Rasmussen's encephalitis: an autoimmune disorder?

Rasmussen's encephalitis is a rare progressive pediatric epileptic syndrome. Recent evidence from experimental animals and patients with the disease suggests an important role for both humoral and cell-mediated immune mechanisms in the pathogenesis of this disease. The glutamate receptor subunit GluR3 may be an important autoantigen in the disease. (This review has been modified from a review published in Current Opinion in Neurology 1996, 9:141-145.)     

Saturation of ecosystems with toxic metals in Sudbury basin, Ontario, Canada

Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant metals in the watershed rather than further emission controls may be required for dealing with high levels of toxic metals in surface waters of the saturated ecosystems.     

Rheological Properties of Solutions and Emulsions Stabilized with Xanthan Gum and Propylene Glycol Alginate

The rheological effects of propylene glycol alginate (PGA) added to solutions and model emulsions containing xanthan gum (XG) were studied using controlled stress rheometry with concentrations appropriate for salad dressings. For samples with XG and XG + PGA blends, solutions and emulsions showed a Newtonian plateau at low shear stresses. The Newtonian plateau of a solution accurately predicted (r²= 1.00) the Newtonian plateau for an emulsion of equivalent gum concentration. Addition of PGA to constant levels of XG showed a more than additive increase in the Newtonian plateau viscosity for solutions and emulsions. For XG aqueous solutions, pseudoplasticity decreased upon addition of PGA. Storage and loss moduli increased with addition of PGA to XG for solutions and emulsions, although G’ for solutions of PGA alone were negligible.     

A customised approach to determining the geomorphic effectiveness of small flood events in a regulated river

The construction of dams significantly alters flow and sediment regimes with subsequent deleterious effects on the morphological and ecological character of rivers. Effective experimental floods can ameliorate the downstream geomorphic impacts of dams. The traditional view is that large floods are required to perform effective geomorphic work, and the geomorphic outcomes of small floods are often overlooked. Many river restoration frameworks do not consider small floods. Yet, there is evidence that the hydrological characteristics that ameliorate specific geomorphic impacts in a river are unique to each river, and a customised approach to setting the right mix of floods (including small experimental floods) is needed. In this study, we modify an existing flood effectiveness model developed for large floods, for determining the geomorphic effectiveness of small floods in a highly regulated Australian river. Two flood classes were added to the model (medium peak stream power and moderate total energy expenditure), and the flood power characteristics were rescaled to reflect the relative difference in the magnitude of the small floods and the magnitude of the geomorphic work performed. Using a step‐wise approach, this customised model determined the geomorphic effectiveness of small floods. The best flood for ameliorating the geomorphic impacts of flow regulation had medium to long duration (10 to 51 days), high peak unit stream power (77 to 123 Wm^?2) and moderate to large total energy expenditure (78,600 to 342,320 × 10³ J). This approach to determining flood effectiveness for small floods is applicable to other geomorphically impacted river channels downstream of dams and can be used to inform experimental flood releases for geomorphic outcomes.     

“Meandering” Effects on the Diffusion of Continuous Dye Plumes in Coastal Currents

Experimental data on the diffusion of fluorescent dye plumes were obtained in the nearshore zone of the Great Lakes. The transport and diffusion of continuous dye plumes may be studied either in a frame of reference moving with the centre of gravity of the plume or in a frame of reference fixed to the stationary source. Conventionally, the former is referred to as “relative” diffusion and the latter as “absolute” diffisuion. The inter-link between the two concepts is explained by the random movements of the centre of gravity of the diffusing dye plume usually referred to as the “meandering”.In the past, experimental data from continuous dye plumes in coastal currents have been used to study “relative” diffusion, neglecting the random movements of the centre of gravity. In reality, however, “meandering” appears to be a more efficient agency than “relative” diffusion from the practical point of view of dispersing effluents over larger volume of the water body.In the present analysis, particular attention is given to delineate the two component physical processes of “relative” diffusion and “meandering” diffusion, by extended sampling of the dye plume to cover time scales of both the processes. Calculated horizontal eddy diffusivity K_y in “absolute” diffusion is greater by a factor of 2 as compared to “relative” diffusion. Very high peak/mean concentration ratios observed as the centre of the plume are a direct result of “meandering” due to large scale turbulent eddies.