ACTIVITY, DEATH AND LYSIS DURING MICROBIAL GROWTH IN A CHEMOSTAT

The significance of death and lysis processes during microbial growth in chemostat cultures is discussed. A structured model is developed to describe such processes and the model is partially verified for carbon limited chemostat cultures of Klebsiella pneumoniae. It seems probable that death and lysis are coincident, when non-viable cells are not considered to be dead.     

The Concept Assessment Kit-Conservation: Supplementary data.

Evaluated the generalizability of M. L. Goldschmid and P. M. Bentler's (1968) Concept Assessment Kit using 21 male and 31 female 1st graders. Results reveal no difference between the Ss' ability to judge the quality of paired stimuli following the perceptual transformation of one member, and their ability to logically explain this equality. Reasons for the discrepancy between these results and those of Goldschmid and Bentler are discussed. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxygen transfer in co‐extruded multilayer active films for food packaging

Oxygen scavenger applications in flexible food packaging are still limited due to the difficulty to ensure scavenging activity during storage and throughout the product shelf life. To avoid fast inactivation of the scavenger, multilayer active structures can be realized by inserting the active layer between two or more inert layers. In this work, an unsteady‐state 1D reaction‐diffusion mass transfer model was developed for predicting and optimizing the barrier‐to‐oxygen performance and the physical configurations of the co‐extruded multilayer active films. The film configuration was a three‐layers structure composed of polyethylene terephthalate (PET) as external inert layers, and PET with a polymeric oxygen scavenger as the core reactive layer. Scavenging activity of the multilayer film increased with the reactive layer thickness. Oxygen absorption reaction at short times decreased proportionally with the thickness of the external layers. The most appropriate combinations of inert‐to‐active film thickness were studied and analyzed. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Electrocatalysis on solid oxide electrolytes

Conclusion Based on the preceding discussion, it is tentatively concluded that the oxide electrolyte cell acts as an oxygen concentration cell and the presence of point defects, such as interstitial protons on the oxide electrolyte surface, enhances the electrochemical reduction of O₂ at the cathode and may be responsible for catalysing the anodic oxidation of H₂.In order to obtain a much better understanding of the fundamentals of electrode processes involving point defects like interstitial protons and F-centres (V ₀ ^x ), it is necessary to investigate the current-overpotential characteristics by performing systematic experiments using various metals as electrodes and a variety of oxides (e.g. ceria) over a wide range of compositions as electrolytes. It is planned to examine the influence of the morphology of the surface on the current-overpotential characteristics by making electron-microscopic, and Auger spectroscopic, measurements. In future work, the magnitude of the individual cathodic and anodic overpotentials will be measured by the introduction of reference electrodes to the system. Having reference electrodes available will greatly facilitate the interpretation of the data and confirmation of proposed electrochemical mechanisms. Also, with the experimental arrangement of Fig. 1 variation of flow-rates normal to the disc, resulting in stagnation flows, will allow gas phase masstransfer rates to be varied, thus allowing the mechanism of the limiting current behaviour in the plateaus of Figs. 3 and 4 to be ascertained.     

Performance blends based on recycled polymers

The recent growth in the post-consumer recycling of plastics presents an opportunity for developing new, value-added blend products from the recycled polymers. However, in order to develop blends with useful performance characteristics, suitable techniques of compatibilization and impact modification must be employed. In this study, reactive toughening and compatibilization techniques have been found to be particularly useful in achieving high thermal embrittlement resistance in the blends of recycled poly(ethylene terephthalate) containing functionalized ethylene copolymers and polycarbonate. Reactive compatibilization of recycled polyolefin blends with poly(ethylene terephthalate) and polyamide has also been investigated.     

Interaction effects between the constituents of carbon artefacts during graphitisation

A crystallographic study, using X-ray diffraction techniques, has been made of the interaction effects between the constituents of coke-binder artefacts when heat-treated to graphitising temperatures. It is shown that petroleum and pitch cokes graphitise to a greater extent separately than when combined in petroleum coke/pitch binder artefacts, but for artefacts based entirely on either petroleum or pitch, this effect of the binder in retarding graphitisation of the grist coke is very much less.     

Evolution of phenolic compounds in virgin olive oil during storage

Phenolic compounds are of fundamental importance to the shelf life of virgin olive oils because of their antioxidative properties. In this paper, the evolution of simple and complex olive oil phenols during 18 mon of storage is studied by high-performance liquid chromatography (HPLC) analysis. The olive oils under examination were from various olive cultivars, harvested in two sectors in the same region at different stages of ripeness. The findings indicate that it is not the variety but rather the ripeness of the olives and the soil and climate that influence the phenol composition of virgin olive oil. In addition, a positive correlation was found between the age of the oils and the tyrosol to total phenols ratio. Lastly, gas chromatography-mass spectrometry analysis confirmed that the unidentified peaks detected by HPLC were of a phenolic nature.     

Predatory response of brown tree snakes to chemical stimuli from human skin

The brown tree snake (Boiga irregularis) is an exotic pest species on Pacific islands, most notably on Guam where it has caused considerable ecological and economic damage. On Guam, the snake commonly associates with people and can be found near or in human habitations. Bites are common, approximately 1 of 1200 emergency room visits to Guam hospitals were reported to be the result of B. irregularis bites; 80% of these victims were attacked while sleeping. Most of the attacks occurred on fingers and hands and the attacks appeared to be predatory, rather than defensive, in nature. In order to characterize the mechanism releasing this unusual behavior, we measured the predatory response of B. irregularis to chemical stimuli from humans and controls using a lab population that originated from Guam and a wild population from the species' native range in Queensland, Australia. To quantify behavior we measured the proportion of snakes displaying predatory behavior to each of the stimuli, the latency to attack, and the number of tongue-flicks displayed. We quantified predatory behavior using the tongue-flick attack score for repeated measures [TFAS(R)], a common method for quantifying predatory behavior in squamate reptiles. Captive brown tree snakes responded to human skin stimuli with feeding behavior, including predatory attacks, at the same frequency as they did to prey stimuli derived from mice, while never responding to controls with such behavior. Captive snakes also responded to human skin stimuli and prey stimuli with significantly higher TFAS(R) scores than to controls, although there were no differences between the human and mouse stimuli. Wild-caught animals in Australia also responded with predatory attacks to human skin stimuli, while not showing predatory behavior to a blank control and with higher TFAS(R) scores to human skin stimuli than to the control. As B. irregularis is a generalized predator that relies heavily on chemical signals to recognize prey, we hypothesize that the snakes recognize compounds on human skin that may be shared with other prey.     

Regenerative Recycling of Automotive Polymer Components: Poly(propylene) Based Car Bumpers

There is a dramatic loss in the mechanical performances at the end of the first life application of bumpers made by a poly(propylene) matrix (PP) and an ethylene‐propylene rubber copolymer as dispersed phase. The use of specific additives during the recycling strongly enhances the mechanical properties of these items. The on purpose designed additive contained a regenerative agent and an antioxidant system. The mixing action of the recycling process re‐establishes the phase compatibility; the antioxidants inhibit oxidation, which speeds up the degradation reactions in the recycling process; eventually the regenerative agent joins short chains possessing suitable reactive groups. These three effects play a different role in restoring original material performance in dependence of the recycling process: for instance the regenerative agent may be nearly useless if chain scission is not the dominant process in the recycling operation and the interfacial adhesion between rubber and the matrix does not assure automatically a ductile mechanical behaviour under impact conditions.

SEM micrograph of the fractured surface of the used bumper recycled with additives.