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Chemistry

Analytical chemistry

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Displaying 951 - 975 of 2094

Metallofullerene with a Distorted Shape: Structural Investigation of Y3N@C78

January 24, 2013
Author(s)
Dan Bearden, Jianyuan Zhang, Fuhrer Tim, Wujun Fu, Tianming Zuo, Liaosa Xu, Harry C. Dorn
In recent decades, the trimetallic nitride template endohedral metallofullerenes (TNT-EMFs),1 which consist of a trimetallic nitride cluster and a fullerene cage, have attracted extensive research interest due to their unique structural characteristics and

Spatial and temporal trends of persistent organic pollutants and mercury in beluga whales (Delphinapterus leucas) from Alaska

January 24, 2013
Author(s)
Jennifer Hoguet, Jessica Reiner, Jennifer Lynch, John Kucklick, Colleen E. Bryan Sallee, Amanda Moors, Rebecca Pugh, Paul R. Becker
Remote locations, such as the Arctic, are often sinks for persistent contaminants which can ultimately bioaccumulate in local wildlife. Assessing temporal contaminant trends in the Arctic is important in understanding whether restrictions on legacy

To Predict Vibrational Spectra, Are Anharmonic Calculations Worthwhile?

January 22, 2013
Author(s)
Ruth L. Jacobsen, Karl K. Irikura, Russell D. Johnson III, Raghu N. Kacker
Anharmonic calculations using vibrational perturbation theory are known to provide near-spectroscopic accuracy when combined with high-level ab initio potential energy functions. However, performance with economical, popular electronic structure methods is

Putting a spin on LA-ICPMS analysis combined with isotope dilution

January 11, 2013
Author(s)
John L. Molloy, Stephen E. Long, Fanny Claverie, Julian Malherbe, Naomi Bier
The determination of Zn, Sr, Ba and Pb in solid samples has been achieved by Laser Ablation Inductively Coupled Plasma Isotope Dilution Mass Spectrometry (LA-ICP-IDMS) using a spinning sampling platform. The fast rotation of a sample and an isotopically

The BIOREMA project part 2: International interlaboratory comparison for biodiesel test methods

January 4, 2013
Author(s)
Michele M. Schantz, Manuela Ulberth-Buchgraber, Monica Potalivo, Andrea Held, Annaratia Baldan, Adriaan van der Veen, Hugo Ent, Valnei Cunha, Romeu Daroda, Ruth Hearn, Richard Brown, Paul Brewer, Brian E. Lang
The results of an interlaboratory comparison, using various measurement methods to carry out biodiesel testing, are presented, and the findings discussed. The interlaboratory comparison was organised within the framework of an EU funded project called

Further Studies with Isolated Absolute Infrared Spectra of Bacteriorhodopsin Photocycle Intermediates: Conformational Changes and Possible Role of a New Proton-Binding Center

January 1, 2013
Author(s)
Richard W. Hendler, Curtis W. Meuse, Paul Smith, John W. Kakareka
We recently published procedures describing the isolation of absolute infrared spectra for the intermediates of the bacteriorhodopsin (BR) photocycle and from these, obtaining transitional difference spectra between consecutive intermediates. In that work

NIST Micronutrients Measurement Quality Assurance Program Winter 2012 Comparability Studies Results for Round Robin LXXI Fat-Soluble Vitamins and Carotenoids in Human Serum and Round Robin 36 Ascorbic Acid in Human Serum

December 21, 2012
Author(s)
David L. Duewer, Jeanice M. Brown Thomas
The National Institute of Standards and Technology coordinates the Micronutrients Measurement Quality Assurance Program (MMQAP) for laboratories that measure fat- and water-soluble vitamins and carotenoids in human serum and plasma. This report describes

Single bead detection with a NMR micro capillary probe

December 6, 2012
Author(s)
Yoshihiro Nakashima, Michael A. Boss, Stephen E. Russek, John M. Moreland
We have developed a nuclear magnetic resonance (NMR) microcapillary probe for the detection of single magnetic microbeads. The geometry of the probe has been optimized so that the signal from the background water has a similar magnitude compared to the

Broad-band frequency references in the near-infrared: accurate dual comb spectroscopy of methane and acetylene

December 1, 2012
Author(s)
Alexander M. Zolot, Fabrizio R. Giorgetta, Esther Baumann, William C. Swann, Ian R. Coddington, Nathan R. Newbury
The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm −1) and acetylene between 193 THz and 199 THz (6430-6630 cm −1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic

Long-term stability of metal-envelope enclosed ionization gauges

December 1, 2012
Author(s)
James A. Fedchak, Dana R. Defibaugh
Ionization vacuum gauges are used as secondary standards by calibration laboratories and as transfer standards in intercomparisons among metrology laboratories. A quantitative measurement of gauge stability with respect to the gauge calibration factor is
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