Ultrasonically induced phthalocyanine degradation: decolouration vs. metal release

The ultrasonically induced degradations of nickel(II) 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine and vanadyl 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine in a biphasic system consisting of chloroform and water are investigated. Decolourisation of the organic phase containing the metallo-phthalocyanines is found to occur rapidly (approximately minutes for 8 ml of ca. 5 microM solution). Analysis of the aqueous solute via ICP-OES, reveals significant amounts of the released nickel ultimately transfers into the aqueous phase but at a rate much slower than that of decolourisation, whereas the vanadium remains within the organic phase suggesting only partial degradation despite efficient decolourisation.     

CVD graphene vs. highly ordered pyrolytic graphite for use in electroanalytical sensing

We explore and contrast the electroanalytical performance of a commercially available CVD grown graphene electrode with that of edge- and basal-plane pyrolytic graphite electrodes constructed from highly ordered pyrolytic graphite for the sensing of biologically important analytes, namely β-nicotinamide adenine dinucleotide (NADH) and uric acid (UA). We demonstrate that for the analytes studied here, in the best case, the electroanalytical performance of the CVD-graphene mimics that of edge plane pyrolytic graphite, suggesting no significant advantage of utilising CVD-graphene in this context.     

Graphene electrochemical supercapacitors: the influence of oxygen functional groups

We have critically compared graphene and graphene oxide as materials for utilisation as supercapacitors indicating that the former exhibits a larger capacitance over the latter which has implications for those fabricating supercapacitors.     

Carmichael numbers with a totient of the form a2?+?nb2

Let φ be the Euler function. Fix , and let be an arbitrary set of primes of positive lower natural density. Using a variant of the Alford–Granville–Pomerance construction, we show that there are infinitely many Carmichael numbers N with a totient of the form , where and is a nonempty product of primes from the set . In particular, for any fixed natural number n, there are infinitely many Carmichael numbers N such that φ(N) = a ² + nb ² for some positive integers a and b.     

Feedback Control Methodologies for Nonlinear Systems

A number of computational methods have been proposed in the literature to design and synthesize feedback controls when the plant is modeled by nonlinear dynamics. However, it is not immediately clear which is the best method for a given problem; this may depend on the nature of the nonlinearities, size of the system, whether the amount of control used or time needed for the method is a concern, and other factors. In this paper, a comprehensive comparison study of five methods for the synthesis of nonlinear control systems is carried out. The performance of the methods on several test problems are studied, and some recommendations are made as to which feedback control method is best to use under various conditions.     

Quantum cosmology in 2+1 and 3+1 dimensions

We study the Wheeler-DeWitt equations for the wave function of the universe in 2+1 and 3+1 dimensions. Perturbation methods are developed and the first few orders areexplicitly calculated for the case of an inflating universe. We find that early quantum fluctuation can produce large-scale inhomogenities in the global structure of the universe at later times.     

TCP, quantum gravity,the cosmological constant and all that...

We study cosmology from the point of view of quantum gravity. Some light is thrown on the nature of time, and it is suggested that the cosmological arrow of time is generated by a spontaneous breakdown of TCP. Conventional cosmological models in which quantum fields interact with a time-dependent gravitational field are shown to describe an approximation to the quantum gravitational wave function which is valid in the long-wavelength limit. Two problems with initial conditions are resolved in models in which a negative bare cosmological constant is cancelled by the classical excitation of a Bose field η with a very flat potential. These models can also give a natural explanation for the observed value of the cosmological constant.     

The flow of an electrically conducting fluid at a rear stagnation point

Summary We consider the impulsively generated magnetohydrodynamic flow at a rear stagnation point. The work of Leibovich is carried further by formulating the inner viscous problem and providing analytical solutions and complete numerical solutions for the entire range of the interaction parameter. It is shown that the present results are consistent with previously obtained numerical solutions to the steady equations of both similarity and non-similarity form.

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Résumé Nous considérons l'écoulement magneto-hydrodynamique impulsivement engendré à un point de stagnation arrière. On porte plus loin l'étude de Leibovich par la formulation du problème visqueux intérieur et en fournissant des solutions analytiques et numériques complètes correspondantes au champ entier du paramètre d'interaction. On montre que les résultats actuels sont en accord avec les solutions numériques, et de similitude et de non-similitude, déjà connues des équations stationnaires.

     

Studies in azide chemistry. Part X [1]. Synthesis of perfluoro-2-azido-1-azacyclohexene

Perfluoro-2-azido-1-azacyclohexene can be prepared by treating perfluoro-1-azacyclohexene with an equimolar proportion of sodium azide (in acetonitrile) or azidotrimethylsilane under mild conditions; ¹⁹F n.m.r. analysis reveals that this new imidoyl azide participates in ring ° chain valence tautomerism, the tetrazolo-isomer constituting 19% of the equilibrium mixture at 35 °C.