Low-temperature reactions: Tunnelling in space.

International audienceChemical reactions with activation barriers generally slow to a halt in the extreme cold of dense interstellar clouds. Low-temperature experiments on the reaction of OH with methanol have now shown that below 200 K there is a major acceleration in the rate that can only be explained by enhanced quantum mechanical tunnelling through the barrier

Fostering coastal resilience to climate change vulnerability in Bangladesh, Brazil, Cameroon and Uruguay: a cross-country comparison

© 2017, Springer Science+Business Media B.V. This paper describes a comparative study of four different cases on vulnerability, hazards and adaptive capacity to climate threats in coastal areas and communities in four developing countries: Bangladesh, Brazil, Cameroon and Uruguay. Coastal areas are vulnerable to sea-level rise (SLR), storm surges and flooding due to their (i) exposure, (ii) concentration of settlements, many of which occupied by less advantaged groups and (iii) the concentration of assets and services seen in these areas. The objective of the paper is twofold: (i) to evaluate current evidence of coastal vulnerability and adaptive capacity and (ii) to compare adaptation strategies being implemented in a sample of developing countries, focusing on successful ones. The followed approach for the case evaluation is based on (i) documenting observed threats and damages, (ii) using indicators of physical and socioeconomic vulnerability and adaptive capacity status and (iii) selecting examples of successful responses. Major conclusions based on cross-case comparison are (a) the studied countries show different vulnerability, adaptive capacity and implementation of responses, (b) innovative community-based (CBA) and ecosystem-based adaptation (EbA) and (c) early warning systems are key approaches and tools to foster climate resilience. A recommendation to foster the resilience of coastal communities and services is that efforts in innovative adaptation strategies to sea-level rise should be intensified and integrated with climate risk management within the national adaption plans (NAPAs) in order to reduce the impacts of hazards

C + C₂H₂: a key reaction in interstellar chemistry

The fast reaction between C(3P) and C2H2 is thought to be an important process in dense interstellar clouds as it provides a mechanism for the growth of carbon chains. This feature article describes a complementary series of recent experimental and theoretical investigations on this reaction. This includes kinetic measurements of rate constants at low temperatures and crossed molecular beam determinations of integral and differential cross sections. The theory employs first-principles electronic structure computations and wave packet dynamics to calculate cross sections and rate constants for forming the linear and cyclic isomers of C3H which can be formed in the reaction. The rate constant and cross section measurements show that there are no barriers in the potential surface for the reaction, whereas the differential cross section experiments provide new evidence for the formation of C3 + H2 products. The theoretical results of overall rate constants and cross sections agree quite well with the experiments, and it is predicted that the linear isomer of C3H should be formed preferentially at low temperatures