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Abstract  

The trace elements in sea water, particularly the pollutant elements (Cu, Cd, As, Zn, Hg and Cr) are present in very low concentrations (in the order of 10−9 g/ml). For the determination of the concentration of these elements the neutron activation analysis has been used successfully. The separation of the impurities has been studied using radioactive tracers by coprecipitation with carriers and on ion exchange resins. The preconcentration technics applied before the irradiation introduces too large “blank” values, which can be reduced by etching the containers with HF—EDTA. In order to have representative samples, the water must be quickly frozen after taking out from the sea. With these precautions, the method developed allows to analyse samples of 3 ml volumes. The results of sea water sample analyses from different areas are presented.

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Periodica Mathematica Hungarica
Authors:
D. Szász
,
L. Kovács
, and
J. Mayer
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Résumé  

Une méthode d'analyse des impuretés dans l'or métallique par activation neutronique, a été mise au point. Après irradiation de 15 heures dans un flux de 2·1014 n·cm−2·sec−1, l'échantillon d'or est traité en cellule blindée. La matrice est séparée des impuretés à analyser par des méthodes électrolytiques. Les impuretés sont généralement séparées en 3 fractions qui sont mesurées par spectrométrie γ. Le traitement des informations est effectué sur ordinateur IBM 360/91 moyennant un programme écrit au laboratoire. 29 éléments sont détectables par cette méthode.

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Abstract

One of the most important manufacturing steps for efficient modules is the encapsulation of the control circuit and the design of the echelon height and convexity value between the casing and the circuit. The paper presents the current manufacturing technology and the development of tools and technology driven by the customers’ requirements. For this reason, a new gluing tool has been developed in the report including a pneumatic open-close machine and special use of plasma technology designed for decreasing the setting time of the glue. The development includes the design of the workplace, working requirements and the optimisation of the expenses. In the paper the results are reported with specific industrial experiences.

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Abstract  

Neutron activation analysis has been used for the determination of trace elements in different wines coming from various french vineyards. The technics used are non destructive for short and middle half-life radionuclides (28Al−76As−49Ca−38Cl−42K−27Mg−56Mn−24Na−52V). A radiochemical separation is necessary for longer half-life radionuclides (60Co−52Cr−134Cs−59Fe−86Rb−65Zn). The results of our study show that the identification of vineyards based on the determination of specific oligo-elements can be proposed. However more data are needed to demonstrate that the knowledge of the amounts of specific oligo-elements in a wine corresponding to a given vineyard can be used for disclose frauds more particularly in the cases of wine watering or mixtures of wines coming from different vineyards.

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Abstract  

A high speed method of thermal analysis was developed to allow the carbonation profile of lime mortars to be followed within a convenient time-frame. The loss in mass on heating, up to 700C, of lime/sand mixtures of different proportions was related to the known quantity of lime in each mixture. It was shown that a heating rate of 50C min–1 produced data which had a very high correlation with known quantities of Ca(OH)2. Thismethod can be used to measure the extent of carbonation at varying depths through a limemortar. This can be repeated at intervals to give an insight into the shape and extent of the carbonation front as it develops over time.

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Abstract  

We report the first quantitative results using a focused cold neutron beam for prompt gamma activation analysis (PGAA). We have measured the prompt gamma signal from known Fe, Cr, Ti, B, and Cd specimens in the focusing geometry, from which we determine the sensitivities for these elements by the method of standard addition. Furthermore, we show results of measurements for homogeneous standard reference materials (boron in SRM 611 glass, and iron and chromium in a steel alloy SRM 160b) to verify the sensitivities determined. Finally, we present a position-dependent study of the Cr to Fe mass ratio in an industrial material, taking advantage of the narrowly focused beam. Existing problems for achieving routine quantitative analysis using the focused beam and suggestions for future directions are discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
A. Plonka
,
J. Mayer
,
D. Metodiewa
,
J. Gebicki
,
A. Zgirski
, and
M. Grabska

Abstract  

The catalytic effects of human superoxide dismutase and bovine ceruloplasmin on superoxide radical dismutation were studied by pulse radiolysis at room temperature. The rate constants for the disappearance of superoxide radicals were found to be (8.1±1.2)·105M–1·s–1 for spontaneous disproportionation, (9.8±1.5)·106 M–1·s–1 in the presence of ceruloplasmin, and (2.1±0.3)·109M–1·s–1 in the presence of superoxide dismutase.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
E. Mackey
,
D. Anderson
,
H. Chen-Mayer
,
R. Downing
,
R. Greenberg
,
G. Lamaze
,
R. Lindstrom
,
D. Mildner
, and
R. Paul

Abstract  

At the National Institute of Standards and Technology, there are two techniques for chemical analysis that use neutron beams from the reactor for target irradiation: neutron depth profiling (NDP) and prompt -ray activation analysis (PGAA). There are two facilities for each technique, one equipped with a thermal neutron beam and the other, with a cold neutron beam. In addition, focused beams of cold neutrons will be used to measure the two-dimensional element distributions by PGAA and three-dimensional distributions by NDP. This paper includes a brief description of the facilities, the measurement capabilities of each, some recent applications of NDP and PGAA, and neutron focusing as applied to these techniques.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
H. Chen-Mayer
,
V. Sharov
,
D. Mildner
,
R. Downing
,
R. Paul
,
R. Lindstrom
,
C. Zeissler
, and
Q. Xiao

Abstract  

A neutron lens has been constructed to focus cold neutrons from the exit of a58Ni neutron guide, which delivers a beam to the Prompt-Gamma Activation Analysis (PGAA) station at the NIST Cold Neutron Research Facility. The lens compresses a neutron beam of cross section 50 mm× 45 mm onto a focal spot of diameter 0.53 mm (fwhm) wich an average gain of 80 in neutron current density. PGAA measurements have been performed to demonstrate the enhanced sensitivity and detection limits for various elements and the spatial resolution in one transverse dimension. For the two test particles (a gadolinium glass bead and cadmium metal of sizes less than 0.5 mm), the gain in the -count rate with the lens is a factor of 60, and the detection limit is improved by a factor of 20. The system can be used for two-dimensional mapping of samples on a sub-millimeter scale to complement other analytical techniques such as neutron depth profiling (NDP).

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