Optical control of electric-field poling in LiTaO₃

We present a room temperature technique for optically inducing periodic domain-inverted structures in bulk (0.2mm thick) LiTaO3. By simultaneous application of an electric field and patterned illumination using UV wavelengths (351nm and 364nm) we demonstrate modulation of the resulting domain profile. We discuss the origins of the observed optical effect and describe our results from repeated domain switching, by cycling the electric field

Influence of light on the coercive field of repoled strontium barium niobate (SBN); the role of secondary repoling

We have found that the application of light to strontium barium niobate (SBN) during electrical repoling stabilises the newly formed domains. This stabilisation becomes apparent when repoling the crystal back into its original domain direction as a change in the distribution of displacement current as a function of voltage. This appears to be the process underlying the other recent work in the area of optical control of domain structures for quasi phase-matching of nonlinear processes. We present an explanation for this effect in terms of the micro-domain structure of SBN. This model should aid in the search for new materials for optical periodic poling

The UN local communities and Indigenous peoples' platform: A traditional ecological knowledge-based evaluation

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2019 The Authors. WIREs Climate Change published by Wiley Periodicals, Inc.This review evaluates the potential of the proposed local communities and Indigenous peoples’ platform to effectively engage traditional ecological knowledge (TEK) for climate policy. Specifically, we assess the platform's potential to enable greater representation and participation of Indigenous peoples (IPs) within the United Nations Framework Convention on Climate Change (UNFCCC). An analytical framework based on the extensive TEK and environmental management literature is developed, with a set of criteria identified against which to evaluate the platform. We find that although the process of designing the platform appears to be inclusive of Indigenous views, the structure itself does not recognize the roles that unequal power relations and colonialism play in marginalizing IPs. Limited attention is paid to the institutional barriers within the UNFCCC and the drawbacks of pursuing knowledge “integration” as an end in itself. Based on this, recommendations for improving the platform structure are put forward including using a rights based framing, giving greater decision-making power to IPs, and developing mechanisms to ensure the holistic integrity of TEK and build the overall resilience of climate mitigation and adaptation systems.Ye

Zeroing in on more photons and gluons

We discuss radiation zeros that are found in gauge tree amplitudes for processes involving multi-photon emission. Previous results are clarified by examples and by further elaboration. The conditions under which such amplitude zeros occur are identical in form to those for the single-photon zeros, and all radiated photons must travel parallel to each other. Any other neutral particle likewise must be massless (e.g. gluon) and travel in that common direction. The relevance to questions like gluon jet identification and computational checks is considered. We use examples to show how certain multi-photon amplitudes evade the zeros, and to demonstrate the connection to a more general result, the decoupling of an external electromagnetic plane wave in the ``null zone". Brief comments are made about zeros associated with other gauge-boson emission.Comment: 26 page

Climate change in the Capricorn Coast: an analysis of stewardship potential

Climate change in the Keppel Bay and Capricorn Coast region: an analysis of stewardship potential was a research project undertaken by the University of the Sunshine Coast, Queensland in 2010, in collaboration with the Great Barrier Reef Marine Park Authority (GBRMPA), Townsville, Queensland. The project collected data on ways to increase community resilience to the impacts of climate change through fostering stewardship in the Capricorn Coast. Data were obtained by engaging key stakeholders through an online survey. The research aims were: • to develop and test a conceptual framework for understanding stewardship in relation to building resilience to climate change in the Capricorn Coast region, and • to identify barriers and opportunities to successful stewardship to build community-based resilience to the impacts of climate change on the Capricorn Coast.ID: 183

Quantum dot emission from site-controlled ngan/gan micropyramid arrays

InxGa1−xN quantum dots have been fabricated by the selective growth of GaN micropyramid arrays topped with InGaN/GaN quantum wells. The spatially, spectrally, and time-resolved emission properties of these structures were measured using cathodoluminescence hyperspectral imaging and low-temperature microphotoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit decay lifetimes of approximately 0.5 ns, with linewidths down to 650 me

Quartic Gauge Couplings and the Radiation Zero in pp to l nu gamma gamma events at the LHC

We report a study of the process pp to l nu gamma gamma at CERN's Large Hadron Collider, using a leading order partonic-level event generator interfaced to the Pythia program for showering and hadronisation and a with a generic detector simulation. The process is sensitive to possible anomalous quartic gauge boson couplings of the form W W gamma gamma. It is shown how unitarity-safe limits may be placed on these anomalous couplings by applying a binned maximum likelihood fit to the distribution of the two-photon invariant mass, M(gamma gamma), below a cutoff of 1TeV. Assuming 30fb-1 of integrated luminosity, the expected limits are two orders of magnitude tighter than those available from LEP. It is also demonstrated how the Standard Model radiation zero feature of the qq to W gamma gamma process may be observed in the difference between the two-photon and charged lepton pseudo-rapidities.Comment: 9 pages, 7 figure

Planktivores and plankton dynamics : effects of fish biomass and planktivore type

Les auteurs ont quantifié les incidences de la biomasse et du type de planctophage dans le cadre d'une étude expérimentale en mésocosmes. Cette étude était conçue en fonction d'un plan factoriel d'expérience combinant cinq niveaux de biomasse de poisson (de O, à 75 g/m3) avec deux types de planctophage, soit l'alose à gésier (#Dorosoma cepedianum), un filtreur, et le crapet arlequin (#Lepomis macrochirus), un chasseur visuel. Une augmentation de la biomasse de poisson était accompagnée d'une baisse du nombre de cladocères, de cyclopoïdes et de chironomides et de la teneur en phosphore particulaire ...; inversement l'abondance de rotifères, de flagellés unicellulaires, d'algues vertes coloniales et unicellulaires, de diatomées pennées, la productivité primaire, la turbidité et les teneurs en chlorophylle a, en phosphore total ... ont augmenté ... Bien que la chaîne des cascades trophiques de l'alose à gésier et celle du crapet soleil soient différentes, la biomasse de poisson jouait un rôle plus important que le type de planctophage comme régulateur des communautés planctoniques et de la qualité de l'eau. (D'après résumé d'auteur