bluuebunny/crossref_metadata_2025 huggingface dataset:
Figures‐of‐merit, their philosophy, design and use
Authors: Jenkins Ron , Gilfrich John V
Published: May 2005

Figures‐of‐merit (FOMs) is a term which is used to define the quantitative measure of performance based on parameters which can be determined by the experimentalist. The FOM may be intuitive, based on previous experience of the analyst or his personal assessment of the importance of certain parameters, or derived, based on measurable parameters or on mathematically deduced data, mostly involving statistics. The FOM may also be a combination of intuitive and derived factors. In this review, a number of commonly used FOMs, due to several authors, are considered. They are categorized by their originators, their type (intuitive, derived or a combination therof), their primary application and the factors on which they are based. The applications discussed include both x‐ray spectrometry and x‐ray diffraction, but many of the principles apply equally to both.
Kα x‐ray emission induced by 1—100 MeV protons
Authors: Bassi Stefano , Gianforma Giuseppe , Silari Marco
Published: May 2005

In the course of a feasibility study of high‐intensity sources of monochromatic x‐rays to be used for XRF, extensive numerical calculations were conducted on the production of characteristic x‐rays by proton bombardment of pure element targets. This paper presents the analytical model used for the computer simulations and compares the x‐ray production by protons and alpha particles. The K x‐ray production cross‐section was calculated by the ECPSSR theoretical model and by Paul's analytical formula. The dependence of the x‐ray yield on projectile energy, target atomic number, target thickness and irradiation geometry is discussed. The thick target Kα x‐ray yields produced by 1—100 MeV proton bombardment were calculated for 66 elements from Na to Pb. From these results, a number of scaling laws and fitting procedures are given for proton‐induced Kα x‐rays.
Analysis of desert rose using PIXE and RBS techniques
Authors: Al‐Kofahi M. M. , Hallak A. B. , Al‐Juwair H. A. , Saafin A. K.
Published: May 2005

Particle‐induced x‐ray emission (PIXE) and Rutherford backscattering spectromatery (RBS) were used to analyse desert rose geological samples. Samples from the rose core and from the rose peripherals were studied. All samples were found to contain C, N, O, Na, Mg, Si, S, Cl, K, Ca, Ti, Mn, Fe and Sr. Core samples were found to contain more silicon than peripheral samples. The extra silicon in the rose core may suggest a mechanism for the formation of the rose through crystal growth on a seed of silicon.
Application of a new treated LiF200 crystal to x‐ray fluorescence analysis of geological samples
Authors: Longerich Henry P.
Published: May 2005

A LiF200 analyzing crystal, which was treated to enhance heavy element sensitivity, was evaluated for application to the analysis of geological silicate materials prepared as pressed pellets. The treated crystal produced up to two‐fold higher sensitivities along with backgrounds which were approximately two‐fold higher. Lower limits of detection were produced, and the treated erystal is recommended for the routine determination of the elements Ni through Nb using K emission and for elements having L emissions in the same energy range. The limit of detection for Nb was reduced from 0.9 to 0.6 ppm (100 s data acquisition) when the treated crystal was used in place of the standard crystal. For elements with lower emission energies, there was a smaller, but significant, lowering of the limit of detection when the treated crystal was used. The advantage of the treated crystal decreased as the emission energy decreased.
Review of recent applications of radioisotope excited x‐ray fluorescence
Authors: Valkovic V. , Markowicz A. , Haselberger N.
Published: May 2005

Radioisotop‐excited x‐ray fluorescence is advantageously applied to many specific analytical problems. It is a method of choice for in situ and on‐line analysis. There is a growing need for in vivo determinations of many elements; radioisotope excitation offers some interesting possibilities. In addition to a review of published applications, current XRF activities in IAEA Laboratories are briefly described.
A simple model for optimization of conical capillaries in XRF analysis
Authors: Lindgren I. , Selin E.
Published: May 2005

The method of total reflection in conical glass capillaries has been used for several decades for obtaining high‐intensity x‐ray microbeams of small spot size. A general problem with this technique is the small critical angle, which is energy dependent. There is a certain loss of intensity if many reflections occur in the capillary. Assuming parallel monoenergetic x‐rays, a simple relationship has been derived for the intensity enhancement as a function of the reflectivity of the glass and the number of reflections. The relationship was used to derive conditions for optimum intensity enhancement. Also for suboptimum conditions the relationship can be used to design entrance and exit diameters and length of the capillary. The model was also applied to a wedge‐shaped slit that consists of two total reflection plates.
Study of diffusion coefficients in multi‐component solutions using the daresbury synchrotron x‐ray fluorescence microprobe
Authors: Anderson P. , Elliott J. C. , Thomas C. R. , Van Langevelde F.
Published: May 2005

In multi‐component solution systems, the diffusion of one component can influence the diffusion of a second; in some instances, especially if the first component is an acid, the second component may diffuse against its own concentration gradient. The fundamental cause of this phenomenon is the local electrical field gradient established when particular ion species in mixtures of ionic components have different transport numbers. In ternary, quaternary and higher order systems, determination of the main and cross‐term diffusion coefficients is difficult, and usually indirect.

The Daresbury x‐ray fluorescence (DXRF) microprobe was used to measure directly the concentrations of individual elements in an aqueous gel 1.45 mm from an interface with a solution of constant composition. The solutions contained known mixtures of cobalt, copper and zinc chlorides with and without hydrobromic acid. Similar measurements were made every 300 s over a period of 3 h. After this, measurements were made at 100 μm intervals from the interface of the gel to a depth of 6 mm to map the concentrations of Co, Cu and Zn.

The diffusion coefficients were estimated by comparison of the concentration–time profiles for each metal with analytical or numerical simulations. The results show a significant coupling of the Cu, Co and Zn diffusive flows with the diffusive flow of the acid.

This work has shown that the DXRF microprobe can be used to measure concentration–distance or concentration–time profiles of many elements simultaneously, thus enabling more direct measurements of multicomponent diffusion coefficients in solution to be made.
Polarized x‐ray spectra of α‐Fe2O3
Authors: Leiro J. A. , Dräger G. , Czolbe W.
Published: May 2005

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Hybridization was shown to occur both between strains of the imperfect diploid yeast Candida albicans and between C. albicans and the distantly related hapoid yeast Candida (Pichia)guilliermondii Protorophic hybrids were selected from croses of multiply marked auxotropic mutants two species. In most cases, mild ultraviolet irradiation of the C. albicans partmer was reqiured.

Examination of auxotropic markers in segregants from the hybrid indicated that recombination, rather than the heterokaryon, formation, had occured in these croses. The DNA content of the hybrids varied from diploid or aneuploid (for crosses between C. albicans and C. guilliermodii) to triploid (for C. albicabs × C. albicans). It seems possible that genetic exchange analogous to this may occur in nature.
Identification of the RNA2 protein of Saccharomyces cerevisiae
Authors: Lee Melanie G. , Lane David P. , Beggs Jean D.
Published: May 2005

The rna2‐1 mutant Saccharomyces cerevisiae. has a consitional lethal phenotype, accumulating high molecular weight RNAs of intron‐conataining nuclear genes at 36°C. The cloned RNA2 gene suppresses this phenotype and the RNA2 gene product has been implicated in RNA splicing. Rabbit antisera have been raised againts an N‐terminal synthetic peptide taken from the RNA2 gene DNA sequence data, and against a β‐galactosidase/RNA2 gene fusion protein. Both antisera identify that same 97‐105 kd protein from S. cerevisiae cell extracts which is consistent with the predicted size of the RNA2 protein (from the 2800 nucleotide transcript size and DNA sequence data).
Physical separation and functional interaction of Kluyveromyces lactis and Saccharomyces cerevisiae ARS elements derived from killer plasmid DNA
Authors: Thompson Arthur , Oliver Stephen G.
Published: May 2005

Teo DNA fragments which have autonomously replicating sequence (ARS) activity in both Saccharomyces cerevisiae and Kluyveromyces lactis have been isolated from the K. lactis kl killer plasmid. One fragment (Kla1) is 700 base pairs (bp) in length plasmids carrying it are mitotically unstable in both hosts. In K. lactis, this instability leads to colonies having a ‘nibbled’ phenotype when grown on selective media and appears to be the results of inefficient plasmid segregation. The other fragment of 1100 bp which was produced during the cloning procedure. Kla2 has been divided into the sub‐fragments Kla2A and Kla2B which have, respectively, ARS activity in K. lactis and S. Cerevisiar but not the other species. This indicates that these two closely elated yeasts have different sequence requrements for ARS activity. Kla2B contains a perfect match to the S. cerevisiae ARS consensus but Kla2A does not. Both Kla2A and Kla1 share a 10 bp sequence as the sole region of homology between them. This sequence, 5‘TCATAATATA3’, is tentatively offered as defining the ARS consensus sequence for K. lactis.
Orthogonal‐field‐alternation gel electrophoresis banding patterns of DNA from yeasts
Authors: De Jonge Peter , De Jongh Francien C. M. , Meijers Robert , Steensma H. Yde , Scheffers W. Alexander
Published: May 2005

Chromosomal DNAs from various yeast species were separated by orthogonal‐field‐alternation gel electrophoresis (OFAGE). To this end we developed a spheroplasting and lysis method to obtain intact DNA from both ascomycetous and basidiomycetous yeasts. The OFAGE banding patterns of 22 ascomycetous and four basidiomycetous yeast strains were compared. The strains represented species from the genera: Brettanomyces, Candida, Croococcus, Filobasidiella, Geotrichum, Hansenula, Kluyveromyces, Pachysolen, Pichia, Rhodosporidium, Rhodotorula, Saccharomyces, Saccharomycodes, Saccharomycopis, Schizosaccharomyces and Zygosaccharomyces. Variations occurred in the number of bands and their positions in the gel, not only among strains of different genera but also among species from the same genus and even between varieties of the same species. The ascomycetous yeasts, with the exeption of Saccharomyces cerevisiae, only showed one to five bands of DNA larger than 1000 kilobase pairs (kb) in general none smaller. The paterns of the four basidiomycetous yeasts revealed also a few large DNA bands but in addition one to six bands ranging in size from 500 to 1000 kb, with the exception of a single smaller chromosome in Rhodotorula mucilaginosa. From the OFAGE banding patterns of strains studied here it appears that in Saach. cerevisiae the partitioning of DNA over chromosomes in unique. But rather than the large number of chromosomes, the presence of four chromosomes with less than 500 kb of DNA is characteristic for Sacch. cerevisiae.
Analysis of DNA sequences homologous with the ARS core consensus in Saccharomyces cerevisiae
Authors: Bouton Amy H. , Stirling Vivianne B. , Smith M. Mitchell
Published: May 2005

We have previously identified an autonomously replicating segment (ARS) near the 3′ end of the histone H4 gene at the copy‐I H3‐H4 locus. We have now searched for additional autonomously replicating segments and sequences homologous with the ARS core consensus sequence near the copy‐II histone H4 gene and both of the histone H3 genes. No new ARS elements were identified by functional cloning assays. However, several matches to the ARS core consensus element were found within the DNA sequencs of the copy‐I and copy‐II genes. An exact match to the ARS core consensus was identified in the region downstream from the copy‐I histone H3 gene and a set of sequences with weak homology was also locatd within the copy‐II region. However, restriction fragments including these sequences did not demonstrate ARS activity on a plasmid in transformed cells.
Yeast flocculation: Kinetics and collision theory
Authors: Stratford M. , Keenan M. H. J.
Published: May 2005

Flocculent yeast cells have an absolute requirement for mechanical energy input in order for flocculation to occur. Flocculation is arrested by cessation of energy input. The initial rate of flocculation increases as the square of the cell concentration. There is a minimum shaking speed to initiate flocculation and thereafter the initial rate of flocculation increases exponentially with the shaking speed. The minimum shaking speed for flocculation to occur increases with pH value. Activation energy for flocculation, derived from Arrhenius‐like plots, varies with pH value. We propose that activation energy is required to overcome mutual repulsion between charged yeast cells and allow flocculent bonds to be formed.
Mapping of the Saccharomyces cerevisiae CDC3, CDC25, and CDC42 genes to chromosome XII by chromosome blotting and tetrad analysis
Authors: Johnson Douglas I. , Jacobs Charles W. , Pringle John R. , Robinson Lucy C. , Carle Georges F. , Olson Maynard V.
Published: May 2005

CDC3, CDC25 and CDC42 were localized to chromosome XII by hybridizing the cloned genes to Southern blots of chromosomes separated by orthogonal‐field‐alternation gel electrophoresis. Meiotic tetrad analyses further localized these genes to the region distal to the RDN1 locus on the right arm of the chromosome. The STE11 gene, which had previously been mapped to chromosome XII (Chaleff and Tatchell, 1985), was found to be tightly linked to ILV5. The data suggest a map order of CEN12‐RDN1‐CDC42‐(CDC25‐CDC3)‐(ILV5‐STE11)‐URA4. Certain oddities of the data set raise the possibility that there may be constraints on the patterns of recombination in this region of chromosome XII.
Possible gene interchange between plasmid and chromosome in yeast
Authors: Utatsu Ikuyo , Imura Toshiaki , Toh‐E Akio
Published: May 2005

Genomic DNAs isolated from 420 yeast strains stocked in the Department of Fermentation Technology, Hiroshima university (HUT) were screened fro the presence of a plasmid sequence both as plasmid or in the chromosome. Five DNA samples gave rise to a positive hybridization signal wht 32P‐labelled Zygosaccharomyces plasmid pSR1 was used as a probe. Two among these contain hybridzing sequences as plasmids while the other three apparently were chromosomal. Two chromosomal DNA segments of HUT 7195 (Zygosaccharomyces spp.) which hybridized with pSR1 probe were cloned and sequenced. Both DNAs hybridized with a plasmid sequence covering the P gene of pSR1. One of hte tow segments contains a large open reading frame which can encode 410 amino acid residues. The deduced amino acid sequence is closely related with that of the P gene of pSR1. The present finding suggests that there was an interchange(s) of a gene between yeast plasmid(s) and chromosomes.
Karyotyping of yeast strains of several genera by field inversion gel electrophoresis
Authors: Johnston John R. , Contopoulou C. Rebecca , Mortimer Robert K.
Published: May 2005

Field inversion gel electrophoresis as been used to improve the resolution of the large chromosomes (>1000 kb) present in Saccharomyces kluyveri and in several genera of yeasts other than Saccharomyces cerevisiae, and thus establish more accurately the electrophoretic karyotype of these yeasts. Field inversion gel electrophoresis has also been used to demonstrate the presence of chromosome length polymorphisms in serveral of the yeasts studied. By Southern blotting techniques the greater degree of relatedness of S. Kluyveri and Kluyberomyces lactis to S. cerevisiae, as compared to that of the other genera of yeasts studied, has been established.
Substrate specificity of the phosphorylated fructose‐1,6‐bisphosphatase dephosphorylating protein phosphatase from Saccharomyces cerevisiae
Authors: Manhart Alexander , Holzer Helmut
Published: May 2005

Enzymatic dephosphorylation of the phosphorylated forms of five different yeast enzymes has been studied: fructose‐1,6‐bisphosphatase, glycogen phosphorylase, neutral trehalase, NAD‐glutamate dehydrogenase and 6‐phosphofructo‐2‐kinase. Phosphorylated fructose‐1,6‐bisphosphatated 6‐phosphofructo‐2‐kinase were present in extracts of starved yeast cells which had been incubated for 10 min with glucose. Phosphorylated glycogen phosphorylase, neutral trehalase and NAD‐glutamate dehydrogenase were obtained by incubation of yeast extract with ATP, cycle AMP and Mg2+. After incubation with commercially available preparations of alkaline phosphatase, all five phosphorylated enzymes studied showed the changes in catalytic activity that would be expected as a consequence of dephosphorylation. The recently purified yeast enzyme which dephosphorylates phosphorylated fructose‐1,6‐bisophosphatase (Horn and Holzer (1987)) however, was found to be active only with the phosphorylated fructose‐1,6‐bisphosphatase, but not with the other four phosphorylated enzymes studied. By contrast, a crude extract from yeast showed dephosphorylating activity towards all five substrates. Substrate specificity with the five phosphorylated enzymes studied of different phosphoprotein phosphatases from yeast prepared by other is discussed.
Genetic control of chromosone stability in the yeast Saccharomyces cerevisiae
Authors: Kouprina N. Yu. , Pashina O. B. , Nikolaishwili N. T. , Tsouladze A. M. , Larionov V. L.
Published: May 2005

We have identified four new genetic loci: CHL2 (on chromosome XII) CHL3 (on chromosomes XII); CHL4 (on chrosomes IV), and CHL5 (on chromosomes IX), controlling mitotic transmission of yeast chromosomes. The frequency of loss of chromosomes is 10–100‐fold in chl5, chl2, chl3 and chl4 mutants than observed in wild‐type strains. The mutants also unstable maintenance of artifcial circular minichromosomes with various chromosomal replicators (ARS) and one of the concentrations loci (CEN3, CEN4, CEN5, or CEN6). The instability of minichrosomes in the chl5, chl2, and chl4 mutants id due to the loss of minichromosomes in mitosis (1 : 0 segregation). In the chl3 mutant the instability of artificial minichromosomes is due to nondisjunction (2 : 0 segregation). The CHL3 gene therfre appears to affect the segregation of chromosomes during cell division.
Metabolic responses of Saccharomyces cerevisiae CBS 8066 and Candida utilis CBS 621 upon transition from glucose limitation to glucose excess
Authors: Van Urk Hendrick , Mark Paul R. , Scheffers W. Alexander , Van Dijken Johannes P.
Published: May 2005

When chemostat cultures of Saccharomyces cerevisiae CBS 8066 and Candida utilis CBS 621, grown under glucose limitation, were pulsed with excess glucose, both organisms initially exhibites similar rates of glucose and oxygen consumption. However, striking differences were apparent between the two yeasts with respect to the production of cell mass in the culture and metabolic excretion. Upon transition from glucose limitation excess, S. cerevisiae produced much ethanol but growth rate close to that under glucose limitation. C. utilis, on the other hand, produced little ethanol and immediately started to accumulated cell mass at a high rate. This high production rate of protein synthesis.

Upon a glucose pulse both yeasts excreated pyuvate. In contrast to C. utilis. S. cerevisiae also excerted various tricarboxylic acid cycle intermediates, both under steady‐state conditions and after exposure to glucose excess, These results and those of theoritical calculations on ATP flows support the hypothesis that the ethanol production as a consequences of pyruvate accumulatiion in S. cerevisiae, occuring transition from glucose limitaion to glucose excess, is caused by a limited capacity of assimilatory pathways.
Cloning of CDC33: A gene essential for growth and sporulation which does not interfere with cAMP production in Saccharomyces cerevisiae
Authors: Verdier Jean‐Michel , Camonis Jacquesh H. , Jacquet Michel
Published: May 2005

The CDC33 gene of Saccharomyces cerevisiae belongs to the class II ‘START’ genes. Its product is required for the initiation of a new cell division cycle (Hartwell, 1974). Many results suggest that the cAMP signalling pathway is one of the major controlling elements of ‘START’. Components of this pathway are encoded by class II ‘START’ genes. The aim of the present study is to determine whether or not the CDC33 gene interferes with the cAMP signalling pathway. We report here the molecular cloning of the CDC33 gene by complementation of the cdc33‒1 thermosensitive mutant. The identity of the cloned gene is confirmed by site‐specific reintegration and segregation analysis. This gene is transcribed into a 900‐nucleotides mRNA and appears to be relatively abundant in the cell. We also show that the CDC33 gene product is essential for sporulation. cdc33‒1 mutant cells are able to enter into the resting state. The cAMP intracellular pool is not modified when the cdc33‒1 mutant is shifted to the restrictive temperature. The cdc33‒1 mutation is not suppressed by other known elements of the cAMP cascade. All these results suggest that the CDC33 ‘START’ gene does not interfere with the cAMP signalling pathway which controls cell division.
Mapping and characterizing a new DNA replication mutant in Saccharomyces cerevisiae
Authors: Eberly Susan L. , Sakai Akira , Sugino Akio
Published: May 2005

A detailed characterization of the mak 1–3 mutation of Saccharomyces cerevisiae has been made possible by modifying its genetic background. The mak1–3 mutation, which confers temperature sensitivity for growth, was originally identified as one of four mak1 mutations (Wickner and Leibowitz, 1976). Mak1–1, 1–2 and 1–4 mutants are deficient in DNA topoisomerase I activity and thus have been renamed ‘top1’ (Thrash et al., 1984). Studies presented here show that the map position of MAK1–3 on chromosome XVI distinguishes it from TOP1 which maps on chromosome XV (Wickner and Leibowitz, 1976). An investigation of in vivo macromolecular synthesis in the mak1–3 mutant shows that it is deficient in DNA replication at the restrictive temperature. Experiments in which DNA synthesis was measured in synchronized cell populations indicate that the mak1–3 mutant is deficient in the initiation step of DNA synthesis. Furthermore, crude extracts from the mak1–3 mutant cells support temperature‐sensitive in vitro DNA synthesis on yeast chromosomal DNA replication origin containing plasmid pARS1, suggesting that the MAK1 gene product is directly required for in vitro DNA replication. The conclusion that mak1–3 is a newly identified DNA replication mutation is based on the observations that it (1) complements all DNA synthesis mutants examined, (2) maps to a previously undetected chromosomal location and (3) has a distinct terminal morphology. In light of these distinctions and of the role mak1–3 plays in DNA replication, it has been renamed ‘dnal’.
Kinetics of growth and glucose transport in glucose‐limited chemostat cultures of Saccharomyces cerevisiae CBS 8066
Authors: Postma Erik , Alexander Scheffers W. , Van Dijken Johannes P.
Published: May 2005

The glucose transport capacity of Saccharomyces cerevisiae CBS 8066 was studied in aerobic glucose‐limited chemostat cultures. Two different transport systems were encountered with affinity constants of 1 and 20 mM, respectively. The capacity of these carriers (Vmax) was dependent on the dilution rate and the residual glucose concentration in the culture. From the residual glucose concentration in the fermenter and the kinetic constants of glucose transport, their in situ contribution to glucose consumption was determined. The sum of these calculated in situ transport rates correlated well with the observed rate of glucose consumption of the culture.

The growth kinetics of S. cerevisiae CBS 8066 in glucose‐limited cultures were rather perculiar. At low dilution rates, at which glucose was completely respired, the glucose concentration in the fermenter was constant at 110 μM, independent of the glucose concentration in the reservoir. At high dilution rates, characterized by the occurrence of both respiration and alcoholic fermentation, the residual substrate concentration followed Monod kinetics. In this case, however, the overall affinity constant was dependent on the reservoir glucose concentration.
Secretion and glycosylation of Clostridium thermocellum endoglucanase A encoded by the celA gene in Saccharomyces cerevisiae
Authors: Benitez J. , Silva A. , Vazquez R. , Noa M. D. , Hollenberg C. P.
Published: May 2005

The Clostridium thermocellum celA gene encoding endoglucanase A is expressed in Saccharomyces cerevisiae but the enzyme produced from the native celA gene is not secreted. After removal of the bacterial signal peptide‐coding sequence, the gene was fused to the promoter and prepro segment of the S. cerevisiae MFα1 gene. This construction directs secretion of active endoglucanase A into the culture medium when introduced in yeast on either replicating or integrating vectors. Secretion of endoglucanase A required growth of transformants on rich medium. The secreted enzyme is a 97 000 Da glycoprotein containing about half of its molecular weight as carbohydrate. This new gene fusion could facilitate further research on protein secretion in yeast by using a cellulase as a marker enzyme.
Yeast flocculation: Calcium specificity
Authors: Stratford Malcolm
Published: May 2005

Expression of flocculation in yeast requires the presence of multi‐charged cations. Calcium ions fulfil this role over a broad pH range. At near neutral pH, magnesium and a variety of transition elements can induce flocculation. Calcium‐induced flocculation was competitively inhibited by excess sodium ions whereas magnesium‐induced flocculation was not competitively inhibited. Potassium and lithium ions caused similar inhibition but to a lesser extent. 45Ca effux from yeast cells was greatly increased by the external presence of buffer and cations. Inhibition of flocculation by chelating agents, EDTA or EGTA, was overcome by excess calcium ions. Flocculation could not be induced, under these conditions, by excess magnesium or transition‐element salts.

It was concluded that yeast flocculation has a direct specific requirement for calcium ions. Other ions cause flocculation indirectly by effecting calcium ion leakage from cells, which is then able to initiate flocculation. Low calcium concentrations were susceptible to competitive inhibition by sodium ions present in most acidic buffers. In addition, citrate ions inhibited flocculation, probably by sequestration of leaked calcium. Flocculation by salts, other than calcium, was thus restricted to a neutral or high pH range.
Detection of specific RNA sequences in yeast by in situ colony hybridization
Authors: Inanov Ivan , Mironova Rumjana , Philipova Doranelly , Venkov Pencho
Published: May 2005

Recently a convenient method for detection of specific RNA sequences in bacteria has been developed (Ivanov and Gigova, 1986) but the original protocol was inapplicable to microorganisms with a rigid cell wall. Here we report a modification of the RNA colony hybridization for use with yeast. The modified method includes the following consecutive procedures: (a) treatment of the yeast colonies on the membrane filter with 10% SDS at 65°C for 30 min; (b) treatment of the same filter with 3 × SSC, 10% formaldehyde at 65°C for 30 min; (c) hybridization with 32 P‐labelled oligonucleotide or (DNA) specific for the RNA sequence of interest. The intensity of the radioactive signals thus obtained is comparable with that of the E. colsi colonies.