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Chemistry

Analytical chemistry

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Displaying 826 - 850 of 2094

Multiheterodyne spectroscopy with optical frequency combs generated from a continuous-wave laser

May 1, 2014
Author(s)
David A. Long, Adam J. Fleisher, Kevin O. Douglass, Stephen E. Maxwell, Katarzyna E. Bielska, Joseph T. Hodges, David F. Plusquellic
Dual-drive Mach-Zehnder modulators were utilized to produce power-leveled optical frequency combs (OFCs) from a continuous-wave laser. The resulting OFCs contained up to fifty unique frequency components and spanned more than 200 GHz. Simple changes to the

Time-resolved surface infrared spectroscopy during atomic layer deposition of TiO2 using tetrakis(dimethylamido)titanium and water

April 23, 2014
Author(s)
Brent A. Sperling, John Hoang, William A. Kimes, James E. Maslar, Kristen L. Steffens, Nhan V. Nguyen
Atomic layer deposition of titanium dioxide using tetrakis(dimethylamido)titanium (TDMAT) and water vapor is studied by reflection-absorption infrared spectroscopy (RAIRS) with a time resolution of 120 ms. Decomposition of the adsorbed TDMAT is observed

Comparison of the Properties of Cellulose Nanocrystals and Cellulose Nanofibrils Isolated From Bacteria, Tunicate, and Wood Processed Using Acid, Enzymatic, Mechanical, and Oxidative Methods

April 18, 2014
Author(s)
Iulia A. Sacui, Jeffrey W. Gilman, Ryan C. Nieuwendaal, Stephan J. Stranick, Henryk Szmacinski, Mehdi Jorfi, Christopher Weder, Johan Foster, Richard Olsson, Daniel Burnett
This work describes the study and characterization of native cellulose nanocrystals and nanofibrils (CNCs, CNFs), whose crystallinity, morphology, aspect ratio, and surface chemistry depend on the raw material source and hydrolysis conditions. Measurement

AN EXAMINATION OF METAL DEPOSITION DERIVED FROM AEROSPACE-RELATED ACTIVITY IN SEVERAL ENVIRONMENTAL MATRICES COLLECTED FROM WATERS SURROUNDING THE KENNEDY SPACE CENTER (KSC), FLORIDA

April 8, 2014
Author(s)
John Bowden, Theresa M. Cantu, Douglas M. Scheidt, Russell H. Lowers, Brian A. Nocito, Vaneica Y. Young, Louis J. Guillette
Metal deposition originating from anthropogenic activity was examined in a two-tier study using environmental samples collected from several locations at the Kennedy Space Center (KSC) and surrounding Merritt Island National Wildlife Refuge (MINWR) with

Isolated line shapes of molecular oxygen: ab initio calculations versus measurements

April 8, 2014
Author(s)
Vincent T. Sironneau, Joseph T. Hodges, Jean M. Hartmann, Julien Lamouroux
We present comparisons between measured isolated line shapes of molecular oxygen in air and those calculated, free of any adjusted parameter, using requantized Classical Molecular Dynamics Simulations (rCMDS). This work extends a previous study made for a

N-methylmesoporphyrin IX fluorescence as a reporter of strand orientation in guanine quadruplexes

April 1, 2014
Author(s)
Navin C. Sabharwal, Victoria Savikhin, Joshua Turek-Herman, John M. Nicoludis, Veronika Szalai, Liliya Yatsunyk
Guanine quadruplexes (GQ) are four-stranded DNA structures formed by guanine-rich DNA sequences. Formation of GQs inhibits cancer cell survival, but detecting GQs in vivo has proved difficult, in part because of GQ structural diversity. Development of GQ

Quantum-noise-limited cavity ring-down spectroscopy

March 29, 2014
Author(s)
David A. Long, Adam J. Fleisher, Szymon S. Wojtewicz, Joseph T. Hodges
Spectroscopic techniques with ultra-high sensitivity allow for the study of a wide variety of physical and chemical phenomena, ranging from the interrogation of individual atoms1 and molecules2,3 to the quantitative extraction of ensemble properties from

Comparison of independently calculated ab-initio normal-mode displacements for the three C-H stretching vibrations of methanol along the internal rotation path

March 19, 2014
Author(s)
Li-Hong Xu, Ronald M. Lees, Jon T. Hougen, Joel M. Bowman, Xinchuan Huang, Stuart Carter
Comparison of graphical displays of normal-mode coefficients from recent quantum chemical projected-frequency calculations with analogous displays constructed after reexamination of results from more extensive higher-level calculations described earlier in

Analytical Capabilities of Chemiresistive Microsensor Arrays in a Simulated Martian Atmosphere

March 6, 2014
Author(s)
Kurt D. Benkstein, Phillip H. Rogers, Christopher B. Montgomery, Jerry Jin, Baranidharan Raman, Stephen Semancik
The capabilities of a chemiresistive microsensor array for detecting and identifying four trace target analytes were examined under a simulated Martian atmosphere. The simulated environment included low oxygen content (0.15 %) balanced by carbon dioxide

Optical self-focusing effect in coherent light scattering with condensates

March 3, 2014
Author(s)
Lu Deng, Edward W. Hagley, C.J. Zhu, G.X. Huang
We present a theoretical investigation of optical self-focusing effects in light scattering with condensates. Using long (>200 μs), red-detuned pulses we show numerically that a nonnegligible self-focusing effect is present that causes rapid optical beam

Certification of Total Arsenic in Blood and Urine Standard Reference Materials by Radiochemical Neutron Activation Analysis and Inductively Coupled Plasma Mass Spectrometry

March 1, 2014
Author(s)
Rick L. Paul, William C. Davis, Karen E. Murphy, Colleen E. Bryan Sallee, Lee L. Yu, William F. Guthrie, Dennis D. Leber, Thomas W. Vetter
A newly developed procedure for determination of arsenic by radiochemical neutron activation analysis was used to measure arsenic in SRM 955c Toxic Elements in Caprine Blood and SRM 2668 Toxic Elements in Frozen Human Urine for the purpose of providing

Dependence of Soot Optical Properties on Particle Morphology: Measurements and Model Comparisons

February 18, 2014
Author(s)
James Radney, Rian You, Xiaofei Ma, Joseph Conny, Michael R. Zachariah, Joseph T. Hodges, Christopher D. Zangmeister
We measure the mass-specific absorption and extinction cross sections for laboratory-generated soot aerosols. Two soot morphologies are investigated, both comprising fractal aggregates of nearly spherical monomers. The first type consists of monomer chains

Filter Material Effects on Particle Absorption Characteristics

February 10, 2014
Author(s)
Cary Presser, Joseph M. Conny, Ashot Nazarian
The absorption coefficient and mass specific absorption cross section were determined for nigrosin-laden quartz, Teflon, and polycarbonate filters in inert surroundings at different steady-state temperatures and particle mass loadings. The objective was to

International Comparison of a Hydrocarbon Gas Standard at the Picomol per Mol Level

February 6, 2014
Author(s)
George C. Rhoderick, David L. Duewer, Eric Apel, Annarita Baldan, Bradley Hall, Alice Harling, Detlev Helmig, Gwi S. Heo, Jacques Hueber, Mi E. Kim, Yong D. Kim, Benjamin Miller, Stephen Montzka, Daniel Reimer
Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the atmosphere, including roles in particulates and ozone formation. Measurements of key non methane hydrocarbons (NMHCs) suggest atmospheric mole fractions ranging

CPTAC Studies 1 and 5: dissecting variability in multi-site LC-MS/MS proteomics through quality metrics and robust hierarchical multivariate statistics

February 4, 2014
Author(s)
Stephen E. Stein, David M. Bunk, Xia Wang, Matthew Chambers, Lorenzo J. Vega-Montoto, David L. Tabb
Shotgun proteomics experiments integrate a complex sequence of processes, any of which can introduce variability. Quality metrics computed from LC-MS/MS data have relied upon identifying MS/MS scans, but a new mode for the QuaMeter software produces

Estimation of the Limit of Detection Using Information Theory Measures

January 31, 2014
Author(s)
Alexander (. Vergara Tinoco, Fonollosa Jordi, Huerta Ramon, Santiago Marco
Definitions of the Limit of Detection (LoD) based on the probability of false positive and/or false negative errors have been proposed over the past years. Although such definitions are straightforward and valid for any kind of analytical system, the
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