4,623 research outputs found

    Applying mesh conformation on shape analysis with missing data

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    A mesh conformation approach that makes use of deformable generic meshes has been applied to establishing correspondences between 3D shapes with missing data. Given a group of shapes with correspondences, we can build up a statistical shape model by applying principal component analysis (PCA). The conformation at first globally maps the generic mesh to the 3D shape based on manually located corresponding landmarks, and then locally deforms the generic mesh to clone the 3D shape. The local deformation is constrained by minimizing the energy of an elastic model. An algorithm was also embedded in the conformation process to fill missing surface data of the shapes. Using synthetic data, we demonstrate that the conformation preserves the configuration of the generic mesh and hence it helps to establish good correspondences for shape analysis. Case studies of the principal component analysis of shapes were presented to illustrate the successes and advantages of our approach

    Estimation of runoff volumes for ungauged catchments in the agricultural areas of Western Australia

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    Describes an analysis of flood runoff volumes from 16 small, gauged catchments in the agricultural areas of south western Australia. It also describes methods for estimating flood runoff volumes from ungauged catchments. The independent variables found to be statistically significant in explaining the variability in flood runoff volumes from the gauged catchments were catchment area, mean annual rainfall and the percentage of the catchment that was cleared. No soil factor was found to be significant

    Soil factors affecting flood runoff on agricultural catchments in Western Australia

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    Reviews methods of including soil properties in flood runoff-predicting equations. Concentrates on practical methods that can be routinely used by soil conservation technicians for flood prediction rather than complex research models. A case is made for collecting soil data from the gauged catchments which are relevant to a perceived runoff mechanism and are capable of being routinely applied in simple flood prediction methodologies

    A description of the soils and geology of the Berkshire Valley experimental catchment

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    Basic land resource data are provided in this report to assist an investigation of the effect of contour banking on surface runoff in the Berkshire Valley experimental catchement. Brief descriptions of the catchment\u27s geology, soils and their inferred hydrological significance are provided and a 1:2000 scale map produced. Of major significance to the hydrologic study is the fact that soil depth and internal drainage conditions were found to be not related to landscape positions

    Non-Competitive Inhibition of Flyhead Acetylcholinesterase by Oxime Carbamates. Kinetic Evidence for Non-productive Binding to the Catalytic Site

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    Reversible inhibition of flyhead acetylcholinesterase (E. C. 3.1.1.7) by two oxime carbamates possessing large N-substituents (isopropyl and allyl) was found to follow competitive kinetics of a biphasic nature with acetylcholine as the substrate. The derived values for the substrate dissociation constants of high and low affinity were in approximate agreement with the Michaelis and the non-competitive substrate inhibition constant for acetylcholine respectively. Data for the dependence of carbamoylation rates of the enzyme upon substrate concentration did not agree with a model derived from reversible inhibition kinetics. Reversible inhibition studies indicated low active site competitive inhibition constants, showing good binding to the active site. Studies upon the carbamoylation rates indicated (i) a non competitive interaction, (ii) very low concentrations of a reversibly-formed enzyme/carbamate complex prior to carbamoylation of the active site. A possible explanation for the discrepancy is discussed whereby a reversible Ki determined from inhibition rate saturation by a »Main plot« measures the concentration of carbamate aligned in the active site following an induced shift of enzyme conformation, whereas competitive inhibition constants (Ki) determined from reversible inhibition experiments determine all binding modes at the active site which interfere with substrate attachment. Carbamates with large N-substituents show this effect more because overlap of the carbamoyl moiety with the catalytic site is less likely due to steric hinderance

    Coulomb interactions in single, charged self-assembled quantum dots: radiative lifetime and recombination energy

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    We present results on the charge dependence of the radiative recombination lifetime, Tau, and the emission energy of excitons confined to single self-assembled InGaAs quantum dots. There are significant dot-to-dot fluctuations in the lifetimes for a particular emission energy. To reach general conclusions, we present the statistical behavior by analyzing data recorded on a large number of individual quantum dots. Exciton charge is controlled with extremely high fidelity through an n-type field effect structure, providing access to the neutral exciton (X0), the biexciton (2X0) and the positively (X1+) and negatively (X1-) charged excitons. We find significant differences in the recombination lifetime of each exciton such that, on average, Tau(X1-) / Tau(X0) = 1.25, Tau(X1+) / Tau(X0) = 1.58 and Tau(2X0) / Tau(X0) = 0.65. We attribute the change in lifetime to significant changes in the single particle hole wave function on charging the dot, an effect more pronounced on charging X0 with a single hole than with a single electron. We verify this interpretation by recasting the experimental data on exciton energies in terms of Coulomb energies. We show directly that the electron-hole Coulomb energy is charge dependent, reducing in value by 5-10% in the presence of an additional electron, and that the electron-electron and hole-hole Coulomb energies are almost equal.Comment: 8 pages, 7 figures, submitted to Phys. Rev.

    Drainage to control waterlogging

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    Drains can be classified in several ways. Drains on flat land have similar drainage effects on either side of the drain and are called relief drains. Drains on sloping land intercept seepage water moving down hillsides and therefore have most effect on the downslope side. They are called interceptor drains. Drains can also be classified as being open drains (that is, open at the ground surface) or buried drains (for example, tube drains)

    Long-term carbon and nitrogen dynamics at SPRUCE revealed through stable isotopes in peat profiles

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    Peatlands encode information about past vegetation dynamics, climate, and microbial processes. Here, we used δ15N and δ13C patterns from 16 peat profiles to deduce how the biogeochemistry of the Marcell S1 forested bog in northern Minnesota responded to environmental and vegetation change over the past  ∼ 10000 years. In multiple regression analyses, δ15N and δ13C correlated strongly with depth, plot location, C∕N, %N, and each other. Correlations with %N, %C, C∕N, and the other isotope accounted for 80% of variance for δ15N and 38% of variance for δ13C, reflecting N and C losses. In contrast, correlations with depth and topography (hummock or hollow) reflected peatland successional history and climate. Higher δ15N in plots closer to uplands may reflect upland-derived DON inputs and accompanying shifts in N dynamics in the lagg drainage area surrounding the bog. The Suess effect (declining δ13CO2 since the Industrial Revolution) lowered δ13C in recent surficial samples. High δ15N from −35 to −55cm probably indicated the depth of ectomycorrhizal activity after tree colonization of the peatland over the last 400 years, as confirmed by the occasional presence of wood down to −35cm depth. High δ13C at  ∼ 4000 years BP (−65 to −105cm) could reflect a transition at that time to slower rates of peat accumulation, when 13C discrimination during peat decomposition may increase in importance. Low δ13C and high δ15N at −213 and −225cm ( ∼ 8500 years BP) corresponded to a warm period during a sedge-dominated rich fen stage. The above processes appear to be the primary drivers of the observed isotopic patterns, whereas there was no clear evidence for methane dynamics influencing δ13C patterns
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