Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances,II: Finite ducts with sources

The radiation of sound from a flanged duct system containing various hard-walled pressure sources and a finite length of non-uniformly lined duct is considered. Reflection coefficients, transmission losses and the directivity of the radiated field are evaluated. Direct comparisons between the results for the non-uniformly lined ducts, a uniformly lined duct and a hard-walled duct are made for fixed values of admittance, liner length and source distributions. Several interesting wave scattering characteristics which relate to the design of aircraft turbofan inlet liners are uncovered.     

Regge-pole dominance in a heavy-ion DWBA calculation

We show Regge-pole dominance in a representative heavy-ion DWBA calculation and display various pole manifestations in both calculated elastic and transfer quantities.     

Pickering emulsions with controllable stability

We prepare solid-stabilized emulsions using paramagnetic particles at an oil/water interface that can undergo macroscopic phase separation upon application of an external magnetic field. A critical field strength is found for which emulsion droplets begin to translate into the continuous-phase fluid. At higher fields, the emulsions destabilize, leading to a fully phase-separated system. This effect is reversible, and long-term stability can be recovered by remixing the components with mechanical agitation.     

Selecting topology and connectivity through metal-directed macrocyclization reactions: a square planar palladium [2]catenate and two noninterlocked isomers

We report the synthesis of a [2]catenate using a square planar palladium(II) template, together with two isomers of the interlocked structure: a single tetradentate macrocycle that adopts a "figure of eight" conformation to encapsulate the metal and a complex in which the two macrocycles of the catenane are not interlocked. The three isomers can each be selectively formed depending on how the building blocks are assembled and cyclized. Olefin metathesis of both building blocks while they are attached to the metal gives the single large macrocycle in 77% yield. Cyclizing the monodentate unit prior to attaching both ligands to the metal gives the [2]catenate in 78% yield. Preforming the tridentate macrocycle produces a complex in two atropisomeric forms-threaded and nonthreaded-in a 2:3 ratio, which do not interconvert in dichloromethane at room temperature over 7 days. RCM of the nonthreaded atropisomer affords the complex with two noninterlocked macrocyclic ligands; RCM of the threaded atropisomer generates the topologically isomeric [2]catenate. Heating the acyclic atropisomers in acetonitrile provides a mechanism for their interconversion via ligand exchange, allowing the threaded:nonthreaded ratio to be varied from 2:3 to 8:1. All three fully ring-closed complexes were characterized unambiguously by 1H NMR spectroscopy and X-ray crystallography. As far as we are aware, this is the first time such a set of three formal topological and constitutional isomers has been described.     

Is energy self sufficiency a realistic goal for Canada?

Canada uses more energy per capita than any other major nation. The primary reasons are geography, climate, energy intensive industries and low energy prices. The country has substantial primary energy resources. This paper utilizes a dynamic energy policy model and a wide range of scenarios to investigate the possibility for long run energy self sufficiency and the related questions of timing, export possibilities and maintaining domestic energy prices below world levels.     

α-particle model of the rotation spectrum of 12C

It is shown that the 0⁺, 2⁺, 4⁺ rotation spectrum and an oblate deformed ground state for ¹²C are consistent with a simple α-particle model for its long range structure.