Verbesserung der Quantifizierung von Elementverteilungen durch Bildverarbeitung

Zusammenfassung Die Ionen-Mikrosonde macht es möglich, Elementverteilungen in Festkörperoberflächen mit einer örtlichen Auflösung von einigen m zu bestimmen. Jedoch werden die gemessenen Intensitätsverteilungen nicht nur durch lokale Änderungen der Element-Konzentrationen hervorgerufen, sondern können durch Matrix und Topographieeffekte beeinflußt sein. Zur Quantifizierung solcher Elementverteilungen ist es daher erforderlich, die gemessenen Intensitätsverteilungen mit örtlich variablen Elementempfindlichkeitsfaktoren in Konzentrationsverteilungen umzurechnen.Zu diesem Zweck wurden Rechenprogramme entwickelt, die es gestatten, digitalisierte Intensitätsverteilungen einer Ionen-Mikrosonde zu messen und zu speichern. Das untersuchte Probengebiet wird anschließend rechnerisch in Bereiche gleichen Analysenverhaltens aufgeteilt. Für die Quantifizierung ist es dann ausreichend, elementspezifische Empfindlichkeitsfaktoren für jeden Bereich zu bestimmen und nicht mehr für jeden gemessenen Bildpunkt separat.Es wird über erste Messungen an Incoloy 800 H berichtet, die mit diesem Verfahren quantifiziert worden sind. Zur Berechnung der Empfindlichkeitsfaktoren wird ein vereinfachtes LTE-Modell benutzt. Die Ergebnisse stimmen innerhalb Faktor zwei mit denen einer Elektronenprobe überein.

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Improvements for quantifying elemental distributions by imageprocessing

Summary It is possible to determine elemental distributions from solid surfaces with a spatial resolution of a few m, by means of an ion-microprobe. However, the differences in intensities measured by this method are not only due to changes in elemental concentrations. They may also be affected by matrix and topographic effects. In order to quantify such elemental distributions, it is necessary to convert the measured distributions of intensities into distributions of concentrations using locally varying sensitivity factors.For this purpose, computer programs have been developed which allow to measure digitized intensity distributions with an ion-microprobe and to store such data. The analyzed sample area is sub sequently segmented by computational means into regions of equal analytical properties. Thus, it is sufficient for the quantification to calculate elemental sensitivity factors for every type of region and not for every point of the analyzed sample area.A report is given about first measurements on Incoloy 800 H which were quantified using the procedure described here. For the calculation of the sensitivity factors a simplified LTE-model is used. The results agree within a factor of two with those of an electronprobe.

     

Simultaneous Determination of Plasma Enrichments of 1-13C- and 15N-Labelled Phenylalanine and Tyrosine

Abstract

A methylchloroformate derivative was used for the simultaneous determination of plasma enrichments of 1-¹³C-phenylalanine, 1-¹³C-tyrosine, ¹⁵N-phenylalanine and ¹⁵N-tyrosine by gas chromatography/mass spectrometry. All four tracer enrichments could be measured in a single GC run. A specific ion fragment was obtained for each tracer. This approach allowed an easy determination of the “tracer to tracee ratios”. Each ion fragment could be measured with an appropriate single-to-noise ratio and precision in samples obtained from 100 μl plasma. The derivatization consists of a fast one-step reaction. Therefore it is well suited for studies involving a large number of samples, such as non-steady state bolus studies.     

MEASUREMENT TECHNIQUES FOR HORIZONTAL FLOW BOILING HEAT TRANSFER WITH PURE AND MIXED REFRIGERANTS

Abstract

A test rig and measurement techniques for horizontal flow boiling of pure and mixed refrigerants are described. Local heat transfer coefficients were measured for R22/R114 and R12/R152a mixtures as well as the corresponding pure components. The test section consists of an S-m-long, 9.1-mm-i.d., electrically heated stainless steel tube and has the distinctive feature of variable heated length. Details of pressure, composition, and fluid and wall temperature measurements are discussed. The composition of subcooled liquid entering test section varied from test to test, and it is recommended that it be measured for each test. For the R22/R114 mixture, local composition measurements in the annular liquid film revealed a composition variation of up to 0.07 mole fraction around the circumference of the heated tube.     

Multivariate determination of 13CO2/12CO2 ratios in exhaled mouse breath with mid-infrared hollow waveguide gas sensors

The ¹²CO₂/¹³CO₂ isotope ratio is a well-known marker in breath for a variety of biochemical processes and enables monitoring, e.g., of the glucose metabolism during sepsis. Using animal models—here, at a mouse intensive care unit—the simultaneous determination of ¹²CO₂ and ¹³CO₂ within small volumes of mouse breath was enabled by coupling a novel low-volume hollow waveguide gas cell to a compact Fourier transform infrared spectrometer combined with multivariate data evaluation based on partial least squares regression along with optimized data preprocessing routines.     

First measurement of the rho spectral function in high-energy nuclear collisions

We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.     

NA60 results on thermal dimuons

The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158 A GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The mass spectrum for M<1 GeV is consistent with a dominant contribution from π ⁺ π ⁻→ρ→μ ⁺ μ ⁻ annihilation. The associated ρ spectral function shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs. The slope parameter T _eff associated with the transverse momentum spectra rises with mass up to the ρ, followed by a sudden decline above. The rise for M<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for M>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated empirical evidence, including also a Planck-like shape of the mass spectra at low p _T and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude with first results on ω in-medium effects.     

Suppression of nucleate boiling of pure and mixed refrigerants in turbulent annular flow

The following issues are addressed: (a) Is suppression of nucleate boiling an appropriate physical mechanism to explain experimental heat transfer coefficient behavior? (b) Is suppression possible under reasonable conditions with refrigerants? (c) Is suppression more or less likely with a binary mixture of refrigerants as compared with either pure fluid? Issue (a) is resolved in favor of traditional suppression theory by critical review of the literature. Issue (b) is resolved by experimental evidence suggesting one must have rather low pressures to suppress nucleation with refrigerants. Issue (c) is resolved by experimental and correlative evidence suggesting systematic differences with mixtures.     

Book review

Communicated by Professor Zimmermann