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Chemistry

Analytical chemistry

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Displaying 876 - 900 of 2086

Isotope Dilution Mass Spectrometry For Quantitative Elemental Analysis Of Powdered Samples By Radiofrequency Pulsed Glow Discharge Time Of Flight Mass Spectrometry

October 15, 2013
Author(s)
John L. Molloy, Julian Malherbe, Fanny Claverie, Beatriz Fernandez, Aitor Alvarez-Toral, Alfredo Sanz-Medel, Rosario Pereiro
In recent years particular effort is being devoted to the development of pulsed glow discharges (PGDs) for mass spectrometry because this powering operation mode could offer important ionization analytical advantages. However, the capabilities of

Time-Resolved Infrared Studies of a Trimethylphosphine Model Derivative of [FeFe]-Hydrogenase

October 1, 2013
Author(s)
Edwin J. Heilweil, Christopher J. Stromberg, Melissa Johnson, James Thuman, Roger G. Letterman, Webster E. Charles
Model compounds that structurally mimic the hydrogen-producing active site of [FeFe] hydrogenases have been explored. In order to explore potential ground-state electronic structure effects on reaction mechanisms compared to hexacarbonyl derivatives, the

Rapid scan absorption spectroscopy using a waveform-driven electro-optic phase modulator in the 1.6- 1.65 ym region

September 25, 2013
Author(s)
Kevin O. Douglass, Stephen Maxwell, Gar W. Truong, Roger D. van Zee, Joseph T. Hodges, David Long, David F. Plusquellic
A method is reported for performing fast optical frequency scans over a bandwidth of 36.9 GHz and at a sweep rate of 40 kHz using a single second-order sideband from an electro-optic phase modulator driven by an arbitrary waveform generator. Single

Effects of Desialylation on Human alpha1-Acid Glycoprotein-Ligand Interactions

September 16, 2013
Author(s)
Richard Y. Huang, Jeffrey W. Hudgens
Human α1-Acid Glycoprotein (AGP), an acute phase glycoprotein, exists predominantly in blood. With its ability to bind basic, lipophilic, and acidic drugs, AGP has served as a drug carrier. It has been shown that the carbohydrate composition of AGP changes

A Missing Link in the Cascade Formation of High Symmetry Fullerene Cages

September 15, 2013
Author(s)
Dan Bearden, Jianyuan Zhang, Harry C. Dorn
Before the discovery of graphene, many versions of a “bottom-up” fullerene formation mechanism had been advanced starting with carbide (C2) that forms small carbon cluster chains and rings. However, in recent years evidence is emerging suggesting a “top

Elemental analyses of soil and sediment fused with lithium borate using isotope dilution laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-IDMS)

September 2, 2013
Author(s)
John L. Molloy, Julian Malherbe, Fanny Claverie, Aitor Alvarez-Toral, Beatriz Fernandez, Rosario Pereiro
Quantitative analysis using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) remains challenging primarily due to elemental fractionation effects and to the lack of appropriate standards available for the wide variety of samples of

Direct measurements of mass-specific optical cross sections of single component aerosol mixtures

July 22, 2013
Author(s)
James Radney, Xiaofei Ma, Keith A. Gillis, Michael R. Zachariah, Joseph T. Hodges, Christopher D. Zangmeister
The optical properties of atmospheric aerosols vary widely, being dependent upon particle composition, morphology and mixing state. This diversity and complexity of aerosols motivates measurement techniques that can discriminate and quantify a variety of

Trace water vapor analysis in specialty gases: sensor and spectroscopic approaches

July 1, 2013
Author(s)
Kristine A. Bertness, Mark W. Raynor, Kevin C. Cossel, Florian B. Adler, Jun Ye
The analysis of water vapor impurity is important in a number of specialty gas applications. However the main driver for the development and advancement of trace H 2O analysis techniques has been the microelectronics industry. The International Technology

Open-Path Dual-Comb Spectroscopy of Greenhouse Gases

June 9, 2013
Author(s)
Greg B. Rieker, Fabrizio R. Giorgetta, William C. Swann, Ian R. Coddington, Laura C. Sinclair, Christopher L. Cromer, Esther Baumann, Alexander M. Zolot, Nathan R. Newbury
Frequency-comb spectroscopy in the near-infrared is used to measure atmospheric CO2 and H2O concentrations over a 2-km outdoor open-air path. This technique shows promise for measurements over length scales between point sensors and satellite systems.

A fitting program for molecules with two equivalent methyl tops and C2v point-group symmetry at equilibrium: Application to existing microwave, millimeter, and sub-millimeter wave measurements of acetone

May 31, 2013
Author(s)
Jon T. Hougen, Vadim V. Ilyushin
A program, called PAM_C2v_2tops, for fitting the high-resolution torsion-rotation spectra of molecules with two equivalent methyl rotors and C2v symmetry at equilibrium is described and applied to the spectrum of acetone [(CH3)2CO]. The G36 permutation

Photochemical Properties of Some Cl-Containing Halogenated Alkanes

May 31, 2013
Author(s)
Vladimir L. Orkin, Victor Khamaganov, E. E. Kasimovskaya, A G. Guschin
Rate constants for the gas phase reactions of OH radicals with three partially halogenated alkanes, CHCl3 (kMC), CHFClCFCl2 (k122a), and CH2CFCl2 (k132c), were measured using a discharge flow – electron paramagnetic resonance technique over the temperature
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