NEUTRON-ACTIVATION DETERMINATION OF GOLD IN THE TECHNOGENIC RAW MATERIALS DIFFERENT IN MINERAL COMPOSITION

<p>The methods of determining the gold content in the technogenic objects of gold mining were analyzed with account of their non-homogeneity and complexity of chemical and mineral composition. A possibility of application of the neutron-activation analysis with the use of the californium source of neutrons for determining the content of fine-grained and extra-fine-grained gold in the technogenic objects including the bottom-ash waste of energy providers is considered. It was demonstrated that the chemical composition of the sample affects the neuron flux distribution inside of the sample which can essentially distort the results of the neutron-activation analysis (NAA). In order to exclude the possible systematic errors, the investigations of the effect of the sample mineral composition on the results of the gold determination using the NAA when loading a large volume of the rock (3–5 kg) into an activation zone and using the matrices of four types: silicate, carbon-containing, iron-containing and titanium magnetite were carried out. It was shown that there is no significant difference in dispersal of the flux of thermal and resonance neutrons from the source of ²⁵²Cf when activating the gold-containing technogenic samples with different mineral compositions. The reduction in the quantity of generated atoms of radionuclide ¹⁹⁸Au in the gold-containing technogenic samples due to absorption of the flux of thermal neutrons from the source of ²⁵²Cf by the macroscales of iron and titanium contained in the sample results in the systematic error of the neutron-activation determination of gold up to 10%.</p>

Spatial Filtering Methods for Local Activation Determination in Fractionated Electrograms from Simulated Infarcted Hearts

The purpose of this work is the enhancement of local activation in multiphasic extracellular recordings coming from infarcted myocardial tissue and, consequently, the distinction of local from distal activation. Deconvolution procedures are applied, in the form of spatial filtering, in order to estimate transmembrane currents from the extracellular recordings. Simulated data are used in order to test the methods. The current source estimates are compared to the actual transmembrane currents and to Laplacian estimates.