bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilizing cellulose ethers as suspension agents in the polymerization of vinyl chloride
Authors: Sarkar Nitis , Archer Wesley L.
Published: May 2005

Proper choice of a suspending agent will help the PVC manufacturer achieve control of resin particle size, particle size distribution, and resin bead porosity. The results of research work at Dow has revealed that certain properties of cellulsoe ethers (a hydroxypropyl methylcellulose ether structure) are useful in helping control the properties of the PVC resin. In vinyl chloride polymerizations, cellulose ethers act as both an emulsifier; and during the polymerization, as a protective colloid to prevent excessive coalescence of the monomer droplets. The average particle size of the organic droplets in the aqueous phase during the PVC polymerization reaction is a function of the interfacial tension, intensity of agitation, viscosity of the two phases, and the volume fraction of the dispersed phase. The average particle size of the PVC resin was found to be a direct function of the interfacial tension multiplied by the 0.2 power of the gel strength of the cellulose ether solution. The interfacial tension of the cellulose ether solution/organic interface is probably the most important factor in determining the resin particle size. Particle size distribution widens with an increase in interfacial tension. Resin bead porosity is also important and is directly related to the solubility of the cellulose ethers in the organic phase. This observation supports the proposed seed stabilization theory that can explain the formation of a porous resin bead. The use of a proper suspension agent like cellulose ethers with or without a secondary surfactant will help control important properties of the PVC resin product. Control of the average molecular wight, degree of substitution, and grouping distribution on the cellulose chain of the cellulose ether suspension agent (all of which affect interfacial tension) is important for the PVC manufacturer.
The efficient, routine use of automated colorimetry in the evaluation of the thermal degradation of PVC formulations
Authors: Prezzavento Bruce A.
Published: May 2005

The thermal degradation of PVC compound involves the development of color. The evaluation of this degradation, and the associated additive performance, is often limited to that perceived by the human eye. This technique provides limited accuracy and precision. A quantitative technique incorporates the use of a colorimeter. Essentially errorless, laborless performance analyses are achieved with automated colorimetry. Elaborate data processing of the computer‐acquired digital information is then available.
The UV resistance of adipate based polymeric plasticizers in PVC
Authors: Eldridge William J.
Published: May 2005

DOA, (di‐2‐ethylhexyl) adipate, is a monomeric ester plasticizer frequently used in PVC compositions to enhance flexibility at low temperatures. DOA has several drawbacks; it lacks permanence in the PVC matrix and it has poorer compatibility than its phthalate homologue (DOP). By reacting adipic acid with polyols, polymer chains of increased molecular weights can be formed. These polyester plasticizers offer increased permanence over DOA. The focus of this paper is to demonstrate how adipate plasticizers, starting with DOA and increasing in molecular weight, affect the performance of flexible vinyl, especially in regard to UV resistance and permanence. The following series of evaluations will show that as the molecular weight of plasticizers increases, the permanence properties (volatility and extraction by various media) increase. The ability to withstand degradation from ultraviolet light also increases with higher molecular weight.
A novel impact modifier system for vinyl siding and profile substrate
Authors: Grohman M.
Published: May 2005

The use of a newly developed ABS impact modifier in coextruded vinyl siding and window profile substrate is discussed. Considerations of toughness at room and low temperature, output, reduced lubricant levels, and weatherability of the finished siding are reviewed. Actual outdoor weathering results are presented, along with long‐term heat aging tests, showing the modifier to have good property retention characteristics.
Scattered primary radiation as an internal standard in X‐ray emission spectrometry: Use in the analysis of copper metallurgical products
Authors: Clark N. H. , Mitchell R. J.
Published: May 2005

The use of scattered primary X‐radiation of various wavelengths in the range 0.250 to 1.999 Å has been studied in the analysis of copper, iron, and silicon (as silica) in copper metallurgical products. In the analysis of copper and iron, the use of relatively short wavelength predominantly incoherently‐scattered radiation is superior to the use of background radiation near the analyte emission line, and it is necessary for the scatter wavelength to be shorter than that of a major absorption edge of a major element in the system. The wavelength 0.889 Å is suggested as the optimum for use in the analysis of copper, and one simple calibration equation provides acceptable analysis over the whole range of CCu from 0 to 42%. Over short ranges wavelengths from 0.362 to 0.889 Å are useful in the analysis of iron; but one single calibration cannot be devised to cover the whole range of CFe from 0 to 56%. The limited results for silicon as silica are included for completeness.
X‐ray spectrometric determination of major elements in silicate rock samples, using a thin film technique based on ion exchange dissolution
Authors: Govindaraju K.
Published: May 2005

A new method of sample preparation with a very high sample dilution range of about 1:70 is proposed for X‐ray spectrometric determination of major elements in silicate rock samples. In spite of this large dilution, sensitivity is not sacrificed as the sample, uniformly distributed in an ion exchange resin (i.e. a light organic matrix), is presented for analysis in a small volume (thin film technique). The fusion product of the sample with lithium borate (40% of sample, 60% of flux) is dissolved by thorough mixing in an aqueous suspension of a strong acid cation exchange resin. During the cation exchange dissolution, the cations originally present in the rock sample are transferred quantitatively and homogeneously onto the resin. The dried resin is then sprinkled uniformly on a plastic adhesive strip in such a way that a single layer of resin beads (about 100 μm) is obtained. The impregnated strip is then analysed, with a counting time of 20 s for all elements except for Mg (100 s).

The analysis of several geochemical standards for Al2O3, Fe2O3, MgO, CaO, TiO2 and K2O shows the practical absence of matrix effects. Furthermore, a working curve could be constructed for each element as a straight line between a high standard and a blank sample (0%), the latter consisting simply of pure dry cation exchange resin in H+ form. As only 90 to 100 mg amounts of resin beads are necessary for making a thin film (diameter 4 cm), microanalysis with 5 to 10 mg of mineral or rock samples also becomes possible.
The detection of outlying observations in replicate X‐ray measurements of sample size three
Authors: Harvey P. K.
Published: May 2005

On the assumption that X‐ray count data are normally distributed, certain tests for detecting outliers or ‘wild’ values within replicate sets of three measurements are compared. Treated as ‘insurance policies’ rather than formal statistical tests, the statistics discussed are useful for monitoring X‐ray data, particularly in computer oriented systems. The problem of the correction of outliers is briefly discussed.
Principal emission lines of the M series
Authors: Jenkins R.
Published: May 2005

A table of the principal emission lines from the M series has been compiled using Bearden's data, supplemented by new measurements. Curve fitting methods have been used to fill additional gaps in the data sets. Measurements have also been made to establish the average relative intensity values of the stronger lines.
The atomic number dependence of the X‐ray continuum intensity and the practical calculation of background in energy dispersive electron microprobe analysis
Authors: Smith D. G. W. , Gold C. M. , Tomlinson D. A.
Published: May 2005

Computer fitting techniques have been used to derive a new expression for the relationship between X‐ray continuum intensity and atomic number for a range of electron acelerating potentials up to 25 kV, continuum energies up to 10 keV and average atomic numbers up to thirty. A practical approach to background corrections in energy dispersive electron microprobe analysis, which utilizes this expression, is outlined. The procedure should lead to significant improvements in both accuracy and detection limits in this method of X‐ray analysis.
X‐ray production as a function of depth for low electron energies
Authors: Brown J. D. , Parobek L.
Published: May 2005

Depth distributions of X‐ray production by electrons in the energy range of six to fifteen key have been measured for Si and Cu characteristic X‐rays in matrices of Al, Ni, Ag and Au. Corrections from these curves show that the modified Philibert absorption correction predicts the wrong dependence on matrix atomic number at these low electron energies, while the Duncomb and Reed atomic number correction shows too strong a dependence on atomic number. The curves should be valuable for comparison with both theoretical and empirical models for quantitative analysis at low energies.
The atomic number and absorption corrections in electron microprobe analysis at low electron energies
Authors: Parobek L. , Brown J. D.
Published: May 2005

From an extensive series of measurements of ϕ(ρz) curves, at electron energies between 6 and 15 KeV, an empirical formula;ϕ(R)=DKn(KR)n−1 exp(−(KR)n) where R=ρz+ρzo, was developed to accurately describe the shape and magnitude of the measured curves. On the basis of this equation a quantitative correction for absorprion and atomic mumber effects has been derived for low electron energies. A comparision of quantitative analysis using the above equation wit other absorption and atomic number corrections shows better agreement between calculated and known concenequation to a correction for fluorescence due to characteristic lines is outlined.
Quantitative energy‐dispersive X‐ray analysis using relative k‐ratios
Authors: Hurley R. G. , Goss R. L.
Published: May 2005

A new energy‐dispersive X‐ray technique has been developed for rapid quantitative analysis in the scanning electron microscope. The relative sensitivity is first established for as many elements as can be obtained in pure solid form. These values need only be measured once for a given accelerating potential and X‐ray take‐off angle. Relative sensitivities for elements not measured may be obtained by interpolation. Quantitative analysis may then be made by dividing the relative characteristic intensity for each element present by its respective elemental sensitivity. The ratios are subsequently adjusted by means of an iterative technique, using one of the commonly used electron microprobe matrix correction methods, until a set of concentrations which total 100% is obtained. The technique offers the advantages that neither the electron beam current nor the counting time enter into the calculations. Therefore, arbitrary counting times and unstable electron beam currents may be used. It is not necessary for standards to be continually analyzed; a single spectrum combined with the original sensitivity data contain all the information required for the analysis.
The atomic number Z=0: Loss and gain on ignition in XRF analysis treated by the JN‐equations
Authors: de Jongh Willy K.
Published: May 2005

During fusion of uncalcined oxide samples there may be a loss of a variable mass of volatile constituents, corresponding with the loss on ignition (LOI). On the other hand, partially reduced samples, such as sinters of iron ores, may contain one or more elements in various states of oxidation related to the gain on ignition in air (GOI). Both phenomena influence the analyte X‐ray fluorescence intensities obtained from the fused sample.

Full explanations are given along with a rigorous mathematical treatment for a proposed method that has demonstrated its practical value in the past decade. It is based on the de Jongh–Norrish equations in which the mass difference LOI–GOI is treated as one element with the assigned atomic number zero. References are made to practical results.
New basic empirical expression for computing tables of X‐ray mass attenuation coefficients
Authors: Thinh Tran Phuc , Leroux Jean
Published: May 2005

This paper describes a new approach for deriving a simple relation between mass attenuation coefficient and X‐ray energy or wavelength. Parameters of the latter have been adjusted to fit all up‐to‐date experimental, interpolated and extrapolated data thus providing means for computing a set of tables covering all values of coefficients usually encountered in applied X‐ray spectroscopy. The accuracy is generally much better than ±5% with respect to the average of well‐established data.
Analysis of the NbGe content in thin films by quantitative x‐ray fluorescence
Authors: Bergel L. , Cadieu F. J.
Published: May 2005

A method is presented for determining the relative amounts of Nb and Ge in thin films of approximately 1 μm thickness which have been deposited onto polycrystalline substrates. Quantitative X‐ray fluorescence is employed using an energy‐dispersive solid state detector and multichannel analyzer system. The principal problem encountered is one of calibrating the observed Ge/Nb intensity ratios in terms of atomic composition. We have used solution standards for comparison with the spectrum of selected dissolved films. The absolute compositions in the region of 25 atomic percent Ge are believed accurate to ±1 atomic percent absolute.
Sulphur and lead determination in petroleum products by raioisotope induced X‐ray fluorescence
Authors: Szöghy I. M. , Poliquin C.
Published: May 2005

A simple additive method, based on 55Fe and 109Cd source induced fluorescence in a helium environment, is presented for sulphur and lead determintion in petroleum products. Although the density of the matrix influences the X‐ray yields, the similarity of photon attenuation in water and petroleum products can be explotied. It is shown that routine system calibration can be achieved by the use of inorganic chemicals dissolved in water instead of organic additives in products. The low pressure helium flow suppresses the argon X‐rays, provides a good background region and increases the detection sensitivity for sulphur.
Si(Li) detector efficiency in standard X‐ray fluorescence geometries
Authors: Szöghy I. M. , Simon J. , Kish L.
Published: May 2005

Si(Li) detector efficieneres are measured up to 100 keV photon energy in typical X‐ray fluorescence geometries using 55Fe, 109Cd, 57Co and 241Am annular sources. The targets are common chemical compounds. The photopeak yield is normalized by the use of a bare CaF2(Eu) scintillator which is free of dead layer. The scintillator response is corrected for escape peak losses. The presented method permits the detection of long term changes in detector response. Discrepancies are found in published nominal detector thicknesses.
The complete spectral response for EDXRF systems—calculation by Monte Carlo and analysis applications. 1—homogeneous samples
Authors: Doster Joseph M. , Gardner Robin P.
Published: May 2005

A Monte Carlo model is derived and combined with an existing detector response function model to ptdict the entire pulse‐height spectra for energy‐dispersive, x‐ray fluorescence systems that consist of an annular‐ring, photon exciting source, a coaxially positioned right circular homogental sample, and a cirular si(Li) detector. A method is dervied and demonstrated for using the predicted and experimental pulse‐height spectra on a chi‐square basis to determine elemental amounts. This approach allows the use of all the information available in an entire energy‐dispersive, x‐ray fluorescence pulse‐hight spectrum for analysis purposes.
X‐ray production in thin films by electrons with energies between 40 and 100 keV. 1—Bremsstrahlung cross‐sections
Authors: Chapman J. N. , Gray C. C. , Robertson B. W. , Nicholson W. A. P.
Published: May 2005

Cross‐sections for bremsstrahlung production in thin films may be derived theoretically only if certain approximations are made or if there is recourse to numerical techniques. In this paper, two approximate equations, one based on the Sommerfeld theory and the other on the Bethe–Heitler theory, are assessed for their accuracy in predicting cross‐sections differential in photon energy and emergence angle when a thin foil target is bombarded with electrons with energies between 40 and 100 keV. Experimental data are presented from eight different target materials and these are processed initially to make comparisons between experimental and theoretical spectral shapes and subsequently to compare observed and predicted absolute cross‐section values. Except for the heaviest target material (Au), the Bethe–Heitler theory provided a satisfactory description of all experimental observations. In contrast, the Sommerfeld theory provided a significantly inferior description of spectral shapes and consistently overestimated absolute cross‐sections by 15–20%.
Routineverfahren zur serienanalytik geologischen materials mittels XRFS
Authors: Müller N.
Published: May 2005

Im Rahmen des österreichischen Rohstoff‐Forschungsprojektes Geochemische Basisuntersuchung von Bach‐ und Flußsedimenten wurden mehr als 25 000 Proben einer Multielementanalytik auf 36 Elemente unterzogen. Neben optischer Spektroskopie mit Kohlebogen‐ und induktiv gekoppelter Plasmaanregung gelgangten wellenlangen‐ und energie‐dispersive XRFS zum Einsatz. Es wird ein Verfahren beschrieben, das
es ermoglicht, die Analyse der Fraktion mit einem Korndurchmesser <0.18 mm auf bis zu 30 Elemente rnit hoher Genauigkeit bei einer breiten Streuung des Matrixbereiches durchzufiihren. Der Grundgedanke dabei ist, eine große Zahl von gut analysierten Referenzproben verschiedenster Zusammensetzung fiir die Eichung heranzuziehen.
X‐ray K absorption edges of cobalt and copper in their tetraphenylporphyrin (TPP) and formate di‐ and tetrahydrate (FDH) (FTH) compounds
Authors: Rajput O. P. , Nigam A. N. , Shrivastava B. D.
Published: May 2005

K absorption edge data for TPP and FDH compounds of cobalt and copper have been recorded. Edge position shifts, changes in edge widths and shifts in the position of first absorption maximum are discussed.
EXAFS studies of some copper and cobalt compounds and complexes in aqueous solution and polycrystalline form
Authors: Koul P. N. , Padalia B. D.
Published: May 2005

Extended x‐ray absorption fine structures (EXAFS) associated with K‐absorption edges of copper and cobalt in their simple compounds and trisethylenediamine complexes both in aqueous solution and in the polycrystalline form have been measured. Bond lengths in these samples have been determined. An attempt is made to give a qualitative explanation for the appearance of some EXAFS peaks in solution that do not occur with the polycrystalline form of the same sample.
The operator model for X‐ray fluorescence and its application to inter‐element effect corrections in XRF analysis
Authors: Werfel Zbigniew W.
Published: May 2005

A new empirical mathematical method for inter‐element effect corrections in XRF analysis is presented. It is based on a special theoretical description of XRF phenomena called OMX (operator model of x‐ray fluorescence), presuming a discrete layer model of the sample structure and using mathematical operators to describe the interaction between sample layers and exciting radiation. The operators formed generally as spectral distributions may be simplified into the matrix form for practical application. The effectiveness of the proposed method was verified experimentally by analysing samples of glass and glass raw materials.
Chemical effects in X‐ray fluorescence analysis
Authors: Kataria S. K. , Govil R. , Saxena A. , Bajpei H. N.
Published: May 2005

Energy‐dispersive x‐ray fluorescence (EDXRF) analysis of manganese compounds has been carried out. A significant dependence of the Mn Kα and Kβ x‐ray yields per incident photon and of the Kβ/Kα ratio on the valence state of manganese in these compounds was observed. The measurement of attenuation coefficients of these compounds, which are used in absorption corrections in XRF analysis, also showed similar effects. These results imply that the EDXRF elemental analysis results have inherent inaccuracies of the order of 10%.
Evaluation of correction algorithms with theoretically calculated influence coefficients in wavelength dispersive XRF
Authors: Vrebos B. A. R. , Helsen J. A.
Published: May 2005

Three correction algorithms for quantitative XRF analysis of samples of infinite thickness have been compared using intensities and influence coefficients calculated from fundamental parameters. Errors due to heterogeneity and counting errors are avoided by this procedure. Both the three‐coefficient model of Lachance and the α‐model of de Jongh proved to be very satisfactory. The choice has to be made depending on the computer facilities available.
Mathematical matrix correction procedures for x‐ray fluorescence analysis. A critical survey
Authors: Tertian R.
Published: May 2005

The complexity of the intensity–concentration relationship in x‐ray fluorescence analysis as well as new requirements for speed and accuracy will induce analysts to resort more and more to mathematical methods for effecting matrix correction. A thorough study of Lachance–Traill coefficients, based on theoretically calculated fluorescence intensities, shows that all ‘binary’ coefficients vary systematically with composition under the usual working conditions with polychromatic excitation, while ‘multicomponent’ coefficients can no longer be represented (i.e. in the form of curves or diagrams) owing to the intricacy of third element effects. For these reasons, we are compelled to turn to a fundamental approach, where two methods are now competing: on the one hand, the classical fundamental parameter method, which permitted the abovementioned investigation, but does not in itself offer a sufficiently coherent solution to the problem of matrix correction; on the other, the new fundamental coefficient method, which accounts for all theoretical implications, but preserves the flexibility and adaptability of the older influence coefficient procedures. Utilizing such effective coefficients in a comparison standard correction algorithm allows one to solve any analytical problem, from the most complicated to the simpler ones, through a kind of ‘à la carte’ procedure. The so‐called empirical algorithms are in principle ineffective for treating the complex corrections which belong to the analysis of compact specimens (e.g. metal alloys). They must be reserved for simpler problems, notably the study of diluted specimens where an experimental calibration remains feasible.
Measurement of the dead time of XRF detection systems using a pulsed beam
Authors: Méray L.
Published: May 2005

A method of measuring the dead time of nuclear detectors using a pulsed beam is described. The application of the method to detectors used in an electron microprobe device is reported and results obtained in this way are presented. The method seems to be suitable for measuring the dead time of any nuclear x‐ray counting system which can be operated with a pulsed beam.
XANES study of tungsten LIII discontinuity in some rare earth tungstates
Authors: Vishnoi A. D. , Sapre V. B. , Mande C.
Published: May 2005

The shape and near edge structure of the LIII absorption discontinuity of tungsten in some rare earth tungstates, RE2(WO4)3, were studied using a 40 cm Cauchois‐type transmission x‐ray spectrograph. Molecular orbital theory was used to interpret the fine structure.
Use of the DuMond arrangement in analytical x‐ray spectrometers
Authors: Verman B. S. , Serikov I. V.
Published: May 2005

A comparison of estimated performance of x‐ray spectrometers employing Cauchouis and DuMond arrangements shows that the latter are 5‐15 times more efficient at the same resolution. These data and the experimental performances of the above spectrometers and of the Soller type in the U Lα1 region with standard granite specimens suggest that it is advisable to develop short‐wavelength analytical spectrometers with the DuMond arrangement.
Mean depth of X‐ray production by electron beams in thick targets
Authors: Gaber M. , El‐Khier A. A. Abou
Published: May 2005

An analytical expression was deduced for calculating the mean depth of ionization, pz, in electron probe x‐ray microanalysis. The data used were generated from previous Monte Carlo calculations for bulk targets of aluminium, titanium, iron, copper, arsenic, indium, tungsten, gold and lead at normal electron incidence for energies ranging from 10 to 40 keV. The results show that the mean depth pz depends on the back scattering coefficient,η, the energy of the incident electron, Eo, the excitation energy of the target atoms, Ec, and the target atomic number, Z. In the case of non‐normal incidence, it is found that the ratio of the mean depth pz(α) at an angle of incidence α to the mean depth pz(0) at normal incidence varies linearly with cos α and depends only on the atomic number of the target material. The effect of the atomic number of the target on the ionization mean depth was also studied.
Calibration of analytical spectrometers and metrological aims of quantitative analysis
Authors: Kotlyarov Yakov B.
Published: May 2005

The mathematical criteria of calibration, which reflect the metrological aims of quantitative analysis, are formulated. It is shown that the traditionally used calibration procedure is not adequate for these criteria when using the analytical techniques which are required to solve jointly the calibration functions for concentrations in the course of the analysis. A procedure which avoids this shortcoming is proposed. It stipulates the simultaneous construction of the calibration functions and is based on the utilization of a specially introduced metrological index, the ‘indicator of the inaccuracy of a sample analysis’. The paper theory is illustrated by examples in x‐ray fluorescence analysis.
LIII subshell intensity ratios of Pb, Th and U
Authors: Tan M. , Sahin Y. , Saplakǧlu A.
Published: May 2005

A study of LIII intensity ratios by using characteristic x‐rays as the exciting radiation is described. Only the LIII subshells of Pb, Th and U were excited by the characteristic x‐rays of the elements used as the secondary sources. A Ge(Li) detector system coupled to a programmable multi‐channel analyser was used in the measurements. Lα1, 2/L1, Lα1, 2/Lβ6 and Lα1, 2/Lβ2, 15 intensity ratios of Pb, Th and U were determined by spectral analysis and were compared with recent theoretical and experimental results.
Effect of non‐radiative transitions on the number and depth distribution of generated x‐ray photons
Authors: L. Lábár János
Published: May 2005

Non‐radiative transitions enhance the generated Lα intensity by 20–50%. A critical assessment of the dependence of the enhancement on the type of ionizing radiation and on the experimental condition is presented. Numerical values of the enhancement are given as a function of atomic number for situations common in EPMA, TEM/EDS and XRF. It is outlined how to incorporate these effects into standardless analysis, the Cliff–Lorimer method and the fundamental parameter approach. It is shown that even conventional EPMA with measurement of standards may be affected if stratified samples are examined. Measurements and Monte Carlo simulations are suggested for testing the latter prediction.
Narrow‐beam attenuation curve as a functional description of a low‐energy x‐ray beam
Authors: Delgado V. , Ortiz P.
Published: May 2005

It is shown that the narrow‐beam attenuation curve can be a functional description of a low‐energy x‐ray beam, as is the spectral distribution. Physical quantities, which are usually calculated by integration over the spectral distribution (differential photon or energy fluence), can also be obtained from the narrow‐beam attenuation curve without any need for an explicit knowledge of the spectral distribution.
Validity of a simple approximation for enhancement calculations
Authors: Rössiger V.
Published: May 2005

For calculating secondary XRF intensities, the substitution of the isotrope emission of the enhancing radiation by an emission with a few discrete angles leads to considerably reduced numerical effort. The validity of this previously suggested approximation of the enhancement effect is discussed for the analsysis of multilayer system in the nm and μm region and for bulk materials.
Characterization of an x‐ray source for the fundamental parameter method
Authors: Pozsgai I.
Published: May 2005

In addition to low detection limits, x‐ray fluorescene analysis (XRF) with a transmission x‐ray source in the scanning electron microscope has other favourable features as a consequence of the microscope environment, e.g. selection of area for XRF by backscattered electron imaging or electron probe microanalysis. Another favourable feature, the ease of determining the energy distribution of the intensity of the x‐ray source, is discussed.
Simultaneous determination of rare earths by x‐ray fluorescence spectrometry using a fundamental parameters method
Authors: Marcó Parra L. M. , Greaves E. D. , Paz J. L. , Sajo‐Bohus L.
Published: May 2005

Concentrates extracted from a lateritic mineral deposit were analysed for their rare earth (RE) content by energy‐dispersive x‐ray fluorescence (XRF) spectrometry. The L emission lines of the lanthanides were excited with the 22.1 keV Ag K radiation from an annular Cd‐109 radioisotope source. The problem of the extensive overlap of the L lines were solved by the AXIL program for deconvolution of XRF spectra. Individual REs were quantified by preparing semi‐transparent pellets of the concentrate with starch which served as dilutant and binder. This allowed correction for sample absorption with the light matrix program of the QXAS analysis package based on the fundamental parameter method. The method allowed the simultaneous determination of 12 rare earths contained in the sample, with a reproducibility of 2.0–29% and accuracy in the range 1.5–24% relative error without the use of standard materials. Detection limits achieved were in the range of 340 ppm for the heavy REs and 4000 ppm for the light REs.
Photon‐excited K x‐ray fluorescence cross‐sections for some light elements in the energy range 20–60 keV
Authors: Rao D. V. , Cesareo R. , Gigante G. E.
Published: May 2005

Kα and Kβ x‐ray fluorescence cross‐sections were experimentally determined for elements in the range 26 ⩽ Z ⩽ 40 at various excitation energies using and x‐ray tube with a secondary exciter system as the excitation source. The x‐ray tube with a secondary target arrangement was used to obtain high intensity with a high degree of monochromatization. Experimental values were compared with the theoretical values calculated using IKβ/IKα ratios based on Hartree—Fock and Hartree—Slater theories. The experimental values for all the elements at various excitation energies were in good agreement with the theoretical values.
Energy‐dispersive measurement and comparison of different spectra from diffraction x‐ray tubes
Authors: Görgl R. , Wobrauschek P. , Streli Ch. , Aiginger H. , Benedikt M.
Published: May 2005

Direct measurement of the spectral distribution emitted by an x‐ray tube with a solid‐state detector is described. Spectral distributions of various x‐ray tubes differing in anode material were measured and compared. Numerical values and relevant data for Cu, Mo and W x‐ray tubes are presented.
Expression of the Drosophila 70 000 Dalton heat shock protein is translationally controlled in yeast
Authors: Collatz Ekkehard , Plesset Judith , Foy James J. , McLaughlin Calvin S.
Published: May 2005

Plasmid pPW229, containing the 2·25 kilobase transcribed sequence for the 70 000 Dalton heat shock protein of Drosophila,1 was integrated into plasmid CV13 and used to transform Saccharomyces cerevisiae. Upon a heat shock, at 41°C for 20 min, a new 70 000 Dalton protein appeared in the transformants. This protein was not detected in transformants grown at 23°C, nor in transfromants carrying the hybrid plasmid from which the structural gene for the 70 000 Dalton protein had been deleted. RNA was isolated from transromants grown at 23°C and from transformants heat shocked at 41°C. RNA complementary to the Drosophila heat shock gene was present in the transformants, grown either at 23°C or heat shocked. No complementary RNA was detected in yeast cells transformed with the hybrid plasmid from which the structural gene had been deleted. The Drosophila heat shock gene in yeast appears to be transcribed constitutively but translated only under heat shock conditions.
Primary structure of the Saccharomyces cerevisiae GAL7 gene
Authors: Tajima Masahiro , Nogi Yasuhisa , Fukasawa Toshio
Published: May 2005

We present the nucleotide sequence of a 1599‐base pair (bp) DNA fragment containing the entire GAL7 gene that encodes galactose‐1‐phosphate uridyltransferase of Saccharomyces cerevisiae. The deduced peptide was composed of 364 amino acid residues. The expected molecular weight was 42 005 daltons, which agreed with the observed value for the purified enzyme.1 The 3′‐end of the GAL7 transcript mapped at a position 82 bp downstream from the UAA termination codon by the S1 nuclease protection experiment. We constructed a GAL7′‐lac′Z fusion on various types of yeast plasmid vectors. The fused gene on any type of vector was induced by galactose and repressed by glucose as for the GAL7 gene on the chromosome. The response of GAL7′‐lac′Z fusion to gal4Δ and gal80Δ regulatory mutations was also similar to the response of the chromosomal GAL7 gene. By using various deletions in the 5′‐flanking region of the gene fusion, we delimited the sequence essential for galactose controlled expression with a 180 bp‐fragment of DNA lying 92 bp upstream of the transcription initiation site.
Structure and nuclear localization signal of the SK13 antiviral protein of Saccharomyces cerevisiae
Authors: Rhee Sang‐Ki , Icho Tateo , Wickner Reed B.
Published: May 2005

The yeast chromosomal genes SK12, SK13, SK14, SK16, SK17 and SK18 repress the replication of double‐stranded RNA viruses, protecting the host from the otherwise lethal effects of the virus. We cloned and sequenced the SK13 gene and found that it encodes a 163 kDa protein including a typical nuclear localization signal. Cell fractionation experiments show that the SK13 gene product is indeed tightly associated with nuclei and that the putative nuclear localization sequence directs β‐galactosidase into the nucleus. However, fusion of a part of the SK13 protein lacking this signal with β‐galactosidase directs β‐galactosidase into the nucleus, suggesting the presence of a second nuclear localization signal. The SK13 gene is only essential in the presence of an M double‐stranded RNA virus.
Divergence and conservation of SUP2(SUP35) gene of yeasts Pichia pinus and Saccharomyces cerevisiae
Authors: Kushnirov Vitaly V. , Ter‐Avanesyan Michael D. , Didichenko Svetlana A. , Smirnov Vladimir N. , Chernoff Yuri O. , Derkach Irina L. , Novikova Olga N. , Inge‐Vechtomov Sergey G. , Neistat Michael A. , Tolstorukov Ilya I.
Published: May 2005

SUP2(SUP35) is an omnipotent suppressor gene, coding for an EF‐1α‐like protein factor, intimately involved in the control of translational accuracy in yeast Saccharomyces cerevisiae.

In the present study a SUP2 gene analogue from yeast Pichia pinus was isolated by complementation of the temperature‐sensitive sup2 mutation of S. cerevisiae.

The nucleotide sequence of the SUP2 gene of P. pinus codes for a protein of 82·4 kDa, exceeding the Sup2 protein of S. cerevisiae by 6 kDa. Like the SUP2 gene product of S. cerevisiae, the Sup2 protein of P. pinus represents a fusion of a unique N‐terminal part of a region homologous to EF‐1α. The comparison of amino acid sequences of the Sup2 proteins reveals high conservations (76%) of the C‐terminal region and low conservation (36%) of the N‐terminal part where, in addition, the homologous correspondence is ambiguous.

Proteins related to the Sup2 of S. cerevisiae where found in P. pinus and some other yeast species by the immunoblotting technique.

The relation between the evolutionary conservation of different regions of the Sup2 protein and their functional significance is discussed.
The MAT locus revisited within a 9·8 kb fragment of chromosome III containing BUD5 and two new open reading frames
Authors: Jacquet Michel , Buhler Jean Marie , Iborra François , Francingues‐Gaillard Marie Claude , Soustelle Christine
Published: May 2005

This paper reports the DNA sequence of a segment of 9·8 kb of the chromosome III. The sequenced DNA contains the MATα locus. The new sequence of the MATα locus differs from the previously reported sequence by six modifications in the W segment. We have found the same modifications in the HML locus. The corrected sequence contains, in HML, an open reading frame (ORF) of 190 codons which ends at the border between the W segment and the flanking DNA. In the MAT locus, this ORF extends in the flanking DNA up to 538 codons. This ORF corresponds to a gene independently identified as BUD5 (Chant et al., 1991). This gene presents homologies with the exchange factors SDC25 and CDC25. A large ORF of 1399 codons is found on the opposite side of MATα (toward the telomere). This ORF corresponds to a new gene YCR724. Next to this gene is a small ORF, YCR725, of 127 codons. The localization of this fragment on chromosome III, originally supposed to be distal from the MAT locus based on genetic distance, illustrates variation in recombination frequency along the chromosome and suggests the existence of hot spots of recombination between MAT and the THR4 locus.
Sequence of the HMR region on chromosome III of Saccharomyces cerevisiae
Authors: Sor Frédéric , Chéret Geneviève , Fabre Francis , Faye Gérard , Fukuhara Hiroshi
Published: May 2005

A 10,095 base DNA fragment from the right arm of chormosome III of Saccharomyces cerevisiae has been sequenced and analysed. It encompasses the silent mating‐type locus HMR. Both HR Ma1 and HM Ra2 genes, as well as their flanking regulatory regions, have been identified. Three new open reading frames longer than 80 amino acid residues were found in this fragment. One of them (YCR137) shows features compatible with a membranous localization and a tansporter function. The other two do not show a similarity with any known gene. A new gene coding for tRNAthra1 (ACU) has been identified. It is located in a region coding for several delta sequences.
Development of a strain of Hansenula polymorpha for the efficient expression of guar α‐galactosidase
Authors: Veale R. A. , Giuseppin M. L. F. , Van Eijk H. M. J. , Sudbery P. E. , Verrips C. T.
Published: May 2005

A strain of the methylotrophic yeast Hansenula polymorpha, A16 has been developed that expresses the guar α‐galactosidase gene to 22.4 mg/g dry cell weight in chemostat cultures at a dilution rate of 0.1 h−1. This corresponds to more than 13.1% of solube cell protein, of which 56–62% is secreted into the medium. The α‐galactosidase gene was flanked by the promoter and terminator sequences of the H. polymorpha mox gene, which can direct expression of the mox gene itself more than 30% of total cell protein under methanol growth. The expression cassette (pUR3510) based on the Saccharomyces cerevisiae plasmid, YEp13, was integrated into the genome. Such transformants were stable in chemostat cultures and exhibited 100% stability for both α‐galactosidase+ and leu+ phenotypes. Chemostat cultures produced higher levels of α‐galactosidase with higher specific productive expressed as mg α‐galactosidase g−1 h−1 compared to batch cultures.
Transport of malic acid in the yeast Schizosaccharomyces pombe: Evidence for proton‐dicarboxylate symport
Authors: Sousa Maria João , Mota Manuel , Leão Cecília
Published: May 2005

The transport system for malic acid present in Schizosaccharomyces pombe cells, growing in batch culture on several corbon sources, has been studied. It was found that the diarboxylic acid crrier of S. Pombe is a proton‐dicarboxylate symporter that allows transport and accumulation as a function of ΔpH with the following kenetic parameters at pH 5·0: Vmax = 0·01 nmol of total malic acids −1 mg (dry weight) of cells, −1and Km = 0·1mM total malica acid uptake (pH 5·0) was accompanied by desappearance of extracellular protons, the uptake rates of which followed Michaelis‐Menten kinetics as a function of the acid conscentration. The Km values, calculated as the concentrations either of anions or of undissociated acid, at various extracellular pH values, pointed to the monoanionic form as the transported species. Furthermore, accumulated free acid suffered rapid efflux after the addition of the portonophore carbonyl cyanid m‐chlorophenyl hydrazone. These results suggested that the transport system was a dicarboxylateproton symporter. Growth of cells in a medium wiht glucose (up to 14%, w/v) and malic acid (1·5%, w/v) also resulted in proton‐dicarboxylate activity, suggesting that the system, besides being constitutive, was still active at high glucose concentratons. The following dicarboxylic acids acted as competitive inhibitors of malic acid transport at pH 5·0: D‐ malic acid, succinic acid, fumaria acid oxaloacetic acid, α‐Ketoglutaric acid, maleic acid, maleic and malonic acid. In addition all of these dicarboxylic acids induced proton movements that followed Michaelis–Menten kinetics. It was concluded that the malic negatively charged form (probably the monoanionic form) was transported by a proton‐symport mechanism and that the carrier appeared to be a common ‘dicarboxylat transport sysmem’. The undissociated acid entered the cells slowly by simple diffusion.
Three yeast genes, PIR1, PIR2 and PIR3, containing internal tandem repeats, are related to each other, and PIR1 and PIR2 are required for tolerance to heat shock
Authors: Toh‐E Akio , Oguchi Tomoko , Matsui Yashushi , Yasunaga Shuichi , Nisogi Hideaki , Tanaka Kazuma
Published: May 2005

We isolated three highly homologous genes, PIR1, PIR2 and PIR3, collectively called the PIR genes. The remarkable feature of their putative amino acid sequence is that they contain a sequence consisting of 18–19 amino acid residues repeated tandemly seven to ten times. Genes homologous to PIR were found in Kluyveromyces lactis and Zygosaccharomyces rouxii but not in Schizosaccharomyces pombe, suggesting that a set of PIR genes plays some role in budding yeast. Bias of codon usage seen in each of the PIR translation products suggests that they are expressed abundantly. The fact that disruption of each gene is viable indicates that none of them is essential. The double disruptants, pir1 pir2, were viable under various conditions, such as higher temperature (37°C) or high salt concentration, but showed a slow‐growing phenotype on an agar slab. Furthermore, they were sensitive to heat shock. Addition of a pir3 disruption to the pir1 pir2 double disruptant brought about no phenotypic difference from the original double mutant. PIR1 and PIR3 are closely linked to each other and are on chromosome XI.
Determinants of flocculence of brewer's yeast during fermentation in wort
Authors: Straver Marika H. , Aar Paul C. V. D. , Smit Gerrit , Kijne Jan W.
Published: May 2005

Ability of Saccharomyces cerevisiae MPY3 cells to flocculate during fermentation in wort was found to be triggered after growth limitation by oxygen shortage and to coincide with a sharp increase in cell surface hydrophobicity of the cells. Presence of oxygen in the pitching wort influenced final cell number, flocculence of the cells and cell surface hydrophobicity. Flocculation ability of cells grown in air‐depleted pitching wort was hampered, concomitant with a decrease in final cell number and in final cell surface hydrophobicity. Addition of ergosterol and Tween 80 to air‐depleted wort restored normal growth of the cells as well as flocculation ability and the increase in cell surface hydrophobicity. The same parameters increased in value after addition of ergosterol and Tween 80 to a fermentation with air‐saturated pitching wort. Hydrophobicity of a non‐flocculent mutant of S. cerevisiae strain MPY3, fermenting in air‐saturated pitching wort, did not increase at cell division arrest. These results support the hypothesis that cell surface hydrophobicity is a major determinant for yeast cells to become flocculent, and suggest that shortage of sterols and unsaturated fatty acids precedes flocculence under brewing conditions.
AFG2, an essential gene in yeast, encodes a new member of the Sec18p, Pas1p, Cdc48p, TBP‐1 family of putative ATPases
Authors: Thorsness Peter E. , White Karen H. , Ong Weoi‐Choo
Published: May 2005

A gene from Saccharomyces cerevisiae was sequenced that encodes a protein with homology to a family of putative ATPases. These homologous proteins include the yeast cell division cycle protein Cdc48p and its mammalian homologues VCP and p97; Sec18p and its mammalian homologue NSF, proteins necessary for fusion of transport vesicles to target membranes in the secretory pathway; Pas1p, a protein necessary for peroxisome biosynthesis in yeast; Yme1p, a yeast mitochondrial protein that influences the rate of DNA escape from mitochondria; and TBP‐1, MSS1 and Sug1p, proteins that interact with transcription factors. This newly sequenced gene, named AFG2 for ATPase family gene, is located on chromosome XII 5′ to the SLP1/VPS33 open reading reading frame and encodes an essential protein of 780 amino acids that is most homologous to Cdc48p.
Analysis of PFK3—A gene involved in particulate phosphofructokinase synthesis reveals additional functions of TPS2 in Saccharomyces cerevisiae
Authors: Sur I. P. , Lobo Z. , Maitra P. K.
Published: May 2005

The pfk3 mutation of Saccharomyces cerevisiae causes glucose‐negativity in a pfk1 genetic background, the mutant is temperature‐sensitive for growth and homozygous diploids do not sporulate. It fails to accumulate trehalose, and has an altered glycogen accumulation profile under glucose‐starvation conditions. pfk3–6, one of the alleles of pfk3, has an altered morphology, forming long chain‐like structures at 36°C. The PFK3 gene was cloned by complementation of the mutant phenotypes. Integrative transformation demonstrated that the complementing fragment encoded the authentic PFK3 gene. The disruption of the gene does not affect viability. Like the EMS‐induced pfk3 mutant, the disruptants are temperature‐sensitive and in a pfk1 genetic background are also glucose‐negative. The PFK3 transcript is induced by heat‐shock. Partial DNA sequence shows that PFK3 is identical to TPS2 (De Virgilio et al., 1993). We demonstrate that, apart from being a structural determinant of trehalose 6‐phosphate phosphatase, PFK3 (TPS2) is required for PFKII synthesis and normal regulation of S. cerevisiae response to nutrient and thermal stresses.