Polyethylene glycol in copper electrodeposition onto a rotating disk electrode

Many of the proprietary additive formulations that have been proposed to control the properties of metal electrodeposits include water soluble macromolecules. Among these are the hydrodynamically interesting polyethylene glycols ‘Polyox’. In the course of a rotating disk electrode study of the effects of additives in copper electrodeposition the present authors had cause to try the effects of low concentrations of Polyox in an acid copper sulphate plating solution. In the presence of an essential trace of chloride ion Polyox very strongly inhibited deposition below a critical overpotential at which current density rises extremely rapidly with increasing overpotential. These results suggest that below the critical overpotential chloride ions hold a film of Polyox onto the electrode surface and may also give the film some lateral cohesion. The film may be a Polyox-cuprous chloride complex. Striking spiral patterns form at the critical overpotential. Their characteristics are explained as the consequences of electrodeposition on a surface containing submicroscopic protrusions and depressions in conditions where current density increases very rapidly with potential.     

Difference in icosahedral short-range order in early and late transition metal liquids

New short-range order data are presented for equilibrium and undercooled liquids of Ti and Ni. These were obtained from in situ synchrotron x-ray diffraction measurements of electrostatically levitated droplets. While the short-range order of liquid Ni is icosahedral, consistent with Frank's hypothesis, significantly distorted icosahedral order is observed in liquid Ti. This is the first experimental observation of distorted icosahedral short-range order in any liquid, although this has been predicted by theoretical studies on atomic clusters.     

Improved surface chemistries, thin film deposition techniques, and stamp designs for nanotransfer printing

Nanotransfer printing represents an additive approach for patterning thin layers of solid materials with nanometer resolution. The surface chemistries, thin film deposition techniques, and stamp designs are all important for the proper operation of this method. This paper presents some details concerning processing procedures and other considerations needed for patterning two- and three-dimensional nanostructures with low density of defects and minimal distortions.     

Unified semi‐analytical wall boundary conditions for inviscid,laminar or turbulent flows in the meshless SPH method

Wall boundary conditions in smoothed particle hydrodynamics (SPH) is a key issue to perform accurate simulations. We propose here a new approach based on a renormalising factor for writing all boundary terms. This factor depends on the local shape of a wall and on the position of a particle relative to the wall, which is described by segments (in two‐dimensions), instead of the cumbersome fictitious or ghost particles used in most existing SPH models. By solving a dynamic equation for the renormalising factor, we significantly improve traditional wall treatment in SPH, for pressure forces, wall friction and turbulent conditions. The new model is demonstrated for cases including hydrostatic conditions for still water in a tank of complex geometry and a dam break over triangular bed profile with sharp angle where significant improved behaviour is obtained in comparison with the conventional boundary techniques. The latter case is also compared with a finite volume and volume‐of‐fluid scheme. The performance of the model for a two‐dimensional laminar flow in a channel is demonstrated where the profiles of velocity are in agreement with the theoretical ones, demonstrating that the derived wall shear stress balances the pressure gradient. Finally, the performance of the model is demonstrated for flow in a schematic fish pass where both the velocity field and turbulent viscosity fields are satisfactorily reproduced compared with mesh‐based codes. Copyright © 2012 John Wiley & Sons, Ltd.     

Eliminating false positive C4 sugar tests on New Zealand Manuka honey

Carbon isotope analyses (δ¹³C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C₄ sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein δ¹³C values should not be greater than +1.0‰, as it indicates the possibility of adulteration with syrups or sugars from C₄ plants such as high fructose corn syrup or cane sugar. We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non‐protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent δ¹³C value of protein further away from the δ¹³C value of the whole honey, giving a false positive result for added C₄ sugar. To eliminate a false positive C₄ sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein δ¹³C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C₄ sugar tests. Copyright © 2010 John Wiley & Sons, Ltd.     

Sharp van der Corput estimates and minimal divided differences

We find the sharp constant in a sublevel set estimate which arises in connection with van der Corput's lemma. In order to do this, we find the nodes that minimise divided differences. We go on to find the sharp constant in the first instance of the van der Corput lemma. With these bounds we improve the constant in the general van der Corput lemma, so that it is asymptotically sharp.