bluuebunny/crossref_metadata_2025 huggingface dataset:
Sampling and sample preparation in EDXRS
Authors: Hołyńska Barbara
Published: May 2005

The principles of sampling, sample storage and sample preparation prior to energy‐dispersive x‐ray spectrometry with special attention paid to the methods of obtaining representative samples of heterogeneous materials such as soil, biological and geological specimens are presented. Problems occur with losses of elements to be determined and also contamination of the sample. Sample preparation prior to analysis of environmental, biological and geological materials with and without chemical pretreatment is discussed. The procedure of sample digestion followed by preconcentration and separation of the elements to be determined is discussed. Reference materials are needed for testing the applied procedures.
Calculation of the enhancement of characteristic radiation due to scattering in radioisotope XRF using exact differential cross‐sections
Authors: Karydas A. G. , Paradellis T.
Published: May 2005

The scattering of either the exciting or the characteristic radiation enhances and reduces the XRF intensity. The resultant enhancement has been calculated using exact differential scattering cross‐sections and employing an arithmetic integration. By using radioactive sources the scattering corrections for some thick pure targets were determined experimentally.
Elemental mapping of bone tissues by the use of capillary focused XRF
Authors: Voglis P. , Attaelmanan A. , Engström P. , Larsson S. , Rindby A. , Boström K. , Helander C. G.
Published: May 2005

A description of the x‐ray microbeam spectrometer at Chalmers University of Technology is given with particular emphasis on the mapping and imaging features. The application of the microbeam technique to the analysis of bone specimens is also described.
Sample preparation and EDXRF analysis of element content in marine algal communities — a tentative approach
Authors: Boman J. , Blanck H. , Standzenieks P. , Pettersson R. P. , Hong N. T.
Published: May 2005

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.
Total reflection x‐ray fluorescence spectrometry of metal samples using synchrotron radiation at SSRL
Authors: Hegedüs F. , Wobrauschek P. , Sommer W. F. , Ryon R. W. , Streli Ch. , Winkler P. , Ferguson P. , Kregsamer P. , Rieder R. , Victoria M. , Horsewell A.
Published: May 2005

It was demonstrated that a total reflection x‐ray fluorescence spectrometer, using monoenergetic synchrotron radiation as the primary x‐ray source, is suitable to measure the concentration of transmutational elements in Cu and Fe metal matrices. In a typical irradiation of copper with 590 MeV protons or with spallation neutrons, where the damage dose is 0.4 dpa (displacement per atom), the calculated concentration of transmutational elements is Ni 25, Co 8 and Fe 8 μg g−1. The results show that the minimum detectable concentrations were lower than these values. The energy of the sychrotron radiation was set just below the K‐edge energy of the matrix element, eliminating the large peak due to the matrix. As an example, in the case of a Cu (Z = 29) matrix, the minimum detectable concentration for Ni (Z = 28) was as low as 3 μg g−1. In order to check systematically the possible geometric arrangements of beam direction–reflector position–detector position, a new vacuum chamber was designed and tested. It provides all technical components for remote control of the adjustment procedure to align the reflector in total reflection geometry. Two ways of positioning the reflector in the beam, vertical to the plane of polarization and parallel to that plane, were investigated, to find the best excitation conditions and lowest limits of detection. A few pg corresponding to a concentration of ng g−1 of samples where the matrix can be easily removed as in aqueous or acidic solutions and 50 ng g−1 concentration of metals in a light matrix as in oil were found as detection limits.
Polarization effects in x‐ray photon diffusion
Authors: Fernández J. E.
Published: May 2005

Polarization effects in x‐ray spectrometry are explained with recourse to transport theroy. Intensity contributions from multiple‐scattering terms of the Rayleigh and Compton effects calculated with two models, one representing rigorously the polarization state (vector model) and the other approximating the effects of polarization by considering always the same average state (scalar model), are compared to show the influence of polarization in a practical way. It is shown that using average polarization represents a first‐order approximation valid for unpolarized source.s As a paradigmatic example it is shown that the full account of polarization, for the case of a sample irradiated with an unpolarized x‐ray source (i.e. x‐ray tube), increases the estimated intensity of the multiplescattering background without modifying the intensity of the first‐order term. The effect of polarization is zero or can be neglected in those scattering chains which contain at least one photoelectric effect. In contrast, it must be considered to correct the computation of the continuous background under the Compton peak, due to collision events of the Rayleigh and Compton effects.
Characteristics of layered synthetic microstructure devices for x‐ray spectrometry applications
Authors: Biltoft P. J.
Published: May 2005

Multi‐layer structures offer the unique ability to control the spectral distribution of x‐rays non‐grazing incidence and to provide the ability to focus x‐rays. This combination of attributes offers some exciting possibilities for x‐ray spectrometry. Double crystal monochromators using multi‐layer structures have shown high energy selectivity with reasonable throughput X‐ray optical systems using multi‐layers deposited on figured substrates have been used to focus x‐rays from a conventional tube to micron‐sized spots. Future x‐ray spectrometers will likely take advantage of the energy selection and focusing capabilities of multi‐layers as they become more readily available. Topics covered in this paper include the modification of spectral emissions from a conventional copper anode x‐ray tube by a multi‐layer, and multi‐layer fabrication and characterization techniques as they apply to energy‐dispersive x‐ray spectrometry.
The number of Kα photons produced on a set of thin targets as a functional description of the fluorescence exciting x‐ray beam
Authors: Delgado Martínez V. , Martínez Hidalgo C.
Published: May 2005

This work suggests a theoretical approach for the description of a primary x‐ray beam by means of the K fluorescence which it excites on a set of thin targets made of pure elements. Physical quantities, defined as weighted integrals over hv of the photon spectral distribution, are obtained directly as weighted integrals of the Kα yields over the variable Ez (the ionization energy of the K shell of the element with atomic number Z), without needing any explicit reconstruction of the spectral distribution. The set of Kα yields produced by an x‐ray beam as a function of Ez is a functional description of the exciting beam. Theoretically, such a description is suited to x‐ray fluorescence analysis.
Sensitive method for the determination of rare earth elements by radioisotope‐excited XRF employing a high‐purity germanium detector in optimized geometry
Authors: Lal Madan , Bajpal H. N. , Joseph Daisy , Patra P. K.
Published: May 2005

A close‐coupled side‐source geometrical configuration is proposed for obtaining a high detection sensitivity for rare earth elements (57 ⩽ Z ⩽ 69) by radioisotope‐excited energy‐dispersive x‐ray fluorescence spectrometry. In this configuration a disc source of241 Am (100 mCi), a high‐purity germanium detector and thin samles of rare earth elements on a Mylar backing are employed in an optimized geometry to achieve detection limits in the range 20–50 ng for these elements in a counting time of 1 h.
L shell fluorescence yields and coster—kronig transition probabilities for the elements with 25 ⩽ Z ⩽ 96
Authors: Puri S. , Mehta D. , Chand B. , Singh Nirmal , Trehan P. N.
Published: May 2005

The values of Li sub‐shell fluorescence yields (ωi) and Coster–Kronig transition probabilities (fij) were evaluated using radiative and non‐radiative transition rates based on the relativistic Dirac–Hartree–Slater (RDHS) model for all the elements in the atomic number range 25 ⩽ Z ⩽ 96. The values of the Coster–Kronig‐corrected fluorescence (vi) and average L shell fluorescence (ϖL) yields were also evaluated and least‐squares fitted to obtain the polynomials representing them as a function of atomic number.
Mα/Lα intensity ratios for Ta, W, Pt, Au, Pb and Bi for electron energies in the 11–40 keV range
Authors: Trincavelli J. , Montoro S. , Van Espen P. , Van Grieken R.
Published: May 2005

Both energy‐ and wavelength‐dispersive systems were used to obtain Mα/Lα intensity ratios for Ta, W, Pt, Au, Pb and Bi at various overvoltages. A table of these ratios corrected for matrix absorption and detector efficiency is presented, in addition to an interpolatory function of Mα/Lα generated ratios vs. overvoltage, for each element. In addition, three different ZAF correction models were used to predict both detected and generated ratios. Finally, experimental Mβ/Mα ratios measured at different overvoltages are presented for the six elements considered.
Determination of incident angle in radioisotope‐excited EDXRF
Authors: Somogyi A. , Pázsit Á
Published: May 2005

Three different methods were used for the determination of the effective incident angle related to EDXRF when radioisotope annular sources are involved: weighted averaging, Compton peak method and minimization of the difference between the certificated and measured concetrations of six international standard samples. By measuring the Compton peak energies of various analytical reagent grade elements and compounds, it was found that the incoherent peak energy depends on the mean atomic number of the matrix, so the effective incident angle is also matrix dependent.
Simultaneous matrix and background correction method and its application in XRF concentration determination of trace elements in geological materials
Authors: Hua Younan , Yap C. T.
Published: May 2005

Compton scattered radiation has been used as an internal standard to compensate for matrix absorption effects; it has also been used separately for background correction. In this work, the simultaneous matrix and background correction method was developed, in which both matrix absorption effects and background correction are performed simultaneously, thereby reducing the measurement time; this is particularly important when dealing with large numbers of samples. It also obviates the problem in the conventional method of correcting for the background when the interference‐free background position near the spectral peaks cannot be found. Application of this method to a large number of geological standard reference materials yields values of trace element concentrations in good agreement with their recommended values.
Lowering the limits of detection of X‐ray fluorescence analysis in the electron microscope
Authors: Barna Á. , Pozsgai I. , Fiori C. E. , Wight S. A.
Published: May 2005

A transmission‐type attachment for energy‐dispersive x‐ray fluorescence analysis was developed. The attachment was designed for analysis to be carried out in a CAMEBAX microanalyzer, where the energy‐dispersive spectrometer detector views the specimen through a hole in the objective lens and the space between the specimen and the pole piece of the objective lens is fairly small. Nevertheless, this type of attachment can be applied in other microanalyzers or scanning electron microscopes. Detection limits between 0.5 and 5 ppm on SRM 612 glass (NIST) and the applicability to the analysis of small particles (SRM 470 glass sphere 90 μm in diameter) are demonstrated.
Analysis of archaeological pottery by X‐ray fluorescence spectrometry applying the limit dilution method
Authors: Carbó M. T. Doménech , Reig F. Bosch , Adelantado J. V. Gimeno , Martinez V. Peris
Published: May 2005

A method for correcting the intensity of x‐ray fluorescence (limit dilution method) is proposed for the analysis of samples with a complex matrix such as ceramic materials of archaeological interest. This method corrects the interelement effects, resolving the wide deviations which occur in the quantitative results obtained by x‐ray fluorescence without correction. The contents of sodium, magnesium, aluminium, silicon, potassium, calcium, titanium and iron in sixteen archaeological ceramic samples of different origins and from different locations were determined. The results obtained are comparable to the values obtained by chemical analysis. A statistical study of the data was carried out to classify the samples hierarchically by cluster analysis of their chemical composition and loss on ignition.
Quantitative analyses of aerosol filters by wavelength‐dispersive X‐ray spectrometry from bulk reference samples
Authors: Quisefit J. P. , de Chateaubourg P. , Garivait S. , Steiner E.
Published: May 2005

The quantitative analysis by X‐ray Fluorescence (XRF) of aerosol filters implies the use of calibration curves obtained from synthetic standards which are relatively difficult to make. Several methods have been developed in the last 10 years. Because of transparency to the exciting X‐rays, the analysis of thin films requires optimization of the sample holder by adding secondary covers, for which the influence of the nature and form of the material to obtain the best detection limits has been studied previously. In addition, some metallic solid samples defined as ‘;filter equivalent’ samples have been used by other workers, but only for lead determination, and without a study of their capability to take into account any instrumental variations. This paper reports a theoretical and practical study of bulk samples defined as ‘;filter equivalents.’ Their capability of always being reliable standards even with large variations in instrumental conditions was controlled. A general process to make multi‐element bulky ‘;filter equivalents’ by means of borate glass discs is described. These have the great advantage of being very easy to manipulate and less fragile than thin films or filters, and resistant to X‐rays even after several calibration checks carried out to estimate the stability of the apparatus. They should have an ‘;infinite lifetime’ if the analyst correctly manipulates and stores them.
Wavelength‐Dispersive X‐ray fluorescence spectrometric technique for determining elements in weld fumes
Authors: Swamy K. , Kaliaperumal R. , Swaminathan G. S.
Published: May 2005

An x‐ray fluorescence spectrometric method is described for the determination of elements present in the fumes evolved during welding. Synthetic standards were prepared using salts of Si, Mn, Cr, Fe, Pb, Cu, Al and Ni for evaluation. The standards were mixed with boric acid in the ratio 1 : 1 and briquettes were prepared by the double pellet method. The samples were collected in filter‐paper discs by exposing them during welding. The average standard deviation of the method is about 7%.
Relative intensities of Lα1, Lβ1 and Lβ2, 3, 15 lines of gold: Photoexcitation with the continuum in and near the threshold region
Authors: Agrawal R. M. , Jha S. N.
Published: May 2005

Variations of the relative intensities of the Lα1, Lβ1 and Lβ2,3,15 lines of gold on their photoexcitation with the continua of x‐ray tubes with W and Mo targets were measured at operating voltages from 15 to 20 kV. The standard procedure for calculating the fluorescence intensity of an x‐ray line excited by a polychromatic x‐ray beam was suitably modified to calculate the relative intensities of these lines. The factors responsible for the differences between the experimental and calculated values are discussed.
Scanning electron microscopy and X‐ray energy‐dispersive spectroscopy of surface micro‐transformations in Ca–P glasses
Authors: Valdrè G.
Published: May 2005

Surface transformations of micro‐granules of a calcium‐phosphate glass (a bio‐glass) were examined by back‐scattered electron (BS) imaging and quantitative x‐ray energy‐dispersive spectroscopy (EDS) in a scanning electron microscope (SEM). All the images were obtained by using a backscattered electron detector of high efficiency and atomic number Z resolution (ΔZ = 0.3). The chemical transformations were induced during in vivo implantation of the bio‐glass in rabbit dorsal muscle sites. The observations showed the presence of an interlayered structure with different BS signal contrast. Quantitative EDS microanalysis performed by profiling the electron beam across the samples indicated the presence of hydrated calcium‐phosphate in the external layer, an inhomogeneous silica‐rich gel‐type layer in the mid‐layer and unaffected original Ca–P glass in the centre. A simple model, based on the balance of the concentrations of the elements (which have diffused) in the different layers, is proposed to explain the contribution of the elements constituting the original glass to the formation of the different layers. This result agrees with the experimental data obtained from image analysis. The microstructural behaviour of this type of glass was elucidated.
Effect of counter ions on X‐ray absorption discontinuity
Authors: Khadikar Padmakar V. , Joshi Shobha , Mangalson Nolan F. , Silk Jeffrey E.
Published: May 2005

This work indicates that counter ion distant neighbours affect the x‐ray absorption discontinuity. Cobalt(III) complexes of ethylenediamine containing different counter ions were used as models for this purpose. The results should provide useful information regarding the influence of counter ion distant neighbours on x‐ray absorption spectra.
Measurement of composition of thin films obtained by sputtering using radioisotope excited X‐ray fluorescence
Authors: Moore J. A. , Elsahlli T.
Published: May 2005

An energy‐dispersive x‐ray fluorescence (EDXRF) apparatus using a radioisotope source with a secondary target (241 Am–Mo) and a Si(Li) x‐ray spectrometer was used to measure the Cu, Sr and Bi contents of thin (100 μg cm−2) films sputtered on to MgO. The results were found to be in excellent agreement with those obtained from MeV Rutherford backscattering (RBS) analysis of the same films. The calibration of the EDXRF apparatus was done by measuring x‐ray intensities excited in thin sol‐gel films of known Cu, Sr and Bi content, as given by the accurately known chemical solutions from which the sol‐gel films were prepared. The experimental calibration constants were in excellent agreement with the theoretical values calculated using a thin‐film equation, which assumes that characteristic x‐ray absorption and secondary excitation are negligible, and the published atomic x‐ray data.
Application of synchrotron radiation XRF analysis in high‐temperature superconducting thin‐film technology
Authors: Trounova V. A. , Danilovich V. S. , Zolotarev K. V. , Predtechensii M. R. , Bobrinok O. F.
Published: May 2005

The method of synchrotron radiation XRF applied to high‐temperature superconducting films can be used for the measurement of the compositions of different compounds of the same element or of the changes in the stoichiometry in the process of thin‐film production. An important advantage of the method is that it possesses very low detection limit (down to 5 × 1013 atoms cm−2) and allows a wide range of film thicknesses to be measured.
Submicrometer phase chemical composition analysis with an electron probe microanalyzer
Authors: Wang Frank Cheng‐Yu
Published: May 2005

Submicrometer phase quantitative analysis is always a challenging problem for electron beam microanalysis because the phase is smaller than the electron beam and the specimen interaction volume. In order to obtain more accurate composition information, other analytical techniques need to be used to clarify the elements present and characterize the valence state of major elements in that submicrometer phase In this study, the electron probe microanalyzer (EPMA) was used to determine the contamination phase in the tungsten carbide‐cobalt ceramic system. The average size of the contamination phase was approximately 0.5 μm in diameter. The chemical composition of the contamination phase was elucidated by combining results from x‐ray mapping, valence state determination and EPMA quantitative analysis data. The effect of the contamination phase in the tungsten carbide‐cobalt ceramic system is also discussed.
Ll, Lα, Lβ and Lγ X‐Ray Production Cross‐Sections in Elements 57 ≤ Z ≤ 92 by 8–50 ke V Photons
Authors: Mann K. S. , Singh N. , Mittal Raj , Sood B. S. , Allawadhi K. L.
Published: May 2005

Cross‐sections for the production of Ll, Lα, Lβ and Lγ x‐rays in 22 elements (57 ≤ Z ≤ 92) by photons of 13 different energies in the range 8–50 ke V are reported. The experimental values of the cross‐sections were determined by measuring the absolute yield of L subshell x‐rays emitted from a target of a given element and thickness when it was bombarded with a known flux of photons of given energy. The theoretical values of the cross‐sections were calculated from the theoretical/semi‐empirical values of subshell photoionization cross‐sections, fluorescence yields, Coster‐Kronig transition probabilities, intra‐shell transition probabilities and radiative decay rates. The present and previous measured and calculated values of the cross‐sections are tabulated to bring out the existing status of L x‐ray production cross‐sections.
Elemental analysis of gel‐grown rare earth molybdate crystals using energy‐dispersive X‐ray fluorescence spectrometry
Authors: Bhat C. K. , Bhat C. L. , Lal Madan , Patra P. K. , Kotru P. N.
Published: May 2005

Rare earth molybdate crystals such as those based on lanthanum, neodymium and some mixed molybdates, grown by the gel method, were analysed for major and trace impurity elemental concentrations using energy‐dispersive X‐ray fluorescence spectrometry in order to understand the characteristics of the material in terms of structural perfection and composition. The method used permits the simultaneous determination of rare earth elements such as La and Nd and also Mo and impurities such as Fe and Zn. Based on the observed concentrations of major elements, it is shown that the formulae so far assumed for some of these composites may be incorrect and may need a major refinement. Monoenergetic X‐rays of 22.1 and 59.6 keV were employed for fluorescence excitation and optimum detection efficiency was obtained for a large number of elements. Pulverized samples mixed with cellulose powder and specimens prepared in the form of pellets were used. The fundamental parameter method was used for the quantitative estimation of elemental concentration.
Peak‐to‐background method for standardless electron microprobe analysis of particles
Authors: Trincavelli J. , Van Grieken R.
Published: May 2005

A peak‐to‐background method was implemented for standardless electron microprobe analysis of bulk samples and particles. First, a study on the choice of the beam entry point was performed; the region of the particle closest to the detector proved to be the most convenient. Then, a very simple algorithm, which does not require any kind of standard, was developed for particle analysis. This method was tested for glass standard particles and the results were compared with those given by other methods; the proposed standardless approach appeared to yield very satisfactory results.
Investigation of M x‐ray emission following photoionization of L and M shell electrons in high‐Z‐elements
Authors: Allawadhi K. L. , Sood B. S. , Mittal Raj , Singh N. , Mann K. S. , Vandana
Published: May 2005

The cross‐sections of M x‐ray emission following photoionization of L and M shell electrons in Au, Pb, Th and U by 59.57 ke V gamma rays were measured. The experimental values of cross‐sections were found to be higher than those calculated from the theoretical values of L and M shell photoionization cross‐sections, the Li subshell to M shell vacancy transfer probabilities and M shell average fluorescence yields. The transfer of vacancies from the Li subshell to the M shell was found to play a significant role in M x‐ray emission. The present status of the experimental and calculated values of the cross‐sections is discussed.
Comparison of the determination of copper, nickel and zinc in contaminated soils by x‐ray fluorescence spectrometry and inductively coupled plasma spectrometry
Authors: Wilson P. , Cooke M. , Cawley J. , Giles L. , West M.
Published: May 2005

Soil samples from a potentially contaminated site were prepared and analysed for their copper, nickel and zinc contents by both inductively coupled plasma (ICP) spectrometry and x‐ray fluorescence (XRF) spectrometry. Results obtained by XRF spectrometry were either comparable with or slightly higher than those obtained by ICP. However, when the results obtained by the two techniques were compared with the threshold values for contamination by the three metals, then each set of results led to the same conclusion with respect to the categorization of the site. Comparability between the two techniques was thus demonstrated and either may be used to screen soil for phytotoxic metals.
EDXRS study of lichens as biomonitors and effects of washing procedure on element concentrations
Authors: Calliari I. , Caniglia G. , Nardi S. , Tollardo A. M. , Callegaro R.
Published: May 2005

A monitoring survey was carried out in North Italy using Pseudevernia furfuracea as a monitor of air pollution. The experiment was carried out on lichen thalli exposed for different periods varying from 3 to 10 months at urban and rural sites, to examine and compare the bioaccumultion of several elements. Every 2 months a fraction fo exposed lichens was collected to analyse the theallus. Each fraction was divided into two parts, one of which was washed in deionized water, in order to quanify the element loss due to the washing procedure. The samples were analysed by energy‐dispersive x‐ray fluorescence spectrmetry in the secondary excitation mode; quantitative analysis was performed by the fundamental parameter method with NIST standard reference materials. The targets for the fluorescence spectrometer were obtained by digestion under pressure with microwave heating. At the end of the exposure period (10 months), nearly all elements, showed highter concentrations at the urban than at the rural site.
L‐subshell Coster–Kronig yields for Tb
Authors: Sánchez Héctor J. , Pérez Roberto D. , Rubio Marcelo , Castellano Gustavo
Published: May 2005

The synchrotron photoionization method was applied to measure L‐subshell Coster–Kronig yields for Tb. This method is based on the capability of tuning the energy of the synchrotron photons producing a selective subshell ionization. A foil sample of Tb was irradiated and characteristic spectra were recorded. Data were analysed using a new formalism (based on a matrix representation) to express x‐ray fluorescence intensities involving Coster–Kronig transitions. The results obtained were f12 = 0.201 ± 0.014, f13 = 0.281 ± 0.027 and f23 = 0.097 ± 0.016. These data represent valuable information for spectroscopists, considering the lack of data for L‐shell parameters.
Chemical effect on intensity ratios of K‐series x‐rays in vanadium, chromium and manganese compounds
Authors: Tamaki Yoichi
Published: May 2005

Kα and Kβ x‐ray fluorescence spectra of various V, Cr and Mn compounds were measured with a Bragg spectrometer. The relative intensities of the Kβ1,3, Kβ2, Kβ′ and Kβ″ lines with respect to the Kα line were determined to confirm the chemical effect on the Kβ/Kα intensity ratio obtained using a Si(Li) detector. Chemical effects on each component line are discussed with respect to the oxidation state of the metal ions. The relative importance of an increase in transition probabilities of the Kβ2 group (Kβ2 and Kβ″) was evaluated in the determination of the overall Kβ/Kα ratio.
Choice of optimum conditions for x‐ray excitation of elements with low atomic number
Authors: Pavlinsky G. V. , Dukhanin A. Yu.
Published: May 2005

The influence of the factors (window thickness, anode material and voltage on the x‐ray tube) that determine the x‐ray fluorescence intensity of elements with low atomic number (boron, carbon, nitrogen, oxygen, fluorine) is considered. The conditions for maximum x‐ray fluorescence intensity of the elements considered are greatly dependent on the matrix composition, as the ionization of an atom by the photo‐ and Auger electrons becomes significant. The calculations, performed for various matrices, show how the decrease in tube window thickness influences the x‐ray fluorescence intensity. Both the effective excitation by the primary radiation of the element measured and main matrix elements, providing high‐energy photo‐ and Auger electrons, should be taken into account when selecting the anode material. It was found that, in contrast to higher atomic number elements, the voltage increase at the tube contributes only insignificantly to the increase in the analytical signal for the elements considered. The software developed provide modelling of any analytical situation aimed at a quick selection of the optimum conditions for analysis of the elements being discussed.
Atomic level widths for x‐ray spectrometry
Authors: Campbell J. L. , Papp T.
Published: May 2005

A self‐consistent set of level widths for the K–N7 subshells is assembled using literature experimental data from a variety of spectroscopic methods. In cases where Coster–Kronig processes contribute significantly, the widths differ from the predictions of the atomic single‐particle model; in the restricted regions where atomic many‐body predictions are available, the agreement is much better. The assembled widths will be useful to Si(Li) spectroscopists who wish to include natural width in the description of spectrometer lineshape; such inclusion will improve accuracy in both fundamental and analytical work. The present database is also of value in identifying where improvements to the currently incomplete knowledge of natural widths are most critical.
On the mechanism of exclusion of M2 double‐stranded RNA by L–A–E, double‐stranded RNA in Saccharomyces cerevisiae
Authors: Hannig Ernest M. , Leibowitz Michael J. , Wickner Reed B.
Published: May 2005

L–A–E double‐stranded RNA (dsRNA), when introduced into cells carrying L–A–H and M2 dsRNAs, does not eliminate the L–A–H dsRNA, but (i) L–A–E does lower the copy number of L–A–H dramatically and (ii) L–A–E eliminates M2 dsRNA from the cell. That these two effects of L–A–E are related is shown by the fact that mutants of a strain carrying L–A–H and M2 selected for their resistance to exclusion of M2 by L–A–E [effect (ii)] have an altered L–A–H whose copy number is not lowered by L–A–E [effect (i)]. Although the L–A in K1 strains (L–A–HN in all cases examined) differs significantly both genetically and physically from the L–A in the K2 strain studied (L–A–H), the L–A–HN from the K1 strains can maintain M2 dsRNA, and the L–A–H from the K2 strains can maintain M1 dsRNA.
Mutations in ARS1 increase the rate of simple loss of plasmids in Saccharomyces cerevisiae
Authors: Strich Randy , Woontner Michael , Scott John F.
Published: May 2005

Autonomously replicating sequence (ARS) elements are DNA sequences that promote extrachromosomal maintenance of plasmids in yeast. Mutations generated in vitro in the ARS1 region were examined for their effect on plasmid maintenance in a yeast centromeric plasmid. Our data show that mutations in the regions surrounding the ARS1 consensus sequence cause increases in the frequency of simple loss (1:0) event without affecting the rate of non‐disjunction (2:0). Removal of the consensus itself causes a drastic increase in the rate of simple loss. Sequences sensitive to mutagenesis were identified in each flanking region and differ with respect o their location and importance o ARS function. These results suggest that the role ARS1 plays in plasmid maintenance deals with the replication and/or localization of the plasmid in yeast.
PHO5 Upstream sequences confer phosphate control on the constitutive PHO3 gene
Authors: Bajwa Wajeeh , Rudolph Hans , Hinnen Albert
Published: May 2005

To identify the sequences involved in the regulation of the yeast acid phosphatase gene (PHO5) we constructed a series of hybrid promoters. Increasing lengths of 5′‐flanking sequences of the PHO5 gene were placed in front of the TATA‐box of constitutively expressed acid phosphatase gene (PHO3).

The PHO5/PHO3 promoter constructions were used to replace the entire PHO5, PHO3 gene cluster on chromosome II. Depending on the length of PHO5 5′‐flanking sequences present the PHO3 gene driven by the hybrid promoter could now be derepressed in response to inorganic phosphate (low Pi) exactly as the PHO5 wild type gene. A critical regulatory element was located between position −402 to −351 (upstream from ATG) and sequences further downstream (from −351 to −300) could increase transcriptional activation. The transcription levels of PHO3 were determined by northern blot analysis, under repressed (high Pi) and derepressed (low Pi) conditions which was paralleled by an increase in extra‐cellular acid phosphatase activity. Fully regulated promoter hybrids showed a 40‐fold induction of mRNA levels, comparable to wild type PHO5 promoter. S1‐nuclease protection experiments revealed that the PHO5 5′‐flanking sequences, placed in front of PHO3, did not change the PHO3 transcription initiation site/s.
Molecular cloning of chromosome I DNA from Saccharomyces cerevisiae: Isolation of the MAK16 gene and analysis of an adjacent gene essential for growth at low temperatures
Authors: Wickner Reed B. , Koh Theodore J. , Crowley Joan C. , O'Neil Judy , Kaback David B.
Published: May 2005

MAK16 is an essential gene on chromosome I defined by the thermosensitive lethal mak16–1 mutation. MAK16 is also necessary for M double‐stranded RNA replication at the permissive temperature for cell growth. As part of an effort to clone all the DNA from chromosome I, plasmids that complemented both the temperature‐sensitive growth defect, and the M1 replication defects of mak16–1 strains were isolated from a plasmid YCp50: Saccharomyces cerevisiae recombinant DNA library. The two plasmids analysed contained overlapping inserts that hybridized proportionally to strains carrying different dosages of chromosome I. Furthermore, integration of a fragment of one of these clones occurred at a site linked to ade1, confirming that this clone was derived from the appropriate region of chromosome I. An open reading frame adjacent to MAK16 potentially coding for a 468 amino acid protein was defined by sequence analysis. 185 amino acids of this open reading frame were replaced with a 1·2 kb fragment carrying the S. cerevisiae URA3 gene by a one‐step gene disruption. The resulting strains grew at a rate indistinguishable from the wild type at 20°C, 30°C, or 37°C, but could not grow at 8°C. The deleted region is thus essential only at 8°C, and we name this gene LTE1 (low temperature essential).
Tryptophan accumulation in Saccharomyces cerevisiae under the influence of an artificial yeast TRP gene cluster
Authors: Prasad Rajendra , Niederberger Peter , Hütter Ralf
Published: May 2005

Plasmid pME559, carrying all five yeast TRP genes, was constructed. This plasmid is a yeast/Escherichia coli shuttle vector based on pBR322 and 2 μm‐DNA sequences derived from plasmid pJDB207. We studied in yeast (i) the stability of the plasmid under selective and non‐selective conditions, (ii) expression of all five TRP genes and (iii) tryptophan accumulation in yeast transformants. These studies were conducted in comparison with an earlier construction, pME554, which differs from plasmid pME559 in the expression of the TRP1 gene and which carries the TRP2 wild type instead of the TRP2fbr mutant allele. For stable maintenance of the plasmids in yeast a selection was necessary. Plasmid pME559 displayed normal expression of all TRP genes, and enzyme levels on average 23‐fold higher than in the wild type strain were found. In comparison, the maximal tryptophan flux observed in such a plasmid‐carrying strain was about ten‐fold higher than the maximal flux capacity in the wild type strain.
Multiplicity of mechanisms of carbon catabolite repression involved in the synthesis of alcohol oxidase in the methylotrophic yeast Pichia pinus
Authors: Sibirny A. A. , Titorenko V. I. , Efremov B. D. , Tolstorukov I. I.
Published: May 2005

The effect of various carbon compounds on the synthesis of alcohol oxidase in a medium with methanol was studied in the wild type strain of Pichia pinus as well as in gcr1 and ecr1 mutants defective in glucose and ethanol repression of methanol metabolic enzymes, respectively. Compounds repressing the synthesis of alcohol oxidase in the wild type strain were divided into four groups. Repression of alcohol oxidase by compounds of the first group (glucose, fructose, mannose, galactose, L‐sorbose and xylose) was impaired only in the gcr1 mutant and that by compounds of the second group (ethanol, acetate, 2‐oxoglutarate and erythritol) only in the ecr1 mutant. Repression by compounds of the third group (malate, dihydroxyacetone) was not impaired in both these regulatory mutants and that by compounds of the fourth group (succinate, fumarate, L‐arabinose, sorbitol, salicin, xylitol and cellobiose) was partially reduced in both gcr1 and ecr1 strains.

Mutation gcr1 causes a significant decrease in phosphofructokinase activity. It also led to a six‐ to seven‐fold increase in intracellular pools of glucose‐6‐phosphate and fructose‐6‐phosphate and to a two‐fold decrase in the intracellular pool of fructose‐1,6‐bisphosphate. In ecr1 strains, a decrese in 2‐oxoglutarate dehydrogenase activity accompanied by an increae in activities of NAD‐ and NADP‐dependent isocitrate dehydrogenases and NAD‐ and NADP‐dependent glutamate dehydrogenases was demonstrated. The intracellular pool of 2‐oxoglutarate was increased 2·5‐fold in ecr1 strains. Genes GCR1 and ECR1 are not linked.

The mechanisms of catabolite repression of alcohol oxidase in methylotrophic yeasts are discussed.
Effects of yeast suspension density on the accumulation ratio of transported solutes
Authors: Kotyk A.
Published: May 2005

The previously described effect of cell suspension density on metabolic and transport phenomena in yeast, apparently caused by inhibition by dissolved carbon dioxide, is also observed with the accumulation ratio of both sugars and amino acids where not only a kinetic but also an energetic factor comes into play. Unlike all previously measured metabolic and transport parameters, the dependence of the accumulation ratio on suspension density is not monotonic but shows a pronounced maximum in the range of 4–8 mg dry wt/ml, depending on yeast species and on cultivation conditions. In Rhodotorula gracilis and in Lodderomyces elongisporus it is not due to CO2 but is semiquantitatively related to the proton‐motive force across the plasma membrane as well as to the intracellular ATP content. It is observed both in oxygen and in argon, over a wide range of pH values and of temperatures, but it is suppressed by metabolic inhibitors. It is expressed only in a range of transported solute concentrations between about 0·1 and 10 mM.
Changes in robosomal properties during adenylate deprivation in the cells of Kluyveromyces lactis
Authors: Ishiguro Junpei , Azuma Yukimasa , Uritani Masahiro , Miyasaki Masazumi
Published: May 2005

In an adenine‐requiring mutant strain of the yeast, Kluyveromyces lactis the intracellular content of ATP is one‐third to one‐fifth that in a protophic wild strain under growing conditions. The quantitatives difference becomes rather small in resisting stationary‐phase cells. Temporary changes in the two‐dimensional protein patterns of mutant ribosomes occur when the ATP content during the transition phase of growth. The transfer of exponentially growing cells to a synthetic complete medium void of adenine induces the same changes in mutant ribosomes within several hours. Identification of robosomal proteins by two‐dimensional gel electrophoresis indicated all changeable proteins (at least five proteins) to belong to 40S ribosomal subunits. The mutant ribosomes prepared from the transitio‐phase cells have much lower activity (below 60%) for poly(U)‐directed polyphenylalanine synthesis than those in exponentially growing or resisting stationary‐phase cells. Thus, changes in ribosomal components associated with the differences in ribosomes activity in a cell‐free system were noted in the adenylate‐deprived cells of K. lactix.
Yeast flocculation: Quantification
Authors: Stratford M. , Keenan M. H. J.
Published: May 2005

Yeast flocculation is an orthokinetic process dependent upon mechanical agitation for all quantitative measurements. From several methods which were assessed, orbital shaking was selected as being the most practical as well as producing the most meaningful results.

Quantitative measurements of flocculation were made in terms of minimum agitation threshold, initial rate, extent of flocculation at equilibrium and flocculated particle size at equilibrium. All these parameters were strain dependent. Critical cell density functions were formed if agitation was limiting regardless of how the agitation was imposed, and are unlikely to be related to bond strength.
The subcellular location of 4‐aminobutyrate aminotransferase in Candida boidinii and its probable role in the breakdown of putrescine and spermidine
Authors: Large Peter J. , Robertson Anne
Published: May 2005

4‐Aminobutyrate aminotransferase (EC 2.6.1.19) was elevated in activity by 20‐ to 40‐fold in cells of the yeast Candida boidinii grown on spermidine, putrescine, 4‐acetamidobutyrate and 4‐aminobutyrate compared with activities detected in cells grown on ammonium, methylamine or 6‐aminohexanoate, confirming previous suggesions that it plays a key role in polyamine breakdown. Other enzymes of the proposed route of polymine breakdown were found to be non‐coordinately induced or derepressed during growth on spermidine or its putative breakdown intermediates. The enzyme was not sedimented from spheroplast lysates at 100 000 × g, and it is concluded that it is conclded that it is probably cytosoilc in its subcellular location (although the data do not exclude the possiblity of its being vacuolar).
Yeast flocculaiton: A dynamic equilibrium
Authors: Stratford Malcolm , Coleman Heather P. , Keenan Michael H. J.
Published: May 2005

The steady state in yeast flocculation is a dynamic equilibrium between flocculated and dispersed yeast cells. The free cell concentraiton is directly proportional to the total cell concentration and may be expressed as an equilibrium constant. Increased agitation decreases floc size and equlibrium constant whilst increasing floc‐surface area and free cell concentration. Values of equilibrium constant are influenced by agitation in a complex relationship probably involving the floc‐surface area and floc momentum.

Inhibition of flocculation by mannose and low pH is reversible and becomes greater with increased agitation. Both these inhibitions appear consistent with a weakening of flocculent bond strength by these inhibitors.
A non‐conserved sequence in the 5′ region of the CYH2 intron from saccharomyces cerevisiae controls splicing efficiency of the pre‐mRNA
Authors: Swida Ulrike , Thüroff Eduardo , Steindert Edith , Käufer Norbert F.
Published: May 2005

The CYH2 gene from Saccharomyces cerevisiae containing one 510 bp intron is spliced inefficiently. We have shown previoulsy that a non‐conserved sequence within the intron is responsible for this low splicing efficiency. Using synthetic oligonucleotides comprising the identified region we show in this report that a very short region contains the specificity to act negatively on the splicing efficiency of the CYH2 gene. Furthermore, this sequence influences the splicing efficiency only when it is placed close to the 5′ splice site of the gene. Investigations with chimeric CYH2/β‐actin genes show that this sequence acts independent from its natural surroundings. We propose that this sequence might interact with splicing factor(s).
Structure and expression of yeast DPR1, a gene essential for the processing and intracellular localiation of ras proteins
Authors: Goodman Lauri E. , Perou Charles M. , Fujiyama Asao , Tamanoi Fuyuhiko
Published: May 2005

The ras protein represent a unique example of membrane proteins which apparently do not utilize the secretory pathway for their membrane localization. Instead, it is belived that palmaitic acid, covalently attached to the protein, acts as an anchor to the membranes. Recent identification of yeast mutants defective in the processing of the ras proteins has provideda novel approach for defining these biosynthetic process. We report here the charcterization of yeast DPR1, a gene essential for the processing of the ras proteins. The sequence of the gene indicates that it encodes a protein of 431 amino acids which contains no significant homology with any known proteins. It is a relatively hydrophilic protein of cysteine. The DPR1 gene product product has been identified in a cell‐free translation system as a proteinhaving an apparent molecular weight of 43 hd. This represents the first step in the translation system as a protein having an apparent molecular weight of 43 kd. This represents the first step in the investigation of a novel protein‐processing pathway, one that id distinct from the secretory pathway.
Genetic analysis in the methylotrophic yeast Hansenula polymorpha
Authors: Gleeson Martin A. , Sudbery Peter E.
Published: May 2005

Techniques are described for the induction, isolation, and characterization of mutants of Hansenula polymorpha. In addition, techniques for controlled passage through the life cycle and genetic analyses, including complementation, tetrad and random spore analysis, have been developed and used to assign mutants to 62 complementation groups. We report that organism conforms to the expected genetics of a homothallic yeast and displays a Mendelian segregation of genes through meiosis. Preliminary mapping data are presented indicating linkage of three genes on a single linkage fragment. Enymatic analysis of methanol‐non‐utilizing mutants identified one class which is totally deficient in the key assimilatroy enzyme, dihydroxyacetone synthase.
Yeast KEX2 protease and mannosyltransferase I are localized to distinct compartments of the secretory pathway
Authors: Cunningham Kyle W. , Wickner William T.
Published: May 2005

The KEX2 protease (product of the KEX2 gene) functions late in the secretory pathway of Saccharomyces cerevisiae by cleaving the polypeptide chains of prepro‐killer toxin and prepro‐α‐factor at paired basic amino acid residues. The intracellular vesicles containing KEX2 protease sedimented in density gradients to a position distinct from those containing mannosyltransferase I (product of the MNN1 gene), a marker enzyme for the Golgi complex. The recovery of intact compartments containing these enzymes approached 80% after sedimentation. We propose that the KEX2 protease and mannosyltransferase I reside within distinct compartments.