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Displaying 32601 - 32625 of 73830

Determination of Bitter Orange Alkaloids in Dietary Supplements Standard Reference Materials by Liquid Chromatography With Ultraviolet Absorbance and Fluorescence Detection

April 24, 2007
Author(s)
Karsten Putzbach, Katherine E. Sharpless, Lane C. Sander
Four adrenergic amines [(+/-) synephrine, (+/-) octopamine, tyramine, and n-methyltyramine) were determined in a variety of Citrus aurantium (Bitter Orange) containing dietary supplements. Two extraction techniques were evaluated in detail: Soxhlet

Determination of Caffeine, and Caffeine-Related Metabolites in Ephedra-Containing Standard Reference Materials Using Liquid Chromatography With Absorbance Detection and Tandem Mass Spectrometry

April 24, 2007
Author(s)
Jeanice M. Brown Thomas, Katherine E. Sharpless, S. Mitvalsky, Mark Roman, James H. Yen, Mary B. Satterfield
The concentration of caffeine and caffeine-related compounds in two ephedra-containing reference materials have been determined by three independent methods with measurements performed by the National Institute of Standards and Technology (NIST) and a

Microfluidic Directed Formation of Liposomes of Controlled Size

April 24, 2007
Author(s)
Andreas Jahn, Wyatt N. Vreeland, Don DeVoe, Laurie E. Locascio, Michael Gaitan
A new method to tailor liposome size and size distribution in a microfluidic format is presented. Liposomes are spherical structures formed from lipid bilayers that are from tens of nanometers to several micrometers in diameter. Liposome size and size

Complex Permittivity Measurements at Millimeter Wave Frequencies

April 23, 2007
Author(s)
Billy F. Riddle, Michael D. Janezic
Contemporary circuit designers are requiring larger bandwidths from microsystems to accomodate the ever-increasing demand for denser content. The electrical performance of these microsystems is intrisically related to the electromagnetic properties of the

Ferroelectric Distortion in SrTiO3 Thin Films on Si(001) by X-Ray Absorption Fine Structure: Experiment and First-Principles Calculations

April 23, 2007
Author(s)
Joseph C. Woicik, Eric L. Shirley, C S. Hellberg, S Sambasivan, Daniel A. Fischer, B D. Chapman, E A. Stern, P Ryan, D L. Ederer, H Li
Ti K and Ti L2,3 edge x-ray absorption fine-structure near-edge spectra of SrTiO3 thin films grown coherently on Si(001) reveal the presence of a ferroelectric (FE) distortion at room temperature. This unique phase is a direct consequence of the

Fracture Toughness through a Welded Pipeline Section - Crack Tip Opening Angle Criterion

April 23, 2007
Author(s)
Philippe P. Darcis, Christopher N. McCowan, Elizabeth S. Drexler, Joseph D. McColskey, Avigdor Shtechman, Thomas A. Siewert
The increasing demand for natural gas as an alternative energy source implies continued growth of gas pipeline installations. This trend compels the natural gas transmission industry to consider the construction of larger-diameter, higher-pressure

Low-field current-hysteretic oscillations in spin-transfer nanocontacts

April 19, 2007
Author(s)
Matthew Pufall, William Rippard, Michael Schneider, Stephen E. Russek
We have measured spin-transfer-driven, large-amplitude, current-hysteretic, low frequency (less than or equal to} 500 MHz), narrowband oscillations in nanocontacts made to spin valve structures. The oscillations occur in zero field, persist up to 5 mT for

X-Ray Induced Fluorescence Measurement of Segregation in a DyI3 Metal-Halide Lamp

April 19, 2007
Author(s)
T Nimalisuriya, John J. Curry, Craig J. Sansonetti, E J. Ridderhof, S Shastri, A J. Flikweert, W W. Stoffels, M Haverlag, J J. van der Mullen
X-ray induced fluorescence measurements, using high energy synchrotron radiation generated on the Sector 1 Insertion Device beamline at the Advanced Photon Source, were performed on a metal-halide lamp containing Hg and DyI$_3}$. Density distributions of

Experimental Vibrational Zero-Point Energies: Diatomic Molecules

April 18, 2007
Author(s)
Karl K. Irikura
Vibrational zero-point energies (ZPEs), as determined from published spectroscopic constants, are derived for 85 diatomic molecules. Standard uncertainties are also provided, including estimated contributions from bias as well as the statistical

Rapid Assessment of Dental Polymers Using Gradient Samples

April 18, 2007
Author(s)
Nancy J. Lin, Peter Drzal, Sheng Lin-Gibson
Dental composites are widely used yet still face challenges including incomplete conversion, polymerization shrinkage, and poor adhesion to tooth structures. High-throughput techniques to quickly assess several material properties in a combinatorial manner

Development of an Experimental Database and Kinetic Models for Surrogate Diesel Fuels

April 16, 2007
Author(s)
J T. Ferrell, N Cernansky, F L. Dryer, Daniel G. Friend, C A. Hergart, C K. Law, R M. McDavid, Christian Mueller, A K. Patel, Heinz Pitsch
Computational fluid dynamic (CFD) simulations that include realistic combustion/emissions chemistry hold the promise of significantly shortening the development time for advanced, high efficiency, low emission engines. However, significant challenges must

Performance of Biometric Quality Measures

April 16, 2007
Author(s)
Patrick Grother, Elham Tabassi
We document methods for the quantitative evaluation of systems that produce a scalar summary of a biometric sample¿s quality. We predicate this on the idea that the quality measure predicts performance, whether by design or correlation. We do this

Conservative Confidence Intervals Based on Weighted Means Statistics

April 15, 2007
Author(s)
Andrew L. Rukhin
For weighted means estimators of the common mean of several normal populations associated (conservative) confidence intervals are constructed. These intervals are compared to several traditional confidence bounds. Monte Carlo simulation results of these

Cancellation of the Collisional Frequency Shift in Caesium Fountain Clocks

April 13, 2007
Author(s)
K Szymaniec, W Chalupczak, Eite Tiesinga, Carl J. Williams, S Weyers, R. Wynands
We have observed that the collisional frequency shift in primary caesium fountain clocks varies with the clock state population composition and, in particular, is zero for a given fraction of the |F = 4, mF = 0> atoms, depending on the initial cloud
Displaying 32601 - 32625 of 73830
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