Adsorption mechanisms of fatty acids on fluorite unraveled by infrared spectroscopy and first-principles calculations.

HYPOTHESIS: The adsorption mechanisms of fatty acids on minerals are largely debated from years, and their understanding is now required to improve flotation processing in the critical context of raw materials. Three wavenumbers have been observed in the literature for the asymmetric stretching vibration of COO- after the adsorption of fatty acids on mineral surfaces. They have been interpreted as different adsorbed forms, such as a precipitate formation, an adsorption of sole or bridged carboxylates, an anion exchange, or adsorbed modes, such as monodentate or bidentate configurations. EXPERIMENTS/THEORY: Diffuse reflectance infrared Fourier transform spectroscopy was combined with ab initio molecular dynamics simulations and simulation of infrared spectra. Fluorite and sodium octanoate - or longer-chain fatty acids - were used as prototypical materials for all the investigations. FINDINGS: At low fatty acids concentration, the asymmetric stretching vibration of COO- peaks at 1560 cm-1 while, at higher concentration, this infrared band converts into a doublet peaking at 1535 and 1575 cm-1. Using simulations, we assign the band at 1560 cm-1 to the adsorption of a carboxylate molecule bridged on a sodium counter-cation and the doublet at 1535 and 1575 cm-1 to the adsorption of the sole carboxylate anion under a monodentate or a bidentate binuclear configuration, respectively. The formation of an adsorbed layer on the mineral surface is initiated by the adsorption of a sodium carboxylate and followed by the adsorption of mixed sole anionic forms. The role of the carboxylate counter-cation is highlighted for the first time, which was totally ignored in the literature beforehand. This particularly opens the path to the development of innovative strategies to enhance the separation contrast between minerals, which is of uttermost importance for the recovery of critical raw materials.

Is There Any Evidence for Rapid, Genetically-Based, Climatic Niche Expansion in the Invasive Common Ragweed?

Climatic niche shifts have been documented in a number of invasive species by comparing the native and adventive climatic ranges in which they occur. However, these shifts likely represent changes in the realized climatic niches of invasive species, and may not necessarily be driven by genetic changes in climatic affinities. Until now the role of rapid niche evolution in the spread of invasive species remains a challenging issue with conflicting results. Here, we document a likely genetically-based climatic niche expansion of an annual plant invader, the common ragweed (Ambrosia artemisiifolia L.), a highly allergenic invasive species causing substantial public health issues. To do so, we looked for recent evolutionary change at the upward migration front of its adventive range in the French Alps. Based on species climatic niche models estimated at both global and regional scales we stratified our sampling design to adequately capture the species niche, and localized populations suspected of niche expansion. Using a combination of species niche modeling, landscape genetics models and common garden measurements, we then related the species genetic structure and its phenotypic architecture across the climatic niche. Our results strongly suggest that the common ragweed is rapidly adapting to local climatic conditions at its invasion front and that it currently expands its niche toward colder and formerly unsuitable climates in the French Alps (i.e. in sites where niche models would not predict its occurrence). Such results, showing that species climatic niches can evolve on very short time scales, have important implications for predictive models of biological invasions that do not account for evolutionary processes.

Interest of the preliminary risk analysis method in a central sterile supply department.

OBJECTIVES: In order to improve its quality-assurance programme based on ISO 9001, the Central Sterile Supply Department of a public university hospital has performed a prospective risk analysis using the Preliminary Risk Analysis method (PRA). The objectives were the achievement of a global risk mapping related to the whole process of sterilising medical devices, and second, the implementation of corrective measures to reduce identified risks. METHODS: A multidisciplinary team, formed in January 2008, validated results at each step of the study. During the analysis, 416 hazardous situations were identified, among which 81 were quoted first in priority and led to the description of 141 risk scenarios. The PRA team assessed 42 scenarios with risk ranking assessed as 'acceptable under control' or 'unacceptable.' They adopted 23 follow-up actions measures and 13 safety parameters. RESULTS AND DISCUSSION: The PRA constitutes an appropriate tool for assessing quality-improvement policy and safety in healthcare facilities that can be easily integrated into standard quality-management systems.