Graded-index magnonics

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics or Institute for Low Temperature Physics and Engineering (Kharkov, Ukraine).The published version can be found at http://hdl.handle.net/10871/22077The wave solutions of the Landau–Lifshitz equation (spin waves) are characterized by some of the most complex and peculiar dispersion relations among all waves. For example, the spin-wave (“magnonic”) dispersion can range from the parabolic law (typical for a quantum-mechanical electron) at short wavelengths to the nonanalytical linear type (typical for light and acoustic phonons) at long wavelengths. Moreover, the long-wavelength magnonic dispersion has a gap and is inherently anisotropic, being naturally negative for a range of relative orientations between the effective field and the spin-wave wave-vector. Nonuniformities in the effective field and magnetization configurations enable the guiding and steering of spin waves in a deliberate manner and there-fore represent landscapes of graded refractive index (graded magnonic index). By analogy to the fields of graded-index photonics and transformation optics, the studies of spin waves in graded magnonic landscapes can be united under the umbrella of the graded-index magnonics theme and are reviewed here with focus on the chal-lenges and opportunities ahead of this exciting research direction.Engineering and Physical Sciences Research Council (EPSRC

Fisheries and Aquaculture and Their Potential Roles in Development: An Assessment of the Current Evidence

Commissioned by the International Sustainability Unity, this report investigates a number of innovative solutions that have been developed to deal with five key challenges that are impeding progress in achieving sustainable fisheries: overcapacity; perverse subsidies; poor governance; lack of data; and by-catch and discards. These key challenges are interlinked and affect the sustainability of fisheries both directly as well as indirectly by undermining instances of good management. Through 22 case studies demonstrating good practice, we explore how these challenges have been addressed around the world and how these approaches might be scaled up and applied in other fisheries. Each case study draws on published material and interviews with key people involved in the fishery. The main report draws lessons from these case studies

Classification and Hypermedia

This paper discusses a research prototype demonstrating an architecture for a hypermedia system, in which the index space has semantic relationships between terms. Information items in a social history museum application are indexed according to spatial, temporal, and subject-based classifications. The spatial and temporal indexes are inter-linked. Measures of semantic closeness over the different classification dimensions allow access to information, which might be missed by retrieval tools that require exact matching of terms used in a request. Illustrative examples of hypermedia navigation tools that make use of semantic closeness are described. A method of integrating different index dimensions drawing on research in numerical taxonomy 1s discussed. The paper goes on to discuss possibilities for a richer set of semantic primitives, that could profitably draw on concepts in the classification research literature

Quantifying the Effect of Power Spectral Density Uncertainty on Gravitational-Wave Parameter Estimation for Compact Binary Sources

In order to perform Bayesian parameter estimation to infer the source properties of gravitational waves from compact binary coalescences (CBCs), the noise characteristics of the detector must be understood. It is typically assumed that the detector noise is stationary and Gaussian, characterized by a power spectral density (PSD) that is measured with infinite precision. We present a new method to incorporate the uncertainty in the power spectral density estimation into the Bayesian inference of the binary source parameters and apply it to the first 11 CBC detections reported by the LIGO- Virgo Collaboration. We find that incorporating the PSD uncertainty only leads to variations in the positions and widths of the binary parameter posteriors on the order of a few percent. Our results are publicly available for download on git [1]

Exciting and steering propagating spin waves using a graded magnonic index

In this thesis, the results of time-resolved magneto-optical imaging experiments, micromagnetic simulations and analytical theory will be presented. These three approaches were used in order to understand how spin waves can be both excited and steered using magnetic non-uniformities (which gives rise to the graded magnonic index). The results presented in this thesis, as a whole, reveal that the graded magnonic index not only can be exploited either to excite or steer propagating spin waves in a deliberate manner, but is in fact a ubiquitous feature that needs to be taken into account when considering any dynamical phenomena in nano- and micro-magnetism.Engineering and Physical Sciences Research Council (EPSRC

Buried alive: Aquatic plants survive in ‘ghost ponds’ under agricultural fields

The widespread loss of wetlands due to agricultural intensification has been highlighted as a major threat to aquatic biodiversity. However, all is not lost as we reveal that the propagules of some aquatic species could survive burial under agricultural fields in the sediments of ‘ghost ponds’ - ponds in-filled during agricultural land consolidation. Our experiments showed at least eight aquatic macrophyte species to germinate from seeds and oospores, following 50–150 years of dormancy in the sediments of ghost ponds. This represents a significant proportion of the expected macrophyte diversity for local farmland ponds, which typically support between 6 and 14 macrophyte species. The rapid (< 6 months) re-colonisation of resurrected ghost ponds by a diverse aquatic vegetation similarly suggests a strong seed-bank influence. Ghost ponds represent abundant, dormant time capsules for aquatic species in agricultural landscapes around the globe, affording opportunities for enhancing landscape-scale aquatic biodiversity and connectivity. While reports of biodiversity loss through agricultural intensification dominate conservation narratives, our study offers a rare positive message, demonstrating that aquatic organisms survive prolonged burial under intensively managed agricultural fields. We urge conservationists and policy makers to consider utilizing and restoring these valuable resources in biodiversity conservation schemes and in agri-environmental approaches and policies

Site-1 protease is essential for endochondral bone formation in mice

Site-1 protease (S1P) has an essential function in the conversion of latent, membrane-bound transcription factors to their free, active form. In mammals, abundant expression of S1P in chondrocytes suggests an involvement in chondrocyte function. To determine the requirement of S1P in cartilage and bone development, we have created cartilage-specific S1P knockout mice (S1Pcko). S1Pcko mice exhibit chondrodysplasia and a complete lack of endochondral ossification even though Runx2 expression, Indian hedgehog signaling, and osteoblastogenesis is intact. However, there is a substantial increase in chondrocyte apoptosis in the cartilage of S1Pcko mice. Extraction of type II collagen is substantially lower from S1Pcko cartilage. In S1Pcko mice, the collagen network is disorganized and collagen becomes entrapped in chondrocytes. Ultrastructural analysis reveals that the endoplasmic reticulum (ER) in S1Pcko chondrocytes is engorged and fragmented in a manner characteristic of severe ER stress. These data suggest that S1P activity is necessary for a specialized ER stress response required by chondrocytes for the genesis of normal cartilage and thus endochondral ossification