dsc-4(qm182), a mutation that suppresses the lengthened defecation cycle of clk-1 also suppresses the delay in germline development. dsc-4 encodes a putative orthologue of microsomal triglyceride transfer protein (MTP), a protein essential for the assembly and secretion of apo-B-containing low density lipoproteins (LDL). The effect of dsc-4 on clk-1(qm30), coupled to studies of apoB homologues in worms led to a model suggesting the possibility of using C. elegans in the study of LDL-like lipoprotein particles. The impact of the level of lipoproteins is particularly evident in the germline developmental rate of the worms. / We report here a further elucidation of clk-1 mutants in the study of the biology of LDL-like particles. In particular, we investigated the effect of targeting LDL receptor-like genes by RNA interference (RNAi) on the egg laying rate of clk-1(qm30). We find positive modulating effects by disruption of these putative LDL receptors. In confirmation of our model of lipoprotein metabolism in clk-1 mutants, we find that disruption of these putative LDL receptors produces strikingly different effects in wild-type, clk-1(qm30) or clk-1(qm30); dsc-4(qm182) animals. / In addition, we report unexpected effects of various clk-1 alleles on the phenotypes of animals in which lrp-1 and rme-2 are disrupted. Specifically, we observe an allele specific amelioration of the phenotypes associated with disruption of these genes (abnormal molting and sterility, respectively). We discuss the possible significance of these findings. (Abstract shortened by UMI.)

No description available.

This thesis describes a novel concept for a field-effect transistor based on metallic channels. Latest research demonstrates that the bulk (3D) properties of many materials begin to change when confined to 2D sheets, or 1D nanowires. Particularly, the bandgap increases and the density of states decreases. In this work, this effect is explored further to demonstrate its application to field-effect transistors. Certain metals such as Gold and Silver in these dimensions have extremely low density of states in particular energy regions and through gate modulation can be partially depleted from electrons thus creating conditions for field-effect. A simulation study of Gold channel FET demonstrates ION/IOFF of 30 and superior current driving capability compared to the state-of-the art 22nm SiGe ETSOI as well as 30nm nanotube transistors.

This thesis describes a novel concept for a field-effect transistor based on metallic channels. Latest research demonstrates that the bulk (3D) properties of many materials begin to change when confined to 2D sheets, or 1D nanowires. Particularly, the bandgap increases and the density of states decreases. In this work, this effect is explored further to demonstrate its application to field-effect transistors. Certain metals such as Gold and Silver in these dimensions have extremely low density of states in particular energy regions and through gate modulation can be partially depleted from electrons thus creating conditions for field-effect. A simulation study of Gold channel FET demonstrates ION/IOFF of 30 and superior current driving capability compared to the state-of-the art 22nm SiGe ETSOI as well as 30nm nanotube transistors.

No description available.

The physical state of the seedbed is of importance to the plant environment as it influences some important processes in the soil such as seedling emergence, water and solute transport, and ease of root penetration. This is affected to a large extent by tillage process, the tillage implement type and the geometry of the implement used. / A field experiment was carried out on a clay soil to determine the effect of the geometry of bladed tillage implements on some soil physical properties after tillage. The soil properties evaluated were bulk density, mean clod size distribution and total pore space after tillage and the extent of loosening achieved. / Implement parameters considered were blade width, rake angle and depth of operation of the implement. Two blade widths of 75 and 150 mm were evaluated in combination with three rake angles of 30, 60 and 90 degrees. Each tillage implement was drawn through the soil at four operating depths of 100, 150, 200 and 250 mm. / Larger rake angles were observed to result in larger mean aggregate sizes and greater bulk density reductions when compared to smaller rake angles. Greater reduction in bulk density was observed with the wider of the two blade widths evaluated. Mean clod size after tillage was also observed to be large for the wider of the two widths evaluated. Irrespective of width and rake angle, greater operating depths resulted in larger mean clod sizes and greater reductions in bulk density as compared to shallower operating depths. Fractal analysis showed the extent of fragmentation to be greater at shallower operating depths, hence the small mean clod sizes obtained.

Our understanding of the nature of Earth’s D” region was changed significantly by a recent finding by Murakami et al. (2004), who revealed a phase transition from perovskite to post-perovskite structure in MgSiO3 at about 125 GPa and 2500 K, corresponding to conditions of the lowermost mantle. A perovskite to post-perovskite phase transition accounts for many unusual features of the D” region, including its notable seismic anisotropy, and also accounts for the unusual topology of the D” discontinuity. However, the experimentally synthesised post-perovskite phase of MgSiO3 is not quenchable to ambient conditions, which means that many of its physical properties remain difficult to determine. On the other hand, there are several post-perovskite oxides, CaIrO3, CaPtO3, CaRhO3 and CaRuO3, which can be quenched to ambient conditions, maintaining their structure. High pressure synthesis of CaIr1-xPtxO3 solid solutions (x = 0, 0.3, 0.5, 0.7) and CaIr0.5Rh0.5O3 was conducted at the University of Edinburgh and Geodynamics Research Center, Ehime University, and structures and physical properties of these novel post-perovskite materials determined. Substantial [100] grain growth was observed in all solid solutions leading to pronounced texture even in powdered materials. Temperature-independent paramagnetism above 150 K and small magnetic entropy observed in heat capacity measurements suggest that CaIrO3 is an intrinsically weak itinerant ferromagnetic metal, while electrical resistivity measurements show that it is a narrow bandgap semiconductor, possibly due to grain boundary effects. CaIrO3 undergoes a magnetic transition at 108K and possesses a saturated magnetic moment of 0.04 μB. Doping with Pt or Rh induces Curie-Weiss paramagnetism and suppresses the magnetic transition. The anisotropic structure and morphology of CaIrO3 combined with the Ir4+ spin-orbit coupling results in a large magnetic anisotropy constant of 1.77 x 106 Jm-3, comparable to values for permanent magnet materials. A new high-pressure phase of CaIr0.5Pt0.5O3 was synthesised at 60GPa, 1900K using a laser-heated DAC (diamond anvil cell) at GRC, Ehime University. Its Raman spectra resemble those of perovskite phases of CaIrO3 and CaMnO3, implying that CaIr0.5Pt0.5O3 undergoes a post-perovskite to perovskite phase transition with increasing pressure. I estimate an increase in thermodynamic Grüneisen parameter γth across the post-perovskite to perovskite transition of 34 %, with similar magnitude to (Mg,Fe)SiO3 and MgGeO3, suggesting that CaIr0.5Pt0.5O3 is a promising analogue for experimentally simulating the competitive stability between perovskite and post-perovskite phase of magnesium silicates in Earth’s lowermost mantle. Such estimation is reliable since the estimated and directly calculated thermodynamic Grüneisen parameter γth from heat capacity show consistent values. The marked effect that Pt has on stabilising the post-perovskite structure in CaIr1-xPtxO3 solid solutions explains why the post-perovskite to perovskite phase transition has not been observed for CaPtO3 in contrast to other quenchable post-perovskite oxides: CaIrO3, CaRhO3 and CaRuO3.Work presented here demonstrates that CaIrO3 solid solutions can be used to provide new insight into factors stabilising post-perovskite structures in Earth’s lowermost mantle.

Limitations on water infiltration and soil aeration through compaction processes have the potential to limit production in irrigated agricultural fields. This project was conducted to determine the impact of sub-soiling with a paraplow (Howard Rotavator) on soil physical properties and processes that are important in affecting soil-water relations and productivity. The paraplow was the subsoiler selected for use in this study because of its ability to loosen the soil at the depth of plowing while producing minimal surface disturbance. The research plots were located on Chernozem and Vertisol soils in the Brown soil zone in the Lake Diefenbaker irrigation district near Birsay, SK. Irrigated and dryland sites were used for comparison. Sub-soiling was able to consistently reduce bulk density of the soil and effects persisted for one to two years under normal precipitation conditions. Excessively wet conditions (2010 and 2011) reduced the effectiveness of the sub-soiling. Tillage induced porosity in the soil was associated with a greater infiltration capacity measured in the field. Yield benefits in crops grown (canola, flax, wheat) from sub-soiling were variable under the wet conditions of 2010 and 2011. A greater benefit was observed under the normal precipitation conditions of 2012 on sites that were paraplowed in 2011. Subsoiling at a depth of 45cm and a row spacing of 45cm (manufacturer’s recommended configuration) was more effective than shallower depth and wider row spacing treatments. A significant yield benefit was only observed at the dryland site established in 2011, and limited yield benefit was observed in the irrigated sites. Over the three years of the study, annual yields from sub-soiling were on average about 5% higher than the un-tilled control. However, yield benefits were variable depending on crop and year. Given an estimated cost of subsoiling of ~$30 per acre, a benefit of sub-soiling that lasts one year would produce close to break-even conditions, and sub-soiling benefits that are consistent and last longer than one year are needed to be cost effective.

There are four big medium density fibreboard (MDF) plants in New Zealand with a total production capacity of close to one million cubic meters per year. A significant quantity of boards (nearly 3% or about 30,000 cubic meters per year) is rejected due to defects such as weak core, low modulus of rupture and elasticity, low internal bonding and delamination. The main cause of these defects, is lack of complete understanding of the inter relationship during the hot-pressing stage between the initial inputs such as temperature, moisture content, platen pressure and its impact on the properties of boards. The best solution is to develop a mathematical model to assist in understanding these relationships and to solve the equations in the model by using advanced software. This will reduce the number of expensive experiments and will enable us to see some of the parameters, which are otherwise difficult to visualise. Several earlier researchers have tried to model hot pressing of wood composites, mostly either for particle board or oriented strand board (OSB), and only a few are for MDF. The type of numerical methods used to solve the model equations and various assumptions, changes from one investigator to the other. The non-availability of source code to convert the mathematical equations into programme, is one of the reasons for this model development. To improve the productivity of MDF plants in New Zealand, there was a need to develop a computer programme which can include all the latest findings and can remove the defects which are present in earlier models. This model attempts a more complete integration than in the previous models of all the components such as heat transfer, moisture movement and vertical density profile formation in a one-dimensional model of hot pressing of MDF. One of the important features added in the heat and mass transfer part of the model is that the equilibrium moisture content (EMC) equation given for solid wood was modified to be applicable for the MDF fibres. In addition, this EMC equation can cover the complete range of hot pressing temperature from 160ºC to 200ºC. The changes in fibre moisture content due to bound water diffusion, which was were earlier neglected, was considered. The resin curing reactions for phenol formaldehyde and urea formaldehyde resins are also incorporated into the model, with the energy and water released during the curing reaction being included in the energy and mass balances. The validation of the heat and mass transfer model was done by comparing the values of core temperature and core pressure from the model and the experiments. The experimental value of core pressure and core temperature is obtained by putting a thermocouple and pressure transducer in the middle of the mat. The experimental core temperature results show qualitative agreement with the predicted results. In the beginning, the core temperatures from both experiment and model overlap each other. In the middle of the press cycle, the experimental core temperature is higher by 10ºC and by the end the difference decreases to 5ºC. The vertical density profile (VDP) is a critical determining factor for the strength and quality of MDF panels. The earlier concept of ratio of modulus of elasticity of the layer to the sum of modulus of elasticity of all the layers in the previous time step, given by Suo and Bowyer (1994), is refined with the latest published findings. The equation given by Carvalho et al. (2001) is used to calculate the MOE of different layers of the mat. The differential equation of a Maxwell element given by Zombori (2001) is used to measure stress, nonlinear strain function and relaxation of fibres. The model gives good agreement of peak and core density at lower platen temperature at 160ºC but with the increase of platen temperature to 198ºC, the rise in peak density is comparatively higher. There is a distinct increase in predicted peak density by 150 kg/m³ in comparison to the experimental result, where the increase is only by 10 kg/m³. There is a large decline (50 kg/m³) in core density in the experimental results in comparison to only a slight decline (13 kg/m³) in the predicted results. The use of Matlab provides a very convenient platform for producing graphical results. The time of computation at present is nearly 20 hrs in a personal computer with Pentium four processor and one GB RAM. The model can predict properties of a pressed board for the standard manufacturing conditions and also the new hot pressing technologies such as the use of steam injection or a cooling zone in the continuous press. A comparative study has been done to show the advantages of using new hot pressing technology. The present model will become an important tool in the hands of wood technologist, process engineers and MDF manufacturing personnel, to better understand the internal processes and to improve production and quality of MDF boards. This theoretical model helped in developing better understanding of internal processes. By using it, we can analyse the impact of platen temperature, moisture content on the core temperature, core pressure and density profile. It gives better insight into the relationship between core pressure and delamination of the board. The model is also able to predict the internal changes in the new hot pressing technologies such as the steam injection pressing and the use of a cooling zone in a continuous press. Using the simulation results, the exact time needed for the complete curing of resin can be calculated and then these results can be applied in the commercial plants. If the pressing time is reduced, then the over all production of both batch press and continuous press will increase. The second part of the project is the development of an empirical model to correlate the physical properties from the MDF board to the mean density. The empirical model is simple and straightforward, and thus can be applied in commercial operation for control and optimization. The empirical model can predict peak density, core density, and modulus of rupture, elasticity and internal bonding within the limits in which those relationships are derived. The model gives good results for thickness ranging from 10 to 13.5 mm and density ranging from 485 kg/m³ to 718 kg/m³.

The density of states of elastic waves in a porous amorphous “mesoglass” has been measured in the strong-scattering regime. Samples were constructed by sintering glass beads percolated on a random lattice. This structure was investigated via x-ray tomography, and fractal behaviour was observed with fractal dimension D = 2.6. Using sufficiently small samples, the individual modes of vibration could be resolved and counted in the Fourier transform of each transmitted ultrasonic pulse. A statistical treatment of the data, designed to account for the possibility of missing modes, was developed, yielding a robust method for measuring the density of states. In the strong-scattering regime, the data are in good agreement with a simple model based on mode conservation, though the density of states significantly exceeds the predictions of the Debye approximation at low frequencies. At intermediate frequencies, an average density of states of 47.1 ± 0.3 MHz⁻¹ mm⁻³ was found, with a frequency dependence of f^(0.01 ± 0.04).