Search Results

You are looking at 11 - 20 of 30 items for

  • Author or Editor: D. Anderson x
  • All content x
Clear All Modify Search

Abstract  

Screening experiments were performed to evaluate reagent systems that deactivate pyrophoric, metallic depleted uranium waste streams at ambient temperature. The results presented led to the selection of two systems, which would be investigated further, for the design of the LLNL onsite treatment process of metallic depleted uranium wastes. The two feasible systems are: (a) 7.5 mol/l H2

Restricted access
Form indexes for DTA or TG curves (S T orS x) must be treated separately. Only forS x can clear relations to be developed for the order of reactionn. In the rational range ofn between 0.5 and 3.0 we found for linear, exponential and hyperbolic programmes these functions were found to be of the type
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$S_x = an^{0,5} + b$$ \end{document}
Restricted access

Summary  

The thermal neutron prompt gamma-ray activation analysis (PGAA) facility, operated by the US Food and Drug Administration and National Institute of Standards and Technology Center for Neutron Research, has been redesigned to lower background radiation levels and improved analytical capabilities. Analysis of 22 element standards and food and botanical certified reference materials revealed significant sensitivity increases and lower limits of detection for H, B, C, N, Na, Al, P, S, Cl, K, Ca, Fe, and Cd. Mass fractions for these elements, as well as Mg, Al, Si, Ti, Mn, Fe, Cu, I, Zn, Sm, and Gd, were determined for 6 dietary supplements.

Restricted access

Abstract  

A method is described for the determination of H, B, Cl, K, Na, S, Ca, and Cd in foods using in-beam neutron capture prompt -ray activation analysis. Special calibration procedures were necessary because of matrix-related thermal neutron scattering-induced sensitivity and background enhancements. Detection limits and sensitivities are presented for best-case and worst-case irradiation conditions. The method was applied to multielement analysis of 41 foods and to B, Cl, and K analysis of 13 orange juice produts in conjunction with analysis by inductively coupled plasma atomic emission spectrometry. The purpose of the latter application was to study B losses during acid digestion.

Restricted access

Abstract  

Neutron-capture prompt γ-ray analysis (PGAA) is an exceptionally good method for the determination of the major and minor elements Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe in most geological matrices. The trace elements H, B, S, Cl, Cd, Sm and Gd can often be readily measured in most geological materials. This technique was applied to volcanic ash samples collected in Washington and Montana by various groups following the May 18 eruption of the Mt. St. Helens volcano, as well as to several particulate samples collected at altitudes between 13 and 18 km by a NASA U-2 research aircraft. Groundfall ash samples show distinct elemental variations versus distance from the volcano. For example, Si/Al ratios vary from 2.85 near the volcano to about 3.70 at≽400 km to the east. Samples collected sequentially at a given location (Almira, Washington) also exhibit variations in the elemental ratios. These sequential samples were also subjected to leaching studies to determine soluble B, Cl and S. On the average, PGAA is able to account for 99.4±1.7% of the mass of each sample when the elements are considered to be in their common oxide forms. The stratospheric samples were collected May 19 on IPC cellulose filters on apparatus in a wing tank of the U-2. The PGAA results indicate that the sample from the greatest altitude resembles ashfall near the volcano, while those at lower altitudes somewhat resemble more distant ashfall.

Restricted access

Abstract  

This manuscript presents a method for categorizing gamma-ray spectra as indicative of benign or threat sources. Reported here is a method of spectral comparison ratios (SCR), which is useful in the targeted detection of specific gamma-ray signature classes. SCRs discriminate between benign and target sources by comparing counts in broad energy bins that are pre-determined using statistical discrimination criteria. The integral component of the SCR method is the location and interdependence of the energy bins, and this work discusses the statistical methods used for choosing their locations along with decision criteria that maximally separate targets from benign sources.

Restricted access

Abstract

For the calculation of kinetic parameters from thermal data files numeric optimization has been well introduced. But suitable starting values near the global minimum of the sum of deviation squares are needed for a successfully parameter estimation. Namely the search for starting values requires a lot of time and diminishes the effectiveness of the total procedure. Therefore we have developed an algorithm of the automatic search of starting values for the optimization of activation energy end frequency factor of a chemical reaction.

This search procedure uses the knowledge of the specific course of the correspondingSDS surface in the near of its global minimum. In this area theSDS describes two plateaus separated by a narrow valley. The search procedure avoids starting values at one of these plateaus. This PC program is part of the complex software package TA-kin v3.3 for kinetic evaluation of thermal measurements.

Restricted access

Abstract  

A computer program was developed for kinetic evaluations of calorimetric experiments to predict the further reaction run under adiabatic conditions. Kinetic modeling is based on elementary reaction steps whose rate laws form a set of differential equations. For the continuous parameter optimization time-temperature data and their derivatives are used. A special calorimeter of the ACTRON series with safety equipment was applied to investigate the kinetics of chemical reactions and to test kinetic on-line evaluations. In the paper, examples for the reaction of n-propanol with o-chlornitrobenzene and for the alcoholysis of phenyl isocyanate are given.

Restricted access