bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic structure and L X‐ray emission spectra of molybdenum carbide, boride, nitride, silicide and silicocarbide
Authors: Acharya B. S. , Sakthivel R. 
Published: May 2005

AbstractK and L emission spectra of the carbide, boride, nitride, silicide and silicocarbide of molybdenum were studied using x‐ray spectrometry method. It was observed that satellite lines influence the K and L spectra in these molybdenum compounds. From the chemical shift of these lines, the nature of the bonding is found to be covalent in these compounds. Further, hybridization of both p‐d and s‐p orbitals plays a major role in shifting these lines and high asymmetry indices. In MoSi2 and MoSi3 C a quasi‐gap is found to be present. The abnormally high value of the I/I ratio was explained on the basis of multi‐hole configuration, shake‐off and Coster‐Kronig processes taking place in these compunds.
Tunable exciting energies for total reflection X‐ray fluorescence spectrometry using a tungsten anode and bandpass filtering
Authors: Knoth Joachim , Schneider Harald , Schwenke Heinrich 
Published: May 2005

AbstractThe applicability of crystal monochromators, X‐ray mirrors and multilayer configurations as filter elements in the primary beam of a total reflection X‐ray fluorescence spectrometer is discussed. The best compromise between detection limits and multielement capability was found to be a double multilayer arrangement with variable distance between the multilayer mirrors. Two multilayers in combination with the respective control units for multilayer distance, tube height and sample positioning provide a free choice of isolated X‐ray lines and narrow energy bands of the bremsstrahlung continuum. This permits optional excitation energies in one instrument. Using a tungsten anode at 60 kV, three arbitrarily selected energies of 9.7, 20 and 40 keV were applied. The effect of tunable exciting energies was demonstrated by means of a standard multielement solution.
L‐subshell fluorescence yields measured with synchrotron radiation
Authors: Sáanchez Héctor J. , Rubio Marcelo , Pérez Roberto D. , Burattini Emilio 
Published: May 2005

AbstractThe synchrotron photoionization method was applied to measure L‐subshell fluorescence yields. This method is based on the capability of tuning the energy of the synchrotron photons producing a selective subshell ionization. Three foil samples of Tb, Ho and Yb were irradiated and their characteristic spectra were recorded. Although it was not possible to obtain absolute results for the three ω, ω and ω fluorescence yields, the poorly known ω and ω coefficients were calculated using theoretical values for the well known ω yield. The results are very reliable and agree with reported theoretical and experimental data. These coefficients are valuable information for spectroscopists considering the lack of data for L1‐ and L2‐subshell parameters. Finally, synchrotron radiation has proved to be a useful tool for fundamental parameter determinations.
Determination of the copper oxidation state in a zeolite catalyst through the X‐ray absorption edge/self‐absorption effect by electron probe microanalysis
Authors: Wang Frank Cheng‐Yu 
Published: May 2005

AbstractOwing to improvements in impregnation techniques, the impregnation of copper compounds into a zeolite framework to form copper zeolite catalysts results in more uniformly distributed and finer (nanoscale size) copper‐containing particles. In order to determine the oxidation state of copper in a copper zeolite catalyst, a method utilizing the X‐ray absorption‐induced (absorption edge/self‐absorption) effect was developed using electron probe microanalysis. This method can provide oxidation state information that is not possible with traditional quantitative microanalysis owing to the electron beam and specimen interaction volume. The advantages and limitations of this method are discussed.
Tree sub‐ring structure analyses by x‐ray microprobe analysis
Authors: Kuczumow Andrzej , Rindby Anders , Larsson Sture 
Published: May 2005

AbstractAn X‐ray capillary microprobe was applied to the investigation of Pinus silvestris wood from Polish forests. The micrometre range of the microprobe gave an insight into the wood sub‐ring structure. The use of transmitted and scattered radiation permitted the detailed tracing of the subtle changes in the density of the wood. The changes in density were connected with the changes in temperature during the growth period. It was established that some kinds of biological activity in the case of Polish conifers covered the whole year, including winter. Samples of wood from the northern Swedish Picea Abies showed totally different mechanisms of winter behaviour.
Experimental investigation of heterogeneity effects in x‐ray fluorescence analysis of hair
Authors: Bacsó József , Uzonyi Imre 
Published: May 2005

AbstractThe effect of heterogeneity on the accuracy of analytical results was experimentally investigated for some biologically important elements in hair, viz. S, Cl, K and Ca. Measurements were carried out by energy‐dispersive x‐ray fluorescence spectrometry using annular 55Fe radioisotope source excitation. The differences between the concentration values from direct hair analysis, using bunches of hair strands for the measurements, and those from ground and pelletized hair samples were compared. On average, the discrepancy in the measured concentrations was ca. 5% for Ca, whereas for S, Cl and K it was higher at ca. 10–15%. Good agreement was found between the experimental values and the theoretical predictions of other workers.
Total reflection PIXE (TPIXE) and RBS for surface analysis
Authors: van Kan J. A. , Vis R. D. 
Published: May 2005

AbstractProton beams with an energy of 2.5 MeV and α beams with an energy of 4.8 MeV at small incident angles (0–35 mrad) were used to analyse surfaces by detecting x‐rays (PIXE) and backscattered protons (RBS). The specimens consisted of a flat substrate, such as Si wafers or quartz, with a thin evaporated coating. PIXE detection limits were investigated as a function of angle. A minimum detection limit for Au, using L x‐rays, was found to be 15% of an atomic layer using an incident angle of 16 mrad and 2.5 MeV protons. For angles between 4 and 20 mrad, both the PIXE and RBS yields drop drastically owing to reflection of the incoming ions. This was confirmed by ion trajectory calculations. At very small angles of a few mrad, was observed that the RBS yield drops faster than the x‐ray yield, which indicates surface channelling.
Application of EDXRF in a survey of concentrations of lead, zinc and arsenic in soil from selected areas in Krakow, Poland
Authors: Ostachowicz Jerzy , Ostachowicz Beata , Hołyńska Barbara , Baran Władysław 
Published: May 2005

AbstractAn investigation on the contamination by heavy metals of the surface layer of soil in the area around steelworks located in an industrial quarter of Krakow and in several locations in the city centre was carried out. Particular attention was paid to soil contamination by Pb, Zn and As. The EDXRF technique with radioisotope excitation was applied with the emission‐transmission method for matrix correction. Analyses of over 140 samples of soil were performed. The concentrations obtained of Pb and Zn were 15–200 and 40–650 μg g−1, respectively, whereas that of As was 0–30 μg g−1. The distributions of Pb contents in two regions of Krakow were similar whereas the distributions of Zn contents were different. Higher concentrations of Zn were observed in the industrial area. Such results suggest that there are different sources of contamination of the soil: the Pb content is from transportation and Zn is mainly from industry.
Analysis of pressed pellets of geological samples using wavelength‐dispersive x‐ray fluorescence spectrometry
Authors: Longerich Henry P. 
Published: May 2005

AbstractThe analysis of silicate geological reference materials for 30 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Ba, Ce, Pb, Th and U) is reported. Samples were prepared as pressed pellets using a phenolic resin. Matrix was uncorrected (NaCl), Lachance–Traill corrected (KFe, Ba and Ce) or Compton corrected (NiNb, Pb, Th and U).
Novel applications of topological indices. I—correlation of edge shifts in x‐ray absorption with wiener indices
Authors: Khadikar Padmakar V. , Joshi Shobha 
Published: May 2005

AbstractA novel application of Wiener indices in estimating edge shifts is described. It is demonstrated that edge shifts in x‐ray K absorption are linearly correlated with Wiener indices. Copper and cobalt complexes were used to establish this linearity. A novel technique of data reduction using topological indices was employed for the first time for correlation purposes in x‐ray absorption studies.
Simple approach to the analysis of oxides, silicates and carbonates using x‐ray fluorescence spectrometry
Authors: Giles H. L. , Hurley P. W. , Webster H. W. M. 
Published: May 2005

AbstractX‐ray fluorescence spectrometry has always been considered to be a comparative method of analysis requiring chemically analysed samples or reference materials for calibration. The fusion technique, which is widely used as the method of sample preparation to eliminate particle size and mineralogical effects, allows the use of synthetic ‘standards’ as the means of calibration, but most laboratories use large numbers to establish the primary calibration line and calculate empirical interelement correction coefficients. In the 1970s, de Jongh proposed the use of theoretically based correction coefficients, and his concept of ‘apparent concentration,’ which is related linearly to the measured intensity, means that in principle only two samples are necessary to define the primary calibration line. This paper describes the use of this principle to calibrate a spectrometer for the 13 most commonly occurring oxides, plus six others, over wide composition ranges. Each calibration line requires one sample, which is made from a commercially available source of the element, a blank or zero sample, which is used for all calibration lines, and a set of theoretical α coefficients calculated using de Jongh's program. Sample preparation is by fusion in Li2B4O7. The calibration was tested using reference materials and was found to be accurate for every element except sulphur.
Analyse spatiale d'une source X à l'aide d'un spectromètre à cristal convexe
Authors: Barré C. , André J.‐M. , Jonnard P. , Bonnelle C. 
Published: May 2005

AbstractUtilisant un spectromètre à cristal convexe, une méthode numérique à été mise au point qui permet de déterminer la taille linéaire d'une source x à partir de la mesure des largeurs spectrales des raies x. Cette méthode à été appliquée à la détermination de la taille d'une étincelle très brève, produite par décharge haute tension au voisinage de pointes de tungstène et de fer. On montre que, dans les conditions d'expérience, l'effet d'élargissement géométrique lié à la taille prédomine sur tous les autres effets d'élargissement.
Polarization effects and photon transport in x‐ray spectrometry
Authors: Fernández J. E. 
Published: May 2005

AbstractThe nature of the scattering interactions in the x‐ray energy regime makes the effect of polarization extremely important, mainly when the incident beam is partially or totally polarized. The effects of the source polarization on the x‐ray spectrum are analysed, stressing the points of interest in each case of unpolarized, linearly polarized and circularly polarized excitation.
Quantitative analysis of individual particles by x‐ray microfluorescence spectrometry
Authors: Lankosz M. , Pella P. A. 
Published: May 2005

AbstractA fundamental parameters method using polychromatic x‐ray microbeam excitation was developed and applied to the quantitative analysis of individual particles from 50–160 μm. From the ratio of the projected area of a particle to the cross‐sectional area of the microbeam, an effective portion of the microbeam irradiating the particle can be determined and used to correct the measured x‐ray intensities. Because particles in this size range may not be infinitely thick and may contain unmeasurable elements such as C and O, calculation of the average mass thickness of the particle allows complete matrix absorption corrections to be made. For this purpose, the ratio of coherent to incoherent x‐ray tube target lines scattered from the particle was used to calculate the average atomic number of the particle, and its mass thickness was determined from incoherent scatter. A parametric equation was derived and tested. In addition, irregularly shaped particles were analyzed using a well known equation usually applied to flat samples having intermediate thickness. Both models were tested with homogeneous glass particles of known composition and size.
Isolation and characterization of a phosphoprotein phosphatase‐deficient mutant in yeast
Authors: Matsumoto Kunihiro , Uno Isao , Kato Kayoko , Ishikawa Tatsuo 
Published: May 2005

AbstractThe ppd1 mutant of yeast, Saccharomyces cerevisiae, was isolated as a suppressor of the cyr2 mutation which caused alteration of the catalytic subunit of cAMP‐dependent protein kinase. Three peaks of phosphoprotein phosphatase activity (peak I, II and III) were identified by DEAE‐Sephacel chromatography of crude extracts of the wild‐type strain. The ppd1 mutant was deficient in peak III phosphoprotein phosphatase activity. The peak III enzyme efficiently utilized the phosphorylated forms of NAD‐dependent glutamate dehydrogenase and trehalase as substrate. The ppd1 mutation did not suppress the cyr1, CYR3 or ras1 ras2 mutations. The ppd1 locus was located on chromosome II and had identical characteristcs with glc1. The ppd1 mutation suppressed the G1 arrest caused by nutritional limitation, but maintained sensitivity to mating pheromone. In diploids homozygous for the ppd1 mutation, no premeiotic DNA replication and commitment to intragenic recombination occurred and no spores were formed, suggesting that the accumulation of phosphorylated proteins in the absence of one of the phosphoprotein phosphatases is required for mitosis but not for the initiation of meiosis.
The PET18 locus of Saccharomyces cerevisiae: A complex locus containing multiple genes
Authors: Toh‐e Akio , Sahashi Yuko 
Published: May 2005

AbstractThe basis of pleiotropy shown by the pet18 mutants of Saccharomyces cerevisiae (rho‐0, KIL‐0 and temperature sensitive growth) was examined by cloning the fragment which complements the defect in growth at 37°C of the pet18 mutants. the cloned DNA could complement the defect in the maintenance of the killer plasmid but did not give the cell the ability to maintain mitochondrial DNA. Sequence analysis of the cloned DNA revealed the presence of four open reading frames, at least two of which are necessary for the complementation activity. By using the cloned DNA as a probe, we found that two independent pet18 mutants have a deletion covering the entire sequence contained in the probe. From these results we predict that the traits of the pet18 mutants that concern temperature sensitivity and killer of the pet18 mutants are controlled by a separate gene(s) from that which participates in the maintenance of mitochondrial DNA.
Identification of polypeptides of the carbon metabolism machinery on the two‐dimensional protein map of Saccharomyces cerevisiae. Location of 23 additional polypeptides
Authors: Bataillé Nelly , Peypouquet Marie‐France , Boucherie Hélian 
Published: May 2005

AbstractUsing a modification of the basic two‐dimensional polyacrylamide gel electrophoresis technique, we have undertaken a systematic identification of the polypeptides of the protein map of Saccharomyces cerevisiae corresponding to components of the carbon metabolism machinery. To the previous location of nine glycolytic enzyme polypeptides on the yeast protein map we add the location of 23 polypeptides. Ten of them were identified as corresponding to cytoplasmic enzymes of the carbon metabolism machinery and 13 were characterized as mitochondrial proteins. The criteria used to establish the identification of these polypeptides spots include migration with purified proteins, immunodetection, overproduction by plasmid–carrying strains and physiological behaviour.
Effects of weak acids and external pH on the intracellular pH of Zygosaccharomyces bailii, and its implications in weak‐acid resistance
Authors: Cole Martin B. , Keenan Michael H. J. 
Published: May 2005

AbstractWeak acids and hydrogen ions in different concentration combinations affect the intracellular pH value (pHi) of Zygosaccharomyces bailii. The lowest pHi value measured was not at the most extreme, but at intermediate conditions of inhibition. Proton and organic‐acid ejection, on a cell volume basis, is greater in cells grown under inhibitory conditions and is stimulated by weak acids, whilst in cells not grown under inhibitory conditions acid efflux is lower and is depressed by weak acids; this may be important in the maintenance of tolerable pHi values in the presence of weak acids. The concentration of benzoic acid measured internally is identical to the value expected from its pK, external pH and pHi. Addition of fructose to starved cells causes both a decreased pHi and a concomitant efflux of previously loaded benzoic acid, quantitatively in accord with the shift in equilibrium of the freely permeable undissociated acid. There is no evidence that weak acids are actively extruded. Protoplast volume also varies with hydrogen‐ion and weak‐acid concentration and this too may play a role in intracellular pH maintenace.
Proliferation of microbodies in Saccharomyces cerevisiae
Authors: Veenhuis M. , Mateblowski M. , Kunau W. H. , Harder W. 
Published: May 2005

AbstractThe development of microbodies in the yeast Saccharomyces cerevisiae was studied in response to different conditions of growth. Various strains of S. cerevisiae were investigated, using cells from the exponential growth phase on glucose as an inocullum in all transfer experiments. Electron microscopy, including serial sectioning, revealed that these cells generally contained one to four small microbodies which were localized in the vicinity of the cell wall and characterized by the presence of catalase. Transfer of these glucose‐grown cells into media supplemented with various compounds known to induce microbody proliferation in other yeasts—i.e. uric acid, alkylated amines, amino acids, C2‐compounds such as ethanol or acetate, in the presence or absence of compounds that induce oxygen radical formation—did not result in a significant change in the number of microbody profiles observed. Marked microbody proliferation was, however, observed after a shift of cells into media containing oleic acid and was associated with the induction of activities of β‐oxidation enzymes. In addition, catalase and isocitrate lyase were present in enhanced levels. Kinetic experiments suggested that these microbodies developed from those originally present in the inoculum cells. In thin sections up to 14 microbody profiles were occasionally observed, often present in small clusters. Their ultimate volume fraction amounted to 8–10% of the cytoplasmic volume.
Cyclic AMP controls the switch between division cycle and resting state programs in response to ammonium availability in Saccharomyces cerevisiae
Authors: Boy‐Marcotte Emmanuelle , Garreau Hervé , Jacquet Michel 
Published: May 2005

AbstractWe have identified a mutation called rcal (for rescue by cAMP) which allows adenylate cyclase‐deficient mutants to divide in the presence of cAMP. We took advantage of this rcal mutation to study the effect of externally added cAMP on the onset of the resting state when cells are starved for ammonium. We measured the resistance of the cells to zymolyase treatment as a parameter of the resting state. We observed that the onset of the resting state is reversibly blocked by cAMP. This inhibitory effect of cAMP is discussed together with the cAMP control of the start. This leads us to propose a model in which the cAMP level, controlled by the availability of nutrients, should trigger the choice between the entry of the cell into the resting state and the initiation of a new division cycle.
Protein phosphorylation in yeast mitochondria: cAMP‐Dependence, submitochondrial localization and substrates of mitochondrial protein kinases
Authors: Müller Günter , Bandlow Wolfhard 
Published: May 2005

AbstractWe describe the identification and submitochondrial localization of four protein kinases and of their target proteins in derepressed yeast mitochondria. The activity of one of the kinases depends on the presence of cyclic AMP (cAMP). It is soluble and localized in the mitochondrial intermembrane space. Its natural target is a polypeptide of 40 kDa molecular mass, which is bound to the inner membrane. Besides this natural target this kinase phosphorylates acidic heterologous proteins, like casein, with high efficiency. The other protein kinases identified so far are cAMP‐independent. At least one is localized in the matrix having its natural substrates (49 and 24 kDa) in the same compartment. Two others are firmly bound to the inner membrane phosphorylating target proteins in the inner membrane (52·5 kDa) and in the intermembrane space (17·5 kDa), respectively.
A nuclear gene required for the expression of the linear DNA‐asociated killer system in the yeast Kluyveromyces lactis
Authors: Wesolowski‐Louvel Micheline , Tanguy‐Rougeau Christine , Fukuhara Hiroshi 
Published: May 2005

AbstractThe killer system of Kluveromyces lactis is associated with two linear DNA plasmids, pGKL1 and pGKL2. The killer toxin and the immunity determinant are coded for by pGKL1. Mutations which we have named KEX1. The KEX1 gene of K. lactis has been cloned by complementation of kex1 mutations by using a recombinant plasmid pool containing the entire Kluyveromyces lactis genome, on a multicopy plasmid KEp6, which contains the Saccharomyces cerevisiae URA3 gene as a marker. Genetic analyses of strains carrying a distrupted kex1 allele demonstrated that the cloned DNA corresponded to the KEX1 gene. The cloned KEX1 gene of K. lactis has low but significant sequence homology with the KEX2 gene of Saccharomyces cerevisiae. In vivo complementation of the kex1 mutations of K. lactis by the KEX2 gene of S. cerevisiae, and complementation of the kex2 mutations of S. Cerevisiae by the KEX1 gene of K. lactis, demonstrated that KEX1 of K. Lactis is functionally related to the KEX2 gene of S. cerevisiae. K. lactis diploids homozygous for kex1 are deficient for sporulation.
Substrate specificity of alcohol dehydrogenase from the yeast Hansenyls polymorpha CBS 4732 and Candida utilis CBS 621
Authors: Verduyn Cornelis , Breedveld Guido J. , Scheffers W. Alexander , Van Dijken Johnnes P. 
Published: May 2005

AbstractThe substrate specificity of alcohol dehydrogenase (ADH) from Hansenula polymorpha and Candida utilis has been compared with that of the classical ADH from baker's yeast. Cell‐free extracts of H. polymorpha and C. utilis exhibited a much higher ratio of butanol to ethanol oxidation than baker's yeast ADH. This was also observed with the purified enzymes. The ratio of activities with ethanol and butanol was pH‐dependent. With the baker's yeast enzyme the activity strongly decreased with increasing chain length, whereas the enzymes form H. polymorpha and C. utilis showed a high reactivity with long‐chain alcohols. In addition, the affinity constant for ethanol was more than tenfold lower than that of the baker's yeast enzyme. The purified preparation yielded several protein bands on polyacrylamide slab gels, each of which showed activity with both ethanol and butanol.