256 research outputs found
Late Holocene mud sedimentation and diagenesis in the Firth of Thames: Bentonites in the making
No full textLate Holocene mud sedimentation in the southern Firth of Thames has been described from analysis of a number of shallow marine sediment cores. Three distinct lithofacies are distinguished on the basis of sediment texture and mineralogy. A laterally extensive greenish grey mud, typically bioturbated and massive, with sporadic uncorrelatable interbedded shell layers is termed the Firth of Thames mud facies. Nearer shore sediments are usually coarser and are subdivided into two facies: a siliciclastic sand facies (river mouth sand facies) comprising more prominent interbeds of sand in mud and associated with sedimentation at the mouth of the Waihou River; and a mixed terrigenous-carbonate gravel facies (delta fan gravel facies) associated with deposition on small delta fans adjacent to streams draining the Coromandel Range. The areal distribution of all three facies over the late Holocene has been controlled largely by northward progradation of the coastal Hauraki Lowland associated with the rapid sediment infilling of the Firth of Thames since sea level reached its present height 6500 y B.P. From seismic evidence the Holocene muds are up to 10m thick. The cores in this study penetrated only to 5.5m sub-bottom depth and yielded an oldest radiocarbon age of 5000 y B.P. The age data indicate an average rate of offshore vertical sediment accumulation of 1.5 mm/y.
Up to 15 km of progradation of the southern shoreline of the coastal Hauraki Lowland has occurred over the late Holocene at an average rate of up to 2.5 m/y, notably from 3500 y B.P to 1200 y B.P. Progradation is evidenced by the occurrence of coarsening-upward sequences in nearer shore cores of the Firth of Thames, as well as their changing faunal composition, particularly the upward increase in abundance of the foraminifer Ammonia beccarri, a good indicator of brackish water conditions, which suggests a gradual seaward encroachment of the freshwater influence of the Waihou River over the late Holocene. Basal muds which are similar in composition to marine sediments of the Firth of Thames are overlain by peat dated at 6025 y B.P in a peat core from Kopouatai Peat Bog, and suggest that marine conditions existed in this inland region of the Hauraki Depression prior to 6025 y B.P.
Muds range from silty clays to clayey silts and consist principally of volcanic glass, smectite and halloysite, with smaller amounts of other volcanic-derived siliciclasts and allophane and illite, as well as skeletal carbonate (mainly aragonite) and organic matter. A contemporaneous decrease in the abundance of volcanic glass (55-15 wt % down-core) and an increase in smectite concentration (8-45 wt % down-core) occurs with sub-bottom depth. Specific mineralogical analyses (XRD and IR) and evidence from scanning electron microscopy suggest the smectite is montmorillonitic in composition and authigenic in nature. Moreover, the absence of smectite in the bottom sediments of rivers draining the Hauraki Lowland precludes a detrital origin.
The diagenetic transformation of volcanic glass to smectite in sediments of the Firth of Thames is described by a sequential kinetic model which involves a parabolic dissolution coupled with a first order precipitation of smectite via the formation of an intermediate hydrated glass phase. The rate constant calculated from the sequential kinetic model is 3.35 x 10⁻⁴y⁻¹. The half-life of the glass is 1475 y, implying rapid early diagenetic alteration of volcanic glass to smectite to form late Holocene bentonitic deposits. Thermodynamic stability considerations imply that the first order precipitaion of smectite may be favoured by conditions of pH and Na⁺ activity typical of interstitial fluids having sea water salinity under mildly anoxic conditions
Inter-vortex spacing in superfluid turbulence: temperature and Reynolds number dependences
No full textThe typical spacing between superfluid vortices in an isothermal turbulent tangle is proportional to the integral scale H rescaled by the quantum Reynolds number Re_K=H.V/K to the power of 3/4, where K is the quantum of circulation around of single vortex [Salort et al.,EPL 2011]. This empirical relation can be seen as the quantum-turbulence version of the corresponding well-know equation giving Kolmogorov dissipative scale in classical turbulence. In 2014, we studied the temperature dependence of the numerical factor (d/H).Re_K^{3/4} in 4He by joint numerical and experimental analysis of steady state turbulence over a wide temperature interval (1.2 - 2.16 K) [Babuin et al., EPL 2014]. Agreement between the two analyses was found good except at the very ends of this temperature interval. We will discuss this issue by presenting additional experimental data obtained by post-processing of superfluid experiments published between 1975 and 1998
From ornament to essence - represented by Gustav Klimt and Egon Schiele
No full textGraduate research paper for painting.AR 695, H.V.1979 Spring
UK Clinicians' Knowledge of and Attitudes to the Prenatal Diagnosis of Single Gene Disorders
No full text
2050 Midwest Structural Masterplan & A Transit Hub for St Louis
No full textThe project initiated with researching the condition of the Midwest, it’s major challenges and potential opportunities within the themes of infrastructure, energy, and landscape. After 5 months of research and analysis, the studio produced a 2050 Structural Masterplan for the Midwest. This masterplan involved a strategy for creating a unified, economically strengthened region along with a set of proposals that highlighted potential solutions to some of the specified challenges. This was executed through the lens of large-scale, top down, future vision planning in order to address very complex and challenging issues. Following the research and Masterplan design, each student selected their own site, project, and program within the context of the Midwest: a multi-modal transit hub (highlighting the increased value of passenger rail and the introduction of a maglev high speed rail) within St Louis (at the location of the existing passenger train station). The goal was to test the ideas of the 2050 Structural Masterplan of the Midwest within a city context and at a building scale. The St Louis Transit Hub focused on integrating multiple modes of transportation while providing a more inviting and welcoming experience into the city. This gateway experience became a guiding concept for the project, offering a gateway for the pedestrian, a gateway for the trains, and a symbolic gateway moment for the inhabitants of St Louis: a moment of passing from one mentality to another (an opportunity to offer education, awareness, and understanding about the challenges and opportunities). A gateway in three dimensions.MaterializationArchitectureArchitectur
Materializing Technologies: Surfacing Focal Things and Practices with Design
No full textToday, the world is populated with what we colloquially refer to as “black boxes.” These are technologies that perform sophisticated operations but obfuscate these complex operations, providing us with little context to what they do, how they work, and the role they play in our lives. In simple terms, this thesis addresses the following broadly framed questions: what parts of these black boxes should be made legible to the layperson? And regarding these parts: how can design be harnessed to reframe them as legible?Ethics & Philosophy of TechnologyHuman Information Communication Desig
Experiments on a natural circulation loop - from void fraction to nuclear
No full textApplied Science
Signal detection in fractional Gaussian noise and an RKHS approach to robust detection and estimation
No full textThis thesis is divided into two parts. In the first part, the problem of signal detection in fractional Gaussian noise is considered. To facilitate the study of this problem, several results related to the reproducing kernel Hilbert space of fractional Brownian motion are presented. In particular, this reproducing kernel Hilbert space is characterized completely and an alternative characterization for the restriction of this class of functions to a compact interval (0,T) is given. Infinite-interval whitening filters for fractional Brownian motion are also developed. Application of these results to the signal detection problem yields necessary and sufficient conditions for a deterministic or stochastic signal to produce a nonsingular shift when embedded in additive fractional Gaussian noise. Also, a formula for the likelihood ratio corresponding to any deterministic nonsingular shift is developed. Finally, some results concerning detector performance in the presence of additive fractional Gaussian noise are presented.In the second part of the thesis, the application of reproducing kernel Hilbert space theory to the problems of robust detection and estimation is investigated. It is shown that this approach provides a general and unified framework in which to analyze the problems of L\sp2 estimation, matched filtering, and quadratic detection in the presence of uncertainties regarding the second-order structure of the random processes involved. Minimax robust solutions to these problems are characterized completely, and some results concerning existence of robust solutions are presented.Made available in DSpace on 2011-05-07T14:14:57Z (GMT). No. of bitstreams: 2
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