Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: Expanding the application range (open access)

Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: Expanding the application range

A modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) gratings and arrays [Proc. SPIE 7077-7 (2007), Opt. Eng. 47(7), 073602-1-5 (2008)] has been proven to be an effective MTF calibration method for a number of interferometric microscopes and a scatterometer [Nucl. Instr. and Meth. A 616, 172-82 (2010]. Here we report on a significant expansion of the application range of the method. We describe the MTF calibration of a 6 inch phase shifting Fizeau interferometer. Beyond providing a direct measurement of the interferometer's MTF, tests with a BPR array surface have revealed an asymmetry in the instrument's data processing algorithm that fundamentally limits its bandwidth. Moreover, the tests have illustrated the effects of the instrument's detrending and filtering procedures on power spectral density measurements. The details of the development of a BPR test sample suitable for calibration of scanning and transmission electron microscopes are also presented. Such a test sample is realized as a multilayer structure with the layer thicknesses of two materials corresponding to BPR sequence. The investigations confirm the universal character of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds …
Date: July 26, 2010
Creator: Yashchuk, Valeriy V; Anderson, Erik H.; Barber, Samuel K.; Bouet, Nathalie; Cambie, Rossana; Conley, Raymond et al.
Object Type: Article
System: The UNT Digital Library
Determination of 237NP and Pu Isotopes in Large Soil Samples by Inductively Coupled Plasma Mass Spectrometry (open access)

Determination of 237NP and Pu Isotopes in Large Soil Samples by Inductively Coupled Plasma Mass Spectrometry

A new method for the determination of {sup 237}Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of {sup 237}Np and Pu isotopes by ICP-MS. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via {sup 238}U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1 x 10{sup 6}. Alpha spectrometry can also be applied so that the shorter-lived {sup 238}Pu isotope can be measured successfully. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu and {sup 238}Pu were measured by alpha spectrometry.
Date: July 26, 2010
Creator: Maxwell, S.
Object Type: Article
System: The UNT Digital Library
Energy-Water Nexus (open access)

Energy-Water Nexus

Conclusions of this presentation are: (1) energy and water are interconnected; (2) new energy sources will place increased demands on water supplies; (3) existing energy sources will be subjected to increasing restrictions on their water use; and (4) integrated decision support tools will need to be developed to help policy makers decide which policies and advanced technologies can address these issues.
Date: July 26, 2010
Creator: Horak, W.
Object Type: Article
System: The UNT Digital Library
Kinetics of Ejected Particles During Laser-Induced Breakdown in Fused Silica (open access)

Kinetics of Ejected Particles During Laser-Induced Breakdown in Fused Silica

None
Date: July 26, 2010
Creator: Raman, R N; Negres, R A & Demos, S G
Object Type: Article
System: The UNT Digital Library
A nanocrystal strain gauge for luminescence detection of mechanical forces (open access)

A nanocrystal strain gauge for luminescence detection of mechanical forces

Local microscale stresses play a crucial role in inhomogeneous mechanical processes from cell motility to material failure. However, it remains difficult to spatially resolve stress at these small length scales. While contact-probe and non-contact based techniques have been used to quantify local mechanical behavior in specific systems with high stiffness or stress and spatial resolution, these methods cannot be used to study a majority of micromechanical systems due to spectroscopic and geometrical constraints. We present here the design and implementation of a luminescent nanocrystal strain gauge, the CdSe/CdS core/shell tetrapod. The tetrapod can be incorporated into many materials, yielding a local stress measurement through optical fluorescence spectroscopy of the electronically confined CdSe core states. The stress response of the tetrapod is calibrated and utilized to study mechanical behavior in single polymer fibers. We expect that tetrapods can be used to investigate local stresses in many other mechanical systems.
Date: July 26, 2010
Creator: Choi, Charina; Koski, Kristie; Olson, Andrew & Alivisatos, Paul
Object Type: Article
System: The UNT Digital Library
RAPID SEPARATION METHOD FOR 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES (open access)

RAPID SEPARATION METHOD FOR 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES

A new rapid method for the determination of {sup 237}Np and Pu isotopes in soil and sediment samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for large soil samples. The new soil method utilizes an acid leaching method, iron/titanium hydroxide precipitation, a lanthanum fluoride soil matrix removal step, and a rapid column separation process with TEVA Resin. The large soil matrix is removed easily and rapidly using this two simple precipitations with high chemical recoveries and effective removal of interferences. Vacuum box technology and rapid flow rates are used to reduce analytical time.
Date: July 26, 2010
Creator: Maxwell, S.; Culligan, B. & Noyes, G.
Object Type: Article
System: The UNT Digital Library
Reaction cross-section predictions for nucleon induced reactions (open access)

Reaction cross-section predictions for nucleon induced reactions

None
Date: July 26, 2010
Creator: Nobre, G P; Thompson, I J; Escher, J E & Dietrich, F S
Object Type: Article
System: The UNT Digital Library
Reaction Mechanisms for Barite Dissolution and Growth (open access)

Reaction Mechanisms for Barite Dissolution and Growth

In Stack and Rustad (2007), the reactive flux method (Rey and Hynes, 1996) and molecular dynamics (MD) were used to simulate the {001} barite-water interface structure and water exchange rate of aqueous barium ions and barium surface species. Atomic-level mineralwater interfacial structure and kinetics are being studied with increasing precision due to advances in spectroscopic methods at synchrotron x-ray sources as well as improved computational capacity. Better characterization of these interfaces in turn is leading to advances in the understanding of many macroscopic geochemical properties. Overall the barite-water interfacial structure was found to compare well to that estimated using X-ray reflectivity (XRR) measurements (Fenter et al., 2001), but there was an important difference: the MD predicted an intricate water structure present at the interface with one major peak and several minor peaks whereas the XRR found only a single layer of water. This discrepancy is thought to result from a limited resolution in the Fenter et al. (2001) study as well as over-coordination of surface sulfates by the MD model.
Date: July 26, 2010
Creator: Stack, Andrew G.
Object Type: Report
System: The UNT Digital Library
Transport of Heat, Water Vapor and Carbon Doxide by Long Period Eddies in the Stable Boundary Layer (open access)

Transport of Heat, Water Vapor and Carbon Doxide by Long Period Eddies in the Stable Boundary Layer

The vertical transport of heat and trace chemicals for a night in April has been studied with a wavelet analysis and conventional one-hour averages. It was found that for the night of April 20, 2009, turbulent kinetic energy, heat and trace chemicals were transported directed downward from the jet core. The most significant periods for this transport were less than 5 minutes and greater than one hour with intermittent transport taking place in the 5 min to 1 hour time frame. The nocturnal boundary layer is characterized by turbulent intermittency, long period oscillations, and a slow approach to equilibrium, (Mahrt, 1999). Although turbulence is usually maintained by surface friction, downward transport from low-level jets can also play an important role in turbulence maintenance and in the transport of scalars, Mahrt (1999), Banta et al. (2006). The eddy covariance flux measurement technique assumes continuous turbulence which is unusual in the stable boundary because significant flux transport occurs via turbulent eddies whose periods are long compared with the averaging time (Goulden et al., 1996). Systematic error in eddy flux measurements is attributed mainly to the neglect of long period eddies. Banta et al. (2006) noted that observations of turbulence below the low …
Date: July 26, 2010
Creator: Kurzeja, R.
Object Type: Article
System: The UNT Digital Library
Turbulence Considerations for Comparing Ecosystem Exchange over Old-Growth and Clear-Cut Stands with Limited Fetch and Complex Canopy Flows (open access)

Turbulence Considerations for Comparing Ecosystem Exchange over Old-Growth and Clear-Cut Stands with Limited Fetch and Complex Canopy Flows

None
Date: July 26, 2010
Creator: Wharton, S.; Paw U, K. T.; Schroeder, M.; Bible, K. & Falk, M.
Object Type: Article
System: The UNT Digital Library