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Abstract  

The following elements: Cr, Zn, Co, Cd, Mn, V are determined in a sample of NBS (spinach) which has to be certified as a new standard. Both neutron activation analysis and atomic absorption spectrometry are used; a good agreement is foudn among the different techniques. Different procedures of samples chemical dissolution are compared.

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Abstract  

Flameless atomic absorption spectroscopy has been successfully applied to the analysis of trace levels of gold, silver and cobalt in milligram quantities of aluminum. The two-line method of background correction was used with good, but not total, success. The reproducibility of the measurements was excellent, and the results compared very well with the expected values.

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Abstract  

An analytical expression for the equivalent thickness of a sample measured in a Marinelli geometry is reported. Using it as input in the formula proposed by Dryak et al.1, self-absorption corrections for Marinelli beakers with arbitrary dimensions can be computed.

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Abstract  

X-ray spectrometric technique has been described to determine the X-ray mass attenuation coefficient, μ/ρ, of X-rays employing HPGe X-ray detector and radioactive sources. The photon intensity is measured by gating the channel of the spectrometer at FWHM/photo peak. Using the technique the “best value” values of μ/ρ were obtained for those thicknesses which lie in the transmission (T) range 0.5 ≥ T ≥ 0.02. Total attenuation cross sections for other elements and lead compounds were measured at photon energies from 17 to 88 keV to study the Bragg’s additivity law near the absorption edge of the lead. The measured values of mass attenuation coefficient values are compared with theoretical values obtained using Winxcom (programme). This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 17–23%.

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Abstract  

Absorption method is shown to be suitable for direct determination of pure β-emitting, isotopes in samples containing more than one β-emitter. This method consists of (1) measurement of the β-counting rate as a function of the thickness of the absorber placed in between the sample and the β-detector and (2) decomposition of the complex absorption curve by computation in order to obtain the contributions of the nuclides to the total counting rate one by one. The method is presented through two examples of its practical application in the field of environmental radioanalysis:90Sr and147Pm isotopes were determined in aerosol samples contaminated by Chernobyl radioactivity and in hot particles of Chernobyl origin using a simple end-window Geiger-Müller counter as a β-detector.

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Abstract  

A non-destructive method based on a neutron absorption technique has been developed for the process-control analysis of235U in uranium-aluminium alloy components during the manufacture of reactor fuel elements. An account of the experimental stages leading to the design and construction of a process-control instrument is included, together with a description of the fully engineered neutron absorptiometer and the initial stages of its calibration.

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Abstract  

Absorption and translocation of acetochlor /2-chloro-N/2-ethyl-6-methylphenyl/-N-/ethoxymenthyl/acetamide/ herbicide were followed in experiments with tolerant corn /Zea mays L./ and sensitive wheat /Triticum aestivum L./ plants by using carbonyl-14C labelled compound. Tolerant plant species absorbed more radioactivity from the nutrient solution than susceptible plant species. However, the root-absorbed radioactivity was translocated to the shoot more readily in the sensitive plants.

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Abstract  

Flameless atomic absorption techniques were used to determine the lead and other atmospheric particulate in the city of Tehran. 640 samples were collected in 20 different stations around the city during four seasons in 1992. The radioactivity of the air samples was also measured by -ray spectrometry using high purity Ge/Li detectors, and a multichannel analyzer. The results were compared with previous measurements in the city of Tehran.

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Journal of Thermal Analysis and Calorimetry
Authors: Maria Villanueva, I. Fraga, J. Rodríguez-Añón, J. Proupín-Castiñeiras, and J. Martín

Abstract  

The diffusive, calorimetric and thermal degradation behavior of different epoxy-amine systems was investigated during water sorption at different temperatures (23, 40 and 70°C). Experimental results showed that the water absorption at these temperatures fitted well to Fick’s law. Influence of water immersion during different periods of time on the glass transition temperatures was studied by differential scanning calorimetry. Thermal degradation of saturated samples was studied by thermogravimetric analysis. Dependence on the selected curing cycle was also checked.

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Abstract  

Synthetic Fe—Mn alkoxide of glycerol samples are submitted to controlled heating conditions and examined by IR absorption spectroscopy. On the other hand, the same sample is studied by infrared emission spectroscopy (IRES), upon heating in situ from 100 to 600°C. The spectral techniques employed in this contribution, especially IRES, show that as a result of the thermal treatments ferromagnetic oxides (manganese ferrite) are formed between 350 and 400°C. Some further spectral changes are seen at higher temperatures.

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