Journal of Research of the National Institute of Standards and Technology

Ultraviolet-C (UV-C) decontamination holds promise in combating the coronavirus disease 2019 pandemic, particularly with its potential to mitigate the N95 respirator shortage. Safe, effective, and reproducible decontamination depends critically on UV-C dose, yet dose is frequently measured and reported incorrectly, which results in misleading and potentially harmful protocols. Understanding best practices in UV-C dose measurement for N95 respirator decontamination is essential to the safety of medical professionals, researchers, and the public...

To calibrate laser power and energy meters, the National Institute of Standards and Technology (NIST) uses several detector-based realizations of the scale for optical radiant flux; these realizations are appropriate for specific laser power/energy ranges and optical coupling configurations. Calibrations from 1 µW to 2 W are currently based upon calorimeters. Validation by comparisons against other primary representations of the optical watt over the last two decades suggests the instruments operate well within their typical reported uncertainty level of 0...

The reflectivity of material lining the inside of a disinfection chamber can have a dramatic effect on the ultraviolet-C (UV-C) radiation dose received across all sides of a contaminated object. Because minimum UV-C dosages are required to reliably inactivate microorganisms, it is crucial for the disinfection chamber to have either multiple UV-C sources or a highly reflective internal surface. This article describes an experimental comparison of four different materials, polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene, silver gloss self-adhesive aluminum, and Rosco matte black Cinefoil, to determine their efficacy as UV-C reflectors by using a custom-designed testing apparatus utilizing a UV-C radiation-emitting diode alongside photochromic UV-C indicators, allowing for a full 360° analysis of a target object and its received UV-C dose...

The National Institute of Standards and Technology (NIST) hosted an international workshop on ultraviolet-C (UV-C) disinfection technologies on January 14-15, 2020, in Gaithersburg, Maryland, in collaboration with the International Ultraviolet Association (IUVA). This successful public event, as evidenced by the participation of more than 150 attendees, with 65% from the ultraviolet technology industry, was part of an ongoing collaborative effort between NIST and the IUVA and its affiliates to examine the measurement and standards needs for pathogen abatement with UV-C in the healthcare whole-room environment...

The development of an international, precompetitive, collaborative, ultraviolet (UV) research consortium is discussed as an opportunity to lay the groundwork for a new UV commercial industry and the supply chain to support this industry. History has demonstrated that consortia can offer promising approaches to solve many common, current industry challenges, such as the paucity of data regarding the doses of ultraviolet-C (UV-C, 200 nm to 280 nm) radiation necessary to achieve the desired reductions in healthcare pathogens and the ability of mobile disinfection devices to deliver adequate doses to the different types of surfaces in a whole-room environment...

Ultraviolet (UV) radiation in the wavelength range 200 nm ≤ λ ≤ 320 nm, which includes both the UV-C and UV-B portions of the spectrum, is known to be effective for inactivation of a wide range of microbial pathogens, including viruses. Previous research has indicated UV-C radiation to be effective for inactivation of severe acute respiratory syndrome coronavirus (SARS-CoV), the virus that caused an outbreak of SARS in 2003. Given the structural similarities of SARS-CoV and SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), it is anticipated that UV radiation should be effective for inactivation of SARS-CoV-2 too...

The tragedy of the radium poisoning of young women dial painters in the 1920s has been the subject of best-selling books, plays, and motion pictures. With knowledge about radium and its accurate measurements in the hands of a very few scientists, what responsibilities did they have to sound the alarm and mitigate the hazards to workers and the general public? This two-part analysis looks at the role of the staff of the U.S. Bureau of Standards (the National Bureau of Standards [NBS] after 1934) in developing measurements and standards for accurate determinations of radium-226 and radon-222 that ultimately led to national standards for exposure to radioactive substances...

The National Institute of Standards and Technology (NIST) developed an experimental technique to measure the dynamic flow stress of metals under rapid heating to study their time-dependent plastic response when heating times are short enough to interrupt or bypass thermally driven microstructural evolution. Such conditions may exist as chips are formed in the machining process. Measurements of American Iron and Steel Institute1045 steel behavior up to 1000 °C showed complex thermal softening due to dynamic strain aging effects and the diffusion-limited austenite transformation process beginning at the A1 temperature (712 °C)...

A documentary standard produced by the American Society of Mechanical Engineers (ASME) for performance evaluation of industrial X-ray computed tomography (XCT) systems for dimensional measurements was released in early 2021. This standard, ASME B89.4.23-2020, specifies test procedures that may be performed to determine whether a system meets the manufacturer's accuracy specifications for acceptance before or after purchase, or for periodic reverification. While there are some core testing requirements in the standard, there is also some flexibility, allowing for a variety of testing configurations that meet the requirements of the standard...

We present a new paradigm for the primary standardization of radionuclide activity per mass of solution (Bq/g). Two key enabling capabilities are 4π decay-energy spectrometry using chip-scale sub-Kelvin microcalorimeters and direct realization of mass by gravimetric inkjet dispensing using an electrostatic force balance. In contrast to traditional traceability, which typically relies on chemical separation of single-radionuclide samples, 4π integral counting, and additional spectrometry methods to verify purity, the system described here has both 4π counting efficiency and spectroscopic resolution sufficient to identify multiple radionuclides in the same sample at once...

The NIST Vacuum Double-Crystal Spectrometer (VDCS) has been modernized and is now capable of recording reference-free wavelength-dispersive spectra in the 2 keV to 12 keV x-ray energy range. The VDCS employs crystals in which the lattice spacings are traceable to the definition of the meter through x-ray optical interferometry with a relative uncertainty ﹤10-⁸. VDCS wavelength determination relies upon precision angle difference measurements for which the encoders of the rotation stages have been calibrated using the circle closure method for accurate, absolute angle measurement...

This paper describes advances in measuring the characteristic spatial distribution of surface temperature and emissivity during laser-metal interaction under conditions relevant for laser powder bed fusion (LPBF) additive manufacturing processes. Detailed descriptions of the measurement process, results, and approaches to determining uncertainties are provided. Measurement uncertainties have complex dependencies on multiple process parameters, so the methodology is demonstrated on one set of process parameters and one material...

A method is described for inactivation of pathogens, especially airborne pathogens, using ultraviolet (UV) radiation emitted directly into occupied spaces and exposing occupants to a dose below the accepted actinic exposure limit (EL). This method is referred to as direct irradiation below exposure limits, or DIBEL. It is demonstrated herein that low-intensity UV radiation below exposure limits can achieve high levels of equivalent air changes per hour (ACHeq ) and can be an effective component of efforts to combat airborne pathogens such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19)...

With steadily increasing use in dimensional metrology applications, especially for delicate parts and those with complex internal features, X-ray computed tomography (XCT) has transitioned from a medical imaging tool to an inspection tool in industrial metrology. This has resulted in the demand for standardized test procedures and performance evaluation standards to enable reliable comparison of different instruments and support claims of metrological traceability. To meet these emerging needs, the American Society of Mechanical Engineers (ASME) recently released the B89...

Ultraviolet-C (UV-C) radiation exposure is an attractive option for rapid and consistent disinfection of interior surfaces in aircraft cabins. In this study, fabric and plastic materials commonly used in aircraft cabins were exposed to UV-C radiation to determine their sensitivity to cumulative damage from frequent application. No significant effect on flame retardancy occurred up to 269 J/cm2 dose, and no effect on tensile or tear strength occurred up to 191 J/cm2 . Changes in color or appearance can occur at lower doses...

A portable calorimeter for direct realization of absorbed dose in medical computed tomography (CT) procedures was constructed and tested in a positron emission tomography (PET) CT scanner. The calorimeter consists of two small thermistors embedded in a polystyrene (PS) cylindrical "core" (1.5 cm diameter) that can be inserted into a cylindrical high-density polyethylene (HDPE) phantom (30 cm diameter). The cylindrical design of core and phantom allows coaxial alignment of the system with the scanner rotation axis, which is necessary to minimize variations in dose that would otherwise occur as the X-ray source is rotated during scanning operations...

The multi-source common-view disciplined clock (MSCVDC) is a recent NIST invention designed to support critical infrastructure timing systems that require a verifiably accurate and fail-safe clock. This paper introduces the MSCVDC, provides a technical description of how it works, and discusses its reliability, redundancy, security, and performance. It also discusses the possibility of a commercially available MSCVDC product.

Uniaxial tensile tests are routinely conducted to obtain stress-strain data for forming applications. It is important to understand the deformation behavior of test specimens at plastic strains, temperatures, and strain rates typically encountered in metal forming processes. In this study, the Johnson-Cook (J-C) flow stress model was used to describe the constitutive behavior of ASTM International (ASTM) A 1008 steel specimens during uniaxial tensile tests at three different average strain rates (10-⁵ s-¹, 10-³ s-¹, and 10-¹ s-¹)...

Three types of uncertainties exist in the estimation of the minimum fracture strength of a full-scale component or structure size. The first, to be called the "model selection uncertainty," is in selecting a statistical distribution that best fits the laboratory test data. The second, to be called the "laboratory-scale strength uncertainty," is in estimating model parameters of a specific distribution from which the minimum failure strength of a material at a certain confidence level is estimated using the laboratory test data...

Disinfection of surfaces by ultraviolet-C (UV-C) radiation is gaining importance in diverse applications. However, there is generally no accepted computational procedure to determine the minimum irradiation times and UV-C doses required for reliable and secure disinfection of surfaces. UV-C dose distributions must be comparable for devices presently on the market and future ones, as well as for the diverse surfaces of objects to be disinfected. A mathematical model is presented to estimate irradiance distributions...