Critical Shear Stress Estimates of Sunken Alberta Bitumen

As observed in several recent spills (e.g., DBL-152, TX; Enbridge-Kalamazoo, MI), under certain circumstances, released oil can sink to the bottom of a water body. Once on the bottom, the oil can move or remobilize into the water column. The National Oceanic and Atmospheric Administration’s (NOAA) Office of Response and Restoration (ORR) uses mathematical models to predict the trajectory of spilled oil. The critical shear stress (CSS) for an oil is used to predict the movement of sunken oil along and off the bottom. The CSS has only been measured for one oil (Hibernian crude). The Coastal Response Research Center (CRRC) at the University of New Hampshire (UNH) has an annular flume equipped with a velocity profiler that can be used to estimate CSS by measuring the instantaneous, three-dimensional water current velocities at which sunken oils undergo movement and erosion of visible oil droplets occur. The CSS of sunken Alberta bitumen was determined by progressively increasing current velocities until deformation, movement and erosion of the stranded oil was observed. Tests were conducted in freshwater at water temperatures of 5, 15 and 25°C. At temperatures ≥ 18.5 ± 1.9 °C, mass erosion of visible droplets was observed in current velocities greater than 20 cm/s (0.39 knots.), corresponding to a CSS of 1.9 Pa. No erosion was observed at temperatures \u3c 18.5 ± 1.9 °C in current velocities up to 100 cm/s (2.25 knots). Understanding the transport and fate of sunken oil is an important prerequisite for recovery of non-buoyant oils. Unfortunately, details regarding environmental conditions and physical properties of crude oil are limited. Spill trajectory modelers make a “best guess” of the expected conditions needed to erode and resuspend oil from the bottom. CSS data are needed for a range of oils. This thesis research estimated CSS for an Alberta bitumen, providing modelers information to predict the behavior of sunken Alberta bitumen

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements