Categorical Aspects of Graphs

In this article, we introduce a categorical characterization of directed and undirected graphs, and explore subcategories of reflexive and simple graphs. We show that there are a number of adjunctions between such subcategories, exploring varying combinations of graph types

Anti-jamming techniques for multichannel SAR imaging

© The Institution of Engineering and Technology 2006 IEE Proceedings online no. 20045090An airborne broadband jammer present in the mainbeam of a synthetic aperture radar (SAR) can potentially destroy a large region of the SAR image. In addition to this, multipath reflections from the ground, known as hot-clutter or terrain scattered interference will add a non-stationary interference component to the image. The goal of interference suppression for SAR is to successfully suppress these interferences while not significantly effecting the image quality by blurring, reducing the resolution or raising the sidelobe level. The paper provides an analysis of the degradation from hot-clutter, the limited restoration that multichannel imaging and slow-time space time adaptive processing (STAP) can provide and how fast-time STAP can improve the final image quality.L. Rosenberg and D. Gra

Quantum Spin Lenses in Atomic Arrays

We propose and discuss `quantum spin lenses', where quantum states of delocalized spin excitations in an atomic medium are `focused' in space in a coherent quantum process down to (essentially) single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D and 3D, and with strings of trapped ions. We discuss both linear and non-linear quantum spin lenses: in a non-linear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.Comment: 13 pages, 9 figure

Phaseguide assisted liquid lamination for magnetic particle-based assays

We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via the use of phaseguide technology; microstructures that control the advancing air–liquid interface of solutions as they enter a microfluidic chamber. This allows manual filling of the device, eliminating the need for external pumping systems, and preparation of the system requires only a few minutes. Here, we apply the platform to two on-chip strategies: (i) a one-step streptavidin–biotin binding assay, and (ii) a two-step C-reactive protein immunoassay. With these, we demonstrate how condensing multiple reaction and washing processes into a single step significantly reduces procedural times, with both assay procedures requiring less than 8 seconds

High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors

Un-cooled, MEMS-based silicon carbide (SiC) static pressure sensors were used for the first time to measure pressure perturbations at temperatures as high as 600 C during laboratory characterization, and subsequently evaluated in a combustor rig operated under various engine conditions to extract the frequencies that are associated with thermoacoustic instabilities. One SiC sensor was placed directly in the flow stream of the combustor rig while a benchmark commercial water-cooled piezoceramic dynamic pressure transducer was co-located axially but kept some distance away from the hot flow stream. In the combustor rig test, the SiC sensor detected thermoacoustic instabilities across a range of engine operating conditions, amplitude magnitude as low as 0.5 psi at 585 C, in good agreement with the benchmark piezoceramic sensor. The SiC sensor experienced low signal to noise ratio at higher temperature, primarily due to the fact that it was a static sensor with low sensitivity

Prediction of the annuloplasty ring size in patients undergoing mitral valve repair using real-time three-dimensional transoesophageal echocardiography

Aims We sought to investigate the additional value of real-time three-dimensional transoesophageal echocardiography (RT 3D TOE)-guided sizing for predicting annuloplasty ring size during mitral valve repair. Methods and results In 53 patients undergoing elective mitral valve repair, an RT 3D TOE was performed pre- and post-operatively. The digitally stored loops were imported into a software for mitral valve assessment. The annuloplasty ring size was predicted by superimposing computer-aided design (CAD) models of annuloplasty rings onto Live 3D zoom loops, measurement of the intercommissural distance, or the height of the anterior mitral leaflet. The surgeon implanted the annuloplasty ring according to the usual surgical technique and was blinded to the echocardiographic measurement results. Pre-operative correlation between the selected ring size with mitral valve assessment and the actual implanted annuloplasty ring size was 0.91. The correlation for measurement of the intercommissural distance was 0.55 and for measurement of the height of the anterior mitral leaflet 0.75. The post-operative correlation with the actual implanted ring size was 0.96 for mitral valve assessment, 0.92 for intercommissural distance, and 0.79 for the anterior mitral leaflet height. Conclusion Superimposition of annuloplasty ring CAD models on the Live 3D zoom loops of the mitral valve using mitral valve assessment is superior to two-dimensional measurements of the intercommissural distance or the height of the anterior mitral leaflet in predicting correct annuloplasty ring size

Influence of the use of Renewable Compatibility Agent Wood Plastic Composite (WPC)

The growing interest in using recycled and natural materials in the application of new composites in recent years implies ecological, economic and versatility benefits. Wood plastic composite (WPC) are considered very attractive materials, as they allow the use of polymers of recycled or virgin origin, associated with forestry by-products. The present work aims to investigate the influence on the mechanical, thermal and morphological resistance of WPC, using oleic acid and glycerol as renewable coupling agents. Composites were also prepared with a commercial compatibility agent in its formulation - maleic anhydride grafted polypropylene (MAPP) - under the same conditions. The composites were prepared in a single-screw extruder, with fixed contents of 5% sawdust with 95% virgin polymer, of this total, 2% were coupling agents: MAPP, oleic acid or glycerol, according to the desired composition. To be evaluated as changes in mechanical properties, tensile and impact strength tests were performed on specimens obtained through the injection molding process. The fracture surfaces of specimens tested in tensile tests were examined using images generated by scanning electron microscopy. The thermal stability of the composites was also investigated by thermogravimetric analysis. The use of glycerol and oleic acid improved the mechanical properties of the composite. An increase in tensile strength is observed when glycerol is added in composite. As for impact strength, the addition of glycerol or oleic acid was around 58% higher in impact strength when compared to without coupling agent. Glycerol and oleic acid are renewable, low-cost alternative to be a potential substitute for the commercial coupling agent MAPP, especially when the main requirement is to obtain better impact resistance properties

Creation of multiple nanodots by single ions

In the challenging search for tools that are able to modify surfaces on the nanometer scale, heavy ions with energies of several 10 MeV are becoming more and more attractive. In contrast to slow ions where nuclear stopping is important and the energy is dissipated into a large volume in the crystal, in the high energy regime the stopping is due to electronic excitations only. Because of the extremely local (< 1 nm) energy deposition with densities of up to 10E19 W/cm^2, nanoscaled hillocks can be created under normal incidence. Usually, each nanodot is due to the impact of a single ion and the dots are randomly distributed. We demonstrate that multiple periodically spaced dots separated by a few 10 nanometers can be created by a single ion if the sample is irradiated under grazing angles of incidence. By varying this angle the number of dots can be controlled.Comment: 12 pages, 6 figure