Two-dimensional numerical modelling of sediment and chemical constituent transport within the lower reaches of the Athabasca River.

Flows and transport of sediment and associated chemical constituents within the lower reaches of the Athabasca River between Fort McMurray and Embarrass Airport are investigated using a two-dimensional (2D) numerical model called Environmental Fluid Dynamics Code (EFDC). The river reach is characterized by complex geometry, including vegetated islands, alternating sand bars and an unpredictable thalweg. The models were setup and validated using available observed data in the region before using them to estimate the levels of cohesive sediment and a select set of chemical constituents, consisting of polycyclic aromatic hydrocarbons (PAHs) and metals, within the river system. Different flow scenarios were considered, and the results show that a large proportion of the cohesive sediment that gets deposited within the study domain originates from the main stem upstream inflow boundary, although Ells River may also contribute substantially during peak flow events. The floodplain, back channels and islands in the river system are found to be the major areas of concern for deposition of sediment and associated chemical constituents. Adsorbed chemical constituents also tend to be greater in the main channel water column, which has higher levels of total suspended sediments, compared to in the flood plain. Moreover, the levels of chemical constituents leaving the river system are found to depend very much on the corresponding river bed concentration levels, resulting in higher outflows with increases in their concentration in the bed sediment.

An integrated numerical framework for water quality modelling in cold-region rivers: A case of the lower Athabasca River.

There is a great deal of interest to determine the state and variations of water quality parameters in the lower Athabasca River (LAR) ecosystem, northern Alberta, Canada, due to industrial developments in the region. As a cold region river, the annual cycle of ice cover formation and breakup play a key role in water quality transformation and transportation processes. An integrated deterministic numerical modelling framework is developed and applied for long-term and detailed simulation of the state and variation (spatial and temporal) of major water quality constituents both in open-water and ice covered conditions in the lower Athabasca River (LAR). The framework is based on the a 1D and a 2D hydrodynamic and water quality models externally coupled with the 1D river ice process models to account for the cold season effects. The models are calibrated/validated using available measured data and applied for simulation of dissolved oxygen (DO) and nutrients (i.e., nitrogen and phosphorus). The results show the effect of winter ice cover on reducing the DO concentration, and a fluctuating temporal trend for DO and nutrients during summer periods with substantial differences in concentration between the main channel and flood plains. This numerical frame work can be the basis for future water quality scenario-based studies in the LAR.

Congenital malaria: a case report.

Malaria is an important vector-borne infectious disease, caused by plasmodium parasite. Congenital malaria, however, is rare and may be acquired either during pregnancy, at the time of delivery or after birth. A case of symptomatic congenital malaria caused by Plasmodium vivax and characterised by fever, irritability, pallor and jaundice, is presented in a 4-week-old infant.

Renal angiomyolipoma, a diagnostic dilemma: a case report.

Angiomyolipomas are the most common benign mesenchymal tumours of the kidney. Most of the angiomyolipomas in adults are asymptomatic and discovered incidentally. We report a case in a symptomatic 55 yrs old male who had a huge retroperitoneal mass abdomen and in whom diagnosis and organ of origin remained unclear until operation and histopathological study was performed. Radiological and fine needle aspiration cytology (FNAC) report of a malignant retroperitoneal tumour was given, but histological examination of the respective tumorous mass showed a benign renal tumour - angiomyolipoma. Our emphasis by reporting this case is to make cytopathologists and radiologists aware of such kind of diagnostic pitfall encountered while reporting retroperitoneal masses.

A rare spectrum of lesions encountered in fibroid uterus: histopathological report.

Symplasmic or atypical leiomyoma and lipoleiomyoma are two very rare morphological variants of leiomyoma of the uterus. Both the tumours show a benign behavior like the classical leiomyoma. But differentiated from the classical leiomyoma by presence of bizarre cellular pattern with paucity of mitosis and presence of mature lipocytes within a leiomyoma respectively. We report one case each of these variants in two routine fibroid uterus specimens of two different patients, as they can be misdiagnosed as leiomyosarcoma and well-differentiated liposarcoma respectively, by inexperienced pathologists.