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  • 1
    Electronic Resource
    Electronic Resource
    Application of the continuous wavelet transform to the fluctuations and electric field analysis in the H-1 heliac : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 503-505 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We apply the continuous wavelet transform (CWT) and a CWT spectral technique to the analysis of the time-resolved fluctuation-driven particle flux in the H-1 heliac. The results confirm that in some cases the outward radial flux reverses its direction. In addition, time-resolved frequency spectra of fluctuation signals obtained by CWT show that the dominant frequency component as a function of time closely follows changes in the radial electric field. This suggests that the VE×B drift velocity dominates the poloidal phase velocity of the fluctuations in the laboratory frame, in which case the time-resolved frequency can be used to characterize the radial electric field. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310583
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  • 2
    Electronic Resource
    Electronic Resource
    Mercury analysis in environmental samples by EDXRF and CV-AAS (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 199-204 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The analysis of total Hg in various environmental matrices was investigated using energy dispersive X-ray fluorescence (EDXRF) for both powdered and digested samples and cold vapor atomic absorption (CV-AAS) for digested samples. Several microwave decomposition procedures were evaluated with respect to the determination of Hg by CV-AAS and EDXRF. The use of different acid mixtures, microwave power settings and decomposition times were compared as well as the analysis on wet and freeze-dried samples. A set of standard reference samples were used to evaluate the procedures: NBS Citrus leaves (1572), NRC Pine needles (1575), NRC Dogfish muscle tissue (DORM-2), NRC Dogfish liver tissue (DOLM-2), BCR Human hair (397), BCR Coking coal (181) and NRC Marine sediment (PACS-1). An H2SO4/HNO3/H2O2 acid mixture was found to be optimal for the complete mineralization and digestion of biological samples for Hg by CV-AAS whereas for EDXRF both the HNO3/H2O2 and H2SO4/HNO3/H2O2 acid mixture gave good results. The detection limit of EDXRF could significantly be decreased (from 0.2 μg/g to 0.058 μg/g) by performing the analysis with digested samples. A good agreement was obtained between CV-AAS and EDXRF analysis. The obtained results were also in good agreement with certified values. The methods were applied to environmental samples (coal, trees, leaves, spinach, fish, sediments) and human hair in a coal mining area and in places where they use coal for cooking in Vietnam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050674
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  • 3
    Electronic Resource
    Electronic Resource
    Sample preparation and EDXRF analysis of element content in marine algal communities  -  a tentative approachPresented at the European Conference on EDXRS. Myconos, Greece, 30 May-6 June 1992. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 260-264 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The relative distribution and retention of elements in algal communities can potentially be used as an ecologically relevant effect parameter in ecotoxicological studies. Energy-dispersive x-ray fluorescence spectrometry (EDXRF) was used for multi-element analysis of samples of marine algae and plankton. The algal samples were microbial periphyton communities, attached to glass substrata that were submerged in marine waters at the Swedish west coast. The phytoplankton samples from the same area were taken in a polyethylene bottle and collected on polycarbonate filters. The EDXRF spectrometer used is based on three-axial geometry. This geometry together with optimized collimation of the x-ray beams results in a low background well suited for the analysis of the small biological samples in this study. The aim of this study was to investigate sample preparation procedures suitable for EDXRF analysis of algal communities. A rapid wash in distilled water, to remove the interfering interstitial sea water, and subsequent transfer of the community to an x-ray foil is the tentatively proposed sample preparation procedure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220416
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  • 4
    Electronic Resource
    Electronic Resource
    Multi-element analysis of tree rings by EDXRF spectrometryPresented at the European Conference on EDXRS. Myconos, Greece, 30 May-6 June 1992. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 281-285 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An EDXRF system for scanning samples in steps of 5 μm was developed. The system is based on a conventional x-ray tube and secondary target in closest possible geometry. For tree ring analysis, which was made in steps of 200 μm, the exciting x-ray beam was allowed to pass through a slit collimator of dimensions 0.1 × 1 mm made of pure silver. The sample holder is movable in steps of 5 μm in three orthogonal directions. The beam path of the exciting and fluorescent radiation can be adjusted in relation to the sample plane by the movable sample holder. Further adjustments can be made by a movable detector platform. All movements are driven by microcomputercontrolled step motors. The detection limits of thick samples, like tree biopsies, are of the order of parts per million for medium-heavy elements. The system was applied to multielement analysis of healthy samples of pine, birch and spruce biopsies. Long-term trends in some trace element concentrations could be seen in these samples, together with the possible influence of stress.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220420
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  • 5
    Electronic Resource
    Electronic Resource
    Polarization effects in a Si(Li) detector (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 325-329 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In previous work time- and position-dependent artifacts and a time-dependent increase in the background radiation of x-ray spectra was observed in planar Sl(Li)detectors for x-rays in the keV region. In the present experiments the time-dependent background was studied by use of a thin x-ray beam. The time-dependent background is considered to be due to incomplete charge collection. The amount of background is greater when the detector is left unexposed to x-rays during the bias time than when the detector is constantly irradiated. The time-dependent background was observed to decay with half-lives of the order of 30 s, 10 min and 1-4 h. The results are interpreted such that polarization of the detector material occurs by traps that are formed under the influence of the bias voltage. During irradiation some of these traps are filled by charges from the hole-electron pairs from the x-ray beam. By using Ramo's theorem and converting the energy scale in the x-ray spectra to detector depth, the polarization effect in the detector can be estimated to proceed with a speed of the order of 1 μm min-1 in an electric field of about 3000 V Cm-1.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300200614
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  • 6
    Electronic Resource
    Electronic Resource
    Beam profile studies in an x-ray fluorescence spectrometer (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 337-341 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: For small samples, the beam intensity in a secondary target conventional x-ray fluorescence (XRF) spectrometer is often not sufficient. As a step in our efforts to optimize the three-axial XRF spectrometer in Gothenburg, the intensity profile of the x-ray beam from the secondary target was studied. The intensity profile was found to be inhomogeneous. For the beam profile studies, mechanical systems were built which can also be used for position determination of small samples. A movable platform for the detector was constructed and equipped with driving and controlling electronics. To improve further the flexibility of the spectrometer, the sample holder was rebuilt to allow for movements of the sample in the x-, y- and z-directions. The possibility of tilting the sample and thus varying the angle between the incoming beam and the sample plane from about 0 to 90° was included in the mechanics of the sample holder. The arrangement can also be used to centre the samples in the spectrometer and to move the sample for analysis of different parts of the sample.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300200616
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  • 7
    Electronic Resource
    Electronic Resource
    Sample area dependence in quantitative EDXRF analysis (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 321-324 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The measurement of small, thin samples with an area of the order of mm2 with the ordinary EDXRF technique requires that special care be taken to include the sample size in the evaluation of element concentrations. Results are reported obtained using a standard procedure for the evalution of small samples used in the author's laboratory. This procedure makes use of an input parameter, viz. a ‘geometrical factor’ corresponding to the sample area which is used in the evaluation software. The results show that an almost straight line can be fitted to describe the parameter as a function of sample area for small samples (with an area of the order of mm2), but that the corrections for inhomogeneity of the beam intensity are needed in many cases. For large samples (with an area of the order of cm2) the parameter is equal to unity.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300200613
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison between two x-ray analysis software packages (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 20 (1991), S. 305-314 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Different types of software for evaluating element concentrations from XRF spectra are based on different concepts and accordingly approach the problem in different mannners. Two software packages for analysis of XRF data were compared, the AXIL package, commercially available from Canberra-Packard, and the XRFAES package, developed and used at the Department of Physics, Chalmers University of Technology, Göteborg. The experimental set-up is presented and a presentation of the packages is given. The comparison is based on evaluation of biological and thin-film samples and deals with: the possibility of analysing samples of different sizes, how the programs react to more or less erroneous input values of gain and zero energy and ease of use, i.e. calibration and different ways of entering input parameters and displaying results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300200611
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  • 9
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    Mercury analysis in environmental samples by EDXRF and CV-AAS (1998)
    Springer
    Details
    Publication Date: 1998-01-20
    Print ISSN: 0937-0633
    Electronic ISSN: 1432-1130
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 10
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    Intra-urban air pollution in a rapidly growing Sahelian city (2012)
    Elsevier
    Details
    Publication Date: 2012-04-01
    Print ISSN: 0160-4120
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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