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  • Author or Editor: J. Räisänen x
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Abstract  

A simple proton beam (PIXE) arrangement developed for a low energy accelerator was used for the determination of absolute concentrations of nine trace elements in human bone samples. The 2.4 MeV proton beam was externalized through a thin (2 μm) aluminiummylar foil. Using an air cooling system, the foil withstood a high current (0.5–1 μA) for a long time. The samples were cooled to prevent damage and volatilization of elements. The induced X-rays were detected with a Si(Li) detector and the external beam was monitored with a second detector, measuring K X-rays induced in atmospheric argon. The mean (SD) trace element levels (ppm) measured in dense bone by comparison with hydroxyapatite/standard mixtures were: Cr<2.0, Mn<2.3, Fe 7.58 (1.55), Ni<2.4, Cu 3.58 (2.16), Zn 144 (27), Pb 12.2 (2.5), Br 12.4 (5.5) and Sr 47.7 (14.3). The detection limits for these elements achieved in this work were about 1 ppm when rather short measuring times (∼10 min) were used. The coefficient of variation of a single measurement, e.g. for Zn, was 3–4%. Because of the slow turnover of dense bone, such measurements provide a means of monitoring long term trace element exposure.

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Abstract  

A systematic study of the relative thick-target yields of prompt γ-rays following proton bombardment has been carried out at Ep=1, 1.7 and 2.4 MeV for the elements Z=3–9, 11–21. The relevant spectra for each element are depicted and a table of the most suitable γ-rays for elemental analysis are given. Depending on the strength of the reaction cross section, the sensitivity limits of the detection vary from ppm to a few percent under practical measuring arrangements. Particular aspects of the measuring techniques are discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Oksanen, J. Meriläinen, J. Räisänen, T. Saarinen, and A. Virtanen

Abstract  

The feasibility of the particle induced X-ray emission (PIXE) technique for varve counting of vertically taken marine and lacustrine sediments was studied aiming at its possible use as a dating procedure by observing the yearly variation of the constituent elements. The samples were impregnated with a low viscosity epoxy resin to obtain slabs with preserved layered structure suitable for the PIXE analyses. PIXE-spectra were taken as a function of depth distance and the normalized X-ray peak area variations were determined. Especially, concentration changes of silicon and iron were found to be clear. Due to the employed sample preparation technique the observed chlorine concentration corresponds to the amount of water in the initial sample. Maximum chlorine concentration appeared at positions where the Si and Fe concentrations were near minimum. By plotting the Si/Cl or Fe/Cl peak area ratios, an even more distinct position dependent variation was noted.

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Abstract  

Proton-induced gamma-ray emission (PIGE) analysis has been applied to the determination of total nitrogen concentration of blood sera from hospital patients. Both the reaction14N(p,p )14N,E = =2313 keV, and the reaction15N(p, )12C,E =4439 keV, have been used. From 37 patients, the range of the nitrogen concentrations obtained was 9.54–16.3 g/l with a mean of 12.0 g/l. The corresponding total protein concentrations varied between 59 and 96 g/l, measured in a clinical laboratory autoanalyser using the biuret method. The range of the albumin concentrations was 29–46 g/l. The nitrogen concentrations correlated well with the total protein concentrations (r=0.802). The multiple correlation of nitrogen versus (albumin+(total protein-albumin)) gives a coefficient of 0.175 for albumin and 0.161 for total protein-albumin. The results agree with expectations and support the potential usefulness of the rapid PIGE method for medical studies.

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Journal of Thermal Analysis and Calorimetry
Authors: Helena Halttunen, J. Nurmi, P. Perkkalainen, I. Pitkänen, and S. Räisänen

Abstract  

The purpose of this study is to find out the effect of the crystal water content on the crystal structure of lactitol monohydrate. Crystal water was removed by drying over silicagel at 40°C and by using phosphorus pentoxide as drying agent at 20°C. The amouts of water removals were identified by thermogravimetry, the melting points and the heat of fusions were calculated from the results of differential scanning calorimetry measurements and the structure of samples were identified by X-ray powder diffraction method. Over 23 w/w% of total water content could removed by gently drying until significant structural changes could be detected. The melting point of anhydrous lactitol obtained by drying lactitol monohydrate was 120°C and the melting enthalpy was 102 J g−1 when measured with heating rate 10°C min−1 by DSC.

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Abstract  

In order to extend the energy range of the systematic investigation on relative thick target yields performed by ANTTILA et al2 for 1Ep 2.4 MeV bombarding energies, gamma spectra and yield data are presented for elements Z=3–9, 11–17, 19–21 in the energy range 2.4Ep 4.2 MeV and the results are discussed from the point of view of PIGE analysis.

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