Headwater watersheds initiate material export to downstream environments. A nested headwater study examined the flux and source of dissolved constituents and water from a perennial stream and four ephemeral/intermittent streams in the Upper Gulf Coastal Plain, Mississippi. Water was collected during storm and baseflow conditions. Multiple linear regression was used to model constituent concentration and calculate flux. Source of water was determined using principle components analysis and end-member mixing analysis. Rain was the major source of water discharged from the ephemeral and intermittent streams, while groundwater was the major source for water discharged by the perennial stream during events. Baseflow from both stream types was dominated by groundwater sources. The perennial stream had an area weighted average yields of 10.1, 0.01, 1.0, 0.6, and 0.03 kg-1 ha-1 yr-1 of DON, NO3--N, NH4+-N, PO4-3, and DOC,respectively. This research highlights the interaction of source water and dissolved constituent flux.

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Widespread sedentary lifestyle and unhealthy eating habits in the last few decades have resulted in a dramatic increase of the number of people affected by obesity, type 2 diabetes, and cardiovascular diseases. The study of these pathological conditions revealed that impaired metabolism often causes these disorders. Lipid metabolism research has contributed significantly to determining mechanisms underlying metabolic disorders. Omega-3 fatty acids are an interesting target for lipidomics studies because they were shown to lower risk of cardiovascular diseases and are hypothesized to regulate lipid metabolism. In this work, I optimized lipid extraction and chemical modification methods for analysis of fatty acids profile of tissue samples and biofluids using comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GCxGC-MS). At first, I evaluated the relative amount of omega-3 fatty acids in red blood cells (Omega-3 index) of people living in Czech Republic in either the capital city (n=476) or the rural region (n=388). For this large-scale project, I extracted phospholipids from red blood cell (RBC) membranes, transesterified them into fatty acid methyl esters (FAMEs), and measured their profile by GCxGC-MS. The mean Omega-3 index was 3.56 mol % and I detected no significant...

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The development and maintenance of multicellular organisms depends fundamentally on cell division, a series of events largely mediated by the mitotic spindle. Errors in spindle formation and/or function are often associated with severe consequences, most notably cancer. In order to elucidate the cause of such errors and the potential for therapeutic intervention, it is imperative to attain a clear understanding of how cell division normally operates. In this regard, this dissertation focuses on the activity of two microtubule-based motor proteins, Eg5 and dynein, prior to and immediately following nuclear envelope breakdown during mitosis. I show that prophase microtubules are remarkably more dynamic than their metaphase counterparts, moving both toward and away from centrosomes across a wide distribution of rates. Inhibition of Eg5, dynein and Kif2a revealed that a subset of this motion is consistent with microtubule flux, a well-established phenomenon temporally limited to metaphase and anaphase spindles by the preceding literature. My data indicates that flux is operational throughout all of mitosis, possibly functioning at early stages to collect centrosomal components. Immediately following prophase, cells begin assembling bipolar spindles. While the establishment of spindle bipolarity fails in the physical or functional absence of Eg5, I show that co-inhibition of dynein restores a cell’s ability to organize microtubules into a bipolar structure. Despite inhibition of both Eg5 and dynein, these spindles are morphologically and functionally equivalent to controls. Together, these data suggest that Eg5 and dynein share an antagonistic relationship and that a balance of forces, rather than a definitive set of players, is important for spindle assembly and function. To determine how Eg5- and dynein-mediated forces functionally coordinate to bring about antagonism during spindle assembly, I utilize a nocodazole washout assay. I show, via in vivo imaging and in silico modeling, that spindle collapse in the absence of functional Eg5 requires dynein activity and an initial intercentrosomal distance of less than 5.5μm. These data are consistent with a model in which dynein antagonizes Eg5 by crosslinking and sliding antiparallel microtubules, a novel role for dynein within the framework of spindle assembly.

Heavy water moderator surrounding each fuel channel is one of the important safety features in CANDU reactors since it provides an in-situ passive heat sink for the fuel in situations where other engineered means of heat removal from fuel channels have failed. In a critical break LOCA scenario, fuel cooling becomes severely degraded due to rapid flow reduction in the affected flow pass of the heat transport system. This can result in pressure tubes experiencing significant heat-up during early stages of the accident when coolant pressure is still high, thereby causing uniform thermal creep strain (ballooning) of the pressure tube (PT) into contact with its calandria tube (CT). The contact of the hot PT with the CT causes rapid redistribution of stored heat from the PT to CT and a large heat flux spike from the CT to the moderator fluid. For conditions where subcooling of the moderator fluid is low, this heat flux spike can cause dryout of the CT. This can detrimentally affect channel integrity if the CT post-dryout temperature becomes sufficiently high to result in continued thermal creep strain deformation of both the PT and the CT. A comprehensive mechanistic model is developed to predict the critical heat flux (CHF) variations along the downward facing outer surface of calandria tube. The model is based on the hydrodynamic model of \cite{Cheung/Haddad1997} which considers a liquid macrolayer beneath an elongated vapor slug on the heated surface. Local dryout is postulated to occur whenever the fresh liquid supply to the macrolayer is not sufficient to compensate for the liquid depletion within the macrolayer due to boiling on the heating surface. A boundary layer analysis is performed, treating the two phase motion as an external buoyancy driven flow, to determine the liquid supply rate and the local CHF. The model takes into account different types of flow regime or slip ratio. It is applicable for a calandria vessel as well, under a sever accident condition where a thermal creep failure is postulated to occur if sustained CHF is instigated in the surrounding shield tank water. Model shows good agreement with the available experimental CHF data. The model has been modified to take into account the effect of subcooling and has been validated against the empirical correction factors. / Dissertation / Doctor of Philosophy (PhD)

<p> The Penman combination model for potential evapotranspiration, using the improved wind function of Businger (1956), and measured net radiation, was tested for daily and hourly totals, over an irrigated perennial ryegrass surface at Simcoe, Norfolk County, Southern Ontario. The standard measurement of evapotranspiration was the energy balance method, using the Bowen ratio. The component fluxes of the energy balance were evaluated for ninety-seven hours on ten separate days. A comparison is made of two days with markedly different moisture availability to show how the magnitude of the component fluxes changed. Also the effect of the plant on the evaporative flux is examined. On days when water was non-limiting the model gave excellent results for hourly and daily totals: within 5% of measured evapotranspiration. When water became limiting the model overestimated by as much as 30%. It is further shown that the Penman model appears to be more sensitive to changes in the evaporative flux than the water equivalent of net radiation, The relationship of cumulative dry matter production of the crop and cumulative potential evapotranspiration was examined and was found to be linear for most of the field season, substantiating the hypothesis of Penman (1962).</p> / Thesis / Master of Arts (MA)

<p> A previous study (Davies and Hay, 1978) described a method of calculating hourly and daily values of global solar radiation for cloudless and cloudy sky conditions. This scheme, requiring only upper air data from daily radiosonde ascents, and hourly surface weather observations, has been used successfully at a number of mid latitude sites (Davies et al., 1975; Suckling and Hay, 1976). In this investigation the extension of this method for use in an Arctic environment is presented. </p> <p> Solar radiation received at the earth's surface is the sum of direct and diffuse components. The flux in cloudless conditions is calculated as the residual after attenuation of solar irradiance by water vapour, ozone, Rayleigh scattering and aerosol. Cloudless sky values are then adjusted for cloud effects, using a cloud layer method similar to that used by Davies et al. in Southern Ontario, Canada. </p> </p> The computed values are compared with values measured at Resolute, N.W.T., Canada. Under cloudless sky conditions hourly and daily calculated values agree well with ·measurements. For days of cloud amount less than 4/10, model overestimates are observed. As cloud amounts increase varying degrees of model underestimation of measured values occur. This is linked with observer inability to adequately specify cloud amount, and the variation of cloud type transmission characteristics for Arctic areas. </p> / Thesis / Bachelor of Arts (BA)

Dans les troupeaux laitiers, le succès de l'insémination artificielle dépend, en grande partie, de la qualité de la semence. D est important de disposer de techniques analytiques fiables permettant d'évaluer la qualité de la semence. Actuellement, aucun paramètre pris isolément n'est corrélé de façon satisfaisante à la fertilité. L'évaluation multiparamétrique de la semence est une option intéressante pour améliorer l'efficacité des tests de fertilité. Ce mémoire porte sur la caractérisation, via la cytometric en flux, des spermatozoïdes bovins cryopréservés. Différents paramètres ont été étudiés tels que la viabilité, l'activité mitochondriale, l'intégrité de la membrane acrosomale, le pH intracellulaire, le Ca2+ intracellulaire et celui emmagasiné dans la cellule. Ces paramètres ont été évalués postdécongélation et suite à cinq heures d'incubation en présence ou non d'héparine comme inducteur de la capacitation. Pour chacune des conditions, on a étudié les effets et les interactions de chacun des paramètres et leur relation avec la fertilité in vivo.

The ability to predict and control laminar-to-turbulent transition in high-speed flow has a substantial effect on heat transfer and skin friction, thus improving the design and operation of hypersonic vehicles. The control of transition on blunt bodies is essential to improve the performance of lifting and control surfaces. The objective of this Ph.D. research is to develop efficient and accurate algorithms for the detection of high-frequency heat flux fluctuations supported by hypersonic flow in transitional boundary layers. The focus of this research is on understanding the mathematical properties of the reconstruction such as regularity, sensitivity to noise, multi-resolution, and accuracy. This research is part of an effort to develop small-footprint heat flux sensors able to measure high-frequency fluctuations on test articles in a hypersonic wind tunnel with a small curvature radius. In the present theoretical/numerical study a multi-resolution formulation for the direct and inverse reconstruction of the heat flux from temperature sensors distributed over a multidimensional solid in a hypersonic flow was developed and validated. The solution method determines the thermal response by approximating the system Green's function with the Galerkin method and optimizes the heat flux distribution by fitting the distributed surface temperature data. Coating and glue layers are treated as separate domains for which the Green's function is obtained independently. Connection conditions for the system Green's function are derived by imposing continuity of heat flux and temperature concurrently at all interfaces. The solution heat flux is decomposed on a space-time basis with the temporal basis a multi-resolution wavelet with arbitrary scaling function. Quadrature formulas for the convolution of wavelets and the Green's function, a reconstruction approach based on isoparametric mapping of three-dimensional geometries, and a boundary wavelet approach for inverse problems were developed and verified. This approach was validated against turbulent conjugate heat transfer simulations at Mach 6 on a blunted wedge at 0 angle of attack and wind tunnel experiments of round impinging jet at Mach 0.7 It was found that multidimensional effects were important near the wedge shoulder in the short time scale, that the L-curve regularization needed to be locally corrected to analyze transitional flows and that proper regularization led to sub-cell resolution of the inverse problem. While the L2 regularization techniques are accurate they are also computationally inefficient and lack mathematical rigor. Optimal non-linear estimators were researched both as means to promote sparsity in the regularization and to pre-threshold the inverse heat conduction problem. A novel class of nonlinear estimators is presented and validated against wind tunnel experiments for a flat-faced cylinder also at Mach 6. The new approach to hypersonic heat flux reconstruction from discrete temperature data developed in this thesis is more efficient and accurate than existing techniques. / Doctor of Philosophy / The harsh environment supported by hypersonic flows is characterized by high-frequency turbulent bursts, acoustic noise, and vibrations that pollute the signals of the sensors that probe at high frequencies the state of the boundary layers developing on the walls. This research describes the search for optimal estimators of the noisy signal, i.e., those that lead to the maximum attenuation of the risk of error pollution by non-coherent scales. This research shows that linear estimators perform poorly at high-frequency and non-linear estimators can be optimized over a sparse projection of the signal in a discrete wavelet basis. Optimal non-linear estimators are developed and validated for wind tunnel experiments conducted at Mach 6 in the Advanced Propulsion and Power Laboratory at Virginia Tech.