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For low-order adaptive optics systems, a method that is able to correct for system aberrations in the final focal plane is presented. The paper presents a novel figure of merit, corresponding to the integrated non-normalized tip-tilt-free optical transfer function. The inherent singular value decomposition modal content of the interaction matrix is used to optimize this figure of merit. The method has proven to be stable and robust, providing a simple mean to facilitate diffraction limited imaging in an experimental setup for ophthalmic applications.

Drylands in Sub-Saharan Africa are subject to rapid and enduring population increase, agricultural expansion, land large-scale infrastructure developments, as well as climate change, affecting some 265 million pastoralists and agro-pastoralists. These changes are promoting a transition from traditional pastoralist ways of life characterized by seasonal mobility, towards more sedentary livelihoods based on more intensive and commercial uses of land-based resources. As part of of this ongoing transition, establishment of enclosures on pastoralist commons is emerging as a default, but highly contested, development pathway. Based on a review of the current enclosure debate across the natural, economic, and social sciences, with a geographical focus on the East African drylands, we discuss the potential and limitations of enclosures as land management tool, and propose a conceptual framework for how enclosures can act as an integral part of sustainable pastoralist land use. Such a framework constitute an important piece of the puzzle for more productively linking the urgent need of innovative ways of managing pastoralist rangelands, to the present international and national commitments to restoration of degraded lands.

Triggered by urbanization and changing land use, coastal transformation is a rapidly increasing phenomenon in the global south, driving dramatic livelihoods impacts. However, the existing literature on small-scale fisheries (SSF) has paid little attention to the way coastal transformations shape conditions for SSF livelihoods communities. This study proposes a new orientation in SSF studies by exploring the assemblage of entangled sociomaterial processes that account for coastal transformations by investigating waterfront transformation in a fishing community in Karnataka, India. Drawing on ethnographic fieldwork, we conclude that an entanglement of sociomaterial processes produces unequal outcomes among stakeholders that subsequently reinforce the political and economic marginalization of certain groups of waterfront users. Moreover, the investigated context-specific waterfront assemblage intimately connects to the broader context of national fishery policy, urbanization, and tourism, directing t...

Efficiency and cost effectiveness are key to the development of new high-density materials with improved ductility and fatigue strength. Better lubricants and improved powder mixing techniques point the way to a comparatively low energy single press, single sinter approach…

Given the complexity of current social structures and environmental problems, attaining a truly sustainable society seems rather improbable today. Not only has society not been planned for the complexity of the preconditions and effects that sustainability entails, sustainability is also unlikely given current individual consumption patterns, prevailing economic worldviews, and the short‐term focus of political processes. In this context, transdisciplinary research is seen more and more as key to attaining social change towards sustainability. In order to do this, non‐academic actors must be extensively involved in knowledge production, and normative considerations have to be explicitly incorporated. This paper targets three key areas for discussion. These are participation, value rationality and mutual learning. The interactions of participation and value rationalities through mutual learning processes are developed through two examples of ongoing transdisciplinary research and collaboration in Western S...

Dryland livestock production systems are changing in many parts of the world, as a result of growing human populations and associated pressure on water and land. Based on a combination of social and natural science methods, we studied a 30-year transformation process from pastoralism to a livestock-based agro-pastoral system in northwestern Kenya, with the overall aim to increase the understanding of the ongoing transition towards intensified agro-pastoralist production systems in dryland East Africa. Key to this transformation was the use of enclosures for land rehabilitation, fodder production, and land and livestock management. Enclosures have more soil carbon and a higher vegetation cover than adjacent areas with open grazing. The level of adoption of enclosures as a management tool has been very high, and their use has enabled agricultural diversification, e.g. increased crop agriculture, poultry production and the inclusion of improved livestock. Following the use of enclosures, livelihoods have become less dependent on livestock migration, are increasingly directed towards agribusinesses and present new opportunities and constraints for women. These livelihood changes are closely associated with, and depend on, an ongoing privatization of land under different tenure regimes. The results indicate that the observed transformation provides opportunities for a pathway towards a sustainable livestock-based agro-pastoral system that could be valid in many dryland areas in East Africa. However, we also show that emergent risks of conflicts and inequalities in relation to land, triggered by the weakening of collective property rights, pose a threat to the sustainability of this pathway. Dryland livestock production systems are changing in many parts of the world, as a result of growing human populations and associated pressure on water and land. Based on a combination of social and natural science methods, we studied a 30-year transformation process from pastoralism to a livestock-based agro-pastoral system in northwestern Kenya, with the overall aim to increase the understanding of the ongoing transition towards intensified agro-pastoralist production systems in dryland East Africa. Key to this transformation was the use of enclosures for land rehabilitation, fodder production, and land and livestock management. Enclosures have more soil carbon and a higher vegetation cover than adjacent areas with open grazing. The level of adoption of enclosures as a management tool has been very high, and their use has enabled agricultural diversification, e.g. increased crop agriculture, poultry production and the inclusion of improved livestock. Following the use of enclosures, livelihoods have become less dependent on livestock migration, are increasingly directed towards agribusinesses and present new opportunities and constraints for women. These livelihood changes are closely associated with, and depend on, an ongoing privatization of land under different tenure regimes. The results indicate that the observed transformation provides opportunities for a pathway towards a sustainable livestock-based agro-pastoral system that could be valid in many dryland areas in East Africa. However, we also show that emergent risks of conflicts and inequalities in relation to land, triggered by the weakening of collective property rights, pose a threat to the sustainability of this pathway.

With global concern on climate change impacts, developing countries are given special attention due their susceptibility. In this paper, change and variability in climate, land use and farmers' perception, adaptation and response to change are examined in Danangou watershed in the Chinese Loess Plateau. The first focus is to look at how climate data recorded at meteorological stations recently have evolved, and how farmers perceived these changes. Further, we want to see how the farmers respond and adapt to climate variability and what the resulting impact on land use is. Finally, other factors causing change in land use are considered. Local precipitation and temperature instrumental data and interview data from farmers were used. The instrumental data shows that the climate is getting warmer and drier, the latter despite large interannual variability. The trend is seen on the local and regional level. Farmers' perception of climatic variability corresponds well with the data record. During the last 20 years, the farmers have become less dependent on agriculture by adopting a more diversified livelihood. This adaptation makes them less vulnerable to climate variability. It was found that government policies and reforms had a stronger influence on land use than climate variability. Small-scale farmers should therefore be considered as adaptive to changing situations, planned and non-consciously planned.

Retinal imaging is limited due to optical aberrations caused by imperfections in the optical media of the eye. Consequently, diffraction limited retinal imaging can be achieved if optical aberrations in the eye are measured and corrected. Information about retinal pathology and structure on a cellular level is thus not available in a clinical setting but only from histological studies of excised retinal tissue. In addition to limitations such as tissue shrinkage and distortion, the main limitation of histological preparations is that longitudinal studies of disease progression and/or results of medical treatment are not possible. Adaptive optics (AO) is the science, technology and art of capturing diffraction-limited images in adverse circumstances that would normally lead to strongly degraded image quality and loss of resolution. In non-military applications, it was first proposed and implemented in astronomy. AO technology has since been applied in many disciplines, including vision science, where retinal features down to a few microns can be resolved by correcting the aberrations of ocular optics. As the focus of this chapter is on AO retinal imaging, we will focus our description to this particular field.

Purpose To demonstrate non-invasive imaging of foveal capillary networks with a high-resolution wide-field dual-conjugate adaptive optics (DCAO) imaging instrument. Methods The foveal capillary networks of five normal subjects were imaged with a novel high-resolution wide-field DCAO instrument. The foveal avascular zone (FAZ) in each image was defined using a manual procedure. An automated algorithm was used to identify vessels and extract morphological FAZ and vessel parameters. Capillary densities were calculated in two annular regions of interest (ROI) outside the FAZ (500 µm and 750 µm outer radius from the foveal center). Results Results: Mean FAZ area was 0.302 ± 0.100 mm2 and mean capillary density (length/area) in the inner ROI was 38.0 ± 4.0 mm-1 and 36.4 ± 4.0 mm-1 in the outer ROI. The difference in ROI capillary density was not significant. Conclusion We have demonstrated our technique for non-invasive imaging and semi-automated detection. Analysis of foveal capillaries yields lower capillary densities than reported in histological studies, but similar results compared to the current clinical gold standard of fluorescein angiography and AO-SLO. The increased field of view of the DCAO instrument opens up new possibilities for high-resolution non-invasive clinical imaging of foveal capillaries.

Purpose The aim of this project is to apply the technique of multi-conjugate adaptive optics (MCAO) for high-resolution imaging of the retina over a wide field-of-view (FOV). Methods MCAO is the principal technique to overcome the limitations of conventional AO systems by increasing the corrected FOV. The current system incorporates two deformable mirrors (DMs). Optically, these two DMs correspond to separate planes along the optical axis of the eye. This allows the correction of field-dependent aberrations and subsequent wide-field high-resolution retinal imaging over a wide FOV. Normative data from healthy subjects was collected in order to determine clinical potential and limitations. Results We have demonstrated the MCAO concept with a current FOV of 7x7 deg on both model and human eyes. The diffraction-limited resolution is around 2 µm on the retina, allowing most cone photoreceptors to be resolved. Retinal morphology of healthy subjects was investigated. The estimated cone separation at a retinal eccentricity of 1.2 deg and 2.5 deg from the fovea was 6 µm and 9 µm, respectively, in agreement with the literature. The relatively narrow depth of focus enables us to image different layers of the retina. Focusing on deeper layers allows us to image the cone photoreceptor layer. By focusing on the upper layers we can also image the retinal capillary layer and nerve fibre layer with the same high resolution. Conclusion Our instrument allows retinal features down to 2 µm to be resolved over a 7x7 deg FOV. We believe that this new technique has a future potential for clinical imaging with an impact particularly important for early diagnosis of retinal diseases.

In this article we present a downscaled laboratory setup emulating five natural guide stars, a layered static atmosphere and a 7.5-m aperture telescope equipped with dual-conjugate adaptive optics at a wavelength of 2.2 microm. Three reconstruction alternatives were evaluated; conventional adaptive optics, field-averaged conventional adaptive optics and dual-conjugate adaptive optics. The results were compared with Zemaxsimulations of the setup. The expected increase of the size of the isoplanatic patch, using dual-conjugate adaptive optics, was confirmed.

Closed loop lab tests of a dual-conjugate adpative optics setup are presented. The corrected field of view is improved compared to ground-layer and single-conjugate adaptive optics. The setup is eventually intended for on-sky observations.

With Euro50 as a convenient telescope laboratory, the Euro50 team has continued development aiming at a European extremely large telescope (ELT). Here, we give a progress report. The needs of science and instrumentation are briefly discussed as is the importance of photometric stability and precision. Results are reported from work on integrated modelling. Details are given concerning point-spread functions (PSFs) obtained with and without adaptive optics (AO). Our results are rather encouraging concerning AO photometry and compensation of edge sensor noise as well as regarding seeing-limited ELT operation. The current status of our development of large deformable mirrors is shown. Low-cost actuators and deflection sensors have been developed as have hierarchic control algorithms. Fabrication of large thin mirror blanks as well as polishing and handling of thin mirrors has been studied experimentally. Regarding adaptive optics, we discuss differential refraction and the limitations imposed by dispersive optical path differences (OPDs) and dispersive anisoplanatism. We report on progress in laser guide star (LGS) performance and a real-time online experiment in multi-conjugate AO (MCAO). We discuss ELTs, high-resolution spectroscopy and pupil slicing with and without use of AO. Finally, we present some recent studies of ELT enclosure options.

The current status of a real-time real-sky dual-conjugate adaptive optics experiment is presented. This experiment is a follow-up on a lab experiment at Lund Observatory that demonstrated dual-conjugate adaptive optics on a static atmosphere. The setup is to be placed at Lund Observatory. This means that the setup will be available 24h a day and does not have to share time with other instruments. The optical design of the experiment is finalized. A siderostat will be used to track the guide object and all other optical components are placed on an optical table. A small telescope, 35 cm aperture, is used and following this a tip-tilt mirror and two deformable mirrors are placed. The wave-front sensor is a Shack-Hartmann sensor using a SciMeasure Li’l Joe CCD39 camera system. The maximum update rate of the setup will be 0.5 kHz and the control system will be running under Linux. The effective wavelength will be 750 nm. All components in the setup have been acquired and the completion of the setup is underway. Collaborating partners in this project are the Applied Optics Group at National University of Ireland, Galway and the Swedish Defense Research Agency. (Less)

The Sustainable Livelihoods Approach (SLA) is often proposed to holistically capture vulnerability in assessments of livelihoods in aid and development programs. The full capacity of the approach has however only rarely been used in these assessments, lacking a clear account of processes of change and flexibility of assets, as well as the ability to quantify all capital assets of a livelihood system. The descriptions of livelihoods so far are in fact non-holistic. This paper attempts to use SLA in its full capacity through a quantification of the different capitals covered; natural, physical, economic, social and human. Further, the relationships between capitals are explored in a Chinese rural context of changing climate and land-use, and examples are given on how investments in one capital in reality can end up being accounted for in other capitals. The results indicate that through an analytical and process-oriented SLA, an effective tool for assessment of vulnerability can be developed. Such a tool would assist development organizations and policy-makers to target poverty traps and escape routes in the face of rapid and multiple changes.

This laboratory demonstrator setup is a downscaled version of a 7.5-maperture telescope with dual-conjugate adaptive optics, a representativestatic atmosphere in the K-band and five natural guide stars in a cross.The demonstrator has been used to evaluate different modes of adaptiveoptics; conventional single-conjugate adaptive optics, field-averagedsingle-conjugate adaptive optics and dual-conjugate adaptive optics.

PURPOSE. To demonstrate noninvasive imaging of human foveal capillary networks with a high-resolution, wide-field, dual-conjugate adaptive optics (DCAO) imaging instrument. METHODS. The foveal capillary networks of five healthy subjects with no previous history of ocular or neurologic disease or surgery were imaged with a novel high-resolution, wide-field DCAO instrument. The foveal avascular zone (FAZ) in each image was defined using a manual procedure. An automated algorithm based on publicly available and custom-written software was used to identify vessels and extract morphologic FAZ and vessel parameters. Capillary densities were calculated in two annular regions of interest (ROIs) outside the FAZ (500 mu m and 750 mu m outer radius from the foveal center) and in the superior, inferior, temporal, and nasal quadrants within the two ROIs. RESULTS. Mean FAZ area was 0.302 +/- 0.100 mm(2), and mean capillary density (length/area) in the inner ROI was 38.0 +/- 4.0 mm(-1) and 36.4 +/- 4.0 mm(-1) in the outer ROI. The difference in ROI capillary density was not significant. There was no significant difference in quadrant capillary density within the two ROIs or between quadrants irrespective of ROI. CONCLUSIONS. The authors have demonstrated a technique for noninvasive imaging and semiautomated detection and analysis of foveal capillaries. In comparison with other studies, their method yielded lower capillary densities than histology but similar results to the current clinical gold standard, fluorescein angiography. The increased field of view of the DCAO instrument opens up new possibilities for high-resolution noninvasive clinical imaging of foveal capillaries. (Invest Ophthalmol Vis Sci. 2011;52:2649-2655) DOI:10.1167/iovs.10-6054 (Less)

In this paper we investigate the performance of a Fourier based algorithm for fast subpixel shift determination of two mutually shifted images subjected to noise. The algorithm will be used for Shack-Hartmann based adaptive optics correction of images of an extended object subjected to dynamical atmospheric fluctuations. The performance of the algorithm is investigated both analytically and by Monte Carlo simulations. Good agreement is achieved in relation to how the precision of the shift estimate depends on image parameters such as contrast, photon counts and readout noise, as well as the dependence on sampling format, zero-padding and field of view. Compared to the conventional method for extended object wavefront sensing, a reduction of the computational cost is gained at a marginal expense of precision.