Perspectives from above and beyond the proton drip-line

This paper will review the dramatic increase in our knowledge of one and two proton unbound nuclei [1] such as recoil decay tagging [2] are revealing unique insights into the structure of nuclei beyond the proton drip-line. These studies of excited states provide complementary information to proton radioactivity studies, particularly regarding the role of deformation [3]. Radioactive beams are being used to study two-proton unbound resonances and to study explosive nuclear astrophysical reactions in the region of the proton drip-line.     

Modelling of natural graphite oxidation using thermal analysis techniques

A natural graphite recommended for use in nuclear applications was analyzed using thermogravimetric analysis. The oxidation behaviour was unlike that expected for flake-like particles. The dynamic data displayed an apparent bimodal reaction rate curve as a function of temperature and degree of conversion. Nevertheless, it was possible to model this behaviour with a single rate constant, i.e. without the need for a parallel reaction type of kinetic mechanism. The approach used in this paper to model the gas–solid reaction of graphite and oxygen, provides a consistent framework to test the validity of complementary isothermal and non-isothermal data for a specific solid state reaction.     

Centrifugal microfluidic system for primary amplification and secondary real-time PCR

Pre-amplification is a basis for numerous polymerase chain reaction (PCR) protocols but bears severe contamination risks due to handling of high-copy DNA samples. Therefore we developed a self-contained centrifugal microfluidic system comprising pre-stored reagents; it enables pre-amplification of specific DNA sequences prior to automated aliquoting and real-time PCR in a modified commercial thermocycler.     

Computational analysis of binary collisions of shear-thinning droplets

Scale-reduced models of transport processes and reactive mixing in sprays require improved closure laws, taking into account the characteristic features of elementary spray processes. The present paper investigates binary droplet collisions as such an elementary process. In the case of shear-thinning liquids considered here, this requires a profound understanding of the influence of the non-Newtonian fluid rheology on the flow inside the colliding drops and the collision complex dynamics. We employ direct numerical simulations based on the Volume-of-Fluid method to study these collisions. The results give a quantitative prediction of the resulting droplet collision diameter as well as a qualitative prediction of the complete time evolution. During collisions, extremely thin fluid lamellae appear inside the expanding complex. These have to be accounted for in a physically sound simulation and we apply a stabilization of the lamella to keep it from rupturing. The simulations show that in all considered cases an effective constant viscosity can be found a posteriori which leads to the same collision dynamics. But this effective viscosity is neither the mean nor the minimum viscosity.     

Photodegradation: a solution for the shopping bag “visual pollution” problem?

Plastic bags pose a “visual pollution” problem as they have a high surface-to-volume ratio and because they are often brightly coloured. Enhanced photo-oxidation is a possible route to accelerate the mineralisation of such litter. Thus we evaluated the effect of selected metal complexes and an anti-oxidant on the accelerated weathering of blown polyethylene and polypropylene films in a QUV tester. It was found that the additives were more effective in polypropylene than in polyethylene. The transition metal complexes, particularly ferric stearate, were very effective photodegradants. Copper stearate provided a measure of UV protection to polyethylene but not to polypropylene. Poly (1,2-dihydro-2,2,4-trimethylquinoline), a commercial anti-oxidant, also caused accelerated UV degradation. This is significant as its use as a prodegradant is not expected to adversely affect the recyclability of the polymers.     

Properties of Mosquito Repellent-Plasticized Poly(lactic acid) Strands

Poly(lactic acid) (PLA) is an attractive candidate for replacing petrochemical polymers because it is fully biodegradable. This study investigated the potential of PLA as a sustainable and environmentally friendly alternative material that can be developed into commercially viable wearable mosquito repellent devices with desirable characteristics. PLA strands containing DEET and IR3535 were prepared by twin screw extrusion compounding and simultaneously functioned as plasticizers for the polymer. The plasticizing effect was investigated by thermal and rheological studies. DSC studies showed that the addition of DEET and IR3535 into PLA strands reduced the glass transition temperature consistent with predictions of the Fox equation, thus proving their efficiency as plasticizers. The rheology of molten samples of neat PLA and PLA/repellents blends, evaluated at 200 °C, was consistent with shear-thinning pseudoplastic behaviour. Raman studies revealed a nonlinear concentration gradient for DEET in the PLA strand, indicating non-Fickian Type II transport controlling the desorption process. Release data obtained at 50 °C showed initial rapid release followed by a slower, near constant rate at longer times. The release rate data were fitted to a novel modification of the Peppas-Sahlin desorption model.