Polyolefin soluble polyisobutylene oligomer‐bound metallophthalocyanine and azo dye additives

Metallophthalocyanines prepared with polyisobutyl (PIB) substituents have very high solubility in organic solvents including saturated hydrocarbons, toluene, and other low polarity organic solvents. In heptane, PIB‐bound metallophthalocyanines have solubility of about 0.1 g/mL at 25 °C, solubility values that are significantly higher than other substituted metallophthalocyanines. PIB terminally functionalized with metallophthalocyanines as well as PIB containing terminal azo dye groups also dissolve in molten hydrocarbon polymers like polyethylene or polypropylene. Thus, these highly chromogenic PIB‐bound dyes can be incorporated uniformly into the polyolefins to form colored polymer solids on cooling. Because only a low concentration of a highly hydrocarbon compatible dye is used, the crystallinity and thermal properties of the colored polyolefin products are not significantly affected. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 545–551     

Iron Chelation in Local Infection

Iron is an essential element in multiple biochemical pathways in humans and pathogens. As part of the innate immune response in local infection, iron availability is restricted locally in order to reduce overproduction of reactive oxygen species by the host and to attenuate bacterial growth. This physiological regulation represents the rationale for the therapeutic use of iron chelators to support induced iron deprivation and to treat infections. In this review paper we discuss the importance of iron regulation through examples of local infection and the potential of iron chelation in treating infection.     

Spontaneous electric fields in films of cis-methyl formate

A recent publication described a new group of spontaneously polarized materials in which electric fields in excess of 10(8) V m(-1) may be present. This phenomenon arises through dipole alignment in solid films formed by straightforward deposition from vapour and characterises a novel class of materials. Here we present further results for the properties of these materials, focusing on films of cis-methyl formate. These films are shown to display some notable new chemical physics. We find the novel result that the degree of dipole alignment and the corresponding electric field in films of cis-methyl formate can have a counter-intuitive temperature dependence, increasing six-fold between 80 K and 89 K, in sharp contrast to the pronounced and expected fall with deposition temperature seen both here between 50 K and 75 K and in numerous other species. A theoretical model demonstrates that the switch of gradient with rising temperature should be a general phenomenon and is associated with crossing of a singularity in the gradient occurring at a set of critical values of temperature and alignment.     

Extended genus of torsion-free finitely generated nilpotent groups of class two

The extended genus of a nilpotent group N is the set of isomorphism classes of nilpotent groups M, not necessarily finitely generated, such that the p-localizations M _p , N _p are isomorphic for all primes p. In this article, for any torsion-free finitely generated nilpotent group N of nilpotency class 2, the extended genus of N is analyzed by assigning to each of its members a sequence of triads of matrices with rational entries, generalizing the sequential representation which has been exploited elsewhere in the case when N is abelian. This approach allows, among other things, to obtain examples of groups in the ordinary (Mislin) genus of N     

An investigation of interface-sharpening schemes for multi-phase mixture flows

This work evaluates several approaches for sharp phase interface-capturing in computations of multi-phase mixture flows. Attention is focused on algebraic interface-capturing strategies that fit directly within a finite-volume MUSCL-type framework, in which dimension-by-dimension reconstruction of interface states based on extrapolated fluid properties is the norm. In this scope, linear, sine-wave, and tangent hyperbola volume-fraction reconstructions are examined for a range of problems, including advection of a volume-fraction discontinuity, the Rayleigh–Taylor instability, a dam-break problem, an axisymmetric jet instability, the Rayleigh instability, and flow within an aerated-liquid injector. An implicit dual-time stepping approach, applied directly to a preconditioned form of the governing equations, is used for time-advancement. The results show that the sharpening strategies are successful in providing two-to-three-cell capturing of volume-fraction discontinuities.     

Composite Particles From Pickering‐Stabilized Radical Mediated Thiol‐Ene Suspension Polymerizations

Pickering stabilization is a facile method to create composite colloidal particles. Inorganic colloidal SiO₂ nanoparticles are often used as the stabilizer for particles instead of the more common amphiphilic surfactants. Here the use of this approach in radical‐mediated thiol‐ene suspension polymerizations using monomers 1,3,5‐triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TTT) and pentaerythritol tetrakis (3‐mercaptopropionate) (PETMP) is described. The resulting micron‐sized crosslinked poly(thioether) colloidal particles are coated with 80 nm silica nanoparticles. The addition of a small amount of various costabilizers is examined (hexadecane, cetyl alcohol and toluene), and while all yielded particles, cetyl alcohol provide more consistent results. Scanning electron microscopy and thermal analysis of the composite particles demonstrate morphologies that are consistent with a raspberry‐like structure. No significant changes to the glass transition temperature are observed, which is consistent with the silica nanoparticles being located at the surface of the polymer particles.     

Predicting water-to-cyclohexane partitioning of the SAMPL5 molecules using dielectric balancing of force fields

Alchemical transformation of solutes using classical fixed-charge force fields is a popular strategy for assessing the free energy of transfer in different environments. Accurate estimations of transfer between phases with significantly different polarities can be difficult because of the static nature of the force fields. Here, we report on an application of such calculations in the SAMPL5 experiment that also involves an effort in balancing solute and solvent interactions via their expected static dielectric constants. This strategy performs well with respect to predictive accuracy and correlation with unknown experimental values. We follow this by performing a series of retrospective investigations which highlight the potential importance of proper balancing in these systems, and we use a null hypothesis analysis to explore potential biases in the comparisons with experiment. The collective findings indicate that considerations of force field compatibility through dielectric behavior is a potential strategy for future improvements in transfer processes between disparate environments.     

A model for the voltammetric behaviour of TiO<Subscript>2</Subscript> memristors

A model is solved based on the Nernst Planck equation to calculate the diffusion and migration currents for a species in a thin layer (about 200 nm) confined between two electrodes. This is proposed to account for the current voltage behaviour of a memristor constructed in a similar fashion. At the working electrode, an electroactive species is oxidised and at the counter electrode, the same species is reduced. Upon application of a simple voltammetric waveform, the migration current exhibits a resistance profile at slow scan rates and hysteresis at faster scan rates, indicative of memristor behaviour.