Comparison of Oxygen Transfer Between an Integrated Fixed-Film Activated Sludge (IFAS) Process and a Conventional Activated Sludge Process (ASP)

The T.Z. Osborne (TZO) Water Reclamation Facility (WRF) located in Greensboro, NC is a 40 million gallon per day (MGD) wastewater treatment plant that includes biological nutrient removal with surface-water discharge. Several process alternatives are being evaluated as strategies to meet forthcoming nutrient limits. Integrated fixed film activated sludge (IFAS) is one of the alternatives being considered for implementation. Due to the limited number of full-scaleo perating IFAS treatment facilities in the United States and the City of Greensboro's desire to experience operating the process, a thorough year-long study was conducted to quantify the nitrification kinetics, aeration requirements, process performance, and potential operational issues. As part of the full-scale evaluation, an off-gas test was performed in accordance with the American Society of Civil Engineers' (ASCE) Protocol. Previously, only one off-gas test had been performed, and it was conducted by another IFAS manufacturer. To our knowledge, the testing described in this report is the first independent off-gas test on an IFAS system to date. Results of the testing indicate that the IFAS process has higher air flux and air use per unit load treated compared to the activated sludge process (ASP), likely due to elevated mixing requirements and high dissolved oxygen (DO) specified by the process manufacturer, with associated lower oxygen transfer efficiency. The relative air use of the IFAS process is in the range of 1.3 to over 3.0 times that of the ASP, and the IFAS process has approximately 25 to 50% more air use for mixing when compared to the ASP.Master of Science in Environmental Engineerin

Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow

We review modeling of astrocyte ion dynamics with a specific focus on the implications of so-called spatial potassium buffering, where excess potassium in the extracellular space (ECS) is transported away to prevent pathological neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for modeling ion dynamics in astrocytes (and brain tissue in general) is outlined and used to study such spatial buffering. We next describe how the ion dynamics of astrocytes may regulate microscopic liquid flow by osmotic effects and how such microscopic flow can be linked to whole-brain macroscopic flow. We thus include the key elements in a putative multiscale theory with astrocytes linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure

Potassium modulation of methionine uptake in astrocytes in vitro

Methionine participates in a large variety of metabolic pathways in brain, and its transport may play an important regulatory role. The properties of methionine uptake were examined in a preparation of neonatal rat brain astrocytes. Uptake is linear for 15 minutes, up to 2.5 μM. At steady state conditions, methionine is concentrated 30–50-fold. Measured methionine homoexchange accounts for a significant fraction of uptake at concentrations greater than 10 μM. We recently reported that methionine uptake is decreased by elevations in extracellular K + . Potassium induced efflux cannot account for this apparent effect; and thus for concentrations less than 2.5μM, and for short times of incubation, measured rates of methionine uptake represent unidirectional flux. At extracellular concentrations of K + equal to 6.9 mM, the apparent V max of methionine transport is 182 pmol/min/mg protein, and the K m is 1.3 μM. Where K + is shifted to 11.9 mM, the K m remains unchanged, and the V max is reduced by half.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45429/1/11064_2004_Article_BF00965129.pd

Visualization of Spatiotemporal Energy Dynamics of Hippocampal Neurons by Mass Spectrometry during a Kainate-Induced Seizure

We report the use of matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry combined with capillary electrophoresis (CE) mass spectrometry to visualize energy metabolism in the mouse hippocampus by imaging energy-related metabolites. We show the distribution patterns of ATP, ADP, and AMP in the hippocampus as well as changes in their amounts and distribution patterns in a murine model of limbic, kainate-induced seizure. As an acute response to kainate administration, we found massive and moderate reductions in ATP and ADP levels, respectively, but no significant changes in AMP levels—especially in cells of the CA3 layer. The results suggest the existence of CA3 neuron-selective energy metabolism at the anhydride bonds of ATP and ADP in the hippocampal neurons during seizure. In addition, metabolome analysis of energy synthesis pathways indicates accelerated glycolysis and possibly TCA cycle activity during seizure, presumably due to the depletion of ATP. Consistent with this result, the observed energy depletion significantly recovered up to 180 min after kainate administration. However, the recovery rate was remarkably low in part of the data-pixel population in the CA3 cell layer region, which likely reflects acute and CA3-selective neural death. Taken together, the present approach successfully revealed the spatiotemporal energy metabolism of the mouse hippocampus at a cellular resolution—both quantitatively and qualitatively. We aim to further elucidate various metabolic processes in the neural system

Posterior fossa tumours in childhood: Associated speech and language disorders post-surgery

Six children aged between 6 and 16 years who had undergone surgery for the removal of a posterior fossa tumour were assessed at least one year postoperatively to determine the incidence and severity of any associated speech or language deficits. Five males and one female were included in the sample. The subjects were administered a battery of speech/language assessments including: a language screening test, an articulation test, a dysarthria assessment and a perceptual speech analysis. The results indicated that dysarthria and/or language impairment occurs in some cases subsequent to surgical removal of posterior fossa tumours. The occurrence of muteness immediately post-surgery would appear to indicate a poor prognosis for speech abilities. A possible link between the occurrence of long term language disabilities in these children and post-surgical radiotherapy is documented