A new constitutive model for prediction of impact rates response of polypropylene

This paper proposes a new constitutive model for predicting the impact rates response of polypropylene. Impact rates, as used here, refer to strain rates greater than 1000 1/s. The model is a physically based, three-dimensional constitutive model which incorporates the contributions of the amorphous, crystalline, pseudo-amorphous and entanglement networks to the constitutive response of polypropylene. The model mathematics is based on the well-known Glass-Rubber model originally developed for glassy polymers but the arguments have herein been extended to semi-crystalline polymers. In order to predict the impact rates behaviour of polypropylene, the model exploits the well-known framework of multiple processes yielding of polymers. This work argues that two dominant viscoelastic relaxation processes – the alpha- and beta-processes – can be associated with the yield responses of polypropylene observed at low-rate-dominant and impact-rates dominant loading regimes. Compression test data on polypropylene have been used to validate the model. The study has found that the model predicts quite well the experimentally observed nonlinear rate-dependent impact response of polypropylene

Label-free smartphone quantitation of bacteria by darkfield imaging of light scattering in fluoropolymer micro capillary film allows portable detection of bacteriophage lysis

Conventional methods for the detection and quantitation of bacteria are slow, laborious and require a laboratory. Microfluidic systems offer faster and portable testing, and smartphone cameras can record colorimetric or fluorometric bioassays, but this requires dye addition. Here, we demonstrate for the first time label-free smartphone detection of bacterial light scattering by darkfield microfluidic imaging to measure bacteria and bacteriophage lysis. A single LED and portable 3D printed imaging box allowed bacterial concentration and growth to be measured by direct imaging of bacterial light scattering. Bacteriophage lysis was detected within a 10-channel microfluidic device made from melt-extruded fluoropolymer micro capillary film, allowing rapid detection of host specificity. Elimination of unwanted reflections and optimising illumination angle are critical for successful darkfield bacterial imaging, with 15° giving maximal intensity. Bacterial sedimentation was directly observed within microfluidic devices, and detection sensitivity significantly increased by allowing bacteria to sediment for 30 min. With this simple, low-cost, 3D printed system bacterial concentrations down to an optical density of 0.1 could be measured corresponding to 8 × 104 colony forming units (CFU) per microdevice, approaching the sensitivity of conventional spectrophotometers. Bacteriophage lysis could be detected at a range of starting cell concentrations. With a low starting cell concentration, the increase in light scatter signal with incubation was prevented in the presence of bacteriophage. Conversely, with high starting cell concentration, the light scatter signal detected at the start was clearly eliminated when phage were added, indicating this simple system allows direct visualisation of bacteriophage eliminating light scattering by lysis

The asymmetric synthesis of aziridines

The report contains an overview of methods available for asymmetric preparation of a range of 1H- aziridines and their N-substituted analogue

A practical alternative to sulfonyl activation of aziridines: Ring-opening of N-diphenylphosphinoyl aziridines by carbon nucleophiles

The ring-opening reaction of N-diphenylphosphinoylaziridines by Copper (I)-modified Grignard reagents proceeds in good to excellent yield and with complete regiospecificit

The synthesis and reactivity of n-diphenylphosphinyl aziridines

The synthesis of enantiopure N-diphenylphosphinyl (Dpp) protected aziridines from 2-aminoalcohols and the reactions of these aziridines with a range of nucleophiles is described

Preparation and ring-opening reactions of N-Diphenylphosphinyl aziridines

Monochiral N-Diphenyphosphinyl aziridines(n-Dpp aziridines)may efficiently be prepared from monochiral 2-aminoalcohols. Such aziridines undergo ring-opening reaction with a variety of nucleophiles in good yield. Dephosphinylation is accomplished under mild conditions