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Abstract  

The success of a systematic application in INAA using γ-lines of ≥50 keV depends on the accuracy and precision and thus on the reproducibility of the measuring conditions. This text describes a procedure based on a 30 mm2 planar ultrapure Ge detector with a multichannel analyzer.

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Abstract  

Some methods for the experimental α-determination in the 1/E1+α epithermal reactorneutron spetrum are critically compared with respect to their accuracy and precision. The analysis is based on the error propagation theory. Besides the general formulae numerical examples are elaborated for specific conditions in the Thetis reactor (Gent) and the WWR-M reactor (Budapest).

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Abstract  

The precision and accuracy of two closely similar radioanalytical methods are compared using the statistical approach (5 parallel experiments for each distribution): sub- and superequivalence isotope dilution analysis and concentration dependent distribution. The solvent extraction system used for both procedures involves the distribution of radiobarium between aqueous phase and nitrobenzene solution of the acid of cobalt dicarbolide H+ {–(3)–1,2–B9C2H11]2 Co and mono-p-nonyl phenyl ether polyethylene glycol HO(CH2 CH3 O)20–(C6H4)C9H13. The influence was tested of the choice of a concrete person to evaluated the results of the analysis by graphic methods upon the precision and accuracy. The advantages and drawbacks of different graphical evaluation procedures are compared.

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Abstract  

Some of the rare earth elements have been determined in U.S.G.S. Standard Rocks W1 and G2 using instrumental neutron activation analysis with a Ge(Li) detector. The experimental conditions were chosen to investigate the precision and accuracy to be expected when using the method for routine purposes. The results are compared with data obtained after chemical group separation of the rare earths and with data reported by other workers; the agreement is, in general, good. La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Se were determined with the instrumental method and, after group separation, data were obtained for Gd, Dy, Ho and Tm in addition. It is concluded that the accuracy of the data obtained with the non-destructive method is, in general, as good as the precision for each element.

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Abstract  

The laboratory for INAA in Delft processes several thousands of samples per year for multielement determinations in a variety of matrices. Samples are measured on different spectrometers (using well-type and coaxial detectors), by different persons and using many different analytical protocols. All these results should be consistent with each other with respect to the degree of accuracy, i.e., the combination of trueness and precision. A rigorous internal quality control program has been implemented with automatic on-line evaluation. Annually an additional evaluation of the internal quality control results is carried out using statistical techniques. The Naji-plot approach has proven to be an important graphical tool since it provides direct insight in both trueness and precision. It is demonstrated that the degree of accuracy of the results obtained under the large variety of operational parameters is under constant improvement.

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Abstract  

The LabSOCS software performs mathematical efficiency calibration of Ge detectors. Extensive tests have been conducted comparing the LabSOCS efficiency calibration with those from traditional radioactive sources for typical laboratory geometries. For this study, 4 NIST-traceable standards containing 13 different energy lines were counted in 7 different geometries that are typical of laboratory samples. The results from the first 13 detectors produced using this process show that efficiency calibrations generated with LabSOCS have an accuracy of 5.1% SD at low energies and 4.2% SD at high energies.

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Abstract  

USGS BCR-1 and G-2, NBS 1633a Coal Fly-Ash and a 7-element synthetic standard for biological material have been analysed in this work by reactor NAA, using the k0-standardization method. The analyses were performed independently in the analytical laboratories of the Institute for Nuclear Sciences (INW), Gent, and the Central Research Institute for Physics (KFKI), Budapest. This procedure allowed not only a comparison with the specified data or with other published values, but enabled a check of the consistency of our own results obtained in largely different experimental circumstances. As concluded the k0-standardization method combines general versatility (with respect to irradiation and counting conditions) with good accuracy, while keeping the experimental work as simple as possible. Since the k0 method is a computer-oriented technique, a FORTRAN IV program was designed and applied on a VAX 11/780 machine.

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Ad hoc decisions during fieldwork reduce the accuracy and reliability of vegetation maps. A method is proposed to objectify vegetation (thematic aspects) mapping (spatial aspects) for monitoring (temporal aspects). The most accurate and reliable description of the vegetation is a list of all plant species found within a plot. Therefore, the proposed method is an interpolation of a spatially representative sample of permanent plots combined with aerial photo interpretation. The method is objective because surveyors do not have to make decisions during fieldwork based on their personal judgement. Moreover, it is flexible, because the classification and interpolation methods can be adapted to specific views or needs depending on the aim of a study. The method was applied to an area in the north of the Netherlands in 1998. A sampling design with a density of 1 plot/ha was used, and interpolated with a perpendicular bisector. In 2002, the number of plots/ha was doubled. The influence of sample density on the mapping results was studied because it is an important decision to be made before fieldwork. Two plots/ha seem to be sufficient in order to obtain reliable information on patterns of plant species composition and vegetation types of the area, and their change over time. However, in patches where vegetation varies on a very small spatial scale this plot density was insufficient.

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Orvosi Hetilap
Authors: Miklós Tóth, Zsolt Vajda, Zoltán Görömbey, Ferenc Molnár, László Major, Judit Tőke, István Szabolcs, Nikolette Szücs, László Kovács, Róbert Kiss, Sándor Czirják, László Fütő, Edit Gláz, Miklós Góth, and Károly Rácz

84 487 492 Lefournier, V., Martinie, M., Vasdev, A. és mtsai: Accuracy of bilateral inferior petrosal or cavernous sinuses sampling

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With the aims of accounting for the effects of the internal thermal resistance of the sample holder on the parameters of recorded DTA curves, and of estimating the difference between the instrument with a thermally insulated sample holder and the gradientless model, a novel two-point method of differential thermal analysis has been developed. Its essence is that two thermoanalytical curves are recorded simultaneously, with the differential thermocouple at central and side positions relative to the sample. The theory of the method has been elaborated, and formulae are derived which allow quantitative estimation of the thermal resistance of the sample holder, depending on the manner of packing and on the state of the sample in the holder, and which also indicate the optimum manner of packing. If the packing is not dense and not uniform, the thermal resistance of the holder increases and the accuracy of instrument calibration at the tail-end of the differential curve decreases by 10–20%. Through introduction of a correction term into the formula, this effect can be eliminated. A basic formula is given for DTA calculation in the general case of a sample holder with non-zero internal thermal résistance.

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