NIST

NIST
  • 文章类型: Journal Article
    军事人员在外国行动时面临的最困难挑战之一是与当地居民进行清晰和成功的沟通。为了解决这个问题,国防高级研究计划局(DARPA)正在通过战术用口语交流和翻译系统(TRANSTAC)计划资助学术机构和工业组织,以开发实用的机器翻译系统。TRANSTAC计划的目标是展示快速开发和现场自由形式的能力,双向,语音到语音翻译系统,使不同语言的人能够在现实世界的战术情况下相互交流,而无需口译员。对这些技术的评估是该计划的重要组成部分,DARPA已要求国家标准与技术研究所(NIST)领导这项工作。本文介绍了TRANSTAC评估的实验设计和度量标准,定量和定性,用于全面评估系统性能。
    One of the most difficult challenges that military personnel face when operating in foreign countries is clear and successful communication with the local population. To address this issue, the Defense Advanced Research Projects Agency (DARPA) is funding academic institutions and industrial organizations through the Spoken Language Communication and Translation System for Tactical Use (TRANSTAC) program to develop practical machine translation systems. The goal of the TRANSTAC program is to demonstrate capabilities to rapidly develop and field free-form, two-way, speech-to-speech translation systems that enable speakers of different languages to communicate with one another in real-world tactical situations without an interpreter. Evaluations of these technologies are a significant part of the program and DARPA has asked the National Institute of Standards and Technology (NIST) to lead this effort. This article presents the experimental design of the TRANSTAC evaluations and the metrics, both quantitative and qualitative, that were used to comprehensively assess the systems\' performance.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Pubmed)

  • 文章类型: Journal Article
    细胞计数是生物制造过程中确定活细胞数的基本测量。生物制造过程中不同细胞类型的性质和细胞计数的预期用途范围可能导致在为每种潜在应用确定合适的计数方法方面的挑战。这通过用户在鉴定感兴趣的细胞和进一步鉴定活细胞中的主观性而进一步放大。用自动化系统代替传统使用的手动计数方法已经减轻了这些问题中的一些。然而,例如,单细胞类型可以在细胞处理的各个阶段表现出不同的物理特性,其进一步被诸如细胞碎片或磁珠的处理杂质混合。这些因素使得开发一种对结果提供高水平置信度的稳健细胞计数方法具有挑战性。标准开发组织的一些举措试图解决细胞计数标准化的这一关键需求。本研究利用基于流动和基于图像的方法在没有参考材料的情况下定量测量细胞浓度和活力。基于国际标准(ISO)和美国国家标准与技术研究所(NIST)提供的工具和指导。在细胞治疗工作流程中在细胞处理的不同阶段检查原代细胞。这项研究的结果定义了一种系统的方法,可以识别最适合特定细胞类型和工作流程的计数方法和参数,以确保准确性和一致性。细胞计数是在细胞和基因治疗的各个步骤中广泛使用的基础方法。本研究中使用的标准可以应用于其他细胞和基因治疗过程,以便能够准确测量指导整个开发和生产过程中的关键决策所需的参数。使用确认所使用的细胞计数方法的适用性的框架可以使过程和最终产品中的可变性最小化。
    Cell counting is a fundamental measurement for determining viable cell numbers in biomanufacturing processes. The properties of different cell types and the range of intended uses for cell counts within a biomanufacturing process can lead to challenges in identifying suitable counting methods for each potential application. This is further amplified by user subjectivity in identifying the cells of interest and further identifying viable cells. Replacement of traditionally used manual counting methods with automated systems has alleviated some of these issues. However, a single cell type can exhibit different physical properties at various stages of cell processing which is further compounded by process impurities such as cell debris or magnetic beads. These factors make it challenging to develop a robust cell counting method that offers a high level of confidence in the results. Several initiatives from standards development organizations have attempted to address this critical need for standardization in cell counting. This study utilizes flow-based and image-based methods for the quantitative measurement of cell concentration and viability in the absence of a reference material, based on the tools and guidance provided by the International of Standards (ISO) and the US National Institute of Standards and Technology (NIST). Primary cells were examined at different stages of cell processing in a cell therapy workflow. Results from this study define a systematic approach that enables the identification of counting methods and parameters that are best suited for specific cell types and workflows to ensure accuracy and consistency. Cell counting is a foundational method used extensively along various steps of cell and gene therapy. The standard used in this study may be applied to other cell and gene therapy processes to enable accurate measurement of parameters required to guide critical decisions throughout the development and production process. Using a framework that confirms the suitability of the cell counting method used can minimize variability in the process and final product.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Pubmed)

  • 文章类型: Journal Article
    据报道,普通人群中维生素D不足的数量有所增加,尤其是在北半球。然而,25(OH)维生素D的常规测量通常与医疗专业人员采集静脉血样本的大量努力有关.因此,这项工作的目的是开发和验证一种简单而微创的方法,使用微量取样技术由未经医学训练的个体自主采血。该测定法可以简化监测两者的维生素D状态,全年风险人群和正常人群。为此,开发了一种无需衍生化的简单甲醇提取方法,并结合UHPLC-HRMS方法来定量毛细血管血液中的25(OH)D2和25(OH)D3。对于样品收集,使用具有VAMS®技术的20μlMitra®装置。通过使用六倍氘标记的25(OH)D3作为内标,经过验证的测定提供了准确(<10%)和精确(<11%)的结果。LOQ为5ng/ml,该方法还被证明足够敏感,可以充分识别潜在的维生素D缺乏(<12ng/ml),和可靠的VAMS®样品(n=20)的概念验证分析产生了预期血液浓度范围内的测试结果。实施VAMS®维生素D状态监测采样可实现更高的频率,直截了当,和时间有效的样本收集。VAMS®确保准确的样品体积,因为它的吸收能力和,因此,避免了与传统DBS相关的区域偏差和均匀性问题。全年定期监测25(OH)D状况,通过及早发现维生素D缺乏症和维生素D缺乏症的高危人群,因此,防止不良健康后果。
    The numbers of vitamin D inadequacies has reportedly increased in the general population, especially in the Northern hemisphere. However, routine measurement of 25(OH) vitamin D is usually associated with a substantial effort due to the requirement of a venous blood sample taken by medical professionals. Thus, the objective of this work is to develop and validate an easy and minimal-invasive method, using a microsampling technique for autonomous blood collections by medically untrained individuals. The assay enables a simplified monitoring of the vitamin D-status in both, risk group and normal population throughout the year. For this purpose, a simple methanol extraction without derivatization combined with a UHPLC-HRMS method was developed to quantify 25(OH)D2 and 25(OH)D3 in capillary blood. For sample collection, a 20 μl Mitra® device with VAMS® technology is used. By employing the six-fold deuterium-labelled 25(OH)D3 as internal standard, the validated assay provides accurate (<10%) and precise (<11%) results. With a LOQ of 5 ng/ml, the approach also proved sensitive enough to adequately identify potential vitamin D deficiencies (< 12 ng/ml), and proof-of-concept analyses of authentic VAMS® samples (n = 20) yielded test results in the expected blood concentration range. Implementing VAMS® sampling for vitamin D-status monitoring enables a higher frequency due to a simplified, straightforward, and time-effective sample collection. VAMS® assures accurate sample volumes because of its absorptive capacities and, thus, area bias and homogeneity issues associated with conventional DBS are avoided. Regular monitoring of 25(OH)D status throughout the year supports people in high-risk groups for vitamin D-deficiency by early identifying inadequacies and, thus, preventing adverse health consequences.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    随着物联网和传感器技术的大规模应用,轻量级密码的研究已经成为一个重要的研究课题。在本文中,提出了一种基于混沌系统的轻量级LZUC(轻量级ZuChongzhi)密码算法,以改进传统的ZUC算法。在这种方法中,设计了进一步的算法,用于将混沌集成到ZUC的轻量化中。第一次,该设计将逻辑混沌系统引入到LFSR(线性反馈移位寄存器)和非线性F函数的密码算法中。改进的LZUC算法不仅在轻量化方面取得了一定的效果,而且输出序列具有良好的统计特性和安全性。要验证LZUC密码的性能,我们对其输出的密钥流进行了NIST统计测试和信息熵分析,并讨论了该算法抵抗弱密钥分析的典型攻击,猜测-确定分析,时间存储的数据权衡分析,和代数分析。此外,我们完成了使用LZUC密码的图像安全系统的设计。直方图分析和相关性分析用于分析明文和密文数据。在文章的最后,LCD显示的明文和密文图像可以进一步可视化,以验证LZUC密码的加密有效性。
    With the massive application of IoT and sensor technologies, the study of lightweight ciphers has become an important research topic. In this paper, an effective lightweight LZUC (lightweight Zu Chongzhi) cipher based on chaotic system is proposed to improve the traditional ZUC algorithm. In this method, a further algorithm is designed for the process of integrating chaos into the lightweighting of ZUC. For the first time, this design introduces the logistic chaotic system into both the LFSR (linear feedback shift register) and nonlinear F-function of the cryptographic algorithm. The improved LZUC algorithm not only achieves a certain effect in lightweighting, but also has good statistical properties and security of the output sequence. To verify the performance of the LZUC cipher, we performed NIST statistical tests and information entropy analysis on its output key streams and discussed the typical attacks on the algorithm\'s resistance to weak key analysis, guess-determination analysis, time-stored data trade-off analysis, and algebraic analysis. In addition, we completed the design of an image security system using the LZUC cipher. Histogram analysis and correlation analysis are used to analyze both plaintext and ciphertext data. At the end of the article, the plaintext and ciphertext images displayed by LCD can be further visualized to verify the encryption effectiveness of the LZUC cipher.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    测量亚微米颗粒的数量浓度和尺寸分布的技术的数量最近已经增加。需要亚微米颗粒标准来提高这些技术的准确性和再现性。标称100nm的荧光标记聚苯乙烯亚微米球体悬浮液的数量浓度,使用七种不同的技术测量200nm和500nm的直径。在可能的情况下还测量直径值。发现直径值在20%以内一致,但是数量浓度值相差两倍。讨论了与不同技术相关的准确性和可重复性,目的是使用数字浓度标准进行仪器校准。其中三种技术用于确定SI可追溯数浓度值,并对三个独立值进行平均以给出共识值。提出了这种共识方法作为认证SI可追溯数字浓度标准的协议。
    The number of techniques to measure number concentrations and size distributions of submicrometer particles has recently increased. Submicrometer particle standards are needed to improve the accuracy and reproducibility of these techniques. The number concentrations of fluorescently labeled polystyrene submicrometer sphere suspensions with nominal 100 nm, 200 nm and 500 nm diameters were measured using seven different techniques. Diameter values were also measured where possible. The diameter values were found to agree within 20%, but the number concentration values differed by as much as a factor of two. Accuracy and reproducibility related with the different techniques are discussed with the goal of using number concentration standards for instrument calibration. Three of the techniques were used to determine SI-traceable number concentration values, and the three independent values were averaged to give consensus values. This consensus approach is proposed as a protocol for certifying SI-traceable number concentration standards.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Pubmed)

  • 文章类型: Journal Article
    使用液相色谱与质谱联用分析食品和饲料中的霉菌毒素被认为是有利的,因为联用技术可以同时测定多种霉菌毒素。多霉菌毒素分析需要特别考虑质量控制参数,以确保在方法开发和常规样品分析中对所有目标霉菌毒素的数据质量进行适当评估。霉菌毒素基质参考材料,特别是经过认证的参考材料,是稳定且均匀的矩阵,具有认证的可追溯性,浓度,以及感兴趣的霉菌毒素的不确定性。将这些参考材料用于单一霉菌毒素分析已成为公认的做法,应扩展到多霉菌毒素分析。本文讨论了提高数据质量的以下基本计量和操作组件:(1)多霉菌毒素参考材料的目的;(2)参考材料的比较,经认证的参考材料,和内部质量控制材料;(3)使用参考材料进行多霉菌毒素分析的优势;(4)多霉菌毒素参考材料的当前趋势和挑战。此处讨论的参考材料的潜在应用可以改善常规的霉菌毒素测定,并将提高结果的准确性和一致性。在霉菌毒素分析领域纳入参考材料的质量控制过程确保成功开发和实施基于液相色谱质谱的多霉菌毒素方法。
    The analysis of mycotoxins in food and feed using liquid chromatography coupled with mass spectrometry is considered advantageous because the hyphenated technology enables simultaneous determination of multiple mycotoxins. Multi-mycotoxin analysis requires special consideration of quality control parameters to ensure proper evaluation of data quality for all target mycotoxins in method development and routine sample analysis. Mycotoxin matrix reference materials, especially certified reference materials, are stable and homogeneous matrices with certified traceability, concentrations, and uncertainty for mycotoxin(s) of interest. The use of these reference materials for single mycotoxin analysis has been a well-accepted practice and should be extended to multi-mycotoxin analysis. This opinion piece discusses the following essential metrological and operational components to improve data quality: (1) purposes of multi-mycotoxin reference materials; (2) comparison of reference materials, certified reference materials, and in-house quality control materials; (3) advantages of using reference materials for multi-mycotoxin analysis; (4) current trends and challenges of multi-mycotoxin reference materials. Potential applications of reference materials discussed here can improve routine mycotoxin determination and will lead to better accuracy and consistency of results. Quality control processes that incorporate reference materials in the field of mycotoxin analysis ensure successful development and implementation of liquid chromatography mass spectrometry-based multi-mycotoxin methods.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    OBJECTIVE: To determine baseline accuracy and reproducibility of T1 and T2 relaxation times over 12 months on a dedicated radiotherapy MRI scanner.
    METHODS: An International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) System Phantom was scanned monthly on a 3T MRI scanner for 1 year. T1 was measured using inversion recovery (T1 -IR) and variable flip angle (T1 -VFA) sequences and T2 was measured using a multi-echo spin echo (T2 -SE) sequence. For each vial in the phantom, accuracy errors (%bias) were determined by the relative differences in measured T1 and T2 times compared to reference values. Reproducibility was measured by the coefficient of variation (CV) of T1 and T2 measurements across monthly scans. Accuracy and reproducibility were mainly assessed on vials with relaxation times expected to be in physiological ranges at 3T.
    RESULTS: A strong linear correlation between measured and reference relaxation times was found for all sequences tested (R2  > 0.997). Baseline bias (and CV[%]) for T1 -IR, T1 -VFA and T2 -SE sequences were +2.0% (2.1), +6.5% (4.2), and +8.5% (1.9), respectively.
    CONCLUSIONS: The accuracy and reproducibility of T1 and T2 on the scanner were considered sufficient for the sequences tested. No longitudinal trends of variation were deduced, suggesting less frequent measurements are required following the establishment of baselines.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Pubmed)

  • 文章类型: Journal Article
    混沌系统在电子学中的应用,例如伪随机数发生器(PRNG),非常吸引人。其中,连续时间的使用较少,因为,除了具有很强的时间相关性,它们需要进一步的计算来获得离散解。这里,首先通过详细分析时间步长和离散化方法对系统的统计和混沌行为的影响进行研究。我们采用了一种基于将时间步长解释为新“地图”参数的方法。根据我们的分析,因此,将它们用作PRNG,应该实现两个动作(i)保持混沌振荡和(ii)破坏内部和时间相关性。然后,我们提出了一种简单的方法来实现基于混沌的PRNG,具有良好的统计特性和高吞吐量,可以应用于任何连续时间混沌系统。我们通过基于信息论的量词(排列熵,排列复杂性,和因果熵×复杂度平面)。我们表明,拟议的PRNG生成的序列成功通过了MarsagliaDiehard和NIST(国家标准与技术研究所)测试。最后,我们表明,它的硬件实现需要很少的资源。
    The use of chaotic systems in electronics, such as Pseudo-Random Number Generators (PRNGs), is very appealing. Among them, continuous-time ones are used less because, in addition to having strong temporal correlations, they require further computations to obtain the discrete solutions. Here, the time step and discretization method selection are first studied by conducting a detailed analysis of their effect on the systems\' statistical and chaotic behavior. We employ an approach based on interpreting the time step as a parameter of the new \"maps\". From our analysis, it follows that to use them as PRNGs, two actions should be achieved (i) to keep the chaotic oscillation and (ii) to destroy the inner and temporal correlations. We then propose a simple methodology to achieve chaos-based PRNGs with good statistical characteristics and high throughput, which can be applied to any continuous-time chaotic system. We analyze the generated sequences by means of quantifiers based on information theory (permutation entropy, permutation complexity, and causal entropy × complexity plane). We show that the proposed PRNG generates sequences that successfully pass Marsaglia Diehard and NIST (National Institute of Standards and Technology) tests. Finally, we show that its hardware implementation requires very few resources.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Sci-hub)

       PDF(Pubmed)

  • 文章类型: Journal Article
    The National Institute of Standards and Technology (NIST) generates and maintains thousands of Standard Reference Materials (SRMs) to serve commerce worldwide. Many SRMs contain metrologically traceable mass fractions of known organic chemicals and are commercially available to aid the analytical chemistry community. One such material, NIST SRM 1957 Organic Contaminants in Non-Fortified Human Serum, was one of the first materials issued by NIST with measurements for per- and polyfluoroalkyl substances (PFAS) listed on the Certificate of Analysis and was commercially available in 2009. Since the release of SRM 1957, nearly 400 units have been sold to date, and over 50 publications related to PFAS measurements have included this material for multiple analytical purposes, such as a quality control material, for interlaboratory comparison, as an in-house comparison tool, for inter- and intra-day measurement accuracy, as an indicator of isomeric patterns of PFAS, and for other uses. This perspective details the ways SRM 1957 is utilized by the analytical community and how data have been reported in the literature. A discussion on accurately comparing SRM data to generated data is included. Furthermore, we conducted an in-depth investigation around additional applications for NIST SRMs, such as a matrix-matched reference material, and for the identification of targeted compounds during high-resolution mass spectrometry data collection. Ultimately, this manuscript illustratively describes the ways to utilize a NIST SRMs for chemicals of emerging concern.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Sci-hub)

       PDF(Pubmed)

  • 文章类型: Journal Article
    统计随机性检验之间的独立性分析最近在文献中引起了极大的关注。统计随机性测试之间的依赖性检测允许人们区分测量相似特征的统计随机性测试,,从而最大限度地减少需要使用的统计随机性测试的数量。在这项工作中,提出了一种利用互信息检测统计相关性的方法。使用互信息的主要优点是能够检测非线性相关性,这是以前工作中使用的线性相关系数无法检测到的。该方法分析了国家标准与技术研究院电池测试之间的相关性,用作评估随机性的标准。实验结果表明,以前未检测到的测试之间存在统计依赖性。
    The analysis of independence between statistical randomness tests has had great attention in the literature recently. Dependency detection between statistical randomness tests allows one to discriminate statistical randomness tests that measure similar characteristics, and thus minimize the amount of statistical randomness tests that need to be used. In this work, a method for detecting statistical dependency by using mutual information is proposed. The main advantage of using mutual information is its ability to detect nonlinear correlations, which cannot be detected by the linear correlation coefficient used in previous work. This method analyzes the correlation between the battery tests of the National Institute of Standards and Technology, used as a standard in the evaluation of randomness. The results of the experiments show the existence of statistical dependencies between the tests that have not been previously detected.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

       PDF(Sci-hub)

       PDF(Pubmed)

公众号