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.

     

Constraints on proton structure from precision atomic-physics measurements

Ground-state hyperfine splittings in hydrogen and muonium are very well measured. Their difference, after correcting for magnetic moment and reduced mass effects, is due solely to proton structure-the large QED contributions for a pointlike nucleus essentially cancel. The rescaled hyperfine difference depends on the Zemach radius, a fundamental measure of the proton, computed as an integral over a product of electric and magnetic proton form factors. The determination of the Zemach radius, (1.019+/-0.016) fm, from atomic physics tightly constrains fits to accelerator measurements of proton form factors. Conversely, we can use muonium data to extract an experimental value for QED corrections to hydrogenic hyperfine data. There is a significant discrepancy between measurement and theory, in the same direction as a corresponding discrepancy in positronium.     

Structural order for one-scale and two-scale potentials

We perform molecular dynamics simulations to investigate the relationship between structural order and waterlike dynamic and thermodynamic anomalies in spherically symmetric potentials having either one or two characteristic length scales. Structural order is characterized by translational and orientational order parameters. We find that (i) dynamic and thermodynamic anomalies exist for both one-scale and two-scale ramp potentials, and (ii) waterlike structural order anomalies exist only for the two-scale ramp potential. Our findings suggest that the waterlike relationship between structural order and anomalies is related to the presence of two different length scales in the potential.     

Glass-transition temperature of water: a simulation study

We report a computer simulation study of the glass transition for water using the extended simple point charge potential. To mimic the difference between standard and hyperquenched glass, we generate glassy configurations with different cooling rates, and we calculate the temperature dependence of the specific heat on heating. The absence of crystallization phenomena allows us, for properly annealed samples, to detect in the specific heat the simultaneous presence of a weak prepeak ("shadow transition") and an intense glass transition peak at higher temperature. Our results support the view-point that the glass transition temperature is higher than the conventionally accepted value 136 K. We also compare our simulation results with the Tool-Narayanaswamy-Moynihan phenomenological model.     

Asymmetric epoxidation of some arylalkenyl sulfones using a modified Juliá-Colonna procedure

A modified procedure for performing the Juliá-Colonna epoxidation reaction effects the oxidation of some vinyl sulfones to generate the corresponding epoxides 5-8 in good to excellent optical purity.     

Comparison between ocean-acoustic fluctuations in parabolic-equation simulations and estimates from integral approximations

Line-integral approximations to the acoustic path integral have been used to estimate the magnitude of the fluctuations in an acoustic signal traveling through an ocean filled with internal waves. These approximations for the root-mean-square (rms) fluctuation and the bias of travel time, rms fluctuation in a vertical arrival angle, and the spreading of the acoustic pulse are compared here to estimates from simulations that use the parabolic equation (PE). PE propagations at 250 Hz with a maximum range of 1000 km were performed. The model environment consisted of one of two sound-speed profiles perturbed by internal waves conforming to the Garrett-Munk (GM) spectral model with strengths of 0.5, 1, and 2 times the GM reference energy level. Integral-approximation (IA) estimates of rms travel-time fluctuations were within statistical uncertainty at 1000 km for the SLICE89 profile, and in disagreement by between 20% and 60% for the Canonical profile. Bias estimates were accurate for the first few hundred kilometers of propagation, but became a strong function of time front ID beyond, with some agreeing with the PE results and others very much larger. The IA structure functions of travel time with depth are predicted to be quadratic with the form theta(2)vc0(-2)deltaz(2), where deltaz is vertical separation, c0 is a reference sound speed, and thetav is the rms fluctuation in an arrival angle. At 1000 km, the PE results were close to quadratic at small deltaz, with values of thetav in disagreement with those of the integral approximation by factors of order 2. Pulse spreads in the PE results were much smaller than predicted by the IA estimates. Results imply that acoustic tomography of internal waves at ranges up to 1000 km can use the IA estimate of travel-time variance with reasonable reliability.     

A route to the structure proposed for puetuberosanol and approaches to the natural products marshrin and phebalosin

Synthesis of the structure claimed for puetuberosanol 1 (using the Juliá-Colonna oxidation in a key step) showed that the natural product was a different material. The isomeric epoxy alcohols 16-18 can be discounted from the alternatives. An analogue 19 of marshrin 2 was prepared but the synthesis of the natural product was thwarted by failure of a Juliá-Colonna oxidation in the key step. The epoxy ketone 29 was prepared by Darzens condensation and was converted into (±)-phebalosin 3.