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Chemistry

Analytical chemistry

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Displaying 826 - 850 of 2086

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

Quantification of total serum transferrin and transferrin sialoforms in human serum; an alternative method for the determination of carbohydrate-deficient transferrin in clinical samples

January 20, 2014
Author(s)
Yoana Y. Nuevo Ordonez, William C. Davis, Raymond F. Anton
Carbohydrate deficient transferrin (CDT) measurements in human serum constitute the most specific marker for chronic heavy alcohol use and congenital disorders of glycosylation in proteins. Therefore, the development of precise and accurate analytical

Measuring order in regioregular poly(3-hexylthiophene) with solid-state 13C CPMAS NMR

January 10, 2014
Author(s)
Ryan C. Nieuwendaal, Chad R. Snyder, Dean M. DeLongchamp
We report on details of molecular packing in high molar mass poly(3-hexylthiophene) (P3HT) by solid-state 13C {1H} cross-polarization magic angle spinning (CPMAS) NMR measurements. The degree of polymer order was estimated for two films of varied drying

Influence of tissue, age, and environmental quality on global levels of genomic methylation in the American alligator (Alligator mississippiensis)

January 7, 2014
Author(s)
Benjamin B. Parrott, John Bowden, Satomi Kohno, Jessica A. Cloy-McCoy, Jacqueline T. Bangma, Thomas R. Rainwater, Phillip M. Wilkinson, John Kucklick, Louis J. Guillette
Epigenetic modifications are key mediators of the interactions between the environment and an organism's genome. DNA methylation represents the best-studied epigenetic modification to date and is known to play key roles in regulating transcriptional

Probing the intracellular glutathione redox potential using in-cell NMR spectroscopy

January 2, 2014
Author(s)
Steve Y. Rhieu, Aaron A. Urbas, Daniel W. Bearden, John P. Marino, Vytautas Reipa, Katrice A. Lippa
Non-invasive and real-time analysis of cellular redox processes has been greatly hampered by lack of suitable measurement techniques. Here we describe an in-cell nuclear magnetic resonance (NMR)-based method for measuring the intracellular glutathione

Nonlinear Vibrational Spectrometry

December 31, 2013
Author(s)
Lee J. Richter
Second order nonlinear spectroscopies such as sum frequency generation (SFG) are intrinsically interface sensitive and enable sub monolayer sensitivity to be achieved at buried, optically accessible interfaces. Vibrationally-resonant SFG allows bond
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