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Chemistry

Analytical chemistry

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Displaying 1076 - 1100 of 2094

Characterization of (1-3,1-6)-b-D-Glucan Side Chain Structure Provides the Basis for a New Model of Fungal Cell Wall Rigidity and Flexibility

November 11, 2011
Author(s)
Daniel W. Bearden, Douglas W. Lowman, Lara J. West, Michael F. Wempe, Trevor D. Power, Harry E. Ensley, Ken Haynes, David L. Williams, Michael D. Kruppa
Glucan is a (1-3)-β-linked glucose polymer with (1-6)-β-linked side chains and a major component of fungal cell walls. Glucans provide structural integrity to the fungal cell wall. The nature of the (1-6)-β-linked side chain structure of fungal (1-3,1-6)-β

In situ monitoring of enzyme-catalyzed (co)polymerizations by Raman spectroscopy

November 10, 2011
Author(s)
Matthew T. Hunley, Atul Bhangale, Santanu S. Kundu, Peter M. Johnson, Michael S. Waters, Richard Gross, Kathryn Beers
In situ, fiber optic-based Raman spectroscopy provided real time monitoring of enzyme-catalyzed ring-opening homo- and copolymerizations of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL). A custom designed reactor equipped with in situ fiber optic probe

Findings and Recommendations from the Joint NIST AGA Workshop on Odor Masking

November 1, 2011
Author(s)
Thomas J. Bruno, Nancy Rawson, Ali Quaraishi
Since the days of the alchemist, the observation that some substances have a smell while other substances do not has been a source of fascination. The sense of smell, or olfaction, is our least understood sense, however it is important for many human

Microwave measurements of proton tunneling and structural parameters for the propiolic acid - formic acid dimer.

October 21, 2011
Author(s)
Adam M. Daly, Kevin O. Douglass, Laszlo C. Sarkozy, Justin L. Neill, Matt T. Muckle, Daniel P. Zaleski, Brooks H. Pate, Stephen G. Kukolich
Microwave spectra of the propiolic acid-formic acid, (Pro-FA) doubly hydrogen bonded complex were measured in the 1-21 GHz range. Rotational spectra for seven isotopomers were obtained and fit. For the parent isotopomer, a total of 138 a-dipole transitions

Determination of Moisture Content of Single-Wall Carbon Nanotubes

October 17, 2011
Author(s)
Rolf L. Zeisler, Rabia Oflaz, Ralph E. Sturgeon, Rick L. Paul, Brian E. Lang, Jeffrey A. Fagan, Joseph W. Lam, Anthony Windust, P Grinberg, Benoit Simard, Christopher T. Kingston
Several techniques were evaluated for the establishment of reliable water/moisture content of single-wall carbon nanotubes. Karl Fischer titration (KF) provides for a direct measure of the water content and was used for benchmarking against results

Impact of surface roughness on diffusion of confined fluids

October 17, 2011
Author(s)
William P. Krekelberg, Vincent K. Shen, Jeffrey R. Errington, Thomas M. Truskett
Using event-driven molecular dynamics simulations, we quantify how the self diffusivity of confined hard-sphere fluids depends on the nature of the confining boundaries. We explore systems with featureless confining boundaries that treat particle-boundary

In Situ Gas Phase Diagnostics for Titanium Nitride Atomic Layer Deposition

October 14, 2011
Author(s)
James E. Maslar, William A. Kimes, Brent A. Sperling
This report describes the performance of a technique for the simultaneous, rapid measurement of major gas phase species present during titanium nitride thermal atomic layer deposition involving tetrakis(dimethylamido) titanium (TDMAT) and ammonia. In this

Chromatographic Sample Collection from Two Phase (gas + liquid) Flows

October 12, 2011
Author(s)
Thomas J. Bruno, Bret Windom
A particularly challenging sample presentation in analytical chemistry is a flowing stream that consists of both a gas and liquid phase, in the situation in which an analysis is needed for both phases, separately. In these cases, the vapor and liquid must

High Frequency Characterization of Contact Resistance and Conductivity of Platinum Nanowires*

October 1, 2011
Author(s)
Kichul Kim, Paul Rice, Thomas M. Wallis, Dazhen Gu, SangHyun S. Lim, Atif A. Imtiaz, Pavel Kabos, Dejan Filipovic
Abstract— Individual platinum (Pt) nanowires (NWs) with 100 nm and 250 nm diameters, embedded in coplanar waveguide (CPW) structures are investigated. Three approaches for characterization of their contact resistance and conductivity at high frequencies

Compressed-Liquid Density Measurements of Methyl Oleate and Methyl Linoleate

September 30, 2011
Author(s)
Stephanie L. Outcalt
Compressed liquid densities of the fatty acid methyl esters methyl linoleate and methyl oleate have been measured with a vibrating-tube densimeter. The temperature and pressure range of the measured data is from 270 K to 470 K, and 0.5 MPa to 50 MPa. The

Reexamination of the C2H3+ microwave and infrared spectra

September 29, 2011
Author(s)
Jon T. Hougen, Laurent H. Coudert
The high-resolution infrared spectrum of C2H3 recorded in the 3 CH stretching region (J. Phys. Chem. 99 (1995) 15611-15623) is re-analyzed using an effective internal axis method (IAM) accounting for the large amplitude hydrogen migration motion. The

Reversed-Flow Chromatographic Determination of Binary Diffusion Coefficients

September 19, 2011
Author(s)
William S. McGivern, Jeffrey A. Manion
A reversed-flow chromatographic apparatus for the measurement of binary diffusion coefficients is described. Hydrocarbons are detected using flame ionization detection, and inert species can be detected by thermal conductivity. We have measured the binary

Construction of a High Power OPO Laser system for Differential Absorption LIDAR

September 13, 2011
Author(s)
Kevin O. Douglass, Stephen E. Maxwell, David F. Plusquellic, Joseph T. Hodges, Roger D. van Zee, Daniel V. Samarov, James R. Whetstone
Our goal is to develop and characterize optical measurement technology to enable accurate quantification of greenhouse-gas emissions to meet the needs of industry and regulators. A 1064 nm pumped high energy optical parametric oscillator (OPO) operating

On the electronic excited state dynamics of vibronic transitions. High resolution electronic spectra of acenaphthene and its argon van der Waals complex in the gas phase.

September 1, 2011
Author(s)
Leonardo Avarez-Valtierra, David F. Plusquellic, John T. Yi, David W. Pratt
Rotationally resolved fluorescence excitation spectroscopy has been used to study the dynamics, electronic distribution, and the relative orientation of the transition moment vector in several vibronic transitions of acenaphthene (ACN) and in its Ar van

Rotationally Resolved C2 Symmetric Conformers of Bis-(4-hydroxyphenyl)methane: Textbook Examples of Excitonic Coupling in the S1 and S2 Electronic States

September 1, 2011
Author(s)
Shin G. Chou, Chirantha P. Rodrigo, Christian Muller, Kevin O. Douglass, Timothy Zwier, David F. Plusquellic
Rotationally resolved microwave and ultraviolet spectra of jet-cooled bis-4 hydroxy)-diphenylmethane (b4HBM) have been obtained using Fourier-transform microwave and UV laser/molecular beam spectrometers. A recent vibronic level study of b4HPM1 has
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