Collective resonances in plasmonic crystals: Size matters

Periodic arrays of metallic nanoparticles may sustain Surface Lattice Resonances (SLRs), which are collective resonances associated with the diffractive coupling of Localized Surface Plasmon Resonances (LSPRs). By investigating a series of arrays with varying number of particles, we traced the evolution of SLRs to its origins. Polarization resolved extinction spectra of arrays formed by a few nanoparticles were measured, and found to be in very good agreement with calculations based on a coupled dipole model. Finite size effects on the optical properties of the arrays are observed, and our results provide insight into the characteristic length scales for collective plasmonic effects: for arrays smaller than 5 x 5 particles, the Q-factors of SLRs are lower than those of LSPRs; for arrays larger than 20 x 20 particles, the Q-factors of SLRs saturate at a much larger value than those of LSPRs; in between, the Q-factors of SLRs are an increasing function of the number of particles in the array.Comment: 4 figure

L'homme et l'animal dans le bassin du lac Tchad

Les Mafa, cultivateurs de mil des Monts Mandara, élèvent aussi quelques poules et du petit bétail. Le bovin, élevé dans un but essentiellement rituel, était sacrifié lors de la fête du taureau, maray. Les vaches, rares sur les pentes en terrasses du pays mafa, ne faisaient pas partie du système social : elles n'entrent pas dans la compensation matrimoniale et ne figurent pas dans les histoires qui opposent animaux domestiques et animaux sauvages. Le taureau "sacré" au contraire était sacrifié pour assurer la perpétuation des clans patrilinéaires. Cependant, de façon surprenante, en 1997 des étudiants mentionnent les vaches comme si elles avaient toujours été partie intégrante du système économique. Il s'agit soit de différences régionales, soit d'investissements nouveaux des Mafa grâce aux moyens apportés par des salaires extérieurs. La place nouvelle des vaches dans la société mafa est examinées en relation avec celle du taureau "sacré" du passé. (Résumé d'auteur

Will the Sustainable Development Goals address the links between poverty and the natural environment?

The relationships between the natural environment and poverty have been a central theme in the sustainability and development literatures. However, they have been less influential in mainstream international development and conservation policies, which often neglect or fail to adequately address these relationships. This paper examines how the Sustainable Development Goals (SDGs) may influence the framing of environment-poverty relationships. We argue that the SDGs’ comprehensive nature could provide an opportunity for better environment-poverty integration. To realise this potential, SDG-related activities will need to challenge the institutional status quo; transform how we measure, understand and implement development; design interventions that reflect local visions of development; make trade-offs between SDGs explicit; and address ultimate drivers of environmental degradation and poverty.Cambridge Humanities Research Gran

Estimating a frequency unseen:an application to ornithology

The second author is involved in a capture-mark-recapture study of some wader species. Part of his program deals with resight observations. On a particular day he visually inspects a fairly stable population to identify the ringed birds by reading their ring-number. Some ringed birds will be missed, so observations are repeated on other days. The issue of main interest is whether, after some repetitions, we can be sufficiently sure that all the ringed birds in the population have been identified or, equivalently, that the frequency of unseen birds is zero. Most current theory is concerned with an asymptotic setting. In our 'exact' context the emphasis is on the determination of the 'probability' that the frequency of unseen birds is zero. This issue is settled by considering the more general problem of 'estimating' the frequency of the unseen birds by providing a predictive inference in the form of a probability distribution. We develop methods of inference based on the assumption of a bird-independent probability p(i) of identifying a ringed bird on day i, as well as without this assumption. In Section 5 we critically examine these approaches