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Chemistry

Analytical chemistry

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Displaying 1276 - 1300 of 2086

Determination of Perfluorinated Alkyl Acid concentrations in Human Serum and Milk Standard Reference Materials

October 28, 2009
Author(s)
Jennifer M. Lynch, Antonia M. Calafat, Kayoko Kato, Mark E. Ellefson, William K. Reagen, Mark Strynar, Steven G. O'Connell, Craig M. Butt, Scott Mabury, Jeff Small, D.C.G. Muir, Stefan D. Leigh, Michele M. Schantz
Standard Reference Materials (SRMs) are homogeneous, well-characterized materials that are used to validate measurement methods and are critical in improving data quality. Disagreements in perfluorinated alkyl acid (PFAA) concentrations measured in

Effect of RP-1 Compositional Variability on Thermophysical Properties

October 6, 2009
Author(s)
Marcia L. Huber, Eric W. Lemmon, Thomas J. Bruno
We compare experimental and predicted thermophysical properties of two samples of rocket propellant RP-1 obtained from different batches of RP-1 that exhibit compositional variations. One sample is atypical, due to a high olefin content. The effect of the

Accumulation of Large Protein Fragments in Prematurely Senescent ARPE-19 Cells

October 1, 2009
Author(s)
Illarion V. Turko, Wei-Li Liao
Senescence of retinal pigment epithelial (RPE) cells is a crucial event in the pathogenesis of age-related macular degeneration (AMD). This study was design to improve the understanding of changes that underlie the RPE senescence. The levels of various

Relative Photon-to-Carrier Efficiencies of Alternating Nanolayers of Zinc Phthalocyanine and C60 Multilayer Films Assessed by Time-Resolved Terahertz Spectroscopy

October 1, 2009
Author(s)
Okan Esenturk, Joseph S. Melinger, Paul A. Lane, Edwin J. Heilweil
Alternating multi-layer and 1:1 blended films of zinc phthalocyanine (ZnPc)and buckminsterfullerene (C60) were investigated as model active layers for solar cells by Time-Resolved Terahertz Spectroscopy (TRTS). Relative photon-to-carrier efficiencies 2

Spectrum Simulation in DTSA-II

October 1, 2009
Author(s)
Nicholas W. Ritchie
Spectrum simulation is a useful practical and pedagogical tool. Particularly with complex samples or trace constituents, a simulation can help to understand the limits of the technique and how to optimize the tools for the optimal measurement. DTSA-II

Submillimeter Spectrum and Analysis of Vibrational and Hyperfine Coupling Effects in (HI)2

October 1, 2009
Author(s)
Laurent H. Coudert, Sergei P. Belov, F. Willaert, B. McElmurry, R. Lucchese, John W. Bevan, Jon T. Hougen
Observed rotational-vibrational transitions of HI dimer in the geared bending mode, centered at 511.9 GHz, are reported. This 50 kHz high resolution spectrum was recorded using a co-axially configured pulsed jet submillimeter spectrometer and the hyperfine

Microwave Spectrum of 1,2-Propanediol

September 1, 2009
Author(s)
Francis J. Lovas, David F. Plusquellic, Brooks Pate, Justin L. Neill, Matt T. Muckle, Anthony J. Remijan
The microwave spectrum of the sugar alcohol 1,2-propanediol (CH3CHOHCH2OH) has been measured over the frequency range 6.5 GHz to 25.0 GHz with several pulsed-beam Fourier-transform microwave spectrometers. Seven conformers of 1,2-propanediol have been

Scaling Factors and Uncertainties for ab Initio Anharmonic Vibrational Frequencies

August 21, 2009
Author(s)
Russell D. Johnson III, Karl K. Irikura, Raghu N. Kacker, Ruediger Kessel
To predict the vibrational spectra of molecules, ab initio calculations are often used to compute harmonic frequencies, which are usually scaled by empirical factors as an approximate correction for errors in the force constants and for anharmonic effects

The Calculation of Natural Gas Viscosity

August 14, 2009
Author(s)
Aaron N. Johnson, William Johansen
The calculation of natural gas viscosity has been implemented many different ways including the use of constants. Different methods of calculating natural gas viscosity may produce values with differences as large as 50%. Increasing natural gas prices

Formation of Silicon-Based Molecular Electronic Structures Using Flip-chip Lamination

August 11, 2009
Author(s)
Mariona Coll Bau, Lauren H. Miller, Lee J. Richter, Daniel R. Hines, Curt A. Richter, Christina A. Hacker
The use of organic molecules to impart electrical surface properties has been a subject of intense research not only from a fundamental perspective but for many technological applications. In particular, organic molecules have been proposed as active

Reference measurements of Hydrogen's Dielectric Permittivity

August 10, 2009
Author(s)
James W. Schmidt, Michael R. Moldover, Eric F. May
We used a quasi-spherical cavity resonator to measure the relative dielectric permittivity ε r of H 2 at frequencies from 2.4 GHz to 7.3 GHz, at pressures up to 6.5 MPa, and at the temperatures 273 K and 293 K. The resonator was calibrated using auxiliary

High Definition Flow

August 1, 2009
Author(s)
John D. Wright, Michael R. Moldover
From pharmaceutical production to the natural gas market, exact flow measurements are critical. Here's how NIST helps keep us all on the same page.
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