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Comparing Five Generations of ActiGraph Devices using an Orbital Shaker.
Med Sci Sports Exerc
January 2025
Energy Metabolism Section, National Institute of Diabetes, Digestive and Kidney Diseases, Diabetes, Endocrinology, and Obesity Branch, National Institutes of Health (NIH), Bethesda, MD.
Introduction: ActiGraph accelerometers are used extensively to objectively assess physical activity, sedentary behavior, and sleep. Here, we present an objective validation of five generations of ActiGraph sensors to characterize potential differences in output arising from changes to hardware or firmware.
Methods: An orbital shaker generated accelerations from 0 to 3700 milli-g in a randomized order to test the wGT3X-BT, GT9X, CentrePoint Insight Watch (CPIW) 1.
Wavemeter calibration by frequency comb.
Metrologia
January 2024
National Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, United States of America.
Upgrades to the vacuum wavelength calibration service at the National Institute of Standards and Technology are reported. The instrumentation centerpiece is an optical frequency comb stabilized to a GPS-disciplined oscillator, thereby providing direct traceability to the SI second. Historically, the service has covered lasers at the popular interferometry wavelengths red and green.
View Article and Find Full Text PDFAssessment of the Performance of the Dose Calibrator Used in Radioactivity Measurement.
Indian J Nucl Med
November 2024
Center for Research and Production of Radioisotopes, Dalat Nuclear Research Institute, Vietnam Atomic Energy Institute (VINATOM), Da Lat City, Lam Dong Province, Vietnam.
Aims: This study aimed to evaluate the principal technical characteristics of a well-type gas-filled ionization chamber dose calibrator used in measuring radiopharmaceutical activity, namely accuracy, repeatability, and linearity. Furthermore, this work also explored the correlation between the device's response and the position and volume of the radiopharmaceutical I-131.
Materials And Methods: Experimental measurements were conducted on the ATOMLAB 500 dose calibrator using NIST traceable Cs-137 source to determine the accuracy and repeatability.
Commutability assessment of new standard reference materials (SRMs) for determining serum total 25-hydroxyvitamin D using ligand binding and liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays.
Anal Bioanal Chem
January 2025
Chemical Sciences Division, National Institute of Standards and Technology (NIST), Gaithersburg, MD, 20899, USA.
Commutability is where the measurement response for a reference material (RM) is the same as for an individual patient sample with the same concentration of analyte measured using two or more measurement systems. Assessment of commutability is essential when the RM is used in a calibration hierarchy or to ensure that clinical measurements are comparable across different measurement procedures and at different times. The commutability of three new Standard Reference Materials (SRMs) for determining serum total 25-hydroxyvitamin D [25(OH)D], defined as the sum of 25-hydroxyvitamin D [25(OH)D] and 25-hydroxyvitamin D [25(OH)D], was assessed through an interlaboratory study.
View Article and Find Full Text PDFImproved Analysis for Intrinsic Properties of Triaxial Accelerometers to Reduce Calibration Uncertainty.
Micromachines (Basel)
December 2024
NIST, Gaithersburg, MD 20899, USA.
We describe a modification of a previously described measurement-analysis protocol to determine the intrinsic properties of triaxial accelerometers by using a measurement protocol based on angular stepwise rotation in the Earth's gravitational field. This study was conducted with MEMS triaxial accelerometers that were co-integrated in four consumer-grade wireless microsensors. The measurements were carried out on low-cost rotation tables in different laboratories in different countries to simulate the reproducibility environment encountered in inter-comparisons of calibration capabilities.
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