The structure of castanaguyone a biisocoumarin plant product

The fruit extract of the Mexican shrub $\text{Zanthoxylum}$$\text{fagara}$ Sarg. has afforded castanaguyone $\text{1}$; it is the first biisocoumarin encountered in nature.     

A note on streaming double refraction in a dilute suspension of rigid spheroids subject to weak Brownian rotations

Summary The phenomenon of streaming double refraction is examined theoretically for simple shear flow of a dilute suspension of rigid spheroids which are subject to weak Brownian rotations. In particular, we employ recently derived expressions for the statistical distribution of particle orientations in the limit of weak rotaryBrown-ian motion to calculate the corresponding limiting behavior of the extinction angle and the birefringencen. These are compared with the earlier results ofScheraga, Edsall, andGadd (17), who utilized a slowly convergent series solution due toPeterlin andStuart for the orientation distribution. The familiar stressoptical relations which have been proposed for various polymeric materials are found to be inapplicable for a suspension of the type considered.     

An experimental study of drop migration in shear flow between concentric cylinders

The phenomenon of migration of liquid drops in Couette flow between concentric cylinders due to non-Newtonian fluid properties and shape deformation has been studied experimentally. The results agree very well with the theory of Chan and Leal, which included the effect of hydrodynamic interaction with the bounding walls, and that of velocity profile curvature in a Couette device. Significant observations that were not reported in previous studies include the migration of a deformable Newtonian drop to an equilibrium position between the centerline and the inner rotor, and the competition between normal stresses and shape deformation effects for the case of a Newtonian drop in a non-Newtonian fluid.     

On the motion of a charged particle in the field of a magnetic monopole

A quantum mechanical treatment of the motion of a charged particle in the field of a fixed magnetic monopole is given, based on a representation of the corresponding vector potential by means of a distribution. The results are closely similar to those obtained in the work of Wu and Yang, which stems from ideas borrowed from mathematical fiber bundle theory. We believe that our method follows more closely the usual quantum mechanical procedures and provides an alternative approach to that of Wu and Yang. Although the present paper deals with non-relativistic problem, it is clear that the extension to the case of a Pauli or Dirac particle can be easily done using spinor monopole harmonics.     

Yield management for privatised air traffic control?

Air Traffic Control (ATC) ensures the safe and expeditious passage of all aircraft in controlled airspace, usually, airspace above 5000–7000?ft or around main airports. Serious airspace congestion has led to demands for more cost-effective ATC and to plans to privatise air traffic services in the UK. These trends offer numerous opportunities to apply Operational Research in the 21st century, especially to improve information management. In a context of ATC privatisation, this paper investigates how applicable yield management (YM) policies are to European ATC. Necessary conditions for the use of YM are examined and difficulties in using YM for ATC are identified. Following this, possible YM solutions are outlined. Finally, the implications of YM for airspace users are addressed.     

Synthesis and Stereochemistry of (1S,3S,4S,7R11R)-3-(4-Nitrophenyl)-11-aza-2,6-dioxatricyclo[5,3,1,04,11]undecane

The reaction of (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediol with glutaraldehyde has been studied. It has been established on the basis of AM1 and PM3 calculations and ¹H NMR spectra recorded in the presence of the shift reagent Eu(fod)₃ that (1S,3S,4S,7R,11R)-3-(4-nitrophenyl)-11-aza-2,6-dioxatricyclo[5,3,1,0^4,11]undecane is formed as the result of the reaction.     

Integrability,existence of global solutions,and wave breaking criteria for a generalization of the Camassa–Holm equation

Recent generalizations of the Camassa–Holm equation are studied from the point of view of existence of global solutions, criteria for wave breaking phenomena and integrability. We provide conditions, based on lower bounds for the first spatial derivative of local solutions, for global well-posedness in Sobolev spaces for the family under consideration. Moreover, we prove that wave breaking phenomena occurs under certain mild hypothesis. Based on the machinery developed by Dubrovin [Commun. Math. Phys. 267, 117–139 (2006)] regarding bi-Hamiltonian deformations, we introduce the notion of quasi-integrability and prove that there exists a unique bi-Hamiltonian structure for the equation only when it is reduced to the Dullin–Gotwald–Holm equation. Our results suggest that a recent shallow water model incorporating Coriollis effects is integrable only in specific situations. Finally, to finish the scheme of geometric integrability of the family of equations initiated in a previous work, we prove that the Dullin–Gotwald–Holm equation describes pseudo-spherical surfaces.     

Salbutamol extraction from urine and its stability in different solutions: identification of methylation products and validation of a quantitative analytical method

Salbutamol is commonly used in asthma treatment, being considered a short‐effect bronchodilator. This drug poses special interest in certain fields of chemical analysis, such as food, clinical and doping analyses, in which it needs to be analyzed with quantitative precision and accuracy. Salbutamol, however, is known to degrade under certain conditions and this is critical if quantitative results must be generated. The present work aimed to investigate salbutamol extraction from urine samples, to determine whether salbutamol is unstable in other solvents as well as in urine samples, to elucidate the structures of the possible degradation products and to validate an analytical method using the extraction procedure evaluated. Stability investigations were performed in urine at different pH values, in methanol and acetone at different temperatures. Semi‐preparative liquid chromatography was performed for the isolation of degradation products, and gas chromatography coupled to mass spectrometry as well as nuclear magnetic resonance were used for identification. Three unreported methylation products were detected in methanolic solutions and had their structures elucidated. Urine samples showed a reduction in salbutamol concentration of up to 25.8% after 5 weeks. These results show that special care must be taken regarding salbutamol quantitative analyses, since degradation either in standard solutions or in urine could lead to incorrect values. Copyright © 2013 John Wiley & Sons, Ltd.