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Chemistry

Analytical chemistry

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Displaying 876 - 900 of 2094

Microsensor Analyses for Trace Targets over Extended Times in a Simulated Martian Environment

November 6, 2013
Author(s)
Kurt D. Benkstein, Phillip H. Rogers, Christopher B. Montgomery, Stephen Semancik, C. Jin, Baranidharan Raman
We have studied the performance of a chemical microsensor array in a simulated Martian environment, which involved a carbon dioxide-rich background with low oxygen content (0.15 %) at low pressure and temperature to mimic the conditions at the Martian

Methods for Optimizing and Extending the Performance of Chemiresistive Gas Microsensors

November 3, 2013
Author(s)
Kurt D. Benkstein, Alexander (. Vergara Tinoco, Christopher B. Montgomery, Baranidharan Raman, Stephen Semancik
This paper briefly describes varied concepts developed and implemented to enhance the performance of gas-phase chemical microsensors. The developments are illustrated for chemiresistive (MEMS) microdevices, and involve efficient, array-based approaches to

Fluctuation Enhanced Sensing (FES) with a Nanostructured Semiconducting Metal Oxide Film for Gas Detection and Classification

October 31, 2013
Author(s)
Bulent Ayhan, Chiman Kwan, Jin Zhou, Laszlo Kish, Kurt D. Benkstein, Phillip H. Rogers, Stephen Semancik
The feasibility of fluctuation-enhanced sensing (FES) for the detection and classification of different gases by using a single microsensor has been experimentally demonstrated. A nanostructured semiconducting metal oxide film has been used as a

Achieving Climate Change Absolute Accuracy in Orbit

October 28, 2013
Author(s)
Bruce Wielicki, Joseph P. Rice
The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a metrology laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks

Connection between thermodynamics and dynamics of simple fluids in highly attractive pores

October 25, 2013
Author(s)
William P. Krekelberg, Vincent K. Shen, Daniel W. Siderius, Thomas M. Truskett, Jeffrey R. Errington
We investigate the structural and diffusive dynamics properties of a model fluid in highly-absorptive cylindrical pores. At subcritical temperatures, self diffusion displays three distinct regimes as a function of average pore density ρ: 1) a decrease in

Spectral line shapes investigation with Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy

October 23, 2013
Author(s)
A. Cygan, S. Wojtewicz, J. Domyslawska, Piotr Maslowski, Katarzyna E. Bielska, M. Piwinski, K. Stec, R.S. Trawinski, F Ozimek, C. Radzewicz, Hisashi Abe, T. Ido, Joseph T. Hodges, D Lisak, R. Ciurylo
A review of recent experiments involving a newly developed Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy (PDH-locked FS-CRDS) system is presented. By comparison to standard FS-CRDS, the PDH lock of the probe laser to the ring

Measurement, Standards, and Data Needs for CO2 Capture Materials: A Critical Review

October 21, 2013
Author(s)
Laura Espinal, Dianne L. Poster, Winnie K. Wong-Ng, Andrew J. Allen, Martin L. Green
The commercial deployment of cost-effective carbon capture technology is hindered partially by the lack of a proper suite of materials-related standards, data, and measurement methods, which would provide critical information for the systematic design of

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
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