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Search Publications by Aaron Urbas, Ph.D.

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Displaying 1 - 13 of 13

A Comparison of Measurement Methods for Alcohol-Based Hand Sanitizers

February 26, 2021
Mary Bedner, Jacolin Murray, Aaron A. Urbas, William A. MacCrehan, Walter Brent Wilson
The production and demand for hand sanitizers have increased dramatically during the coronavirus disease 2019 (COVID-19) health emergency. To be deemed effective and safe, hand sanitizers should contain at least 60 % alcohol (typically ethanol) as well as

Expanding NIST’s Calibration of Fluorescent Microspheres for Flow Cytometry to More Fluorescence Channels and Smaller Particles

September 16, 2020
Paul C. DeRose, Linhua Tian, Elzafir B. Elsheikh, Aaron A. Urbas, Yu-Zhong Zhang, Lili Wang
NIST, NIH and other industry stakeholders have been working together to enable fluorescence intensities of flow cytometer calibration beads to be assigned quantitative “ERF” values with high accuracy and precision. The ultimate goal of this effort is to

An untargeted approach to determine the authenticity of Ginkgo biloba L. plant materials and dried leaf extracts by liquid chromatography-mass spectrometry (LC-HRMS) and chemometrics.

August 5, 2020
Meryl B. Cruz, Benjamin Place, Laura J. Wood, Aaron A. Urbas, Werickson Rocha, Andrzej Wasik
The lack of stringent regulations regarding raw materials for herbal supplements used for medicinal purposes has been a constant challenge in the industry. Ginkgo biloba L. leaf extracts attract consumers because of the supposed positive effect on mental

NIST Pathlength and Monoclonal Antibody Standards for the Quality Control of Absorbance Measurements of Protein Biopharmaceuticals

May 8, 2018
Kenneth D. Cole, Paul C. DeRose, Hua-Jun He, Erica V. Stein, Brian E. Lang, John E. Schiel, Aaron A. Urbas, Evelyn Solis, Steven J. Choquette
A rapid, and reliable method to determine protein concentration is by absorbance measurements in the ultraviolet (UV) spectrum. NIST has developed Standard Reference Material (SRM) 2082 as a pathlength standard for absorbance measurements in the UV for use

Development of NIST Standard Reference Material 2082, a Pathlength Standard for Measurements in the Ultraviolet Spectrum

July 10, 2017
Brian Lang, Aaron A. Urbas, Paul C. DeRose, Hung-Kung Liu, John C. Travis, Steven J. Choquette, Kenneth D. Cole
New spectrophotometers and cuvettes have been designed to allow the measurement of absorbance values from samples using microliter volume sizes. These measurements are done using short pathlengths to decrease the sample volumes required. The major

An azeotropic cross-linked styrene-methacrylate network formed through rapid visible-light photo- polymerization

July 15, 2016
Yin Yang, Aaron A. Urbas, Andres Gonzalez-Bonet, Richard J. Sheridan, Jonathan E. Seppala, Kathryn L. Beers, Jirun Sun
A system containing well-defined functional material, a clinically practical procedure to make the material in situ, and proper analytical tools for chemical structure and kinetic studies is appealing, but currently unavailable. Herein, we introduce an all

Particle Fabrication Using Inkjet Printing onto Hydrophobic Surfaces for Optimization and Calibration of Trace Contraband Detection Sensors

November 24, 2015
John G. Gillen, Marcela N. Najarro, Matthew E. Staymates, Scott A. Wight, Marlon L. Walker, Jennifer R. Verkouteren, Eric S. Windsor, Aaron A. Urbas
A method has been developed to fabricate patterned arrays of micrometer-sized monodisperse solid particles of ammonium nitrate on hydrophobic silicon surfaces using inkjet printing. The method relies on dispensing one or more microdrops (typically 50 pL

Proceedings of SPIE

March 4, 2015
Maritoni A. Litorja, Aaron A. Urbas, Yuqin Zong
The fluorescent light detected by a clinical imager is assumed to be proportional to the amount of fluorescent substance present in the sample. Unfortunately, there are many factors that can add or subtract to the light signal directly attributable to the

A thermodynamic investigation of the cellulose allomorphs: cellulose(am), cellulose I?(cr), cellulose II(cr), and cellulose III(cr)

November 11, 2014
Robert N. Goldberg, Jacob Schliesser, Ashutosh Mittal, Stephen R. Decker, Ana Filipa L. Santos, Vera L. Freitas, Aaron A. Urbas, Brian E. Lang, Christian Heisse, Maria D. Ribeiro da Silva, Brian F. Woodfield, Rui Katahira, Wei Wang, David K. Johnson
The thermochemistry of samples of amorphous cellulose, cellulose I, cellulose II, and cellulose III was studied by using oxygen bomb calorimetry, solution calorimetry in which the solvent was cadoxen, and with a Physical Property Measurement System (PPMS)

Probing the intracellular glutathione redox potential using in-cell NMR spectroscopy

January 2, 2014
Steve Y. Rhieu, Aaron A. Urbas, Daniel W. Bearden, John P. Marino, Vytautas Reipa, Katrice A. Lippa
Non-invasive and real-time analysis of cellular redox processes has been greatly hampered by lack of suitable measurement techniques. Here we describe an in-cell nuclear magnetic resonance (NMR)-based method for measuring the intracellular glutathione

Quantitative measurements of glutathione in yeast cell lysate using 1H NMR

February 20, 2013
Steve Y. Rhieu, Aaron A. Urbas, Katrice Lippa, Vytas Reipa
A method for quantifying the level of glutathione (GSH) in yeast cell lysate is described using 1H NMR analysis. For quantification purposes, the 1H resonances corresponding to the Cys βCH2 of GSH were identified as having the fewest overlapping spectral

Automated Spectral Smoothing with Spatially Adaptive Penalized Least-Squares

June 1, 2011
Aaron A. Urbas, Steven J. Choquette
A variety of data smoothing techniques exist to address the issue of noise in spectroscopic data. The vast majority, however, require parameter specification by a knowledgeable user, which is typically accomplished by trial and error. In most situations