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Eschrig M.,Royal Holloway, University of London
Reports on Progress in Physics | Year: 2015

During the past 15 years a new field has emerged, which combines superconductivity and spintronics, with the goal to pave a way for new types of devices for applications combining the virtues of both by offering the possibility of long-range spin-polarized supercurrents. Such supercurrents constitute a fruitful basis for the study of fundamental physics as they combine macroscopic quantum coherence with microscopic exchange interactions, spin selectivity, and spin transport. This report follows recent developments in the controlled creation of long-range equalspin triplet supercurrents in ferromagnets and its contribution to spintronics. The mutual proximityinduced modification of order in superconductor-ferromagnet hybrid structures introduces in a natural way such evasive phenomena as triplet superconductivity, odd-frequency pairing, FuldeFerrellLarkinOvchinnikov pairing, long-range equal-spin supercurrents, π-Josephson junctions, as well as long-range magnetic proximity effects. All these effects were rather exotic before 2000, when improvements in nanofabrication and materials control allowed for a new quality of hybrid structures. Guided by pioneering theoretical studies, experimental progress evolved rapidly, and since 2010 triplet supercurrents are routinely produced and observed. We have entered a new stage of studying new phases of matter previously out of our reach, and of merging the hitherto disparate fields of superconductivity and spintronics to a new research direction: super-spintronics. © 2015 IOP Publishing Ltd. Source

Davis C.J.,Royal Holloway, University of London
Psychological Review | Year: 2010

Visual word identification requires readers to code the identity and order of the letters in a word and match this code against previously learned codes. Current models of this lexical matching process posit context-specific letter codes in which letter representations are tied to either specific serial positions or specific local contexts (e.g., letter clusters). The spatial coding model described here adopts a different approach to letter position coding and lexical matching based on context-independent letter representations. In this model, letter position is coded dynamically, with a scheme called spatial coding. Lexical matching is achieved via a method called superposition matching, in which input codes and learned codes are matched on the basis of the relative positions of their common letters. Simulations of the model illustrate its ability to explain a broad range of results from the masked form priming literature, as well as to capture benchmark findings from the unprimed lexical decision task. © 2010 American Psychological Association. Source

Cutting S.M.,Royal Holloway, University of London
Food Microbiology | Year: 2011

Bacterial spore formers are being used as probiotic supplements for use in animal feeds, for human dietary supplements as well as in registered medicines. Their heat stability and ability to survive the gastric barrier makes them attractive as food additives and this use is now being taken forward. While often considered soil organisms this conception is misplaced and Bacilli should be considered as gut commensals. This review summarises the current use of Bacillus species as probiotics, their safety, mode of action as well as their commercial applications. © 2010 Elsevier Ltd. Source

Gudmundsson A.,Royal Holloway, University of London
Journal of Volcanology and Geothermal Research | Year: 2012

An existing magma chamber is normally a necessary condition for the generation of a large volcanic edifice. Most magma chambers form through repeated magma injections, commonly sills, and gradually expand and change their shapes. Highly irregular magma-chamber shapes are thermo-mechanically unstable; common long-term equilibrium shapes are comparatively smooth and approximate those of ellipsoids of revolution. Some chambers, particularly small and sill-like, may be totally molten. Most chambers, however, are only partially molten, the main part of the chamber being crystal mush, a porous material. During an eruption, magma is drawn from the crystal mush towards a molten zone beneath the lower end of the feeder dyke. Magma transport to the feeder dyke, however, depends on the chamber's internal structure; in particular on whether the chamber contains pressure compartments that are, to a degree, isolated from other compartments. It is only during large drops in the hydraulic potential beneath the feeder dyke that other compartments become likely to supply magma to the erupting compartment, thereby contributing to its excess pressure (the pressure needed to rupture a magma chamber) and the duration of the eruption.Simple analytical models suggest that during a typical eruption, the excess-pressure in the chamber decreases exponentially. This result applies to a magma chamber that (a) is homogeneous and totally fluid (contains no compartments), (b) is not subject to significant replenishment (inflow of new magma into the chamber) during the eruption, and (c) contains magma where exsolution of gas has no significant effect on the excess pressure. For a chamber consisting of pressure compartments, the exponential excess-pressure decline applies primarily to a single erupting compartment. When more than one compartment contributes magma to the eruption, the excess pressure may decline much more slowly and irregularly.Excess pressure is normally similar to the in-situ tensile strength of the host rock, 0.5-9. MPa. These in-situ strength estimates are based on hydraulic fracture measurements in drill-holes worldwide down to crustal depths of about 9. km. These measurements do not support some recent magma-chamber stress models that predict (a) extra gravity-related wall-parallel stresses at the boundaries of magma chambers and (b) magma-chamber excess pressures prior to rupture of as much as hundreds of mega-pascals, particularly at great depths.General stress models of magma chambers are of two main types: analytical and numerical. Earlier analytical models were based on a nucleus-of-strain source (a 'point pressure source') for the magma chamber, and have been very useful for rough estimates of magma-chamber depths from surface deformation during unrest periods. More recent models assume the magma chamber to be axisymmetric ellipsoids or, in two-dimensions, ellipses of various shapes. Nearly all these models use the excess pressure in the chamber as the only loading (since lithostatic stress effects are then automatically taken into account), assume the chamber to be totally molten, and predict similar local stress fields. The predicted stress fields are generally in agreement with the world-wide stress measurements in drill-holes and, in particular, with the in-situ tensile-strength estimates.Recent numerical models consider magma-chambers of various (ideal) shapes and sizes in relation to their depths below the Earth's surface. They also take into account crustal heterogeneities and anisotropies; in particular the effects of the effects of a nearby free surface and horizontal and inclined (dipping) mechanical layering. The results show that the free surface may have strong effects on the local stresses if the chamber is comparatively close to the surface. The mechanical layering, however, may have even stronger effects. For realistic layering, and other heterogeneities, the numerical models predict complex local stresses around magma chambers, with implications for dyke paths, dyke arrest, and ring-fault formation. © 2012 Elsevier B.V. Source

Cresswell T.,Royal Holloway, University of London
Environment and Planning D: Society and Space | Year: 2010

This paper proposes an approach to mobility that takes both historical mobilities and forms of immobility seriously. It is argued that is important for the development of a politics of mobility. To do this it suggests that mobility can be thought of as an entanglement of movement, representation, and practice. Following this it argues for a more finely developed politics of mobility that thinks below the level of mobility and immobility in terms of motive force, speed, rhythm, route, experience, and friction. Finally, it outlines a notion of 'constellations of mobility' that entails considering the historical existence of fragile senses of movement, meaning, and practice marked by distinct forms of mobile politics and regulation. © 2010 Pion Ltd and its Licensors. Source

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