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We report on a recent workshop dedicated to additive manufacturing (AM) of ceramics that was held at the National Institute of Standards and Technology (NIST) in November 2019. This two-day all-invited meeting brought together experts from industry, government agencies and academia to review the state of the field and identify the most pressing applied materials research and metrology issues which, if addressed, could accelerate the incorporation of AM methods into commercial ceramic manufacturing. Besides the AM technologies, the discussions included consideration of the necessary post-processing steps. We highlight some of the successes and challenges for the adoption of ceramics AM on an industrial scale, as viewed by the workshop participants. We also propose actions for the ceramic community to facilitate the wider commercialization of these fabrication methods.

PURPOSE To investigate the variability and stability of brachytherapy source strength calibration coefficients for air-communicating and pressurized well-type ionization chambers among high-dose rate (HDR), low-dose rate (LDR), and electronic brachytherapy (EBT) source qualities. These qualities of an ionization chamber are important features to assess given their role in maintaining traceability to a primary national standards laboratory and facilitating efficacious patient care in brachytherapy. METHODS The calibration records from the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) customer well-type ionization chamber database were retrospectively analyzed for calibrations performed between 1996 and 2019. A statistical analysis was performed and differentiated among calibration type to quantify the distribution of chamber calibration coefficients among several chamber models. Distributions were quantified based on their moments and by quantile analysis. For LDR calibrations, chamber response was further differentiated by seed type to study the variability in seed dependence within and across chamber models. In addition to these metrics, the calibration lineage at the UWADCL was used to assess the stability of these calibration coefficients among chamber model and source type based on the ratio of subsequent calibration coefficients. RESULTS The distribution of brachytherapy source strength calibration coefficients for a particular chamber model is not necessarily normally distributed and is sensitive to changes in the machining tolerances or design of the chamber model. Calibration source quality also influenced the distributions of calibration coefficients for a chamber model; the air-kerma rate calibration coefficients for EBT sources were the most variable followed by LDR and then HDR source types. The stability of a chamber's source strength calibration coefficient exhibited a similar dependence on the source quality. Air-communicating and pressurized chambers exhibited an average stability between subsequent calibrations of 0.2% and 3.0%, respectively, for HDR calibrations, but could exhibit more than double this variability characteristic of their leptokurtic distributions. For LDR calibrations, the spread and stability in a model's calibration ratio toward another seed type is extensive and notable. For some seed types and chamber models exhibit variations of

A critical component of many tissue-engineered medical products (TEMPs) is the scaffold or biomaterial. The industry's understanding of scaffold properties and their influence on cell behavior has advanced, but our technical capability to reliably characterize scaffolds requires improvement, especially to enable large-scale manufacturing. In response to the key findings from the 2013 ASTM International Workshop of Standards and Measurements for Tissue Engineering Scaffolds, the National Institute of Standards and Technology (NIST), ASTM International, BiofabUSA, and the Standards Coordinating Body (SCB) organized a workshop in 2018 titled, "Characterization of Fiber-Based Scaffolds". The goal was to convene a group of 40 key industry stakeholders to identify major roadblocks in measurements of fiber-based scaffold properties. This report provides an overview of the findings from this collaborative workshop. The four major consensus findings were that (a) there is need for a documentary standard guide that would aid developers in the selection of test methods for characterizing fiber-based scaffolds; (b) there is a need for a strategy to assess the quality of porosity and pore size measurements, which could potentially be ameliorated by the development of a reference material; (b) there are challenges with the lexicon used to describe and assess scaffolds; and (d) the vast array of product applications makes it challenging to identify consensus test methods. As a result of these findings, a working group was formed to develop an ASTM Standard Guide for Characterizing Fiber-Based Constructs that will provide developers guidance on selecting measurements for characterizing fiber-based scaffolds.

Purpose Before MR fingerprinting (MRF) can be adopted clinically, the derived quantitative values must be proven accurate and repeatable over a range of T1 and T2 values and temperatures. Correct assessment of accuracy and precision as well as comparison between measurements can only be performed when temperature is either controlled or corrected for. The purpose of this study was to investigate the temperature dependence of T1 and T2 MRF values and evaluate the accuracy and repeatability of temperature-corrected relaxation values derived from a B1-corrected MRF–fast imaging with steady-state precession implementation using 2 different dictionary sizes. Methods The International Society of MR in Medicine/National Institute of Standards and Technology phantom was scanned using an MRF sequence of 2 different lengths, a variable flip angle T1, and a multi-echo spin echo T2 at 14 temperatures ranging from 15°C to 28°C and investigated with a linear regression model. Temperature-corrected accuracy was evaluated by correlating T1 and T2 times from each MRF dictionary with reference values. Repeatability was assessed using the coefficient of variation, with measurements taken over 30 separate sessions. Results There was a statistically significant fit of the model for MRF-derived T1 and T2 and temperature (p < 0.05) for all the spheres with a T1 > 500 ms. Both MRF methods showed a strong linear correlation with reference values for T1 (R2 = 0.996) and T2 (R2 = 0.982). MRF repeatability for T1 values was ≤1.4% and for T2 values was ≤3.4%. Conclusion MRF demonstrated relaxation times with a temperature dependence similar to that of conventional mapping methods. Temperature-corrected T1 and T2 values from both dictionaries showed adequate accuracy and excellent repeatability in this phantom study.

BACKGROUND Scanner upgrades due to software and hardware changes are an inevitable part of MR research and, without quality assurance protocols, can jeopardize studies. PURPOSE To evaluate changes in T1 relaxation time by inversion recovery (IR) and variable flip angle (VFA) measurements on a 3T system that underwent an "everything but the magnet" upgrade. STUDY TYPE Longitudinal. PHANTOM An International Society of Magnetic Resonance in Medicine / National Institute of Standards and Technology (ISMRM/NIST) system phantom with repeated measurements across multiple (n = 3) days. FIELD STRENGTH/SEQUENCE T1 IR, VFA at 3T. ASSESSMENT The T1 measurements by IR and VFA were compared with the nuclear magnetic resonance (NMR) measurements, which constitute the known values for the ISMRM/NIST system phantom, to determine the measurement error. STATISTICAL TESTS Descriptive. RESULTS The T1 VFA measurement errors were distributed around zero (-15% to +10%) on the original system and then the errors were distributed entirely above zero post-upgrade (+5% to 30%). The T1 IR results had a dramatic increase in error distribution (±5% original, ±20% post-upgrade) prior to the identification of signal saturation as an issue. Once the signal saturation was accounted for, the T1 IR errors decreased to ±10% post-upgrade. DATA CONCLUSION The T1 VFA measurement differences between the original and post-upgrade systems can be entirely attributed to contributions from B1 . The T1 IR measurements demonstrate the need for quantitative quality assurance (QA) processes. The site under study passed the QA protocols in place, which did not identify the increased T1 error, nor the signal saturation issue. To improve on this study, we would make systematic, quantitative measurements at intervals less than a year and following any hardware or software upgrade. LEVEL OF EVIDENCE 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2019;50:1948-1954.

Rationale In recent years, the primary reference material (RM) for the VPDB scale, NBS19, has become unavailable, and the RM used for low-end scale-anchoring, LSVEC, was found unsuitable due a drift in the δ13 C value. Given these problems, new RMs aimed at realising the VPDB δ13 C scale with low uncertainty were produced. Establishing the consistency of the new RMs with the "old" RMs prompted our revision of the underlying principles of RM value assignments, and the VPDB δ13 C scale realisation and its long-term sustainability. Methods Analysis of major developments of the VPDB scale, a review of the contemporary requirements for RMs, and comparison with well-established measurement scales have been performed, with the aim of revising the VPDB δ13 C scale, principles of RM value assignments, and calibrator hierarchy. Requirements for scale-anchoring RMs with low uncertainty and measures to establish the scale sustainability have been formulated. Results The revised scale realisation is based on multiple reference points, well-defined calibration hierarchy and the use of well-understood methods for value assignment. The realisation scheme includes the new primary RM IAEA-603 and scale-anchoring RMs IAEA-610, IAEA-611 and IAEA-612, covering δ13 C from +2.46 to -36.7 ‰ VPDB, with uncertainties, including inhomogeneity and stability assessment, of less than 0.015 ‰. The values of these four RMs were assigned in a mutually consistent way; agreement between measurements made using this realisation with those made using the VPDB scale of 2006 has been demonstrated on NIST CO2 RMs 8562-8564. Conclusions Multipoint-anchoring of the VPDB δ13 C scale provides several distinct "points" on the scale as means for cross-measurements to check the stability and viability of RMs and detect drift of values, if any. This ensures that the δ13 C scale is suitable for the most demanding applications, and provides options for developing further RMs with high accuracy inside a robust scale realisation scheme.

The iSwathX web application processes and normalizes mass spectrometry-based proteomics spectral libraries generated in the data-dependent acquisition (DDA) approach. These libraries are stored in various proteomics repositories such as PeptideAtlas and NIST, or are user-generated and provide reference data for data-independent acquisition (DIA) targeted data extraction and analysis. iSwathX 2.0 can efficiently normalize DDA data from different instruments, gathered at different instances, and make it compatible with specific DIA experiments. Novel functions for parallel processing of DDA libraries and DIA report files, along with various data visualizations, are available in iSwathX 2.0. The step-by-step protocols provided here describe how the libraries are uploaded, processed, visualized, and downloaded using various modules of the application. They also provide detailed guidelines on the use of DIA report files for data analysis and visualization. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Processing, combining, and visualizing two DDA libraries Basic Protocol 2: Parallel processing and combination of multiple DDA libraries Basic Protocol 3: Downstream processing, comparison, and visualization of DIA report files.

The same-source problem remains a major challenge in forensic toolmark and firearm examination. Here, we investigate the applicability of the Chumbley method (J Forensic Sci, 2018, 63, 849; J Forensic Sci, 2010, 55, 953) (10,12), developed for screwdriver markings, for same-source identification of striations on bullet LEAs. The Hamby datasets 44 and 252 measured by NIST and CSAFE (high-resolution scans) are used here. We provide methods to identify parameters that minimize error rates for matching of LEAs, and a remedial algorithm to alleviate the problem of failed tests, while increasing the power of the test and reducing error rates. For 85,491 land-to-land comparisons (84,235 known nonmatches and 1256 known matches), the adapted test does not provide a result in 176 situations (originally more than 500). The Type I and Type II error rates are 7.2% (6105 out of 84,235) and 21.4% (271 out of 1256), respectively. This puts the proposed method on similar footing as other single-feature matching approaches in the literature.

Experimental and analytical studies on the cyclic behaviour of deep, slender wide-flange steel beam-columns funded by the National Institute of Standards and Technology (NIST) is ongoing at the University of California at San Diego (UCSD). In parallel with full-scale column tests, numerical simulations of columns under monotonic and cyclic loading conditions were conducted to generate a wide-ranging database of results. A correlation study using results from the full-scale tests was conducted to validate the numerical simulation procedure. The simulated columns covered a wide range of cross-sectional (local) and member (global) slenderness ratios, axial force level, and yield stress. Regression analyses were conducted to construct moment-rotation responses, ‘backbone curves’, for use in performance-based evaluations of steel moment frames. The database is divided into three groups based on observed buckling modes. Computational expressions for the key parameters that define the backbone curves are presented.

Summary This paper presents implementation of a chaotic cellular neural network (CNN)-based true random number generator on a field programmable gate array (FPGA) board. In this implementation, discrete time model of the chaotic CNN is used as the entropy source. Random number series are generated for three scenarios. Obtained number series are tested by using NIST 800.22 statistical test suite. Also, the scale index technique is carried out for these three scenarios to determine the degree of non-periodicity for key stream. Copyright © 2017 John Wiley & Sons, Ltd.

Gas chromatography-mass spectrometry (GC-MS) is an important analytical technique for the analysis of organophosphorus pesticides in food products. Because of the complex matrices of food products, multiple preprocessing steps are required prior to performing the GC-MS analysis. Despite that, it is difficult to totally eliminate the interference of complex matrix background. In this work, we introduce an entropy minimization technique that can eliminate the need for comprehensive preprocessing steps to detect organophosphorus pesticides in a fortified orange juice sample. The pure mass spectra and extracted-ion chromatograms of the pesticides were extracted and reconstructed. The results achieved higher National Institute of Standard and Technology (NIST) match scores in comparison to the conventional background subtraction technique. Taken together, the entropy minimization technique is capable of providing rapid qualitative and quantitative analyses of complex GC-MS data. This technique is expected to have great potential for natural products and food analysis applications.

Tandem mass spectral library search (MS/MS) is the fastest way to correctly annotate MS/MS spectra from screening small molecules in fields such as environmental analysis, drug screening, lipid analysis, and metabolomics. The confidence in MS/MS-based annotation of chemical structures is impacted by instrumental settings and requirements, data acquisition modes including data-dependent and data-independent methods, library scoring algorithms, as well as post-curation steps. We critically discuss parameters that influence search results, such as mass accuracy, precursor ion isolation width, intensity thresholds, centroiding algorithms, and acquisition speed. A range of publicly and commercially available MS/MS databases such as NIST, MassBank, MoNA, LipidBlast, Wiley MSforID, and METLIN are surveyed. In addition, software tools including NIST MS Search, MS-DIAL, Mass Frontier, SmileMS, Mass++, and XCMS(2) to perform fast MS/MS search are discussed. MS/MS scoring algorithms and challenges during compound annotation are reviewed. Advanced methods such as the in silico generation of tandem mass spectra using quantum chemistry and machine learning methods are covered. Community efforts for curation and sharing of tandem mass spectra that will allow for faster distribution of scientific discoveries are discussed.

INAA, ICP-AES and ICP-MS were used to elementally characterise four environmental reference materials – NIST SRM 1646a (Estuarine Sediment), NIST SRM 1400 (Bone Ash), IAEA-395 (Urban Dust) and IAEA-450 (Algae). An analytical scheme consisting of the three methods was first applied to NIST SRM 1646a to validate the methodology because it has been extensively analysed and has certified values for many elements. With repeated analyses of NIST SRM 1646a, the accuracy and measurement repeatability of the data obtained were evaluated based on two statistical calculations (zeta-score and Horwitz ratio) and were observed to be good enough for the analytical scheme to be applied to similar sorts of environmental/geochemical samples. Applying the same approach to NIST SRM 1400, IAEA-395 and IAEA-450, enabled mass fractions of 29, 38 and 28 elements to be determined, respectively. Among these results, the data for rare earth elements are of particular interest, not only for IAEA-450 but also for the other three reference samples. The data for Pr, Gd, Dy, Ho, Er and Tm in NIST SRM 1646a are newly reported in this study. By using small test portions (

Summary Piecewise linear one-dimensional maps have been proposed as the basis for low-power analog and mixed-signal true random number generators (TRNGs). Recent research has moved towards conceiving maps that operate robustly under the consideration of parameter variations. In this paper, we introduce an oscillator circuit mapping a low-complexity map known as the skew-tent. This oscillator is employed as the basis for a TRNG scheme. Simulation results in TSMC 0.18 μm validate the chaotic oscillator and the randomness of the TRNG scheme is verified with the NIST test suite 800-22. Copyright © 2016 John Wiley & Sons, Ltd.

Electrospray Ionization and collision induced dissociation tandem mass spectrometry are usually employed to obtain compound identification through a mass spectra match. Different algorithms have been developed for this purpose (for example the nist match algorithm). These approaches compare the tandem mass spectra of the unknown analyte with the tandem mass spectra spectra of known compounds inserted in a database. The compounds are usually identified on the basis of spectral match value associated with a probability of recognition. However, this approach is not usually applied to multiple reaction monitoring transition spectra achieved by means of triple quadrupole apparatus, mainly due to the lack of a transition spectra database. The Surface Activated Chemical Ionization-Electrospray-NIST Bayesian model database search (SANIST) platform has been recently developed for new potential metabolite biomarker discovery, to confirm their identity and to use them for clinical and diagnostic applications. Here, we present an improved version of the SANIST platform that extends its application to forensic, pharmaceutical, and food analysis studies, where the compound identification rules are strict. The European Union (EU) has set directives for compound identification (EU directive 2002/657/EC). We have applied the SANIST method to identification of 11-nor-9-carboxytetrahydro-cannabinol in urine samples (an example of a forensic application), circulating levels of the immunosuppressive drug tacrolimus in blood (an example of a pharmaceutical application) and glyphosate in fruit juice (an example of a food analysis application) that meet the EU directive requirements. Copyright © 2016 John Wiley & Sons, Ltd.

Purpose The purpose of this study was to evaluate accuracy and repeatability of T1 and T2 estimates of a MR fingerprinting (MRF) method using the ISMRM/NIST MRI system phantom. Methods The ISMRM/NIST MRI system phantom contains multiple compartments with standardized T1, T2, and proton density values. Conventional inversion-recovery spin echo and spin echo methods were used to characterize the T1 and T2 values in the phantom. The phantom was scanned using the MRF-FISP method over 34 consecutive days. The mean T1 and T2 values were compared with the values from the spin echo methods. The repeatability was characterized as the coefficient of variation of the measurements over 34 days. Results T1 and T2 values from MRF-FISP over 34 days showed a strong linear correlation with the measurements from the spin echo methods (R2 = 0.999 for T1; R2 = 0.996 for T2). The MRF estimates over the wide ranges of T1 and T2 values have less than 5% variation, except for the shortest T2 relaxation times where the method still maintains less than 8% variation. Conclusion MRF measurements of T1 and T2 are highly repeatable over time and across wide ranges of T1 and T2 values. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

A quantum random number generator (QRNG) based on a silicon nanocrystals (Si-NCs) light emitting device (LED) coupled with a silicon single photon avalanche photodiode (Si-SPAD) is presented. A simple setup is used for the generation of random bits. The modeled approach assures a negligible bias on datasets of ∼100 Mbits length. The raw data pass all the statistical tests in the National Institute of Standards and Technology (NIST) suite without any post-processing operations. The bit-rate of 0.6 Mbps is achieved. The information-theoretically provable randomness extractor of Toeplitz-hashing function is applied to longer datasets (∼1 Gbits) to extract the randomness, to minimize the bias, and consequently pass all the NIST tests. Stabilizing the temperature, resetting the applied current to the LED, or a feedback system can also be used as parameter control solutions to generate good quality, long datasets of random numbers suitable for cryptographic applications.

This article is intended to introduce and familiarize systems engineers with ongoing developments in the field of systems security engineering and particularly the effort to develop NIST Special Publication 800-160 Systems Security Engineering, which provides security considerations for engineering trustworthy secure systems.

This article delivers a look at current and evolving policy, guidance, and standards surrounding security activities in the systems engineering lifecycle. Emphasis is placed on systems security engineering (SSE) and how application of systems engineering concepts and processes in an agile manner (agile systems engineering) throughout the lifecycle is the way to deal with the dynamic and diverse world of cyber threats to a system (Dove 2014). This paper is a follow-on to “Response to Cyber Security Demands for Agility” (Nejib-Beyer 2014) published in the International Council on Systems Engineering (INCOSE) INSIGHT in 2014. The focus of that research was bringing attention to cyber security and the importance of other disciplines towards contributing to secure systems. Since that time many of these domains have further developed their own standards, processes, and guidance in the area of cyber security. What we require now is a way to take these domain-focused concepts and integrate them into and across a systems lifecycle. The best way to achieve this is as part of the systems engineering function. Designing and building secure systems requires a seamless integration of security into systems engineering processes and agile methodologies adopted to constantly revisit, reevaluate, and re-design as part of a risk management process. The framework that will be discussed in this paper will focus on taking currently evolving guidance in SSE and breaking that down into products and tools for systems engineers to easily determine the relationship and value between SSE and systems engineering. In addition, quick reference guides will further enhance and enable successful development and integration of SSE artifacts into systems engineering artifacts. One of the companion pieces needed in the existing SSE documentation is a mapping of work products/artifacts generated during the lifecycle/technical processes and the responsible and contributing parties. Critical to the success of the new guidance, such as the National Institute of Standards and Technology (NIST) Special Publication (SP) 800-160, Systems Security Engineering, is a clear accountability and acceptance of all disciplines on their contributions and influence towards developing a secure system. We present an SSE roles and responsibilities framework concept for consideration. The framework is an implementation tool to be used along with existing guidance in the area of SSE and systems engineering to clearly demonstrate that program protection is not the responsibility of any one person or discipline, it is the responsibility of an entire team of individuals planning, developing, deploying, operating & maintaining (O&M), and retiring a system. SSE is the “glue” that binds all of this together during the systems engineering lifecycle to enhance system security.

In this work, a self-contained numerical simulation tool for nanoscale Ion-Sensitive Field-Effect Transistor ISFET is developed. The tool is based on merging nanoscale ballistic MOSFET analytical equations with the Gouy-Chapman-Stern model equations of ISFET to form a system of nonlinear equations that can be solved iteratively to yield ISFET output current. The numerical solution is accomplished using Newton-Raphson method with efficient trust-region-dogleg algorithm using MATLAB software coding. The tool is used to optimize the sensitivity and linearity of nanoscale ISFETs, and to study their dependence on reference voltage, drain current level, and gate-insulator thickness. Moreover, a comparison between three types of insulators, SiO2, Si3N4, and Al2O3, has been made. The tool is given the name: NIST Nanoscale ISFET Simulation Tool. It can be used as a guide for design and optimization of nanoscale ISFETs and can be applied for both single-gate and double-gate structures. Copyright © 2016 John Wiley & Sons, Ltd.

In this study the homogeneity of the zinc isotopic composition in the NIST SRM 683 reference material was examined by measuring the Zn isotopic signature in microdrilled sample powders from two metal nuggets. Zinc was purified using AG MP-1M resin and then measured by MC-ICP-MS. Instrumental mass bias was corrected using the “sample-standard bracketing” method and empirical external normalisation with Cu doping. After evaluating the potential effects of varying acid mass fractions and different matrices, high-precision Zn isotope data were obtained with an intermediate measurement precision better than ± 0.05‰ (d 66 Zn, 2s) over a period of 5 months. The d 66 ZnJMC-Lyon mean values of eighty-four and fourteen drilled powders from two nuggets were 0.11 ± 0.02‰ and 0.12 ± 0.02‰, respectively, indicating that NIST SRM 683 is a good isotopic reference material with homogeneous Zn isotopes. The Zn isotopic compositions of seventeen rock reference materials were also determined, and their d 66 Zn values were in agreement with most previously published data within 2s. The d 66 Zn values of most of the rock reference materials analysed were in the range 0.22–0.36‰, except for GSP-2 (1.07 ± 0.06‰, n = 12), NOD-A-1 (0.96 ± 0.03‰, n = 6) and NOD-P-1 (0.78 ± 0.03‰, n = 6). These comprehensive data should serve as reference values for quality assurance and interlaboratory calibration exercises.

To enable quality control of measurement procedures for determinations of Mg isotope amount ratios, expressed as δ26Mg and δ25Mg values, in Earth-surface studies, the δ26Mg and δ25Mg values of eight reference materials (RMs) were determined by interlaboratory comparison between five laboratories and considering published data, if available. These matrix RMs, including river water SLRS-5, spring water NIST SRM 1640a, Dead Sea brine DSW-1, dolomites JDo-1 and BCS-CRM 512, limestone BCS-CRM 513, soil NIST SRM 2709a and vegetation NIST SRM 1515, are representative of a wide range of Earth-surface materials from low-temperature environments. The interlaboratory variability, 2s (twice the standard deviation), of all eight RMs ranges from 0.05 to 0.17‰ in δ26Mg. Thus, it is suggested that all these materials are suitable for validation of δ26Mg and δ25Mg determinations in Earth-surface geochemical studies.

Rationale Library-based compound identification with electron ionization (EI) mass spectrometry (MS) is a well-established identification method which provides the names and structures of sample compounds up to the isomer level. The library (such as NIST) search algorithm compares different EI mass spectra in the library's database with the measured EI mass spectrum, assigning each of them a similarity score called 'Match' and an overall identification probability. Cold EI, electron ionization of vibrationally cold molecules in supersonic molecular beams, provides mass spectra with all the standard EI fragment ions combined with enhanced Molecular Ions and high-mass fragments. As a result, Cold EI mass spectra differ from those provided by standard EI and tend to yield lower matching scores. However, in most cases, library identification actually improves with Cold EI, as library identification probabilities for the correct library mass spectra increase, despite the lower matching factors. Methods This research examined the way that enhanced molecular ion abundances affect library identification probability and the way that Cold EI mass spectra, which include enhanced molecular ions and high-mass fragment ions, typically improve library identification results. It involved several computer simulations, which incrementally modified the relative abundances of the various ions and analyzed the resulting mass spectra. Results The simulation results support previous measurements, showing that while enhanced molecular ion and high-mass fragment ions lower the matching factor of the correct library compound, the matching factors of the incorrect library candidates are lowered even more, resulting in a rise in the identification probability for the correct compound. Conclusions This behavior which was previously observed by analyzing Cold EI mass spectra can be explained by the fact that high-mass ions, and especially the molecular ion, characterize a compound more than low-mass ions and therefore carries more weight in library search identification algorithms. These ions are uniquely abundant in Cold EI, which therefore enables enhanced compound characterization along with improved NIST library based identification. Copyright © 2015 John Wiley & Sons, Ltd.

Image authentication includes techniques that detect unauthorized changes in digital pictures. Image authentication is generally categorized into two primary categories, active and passive methods. In this paper, a new active image authentication method is proposed for tamper detection based on contourlet transform. Cellular automata and 'Game of Life' are also used to improve the detection of tampered area. A pseudo-random number generator based on cellular automata has been used to improve security of proposed technique. We evaluates security and randomness of proposed pseudo-random number generator using by NIST statistical test suite. Experimental results show that the proposed method is sensitive to any tampers, and it can detect forged areas of the images. Visual quality of image after embedding process is desirable due to Peak Signal-to-Noise Ratio PSNR measure. Copyright © 2015 John Wiley & Sons, Ltd.

Performance of several library search algorithms (against EI mass spectral databases) implemented in commercial software products ( acd/specdb, chemstation, gc/ms solution and ms search) was estimated. Test set contained 1000 mass spectra, which were randomly selected from NIST'08 (RepLib) mass spectral database. It was shown that composite (also known as identity) algorithm implemented in ms search (NIST) software gives statistically the best results: the correct compound occupied the first position in the list of possible candidates in 81% of cases; the correct compound was within the list of top ten candidates in 98% of cases. It was found that use of presearch option can lead to rejection of the correct answer from the list of possible candidates (therefore presearch option should not be used, if possible). Overall performance of library search algorithms was estimated using receiver operating characteristic curves.

An efficient, clean procedure for the measurement of element mass fractions in bulk rock nanoparticulate pressed powder pellets (PPPs) by 193 nm laser ablation ICP-MS is presented. Samples were pulverised by wet milling and pelletised with microcrystalline cellulose as a binder, allowing non-cohesive materials such as quartz or ceramics to be processed. The LA-ICP-MS PPP analytical procedure was optimised and evaluated using six different geological reference materials (JP-1, UB-N, BCR-2, GSP-2, OKUM and MUH-1), with rigorous procedural blank quantification employing synthetic quartz. Measurement trueness of the procedure was equivalent to that achieved by solution ICP-MS and LA-ICPMS analysis of glass. The measurement repeatability was as low as 0.5–2% (1s, n = 6) and, accordingly, PPP homogeneity could be demonstrated. Calibration based on the reference glasses NIST SRM 610, NIST SRM 612, BCR- 2G and GSD-1G revealed matrix effects for glass and PPP measurement with NIST SRM 613; using basalt glasses eliminated this problem. Most significantly, trace elements not commonly measured (flux elements Li, B; chalcophile elements As, Sb, Tl, In, Bi) could be quantified. The PPP-LA-ICP-MS method overcomes common problems and limitations in analytical geochemistry and thus represents an efficient and accurate alternative for bulk rock analysis.

Compound identification is a critical process in metabolomics. The widely used approach for compound identification in gas chromatography-mass spectrometry (GC-MS) based metabolomics is the spectrum matching, in which the mass spectral similarity between an experimental mass spectrum and each mass spectrum in a reference library is calculated. While various similarity measures have been developed to improve the overall accuracy of compound identification, little attention has been paid to reducing the false discovery rate. We, therefore, develop an approach for controlling false identification rate using the distribution of the difference between the first and the second highest spectral similarity scores. We further propose a model-based approach to achieving a desired true positive rate. The developed method is applied to the NIST mass spectral library and its performance is compared with the conventional approach that uses only the maximum spectral similarity score. The results show that the developed method achieves a significantly higher F1 score and positive predictive value than those of the conventional approach.

The scanning electron microscope (SEM) has gone through a tremendous evolution to become indispensable for many and diverse scientific and industrial applications. The improvements have significantly enriched and augmented the overall SEM performance and have made the instrument far easier to operate. But, the ease of operation also might lead, through operator complacency, to poor results. In addition, the user friendliness has seemingly reduced the need for thorough operator training for using these complex instruments. One might then conclude that the SEM is just a very expensive digital camera or another peripheral device for a computer. Hence, a person using the instrument may be lulled into thinking that all of the potential pitfalls have been eliminated and they believe everything they see on the micrograph is always correct. But, this may not be the case. An earlier paper (Part 1), discussed some of the potential issues related to signal generation in the SEM, instrument calibration, electron beam interactions and the need for physics-based modeling to understand the actual image formation mechanisms. All these were summed together in a discussion of how these issues effect measurements made with the instrument. This second paper discusses another major issue confronting the microscopist: electron-beam-induced specimen contamination. Over the years, NIST has done a great deal of research into the issue of sample contamination and its removal and elimination and some of this work is reviewed and discussed here.

The use of laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) in the measurement of uranium concentration for fission-track (FT) dating can provide additional geochronological information by simultaneously acquiring data for U–Pb dating. To circumvent the use of several calibration factors with uncertainties in the FT age equation (i.e. the decay constant, values related to neutron irradiation, and observation efficiencies), the zeta calibration, which is based on the analysis of age-known standard samples, is recommended internationally. In this report, procedures to acquire LA-ICP-MS data for simultaneous dating by FT and U–Pb methods, the age equation with zeta-equivalent calibration, and the statistical treatment of FT age data, are proposed. An excimer laser beam with 20 μm diameter was used for sampling. We empirically determined zeta calibration constants against NIST SRM610 for FT zircon and apatite dating by analyzing several age standards. The data agreed with the calculated values, which can be obtained using reasonable constants in the equation. The correction factor in 238U–206Pb age determination with NIST SRM610 as an external standard was defined as 0.920 ± 0.034 by analyzing several standards (FCT, Plesovice, Duluth, GJ-1). Based on this calibration system, zircons from the Nisatai Dacite, Japan, which is a secondary age standard commonly used in the Japanese FT community, were simultaneously dated to be 22 Ma by FT and U–Pb methods on the same grains.

A tandem mass spectral database system consists of a library of reference spectra and a search program. State-of-the-art search programs show a high tolerance for variability in compound-specific fragmentation patterns produced by collision-induced decomposition and enable sensitive and specific 'identity search'. In this communication, performance characteristics of two search algorithms combined with the 'Wiley Registry of Tandem Mass Spectral Data, MSforID' (Wiley Registry MSMS, John Wiley and Sons, Hoboken, NJ, USA) were evaluated. The search algorithms tested were the MSMS search algorithm implemented in the NIST MS Search program 2.0g (NIST, Gaithersburg, MD, USA) and the MSforID algorithm (John Wiley and Sons, Hoboken, NJ, USA). Sample spectra were acquired on different instruments and, thus, covered a broad range of possible experimental conditions or were generated in silico. For each algorithm, more than 30,000 matches were performed. Statistical evaluation of the library search results revealed that principally both search algorithms can be combined with the Wiley Registry MSMS to create a reliable identification tool. It appears, however, that a higher degree of spectral similarity is necessary to obtain a correct match with the NIST MS Search program. This characteristic of the NIST MS Search program has a positive effect on specificity as it helps to avoid false positive matches (type I errors), but reduces sensitivity. Thus, particularly with sample spectra acquired on instruments differing in their Setup from tandem-in-space type fragmentation, a comparably higher number of false negative matches (type II errors) were observed by searching the Wiley Registry MSMS.

Tandem mass spectral libraries are versatile tools for small molecular identification finding application in forensic science, doping control, drug monitoring, food and environmental analysis, as well as metabolomics. Two important libraries are the 'Wiley Registry of Tandem Mass Spectral Data, MSforID' (Wiley Registry MSMS) and the collection of MS/MS spectra part of the 2011 edition of the 'NIST/NIH/EPA Mass Spectral Library' (NIST 11 MSMS). Herein, the sensitivity and robustness of the Wiley Registry MSMS were evaluated using spectra extracted from the NIST 11 MSMS library. The sample set was found to be heterogeneous in terms of mass spectral resolution, type of CID, as well as applied collision energies. Nevertheless, sensitive compound identification with a true positive identification rate ≥95% was possible using either the MSforID Search program or the NIST MS Search program 2.0g for matching. To rate the performance of the Wiley Registry MSMS, cross-validation experiments were repeated using subcollections of NIST 11 MSMS as reference library and spectra extracted from the Wiley Registry MSMS as positive controls. Unexpectedly, with both search algorithms tested, correct results were obtained in less than 88% of cases. We examined possible causes for the results of the cross validation study. The large number of precursor ions represented by a single tandem mass spectrum only was identified as the basic cause for the comparably lower sensitivity of the NIST library.

Mass spectrometry (MS) is an important analytical technique for the detection and identification of small compounds. The main bottleneck in the interpretation of metabolite profiling or screening experiments is the identification of unknown compounds from tandem mass spectra. Spectral libraries for tandem MS, such as MassBank or NIST, contain reference spectra for many compounds, but their limited chemical coverage reduces the chance for a correct and reliable identification of unknown spectra outside the database domain. On the other hand, compound databases like PubChem or ChemSpider have a much larger coverage of the chemical space, but they cannot be queried with spectral information directly. Recently, computational mass spectrometry methods and in silico fragmentation prediction allow users to search such databases of chemical structures. We present a new strategy called MetFusion to combine identification results from several resources, in particular, from the in silico fragmenter MetFrag with the spectral library MassBank to improve compound identification. We evaluate the performance on a set of 1062 spectra and achieve an improved ranking of the correct compound from rank 28 using MetFrag alone, to rank 7 with MetFusion, even if the correct compound and similar compounds are absent from the spectral library. On the basis of the evaluation, we extrapolate the performance of MetFusion to the KEGG compound database.

One of the key benefits of using intrusion-tolerant systems is the possibility of ensuring correct behavior in the presence of attacks and intrusions. These security gains are directly dependent on the components exhibiting failure diversity. To what extent failure diversity is observed in practical deployment depends on how diverse are the components that constitute the system. In this paper, we present a study with operating system's OS's vulnerability data from the NIST National Vulnerability Database NVD. We have analyzed the vulnerabilities of 11 different OSs over a period of 18years, to check how many of these vulnerabilities occur in more than one OS. We found this number to be low for several combinations of OSs. Hence, although there are a few caveats on the use of NVD data to support definitive conclusions, our analysis shows that by selecting appropriate OSs, one can preclude or reduce substantially common vulnerabilities from occurring in the replicas of the intrusion-tolerant system. Copyright © 2013 John Wiley & Sons, Ltd.

SRM 2569 Lead Paint Films for Children's Products is a new Standard Reference Material (SRM) developed for use primarily with X-ray fluorescence spectrometry (XRF) instrumentation. It consists of three paint coatings, with nominally 0, 90, and 300 mg/kg of Pb added, on polyester substrates. The levels of Pb are appropriate for use when validating test methods intended for testing product compliance with the Consumer Product Safety Improvement Act. The Pb mass fraction, mass Pb per unit area, paint density, and paint thickness are all characterized to make these materials useful to users of different XRF instrumentation. These parameters are consistent with one another and can be used to demonstrate mathematical conversions between units of mass fraction and mass per unit area. The assigned values for these parameters were obtained through direct determinations using instrumental methods and via calculations using measured values for paint ingredients, paint composition, and physical properties. The paints are highly homogeneous among units, although within units, some localized areas enriched in Pb can be observed using microbeam XRF instrumentation. For this reason, SRM 2569 is not recommended for use with measured areas smaller than 1 mm diameter. The development of SRM 2569 is a good case study for the use of multiple, interrelated parameters and test methods to demonstrate the comparability of values derived from a variety of measurement processes. Published 2012. This article is a US Government work and is in the public domain in the USA.

In this paper, we have presented an optimization approach to document summarization. The potential of optimization based document summarization models has not been well explored to date. This is partially the difficulty to formulate the criteria used for objective assessment. We modeled document summarization as the linear and nonlinear optimization problems. These models generally attempt simultaneously to balance coverage and diversity in the summary. To solve the optimization problem we developed a novel particle swarm optimization (PSO) algorithm. Experiments showed our linear and nonlinear models produce very competitive results, which significantly outperform the NIST baselines in both years. More important, although linear and nonlinear models are comparable to the top three systems S24, S15, and S12 in the DUC2006, they are even superior to the best participating system in the DUC2005.

Research into natural mass-dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC-ICP-MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double-spike techniques, sample-calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in-house Cd solutions used as zero-delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round-robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in-house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero-delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio 114Cd/110Cd for NIST SRM 3108 lies within ∼ 10 ppm Da−1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use. La recherche sur le fractionnement naturel dependant de la masse des isotopes stables du cadmium a connu une expansion rapide ces dernieres annees. Les methodologies sont diverses mais la technique MC-ICP-MS est favorisee par tous les laboratoires saut un, qui utilise le TIMS. Pour quantifier le fractionnement isotopique et corriger les biais instrumentaux sur la masse, les techniques dites du « double spike », du « bracketing » par un echantillon etalon et du dopage elementaire ont ete utilises. Toutefois, la comparaison entre les differentes bases de donnees a ete rendue difficile par la multitude des solutions internes de Cd utilisees en tant que reference ‘delta-zero’ dans les differents laboratoires. L’absence d’un materiau de reference isotopique approprie pour le Cd est prejudiciable pour les progres dans le long terme. Nous avons mene un vaste test «round-robin» du NIST SRM 3108 et des decalages isotopiques du Cd par rapport aux materiaux de reference communement utilises en interne dans les laboratoires. Ici, nous preconisons le NIST SRM 3108 a la fois comme etalon de mesure des isotopes du Cd et comme point de reference isotopique pour le Cd, et nous encourageons son utilisation comme ‘delta-zero’ dans les etudes futures. La purete du NIST SRM 3108 a eteevaluee en ce qui concerne les interferences isobares et moleculaires polyatomiques, et les niveaux de concentration de Zn, Pd et Sn trouve ne sont pas significatifs. Le rapport isotopique 114Cd/110Cd du NIST SRM 3108 se situe dans les limites ∼ 10 ppm Da−1 des meilleures estimations pour la Terre silicatee, et est validee pour toutes les technologies de mesure couramment utilisees.

Results from a standardization study cosponsored by the International Society for Advancement of Cytometry (ISAC) and the US National Institute of Standards and Technology (NIST) are reported. The study evaluated the variability of assigning intensity values to fluorophore standard beads by bead manufacturers and the variability of cross calibrating the standard beads to stained polymer beads (hard-dyed beads) using different flow cytometers. Hard dyed beads are generally not spectrally matched to the fluorophores used to stain cells, and spectral response varies among flow cytometers. Thus if hard dyed beads are used as fluorescence calibrators, one expects calibration for specific fluorophores (e.g., FITC or PE) to vary among different instruments. Using standard beads surface-stained with specific fluorophores (FITC, PE, APC, and Pacific Blue™), the study compared the measured intensity of fluorophore standard beads to that of hard dyed beads through cross calibration on 133 different flow cytometers. Using robust CV as a measure of variability, the variation of cross calibrated values was typically 20% or more for a particular hard dyed bead in a specific detection channel. The variation across different instrument models was often greater than the variation within a particular instrument model. As a separate part of the study, NIST and four bead manufacturers used a NIST supplied protocol and calibrated fluorophore solution standards to assign intensity values to the fluorophore beads. Values assigned to the reference beads by different groups varied by orders of magnitude in most cases, reflecting differences in instrumentation used to perform the calibration. The study concluded that the use of any spectrally unmatched hard dyed bead as a general fluorescence calibrator must be verified and characterized for every particular instrument model. Close interaction between bead manufacturers and NIST is recommended to have reliable and uniformly assigned fluorescence standard beads.

A viscosity standard is needed to replace the National Institute of Standards and Technology (NIST) glasses currently being used to calibrate viscosity measurement equipment. The current NIST glasses are either unavailable or less than ideal for calibrating equipment to measure the viscosity of high-level waste glasses. This report documents the results of a viscosity round robin study conducted on the Defense Waste Processing Facility (DWPF) startup frit. DWPF startup frit was selected because its viscosity-temperature relationship is similar to most DWPF and Hanford high-level waste glass compositions. The glass underwent grinding and blending to homogenize the large (100 lb) batch. Portions of the batch were supplied to the laboratories (named A through H) for viscosity measurements following a specified temperature schedule with a temperature range of 1150 C to 950 C and with an option to measure viscosity at lower temperatures if their equipment was capable of measuring at the higher viscosities. Results were used to fit the Vogel-Tamman-Fulcher and Arrhenius equations to viscosity as a function of temperature for the entire temperature range of 460 C through 1250 C as well as the limited temperature interval of approximately 950 C through 1250 C. The standard errors for confidence andmore » prediction were determined for the fitted models.« less

There are significant differences between the atomic orbital energies listed in the evaluated photon data library EPDL97 and values published elsewhere. In particular, comparisons with the values adopted by the National Institute of Standards and Technology (NIST) show discrepancies up to several hundred electron volts. Although the uncertainties in the EPDL97 atomic orbital energies were recognised by the original authors, the library has subsequently been widely adopted as a primary source of photon transport and atomic relaxation data. We compare experimentally measured X-ray fluorescence spectra with fits using the EPDL97 and NIST line energies. Our results strongly favour the NIST energies for K-shell and L-shell fluorescent X-rays and show that the EPDL97 atomic orbital energy values should not be used for applications, such as X-ray fluorescence, where atomic relaxation phenomena are important. Copyright © 2012 John Wiley & Sons, Ltd.

Molybdenum concentration and δ98/95Mo values for NIST SRM 610 and 612 (solid glass), NIST SRM 3134 (lot 891307; liquid) and IAPSO seawater reference material are presented based on comparative measurements by MC-ICP-MS performed in laboratories at the Universities of Bern and Oxford. NIST SRM 3134 and NIST SRM 610 and 612 were found to have identical and homogeneous 98Mo/95Mo ratios at a test portion mass of 0.02 g. We suggest, therefore, that NIST SRM 3134 should be used as reference for the δ–Mo notation and to employ NIST SRM 610 or 612 as solid silicate secondary measurement standards, in the absence of an isotopically homogeneous solid geological reference material for Mo. The δ98/95MoJMC Bern composition (Johnson Matthey ICP standard solution, lot 602332B as reference) of NIST SRM 3134 was 0.25 ± 0.09‰ (2s). Based on five new values, we determined more precisely the mean open ocean δ98/95MoSRM 3134 value of 2.09 ± 0.07‰, which equals the value of δ98/95MoJMC Bern of 2.34 ± 0.07‰. We also refined the Mo concentration data for NIST SRM 610 to 412 ± 9 μg g−1 (2s) and NIST SRM 612 to 6.4 ± 0.7 μg g−1 by isotope dilution. We propose these concentration data as new working values, which allow for more accurate in situ Mo determination using laser ablation ICP-MS or SIMS.

We show that synchrotron x-ray microtomography ({mu}CT) followed by digital data extraction can be used to examine the size distribution and particle morphologies of the polydisperse (750 to 2450 {micro}m diameter) particle size standard NIST 1019b. Our size distribution results are within errors of certified values with data collected at 19.5 {micro}m/voxel. One of the advantages of using {mu}CT to investigate the particles examined here is that the morphology of the glass beads can be directly examined. We use the shape metrics aspect ratio and sphericity to examine of individual standard beads morphologies as a function of spherical equivalent diameters. We find that the majority of standard beads possess near-spherical aspect ratios and sphericities, but deviations are present at the lower end of the size range. The majority (> 98%) of particles also possess an equant form when examined using a common measure of equidimensionality. Although the NIST 1019b standard consists of loose particles, we point out that an advantage of {mu}CT is that coherent materials comprised of particles can be examined without disaggregation.

The emergence of MS-based proteomic platforms as a prominent technology utilized in biochemical and biomedical research has increased the need for high-quality MS measurements. To address this need, National Institute of Standards and Technology (NIST) reference material (RM) 8323 yeast protein extract is introduced as a proteomics quality control material for benchmarking the preanalytical and analytical performance of proteomics-based experimental workflows. RM 8323 yeast protein extract is based upon the well-characterized eukaryote Saccharomyces cerevisiae and can be utilized in the design and optimization of proteomics-based methodologies from sample preparation to data analysis. To demonstrate its utility as a proteomics quality control material, we coupled LC-MS/MS measurements of RM 8323 with the NIST MS Quality Control (MSQC) performance metrics to quantitatively assess the LC-MS/MS instrumentation parameters that influence measurement accuracy, repeatability, and reproducibility. Due to the complexity of the yeast proteome, we also demonstrate how NIST RM 8323, along with the NIST MSQC performance metrics, can be used in the evaluation and optimization of proteomics-based sample preparation methods.

Purpose: To perform a comparison of the interim air-kerma strength standard for high dose rate (HDR)192Ir brachytherapy sources maintained by the University of Wisconsin Accredited DosimetryCalibration Laboratory (UWADCL) with measurements of the various sourcemodels using modified techniques from the literature. The current interim standard was established by Goetsch et al. in 1991 and has remained unchanged to date. Methods: The improved, laser-aligned seven-distance apparatus of the University of Wisconsin Medical Radiation Research Center (UWMRRC) was used to perform air-kerma strength measurements of five different HDR192Ir sourcemodels. The results of these measurements were compared with those from well chambers traceable to the original standard. Alternative methodologies for interpolating the 192Ir air-kerma calibration coefficient from the NIST air-kerma standards at 137Cs and 250 kVp x rays (M250) were investigated and intercompared. As part of the interpolation method comparison, the Monte Carlo code EGSnrc was used to calculate updated values of A wall for the Exradin A3 chamber used for air-kerma strength measurements. The effects of air attenuation and scatter, room scatter, as well as the solution method were investigated in detail. Results: The average measurements when using the inverseN Kinterpolation method for the Classic Nucletron, Nucletron microSelectron, VariSource VS2000, GammaMed Plus, and Flexisource were found to be 0.47%, −0.10%, −1.13%, −0.20%, and 0.89% different than the existing standard, respectively. A further investigation of the differences observed between the sources was performed using MCNP5 Monte Carlo simulations of each sourcemodel inside a full model of an HDR 1000 Plus well chamber. Conclusions: Although the differences between the sourcemodels were found to be statistically significant, the equally weighted average difference between the seven-distance measurements and the well chambers was 0.01%, confirming that it is not necessary to update the current standard maintained at the UWADCL.