Multi-sample cluster analysis using Akaike's Information Criterion

Summary Multi-sample cluster analysis, the problem of grouping samples, is studied from an information-theoretic viewpoint via Akaike's Information Criterion (AIC). This criterion combines the maximum value of the likelihood with the number of parameters used in achieving that value. The multi-sample cluster problem is defined, and AIC is developed for this problem. The form of AIC is derived in both the multivariate analysis of variance (MANOVA) model and in the multivariate model with varying mean vectors and variance-covariance matrices. Numerical examples are presented for AIC and another criterion calledw-square. The results demonstrate the utility of AIC in identifying the best clustering alternatives. This research was supported by Office of Naval Research Contract N00014-80-C-0408, Task NR042-443 and Army Research Office Contract DAAG 29-82-K-0155, at the University of Illinois at Chicago.     

Investigation of intramolecular sulfur-nitro interactions in 2-(2′-pyridylthio)-3-nitropyridine by 13C-NMR spectroscopy and x-ray crystallography

The single crystal X-ray diffraction structure of 2-(2′-pyridylthio)-3-nitropyridine is reported. A non-bonded interaction was observed between the sulfur atom and one of the oxygen atoms of the nitro group with an interatomic distance of 2.678 A. Examination of the molecule's behavior in solution by ¹³C-nmr spin-lattice (T₁) relaxation measurements showed the non-nitro bearing pyridyl ring to reorient anisotropically about the C2′-C5′ bond axis. In contrast, the nitro substituted pyridine ring did not appear to exhibit anisotropic reorientation about the corresponding C2-C5 bond axis. Rather, approximately equivalent relaxation times were noted for all protonated ring carbons, indicating that the relaxations of this portion of the molecule were governed by the overall isotropic reorientation of the system. Based on these observations, it was concluded that the intramolecular sulfur-nitro interaction also operates in the solution state and is sufficiently strong to prevent free rotation of the substituted portion of the molecule about the C2-S bond axis.     

Semimicro determination of carbon in organic compounds by closed flask combustion: Evaluation of the method

Summary A procedure is described for the determination of carbon by closed flask combustion. It involves electrical ignition of the sample (15–20 mg) wrapped in a high melting glass fiber, absorption of the CO₂ in NaOH-BaCl₂ solution, separation and dissolution of the BaCO₃ formed in HCl and back titration with NaOH. This method has been tested with organic compounds containing nitrogen, sulfur and chlorine.

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Zusammenfassung Ein Verfahren zur Kohlenstoffbestimmung mit Hilfe der Kolbenverbrennung wurde beschrieben. 15 bis 20 mg der in hochschmelzender Glasfaser verpackten Probe werden elektrisch gezündet, das Kohlendioxid in einer Natronlauge-Bariumchloridlösung absorbiert, das Bariumcarbonat abgetrennt, in Salzsäure gelöst und mit Natronlauge zurücktitriert. Das Verfahren wurde mit organischen Verbindungen überprüft, die Stickstoff, Schwefel bzw. Chlor enthielten.

     

Superconductivity in ordering systems

We analyse the behaviour of 2-order parameter systems (where one subsystem is superconducting) in constant external ordering fields and find the spatial distribution of the order parameters.The authors would like to thank Prof. B. T.Matthias and Prof. T. L.Birman for useful discussions.     

Analysis of the urban atmosphere and air pollution source effluents for Phenalen-1-one and 7 H-benz(de)anthracen-7-one

Summary Through the use of one- and two-dimensional thin-layer chromatography and direct spectrophotofluorometric examination of thin-layer plates, two members of a new family of compounds have been found in the atmosphere. Phenalen-1-one and 7 H-benz(de)anthracen-7-one were identified and determined in particulates obtained from urban atmospheres and air pollution source effluents. Scanning techniques and other methods of analysis were also used in characterization and estimation. Two-dimensional thin-layer chromatography followed by direct spectrophotofluorometric analysis appears to be the most promising chromatographic method for the routine analysis of chemical compounds in complex mixtures. It approaches colorimetric analysis in simplicity and speed and surpasses it in sensitivity, selectivity and the amount of information that can be obtained from one analysis.

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Zusammenfassung Durch ein und zweidimensionale Dünnschichtchromatographie und direkte Spektralfluoreszenzanalyse der Dünnschichtplatten wurden zwei Vertreter einer neuen Verbindungsklasse in der Atmosphäre gefunden. Phenalen-1-on und 7 H-benz(de)anthracen-7-on wurden identifiziert und in Partikeln bestimmt, die aus Stadtatmosphäre bzw. aus Quellen der Luftverunreinigung gewonnen wurden. Scanning-Verfahren und andere Analysenmethoden wurden zur Charakterisierung und Bestimmung gleichfalls herangezogen. Die zweidimensionale Dünnschichtchromatographie mit nachfolgender direkter Fluoreszenzmessung scheint jedoch für Routine-untersuchungen das beste chromatographische Verfahren für komplexe Gemische zu sein. Es entspricht an Einfachheit und Schnelligkeit der Kolorimetrie und übertrifft diese an Empfindlichkeit, Selektivität und Aussagokraft bei Durchführung einer einzigen Bestimmung.

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Résumé On a découvert dans l'atmosphère une nouvelle famille de composés en utilisant la Chromatographie en couche mince, uni et bidimensionnelle et l'examen direct spectrofluorimétrique des plaques avec couches minces. On a identifié la phénalène one-1 et la benzo(de) anthracène-7 H one-7 et on en a fait le dosage dans les particules prélevées dans l'atmosphère urbaine et dans les effluents des sources de pollution de l'air. On a utilisé des techniques d'examen et d'autres méthodes d'analyse pour la caractérisation et l'estimation. La Chromatographie en couche mince bi-dimensionnelle suivie d'une analyse spectrofluorimétrique directe semble être la méthode chromatographique la plus prometteuse pour l'analyse en série de composés chimiques en mélanges complexes. Elle se rapproche de l'analyse colorimétrique par sa simplicité et sa vitesse et la dépasse en sensibilité, en sélectivité et par le nombre de renseignements que l'on peut tirer d'une seule analyse.