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Chemistry

Analytical chemistry

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Displaying 951 - 975 of 2086

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

Immobilization of Proteins on Carboxylic Acid-Functionalized Nanopatterns

November 28, 2012
Author(s)
John Peter Ngunjiri, Daniel J. Stark, Tian Tian, Kimberly Briggman, Jayne C. Garno
The immobilization of proteins on nanopatterned surfaces was investigated using in situ atomic force microscopy (AFM) and ex situ infrared reflectance-absorption spectroscopy (IRAS). The AFM-based lithography technique of nanografting provided control of

Absolute line intensities for ethylene from 1800 to 2350 cm-1.

November 17, 2012
Author(s)
Walter J. Lafferty, Jean-Marie Flaud, A. Ben Hassen, F. K. Kwabia Tchana, X Landsheere, H Aroui
Fourteen Fourier transform spectra of ethylene (C2H4) have been recorded in the 1800-2350 spectral domain with different path-lengths and pressures and used to derive individual line intensities for lines belonging to the ν7 + ν8, ν4 + ν8 , ν6 + ν10, ν6 +

High-resolution infrared studies of the V10, V11, V14, and V18 levels of [1.1.1] propellane

November 15, 2012
Author(s)
Robynne Kirkpatrick, Tony Masiello, Mathew A. Martin, Joseph W. Nibler, Arthur Maki, Alfons Weber, Thomas A. Blake
This paper is a continuation of earlier work for which the high resolution infrared spectrum of [1.1.1]propellane was measured and its k and l structure resolved for the first time. Here we present results from an analysis of more than 16,000 transitions

East versus West: Organic Contaminant Differences in Brown Pelican (Pelecanus occidentalis) Eggs from South Carolina, USA and the Gulf of California, Mexico

November 1, 2012
Author(s)
Stacy S. Schuur, Daniel W. Anderson, Patrick G. Jodice, Joyce E. Stuckey
Brown pelicans (Pelecanus occidentalis) were listed as endangered in the United States in 1970, largely due to reproductive failure and mortality caused by organochlorine contaminants, such as DDT. The southeast population, P.o. carolinensis, was delisted
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