[en] Short communication

[en] Published in summary form only

[en] Published in summary form only

[en] Published in summary form only

No abstract available

[en] In this paper a chamber design for Pixe analysis at nuclear center of Algiers is described. This chamber provides as fast vacuum rise and several possibilities of irradiation

[en] Short communication

[en] One of the latest methods of chemical analysis, namely the PIXE method (particle-induced X-ray emission) is discussed. The history is briefly described of the physical effect known since 1912 on which the method is based. The principle of the method is described, as are the operation of the Si(Li) X-ray detector and the origin of the spectrum of the analyzed sample. A graph example of the PIXE spectrum is given and the significance explained of peaks. The principle is described of computer processing of the spectrum and it is explained why despite the essential simplicity of the method, the laboratory equipment for PIXE analyses is no cheap matter. Among the listed advantages of the method, the possibility of simultaneous detection of all elements present in the sample at roughly the same sensitivity for all of them is the most important. Other important aspects are the speed of analysis, the fact that the sample is usually not damaged, and the simple preparation of targets. The method is most widely used in ecology, biology and medicine. Czechoslovakia is the 12th state in the world where this type of analysis is being used. Czechoslovak organizations using the method are listed. (A.K.)

[en] The importance of statistical evaluation of multielemental data is illustrated using the data collected in a macro- and micro-PIXE analysis of human brain tumours. By employing a multivariate statistical classification methodology (SIMCA) it was shown that the total information collected from each specimen separates three types of tissue: High malignant, less malignant and normal brain tissue. This makes a classification of a given specimen possible based on the elemental concentrations. Partial least squares regression (PLS), a multivariate regression method, made it possible to study the relative importance of the examined nine trace elements, the dry/wet weight ratio and the age of the patient in predicting the survival time after operation for patients with the high malignant form, astrocytomas grade III-IV. The elemental maps from a microprobe analysis were also subjected to multivariate analysis. This showed that the six elements sorted into maps could be presented in three maps containing all the relevant information. The intensity in these maps is proportional to the value (score) of the actual pixel along the calculated principal components. (orig.)

No abstract available