No description available.

No description available.

Measurements of radiogenic isotopes can in principle constrain the melting, melt migration, and solid state convection that occurs in the Earth's mantle, but to do so requires suitable quantitative models. A new statistical model is introduced to better understand the observed heterogeneity in isotopic ratios 143Nd/144Nd, 87Sr/86Sr, 176Hf/177Hf,208Pb/204Pb, 206Pb/204Pb and 207Pb/204Pb measured on mid-ocean ridge basalt. The model is highly idealised, analytically tractable, and contains the essential physical processes involved: radioactive decay, the stirring and recycling of mantle convection, partial melting, and the mixing of melts. Comparison of the modelled heterogeneity with that observed constrains model parameters, which in turn constrains aspects of mantle convection and melting. The model provides a new interpretation of the 2.0 Ga lead-lead pseudo-isochron age in terms of an age distribution of mantle material. Simple equations relate the pseudo-isochron age to the rate of melting and decay constants. These equations are different from, but related to and more general than, those found previously for standard geochemical box models. The results are in good agreement with numerical simulations of mantle convection. The 2.0 Ga pseudo-isochron age is shown to infer a 0.5 Ga average time scale for melting of mantle material. Geochemical and geological evidence suggests that melt travels to the surface via a network of channels under the ridge. Motivated by this, the fluid dynamical problem of a open melt conduit surrounded by a deformable porous medium is studied. Previous work has shown that the conduit supports solitary waves of elevation, with a region of trapped melt travelling with the wave. The new analysis comes to a different conclusion, showing that the solitary wave is instead one of depression, without a region of trapped melt.

No description available.

Mantle convection is the principal control on the thermal and geological evolution of the earth, including the motion of the tectonic plates, which in turn influences earthquakes, tsunamis, and volcanic eruptions. This system is governed by the equations for balance of mass, momentum, and energy for a viscous incompressible non-Newtonian fluid. Taking present-day temperatures as given, the time dependence can be neglected, eliminating the energy equation. In this case, the physics of the mantle are modeled by the Stokes equation with nonlinear rheology (the so-called forward problem). This dissertation focuses on solving the mantle convection inverse problem governed by the nonlinear Stokes forward problem with full nonlinear rheology, with an infinite-dimensional adjoint-based inversion method. The need for inverse methods in the study of mantle convection stems from the fact that the constitutive parameters are subject to uncertainty. Inversion for nonlinear rheology parameters presents considerable difficulties, which are explored in this dissertation. A spectral analysis of the Hessian operator is performed to investigate the ill-posedness of the inverse problem. The general form of the numerical eigenvalues is found to agree with that of the theoretically-derived ones (based on a model 1D Stokes problem), both of which collapse rapidly to zero, suggesting a high degree of ill-posedness. This motivates the use in this thesis of regularizations that are of Tikhonov type (favoring smooth viscosity) and total variation type (favoring piecewise-smooth viscosity). In addition, the eigenfunctions of the Hessian indicate that increasingly smaller length scales of viscosity are increasingly less observable, and that resolution decays with depth. The wide range of spatial scales of interest (varying from 1 km scale associated with plate boundaries to 10⁴ km global scales) prompts the use of adaptive mesh refinement in a parallel framework. The results show that both higher levels of nonlinearity and larger orders of magnitude of variation in the viscosity cause the inverse problem to be more ill-conditioned, increasing the difficulty of solving the inverse problem. Despite the severe ill-posedness of the inverse problem, stemming from the small number of observations compared to large number of degrees of freedom of the viscosity parameters, with the correct regularization weight and the right type of regularization, it is possible to reasonably infer information about the viscosity of the mantle, particularly in shallow regions. A number of 2D and 3D inversions are shown to demonstrate these capabilities. / text

No description available.

Mantle cell lymphoma (MCL) is characterized by the presence of the t(11 ;14)(g13 ;g32) translocation which results in cyclin Dl over-expression. MCL is one of the most difficult lymphoproliferative disorders to manage with a median survival rate of 43 months from diagnosis. The poor prognosis associated with MCL is due in large part to its late classification as a separate clinical entity leading to a dearth in available pre-clinical models. The specific objectives of the research described in this thesis were (1) to establish MCL preclinical models of disease and (2) to evaluate deregulated cell signaling pathways in MCL that can impact treatment response. Pre-clinical models of MCL were established from pre-existing cell lines containing the t(11 ;14)(g13 ;g32). These cell lines were previously misclassified because they were developed prior to the classification of MCL as a distinct lymphoma subtype. With the establishment of MCL models, deregulated cell signaling pathways in MCL and response to different treatment strategies were investigated. These included an investigation of the cell signaling pathways activated in bcl-2 over-expressing MCL cells that were treated with oblimersen; a molecular gene silencing strategy that effectively suppresses bcl-2 in vitro and in vivo. Silencing bcl-2 provided insight into which pathways were influenced by bcl-2 over-expression in MCL. More specifically loss of cyclin D1, NF-KB, p53, bax and p27 were observed following bcl-2 silencing. Additional studies investigated how abnormal expression of CD40/CD40L and Fas/FasL along with bcl-2 family members contributes to B cell clonal expansion and influences Rituximab-mediated cell death in MCL models. Rituximab is a chimeric monoclonal antibody targeted against B cells and both Rituximab-sensitive and insensitive MCL models were defined. An abnormally high expression of bcl-2, bcl-x L, mcl-1, CD40/CD40L and Fas were observed in all MCL cells, as well as high levels of soluble FasL, capable of blocking Fas-mediated apoptosis. These deregulated pathways were associated with response to Rituximab treatment in a sensitive MCL model. These studies demonstrated some of the key pathways associated with treatment response in MCL, and the establishment of well characterized MCL models enables us to continue to explore new treatment strategies currently being studied in other lymphomas.

Mantle cell lymphoma (MCL) is characterized by the presence of the t(11 ;14)(g13 ;g32) translocation which results in cyclin Dl over-expression. MCL is one of the most difficult lymphoproliferative disorders to manage with a median survival rate of 43 months from diagnosis. The poor prognosis associated with MCL is due in large part to its late classification as a separate clinical entity leading to a dearth in available pre-clinical models. The specific objectives of the research described in this thesis were (1) to establish MCL preclinical models of disease and (2) to evaluate deregulated cell signaling pathways in MCL that can impact treatment response. Pre-clinical models of MCL were established from pre-existing cell lines containing the t(11 ;14)(g13 ;g32). These cell lines were previously misclassified because they were developed prior to the classification of MCL as a distinct lymphoma subtype. With the establishment of MCL models, deregulated cell signaling pathways in MCL and response to different treatment strategies were investigated. These included an investigation of the cell signaling pathways activated in bcl-2 over-expressing MCL cells that were treated with oblimersen; a molecular gene silencing strategy that effectively suppresses bcl-2 in vitro and in vivo. Silencing bcl-2 provided insight into which pathways were influenced by bcl-2 over-expression in MCL. More specifically loss of cyclin D1, NF-KB, p53, bax and p27 were observed following bcl-2 silencing. Additional studies investigated how abnormal expression of CD40/CD40L and Fas/FasL along with bcl-2 family members contributes to B cell clonal expansion and influences Rituximab-mediated cell death in MCL models. Rituximab is a chimeric monoclonal antibody targeted against B cells and both Rituximab-sensitive and insensitive MCL models were defined. An abnormally high expression of bcl-2, bcl-x L, mcl-1, CD40/CD40L and Fas were observed in all MCL cells, as well as high levels of soluble FasL, capable of blocking Fas-mediated apoptosis. These deregulated pathways were associated with response to Rituximab treatment in a sensitive MCL model. These studies demonstrated some of the key pathways associated with treatment response in MCL, and the establishment of well characterized MCL models enables us to continue to explore new treatment strategies currently being studied in other lymphomas.

Group 2 kimberlites from South Africa, and lamproites from Western Australia and North America are relatively unfractionated mantle-derived igneous rocks, situated on or close to ancient cratonic areas. They are characterised by high trace element contents, while the range in N d and Sr isotopes encompasses much of that reported for various upper and lower crustal rocks. It is argued that these features are not due to crustal contamination during magma ascent, rather they are source and extraction phenomena. The mantle source regions of these rocks were ancient (~ 1.0 to 2.5 Ga) and variably trace element enriched. Preservation of such regions within the mantle is most probable in the relatively 'cold' and 'rigid' subcontinental mantle lithosphere, which is believed to have been isolated from the convecting asthenosphere for a long time. The source regions of the kimberlites and lamproites were situated at various depths within the subcontinental mantle lithosphere, from within the amphibole stability field « 100 km) to within the diamond stability field (> 150 km). Low degrees of partial melting « 1 %), together with volatile composition and depth of melting, have significantly influenced the composition of the resultant kimberlite and lamproite magmas. Those magmas that originated from within the diamond stability field contain abundant entrained and dis aggregated mantle peridotite. This feature is related to melt migration and rapid ascent to the surface, from these mantle depths. The Sr, Nd and Pb isotope data record evidence of variable, but related trace element enrichment styles. The origin of these trace elements is either from recycled continental crust (e.g. pelagic sediment), or from intra-mantle processes (e.g. the migration and crystallisation of small volume silicate melts with variable volatile compositions). The available data are insufficient to determine between the models and further work in this area is required.

The work contained within this thesis is concerned with a theoretical investigatiop of both laminar and thermally driven types of cavity flow, together with an analysis of their associated mixing processes which find applications to Industrial mixing and also to the environment. The mixing efficiency has been viewed from two perspectives namely the tracking of a selection of fluid particles, and also the simulation of the dispersive mixing of a coloured fluid element as carried along by the flow. This thesis also incorporates features of both Newtonian and a wide range of non-Newtonian fluids.