Absolute absorption and fluorescence measurements over a dynamic range of 106^6 with cavity-enhanced laser-induced fluorescence

We describe a novel experimental setup that combines the advantages of both laser-induced fluorescence and cavity ring-down techniques. The simultaneous and correlated measurement of the ring-down and fluorescence signals yields absolute absorption coefficients for the fluorescence measurement. The combined measurement is conducted with the same sample in a single, pulsed laser beam. The fluorescence measurement extends the dynamic range of a stand-alone cavity ring-down setup from typically three to at least six orders of magnitude. The presence of the cavity improves the quality of the signal, in particular the signal-to-noise ratio. The methodology, dubbed cavity-enhanced laser-induced fluorescence (CELIF), is developed and rigorously tested against the spectroscopy of 1,4-bis(phenylethynyl)benzene in a molecular beam and density measurements in a cell. We outline how the method can be utilised to determine absolute quantities: absorption cross sections, sample densities and fluorescence quantum yields.Comment: 12 pages, 6 figures, submitted to J. Chem. Phy

Deliberative democracy and the climate crisis

No democratic state has yet implemented a climate plan strong enough to meet the goals of the Paris Agreement. This has led some to argue that democracy cannot cope with a challenge of this magnitude. In this article, we take stock of the claim that a more deliberative democratic system can strengthen our ability to respond effectively to the climate crisis. The most visible development in this direction is the recent citizens’ assemblies on climate change in Ireland, France, and the UK. We begin our analysis of the promise of deliberative democracy with a recognition of the difficulties that democracies face in tackling climate change, including short-termism; the ways in which scientific and expert evidence are used; the influence of powerful political interests; and the relationship between people and the politicians that represent them. We then introduce the theoretical tradition of deliberative democracy and examine how it might ameliorate the challenges democracies face in responding to the climate crisis. We evaluate the contribution of deliberative mini-publics, such as citizens’ assemblies and juries, and look beyond these formal processes to examine how deliberation can be embedded in political and social systems around the world. We conclude that deliberation-based reforms to democratic systems, including but not limited to deliberative mini-publics, are a necessary and potentially transformative ingredient in climate action

Complex networks created by aggregation

We study aggregation as a mechanism for the creation of complex networks. In this evolution process vertices merge together, which increases the number of highly connected hubs. We study a range of complex network architectures produced by the aggregation. Fat-tailed (in particular, scale-free) distributions of connections are obtained both for networks with a finite number of vertices and growing networks. We observe a strong variation of a network structure with growing density of connections and find the phase transition of the condensation of edges. Finally, we demonstrate the importance of structural correlations in these networks.Comment: 12 pages, 13 figure