Combining configurational entropy and self-concentration to describe the component dynamics in miscible polymer blends

We provide a new approach to describe the component segmental dynamics of miscible polymer blends combining the concept of chain connectivity, expressed in terms of the self-concentration, and the Adam-Gibbs model. The results show an excellent agreement between the prediction of our approach and the experimental data. The self-concentrations obtained yield length scales between 1 and 3.2 nm depending on the temperature, the flexibility of the polymer, expressed in terms of the Kuhn segment, and its concentration in the blends, at temperatures above the glass transition range of the blend.     

Acylaluminum dichlorides

Evidence has been obtained for the formation of acylaluminium dichlorides by transmetalation between Cp₂Zr(Cl)(acyl) and AlCl₃. They have been shown to be reactive toward electrophiles at both the carbon and the oxygen of the acyl group.     

Explicit calculation of a tricritical point in a Pauli paramagnetically limited superconductor

We extend the Maki-Tsuneto Green's function formulation for the critical magnetic field vs temperature of a Pauli paramagnetically limited thin film superconductor to include the field conjugate to the order parameter and show the system displays a tricritical point. We present numerical calculations within the mean field theory in the neighborhood of the tricritical point and describe an explicit experimental arrangement for producing an adjustable staggered field.     

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.     

Forced response of a cantilever beam with a dry friction damper attached,part I: Theory

A theoretical-experimental study of the forced vibration response of a cantilevered beam with Coulomb damping non-linearity is described. Particular emphasis is placed upon the types of non-linear behavior and system response spectral characteristics observed theoretically and experimentally, upon the design of the experimental apparatus and the utilization of associated instrumentation, and upon the methodology developed for system calibration. Several system configurations are explored, with similarities and deviations analyzed and discussed. This paper, Part I, is devoted to the theory and the companion paper, Part II [1] to the experiments including correlation with theory.     

Ring inversion process for a series of 3,5‐dialkyl‐1‐oxa‐3,5‐diazacyclohexanes: 1H DNMR study and semiempirical calculations

The ring inversion process for a series of 3,5‐dialkyl‐1‐oxa‐3,5‐diazacyclohexanes was studied using proton dynamic nuclear magnetic resonance (¹H DNMR) spectroscopy in conjunction with semiempirical calculations. At low temperature, the ring methylene protons decoalesced into two AB spin systems in a 2:1 ratio. Lineshape simulations of the DNMR spectra provided first‐order rate constants for magnetic exchange. The energy barrier for each inversion reaction was calculated from the respective rate constants. In general, as the size of the N‐alkyl group increased, the barrier to ring inversion decreased. A similar trend was seen in semiempirical calculations that modeled the ring inversion process. Copyright © 2010 John Wiley & Sons, Ltd.     

da Vinci fluids,catch-up dynamics and dense granular flow

We introduce and study a da Vinci fluid, a fluid whose dissipation is dominated by solid friction. We analyse the flow rheology of a discrete model and then coarse-grain it to the continuum. We find that the model gives rise to behaviour that is characteristic of dense granular fluids. In particular, it leads to plug flow. We analyse the nucleation mechanism of plugs and their development. We find that plug boundaries generically expand and we calculate the growth rate of plug regions. In systems whose internal effective dynamic and static friction coefficients are relatively uniform we find that the linear size of plug regions grows as (time)^1/3 . The suitability of the model to granular materials is discussed.     

Efficient optimisation of per-channel pre-compensation in WDM 20-Gbit/s RZ-DPSK transmission in non-slope matched submarine links

We propose a computationally efficient method to the per-channel dispersion optimisation applied to 50 GHz-spaced N × 20-Gbit/s wavelength division multiplexing return-to-zero differential phase shift keying transmission in non-zero dispersion-shifted fibre based submarine systems.