The distribution of fluorine and other elements in teeth using proton induced reaction analysis techniques

Proton induced gamma-ray emission (PIGE) and proton induced X-ray emission (PIXE) analysis was employed to investigate the distribution of the concentration of fluorine and ten other elements along sections of teeth samples, extracted from eight individuals. These sections which included the bulk of dentine and enamel were scanned using a proton beam of 250 m diameter. Rutberford backscattering spectra were also collected in order to obtain information about the concentration of major elements and to correct for matrix inhomogeneities.     

Analysis of an ancient bronze statue by external beam pixe

A quantitative analysis of an ancient Buddha statue was performed by external beam Proton Induced X-ray Emission for the purpose of identifying its originality. It is shown how the PIXE method can be applied for archeological study. The elemental composition of the statue is compared with that of several samples with definite ages. The experiment was performed by extracting 2.4 MeV proton beam through a 2 mm diameter collimator and 7.6 m kapton foil to the He atmosphere. X-rays were measured by a Si(Li) detector. The analysed elements were Fe, Cu, Ag, Au and Hg for gold coating and Fe, Ni, Cu, Zn, As, Ag, Sn, Au, Pb and Bi for bronze body.     

Proton induced X-ray emission (PIXE) analysis on thick samples exemplified on the rare earth elements

Summary A semiempirical procedure is developed for the calculation of the signal intensity for thick sample PIXE experiments. The calculated X-ray intensity emerged out of a thick sample is factorized into the overall produced intensity within a thick sample and an effective transmission factor for the X-ray self-absorption.The accuracy of this procedure is limited by the reliability of the experimental input parameters to about ±25%.We find as an important result of this study: The signal intensity is calculated as a function of the various experimental parameters, i.e. proton energy and sample composition including interelement- and matrix effects. This function is presented as a closed equation, which can be applied very easily, i.e. without large scale computers, to calculate the sample elemental concentration. The mass absorption coefficient of the sample most strongly influences the effective transmission term.Enhancement corrections are calculated for additional interfering rare earth elements j. No significant interelement-effects appear at concentrations c _j 2 weight%, where analysis by PIXE may be interesting. The calculated results agree well with experimental data for the rare earth elements in different matrices.Dedicated to Karl Gleu on the occasion of his 80th birthday     

Application of PIXE analysis to environmental samples stable element distribution in sea algae by scanning microprobe analysis

The resolution of a 33±3 m microprobe focussed with quadrupole doublet installed at the 3 MV Van de Graaff of the National Institute of Radiological Sciences was used for this analysis. Brown algae, Hijiki,Hizikia fusiforme was the sample target bombarded with a 2 MeV proton beam collimated mechanically into a rectangular image of 100 m × 700 m. Scanning across the sample target prepared into a longitudinal section from the caulis of the algae provided the following observations. More than 12 elements such as Al, Si, P, Cl, Ca, Mn, Fe, Cu, Zn, As, Br and Sr were determined simultaneously, together with their distributional information across the diameter. In the medullary layer, Mn and Zn were specific in their accumulation, while the deposition of Fe, Cu, As and Br were observed to be high in the epithelial layer, especially Fe and Cu which were found on the surface, where they contact ambient sea water, but no significant change in pattern was indicated for such elements as Al, P and Cl. The PIXE microprobe analysis was, therefore, effective in its detectability for elements below a few ppm level, resultantly provides further possibilities for collecting information from bio-medical and environmental samples on trace characterization of elements.     

Development of a PIXE method at high energy with the ARRONAX cyclotron

The high energy PIXE (HEPIXE) method is a multi-elemental non-destructive ion beam analysis technique. It is based on the detection of the X-ray emitted due to the interaction of high energy particle beam with a sample. This technique is fast and allows the analysis of heavy and medium elements in thin (μm), thick (mm) and multilayer samples. At the ARRONAX facility (Nantes, France), the HEPIXE method has been used to determine the composition of natural and synthetic sodalites. Photochromic properties of these samples are supposed to come from the trace elements (concentration in the ppm range) present in the samples. Taking advantage of the 70 MeV proton beam available at our facility, the HEPIXE method has been also used to study multilayer samples. It has been shown that it is possible to determine the composition of each layer, their thicknesses and their depth position by analyzing the recorded X-ray spectra.     

Powder dilution as a new method of elimination of interelement effects in energy-dispersive X-ray fluorescence analysis

Summary If the concentration of elements with Z>22 (Ti) is to be determined in mineral samples and if the concentration of any of these elements is greater than 1%, the sample is diluted by grinding it together with an appropriate amount of quartz powder in an agate mortar mill. The diluted sample is measured in powdered form in a spectro-cup at practically infinite thickness by energy-dispersive X-ray fluorescence; the counting rates are corrected by means of the Compton scattering peak and evaluated by use of calibration curves obtained by measuring standards on the basis of silica gel. The applicability of this method is established by measuring the concentrations of 12 elements with Z>22 in 14 mineral samples of varying composition.We thank the Bundesministerium für Forschung und Technologie for financial support and the Uranerzbergbau GmbH, Bonn, for supplying the mineral samples.     

Determination of sulphur in fly ash by instrumental proton activation analysis

A method for the determination of sulphur in fly ash by instrumental proton activation analysis using the³⁴S/p,n/^34mCl reaction was developed. The 2128.5 keV and 3305.0 keV -rays of^34mCl /t=32.0 min/ were measured on a Ge/Li/ -spectrometer, shielded with a lead absorber to attenuate low energy -rays. Irradiation and measuring conditions were optimized. The detection limit for instrumental analysis is 0.3 to 1 mg g^–1 and the standard deviation is cca. 4% for a typical sample.     

Trace elements in human fingernails: Measurement by proton-induced X-ray emission

The method of proton particle-induced X-ray emission (proton PIXE) has been employed to study the trace element composition of human fingernails. The samples were colleted from 51 subjects randomly selected from a working community of about 500 adults and they were analyzed by the thick-target external beam technique of the PIXE method. The samples were exposed to the proton beam as 1-mm thick pellets and irradiated with 2 MeV protons having 20 nA beam intensity. For 40 C irradiations, the concentration of fourteen elements, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Rb, Sr and Pb, were measured by comparison with a calibration obtained from the NBS orchard leaf standard (SRM 1571). Some anomalous cases have been revealed from this study and they are attributed to environmental factors. The frequency distributions of the elements are presented and the results compared with available data.This research received financial support from the International Atomic Energy Agency, Vienna, under the research contract RC/2536/RBl.     

The status of trace and minor elements in pulses: A PIXE measurement

The proton particle induced X-ray emission (proton PIXE) technique has been employed to study the heavy element status (essential and toxic) in five different varieties of pulses commonly cultivated and consumed in Bangladesh. In this analysis, the samples were irradiated in air with 2 MeV protons having 30 nA beam intensity for characteristic X-ray excitation. For 40 μC irradiations, the concentration of ten elements (K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, and Rb) was determined by comparison with a calibration obtained from the NBS orchard leaf standard, SRM 1571. In a comparative study with atomic absorption spectrophotometric (AAS) measurements of some elements in lathyrus sativus, the data were found to be in good agreement. The results obtained from the present study are discussed and compared with available data.     

Quantitative Bestimmung leichter Elemente mit Hilfe der R?ntgenfluorescenzanalyse: Kalium

Zusammenfassung Es wird ein Verfahren für die quantitative Bestimmung von Kalium mit Hilfe der energiedispersiven Röntgenfluorescenzanalyse beschrieben, das für die Anwendung auf Wasserproben ausgearbeitet wurde. Das Kalium wird als Tetraphenylborat gefällt und gemessen. Zur Anregung der Fluorescenzstrahlung dient eine Röntgenröhre mit Wolframanode und Titan als Sekundärtarget, zur Messung der Röntgenspektren wird ein Si(Li)-Detektor verwendet. Unter den beschriebenen Versuchsbedingungen können 0,1–1000 g (0,04–400 g/cm²) Kalium bestimmt werden.

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Quantitative determination of ligth elements by X-ray fluorescence analysis: Potassium

Summary A procedure is described for the quantitative determination of potassium in water samples, using energy dispersive X-ray fluorescence analysis. Potassium is precipitated and measured as tetraphenyloborate. The fluorescence radiation is excited employing a tungsten X-ray tube and titanium as secondary target. A Si(Li)-detector is used for measuring the X-ray spectra. With the conditions described, 0.1–1000 g (0.04–400 g/cm²) of potassium can be determined.

     

The mobility of protonated aminoalcohols: Evidence for proton-induced cyclization

The reduced mobility in air, at 200C, of protonated aminoalcohols was measured by ion mobility spectrometry (IMS). The relatively high mobilities that were measured indicated that proton-induced cyclization took place in the aminoalcohols, similar to what was previously observed in diamines. This conclusion is in agreement with the proton affinities (PA) of these compounds that indicated that the proton was more strongly attached to the molecule than in normal aliphatic amines. It was also found that the, = aminoalcohols had slightly higher mobilities than their corresponding 1,2 isomers, further supporting the conclusion for proton-induced cyclization.     

Electron microscopy of submicron particles in natural waters—Morphology and elemental analysis of particles in fresh waters

Submicron particles larger than about 0.1m in pond and river waters were collected on a carbon film mounted on a specimen grid by centrifugation and then studied morphologically and analyzed for major elements heavier than sodium, with a high-resolution transmission electron microscope equipped with an energy dispersive X-ray analyzer. If available, the data were compared with those of particles artificially prepared under various conditions. Four typical particles—aluminosilicate, quartz, fine-particle aggregates containing silica and iron(III) oxide, and microorganisms—were found in fresh waters.     

Frustrated Gas Hydrate Frameworks in the Model of Strong and Weak Hydrogen Bonds

The topological model of strong and weak H-bonds suggested previously was used for structure investigation of the ground energy state of the proton subsystem of gas hydrate frameworks. It is shown that gas hydrate frameworks are frustrated systems, that is, configurations consisting of exclusively strong H-bonds may not exist in view of combinatorial and topological constraints. Rough estimates were obtained for the maximal and minimal fractions of strong H-bonds (65 and 6%, respectively).     

Structural role of hydrogen bond networks in amino acid–acid systems. (I) The network with highly polarizable OHO hydrogen bonds in sarcosine–methanesulfonic acid (2:1) crystal

The sarcosine–methanesulfonic acid (2:1) crystal was selected for examination of two problems: relations between different components of the amino acid–acid hydrogen bond network and a role of very strong and highly polarizable OHO hydrogen bond in the main structural units of the crystal: sarcosinium–sarcosine dimers (complexes). Our observations are based on phase transitions of the crystal monitored by DSC, X-ray diffraction and temperature evolutions of selected bands of IR spectra. Our experimental and DFT results provide information on the potential energy profile of the OHO proton and its evolution with temperature. The OO distance of the primary hydrogen bond remains almost unchanged and its proton is strongly delocalized and sensitive on neighbour NHO hydrogen bond. We propose a possible mechanism of the phase transitions and coupling between νCO vibrations of the carboxyl group and moving of the proton in neighbour OHO hydrogen bridge.     

A new approach to the study of normalized appearance energy of hot atom reaction product in optical isomers of tris/acetylacetonato/ruthenium/III/

Appearance energy is originally the threshold energy at which récoil products begin to be observed. This was determined by /, '/ reactions. Afterwards, an alternative technique has been developed to determine it by summing up recoil energy spectrum. The latter technique assumed a step function rising at energy E_O in the yield-energy relation. E_O should be defined as normalized appearance energy /NAE/, because it is not threshold energy in its original sense. The NAE for isomerization from to /or reverse/ in Ru/acac/₃ was estimated to be 29 eV, and that for free atom /or ion/ formation was calculated to be 34 eV. The 5 eV difference seems to indicate an energy interval in which isomerization effectively occurs in the recoil reaction.     

On the unusual fluorescence X-ray intensity variations in iron-silicon and aluminium-silicon-copper alloys

Summary The unusual fluorescence X-ray intensity variations in iron-silicon and aluminium-silicon-copper alloys have been investigated. In these alloys, the unusual behaviour was found not only in the fluorescence X-ray intensity of the Si K line but also in that of Fe K. It was confirmed that the phenomenon occurred not only when the primary crystals having large differences of the mass-absorption coefficients for the X-ray of the elements to be analyzed precipitated on both sides of the eutectic point and/or the intermetallic compound but also when there was a large difference in the effective volume ratio between the primary phase and the secondary phase. Therefore, the phenomenon should be considered in the fluorescence X-ray analysis of actual samples such as alloys of light metals, ores, oxides, and other compounds.

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Über ungewöhnliche Intensitätsveränderungen bei der Röntgenfluorescenz von Fe-Si- und Al-Si-Cu-Legierungen

Zusammenfassung Das ungewöhnliche Verhalten wurde bei der Si K- und auch bei der Fe K-Linie festgestellt. Die Erscheinung tritt nicht nur auf, wenn Primärkristalle mit stark unterschiedlichen Massenabsorptionskoeffizienten für die Röntgenlinien der zu untersuchenden Elemente sich auf beiden Seiten des eutektischen Punktes und/oder der intermetallischen Verbindung abscheiden, sondern auch, wenn ein großer Unterschied im effektiven Volumenverhältnis zwischen der primären und sekundären Phase vorhanden ist. Diese Veränderungen müssen bei der Röntgenfluorescenzanalyse von Leichtmetallegierungen, Erzen, Oxiden u. ä. berücksichtigt werden.

     

A Mixed Quantum-Classical Approach for Computing Effects of Intramolecular Motion on the Low-Barrier Hydrogen Bond

The fractionation factor is defined as the equilibrium constant for the reaction: R – H + DOH R – D + HOH. Of interest are values of fractionation factors for reactions where reactants and/or products form intramolecular low-barrier hydrogen bonds. Experimentally measured isotopic fractionation factors are usually interpreted via a one-dimensional potential energy surface along the intrinsic proton hydrogen bond coordinate. Such a one-dimensional picture cannot be completely correct. Intramolecular motions, such as vibrations and librations, can modulate the underlying potential energy surface along the hydrogen bond coordinate and thus affect the isotopic fractionation factor. We have recently generated a picture of the motion of the proton in a low-barrier hydrogen bond as taking place in an effective single-dimensional potential, which we term the potential of mean force (PMF). In this paper, we compute the PMF for a molecule with an intramolecular hydrogen bond in order to quantify the effect of intramolecular motions on the fractionation factor. The PMF and isotopic fractionation factor are computed with a combination of high-level density functional theory and molecular dynamics simulations.     

Determination of trace elements in small water samples by total reflexion X-ray fluorescence (TXRF) and by neutron activation analysis (NAA)

The problems encountered in the determination of trace elements in small sample volumes of the order of 1 to 10 l (e.g. in droplets of water) are discussed. Total reflexion X-ray fluorescence (TXRF) and neutron activation analysis (NAA) are applied for the determination of Na, Mg, K, Ca, Mn, Fe, Co, and Cu in concentrations of 0.01 to 10 mg/L in 1 to 10 L of water. The applied methods are described, the results are discussed and the advantages of TXRF are brought forward.     

Studies of crystalline native celluloses using potential energy calculations

Energies for various trial packing arrangements of unit cells for the I and I phases of native cellulose discovered by Sugiyamaet al. were evaluated. Both a rigid-ring method, PLMR, and the full-optimization, molecular mechanics program, MM3(90), were used. For both phases the models that had the lowest PLMR energy also had the lowest MM3 energy. Both calculated models have the chains packed up, O6s intg positions, and the same sheets of hydrogen-bonded chains. The I structure model is essentially identical to that proposed previously for ramie cellulose by Woodcock and Sarko. It is also the same as the best parallel model previously proposed that was based on the X-ray data of Mann, Gonzalez and Wellard, once the various unit cell conventions are considered. Also, the energies from both methods for all three celluloses, I, I and II, are in the order that rationalizes their relative stabilites.     

Initial Stage of Mechanical Alloying in Fe(80)X(20) (X = Mo, W) Systems

The kinetics of an initial stage of mechanical alloying in Fe/Mo and Fe/W (80 : 20, at. %) systems was studied by X-ray diffraction and Mössbauer spectroscopy. It was established that, upon mechanical treatment, X (Mo, W) passes into the Fe lattice to form an -Fe(X) solid solution, and a phase of pure iron exists in the systems for a long time together with the forming solution. The reverse dissolution (Fe in the X lattice) did not occur. Quantitatuve characteristics of the process (work of formation of intergrain surface and energy yields of the consumption of initial components and formation of a solid solution) were estimated in the energy units. It was shown that, upon annealing, a supersaturated solid solution separates into a solution with the equilibrium concentration X, an intermetallic compound Fe₇X₆, and an amorphous phase (the effect of inverse melting).