bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of diffusion coefficients in multi‐component solutions using the daresbury synchrotron x‐ray fluorescence microprobe
Authors: Anderson P. , Elliott J. C. , Thomas C. R. , Van Langevelde F. 
Published: May 2005

AbstractIn multi‐component solution systems, the diffusion of one component can influence the diffusion of a second; in some instances, especially if the first component is an acid, the second component may diffuse against its own concentration gradient. The fundamental cause of this phenomenon is the local electrical field gradient established when particular ion species in mixtures of ionic components have different transport numbers. In ternary, quaternary and higher order systems, determination of the main and cross‐term diffusion coefficients is difficult, and usually indirect.The Daresbury x‐ray fluorescence (DXRF) microprobe was used to measure directly the concentrations of individual elements in an aqueous gel 1.45 mm from an interface with a solution of constant composition. The solutions contained known mixtures of cobalt, copper and zinc chlorides with and without hydrobromic acid. Similar measurements were made every 300 s over a period of 3 h. After this, measurements were made at 100 μm intervals from the interface of the gel to a depth of 6 mm to map the concentrations of Co, Cu and Zn.The diffusion coefficients were estimated by comparison of the concentration–time profiles for each metal with analytical or numerical simulations. The results show a significant coupling of the Cu, Co and Zn diffusive flows with the diffusive flow of the acid.This work has shown that the DXRF microprobe can be used to measure concentration–distance or concentration–time profiles of many elements simultaneously, thus enabling more direct measurements of multicomponent diffusion coefficients in solution to be made.
Polarized x‐ray spectra of α‐Fe2O3
Authors: Leiro J. A. , Dräger G. , Czolbe W. 
Published: May 2005

AbstractThe linearly polarized Fe K absorption and Fe Lα emission spectra of α‐Fe2O3 were measured. Also, the usual Fe K emission band is presented. These measurements were compared with results of multiplet theory and cluster calculations. The spectra are also compared with x‐ray photoemission and inverse phtoemission data.
Considerations on a 3D‐XRF by pixel scanning and variable x‐ray geometry
Authors: Ebel M. F. , Ebel H. , Svagera R. , Heller M. , Wernisch J. , Kaitna R. 
Published: May 2005

AbstractThe principle of a three‐dimensional x‐ray fluorescence analysis was verified by the example of lateral thickness distributions of Zn‐layers on steel. The results of the experiments were compared with those of measurements performed on a cross‐section with a scanning electron microscope. This comparison confirmed the XRF results and indicated the limitations of the method due to the present value of the lateral resolution of 1 mm, and the applicability of Zn Kα and Fe Kα radiation to layer thicknesses of ca. 20 μm.
Depth profiling by XFA with selective excitation and variation of incidence and take‐off angle of x‐rays
Authors: Ebel H. , Ebel M. F. , Svagera R. , Heller M. , Pöhn C. , Kaitna R. 
Published: May 2005

AbstractA method for the determination of the composition and thickness of thin AlxGa1‐xAs films on GaAs substrates by means of energy‐dispersive XFA with variable x‐ray geometry and with selective excitation of characteristic sample radiations is developed. It can be applied without reference samples. The method was derived from XFA with variable take‐off angle. An outline of the theory of the method and the evaluation of measured characteristic signals for an unknown composition x and thickness D of the films is given. This method can be applied to the determination of the compositions and thicknesses of thin multi‐element films.
Use of Al2O3 as a Barkla scatterer for the production of polarized excitation radiation in EDXRF
Authors: Swoboda Walter , Beckhoff Burkhard , Kanngießer Birgit , Scheer Jens 
Published: May 2005

AbstractA simple model is presented for calculating the spectral scatter efficiency of Barkla scatterers. It was found that they can be divided into three distinct groups according to their scattering behaviour. Results are presented graphically for a selection of scatters. The experimental comparison of the scatterers thus selected, viz. B4C, graphite and Al2O3, showed that Al2O3 is suitable for the analysis of a wide range of elements. Further experimental conditions such as filtering and choice of the tube anode were investigated.
Relative intensities of Lα1, Lβ1 and Lβ2,3,15 lines of gold: Electron beam excitation in the near‐threshold region of the L shell
Authors: Jha S. N. , Agrawal R. M. 
Published: May 2005

AbstractVariations of the relative intensities of the Lα1, Lβ1 and Lβ2,3,15 lines of gold from an x‐ray tube with its operating voltage in the near‐threshold region of Au L subshells were studied. Large variations in the intensity ratios were observed for the lines originating from different subshells, which attain limiting values at high excitation overvoltages. These variations are primarily due to the variation with the electron beam energy of the realative numbers of initial ionizations created by the electron beam in different subshells. Attempts have been made to explain these variations by calculating the relative intensity values of these lines using various empirical expressions available.
Empirical equations for calculating wavelengths of x‐ray characteristic lines and absorption edges
Authors: Norrish K. , Tao G. Y. 
Published: May 2005

AbstractEmpirical equations for calculating the wavelengths of x‐ray characteristic lines and absorption edges were proposed and their effectiveness was compared with that of the empirical equations used in the programs MAGIC IV, FRAME C and NBSGSC. The proposed equations were proved to give the smallest number of mistakes which lead to an error of the calculated wavelength causing an analytical line to be on the wrong side of an absorption edge.
Applicability of annular‐source excited systems in quantitative XRF analysis
Authors: Bernasconi G. , Bamford S. A. , Dosan B. , Haselberger N. , Markowicz A. , Mahmoud A. , Valkovic V. 
Published: May 2005

AbstractRadioisotope‐excited XRF systems, using annular sources, are widely used in view of their simplicity, wide availability, relatively low price for the complete system and good overall performance with respect to accuracy and detection limits. However, some problems arise when the use of fundamental‐parameter techniques for quantitative analysis is attempted. These problems are due to the fact that the systems operate with large solid angles for incoming and emerging radiation, and both the incident and take‐off angles are not trivial. In this paper, an improved way to calculate ‘effective’ values for the incident and take‐off angles, using Monte Carlo (MC) integration techniques, is shown. In addition, a study of the applicability of the ‘;effective’ angles for analysing different samples, or standards, was carried out. The MC method allows also calculation of the excitation‐detection efficiency for different parts of the sample and estimation of the overall efficiency of a source‐excited XRF set‐up. The former information is useful in the design of optimized XRF set‐ups and prediction of the response of inhomogeneous samples. A study of the sensitivity of the results due to sample characteristics and a comparison of the results with experimentally determined values for incident and take‐off angles is also presented. A flexible and user‐friendly computer program was developed in order to perform efficiently the lengthy calculations involved.
X‐Ray fluorescence analysis of base metal sulphide and iron–manganese oxide ore samples in fused glass disc
Authors: Spangenberg J. , Fontbote L. , Pernicka E. 
Published: May 2005

AbstractA procedure for the wavelength‐dispersive x‐ray fluorescence determination of major, minor and trace elements in fused discs of base metal sulphide ores and of iron–manganese oxide ores is described. The objective was to obtain reasonable chemical analyses of ore samples of a wide compositional range. Owing to the scarcity of well characterized geochemical reference ore samples, calibration was done with synthetic glass disc standards. The concentration range and the association of the elements considered in the standards take into account the geochemistry of most ore types. A fusion method with a high dilution ratio (sample‐to‐lithium tetraborate ratio= 1 : 10) was used to reduce the matrix effects. This allows a direct comparison of the synthetic standards with unknown geological sample discs. Two different methods of data reduction of the measured intensities were tested: (1) intensity‐based correction method for the determination of major, minor and trace elements and (2) peak/background ratio method for the determination of minor and trace elements. A critical evaluation of the reproducibility, as judged from duplicate analyses, and the accuracy, estimated by comparison with international reference materials, showed the procedure to be capable of obtaining reasonable chemical analyses for most elements of geological interest.
Silicon particle size effect in X‐ray fluorescence analysis of pitch
Authors: Feret F. R. 
Published: May 2005

AbstractA Si particle size effect was identified in the x‐ray fluorescence analysis of pitch, and is explained and quantified. Theoretical calculations were carried out to model the Si Kα intensity change with the SiO2 particle size. The effective thickness of the analytical layer, the inter‐element effect (using theoretical alpha coefficients) and the sensitivity and lower limit of detection were calculated for the analytes in pitch using a Philips PW 1400 spectrometer.
X‐Ray fluorescence escape peaks in HgI2 detectors
Authors: Liu‐Xu X. , Heitz Ch. , Siffert P. , Régal R. 
Published: May 2005

AbstractA mathematical model for the estimation of the relative intensities of the escape peaks in HgI2 detectors is presented. Comparison of calculated results with experimental values for various x‐ray energies shows satisfactory agreement. The method can be used to evaluate directly the sensitive thickness of an HgI2 detector through the escape to total peak intensity ratio.
EDXRF of complex objects: Some problems and solutions
Authors: Smolniakov V. I. 
Published: May 2005

AbstractSome complex cases of EDXRF spectrometry for heavy element determinations are considered. The main problem in all these cases is the determination of the elements of interest at low concentrations in the presence of absorbing and interfering matrix elements at high concentrations. One example deals with the reduction of the detection limits for the determination of rhenium in copper–lead polymetallic ores and concentrates, when the rhenium L‐series radiation of low intensity is used. A linear dependence of the analytical parameter for rhenium concentrations in the range 0.5‐30 ppm is obtained. Different types of spectrometry for characteristic radiation of K‐series of the elements from rare earths to lead with detection limits from 10 to 0.1 ppm are considered. Some applications of annular radioisotope sources as an alternative to x‐ray tubes are investigated.
Feasibility of intense monochromatic x‐ray source in the 1–100 keV range by proton bombardment of metallic targets
Authors: Cicardi Carlo , Milazzo Mario , Manfredi Giacomo , Silari Marco 
Published: May 2005

AbstractX‐ray sources produced by a standard x‐ray tube coupled to a secondary anode and by proton irradiation generate x‐ray spectra which are nearly equivalent and sufficiently monochromatic for many applications. The advantage with protons lies in the much higher intensity values achievable. A comprehensive theoretical and experimental study has been conducted on the production of intense sources of monochromatic x‐rays by bombardment of pure element targets with protons and helium ions with energies between 10 and 100 MeV and very low currents (from nA to μA). The accompanying production of intense background due to nuclear reactions proved, however, to be unavoidable in practice, counterbalancing the advantage of the intense characteristic x‐ray yield. By keeping the proton energy below the Coulomb barrier, no nuclear background is expected. A very intense source of monochromatic x‐rays, tunable in the 1–100 keV range, can be obtained by coupling a low‐energy (2–4 MeV), high‐current proton accelerator with an irradiation chamber provided with a multiple target system and collimator. The radiofrequency quadrupole (RFQ) is a proton accelerator which is compact and reliable. Commercial versions can provide up to 1 mA average current at energies of 2–4 MeV. Estimates of the photon intensities achievable by 2 MeV/1 mA and 4 MeV/0.5 mA proton beams obtained from an RFQ indicate that such a compact source can provide fluxes larger than 1013 s−1 sr−1 for x‐ray energies up to about 6.4 keV (iron primary target), in excess of 1011 s−1 sr−1 for x‐ray energies up to about 26 keV (antimony primary target) and still around 1010 s−1 sr−1 for the hardest x‐ray energies produced by the heaviest targets. These figures are 4–6 orders of magnitude higher than those achievable with conventional systems. The power dissipation in the target (1–2 kW cm−2) can be handled with a conventional water cooling system. The energy can be tuned by selecting the appropriate target. Comparisons among intensities achievable from this compact photon source, conventional x‐ray tubes and synchrotron light sources are presented. Fields where such a source can be applied are discussed.
Intercomparison between energy‐dispersive x‐ray fluorescence and stripping potentiometry for the determination of copper levels in human serum
Authors: Viksna A. , Mwiruki G. , Jagner D. , Selin E. 
Published: May 2005

AbstractThe accurate determination of trace elements in blood serum samples is important for establishing nutritional status and/or determining the influence of environmental or pathogenic factors in humans. XRF has for a long time been used as a rapid and convenient method for trace element determinations. However, many other methods are in use, including stripping potentiometry (SP). This is generally known to have much lower detection limits than XRF. In order to compare the two methods, which are based on entirely different physical principles, both methods were used for the determination of copper in two different kinds of serum samples, a standard serum (Seronorm) and a sample taken from a hospital in Sweden. Both methods agreed within the standard deviation of each method. The sample preparation for both methods and the quality of the standard serum are discussed.
Ferro‐alloy analysis by x‐ray fluorescence spectrometry
Authors: Rutherford R. T. 
Published: May 2005

AbstractA method is presented for the accurate and comparatively rapid analysis of ferro‐alloys by x‐ray fluorescence spectrometry. It involves oxidation and fusion of the ferro‐alloys to produce a glass disc/bead. The method is also used for the analysis of oxide materials containing metallic iron, manganese, aluminium and silicon. The equipment and materials used are readily available in most laboratories using XRF instrumentation.
Comparison of Fe2O3 and Fe metal for the preparation of fused bead synthetic calibration samples
Authors: Giles H. L. , Hurley P. W. , Ingham M. N. 
Published: May 2005

AbstractDuring the assessment of the accuracy of a method for the XRF analysis of oxides, silicates and carbonates using synthetically prepared fused bead calibration samples, it was found that for iron there was a consistent bias when comparing the x‐ray results for 43 Reference Materials with the certified values. This paper offers an explanation for this bias, which was of the order of 1.5% relative over the concentration range 0–100% Fe2O3.
Determination of vanadium and nickel in oil, asphaltene and bitumen using thin‐film energy‐dispersive x‐ray fluorescence spectrometry
Authors: Civici N. 
Published: May 2005

AbstractThe concentration of vanadium and nickel in crude oils, bitumen and asphaltenes is an important parameter from the viewpoint of oil exploration. This kind of sample can be successfully analysed by energy‐dispersive x‐ray fluorescence spectrometry. A thin‐film sample preparation procedure is described. This involves first the addition to the sample of an internal standard, Pb, as a solution in chloroform, then pipetting some of the obtained solution on a thin Mylar foil, which covers the sample holder, followed by solvent evaporation, leaving a thin film. Laboratory‐prepared and commercial standards were used for calibration. Detection limits of 5 ppm for V and 2 ppm for Ni were obtained. The overall precision of the procedure expressed as relative standard deviation was 7%. Results obtained by two calibration procedures and other reported results for some samples are compared.
New EDXRS exploitation of compton scattering properties
Authors: Tartari A. , Fernández J. E. , Casnati E. , Baraldi C. 
Published: May 2005

AbstractThe exploitation of the information that can be obtained from the energy analysis of Compton‐scattered photons is discussed. It is shown that the use of the high‐energy wing part of this energy distribution adds a further tool for EDXRS analysis other than the evaluation of the total fluence area of the Compton (or incoherent) distribution and the total fluence area of the Rayleigh (or coherent) peak. Special attention is paid to those situations for which easy and unambiguous coherent peak evaluation is prevented.
Comparison of emission–transmission and elemental sensitivity Methods for determining the trace element content of biological samples
Authors: Somogyi A. , Pázsit Á. 
Published: May 2005

AbstractTwo widely used concentration calculation techniques, emission–transmission and elemental sensitivity methods, were compared. In the determination of the trace element content of environmental materials (e. g. plants, soil), the mass absorption coefficients for the exciting and characteristic x‐rays are dominated of the ‘non‐detectable’, light major components. When using the elemental sensitivity method, these mass absorption coefficients must be a known a priori. When using the emission–transmission method, the combined attenuation of the incident and fluorescence x‐rays within the specimen for the ith element is determined experimentally. The trace element content of biological materials was determined with both methods and the concentrations obtained were compared by t‐test and one‐way analysis of variance methods. In the case of available reference materials the concentration values obtained with these methods were compared with the certified values.
The nuclear microprobe—advances in micro PIXE and complementary techniques
Authors: Malmqvist Klas 
Published: May 2005

AbstractThe nuclear microprobe is an analytical instrument using ion beams produced in accelerators, which generate charged particles with energies of MeV as compared with keV for the electrons used in electron microscopes. The dependence on such an accelerator obviously limits the direct use of the nuclear microprobe in most analytical laboratories and represents an important drawback. However, it is demonstrated that although the nuclear microprobe is a complex technique, it is still a powerful instrument with some unique properties for quantitative trace element microanalysis and imaging.
XANES studies of some copper(II) mixed‐ligand complexes in solid form and in aqueous solution
Authors: Mishra A. , Shrivastava B. D. , Sharma Pradeep , Joshi S. K. 
Published: May 2005

AbstractX‐ray K‐absorption spectra of seven structurally important copper(II) mixed‐ligand complexes were recorded using a 0.4 m radius Cauchois‐type bent crystal x‐ray spectrograph. The spectra of the complexes were recorded in both the solid and in aqueous solution. The observed x‐ray parameters, e.g. chemical shifts, edge widths, shift of the principal absorption maximum and structure of the K‐edge, were used to interpret the proposed structure of the complexes.
Detection of transmutational elements in copper by means of total reflection x‐ray fluorescence spectrometry using synchrotron radiation
Authors: Hegedüs F. , Wobrauschek P. , Streli Ch. , Winkler P. , Rieder R. , Ladisich W. , Victoria M. , Ryon R. W. , Sommer W. F. 
Published: May 2005

AbstractHigh‐purity copper samples were irradiated with high‐energy protons and neutrons. The concentration of transmutational elements was measured by means of the total reflection x‐ray fluorescence method using synchrotron radiation. The spectra of non‐irradiated samples were substracted from the spectra of the irradiated samples. By this evaluation method, the minimum detectable concentration was as low as 1.5 μg g−1 in a copper matrix.
A procedure using polychromatic excitation and scattered radiation for matrix correction in x‐ray microfluorescence analysis
Authors: Lankosz M. , Pella P. A. 
Published: May 2005

AbstractA fundamental‐parameters method using x‐ray tube excitation was developed for use in the x‐ray microfluorescence analysis of flat, optically polished geological specimens. In this procedure, the coherent and incoherent tube target lines scattered from the sample are used to calculate the average atomic number and mass thickness of the sample. The polychromatic tube spectral distribution is calculated from a published algorithm. Since elements such as carbon, hydrogen and oxygen are unmeasurable, their contribution for the purposes of matrix correction can be represented by two hypothetical elements which span each side of the calculated average atomic number of the low‐Z matrix. This procedure is applicable to infinitely thick samples and also those of intermediate thickness, and was tested on glasses of known composition.
Inter‐ and intra‐species crosses between Candida albicans and Candida guilliermondii
Authors: Suzuki T. , Rogers A. L. , Magee P. T. 
Published: May 2005

AbstractHybridization was shown to occur both between strains of the imperfect diploid yeast Candida albicans and between C. albicans and the distantly related hapoid yeast Candida (Pichia)guilliermondii Protorophic hybrids were selected from croses of multiply marked auxotropic mutants two species. In most cases, mild ultraviolet irradiation of the C. albicans partmer was reqiured.Examination of auxotropic markers in segregants from the hybrid indicated that recombination, rather than the heterokaryon, formation, had occured in these croses. The DNA content of the hybrids varied from diploid or aneuploid (for crosses between C. albicans and C. guilliermodii) to triploid (for C. albicabs × C. albicans). It seems possible that genetic exchange analogous to this may occur in nature.
Identification of the RNA2 protein of Saccharomyces cerevisiae
Authors: Lee Melanie G. , Lane David P. , Beggs Jean D. 
Published: May 2005

AbstractThe rna2‐1 mutant Saccharomyces cerevisiae. has a consitional lethal phenotype, accumulating high molecular weight RNAs of intron‐conataining nuclear genes at 36°C. The cloned RNA2 gene suppresses this phenotype and the RNA2 gene product has been implicated in RNA splicing. Rabbit antisera have been raised againts an N‐terminal synthetic peptide taken from the RNA2 gene DNA sequence data, and against a β‐galactosidase/RNA2 gene fusion protein. Both antisera identify that same 97‐105 kd protein from S. cerevisiae cell extracts which is consistent with the predicted size of the RNA2 protein (from the 2800 nucleotide transcript size and DNA sequence data).