatopia2001.Media Contact: Philip Bulman, (301) 975-5661; [email protected].

NEW ONLINE NEWSLETTER LINKSRESEARCHERS AND FIREFIGHTERSMillions of dollars are spent annually in fire preventionresearch to lessen a toll which, in the United States,amounts yearly to more than 5000 deaths, 25 000injuries and $9 billion in direct property loss. To informthe firefighting community of this work, NIST and theUnited States Fire Administration have launched anonline newsletter, FIRE.GOV, at www.fire.gov.

The free quarterly publication, started in response toa call by the International Association of Fire Chiefs (anorganization representing more than 12 000 chief fireand emergency officers), provides information aboutresearch activities that could impact firefighting safetyand effectiveness. Contact information is providedso that firefighters can interact directly with theresearchers.

The first issue includes reports on techniques formeasuring the performance of protective clothing, thefire suppression effectiveness of compressed air foam,the search for an environmentally friendly suppressantfor liquid fuel fires, as well as an account of scientificforums on urban/wildland firefighting technology.Future issues will consider other non-commercial fireresearch activities performed by government, universi-ties, industry and fire departments.

The newsletter can be viewed in HTML or down-loaded in a PDF version. Subscriptions to FIRE.GOV,providing delivery of new issues via e-mail, are availableonline. For more information, contact FIRE.GOV editorDave Evans, (301) 975-6897; [email protected] Contact: John Blair, (301) 975-4261; [email protected].

NIST LAUNCHES SERIES OF GUIDES TO EUDIRECTIVESThree newly issued NIST guides to European Uniondirectives on machinery, low-voltage equipment andelectromagnetic compatibility can help U.S. manu-facturers carry out the steps necessary to demonstratecompliance with the EU-wide requirements and gainunfettered access to the 18-nation market.

The easy-to-use introductory references are designedto acquaint businesses and government officials with thedirectives’ essential requirements and their relationshipto other EU product safety laws. Each one lists the typesof products covered by the particular directive (as wellas those that are excluded) and addresses issues regard-ing the treatment of components incorporated intomarket-ready products. In addition, the guides explainthe hierarchy of EU, international and national standardsthat might be used to satisfy the directives. Eachcontains the text of the relevant directive and a list ofapplicable EU harmonized standards.

Intended to foster the free movement of goods amongnations that make up the European Economic Area,the laws are among the more than 20 “new approach”directives approved by the EU’s governing body since1992. Products that comply with relevant directivesmerit the required “CE mark”—kin to a passport forproducts marketed in Europe.

The directive on low-voltage equipment, such asappliances and power tools, is designed to preventelectrical hazards to people, pets, livestock and prop-erty, while the machinery directive aims to ensure thesafety of industrial equipment. The electromagneticcompatibility directive applies to a wide range ofproducts and is intended to prevent electrical andmagnetic disturbances that can undermine theperformance of other products and systems.

The new publications are available at NIST’s confor-mity assessment web site at http://ts.nist.gov/ca. Theyare the first in a series of NIST-commissioned guides onselected EU new approach directives. The series is beingdeveloped with the Commerce Department’s Inter-national Trade Administration.

A limited number of NIST’s guides to the EU direc-tives will be available. Specify the directive of interestand send a self-addressed mailing label to MaureenBreitenberg, NIST, 100 Bureau Dr., Stop 2100,Gaithersburg, MD 20899-2100.Media Contact: Mark Bello, (301) 975-3776; [email protected].

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NOVEMBER CONFERENCE TACKLES TEXTRETRIEVAL SYSTEMSEveryone knows that “looking for a needle in ahaystack” is tough work. However, when the needles aresingle bits of information and the haystack is theenormous collection of data available via the Internet,one needs help to do the search.

That’s where text retrieval systems-the tools used totrack down and isolate those needles-come in. Develop-ing more powerful, faster and easier-to-use textretrieval systems to meet the demands of the Informa-tion Age requires a coordinated research effort. There-fore, NIST and the Defense Department have held theText Retrieval Conference (known as TREC) since1992 to provide the infrastructure necessary for large-scale evaluation of text retrieval methodologies. The10th TREC will be held on Nov. 13-16, 2001, at NISTheadquarters in Gaithersburg, MD.

TREC is overseen by a program committee consist-ing of representatives from government, industry andacademia. For each TREC, NIST provides a test set ofdocuments and questions. Participants run their ownretrieval systems on the data and return to NIST a list ofthe retrieved top-ranked documents. NIST pools theindividual results, judges the retrieved documents forcorrectness, and evaluates the results. The TREC cycleends with a workshop that is a forum for participants toshare their experiences.

This year, TREC is expanding to include, for the firsttime, a video track, because a growing amount of infor-mation is being stored in that form. This is a step towardincluding a general multimedia track in future years.Other topics will include web search engine systemsand cross-language systems.

Attendance is limited to researchers and groups whosubmit search results to the conference. For moreinformation on TREC, go to http://trec.nist.gov orcontact Ellen Voorhees, (301) 975-3761; [email protected] Contact: Philip Bulman, (301) 975-5661;[email protected].

FALL CONFERENCE TO SHOWCASE NEWCASES FOR CHARTERS OF FREEDOMMillions of Americans consider three documents—theConstitution, the Bill of Rights, and the Declaration ofIndependence—tangible, irreplaceable works of politi-cal genius and national patriotism. This ConstitutionDay, Sept. 17, 2001, NIST will host a scientific confer-ence celebrating its current role in preserving these“Charters of Freedom” for future generations. Theconference will be held at NIST headquarters inGaithersburg, MD.

The NIST-built encasement for the Bill of Rights willbe formally transferred to the National Archives andRecords Administration during the conference’s open-ing ceremony. The handover completes a two-yearproject to make nine state-of-the-art encasements thatwill secure the Charters against all types of environ-mental assault including light, oxygen and humidity.Five of the gold-plated titanium frames will hold thefour pages of the Constitution and its transmittal page,which was signed by George Washington. One encase-ment will hold the Declaration of Independence andanother, the Bill of Rights. Two prototype frames, builtat the start of the project, will be used as spares.

The Charters will be moved to their new “homes”while away from public display between July 5, 2001,and sometime in 2003.

Conference speakers will describe the currentCharters encasements—built by NIST in the 1950s—and present data on their performance. They will thendiscuss the design, manufacture and initial performanceof the new NIST cases that embody the best manufactur-ing and preservation technology have to offer. Cutawaymodels of the two case sizes manufactured will be ondisplay.

Detailed design and production information on thenew Charters encasements, historical background on thedocuments and their 1950s preservation, visuals andmore are available at www.nist.gov/charters. Also avail-able is a link to the web site for the Sept. 17 conference,“A History of Encasements: Technology Preserving theCharters of Freedom.”Media Contact: John Blair, (301) 975-4261; [email protected].

NIST FORMS TEAM TO TACKLE INSPECTIONSOFTWARE PROBLEMSAutomating the process of product inspection duringmanufacturing should cut product development cycletime and manufacturing costs. However, the widevariety of inspection software and hardware products onthe market may make it difficult to achieve full benefitfrom an automated process. Common interfaces may benon-existent, measurement programs may requireretooling to make them compatible with new or addedsoftware packages, and training for multiple operatorinterfaces adds to production costs and delaysinspections.

Last month, NIST joined manufacturers and informa-tion technology vendors in an effort to overcome soft-ware interface barriers for automated dimensional mea-surement. The new group, known as the MetrologyInteroperability Consortium, will be developing andtesting interoperability standards for the hardware andsoftware components used.

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The consortium’s 3 year action plan includes:cataloguing gaps in current standards; evaluating currentand developing standards for particular interfaces todetermine which ones deserve support; identifying andassisting in harmonization of competing or overlappingstandards; developing specifications for interfaceswhere no satisfactory non-proprietary standard exists;and assembling consensus user requirements to provideas input to standards developing organizations.

Finally, consortium members will develop andperform conformance and interoperability tests for soft-ware that incorporates the standards. Projects thatrequire testing will be carried out using a NationalMetrology Testbed that consists of equipment and soft-ware owned and operated by the participants at theirown sites. NIST will develop procedures and tools forconformance and interoperability testing.

Membership in the Metrology InteroperabilityConsortium is open to users, vendors and thirdparty organizations. For more information, contact AlWavering, (301) 975-3461; [email protected] Contact: John Blair, (301) 975-4261; [email protected].

WORK WELL UNDER WAY ON WORLD’SPREMIER MEASUREMENT LABA drive past NIST headquarters in Gaithersburg, MD,these days might have you looking twice. There’s anever-growing stockpile of dirt on the campus’ southernside from excavations, five (and soon to be six) cranespoised high above a construction site and the sight ofpeople and machines busily at work on a very specialbuilding.

When it is ready for occupancy in 2004, the47 480 m2 (511 070 ft2), $235.2 million AdvancedMeasurement Laboratory will give NIST and its part-ners in U.S. industry and science access to research anddevelopment capabilities not available anywhere else inthe world. The laboratory will have state-of-the-artcontrols for humidity, temperature, vibration, and airquality. Two of the AML’s five wings will be builtunderground with special active and passive vibrationisolation systems. The unique characteristics will helpits occupants achieve higher quality reference materials,improved measurements and standards, and morerapidly developed research advances.

Instrument East, currently scheduled to wrap up inmid-2003, will be the first portion of the AML finished.Other target completion dates are mid-to-late 2003 forthe cleanroom and the Metrology East wing, and late2003 for the Instrument West and Metrology Westwings.

For more information on the AML, along with anartist’s rendition of the finished facility and a livewebcam view of the construction site, go to http://aml.nist.gov.Media Contact: Michael E. Newman, (301) 975-3025;[email protected].

RADIOMETRIC CHARACTERIZATIONPERFORMED AT NIST IMPROVES ACCURACYOF THE MARINE OPTICAL SPECTROGRAPHThe Marine Optical Buoy (MOBY) project is a partNASA’s Earth Observing System Program, andsupports the validation of satellite ocean color imagerydata that are used for understanding the global carboncycle. The Marine Optical Spectrographic (MOS)system is used in MOBY to derive water-leavingradiance.

For the first time, a rigorous study of the radiometricproperties of the MOS was performed using NIST’sSpectral Irradiance and Radiance Calibrations withUniform Sources (SIRCUS) facility, which usesbroadly tunable lasers and integrating spheres tocalibrate and characterize a wide variety of detector-based instrumentation. Using the measurements fromSIRCUS, physicists at NIST assessed the effect of straylight on MOS measurements of water-leaving radiance.A stray-light-correction algorithm was developed andapplied to a subset of MOS data sets, greatly reducingthe uncertainty in these measurements. This work willhave immediate impact on the ocean-color remote-sensing community.CONTACTS: Carol Johnson, (301) 975-2322;[email protected] or Steve Brown, (301) 975-5167;[email protected].

NIST AND NFPA PROFILE SMOKE TOXICITYHAZARDSmoke toxicity has been a recurring theme for firesafety professionals for over four decades. Therecontinues to be difficulty and controversy in assessingand addressing the contribution of the sublethal effectsof smoke in hazard and risk analyses. NIST and theNational Fire Protection Association have completedthe first phase of the “International Study of theSublethal Effects of Fire Smoke on Survival andHealth” to provide scientific information on this topicfor public policy makers and product manufacturers.This report estimates the magnitude and impact ofsublethal exposures to smoke on the U.S. population,provides the best available, previously published lethaland incapacitating toxic potency values for smoke from

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commercial products, determines the potential forvarious size fires to produce smoke yields that couldresult in sublethal exposures, and provides state-of-the-art information on the production of condensed compo-nents of smoke and their evolutionary changes duringtransport from fire.CONTACT: Dick Gann, (301) 975-6866; [email protected].

NIST TEAM DEVELOPS SCREENING TOOLFOR NEW FIRE SUPPRESSANTSThe Next Generation Fire Suppression TechnologyProgram, led by a NIST scientist, is the Department ofDefense’s research effort to identify alternatives to thecommonly used fire suppressant halon 1301 (CF3Br),now known to deplete stratospheric ozone. A keyportion of this program is the development of tools toevaluate the fire suppression performance of newcandidate extinguishants for use in suppressing in-flightaircraft fires. A NIST team has completed work on theTransient Application, Recirculating Pool Fire(TARPF) Facility. This device measures the suppres-sion effectiveness of impulsively discharged gases(such as from a pressurized storage bottle or solidpropellant gas generator), the impact of a hot surface oncontinuous suppression, the impact of a recirculatingflow; and the impact of a liquid spray. The flow patternsin the device have been modeled to extend theapplicability of the experimental results to a variety ofconditions prevalent during aircraft fires.CONTACT: William Grosshandler, (301) 975-2310;[email protected].

WORK BY NIST RESEARCHER SUGGESTSPERFORMANCE BREAKTHROUGH INSPEAKER RECOGNITIONA possible performance breakthrough by a NIST scien-tist involving significant reduction in error rates wasreported at the 2001 Speaker Recognition Workshop,held in May 2001, in Linthicum, MD. Hosted by NIST,the workshop reviewed the recently concluded 2001Speaker Recognition Evaluation. Twelve academic andindustrial research organizations participated: six fromthe United States, three from France, and one each fromSpain, India, and Australia.

The evaluation covered several basic tasks involvedin text-independent speaker recognition and includedeight different tests. Sites achieving the best scores on

the tests were noted, although differences between com-peting systems were sometimes small. NIST researchersgave three presentations at the workshop, analyzingperformance results for different parts of the evaluation.Most of the data used in the evaluation were excerptsfrom the Switchboard Corpora of conversationaltelephone speech, generated at NIST. A new Switch-board Cellular Corpus was used at the workshop,marking the first time that cellular telephone data hasbeen used in a speaker recognition evaluation. Suchcellular data will serve as primary data in the nextevaluation.

In a possible performance breakthrough based onresults of preliminary work, a NIST researcher showedthat much useful information for characterizingspeakers could be found in longer-term speech charac-teristics, particularly the frequent usage of certainwords or phrases. He showed that such “idiolectal”features of speech, obtainable from word transcripts,even errorful transcripts produced by automatic speechrecognizers, could greatly enhance performance. Forthis task, he used test segments consisting of entireconversation sides (taken from conversations of 5 to10 minutes each) and training data for each speakerconsisting of several, preferably at least eight, suchconversation sides.

To further explore the use of idiolectal characteristicsof speakers in speaker recognition, a new extended dataone-speaker detection task was included in this year’sevaluation. For this evaluation, systems were providedwith much larger amounts of training and test data andwith word transcripts generated by an automatic speechrecognizer. Speaker detection performance was evalu-ated by measuring the correctness of detection decisionsby the systems. These decision scores were used toproduce error trade-off curves in order to see howmisses may be traded off against false alarms. Twosites, MIT-Lincoln Laboratory and R523 (DoD),produced systems for this evaluation. Their performanceresults were quite impressive, reducing previously seenerror rates on such data by up to an order of magnitude.

This work is an exciting development that could havesignificant applications and that brings togetheremerging speech recognition and speaker recognitiontechnologies. More information about the speakerrecognition program is available on the web at http://www.nist.gov/speech/tests/spk/index.htm.CONTACT: Alvin Martin, (301) 975-3169; [email protected].

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NIST PUBLISHES SPECIAL PUBLICATION250-58: CALIBRATION OF X-RAY ANDGAMMA-RAY MEASURING INSTRUMENTSNIST has recently revised and published a key Measure-ment Services Guide, NIST Special Publication 250-58,which describes completely the x-ray and gamma-raycalibration services provided at NIST. This publicationreplaces the 1988 NBS Special Publication 250-16 thathas been widely distributed for the past decade to thoseinterested in x-ray and gamma-ray measurements formedical applications. This revised edition now includesdetails of the NIST mammography calibration facility,results of recent international x-ray comparisons, newreference beam quality parameters, and documentationof current uncertainties associated with the calibrationservice.

The calibration and irradiation of instruments thatmeasure x rays and gamma rays are performed in termsof the physical quantity: air-kerma. The measurementof air-kerma and the calibration process involves acomparison of the test instrument to a NIST primarystandard, which includes four free-air ionizationchambers for x rays and cavity ionization chambers forgamma rays. The document will be useful to those whouse the NIST radiation calibration service and for otherswho are currently developing services similar to thoseprovided at NIST. SP 250-58 will soon be available onthe web.CONTACTS: Michelle O’Brien, (301) 975-2014;[email protected] or Paul Lamperti, (301) 975-5591; [email protected].

SPONTANEOUS COHERENT MICROWAVEEMISSION AT SURF IIIFollowing the long established theory of synchrotronradiation emission, all synchrotron radiation is emittedin harmonics of the frequency of the acceleratingradio-frequency field. Researchers at NIST have madethis “picket-fence” structure visible at the SynchrotronUltraviolet Radiation Facility, SURF III, for microwaveradiation emitted at frequencies around 10 GHz, whichcorresponds to the 100th harmonic. This microwaveradiation was easily detectable, because of its coherentenhancement by a “sawtooth” or longitudinal bunchinstability in the electron beam. A collaborative study ofthis phenomenon with researchers at the ArgonneNational Laboratory’s Advanced Photon Source isreported in the May 2001 issue of the journal PhysicalReview Special Topics—Accelerators and Beams.

The major breakthrough in this study was the identifi-cation of the connection between spontaneous coherentsynchrotron radiation emission, micro-bunching,intensity noise in the visible spectral range, and the

sawtooth instability, which has long been known toaffect SURF under certain operating conditions. Thisgreater understanding of SURF III beam dynamics hascontributed significant improvements in beam stabilitythat have been obtained recently.CONTACT: Uwe Arp, (301) 975-3233; [email protected].

SINGLE-CRYSTAL CRITICAL DIMENSIONREFERENCE MATERIALS DELIVERED BYNIST RESEARCHERS TO INTERNATIONALSEMATECHNIST researchers have delivered prototype criticaldimension reference materials for calibrating linewidthmetrology instruments used in manufacturing semi-conductor devices to International SEMATECH (ISMT)for evaluation by member companies. The work was theresult of collaborations with ISMT, a private company,Sandia National Laboratories, and NIST to fabricate,test, and evaluate this new class of reference artifacts tomeet the goals of the Semiconductor Industry Associa-tion’s International Technology Roadmap for Semicon-ductors (ITRS). ITRS states that it is critically importantto have suitable reference materials for lithographysupport available for development of advanced materialsand process tools as well as on-wafer measurements forintegrated circuit (IC) manufacturing. The ITRSprojects the decrease of gate linewidths used in state-of-the-art IC manufacturing from present levels of approx-imately 250 nm to below 70 nm within several years.Until now, such reference materials have been unavail-able because of the lack of a technology needed for theirfabrication and certification.

In order to be compatible with users’ metrologyinstruments, test chips containing the reference featureswere mounted in a “reference-material carrier” waferalso developed by NIST staff. This carrier consists of ablank 200 mm silicon wafer with a recessed “pocket”etched in the center with dimensions appropriate toaccommodate the chip. Fifteen carrier wafers, each con-taining a chip with a reference feature having a criticaldimension in a range from 80 nm to 140 nm, weredelivered to ISMT for evaluation by its membercompanies.

The technical approach was to design the referencefeatures into electrical test structures, thus enabling thedetermination of their electrical linewidth. A selectionof 36 test structures was incorporated into the test chipthat was patterned in the device layer of 110 silicon-on-insulator wafers based on well-established siliconmicro-machining technology that produced feature side-walls having near-atomic planarity. Primary calibrationof the critical dimension of the test-structures on all the

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test chips was accomplished by means of high cost,low speed High Resolution Transmission ElectronMicroscopy (HRTEM) imaging and lattice-planecounting at a limited number of sites on the wafer.HRTEM provides nanometer-level accuracy, but issample-destructive and is prohibitively costly to imple-ment on all reference features. The samples delivered toISMT were calibrated via a statistical correlation withtheir high-precision electrical critical dimensionmeasurement.CONTACT: Michael Cresswell, (301) 975-2072;[email protected].

NIST DEMONSTRATES REMOTE OPERATIONOF 10 V JOSEPHSON VOLTAGE STANDARDSYSTEMA NIST scientist recently demonstrated the newWindows version of the control software for the 10 VJosephson Voltage Standard (JVS) system. This soft-ware is the first to provide remote operating capabilityof JVS systems. A laptop computer with a modemconnection in a conference room in Gaithersburg wasused to dial-up the 10 V JVS in the Josephson ArrayTechnology Lab in Boulder. Complete remote control ofthe system was demonstrated by performing a numberof calibrations. The new software will replace olderDOS-based software, making the system compatiblewith current computer hardware and software. Remoteoperation will reduce operating costs of JVS systems byallowing an operator or repair expert to monitor,control, and diagnose JVS systems from any location.Future enhancements will allows JVS operators tocollect statistics and perform all the capabilities of theearlier DOS-based software.CONTACT: Charlie Burroughs (303) 497-3906;[email protected].

CONSTANT VOLTAGE STEPS IN JOSEPHSONJUNCTION SERIES ARRAYS AT 10 KNIST is collaborating with Japan’s ElectrotechnicalInstitute, which has recently become part of theNational Institute of Advanced Industrial Science andTechnology (AIST), to develop a higher temperatureprogrammable voltage standard, so that this system canoperate with a practical cryocooler. NIST has providedfabrication development advice and circuit designs andcircuit testing. After considerable improvements in theirfabrication process over the last two years, including theaddition of two planarization steps and the addition ofNbN wiring, the Japanese group has made the first all-

NbN arrays with useful operating margins. Arrays of4096 junctions have sufficient uniformity at a 10 Koperating temperature to generate constant voltagesteps.

NIST hopes to continue this collaboration with AISTand begin stacking the junctions for lumped arrays. Theuniformity is also good enough to begin designingcircuits with 33 000 (unstacked) junctions for 10 Kprogrammable voltage standard circuits.CONTACT: Samuel Benz, (303) 497-5258; [email protected].

SEVEN-TIMES RESOLUTION IMPROVEMENTIN NARROWBAND POLARIZATION-MODEDISPERSIONMeasurements Polarization-mode dispersion (PMD) isthe parameter currently limiting higher data rates inoptical fiber communications. Therefore, it is critical tohave PMD metrology able to characterize these systems.In order to achieve high data rates, wavelength channelspacings are steadily decreasing from 200 GHz to25 GHz and narrower. Fundamental tradeoffs exist inthe measurement of PMD that bring higher measure-ment uncertainty as the measurement bandwidth isreduced. In 1998, in an effort to address narrow-bandPMD measurement needs, NIST demonstrated aModulation-Phase Shift (MPS) technique able tomeasure PMD in a narrow 4 GHz bandwidth. Thatsystem had a PMD resolution of 150 fs. Whilethe technique was a useful improvement, thePMD resolution was poor compared to resolutionsof a few femtoseconds achievable by wider-band-width PMD techniques such as Jones Matrix Eigen-analysis.

Now, NIST has assembled a second-generation MPSsystem that has demonstrated a PMD resolution of about20 fs in a bandwidth of 5 GHz, an approximate seven-fold improvement over the previous MPS system. We arenot aware of any other MPS system with such high PMDresolution. The system is based an RF comb-generatorthat modulates laser light at 2.46 GHz and mixes thedetected power to a 123 MHz frequency measurable bya low-phase-noise RF lock-in amplifier. The PMDresolution of the system appears to be limited by thephase noise of the lock-in amplifier itself. We have alsofound the technique to be surprisingly susceptible tooptical reflections in the component under test. Futurework will be done toward reducing optical reflectionsand their effects.CONTACT: Sarah Gilbert, (303) 497-3120; [email protected].

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UNIFORM Ti-BARRIER JOSEPHSONJUNCTION ARRAYS FOR AC JOSEPHSONVOLTAGE STANDARDNIST researchers have made the first uniform arrays ofJosephson junctions using titanium as a junction barriermaterial. We have focused on using Ti because it canbe reactive ion etched with the superconducting Nbelectrodes. A considerable effort has been made inexperimenting with different etch chemistries toimprove the etch anisotropy for etching pentalayerNb-Ti-Nb-Ti-Nb junction stacks. Two verticallystacked junctions fabricated with this process shouldhave nearly identical areas that very closely match thephotoresist dimensions.

Using this new process we recently fabricated arraysof single (unstacked) Nb-Ti-Nb junctions in microwavecircuits designed for arbitrary waveform synthesis.These junction arrays are embedded in microwavecircuits, which are used to evaluate the junction unifor-mity. We successfully generated constant-voltage stepsin 1000- and 4100-junction series arrays. This is a verygood result because it shows that the correct voltage isgenerated over significant current range for a broadrange of frequencies for this large 4100-junction array.This indicates good junction uniformity as well as goodmicrowave uniformity for the entire circuit design. Mostof the structure in this circuit is caused by filterresonances, which are also under development. Stacked2-junction pentalayer arrays are under development.CONTACT: Samuel Benz, (303) 497-5258; [email protected].

RESONATING TORQUE MICROBALANCEDEVELOPED FOR IN SITU MEASUREMENTSOF FERROMAGNETIC FILMS WITHSUB-MONOLAYER SENSTIVITYWork at NIST to develop ultra-sensitive magnetometersbased on micromechanical sensors has led to a newinstrument for in situ measurements of ferromagneticfilms. In particular, measurements of thin-film proper-ties critical to the development of read head sensors andmagnetic recording media are being investigated.

The production and development of many contempo-rary magnetic devices require that consistent growthconditions be maintained during thin-film depositionprocessing steps. Typically, film properties are deter-mined ex situ with induction-field (B-H ) loopers thatmeasure the Mstf product for the film, where Ms and tf

are the saturation magnetization and the thickness of thefilm, respectively. The goal of this project is to developan instrument that depends on inexpensive, batch-fabricated, micromechanical substrates for quantitativemeasurements with sub-monolayer magnetic momentsensitivity.

NIST scientists are the developers of an instrumentthat measures the magnetic torque on a film as it isbeing deposited onto a single-crystal silicon micro-cantilever. An optical fiber interferometer is used tomeasure the deflection of the cantilever. Optic-fiberdetectors work well in the high noise environmenttypical of deposition systems. The magnetic torque isapplied near the mechanical resonance of the cantileverto take advantage of the quality factor enhancement ofthe mechanical torque signal. Dynamic feedback is usedto balance the magnetic torque by applying a mechani-cal force at the base of the cantilever that is just equaland opposite to the magnetic torque. The dynamicfeedback approach minimizes the mass loading and theeffects of temperature-dependent elastic modulus thatchange the resonant frequency of the cantilever duringdeposition. The cantilevers were custom designed forthis application and fabricated in the new NIST micro-electromechanical sensors fabrication facility inBoulder.

The technique provides a way to make quantitativemeasurements of the saturation magnetization of thin-film samples with very small total magnetic moments.The Brownian motion of the cantilever sensor funda-mentally limits its ultimate sensitivity; at room temper-ature this corresponds to a 0.02 nm thick ferromagneticfilm with the current cantilever geometry.CONTACT: John Moreland, (303) 497-3641; [email protected].

DIRECTORY OF PRIVATE-SECTOR PRODUCTCERTIFICATION PROGRAM UPDATEDThe 2001 edition of the NIST Special Publication 903,Directory of U.S. Private Sector Product CertificationPrograms, is available. NIST is obligated to provideconformity assessment information, including informa-tion on private sector certification bodies, under anumber of acts and international and regional tradeagreements. This directory helps fulfill some of thoseobligations and also aids in recognizing the diversity,and therefore the complexity, of U.S. private sectorproduct certification activities.

The revised directory summarizes the product certifi-cation activities of over 122 non-governmental organiza-tions based in the United States. It includes organiza-tions that operate strictly within the United States, thosethat operate at both the U.S. and international levels, andthose that operate as the U.S. component of an inter-national program. The directory includes only productor facility-related certification programs. It does notattempt to address programs that certify, register, oraccredit services, professional skills, or quality/environ-mental management systems. However, an appendix has

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been included in the directory to provide informationobtained from the websites of major certifier organiza-tions that did not respond to several requests for infor-mation on their programs.

The directory includes organizations which: ad-minister a certification program and certify that prod-ucts meet some criteria; administer a program usingan independent, third party certifier; or serve as theindependent, third parties certifier for a program admin-istered by another organization. Entries in the directorydescribe the type and purpose of each organization, thenature of the activity, products certified, standards usedin the assessment, certification requirements, and anyaccreditation or recognition by a U.S. or foreign privatesector or government agency, availability of services,methods of cost determination, and other relevantdetails. Where available, a representation of the organi-zation’s mark is included with each entry, as well as apictorial index of all such marks.

Special Publication 903 is designed to meet the needsof federal agencies and standards writers, as well asmanufacturers, engineers, purchasing agents, distribu-tors, and others concerned with product-related certifi-cation procedures.CONTACT: Maureen Breitenberg, (301) 975-4031;[email protected].

NOVEL COMBINATORIAL METHODS FORINORGANIC THIN FILMSOver the past decade, combinatorial chemistry, whichinvolves high throughput synthesis and analysis of amultivariable “library” containing a large number ofminiaturized samples, has revolutionized the drugdiscovery process in the pharmaceuticals industry.Recently, materials scientists have been applying combi-natorial principles to the discovery and optimizationof inorganic thin films for electronic, photonic, andmagnetic devices; this requires unique tools for libraryfabrication and characterization. Researchers at NISThave developed a novel dual-beam, dual-target pulsedlaser deposition process for the fabrication of composi-tionally-graded thin film libraries. The depositionsystem has high-speed, in situ diagnostics, which permitreal-time fine-tuning of the two laser plumes to opti-mize the deposition parameters. This technique is appli-cable to a wide range of complex oxides, metals, andmetal/oxide composites. To date, libraries of BaTiO3-SrTiO3, a material of interest for wireless communica-tion devices, have been deposited on silicon substrates.Film thickness has been mapped at a spatial resolutionof 0.3 mm using a spectroscopic reflectometry appara-tus designed by NIST researchers. Composition and

dielectric properties of the libraries are being character-ized by high throughput measurement techniques.CONTACT: Peter Schenck, (301) 975-5758; [email protected].

ELASTIC CHARACTERIZATION OFANISOTROPIC THIN FILMS USING SAWDISPERSIONNIST is developing theoretical and experimentaltechniques for non-destructive measurement of elasticcharacteristics of anisotropic thin films. Presently thereis a strong industrial interest in elastic characterizationof thin films because they have applications in elec-tronic, photonic, and magnetic devices and are also usedas wear and corrosion resistant coatings on ordinarymaterials. Material parameters of interest for elasticcharacterization of a film are the elastic constants of thefilm, its density, and thickness. In general, the films aswell as the substrate in modern materials are elasticallyanisotropic. Current theoretical and experimentalmethods of non-destructive characterization are notconvenient for anisotropic layered solids.

Experimentally, NIST measures the phase velocity ofa surface acoustic wave (SAW) over a broad frequencyrange. NIST created a laser-ultrasonic apparatus forbroadband SAWs. The system incorporates a 0.2 nspulsed laser for SAW generation and a Michelson inter-ferometer detector with bandwidth over 800 MHz. NISTused this apparatus to measure dispersion relations inseveral samples including titanium nitride films onsingle-crystal silicon and stainless steel samples. Thethickness of these films ranged from about 250 nm to3500 nm.

For the purpose of analysis of the dispersion data forSAWs, NIST developed a computationally efficientrepresentation of the Green’s function to model theelastodynamic characteristics of an anisotropic thin filmon an anisotropic substrate. In this model, the Green’sfunction is represented in terms of a delta function ofspace and time in slowness space. For anisotropic solids,this representation is computationally more convenientthan the convention Fourier reciprocal space andfrequency representation. Our model can account forsurface texture of the film and imperfect interfacialbonding between the film and the substrate. The elasto-dynamic model is used to calculate the dispersion ofsurface acoustic waves in the film and also provides anefficient algorithm for the inverse problem of character-izing the film from measured values of the dispersion.NIST applied this method to calculate SAW velocities invarious isotropic and anisotropic films includingtextured polycrystalline films of TiN on single-crystal

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Si and to estimate the elastic constants of the films.Excellent agreement is obtained between the theoreticaland measured values of the SAW velocities in mostcases.CONTACTS: Vinod Tewary, (303) 497-5753; [email protected] or Donna Hurley, (303) 497-3081;[email protected].

COMBINATORIAL CHARACTERIZATION OFBLOCK COPOLYMER FILM MORPHOLOGYCombinatorial methods have been successfully appliedby researchers at NIST to observe novel morphologiesand to establish fundamental kinetic relationships in theordering properties of block copolymer films. Copoly-mers are a class of polymer materials that have largepotential for commercial applications. Unique proper-ties in melts, blends and solutions lead to their use asadhesives, emulsifying agents, thermoplastic elas-tomers, compatibilizers, etc. Block copolymers are animportant sub-class of copolymers consisting of poly-mers of different chemistry that are covalently linked.

A key question in block copolymers is the nature ofinteractions between blocks, as well as block inter-actions with different materials. To address this questionNIST researchers exploited the ability of block copoly-mers to form quantized periodic structures, such aslamellae, that directly reflect molecular parameters suchas block lengths, chemical interactions between theblock constituents, and interactions with an external(substrate) material in thin films. The work of the NISTresearchers published in Physical Review Letters andJournal of Polymers Science Polymer: Part B PolymerPhysics , demonstrates that these fundamental propertiescan be very efficiently determined in a high-throughputmanner using a combinatorial approach. This wasaccomplished by flow-coating multiple films havingdifferent molecular masses and gradients in film thick-ness. Each “library,” the size of a standard microscopeslide, contains as many as 1500 differentiable experi-mental conditions, including process variables oftemperature and time. Novel morphologies observedincluding a labyrinthine (or spinodal) surface patternsas well as extended smooth regions. These morphologiesare related to an enthalpic vs entropic balance of inter-actions in block copolymers. In addition, the size of thesurface patterns unexpectedly displayed an inverserelationship with molecular mass that can be attributedto the copolymer surface elasticity.CONTACT: Alamgir Karim, (301) 975-6588; [email protected].

BIOMIMETIC MEMBRANE STUDIES USINGNEUTRON REFLECTOMETRYStructures that serve as models of cell membranes are offundamental importance in understanding such keybiological processes as phospholipid self-assembly,molecular recognition and cell-protein interactions.Recent improvements in neutron reflectometry at theNIST Center for Neutron Research (NCNR),coupled with advances in biomimetic film fabrication atNIST, afford enhanced sensitivity for the study ofmembranes and membrane-protein complexes.

New phase-sensitive measurement techniques andmodel-independent data analysis methods developed atthe NCNR have demonstrated the feasibility of obtain-ing reliable depth profiles of supported membranes incontact with biologically relevant aqueous environments,achieving subnanometer spatial resolutions.

Using these methods, the depth profile of abiomimetic membrane consisting of a self-assembledalkanethiol monolayer, anchored to a gold film, and aphospholipid layer self-assembled in situ from vesiclesin solution has been measured. The results compare wellwith molecular dynamics simulations. The interaction ofthe peptide melittin with similar biomimetic films hasalso been probed, revealing that the small proteinpenetrates into the phospholipid leaflet of the film andperturbs the underlying alkane layer. Work usingthese advanced neutron capabilities is underway tostudy biomimetic films produced on engineered andcushioned surfaces which will enable the investigationof trans-membrane proteins.CONTACTS: Norman Berk, (301) 975-6224; [email protected] or Charles Majkrzak, (301) 975-5251;[email protected] or Anne Plant, (301) 975-3124; [email protected].

A SOFTWARE TOOL FOR GENERATION OFMONSEL LIBRARIESA means of simulating electron trajectories andsecondary generation in scanning electron microscopesamples is an essential piece of the library-basedlinewidth measurement system being developed undercontract with SEMATECH. The NIST code for doingthis, called “MONSEL,” has some important advantagescompared to commercial codes. Developed at NIST,it adopts a more fundamental approach, simulating, forexample, secondary electron trajectories in detailinstead of treating them in an average way, and becauseof this a commercial code with free parameters mayadjust those parameters in order to obtain agreement

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with the MONSEL results. However, MONSEL lackssome of the convenience features present in commercialsoftware. Particularly relevant for our library-basedlinewidth measurement system is the fact thatMONSEL’s inputs are in the form of files, which mustbe painstakingly edited for each of the hundreds ofsimulations that must be performed to generate a library.Accordingly, we have developed a new software tool thatautomatically: generates the input files required foreach of the possible combinations of user-specified edgeshape parameters; generates a batch file that runsMONSEL once for each such parameter combinationand copies MONSEL’s output file to a file with a uniquename; and generates a directory of these file names andthe shape parameters that are associated with them. Thenew tool was used to begin simulations for two newmodel libraries, one for an isolated polysilicon line andone for densely packed polysilicon lines, on four ofNIST’s high performance computers. The simulationsare expected to require approximately a week on each ofthe four computers to complete.CONTACT: John Villarrubia, (301) 975-3958; [email protected].

PROCEEDINGS OF THE WORKSHOP ONMEASUREMENT TRACEABILITY FOR CLINICALLABORATORY TESTING AND IN VITRODIAGNOSTIC TEST SYSTEMSThe Proceedings of the Workshop on MeasurementTraceability for Clinical Laboratory Testing and In VitroDiagnostic Test Systems is now available on CD in PDFformat. This NIST-hosted workshop was held inNovember 2000 to address the standards needs of theclinical laboratory community in light of new inter-national requirements. The workshop was cosponsoredby several organizations having vested interest in devel-oping a globally recognized clinical traceabilityinfrastructure. This publication documents 10 talksgiven by national and international experts who pro-vided the background and current status of the trace-ability structure for clinical laboratory measurementsworldwide. It also includes the record of a candiddiscussion of issues and concerns as expressed by stake-holders and experts from around the world. There wasgeneral consensus among the 135 participants thathealthcare is now more than ever a global issue and aglobal commodity, demanding global solutions. Thesense of urgency, commitment, and dedication of thesestakeholders is uniquely captured in this workshoprecord.CONTACTS: William Koch (301) 975-8301; [email protected] or Ellyn Beary, (301) 975-8307; [email protected].

NIST CO-SPONSORS IT ACCESSIBILITY 2001CONFERENCENIST, along with with a private company and theInformation Technology Association of America,co-sponsored the IT Accessibility 2001 Conference inMay 2001, at NIST. The conference drew attendeesfrom industry, federal and state government, advocacygroups, accessibility centers, and academia.

Speakers included accessibility experts, IT develop-ers, research and standards experts, representatives fromaccessibility centers, and federal and state agencies.Presentations focused on current and future strategiesfor creating an environment with easy accessibility toinformation technology by people with disabilities.Government representatives for the U.S. Access Board,GSA, the Department of Justice, and the Department ofEducation addressed the federal Section 508 regulationsrequiring accessibility of IT by government agencies.Several web developers presented their experiences indesigning accessible websites.

Exhibits and demonstrations supplemented thespeaker program and helped provide attendees with anoverview of available IT accessibility products andservices. Exhibits covered a wide range of informationappliances and services, including an accessibleelectronic voting machine, computer screen readers(which use speech synthesizers to “read” text anddescriptions on a web page for visually impairedpersons), and the NIST rotating Braille reader. Ademonstration of near real-time closed-captioning of thewebcasting of the presentations was provided andshown via webcast on a TV monitor in the conferenceauditorium.

The webcast of the conference are available at http://www.nist.gov/ITaccess2001.CONTACT: Leslie Collica, (301) 975-8516; [email protected].

NIST HOSTS LARGE VOCABULARYCONVERSATIONAL SPEECH RECOGNITIONWORKSHOPNIST hosted the 2001 Workshop on Large VocabularyConversational Speech Recognition, in May 2001,in Linthicum, MD. Workshop participants reviewed theresults of this year’s evaluation conducted by thedivision in cooperation with DoD sponsors. Participat-ing sites developed systems to automatically generateword-level transcriptions of recorded telephone conver-sations; these were scored against official referencetranscriptions. Eight research groups from the UnitedStates and Europe participated in parts of the evaluationand discussed their work at the workshop.

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This year’s test set was the largest ever in size, involv-ing 60 5-minute telephone conversations from threedifferent corpora. One of these was the new Switch-board-Cellular Corpus, marking the first time evaluationhas been done on cellular telephone data. NISTresearchers presented an analysis of the evaluationresults and compared these results to those of previousevaluations. Overall performance results of the bestsystems, measured by word error rate, were the bestoutcome ever achieved on the Switchboard-2 Corpus.As in recent years, the system achieving the lowest worderror rates on each corpus this year was that developedby Cambridge University. As in the 2000 evaluation, aseparate non-competitive evaluation was conducted on asubset of the test data, in which sites were asked togenerate transcriptions at both the word and phoneticlevels. Researchers at the International ComputerScience Institute in Berkeley, CA analyzed the results,and the findings were presented at the workshop.The website is http://www.nist.gov/speech/tests/ctr/h5_2001/index.htm.CONTACT: Alvin Martin, (301) 975-3169; [email protected].

NIST COLLABORATES WITH NEMI ONSTANDARDS PROJECT FOR LEAD-FREESOLDERSTin-lead (Sn-Pb) solder has been used extensively as anelectrodeposited surface finish for component contacts/leads in the electronics industry because such coatingsprovide excellent solderability, ductility, electricalconductivity and corrosion resistance. The codepositionof Pb and Sn has been found to be effective in retardingSn whisker growth and hence, has been the industrystandard for over 20 years. In the absence of Pb,whiskers tend to grow spontaneously from electrode-posited Sn films, which can lead to electrical shortcircuits and device failure. Now that lead-free solderalloys have been introduced, electronic manufacturersare seeking a surface finish technology that will preventSn whisker growth without the use of Pb.

Researchers at NIST are working to identify the basicmechanisms of Sn whisker growth by systematicallystudying correlations between deposit microstructure,whisker formation and electrodeposition parameters.For example, Sn-Cu solder has been mentioned as apossible replacement for Sn-Pb; however the NIST teamhas recently found that the addition of Cu2+ to the Snplating bath actually increases the probability and thespeed at which whiskers form. Gaining a fundamentalunderstanding of the whisker growth mechanism isrequired to help eliminate the problem and to develop areliable test method for predicting whisker growth

which the microelectronics industry requires. Towardsthis end, NIST is participating in a new NationalElectronics Manufacturing Initiative standards develop-ment project to help develop a robust test method forpredicting whisker growth for industrial surface finishsystems.CONTACT: Christian Johnson, (301) 975-6409;[email protected].

Standard Reference Materials

NEW ABSOLUTE MAGNETIC MOMENTSTANDARD REFERENCE MATERIAL FORTHE RECORDING INDUSTRYA new Standard Reference Material (SRM) for use incalibrating the magnetometers used in the recordingindustry and research laboratories has been issued.Industry should find this SRM (SRM 762) more usefulthan the existing SRM (SRM 772a) because its geo-metry is similar to the sample shapes used for recordingtape or hard disk samples, and it will eliminate the needfor applying shape corrections for accurate measure-ments. Because the magnetic properties of metalsdepend on thermomechanical processing history andgeometry as well as purity, the properties of the nickeldisks used for this SRM were certified using theabsolute magnetometer developed by NIST. Thesaturation moment of the new SRM (1.75 mAm2 or1.75 emu) is about half that of the old SRM which maybe advantageous for some magnetometers. The newSRM is certified for applied fields between 280 kA/mand 4000 kA/m (3500 Oe and 50 000 Oe) and fortemperatures between 280 K and 310 K.CONTACT: Robert D. Shull, (301) 975-6035; [email protected].

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The International System of Units (SI)The Modern Metric System

Uncertain about the InternationalSystem of Units (universally abbreviatedSI), the modern metric system usedthroughout the world? Do you need toknow the proper way to express the resultsof measurements and the values of quanti-ties in units of the SI? Do you need to knowthe NIST policy on the use of the SI? Thenyou need the 1995 edition of the NationalInstitute of Standards and TechnologySpecial Publication 811, Guide for the Useof the International System of Units (SI) .

The 1995 edition of the National Institute of Standards and Technology Special Publication 811,Guide for the Use of the International System of Units (SI) , by Barry N. Taylor, is now available.

The 1995 edition of SP 811 corrects a number of misprints in the 1991 edition, incorporates asignificant amount of additional material intended to answer frequently asked questions concerningthe SI and SI usage, and updates the bibliography. The added material includes a check list forreviewing the consistency of written documents with the SI. Some changes in format have alsobeen made in an attempt to improve the ease of use of SP 811.

The topics covered by SP 811 include:• NIST policy on the use of the SI in NIST publications.• Classes of SI units, those SI derived units that have special names and symbols, and the SI

prefixes that are used to form decimal multiples and submultiples of SI units.• Those units outside the SI that may be used with the SI and those that may not.• Rules and style conventions for printing and using quantity symbols, unit symbols, and prefix

symbols, and for spelling unit names.• Rules and style conventions for expressing the results of measurements and the values of quan-

tities.• Definitions of the SI base units.• Conversion factors for converting values of quantities expressed in units that are mainly unac-

ceptable for use with the SI to values expressed mainly in units of the SI.• Rounding numbers and rounding converted numerical values of quantities.

Single copies of the 84-page SP 811 may be obtained from the NIST Calibration Program,100 Bureau Dr., Building 820, Room 236, Stop 2330, Gaithersburg, MD 20899-2330, telephone:301-975-2002, fax: 301-869-3548.

Special Publication 811

1995 Edition

Guide for the Use of the International

System of Units (SI)

Barry N. Taylor

United States Department of Commerce

Technology Administration

National Institute of Standards and Technology

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