Distinction of coals and their extracts by field ionization mass spectrometry and pattern recognition

Summary For the first time, uni- and multivariate statistical methods have been performed, using data sets of pyrolysis (Py)-field ionization (FI)-mass spectrometry (MS) in the range from m/z 70 to m/z 1,000. Py-FIMS is a suitable tool to characterize the volatile fractions of different coals and their pyridine extracts in vacuum. The features of this method are reduced mass spectrometric fragmentation and thermal production of high-mass primary fragments. Heating in the range from 50 to 500° C with a rate of 0.4° C/s gives very similar spectra and high relative abundance of every possible ion between m/z 200 and m/z 800, therefore it is not easy to distinguish the coals and their extracts. However, by non-linear mapping, all coals investigated and their corresponding extracts are clearly separated. Feature scaling using Fisher ratios showed, that the most characteristic ions for obtaining this clear differentiation are only of minor relative abundance. The examples of three different coals and their pyridine extracts shown here, indicate the potential of the combination of mass spectrometric and chemometric methods for detecting slight differences in very complex mixtures of substances or pyrolysates of fossil fuels.

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Unterscheidung von Kohlen und ihrer Extrakte durch Feldionisations-Massenspektrometrie und Mustererkennung

Zusammenfassung Erstmalig werden uni- und multivariate statistische Methoden für Datensätze der Pyrolyse (Py)-Feldionisations (FI)-Massenspektrometrie (MS) im Massenbereich von m/z 70 bis m/z 1000 angewandt. Py-FIMS ist ein sehr leistungsfähiges Verfahren um den Anteil der im Hochvakuum flüchtigen Fraktionen von verschiedenen Kohlen und deren Pyridinextrakten zu charakterisieren. Das Verfahren ist durch eine stark reduzierte massenspektrometrische Fragmentierung und Erzeugung von thermischen Primärbruchstücken hohen Molekulargewichtes gekennzeichnet. Im Temperaturbereich von 50° bis 500° C ergeben sich bei einer Heizrate von 0,4° C/s sehr ähnliche Massenspektren in denen praktisch jede Massenzahl im Bereich von m/z 200 bis m/z 800 belegt ist. Daher ist die Unterscheidung der Massenspektren von Kohlesorten untereinander und den dazugehörenden Kohleextrakten schwierig. Durch nicht-lineare Projektionen konnten jedoch alle untersuchten Kohlen und ihre Pyridinextrakte schnell und eindeutig getrennt werden. Merkmalerkennung aufgrund der Fisher-Quotienten zeigte, daß die meisten charakteristischen Ionen die zu einer klaren Differenzierung genutzt werden können, nur Signale sehr geringer relativer Häufigkeit darstellen. Aus den gezeigten Beispielen von drei Kohlesorten und deren Pyridinextrakten wird deutlich, welche analytischen Möglichkeiten in der Methodenkombination von Massenspektrometrie mit schonender Ionisierung und Mustererkennung eröffnet werden, mit der auch geringfügige Differenzen in sehr komplexen Mischungen oder Pyrolysaten von fossilen Brennstoffen erkannt werden können.

     

Solvability criteria for systems of fuzzy relation equations

By solving systems of fuzzy relation equations, qualitative process models can be obtained. To give more information on the solving procedure and to help constructing models, solvability criteria for-systems of fuzzy relation equations are necessary. In this article such criteria will be developed. Both methods are considered. In addition to some ideas on general , the is evaluated in detail. Criteria of practical use will be developed. These criteria will limit the variety of premise intersections to guarantee solvability. Nevertheless, they will still allow to model the significant behaviour of the processes.     

Extending Färe and Zelenyuk (2003)

In our recent work, Färe and Zelenyuk (2003) [On aggregate Farrell efficiency scores. European Journal of Operational Research 146 (3), 615–620], we have proposed a way of aggregating Farrell-type efficiency scores with weights (and aggregation function) derived from economic-type optimization behaviour. In this comment we correct a mathematical error present in that work as well as generalize the price-independent weights we have proposed earlier.     

Characterization of modification sites during peptide synthesis using liquid secondary ion/collision-induced dissociation mass spectrometry and a computer program

Side-reactions often occur during peptide synthesis resulting in modified amino acid moieties. To identify these residues, liquid secondary ion/collision-induced dissociation mass spectra were recorded. The main fragments are generated by cleavage of the peptide bond. To facilitate interpretation of the spectra and assignment of the structure, a simple, but flexible and efficient, computer program is presented. The program allows the verification of the correct structure of the synthesized peptides and the deduction of the type of side-products formed, such as alkylation of tryptophan residues.     

On the construction of optimal mixed finite element methods for the linear elasticity problem

Summary The mixed finite element method for the linear elasticity problem is considered. We propose a systematic way of designing methods with optimal convergence rates for both the stress tensor and the displacement. The ideas are applied in some examples.     

Study on the sensitive and selective adsorption voltammetry of vanadium with antipyrylazo III (APA III)

The sensitive and selective adsorption voltammetric determination of the vanadium(V)-antipyrylazoIII complex in HAc-NaAc solution is investigated. The V-complex is strongly adsorbed onto a stationary Hg-electrode and is reduced at a potential more negative than that corresponding to the reduction of its ligand. The conditions for determining vanadium are investigated and the mechanism of the reduction peak of the vanadium complex is discussed, as also the influence of foreign ions on the determination of vanadium. An at least 20-fold excess of foreign ions does not cause any interference. The detection limit is 4×10^–10 mol/l V with 3 min enrichment time.     

Closest 4-leaf power is fixed-parameter tractable

The NP-complete Closest 4-Leaf Power problem asks, given an undirected graph, whether it can be modified by at most r edge insertions or deletions such that it becomes a 4-leaf power. Herein, a 4-leaf power is a graph that can be constructed by considering an unrooted tree—the 4-leaf root—with leaves one-to-one labeled by the graph vertices, where we connect two graph vertices by an edge iff their corresponding leaves are at distance at most 4 in the tree. Complementing previous work on Closest 2-Leaf Power and Closest 3-Leaf Power, we give the first algorithmic result for Closest 4-Leaf Power, showing that Closest 4-Leaf Power is fixed-parameter tractable with respect to the parameter r.     

Semi-discrete Galerkin approximation of the single layer equation by general splines

This paper deals with a semi-discrete version of the Galerkin method for the single-layer equation in a plane, in which the outer integral is approximated by a quadrature rule. A feature of the analysis is that it does not require high precision quadrature or exceptional smoothness of the data. Instead, the assumptions on the quadrature rule are that constant functions are integrated exactly, that the rule is based on sufficiently many quadrature points to resolve the approximation space, and that the Peano constant of the rule is sufficiently small. It is then shown that the semi-discrete Galerkin approximation is well posed. For the trial and test spaces we consider quite general piecewise polynomials on quasi-uniform meshes, ranging from discontinuous piecewise polynomials to smoothest splines. Since it is not assumed that the quadrature rule integrates products of basis functions exactly, one might expect degradation in the rate of convergence. To the contrary, it is shown that the semi-discrete Galerkin approximation will converge at the same rate as the corresponding Galerkin approximation in the and norms. Received March 15, 1996 / Revised version received June 2, 1997