Not available / text

Laminated and annually-laminated sediments are found in Loe Pool. The origins of such laminations are investigated and evidence for their conditions of formation are presented. In all sediment analysed the combustion residue was greater than 80%, and in the black and grey annually-laminated sediment the organic matter was less than 3%. This indicated that the sediment was dominated by a minerogenic input. The high lacustrine sediment concentrations of copper, zinc and other heavy metals together with evidence from analysis of magnetic variables which indicated high levels of haematite, confirmed that a major sediment source was effluent from mine waste. Analysis of individual black and grey annual laminations revealed increased concentrations of chlorophyll c, phaeopigments and perylene together with a lower C: N ratio in the black lamination. This indicated formation of the black layer in the summer months. From the high iron: manganese ratio and the low concentrations of calcium and carbonate in the black lamination as compared with the grey layer it was apparent that the black lamination was formed under conditions of oxygen shortage, and the grey lamination was formed when the bottom waters were fully oxygenated. It was concluded that from the analysis of selected physical and chemical properties of individual laminations it was possible to identify the principal sediment source, the likely season of deposition of each lamination and the palaeo-redox condition of the lake at that time. From this information a hypothesis of the formation of the laminated sediments in Loe Pool is proposed. It is suggested that a dominant factor controlling sediment composition was the redox conditions at the time of deposition. These conditions were primarily influenced by lake depth, lake mixing, input of allochthonous material and the oxygen demand of sedimenting material.

Limits on power consumption, complexity, and on-chip latency have focused computer architects on power-efficient designs that exploit parallelism. One approach divides programs into atomic blocks of operations that execute semi-independently, which efficiently creates a large window of potentially concurrent operations. This dissertation studies the intertwined roles of the compiler, architecture, and microarchitecture in achieving efficiency and high performance with a block-atomic architecture. For such an architecture to achieve high performance the compiler must form blocks effectively. The compiler must create large blocks of instructions to amortize the per-block overhead, but control flow and content restrictions limit the compiler's options. Block formation should consider factors such of frequency of execution, block size such as selecting control-flow paths that are frequently executed, and exploiting locality of computations to reduce communication overheads. This dissertation determines what characteristics of programs influence block formation and proposes techniques to generate effective blocks. The first contribution is a method for solving phase-ordering problems inherent to block formation, mitigating the tension between block-enlarging optimizations---if-conversion, tail duplication, loop unrolling, and loop peeling---as well as scalar optimizations. Given these optimizations, analysis shows that the remaining obstacles to creating larger blocks are inherent in the control flow structure of applications, and furthermore that any fixed block size entails a sizable amount of wasted space. To eliminate this overhead, this dissertation proposes an architectural implementation of variable-size blocks that allow the compiler to dramatically improve block efficiency. We use these mechanisms to develop policies for block formation that achieve high performance on a range of applications and processor configurations. We find that the best policies differ significantly depending on the number of participating cores. Using machine learning, we discover generalized policies for particular hardware configurations and find that the best policy varies significantly between applications and based on the number of parallel resources available in the microarchitecture. These results show that effective and efficient block-atomic execution is possible when the compiler and microarchitecture are designed cooperatively. / text

published_or_final_version / Chemistry / Master / Master of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

No description available.

Powerful forces are at work in giant Ly α nebulae, a rare and mysterious population in the high redshift universe. Much like the spatially extended emission line halos around high redshift radio galaxies . but without the strong radio emission . Ly α nebulae (or Ly α 'blobs') boast copious Ly α emission (10⁴⁴ erg s⁻¹), large sizes (∼100 kpc), complex gas morphologies, and the company of numerous compact, star-forming galaxies, and may offer a window into dramatic episodes of massive galaxy formation. The small sample sizes and complex inner workings of Ly α nebulae have limited progress on understanding the their space density, environments, and physical conditions. This thesis strives to answer fundamental questions about Ly α nebulae and pave the way for understanding their role in the build up of massive galaxy systems. To address the frequency of collapse of these massive structures, we carried out the largest systematic Ly α nebula survey to date and measured the Ly α nebula space density. As an unbiased test of the environment of Ly α nebulae, we studied the surroundings of a Ly α nebula and confirmed that Ly α nebulae reside preferentially in overdense regions. To disentangle the sources of ionization, we took a census of all the compact ionization sources within a large Ly α nebula using high resolution imaging. Finally, we used photoionization modeling to put constraints on the physical conditions, the metallicity, and the sources of ionization within Ly α nebulae. Future work will be able to build on this thesis by expanding the systematic search for Ly α nebulae to other existing deep broad-band datasets, mapping the three-dimensional overdense structures in which Ly α nebulae live out to ≥ 50 (comoving) Mpc scales, and disentangling multiple sources of ionization within a larger sample of individual systems using deep optical and near-infrared spectroscopy and detailed photoionization modeling.

In many robotics tasks, it is advantageous for robots to assemble into formations. In many of these applications, it is useful for the robots to have differing capabilities (i.e., be heterogeneous). These differences are task specific, but the most obvious differences lie in sensing and locomotion capabilities. Groups of robots may also have only imperfect or partially-known information about one another as well. One key piece of information that robots lack is how many other robots are in the environment. This thesis describes a method for formation control that allows heterogeneous robots with limited information to dynamically assemble into formations, merge smaller formations together, and correct errors that may arise in the formation. The approach is shown to be scalable and robust against robot failure, and is evaluated in multiple simulated environments.

Stars form from collapsing massive clouds of gas and dust. The UV and optical light emitted by a forming or recently-formed star is absorbed by the surrounding cloud and is re-radiated thermally at infrared and submillimetre wavelengths. Observations in the submillimetre spectrum are uniquely sensitive to star formation in the early Universe, as the peak of the thermal emission is redshifted to submillimetre wavelengths. The coolest objects in star forming regions in our own Galaxy, including heavily-obscured proto-stars and starless gravitationally-bound clumps, are also uniquely bright in the submillimetre spectrum. The Earth's atmosphere is mostly opaque at these wavelengths, however, limiting the spectral coverage and sensitivity achievable from ground-based observatories. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) observes the sky from an altitude of 40 km, above 99.5% of the atmosphere, using a long-duration scientific balloon platform. BLAST observes at 3 broad-band wavelengths spanning 250-500 micron, taking advantage of detector technology developed for the space-based instrument SPIRE, scheduled for launch in 2008. The greatly-enhanced atmospheric transmission at float altitudes, increased detector sensitivity and large number of detector elements allow BLAST to survey much larger fields in a much smaller time than can be accomplished with ground-based instruments. It is expected that in a single 10-day flight, BLAST will detect ~10000 extragalactic sources, ~100 times the number detected in 10 years of ground-based observations, and 1000s of Galactic star-forming sources, a large fraction of which are not seen by infrared telescopes. The instrument has performed 2 scientific flights, in the summer of 2005 and winter of 2006, for a total of 16 days of observing time. This thesis discusses the design of the instrument, performance of the flights, and presents the analysis of 2 of the fields observed during the first flight. A failure in the optical system during the first flight precluded sensitive extragalactic observations, so the majority of the flight was spent observing Galactic targets. We anticipate exciting extragalactic and Galactic results from the 2006 data.

Experiment was done in 2005–2006 years in the base of Vilnius pedagogical university in Chemistry institute. The title of this experiment is „Formation peculiarity of copper aluminates“. The author of this experiment is Jurgita Rakauskaitė and the director of this experiment is doc. dr. Raimondas Giraitis. The aim of this work was to synthesize CuAlO2 and CuAl2O4 from compounds of certain copper, alunimium nitrates and sulfates, and to compare dependance of copper aluminates formation on time and temperature. Firstly, reagents were crushed into powder, pressed and heated, changing heating time and temperature. For the reseach were used these methods: microstructural analysis, differential thermal analysis (DTA), X – ray difractional (XRD) analysis and scanning electron microscopy (SEM). When all the reseaches were finished, these conclusions were made: CuAl2O4 from nitrates begins to form at 750oC and CuAl2O4 from sulfates begins its crystalisation at 700oC. When the temperature is higher than 950oC, formation of CuAlO2 begins. The higher the temperature is, the less time the copper aluminates take to form. Copper aluminates, formed from solid phase, made small crystals and formed from liquid phase made big various shape crystals.