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Chemistry

Analytical chemistry

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Displaying 751 - 775 of 2086

Rapid DNA melting analyses using a microfabricated electrochemical platform

January 1, 2015
Author(s)
Zuliang Shen, Stephen Semancik, Herman O. Sintim
A new microscale platform is reported which is based on microfabrication methods that integrate thermal control and multi-electrode components to enable rapid temperature-dependent electrochemical measurements on small volume fluid samples. We demonstrate

Reevaluation of Neutron Flux Characterization Parameters for NIST RT-2 Facility

December 31, 2014
Author(s)
Dagistan Sahin, Vladimir Radulovic, Richard M. Lindstrom, Andrej Trkov
It has been difficult to characterize the thermal to epithermal neutron flux ratio (f) and the measure of the nonideal epithermal neutron flux distribution (α) for the RT-2 pneumatic rabbit facility at the NIST National Bureau of Standards Reactor (NBSR)

Update on Ozone-Depleting Substances (ODSs) and Other Gases of Interest to the Montreal Protocol, Chapter 1 in Scientific Assessment of Ozone Depletion: 2014, Global Ozone Research and Monitoring Project-Report No.55, 416 pp., World Meteorological Organiz

December 30, 2014
Author(s)
Lucy J. Carpenter, Stefan Reimann, Andreas Engel, Stephen Montzka, James B. Burkholder, Cathy Clerbaux, Bradley Hall, Shari A. Yvon-Lewis, Donald R. Blake, Marcel Dorf, Geoffre S. Dutton, Paul J. Fraser, Lucien Froidevaux, Fran?ois Hendrick, Jianxin Hu, Ashley Jones, Paul B. Krummel, Lambert J. Kuijpers, Michael J. Kurylo, Qing Liang, Emmanuel Mahieu, Jens M?hle, Simon O?Doherty, Keiichi Ohnishi, Vladimir L. Orkin, Klaus Pfeilsticker, Matt Rigby, Isobel J. Simpson, Yoko Yokouchi
Changes in the global atmospheric abundance of a substance are determined by the balance between its emissions and removal. Declines observed for ozone-depleting substances (ODSs) controlled under the Montreal Protocol are due to global emission reductions

Interrogating the Carbon and Oxygen K-edge NEXAFS of a CO2-dosed Hyperbranched Aminosilica

December 19, 2014
Author(s)
Laura Espinal, Martin L. Green, Dean M. DeLongchamp, Watcharop Chaikittisilp, Jarod C. Horn, Miles Sakwa-Novak, Cherno Jaye, Daniel A. Fischer, Nicholas Brunelli, Christopher Jones
Near edge x-ray absorption fine structure (NEXAFS) spectroscopy was used to study the adsorption of CO2 in a hyperbranched aminosilica (HAS) compound, a porous solid state material with great potential for carbon capture applications. After dosing a

Microwave Rotational Spectral Study of CH3CN-H2O and Ar-CH3CN

December 17, 2014
Author(s)
Francis J. Lovas, J. Sobhanadrib
The microwave spectrum of the molecular complex of acetonitrile (CH3CN) with water (H2O) has been studied with a pulsed-beam Fourier Transform Microwave Spectrometer (FTMW) from a gas sample of 1 % by volume of CH3CN in Ar flowed over a water sample. The

Absolute line intensities for oxirane in the 11.4 micron spectral region.

December 15, 2014
Author(s)
Walter J. Lafferty, Jean-Marie Flaud, Fridolin Kwabia
Absolute individual line intensities of numerous transitions of the fundamental ν15, ν12 and ν5 bands of oxirane (ethylene oxide, cyc-C2H4O) have been measured in the 790-940 cm-1 region using seven high-resolution Fourier transform spectra recorded at 0

Microwave Determination of the Volume of a Pressure Vessel

December 9, 2014
Author(s)
Michael R. Moldover, James W. Schmidt, Keith A. Gillis, James B. Mehl, John D. Wright
Using microwave techniques that are scalable to very large volumes, we measured the interior volume of a 0.3 m 3, commercially-manufactured, pressure vessel with an uncertainty of 0.05 %, as confirmed by independent, more-accurate, gas-expansion

Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

December 8, 2014
Author(s)
Justin M. Shaw, Patrik Grychtol, Dmitriy Zusin, Ronny J. Knut, Tenio Popmintchev, Hans T. Nembach, Avner Fleischer, Henry Kapteyn, Margaret Murnane, Ofer Kfir, Oren Cohen
Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, this capability was available only at large-scale X-ray free-electron lasers or synchrotrons. Here we

High Resolution Surface Plasmon Resonance Imaging for Single Cells

November 30, 2014
Author(s)
Alexander Peterson, Michael Halter, Alessandro Tona, Anne Plant
Background Surface plasmon resonance imaging (SPRI) is a label-free technique that can image refractive index changes at an interface. We have previously shown that SPRI can be used to study the dynamics of cell-substratum interactions. However

Characterization of AlgMsp, an Alginate Lyase from Microbulbifer sp. 6532A

November 19, 2014
Author(s)
Jeffrey W. Hudgens, Steven M. Swift, Ryan D. Heselpoth, Patrick M. Bales, Daniel C. Nelson
Alginate is a polysaccharide produced by certain seaweeds and bacteria that consists of mannuronic acid and guluronic acid residues. Seaweed alginate is used in food and industrial chemical processes, while the biosynthesis of bacterial alginate is

Accurate determination of the size distribution for polydisperse, cationic metallic nanomaterials by asymmetric-flow field flow fractionation

November 13, 2014
Author(s)
Julien C. Gigault, Thao M. Nguyen, John M. Pettibone, Vincent A. Hackley
In this work we have developed and validated a methodology for determining the size distribution in polydisperse cationic nanoparticle (NP) samples using asymmetric-flow field flow fractionation (A4F), where known compositional influence of previously used

Line shapes, positions and intensities of water transitions near 1.28 microns

November 7, 2014
Author(s)
Vincent T. Sironneau, Joseph T. Hodges
We present measurements of approximately 70 isolated, self-broadened, water vapor lines which are assigned to the (1,0,1)(0,0,0), (0,0,2)(0,0,0), (1,2,0)(0,0,0), and (2,0,0)(0,0,0) vibrational bands and which occur in the transparency window region

Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshape near 2.06 um

November 3, 2014
Author(s)
Thinh Q. Bui, David Long, Agata Cygan, Vincent T. Sironneau, Daniel Hogan, Priyanka M. Rapusinghe, Mitchio Okumura
Frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) was used to study CO2 lineshapes in the (20013)←(00001) band centered near 2.06 um. Two rovibrational transitions were chosen for this study to measure non-Voigt collisional effects for air

Frequency-Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths

October 29, 2014
Author(s)
Greg B. Rieker, Fabrizio R. Giorgetta, William C. Swann, Jonathan Kofler, Alexander M. Zolot, Laura C. Sinclair, Esther Baumann, Christopher L. Cromer, G. Petron, Colm Sweeney, P P. Tans, Ian R. Coddington, Nathan R. Newbury
We demonstrate frequency comb tooth-by-tooth measurements of atmospheric gas absorption across a 2-km, turbulent, open-air path through coherent dual-comb spectroscopy. High accuracy, high signal-to-noise transmission spectra are acquired spanning 5990 to

Path degeneracy and EXAFS analysis of disordered materials

October 24, 2014
Author(s)
Bruce D. Ravel
The analysis of EXAFS data measured on a material with a disordered local configuration environment around the absorbing atom can be challenging due to the proliferation of photoelectron scattering paths that must be considered in the analysis. In the case

Modeling RP-1 fuel advanced distillation data using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry and partial least squares analysis

October 15, 2014
Author(s)
Thomas J. Bruno, Benjamin Kehimkar, Brendon Parsons, Jamin C. Hoggard, M. C. Billingsley, R. E. Synovec
Recent efforts in predicting rocket propulsion (RP-1) fuel performance through modeling put greater emphasis on obtaining detailed and accurate fuel properties, as well as to elucidate the relationships between fuel composition and their properties. Herein
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