Journal of Research of the National Institute of Standards and Technology … · 1997-06-02 ·...

Volume 102, Number 2, March–April 1997Journal 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 820, Room 126, Gaithersburg,MD 20899-0001; telephone: 301/975-3572.

NORTH AMERICAN METROLOGY ANDCALIBRATION MEETINGSTwo NIST representatives attended the North Americanregional meetings on collaboration in metrology,NORAMET, and the Calibration Cooperation, NACC,at the National Research Council in Ottawa, Ontario,Nov. 13, 1996.

NORAMET ensures cooperation among the nationalmeasurement institutes in Canada, the United States,and Mexico. Ongoing work of technical groups in allmeasurement disciplines was reviewed, and plans wereestablished to conduct experiments to assess measure-ment equivalency among the three national institutes.This work is vital for securing the measurement founda-tion for international trade and laboratory accreditationbased on national systems of measurement services.

NACC works toward mutual recognition of the equiv-alency of the national calibration laboratory accredita-tion programs in the three countries. This also willstrengthen the foundation for international trade basedon the recognition and acceptance of calibration dataproduced in accredited calibration laboratories. Thenecessary documents concerning rules of operation andthe ground rules upon which assessments of the calibra-tion laboratory accreditation programs in the threecountries will be conducted were discussed. The impactof mutual recognition agreements on current and futuretrade negotiations occurring under free trade agree-ments, such as NAFTA (North American Free TradeAgreement), was discussed at length.

News Briefs

ENERGY-RELATED INVENTIONS PROGRAMMAKES RECOMMENDATIONSDuring the month of November, NIST recommended aninnovative method for producing glass fiber for com-mercialization to its Department of Energy partnerunder the Energy-Related Inventions Program.

The new method is a unique hardware design andprocess for producing glass fiber. The technology willbe used in both the fiber glass insulation industry andthe composite materials industry where glass fiberis used as a reinforcing member of the compositestructures.

NEW NIST REFERENCE ANTENNA REDUCESCALIBRATION ERRORS RESULTING FROMAMBIENT ELECTROMAGNETIC FIELDSThe increasing use of wireless communication productsdemands ever higher levels of calibration accuracy tosupport them. For example, manufacturers must be ableto delineate precisely the performance characteristics ofantennas they employ in-house and those they designinto their products. Outdoor calibration test ranges areused frequently, but it has been very difficult to obtain apure signal from traditional broadband referenceantennas used at these ranges, because the signal outputcontains contributions from the ambient electro-magnetic fields of all frequencies present at the calibra-tion site.

Researchers at NIST have developed an improvedradiofrequency standard antenna for the calibrationsystem used with the open-area test site by devising ameans to discriminate against the out-of-band interfer-ence while maintaining the integrity of the signal. Thekey element of the system is a new radiofrequency elec-tro-optic modulator that converts the radiofrequencysignal from the antenna to a lightwave signal that can bepiped to the measuring instrumentation via a noncon-ducting optical fiber. Using the nonconducting fiber

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provides a twofold advantage: it preserves the integrityof the signal, and it does not interfere with the electro-magnetic field the antenna is measuring. The newmodulator is expected to be applicable to calibrationsystems at other sites than NIST’s.

NIST IMPROVES ACCURACY OFNONDESTRUCTIVE METHODS FORMEASURING DIELECTRIC AND MAGNETICPROPERTIES OF MATERIALS ATRF/MICROWAVE FREQUENCIESApplications of newly emerging microwave technol-ogies require that the microwave energy be very accu-rately focused, directed, and processed using special-ized circuitry and phased-array antennas that aregenerally mounted on a thin layer of polymer or ceramicdielectric, termed a substrate. Usually, efficient andcost-effective design of such high-performance systemsrequires that the dielectric properties of the substratematerials be known with a relative uncertainty of lessthan 63 %. However, most of the characterizationtechniques involve preparing a machined sample of thematerial under test; i.e., they are destructive and unsuit-able for use in production-line settings. A very widelyused commercially available nondestructive and broad-band measurement method involves placing an open-ended coaxial probe in contact with the material undertest and deriving its dielectric parameters by measuringthe probe admittance by means of an automatic networkanalyzer. However, measurements performed by NISTresearchers and by others on thin substrates have shownconsistently that such measurements have a relativeuncertainty no less than610 % and generally degradefurther with increasing relative permittivity of thematerial under test. This limit primarily relates toinadequacies in the electromagnetic model used todescribe the measurement and solutions to this modelbased on oversimplified assumptions. The most signifi-cant of these is disregard of the “lift-off” factor, definedas the unavoidable presence of an air gap between probeface and material surface. Even where the probe appearsto be in good contact with a polished material surface,NIST has shown that an unavoidable air gap of 50mm to100mm has a very significant influence on probeadmittance. For some specialized applications, such asthe use of a probe for process control in moving assem-bly lines, lift-off must be included for the measurementto be useful at all.

In efforts to improve significantly the measurementaccuracy of the open-ended coaxial probe, NISTresearchers have developed full-field solutions (the mostaccurate) for a much improved model that includes theair gap lift-off; finite layer thickness, with provision for

both dielectric and magnetic properties; and the pres-ence of an optional conductive layer (for measuringcopper-clad substrates). By deliberately including asmall and known probe lift-off in the measurementprocess through the use of micrometer-equipped probes,measurement uncertainties as small as63 % or lesshave been demonstrated routinely. The new NISTcoaxial probe software also now supports additionalmeasurement options and is compatible with operationon a personal computer.

NIST PROVIDES IMPROVED TECHNIQUE TOCHARACTERIZE LOW-FREQUENCYANECHOIC CHAMBERS USED TODEMONSTRATE COMPLIANCE WITHINTERNATIONAL EMI/EMC STANDARDSBy late 1995, rapid mobilization on the part of countriesin the European Union with respect to standards forelectromagnetic interference and electromagneticcompatibility (EMI/EMC) had created a “preparedness”gap for American manufacturers. NIST has beenworking actively with industry to diminish this gap inseveral ways.

As a first step, NIST staff joined with industry leadersto organize and host NIST’s 1996 EMI/EMC workshop,which was designed to identify and set priorities fordealing with the gap. Feedback from the workshop hashad a major influence on the direction of NIST’s EMI/EMC program and has identified specific issues to beaddressed. An issue assigned high priority at the work-shop was the need to demonstrate that electronic prod-ucts developed by U.S. firms are in compliance withboth domestic and international regulations and require-ments for interference and susceptibility. Semi-anechoicand fully anechoic chambers are important and cost-effective tools for demonstrating compliance, butcharacterization and performance verification of thesechambers has been difficult and time consuming. Evenso, the number of domestically designed and manufac-tured low-frequency (20 MHz to 1 GHz) anechoic andsemi-anechoic electromagnetic test chambers in use hasbeen increasing steadily.

To meet industry’s needs, NIST researchers havedeveloped procedures centering on a new chamberfigure of merit based on the decay time of the chamber.This decay time is in turn based on the average reflectioncoefficient of the energy incident on the chamber walls.Implementation of the new technique avoids labor-intensive measurements and eliminates complex, inten-sive, time consuming and, therefore, costly numericalanalysis by making use of simplifying approximationsthat can be shown not to affect the utility of the result.It also enables assessment of chamber performance by

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means of a single parameter, a significant improvementover existing methods, which have a strong dependenceon setup and instrumentation. Details of the work havebeen published in the IEEE Transactions on Electro-magnetic Compatibility, Vol. 38, No. 4, 1996. Stillunder development is a procedure for relating chamberfigure of merit to chamber capability for supportingspecific tests.

FINISH MACHINING OF HARDENED STEELSVS GRINDINGFinish machining of hardened steels has been receivingincreased attention as an alternative to grinding. Poten-tially, single-point cutting offers benefits over grindingsuch as lower equipment costs, shorter setup time,reduced process steps, better surface integrity, andelimination of metal-working fluid. However, tool wearremains a major cost-related barrier. Two NISTresearchers have performed studies of finishing perfor-mance in turning of hardened powder metallurgy (PM)AISI M50 steel using cubic boron nitride tools. Theirdata indicate that tool wear and flank wear rate areunusually small and relatively insensitive to cuttingconditions. They attribute these findings to the refinedtransition metal carbides in workpieces which tend toreduce chemical reactivity during cutting and minimizeabrasive wear of cutting tools. Surface finish obtained ata fine feed and small depth of cut is in the range of60 nm to 120 nm Ra. These results suggest that PMsteels might be used for machinability enhancement inhigh-speed finishing hardened die and mold processes.

MEASUREMENTS AND STANDARDSACTIVITIES IN SUPPORT OF NEW NITRICOXIDE INHALATION THERAPY FORNEWBORNSPediatric researchers are working under NationalInstitute of Child Health and Development (NICHD)and Food and Drug Administration (FDA) guidelines toevaluate the therapeutic value of inhaled nitric oxide(NO) in newborn patients. When inhaled with oxygenvia a ventilator, dilute concentrations (<100mmol/mol)of NO have shown dramatic results as a pulmonaryvasodilator in some newborn patients. However, onceNO is mixed with oxygen, spontaneous formation ofNitrogen dioxide (NO2) occurs. This can cause pul-monary edema and other problems in the respiratorysystem, especially at NO2 concentrations above 5mmol/mol.

For the past 2 years, researchers at NIST have beenworking with the NICHD to assist pediatric researcherswho are evaluating inhaled NO therapy to understand

the kinetics of NO2 formation under conditions expectedto be used. The rate of NO2 formation under theseconditions was determined to be 0.137mmol/mol foreach second of dwell time. It was concluded that atanticipated dwell times of < 0.5 s, no significant levelsof NO2 should reach the patient during treatment. There-fore, clinical trials on inhaled nitric oxide (INO) therapyfor treatment of persistent pulmonary hypertension innewborn children were initiated and have been com-pleted recently. Based on preliminary results from thesetrials, it is expected that the FDA will soon approve theuse of nitric oxide in inhalation therapy. Because of thepotential for adverse effects, levels of NO and NO2 mustbe monitored continuously in a typical matrix of> 0.8 mole fraction of oxygen during the therapy.Measurements made with electrochemical sensors andchemiluminescence detectors commonly used for moni-toring NO2 were compared with measurements madeusing NIST tunable diode laser absorption spectrometry,which can accurately measure NO2 levelsindependent ofoxygen content at concentrations well below those thattrigger adverse effects in newborns. NO2 electrochemi-cal sensors did not work well in the oxygen-rich matrix,indicating NO2 concentrations orders of magnitudehigher than actually present. Chemiluminescent-basedinstruments performed better but in some cases regis-tered negative values for NO2 causing user lack ofconfidence.

A prototype facility has been established at NIST toallow INO sensor and instrument manufacturers toevaluate the performance of their devices for measuringNO and NO2 under simulated therapeutic conditions.During a recent workshop held at NIST for pediatricresearchers, in the presence of a senior scientist fromFDA’s Anesthesiology and Respiratory Devices TherapyPanel, technical experts used this facility to test newchemiluminescence monitors and solid-state sensordevices designed to perform in high oxygen environ-ments. The performance of these devices was farsuperior to those evaluated at NIST a year ago, andNIST is planning additional workshops of this nature toassist the FDA in tackling the tough job of evaluatingNO and NO2 monitoring instrumentation for use in thistherapy.

NONCONTACT ANALYSIS OF OXYGENATESIN GASOLINE USING FT-NEAR INFRAREDAND FT-RAMAN SPECTROSCOPIESOxygenated fuels, blends of gasolines with alcohol orother oxygen-containing materials, are designed toreduce carbon monoxide emissions. To support theenforcement of environmental air regulations, NISTprovides eight oxygenated gasoline Standard Reference

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Materials (SRMs). These SRMs, provided in 20 mLsealed glass ampoules, contain gasoline and one of fouroxygenates [ethanol (ETOH), methyl tert-butyl ether(MTBE), tert-amyl methyl ether (TAME), or ethyltert-butyl ether (ETBE)] at either the 2.0 % or 2.7 %oxygen mass fraction levels.

The current method used to certify these materials iscapillary gas chromatography (GC) with flame ioniza-tion detection. Although this separation-based techniqueprovides excellent precision and accuracy, it requiresopening the ampoules. As a result, these SRMs must bebatch-certified with the expanded uncertainty in theirassigned values incorporating an estimate of batchheterogeneity. While the current expanded uncertaintyfor all these SRMs is an acceptable 0.04 % to 0.06 %mass fraction of oxygen, most of the batch heterogene-ity component is attributable to a few “outlier”ampoules. These statistical outliers are thought to resultfrom errors in the flame-sealing procedure and/orsample handling. The expanded uncertainties for allsuch SRMs could be lowered if each individual SRMampoule could be characterized and obvious “outliers”discarded from the batch. This requires a nondestructive,rapid, and precise analytical method.

NIST researchers have found that sealed SRMampoules can be analyzed directly for oxygenate contentusing Fourier transform-near infrared (FT-NIR) andFourier transform-Raman spectroscopic methods. Boththe Raman and FT-NIR methods are capable ofquantifying the oxygenate concentration to within theexpanded 95 % confidence interval levels afforded bythe GC measurements. Furthermore, such spectro-scopic determinations of the oxygenate concentrationin individual ampoules can be accomplished in lessthan 1 min. Of the two spectroscopic methods, NIRgives better estimates (lower standard deviations)of oxygenate concentration and the Raman method isbetter at identifying the specific oxygenate in unknowndata sets.

NIST researchers have constructed and evaluated aprototype instrument that combines the two techniquesto maximize their utility for the analysis of suchcomplex mixtures. To do this, they added a fiber-coupled tungsten source to their commercial FT-Ramaninstrument. Because the FT-Raman instrument uses a1.06mm source, the Raman-scattered light is emitted inthe 10 000 cm21 to 5000 cm21 (absolute) region. Thiscorresponds to the second overtone and first combina-tion band region used for the analysis in the FT-NIRspectrometer. Thus, the same germanium detector maybe used to measure both the Raman and NIR absorbance

spectra of a sample. The mass fraction errors of MTBE-in-gasoline samples obtained from the initial combina-tion spectra acquired on the hybrid instrument wereabout 0.5 %. Work is in progress to extend this techniqueto the determination of water content in a gasohol SRM,to assist in the certification of a new synthetic fuel SRM,and to determine other functional moieties, such asolefins.

CONTROVERSIES SETTLED OVERFUNDAMENTAL PROPERTIES OF THEHYDROXYMETHYL RA DICALThe highly reactive hydroxymethyl radical (CH2OH)and cation (CH2OH+) play important roles in combus-tion, atmospheric pollution chemistry, catalysis, and ionprocesses. Because of their importance, they are alsoamong the most studied unstable species. Despite thisintensive study, the thermochemical properties of thesespecies have remained uncertain and controversial. Forexample, thermochemical functions of CH2OH calcu-lated from ion data and from kinetic data divergeirreconcilably. Accurate thermochemical functions arerequired for models of many chemical processes.

By using state-of-the-art spectroscopic measure-ments and ab initio calculations, NIST chemists haveresolved these controversies and reported accuratethermochemical values. This work is reported in theDecember 18, 1996 issue of the Journal of PhysicalChemistry. The key discovery during this research wasthat hydroxymethyl radicals contain higher molecularsymmetry than previously was believed or is deducedintuitively. Such higher symmetry completely changesthe rules by which spectroscopic and kinetic data areused during thermochemical calculations.

The higher molecular symmetry of the CH2OHradical was discovered during experiments conducted atNIST. These experiments used resonance-enhancedmultiphoton ionization (REMPI) spectroscopy toobserve extremely weak, very low energy vibrationallevels of CH2OH—such levels could exist only ifCH2OH contained higher symmetry. Extensive ab initiocalculations were performed on the NIST super-computer to duplicate these data and confirm the highermolecular symmetry. Using rules dictated by the highermolecular symmetry and the new spectroscopic data,previously reported ion and kinetic data were re-evalu-ated to obtain thermochemical functions for CH2OH andCH2OH+. Not only are these new functions accurate,but they reconcile the controversies existent betweenprevious evaluations based on ion and kinetic data.

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RESEARCH OF NIST SCIENTISTSHIGHLIGHTED ON SEPTEMBER ANDOCTOBER COVERS OF SCANNINGThe research of NIST scientists were featured onthe covers of the September and October issues ofSCANNING. On the September cover (with accompany-ing article) is a digital x-ray phase map derived from aprocedure developed at NIST by a guest worker fromthe Jozef Stefan Institute, Department of Ceramics,Ljubljana, Slovenia. Phase mapping is used for theidentification and interrogation of the chemical rela-tionships of phases in complex high-technologymaterials. The method was first applied to BiSrCaCuO(BSCCO) highTc superconductor specimens, which arechemically complex and can have eight or nine phasespresent. Determining the phase relationships and relatedphase diagram of this material is difficult but critical tounderstanding the chemical phase-property relation-ships. X-ray mapping of the phases in specimensproduced under different conditions provides a betterunderstanding of the phase diagram, leading to bettermethods for producing practical superconductingmaterials. The procedure digitally maps the fivecations—Bi, Pb, Sr, Ca, and Cu—with wavelengthspectrometers on an electron microprobe, calculates theconcentration of each cation from standards data, andcompares the concentration of each element or combi-nation of elements at each pixel with a set of phaserules. The pixels that satisfy a unique phase rule aregiven a color to label the phase. A graphics interfacewas developed for adjusting the phase rules to accom-modate various uncertainties in the data and observe thechanges of the phase labels of the compositional maps.Previous to this development, only multiphase systemsof three phases or less could be readily identified withcompositional mapping.

The October cover (with accompanying article)depicts an image of machining debris remaining at thebottom of a blind hole after twist drilling in brass usingthe environmental scanning electron microscope(ESEM). The ESEM is a remarkable variation of aconventional SEM that permits the specimen to resideat pressures six to eight orders of magnitude higher thanthe conventional SEM, while retaining much of theresolution and analytical functionality. In the conven-tional SEM, the specimen must be kept under highvacuum, typically 100m-Pa. Whereas in the ESEM, thespecimen chamber pressure can be in the range 100 Pato 2500 Pa, which permits examination of high vaporpressure samples as well as in situ experiments involv-ing chemical reactions. The high gas pressure of theESEM prohibits the use of conventional electrondetectors that involve high potentials (e.g., 10 kV) butdoes enable a new type of ESEM electron detector, the

gaseous secondary electron detector (GSED), which isbased on modest secondary electron acceleration andcollision-ionization cascade amplification. Because thedepth of a hole would preclude signal collection, animage such as that shown on theSCANNINGcoverwould not be possible with a conventional high vacuumSEM/ detector system while with the ESEM GSED thegas ionization-amplification readily extracted a strongsignal. In a series of tests described in the paper, holesas deep as 8 mm with aspect ratios (depth/diameter) of5:1 were successfully imaged with the ESEM/GSED,including insulating as well as conducting materials. Inaddition to high-resolution imaging under extremeconditions, the ESEM provides new analytical capabili-ties to NIST scientists.

SALT DEPOSITION INVESTIGATED INSUPERCRITICAL WATER OXIDATIONREACTORSIn a collaborative effort with the Massachusetts Instituteof Technology, NIST personnel are investigating thedeposition of sodium sulfate (Na2SO4) on the walls ofsupercritical water oxidation (SCWO) reactors. Theresults of this work have given new insights to themechanisms of the salt deposition process in an aqueoussupercritical fluid.

SCWO technology shows promise for effectiveremediation of many toxic wastes. SCWO takes place inwater at temperatures and pressures above the criticalpoint of pure water (647 K and 22 MPa). The processbrings together water, organic waste and oxidant at highpressures (25 MPa or more) and moderate temperatures(650 K and above) where the organics are completelyoxidized to water, carbon dioxide, and molecular nitro-gen. However, before the technology can bedeployedwidely, fouling of reactor surfaces due to scale buildupby salts, which have low solubility in supercriticalwater, must be understood and controlled. These saltsare formed when neutralizing bases are injected intoreactors to minimize corrosion of reactor materials.There is scant knowledge of the deposition process aswell as the thermophysical properties of aqueous salts atthese elevated conditions. However, for limiting cases,the scale buildup in these reactors can be modeled andexperiments designed to evaluate the model.

The experiments, conducted at NIST, use a 4 mm ODheated cylinder inserted into the cross flow of a super-critical Na2SO4 solution of mass fraction 4 %flowing at about 0.16 g/s for varying amounts of time.The solution impinging on the heated cylinder ispreheated to a temperature close to that at which precip-itation begins, while the heated cylinder is maintainedslightly above this precipitation temperature, thus limit-ing deposition almost exclusively to the surface of the

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cylinder. For exposure times of 600 s or less, the scalebuildup is on the order of the diameter of the cylinder.The experimental deposition rate, when interpreted withthe model, indicates that the salt is transported to thecylinder in molecular form and nucleates there withlittle, if any, salt nucleating homogeneously in the bulkflow. Thus, molecular diffusion, not Brownian motion,is the primary transport mechanism. The model furtherreveals that the thermal diffusivity is comparable orslightly greater than the mass diffusivity of the Na2SO4

solution, which suggests gas-like behavior, despite theliquid-like (ø0.6 g/ml) densities at these near-criticalconditions. This contrasts sharply with ambient liquidswhere the relative mass diffusion rates are nearly 2000times slower. Thus, the experiments and model identifythe mechanism of salt deposition, reveal informationhitherto lacking on the transport properties of saltsolutions, and offer an opportunity to predict andcontrol salt deposition.

SURF II USED FOR PROTEIN ANALYSISA NIST scientist has used SURF II (the SynchrotronUltraviolet Radiation Facility) for the measurement ofelectroreflectance from metal surfaces with adsorbedproteins. This technique requires the measurement ofthe change in reflectance induced by a sinusoidallyvarying applied potential. The bare metal surface has acharacteristic reflectance signature in the 250 nm to400 nm spectral region due to electron plasma oscilla-tions. However, adsorbed species can alter the signaldramatically. This is especially true if the adsorbedmolecule is a protein with a metal site that can bereduced and oxidized by electrons from the electrode.The photon absorption tends to be very different in thetwo redox states, leading to a large reflection modula-tion amplitude, which can be used to determine electrontransfer rates between certain metaloproteins andelectrodes.

The NIST Scientist found that synchrotron radiationfrom SURF II is highly stable, continuously tunable, andresults in a greatly improved signal-to-noise ratio overother available UV sources. He observed intrinsicintensity noise at a level of 10–5 in the 10 Hz to 100 Hzregion, of paramount importance for observingelectroreflectance modulations of typical magnitude1 part in 104. These are results obtained in the firstexperiment on cytochrome-c immobilized on anevaporated gold electrode.

DEVELOPMENT OF NEW INFRARED SOURCENIST scientists have collaborated on a project resultingin the development of a new, brighter, infrared (IR)source. The new source yields better signal-to-noiseratios, and therefore higher accuracy, in IR measure-ments. The source is a stabilized argon arc, which hasbeen characterized in the spectral range of 1mm to20 mm. Its radiance was calibrated and found to beapproximately equal over much of this range to that ofa 10 000 K blackbody. A high-resolution spectrumtaken with a Fourier transform IR instrument showsmostly line emission below 5mm and pure continuumbetween 5mm and 20mm. The stability and geometri-cal properties of the radiance were determined as wellas itsdependence on pressure and current. As a result of thisproject, this source is being used in calibrating IR detec-tors as well as in projects aimed at advancing IRmeasurements and technology.

DEEP-UV INDEX-OF-REFRACTIONMEASUREMENTS FOR PHOTOLITHOGRAPHYNIST researchers have completed initial measurementsof the index of refraction of fused silica near 193 nm.These measurements are critical in the race to developphotolithographic wafer steppers for future-generationintegrated circuit manufacturing. This collabora-tive project, with MIT Lincoln Laboratory andSEMATECH, seeks to develop the infrastructurerequired to utilize 193 nm, deep-UV excimer laser emis-sion to form 0.18mm feature sizes for such products asgigabit memory chips. These results keep industry ontrack to meet the Semiconductor Industry Associationroadmap target date of 2001 for commercial productionof these chips.

The NIST researchers have made high accuracy,temperature- and wavelength-dependent index-of-refraction measurements on optical materials that arerequired for such photolithography. Design engineersrequire this precision data to achieve the exacting perfor-mance requirements of the photolithography tools. Tomeet the immediate need, the researchers upgraded aprecision refractometer, including precisely character-ized UV line sources, to enable minimum deviationangle, refractive index measurements that have a relativeuncertainty of 1 part in 105 with a temperature controlof 0.1 8C. For the longer term and for shorter wave-lengths, they are developing interferometric methodscapable of even higher accuracy.

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RAMAN SPECTROSCOPY WORKSHOPADDRESSES NEEDS IN ADVANCEDTECHNOLOGYA workshop on Raman Spectroscopy in Optical andMaterial Sciences was held Dec. 10, 1996, as part of theRaman spectroscopy program at NIST. The workshopwas devoted to the use of Raman spectroscopy for theunderstanding and characterization of condensed-phasematerials of contemporary importance in technologyand industry. Invited speakers from NIST, industry, andgovernment laboratories described research areas inwhich Raman spectroscopy plays an important role.Present were representatives from the Army ResearchLaboratory at Ft. Belvoir, the University of Maryland,Howard University, private industry, and NIST.

The eight invited talks were followed by a talkdescribing the NIST Magneto-Raman SpectroscopyLaboratory including the presentation of the results ofcurrent research, and an announcement of the facility’savailability as a user laboratory for the NIST staff andother interested parties.

The workshop concluded with a discussion of thecurrent state of Raman spectroscopic research in opticaland material sciences, its outlook for the future, and theneeds to be met by the user laboratory. The participantsstressed the needs for a computer searchable, criticallyevaluated database of Raman spectral data of organicmaterials and polymers, and the development of new andimproved measurement probes based on fiber opticsas well as further developments in Raman imagingtechniques.

RADIONUCLIDE SPECIATION STANDARDEXTRACTION METHODThe remediation of land contaminated with radio-nuclides from the nuclear power and defense industriesis a national concern. However, the behavior of radio-active elements in the environment is fundamentallydependent upon their physico-chemical form, or specia-tion (e.g., hosted in organic complexes, adsorbed toexchangeable positions, occluded within clay-minerallattice sites, etc.). No technique currently exists thatallows for direct measurement of environmental-levelradionuclide speciation in soil or sediment. The mostwidely applied indirect technique has been sequentialchemical extraction techniques designed to chemicallyfractionate soil and sediment matrices into specificallydefined fractions. Although such methods are usedwidely, no standard method currently exists.

NIST is collaborating with the Florida State Univer-sity to establish a standard sequential chemical leachingmethod to characterize environmental soils and sedi-ments. The method will provide selective dissolution of

discrete geochemical phases of soil and sedimentsamples. Results from the application of the method willbe used for identifying the primary radionuclide hostphases of radiological contaminants and thus can beapplied to risk assessments and the development ofsound remediation strategies.

Exploratory experiments conducted on a marinesediment indicate that stable element analyses conductedin tandem with radiometric measurements are requiredto assess phase specificity of selective leaches. Certainchemical reactants and solvents improve the selectivityof the analyses, and certain radioactive elements tend tobe associated with particular matrices. The next phaseof the collaboration will focus on the optimization of theextraction protocol for extraction efficiency and selec-tivity. The data from this experimental work will bevaluable to interpret the behavior of uranium, pluto-nium, and other high-priority radionuclides from thegeologic components in the NIST natural-matrix SRMs.

FREQUENCY SYNTHESIZERS FOR PRIMARYFREQUENCY STANDARDSOver the last several years a NIST scientist has devel-oped a state-of-the-art synthesizer design that shouldprove useful for the next several generations of primaryatomic frequency standards. These new generations ofstandards demand exceptionally low-phase-noisesources for interrogation of the clock transition. Thissynthesizer exhibits a fractional frequency stability of10–16 at 20 min and 10–17 at 1 day. The synthesizeris being used on NIST-7, NIST’s primary cesiumfrequency standard, and the linear ion standard, and itshould be more than adequate for the cesium-fountainfrequency standards now under development. Copies ofthe synthesizer have been delivered to other Federallaboratories and to other standards laboratories aroundthe world.

DEMONSTRATION OF A CRYOGENICLINEAR-ION-TRAP FREQUENCY STANDARDNIST scientists have developed a cryogenic linear-ion-trap system that can be used to investigate bothmicrowave and optical frequency standards. Presently,the ion used for both standards is199Hg+. Trapping ofions eliminates the first-order Doppler shift, and lasercooling reduces the second-order Doppler shift to a verylow value. Since observation times can be extremelylong, linewidths can be very narrow, leading to highstability even for a small number of ions. For thissystem, fundamental systematic uncertainties are knownto nearly one part in 1018 on the optical clock transition.(Of course, other technical problems might limit theperformance short of this goal.)

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In a preliminary test of the microwave standard, thescientists have demonstrated a frequency stability of3310–15 1000 s, but further work should improve thisresult. The dominant systematic effect appears to becaused by a second-order magnetic field shift due to thepresence of currents flowing in the trap electrodes at thetrap drive frequency. Efforts are currently under way toreduce this shift and establish a calibration procedure toremove its effects.

QUANTUM STATES OF MOTION OF ATRAPPED ATOMIn a generalization of their earlier “Schro¨dinger cat”work researchers at NIST have recently reported thecreation and full determination of several quantum statesof motion of a9Be+ ion bound in an rf (Paul) trap. Thestates were coherently prepared from an ion that wasinitially laser cooled to the zero-point of motion. Theythen created states having both classical and nonclassi-cal character, including thermal, number, coherent,squeezed, and “Schro¨dinger cat” states. Finally, theyfully reconstructed the motional state using two novelschemes. One determines the density matrix in thenumber state basis, and the other determines the Wignerfunction. These techniques, which are scaleable toseveral simultaneously trapped ions and to otherquantum systems, should allow for well-controlledexperiments on decoherence and related phenomena onthe quantum-classical borderline.

TELECOMMUNICATIONS SYNCHRONIZATIONNIST is leading efforts to integrate synchronizationtechniques developed by the telecommunications indus-try with those developed by the metrology community.As part of this effort, NIST has now sponsored fiveannual workshops on synchronization, with attendancegrowing to more than 60 participants per year, mostlyfrom U.S. industry. These workshops grew out of earlierNIST work on synchronization interface standards;industry then asked for assistance in developing moreuseful timing measures. The rapid success of thisventure, along with the rapid acceptance of the results asnational and international standards, cemented a work-ing relationship that has stimulated the continuation ofthe workshop into something that more nearly repre-sents an annual conference on telecommunicationssynchronization.

In a related project, NIST scientists are developing asystem for two-way time transfer in optical-fiber

(SONET) links for application to synchronization ofnetwork nodes. The system stability has been shown tobe better than 100 ps over a period of 4 hours. Thiswork responds to growing international interest in trans-mitting timing signals for use within the network.

MOLECULAR BEAM EPITAXY CHAMBERCOMMISSIONED AT THE COLD NEUTRONRESEARCH FACILITYA molecular beam epitaxy (MBE) facility customdesigned for the specific requirements of neutronscattering recently was commissioned at the NIST ColdNeutron Research Facility (CNRE). It can be used toepitaxially grow single crystal thin films, hetero-structures, and superlattices. It also can be used as aprotective ultrahigh vacuum environment for both bulkand thin film surface investigations, and as an ultracleanenvironment for loading interstitials—all whileperforming in-situ neutron scattering investigations.This chamber will have a wide variety of applications,including studies of surface magnetism and artificialmagnetic structures, Si/SiO2 interface structure, criticalphenomena, and hydrogen in materials. It already hasbeen used to study the effects of hydrogen on themagnetic ordering of Fe layers in Fe/V superlattices.While several such chambers are used at synchrotronfacilities around the world, this is the only MBEchamber in place at a neutron scattering facility.

To accommodate the many requirements of neutronreflectivity as well as the demands of the experiments tobe investigated, the MBE chamber was designed withmany unique features. These include large diametersamples (ø75 mm) with temperature control fromø15 K to ø1300 K, a 30 mm flood ion gun for surfacecleaning of substrates and samples grown elsewhere, alarge cylindrical neutron window that allows both re-flectivity measurements and grazing angle neutron dif-fraction measurements, a unique feedthrough to applymagnetic fields to the sample, and a gas loading system.

Although this chamber was designed to be flexibleenough to operate on a wide variety of neutron spec-trometers, its primary location will be the NIST polar-ized neutron reflectometer. This reflectometer, after itsrecent move to a cold neutron position in the CNRF, hasachieved a factor of five increase in intensity over that inthe reactor hall—with lower background. Now, reflec-tivities down to 1310–8, the best achieved worldwide todate, have been measured. The combination of highreflectivity sensitivity and MBE chamber versatilitywill allow measurements of totally new phenomena inphysics, chemistry, and materials science.

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NIST RESEARCH CITED AS SIGNIFICANTCONTRIBUTION TO POLYMER PHYSICSNIST research on phase separation in ultrathin filmsmade from polymer blends was selected by the Ameri-can Physical Society (APS) as one of the significantaccomplishments in physics for 1996. The NISTresearch addressed how the miscibility and mobility ofpolymer blend components and the morphology of theblend films are modified when these films are madevery thin. The observations help explain why the proper-ties of thin polymer blend films are often different frombulk polymer materials and may lead to better waysof controlling properties during the manufacturingprocess. Ultrathin polymer films are importantcomponents of advanced technologies such as micro-electronics.

The NIST studies on films of polystyrene and poly-butadiene on silicon substrates revealed a wide range ofnew phenomena in phase separation when films werethin enough (< 200 nm) to suppress the normal tendencyof the dissimilar polymer components to phase separateinto layers transverse to the film surface, as commonlyseen in thicker blend films. Optical photographs of thephase separation in these “ultrathin” films had theappearance of the bicontinuous fluid pattern character-istic of phase separation (“spinodal pattern”) in the casewhere the polymers have nearly equal compositions.Atomic force microscopy revealed that the opticalpatterns arose from undulations of the polymer-airboundary associated with variations of the surfacetension within the film. The thicker “ultrathin” films(100 nm) showed a coarsening of the pattern sizesimilar to bulk blends, apart from a change in thecoarsen ing rate arising from the thin film geometry.The thinner (20 nm) films, however, exhibited a qualita-tively different coarsening kinetics consistent withrecent computer simulations of phase separation inideally two-dimensional fluids. Finally, a 200 nm filmwas examined and found to give no surface patternformation over an extended period of time (days), asexpected for a film phase separating transverse to thesolid substrate.

These NIST experiments revealed novel phase separa-tion processes in ultrathin polymer films that aresensitive to film thickness and the chemical nature ofthe solid substrate. Many further fundamental questionsarise from this research. How is the critical temperaturefor phase separation altered in ultrathin films? Whatcontrols the characteristic length below which the novelsurface pattern formation occurs? Can the surfacemorphology be controlled? An understanding of thesequestions will advance rational design of ultrathin films.

MONITORING TEXTURE DEVELOPMENTDURING THE ROLLING OF COPPERAND BRASSA private company has a long tradition of preciselytailoring its sheet metal products to meet user’s needs.This involves maintaining careful control over thetextures and grain sizes developed during each rollingand annealing step in the production process. Sincemetallographic examination and x-ray diffraction deter-mination of these microstructural features are timeconsuming, off-line processes, the company signed aCooperative Research and Development Agreementwith NIST to apply its experience with on-line monitor-ing of texture and formability in steel to this problem.

NIST scientists combined recent theoretical develop-ments in ultrasonic wave propagation in anisotropicplates with new measurement techniques to develop arapid method for converting accurate measurements ofthe velocity of ultrasonic Lamb waves into a mathemat-ical description of the preferred orientations of the grainstructure of the sheet (i.e., its texture). By combiningcommercial instrumentation with carefully designedelectromagnetic transducers, a system for monitoringthe development of texture as the cast alloys are rolledinto tin sheet was designed and made available to thecompany.

The system also is capable of following the changes intexture as the sheet is annealed to produce the finalproperties that meet the needs of the ultimate customer.Because the mathematical description of the texturemeasured by the ultrasonic waves reduces to numericalvalues for three coefficients, the development of thetexture from casting through rolling and annealing to thefinal product may be traced easily by a curve in thethree-dimensional space defined by the three numericalcoefficients. Thus, an optimum path for producing aparticular product may be developed and monitoredduring production.

SCANNING ACOUSTIC IMAGING OF STRESSIN MATERIALSAcoustic microscopy relies on computer analysis ofacoustic waves that are radiated into a material anddetected using acoustic microscope lenses. Acoustictechniques long have been used to detect cracks andpatterns of mechanical stress in materials by measuringthe speed of ultrasound waves following different paths.A further development by NIST of this technique,described in a recent issue of Nature (Vol. 384,No. 6604, pp. 52-55), achieves high spatial resolution byexploiting interference between polarized acoustic

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waves. The ability to map internal stresses nondestruc-tively will be particularly useful for examining compo-nents such as microelectronic devices, engine parts,layered composites that may delaminate under stress,and welds in pressure vessels. Detailed theoreticalanalysis for many practical deployments is in progress.Further information is available on the World WideWeb (http://www.ctcms.nist.gov/kfrankli/stresses.html).NIST recently was issued two U.S. patents on thistechnique.

NIST DEVELOPS MEASUREMENT METHODFOR LEAN FLAMMABILITY LIMITS OFREFRIGERANTSThe refrigeration industry is examining new refrigerantsas chlorofluorocarbons are being phased out due to theirharmful effect on stratospheric ozone. Some of the newcandidates are flammable. While some of these arebeing used in the pure state, the more flammablechemicals are often blended with nonflammable part-ners to reduce fire hazard. The current standard testmethod for measuring the flammability of either purechemicals or blends is time consuming to operate andhas a high degree of uncertainty, especially for weaklyflammable refrigerants. Under sponsorship of the AirConditioning and Refrigeration Technology Institute,two NIST scientists have developed a new, robust, andrapid method for measuring the lean flammability limitof the refrigerant in air. The device consists of two flowsof premixed refrigerant and air, aimed at each other. Aplanar flame forms where they meet. As the fractionof refrigerant is reduced, the flame weakens and thenextinguishes. The lean limit is determined as the mini-mum fraction of refrigerant in the mixtures before theflame goes out. The measurements are performed atdifferent flow velocities and extrapolated to zero veloc-ity, and the resulting value is a basic property of therefrigerant. The uncertainty for difluoro-methane isabout 5 %. The findings are being published in Combus-tion and Flame, the journal of the Combustion Institute.

NIST SCIENTISTS DEVELOP NEW CLASSOF FIRE-RETARDANT MATERIALSAs materials evolve to a higher degree of functionalityand safety, new types of formulations are needed.Scientists have been examining novel materials formedby reacting a host organic resin with fine clay particles.At low clay additions (mass fractions of less than 20 %),a polymer layered silicate nanocomposite is formed.NIST scientists working with another government labo-ratory, have shown that these materials also offer a newmeans for achieving a high degree of fire retardancy.

Reaction of nylon-6 with only 5 % clay results in aproduct whose peak rate of heat release is reduced by afactor of three. The rate of heat release is the principalproperty controlling fire growth. The mechanism thatresults in this significant improvement in fire safety isdifferent from that in simple mixtures and is leading toapproaches for other resins.

NIST CO-SPONSORS GREEN BUILDINGCONFERENCENIST joined with U.S. Green Building Council, theAmerican Institute of Architects, and the San Diego Gasand Electric Company to sponsor the “Third Interna-tional Green Building Conference.” Green buildings aredefined as those designed, constructed, operated, anddemolished in ways so as to have a minimum impact ontheir global neighborhood, and internal environments.The conference, held in San Diego, CA, Nov. 17-19,1996, brought together experts in the field of greenbuildings. Approximately 300 people attended thisconference, including representatives from industry,academia, and government. International professionalspresented the latest information on sustainable practices,materials, and technologies.

A highlight of the conference was a presentation thatincluded a world overview of building-integrated photo-voltaic activity with a country-by-country description ofcomponent and systems development with selectedexamples of Solar Electric Architecture. The presenta-tion and 19 others are included in the proceedings fromthe conference, NIST Special Publication 908, ThirdInternational Green Building Conference and Exposi-tion-1996. The proceedings may be obtained by contact-ing Paula Svincek, ext. 5648.

NIST RESEARCH ADVANCES A STANDARDNEEDED FOR INTERACTIVE CABLE TVFour private companies have worked with NIST todevelop standard specifications for cable TV over hybridfiber coaxial networks. Working jointly with thesecompanies and other members of the IEEE 802.14standards group, NIST conducted an unbiased perfor-mance evaluation of the media access control (MAC)protocols that had been submitted to the standardsgroup. Researchers implemented the candidate MACprotocols using a commercial network simulationpackage. The results from this work have been reportedto the IEEE 802.14 group, and the software simulationmodules have been released to the public. Thesemodules currently are used by several companies asthey develop their own standards-conformant MACprotocols.

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NEW PUBLICATION DESCRIBES STRUCTUREDTESTING METHODOLOGYNIST Special Publication 500-235, Structured Testing:A Testing MethodologyUsing the Cyclomatic Complex-ity Metric, describes the structured testing methodologyfor software testing, known as basis path testing. Basedon the cyclomatic complexity measure, structuredtesting uses the control flow structure of software toestablish path coverage criteria. The resulting test setsprovide more thorough testing than statement andbranch coverage. The publication also presents exten-sions of the fundamental structured testing techniquesfor integration testing and object-oriented systems anddescribes several related software complexity metrics.

NIST RESEARCHERS CONSIDERDIFFUSE-INTERFACE MODEL FORFLUID-FLUID SYSTEMSNISTIR 5887, A Diffuse-Interface Description of FluidSystems, describes a diffuse-interface model forfluid-fluid systems. In classical models, an interfacebetween two fluids is treated as infinitely thin, or sharp,and is endowed with properties such as surface tension.Diffuse-interface theories replace this sharp interfacewith continuous variations of an order parameter such asdensity in a way consistent with microscopic theories ofthe interface. NIST researchers related the diffuse-interface model to classical, sharp interface models byderiving asymptotically the governing equations and theassociated boundary conditions used in the sharp-inter-face formulation. The diffuse-interface approach isillustrated by modeling internal gravity waves. Resultsreveal a singularity in the diffuse-interface model in thelimit of incompressible perturbations.

WULFFMAN MAKES 3-D IMAGES“CRYSTAL CLEAR”Wulffman? Despite the unusual moniker, this new NISTproduct isn’t the agency’s tribute to Lon Chaney Jr. ora device that grows hair when the moon is full.

Wulffman, an interactive computer program fordrawing crystal shapes, was produced by researchers atNIST. The program is designed to help materialsscientists quickly visualize three-dimensional facetedcrystals and “quasi-crystals.”

The program gets its distinctive name from the term“Wulff shape,” known to materials scientists as thecrystal shape that an element or combination of elementswill form naturally because it requires the least amountof energy. Given a crystal’s symmetry and surfaceenergies for specific crystal planes. Wulffman con-structs an image of the crystal’s Wulff shape.

Wulffman’s creators hope the program will be usefulfor designing new materials where crystal shapes affectthe material’s bulk properties. For example, a majorcompany already is using it to help design reflectivepaint It also should be useful as a teaching tool. Theprogram is designed to run on Unix workstations. Forfurther information and to download the program, visitthe Wulffman website at http://www.ctcms.nist.gov/zryan/wulffman.

NEW MEASUREMENT CONSORTIUMTO AID INDUSTRYEngineers and measurement experts at suppliers,manufacturers, and users of ceramics can join a neweffort to find agreement on technical measurementmethods for ceramic powders—from raw materials tothe final product—that can ultimately enhance thecompetitiveness of the U.S. ceramic processing indus-try. The Ceramic Processing Characterization Consor-tium, now being formed by NIST, will work tostrengthen the measurement and standards infrastruc-ture for ceramic particulate systems.

The consortium’s mission is vital to ceramistsbecause measuring a dense ceramic means thoroughlyunderstanding the physical and chemical characteristicsof the powder that made it. This makes ceramics farmore dependent than plastics or metals on accuratemeasurements of raw materials. Because the focus onmeasurement and standards is a shared concern, resultsof the consortium will be generic, open, and freelyshared with anyone who is interested.

To join the consortium, which has no membershipfee, each member’s organization must establish amemorandum of understanding with NIST. For moreinformation, contact George Onoda, A256 MaterialsBuilding, NIST, Gaithersburg, MD 20899-0001,( 3 0 1 ) 9 7 5 - 4 4 8 9 , f a x : ( 3 0 1 ) 9 9 0 - 8 7 2 9 ,[email protected], or visit the CPCC web site athttp:/ /www.ceramics.nist.gov/programs/cpcc/index.htm.

NEW METHOD OF DETECTING PIPELINEFLAWS PATENTEDScientists at NIST have received a patent for a newmethod of measuring wall thickness and detectingflaws (such as cracks, delamination, scaling, andcorrosion) in natural-gas pipelines by using ultrasound.Use of ultrasound inspections is common for oilpipelines but has been less effective for the natural gasvariety. Gas is a poor coupling agent for the ultrasonicsignals emanating from the transducer to the pipe wall.

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The NIST researchers showed that use of wide-band,well-dampened ceramic transducers and high-dynamic-range receiver amplifiers can overcome signal losses.They also demonstrated that by using a diplexer, thesame transducer can be used to generate and detect theultrasonic signals.

“This method is inherently suitable for the task,because it relies on the use of the natural gas as thecoupling fluid for transmitting the probing ultrasonicsignals into and out of the pipe wall,” the patent states.

NIST is working currently with the SouthwestResearch Institute, under a contract with the GasResearch Institute, to show the practicality of the tech-nology. For a copy of the patent, contact SarabethHarris, Div. 104, NIST, Boulder, CO 80303-3328,(303) 497-3237, [email protected]. For techni-cal information, contact Chris Fortunko, Div. 853,NIST, Boulder, CO 80303-3328, (303) 497-3062,[email protected] or Jerry L. Jackson, SWRI,6220 Culebra Rd., P.O. Drawer 28510, San Antonio, TX78228, (210) 522-2957, [email protected].

NACLA PROPOSAL ACCEPTED BY U.S.LABORATORY COMMUNITYRepresentatives of the nation’s conformity assessmentcommunity decided at an open forum at NIST on Jan. 7,1997, to go forward with a proposal to establishthe National Council for Laboratory Accreditation(NACLA). NACLA will be a cooperative partnershipbetween the public and private sectors to provide acomprehensive U.S. national laboratory accreditationinfrastructure. In the resulting system, the testing andcalibration data from a laboratory accredited by aNACLA-recognized body will receive worldwideacceptance based on the laboratory’s competence. Theopen forum, co-sponsored by NIST, ANSI, and ACIL,(formerly the American Council of Independent Labora-tories) was attended by more than 350 interestedstakeholders from laboratories, accreditors, and thosewho require accreditation, both from industry andgovernment. Immediate plans call for the election of abalanced, interim board of directors made up ofmembers from the various stakeholders. The board willlay out a proposal for NACLA functions and a perma-nent structure. These proposals will be reviewed bystakeholders at future public meetings.

ENERGY-RELATED INVENTIONS PROGRAMMAKES RECOMMENDATIONSDuring the month of December 1996, NIST recom-mended the following two innovative technologies forcommercialization to its Department of Energy partner

under the Energy-Related Inventions Program: Methodfor forming thin semiconductor films—a process tomanufacture cadmium telluride (CdTe) photovoltaiccells by fusing nano particles of CdTe on a metal orglass support plate; Cyclic microwave treatment ofpressed garments—a process for using microwaves toset the permanent press or fire-retardant chemicals ingarments.

APPLICATION OF CRYOGENIC DETECTOR TOMASS SPECTROSCOPY SHOWS PROMISE OFGREATLY ENHANCED PERFORMANCE FORLARGE MOLECULESNIST researchers in collaboration with researchersfrom the University of Neuchatel and George MasonUniversity, recently performed initial experimentsdemonstrating the utility of a NIS (normal-insulator-superconductor) tunnel junction as a molecular detectorin a MALDI-TOF (matrix assisted laser desorption andionization2time-of-flight) mass spectrometer. Conven-tional MALDI-TOF spectrometers, which use anelectron multiplier as the detector, are not useful foranalysis of biological macromolecules such as DNA, inpart because only a small fraction of high-molecular-weight species are detected. In contrast, the NIS detec-tor, fabricated on a silicon nitride membrane for thermalisolation and cooled to 100 mK, promises nearly 100 %detection efficiency, fast response time, and accuratecalorimetric energy measurement even for macro-molecules. The detection efficiency and response timeassure accuracy in the time-of-flight mass determina-tion, while the calorimetric energy deposited in thedetector provides an important check on the ionizationstate of the molecule. In recent experiments with bovineserum albumin (BSA), having a molecular weight of66 000m, singly and doubly ionized molecules weredistinguished easily with an NIS detector having a risetime of about 1s. If the full potential of such detectorsis realized, MALDI-TOF spectrometers may reduce thetime and sample size required for DNA sequencing toa small fraction of that presently required with gelelectrophoresis.

NIST DEMONSTRATES 61 V SNSJOSEPHSON-JUNCTION PROGRAMMABLEVOLTAGE STANDARD ARRAYVoltage standards that can be quickly switched betweenlevels are needed by U.S. industry for characterizingdigital-to-analog (D/A) and analog-to-digital converters.NIST has developed such a programmable voltagestandard that will enable fast dc voltage measurementson a microsecond scale. The new circuit has the

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equivalent resolution of a 9-bit D/A converter and anaccuracy of 30 bits.

The heart of the circuit is an array of 32 768 Joseph-son junctions. In order to achieve programmability, thearray is divided into a binary sequence of segments, inwhich the least significant bit has 128 junctions and themost significant bit has 16 384 junctions. The voltageacross the array is programmed by biasing eachsegment at one of three constant voltage steps at V = 0and6Nf /KJ , whereN is the number of junctions in thearray segment,f is the microwave signal frequency, andKJ = 483 597.9 GHz/V, the Josephson constant. Whenthis array is driven with a 16.0 GHz microwave signal, itproduces 1023 selectable reference voltages in incre-ments of 4.235 mV from –1.085 V to +1.085 V. Thevoltage steps of the whole array were found to be flatover a current range of about 2 mA.

The circuits are based on a novel superconductor-normal-superconductor (SNS) junction technologydeveloped at NIST. In this technology, a high-resistivitypalladium-gold alloy is used as the normal metal barriersandwiched between two superconducting niobiumelectrodes. The 2.5mm32.5mm junctions have an area1/130 times the area of junctions in the present dcvoltage standard. The initial test has shown functionalityof the full circuit proving that all 32 768 junctions areworking as desired. This demonstrates a level of junc-tion and microwave distribution uniformity about fivetimes better than is typically achieved in the previoustechnology.

OIDA CALLS FOR NIST ASSISTANCEIn a report previewed at its Annual Forum inWashington, DC, Oct. 17–18, 1996, the OptoelectronicsIndustry Development Association (OIDA), called forNIST assistance in addressing several problems relatedto optoelectronics manufacturing. The report summa-rizes the results of a 6-month-long study of manufactur-ing infrastructure which focused on four areas ofoptoelectronics: semiconductor components, passive

components, optical storage media, and packaging.In the semiconductor components area, the OIDA

asked for assistance related to the purity and analysis ofstarting materials and for broad assistance in measure-ment technology andreference standards. In the passivecomponent area, OIDA asked for assistance in loweringthe cost of measurements and for NIST consideration ofprograms to develop broader functionality in a single setof technologies, toenable large volume applications. Foroptical storage, it called for NIST to work withmedia manufacturers to define critical measurementissues and to help in their solution. These are among 15recommendations contained in the report.

The OIDA has decided that the semiconductorcomponents area should have the highest priority and ispreparing to lead discussions among NIST, SandiaNational Labs, and a group of manufacturers to developan action plan.

ELECTRON-BEAM LITHOGRAPHYCAPABILITY AVAILABLE IN GAITHERSBURGThree NIST scientists have developed and installed anelectron-beam lithography (EBL) capability at theNIST Gaithersburg laboratories. This EBL facility isthe first available on the Gaithersburg site and willextend nanoscale device fabrication capabilities signifi-cantly. EBL capabilities have been available in NIST’sBoulder facility for some time.

As implemented in the Gaithersburg facility, EBLgives researchers the ability to define thin-film struc-tures with lateral dimensions below 100 nm. The capa-bility is realized using a commercial scanning electronmicroscope, together with a separate computer con-troller, which outputs two voltages to control the lateralposition of the electron beam. Together with a CADsoftware package, this allows definition of the patternon the computer, followed by a rastering of the electronbeam on the substrate.

The researchers have made various test patterns, aswell as electrical and optical devices, with typicalminimum feature sizes as small as 50 nm. NISTresearchers in Gaithersburg will use EBL to fabricatesingle-electron tunneling devices for a capacitancestandard and later perhaps for a current standard. Theywill also use it to build fine-scale test structures forsupporting U.S. advanced semiconductor manufactur-ing and for related nanostructures research.

NATIONAL ADVANCED MANUFACTURINGTESTBED (NAMT) UNVEILEDNIST recently unveiled its new National AdvancedManufacturing Testbed (NAMT). The NAMT is aNIST-hosted and initiated program that is addressingmeasurements and standards needs associated withinformation-based manufacturing. In the NAMT, NISTis using a recently developed infrastructure foradvanced computing and communications to enable orfacilitate a series of manufacturing research projectsconducted collaboratively with multiple partnersresiding at several locations. NAMT projects arecharacterized by the transfer and use of data, video, andaudio information among partner facilities in theperformance of leading-edge research across thespectrum of manufacturing technologies.

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The existing NAMT technical portfolio consists offour projects that have roughly two dozen industrial,government, and academic partners: (1) nanomanufac-turing of atom-based standards, which is focusing on thefabrication, measurement, and dissemination of dimen-sional reference standards with geometric featuresbased upon atomic lattice properties; (2) machine toolperformance models and machine data repositories,which is developing performance-based predictivemodels for machine tools and coordinate measuringmachines that accurately represent real-world manu-facturing and measurement capabilities in a virtualenvironment; (3) characterization, simulation, andremote access of hexapod machines, which is develop-ing tools and methodologies for collaboratively using,characterizing, simulating, and enhancing the perfor-mance of a revolutionary new class of parallel-actuatedmachine tools; and (4) framework for discrete partsmanufacturing, which is developing specifications forintegrating heterogeneous software applications withindistributed manufacturing systems, thus promotinginteroperability.

IMPROVED PROCESS CONTROL INSEMICONDUCTOR PROCESSINGMany semiconductor processes use the thermal massflowmeter, or mass flow controller (MFC), to deliverknown flows of gas to the processing chamber. Manyhundreds of these devices are found on a typical fabrica-tion line. Critical semiconductor processes now requirerelative flow measurement uncertainties of 1 % or lessover the range of 10–7 to 10–3 mol/s. MFCs can providethe wide flow range and are tolerant to the corrosivegases required for semiconductor processing; however,they long have been suspected as having uncertaintiesmuch higher than the “few percent” claimed by themanufacturers. As part of the National SemiconductorMetrology Program, scientists at NIST have carefullyevaluated the operating characteristics of low-gas-flowMFCs from five major manufacturers to determine ifthe required uncertainties can be met.

In a calibration of the meters against the NISTprimary standard using nitrogen gas, two of the fivemeters had relative uncertainties of 7 % and 17 %,significantly outside the ascribed uncertainty (61 %).The long-term stability of all the meters was within61 % over 1 year, indicating that, with recalibration, allthe units would meet the requirements for processcontrol. Although MFCs are used with a variety ofgases, most MFCs are calibrated using nitrogen, and gas

correction factors are applied to determine the flow withother gases. The meters were calibrated at NIST withseveral gases, and the correction factors were measuredand compared to the manufacturers’ reported values.Reported values were in moderately good agreement forhelium, argon, and sulfur hexafluoride (–0.7 % to 1.6 %average deviation), while the correction factors forhydrogen and hexafluoroethane were not (10.2 % and7.7 % average deviation, for all the units). Hence, toachieve the relative uncertainties of 1 % or less requiredfor semiconductor processing, MFCs must be calibratedwith the gas to be used at conditions close to theconditions of use. To provide measurement assurancefor the reference flow meters used by the manufacturersin the calibration of their meters, NIST has developed ahigh-repeatability flow transfer standard using an ultra-stable laminar flow element, which has a relative uncer-tainty of 0.07 %. This transfer standard has been usedthis past year in flow proficiency tests over a flow rangeof 10–6 to 10–3 mol/s at four MFC manufacturers andtwo equipment suppliers’ laboratories.

NIST SCIENTIST ELECTED CHAIR OFINTERNATIONAL MANAGEMENT BODYAt the November 1996 annual meeting of the inter-national steering committee of the Network for theDetection of Stratospheric Change (NDSC), a NISTscientist was re-elected committee chair for a new three-year term. The NDSC is a ground-based, long-terminternational measurement and analysis networkdesigned to make the observations through whichchanges in the physical and chemical state of the strato-sphere can be determined and understood. This dualobjective of observation and understanding requireshigh-precision, state-of-the-art measurements of ozone,as well as a broad range of chemical species and dynam-ical tracers that influence ozone. On a shorter time-scale, the NDSC provides independent calibration forsatellite sensors and produces a useful data set for test-ing and improving stratospheric models. It consists ofnearly 50 measurement sites in nearly 20 differentcountries and has been endorsed by the United NationsEnvironment Program, by the International OzoneCommission of the International Association ofMeteorology and Atmospheric Physics, and by theWorld Meteorological Organization (WMO) as a majorcontributor of WMO’s Global Ozone Observing Systemwithin the framework of its Global Atmosphere Watch.The steering committee is the primary managerial bodyof the NDSC.

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INFRARED ARRAYS FOR FTIR MICROSCOPYInfrared spectroscopy long has been used to identifychemical species and their environments. Molecules ofdifferent species have characteristic spectral absorptionfeatures in the 2.5mm to 11mm wavelength region,which provides distinctive “fingerprints” for theiridentity. Coupled with microscopy, spatially resolvedinfrared spectroscopy is a versatile measurement toolwith applications including materials and film charac-terization, biological research, and medical diagnosis.However, the application of infrared microscopy hasbeen limited by the brightness of infrared sources andby the use of single-element infrared detectors,which necessitate slow rastering of the probed areas togenerate images.

Researchers at NIST and National Institutes of Health(NIH) have demonstrated rapid, sensitive spectralimaging in the infrared fingerprint region by attachingNIST’s mercury-cadmium-telluride (MCT) infrareddetector array to NIH’s step-scan Fourier transforminfrared microscope. The NIST MCT array is a2563256 pixel focal-plane detector array, originallydesigned for DoD projects but now available for civilianapplications. An interferometer with a glow-bar sourcesteps its moving mirror through successive positionswhile the MCT array obtains background-correctedinfrared images. In this way, 65 536 time-domain inter-ferograms are obtained, each corresponding to aspecific spatial position of the sample. Fourier trans-forming this massive data set (approximately 100 MB)yields spectrally sensitive images with 10m spatialresolution and 16 cm–1 spectral resolution over the entire2.5mm to 11mm spectral region. The NIST/NIH teamobtained chemical images of inhomogeneous polymerand lipid samples, laminates, and brain tissue, illustrat-ing a wide range of industrial and biomedicalapplications for this unique apparatus and new imagingtechnique.

POLYMERS DESIGNED WITH MINIMALSHRINKAGE DURING POLYMERIZATIONMonomers prepared recently at NIST have attracted theattention of several companies with interests as diverseas dental composite restoratives, lithographic materials,and adhesive coatings. All of these polymer-basedapplications currently suffer from deficiencies inducedby excessive polymerization shrinkage. In the NISTwork, a simple method was devised for the preparationof spiro orthocarbonate (SOC) monomers that arecharacterized by their unusual ability to polymerizewith an expansion in volume. The combination ofexpanding SOC monomers with conventionalmonomers that contract allows a means to controlpolymerization shrinkage and its deleterious effects.

The new SOC monomers are actually pre-polymerscontaining many SOC units repeated along a backbonestructure. A cationic double ring-opening polymeriza-tion process converts the liquid multi-functionalprepolymer into a rigid, three dimensional network withvolumetric expansions of 2 % to 3 %.

One of the initial applications of these SOCmonomers is as a component of dental compositerestorative materials where problems associated withpolymerization shrinkage are well documented. Thecuring contraction results in tooth deflection, whichgenerates pain when the bonding is good and the forma-tion of gaps when the adhesion between the restorationand tooth fails. Copolymerization studies involving SOCprepolymers and traditional methacrylate monomersused in dentistry have been conducted. Results show thatpractical hybrid composites with extremely low poly-merization shrinkage values and good mechanicalstrength properties can be produced. Meetings havebeen held with several dental materials manufacturers todiscuss the potential of these new monomers.

USING MAGNETOSTRICTION TO MEASURETHE STRENGTH OF STEELDuring the magnetization of a ferromagnetic materialsuch as steel, magnetic domain walls sweep through thematerial and interact with the same microstructuralfeatures that determine its strength. As a result, suchmeasurable properties as Barkhausen noise, coerciveforce, and differential permeability have been used asnondestructive predictors of the mechanical strength offinished steel products. These magnetic properties areassociated with the low field properties of the hysteresisloop and, therefore, can be influenced strongly by thepart geometry and extraneous magnetic fields. Duringrecent studies at NIST of a noncontacting method ofmeasuring the magnetostrictive coefficients of highstrength low alloy (HSLA) steels at high and intermedi-ate fields, it was observed that the magnetic fields’dependence of the coefficients was sensitive to the de-velopment of the precipitates that give these materialstheir high strengths. Thus, it appears possible to developa noncontacting and nondestructive probe for predictingthe strength of the HSLA steel products currently beingproduced in large quantities by the steel mills. Themethod of making the magnetostrictive measurements isbased on theoretical and experimental studies performedin the 1970’s to explain the role of magnetostriction inthe efficiency of electromagnetic transducers (EMATs)when applied to ferromagnetic materials. This effi-ciency can be deduced from measurements of theenhanced strength of ultrasonic signals produced byEMATs when operated on steels at relatively easilyobtained applied fields.

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NEW RECORD SETTING VALUES FORGIANT MAGNETORESISTANCE SPIN VALVESMEASUREDIn the few years since they were discovered, giantmagnetoresistance (GMR) spin valves have become ahot topic in the computer industry. These ultrathinmagnetic multilayer films are being developed by harddisk drive manufacturers as magnetic read-heads withunprecedented sensitivity for reading ultrahigh densityhard disks. Another potential application for GMR spinvalves is magnetoresistive random access memory(MRAM) chips, which may become a non-volatilereplacement for dynamic random access memories.Industrial development is being supported strongly bythe Defense Advanced Research Projects Agency.Recent investigations at NIST have discovered that thehighest GMR values are not found in films grown in thebest vacuum. Some impurities, most notably oxygenatoms, actually increase the GMR by acting as a surfac-tant during film growth and suppressing defects. Bydeliberately introducing minute amounts of oxygen intoan otherwise extremely clean deposition system, thelargest GMR values ever reported for two basic types ofspin valves were achieved, 25.8 % for symmetric spinvalves, 19 % for bottom spin valves. These NIST accom-plishments constitute an important step toward therealization of GMR read-heads and MRAM chips.

OBJECT-ORIENTED FINITE-ELEMENT CODEDEVELOPED FOR MICROMECHANICALANALYSES OF MICROSTRUCTURESAlthough material microstructures are heralded as thepalette from which materials scientists can design andtailor material properties, no general methods exist forevaluating the behavior of a particular microstructure orfor relating microstructural images to macroscopicbehavior. Toward this objective, an object-orientedfinite-element code (OOF) is being developed. OOF isdesigned to help materials scientists calculate macro-scopic properties from microstructural images. Thegoal is to assign materials properties to all parts of animage and to perform finite-element calculations on theprocessed image, applying appropriate boundary condi-tions, temperature changes, distortions, etc. Thus far,OOF has been used to investigate micromechanicalproperties of several ceramic systems, including effectsof glass composition and grain morphology onresidualstress and fracture of silicon nitride, effects of porosityon elastic properties of thermal barrier coatings, andresidual stress distributions in highly anisotropic ceram-ics. A beta version of OOF for SGI workstations isavailable as public domain software on the Internet in aNIST software archive. A link to this archive, as well as

a description for using OOF can be found at the WWWaddress: http://www. ctcms.nist.gov/~wcraig/oof.html.

A portable X-Windows version is under development.

PHOTOVOLTAIC SOLAR WATER HEATINGSYSTEM AT GREAT SMOKY MOUNTAINSNATIONAL PARKA photovoltaic solar water heating system recently wasinstalled to heat water used in the restroom facilities atthe main visitors center within the Great Smoky Moun-tains National Park (GSMNP). Four to five millionpeople visit the GSMNP each year. The system is basedupon technology patented by NIST scientists.

This effort is a joint cooperative venture with theTennessee Valley Authority, NIST, Sevier CountyElectric System, and the National Park Service. Thesystem is being monitored to learn how well the systemperforms and to collect solar radiation data for theGSMNP personnel. The system performance data willbe used by NIST to verify computer prediction modelsbeing developed by the University of Wisconsin. TVAwill use the data to document the potential for reductionin energy and peak demand on their utility. The systemis being monitored by measuring the energy supplied bythe photovoltaic array, the energy supplied by theelectrical utility grid, and the volume of water con-sumed. Data are collected every 10 s and forwardedweekly to NIST for analysis.

For more information on this system, contact PaulaSvincek, ext. 5648 or visit the pvsolar page at http://bfrl.nist.gov/863/pvsolar/flyer.html.

APARTMENT BUILDING BURNED TOMEASURE FIRE FIGHTING EFFECTIVENESS

On Jan. 7, 1997, NIST scientists conducted a full-scale fire suppression experiment with an eight-unitapartment building in Mobile, AL. This experiment wasconducted in conjunction with the Bureau of Alcohol,Tobacco and Firearms and the Mobile Fire and RescueDepartment.

The objective of the experiment was to examine thesuppression effectiveness of water and Class A foamsolution at flow rates of 475 L/min used in full-scalefire fighting. These results will be compared with thesmaller fire suppression experiments conducted byNIST under the sponsorship of the U.S. Fire Adminis-tration. The fire suppression experiments conductedduring the USFA program involved residential housefires. Unfortunately, even at fire fighting flows as low as38 L/min the house fires were extinguished easily usingplain water. Larger fires were needed to challenge firefighting equipment sufficiently to measure any differ-ences in performance by different suppressants.

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After fire suppression experiments were completed,BAFT agents conducted a post-fire investigation of thebuilding for training purposes. In addition, a cameracrew from the public television program, NOVA, filmedthe experiment for inclusion in a series on survival tech-nologies. The show isscheduled to be aired during the1998 season.

NIST HOSTS FIFTH ANNUAL TRECWORKSHOPOn Nov. 20-22, 1996, NIST and the Defense AdvancedResearch Projects Agency (DARPA) co-sponsored thefifth Text REtrieval Conference (TREC-5) Workshop aspart of the TIPSTER Text Program. Started in 1992, theconference series is designed to promote research ininformation retrieval by providing appropriate testcollections, uniform scoring procedures, and a forum fororganizations interested in comparing their results.Thirty-eight groups participated, including representa-tives from nine different countries and 10 companies.All participants used the same test collection that con-sists of about 2 gigabytes of text (over 1 million docu-ments) and a given set of information needs. Two newretrieval tasks were introduced in the TREC-5 confer-ence: retrieving Chinese documents and retrievingdocuments that have been corrupted through opticalcharacter recognition (OCR) scanning.

TREC-5 proceedings, to be published in the spring,are available on the NIST TREC Web site, http://www-nlpir.nist.gov/trec. Also available are the proceedingsfrom TREC-4, which have been published as NISTSpecial Publication 500-236, The Fourth Text REtrievalConference (TREC-4).

MATRIX MARKET EXCHANGE FORMATSPROPOSEDNISTIR 5935, Matrix Market Exchange Formats: InitialDesign, proposes elementary ASCII exchange formatsfor matrices. Specific instances of the format aredefined for dense and sparse matrices with real,complex, integer, and pattern entries, with special casesfor symmetric, skew-symmetric, and Hermitianmatrices.

OPTICAL CHARACTER RECOGNITION (OCR)WORK ADVANCESNISTIR 5932, Design, Integration, and Evaluation ofForm-Based Handprint and OCR Systems, addresseskey issues in the design, integration, and evaluation of

end-to-end systems for recognizing form-based hand-print and cursive handwriting that arise in data entryapplications. The applications include recognition ofalphanumerals from tax, census, and insurance forms,bank checks, etc. To succeed in these applications, asystem should be as accurate as possible and, at the sametime, should minimize human intervention to correctthat part of the text that machines fail to recognize.

Strong interdependence between the modules of anOCR system argues for an end-to-end system design andevaluation. Design issues such as system training, confi-dence measures, and the role of correction mechanismsemployed byhumans need to be considered. NISTresearchers recommend a fairly general process forsystem integration and argue in favor of system-levelevaluation. NISTIR 5932 documents several case studiesinvolving OCR systems that have undergone large-scaleevaluations, including the NIST form-based recognitionsystem and several commercial systems.

SQL TEST SUITE, VERSION 6.0, AVAILABLEON THE WEBThe SQL Test Suite, Version 6.0, used to validatecommercial SQL products for conformance to SQLstandards specified by the International Organization forStandardization, the American National StandardsInstitute (ANSI), and Federal Information ProcessingStandards (FIPS), can be downloaded from URL http://www.itl.nist.gov/div897/ctg/software.htm[pubsoft andselect SQL.

Completed December 31, 1996, the SQL Test Suite,Version 6.0, was developed jointly by NIST, the NationalComputing Centre Limited (NCC) in the UnitedKingdom, and Computer Logic R&D in Greece. TheEuropean contributions to the test suite were producedunder sponsorship from the European Community(EC).

The technical goal of the test suite is to help evaluateconformance of SQL implementations to Entry SQL orIntermediate SQL, as specified in ANSI X3.135-1992and ISO/IEC 9075:1992, through one or more standardprogramming language interfaces. The test suitecontains new tests to validate the Intermediate SQL leveland additional tests to evaluate conformance to FIPS127-2, Database Language SQL, specification ofTransitional SQL, sizing parameters for databaseconstructs and flagging of extensions, as well asX/Open Extensions for features specified in the X/OpenCAE Specification. The test suite contains schemas andtest programs for Interactive SQL and 10 differentprogramming language test suite types: Embedded C,Embedded COBOL, Embedded Fortran, Embedded

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Ada, Embedded Pascal, Module Language C, ModuleLanguage COBOL, Module Language Fortran, ModuleLanguage Ada, and Module Language Pascal.

NIST HELPS PUT AUTOMATION IN THEDRIVER’S SEATFasten your seatbelts, surrender the steering wheel andcruise control, and let AUTONAV do the driving for you.Automated driving on streets and highways or driver-free reconnaissance over unpaved terrain behind enemylines are two of the goals motivating work recentlybegun by a team of German and U.S. researchers.

The collaborators aim to develop a “next generationautonomous vehicle navigation control system.”NIST, the Army Research Laboratory and the DavidSarnoff Research Center will be exchanging technologywith counterparts from Germany’s University ofBundeswehr and a unit of a German automotive andaerospace company.

NIST’s contributions include its real-time controlsystem architecture, reference-model framework andhardware elements of a control system. The Germantechnologies havebeen demonstrated in self-guidedvans and passenger cars that have logged thousands ofkilometers on the country’s autobahn.

AUTONAV’s goals are to extend the performance andcapabilities of these technologies, incorporate andevaluate new ones, and, ultimately, develop a standardplatform that manufacturers can use as the basis for therobotic or semiautomated vehicles of the future. Fortechnical information, contact Maris Juberts, B124Metrology Building, NIST, Gaithersburg, MD 20899-0001, (301) 975-3424, <[email protected]>.

NEW WAY OFFERED TO BETTER PREDICTCLOCK BEHAVIORFor those who operate extremely precise clocksand oscillators, a principal task is characterizing thefrequency stability of the devices. One recommendedmethod has been to use the two-sample frequencyvariance known as the Allan variance statistic.

Recent NIST analysis has shown that this statistic hassensitivities and dependencies that make it less accuratefor certain types of oscillator behavior and measurementprotocols. A new data manipulation, dubbed “TOTALVARIANCE,” has been devised that time-shifts thesampling window. Instead of a limited two-samplemeasurement, the multisample approach estimates allpossible observed frequency deviations over a set periodof time. Previously seen estimation errors are reducedby as much as 100-fold.

Use of the “TOTAL VARIANCE” method results inmore accurate predictions of the time errors that evolveafter a precision clock is synchronized. Details of thenew sample variance method are available in a paper,“An Extension of the Allan Variance with IncreasedConfidence at Long Term.” For a copy of paperno. 5-97, contact Sarabeth Harris, Div. 104, NIST,Boulder, CO 80303-3328, (303) 497-3237,<[email protected]>.

NATIONAL RESOURCE FOR GLOBALSTANDARDS LAUNCHEDThe American National Standards Institute announcedon Feb. 25, 1997, that its NSSN: A Global StandardsNetwork is officially open for business.

The NSSN (formerly known as the NationalStandards Systems Network) is a World Wide Web-based, comprehensive source of information onregional, national, and international standards fromprivate-sector organizations and Federal Governmentagencies. The network links the heterogeneous data-bases of these groups, giving NSSN users the ability tosearch multiple standards databases in a few minutes.Examples of standards included are those that set crite-ria for safety in consumer products, compatibilitybetween computer software packages, and quality ofexported products and services (such as the ISO 9000series of standards). Information on over 100 000standards—including about 30 000 military specifica-tions—will be in the NSSN database by year’s end. Thenew service is the result of a partnership between ANSIand NIST. The “NSSN Basic” service is free and locatedat <http://www.nssn.org on the World Wide Web. Userscan search for standards by a document number, key-word or developer’s name. Links to the WWW pages ofspecific developers are provided for additional informa-tion or ordering. “NSSN Enhanced,” available later thisyear, will be a subscription service with more data aboutindividual standards and an automatic alert to provideimmediate notification of standards development andmaintenance changes.

NEW GUIDELINES AVAILABLE FOR QUAKE“SHOCK ABSORBERS”Slide to the left, slide to the right and don’t fall down.No, it’s not a new dance, but a building with shockabsorbers—a feature that could someday save more livesand property in earthquake-prone regions of the UnitedStates.

NIST researchers have taken the first step towardmaking it easier for the construction industry to include

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these shock absorbers—more commonly called seismicbase isolation systems—in their building plans. NISThas developed performance guidelines for the devicesthat can be used as standards for reliability and capacity.

Seismic base isolation systems, designed to protectstructures of fewer than 10 stories from the dangerouseffects of strong ground shaking, isolate a structure fromthe moving ground by inserting a flexible rubber layer,or Teflon steel sliding panel interface, at or near thestructure’s foundation. The interface isolates the shakingof the ground from the shaking of the structure,minimizing damage.

Up to now, these devices had to be custom designedfor each site and individually tested. New testingstandards, based on the NIST guidelines, will defineminimum levels of reliability and capacity. The sale of“off-the-shelf” isolation systems could then become areality.

Approval of testing standards by the AmericanSociety of Civil Engineers is expected by the end of theyear. For technical information, contact AndrewW. Taylor, B158 Technology Building, NIST,Gaithersburg, MD 20899-0001, (301) 975-6078,<[email protected]>.

PARTNERS DRAMATICALLY IMPROVEELECTRON SCOPE’S VISIONA new scanning electron microscope stage, jointlydeveloped by NIST, a small Massachusetts firm andSEMATECH, will permit chip makers and other SEMusers to cover nearly all angles when examining theirsamples. To be commercialized by the maker of customaccessories for electron microscopes, the new stagedoubles the viewing range of typical SEMs andincreases the tilt to better than 908 from the horizontal,as compared to the current 608.

Such improved performance capabilities are expectedto increase the utility of SEMs as measurement andresearch tools. Retrofitted on the SEM that NIST usesfor dimensional measurements, the stage enables high-resolution, cross-sectional images of films andsubstrates. It also benefits measurements of so-calledcritical dimensions (also known as minimum featuresizes) on integrated circuits and the photomasks used tomake them.

NIST has been working with SEMATECH, theconsortium of U.S. chip makers and their equipmentsuppliers, to improve the measurement performance ofSEMs and other microscopes used in semiconductormanufacturing. Representatives of several SEMATECHmember companies have visited NIST to preview the

new stage. For technical information, contactMichael Postek, A347 Technology Building,NIST, Gaithersburg, MD 20899-0001, (301) 975-2299,<[email protected]>.

DNA DAMAGE/REPAIR COURSE SCHEDULEDFOR OCTOBERNIST, with support from a NATO grant, is organizing anAdvanced Study Institute on DNA Damage and Repairto be held Oct. 14-24, 1997, in Antalya, Turkey. A NISTsenior scientist who is a well-known expert in DNAdamage and repair, is leading the international organiz-ing committee for this high-level tutorial course.

The ASI will cover state-of-the-art knowledge andrecent developments in DNA damage and repair, oxygenfree radical effects, cellular protection and biologicalconsequences. Presentations will be geared for postdoc-toral and higher level scientists.

Approximately 70 applicants will receive supportfrom the NATO grant to participate in the ASI. Scientistswho are not eligible for this support but wish to attendshould submit an application form, a resume of no morethan three pages, a brief justification for participating, arecommendation letter from their supervisor and an ab-stract of their work. The use of electronic mail forapplications is encouraged. The application deadline isJune 15, 1997. Applicants will be notified of the deci-sion of the organizing committee by Aug. 1, 1997. Formore information and/or application forms, write toMiral Dizdaroglu, A353 Chemistry Building, NIST,Gaithersburg, MD 20899-0001, fax: (301) 330-3447,<[email protected]>.

NIST IMPROVES PYROELECTRIC OPTICALDETECTORResearchers at NIST have developed an improvedpyroelectric detector, which, in turn, may improve theperformance of products containing these sensors. Suchproducts include burglar alarms, infrared motion detec-tors, automotive pollution sensors and a variety of mili-tary applications that depend on smart sensors.

A pyroelectric detector contains a material thatproduces a charge when heated. When the material isplaced between electrodes and connected to a sensingcircuit, a current is generated. These sensors are limitedby their acoustic sensitivity, which can trigger falsealarms.

The NIST solution (for which a provisional patent hasbeen submitted) is to engineer two or more pyroelectricdomains within a single crystal. This significantly

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reduces the noise problem, simplifies the constructionby using only one piece of material and simplifies theelectrode pattern. For paper no. 6-97 describing thisdevelopment, contact Sarabeth Harris, Div. 104,NIST, Boulder, CO 80303-3328, (303) 497-3237,<[email protected]>.

IMPROVED SOFTWARE SPEEDS PCCHEMICAL ANALYSISResearchers who use electron microscopes for x-rayspectrometric analysis will be able to save hours design-ing experiments with an improved software/databasepackage from NIST and the National Institutes ofHealth. The Desktop Spectrum Analyzer and X-RayDatabase Version 2.5 allows scientists to simulatemeasurements in an electron microscope. It also helpsthem predict whether an experiment will producespectra for accurate analyses without using laboratorytrial and error to do so.

Available for Macintosh personal computers since1992, the new version will operate on a PowerMac orany Macintosh computer with 5 MB of memory and amath co-processor. The database includes more quanti-tative analysis procedures and improved user interfaces.Prospective buyers can request a free demonstration diskfrom the NIST Standard Reference Data Program bycalling (301) 975-2208. Desktop Spectrum Analyzerand X-Ray Database Version 2.5 is available for $815.An upgrade for the PowerMac is $100, and a 68 kilobyteupgrade is free. Order from the SRDP, Rm. 113,Building 820, Gaithersburg, MD 20899-0001,fax: (301) 926-0416, <[email protected]>.

NEW PRODUCT RESULTS FROMCENTER’S AIDThroughout the country, centers affiliated with NIST’sManufacturing Extension Partnership are helpingAmerica’s smaller manufacturers improve their perfor-mance and competitive edge. For example, the Connect-icut State Technology Extension Program CONN/STEPrecently worked with a company, to develop a new gage,which is helping the company expand its productioncapabilities.

The majority of the company’s business is precisionmachining of round parts for the aerospace and defenseindustries. But the company’s gage for measuring theseparts was time consuming and unreliable. With CONN/STEP’s assistance, the company developed a new devicethat could quickly and accurately measure the dimen-

sions of any cylindrical part. Not only did the gagespeed up the company’s manufacturing process, but thecompany plans on producing and selling it in the nearfuture. The president says, “Without CONN/STEP’sassistance we would not have been able to afford under-taking the massive step from R&D to production....CONN/STEP helped us accelerate our new productintroduction and we look forward to expanding ourproduction capabilities and employment.” Other MEPcenter/client collaborative achievements are chronicledonline at <http://www.nist.mep.gov>. Click on “Aboutthe MEP,” then “Success Stories.” For print copies, callthe MEP at (301) 975-5020.

COLLABORATION UNDER WAY FORCONSTRUCTION MATERIALSThe NIST National Voluntary Laboratory AccreditationProgram and the International Conference of BuildingOfficials’ Evaluation Service Inc. signed a memoran-dum of understanding (MOU) on Feb. 18, 1997, to worktoward a mutual recognition agreement to recognizetheir respective accreditations of laboratories that testconstruction materials.

The MRA, which will be based on ISO/IEC Guides25 and 58 and other appropriate inter-national standards,will help eliminate duplicate accreditations in commonareas. Both the MOU and upcoming MRA are examplesof the ongoing effort by NIST under the NationalTechnology and Transfer Act to provide leadership incoordinating standards and conformity assessmentactivities with government bodies—as well as theprivate sector—to meet the needs of U.S. industry in theglobal marketplace.

ICBO provides its more than 2300 state and localgovernment members in the south, southeast, southwest,and Atlantic seaboard regions of the United States witha recognized consensus standards program through theICBO model building code. ICBO ES Inc. has more than15 accredited laboratories to test products related to theconstruction industry, with primary emphasis on thoseproducts and systems used in the design and construc-tion of buildings. NVLAP has approximately 20 labsaccredited in construction materials testing. There aremore than 700 domestic and foreign testing and calibra-tion laboratories in the overall NIST/NVLAP programthat are accredited in terms of meeting internationalstandards. For more information, contact James L.Cigler, NVLAP, Room 282, Building 820, NIST,Gaithersburg, MD 20899-0001,(301) 975-4016,fax: (301) 926-2884, <[email protected]>.

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Standard Reference Materials

SRM IS GOLD TO STEEL INDUSTRYFOR 90 YEARSAs NIST scientists well know standard referencematerials (SRMs) come and go. Many NIST SRMschange or are discontinued as industry needs change.One notable exception, Standard Reference Material5m, is celebrating its 90th anniversary of continuousservice to the U.S. steel industry.

Recently renewed for the 16th time, NIST’s cast ironSRM has changed little since the agency’s predecessor,the National Bureau of Standards, adopted it from theAmerican Fundaments Association in 1906. With salesof 50 to 70 units annually, it remains a popular andreliable standard for steel manufacturers. Foundriesuse SRM 5m to verify the accuracy of their chemicalanalyses.

In cooperation with the American Society for Testingand Materials, NIST has certified the concentration of12 elements, among which are carbon, manganese,phosphorous, silicon, and sulfur. Foundries and otheranalyzing elements in cast iron can purchase a 15 gbottle of SRM 5m for $215. For ordering information,contact the NIST Standard Reference MaterialsProgram, Building 202, Room 204, Gaithersburg, MD20899-0001. (301) 975-6776, fax: (301) 975-3730,e-mail: [email protected].

Standard Reference Data

GET DATABASE ON STEAM PROPERTIESWHILE IT’S HOTThe NIST Standard Reference Data Program’s Version2.0 of the NIST/ASME properties of steam database isnow available. The updated SRD is based on the mostrecent International Association for the Properties ofWater and Steam formulation for general and scientificuse of the thermodynamic properties of water.

Developed in conjunction with the American Societyof Mechanical Engineers (ASME), the STEAM data-

base is the U.S. implementation of an internationalstandard. Some of the thermophysical propertiescovered include temperature, pressure, volume, quality,enthalpy, entropy, thermal conductivity, viscosity,dielectric constant, and surface tension.

The database generates tables and plots of propertyvalues at specified conditions corresponding to satura-tion conditions, a fixed property value (such asisotherm) or individual values of two independentariables. Vapor-liquid, vapor-solid and liquid-solidsaturation calculations are available with either tempera-ture or pressure specified. The user can specify whichproperties to display and which units to use duringentering and displaying of data. To order, contactthe SRDP, NIST, Gaithersburg, MD 20899-0001,(301) 975-2208, fax: (301) 926-0416, e-mail:[email protected]. The price is $50 for executable, or$190 for executable and source code (FORTRAN).

SRD UPGRADE OFFERS RAPID ACCESS TOLIGAND STABILITY DATAResearch chemists and chemical engineers can nowaccess stability data for a wide variety of ligandsthrough an upgrade of NIST Standard ReferenceDatabase 46, NIST Critically Selected StabilityConstants of Metal Complexes.

Ligands, which are atoms or groups of atoms boundto a central atom, interact with hydrogen and other metalions in water. These interactions are a concern formining engineers, geologists,manufacturing engineersin controlling industrial processes such as electroplatingand finishing, scientists studying the stability of materi-als in the environment, biologists studying membranestructures, and chemists developing fertilizers andpesticides.

Version 3.0 of the database contains data for morethan 5300 ligands, rapid bibliography searching andstreamlined commands. The database will run onpersonal computers with PC or MS-DOS 2.1 or greaterand at least nine megabytes free hard disk space. NISTDatabase 46 is available for $240. Owners of previousversions may upgrade for $150. To order, contact theNIST Standard Reference Data Program, Building820, Room 113, Gaithersburg, MD 20899-0001,(301) 975-2208, fax: (301) 926-0416, <[email protected]>. The SRD Products Catalog can be foundon-line at <http://www.nist.gov/srd>.

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May 5–7, 1997VACUUM GAUGE

CALIBRATION WORKSHOP

Location: National Institute ofStandards and TechnologyGaithersburg, MD

Sponsor: NIST.Audience: U.S. vacuum community/calibration per-sonnel.Format: Lecture.Purpose: To provide instruction and hands-on practicein the use and calibration of vacuum groups. Emphasisis on the use of the molecular drag (spinning rotor)gauge.Topics: Vacuum systems, ion gauges and controllers,spinning rotor gauges, laboratory practice with spin-ning rotor gauge and review.Technical Contact: Ana Salazar, NIST, Building 220,Room A55, Gaithersburg, MD 20899-0001,phone: 301/975-4840, fax: 301/208-6962, email:[email protected].

May 19–23, 1997CONFERENCE ON RADIONUCLIDE

METROLOGY AND ITSAPPLICATIONS-ICRM ‘97


Sponsors: International Committee for RadionuclideMetrology (ICRM) and NIST.Audience: Radionuclide metrology community.Format: Oral and poster presentations and businessmeetings of the ICRM working groups on radionuclidemetrology and its applications.Purpose: To provide an opportunity for the exchangeof information on techniques and applications ofradionuclide metrology and to encourage internationalcooperation in this field.

Calendar

Topics: Alpha-particle spectrometry, gamma-ray andbeta-particle spectrometry, life sciences, low-levelmeasurements, radionuclide metrology techniques(including direct activity measurements), and nucleardecay data (measurements and evaluations).Technical Contact: J.M.R. Hutchinson, NIST,Building 245, Room C114, Gaithersburg, MD 20899-0001, phone: 301/975-5543, fax: 301/926-7416,email: [email protected], WWW Homepage:http://physics.nist.gov/Divisions/Div846/icrm.html.

June 8–13, 19971997 IEEE MTT-S INTERNATIONAL

MICROWAVE SYMPOSIUM

Location: Colorado Convention CenterDenver, CO

Sponsors: Institute of Electrical and ElectronicsEngineers (IEEE) Microwave Theory and TechniquesSociety and NIST.Audience: Microwave engineers.Format: Symposium, workshops, and exhibitions.Purpose: To present the latest developments inmicrowave technology.Topics: Microwave components, power generation,amplification, monolithic technology,millimeter waves,field theory, computer-aided design, measurements,wireless communications, and radio-frequency (rf)technology.Technical Contacts: Claude Weil, Chair, Electro-magnetic Fields Division, NIST, 325 Broadway,Boulder, CO 80303-3328, phone: 303/497-5305,fax: 303/497-6665, email: [email protected] Marks, Vice-Chair, Electromagnetic FieldsDivision, NIST, 325 Broadway, Boulder, CO 80303-3328, phone: 303/497-3037, fax: 303/497-7828,email: [email protected]. Motohisa Kanda,Vice-Chair, Electromagnetic Fields Division,NIST, 325 Broadway, Boulder, CO 80303-3328,phone: 303/497-5320, fax: 303/497-6665, email:[email protected], WWW Homepage:http://www.boulder.nist.gov/ims/.

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June 9–10, 1997YEAR 2000 INTERNATIONAL SYMPOSIUM

“MASTERING THE MILLENNIUM ROLLOVER”


Sponsors: NIST, Data Administration ManagementAssociation, National Capitol Region (DAMA NCR),Interagency Working Group on the Year 2000,U.S. Office of Management and Budget, U.S. FederalAviation Administration, and U.S. Department ofDefense.Audience: International and national government,academia, and industry.Format: Concurrent sessions, panels, speakers, andvendors.Purpose: To provide as much information and discus-sion as possible on this subject in order to assist organi-zations and international trading partners in dealingwith the issue.Topics: Awareness, assessment, renovation, validation,implementation, and applications.Technical Contact: Judith Newton, NIST, Building820, Room 562, Gaithersburg, MD 20899-0001,phone: 301/975-3256, fax: 301/948-6213, email:[email protected], WWW Homepage: http://speckle.ncsl.nist.gov/~fisher/y2kis0.htm.

June 16–20, 199712th ANNUAL CONFERENCE ON

COMPUTER ASSURANCE(COMPASS ’97)


Sponsors: NIST and the Institute of Electrical andElectronics Engineers (IEEE).Audience: Industry, government, and academia.Format: General sessions and tutorials.Purpose: To bring together researchers, developers,and evaluators who work on problems related to speci-fying, building, and certifying high-assurance computersystems.Topics: Systems integrity, software safety, and processsecurity.Technical Contact: Dolores Wallace, NIST, Building820, Room 517, Gaithersburg, MD 20899-0001,phone: 301/975-3340, fax: 301/926-3696 email:[email protected], WWW Homepage: http://hissa.ncsl.nist.gov/compass/.

June 22-27, 199713th SYMPOSIUM ON

THERMOPHYSICAL PROPERTIES

Location: University of Colorado at BoulderBoulder, CO

Sponsors: NIST and American Society of MechanicalEngineers.Audience: International, industrial, governmental, andacademic scientists, and engineers.Format: Plenary and parallel sessions.Purpose: Theoretical, experimental, and appliedaspects of thermophysical properties of gases, liquidsand solids will be covered by invited and contributedpapers.Topics: Equilibrium and non-equilibrium thermo-dynamics, supercritical fluids, refrigerants, aqueoussystems, advanced materials, condensed matter atextreme conditions, computer simulations, thin films,polymers, wetting and interfaces with natural gas,complex fluids, process design, optical and acoustictechniques, low gravity, critical behavior, fluid structureand databases.Technical Contact: William Haynes, NIST, 325Broadway, Boulder, CO 80303-3328, phone:303/497-3247, fax: 303/497-5044, email: [email protected], WWW Homepage:http://www.boulder.nist.gov/div838/symp13.

June 23–24, 1997TIME AND FREQUENCY

SEMINAR-INTRODUCTION LEVEL I

Location: The Broker InnBoulder, CO

Sponsor: NIST.Audience: Beginning mathematicians, scientists,engineers, and planners of time and frequency.Format: Lecture.Purpose: A variety of modern electronic systemsdepend critically on precise timing or an ultra-stablefrequency reference. The clocks and oscillators in suchsystems, therefore, must be characterized carefully. Thisseminar focuses on common methods of measuring andinterpreting oscillator and clock performance and howthese results affect overall system performance.Topics: Fundamentals of time and timekeeping, defini-tions of terms, and measurement methods and analysistechniques in the time domain and frequency.Technical Contact: David Howe, NIST, 325 Broad-way, Boulder, CO 80303-3328, phone: 303/497-3277,fax: 303/497-6461, email: [email protected].

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June 26–28, 1997TIME AND FREQUENCY

SEMINAR-LEVEL II

Location: The Broker InnBoulder, CO

Sponsor: NIST.Audience: Scientists, engineers, and laboratory techni-cians involved in the time and frequency system.Format: Lecture.Purpose: To learn specialized measurement techniquesfor quantifying frequency stability and spectral purityof an oscillator. Typical commercial oscillators andatomic frequency standards will be described withexplanations for their composite parts. An overview ofmethods of timekeeping and synchronization willfollow.Topics: Short-term stability, long-term stability,measurement techniques, noise statistics of oscillatorsignals, special purity measurement, performance andspecifications of quartz oscillators, characterization ofcommercial frequency standards, synchronization intelecom systems, timekeeping and time scales, and GPSand other dissemination services.Technical Contact: David Howe, NIST, 325 Broad-way, Boulder, CO 80303-3328, phone: 303/497-3277,fax: 303/497-6461, email: [email protected].

July 14–18, 19974th INTERNATIONAL MEETING ON

CHEMICAL KINETICS


Sponsors: NIST, Environmental Protection Agency(EPA), and the National Aeronautics and Space Admin-istration (NASA).Audience: Scientists.Format: Lectures and posters.Purpose: To bring together scientists from differentdisciplines who use chemical kinetics to explore areasof common interest.Topics: Free radical thermodynamics, reactions ofperoxyl radicals, halogen oxides, and others.Technical contact: Robert Huie, NIST, Building 222,Room A261, Gaithersburg, MD 20899-0001,phone: 301/975-2559, fax: 301/975-3672, email:[email protected], WWW Homepage: http://www.nist.gov/cstl/div838/kinet_conf/conference.html.

August 4-6, 1997WORKSHOP ON ULTRASONIC ANDDIELECTRIC CHARACTERIZATION

TECHNIQUES FOR SUSPENDEDPARTICULATES


Sponsors: NIST, American Ceramic Society, andAmerican Chemical Society Colloid Division.Audience: International scientists and engineers.Format: Invited and submitted plenary lectures.Purpose: To discuss most recent advances in theoryand instrumentation and share experience in specificmaterials applications for techniques based on high-frequency electric and acoustic fields.Topics: Electroacoustic spectroscopy, acoustic attenua-tion spectroscopy, dielectric spectroscopy, concentratedsuspensions and emulsions, and powder processing.Technical Contacts: Dr. Vince Hackley, NIST, Build-ing 223, Room A256, Gaithersburg, MD 20899-0001,phone: 301/975-5790, fax: 301/990-8729, email:[email protected]. Dr. John Texter, Eastman-Kodak Co., Rochester, NY 14650-2109, phone:716/477-3019, fax: 716/722-5411, email: [email protected], WWW Homepage: http://www.ceramics.nist.gov/events/udct/udct.htm

August 11–13, 19972ND ANNUAL WIRELESS

COMMUNICATIONS CONFERENCE

Location: Regal Harvest HouseBoulder, CO

Sponsors: NIST, International Microelectronics andPackaging Society, IEEE Communications Society-Pike’s Peak Chapter, IEEE Microwave Theory andTechniques Society, and Institute for Telecommunica-tions Science.Audience: Commercial wireless industry.Format: Single track, technical presentations, work-shop, panel discussion session, and exhibition.Purpose: The success of last year’s conference demon-strated the appeal of a symposium focused on techno-logical advances in the commercial wireless industry.Topics: Systems: PCS, cellular, paging, wirelessLANs, LMDS, etc.; active components; passive compo-nents; packaging; antennas, propagation, compatibility,and interference; and measurements.

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Technical Contact: Chairman Roger Marks, NIST,325 Broadway, Boulder, CO 80303-3328, phone:303/497-3037, fax: 303/497-7828, email: [email protected]. Technical Program Chair: Michael S.Heutmaker, Lucent Technologies, P.O. Box 900,RM2-2063, Princeton, NJ 08542-0900, phone:609/639-3116, fax: 609/639-3197, email: [email protected]. WWW Homepage: http://www.boulder.nist.gov/wcc.

August 11-15, 19972ND INTERNATIONAL CONFERENCE ON

FIRE RESEARCH AND ENGINEERING


Sponsors: NIST and Society of Fire ProtectionEngineers.Audience: Grantees, other agencies, private industry,fire protection engineers, and consultants in the fireresearch area.Format: Technical presentations, workshops, and casestudies.Purpose: To bring together leaders in the fire researchand fire safety engineering communities from aroundthe world.Topic: Fire safety applications.Technical Contact: Nora Jason, NIST, Building 224,Room A252, Gaithersburg, MD 20899-0001, phone:301/975-6862, fax: 301/975-4052, email: [email protected].

August 18–22, 1997INTERNATIONAL CONFERENCE ON

FUNDAMENTALS OF FRACTURE


Sponsors: NIST and Institute for Mechanics andMaterials (IMM).Audience: Scientists.Format: Lecture.

Purpose: The goals of the conference will be toprovide a vehicle for the presentation and discussion ofcurrent research and future challenges in fracturescience. The focus is on the fundamental aspects offracture in the disciplines of mechanics, metallurgy,ceramics, polymer science, physics and chemistry.Topics: Fracture in materials.Technical Contact: Robb Thomson, NIST, Building223, Room A124, Gaithersburg, MD 20899-0001,phone: 301/975-5665, fax: 301/926-8349, email:[email protected], WWW Homepage: http://www.ctcms.nist.gov/~robb/icff.html.

Tutorials-September 22, 1997Conference-September 23-25, 1997INTELLIGENT SYSTEMS AND

APPLIED SEMIOTICS ’97A LEARNING PERSPECTIVE (ISAS ’97)


Sponsors: Institute of Electrical and ElectronicsEngineering, National Science Foundation, ArmyResearch Office, and NIST.Audience: Leading researchers in the area of intelli-gent systems, including design and application.Format: The conference will be organized in threeparallel tracks including nine workshops, preceded by aday of relevant tutorials.Purpose: This meeting is dedicated to applied semi-otics and its application in large and complex systems,including intelligent machines. ISAS ’97 will focus onlearning processes.Topics: Learning in large symbolic structures, systemsof symbol and knowledge representation emerging fromlearning processes, and systems and machines designedto acquire knowledge and act intelligently.Technical Contact: Richard Quintero, NIST, Building220, Room B124, Gaithersburg, MD 20899-0001,phone: 301/975-3445, fax: 301/998-9688, email:[email protected], WWW Homepage: http://isd.cme.nist.gov/proj/semiotics97.

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May–June 1995

Volume 100, Number 3

Journal of Research of the

National

Institute of

Standards and

Technology

U.S. Department of Commerce

Technology Administration

National Institute of Standards and Technology

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,Building 820, Room 232, Gaithersburg, MD 20899-0001, telephone: 301-975-2002, fax:301-948-3825.

Special Publication 811

1995 Edition

Guide for the Use of the International

System of Units (SI)

Barry N. Taylor

United States Department of Commerce



Evaluating and Expressing the Uncertaintyof Measurement Results

Uncertain about expressing measure-ment uncertainty? Do you need to knowhow NIST states the uncertainty of its mea-surement results and how you can imple-ment their internationally accepted methodin your own laboratory? Then you need thenewly available 1994 edition of theNational Institute of Standards and Tech-nology Technical Note 1297,Guidelinesfor Evaluating and Expressing the Uncer-tainty of NIST Measurement Results.

The 1994 edition of the National Institute of Standards and Technology Technical Note 1297,Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, by BarryN. Taylor and Chris E. Kuyatt is now available.

The 1994 edition of TN 1297 includes a new appendix—Appendix D—which clarifies and givesadditional guidance on a number of topics related to measurement uncertainty, including the useof certain terms such as accuracy and precision. Very minor word changes have also been madein a few portions of the text of the 1993 edition in order to recognize the official publication inOctober 1993 by the International Organization for Standardization (ISO) of theGuide to theExpression of Uncertainty in Measurementon which TN 1297 is based. However, the NIST policyon measurement uncertainty, Statements of Uncertainty Associated with Measurement Results,which is reproduced as Appendix C of TN 1297, is unchanged.

It is expected that the 1994 edition of TN 1297 will be even more useful than its immediatepredecessor, the 1993 edition, of which 10 000 copies were distributed worldwide.

Those United States readers who wish to delve into the subject of measurement uncertainty ingreater depth may purchase a copy of the 100-page ISOGuidefrom the Sales Department of theAmerican National Standards Institute (ANSI), 105-111 South State Street, Hackensack,NJ 07601. Copies may also be purchased from the ISO Central Secretariat, 1 rue de Varembe´,Case postale 56, CH-1211 Gene`ve 20, Switzerland.

Single copies of the 20-page TN 1297 may be obtained from the NIST Calibration Program,Building 820, Room 232, Gaithersburg, MD 20899-0001, telephone: 301-975-2002,fax: 301-948-3825.

NIST Technical Note 1297

1994 Edition

Guidelines for Evaluating and Expressing

the Uncertainty of NIST Measurement Results

Barry N. Taylor and Chris E. Kuyatt

United States Department of Commerce



NISTTechnical PublicationsPeriodical

Journal of Research of the National Institute of Standards and Technology—Reports NIST researchand development in those disciplines of the physical and engineering sciences in which the Institute isactive. These include physics, chemistry, engineering, mathematics, and computer sciences. Papers cover abroad range of subjects, with major emphasis on measurement methodology and thebasic technologyunderlying standardization. Also included from time to time are survey articles on topics closely related tothe Institute’s technical and scientific programs. Issued six times a year.

Nonperiodicals

Monographs—Major contributions to the technical literature on various subjects related to theInstitute’s scientific and technical activities.Handbooks—Recommended codes of engineering and industrial practice (including safety codes) devel-oped in cooperation with interested industries, professional organizations, and regulatory bodies.Special Publications—Include proceedings of conferences sponsored by NIST, NIST annual reports, andother special publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

National Standard Reference Data Series—Provides quantitative data on the physical and chemicalproperties of materials, compiled from the world’s literature and critically evaluated. Developed under aworldwide program coordinated by NIST under the authority of the National Standard Data Act (PublicLaw 90-396). NOTE: The Journal of Physical and Chemical Reference Data (JPCRD) is publishedbimonthly for NIST by the American Chemical Society (ACS) and the American Institute of Physics (AIP).Subscriptions, reprints, and supplements are available from ACS, 1155 Sixteenth St., NW, Washington, DC20056.Building Science Series—Disseminates technical information developed at the Institute on buildingmaterials, components, systems, and whole structures. The series presents research results, test methods, andperformance criteria related to the structural and environmental functions and the durability and safetycharacteristics of building elements and systems.Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment ofa subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of thesubject area. Often serve as a vehicle for final reports of work performed at NIST under the sponsorship ofother government agencies.Voluntary Product Standards—Developed under procedures published by the Department of Commercein Part 10, Title 15, of the Code of Federal Regulations. The standards establish nationally recognizedrequirements for products, and provide all concerned interests with a basis for common understanding ofthe characteristics of the products. NIST administers this program in support of the efforts of private-sectorstandardizing organizations.

Order thefollowing NIST publications—FIPS and NISTIRs—from the National Technical InformationService, Springfield, VA 22161.Federal Information Processing Standards Publications (FIPS PUB)—Publications in this seriescollectively constitute the Federal Information Processing Standards Register. The Register serves as theofficial source of information in the Federal Government regarding standards issued by NIST pursuant tothe Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat.1127), and as implemented by Executive Order 11717 (38 FR 12315, dated May 11, 1973) and Part 6 ofTitle 15 CFR (Code of Federal Regulations).NIST Interagency Reports (NISTIR)—A special series of interim or final reports on work performed byNIST for outside sponsors (both government and nongovernment). In general, initial distribution is handledby the sponsor; public distribution is by the National Technical Information Service, Springfield, VA 22161,in paper copy or microfiche form.

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