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  • Author or Editor: M. Varga x
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Abstract  

Electrodeposited 226Ra sources were prepared and measured in order to perform a detailed study of the energy resolutions attained with two recent electrodeposition procedures for preparing spectrometric radium sources. The values of the energy resolution for the high-energy emission of 226Ra and for the single-emissions of 210Poand 222Rn were calculated by fitting the data with a curve formed by the convolution of two left-handed exponentials with a Gaussian function. Significant differences between the energy resolutions for the aforementioned radionuclides were observed. The 210Po energy resolutions were, in general, somewhat better than those obtained for 226Ra. On the contrary, the energy resolutions found for 222Rn were notably poorer than those obtained for 226Ra and 210Po. These discrepancies can be satisfactorily explained by taking into consideration the distribution of these nuclides in the sources and the effect of radon diffusion involved in this type of thin deposit.

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Authors: M Bielik and P Varga
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Authors: M. Radulian and P. Varga
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Abstract  

The energy distribution of the alpha particles emitted from a source is in general complex. Only under particular circumstances, as in the case of very thin sources measured at large distances from the detector, can the energy distribution be approximated theoretically. In this work, we used the well-known code SRIM to simulate the interaction of alpha particles within a thin radioactive source and within the entrance window of a typical Si semiconductor detector. We considered several thin alpha particle sources measured at a large source-to-detector distance (small solid angle), in order to compare the distributions obtained by simulation with those determined by the theoretical model applied to this case. The study was performed for a variety of realistic alpha particle sources: UF4, UO2, U3O8, Gd2O3, and BaSO4, considering as alpha emitters 235U, 233U, 148Gd and 226Ra. For all these cases, we obtained the distributions due to the source and due to the entrance window of the detector, and also the final distribution given by the convolution of these two distributions. All the energy distributions obtained by simulation showed, in general, good agreement with the predictions given by the theoretical model, which includes corrections for Bohr straggling.

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The present study was carried out at a dune slack meadow near Mórahalom town in the Southern part of the Great Hungarian Plain. The area of the grassland is approximately 840,000 m 2 . The vegetation is mosaic-like in accordance with the variable microrelief and water content. The lower part of the grassland consists of various types of saltmarshes and wet meadows and at the upper microrelief, Pannonic sand steppe patches occur. True bug assemblages were sampled at 16 patches using 5×50 sweeps at each sampling site. The sampling was repeated three times in both 2007 and 2008. The area, the perimeter, the shape index of the sampled patches as well as the diversity of the surrounding patches were assessed as “landscape parameters”. The plant species number and diversity of the sampled patches were estimated from the data of 5×5 m coenological quadrats. Altogether 66,087 adult individuals belonging to 153 species were collected. The ordination methods showed that the true bug assemblages of the sampling patches differ from each other in accordance with the vegetation type. These assemblages differed in their species composition and diversity as well as in their assemblage structure. The results suggested that the vegetation type based on plant species composition determined the true bug assemblages.

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Abstract  

The effect of source-sample-detector geometry on the analytical sensitivity of Si(Li) detector X-ray spectrometer was investigated. The theoretically calculated and experimentally determined sensitivity values are in good agreement in case of a matrix having average atomic number of Z=10.

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Abstract  

A detailed study of the influence of barium on the electrodeposition of226Ra was made using two different procedures. High yields (80–90%) were attained when the amounts of barium were not very significant. However, the226Ra yields fell drastically for amounts slightly greater than 0.10–0.15 mg of Ba, according to the electrodeposition procedure. Samples containing trace amounts of barium less than 100–150 g can thus be treated with no barium-radium separation being required.210Po was also deposited, although practically no influence of barium on the Po plating was observed. The225Ra resolution rose uniformly (25 to 55 keV) as the amount of barium rose up to 1 mg. These resolutions allow one to make a direct accurate determination of226Ra as well as an indirect determination of224Ra and223Ra via measurement of their daughter products.

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In spite, that Venturia inaequalis (Cke.) Wint. is one of the most serious fungal disease in apple orchards and it has been studied from numerous points of view, few studies examined the anatomical differences between scab resistant (Vf cultivars) and susceptible apple cultivars. We have investigated the possible anatomical background of the resistance or susceptibility against apple scab in gradually decaying fallen apple leaves. Specific differences were observed in the process of leaf degradation and in the structure of leaf tissues of each cultivar. The epidermis and the cuticle have continually become thinner during leaf degradation in the leaves of two resistant cultivars, while great deformations were observed in the leaf tissues of the susceptible cultivars caused by the hyphae in the mesophyllum and subcuticular stromas. When comparing the non-infected parts of susceptible leaves with those of the resistant cultivars, we documented earlier disintegration of the parenchyma and declined cohesion between the tissue elements. Fungal hyphae appeared on each cultivar but subcuticular stromas developed and hyphae could break through the epidermis and get into mesophyllum only in susceptible leaves. We have discovered calcium oxalate crystals in the mesophyllum of the leaves of each cultivars, that seems to be a general feature of apple leaves, which was not documented previously.

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