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Chemistry

Analytical chemistry

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Displaying 1126 - 1150 of 2094

Amplification of the optical absorption cross section for aerosols of soot with a nonabsorbing coating from photoacoustic measurements

May 13, 2011
Author(s)
Pedro Bueno, Daniel K. Havey, George W. Mulholland, Joseph T. Hodges, Keith A. Gillis, Russell R. Dickerson, Michael R. Zachariah
A quantitative understanding of the absorption and scattering properties of mixed soot and aerosol particles is necessary for evaluating the Earth's energy balance. Uncertainty in the net radiative forcing of atmospheric aerosols is relatively large and

Comparison of Diesel Fuel Oxygenates with Composition-Explicit Distillation Curve Method Part 1: Linear Compounds with One to Three Oxygens

May 2, 2011
Author(s)
Thomas J. Bruno, Tara Lovestead, Jennifer Riggs, Erica Jorgensen, Marcia L. Huber
There is a great deal of interest in formulating oxygenated diesel fuels that produce low particulate emissions. The most common oxygenating additives for diesel fuels include the glycol ethers, glycol esters, alcohols, ethers and ketones. It is important

Characterization of the First Order Nonlinear Stiffened Elasticity of the Piezoelectric Layer in Bulk Acoustic Wave Resonators

May 1, 2011
Author(s)
Juan C. Collado Gomez, Eduard Rocas, Jordi Mateu, Nathan D. Orloff, James C. Booth, Alberto Padillo, Juan Callaghan
This work proposes a procedure to characterize the intrinsic nonlinearities of bulk acoustic wave resonators by performing one port measurements of the second harmonic and second order intermodulation spurious signals. Closed-form expressions have been

Dual comb spectroscopy from 1.25 to 1.7 ym

May 1, 2011
Author(s)
Alexander M. Zolot, Ian R. Coddington, Fabrizio R. Giorgetta, Esther Baumann, William C. Swann, Nathan R. Newbury
A coherent dual comb spectrometer spanning much of the near infrared was constructed from broadened erbium fiber lasers. Gas phase water, methane and acetylene spectra were measured and characterized toward establishing new frequency standards.

Conformer-specific vibronic spectroscopy and vibronic coupling in a flexible bichromophore: bis-(4-hydroxyphenyl)methane

April 28, 2011
Author(s)
Chirantha P. Rodrigo, Christian Muller, Nathan Pillsbury, William H. James III, David F. Plusquellic, Timothy Zwier
The vibronic spectroscopy of jet-cooled bis-(4-hydroxyphenyl)methane (b4HPM) has been explored using fluorescence excitation (FE), dispersed fluorescence (DFL), UV-UV holeburning (UVHB), UV depletion (UVD), and fluorescence-dip infrared (FDIR)

High Pressure Viscosity Measurements of 1,1,1,2-Tetrafluoroethane

April 27, 2011
Author(s)
Arno R. Laesecke, Scott Bair
Viscosity measurements have been carried out with a falling-cylinder instrument in the compressed liquid and supercritical region of the hydrofluorocarbon 1,1,1,2-tetrafluoroethane (R134a). A highly pure sample was used. The measurement region at

Chirped-pulse terahertz spectroscopy for broadband trace gas sensing

April 22, 2011
Author(s)
Eyal Gerecht, Kevin O. Douglass, David F. Plusquellic
We report the first demonstration of a broadband trace gas sensor based on chirp-pulse terahertz spectroscopy. The advent of newly developed solid state sources and heterodyne detectors for the terahertz frequency range have made it possible to generate

Recent Advances in Electrochemical Glyco-biosensing

April 8, 2011
Author(s)
Rebecca A. Zangmeister, Germarie Sanchez-Pomales
Biosensors based on electrochemical transduction mechanisms have recently made advances into the field of glycan analysis. These glyco-biosensor assays offer simple, rapid, sensitive and economical approaches to the measurement need for rapid glycan

Geographical variation of Persistent Organic Pollutants in eggs of threatened loggerhead sea turtles (Caretta caretta) from Southeastern USA

April 4, 2011
Author(s)
Jennifer M. Lynch, Juan Alava, Jeanette Wyneken, Larry Crowder, Geoffrey Scott, John R. Kucklick
Persistent organic pollutants (POPs) are a recognized man-made threat to sea turtle populations, but the uncertainty surrounding exposure and sensitivity of sea turtles to contaminants is great and makes decision making difficult for conservation managers

Searching for applications with a fine-toothed comb

April 1, 2011
Author(s)
Nathan R. Newbury
Frequency combs, like many ground-breaking technologies, are simple in concept; they results from the spectrum of any regular train of optical pulses. What is remarkable is that this simple picture can be actually realized in a number of different

X-ray Emission Spectroscopy of Nitrogen-rich Compounds

March 31, 2011
Author(s)
Terrence J. Jach, Fernando D. Vila, W. T. Elam, J. D. Denlinger, John J. Rehr
Non-resonant x-ray emission spectroscopy was used to compare the nitrogen-rich compounds ammonium nitrate, trinitrotoluene, and cyclotrimethylene-trinitramine. They are representative of crystalline and molecular structures of special importance in

Electron Ionization Mass Spectra of Alkylated Sulfabenzamides

March 30, 2011
Author(s)
Nino G. Todua, Kirill V. Tretyakov, Roman S. Borisov, Dmitry I. Zhilyaev, Vladimir G. Zaikin, Stephen E. Stein, Anzor I. Mikaia
Mono-, di- and trialkyl derivatives of "sulfabenzamide" (N-4-aminophenylsulfonyl-benzamide) are prepared and their EI mass spectra are examined. It is found that the fragmentation of N- alkylsulfabenzamides (Alkyl = CH3 to n-C5H11) proceeds via a very

Ozone-Depleting Substances (ODSs) and Related Chemicals, Chapter 1 in Scientific Assessment of Ozone Depletion: 2010, Global Ozone Research and Monitoring Project-Report No.52, 516 pp., World Meteorological Organization, Geneva, Switzerland, 2011.

March 30, 2011
Author(s)
Stephen A. Montzka, S. Reimannander, Andreas Engel, Kirstin Kruger, O?Doherty Simon, William T. Sturges , Donald R. Blake , Marcel Dorf Dorf, Paul J. Fraser , Lucien Froidevaux , Kenneth Jucks, Karin Kreher, Michael J. Kurylo III, Abdelwahid Mellouki , John Miller , Ole J. Nielsen , Vladimir L. Orkin, Ronald G. Prinn , Robert Rhew , Michelle L. Santee , Andreas Stohl , Daniel P. Verdonik
The present document will be part of the information upon which the Parties to the United Nations Montreal Protocol will base their future decisions regarding protection of the stratospheric ozone layer. OVERVIEW It has been recognized since the 1970s that

Quantification and Compensation of Unintentional Analyte Aggregation in Electrospray Sampling

March 30, 2011
Author(s)
Mingdong M. Li, Suvajyoti S. Guha, Rebecca A. Zangmeister, Michael J. Tarlov, Michael R. Zachariah
Electrospray (ES) sources are commonly used to introduce non-volatile materials (e.g. nanoparticles, proteins, etc.) in to the gas phase for characterization by mass spectrometry and ion mobility. Recent studies in our group using electrospray ion mobility

CONTINUOUS FLOW ENZYME-CATALYZED POLYMERIZATION IN A MICROREACTOR

March 25, 2011
Author(s)
Santanu S. Kundu, Atul S. Bhangale, William E. Wallace, Kathleen M. Flynn, Charles M. Guttman, Richard Gross, Kathryn L. Beers
Enzymes immobilized on solid supports are increasingly used for chemical transformation because the process is greener and sustainable. Here we use microreactors to study enzyme catalyzed ring opening polymerization of -caprolactone to polycaprolactone. A
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