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  • Author or Editor: A. Aksoy x
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Abstract  

The absolute total and full-energy peak (FEP) efficiencies of a high purity germanium (HPGe) photon detector are measured in the energy range from 40 keV to 1500 keV. The functional parameters are fitted to the calibration points from 14 long-lived standard sources (129I,241Am,109Cd,57Co,139Ce,137Cs,54Mn,65Zn,60Co,22Na,133Ba,152Eu,154Eu and166mHo) within an accuracy better than the quoted uncertainty of the calibration sources. The efficiencies in far and close geometries are compared.

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Abstract  

Samples of nominal 18 carat and 21 carat gold jewelleries from the local market were non-destructively bulk analyzed using neutron activation analysis. Neutrons of 14 MeV energy were used with a fast pneumatic sample transfer system. The actual gold contents, as well as the composition of the base metals in these samples were determined. The fast neutron activation was found to be an efficient, quick and accurate method of characterizing the precious metal objects routinely in bulk, with a large sample throughput. The results demonstrate the commercial availability of the technique for non-destructive bulk analysis of precious metal objects.

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Abstract  

The elemental analysis of Pt-Re/alumina catalysts was carried out by nondestructive and bulk neutron activation analysis. Samples were irradiated with a241Am-Be source-based as well as accelerator-based thermal neutrons and induced activities were measured by a HPGe detector with a PC-based data acquisition and analysis system. An appropriate calibration technique was established for the determination of the respective ratios of each element present in the catalysts. The technique proved to be useful for the determination of low concentrations of Pt and Re in the catalyst samples.

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Abstract  

Extensive sedimentary phosphate deposits exist in the Sirhan-Turayf basin in northwestern Saudi Arabia containing significant amounts of uranium, thorium, vanadium and rare earth elements. The determination of the concentration and pattern of distribution of some of these elements is essential for economic aspects. This study reports the analysis of vanadium in selected phosphate rock samples from the basin using accelerator-based thermal neutrons activation analysis (TNAA). Samples were irradiated in a thermal neutron flux of 2.5·106 n·cm−2·s−1. The induced activity was measured with a HP-GMX detector coupled to a PC-based data acquisition and analysis system. The facility was calibrated using certified standards of vanadium. The minimum detection limit of vanadium was about 1 mg. Three independent measurements on each sample yielded comparable results indicating the reliability of the technique. The vanadium concentrations in the samples vary from 23 to 457 ppm.

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In this study, the antibacterial and antioxidant activities of dried fruit extract of cranberry (gilaburu, Viburnum opulus) were determined. The total phenolic content was found to be 131.99±2.11 mg gallic acid equivalent (GAE) g-1 in the cranberry fruit extract (CFE). The antioxidant activity of the extract was found to be 315.50±8.2 mg g-1 in dried methanol extract. At 2, 5, 10 and 15% concentrations the extracts were tested for their antibacterial effects by using the agar diffusion method against ten bacteria, some of them pathogenic and some of them spoilage microorganisms. All bacteria were inhibited by 10 and 15% concentrations of the CFE. Methanol (control) had no inhibitory effect on all the tested bacteria. The most sensitive of the bacteria was A. hydrophila, whereas the most resistant bacterium was Y. enterocolitica.

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Abstract  

An instrumental thermal neutron activation analysis facility based, on a 16 Ci241 Am–Be source, a high resolution -ray spectrometry setup and a PC-based data acquisition system at KFUPM is described. The thermal neutron flux distribution was determined from the induced activities of high purity indium foils. The absolute thermal neutron flux was calculated from the activities of bare and cadmium-covered gold foils at a position of 3 cm from the soource at which the flux reaches a maximum. The facility tests were carried out with the determination of manganese concentrations in six types of industrially important steel samples. The result of 1.33% manganese in SS-304 steel sample was in excellent agreement with the literature value. The method is nondestructive, economical and ideal for bulk analysis.

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Abstract  

Phosphorite deposits from northwestern Saudi Arabia were analyzed by natural radioactivity measurements to detect the presence of radioactive elements. PIXE was used to obtain an average elemental composition of these deposits. From the analysis of radiations from 238U, 232Th and 40K isotopes, the samples were found to contain U, Th and K in concentrations up to 130 ppm, 30 ppm and 2.5 wt%, respectively. PIXE showed the presence of a number of trace elements such as Ca, V, Cr, Fe, Ni, Cu, Zn, As, Sr, Y and U in concentrations ranging from a few ppm to several hundred ppm. The occurrence of these radioactive and non-radioactive elements are discussed for their geological significance in the phosphorite deposits.

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Ant responses were tested under both the natural geomagnetic and artificially induced Earth-strength electromagnetic field. Foragers were trained for a month to visit a food source at the north arm accessed through an orientation platform assembly. Under the natural geomagnetic field, when all other orientational cues were eliminated, results indicated significant heterogeneity of ant distribution with the majority seeking geomagnetic north in darkness. However, in light, foragers failed to discriminate geomagnetic north. Under shifted artificial electromagnetic field, orientation was predominantly on the artificial magnetic N/S axis with a significant preference for the artificial north in both light and dark conditions.

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