Debut: collected studies on nitroxide-mediated controlled radical polymerization

176 hlm. : ilus. ; tab. ; 24 cm

How are we creative together?: comparing sociocognitive and sociocultural answers

The present article aims to distinguish between a sociocognitive and a sociocultural approach to forms of “collective” creativity. While the first is well-illustrated by studies of group or team creativity, the second has generally supported investigations of collaborative creativity, most of them performed in the last few decades. The comparison between these two fields takes different levels into account, from the epistemological position adopted to issues concerning the theories and methods used. Special attention is given to reviewing models of creativity. However, although the literature on group creativity contains several cognitive models, there is a scarcity of such constructions for collaborative creativity. This is why a secondary aim of this material is to introduce a sociocultural theoretical framework and discuss its implications for developing situated models of creativity. In the end, the similarities and differences between the two paradigms are examined with reference to both theory and research and arguments are given for why it would be beneficial for sociocognitivists and socioculturalists to engage in a more consistent dialogue

Introducing Porosity in Colloidal Biocoatings to Increase Bacterial Viability

A biocoating confines non-growing, metabolically-active bacteria within a synthetic colloidal polymer (i.e. latex) film. Bacteria encapsulated inside biocoatings can perform useful functions, such as a biocatalyst in wastewater treatment. A biocoating needs to have high a permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. Tuning the porosity architecture is a challenge. Here, we exploited rigid tubular nanoclays (halloysite) and non-toxic latex particles (with a relatively high glass transition temperature) as the colloidal “building blocks” to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of yellow fluorescent protein. A custom-built apparatus was used to measure the permeability of a fluorescein sodium salt in the biocoatings. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 110-4 m h-1. The effects of this increase in permeability was demonstrated through a specially-developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a non-optimized coating made from latex particles alone

Thermodynamical analysis of a double acting reciprocating magnetic refrigerator

SIGLEAvailable from CEN Saclay, Service de Documentation, 91191 - Gif-sur-Yvette Cedex (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Tracking the impacts of El Niño drought and fire in human-modified Amazonian forests

With humanity facing an unprecedented climate crisis, the conservation of tropical forests has never been so important – their vast terrestrial carbon stocks can be turned into emissions by climatic and human disturbances. However, the duration of these effects is poorly understood, and it is unclear whether impacts are amplified in forests with a history of previous human disturbance. Here, we focus on the Amazonian epicenter of the 2015–16 El Niño, a region that encompasses 1.2% of the Brazilian Amazon. We quantify, at high temporal resolution, the impacts of an extreme El Niño (EN) drought and extensive forest fires on plant mortality and carbon loss in undisturbed and human-modified forests. Mortality remained higher than pre-El Niño levels for 36 mo in EN-drought–affected forests and for 30 mo in EN-fire–affected forests. In EN-fire–affected forests, human disturbance significantly increased plant mortality. Our investigation of the ecological and physiological predictors of tree mortality showed that trees with lower wood density, bark thickness and leaf nitrogen content, as well as those that experienced greater fire intensity, were more vulnerable. Across the region, the 2015–16 El Niño led to the death of an estimated 2.5 ± 0.3 billion stems, resulting in emissions of 495 ± 94 Tg CO2. Three years after the El Niño, plant growth and recruitment had offset only 37% of emissions. Our results show that limiting forest disturbance will not only help maintain carbon stocks, but will also maximize the resistance of Amazonian forests if fires do occur.