Radioelement contents of rock samples collected from some locations in the Sokoto Basin of Nigeria, where radiometric anomalies had earlier been delineated by gamma-ray spectrometric surveys, were determined by X-ray fluorescence technique using238Pu and109Cd excitation sources. The uranium contents determined were compared with delayed neutron counting results, while flame emission spectrometry was used to cross-check potassium contents. The analyses revealed uranium and thorium enrichments, with U/Th ratio of about 1.8, and negligible potassium concentrations in most samples.
Nuclear and atomic methods of analysis, which rely on the detection of prompt and delayed radiations, emitted as a result of interactions between radiation probe and target, for determining the elemental concentration in vivo and in vitro, are summarily reviewed, with reference to bone analysis; the demand for methods which provide information about elemental distribution is highlighted. The way neutrons can be used as probes to investigate the composition and structure of objects by employed the principles of computerised tomography are outlined and the novel modes of utilisation are briefly described: neutron transmission tomography, neutron induced prompt gammaray emission tomography and neutron induced delayed gamma-ray emission tomography. The latter method, alternatively termed neutron activation tomography, is then used to determine on-destructively the distribution of Na in selected planes of a human tibia, in vitro, by measuring the activity of24Na using a NaI(Tl) and a Ge(Li) detector in a tomographic scanner which incorporates a microcomputer for control, data acquisition and image reconstruction. The problems of attenuation and scattering are discussed as are the limitations for quantitative results of this useful new mode of tomography which provided information about composition and elemental distribution in a material.
A fast, sensitive and routine methode for quantitative analysis of uranium and thorium in natural samples is described. The
identification is done by counting the delayed neutrons of mainly the short living fission products after sample-irradiation
with and without cadmium shielding. The rabbit system used is installed at the Forschungsreaktor Neuherberg, type TRIGA Mark
III. The limits of detection (relative to 2 g of sample weight) were specified to be 20 ppb (U) and 3 ppm (Th) using puls
irradiations, 150 ppb (U) and 15 ppm (Th) using 1 MW steady state reactor power. A single determination is done within less
than 60 s. The methods were proved by about 3000 measurements also including comparison experiments.
High resolution (K) X-ray spectrometry preceded by activation with fast neutrons, neutrons from an isotope-source, and charged particles, is a novel development in the field of activation analysis. This paper describes the capabilities of these techniques and evaluates their analytical potential for the specific determination of the rare earths and Platinum Group Elements (PGE's) in small samples. The investigation took the form of a feasibility study which relied heavily on the low energy sensitivity of the detector used. Detection of the delayed X-rays was achieved with a 100 mm2 Ge detector whose ability to produce optimum photopeak-to-noise ratios formed the basis exploited in this investigation. Analytical conditions are demonstrated over a range of concentrations for the elements of interest and the potential of the technique for application to the general routine analysis of the rare earths and PGE's are discussed.
Authors:Gábor Skaliczki, M. Weszl, K. Schandl, T. Major, M. Kovács, J. Skaliczki, H. Redl, M. Szendrői, K. Szigeti, D. Máté, Cs Dobó-Nagy, and Zs Lacza
Purpose: The clinical demand for bone grafting materials necessitated the development of animal models. Critical size defect model has been criticized recently, mainly for its inaccuracy. Our objective was to develop a dependable animal model that would provide compromised bone healing, and would allow the investigation of bone substitutes. Methods: In the first group a critical size defect was created in the femur of adult male Wistar rats, and a non-critical defect in the remaining animals (Groups II, III and IV). The defect was left empty in group II, while in groups III and IV a spacer was interposed into the gap. Osteoblast activity was evaluated by NanoSPECT/CT imaging system. New bone formation and assessment of a union or non-union was observed by μCT and histology. Results: The interposition model proved to be highly reproducible and provided a bone defect with compromised bone healing. Significant bone regeneration processes were observed four weeks after removal of the spacer. Conclusion: Our results have shown that when early bone healing is inhibited by the physical interposition of a spacer, the regeneration process is compromised for a further 4 weeks and results in a bone defect during the time-course of the study.
In the junction capacity calculation methods the passenger car unit has a very important effect, because heavy vehicle traffic flow can only be counted with passenger car unit. Since not the proper passenger car unit values are used in the current practice, the results of junction capacity calculations cannot be regarded as correct, either. This research is focused on finding an answer as to whether the results are more precise if models with three junctions are examined rather than models with one junction.