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Chemistry

Analytical chemistry

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Displaying 1151 - 1175 of 2086

Comparison of the Sensitivity and Image Contrast in Spontaneous Raman and Coherent Stokes Raman Scattering Microscopy of Geometry Controlled Samples

February 9, 2011
Author(s)
Hyun M. Kim, Chris A. Michaels, Garnett W. Bryant, Stephan J. Stranick
We experimentally compare the performance and contrast differences between spontaneous and coherent Stokes Raman scattering microscopy. We demonstrate the differences on a series of geometry controlled samples that range in complexity from a point (array

Passive Intermodulation due to Self-Heating in Printed Transmission Lines*

February 2, 2011
Author(s)
Eduard Rocas, Juan C. Collado Gomez, Nathan D. Orloff, Jordi Mateu, James C. Booth, Juan M. O'Callaghan, Alberto Padilla
Abstract—This article proposes a mechanism by which third-order intermodulation distortion due to self-heating is generated in transmission lines. The work shows how transmission lines made of several materials whose properties are independent of the

Approximate theoretical model for the five electronic states (? = 5/2, 3/2, 3/2, 1/2, 1/2) arising from the ground 3d9 configuration in nickel halide molecules and for the rotational levels of the two ? = 1/2 states in this manifold

January 25, 2011
Author(s)
Jon T. Hougen
This paper is divided into two parts. In the first part an effective Hamiltonian for a non-rotating diatomic molecule containing only crystal-field and spin-orbit operators is set up to describe the energies of the five spin-orbit components that arise in

Influence of substrate on crystallization in polythiophene/fullerene blends

January 13, 2011
Author(s)
Lee J. Richter, Christine He, David Germack, R Joseph Kline, Dean DeLongchamp, Daniel A. Fischer, Chad R. Snyder, James G. Kushmerick
The nanoscale morphology of the active layer in organic, bulk heterojunction (BHJ) solar cells is crucial to device performance. Often a combination of casting conditions and post deposition thermal treatment are used to optimize the morphology. In general

Quantification of cholesterol-metabolizing P450s CYP27A1 and CYP46A1 in neural tissues reveals a lack of enzyme-product correlations in human retina but not human brain

January 7, 2011
Author(s)
Wei-Li Liao, Gun-Young Heo, Nathan G. Dodder, Rachel Reem, Natalia Mast, Suber Huang, Pier L. DiPatre, Illarion Turko, Irina A. Pikuleva
Improper cholesterol metabolism in the brain causes neurological diseases. Factors affecting cholesterol homeostasis includes cholesterol hydroxylation reactions, which are regulated by cytochrome P450 enzymes. One approach to estimate the total enzymatic

Performance of a coherent dual frequency comb spectrometer

January 1, 2011
Author(s)
Nathan R. Newbury, Esther Baumann, Ian R. Coddington, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
We discuss the performance of a coherent dual frequency comb spectrometer in terms of signal-to-noise ratio, resolution, and accuracy based on experimental data in the near and short-wave infrared centered at 1.5 and 3.4 micrometers.

Electrospray Tandem Quadrupole Fragmentation of Quinolone Drugs and Related Ions. On the Reversibility of Water Loss from Protonated Molecules

November 30, 2010
Author(s)
Pedatsur Neta, Bhaskar Godugu, Yuxue Liang, Yamil Simon, Xiaoyu Yang, Stephen E. Stein
Selected reaction monitoring (SRM) of quinolone drugs showed1 different sensitivities in aqueous solution vs. biological extract. The authors suggested formation of two singly protonated ions with different behavior, one undergoing loss of H 2O and the

Novel Reduced Pressure-Balance Syringe for Chromatographic Analysis

November 19, 2010
Author(s)
Bret Windom, Thomas J. Bruno
When withdrawing a fluid sample from an apparatus at reduced pressures for additional chromatographic analyses, a gas tight plunger syringe proves ineffective as it does not create a substantial pressure differential to pull a fluid from a reduced pressure

A Microwave Study of Hydrogen-Transfer-Triggered Methyl-Group Rotation in 5-Methyltropolone

November 10, 2010
Author(s)
Vadim V. Ilyushin, Emily A. Cloessner, Yung-Ching Chou, Laura B. Picraux, Jon T. Hougen, Richard Lavrich
We present here the first experimental and theoretical study of the microwave spectrum of 5-methyltropolone, which can be visualized as a 7-membered aromatic carbon ring with a five-membered hydrogen-bonded cyclic structure at the top and a methyl group at

Electron ionization and gas-phase ion molecule reactions of methylcyclohexane

November 9, 2010
Author(s)
C. Q. Jiao, Karl Irikura, S, F. Adams, A Garscadden
Absolute cross sections for electron impact ionization of methylcyclohexane (MCH, C 7H 14) are measured as a function of the electron energy in a range of 10 to 200 eV. The reactions between selected hydrocarbon ions with MCH, mainly via hydride transfer

High precision, broadband optical measurements with fiber laser frequency combs

November 2, 2010
Author(s)
Nathan R. Newbury, Ian R. Coddington, Esther Baumann, Fabrizio R. Giorgetta, William C. Swann, Alexander M. Zolot
Optical frequency combs have been used extensively, and with remarkable success, to measure the absolute frequency of cw lasers. The use of frequency combs has also expanded to include applications such as precision ranging, component metrology, and
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