Cross-grid display and computer input study Final report, Apr. - Dec. 1969

Feasibility of plasma panels as graphic display device

Visco-elastic finite element analysis of subduction zones

A new visco-elastic finite element method is developed and applied to some of the processes in subduction zones. The effects of phase changes are simulated by deriving an equation of state for the mantle under mineralogical equilibrium. Using the elastic parameters determined from this equation, the stresses due to the contraction of the descending slab as it changes phase at the olivinespinel transition are shown to be about 8 x 10 (^8) n/m (^2). The phase changes are also shown to play an important role in the flexure and bending of the lithosphere from the earth's surface to plunge at 45 – 60o into the asthenosphere. The phase changes effectively reduce the bulk modulus and so the lithosphere bends more easily. The major bending is at 30 - 60 km depth where the stresses due to bending extend the area of phase transitions so that it extends throughout the thickness of the descending slab. Phase changes and fracture combine to reduce the flexural parameters of the lithosphere to that estimated from the shape of the outer-rise. Thin plate theory, however, is shown to be inapplicable to this region. Tensional stresses aligned parallel to the dip of the descending slab are shown to be necessary to maintain the large negative gravity anomaly associated with subduction zones. This applies in all subduction zones, and local stresses must be responsible for the earthquakes indicating down dip compression in the upper part of the descending slab. The shear zone between two converging plates can be adequately modelled in visco-elastic finite element analysis by a row of elements whose viscosity is 2-3 orders of magnitude lower than the surrounding rocks

A Partial Taxonomy of Substitutability and Interchangeability

Substitutability, interchangeability and related concepts in Constraint Programming were introduced approximately twenty years ago and have given rise to considerable subsequent research. We survey this work, classify, and relate the different concepts, and indicate directions for future work, in particular with respect to making connections with research into symmetry breaking. This paper is a condensed version of a larger work in progress.Comment: 18 pages, The 10th International Workshop on Symmetry in Constraint Satisfaction Problems (SymCon'10

The tail of the Jurassic fish Leedsichthys problematicus (Osteichthyes: Actinopterygii) collected by Alfred Nicholson Leeds - an example of the importance of historical records in palaeontology

The specimen of the tail of <i>Leedsichthys problematicus</i>, now in The Natural History Museum, London, was one of the most spectacular fossil vertebrates from the Oxford Clay Formation of Peterborough, but as an isolated find it shares no bones in common with the holotype of the genus and species. However, a letter from Alfred Nicholson Leeds and related documents cast valuable new light on the excavation of the tail, indicating that it was discovered with cranial bones, gill-rakers, and two pectoral fins, thereby including elements that can potentially be compared with those of the holotype. The documents also clearly indicate that The Natural History Museum's specimen is not part of the same individual as any other numbered specimen of <i>Leedsichthys</i> as had been speculated on other occasions. The maximum size of the animal represented by The Natural History Museum's specimen was possibly around 9 metres, considerably less than previous estimates of up to 27.6 metres for <i>Leedsichthys</i>. Historical documentary evidence should therefore be rigorously checked both when studying historical specimens in science, and in preparing text for museum display labels

Effects of respiratory inhibitors on growth

Effects of respiratory inhibitors on growt

Study of the volume and spin collapse in orthoferrite LuFeO_3 using LDA+U

Rare earth (R) orthoferrites RFeO_3 exhibit large volume transitions associated with a spin collapse. We present here ab initio calculations on LuFeO_3. We show that taking into account the strong correlation among the Fe-3d electrons is necessary. Indeed, with the LDA+U method in the Projector Augmented Wave (PAW), we are able to describe the isostructural phase transition at 50 GPa, as well as a volume discontinuity of 6.0% at the transition and the considerable reduction of the magnetic moment on the Fe ions. We further investigate the effect of the variation of U and J and find a linear dependence of the transition pressure on these parameters. We give an interpretation for the non-intuitive effect of J. This emphasizes the need for a correct determination of these parameters especially when the LDA+U is applied to systems (e.g in geophysical investigations) where the transition pressure is a priori unknown