Radical housing (dis)encounters: reframing housing research and praxis

We came to this issue before the outbreak of Covid-19, and we release it amidst what feels like an entirely new, and yet also entirely known world-order—a place of multiple and multiplying crises that existed before the pandemic and continue, relentlessly, to render certain people, bodies and homes disposable. It is against this cruelty, but also with a renewed sense of radical hope in justice everywhere, that RHJ first came to be. The majority of contributions to Issue 2.2 emerge from a long process of designing and selecting participants for the event Radical Housing Encounters: translocal conversations on knowledge and praxis. This event was meant to take place in person, in three separate locations simultaneously, at the end of May 2020. Through it, we sought to define and re-define radical housing knowledge and practice, paying particular attention to diverse methodological, theoretical and ethical approaches deployed in both research and militant practice around the globe. While disappointed that the event could not take place as originally planned, its rationale and ethics of care are central to the making of this issue and are reflected in the texts of its contributors as well as the process of organising the issue

Asymmetries in adaptive optics point spread functions

An explanation for the origin of asymmetry along the preferential axis of the PSF of an AO system is developed. When phase errors from high altitude turbulence scintillate due to Fresnel propagation, wavefront amplitude errors may be spatially offset from residual phase errors. These correlated errors appear as asymmetry in the image plane under the Fraunhofer condition. In an analytic model with an open-loop AO system, the strength of the asymmetry is calculated for a single mode of phase aberration, which generalizes to two dimensions under a Fourier decomposition of the complex illumination. Other parameters included are the spatial offset of the AO correction, which is the wind velocity in the frozen flow regime multiplied by the effective AO time delay, and propagation distance or altitude of the turbulent layer. In this model, the asymmetry is strongest when the wind is slow and nearest to the coronagraphic mask when the turbulent layer is far away, such as when the telescope is pointing low towards the horizon. A great emphasis is made about the fact that the brighter asymmetric lobe of the PSF points in the opposite direction as the wind, which is consistent analytically with the clarification that the image plane electric field distribution is actually the inverse Fourier transform of the aperture plane. Validation of this understanding is made with observations taken from the Gemini Planet Imager, as well as being reproducible in end-to-end AO simulations

Integrating Conservation and Development in the Field: Implementing Ecosystem Service Projects

Ecosystem services can bridge biodiversity conservation and development needs, but there is little information available on how conservation organizations implement such projects. We documented 103 ecosystem service projects - from 37 countries - implemented by The Nature Conservancy (TNC) and the World Wildlife Fund (WWF). These projects commonly involved traditional conservation tactics, such as land purchase and restoration, but also adopted new approaches, such as targeting working landscapes, using new financial tools, and drawing new funding and partners from the corporate sector. We identified nine specific project types, characterized by consistent combinations of tools and activities. TNC and WWF used project types differently; TNC focused more on land purchase, whereas WWF concentrated more on developing markets. Both organizations showed some alignment of project type with socioeconomic conditions. For example, land purchases were used in countries with relatively secure property rights, while access to clean water or food was targeted when these human needs were unmet

Asymmetries in adaptive optics point spread functions

An explanation for the origin of asymmetry along the preferential axis of the point spread function (PSF) of an AO system is developed. When phase errors from high-altitude turbulence scintillate due to Fresnel propagation, wavefront amplitude errors may be spatially offset from residual phase errors. These correlated errors appear as asymmetry in the image plane under the Fraunhofer condition. In an analytic model with an open-loop AO system, the strength of the asymmetry is calculated for a single mode of phase aberration, which generalizes to two dimensions under a Fourier decomposition of the complex illumination. Other parameters included are the spatial offset of the AO correction, which is the wind velocity in the frozen flow regime multiplied by the effective AO time delay and propagation distance or altitude of the turbulent layer. In this model, the asymmetry is strongest when the wind is slow and nearest to the coronagraphic mask when the turbulent layer is far away, such as when the telescope is pointing low toward the horizon. A great emphasis is made about the fact that the brighter asymmetric lobe of the PSF points in the opposite direction as the wind, which is consistent analytically with the clarification that the image plane electric field distribution is actually the inverse Fourier transform of the aperture plane. Validation of this understanding is made with observations taken from the Gemini Planet Imager, as well as being reproducible in end-to-end AO simulations. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]